# Anatomical Record 14 (1918)

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# THE ANATOMICAL RECORD

Editorial Board

Irving Hakdesty Tulane UnlverBity

Clarence M. Jackson University of Minnesota

Thomas G. Lee University of Minnesota

Frederic T. Lewis Harvard University

Warren H. Lewis Johns Hopkins University

Charles F. W. McClure Princeton University

WiLLIAM S. Miller University of Wisconsin

Florence R. Sabin Johns Hopkins University

George L. Streeter University of Michigan

G. Carl Huber, Managing Editor

1330 Hill Street. Ann Arbor. Michigan

VOLUME 14 JANUARY-JULY, 1918

PHILADELPHIA THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY

## Contents

### No. 1. JANUARY

Frontispiece. Portrait of Franklin P. Mall 1

G. Carl HuBER. Franklin Paine Mall. In Memoriam 3

Proceedings of the American Association of Anatomi.st.s. Thirty-fourt session 19

Proceedings of the American Association of Anatomists. Abstracts 25

Proceedings of the American Association of Anatomists. Demonstrations 53

American Association of Anatomists. List of officers and members 59

Proceedings of the American Society of Zoologists. Fifteenth Annual Meeting 77

Proceedings of the American Society of Zoologists. Abstracts 85

American Society o Zoologists. List of officers and members 107

Herbert E. Metcalp and Katharine D. Metcalf. Persistence of the posterior cardinal veins in an adult cat. One figure 123

E. K. HosKiNS. Microscope lamps for students 126

Byron L. Robinson. Concerning the renal portal system in Chrysemys marginata. Two figures 127

Leslie B. Aret. Observations on the shape of the erythroplastid in the wing of the bat 135

### No. 2. FEBRUARY

Walter X. Hess. A seasonal study of the kidney of the five-spined stickleback Eucalia inconstans Caj'uga Jordan. Ten figures 141

Lynn Arthur Hoag. Histology of the sensory root of the trigeminal nerve of the rat (Mus Norvegicus) 165

### No. 3. MARCH

William F. Allen. Advantages of sagittal sections of pig embryos for a medical embryology course. Eight figures 183

Ivan E. Wallin. On the branchial epithelium of Ammocoetes. Eight figures (two plates) 205

### No. 4. APRIL

G. Carl Huber. On the anlage and morphogenesis of the chorda dorsalis in mammalia, in particular the guinea pig (Cavia cobaya). Fourteen figures 217

### No. 5. MAY

C. E. McClung. Some considerations regarding microscopical technique 265

Oscar Riddle. Further observations on the relative size and form of the right and left

teste : of pigeons in health and disease and as influenced by hybridity 283

AL\RT T. H.\RM,\x. A probable case of superfetation in the cow 335

M.\YN.\RD M. Metc.\lf. Darwinism and Nations. Supplement to the Proceedings of The .American Society of Zoologists, published in The Anatomical Record, volume 14, number 1, Januarj-, 1918 1

### No. 6. JUNE

SjTnposium. The teaching of anatomy and the inculcation of scientific methods and interest

C. R. Bardeen. The value of the Roentgen-ray and the living model in teaching and research in human anatomy ' 337

A. G. PoHLMAX. Ways and means in the teaching of gross anatomy 341

C. M. J.tcK.sox. How can anatomy be taught as a science and fulfill its purpose as a foundation for medicine? 351

George S. Huxtixgto.v. Modern problems of evolution, variation and inheritance in the anatomical part of the medical curriculum. Eighteen figures and seventeen plates 359

Discussion by H. W. Schultc, C. R. Stockard, C. H. Danforth, E. R. Clark, V. E. Emmel, S. W. Ranson, E. R. Hoskins, H. S. Murphy 447

### No. 7. JULY

Jescs Rafael Ri.squez t J. M. Romero Sierr.\. Un caso de ectopia cardiaca e.xtra tora.xica. One figure 457

William H. F. .\ddiso.n- axd J. Mo.nroe Thori.n-gtox. The behavior of the phagocytic

cells of the peritoneal fluid toward particulate matter 467

H. E. Jorda.v. a study of a 7 mm. human embryo; with special reference to its peculiar

spirally twisted form, and its large aortic cell-clusters. Seven figures (one plate) . . 479 J. I. Fa.vz. The use of sandpaper in the preparation of histologic ground sections on hard substances 493

## FRANKLIN PAINE MALL

1862-1917

Ix Memokiam

This hour, of our busy session, has been set aside to enable us to voice our deep appreciation, our gratitude and affection of one who has been wont to meet with us, one of our members whose busy and eventful life, but recently and all too suddenly was brought to an end. On November 17 we were shocked and grieved to learn of the death of Franklin Paine ^lall. Professor of Anatomj' at Johns Hopkins University and Director of the Department of Embryology of the Carnegie Institution of Washington. We who in thought lingered at his bedside during the final week of illness, though separated by boundaries of states, we who were made hopeful or sorrowed as bulletins were received, and were in a measure led to anticipate the end, were none the less unprepared to sustain the grief which came with the realization of the sudden ending of a career which has meant so much to the development of scientific .Anatomy in America. On this 17th day of November there came to a close the lives of two notable personalities with international standing. The one, Auguste Rodin, with years nimiljering more than three score and ten, who labored more than half a centurj- to reach fame, one whose molded clay and chiseled stone expressed structure and movement; the other, our departed member, who in the scarce more than half century of life, obtained a commanding position early in his career and of his brief span was for nearly a quarter of a century recognized at home and abroad as an able investigator, with wide sjTnpathies, and keen and broad \-ision: one who saw life in a dead section; one who has been teacher to many of us though we held not the formal relation of pupils.

An address, in memorj- of Franklin Paine Mall, presented at the thirty-fourth session of the American Association of Anatomists, convened at the Unis'ersity of Minnesota, December 27 to 29, 1917.

We are at the moment too near to sorrow to sketch with full justice this life. I have been the more willing to give expression to our feelings, at this time, since I fully realize that no word of eulogy of mine is needed to bring him to your appreciation. We are all familiar with the results of his labor. To nearly all of us there has been a personal side, not revealed in printed page. To me, he has l^een a helpful friend of many years standing, one whose frank though kindly criticism as well as encouraging word, whether written or spoken, have been appreciated and have influenced my endeavors and will influence them to the end of my labors.

The years immediately following graduation in medicine, Doctor Mall spent in study in Europe. The first year (1884) at Heidelberg, where he pursued various medical subjects, lived the life of a student and perfected himself in the German language. In his discussion of liberty in medical education, with special reference to sequence or courses, we read "If a student desires to take pathological histology without having had normal histology and the instructor did not object, the student would have to take the consequences. I myself did this as a student at Heidelberg and to this dayl have not regretted it." The years of 1885-86 were spent in Leipzig and the greater part of this time in Ludwig's laboratory, and he was profoundly influenced by this teacher, one whom Alinot has characterized "as the greatest teacher of the art of scientific research whom he had ever met." The influence of Ludwig was the dominant one in molding his future scientific ideals as well as his attitude toward medical education. The happy relations existing in the laboratory between Ludwig and his pupils was one which impressed him greatly and was emulated l?y him in his own laboratory in later years. During his second year at Leipzig a part of the time was spent in study in the laboratory of His. This great teacher of anatomy was not so congenial and less approachable. In his account of the life of Wilhelm His he informs us that "When

I knocked at his door at first I was turned away, but after appearing a number of times I was finally accepted." Teacher and pupil became intimate friends in later years. Doctor :Mall spent many summers in Leipzig working with His. Their intimacy w^as based on common interests in smiilar scientific problems. The clear reasoning and direct manner of formulating and solving problems, characteristic of His, impressed and influenced his pupil and co-worker. The results of his two years of study at Leipzig are embodied in two publications, one from each of the two laboratories in which his special work was carried on — "Die Blut-und Ljaiiphwege im Diinndarm des Hundes" and "Entwickelung der Brancliialbogen und Spalten des Hlinchens," characteristic of the spirit of the two laboratories and in a measure foreshadowing the main lines of his future work.

On his return to America Doctor Mall was called to Baltunore, where he entered upon the duties of Fellow in Pathology, under Professor Welch (1886-88) in association with Doctors Halstead and Councilman. He was named Instructor in Pathology, 188889. These were further years of training, devoted to investigation, as attested by a nvunber of publications. It is deemed fitting to emphasize here this long period of training devoted to research, and the breadth of the training — physiology, embryology and pathologj'. Doctor ^lall has often, in spoken and written word, stressed the necessity *of training in research as a preparation for an academic career and has pled for the opportunity for such training in our American IMedical Schools. "In America," he writes, "we frequently find recent graduates who tell us they would follow an academic career if their future were assured as far as salary is concerned. Little do they realize that this attitude of mind alone would exclude them absolutely from such a career."

With the opening of Clark L'niversity Doctor Mall became Adjunct Professor of Vertebrate Anatomy (1889-92), and with the foundation of Chicago L^nivensity, Professor of Anatomy (1892-93). With the establishment of the School of Medicine at Johns Hopkins University, he returned to Baltimore to enter upon the duties of Professor of Anatomy and Director of the Laboratory, which position he held at the time of his death, assuming in 1914. in conjunction, the directorship of the newly created Department of Embryology of the Carnegie Institution of Washington. The University of Michigan honored him and honored itself by conferring the degree of A.^I., in 1900, and the degree of Sc.D., in 1908. He received the degree of LL.D., from the Universitj^ of Wisconsin, in 1904. His sympathies in the sciences, more particularly in the Biological sciences were broad, and in an ad\'isory capacity, as a member of committees or of boards, he did much to promote his chosen and allied sciences. He was sometime a trustee of the Woods Hole Biological Laboratory', member of the Advisory Board of The Wistar Institute, member of the committee of brain research of the International Association of Academies, member of the National Academy of Sciences, of the .Imerican Philosophical A.ssociation, Fellow of the College of Physicians of Philadelphia and member of many learned societies of America.

Doctor flail's publications mmiber somewhat over one hundred. Time does not permit, nor is this the opportunity to present a bibhographic list and discuss critically these publications. This I am attempting for record elsewhere. However, a fleeting survey may here be permitted. His Leipzig teachers, Ludwig and His, were sometime teachers both of anatomy and physiology and many of Ludwig's researches were of phj'siological problems studied chiefly on an anatomical basis, bringing structures and course of blood vessels in relation with function of organs. This functional or physiological anatomy is exemplified in his studies of the blood and lymph vessels of the dog's small intestine and stomach, his studies of the spleen lobule, and of the structural unit of the hver. Finished contributions of studies in which methods of vascular injection, corrosion injection, maceration and differential digestion where used to advantage in reachmg definite conclusions. Of his more purely physiologic researches maj^ be mentioned the studies of the vasomotor supply of the Portal System. His careful and illxuninating studies of the histogenesis of the connective tissue from mesenchjanal syncytium and of collagenous, yellow elastic and reticular fibrils have given us a new conception of the structure of connective tissue. However, from the time of his early studies in embr3-olog\' in the His laboratory, resulting in his first publication, embryology and histogenesis have been the chief theme of his investigation, his real program for modern anatomy. The embryological studies contributed by himself, with many others emanating from liis laboratory, have greatly extended the bounds of our knowledge of developmental processes, especially as concerns the human embryo, the development of which, except for earliest stages, is now better understood than that of any other mammal, and this largely through his labors, his cooperation or his incentive. Dottor Mall's first embryological contribution dealt with the development of the branchial cleft region of the chick, followed in close succession by a series of studies of this region, both in chick and mammals. These were followed by a series of papers on the development of the coelomic caAdty, culminating in his well known contribution to the development of the hmnan coelom. His study of a human embryo 26 days old, falling to the early period of his work (1891) exemplifies a characteristic of the embrj-ological work of His, namel}', that he viewed the embr3-o as a whole and carried the investigation to its logical conclusion. This study has been the prototj^pe for other investigations of himian and other mammaUan embrj'os. The contribution to the development of the hmnan intestine and its position in the adult exemplifies another tj-pe of embryological work, one worth}- of special commendation. Of it. His has stated in a private letter — "What is lacking in the majority of contributions to embryology is a fundamental conception of the transition phases from early developmental stages to fetal and adult stages. For the intestine you have now completed this chain, from begmning to end, and this I hold to be a great advance. This broad conception of embryologic investigation characterizes other of his contributions; his studies on the development of the heart, normal and pathological, and of the structure of the adult heart, his studies of the •structural unit of the liver, of the blood vessels of the brain and other \essels, all bring to conclusion developmental stages and give the key to modern anatomic investigation. With the increase in the size of the human embryological collection at Johns Hopkins University, the need of determining more definitely the age relation to the size of the human embryo, the sequence of stages and a uniform and well authenticated designation of stages, became apparent, and much thought was given this phase of embryologic investigation. The results of these reflections have appeared in a number of publications which have proven essential and helpful in the correlation of investigations on the human embryo. The ever-growing collection of human embryos contained many specimens of pathologic ova and yoimg embr^-os, which have formed the basis for a number of monographic contributions dealing with the pathology of early human embrj'os, the causes underlying the origin of human monsters, of cyclopia in the hiunan embrj-o, the frequency of localized anomalies in human embrj'os and infants at birth, the causes of tubal pregnane}' and the fate of the embrj'o in tubal pregnancy. INIuch of this later work was pioneer work and of the greatest value: of interest not only to the speciahst but of a wide general interest. The "^lanual of Human Embryology," edited bj^ Keibel and ^laU, and pubhshed simultaneouslj' in German and in English, marks a milestone in the progress of our knowledge of hiuiian development and embodies the crj^stallized thought of Doctor ]\Iall and his co-workers.

Doctor ^lall was for many j'ears vitally interested in the question of medical education. From the time of his early Leipzig days, influenced bj- the attitude existing between Ludwig and his pupils, influenced also by this able investigator's views on medical education and on university education in general, he agitated for more libert}- in medical education. "How different is the stud}^ of medicine in Em-ope than in .\nierica. There freedom reigns and students wander from place to place, being controlled only by a fairly rational system of examinations in case thej^ wish to graduate," we hear hun saj^ And again — "Liberty to the student should not mean Ucense to him, but rather liberty also to the instructor." He has argued for more liberal curricula, concentration of courses, opportunitj- for electives on the part of the student, but also for more freedom from routine and better faciUties for research on the part of the teacher. "A medical department of a University must consist of a Rroup of independent departments, each a complete organization in itself, existing primarily as a conservator of the branch it represents. Teaching beginners may become its chief work, but should never be its chief ideal." I am not prepared to say just how much of the improvement in medical education witnessed during the past decade is due to liis influence, direct or indirect, though I feel that he has been a potent factor; and may we come to a nearer realization of his ideals.

His chief concern was of necessity with departments of anatomy. On entering upon the real work of his life, at Johns Hopkins University, he was able to organize a department of anatomy unhampered by traditions, and in an environment of academic freedom, surrounded by departments devoted to scientific research, he was able, from the beginning, to realize certain of his ideals. The work of the department was placed on a broad basis. "To bring about desired reform it is necessary to have represented in an anatomical department, even in a medical school, all which naturally belongs to this science. The study of anatomy begins with the cell, ends with the entire individual, and includes man," we were informed in his remarks to this association as president. And again — "A subject like anatomy, taught for many centuries, has recently been made a new science tlirough the studies in embryology and histology." His was the first department of anatomy in America in which all divisions of anatomy were thus correlated, not alone in printed announcement but in daily practice. Other medical schools have followed, l)ut .some have been tardy followers. From the beginning much needed reform was instituted in the dissecting room; his was not a 'dissecting room' l)ut a laboratory. Consideration was given to adequate preservation of material. The aim from the beginning was to make the study of anatomy inductive, and a type of instruction in gross anatomy was inaugurated and carried on with eminent success, which if followed by man}' of us would inevitably have cost us our positions.

It is pecuharly fitting and appropriate that an appreciation of the life and influence of Doctor ^lall should be presented at a session of the American Association of Anatomists. Some time its President and for a large number of years member of its executive committee, ever interested in its wellfare and keenly appreciative of its growth in nvmibers and influence and ever appreciating character of papers and demonstrations presented at its yearly sessions; to him this expressed growth of anatomy in -America. Three years ago, this association ai5sembled in its thirty-first session recorded in resolution its profound sense of sorrow and deep feeling of the loss sustained by. the death of Charles Sedgwick ^klinot, he having died the 19th of November preceding. We recorded in appropriate words our appreciation of his labors in furthering the affairs of this association. I recall distinctly a session of this society, held in New Haven some twenty years ago, one of the first I attended. This session marked the turning point in the growth and development of our association. Plans for reorganization were then instituted. At a subsequent meeting, Professor Huntington was elected to the presidency, which office he held for a period of four years, important years in our evolution. I became j'our secretary during this period and was permitted to come in closer official connection, and to serve in this capacity, during the terms of presidency of three of our members who more than others were responsible for the reforming of the aims and ideals of our society: Huntington, ^linot, ^lall. I recall the many letters received from Doctor Mall during this period, full of discussion of plans for furthering our common interests and elevating our ideals, with e\'er-growing lists of names proposed for new members, with plans and suggestions for furthering the development .of our journals and their relation to our membership. In all ever striving with unselfish devotion and sacrifice of time, for the furthering of the affairs of this association, and thus developing scientific anatomy in America. *

Such has been his life; here briefly, all too briefly and I realize inadequately told. I cannot leave its appreciation without referring to the loving care and affectionate solicitude with which it has been watched over bj^ his trusted wife. Who, trained in anatomy, was fuily appreciative of his endeavors and ever interested in the development and realization of his ideals. We who have been permitted to partake of the kindly and sincere hospitality of their home, will cherish pleasant memories. To her and to the family, we as individuals and collectively as an association, extend our most sincere and heartfelt sympathy. May the knowledge that this profound sorrow is mutually borne, lighten their grief.

In closing I make use of the opening paragraph of his account of the life and influence of Wilhelm His, his teacher and his friend — The ancient science of anatomy has been perpetuated and extended during the many centuries of its existence bj^ great men who have dedicated their lives to it. The list is a long one for the development of the science has been slow and progressive from the earliest ages to the present time; we find in it on the one hand, some of the greatest who have ever lived — Aristotle, Vesalius — on the other, the names of those who rank as leaders of a generation, Bichat, His." To the names of Bichat and His, I would add, with your accord, the name of Mall.

G. Carl Huber.

## Proceedings Of The American Association Of Anatomists

Thirty-FOURTH SESSION

Institute of Anatomy, University of Minnesota, Minneapolis,

Minnesota

December 27, 28 and 29, 1917

Thuksday, December 27, 10.00 a.m.

The thirty-fourth session of the -\merican Association of Anatomists was called to order by President Henry H. Donaldson, who appointed the following committees:

Committee on Nominations for 1918: Professor Thomas G. Lee, Chairman; Professors A. G. Pohknan and W. H. F. Addison.

Auditing Committee: Professor H. ]\I. Evans, Chainiian; and Professor C. R. Bardeen.

The morning session was devoted to a symposium on "The Teaching of Anatomy and the Inculcation of Scientific ^Methods and Interest." Followmg this an address was delivered by Professor G. Carl Huber in memory of Professor Franklin P. Mall.

Thursday, 12.1.5 P.M. Association Business Meeting, President Henry H. Donaldson, Presiding.

The Secretar}^ reported that the minutes of the Thirty-third Session were printed in full in The Anatomical Record, volume 11, number (3, pages 311 to 315, and read the minutes as printed. On motion, seconded and carried, the minutes of the Thirtythird Session were approved by the Association as printed in The Anatomical Record.

Professor Evans reported for the Auditing Committee as follows: The undersigned Auditing Conrniittee has examined the accounts of Doctor Charles R. Stockard, Secretary-Treasurer

19

THE ANATOMICAL RECORD. VOL. 14, NO. 1

20 AMERICAN ASSOCIATION OF ANATOMISTS

of the American Association of Anatomists and finds the same to be correct with proper vouchers for expenditures and bank balance on December 19, 1917, of 8303.83.

[Signed] H. M. Ev.^ns,

C. R. B.VRDEEN.

The Treasurer made the following report for the year 1917:

Balance on hand December 23, 1916, when accounts were last

audited $264.34 Receipts from dues 1917 2400.75 Total deposits ".$2665.09

Expenditures for 1917:

Postage and telegrams S40 00

Printing and Stationery 22.70

Collection and exchange 1 .31

Stenography-typewriting 41 .75

Wistar Institute for subscriptions. Journal of Anatomy,

Anatomical Record, etc 2255 .50

Total expenditures 2361 .26

Balance on hand $303. &3 Balance on hand, deposited in the name of the American Association of Anatomists in the Corn Exchange Bank, New York City. On motion the reports of the Auditing Committee and the Treasurer were accepted and adopted. The Secretary announced that the Committee on Nominations, through its Chairman, Professor J. P. ^Ic^Murrich, places before the Association the following names : For President, Professor R. R. Bensley; for Vice-President, Professor C. R. Bardeen; for Secretarj'-Treasurer, Professor C. R. Stockard; for members of the Executive Conmiittee, term expiring 1921, Professors G. S. Huntington and H. E. Jordan. On motion the Secretarj' was instructed to cast a ballot for the election of the above named officers. Dr. G. L. Streeter was elected to serve the unexpired term on the executive committee made vacant by the death of Professor Mall. The Secretary presented the following names reconmaended PROCEEDINGS 21 by the Executive Cominittee for election to membership in the American Association of Anatomists. Appleby, J. I., A.B., Graduate Assistant in Anatomy, University of Missouri, Columbia, Mo. Batson, O. v., A.B., Medical student at Washington University, Washington University Medical School, St. Louis, Mo. Cameron, John, M.D., D.Sc, F.R.S.E., Professor of Anatomy, Dalhousie Medical College, Halifax, Xova Scotia. Cakdwell, John C, M.D., Professor of Physiology, Long Island College Hospital, Henry and Amity Sts., Brooklyn, A^ew York. Carter, James Thornton, D.D.S., Research Worker, Department of Zoology, University College, 1 Hanover Square, London, 11'., England. Cash, James Robert, A.B., A.M., Student of Medicine, Johns Hopkins Medical School, Baltimore, Maryland. Chapman, W. B., A.B., Medical Student, Washington University Medical School, St. Louis, Mo. CoNEL, Jesse LeRoy, Ph.D., Instructor in the Department of Anatomy, New York University, 338 East 26lh St., New York City. CooKMAN, Alfred, A.B., Instructor iu Agriculture and Biology, Long Beach, High School, Long Beach, Cal. Craigie, E. HoHNE, A.B., Instructor in the Department of Biology, University of Toronto, Toronto, Canada. Crosby, Elizabeth Caroline, Ph.D., Principal of High School, Petersburg, Michigan. Donaldson, John C, B.S., M.D., Instructor in Anatomy. University of Cincinnati Medical College, Cincinnati, Ohio. Elwtn, Adolph, A.M., Assistant Professor of Anatomy, Long Island College Hospital; Hoagland Laboratory, Henry and Pacific Sts., Brooklyn, New York. Evans, Thomas Hor.^ce, M.D., As.sociate Professor of Anatomy, Long Island College Hospital, Henry and Amity Sts., Brooklyn, New York. FoRMAN, Jonathan, A.B., M.D., Assistant Professor of Pathology, College of Medicine, Ohio State L^niversity, Naval Hospital, HamptonMoads, Virginia. GiLLASPiE, C, M.D., Professor of Anatomy, University of Colorado, School of Medicine, Boulder, Colorado. Outsell, Robert S., A.B., Teaching fellow in Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Hemleb, Wm. Francis, ^I.D., Assistant Professor of Anatomy, Georgetown Univer.sity, Washington, D. C. HiNES, Marion, A.B., Instructor in Anatomy, University of Chicago, Chicago, Illinois. Kittelson, John A., B.S., A.M., Instructor in Anatomj', University of Nebraska College of Medicine, Omaha, Neb. McJttnkin, F. a., M.A., M.D., Professor of Pathology, Marquette University School of Medicine, Milwaukee, Wisconsin. Magath, Thomas B^-rd, M.S., Ph.D., Instructor in Anatomy, University of Illinois, College of Medicitie, Chicago, III. 22 AMERICAN ASSOCIATION OF ANATOMISTS O'DoNAGHUE, Charles H., D.Sc, F.Z.S., Senior Assistant in Zoloogy and Comparative Anatomy, Unitfersily College, Gou-er St., London W. C, England. OsTERUD, Hjalmar L., A.B., A.M., Teaching Fellow in Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Ott, Martin D., A.B., Fellow in Anatomy, University of Minnesota, Institute of Anatomy, Minneaplois, Minn. Reinke, Edwin, Ph.D., Associate Professor of Zoology, Vanderbilt University, Nashinlle, Tenn. Robinson, Byron L., A.B., M.A., Teaching Fellow in Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Sanford, Eldon Williams, M.A., Ph.D., Assistant in Anatomy, Johns Hopkins Medical School, Baltimore, Maryland. Sullivan, Walter Edward, A.M.. Ph.D., Professor of Anatomy, Tufts College Medical School, 416 Huntington Avenue, Boston, Mass. Warren, James H., A.B., M.D., Assistant Professor of Anatomy, College of Medicine, Ohio State University, 469 Indianola Blvd., Columbus, Ohio. Watson, David Meredith Sears, M.Sc, F.Z.S., Lecturer in Vertebrate Paleontology, University College, Gouer St., London W. C, England. On motion, the Secretary was instructed to cast a ballot for all the candidates proposed by the Executive Committee. Carried. The Secretary announced the following names as having been dropped from the list of members on account of non-payment of the last two years' dues: Dr. J. H. Hathaway, Professor of Anatomy, Detroit Medical College; Dr E A. Spitzka, 63 East 91st St., New York; and Dr. P. A. West, Johns Hopkins :\Iedical School, Baltimore, Md. It was announced by the Secretary that the following committee had been appointed during the past year to represent the Science of Anatomy in the National Research Council: Chairman, H. H. Donaldson; members, F. L. Barker, R. R. Bensley, Irving Hardesty, Ales Hrdhcka, G. C. Huber, C. M. Jackson, F. P. ^lall (deceased) and C. R. Stockard. Announcement was also made of the action of the Executive Committee to set aside a sum up to the amount of S40 to be used by the Committee appointed at the last annual meeting to consider the nomenclature relating to the Sympathetic Nervous System. Professor Huber made a report of progress for the above conmiittee, and the committee consisting of Professors Huber, Hardesty and Ranson was continued. PROCEEDINGS 23 Professor Huber then mo\-ed that the association request The Wistar Institute to publish the abstracts of the papers presented at this meeting in the January number of The Anatomical Record as has been done in the past. The motion was seconded and carried. Dr. Greenman, the Director of The Wistar Institute, expressed his willingness to continue to publish the abstracts if the Association considered this a desirable thing to do. On motion the business session adjourned. Saturday, December 29. A Short Business Session followed THE morning Scientific Session. It was moved by Professor Huntington and voted that the Association express through the Secretary its thanks and sincere appreciation of the cordial hospitality and the unparalleled manner with which the Association had been accommodated and entertained by the University of Minnesota. In particular the thanks and appreciation of the Association are expressed to Professors Jackson and Lee and their associates in the Institute of Anatomy. The meeting was then adjourned. Charles R. Stockard, Secretary of the Thirty-Fuurth Session oj the American Association of Anatomists. ABSTRACTS OF PAPERS PRESENTED AT THE THIRTY-FOURTH SESSION OF THE AIM ERIC AN ASSOCIATION OF ANATOMISTS December 27, 28 and 29, 1917 AT MINNEAPOLIS 24 ABSTRACTS 1. The behavior of the phagocytic cells of the peritoneal fluid toward particulate matter. William H. F. Addisox and J. ]\Ioxroe Thor ixGTON, University of Pennsylvania. By comparing the behavior of peritoneal-fluid cells toward coarse suspensions with their reaction toward more finely divided matter, something is learned of the differences in range of activity of several phagocytic-cell types, and factors are suggested for consideration in the analysis of phagocytosis. The experimental animal was the albino rat and we have chiefly made use of carbon suspension, filtered carmine, and colloidal trypan blue. After injection, a visible phagocytic reaction to carbon suspension appears within the non-granular macrophages in about two hours, the reaction advancing markedly in from four to sLx hours. On the other hand, filtered carmine appears at from eight to twelve hours, while colloidal trypan blue is not usually visible before 24 to 36 hours. An important factor in phagocytosis is the state of irritabOity of the cell membrane. Our interpretation is that we are deaUng with relatively non-toxic systems, each producing visible phagocytosis with a rapidity dependent upon the degree of u'ritation which its particles exert upon the phagocytic cells. Thus, particles of large size produce phagoc}i:osis more rapidly than smaller particles. In colloids, if the size of the molecular aggregate be increased, as by electrolytic precipitation, the rapidity of phagocytosis is accelerated. In none of our experiments were the basopluhc or eosinopliilic cells phagocytic. Phagocj-tosis is shown principally by the non-granular macrophages, and, in the case of carbon and carmine, by the polymorphonuclearleucocytes which appear secondarily and which exhibit a more limited range of phagocytic activity. £. On the development of the eyelids in the albino rat. William H. F. Addisox and Harold W. How, University of Pennsylvania. Two noticeable features are the late period in gestation at which the eyehds develop and the rapidity of their formation. At the end of 17 days' gestation, the lids are merely shght ridges, but by the end of the eighteenth day the ej^elids have met and fused. Tliis is but 3 days before the normal time of birth. Comparing tliis stage of development of the eyehd in rat with several other species, we find that in rabbit (Lepus), with gestation period of from 28 to 30 days, the eyehds fuse at 20 days. In pig (Sus), with a gestation period of about 120 days, the lids fuse between the thirtj'-fifth and fortieth days. (Estimated from tables by O. Charnock Bradlej-, Jour. Anat. and Phj^s., 1906.) In man the lids fuse about the seventieth da.y. The opening of the lids in the rat usuallj^ takes place on the fourteenth day after bulh, and in man about the end of the sixth fetal month. A comparison of the histological structure of the retinae of rat and man at the stages 1) of fusion and 2) of opening of the ej^elids shows a marked similaritj-. In each, at the time of fusion of the lids, the cellular laj^er of the retina shows a subdivision into two zones. At time of opening of lids, all layers of the mature retina have been established. There is apparentlj- correlation between the development of the eyelids and of the retina. 3. The relation of normal thyroid-gland development to bodily growth and differentiation in Rana, Biifo, and Amblystoma. Bennet M. Allen, University of Kansas. In Amblj'stoma both fore and hind Umbs begin to grow before any colloid is formed in the thyroid gland. In Bufo it appears almost immediately after limbs have begun to grow, while in Rana pipiens it appears practically simultaneously with anlage of the hind limbs. In aU three forms there is a rapid growth of the gland, and this corresponds closelj" with limb development. In all three forms the thj-roid gland is well developed and contains a large amount of colloid long before metamorphosis is completed. In axolotls of 140-160 mm. length from Colorado the thyroid gland was found to be approximately of equal size and structurally similar to that of adult Amblystoma tigrinimi. Colloid was present in large amount in both, but the axolotls were not well enough preserved to enable one to judge of its density. Although the thyroid gland of Bufo is actually smaller at metamorphosLS than that of Rana or Ambh^stoma, its proportion to body size is greater than in either Amblj'stoma or Rana. Tliis is probably correlated with the shortness of its lai-val life and the greater rapidity of its metamorphosis. There is a clear correspondence l^etween the normal development of the thyroid gland and normal progress toward metamorphosis, although limb development may be partly independent of it. 4. Further .itudies upon amphibian larvae from which the anterior lobe of the hypophysis had been removed. Bennet M. Allen, University of Kansas. The anterior lobe of the hypophysis was removed from larvae of Rana pipiens and Bufo lentiginosus as described in an earlier paper. The observations previouslj^ published were verified and much extended because of greater success in rearing the operated tadpoles. Several arc still alive. Limb development in Ijoth species is greatly retarded, running parallel with the condition in tadpoles from which the thyroid gland has been extirpated. In Bufo there is a color change to a light yellow-brown, and contrary to the case in Rana there is little retardation of bodily growth. The pars nervosa of the hypophysis forms normalh' in tadpoles, both Rana and Bufo, from wliich the anlage of the anterior lobe has been removed. There is of course no pars intermedia formed. Gonads of operated Rana tadpoles were compared with normal con PROCEEDINGS 27 trols of the same size killed several months before. They showed the same features as to size, structure, and gerni-cell development as seen in the controls. The same correspondence in the gonads was noted when comparison was made with some small thj-roidless tadpoles of the same size killed at the same time. The retardation of bochly growth in Rana prevented the gonads from reaching the size attained in the controls at metamorphosis three months before. In Bufo, however, the operated tadpoles reached a bulk double that at metamorphosis. Corresponding^, the gonads and germ cells developed far beyond the condition attained at the time of metamoi'phosis in the controls. 5. A method of fixing rat testis by which both cijtological details and the normal relationship between interstitial tissue and the tubules are obtained. EzR.4. Allen, Philadelphia School of PedagogJ^ The unfortunate separation of the interstitial tissue from the tubules in the rat testis as usuall.v obtained may be obviated by injecting the blood-vessels with picro-formol-acetic-chromic acid-urea fixative ('B-lo'), after washing out the blood by normal salt or Locke's solution. Fluids and animal are kept at about 38°C. When the organs are seen to be quite hard ihey are removed, cut into plates from 2 to 4 mm. thick with a safety-razor blade, and placed in fresh warm fixing fluid for about an hour. Further treatment is as described by the author in his article on technique in The Anatomical Record, vol. 10, July, 1916. The slight pressure needed can be obtained from the laboratory air supply or by means of an atomizer bulb. In either case, the source of pressure should act upon the air in an air flask, which in turn is connected with the bottle containing the injecting fluid. A mercury manometer attached to the air flask shows the amount of pressure used. The method fixes all organs equally well. It preserves intact the delicate vessels in the central portion of the villi. In the testis I have obtained the chromosomes well separated and thoroughy workable in those stages in which sad clumping is the rule. The histological picture is perfect. Since the interstitial tissue is not torn loose from the tubules, its relative volume is easily measurable. 6. Movements in the visual cells and retinal pigment to light of graded intensities. Leslie B. Arey, Northwestern University Medical School. The visual cells and retinal pigment of many of the lower vertebrates exhibit striking movements in light and in darkness. Previously reported experimentation having established that the rapidity of these changes had been greatly overestimated, the validity of a similar widespread impression regarding their extremely low thi-eshold of sensitivity was next investigated. Such a determination is important in view of a further (but discord 28 .^-MERICAX ASSOCIATION" OF AXATOMISTS ant) assumption that the positional changes of the visual cells in bright light and dim light favor cone-vision and rod-vision respectively, while the corresponding movements in the retinal ])igment also meehanicall.y increase visual efficiency. In other words, to derive the reputed adaptive benefits from such jDhotomechanical changes, the responses in dim light must be essentially identical with those known to occur in total darkness; this assumption, however, is wholly gratuitous. The responses of these elements to light of graded intensities prove that the threshold of stimulation is surprisingly high. In general, the maximum light-response is first elicited at an intensity which just permits the reading of ordinary print. Hence the assumed high photic sensitivity of the visual cells and retinal pigment is disproved, while the mechanical conditions for a theoretically moi'e efficient twihght-vision and bright light-vision are established on an experimental basis. 7. The development of the pars tuberalis of the rabbit's hypophi/sis. Wayxe J. Atwell,' Department of Anatomy, Medical School. University of Michigan. For the rabbit it has been possible to trace the development of the paired anlagen of the pars tuberalis of the hypophysis from an earlier stage than that given by Tilnej' ('13) for the chick and the cat, or by Miller ('16) for the pig. From the thickened epithelium which early lies in front of Eathke's pocket two thickened ridges are developed. . These ridge-like eminences may be called the lateral lobes, and are evident in embryos of 10 days. At 14 days these lobes have begun to grow out laterally and are more sharply constricted from the body of the hyjjophysis. The lateral lobes are the anlagen of the pars tuberahs of the adult hypophysis. They begin to be in relation with the brain wall at 16 da3's of development, and by 19 days a considerable portion lies spread out under the diencephalic floor. There are present at this stage two blunt nasal horns extending toward the optic chiasm and two sharper caudal horns extending backward to surround the neck of the neural lobe. The caudal horns have completeh^ surrounded the infundibulum and ha^'e met in the mid-line by the end of the twenty-eighth day. The nasal horns fuse with each other a day or so later. Since the lateral lobes of the mammalian hypophysis may be seen early in development, it is now easier to consider them homologous with the lateral lobes of the reptihan hypophysis. Because of its paked origin, theanterior part of the pars tuberaes cannot be homologized with the 'Vorraum' of the reptiles, as is donil by Woerdeman ('14). PROCEEDIXGS 29 8. Observations on the mcnements of chick etrjbryos. 0. V. Batsox. Anatomical Department. Universitv of ^lissouri. (Introduced bv E. R. Clark.) The spontaneous rhj-thmic movements of chick embrvos. which occur periodically throughout the greater part of the incubation period, were foimd to begin at 84-96 hours in chicks incubated at SS^-SO"". Contrary to pre^-ious findings, movements in chicks around 96 hours occurred as a response to stimulation with a needle, especially when apphed over the myotomes in the wing-bud region. Later stages have not yet been tested. Complete section of the cord in three-day chicks does not modify the movements, and chicks so operated upon show no physiological or gross anatomical differences from unoperated chicks after hatching. .\fter removal of a section of the cord in the lower cer^iciil region for a distance of thiee body segments, at 96 hours, the usual rh>Thmic movements, invohing the entire body, were stiU present at six days. After incomplete removal of the cord posterior to the wing-bud, at three days, rh>-thmic movements were stiU observed at seven da>"s. It is clear, therefore, that the periodic rhj-thmic movement of chicks is probably not a neuro-muscular phenomenon. Rh>-thmic periodic movements persist if the egg is incubated at reduced temperatures after movement has begun. Periodic motility is not lost until 20"C. is reached. Raising the temperatine to 20.o°C. induces motility. Rhj-thm begins at 21"C. At no temperature is there a quiescence indicating a latent period of adaptabihtj\ 9. Histological changes in the placenta in the Toxaemias of pregnancy. J. L. Bremer. Harvard Medical School. In 191.5 I called attention to certain thin epithelial plates to be found in the surface layer of the placental villi, in intimate connection with the underh-ing fetal capillaries, similar in appearance and relations to the epithelial plates of the \-isceral layer of the capsule of the renal or mesonephric glomerulus, and showed that such plates were present in the placenta only dm-ing the degeneration or absence of the mesonephi-os in any particular type of embrj-o. It was suggested that the presence of these plates showed the ability of the placenta to remove from the fetal blood certain excretory substanqes and to a-ssume for the fetus the function of the glomeruh. The function of the rensl or mesonephric tubules may be assumed by portions of the s\"ncj"tial surface layer of the villi. Normally the plates are widely scattered and only found after careful search. In certain toxaemic or eclamptic placentae, on the other hand, they are very numerous in eveiy microscopic field, so that the fetal blood in the greater part of its course through the placental capillaries is separated from the maternal blood only by a thin osmotic membrane, composed of fetal endotheUum and epitheUal plate. The fetal capillaries are often dilated, but this does not seem to be 30 AMERICAN ASSOCIATION OF ANATOMISTS the cause of the increased extent of plates, by simple stretcliing, since the thicker syncj-tial layer is at the same time reduced in extent. 10. Early stages in the development of the femur of the pig with reference to the influence of muscular activity upon its ossification. Eben Carey, Department of Anatorav, Creighton University, Omaha, Nebr. The earliest bone formed about the middle of the cartilaginous femur has been shown previously (Anat. Rec, vol. 11, no. 6) to develop more rapidly on the aspect directed towards the quadriceps extensor muscle than on that which is du-ected toward the hamstring muscles. The present paper attempts to correlate tliis unequal growth with the combined muscle forces manifested in the rotation of the limb. The preaxial border of the limb begins to turn mesiad in embryos of 19 to 22 mm., and rotation is completed in embrj'os of 40 to 50 mm. With the inception of rotation the femur begins to acquire a curvature, the convexity of which is directed towards the quadriceps extensor muscle. That the thigh musculature is capable of contracting at this period is shown by its response to Faradism in the living embryo. In the development of mj^ofibrils the quadriceps extensor muscle is appreciably in advance of the hamstrings. The curvature of the femur, therefore, coincides with the rotation of the limb and the manifestations of contractility on the part of the thigh musculature. A fibroblastic perichondrium appears first on the weakest aspect of the curved cartilage, viz., the convex surface at its region of maximum bending. The greater density of this tissue seems indirectly to favor senescent changes in the cartilage by preventing the access of blood-vessels. At all events, the use of injections reveals the presence of continuous vessels outside of the fibroblastic tissue only, while on the concavity-, in the less modified mesenchjane, thej' approach nearer the cartilage. Bone appears first upon the convexitj-, and in subsequent stages develops there more rapidlj' than on the concavity. This early bone formation coincides in time with the manifestation of contractilitj' of the thigh musculature and in site, like the antecedent fibrogenesis, with the region of greatest mechanical tensile stress incidental to the rotation of the limb and bending of the femur. 11. The development of the lymphatics in the stomach of the embryo pig. James R. Cash, Anatomical Laboratory, Johns Hopkins University. (Introduced by R. S. C 'unningham.) By injecting the retroperitoneal Sac in embryo pigs, it appears that, at about 30 mm., numerous lymphatic sprouts pass from its anterior part onto the stomach at the esophageal opening, around which they develop annularly. From this ring lymphatics grow in all directions, but especially along three paths, i.e., the lesser curvature, toward both cardia and jjylorus, while from the caudal side of the ring two principal lymphatic vessels sweep ventralward, under the spleen, to the greater PROCEEDINGS 31 curvature, along which thej- run toward both cardia and pj-lorus, anastomosing with the branches running to these points from the esophageal ring. The entire stomach is well covered with IjTnphatics at 60-70 mm., growth taking place in all directions from the ring and its principal branches. The retroperitoneal sac also sends several vessels directly to the pylorus through the duodenal mesentery. In the pyloric region, especially in the older specimens, 70-150 mm., the IjTnpha-tic plexus is seen to be much more dense and its vessels of smaller caliber than elsewhere in the stomach. Such facts may be of significance in relation to metastatic growths in this region. Microscopically, two principal gastric, hniiphatic plexuses are seen: one in the loose subserous tissue, the other in the submucosa. Both plexuses are verj' dense and their vessels relatively large. They are connected bj- a much less dense plexus traversing the muscularis. From the submucosal plexus numerous branches to the mucosa are seen which run in close relation to the blood-vessels. 12. The effect of the heart-beat upon the development of the vascular system in the chick. W. B. Chapm.\n, Anatomical Laboratory, University' of Missouri. (Introduced bj^ E. R. Clark.) In order to test the question as to how much the development of the main vessels of chick embrj'os, particularh' those of the yolk sac, is dependent upon mechanical factors concerned vrith the circulation, the heart was removed before circulation had been established, with the following results: The embryo and area vasculosa remain alive for eight days after the operation, and considerable growth takes place, particularly in the area vasculosa. The development of blood-vessels proceeds in a normal manner a short time beyond that at which the circulation usually commences. During this time there are formed in the extra-embryonic region vessels identical with the normal anterior vitelline veins, which fuse anterior to the embryo as in normal chicks, while the sinus terminahs passes through a cj'cle of development which markedly imitates the normal. On the other hand, certain vessles which normally chfferentiate early, the omphalo-mesenteric arteries and veins and the posterior vitelline veins, are not formed. With the expansion of the vascular area, there is a continued formation of new capillaries; the property of sprout formation being apparently retained until death. After the third daj% however, this is confined to the marginal portions of the area. Near the embryo, in the area pellucida, new formation has ceased at three days, and regressive changes commence; connecting capillaries are retracted, leaving isolated or nearlj- isolated endothelial blisters distended with fluid or cells. This regressive process advances gradually into the vessels of the area opaca. 32 AMERICAN ASSOCIATIOX OF AXATOMISTS 13. Phagocytosis of carbon and carmine granules in the transparent tails of tadpoles. Eliot R. Clark and Eleaxor Lixtox Clark, Anatomical Laboratory, University of ^lissouri. Small amounts of india ink and of suspensions of carmine granules were injected into the transparent taUs of tadpoles and the region observed, on successive days, under the compound microscope, with the tadpoles anaesthetized with chloretone. Leucocj'tes were the first cells to react to the presence of these foreign particles, migrating toward them and actively engulfing them. Some of these leucoej-tes, containing foreign granules, were observed to enter near-by blood-vessels. Others wandered off through the tissue spaces of the tail. A daj- after injection, the stellate connective tissue cells began to ingest the foreign particles. Carbon and carmine granules thus phago-: cytized were located on the branched processes and in the cell bodies at the base of these processes. In such a transparent region, where individual living cells maj' be observed and followed for days and different cell t}-pes identified with ease, it is clear that mesenchyme cells are active phagoc}i;es of foreign particles. Lj-mphatic capillaries were not observed to grow toward the injected carbon or carmine; but when the granules were injected into the lumen of a lymphatic, the endothelial cells took up these foreign particles and stored them in the perinuclear areas. 14- On the reaction of certain cells in the tadpole's tail toward vital dyes. Eleaxor Lixtox Clark and Eliot R. Clark, Anatomical Lab oratoiy. University of Missouri. In the course of observations on the growth ajid reactive powei-s of the cells and tissues in the transparent tails of tadpoles, it seemed advisable to studj'^ the effect of vital staining on these cells. Tadpoles were placed in solutions of various dyes and, aft-er staining, were observed in a micro-aquarium, under chloretone anaesthesia. The three dyes, neutral red, bismark brown, and tiypan blue, were used aJmost exclusiveh-, because of the similarity of their action and because they all stained the lymphatic endothelium with especial distinctness. The more high!}- diffusible of these dyes — neutral red and bismark brown — stain the cells more rapidly than the colloidal dye, ti-\-pan blue. Neutral red and liismark brown stain small, regular and apparently preformed grapules in the epidermal cells. In addition, the contents of a richly branching subepidermal sj'stem are brilliantly stained with neutral red. Trypan blue does not stain the epidermis. All three d\'es stain an occasional, probably preformed granule in the walls of blood-vessels. Neutral red, bismark brown, and trypan blue are all deposited as accumulations of dye granules in the perinuclear areas of the hnnphatics. in certain wandering cells and leucocj'tes, and on theproces.sesof the mesenchyme cells. The physiological relationship shown by this reaction toward these vital dyes on the part PROCEEDINGS 33 of these different tj-pes of cells is probably due to theii- common property of phagocytosis. 15. On the origin of the corpus luteum of the sow from both granulosa and theca interna. George W. Corxer. .\natomical Laboratory, University of California. The ovary of the sow possesses certain advantages for the solution of this problem. The paper is based upon a large series in which the stage of the reproductive cycle was determined by observation of the li'ving animals and of their ova. The results may be smumarized as follows : In swine the membrana granulosa is retained intact after the rupture of the Graafian folhcle. Its cells increase in size without division, their cjiioplasm becomes laden with lipoid substances, and they become the larger elements commonly called 'lutein cells' in the fully formed corpus luteum. The membrana granulosa is invaded by blood capillaries from the theca interna, which ramify to form an extensive vascular plexus throughout the new structure. The large lipoid-laden cells .of the theca interna are increased in number by mitotic di\'ision, lose many or all of their fattj' inclusions, and pass into the corpus luteiun to become lodged between the granulosa cells throughout the whole structure. There is no evidence that cells of the theca interna are ever converted into fibroblasts of the usual spindle-cell type or that they lay down the fibrils of the close-meshed reticulum which is present in the corpus lutemn. There appears to be good evidence that some of the theca interna cells persist throughout pregnancy as distinct elements of the corpus luteum, but the exact fate of all of them cannot be learned by present methods because of a confusing resemblance between some of the theca and some of the granulosa derivatives. 16. Observations on brachydactylism in the fowl. C. H. Daxforth, Department of Anatomy, Washington University of IMedical School. A form of brachA'dactylism affecting particularly the fourth digit is of common occiu-rence in the fowl. It is usually associated with booting (feathered tarsi). The extent to which the fourth toe is shortened ranges from a condition in which all five phalanges are present, but with a total length slightly less than normal, to a condition in which the toe is greatly shortened and the number of phalanges reduced to two. The fourth phalanx is the fir.st to be affected, followed by the third, and then by the fifth. The skeletal elements seem to disappear through a process of coalescence rather than one of suppres.sion. Examination of developmental stages show that the brachydact^'l digits are already noticeably shortened at a time when the cartilaginous anlagen of the phalanges are still in a rudimentarj" condition, which suggest that the brachydactylism is due not to a defect inherent in the skeletal system, but more probablj' to an inf^ience that acts on the toe as a whole. The possibility of booting as a causative 34 AMERICAN ASSOCIATION OF ANATOMISTS factor seems to be definitely eliminated by the fact that brachj'dactjdism may be clearly apparent before the first feather germs appear on the tarsi. It seems probable that both conditions are induced bj^ some common cause, which is effective from the eighth to the tenth day of incubation. Breeding records indicate that brachydactylism is transmitted in about the same proportions as polydactylism and booting. With the latter it shows a close correlation, with the former none. 17. Further experiments with colloidal dyes. Hal Downey, University of Minnesota. Sections of vena cava or portal vein tied off from J to 2^ hours after intravenous injection (the animal being kept alive in the mean time) of trj-pan blue or pyrrhol blue frequentlj' contain numerous polymorphonuclears with dye gi-anules. Similar cells maj' also be foimd in the spleen pulp, liver, and limg. The}' are more numerous if the vessels and organs are removed some time after the death of the animal. Subcutaneous injections of these dyes result ii^ the migration of numeroiis polymorphonuclears into the tissue in from 5 to 24 hours. They will rapidly gather up any free dye available and store it in the form of granules. If, however, all the dye is bound to cells and fibers of the connective tissue, when the polymorphonuclears reach the scene they will get none of it. The granules of eosinophil leucocytes of rat stain brillianth' in trypan blue and the cells degenerate rapidly. In the early stages endothelial cells, fibroblasts, and Ijanphocj'tes also show the toxic effects of the dj^es, but most of these cells are able to recover. Their nuclei enlarge and absorb much of the dye, and frequently some of the cj'toplasm also. The latter may show diffuse staining. Later the dye is liberated from these cells and stored in the form of granules in l3nnphocj'1es, fibroblasts, and clasmatoc>'tes. Much of the dj'e is absorbed from the subcutaneous tissue by blood capillaries and larger vessels, and the polymorphonuclears witliin these vessels frequently contain dye granules. 18. Studies on the ovary of the spermophile with special reference to the corpus luteum. Della Gay Drips, Institute of Anatomy, University of [Minnesota. (Introduced bj' Thomas G. Lee.) The cycle of changes occurring annually in the ovaries of Citellus is presented with detailed histologic descriptions of the corpus luteum at each stage of its development. Specific stains are used to bring out the nuclear and protoplasmic characteristics of the luteal cells. Thi-ee phases are thus noted in the life cycle of the corpus luteum. First, is a phase characterized bj' the presence of great numbers of red granules, undoubtedly secretion granules in the protoplasm of the luteal cells. This phase embraces practically all of the period of pregnancy. Second, is the Lipoid phase, so-called because PROCEEDINGS 35 of the abundance of lipoid droplets in the protoplasm of the cells. This phase begins some time before parturition and lasts for about six weeks afterwards, which is also about the time that the normal involution of the uterus becomes complete. And, tliird, is the phase of regression. Certain experimental studies are reported, such as the effects of single and double ovariectomy on pregnant and nonpregnant animals. Single ovariectom.y is negative in results. Double ovariectomj' in non-pregnant animals causes a vcrj- gradual functional atrophy of the uterus. In pregnant animals, this procedure causes abortion, except when it is performed very late in pregnancy. From the results of the histologic and experimental studies it is concluded that the corpora lutea produce two internal secretions which preside over changes occurring in the uterus incident to pregnancJ^ The early secretion effects the normal implantation and development of the embryo and the late lipoid secretion helps to bring about the normal involution of the uterus. 19. The localization of hematogenic activity in the embryonic liver. V. E. Emmel, University of Illinois, ^ledical School. The present paper is a presentation of the results of a study of phagocj-tic activity, giant cells and the differentiation of mesamoeboids and erj-throblasts in the liver of pig embryos at different stages of development. The data is analyzed with reference to the growth of the liver and the correlated changes in hepatic structure. 20. Feeding rats on glands of internal secretion. J. F. Gn)ERXATSCH, Cornell University Medical College, New York Citj-. Seven sets of albino rats are being reared on a mixed diet. Six sets receive in addition desiccated thjToid, thj-mus, hypophysis, testicle, ovary, mammary gland, respectively. The following data can be given so far; they are not final, since the growth curves are changing constantly, due probably to an apparent increase in vitality of the entire stock. The thyroid-treated animals form a group by themselves and cannot be discussed here. The remaining rats may be put in three groups: 1) hypophysis, thymus; 2) normal; 3) testicle, ovarj-. The animals in (1) grow faster, especially hj-poplwsis, than the normal; those in (3) slower. Testicleand ovary-treated animals do not live as long as the others, decline in weight often begins under seven months. Males treated with ovary grow slightly better than those treated with testicle, while females treated with testicle grow somewhat faster than those fed on ovary. Rats fed on hj'pophysis or thymus are fine breeders; the females build good nests and usualh- take good care of their young. Few young die earlj^ and seldom are entire litters lost during the nursing period. Rats fed on hypophysis seem to be somewhat precocious in their adolescence, and then sometimes the first litter is poor. Females treated with testicle or ovary are rather poor mothers often THE ANATOMICAL RECORD, VOL. 14, XO. 1 36 AMERICAN ASSOCIATIOK OF ANATOMISTS some 3'ouug die early or entire litters may be lost. Yet the average sizes of the litters are not very different. Indicating b.y ten the size of a normal litter, the other litters would range as follows: Ovary, 10.41; mammary, 10.33; thymus, 9.81; testicle, 9.75; hypophysis, 9.18. In the thyroid-treated rats, if pregnancy sets in at all, there are many abortions or the young die earl.y. 21. Tests upon devices for the -prevention of war deafness. Stacy R. Guild, Anatomical Laboratory, University of Michigan. Apparatus made to adapt devices to guinea-pigs. Injurious detonations produced by 0.45 Colt automatic, fired once at 15 cm. along 'protected' side. Killed after two days; injection fixation for cochleae; middle-ear parts observed during cochlear removal. Cochleae are still in process of preparation for sectioning; this report covers middle-ear observations only. In numerous controls tympanic membranes ruptured regularly; and coagulate, usuall.y associated with edema, was present. Of four animals with a "Scientific Ear Drum Protector 'Tommy,' " one had a single area of coagulate. Three animals with " Mallock-Armstrong Ear Defender," one had two areas of coagulate. Three animals with wax cone of Italian navy type; two had small amounts of coagulate. Four animals with vaseline-soaked cotton, one had radial streak of coagulate on the tympanic membrane and some along the tympanic ring and sUght edema. Three animals with glycerin-soaked cotton, two had small amounts of coagulate with edema. Three animals with drj' cotton, one had radial slit of tympanic membrane, all had coagulate, two with edema. Three aninials with "Elliott Perfect Ear Protector," one had membrane off along j circumference and was edematovis, the other two had coagulate, one with slight edema. Three animals with a device invented by Dr. J. G. Wilson and Prof. A. Michelson, one had a 3-mm. hole in the membrane and all had coagulate. Tests are being made by tambours as a check and will be reported at Minneapolis. The cochlea - will give a further check on the relative efficiency. 22. The development of the opossum during the first four days. Carl Hartman, The Wistar Institute, Philadelphia, and the University of Texas. (Introduced by M. J. Greenman.) Parturition occurs thirteen days after copulation and approximatelj- ten days after ovulation. The first naturation takes place in the ovary; semination in the oviduct, where the albumen and the shell are added. Pronuclei were seen in uterine eggs. A variable amount of yolk is extruded at first cleavage. The process by which the first two pairs of blastomeros come to have the crossed arrangement will be discussed. The blastocyst is completed at about the 40-cell stage. Polar differentiation begins by attenuation of the non-formative cells, which are lineal descendants of one of the first two blastomeres. Cells in ttu thick formative area soon ]>rohferate entoderm, which PROCEEDINGS 37 process is completed about the end of the third day (egg, 0.8 mm.; vesicle, one-half that size). The albumen is gradually absorbed, and at about the end of the fourth daj^ the mesoderm formation begins (vesicle, 1.6 mm. in diameter). For the study of these stages preceding that of the primitive streak 84 uteri of 53 diflferent females j'ielded 1055 eggs, of which about two-thirds were fertiUzed and normal. Photographs of the living eggs fresh from the animals (taken at Austin, Texas, by Dr. C. H. Heuser, of The Wistar Institute) as well as of fixed eggs and of preparations will be shown. S3. The embryonic 'fissura hippocampi' in man. Marion Hixes, Department of Anatomy, University of Cliicago and the Carnegie Institution of Washington, Laboratory of Embryology. (By invitation.) Although the deep furrows, known as the transitory fissures of the medial wall of the cerebral hemisphere of fetal brains between the third and the fifth rnontlis are artefacts, the wall is not 'perfectly smooth' in embrvos of seven to fourteen weeks. A shallow, but complete infolding of the wall extends from the rostral to the caudal pole. The nervous tissue, which hes at the bottom of this groove, consists of an inner, narrow, nucleated zone and a wide, ceU-free area Indeed, in the earlier stages, this is the onty part of the cerebral hemisphere in which the matrix and the marginal velum of His are distinct. In a 11.6-nmi. embrj'o, this area occupies the mediodorsal sector of the cerebral evagination. In one, 14 nun., it lies more medial, while in a 20-nam. it is almost centromedial. This sulcus, deepened by maceration, is doubtless the fissura liippocampi of amphibians and reptiles. In the rostral part of the medial sector, ventral to the primordium hippocampi Ls an area, wliich resembles, in arrangement and position, the septal nucleus of lower vertebrates. The most dorsal part of tliis nucleus is continuous with the fascia dentata. A ventricular sulcus separates its ventral part from the prunordium hippocampi and the definitive fascia dentata. The anterior commissure appears in the 39-nim. stage, the dorsal (pallia!) commissm-e, in the 60-mm. Therefore, in the com-se of its development, the medial olfactory cortex of man is as extensive as that of any other vertebrate. 24- The reaction of .ielachii to vital stains. E. R. and ]\I. ^I. Hoskixs, New York University and Belle\Tie Hospital INIechcal College. Intravenous injections into ]\Iustelus, of the following substances, were made: 1. a) Tr\-pan blue. Autopsy ater five days. Phagoc3i:osed freely bj-^ endothehum of larger blood-vessels withui gills, hepatic sinusoids, and spleen, by parenchj-ma of liver, and hy splenic cells. JNIany cu-culating phagocj-tes (probably endothehal cells and splenic cells) contained the stain. It was found also in the bile. The hver and spleen were dark blue in color. The stomach, spiial valve, kidney, digiti 3S AMERICAN ASSOCIATION OF ANATOiAIISTS form gland, and skin were light liluc in color from circulating stain. A very few particles of stain were found in the renal and digitiformgland endothelium, and epithelium of the latter, b) Trypan blue, 36 hours. All organs light blue, but very little phagocytosis had occurred. 2. a) Carmine (coarse granules). Autopsies at various periods to four days. Results: Same as (1. a) in general, but cells are not able to ingest large granules easily, b) Filtered carmine. Not recovered. 3. Congo-red. Gross specimens, same results as above. Recovered in bile. 4. Neutral-red 1916. Results same as Congo-red. 1917, slight amount passed through the renal epitheUum. 25. On the anlage and morphogenesh of the chorda dorsalis in mammalia, in particular the guinea-pig (Cavia cobaya). G. Carl Huber, Department of Anatomy, University of Michigan. In mammalia, the head process is a derivative of the ectoderm of the primitive node region ill the axial portion of the embryonic area, and grows cephalad between ectoderm and entoderm to the region interpreted as the future pharyngeal membrane. The caudal end of the head process, through jjseudo-growth and through rearrangement of cells, develops into the chordal canal, separated from both ectoderm and entoderm, with lumen which in the guinea-pig at no time reaches the dorsal surface of the ectoderm. AAith further development the chordal canal grows further and further cephalad, but at no time reaches the anterior limits of the head process. The chordal canal at all stages of development is in close relation w-ith the underlying entoderm, which extends as an uninteriupted laj-er of plate-like cells central to the chordal canal. The chordal canal in further differentiation develops a cleft on its ventral surface, thus assuming the form of an inverted trough; the entoderm likewise develops a cleft, ventral to the open choreal canal, the entoderm extending, however, beneath the borders of the chordal plate, the latter at no time becoming definitely incorporated into the entoderm. Caudal to the primitive node, the entoderm is at no time interrupted ventral to the chordal anlage, and later, chorda dorsahs. It is the contention that the head process, and through tliis the chordal canal and plate and chorda dorsahs are to be interpreted as ectodermal derivatives. 26. The innervation of the lateral-line organs in Squalu^ acanthias. Sally P. Hughes, Grinnell College. (Introduced by H. W. Norris.l The lateral-line nerve fibers in- Squalus acanthias are distributed through: 1) ramus ophthalmicus superficialis MI to the supraorbital canal and the suprarostral groups of ampullae of Lorenzini; 2) r. buccahs VH to the infraorlntal canal and the ventral ampullae; 3) r. oticus VII to the lateral division of the infraorbital canal as far posteriorly as the supratemporal commissure, 4) r. mandibularis externus ^TI to the jugular ampullae and the mandibular and hyo PROCEEDIXGS 39 mandibular canals; 5) r. supratemporalis IX supplying the first three ramuU to the main trunk canal; 6) r. supratemporalis X innervating the supratemporal commissure and se'nding six ramuli to the main canal; 7) r. dorsalis X with the next four ramuh to the main canal, and 8) truncus lateralis X to the main lateral canal of the trunk. The innervation of the 'pit-organs', recently discovered bj^ Johnston ('17), is through: 1) ramus supratemporalis X, to those anterior to the external opening of the endolymphatic duct; 2) r. dorsalis X, to the dorsal series; 3) r. mandibularis externus VII, to the mandibular series. The innervation of the group of pit-organs at the base of the yolk-stalk was not determined. There occur on each side two rudimentary lateral Une organs: one on the anterior border of the spiracle, with innervation from the ramus oticus VII, strictly comparable in structure, position and innervation to the 'rudimentary canal-organ' found by AUis in Amia; and a second of sinulivr .structure, found near the n- id -ventral line of the hyoid region, with innervation from the r. mandibularis externus VII. This account agrees with Strong's abstract (1895), with ]\Ietcalf (1915), and with Landacre (1916). Johnston (1917) ignores the lateral line component in the IXth nerve and the branches of the r. supratemporalis X and r. dorsahs X to the main canal. 27. Mutation in mammalian evolution. Geo. S. Huntington', Columbia University. In the phylogeny of the vertebrate lung the mammahan groups of the rodent Hj-stricomorphs and carnivore ^lustehds show the derivation of the dominant asjanmetrical type from an archeal plan in the following evolutionary series: 1. Prmiitive bilateral hyparterial symmetry with tracheal bulla, without carchac bronchus: Htjstrix cristata. 2. Bilateral hj^parterial t^-pe with tracheal bulla and cardiac bronchus: Taxidea americana. 3. Bilateral hj^jarterial tj-pe with resolution of bulla into bifurcation of stem-bronchi: Hystrix afroe-australis, Hystrix longicauda. 4. Estabhshment of prevalent asymmetrical mammahan tj-pe of right eparterial and left hj'parterial bronchial tree as the normal condition: Erethizon dorsatus. 5. Within this genus the phylogenetic shift from the earlier to the subsequent conchtion is of relatively recent accomphslunent, as evidenced by the occurrence of individual variants showing transitional stages. 6. In the Hystricomorph Sphingurus one of the earty transitional stages, variant in Erethizon, appears as the fixed normal tj^pe. 7. "The later transitional phase leading up to the final estabhshment of the prevalent mammalian tree appears as the normal type in the mustelid Galictis. 8. The evolutionarj^ differentiation exhibited in this series is accomphshed not by continuous variation or bj- migration of bronchial components, but by well-defined mutations. 40 AMERICAN ASSOCIATION OF ANATOMISTS It thus becomes possible to follow the relation of mutant variation to mammahan evolution in an organ, removed from direct environmental influences, within two closely limited mammaUan groups. 28. Additmial notes concerning the development of the lobule of tlie pig's liver. Franklin P. Johnson, University of JMissouri. When the hepatic lobule reaches a certain maxinimn size, its central vein bifurcates; with its further increase in size, which usually takes place by a lengthening of the lobule at right angles to its central vein, the branches of the central vein grow toward the poles of the lobule. A sphtting of the lobule follows shortly afterward, usually in the plane of original central vein and at right angles to its new branches. The sphtting is accompanied in the later stages by an ingro\\i:h of a new connective-tissue septimi, which is later invaded by branches of the portal vein; hi the younger stages by the branches of the portal veins alone. In this way, two lobules are formed from one, the old central vein later becoming a sublobular vein. The branches of the portal vein likewise bifiu-cate spreading themselves between the lobules. By repeated divisions whole groups of lobules arise from single ones, the genealogy of which may be roughly determined by a study of the brandling of the hepatic vein. Occasionally new central veins arise from the hepatic and variations in the sphtting process occur. The increase in the size of the liver takes place by both peripheral and central growth, probably to a somewhat greater extent by the former. The latter process unplios a rearrangement of the internal structures, but tliis takes place by a gradual chsplacement of large masses of liver tissue. 39. On the question of commissural neurones in the autonomic ganglia. Sydney E. Johnson, Northwestern University Mechcal School. The question of the origin of the spiral fibers and pericellular networks of autonomic gangha has given rise to two opposed views. Elu'hch, Retzius, Langley, and others believe that they are terminations of cerebro-spinal, preganglionic neurones. Some authors (Dogiel, von Lenhossek, Huber) have, on the other hand, claimed that endings of other types of neurones (commissural, sensory) are also found in these gangha. The writer has produced experimental evidence in favor of the first view. Frogs were used for the experiments, as then- autonomic ganglion cells are unipolar and the liistological pictures are not confused by the presence of dentrites. Three different lots of frogs were operated. Results of the first two lots of frogs were, if considered separately, inconclusive. The tlikd lot gave rather striking results. In these the spinal cord was destroyed and the trunci .sympatliici cut. This double operation eliminated the possibility (allowing time for degeneration) of preganghonic fibers reaching the posterior gangha, while preganglionic fibers PROCEEDINGS 41 could reach the anterior ganglia by running from the tlu-ee anterior spinal nerves caudad or eephalad for some distance in the truncus sympatliicus. In the posterior gangha all of the spirals and pericellular networks disappeared, wliile in the anterior gangha a very few could still be demonstrated. The evidence thus afforded appears to show: 1) that the spiral and pericellular fibers are of cerebrospinal origin; 2) that these preganghonic fibers may run some distance in the truncus sympatliicus before terminating in a network on a postganghonic cell, and 3) that commissural connections do not occur in the autonomic ganglia of the frog. SO. The history of the nucleus caudatus and the stria terminalis in vertebrates. J. B JoHXSTOx, Universitj- of ]\Iinnesota. The caudate nucleus consists of two parts, ventral and dorsal, which are distinct in structure and origin and in functional relations. The ventral portion is closely related to the olfactory and paroKactory nuclei, the bed of the anterior commissure and the medial part of the amygdaloid complex. The dorsal portion forms the chief part of the ridge wliich in man is called the 'tail' of the caudate nucleus. It is closely related to the • lentiform nucleus, especially behind the internal capsule where these two enter into a common mass lateral to the amygdaloid complex. The ventral portion is a part of the olfactory apparatus tlu'oughout the vertebrate series. The dorsal portion becomes prominent first in the reptiles where it forms the dorsal ventricular ridge. Its development in reptiles and mammals shows that it is derived from the lateral border of the paUiimi. The dorsal portion has fiber connections with the internal capsule and the palhum. The stria terminahs is a complex bundle connecting the rostral and caudal parts of the olfactory apparatus. It and the gray mass in which it is imbedded (ventral portion of caudate) have Ijeen greatly elongated in mammals on account of the increased volume of the internal capsule. .31. The distribution of fractures of the femur. John C. Koch. The mathematical analysis of the normal adult femiu-, presented by the writer at the last annual meeting' of the association, is used as the basis of a comparison of the theoretical distribution of fractures of the femur and the actual distribution of the entire series of such fractures treated at the Johns Hopkins Hospital since its estabhslunent in 1893. The theoretical chstribution is calculated and a grapliic chart is constructed representing the relative tendency to fracture at any given segment, based upon the following assumptions: 1. The tendency for a fracture to occur at any point varies inversely as the least strength of the bone in that segment. 2. Blows of the same intensity are equally apt to be received at any point along the femur. Although blows may varj^ in intensitj-, they tend to be equally distributed. 42 AMERICAN ASSOCIATION OF ANATOMISTS 3. The tendency' to break at any point varies directly as the distance from the nearer support, the femur being supported at both ends in every case of fracture. A second chart shows the percentage distribution of the fractures of the femur treated at Jolms Hopkins Hospital, and every case in whkh it has been possible to determine with reasonable accm-acj' the position of the fracture has been included in the series studied, except those in wliich fracture was due to kno\\TQ bone chsease and fractures of the head and neck of the femur. A close agreement of the theoretical and actual distribution. of the fractures of the femur is shown by the charts. 32. The distribution of sympathetic neurones in the myenteric and submucous plexuses in the small intestine of the cat. Albert Kuntz, St. Louis University School of Medicine. As determined by actual coimts of the sympathetic cells present in transverse sections of the small intestine of the cat, sj'mpathetic neurones are most numerous in the myenteric plexus at the pyloric end of the duodenum. Advancing distallj', their number diminishes rapidly until a low point is reached in the upper ileum. Distal to tuis point, relativel,y little variation occurs imtil a point approximately 12 inches from the ileocolic valve is reached. From this point to the ileocohc valve there occuis a gradual and steady increase. In the submucous plexus sj'mpathetic nem-ones are most numerous apy,roxin ately 2 inches distal to the pyloris. Advancuig distally, their number dmiinishes rapidly until a low i:)oint is reached somewhat proximal to the low point in the myenteric plexus in the upper ilemn. Distal to tlois point, there is a rapid increase until a relative high point is reached just distal to the low point in the myenteric plexus. Advancing farther distally, the number of sympathetic neurones diminishes very rapidly imtil another low point is reached, after wliich there occurs relative!}' little variation until a point approximate!}- 12 inches from the ileocolic valve is reached. Distal to tliis point, tliere occvu's a very rajjid rLse, reacliing its maximum approximate!}' 6 inches from the termination of the small intestine, then a sharp decline toward the ileocolic valve. S3. The origin of cartilage from ectoderm in the urodeles. F. L. Landacre and J. H. Warren, The Ohio State University. A study of urodele embryos demonstrates conclusively that the origin of all the branchial cartilages, except the second basi-branchial, and of tlie anterior portion of tlie trabeculae arise from tlie neural crest. The neural crest migrates ventrally into the mandibular and l^ranchial bars. The dorsal region of the neural crest forms portions of the V, VII, IX, and X ganglia, while the ventral portions differentiate into cartilages of the corresponding bars. The liistological distinctions between mesenchvme derived from ectoderm and that derived from endo PROCEEDINGS 43 derm disappear in later stages, but during the earlier stages of growth are easily recognizable." These histological distinctions rest upon: a) The size of the cells; b) the size and number of yolk granules in the individual cells; c) the reaction to stains; d) pigmentation; e) the continuit}' of cell masses. The greatest difficulties encountered in distinguishing ectodermal from endodermal mesenchyme arise where the two tj^pes of tissue overlap and mingle or where ectodermal mesenchj'me is withdrawing from an area by migration and is being replaced by endodermal mesencfi^Tne or where it is apparent h' undergoing cytolj^sis. The distinction between ectodermal and endodermal mesenchyme indicated above seems possible at present onh' iu types where there are yolk-laden cells, although it has been affirmed for other tj'pes. This distinction is recognizable in frog embrj-os, and if it exists in higher forms, it would explain some of the anomalies found in tumor formation in mammals. 34. The implantation of the blastocyst and the formation of the decidual canty in Dipodemys. Thomas G. Lee, Institute of Anatomy, University of ^iinnesota. This rodent, of the family Heteromj-idae, is the third example thus far known among the Rodentia to be characterized by a perforation of the uterine epitheUum and the passage of the ovum out into the stroma of the uterine mucosa to form an independent decidual cavity. The first, was the guinea-pig described bj' Graf Spee, the second was Geomys, previously noted bj- the present writer. The perforation is thi-ough the antimesometrial wall, the blastocyst at the time of.extrusion is larger and older than in the guinea-pig, the inner cell mass is distinct, the yolk sac large and differentiated into the inner visceral layer and the thinner parietal layer which is closely applied to enveloping trophoblast. The stroma of the mucosa becomes oedematous and filled with proliferating vessels; there is for a time a functional yolk-sac placenta. There is entypy or the so-called inversion of germ layers, the inner cell mass elongates, becomes hollowed out to form the amnion, the ectoplacental conus is small. In the uterine lumen at a point a short distance on either side of the site of perforation, a diverticulmn is formed, which extends dorsoventralh' and laterally; bj- this means that area of uterine mucosa destined to form the walls of the decidual cavity is isolated except at the mesometrial pole to provide for vascular and nerve supph', and a septum at the antimesometrial pole; this extensive diverticulum is lined with the uterine epithelium. 35. Bone-repair in the rat vitally stained with trypan blue. C. C. Macklin, Department of Anatomy, Johns Hopkins Universitj^. Healing fractures of the tibia, femur, and rib and healing trephine wounds of the skull were studied in twenty rats, the series extending 44 .\MERICAN ASSOCIATION' OF AXATOMISTS from the second to the seventy-first day of repau-. Trjiian blue, in 1 per cent aqueous solution, was admuiistered intraperitonealh' two days before death. in the early stages the usual inflanimatorj' reaction occurs. Macrophages in great numbers congregate at the site of the injury and phagocj-t«ze the tissue waste. They are probably derived principally from the small lymphocyte-like cells of the blood, but also from the local macrophages. Their period of greatest efficiency is from the third to the sixth day, inclusive. ]\Iost of them perish in situ, when theii- work is done, by undergoing disintegration. A few pohTnorphonuclear leucocj-tes were associated with the macrophages. Xo dye granules were found in them. Dm-ing the period of removal of the provisional callus the numerous reticulum cells of its spaces develop intense phagocytic abihty, manifested in their striking vital staining. Thej' are regarded as being concerned in callus erosion to the extent that they phagocj'tize the products of callus breakdown — probably the tissue waste from the dissolving matrix. Then- period of greatest efficiency is from the tenth to the twentieth day. They resen ble in structure and function the macrophages of developing bone described by Shipley and Macklin (Amer. Jour, of Physiol, 42, p. 117). Multiaucleate cells, looking like osteoclasts, were found in the callus. Their nmuber bore no direct relationship to the amount of callus destruction evidently progressing and they contained no dyestuff. 36. On the behanor of Bufo and Rana toicard^ colloidal dyes of the acidazo group. C. F. W. McClure, Princeton University.* Among the 140 larvae of Bufo placed on the thu-d and fourth days after fertihzation in solutions of Niagara and trj-pan blue (1 : 1500), 66 sectioned at intervals before the ninth daj' showed, with three exceptions, that no dye granules had been stored in any cell. In all except two of 31 larvae killed on the ninth day, and in 43 killed later, dye granules were invariably foimd, ^^'hen larvae were placed in solutions after the ninth day, the ingestion and storage of dye granules by the cj'toplasm of certain cells was essentially a question of hours. Dye granules were observed in Bufo on the ninth day after fertilization in epithelivnn of pronephros and pharj-nx, Kupffer's cells, hanphatic endothelium, endothelium of renal-portal, postcardinal, and portal v'eins, in a few lymjihocj-tes, and occasionally in the endothelium of aortic arches and inferior and external jugular veins. On tenth day dye granules were first observed' in the mesonephric epithelium, and at a still later stage in the spleen. As Wislocki states, venous endothelium in Rana does not 'stain.' These and other experiments indicate that the initiation of phagocv-tosis in young amphibian larvae, is not influenced primarih- by the length of tune larvae remain in dye solutions, but is correlated with the attainment of a distinctive ontogenetic stage. PROCEEDINGS 45 Partial immersion of body of larva or adult in solutions shows integument to be a portal of entry for the dye. Feeding expermients on adults show that dye may also reach cu-culation through ahmentarj^ canal. Wislocki's method of ^-itally staining lymphatics does not specifically differentiate h-mphatic endothehum and, like the injection method, is capable of demonstrating them only after continuous vessels are formed. 37. The form of tracheal and bronchial cartilages. (Lantern.) W. S. ^IiLLER, Anatomical Laboratory, University' of AVisconsin. Horner, of Philadelpliia, in 1839 gave the earliest description of the form of the cartilages at the place where bronclii divide, ascribing to them a saddle shape. Jonas King, of Guy's Hospital, followed in 1840 with a short paper wliich was illustrated bj' a few unsatisfactory drawings of cartilages in situ. King found that not all cartilages situated at the dividing point of bronclii had the characteristic shape ascribed to them by Horner. Since the time of King no attempt has been made to illustrate in plastic form the cartilages of the trachea or bronchi. The cartilages of the bronchi are usually described as being irregular plates scattered along the bronchi, gi-aduaUj^ din inishing in number and size. Finding the usual descriptions unsatisfactor}-, reconstructions were made from the lung of man and various mammals to determine the actual shape and arrangement of the cartilages. 38. On certain persistent unit.? of anatomical structure. Rot L. ]\Ioodie, Department of Anatomy', College of iledicine, University of Illinois, Chicago. The units of structure to which attention is called are those histological structures and • impressions of soft parts which have been preserved in the rocks of past ages with sufficient clearness as to details of organization to give us adequate information as a basis for an opinion. Those persistent units of anatomical structure which will concei-n us here are: the osseous lacunae, the Haversian s.vstem of osseous lamellae, the perforating fibers of Sharpey, the cross striation of muscle fibers, the form of the brain, the form of the alimentarjcanal, the arrangement of the lateral-line organs, the sinus paranasales, and other matters of organization on which we have paleontological information. The first osseous material to be developed on the bodies of the early vertebrates was in the form of a bony sheath, capping and partialh' surrounding the dorsal spine of the early shark-like vertebrates of the Ordovician and Silurian. These sheaths in microscopic section show tj'pical osseous lacunae which do not differ in any essential respect from modern lacimae, save perhaps in the slighter development of the canahculi. The oldest known Haversian system, apparently, occurs in the 46 AMERICAN ASSOCIATION OF ANATOMISTS Devonian Arthrodire, Dinichthj^s. This is a primitive system differing only in minor respect from "the modern Haversian systems of mammalian bones. The fundamental plan was laid down early, and no departure has since been made. The oldest known perforating fibers of Sharpey are found in the humerus of a mosasaur from the Cretaceous of Kansas. These occm' in bundles, very like modern fibers. In the material so far studied there is no evidence that these fibers penetrate a series of Haversian lamellae. The cross striation of musculature was first made known by Dean. There is little difference in the striation of the Devonian shark, Cladoselache, described by Dean, and the modern shark. The ancient tissue presents coarser striations, but the plan is essentially the same. The form of such structures as the brain in fishes, the alimentary canal in amphibians, the lateral-line canals in amj^hibians, and the sinus paranasales in early mammals all tend to show that there are certain features in anatomical structure which have been only slightly affected in the great evolutional changes which have been brought al:)out in other features of animal organization. 39. Studies on the Mammary Gland. IV. The histology of the ynammary gland in the male and female albino rat from birth to ten weeks of age. J. A. Myers, Institute of Anatomy, University of Minnesota, Minneapolis. At the time of birth the attached end of the primary duet is represented by a solid cord of cells which attaches to the epidermis in the male and the medial side of the developing nipple in the female. The free end of the primary duct possesses an incomplete lumen. The secondary and tertiarj' ducts present walls of three or four cells in thickness. The cells nearest the lumina have not yet become arranged in definite layers. The walls of the terminal ducts are somewhat thinner than those just described. In rats of ten days the epithelium of all ducts from the primary through the terminal ducts is arranged in two layers. The inner layer is composed of cuboidal cells quite uniform in size, while in the outer layer the cells are more irregular in size and shape. At nine weeks the epithelium is still present as two layers in most of the ducts. In a few instances, however, the terminal ends present a single layer of cells. Weigert's resorcin-fuchsin stain reveals a few elastic tissue fibers in the later stages, more having been observed in the first few weeks of life. Glands of several early stages have been stained with Bell's differential fat stain, scarlet reel, osmic acid, and Herkhcimer's stain. At present no definite newljorn secretion has been observed. In a few cases, however, small dioplets of fat have appeared in the walls of the milk ducts. PROCEEDINGS 47 Jfi. The eyeball and associated sti'udures in the coecilians. H. ^\'. NoRRis, Grinnell College. In the coecilians the typical amphibian eyeball musculature and eyemuscle nerves have been modified, first, b}' the degeneration of muscles and nerves to the point even of complete disappearance; second, by the transfer in function and anatomical relations of certain muscles from the eyebaO to adjacent organs, as the retractor bulbi transformed into a retractor tentaculi, the rectus internus changed into a retractor of the tentacular sheath, the levator bulbi modified to a compressor muscle of the orbital glands. Genera studied: Coecilia, Dermophis, Geotrypetes, Herpele, Ichthyophis. 41. Lateral asy}?i7netry in chick embryos developing irithout circidation. (Lantern.) C. W. M. Poyxtee, University of Nebraska, Omaha. In a series of chick embryos, in which the development was distiu^bed in order to studj' the process of disassociation, it was noticed that lateral asraunetrj' frequently occurred. The eyes which were among the first structures to show a reaction to the disturbance presented some interesting examples of disassociation and delaj'ed development. These conditions possibly throw some light on one way, at least, in which monophthahnica asjTiimetrica may develop. Embryos in which the circulation was destroyed or its development prevented by operation, showed 80 per cent in which lateral asymmetrical development or degeneration occurred; of these 100 per cent exhibited a greater reaction in the left ej^e. Embryos placed in the refrigerator at 12 degrees for varj'ing periods, then allowed to continue development, showed a large percentage of eye and ear deformities, but only a small nmuber of examples of lateral asjTnmetry. Embrj'os inoculated with staph}'lococcus showed 25 per cent asjnnmetry, only slightly over half of these being on the left side. The lateral disturbance is not confined to the eyes, the ears presenting the same type of asjTnmetry, though less frequently', and the entu-e lateral half of the body may share in the delayed development or disassociation. In this study the disturbances to development are so profound that in a short time death of the entire embryo occurs; consequently, there is no opportunity' to observe a regenerative process. These experunents suggest that the ej'es are not equally resistant to all the factors operating; the left eye is more suceptible than the right, regardless of whether rotation occurs normally or is reversed. 48. Afferent fibers of the truncus sympathicus and splanchnic nerves in the cat. S. W. R.\nsox, Northwestern University Medical School. The truncus sympathicus in the neck contains no sensory fibers, and in the upper thoracic segments only a few. But in the lower thoracic region, it contains a great many such fibers destined for the splanchnic nerves. These sensory fibers include myelinated axons of all sizes and 48 AilERICAN ASSOCIATIOX OF ANATOMISTS man J- that are unmj-elinated. Thej- come from the spinal gangUa by waj' of the white rami. The splanchnic nerves are composed exclusively or almost exclusively of fibers derived from the white rami and contain in addition to the myelinated and unmyelinated sensory fibers also mj'ehnated preganglionic efferent fibers. They contain few if any fibers arising from the ganglia of the truncus sj-mpathicus. The descending fibers from the white rami run in well-defined bundles in the trimcus sj-mpathicus, the afferent and efferent fibers from a given ramus mixed together, but separate from the fibers coming from the other rami. These bundles degenerate after section of the corresponding spinal nerve. If the roots of a spinal nerve are cut proximal to the spinal gangUon, the fine myelinated efferent fibers of the bundle degenerate and the sensorj- fibers stand out alone. If the roots are cut distal to the spinal ganghon, all the fibers of the bundle, including the unmyehnated sensorj- fibers, degenerate. The fibers from adjacent bundles intermingle very little if at all. 43. Cyclic changes in the interstitial cells of the ovary in the woodchuck (Marmota monax). A. T. Rasmussen, Institute of Anatomy, University of ^linnesota. From an examination of 144 ovaries, representing every month, it is evident that the interstitial cells vary greath' with the seasons of the year. The}' are minimal in late smnmer. During autumn and winter (involving hibernation) there is a shght gradual increase in the Hpoids and hence in the size of the cells. There is no sudden change at the onset of liibernation but after waking up from winter-sleep (in iNIarch) and rutting begins, there is a marked hypertrophy. The cells increase in size and possibly in number. A few are ahnost free from large lipoid granules and the rest contain abundant cji;oplasm between the fattj- droplets. There is a distinct increase in fuchsinophilgranules. ^laximum development is seen at the beginning of pregnancy. AMth the gro^-th of corpora lutea, interstitial cells decrease, but are particularly rich in hpoids. In mid-summer, aboui two mouths after parturition, when corpora lutea are rapidlj- degenerating, the interstitial cells lose all or nearljall their fattj' content. The nuclei generaUj^ decrease in size and but Uttle c.ytoplasm remains. Possiblj- some cells disappear entirely. Mitochondria, which are mostly round with onlj- a few short straight or sUghth' curved rods and which are demonstrable at all times, largely persist . Thus the interstitial cells of the ovary closely pai-allel the changes in the homologous cells of the testis of this species. Pigment granules similar to those in the testis are not found in the interstitial cells of the ovary. PROCEEDINGS 49 44- On the growth of the rarioiis organs of the body during fetal life. Richard E. ScAiiMOx, Institute of Anatomy, University of ^Nlin nesota. A summarj- of a statistical study of the growth of the principal organs of the body during fetal life and of their average weights and normal variations in weight at birth. 4-5. On the development and finer structure of the sucMng-pad (Corpus adiposum buccae). Richard E. Scammox. Institute of Anatomj-. University of ^linnesota. A description of the general development of the sucking-pad during fetal life with a description of its structure at birth. 46. On the time of obliteration of the fetal blood-passages after birth. R. E. Scammox and E. H. Xorris. Institute of Anatomy. University of Minnesota. A statistical study of the time of obhteration of the Imnina of the ductus arteriosus and ductus venosus and of the closure of the foramen ovale in man. 47. Material for a study of the Megapodiidce. R . AY. Shufeldt, Washington. D. C. This verj' elaborate memoir on the moimd birds was completed two years or more ago, and accepted in Germany for pubhcation in the Zoologische Jahrbiicher. That MS. and its plates were last heard from in Jena, since which time the world war has come about. Since this. too. the entire manuscript, with its twenty-one plates containing many figures, some of which are colored, has been reproduced for pubhcation. and is now ready to go to press. AU the material upon which the work is based belongs in the collections of the Division of Birds of the U. S. Xational Museiun: it consists of the skins and eggs of quite a munber of the Megapodiidse. including the skeletons of the Xicobar species as well as the rare Megacephalmn maleo. A detailed account of the osteologj- of these latter two is presented. There are among the plates colored heads of INIegapodiur nicobariencis. ]M. cumingi, Catheturus lathami. and Megacephalum maleo. The latter species is here figured for the first time; with the correct coloring for its head. AU previous authors have represented this as being black: but. as recently pointed out by Renshaw. the casque is bright blue, the cuhnen red. and most of the biU pea green. This is a remarkablj- handsome bird in life, the plumage of its body being of a blackish brown, with green reflections on the tail. The most striking part of all its plumage, however, is the elegant pinkish salmon color of the entire under parts. The close comparative study of aU this goes to show that there can now be no question as to the ^legapodes being a separate family from the Cracidae. and most assiu'edly from other families of gaUinaceous birds, as the guinea-fowls and turkeys. It is clear from what is set forth in the memoir, presenting, as it does, many new facts in the 50 AMERICAN ASSOCIATION OF ANATOMISTS morphologj- of the j\Iegapodiida\ and other matters related to them, that it does not tend in any way to disturb the views set forth by many previous writers with respect to their taxonomy. Indeed, it confirms a fact long ago announced by me, that is, what I pointed out as early as 1904 in the American Naturalist to the effect that the mound" birds (Megapodiida?) belong in the suborder Gallinse (Family I.) next above the Cracida; in a linear arrangement; and should the monograph from which these brief notes are abstracted "settle this point, or even assist in settUng it for all tune, I shall certainly feel that my labor upon it has not been entirely devoid of useful results. 48. The skeleton in the ' Kea parrot' of New Zealand (Nestor notabilis). E. W. Shufeldt, Washington, D. C. This paper presents a complete account of the skeleton of this remarkable bird, and is illustrated by sixteen figures on seven plates. No part of this work has ever appeared before and no full account of the 'Kea' has heretofore been pubhshed. Durmg the smnmer of 1917, the Department of Tourist and Health Resorts, New Zealand Government, presented to the National Zoological Park, at Washington, D. C, nine adult specunens of this famous 'Kea parrot' (Nestor notabilis). ^Vhen the shipment arrived at the park, August 31, 1917, one bird was found dead in the crate and was transferred to the National Museum to be prepared as a skeletal accession to the collection. It is the description of this skeleton which forms the subject matter of the present paper. It has for its object the shedding of additional hght upon what has abeady been set forth in literature by previous authors on the taxonomy of the genus Nestor or the place of that genus in the system. By avian systematists this has generally been held to be that, as a group, small as it is, it forms a separate family, namely the Nestoridse. The late 'very eminent British ornithologist, Alfred Newton, F.R.S., sets forth in hLs Dictionary of Birds that "The position of the genus Nestor in the OnhuPsittaci. must be regarded as uncertain." Count T. Salvadori, in the Catalogue of Birds of the British Museum, after a very cursory examination of its skeleton, relegated these parrots to a farnily, Nestoridae; many other writers have followed him in this regard. Dr. Frank E. Beddard, F.R.S., in his excellent work on "The Structure and Classification of Birds" (London, 1898), devotes some little attention to Nestor. After passing in review what has been thus far worked out upon its anatomy, Doctor Beddard presents the suborrlcr P.sittaci as arrayed by Garrod in his work, and in it we find two families, one of which is the Psittacidse. In this family the subfamily Arinae is created to contain Ara, Conurus, Bolborhynchus, Caica, Psittacus, Pa'ocephalus, and Nestor. In other words, the 'Kea' in this classification is only entitled to generic rank, and belongs in the family Psittcida\ Like so much of Garrod's work in the classification of birds, this is a totally unnatural scheme, as anyone PROCEEDINGS 51 who has studied the skeletons of Conurus. Ara, and Nestor and compared them will contend. He almost invariably based his conclusions upon altogether too few characters. The skull of Nestor, for example, presents many characters quite different from those of Conurus and the macaws, ajid this appUes to other parts of its skeleton. All this will be dul_v and most fully set forth in the memoir when pubhshed, of which this is but a verj' brief abstract. 49. Weights of various parts of the brain in normal and underfed albino rats at different ages. C. A. Stewart, Institute of Anatomy, University of Minnesota, ^linneapolis. The olfactory bulbs increase from an average of slightly more than 2 per cent of the normal brain weight at birth to more than 4 per cent at ten weeks. In the adult the relative weight (and possibly the absolute weight) apparently decreases. The telencephalon and diencephalon (excluding olfactory bulbs) collectively form about 66 per cent of the entire normal brain weight at birth, 69 per cent at three weeks, and 6.3 per cent in the adult. The crura cerebri, pons. ' and medulla oblongata collectively decrease from an average of nearly 27 per cent of the normal brain at birth to about 20 per cent in the adult. The cerebellum increases from an average of 3.5 per cent of the brain in the newborn to approximately 1-1 per cent at ten weeks of age and later. In underfed rats weighing 10 grams when three weeks of age the brain is considerably heavier than in normal younger rats of the same body weight, the increase being shared by each of the various parts of the brain mentioned above. The relative weights of the telencephalon and diencephalon (excluding the olfactorv bulbs) and also of the brain stem (including crura cerebri, pons, and medulla oblongata) apparently- decrease slightly in the test rats, while the cerebelliun increases in percentage of the entire brain weight. The relative weight of the olfactorj' bulbs remains practically unchanged. 50. Normal and abnormal development in individuals exhibiting different degrees of twinning. CLantern.) Charles R. Stockard, Cornell Universit}' ^ledical College, New York City. A group of 38 individuals, ranging from a double-headed to a complete twin condition, was selected at random in a trout hatchery and given to me for study. These specimens have been arranged in a graded series and studied in order to determine the degree of perfection in the development of theii- heads. The great majority of them, 26, are bilaterally sj-mmetrical, the two heads being equal in size. Without exception, in all these cases the two heads are normal in general appearance, and so far as their eyes and mouths are concerned are tjpically perfect. Eleven of the young fish are asjTnmetrical; one head in the double-headed types or one THE A-XATOUtCAI. BECOBl> VOL. 14, NO. I 52 AMERICAN ASSOCIATION OF ANATOMISTS member of the joined twins being normal in size and perfectly developed, while the other head or body is inferior in size and in every case is abnormally developed, particularly in respect to its ej'es. Only one specmien of the 3M had both heads deformed, j^et on analysis this one is in perfect accord with the group. The conditions shown by these specimens furnish most valuable material for an understanding of the causes of many kinds of abnormal development, and they will be discussed from this standpoint. 51. Observations on gray hair and alleged sudden blanching of hair. R. M. Strong, Vanderbilt University Medical School. Various statements occur in the literature of hair color, concerning the causes of grajmess or canities. Usually it is recognized that absence of pigment is a cause, but it is also commonly stated that the entrance of air into hair is a factor. My own observations have led me to doubt whether gray hairs ordinarily contain any more air or other gaseous material than colored hair. All haks have a great number of both internal and superficial reflecting surfaces due to incomplete fusion of the constituent cells, which alone can account for whiteness when pigment is not present to absorb the incident light. ^'arious standard text-books of dermatology still credit the old accounts of sudden loss of hair color. This subject has interested me for about fifteen years, and I have discussed it often with clinicians, especially dermatologists. Onlj- one alleged case has come to my attention during this period. Hair specimens of this were obtained and the circumstances investigated carefulty. No good evidence was obtained that the white hairs were blanched suddenly or were in any way abnormal. All statements in the hterature of such phenomena were made in a less critical period than the present. It is my judgment that, until more satisfying evidence is obtained of the actual occurrence of such phenomena, we should regard sudden blanching of the hair as improbable. Xo method by which it could take place is known to me. This is a preliminarj' report of work on gray hair, not j'et complete. DEMONSTRATIONS /. Experiments upon the glands of internal secretion in Rana and Bufo larvae. Bennet M. Allen, University of Kansas. 2. Positional changes in the visual cells and retinal pigment to graded intensities of light. L. B. Arey. Northwestern University Medical School. 3. Models illustrating the development of the hypophysis cerebri of the frog. Way^'E J. Atwell, Department of Anatomy, Medical School of the University of Michigan. 4. X-ray plates illustrating anatomy in the living. C. R. Bardeex, University' of Wisconsin. 5. Models and corrosion preparations showing the branching of the hepatic ducts in human embryos and newborn. E. A. Baumgartner, Department of Anatom}^, Washington University Medical School. The hepatic anlage in a 4.2 nun. human embryo is round, extending cranially and v^ntrally from its wide connection with the gut. Hepatic trabcculae grow from its lateral and ventral surfaces. A short caudal portion bears no traveculae and is probably the pars cystica. A single ventral pancreatic anlage projects from the right side of the caudal end of the hepatic outgrowth caudal to the pars cystica. In- a 7.5 mm. specmien the hepatic duct divides near its origin into a small right ductule and a very much enlarged plate-like duct from which hepatic trabeculae are given off in all directions. The gall bladder is attached to the common duct by a short cystic duct. A model of a 17 mm. embrj-o shows the distal end of the gall bladder directed cranialward. The hepatic duct and its right subdivision are lengthened. Hepatic trabeculae arise from the right and left ducts. Another specimen of the same size shows several small hepatic ducts arising from the cj^stic duct, one of which anastomoses with a radicle arising from the hepatic duct. Tliis specimen also shows an enlarged distal end of the hepatic duct, similar to that in younger stages. Models of 25 mm. and 41 mm. embrj^os show gi-owth in length of cystic and hepatic ducts. In the 41 mm. specimen the hepatic duct breaks up into several laterally-projecting ducts from which many hepatic trabeculae are given oft". Corrosion preparations of the hepatic tree in several new bonis have been made. These show as a rule a right and a left hepatic duct with smaller and larger subdivisions spreading into the liver. 53 54 AMERICAN ASSOCIATION OF ANATOMISTS 6. Microscopical preparations of a closely graded series of hind limbs of pigs shoiving the early stages in the development of the femur and the thigh musculature. Eben J. Carey, Department of Anatomy, Creighton University. 7. Preparations illustrating the origin of the corpus luteum of the sow. George W. Corner, Anatomical Laboratory, University of California. 8. Stages in the development of brachydactylism in the foivl. C. H. Danforth, Department of Anatomy, Washington University Medical School. Feet of brachydactyl chick embryos fixed on abovit the tenth tlay of incubation and stained mi toto by the Van Wijhe method show various degrees of diminution in the cartilaginous skeleton of digits IV. The preparations are thought to indicate that the reduction in the number of phalangeal cartilages is due to a fusion of the anlagen of these elements. The skeletal elements of the feet of a few adult birds are shown for comparison. 9. Material illustrating the early reactions of blood and tis.sue cells to colloidal dyes. Hal Downey, University of Minnesota. 10. Microscopic sections of the ovaries of the spermophile (citellus) showing secretory granules and lipoids characteristic of the periods of the annual dioestrus cycle. Della Gay Drips (Introduced by Thomas G. Lee), Institute of Anatomj^ University of Minnesota. 11. Demonstrations illustrating hematogenesis in the embryonic liver as correlated with different stage in hepatic development. V. E. Emmel, University of Illinois Medical School. 12. Further observations concerning the relation of the aortic cell clusters and degenerating aortic rami. The Demonstrations consist of a series of sections and drawings showing: (a) The Intimate Association of Aortic Cell Clusters and Ai-terial Cell Masses in Aortic Rami. (6) Aortic Cell Clusters in Relation to Atrophying Roots of the Superior Mesenteric Artery, (c) The Relation of Cell Clusters Within the Lumen of the Superior Mesenteric Artery to Degenerating Aortic Rami. V. E. Emmel, University of Illinois Medical School. 13. The growth of the limb-skeleton of Okapia Johnsioni. F. W. Heagey, Department of Anatomy, Creighton ITniversity. This material was collected by the Lang-Chapin expedition of the American Museum of Natural History in Belgian Congo, Afri'ca. It has been loaned to the Department of Anatomy of Creighton University for study. This collection consists of six complete skeletons of Okapia ranging in size from an embryo 120 mm. in length to a young indi^•idual that has attained about one-third the adult growth. PROCEEDINGS 55 14- Further experiments with the effect of heat upon the chromosomes of Cumin^ia. ^Iahg-ujet ^l. Hoskins, New York University and Belleviie Hospital Medical College. 15. Specimens and slides of further experiments with thyroidectomy in Amphibia. {Ratia Sylvatica.) E. R. Hoskixs and M. ]M. Hoskixs, New York University and Belle\Tie Hospital Medical College. 16. A wax model of the left half of the medulla oblongata of Squalus acanthias ("pup" stage), showing an analysis of the cranial ganglia. S.\LLT P. Hughes, Zoological Laboratorj-, Grinnell College. 17. The effect of inanition upon the growth and structure of the supraren-al gland in the albino rat. C. M. Jackson, Institute of Anatomy, Universit}' of ilinnesota. 18. A wax-cast model of the human nasal cavity and paranasal .sinuses. C. jNI. Jacksox and C. E. Coxxor, Institute of Anatomj', University of Minnesota. 19. An instrument for the measurement of human hairs. A. E. Jexks, (by invitation^, Department of Anthropology, University of Minnesota. SO. Autonomic ganglia of the frog before and after degeneration of the preganglionic fibres. S. E. Johxsox, Northwestern University Medical School. 21. (a) Neurological methods; celloidin sections; .staining; mounting and storing sections, (b) Nucleus caudatus and other recent forebrain studies. J. B. Johnstox*, University of Minnesota. 22. The implantation of the ovum and early development in the rodent dipodomys. Thomas G. Lee, Institute of Anatomy, University of Minnesota. 23. X-ray photographs of injected blood vessels as illustrated by stereorentgenograms of the lung. W. S. ^Miller, University of Wisconsin. By sKght modification of Gage's corn starch injection mash using various pigments different degrees of density may be obtained. 24. Certain persistent units of anatomical .structure. Roy L. Moodie, University of Ilhnois. 25. The arterial supply of the human hypophysis. Stuart ^Mudd, (introduced bj- Dr. R. J. TerrjO, Wasliington University !Metlical School, St. Louis. Three methods are being used: a) Injection with thin celloidin and corrosion bj artificial gastric juice — somewhat unsatisfactory be 56 .\iIERIC.iX ASSOCIATIOX OF AXATOMISTS cause of difficulty of injecting finer vessels, and because relations of arteries to tissues are not preser\-ed; b) wax reconstructions of thick coUoidin sections of foetal specimens — sections not j'et studied; c) dissection under binocular of gelatin — injected vessels. Brains for dissection are injected thi'ough the common carotid, with contra-lateral carotid, both vertebrals and external and internal jugular veins ligatured. Robin's Prussian blue and carmin have been used. The base of the brain in the region of the sella turcica and the underh-ing bone are removed and preserved in fonnaUn. The brain and meninges are carefully freed from the underhing bone, dehydrated and cleared in cedar oil. The}' ma.v then best be dissected under oil of wintergreen with a binocular. The brains are dissected through their underlj-ing meninges successively upon two planes: 1) an intradural plane, comprising the internal carotids and their branches witliin the cavernous sinus; 2) a subdural plane comprising the circle of Willis and its branches. Four brains only in the intradural plane have thus far been dissected. In each of these four brains there are found, arising from each internal carotid at its first and superiorly convex flexiu-e in the cavernous sinus, an artery of approximately one to two miUimeters in diameter which quickly breaks up into several somewhat variable branches. . These branches, together with an inconstant arterj' which may arise from the carotid in the sinus cavernosus more anteriorly, supply the semilunar ganglion, the third, fourth, fifth and sixth nerves in this region and the contiguous dura mater. One of the branches on each side, ramifying, courses between the laj-ers of the dura across the posterior lobe; twigs are sent also to the dura and may even be sent to the anterior lobe. The branch described is probably sufficient to supplj' the posterior lobe, but apparentlj' does not form a considerable element in the suppl}' of the highly vascular anterior lobe. 26. (a) The fetal development of the mammary gland in male and female albino rati. (Wax reconstructions and stained sections.) (6) The development of the mammary gland in male and female albino rats from birth to ten weeks of age. (Wax reconstruction, cleared preparation and stained sections.) J. A. ^Iyers, Institute of Anatomy, University of ilinne'jota. 27. Preparations ami drawings illustrating the structure of the truncus '.'iympathicus rami communicantes and splanchnic nerves in the cat. S. W. Raxsox, Xorthwestern University ^ledical School. 28. Histological preparations showing the cyclic changes in the inter' stitial cells of the testis and of the ovary in the woodchuck {Marmota monax). A. T. Rasmussex, Institute of Anatomy, University of Minnesota. PROCEEDINGS 57 29. Mojisters of excess and of defect. Daniel G. Revell, Department of Anatomy, University of Alberta. Photographs, roentgenograms and sections showing deduplications and deficiencies in chick, pig, human and other specimens. SO. On the growth of the various organs of the body during fetal life. R. E. Sc.\irMON, Institute of Anatomy, University of ^linnesota. Field graphs and curves of the rate of growth of the various organs of the body during the greater part of fetal Ufe, based upon material from autopsies in the Institute of Pathology of the University of Minnesota and on cases coOected from the literature. Tables showing the average weight and the degree of variation in the weight of the principal organs of the bodj- at birth. SI- Sections showing the origin, development and finer structure of the sucking-pad in man. R. E. ScAiiMOX, Institute of Anatomy, Universit}^ of Minnesota. S2. Various parts of the hrain in normal and underfed albino rat at different ages. C. A. Stewart, Institute of Anatomy, University of Minnesota. 55. Van Wijhe preparations of the primordial cranium of the cat. R. J. Terry, Washington University ^Medical School. Embr>'os measuring 10.5. 15, 2-1 and 30 mm. in length, prepared by Van Wijhe's method of staining and clearing, reveal in the clearest way the beginning, direction and extent of the processes of cartilage formation. Of special interest in these specimens is the evidence given of independence of chondrification of the otic capsule, parts in the cranial side waU and elements of the ethmoidal skeleton. In the specimen of 10.5 nmi. may be seen the hypophj'seal cartilage, the beginning of the otic capsule, Meckel's cartilage, parachordal plate and lateral occipital arches. The preparation of the 15 mm. embryo shows the septal, paratectal and paranasal cartilages, the ala orbitaUs, ala temporalis, commissura orbito-parietahs, basal plate, hypoglossal foramen and lamina parietalis. The cranimn of the 24 mm. embryo is of special interest in giving evidence of the relations of the suprafacial commissure to the parietal plate. Chondrification of the cranium has reached its maximum in the 30 mm. specimen. 34. A. teaching model of a 10 mm. pig embryo. Ivan E. Wallin, Marquette University. 56. Models illustrating the early development of the liver and hepatic ducts in the mouse. H. W. Wellmerling, (introduced by E. A. Baumgartner), Washington University IMedical School. 58 AMERICAN ASSOCIATION OF ANATOMISTS The liver in 3 mm. embryos is a wide outgrowth of the gut witli many small projections. Ventral to the hepatic portion i.s the small, rounded anlage of the gall bladder, Hammar's pars cystica of the hepatic anlage. The common tluct in .3.5 mm. embryo has a wide dorsal connection with the gut and bears on its caudal surface the anlage of the ventral pancreas and a large gall bladder. Hepatic trabeculae are attached to the cranial surface of the cystic duct, as well as to the hepatic duct proper which extend.s a few sections from this surface at the level of the ventral pancreas. In a 6 mm. embryo the ventral pancreas extends caudalward and to the right of the mid-line of the gut. The common duct has lengthened, and gives rise to the cystic duct which extends ventrally. A 10 nun. embryo shows great growth of the duct system. The common duct, as well as the dorsal pancreatic duct, arises from the dorsal surface of the gut. A short distance from its origin the common duct gives off caudally the ventral pancreatic duct, then turns cranialward jind gives off hepatic ducts in all directions. Beyond this region it divides into two, a small left and a large right duct, from the ventral surface of which a long cystic duct extends ventrally and to the left. From the anterior end of the two hepatic ducts smaller ducts pass outward giving off trabeculae. Some of these smaller ducts projecting medially from the two larger ducts anastomose. 36. Graphic reconstruction of the cranial nerves of the comnion garter snake. W. A. Willabd, University of Nebraska, College of Medicine. 37. Specimens showing the differentiation of angioblasts, the method of the formation of the lumen of blood-vessels and the diffcrentintion of redblocd-cells as made out in the living chick. Florence R. Sabin, Johns Hopkins Medical School. AMERICAN ASSOCIATION OF ANATOMISTS OFFICERS AND LIST OF MEMBERS Officers President Robert R. Bensley Vice-President Chakles R. Bardeex Secretary-Treasurer Charles R. Stockahd Executive Committee For term expiring 1918 Hermann von W. Schulte, John L. Bremer For term expiring 1919. Eliot R. Clark, Reuben M. Strong For term expiring 1920 George L. Streeter, J. Playfair McMurrich For term expiring 1921 George S. Huntixgton, Harvey E. Jordan Delegate to the Council of A.A.A.S. Simon Henry Gage Committee on Nominations for 1918 Thomas G. Lee, Chairman, A. G. Pohlman, and W. H. F. Addison Honorary Members S. Ram6n y Cajal Madrid, Spain John Clbland Glasgow, Scotland Camillo Golgi Pavia, Italy Oscar Hertwig Berlin, Germany Alexander Macalister Cambridge, England A. Nicolas Paris, France L. Ranvier Paris, France GusTAV Retzius Stockholm, Sweden Wilhelm Roux Halle, Germany Carl Toldt Vienna, Austria Wilhelm von Waldeyer Berlin, Germany Members Addison,WilliamHenryFitzgerald,B.A.,M.D., Assistant Professor of Normal Histology and Embryology, University of Pennsylvania, 39S3 Pine Street, Philadelphia, Pa. Allen, Bennet Mills, Ph.D., Professor of Zoology, University of Kansas, 16BS Indiana Street, Lawrence, Kans. Allen, Ezra, A.M., Ph.D., Pioiessoi oi Biology, Philadelphia School of Pedagogy, 125 Thompson Ave., Ardmore, Pa. 59 60 .\AIERICAN ASSOCIATION OF ANATOMISTS Allen, William F., A.M., Ph.D., Professor of Anatomy, University of Oregon Medical School, Portland, Oregon. Allis, Edward Phelps, Jr., JM.D., LL.D., PaZai's de Carnoles, Mentone, France. Amsbaugh, a. E., A.B., Student of Medicine, University of California, 1038 Santa Clara Avenue, Alameda, Calif. Appleby, J. I., A.B., Graduate Assistant in Anatomy, University of Missouri, Columbia, Mo. Arey, Leslie B., Ph.D., Associate Professor of Anatomy, Northwestern University Medical School, 2421 Dearborn Street, Chicago, III. Atwell, Wayne Jason, A.M., Ph.D.. Instructor in Anatomy, University of Michigan, 617 Whaley Court, Ann Arbor, Michigan. Badertscher, Jacob A., Ph.M., Ph.D., Associate Professor of Anatomy, Indiana University School of Medicine, 312 S. Fees Ave., Bloomington, Ind. Bagley, Jr., Charles, M.D., Phipps Institute, Johns Hopkins Hospital, Baltimore, Md. Bailey, Percival, B.S., Associate in Anatomy, University of Chicago, Chicago, HI. Baitsell, George Alfred, Ph.D., Instructor in Biology, Yale University, New Haven, Conn. Baker, Fr.\nk, M.D., Ph.D., LL.D. (Vice-Pres. '88-'91, Pres. '96-'97), Professor of Anatomy, Medical Department, Georgetown University, 1901 Billmore Street. Washington, D. C. Baldwin, Wesley Manning, A.M., M.D., Professor of Anatomy, .4 Jban?/ Medical College, Albany, N. Y. Bardeen, Charles Russell, A.B., M.D. (Ex. Com. '06-'09, Vice-President '18-), Professor of Anatomy and Dean of Medical School, University of Wisconsin, Science Hall, Madison, Wis. Bartelmez, George W., Ph.D., Associate Professor of Anatomy, University of Chicago, Chicago, III. Bates, George Andrew, M.S., D.M.D., Professor of Histology and Embryology, Tvfts College Medical School, Boston, Mass. Batson, O. v., A.B., Medical student at Washington University, Washington University Medical School, St. Louis, Mo. Batoigartner, Edwin A., Ph.D., Associate in Anatomy, Washington University Medical School, St. Louis, Mo. Baumgartner, William J., A.M., Associate Professor of Zoology, University of Kansas, Lawrence, Kans. Bayon, Henry, B.A., M.D., Associate Professor of Anatomy, Tulane University, 2212 Napoleon Avenue, New Orleans, La. Bean, Robert Bennett, B.S., M.D., Professor of Anatomy, University of Virginia, University. Virginia. Begg, Alexander S., M.D., Instructor in Anatomy, Harvard Medical School. Boston, Mass. (Captain Medical Reserve U. S. Army). Bensley, Robert Russell, A.B., M.B. (Second Vice-Pres. '06-'07, Ex. Com. '08-'12, President '18-), Professor of Anatomy, University of Chicago, Chicago, III. Bevan, Arthur Dean, M.D. (Ex. Com.'96-'98), Professor of Surgery, University of Chicago, 2917 Michigan Avenue, Chicago, III. MEMBERS 61 BiGELOw, Robert P., Ph.D., Associate Professor of Zoology and Parasitology, Massachusetts Institute of Technology, Cambridge, Mass. Black, DA^^DSo^', B.A., M.B., Assistant Professor of Anatomy, Western Reserve University, Medical Department, 1S5S East 9th Street, Cleveland, Ohio. (Captain Canadian Medical Corps.) Blair, Vilrat Papin, A.M., M.D., Clinical Professor of Surgery, Medical Department, Washington University, 400 Metropolitan Building, St. Louis, Mo. Blaisdell, Frank Ellsworth, Sr., M.D., Assistant Professor of Surgery, Medical Department of Stanford Universitj', 15H0 Lake Street, San Francisco, Calif. Bl.\ke, Joseph Augustus, A.B., M.D., 40 Ave. Henri Martin, Paris, France. BoNNEY, Charles W., A.B., M.D., Demonstrator in Anatomy, Jefferson Medical College, Philadelphia, Pa. BoTDEN, Edward Allen, A.M., Ph.D., Instructor of Comparative Anatomy, Harvard Medical School, Boston, Mass. Bremer, John Lewis, A.B., M.D. (Ex. Com. '15-), Associate Professor of Histology, Harvard Medical School, Boston, Mass. BR0ADN.iX, John W., Ph.G., M.D., Associate Professor of Anatomy, .Medical College of Virginia, Richmond, Va. Brookover, Ch.arles, Ph.D., Professor of Anatomy, University of Louisville, Medical Department, Louisville, Ky. Brooks, William Allen, A.M., M.D., 167 Beacon Street, Boston, Mass. Brown, A, J., A.B., M.D., Instructor in Anatomy, Columbia University, 156 East 64th Street, Xew York, N. Y. Browning, William, Ph.D., M.D., Professor of Xeurology, Long Island College Hospital, 54 Lefferts Place, Brooklyn, N . Y . Bryce, Thom.\s H.,M.A., M.D., Professor of Anatomy, University of Glasgow, No. 2, The University, Glasgow, Scotland. Bullard, H. Hays, A.M., Ph.D., M.D., Assistant in Pathology, Department of Pathology, Johns Hopkins Medical School, Baltimore, Md. Bunting, Charles Henry, B.S., M.D., Professor of Pathologj', University of Wisconsin, Madison, Wis. Burr, Harold Saxton, Ph.B., Ph.D., Instructor in Anatomy, School of Medicine, Yale University, 150 York Street, New Haven, Conn. Burrows, Moxtrose T., A.B.-. M.D., Assistant Professor of Pathology, Washington University Medical School, St. Louis, Mo. Byrnes, Charles M., B.S., M.D., Instructor in Neurologj', Johns Hopkins Medical School, 207 East Preston Street, Baltimore, Md. Camero.n-, John, M.D., D.Sc, F.R.S.E., Professor of Anatomj-, Dalhousie Medical College, Halifax, Nova Scotia. Campbell, Willi.\m Francij, A.B., M.D., Professor of Anatomy and Histology, Long Island College Hospital, S94 Clinton Avenue, Brookhjn, N . Y . Cardwell, John C, M.D., Professor of Physiology, Long Island College Hospital, Henry and Amity Sts., Brooklyn, New York. Carey, Eben J., Instructor in Anatomy, Creighton University Medical Department, Omaha, Neb. Carpenter, Frederick Walton, Ph.D., Professor of Biology, Tnn{«j/ College, Hartford, Conn. 62 AMERICAN ASSOCIATION OF ANATOMISTS Carter, James Thornton, D.D.S., Research Worker, Department of Zoology, University College, 1 Hanover Square, London, W., England. Carver, GailL., A.B., A.M., Professor of Biology, Mercer Universily, Macon, Ga. Casamajor, Louis, A.M., M.D., Assistant Professor of Neurology, Columbia University, 437 West S9th Street, New York City. Cash, James Robert, A.B., A.M., Student of Medicine, Johns Hopkins Medical School, Baltimore, Maryland. Chambers, Robert, Jr., A.M., Ph.D., Instructor in Anatomy, Cornell Universily Medical College, New York City. Chap.man, W. B., A.B., Medical >Student, Washington University Medical School, St. Louis, Mo. Cheever, David, A.B., M.D., Assistant Professor of Surgical Anatomy, Harvard Medical School, BO Hereford Street, Boston, Mass. Chidester, Floyd E., A.M., Ph.D., Professor of Zoology, Rutgers College, Neiv Brunswick, N. J. Child, Charles Manning, Ph.D., Professor of Zoology, University of Chicago, Chicago, III. Chillingworth, Felix P., M.D., Assistant Professor of Physiology and Pharmacology, Tulane University, A'ew Orleans, La. Clapp, Cornelia Maria, Ph.D., Professor of Zoology, Mount Holyoke College, South Hadley, Mass. Clark, Elbert, B.S., M.D., Assistant Professor of Anatomy, University of Chicago, Chicago, III. Clark, Eleanor Linton, A.M., Research Worker, Department of Anatomy. 413 S. 6th Street, University of Missouri, Columbia, Mo. Clark, Eliot R., A.B., M.D. (Ex. Com. '16-), Professor of Anatomy, University of Missouri, 413 S. 6th Street, Columbia, Mo. CoE, Wesley R., Ph.D., Professor of Biology, Yale University, Osborne Zoological Laboratory, New Haven, Conn. Coghill, George E., Ph.D., Professor of Anatomy, University of Kansas Medical School, R. F. D. No. 9, Lawrence, Kans. Cohn, Alfred E., A.B., M.D., Associate Member, Rockefeller Institute for Medical Research, 315 Central Park West, New York, N. Y. Cohoe, Benson A., A.B., M.B., Associate Professor of Therapeutics, University of Pittsburgh, 705 North Highland Avenue, Pittsburgh, Pa. Conant, William Merritt, M.D., Professor of Clinical Surgery, Tufts Medical School, 4^6 Commonwealth Avenue, Boston, Mass. CoNEL, Jesse LeRoy, Ph.D., Instructor in the Department of Anatomy, New York University, S3S East mth St., New York City. CoNGDON, Edgar Davidson, Ph.D., Assistant Professor of Anatomy, Leland Stanford University, School of Medicine, 330 Coleridge Avenue, Palo Alto, Calif. Conklin, Edwin Grant, A.M., Ph.D., Sc.D., Professor of Biology, Princeton University, 139 Broadmead Avenue, Princeton, N . J. CooKMAN, Alfred, A.B., Instructor in Agriculture and Biology, Long Beach High School, Long Beach, Cal. Corner, George W., A.B., M.D., Assistant Professor of Anatomy, Anatomical Laboratory, Universily of California. Berkeley, Calif. MEMBERS 63 Corning, H. K., M.D., Professor of Anatomy, Bundesstr. 17, Basel, Siviizer land. CowDRY, Edmund V., Ph.D., Associate in Anatomy, Anatomical Laboratory, Johns Hopkins Medical School, Baltimore, Md. Craig, Joseph David, A.M., M.D., IS Ten Broeck Street, Albany, N. Y. Craigie, E. Horxe, A.B., Instructor in the Department of Biology, University of Toronto, Toronto, Canada. Chile, George W., A.M., M.D., F.A.C.S., Professor of Surgery, Western Reserve University, gl4 Osborn Building, Cleveland, Ohio. (Major Medical Corps.) Crosby, Elizabeth Caroline, Ph.D., Principal of High School, Petersburg, Michigan. CuLLEN, Thomas S., M.D., 30 E. Eager Street, Baltimore, Md. CxjMMiNS, Harold, A.B., Instructor in Histology and Embryology, Vanderbill University Medical School, Xashville, Tenn. Cunningham, Robert S., B.S., A.M.,M.D., Instructor in Anatomy, Johns Hopkins Medical School, Baltimore, Md. Curtis, George M., A.M., Ph.D., Professor of Anatomj', Vanderbilt University Medical School, 1812 Broad Street, Xashville, Tenn. Dahlgren, Ulric, A.B., M.S., Professor of Biology, Princeton University, 204 Guyot Hall, Princeton, N. J. Danchakoff, Vera, M.D., Assistant Professor of Anatomy, Columbia University, 4S7 W. 59th Street, New York City. Danforth, Charles Haskell, A.M., Ph.D., Associate Professor of Anatomj', Washington University Medical School, St. Louis, Mo. Darrach, William, A.M., M.D., Assistant Attending Surgeon, Presbyterian Hospital, Instructor in Clinical Surgery, Columbia University, 4? West 50th Street, Neiv York, N. Y. Davis, David M., B.S., M.D., Instructor in Urology and Pathologist, Brady Urological Institute, Johns Hopkins Hospital, 1312 Eutaw Place, Baltimore, Md. Davis, Henry K., A.B., A.M., Instructor in Anatomy, Cornell University Medical College, Ithaca, N . Y . Dean, B.ashford, A.M., Ph.D., Professor of Vertebrate Zoology, Columbia University, Curator of Fishes and Reptiles, American Museum Natural History, Riverdale-on-Hudson, New York City. Detwiler, S.vmuel Ra-VDALL, Ph.B., A.M., Yale University, Osborne Zoological Laboratory, New Haven, Conn. Dexter, Franklin, M.D., S47 Marlborough Street. Boston, Mass. Dixon, A. Francis, M.B., Sc.D., University Professor of Anatomy, Trinity College. 7.^ Grosvenor Road. Ratlimincs, Dublin. Ireland. DoDSON, John Milton, A.M., M.D., Dean and Professor of Medicine, Rush Medical College, University of Chicago, 5S17 Blackston Avenue, Chicago, III. Dolley, D. H., A.m., M.D., Professor of Pathology, University of Missouri, Columbia, Mo. Donaldson, Henry Herbert, Ph.D., D.Sc. (Ex. Com. '09-'13, Pres. '16-), Professor of Neurology, The Wistar Institute of Anatomy and Biology, Woodland Avenue and 36th Street, Philadelphia, Pa. 64 AMERIC.\Is' ASSOCIATION OF ANATOMISTS Donaldson, John C, B.S., M.D., Instructor in Anatomy, University of Cincinnati Medical College, Cincinnati, Ohio. Downey, Hal, A.M., Ph.D., Professor of Histology, Department of Animal Biology, University of Minnesota, Minneapolis, Minn. DuBREuiL, G., M.D., Professor of Anatomy, Instilut d'Anatomie. FacuUe de Medicine, Bordeaux, France. Ddesberg, Jules, M.D., Research Associate, Carnegie Institution, Department of Embryologj', Johns Hopkins Medical School, Baltimore, Md. Dunn, Elizabeth Hopkins, A.M., M.D., Marine Biological Laboratory, Woods Hole, Mass. Eaton, Paul Bakxes, A.B., M.D., 1306 W. Lerington St., Baltimore, Md. EccLES, Robert G., M.D., Phar.D., 681 Tenth Street, Brooklyn, N. Y. Edwards, Charles Lincoln, Ph.D., Director of Nature Stud5', Los Angeles City Schools, 10S2 West S9th Place, Los Angeles, Calif. Eggerth, Arnold Henry, Assistant in Bacteriology, University of Michigan, Ann Arbor, Michigan. Elwtn, Adolph, A.m., Assistant Professor of Anatomy, Long Island College Hospital; Instructor of Zoology, Columbia University, Henry and Pacific Sts., Brooklyn, N'ew i^ork. Emmel, Victor E., M.S., Ph.D., Assistant Professor of Anatomy, L'niversity of Illinois College of Medicine, Congress and Honore Streets, Chicago, III. EssicK, Charles Rhein, B.A., M.D., oZO Franklin Street, Reading, Pa. Evans, Herbert McLean, B.S., M.D., Professor of Anatomy, University of California, Berkeley, Calif. Evans, Thomas Horace, M.D., Associate Professor of Anatomy, Long Island College Hospital, Henry and Amity Sts., Brooklyn, New York. Evatt, Evelyn John, B.S., M.B., Professor of Anatomy, Royal College of Surgeons, Dublin, Ireland. Eycleshymer, Albert Chauncey, Ph.D., M.D., Professor of Anatomy, Medical College, University of Illinois, Honore and Congress Streets, Chicago. III. Ferris, Harry Burr, A.B., M.D., Hunt Professor of Anatomy and Head of the Department of Anatomy, Medical Department, Yale University ,395 St . Ronan Street, New Haven, Conn. Fetterolf, George, A.B., M.D., Sc.D., Assistant Professor of Anatomy, University of Pennsylvania, ISi South 20th Street, Philadelphia, Pa. FiscHELis, Philip, M.D., Assistant Professor and Director of the Laboratory of Histology and Embryology, Medical School. Temple University, 8B8 North 5th Street, Philadelphia, Pa. Fisher, Homer G., A.M., Student, Johns Hopkins Medical School, Baltimore, Md. Flint, Joseph Marshall, B.S., A.M., M.D. (Second Vice-Pres. '00-'04), Professor of Surgery, Yale University, 3S0 Temple Street, New Haven, Conn. FoRMAN, Jonathan, A.B., M.D., Assistant Professor of Pathology, College of Medicine, Ohio State University, Naval Hospital, Hampton Roads, Virginia. Gage, Simon Henry, B.S. (Ex. Com. '06-'ll), Professor of Histology, and Embryology, Emeritus, Cornell University, 4 South Avenue, Ithaca, N. Y. Gallaudet, Bern Budd, A.M., M.D., Assistant Professor of Anatomy, Columbia University, Consulting Surgeon Bellevue Hospital, 105 East 19th Street, New York, N. Y. MEMBERS 65 Geddes, a. C.vmpbell, M.B., M.D., Ch.B., F.R.S.E., Professor of Anatomy, McGill University, Manireal, Canada. (Officer Canadian Medical Corps.) Gbe, Wilson, M.A., Ph.D., Professor of Biology, Emory University, Oxford, Ga. GiBsox, G. H., !M.D., Stipendiary Magistrate, Doctor of Medicine, Waitangi Chatham Islands, Xew Zealand. Gibson, James A., M.D., Professor of .\natomy, Medical Department, University of Buffalo, 2Jf High Street, Buffalo, N. Y. GiLLASPiE, C, ;\I.D., Professor of Anatomy, University of Colorado, School of Medicine, Boulder, Colorado. GILM.A.X, Philip Kingsworth, B.A., M.D., F.A.C.S., Clinical Instructor of Surgerj-, Stanford University Medical School, 350 Post Street, San Francisco, Calif. Globus, J. H., B.A., M.D.. Pathologist, Montefiore Home and Hospital, Bronx, Neic York City. GoETSCH, Emil, Ph.D., M.D., Associate Surgeon, Johns Hopkins Hospital, Baltimore, Md. Greene, Charles W., A.M., Ph.D., Professor of Physiology and Pharmacology, Universitj- of Missouri, 814 Virginia Avenue, Columbia, Mo. Greenman, Milton J., Ph.B., M.D., Sc.D., Director of The Wistar Institute of Anatomy and Biology, 36th Street and Woodland Avenue, Philadelphia, Pa. Gudernatsch, J. F., Ph.D., Assistant Professor of Anatomy, Cornell University Medical College, A^ew York City. Guild, Stacv R., A.M., Instructor in Anatomy, University of Michigan, 12-21 Olivia Avenue, Ann Arbor, Mich. Gutsell, Robert S., A.B., Teaching Fellow in Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. GuYER, Michael F., Ph.D., Professor of Zoology, University of Wisconsin, Madison, Wis. Halsted, Willi AM Stewart, M.D., Sc.D., LL.D., F.R.C.S., Professor of Surgery, Johns Hopkins University, 1201 Eutaw Place, Baltimore, Md. Hamann, C.\kl a., M.D. (Ex. Com. '02-'04), Professor of Applied Anatom}' and Clinical Surgery, Western Reserve University, 416 Osborn Building, Cleveland , Ohio. Hardestt, Irving, A.B., Ph.D. (Ex. Com. '10 and '12-'15), Professor of Anatomy and head of Department of .\natomy, Richardson Memorial Building, Tulane University of Louisiana, New Orleans, La. Hare, Earl R., A.B., M.D., F.A.C!S., 623 Syndicate Building, Minneapolis, .Minn. Harrison, Ross Granville, Ph.D., M.D. (Pres. '12-'14), Bronson Professor of Comparative Anatomy, Osborne Zoological Laboratory, Yale University, New Haven, Conn. Harvey, Basil Coleman Hy.'itt, A.B., M.B., Associate Professor of Anatomy, University of Chicago, Department of A natomy. University of Chicago, Chicago, III. (Captain Medical Officers Reserve Corps, U. S. .\rmy.) Hatai, Shinkishi, Ph.D., Associate in Neurology, Wistar Institute of Anatotny and Biology, 36th Street and Woodland Avenue, Philadelphia, Pa. Hazen, Charles Morse, A.M., M.D., Professor of Physiology, Medical College of Virginia, Richmond, Bon Air, Va. 66 AMERICAN ASSOCTATION OF ANATOMISTS Heaget, Francis Wenger, A.B., M.D., Assistant Professor of Anatomy, Creigh ton Medical College, Omaha, Neb. Heisler, John C, M.D., Professor of Anatomy, University of Pennsylvania, 3829 Walnut Street, Philadelphia, Pa. Heldt, Thomas Johanes, A.M., M.D., Clinical Assistant in Psychiatry, P.v;/ chialric Institute, Ward's Island, New York City. Hemler, Wm. Francis, M.D., Assistant Professor of Anatomy, Georgetown Vni versity, Washington, D. C. Herrick, Charles Judson, Ph.D. (Ex. Com. '13-) Professor of Neurology, University of Chicago, Laboratory of Anatomy, University of Chicago, Chicago, III. Hertzler, Arthur E., M.D., F.A.C.S., Associate in Surgery, University of Kansas, 1316 Rialto Building, Kansas City, Mo. Herzog, Maximilian, M.D., LL.D., Professor of Pathology and Dean Medical Department, Lagola University, 1S58 Fulton Street, Chicago, III. Heuser, Chester H., A.M., Ph.D., Fellow in Anatomy, Wistar Institute of Anatomy, S6th Street and Woodland Avenue, Philadelphia, Pa. Hewson, Addinell, A.M., M.D., Professor of Anatomy, Philadelphia Polyclinic for Graduates in Medicine, Professor of Anatomy and Histology, Temple University, 21£0 Spruce Street, Philadelphia, Pa. Hill, Howard, M.D., 1334 Rialto Building, Kansas City, Mo. Hill, James Peter, D.Sc, F.R.vS., Todrell Professor of Zoology and Comparative Anatomy, University of London, University College, Gower Street, London, W.C., England. Hilton, William A., Ph.D., Professor of Zoology, Pomona College, Direc'or Laguna Marine Laboratory, Claremont, Calif. Hines, Marion, A.B., Instructor in Anatomy, University of Chicago, Chicago, Illinois. Hoeve, Htjbertus H. J., M.D., Hoeve Hospital, Meherrin, Virginia. Holt, Caroline M., A.M., Ph.D., Instructor in Biology, Simmons College, Boston, Mass. Hooker, Davenport, M.A^Ph.D., Assistant Professor of Anatomy, Anatomical Laboratory, Yale University School of Medicine, Neio Haven, Conn. Hopewell-Smith, Arthur, L.R.C.P. M.R.C.S., L.D.S., Professor of Dental Histology and Comparative Odontology, University of Pennsylvania Dental College, Philadelphia, Pa. Hopkins, Grant Sherman, Sc.D., D.V.M., Professor Comparative Veterinary Anatomy, Cornell University, Ithnca, N . Y . HosKiNS, E. R., A.M., Ph.D., Acting Assistant Professor of Anatomy, New York University and Bellevue Medical College, SSS East 26th Street, New York City. HosKiNs, Margaret Morris, Ph.D., Instructor in Histology and Embryology, New York University and Bellevue Medical College, 338 East 26th Street, New York City. HrdliCka, Ales, M.D., Curator of the Division of Physical Anthropology, United States National Muse^tm, Washington, D. C. Huber, G.Carl, M.D. (Second Vice-Pres. 'OO-'Ol, Secretary-Treasurer '02-' 14, Pres. '14-'16) Professor of Anatomy and Director of the Anatomical Labora tories,_University of Michigan, 1330 Hill Street, Ann Arbor, Mich. MEMBERS 67 Huntington, George S., A.M., M.D., D.Sc, LL.D. (Ex. Com. '95-'97, '04-'07, 'IS-, Pres. '99-'03), Professor of Anatomy, Columbia University, J,S7 West 59th Street, New York, N. Y. Ingalls, N. William, M.D., Associate Professor of Anatomy, Western Reserve University, St. Clair and East 9th Streets, Cleveland, Ohio. Jackson, Clarence M., M.S., M.D. (Ex. Com. '10-'14, Vice-Pres. '16), Professor and Head of the Department of Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Jenkins, George B., M.D., Professor of Anatomy, Department of Anatomy, State University of Iowa, Iowa City, Iowa. Johnson, Charles Eugene, A.M., Ph.D., Instructor in Comparative Anatomy of Vertebrates, Department of Animal Biology, University of Minnesota, Minneapolis, Minn. Johnson, Franklin P., A.M., Ph.D., Associate Professor of Anatomy, University of Missouri, 41^ Stewart Road, Columbia, Mo. Johnson, Sydney E., M.S., Ph.D., Instructor in Anatomy, Northwestern University Medical School, Chicago, III. Johnston, John B., Ph.D., Professor of Comparative Neurology, University of Minnesota, Minneapolis, Minn. Jordan, Harvey Ernest, Ph.D. (Ex. Com. 'IS-), Professor of Histology and Embryology, University of Virginia, 34 University Place, Charlottsvilie, Va. Kampmeier, Otto Frederick, A.B., Ph.D., Assistant Professor of Comparative Anatomy and Embryology, School of Medicine, University of Pittsburgh, Pittsburgh, Pa. Kappers, Cornelius Ubbo Aribns, M.D., Director of the Central Institute for Brain Research of Holland, Mauritskade 81, Amsterdam, Holland. Keegan, John J., A.M., M.D., Pathological House Officer, Peter Bent Brigham Hospital, 721 Huntington Avenue, Boston, Mass. Kbiller, William, L.R.C.P. and F.R.C.S.Ed. (Second Vice-Pres. '98-'99), Professor of Anatomy, Medical Department University of Texas, State Medical College, Galveston, Texas. Keith, Arthur, M.D., LL.D., F.R.C.S., F.R.S., Hunterian Professor of Anatomy, College of Surgeons, London, England. Kernan, John D., Jr., A.B., ^I.D., Assistant in Anatomy, Columbia University, 1S6 East 79th Street, New York City. Kerr, Abram T., B.S., M.D. (Ex. Com. '10-'14), Professor of Anatomy, Cornell University Medical College, Ithaca, N. Y. Key, J. A., B.S., Student, Johns Hopkins Medical School, Baltimore, Md. Kingery, Hugh McMillan, A.M., Instructor in Histology and Embryology, Cornell University, Ithaca, N. Y. Kingsbury, Benjamin F., Ph.D., M.D., Professor of Histology and Embryology Cornell University, 802 University Avenue, Ithaca, A'. Y. Kingsley, John Sterling, Se.D., Professor of Zoology, University of Illinois, Urbana, III. King, Helen Dean, A.B., A.M., Ph.D., Assistant Professor of Embryology, Wistar Institute of Anatomy, 36th Street and Woodland Avenue, Philadelphia, Pa. KiRKHAM, William Barri, Ph.D., Assistant Professor of Biology, Sheffield Scientific School, Yale University, 103 Everit Street, Neiv Haven, Conn. THE ANATOMICAL RECORD, VOL. 14, XO. 1 68 AMERICAN ASSOCIATION OF ANATOMISTS KiTTELSON, John A., B.S., A.M., Instructor in Anatomy, i'mversity of Nebraska College of Medicine, Omaha, Neb. Knower, Henry McE., A.B., Ph.D. (Ex. Com. '11-'15), Professor of Anatomy, Medical College, University of Cincinnati, Cincinnati, Ohio. Koch, John C, B.S., M.D.. 704 North Strieker Street, Baltimore, Md. KoFOiD, Charles Atwood, Ph.D., Professor of Zoology, University of California, , Assistant Director San Diego Marine Biological Station, S616 Etna Street, Berkeley, Calif. KtjNiTOMO, Kanae, M.D., Professor of Anatomy, Nagasaki Medical School, Nagasaki, Japan. K0NKEL, Beverly Waugh, Ph.B., Ph.D., Professor of Zoology, Lafayette College, Easton, Pa. KuNTZ, Albert, Ph.D., Associate Professor of Histology and Biology, Department of Anatomy, St. Louis University School of Medicine, St. Louis, Mo. Kdtchin, Mrs. Harriet Lehmann, A.M., "The Mapleicood," Green Lake, Wisconsin. Ktes, Preston, A.M., M.D., Assistant Professor of Experimental Pathology, Department of Pathology, University of Chicago, Chicago, III. Lambert, Adrian V. S., A.B., M.D., 168 East 71st Street, New York, N. Y. Landacre, Francis Leroy, Ph.D., Professor of Anatomy, Ohio State University, 2026 Inka Avenue, Coluinhiis, Ohio. Lane, Michael Andrew, B.S., 122 S. California Avenne, Chicago, III. LATIMER, Homer B., A.M., Associate Professor of Zoology, University of Nebraska, 1226 South 26th Street, Lincoln, Neb. Laurens, Henry, Ph.D., Assistant Professor of Biology, Yale University, Osborne Zoological Laboratory, New Haven, Conn. Lee, Thomas G., B.S., M.D. (Ex. Com. '08-'10, Vice Pres. '12-'14), Professor of Comparative Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Leidy, Joseph, Jr., A.M., M.D., 1S19 Locust Street, Philadelphia, Pa.. Lewis, Dean D., M.D., Assistant Professor of Surgery, Rush Medical College, People's Gas Building, Chicago, III. Lewis, Frederic T., A.M., M.D. (Ex. Com. '09-'13, Vioe-Pres. '14-'16), Associate Professor of Embryology, Harvard Medical School, Boston, Mass. Lewis, Margaret Reed, M. A., Collaborator, Department of Embryology, Carnegie Institution of Washington, Johns Hopkins Medical School, Baltimore, Md. Lewis, Warren Harmon, B.S., M.D. (Ex.Com.'09-'ll, '14-), Professor of Physiological Anatomy, Johns Hopkins Medical School, Baltimore, Md. LiLLiE, Frank Rathay, Ph.D., Professor of Embryology, Chairman of Department of Zoology, University of Chicago; Director Marine Biological Laboratory, Woods Hole, Mass., University of Chicago, Chicago, III. LiNEBACK, Paul Eugene, A.B.,M.D., Associate Professor of Anatomy, Atlanta Medical College, Emory University, Atlanta, Ga. Locy, William A., Ph.D., Sc.D., Professor of Zoology and Director of the Zoological Laboratory, Nortliwestern University, 1 745 Orrington A venue, Evanston ,111. LoEB, Hanau Wolf, A.M., M.D., Professor and Director of the Department of the Diseases of the Ear, Nose and Throat, St. Louis University, 537 North Grand Avenue, St. Louis, Mo. MEMBERS 69 Lord, Frederic P., A.B., M.D., Professor of Anatomy, Dartmouth' Medical School, Hanover, N . H . Low-ret, Latvson Gentry, A.M., M.D., Assistant in Neuropathology, Harvard Medical School; Psychopathic Hospital, 74 Fenwood Road, Boston, Mass. Macklin, C. C, I\LB., Associate in Anatomy, Department of Anatomy, Johns Hopkins Medical School, Baltimore, Md. McCmxG, Clarence E., A.M., Ph.D., Professor of Zoology, University of Pennsylvania, Philadelphia, Pa. McClure, Charles Freeman Williams, A.^L, Sc.D. (Vice-Pres. 'lO-'ll. Ex. Com. '12-'16), Professor of Comparative Anatomy, Princeton University, Princeton, X. J. McCoRMACK, William Eli, M.D., Adjunct Professor of Anatomy, University ■ of Louisville, Medical Department, 101 11". Chestnut Street, Louisville, Ky. McCoTTER, RoLLO E., M.D., Professor of Anatomy, Medical Department, University of Michigan, lOiS Ferdon Road. Ann Arbor, Mich. McFarland, Frank Mace, A.^L, Ph.D., Professor of Histology, Leland Stanford Junior University, 3 Cabrillo Avenue, Stanford University, Calif. McGiLL, Caroline, A.M., Ph.D., M.D., Physician, 513 Daly Bank Building, Butte, Mont. McJuNKiN, F.A., M.A., M.D., Professor of Pathology, .Marquette University, School of Medicine, Milwaukee, Wisconsin. McKibben, Paul S., Ph.D., Professor of Anatomy, Faculty of Medicine, Western University, London, Ontario, Canada. McMuRRiCH, James Playfair, A.M., Ph.D., LL.D. (Ex. Com. '06-'07, '17, Pres. '08-09), Professor of Anatomy, University of Toronto, 75 Forest Hill Road, Toronto, Canada. McWhorter, John E., M.D., Worker under George Crocker Research Fund, College of Physicians and Surgeons, Columbia University, g05 West 107th Street, New York, X. Y. Magath, Thomas By-rd, Ph.B., M.S., Ph.D., Instructor in Anatomy, University of Ulinbis, College of .Medicine, Chicago, III. Mangpm, Charles S., A.B., M.D., Professor of Anatomy, University of North Carolina, Chapel Hill, N. C. Malone, Edward Fall, A.B., M.D., Associate Professor of Anatomy, University of Cincinnati, College of Medicine, Station V, Cincinnati , Ohio. Mark, Edward Laurens, Ph.D., LL.D., Hersey Professor of Anatomy, and Director of the Zoological Laboratory, Harvard University, 109 Irving Street, Cambridge, Mass. Matas, Rudolph, M.D., LL.D., Professor of Surgery, Tulane University of Louisiana, 2S55 St. Charles Avenue, New Orleans, La. Maximow, Alexander, M.D., Professor of Histology and Embryology at the Imperial Military Academy of Medif^ine. Petrograd, Russia, Botkinskaja S, Petrograd, Russia. Mellus, Edward Lindon, M.D., 12 Fuller Street, Brookline, Mass. Mercer, William F., Ph.M., Ph.D., Professor of Biology, Ohio University, Box S84, Athens, Ohio. 70 AMERICAN ASSOCIATION OF ANATOMISTS Methexv, D. Gregg, M.D., L R.C.P., L.R.C.S., Edin.— L.F.P.S., Glasg., Assistant Professor of Anatomy, Jefferson Medical College, Uth and Clinton Streets, Philadelphia, Pa. Meyer, Adolf, M.D., LL.D., Professor of Psychiatry and Director of the Henry Phipps Psychiatric Clinic, Johns Hopkins Hospital, Baltimore, Md. Meter, Arthur W., S.B., M.D. (Ex. Com. '12-'16), Professor of Anatomy, Leland Stanford Junior University, Stanford University, Calif. Miller, Adam M., A.M., Professor of Anatomy, Long Island College Hospital, 335 Henry Street, Brooklyn, X. Y. Miller, M. M., Ph.D., Instructor in Anatomy, North Western University .Medical School, Chicago, Ul. Miller, WiLLi.\M Snow, M.D. (Vice-Pres. '08-'09), Professor of Anatomy, Universitj' of Wisconsin, 2001 Jefferson Street, Madison, Wis. Mi.x;ter, Samuel Jason, B.S., M.D., Visiting Surgeon Massachusetts General Hospital, 180 Marlboro Street, Boston, Mass. MooDiE, Roy L., A.B., Ph.D., Instructor in Anatomy, University of Illinois Medical College, Congress and Honore Streets, Chicago, III. Moody, Robert Obton, B.S., M.D., Associate Professor of Anatomy, University of California, S826 Garber Street, Berkeley, Calif. Morrill, Charles V., A.M., Ph.D., Instructor in Anatomy, Cornell University Medical School, 1st Avenue and 28th Street, New York, N' . Y. Muller, Henry- R., A.B., M.D., Assistant in Pathology, Cornell University Medical College, 1st Avenue and 28th Street, New York, N. Y . MuNsoN, John P., M.S., Ph.D., Head of the Department of Biology, Washington State Normal School, 706 North .Anderson Street, Ellensburg, Washington. MuRPHEY', Howard S., D.V.M., Professor of Anatomy and Histology, 519 Welch Avenue, Station A, Ames, la. Murray, H. A., Jr., A.B., Student, Columbia University, College of Physicians and Surgeons, 437 West 59th Street, New York City. Myers, Burton D., A.M., M.D. , Professor of Anatomy and Secretary of the Indiana Universit}' School of Medicine, Indiana University, Bloomington, Ind. Myers, Jay A., M.S., Ph.D., Instructor in Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Myers, Mae Lichten-walner, M.D., Associate Professor of Anatomy and Director of the Laboratories of Histology and Embrj'ology, Women's Medical College of Pennsylvania, North College Avenue and 21 si Street, Philadelphia, Pa. Nachtbieb, Henrt Francis, B.S., Professor of Animal Biology and Head of the Department, University of Minnesota, Minneapolis, Minn. Neal, Herbert Vincent, A.M., Ph.D., Professor of Zoology, Tufts College, Tufts College, Mass. XoBLE, Harriet Isabel, 262 Putnam Avenue, Brooklyn, N. Y. NoRRis, Edgar H., B.S., A.M., Assistant in Anatomy, Institute of Anatomy, University of Minnesota. Minneapolis, Minn. NoBEis, H. W., A.B., Professor of Zoology, Grinnell College, Grinnell, Iowa. O'DoN.^GHUE, Charles H., D.Sc, F.Z.S., Senior Assistant in Zoology and Comparative .\natomy. University College, Gower St., London W. C, England. OsTERCD, Hjalmar L., A.B., A.M., Teachin-g Ffellow in Anatomy, Institute of .inatomy. University of Minnesota, .Minneapolis, Minn. MEMBERS 71 Ott, Martin D., A.B., Fellow in Anatomy, University of Minnesota, Institute of Anatomy, Minneapolis, Minn. Painter, Theophilus S., Ph.D., Adjunct Professor of Zoology, School of Zoology, University of Texas, Austin, Texas. Papanicolaou, George, Ph.D., M.D., Instructor in Anatomy, Cornell University Medical College, New Y'ork City. Papez, James Wenceslas, B.A., M.D., Professor of Gross Anatomy and Xeurolog)', Atlanta Medical College, Atlanta, Ga. Parker, George Howard, D.Sc, Professor of Zoology, Harvard University, 16 Berkeley Street, Cambridge, Mass. Paton, Stewart, A.B., M.D., Lecturer in Neurobiology, Princeton University, Princeton, \ . J . Patten, William, Ph.D., Professor of Zoology, Dartmouth College, Hanover, N. H. Paterson, a. ^Ielville, M.D., F.R.C.S., Professor of Anatomy, University of Liverpool, Liverpool, England. Patterson, John Thom.^s, Ph.D., Professor and Chairman of the School of Zoology, University of Texas, University Station, Austin, Texas. Pfeiffer, John A. F., M.A., M.D., Senior Assistant Physician and Pathologist, Government Hospital for the Insane, Washington, D. C. PiERSOL, George A., M.D., Sc.D. (Vice-Pres. '93-'94, '9S-'99, '06-'07, Pres. '10'11), Professor of Anatomy, University of Pennsylvania, 4724 Chester Avenue, Philadelphia, Pa. Piersol, William Hunter, A .B . , M .B . , Associate Professor of Histology and Embryolog}', University of Toronto, 26 Albany Avenue, Toronto, Canada. Pohlman, Augustus G., M.D., Professor of Anatomy, Medical Department, St. Louis University, 1402 South Grand Avenue, St. Louis, Mo. Potter, Peter, M.S., M.D., Oculist and Aurist, Murray Hospital, Butte, Montana, 4II-4IS Hennessy Building, Butte, Montana. PoTNTER, Charles W.M., B.S.,M.D., Professor of Anatomy, College of Medicine, University of Nebraska, Omaha, Neb. Prentiss, H. J., M.D., !M.E., Professor of Anatomy, State University of Iowa, Iowa City, Iowa. Prtor, Joseph William, M.D., Professor of Anatomy and Physiology, State College of Kentucky, 261 North Broadway, Lexington, Ky. Radasch, Henry E., M.S., M.D., Assistant Professor of Histology and Embryology, Jefferson Medical College, Daniel Baugh Institute of Anatomy, 11th and Clinton Streets, Philadelphia, Pa. Ranson, Stephen W., M.D., Ph.D., Professor of Anatomy, Northwestern University Medical School, 2431 Dearborn Street, Chicago, III. Rasmussen, Andrew T., A.B., Ph.D., Instructor in Neurology, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Reagan, Franklin P., Ph.D., Procter Fellow in Comparative Anatomy, Princeton University, Princeton, N. J. Reed, Hugh Daniel, Ph.D., Assistant Professor of Zoology, Cornell University, McGriiw Holl, Ithaca, A". }'. Reinke, Edwin, Ph.D., Associate Professor of Zoology, Vanderbilt University, Nashville, Tenn. 72 AMERICAN ASSOCIATION OF ANATOMISTS Retzer, Robert, M.D., Associate Professor of Anatomy, University of Pittsburgh, Anatomical Laboratories, University of Pittsburgh, Pittsburgh, Pa. Revell, Daniel Graisberry, A.B., M.B., Professor of Anatomy, University of Alberta, Edmonton, Alberta, Canada. Rhinehart, D.A., A.M., M.D., Professor of Anatomy, University of Arkansas, Old State House, Little Rock. Ark. Rice, Edward Loranus, Ph.D., Professor of Zoology, Ohio Wesleyan University, Delaware, Ohio. RiNGOEN, Adolph R., A.M.. Assistant in Zoology, University of Minnesota, Minneapolis, Minn. Robertson, Albert Duncan, B.A., Professor of Biology, Western University, London, Ontario, Canada. Robinson, Arthur', M.D., F.R.C.S. (Edinburgh), Professor of Anatomy, University of Edinburgh, The University , Anatomy Department, Edinburgh, Scotland. Robinson, Byron L., A.B., M.A., Teaching Fellow in Anatomj', Institute of Anatomy, University of Minnesota, Minneapolis, Minn. Rose, Frank H., A.B., Austin Teaching Fellow, Department of Anatomy, Harvard Medical School, Boston, Mass. Ruth, Edward S., M.D., Professor of Anatomy, University of the Philippines, College of Medicine and Surgery, Manila, P. I. Sabin, Florence R., B.S., M.D., Sc.D. (Second Vice-Pres. '08-'09), Associate Professor of Anatomy, Johns Hapkins University, Medical Department, Baltimore, Md. Sanford, Eldon Williams, M.A., Ph.D., Assistant in Anatomy, Johns Hopkins Medical School, Baltimore, Maryland. Santee, Harris E., A.M., Ph.D., M.D., Professor of Anatomy, Jenner Medical College, and Professor of Neural Anatomy, Chicago College of Medicine and Surger}', B806 Warren Avenue, Chicago, III. ScAMMON, Richard E., Ph.D., Professor of Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn. SCHAEFER, Marie Charlotte, M.D., Associate Professor of Biology, Histology and Embryology, Medical Department, University of Texas, 701 North Pine Street, San Antonio, Texas. ScHAEFFER, Jacob Parsons, A.M., M.D., Ph.D., Professor of Anatomy and Director of the Daniel Baugh Institute of Anatomy, Jefferson Medical C, allege, 10th and Walnut Streets, Philadelphia, Pa. ScHOCHET, Sidney Sigsfried, M.D., Instructor in Gynaecology, Northwestern University, Marshall Field, Annex Building, Chicago, III. Schoemaker, Daniel M., B.S., M.D., Professor of Anatomy, Medical Department, St. Louis University, 1402 South Grand Avenue, St. Louis, Mo. Schulte, Hermann von W., A.B., M.D. (Ex. Com. '15) Professor of Anatomy, Creighton Medical College, Omaha, 'Neb. Schultz, Adolph H., Ph.D., Collaborator in Embryology, Carnegie Institution, Johns Hopkins Medical School, Baltimore, Md. Schmitter, Ferdinand, A.B., M.D., Majvr Medical Corps, U . S. Army, Columbus Barracks, Colunibus, Ohio. Scott, John W., A.M., Ph.D., Professor of Zoology, University of Wyoming, Laramie, Wyo. MEMBERS 73 Scott, Katherinb Julia, A.B., M.D., Instructor in Anatomy, Department of Anatomy. University of California, Berkeley, Calif. Selling, Lawrence, A.B., M.D., Selling Building, Portland, Ore. Senior, H. D., M.B., D.Sc, F.R.C.S., Professor of Anatomy, New York Universit5', and Bellevue Hospital Medical College, 338 East 26lh Street, New York, N. Y. (Middlesex War Hospital, Xapsbury, Herts, England. Sharp, Cl.^tton, A.B., M.D., Instructor in Anatomy, Columbia University, 437 West 59th Street. New York City. Sheldon, Ralph Edward, A.M., M.S., Ph.D., Professor of Anatomy, University of Pittsburgh Medical School, Grant Boulevard, Pittsburgh, Pa. Shields. Randolph Tucker, A.B.. M.D., Professorof Histology and Embryology, School of Medicine, Shantung Christian University, Tsinanfu, Shantung, China. Shufeldt,R.W,, M,D,, Major Medical Corps, U, S. A. {Retired) , S3B6 Eighteenth Street, A'. W., Washington, D. C. Silvester, Charles Frederick, Curator of the Zoological Museum and Assistant in Anatomy, Princeton University,. 10 Nassau Hall, Princeton, N. J. Simpson, Sutherland, M.D., D.Sc, F.R.S.E. (Edin.), Professor of Physiology, Cornell University Medical College, Ithaca, N. Y. SissoN, Septimus, B.S., V.S,, Professor of Comparative Anatomy, Ohio State University, 274 Hth Avenue, Columbus, Ohio. Sluder, Greenfield, M.D., Clinical Professor of Laryngology, Washington University Medical School, 3542 Washington Avenue, St. Louis, Mo. S.mith, George Milton, A.B., M.D., Attending Surgeon Waterbury Hospital, 47 Pine Street, Waterbury, Conn. Smith, Grafton Elliot, M.A., M,D,, F.R.S., Professor of Anatomy and De.-n of the Faculty of Medicine, The University, Manchester, England. S-mith, H. p., A,B., Research Fellow (Hooper Foundation for Medical Research), University of California, / St. Geo. Court, East 18th Street, Oakland, Calif. Smith, J. Holmes, M.D., Professor of Anatomy, L^niversity of Maryland, Greene and Lombard Streets, Baltimore, Md. Smith, M. DeForest, A.B., M.D., 43 East 25th Street, New York City. Smith, Philip Edward, M.S., Ph.D., Instructor in Anatomy, University of California, 1918 Haste Street, Berkeley, Calif. Smith, Wilbur Cleland, M.D., Assistant Professor of Anatomy, Tulane University, New Orleans, La. Snow, Perry G., A.B., M.D., Dean and Professor of Anatomy, University of Utah Medical School, Salt Lake City, Utah. Steensland, Halbert Severin, B.S., M.D., Professor of Pathology and Director of the Pathological Laboratory, College of Medicine, Syracuse University, 509 Orange Street, Syracuse, N. Y. Stewart, Chester A., A.M., Instructor in Anatomy, Institute of Anatomy, University of Minnesota. Minneapolis, Minn. Stiles, Henry Wilson, M.D., Professor of Anatomy, College of Medicine, Syracuse University, 309 Orange Street, Syracuse, N. Y. Stockard, Charles Rupert, M.S., Ph.D. (Secretary-Treasurer '14-), Professor of Anatomy, Cornell University Medical College, Neio York, N. Y. 74 AMERICAN ASSOCIATION OF ANATOMISTS Stotsenbueg, James M., M.D., Instructor in Anatomy, Wistar Inslituie of Anatomy and Biology, Philadelphia, Pa. Streeter, George L., A.M., M.D., (Ex. Com. '18-), Research Associate in Embryology, Carnegie Institution, Johns Hopkins Medical School, Baltimore, Md. Stromsten, Frank Albert, D.Sc, Assistant Professor of Animal Biology. State University of Iowa, 9^3 Iowa Avenue, Iowa City, Iowa. Strong, Oliver S., .A..M., Ph.D., Assistant Professor of Neurology, Columbia University, 4S7 West 59th Street, New York, N. Y. Strong, Reuben Myron, A.B., A.M., Ph.D. (Ex-Com. '16-), Professor of Microscopic Anatomy, Vanderbilt University Medical School, Nashville, Tenn. Sullivan, Walter Edward, A.M., Ph.D., Professor of Anatomy, Tufts College Medical School, 4'6 Huntington Avenue, Boston, Mass. Sundwall, John, Ph.D., M.D., Professor of Anatomy, University of Kansas, Lawrence, Kans. Sutton, Alan Calle.vder. A.B., M.D., Johns Hopkins Medical School, Baltimore, Md. (Abroad as Lieutenant in Medical Officers Reserve Corps.) Symington, Johnson, M.D., F.R.C.S., F.R.S., Professor of Anatomy, Queens University, Belfast, Ireland. Swift, Charles H.,M.D., Ph.D., Instructor in Anatomy, Department of Anatomy, University of Chicago, 56S3 Maryland Avenue, Chicago, III. Swindle, Gaylord, Ph.D., Instructor in Anatomy, Washington University Medical School, St. Louis, Mo. Taintor, F. J., M.D., Assistant Professor of Anatomy, St. Louis University, St. Louis, Mo. Taylor, Edward W., A.M., M.D., Assistant Professor of Neurology, Harvard Medical School, 457 Marlboro Street, Boston, Mass. Terry, Robert James, A.B., M.D. (Ex. Com. '08-'12), Professor of Anatomy, Washington University Medical School, St. Lcuis, Mo. Thompson, Arthur, M.A., M.B., LL.D., F.R.C.S., Professor of Anatomy, University of Oxford, Department of Human Anatomy, Oxford, England. Thorkelson, Jacob, M.D., Dillon, Mont. Thro, William C, A.M., M.D., Assistant Professor of Clinical Pathology, Cornell University Medical School, 38th Street and 1st Avenue, New York, N . Y . ThiJuinger, Joseph M., M.D., Professor of Anatomy, University of Alabama, School of Medicine, Mobile, Ala. Thyng, Frederick Wilbur, Ph.D., Assistant Professor of Anatomy, University and Bellevue Hospital Medical College, 3SS East S6th Street, New York, N.Y. Tilnby, Frederick, A.B., M.D., Professor of Neurology, Columbia University, 161 Henry Street, Brooklyn, N . Y. Todd, Thomas Wingate, M.B., Ch.B. (Mane), F.R.C.S. (Eng.), Professor of Anatomy, Medical Department Western Reserve University, Cleveland, Ohio. Tracy, Henry C, A.M., Ph.D., Professor of Anatomy, Marquette Medical School, Fourth and Reservoir Streets, Milwaukee, Wis. TuPPER, Paul Yoer, M.D., Clinical Professor of Surgery, Washington University Medical School, Wall Building, St. Louis, Mo. MEMBERS 75 Turner, C. L., B.A., M.A., Instructor in the Uepartiiient of Anatomy and Biology, Marquette Universily School of Medicine, Milwaukee, Wis. Waite, Frederick Clayton, A.M., Ph.D., Professor of Histology and Embryology, Western Reserve Universitj' School of Medicine, 1S5S East 9th Street, Cleveland, Ohio. Walker, George, M.D., Instructor in Surgery, Johns Hopkins University, corner Charles and Center Streets, Baltimore, Md. Walltn, Ivan E., M.A., D.Sc, Assistant Professor of Anatomy, Marqxiette University Medical College, Mihcaukee, Wis. Warren, James H., A.B., M.D., Assistant Professor of Anatomy, College of Medicine, Ohio State University, 469 Indianola Blvd., Columbus, Ohio. Warren, John, A.B., M.D., Associate Professor of Anatomy, Harvard Medical School, 2i0 Longwood Avenue, Boston, Mass. fiMajor Medical Reserve U. S. Army.) Waterston, David, M.A., M.D., F.R.C.S.Ed., Butte Professor of Anatomy, University of St. Andrews, St. Andrews, Fife, Scotland. Watkins, Richard W.'.tkin, B.S., Cedar Grove Farm, Granville, Ohio. Watson, Da^id Meredith Sears, M.Sc, F.Z.S., Lecturer in Vertebrate Paleontology, University College, Gower St., London W. C, England. Watt, J ames Crawford, B. A., M.B., Lecturer in Anatomy, University of Toronto, 20 Hawthorne Avenue, Toronto, Canada. Weed, Lewis Hill, A.M., M.D., Assistant Professor of Anatomy, Johns Hopkins Medical School, Baltimore, Md. Weidenreich, Franz, M.D., a.o. Professor and Prosector of Anatomy, 19 Vogesen Street, Strassburg, i. Els. Germany. Werber, Ernest I., Ph.D., Osborn Zoological Laboratory, Yale University, New Haven, Conn. West, Randolph, A.M., Student, College of Physicians and Surgeons, Columbia University, 437 West 59ih Street, Neiv York, N. Y. Wh^eldon, Thomas Foster, A.B., A.M., Bullard Fellow, Depnrlmenl of Anatomy, Harvard Medical School, Boston, Mass. Wheeler, Theodora, A.B., M.D., Carnegie Laboratory of Embryology, ,/ohns Hopkins Medical School, Baltimore, Md. White, Harry Oscar, M.D., Professor of Anatomy, Medical Department, University of Southern California, 516 E. Washington Street, Los Angeles, Calif. Whittenborg, a. H., M.D., Prof essor of Anatomy, College of Medicine, I'niversity of Tennessee, 718 Union Avenue, Rogers Hall, Memphis, Tenn. Wilder, Harris Hawthorne, Ph.D., Professor of Zoology, Smith College, S7 Belmont Avc7iue, Northampton, Mass. WiLLiA.Ms, James Willard, B.A., M.A., Professor of Biology, College of Yale in China, Changsha, China. [Care of G. H. Malone, Nanking, China.) Williams, Stephen Riggs, A.M., Ph.D., Professor of Zoology and Geology, Miami University, Oxford, Ohio. Willard, William A., A.M., Ph.D., Professor of Anatomy, University of Nebraska, College of Medicine, 42d Street and Dewey Avenue, Omaha, Neb. Wilson, J. Gorden, M.A., M.B., CM. (Edin.), Professor of Otology, North , western University Medical School, 2437 Dearborn Street, Chicago, HI. 76 AMERICAN ASSOCIATION OF ANATOMISTS Wilson, James Thomas, M.B., F.R.S., Challis Professor of Anatomy, University, Sydney, Australia. Wilson, Louis Blanchard, M.D., Director of Pathology Division, Mayo Clinic and Mayo Foundation, Professor of Pathology in the University of Minnesota, Mayo Clinic, Rochester, Minn. WiSLOCKi, George Bernays, A.B., M.D., Assistant in Anatomy, Johns Hopkins Medical School, Baltimore, Md. WiTHERSPOON, Thomas Caset, M.D., 307 Granite Street, Butte, Mont. Worcester, John Locke, M.D., Assistant Professor of Anatomy, University of Washington, Seattle, Washington. PROCEEDINGS OF THE AMERICAN SOCIETY OF ZOOLOGISTS FIFTEEXTH ANNUAL ^MEETING The fifteenth Annual Meeting of the .American Society of Zoologists was held, December 27 and 28, 1917, at the University of ^linnesota. Animal Morphology Building, ^Minneapolis, Minnesota. BUSINESS SESSION The business session was called to order by the President, Maynard ^I. ^letcalf, at 2.00 p.m., December 28. The Secretary being absent, W. C. Curtis consented to serve in this capacity for the meeting. Election of Members The following new members were elected upon nomination by the Executive Committee: BoYDEX, E. A., Ph.D. (Harvard), Instructor Comparative Anatomy, Harvard Medical School, 61 Clark Street, Newton Center, Mass. GuBERLET, J. E., A.M., Ph.D. (Illinois), Professor of Biology, Carroll College, Waukesha, Wis. Hanxe, R. T., A.B., M.A., Ph.D. (Pennsylvania), Assistant in Zoology, University of Pennsylvania. Zoological Laboratory, University of Pennsylvania, Philadelphia, Pa. HiCKEBXELL, L. M., A.B., A.M., Ph.D. (Princeton), Assistant Professor of Zoologj', Syracuse University, 1052 Ackerman Avenue, Syracuse, N. Y. Hyman, L. H., Ph.D. (Chicago), Research Assistant, Chicago University, Hull Zoological Laboratory. Chicago Utiivtrsity, Chicago, III. Michael. E. L., A.B., M.S. (California), Assistant Scripps Institution, La Jolla, California. Parshley, H. M., A.m.. Sc.D. (Harvard), Assistant Professor of Zoology, Smith College, 2S0 Elm Street, Xorthamplon, Mass. Streeter, George L.. A.M., M.D., Research Associate in Embryology, Carnegie Institution, Johns Hopkins Medical School, Baltimore, Md. YocuM, H. B., A.B, (Oberlin), M.A., Ph.D. (California), Professor of Zoology, Washburn College. 1813 Huntoon Street, Topeka. Kansas. 78 AMERICAN SOCIETY OF ZOOLOGISTS Election of Officers The nominations for officers made by the Committee on Nominations (H. V. Wilson, W. E. Kellicott and W. C. Curtis) were unaniniously elected. George Lefevre, for president during the year 1918. L. L. Woodruff, for vice-president during the year 1918. M. M. Metcalf, for member, Executive Committee to serve five years. Report of the Treasurer The following financial statement submitted by the SecretaryTreasurer, Caswell Grave, was read and accepted subject to its approval by an Auditing Conunittee consisting of Prof. H. S. Jennings and S. 0; Mast. Receipts during the year, 1917: Balance on hand .Tanuary 1, 1917 •. 8649.58 Dues for 191fi, (8) ; 52.50 Dues for 1917, 13 at 11.50 149.50 Dues for 1917, 183 at 7.00 1281 .00 Dues for 1917, 62 at 5.00 310.00 Dues for 1917, 2 at 6.50 Life Members 13.00 Dues for 1917, 1 at 4.50 Life Member 4.50 Divident (4th) Ind'l. Sav. and Lo.an Co 15.00 Interest at 4 per cent on Saving Bank deposits 29.43 Total$2504.51

Expenditures during the year, 1917:

Express charges $2.16 Telegram and telephone calls 1 . 55 Stationery, stamps, postcards 23 . 21 Typewriting and clerical assistance '. . . . 20.74 Printing announcements and programs 43.25 Loose leaf book for membership index 2.75 269 subscriptions for Journals, Wistar Inst 1677.00 Total$1770.66

Balance on hand December 28, 1917 $733.85 Report of Auditing Committee The Auditing Committee, to which the accounts of the Secretary-Treasurer were submitted in Baltimore January 7, 1918, has made the following report: PROCEEDINGS 79 Baltimore, Md., January 7, 1918. We have examined the accounts of the Secretary-Treasurer and find them to be correct. [Signed] H. S. Jennings, S. O. :\Iast. RESOLUTIONS The following resolutions were passed by unanimous votes: Concerning Time and Place for Annual Meetings In proposing the resolution concerning affiliations with other biological societies, the Executive Committee made the following statement : The Executive Committee of the .\merican Society of Zoologists wishes to dii-eet attention to the advantage of frequently holding our mid-winter meetings at the same place with those of other biological societies. We are aheady affiliated with the American Society of Naturahsts and generally meet in the same place with them, having usually one common session for the reading of scientific papers and one or more common social gatherings. We now frequently meet in the same place with others of the biological societies. It is hardly practicable, and probably is not desirable, each year to have all these societies meet in the same city, but it probably could to advantage be arranged to bring a good many of them together each year. When such a group of societies are gathered in one city, it may sometimes be advantageous to have one or possible more sessions in which two or more of the societies join, and a joint dinner or a common smoker for several or perhaps all of the societies is very pleasant. Yet, on the other hand, it would doubtless be unfortunate to have any organization, or any agreement, that would compel invariably joint sessions or even meeting in the same city. Your Executive Committee has considered how to secure the advantages of cooperation between the several societies without any interference with the complete freedom of each society each year to follow its own judgment as to place of meeting and natme of program. Some have suggested having a coordinating society of which we should all be members, but we have felt that this involved probably too much organization. The Physiological, Biochemical. Pharmacological and Pathological Societies have afiihated by a very siniplc method, namely by having the presidents and secretaries of the several Societies serve together as an executive committee for the affihated group, it being the intention of these four societies to have a common meeting place and some joint sessions. This plan, while well adapted for a small group of societies studying closely related subjects, might 80 AMERICAN SOCIETY OF ZOOLOGISTS not work out so well for a larger more diverse group if it implied an obligation for all the societies to meet together. Something still more flexible seems desirable, some arrangement that leaves each society free fiom any pressure to meet with the group, if, any year, special considerations should make separation advantageous. We propose for your consideration, and, if it meets your approval, for .your adoption, the following plan, namely to have our President and Secretaiy instructed to consult from year to year with the Presidents and Secretaries of the other biological societies in regard to common meeting place, joint sessions for scientific discussion, joint social gatherings, perhaps some avoidance of simultaneous discussion of the same subject in different societies, and any other matters of cooperation or coordination that may be proposed. Such consultation between the executive officers of the societies would put no pressure upon any society, but would provide a means for working out so much of cooperation and coordination as may from year to j'ear seem natural and advantageous. It is an arrangement so flexible as not to interfere with the growth of new interests and special affiliations, and yet it provides for the consideration annually of the relations between the societies in their meetings. If from such a consultation there should grow closer affiliation between some of the societies, such as has arisen in the Experimental Biology group, this woidd still not interfere with the continuance of the plan of general consideiation of possible joint ari'angements for any one year between a still larger mmiber of the societies. The plan we propose to you seems to give absolute freedom to each society and not even to exert pi-essure upon any, yet will secure to each a knowledge of the others plans and will provide a means for securing so much of cooperation each year as is desired. We therefoie propose to you the following resolution: — The Ameiican Society of Zoologists would call to the attention of the other professional biological societies the advisability of fiequently selecting a common time and place for their annual meetings, anil the President and Secretary are hereby instructed to consult with their respective Presidents and Secretaries of the American Association of Anatomists, American Society of Naturalists, the Botanical Society of Amei'ica, the Ecological Society' of America, and The Federation of Amei-ican Societies for Experimental Biology with the object of accomplishing this purpose for the meetings of 1918. The results of this consultation are to be submitted to the E.xecutive Committee for a final vote. And we further recommend that this report be brought again to the Societ.y at its next annual meeting with a view to its adoption as a pcinianent policy. We would call attention to the fact that passing this resolution does not change our relation to the Societj'^ of Naturalists, nor would passing of a similar lesolution by an other society interfere with an.y aflfiliations it may already have formed. PROCEEDINGS 81 The Society will note that our present By-Liiw 2, c contemplates just such action as is now recommended. Defining the duties and privileges of the Secretary-Treasurer, it says: "Whenever the proper officers of a number of related societies shall have a conference with a view to determining a common time and place for the several annual meetings, he shall act as the delegate of this Society." Our present Secretary suggests including also the President of the Society in this conference, to conform to the plan of the Federation for Experimental Biology, and this suggestion has been embodied in our report. The Society, on the motion by Mr. Lefevre, directed that a copy of this resolution be carried to the American Society of NaturaHsts in session at Pittsburgh. Concerning the Life and Work of Franklin Paine Mall During the year just closing death has called from our ranks the genial and able anatomist and embryologist Franklin Paine Mall. In his death American science has losst one of its eminent. devotees. Always true to the highest ideals of the investigator and teacher he endeared himself to all who were fortunate enough to become acquainted with him. His labors have been ended but the influence of his numerous publications and the excellence of his work will continue. In memory of his worth as a man and a scholar and in recognition of his devotion and contribution to Zoology we inscribe these minutes in the permanent records of the Society. This resolution was passed by a rising vote. Endorsement of Work of the Wistar Institute The American Society of Zoologists heartily endorses the existing arrangement regarding the Journals published by The Wistar Institute and expresses its thanks and appreciation for the services rendered through the Bibliographic Card Sj'stem. Concerning the Biological Station at Fair-port, Iowa The American Society of Zoologists, assembled in Minneapolis, having learned of the recent destruction by fire of the laboratory of the Biological Station at Fairport, Iowa, extends its sympath.y to the U. S. Bureau of Fisheries, and expresses the earnest hope that means will be found for the early restoration of the building and the resumption of the valuable work of the Station. 82 AMERICAN SOCIETY OF ZOOLOGISTS Of Appreciation for the Hospitality of the University of Minnesota The American Society of Zoologists thanivs the University of Minnesota and the local committee for the cordial reception and many attentions incident to the meetings in Minneapolis December 27 and 28, 1917. The Secretary of the society is hereby instructed to forward copies of this resolution to President Burton and to the chairman of the local committee, Prof. H. F. Nachtrieb. In regard to fisheries Whereas, the new economic conditions relating to the nation's food supply brought upon us by the world-war, make it vitally important that there should be a more thorough development, a greater utilization, and a more intelligent conserva.tion of our fishery resources, and \\'hereas, the Federal Government maintains more than sixty Agricultural Stations, each liberally equipped with materials, funds and men engaged in investigation and experimentation in the interests of agriculture, and Whereas, the Federal Covernment has as yet only one or two very poorly equipped and cheaply conducted stations at which investigation and expei'imentation in the interests of agriculture maj' be carried on, therefore be it Resolved by the American Society of Zoologists, that the Congress be requested to provide an adequate number of Fisheries Experiment Stations, equipped with material, funds and expert and practical personnel to do for the products of the seas, rivers and lakes what the Agricultural Experiment Stations and the Department of Agriculture are doing so well for the products of the land." In regard to problems of North Pacific Whereas, the world-war has brought home to us as never before a realization of the necessity of full and accurate knowledge of our food resources and the necessity of developing and utilizing these resources to the maximum extent compatil)le with their adequate conservation, and Whereas, our knowledge of the fishery resources of the North Pacific is very imperfect and wholly inadequate to serve as a basis for trustworthy conclusions as to the extent and permanence of these resources, or as to what is necessary for their preservation, therefore, be it Resolved by the American Society of Zoologists that the proper department or departments of the United States Government he urged to take such steps as may be necessary to provide for a comprehensive and thorough exploration of the Pacific with a view to the development. PROCEEDINGS 83 greater utilization, aiKJ adequate conservation of its fisher^' resources of whatever kind, and that, if possible, such exploration be undertaken in co-operation with other governments possessing territory bordering the Pacific Ocean. Symposium At the session held at 2.00 p.m., Friday, December 28, a symposium on the subject, "The Value and Service of Zoological Science" was held with papers as follows: 1. Utilitarian Values, bj^ F. M. Guyer. 2. Philosophical Values, by W. E. Ritter. 3. Value to the Individual, by H. B. Torrey. 4. Spiritual \'alue, by W. C. Curtis. Arrangement will be made for the publication of these papers. Presidential Address The address by the President of the Society, Maynard M. Metcalf, on the subject, "Darwinism and Nations," will be published in Science. Exhibits The following exhibits were made in room 201 in the Animal Morphology building. 1. Prawings illustrating the Anatomy of the Tubinares. R. M. Strong, Vanderbilt University Medical School. 2. Rabbit with Abnormal Eye Showing the Result of Maternal Antiserum Treatment. M. F. Guyer, University of Wisconsin. 3. The Effect of Removal of Eye-stalks upon Body Color in Cambarus. Charles Zeleny, University of Illinois. 4. Animal Parasites. Franklin D. Barker, University of Nebraska. Papers Read At sessions held during the forenoon and afternoon of Thursday, December 27, and the forenoon of Friday, December 28, papers listed on the program were read, eighteen in full, twentythree by title. THE ANATOMICAL RECORD, VOL. 14, NO. 1 84 AMERICAN SOCIETY OF ZOOLOGISTS Abstracts Abstracts of all papers accepted for the program are printed as part of the proceedings of the meeting. ABSTRACTS 1. The olfactory organs of a Coleopterous larva. N. E. McIndoo, Bureau of Entomology, U. S. Dept. Agriculture. Up to date the writer has described the olfactory pores in Hymenoptera, Coleoptera, and Lepidoptera. As yet no olfactory organs in any larval insect have ever been described, although it is generally supposed that larvae can smell. Since all larvae are more or less selective in regard to their food which constantly emits odors, it would seem that larvae should have organs to receive these odors, The present papers deals with the morphology of the olfactor}- pores in the larva of the "fig-eater," Allorhina (Cotinis) nitida L. Olfactory pores were found on the antennae, on all the mouth parts, on the thorax at the bases of the legs, and on the legs. The total numeer varies from 1254 to 141.3. with 1359 as an average, which is about equal to that of an adult beetle of the same species. With one exception, the structure of these olfactory pores is similar to that of those found in adult beetles. In the larva the single olfactory organs are widelj' scattered on all the parts above enumerated, but the compound organs are found only on the distal halves of the last antennal segments. A compound organ consists of a group of cL seh' compact olfactory cells and a thin chitinous plate which bears a pore aperture for each sense cell. On an average, a larva has 25 compound organs whose pore apertures number 625. The antennae of this larva have no sense organs other than the single and compound olfactory organs and tactile hairs. 2. The relation of the thyroid gland to regeneration in Rana pipiens. Bexxet M. Allex, University of Kansas. These experiments involved three classes of tadpoles: 1. Tadpoles from which the thyroid gland had been extirpated — absence of thyroid secretion. 2. Normal control tadpoles. 3. Tadpoles to which thyroid extracts were fed — excess of thyroid materials. In each case approxunately the terminal half of the tail was I'emoved. Regeneration proceeded normalh' in quantity and in quality of all three groups. There was a certain amount of individual variation in the degree of regeneration, dependent upon the amount of material removed, the age. and upon individual factors, but the range in amount of regeneration was proportional in all three classes. The tadpoles used ranged in total length from 16.7 mm. to 58 mm. Class 3 was composed of tadpoles of intermediate size, ranging from 32.8 mm. to 45.1 mm. The amount of regeneration'in this group was nearly proportional to that in corresponding controls, in spite of the fact that the thyroid feeding had caused a marked shrinkage in body length and had caused one-half of the specimens to develop to the 85 86 AMERICAN SOCIETY OF ZOOLOGISTS stage where one or both of the fore Unibs had broken through the skin. We conchide from these experiments that the thyroid gland does not influence the process of regeneration. S. Modifications produced in uterine young by treatment of the mother ivith specific antiserum. M. F. Guyer, University of Wisconsin. Fowls repeatedly injected with rabbit lenses yielded a serum which when injected into pregnant rabbits attacked the lenses of some of the uterine young, though apparently without effect on the lenses of the mothers. Similar results were obtained in mice. The affected lenses were rendered opaque or hquid. The most striking case is that of a male rabbit which though now adult still has a greatly dwarfed and opaqued left eye. This animal will be exhibited. 4. Extirpation of the thymii.s gland in Rana pipiens larvae. Bennet M. Allex, University of Kansas. The thymus-gland anlagen were removed at their very inception, 8 mm. to 9 mm. tadpoles. This was accomphshed by cutting into each side of the head with a cataract needle. Although the severity of the operation retarded development for a time, recovery was rapid and complete. Seven specimens were reared to the time of metamorphosis, attaining normal size and appearance. All died or were killed at this time. It is impossible from the material at hand to determine whether the high mortality at this time was due to the absence of the thjnnus gland or to other causes. It was in sharp contrast to the fate of the controls. Further experiments will be made upon this point next j^ear. They appeared to be structurally normal in every regard. The characteristic features of metamorphosis occurred. A careful study of the thymus-gland region of each specimen showed that the glands had in each case been successfully removed. Five out of the seven were males. Sexual differentiation was complete, and measurements showed the gonads to be altogether normal in size as compared with metamorphosed controls. A comparison of sections of the gonads of operated and control specimens showed those of both to be identical in structure and in the developmental stage reached by the germ cells. 5. The influence of thyroid and hypophysis removal upon general body growth and upon the development of the limbs of Rana and Bufo. Bennet M. Allen, University of Kansas. From a large niunber of tadpoles of these two types the thyroid gland was removed, while fi-om others the anterior lobe of the hyjjophysis was removed. In both species the removal of either of these glands caused the development of the limbs to be very greatly retarded from the time "of their first appearance. In Rana pipiens removal of the hypophysis caused a marked retardation of general body growth, to which a corresponding retardation of hnib growth was clo.sely correlated. The.se tadpoles finally attained a total length PROCEEDINGS 87 of 48.9 mm. and a hind-leg length of 1.48 mm. This was in marked contrast to the continued growth of the general body dimensions and of corresponding hind-limb length in thyroidless tadpoles of this species. In Biifo lentiginosus the results were not so divergent. The removal of the anterior lobe of the hypophysis early caused a color change from black to golden yeUow. The absence of either gland caused retardation in limb development. Tadpoles deprived of the anterior lobe of the hypophysis reached a length far in excess of that reached in normal tadpoles. The limbs grew to about threefifths the length attained in normal toads at metamorphosis. Thyroidless specimens grew somewhat larger than the foregoing, reaching a length of trunk almost twice that of normal toads at metamorphosis, while the hind legs and fore legs grew to a length greater than found in normal toads at metamorphosis. In none of the operated tadpoles did the fore limbs break through the skin. 6. Function^] and rudimentary spermatosoa of rotifers (illustrated with lantern). D. D. Whitxet, University of Nebraska. The later stages in the spermatogenesis of the marine rotifer Brachionus mulleri have been carefully reexamined and two interesting additional facts discovered. The normal and rudimentary spermatid cells occur in the ratio of 2:1. By staining with Delafield's haematoxj-lin. a coarse network of chroraatin-like material can be seen in both the normal and the rudimentary cells. This would seem to indicate that in the spermatoc%-te division some of the chromatin material passes into both kinds of cells. As the normal cells develop and mature into the ripe spermatozoa, the heads become very large and somewhat rounded in shape, but aU remain attached to a common central tissue and may form one or more clusters of spermatozoa. The long, vigorous tails have verj" weak connections with the heads, and when a male individual is sUghtly compressed imder a cover-glass the tails become detached from the heads and may be extruded from the body. If the males are further compressed the heads are also extruded. The tails are capable of swimming aroxind in the cultiu-e water for a considerable length of time, and were formerly considered to be the entire spermatozoa. The smaller rudimentary cells at first resemble in form the normal cells, but as they develop such produce a short immotile and tail-like process somewhat spindle-shaped at one end of the cell. This process normally becomes detached from the larger part of the cell while in the testis and may be readily seen inside of a h\'ing uncrushed male. These small detached spindle-like bodies were formerly considered to be the complete rudimentary spermatozoa. No chromatin-hke material, however, can be demonstrated in these bodies, but a considerable quantity can be seen in the other and larger portions of these cells from which these immotile bodies have become detached. Consequently these bodies cannot be the entire rudimentary sperm cells, but are probably to be regarded as rudimentary- tails of the rudimentarj-^ sperm cells. 88 AMERICAN SOCIETY OF ZOOLOGISTS 7. Irregular rate of division of Ameba. A. A. Schaeffer, University of Tennessee. Amoeba proteus, A. discoides, and A. dubia were individually pedigreed for a large number of generations, a record being kept of all the progeny from the single individual fathering the pedigree. The division rate is perfectly irregular, varying from two or three divisions in twenty-four hours to only one division in eight or more days. The progeny of the rapidly dividing and of the slowly dividing do not indicate by their subsequent divisions their previous rate of reproduction. The rate of reproduction of . unequal-sized sisters and of their immediate progeny was not influenced bj' the size of the sisters, but only a verj' few cases of this kind were observed. It seems as if some material which 1 as an influence on the rate of reproduction is unequally divided during the division process. Multinuclear individuals were frequently observed. The amebas remained quite normal throughout most of the experiments. 8. Opalina and the origin of the Ciliata. M. M. Metcalf, Orchard Laborator3^ Opalina characters — 1) reproduces by both longitudinal [Flagellata] and transverse [Cihata] fission; 2) sexual act complete fusion of dissimilar gametes [Flagellata]; 3) no kinetic center (centrosome) [unique]; 4) kinetoplasm in form of basal granules of the cilia and a network of neural fibrillae connecting these [Ciliata]; 5) uninucleate at sexual period, pleurinucleate during the rest of life cycle [unique]; 6) in pleurinucleate condition all nuclei alike; 7) in each nucleus trophochromatin and idiochromatin distinct (except in origin) ; in the binucleate species the trophochromatin is in massive chromosomes of constant, definite form and nmnber, apparently equal in number to the granular idiochromosomes, and their division in mitosis is regular; in the multinucleate species the trophochromatin masses are not constant in nimiber, size, or form, and divide irregularly in mitosis; the trophochromatin is extruded from the nuclei at the sexual period; (8) the pseudopleurinucleate condition is due to temporary suppression of the divisions of the body, the nuclei having divided; 9) this delay in completion of mitosis affects also the nuclei, which in numerous species do not complete their division promptly, but come to 'rest' in different stages of the incon plete mitosis. In the sixty (?) species studied, forty (?) of them new, a complete series is seen from uninucleate forms with nucleus in an anaphase of mitosis, through uninucleate species with telophase nuclei, binucleate species with resting nuclei of the usual type, binucleate species with two prophase nuclei, still others with two telophase nuclei, quadrinucleate species, multinucleate species, and finally an elongated multinucleated species whose transverse body divisions have started, but are arrested while incomplete, giving an appearance of metamerizdtion. The binucleate Opalines form a genus, Protoopalina, distinct from the multinucleate species, Opalina proper, the chief distinctions being in nuclear charac PROCEEDINGS 89 ters. The Opalinidae are an offshoot from the primitive Cihata before the latter had acquired true binuelearity and the subsequent dimorphism of nuclei. They should be classed as Portociliata, under the Cihata. The Astommata (Discophrya, Anoplophrya, Hoplitophrj'a, etc.) are Eucihata, having arisen much later, after the dimorphic nuclei were acquired. They are not closely related to the Opahnidae. 9. Full-eye and emarginate-eye from bar-eye in Drosophila without change in the bar gene. Ch.4.rles Zelexy, University of Illinois. In the course of selection ejqjerimcnts for high-facet number in the sex-linked bar-eA-ed stock of Drosophila, full-ej-ed individuals have been produced which are somatically indistinguishable from wild ones. These fuU-eyed flies are geneticallj' of two very distinct tj^ies. One t\T)e is the result of a reverse mutation invohong the return of the bar gene to the original full-producmg condition. Its hereditary behavior is similar to that of the wild Drosophila in all the tests that have been made. Such flies have already been described by May. The other tj-pe retains the bar gene unchanged, the somatic appearance of full-eyed being due to the formation of a modifj'ing gene outside of the sex-chromosomes. This new gene acts as a recessive factor, since it is without somatic effect in single dose. It is effective in producing full-eye when present in double dose in females heterozygous lor the bar gene. Such full-eyed females when crossed with full-eyed males produce males half of whom are low bar and females half of whom are heterozygous bar. In males with the bar gene and in females homozj^gous for the bar gene, the double dose of the new gene produces an eye which is nearly full, but which differs from full in the presence of a defect at the anterior margin. Such an eye may be designated by the term 'emarginate.' 'Emarginate' females when crossed with full wild males give males all of whom are low bar and females all of whom are heterozj'gous. 10. Genetic relation of winged and wingless forms to each other and to the sexes in the aphid Macrosiphum solanifolii. A. Franklin Shull, University of ]\Iichigan. In the greenhouse, since the experiments began, this species has passed through the sexual phase three times. In two of these periods every indi\adual either was sexual or produced only sexual progeny in the immediately following generations, so that the experiments could be continued only by hatching the fertilized eggs. In the third, only two parthenogenetic females were left, toward the end of the sexual phase, to continue the Ime. During the parthenogenetic portion of the cycle, the frequency with which winged females appeared was very variable, often with a steadily progressive change in their frequency. At any one tim_e, however, wingless mothers produced many more winged offspring than did winged mothers. On the average, winged mothers produced chiefly 90 AMERICAN SOCIETY OF ZOOLOGISTS wingless offspring, while wingless mothers produced chiefly winged offspring. ■ During the sexual phase, winged mothers profluced chiefly sexual females, while wingless mothers produced cliiefly males. The males often appeared mostly near the end of their respective families. 11. Parthenogenesis and inheritance in grouse locusts. Robert K. Nabours, Kansas Agricultiu-al College Experiment Station. Persistent efforts at crossing forms of Paratettix (sp.?) with the forms of another apparenth* closely' related group (genus?) have so far failed. However, it has been discovered that the 9 9 of the latter group (genus?) may reproduce parthenogenetically, the offspring in such instances being exclusively 9 9 . Some of these have now arrived at the third parthenogenetic generation, in considerable muubers, never having l)een exposed to males of any kind. After producing parthenogeneticall.y a batch, or more, all exactly like herself, ahomozj^gous 9 , if then mated with a homozygous cf' of a different color pattern gives offspring of the expected uniformly intermediate pattern, with cf cf and 9 9 in approximately equal numbers. Heterozygous 9 9 partheolgenetically produce 9 offspring about half showing the pattern of the cf grandparent and half the pattern of the 9 grandparent, with occasional non-disjunction, which is not uncommon in this group. 12. The winter cycle of egg-production. H. D. Goodale, Massachusetts Agricultural Experiment Station. The winter cj'cle of egg production was first described by Pearl, whose evidence is all mass evidence. No criteria by which the presence or absence of the cycle could be recognized in the individual have been presented. Pearl finds, furthermore, that the winter cycle is a normal part of the egg production of most Barred Plymouth Rocks. A detailed study of the problem in our Rhode Island Reds shows — First. — The best criterion of the existence of a winter cycle is the presence of a pause in production, usually ten days or over in length, which follows an egg-laying period of considerable length, the pause beginning, as a nde, in January or February. Rate of production, as shown by monthly production, does not furnish a satisfactory means of recognizing the cycle. Second. — Many Rhode Island Reds lack the winter cycle, i.e., lay witliout interruption throughout the winter. Third. — The character is probably inherited, for some families exhibit the cycle while others lack it. The evidence points to the simple Mendelian fornuila as the mode of inheritance. 13. A -pedigreed strain of 'twin' Oxytricha. J. A. Dawson, Osborn Zoological Laboratory, Yale University. (Introduced by L. L. Woodruff.) There appeared, on July 27, 1917, in a six-day-old stock culture PROCEEDINGS 91 from a pedigreed race of Oxj-tricha, several pairs of apparently fused animals. These were isolated and from them pedigreed strains of double or 'twin' animals have been carried, thus far, for over one hundred generations, twin producing twin in each generation. The two cells forming a 'twin' are closely and firmly fused dorsally, though the anterior ends are very slightly separated. The 'twins' swim actively with a characteristic rapid rotation on their long axis. The normal single animal of the race from which the 'twin' strain was derived has the macronucleus in two portions, as is usual in the genus Ors-tricha, but no demonstrable micronuclei. Cytological studj' of the 'twins' shows simply a doubling of the normal characteristics. Reproduction of 'twins' is by transverse fission, and has given, in certain cases, as high as 100 per cent of 'twin' progeny for five generations. Occasionally a 'twin' separates into two single animals, M'hich are normal in every respect, except that the anal ends, where separation occurs, retain for an hour or so pointed projections. 'Twins' which show a sUghtly more marked separation at the anterior end form, when transverse fission takes place, two normal single animals from the anterior end and one 'twin' from the posterior end. Normal single animals resulting from ' twins' continue to di%ade as asual. The division rate of the 'twin' strain is equal to, or slightly greater than, that, of the race of normal animals from- which it arose. The proportion of the animals remaining 'twins' seems to be increasing as the strain grows older. The 'twins' of the present generation are apparently identical in structure with those which originated the strain. A morphological and physiological study of this 'twin' strain is in progress. 14. Selection for high-facet and for low-facet number in the bar-eyed race of Drosophila. Charles Zelent, University of Illinois. In the sex-linked bar-eyed race of Drosophila, selection for highfacet and for low-facet number is effective. Crosses show that the modifj-ing factors involved are not sex-linked. The effect of selection therefore cannot be due to differences in the bar gene, either preexistent or produced dining the course of selection. Nor can it be due to raodijfj'ing genes in the sex chromosomes. Genes in the autosomes must therefore be responsible. That some of these genes appeared before the beginning of the present experiment is indicated by the pronounced effect of the first selections. That others are appearing during its progress, at least in some of the lines, is indicated by the continued effect of selection through many generations in these Lines. There are also changes of greater degree involving a return at one step to the full-eye. These are of two distinct tj-pes: one, an autosomal change like those responsible for the smaller increases in facet number and the other a return of the bar gene itself to the original wild condition. It is evident that in this one experiment three separate conditions contribute to the effectiveness of selection for high-facet number: first, the differences in accessory 92 AMERICAN SOCIETY OF ZOOLOGISTS autosomal genes present at the beginning of selection; second, the new autosomal genes arising during the course of selection, and, third, the mutations in the bar gene. 15. Relative effectiveness of food and other conditions in the production of males in the rotifer, Hydatina senta. A. Franklin Shull, University of Michigan. In a previous paper upon oxygen as a factor in the production of males the actual presence of an excess of oxygen in the water was not demonstrated, though it was necessary to assume from the conditions of the experiments that additional oxygen was dissolved. The amount of oxygen in water similarly treated has now been measured, and compared with untreated water, and with water in which Euglena was reared. The former experiments have been in substance repeated upon several lines with some variability in the results. In some lines the increase in male-production in the presence of oxygen was again demonstrated. One line showed practically no effect of oxygen. Whether this line responds to oxygen in other ways is still under investigation. None of the lines produced more males in the control than in the oxygenated water. At the same time, controls which were fed upon Euglena were maintained. The production of males was increased considerably Aore in these than in the oxygen cultures, though in no case were the results as striking as those obtained by Whitney, who used Chlamydomonas as food. If all the excess of male-production in the Euglena experiments not attributable to oxygen was due to food, as is fairly to be assumed, food is a much m.ore potent factor in male-production than is oxygen. Oxygen appears to increase male-production a little more than creatin, of the greatest concentration that may be safely used, reduces it. Euglena increases male-production a little more than manure solution, of the concf ntration com n only used in food cultures, decrease s it. 16. Concerning the summer plumage of the drake. H. D. Goodale, Massachusetts Agricultural Experiment Station. Some ducks, such as the Gray Call, Mallard and Rouen, molt early in the summer (Jmie). The new plumage, called the summer plumage, is entirely imlike the old, since it .strongly resembles that of the female. If the testes of the male are completely removed, the change in color no longer occurs, although the birds molt. Further studies of the problem show that, potentially, the change in color of the intact male takes place two or throe months prior to the actual change, for the potential change, at will, may be rendered actual by removing feathers and thus inducing a growth of new ones. The new feathers that come in late in the winter are like the old, but those pulled a little later (March) are like the summer plumage. This change coincides approximately with the beginning oi manifestations of sexual activity. PROCEEDINGS 93 It has also been foiind that about the time the summer plumage reaches its height, sexual activity diminishes or disappears. At this time the reproductive system of the male contains few or no spermatozoa. The summer plumage no sooner reaches its height than the change back to the breeding plumage begins. It is apparent, therefore, that the summer plumage develops coineidently with the period of greatest activity of the testes, while the breeding plumage, so-called, develops during the quiescent period. The histological changes in the testes are being examined. 17. Functional inertia in the movement of Ameba. A. A. Schaeffer, University of Tennessee. The path of an ameba has character; that is, the direction in which an ameba is moving at any time is influenced by the direction in which the ameba has been moving just previously. The tendency to move in straight paths is not due to mere mechanical inertia of the streaming protoplasm, nor is it due to anj' form of sense perception known to man. Nor is the tendency to move in straight paths the result of minimal external stimulation or of the absence of external stimulation. Occasionally a slight lateral external stimulus produces a visible response, and yet the original (straight) path is maintained. The encircling of objects, a phenomenon of rather frequent occurrence, may be explained as due to a balance between the effect of functional inertia of movement and the effect of a mild positive stimulus. These conclusions are based on exTDerimental records of a number of species of amebas. 18. Acidosis the cause of death at high temperature. Alfred Goldsborough Mayer, Carnegie Institution of Washington. Those corals which have the highest rate of metabolism, as measured by oxygen consumption, are the ones that are most readily killed by high temperature, as will appear from the following table: NAME OF CORAL CONSTANT TEMPERATURE WHICH 16 JUST SITFFICIENT TO CAUSE DE.\TH IF EXPOSED TO IT FOR ONE HOUR REL.VTIVE OXYGEN COXSUMPTION' PER HOUR PER GRAM OF LIVING SUBSTANCE OF EACH CORAL Acropora muricata °c. 34.7 35.6 36.8 37.05 38 2 18.7 Orbicella annularis Maeandra areolata Favia fragum Siderastrea radians. . . 6.1 5.5 3.8 1 Moreover, ability to resist high temperature is proportionate to a coral's ability to resist the poisonous effects of carbon-dioxide gas dissolved in seawater. Death in the presence of CO2 is not due to asphyxiation, for all corals can survive for more than six hours in sea 94 AMERICAN SOCIETY OF ZOOLOGISTS water deprived of oxygen luidcr an air pump. Moreover, the death temperature is the same whether the oxygen is 3.0 times the normal or reduced to 0.3 its normal concentration. Thus high temperature does not cause death through asphyxiation, but more probably through the acciunulation of acid in the tissues. 19. An analysis of the respiration of Cassiopea, and the natxire of the nervous control of its rate of metabolism. Lewis R. Gary, Prmceton University. The oxygen consumption was tleterniined by the Winkler method, usmg sufficiently large respiration chambers to provide against the reduction of the oxygen tension to a point sufficiently low to interfere with the normal respiration of the experimental material. All experhiients were perforu'ed upon half disks to avoid the introduction of individual variation, in nietabolic activity, which has been fomid to be very marked in this organism. In a series of experiments devised to determme the respiration of the several tissues of the disk it was fomid that takmg the oxygen consumption of a half disk pulsatmg under the control of its sense organs as 100 per cent that of the different tissues was as follows: per cent Active muscles 36.1.') Epithelia (including inactive muscles) 60 . 23 Nerves and sense organs 1 .37 Mesogloea (and bacteria?) 2 . 25 When the muscles are inactive, the ectodermal tissues of the exun-brella use 60.5 per cent as much oxygen as those of the subumbrella. This figiu-e represents, as closely as it could be determined, the relative mass of protoplasmic tissue in the two epithelia. When the muscular activity of a specimen is taken from nervous control by removing the sense organs and starting a circuit wave of contraction in a labyrmth of the subumbrella tissue, the rate of pulsation can be controlled by the length of the labyrinth so that the rates of the 'active' and 'activated' halves will be the same. Under these conditions, the oxj'gen consumjition is greatest for the active half disk, as is also the rate of regeneration when si)ecimens have been subjected to the same type of operation. The control of metabolic activit} by the nerve centers seems, therefore, to be exercised through the general epithelial covering of the body as well as through the specialized contractile tissues. SO. The rate of intracellular oxidation in Paramecium caudatum and its relation to the toxic action of KNC. E. J. Lund, University of Minnesota. It is generally assumed that the toxic action of KNC upon cells and organisms in general is due to an inhibitory effect of KNC upon intracellular oxidations. This conclusion originates from the experiments on mammals by Geppert (Zeitschr. f. klin. Med., vol. 15, '89) and is PROCEEDINGS 95 based primarily upon experiments on the effect of KNC on echinodenu eggs by Warbm-g (Ergeb. d. Phys., vol. 14, '14), Loeb, and others. Data will be presented which show that the rate of intracellular oxidation Ln Paramecium caudatiun is independent of the toxic action of KNC. The oxidations go on at the same rate in cells which are undergoing visible death changes, as in normal cells. Concentrations of KNC varj-ing from ]M/272 to ]\I/27200 are equally ineffective in inhibiting the normal rate of oxidations. After c^-tolysis by KNC oxidations apparently cease. It is obvious that conclusions and inferences based on the supposed specific action of KNC on intracellular oxidations in other cells than those where proof of such .specific action is given is unwarranted. 21. The sensory behavior of Chiton. Leslie B. Arey, Northwestern University ]\Iedical School. A comprehensive investigation of the sensory capacity of this generalized mollusc not only prondses facts of intrinsically fundamental unportance, but also paves the way for future quantitative attacks on problems of general sensory physiology. This sluggish and seemingly improniising animal gives surprisingly clear-cut responses to a large variety of sensory stimuli. The effects of touch, light (including shading), temperature, gravity, currents, chemicals, \'ibrations, etc., have been tested quantitatively and the results analyzed. 22. Reversals of phototaxis and carbon dioxide production in maij-fly Nymphs. (Lantern.) W. C. Allee, Lake Forest College. The phototactic reactions of a species of may-fly nymphs (Heptageninae) were reversed by treatment with various chemicals. The rate of carbon dioxide production of nymphs experimentally reversed was compared with that of untreated nymphs by means of Tashiro's Biometer with the following results: Hydrochloric acid (m/25) caused reversals soon after treatment began or after an interval of about 35 minutes. In the first case the animals were stimulated; in the second, they were depressed as indicated by the rate of production of carbon dioxide. These nymphs are normally negative to light. Only 20 per cent of the untreatetl nymphs give a positive reaction. Such positive nymphs were also reversed by treatment with hA'drochloric acid. Potassium cj'anide caused reversals which were always accompanied by depression. Ethyl alcohol acted in the same way as hydrochloric acid, first stimulating and later depressing, but was not so elTective in causing reversals as the other reagents. Nymphs may be reversed bj"" long exposure to light. This caused an increase in the rate of carbon dioxide production. In preliminary experinients, with other species of may-fly nymphs, Child's cyanide method gave similar results. 96 .^ilERIC.VN SOCIETY OF ZOOLOGISTS All nymphs that reversed their light reactions were either stimulated or depressed, but stimulation or depression did not necessarily involve reversal. S3. Tactile reactions of the de-eyed hamlet. W. J. Crozxer. Bermuda Biological Station. The de-eyed hamlet (Epinephelus striatus) gives well-defined reactions to the near approach of solid bodies. In the seeing fish this sensitivity is present, but motor effects which it might induce are almost completely inhibited. ^lechanical deformations in the water, of minute amplitude, are the source of stimulation (not chemical or electrical disturbances). The presence of this exceedingly delicate form of sensitivity, generally distributed over the surface of the fish, and leading to deliberate reactions of a definite character, can (both directly and by differential narcosis) be used to detect the influence of chemical excitants, locally applied, upon the end organs of the tactile sense. Although the existence of this form of irritabilitj' vitiates any direct study of the mode of excitation in ' common chemical' sense reactions, it can be clearly dem.onstrated that the generalh' distributed 'common chemical' sensitivity of this fish does not involve tactile receptors. Since the hamlet with well-developed eyes exhibits a high degree of tactile discrin ination, such as has been described for the bhnd cave fishes Eigenii ann), although its existence would be quite overlooked unfess blinded animals were studied, it is unnecessary to suppose that the end organs of this form of sensitivity have been determined either by blindness or by life in caves. ^4- The effect of temperature upon facet number in the bar-eyed race of Drosophila. E. W. Seyster, University of Illinois. (Introduced by Charles Zelent.) In connection with selection experiments in progress in the Zoological Laboratory at the University of Illinois, a study was made of the effect of temperature upon facet number in the imselected bar-eyed race of Drosophila. It was found that facet number decreases with increase in developmental temperature. In males the average facet Qiunbers were: 165 at 17°, 114 at 22°, and 72 at 28°. In females the numbers were: 140 at 17°, 85 at 22°, and 48 at 28°. This gives for males a decrease of 7.3 per cent per degree between 17° and 22° and of 7.5 per cent between 22° and 28°. The corresponding decreases for females are 9.6 per cent per degree between 17° and 22° and 9.3 per cent between 22° and 28°. The facet number at 17° is approximately 2.3 times that at 28° in males and 2.9 times in females. The relation is the reverse of that ordinarily given for chemical reactions and may be explained on the assumption tliat the chemical activity of an inhibitor of facet number is the effective agent concerned. According to preliminary experiments, the period in which temperature is effective at 28° comes somewhere between 2^ and 4 1 days PROCEEDINGS 97 after the lajing of the eggs. At this temperature the larva usually pupates on the seventh day. 85. The nature of the orienting light stimulus in Vanessa antiopa, WnxiAM L. DoLLET, Jr., Randolph-Macon College, Ashland, Va. Vanessa antiopa, when exposed to two lights of equal intensity the rays of which are at right angles, moves in general toward a point half way between the sources. If, however, one of the hghts is made intermittent by placing a revolving sector-wheel in the beam and the illuniination in the two beams is equal, the behavior of Vanessa is very different. If one-fourth of the wheel is removed, the degree of stimulation of the intermittent light varies, in proportion to its flash-frequency, from 2 to 20 per second. If one-half of the wheel is removed, the effect of this intermittent light is very similar to that described above, except that when the flash-frequency is low the stimulus is stronger than when less of the wheel is removed. If, however, thre^ fourths of the wheel is removed, although the stimulus of this intermittent light tends to vary in proportion to the flash-frequency, the difference in the effect produced upon the organisms by revoh-ing the sector-wheel slowly and rapidly is not so great as it is when the aperture in the wheel is smaller. Moreover, when the flash-frequency is low, 2, 5, and 10 pfr second, intermittent light produced by a rotating sector-wheel three-fourths of which is removed is stronger as a stimulus than when less of the wheel is removed. The reverse is true when the flash frequently is high, 20 and 30 per second. These results seem to indicate that the orienting .stimulus in light may be due to the continuous action of light. They also show that light may produce orientation through a change of intensity if the flash of light is short enough and if it is not followed by too long a period of darkness. 26. The relative sensitimty of Vohox to spectral lights of equal radiant energy content. Hexbt L.\.rREXs and Hexry D. Hooker, Jr., Osborn ^lemorial Laboratories, Yale University. The physiological effects of spectral lights of equal radiant energycontent have been investigated in accordance with the program outlined in a recent paper (Amer. Jour. Physiol., vol. 44, p. 504). Results warranting publication have been obtained so far in one case, namely, ^'olvox globator. Dark-adapted, positive forms were used. The presentation time requisite to initiate a motor reaction was determined for each of the twenty-three lights. The speed of locomotion toward each was determined and cooipared to the spaed of the same individuals toward a white light of the same radiant power. The reactions to white and colored light coming from opposite directions, and the speed of locomotion, were determined and compared to the speed of the same individuals reacting to the white light alone, and to the colored light alone. The following results have been obtained: All the lights (ranging from 420 mm to 670 mm) induce positive motor reactions. The most 98 AMERICAN SOCIETY OF ZOOLOGISTS effective wave-length is iii the immediate neighborhooil of 494 /i/j. The curve of relative stimulating value, as shown bj- the presentation time, is a nornial curve of error. When organisms are exposed to white and colored light of equal radiant power commg from opposite directions, they move toward the colored lights of wave-length 574 nfi and less, but away from the colored lights of longer wave-length. 27. The influence of excessive sexual activity of male rabbits. 1 . On the nature of the seminal discharge. Orren Lloyd-Jones A^^D F. A. Hays. Li general, the plan of the experiment was to couple the male in as rapid succession as possible to 'preliminaiy' females and then to mate him once to the female from which a litter was desired, Litters of rabbits were obtained and semen studies were made from the fifth, tenth, fifteenth, and twentieth copulations in from one to four hom's. Semen was recovered from the females by catheter. The data show a decrease in amount of discharge and in the number of sperm per cubic millimeter as the number of copulations increases. The rate of progressive linear motion of the sperm was determined by the use of the ruled surface of the cj'tometer and a stop-watch. Sperm move forward in semen diluted nine times with an isotonic solution at a rate of 0.02 to 0.03 mm. per second. It appears that the velocit}^ of those sperm wliich show the progressive vi bra tile type of motion is not affected by the number of copulations. Bvit the type of motion is influenced; in semen from the twentieth service there are few 'progressive movers,' and many 'spiral movers' and 'bunters.' The duration of motion was recorded as per cent of sperm active at four-hour intervals after recovery. The sperm from the higher-seiwice groups shows a more rapid decline in the per cent of sperm active. Motility persists longer in semen diluted nine times than in undiluted semen. There is a marked and regular decline in per cent of pregnancies induced as the service number increases. The number of young m the litter was not affected imtil the twentieth service, when there was a pronounced falling off in litter size. 28. Further experiments on the transmission of swamp fever . (Lantern.) John W. Scott, University of Wyoming. Some miportant results have been found since reporting on this subject a year ago. We have f u rther proof that swamp fever may be transmitted from sick to well horses by means of Stomoxys calcitrans. We now have definite proof that the disease may be transmitted by Tabaims. The transmission is a mechanical one, but it is interesting to note that both acute and chronic cases may be produced by such transmission. Mechanical transmission by means of a hypodermic needle contaminated with extremeh' small amounts of uifected blood is sufficient to produce the disease; this indicates that the insect theory of transmission is adequate. Other facts brought out include the following: Apparent immunitj' may be developed, and the horse still be a carrier of the virus. Horses suffering a light attack and showing few symptoms may carry virulent PROCEEDINGS 99 blood, and subinjections from these produce severe cases. Cases produced bj' subinjections of blood are, as a rule, not so severe as cases reported from the field, but many mild cases are probably overlooked in the field. The disease may be transmitted by infected mares to their sucking colts, as shown by the Japanese Commission. The amount of blood used in subinjection also bears rouglily an inverse relation to the length of the subsequent incubation period. Finally, during the progress of the disease, there is a decrease in the total hemoglobin content per cubic centimeter which is approximately proportional to the characteristic decrease in the number of red corpuscles. 29. Effect of chemicals on reversion in orientation to light in the colonial form, Spondylomorum quarternarium. S. O. Mast, Johns Hopkins University. Spondylomorum orients fairly precisely in hght. It is negative under certain conditions and positive under others. The effect of chemicals on the sense of orientation was ascertained both by adding minute traces of the substances tested to the solution m wliich the organisms were exposed to hght xmtil it became so concentrated that they no longer reacted and by putting organisms directly from the culture solutions into watch-glasses containing culture solutions with known amounts of chemicals added. The illumination and the temperature were constant throughout each experiment. The following substances cause negative specimens to become positive: Acetic, carbonic, hydrochloric, nitric, sulphuric, formic, boric, chromic, taimic, tartaric, and oxalic acids, chloroform, ether, and chloral hydrate. The following substances have no effect on the sense of orientation: sodium, potassium and ammonium hydrates, magnesium sulphate, sodium chlorid, calcium chlorid, potassium nitrate, formalin, sugar, oxj'gen, hydrogen peroxid, potassium cyanide, and strychnin. For the following substances the effect is questionable: ethyl alcohol, ammonium chlorid, and distilled water. The effect of acids is not specificalty related with the hydrogen ionconcentration. The culture solution in which Spondylomorum Jived was continuously fairly strongly alkahne. When a trace of acid is added to such a solution Spondylomorum usually becomes strongly positive at once; but it remains positive only a moment, then it becomes negative and remains so. If more acid is now added, it again becomes positive, etc. Tests with neutral red show that Spondylomorum may become positive when the solution is still strongly alkaline and that it may still be negative when the solution is neutral or even shghtly acid. It consequently appears that if the sense of orientation in this organism is dependent upon either the hydrogen or the hydroxj'l ions, it must be dependent upon the time rate of change in the concentration of the ions. However, the fact that chloroform and ether produce the same effect as acids indicates that it is not dependent upon the ions mentioned. THE ANATOMICAL RECORD, VOL. 14, NO. 1 100 AMEEICAN SOCIETY OF ZOOLOGISTS 50. The rate of iJitracellular oxidation in Paramecium caudatum and its relation to oxygen concerdration. E. J. Lund, University of Minnesota. Measurements of the oxygen consumption by Paramecium caudatum when placed in water containing concentrations of oxygen which vary from those which are toxic (two to three times the oxygen concentration in distilled water at N. T. P.) to about 1/50 of this concentration, show that the rate of oxygen consumption is not affected by varying the concentration between these limits, temperature and other conditions being the same. 51. Assortive mating in a nudibranch. W. J. Crozier, Bermuda Biological Station. From measurements of the lengths of 148 couples of Chromodoris zebra there was found a correlation coefficient = 0.626 for the lengths of two members of a pair copulating in nature. Mass experiments and studies of individual behavior show how this correlation is the result of true assortive mating. Egg-masses laid by this hermaphroditic mollusc contained 2,300 to 20,000 eggs, depending upon the size of the animal (4 to 18 cm. length). Mutual fertilization is practiced, and one egg-mass is the consequence of each insemination. Assortive coupling leads a) to the conservation of gametes, and direetlj^ b) to the fertilization of the greatest number of eggs — as has been ascertained by direct observation; it thus helps to insure the establishment of the largest possible number of larvae. The assortive conjugation of Chromodoris and the adaptive consequences to which this process gives rise are determined in a mechanical way by the structure of the nudibranch. An important instance is thus afforded of the way in which certain types of 'adaptive' behavior are to be explamed. 32. The habits of the yelloio perch. A. S. Pearse, University of Wisconsin. Perch in a small, shallow, muddy lake and in a large, clear, deep lake were examined weekly for two years. Food consisted of the following items expressed in volumetric percentages: chironomid larvae, 25; cladocerans, 22; Corethra larvae, 6.4; silt and bottom debris, 6; fish, 5.2; amphipods, 3.6; plants, 3.5; Sialis larvae, 3.4; caddis fly larvae, 2.1; oligochaetes, 1.5; crayfishes, 1.5; odonate nymphs, 1.4; clams, 1.2; algae, 1.2; snails, 1.1; ephemerid nymphs, 0.9; calcium carbonate crystals, 0.5; midges, 0.5; leeches, 0.4; Hemiptera, 0.3; mites, 0.3; midge pupae, 0.2; copepods, 0.1; ostracods, 0.09. There were seasonal variations, but an adult perch ate an amount equal to 7 per cent of its own weight daily. Digestion was thrice as rapid in summer as in winter. Perch are continually moving from place to place, but do not make rapid vertical migrations, except that they move upward somewhat at night. During most of the year they re PROCEEDINGS 101 main in deep water, but come in shore to breed in spring when water reaches 7°-10°C., the males preceding the females to the spawning groimds. During late sunmier and early autumn the perch in certain lakes mostly forsake the stagnant, oxj-gen-free water near the bottom. They can, however, live for over two hours in such stagnant water, and while in it draw to some extent on the reser^'e oxj^gen in the swim bladder. SS. Reversion in orientation to light in the colonial forms, Volvox globator and Pandorina Morum. S. 0. Mast, John Hopkins University. Volvox and Pandorina react verj- strongly to light and they orient precisely. Ordinarily they are negative ia strong and positive in weak light, but under certain conditions the opposite is true. The sense of orientation is dependent upon the time of exposure as well as upon the intensity of the illumination. In \olvox no definite results were obtained, but in Pandorina it was found that in weak light it required a longer exposure to make positive individuals negative than it did in strong light. In strong light, however, it required more energy than it did in weak Ught, e.g., in one experiment it required 80.000 metercandle-hoiu-s in an illumination of 16.000 meter-candles : 24.000 m.c. hrs. in 4,000 m.c; 7,000 m.c.hi-s. in 1,000 m.c; 2,000 m.c.hrs. in 250 m.c; 888 m.c.hrs. in 111 m.c, and 444 m.c.hrs. in 27 m.c. Under certain conditions a sudden decrease in illumination, e.g., from direct to diffuse sunUght, makes negative colonies positive; but after having been positive in the diffuse light for a moment they maj' become negative again without any further change in illumination. The reversion in Light is not primardj- dependent upon photosjTithesis. Red and yellow light, in which photosj-nthesis is relatively strong, have little effect on reversion in orientation, while blue and green, in which photosvTithesis is weak, have an effect nearly as great as white hght. Increase in temperature causes negative specimens to become positive and decrease causes the opposite, but neither the degree nor the extent of change in the temperature is specific in its effect. Under certain conditions, the colonies ma^- be negative or positive in practically all temperatures in which thej' orient at all. Alkalis and salts have no effect on reversion, neither in negative nor in positive colonies. Acids and some anesthetics, especially chloroform, cause negative colonies to become strongly positive; but reversion is not specifically dependent upon the concentration of the chemicals. Colonies which are positive in a solution having a given chemical concentration may be negative in the same solution or even in a weaker solution. The sense of orientation is dependent upon the age of the colonies. Young colonies are more likely to be negative than old ones. In a given solution the j-oung specimens frequently collect at the side of the dish farthest from the light, while the old ones collect at the opposite side. 102 AMERICAN SOCIETY OP ZOOLOGISTS SJf. The total quantity of -plankton produced by a lake. C. Juday, University of Wisconsin. Investigations on lakes in the vicinity of Madison, Wisconsin, show that the larger plankton organisms, those that are readily obtained with the standard silk-gauze net, do not constitute as large a portion of the total plankton, generally, as the smaller organisms which are lost through the meshes of the net and which can be obtained with a centrifuge. The organic matter of the centrifuge plankton varies from a minimum somewhat smaller than the net plankton to a maximum twenty-five times as great; dm^ing most of the year the former is three to five times as great as the latter. 35. On the parasitism of Carboniferous crinoids. Roy L. Moodie, University of Illinois, College of Medicine. While engaged in reviewing the literatui'e of paleontology in the course of a search for paleontological evidences bearing on the antiquity of disease, the writer was interested in noting several cases of parasitism by myzostomid worms in the stems of fossil crinoids. Later several specimens of enlarged crinoid stems from the Carboniferous were loaned for stuth' by the University of Chicago. Etheridge, in 1880, first called attention to the swollen crinoid stems from the Carboniferous of England. Later, von Graff, in 1885, published a memoir on the deformities of crinoid stems, and showed that the deformities were due to parasitic worms, which had already been suggested by Etheridge. Von Graff i^ublished his paper in the Paleontographica and illustrated it with an excellent lithographic plate. He reviewed the subject of parasitism of crinoid stems and cited the work of the Challenger expedition on this sul> ject, suggesting that since the deformities of the recent crinoids were usually due to myzostomids that there was no reason to suppose that the fossil deformities were due to any other cause. John M. Clark has written an excellent paper on the pre-Carboniferous evidences of communism and commensalism, calling his study "The Beginnings of Dependent Life." In his extensive collections he has found no trace of defiiiite parasitism, but certainly the cases described by him may be regarded as the beginnings of parasitism. It seems probable, at present, that true parasitism was not attained until the Carboniferous period. The specimen of crinoid stems at the writer's disposal show great tumor-like masses, due doubtless to the pathological influence exerted by the parasites. Von Graff found definite evidences of the carbonized remains of the parasite, and referred it to the myzostomids. In the present instances we are not in a position to say what the parasite was. Section of the material adds little to the facts already described by von Graff, but simjily records another instance of parasitized crinoid stems — the first record, so far as can be determined, of parasitism in American fossil crinoids. Unfortimatelj, the present material has been completely mineralized, so that nothing is left of the original animal structure save its form. PROCEEDINGS 103 So far as known at present, no fossil animals suffered from disease prior to the Permian when caries of the bone and callus formation are known. However, if we may regard parasitism as a form of disease, we witness in the Carboniferous the very begmnings of disease, which is manifest to-day in such a vast multitude of forms. Diseases, like animals and plants, present certain persistent tjqies, such as caries, pyorrhea, parasitism, necroses, osteoperiotitis, and various arthritides, which arose ear ty, .prior to the Cretaceous, and have persisted down to the present in an almost imchanged form. 36. The Acanthocephala of North American birds. H. J. Van Cleave, University of Illinois. But four genera, comprising a total of eight species, of Acanthocephala have been reported from North American birds. Through the U. S. Government Collections the waiter has had access to materials containing specimens belonging to four additional genera, which are now reported from North America for the fii'st time. Corynosoma constridum occurs in Oidemia americana. Echinorhynchus rectus Linton has been reexamined and showm to belong to the genus Plagiorhynchus. Another species, P. formosus, has been found in Colaptes auratus. Polymorphus obtusus has been .taken from Anhinga anhinga. Mediorhynchus grandis has been assigned to the genus Heteroplus. This last genus belongs in the family Centrorhjmchidae rather than in the GigantorhjTichidae, as proposed by Kostylew, its founder. There are, then, a total of thirteen valid species of Acanthocephala known to occur in North American birds. In addition, four species mentioned by Leidy are insufficiently described to permit of their being placed with accuracy in the modern classification. Among birds the occurrence of two different species of Acanthocephala within the same host individual has never come under observation of the writer, nor has any positive case wherein two different genera have been found in the same species of host. Further evidence is added in support of the hj'pothesis that the Acanthocephala parasitic in fresh-water and terrestrial hosts of North American stand as a distinctive faima. Comparisons of infestations of birds in Eiu"ope and in North America shows that in most cases families of birds common to the two continents harbor entirely different genera of Acanthocephala. 37. The morphology and life history of a new trematode parasite, Lissorckis fairporti nov. gen., el nov. spec, from the buffalo fish, Ictiobus. Thoil\s Byrd Magath, Department of Anatomy, University of Illinois College of Medicine. (Introduced by Roy L. Moodie.) A careful study of the morphology and life history of Lissorckis fairporti nov. gen., et nov. spec, has been made. This parasite occurs in about 50 per cent of the experimentalh' raised buffalo fish (Ictiobus bubahis and Ictiobus cyprinella) in the ponds at the United States Bureau of Fisheries Biological Station at Fairport, Iowa. It is found 104 AMERICAN SOCIETY OF ZOOLOGISTS in relatively small numbers per host in the intestine, and there is evidence to show that it has been responsible for the large death rate sometimes noted among buffalo fish during their first summer. The new genus Lissorchis cannot be placed in any of the existing subfamilies, and the new subfamily Lissorchiinae has been created to contain it. The description of the genus is as follows: Distomes; body flattened, elongate, tapering posteriorly and of moderate size. Cuticula covered with small spines; fleshy spines around suckers. Acetabulum powerful and as large or larger than the oral sucker which is also well developed. Prepharynx and esophagus much reduced; intestinal crura not reaching the posterior end. Excretory system Y-shaped, branching anterior to the testes. Genital pore marginal and sinistral, situated below the middle of the acetabulum. Ovary mesial and lobed, no seminal receptacle; Laurer's canal present. Uterus coiled and extending from beyond the genital pore to the posterior tip of the body, filled with small, thin-shelled eggs. Testes ovoid, large, mesial, and unlobed, lying in a straight line with the ovary and posterior to it. Very large seminal vesicle and well-developed cirrus anterior to eetal end of uterus. Vitallaria extending on either side from posterior of acetabulum to half way between posterior tip and acetabulum. Vitallarial sac present and Mehlis' gland large. Habitat: Intestine of fresh-water fishes. The life history was obtained experimentally and followetl to some extent in the field. The cercaria of this form has been described and found in Planorbis trivolvis; it belongs to the xiphidiocercaria. Experimentally, it encj^sted in chironomid larvae after boring through their skin, and when these were fed to buffalo fish the worm was freed from the cyst and developed to stages like those found in nature in infectiKl fish. Observations indicate that the eggs from the adult trematodes hatch in the late fall, live over winter in the liver of Planorbis trivolvis, and multiply in sporocysts. In the summer the cercariae find their way to water, infect chironomid larvae, and in turn the buffalo fish when they eat the infected larvae. Fish cannot be infected by directly feeding them with the cercaria. Note: This paper will appear in the Journal of Parasitology as a contribution from the laboratory of the U. S. Bureau of Fisheries, Fairport, la. 38. Easily available sources of material for the study of animal parasites. Fkanklin D. Barker, University of Nebraska. Animal parasites afford one of the most interesting and practical groups of animals for studj'. Their use neglected due to erroneous idea of mipleasantness and difficulty in securing material. Easily available sources are as follows: Protozoa. 1. Entamoeba sp.?, in small intestine of mice. 2. Sporo zoa: a. Gregarina, several species in intestine of grasshopper and cricket. b. Monocystis agilis, in senunal vesicles of earth worms, c. Hemogre garina sp.?, blood of snakes. 3. Ciliata: a. Opalina, several species in PROCEEDINGS 105 cloaca of frog. b. Nydotherus sp.?, species in cloaca of frog. 4. Flagellata: a. Trypanosoma leicisi, in blood of rat. b. Herpeto?no»as muscae, in intestine of house fly. Plathelviinthes. — 1. Trematoda. a. Pneumonoecus, several species in lungs of frog. b. Amphimerus ovalis, in bile ducts of soft-shell turtle, c. jSIiracidiuin stage in eggs of trematodes sp.?, in intestine of frog. d. Redia and cercaria stages in liver, reproductive glands, and tentacles of water snails. 2. Cestoda: a. Taenia serrata, in intestine of dog. b. Taenia serialis, in intestine of dog. c. Dipylidium caninum, in intestine of dog and cat. d. Cysticercus stage, Cysticercus piriformis, on omentum, mesentery, and intestine of cotton-tail rabbit, e. Onchosphere stage in eggs of Hymenolopis diminuia, in intestine of rat, also in eggs of gravid proglottids of T. serrata. Nemathelminthes. 1. Nematoda: a, Ascaris suum, in intestine of pig. b. Belascaris marginata, in intestine and stomach of dog and cat. c. Ancylostoma caninum (hookworm), in intestine of dog. d. Oxyuris ambigua, in intestine of rabbit. 2. Acanthocephala, several species in intestine of turtles and fish. 3. Gordius sp.?,» in fresh water ponds and ditches. Arthropoda. — 1. Fleas: a. Ctenocephalus canis, on hair of dog and cat. 2. Mosquitoes: a. Culex sp.?, b. Anopheles sp.? — eggs, larva and pupa — in rain barrels and ditches. 3. Lice: a. Menopon pallidum, on chickens. Identification descriptions and drawmgs are given. Methods of collecting, preserving and mounting are indicated. Animal parasites may be obtained from Ward's Natural Science Establishment, Rochester, N. Y., and Western Biological Supply Co., Lincoln, Nebr., and other biological supply houses. • 39. The need for extensive oceanographic and biologic explorations in the A^orth Pacific. Wm. E. Hitter, University of California. The need indicated is both scientific and economic, and would involve an imdertaking of such magnitude that nothing less than the National Government would be equal to it. It should realh' be international and include the United States, Canada, and Japan at least. Enough is already known about this oceanic area and the organisms inhabiting it to bring out the fact that it presents differences from its nearest of kin, the North Atlantic, so considerable as to make it impossible to apply to it in detail generalizations reached by investigations of the corresponding Atlantic area. Illustrative of these differences on the oceanographic side may be mentioned the greater size and average depth of the Pacific; its greater isolation from the Arctic Ocean; its much more fully developed phenomenon of upwelling water; its simpler and less sharplj' defined system of currents; the relative paucity, so far as the North American continent is concerned, of incursion of fresh water into the Pacific; and finally the somewhat lower specific gravity of North Pacific water. On the biological side, illustrative diSerences are seen in the rela 106 AMERICAN SOCIETY OF ZOOLOGISTS tively meager development of a Pacific sargassum; in the Pacific's seal herds; in its salmon fauna with an oceanic phase, and in the kelp beds of its eastern margin. These and other known differences make it highly probable that still others, perhaps more subtle and far-reaching, would be brought to light i)y adequate investigations, and so argue strongly for such investigations. The paper is presented largely for the purpose of forwarding a plan alreadj' on foot for inaugurating the researches. 40. Some notes with reference to infection ivith Sarcocystis tenella. John W. Scott, University of Wyoming. Since the life historj- of this parasite is not known and sincQ apparently 100 per cent of Wyoming range sheep are infected, the following notes will be of some interest. Lambs were kept in a dry lot from birth, and some were grazed with and without water being present. In all cases where lambs were grazed 100 per cent were infected. Some of the control lambs kept in the tlry lot with pure water supply and fed on baled native hay cut the pre\dous season, also became infected. Infection apparently does not take place in uteri, though the proof of tliis rests only on one definite case. Infection seems to occur only during the summer or early fall, not during the late fall, winter, or early spring. Proof of this rests upon results of the examination of lambs killed at different seasons. While sarcocj^sts vary greatly in size in lambs with identical treatment, the mean size gradually increases with age. However, the variation from an average mean size does not increase with age; hence an indication of early or summer infection. Another proof is that neither the percentage of lambs mfected nor the amount of infection per cubic centimeter of muscle, increases during the wmter. The amount of infection is verv largely' correlated with pasture conditions, and there is some proof that it is correlated with the presence of certain insects. Further discussion will appear in a paper soon to be published. AMERICAN SOCIETY OF ZOOLOGISTS OFFICERS AND LIST OF .MEMBERS OF THE SOCIETY Officers President George Lefevre Vice-President L. L. Woodruff Secretary-Treasurer Caswell Grave Executive Committee A. F. Shull L. J. Cole R. P. Bigelow H. V. Wilson iM. M. Metcalf HOXORARY MEMBER , James Viscount Bryce, Hindleap, Forest Row, Sussex, England. LIFE MEMBERS Andrews, Ethan Allen, Ph.B. (Yale), Ph.D. (Johns Hopkins), Professor of Zoology, Johns Hopkins University, Baltimore, Md. Dean Bashford, A.B. (College of City of New York), A.M., Ph.D. (Columbia), Professor of Vertebrate Zoology, Columbia University; Curator of Fishes and Reptiles, America7i Museum Natural History, Riverdale-on-H udson, New York. Hensh.vw, Samuel, Director of Museum of Comparative Zoology, 8 Fayerweather Street, Cambridge, Mass. Mater, Alfred Goldsborough, iI.E. (Stevens Inst. Tech.), Sc.D. (Harvard), Director Department Marine Biology, Carnegie Institution of Washington, 276 N'assau Street, Princeton, N. J. Metcalf, Matnard M.ato, A.B., D.Sc. (Oberlin), Ph.D. (.lohns Hopkins), 128 Forest Street, Oberlin, Ohio. MooKE J. Percy, Ph.D. (Pennsylvania), Professor of Zoology, University of Pennsylvania, Philadelphia, Pa. Randoli-h, Harriet, A.B. (BrjTi :Mawr), Ph.D. (Zurich), 1310 South Fortyseventh Street, Philadelphia, Pa. Stiles, Charles W., A.M., Ph.D. (Leipzig), S.M., S.D. (Wesleyan), Professor of Zoology, United States Public Health and Marine Hospital Ser\dce, Hygienic Laboratory. Twenty-fifth and E Streets, N. W., Washington, D. C. (October 1-May 1); Wilmington, N. C. (May-October 1). MEMBERS Abbott, James Francis, A.B., A.M. (Leland Stanford), Ph.D. (Chicago), Professor of Zoology, Washington University, St. Louis, Mo. 107 108 AMERICAN SOCIETY OF ZOOLOGISTS AcKERT, James Edward, A.B., A.M., Ph.D. (University of Illinois), Assistant Professor of Zoology, Kansas Slate Agricultural College, Manhattan, Kan. Allee, Warder Clyde, S.B. (Earlham College), S.M. (Chicago), Ph.D. (Chicago), Professor of Biology, Lake Forest College, Lake Forest, III. Allen, Bennet Mills, Ph.B. (De Pauw), Ph.D. (Chicago), Professor of Zoology, University of Kansas, Lawrence, Kan. Allen, Ezra, A.M., PhJD. (University of Pennsylvania), Professor of Biology, Philadelphia School of Pedagogy, 12th above Spring Garden, Philadelphia, Pa. Aret, Leslie Brainerd, Ph.D. (Harvard), Associate Professor in Anatomy, Northwestern University Medical School, 3431 Dearborn Street, Chicago, III. Baitsell, George Alfred, B.S. (Central College, Iowa), M.A., Ph.D. (Yale), Instructor in Biology in Yale University, Osborn Zoological Laboratory, Yale Statio7i, New Haven, Conn. Banta, Arthur Mangun, A.B., A.M. (Indiana), Ph. D. (Harvard), Resident Investigator, Station for Experimental Evolution, Carnegie Institution, Cold Spring Harbor, Long Island, N. Y. Bardeen, Charles Russell, A.B. (Harvard), M.D. (Johns Hopkins), Professor of Anatomy and Dean of the College of Medicine, University of Wisconsin, Madison, Wis. Barker, Franklin D., A.B., A.M. (Ottawa University, Kansas), Ph.D. (Nebraska), Professor of Medical Zoology and Parasitology, University of Nebraska, Station A, Lincoln. Neb. Barrows, William Martin, B.S. (Michigan Agricultural College), S.B., S.M. (in Biology) (Harvard), 371 Harvard Street, Cambridge, Mass. Bartelmez, George W., Ph.D. (Chicago), Assistant Professor of Anatomy, University of Chicago, Chicago, III. Basset, Gardner Cheney, Ph.D. (Johns Hopkins), University of Pittsburgh, Pittsburgh, Pa. Baumgartner, William Jacob, A.B., A.M. (Kansas), Associate Professor of Zoolog}', University of Kansas, 1209 Ohio Street, Lawrence, Kan. Beckwith, Cora Jipson, B.S. (Michigan), M.A., Ph.D. (Columbia), Associate Professor of Zoology, Vassar College, Poughkeepsie, N. Y. BiGELOw, Maurice Alpheus, B.S. (Ohio Wesleyan), M.S. (Northwestern), Ph.D. (Harvard), Professor of Biology, Teachers' College, 525 West 120th Street, New York City. Bigelow, Robert Payne, S.B. (Harvard), Ph.D. (Johns Hopkins), Associate Professor of Zoology and Parasitology, Massachusetts Institute of Technology, Cambridge, Mass. BiNFORD, Raymond, B.S. (Earlham), S.M. (Chicago), Ph.D. (Johns Hopkins), Professor of Zoology at Earlham College, Earlham College, Richmond, Ind., Earlham P. O. Boring, Alice Middleton, A.B., A.M., Ph.D. (Bryn Mawr), Associate Professor of Zoology, University of Maine, Orono, Maine. Boydbn, E. A., Ph.D. (Harvard), Instructor Comparative Anatomy, Harvard Medical School, 61 Clark Street, Newton Center, Mass. Brdner, Henry Lane, A.B. (Abingdon), Ph.D. (Freiburg), Professor of Biology, Butler College, 324 South Hitter Avenue, Indianapolis, Ind. MEMBERS 109 BuDiNGTOx, Robert Allyn, B.A., M.A. (Williams), Professor of Zoology, Oberlin College, Qberlin, Ohio. BuMPrs, Hermox Caret, Ph.D., LL.D. (Clark), Ph.B., D.Sc. (Brown), D.Sc. (Tufts) President of Tufts College, Tufls College, Mass. BcTRROWs, Montrose T., A.B. (Kansas), M.D. (Johns Hopkins), Acting Resident Pathologist, Johns Hopkins Hospital, Baltimore, Md. Byrnes, Esther F., Ph.D., (Bryn Mawr) 19S Jefferson Avenue, Brooklyn, N. Y. Calkins, Gary N., B.S. (Mass. Inst. Tech.), Ph.D., (Columbia) Professor of Protozoolog}-, Columbia University, A'eui York City. Calvert, Philip Powell, Ph.D. (Pennsylvania), Professor of Zoology, University of Pennsylvania, Zoological Laboratory, Philadelphia, Pa. Carothers, E. Eleanor, A.B., A.M., Ph.D., Zoological Building, University of Pennsylvania, Philadelphia, Pa. Carpenter, Frederic Walton, B.S. (New York Univ.), A.M., Ph.D., (Harvard), Professor of Biology, Trinity College, Hartford, Conn. Cart, Lewis R., B.S., M.S. (Maine), M.A., Ph.D. (Princeton), Asst. Prof, of Biology, Princeton University, Princeton, N. J . Casteel, Dana Br.4.ckenridge, A.B. (Allegheny), A.M. (Ohio Wesleyan), Ph.D. (University of Pennsylvania), Associate Professor of Zoology, University of Texas, Austin, Texas. Castle, W'illiam E., A.B. (Denison), A.M., Ph.D. (Harvard), Professor of Zoology in Harvard University, Payson Road, Belmont, Mass. Chamberlin, Ralph V., B.S. (Utah), Ph.D. (Cornell), Curator of Arachnida, Myriopoda and Annelida, Mus. Comp. Zoology, Harvard University, Museum Comp. Zoology, Cambridge, Mass. Chambers, Robert, Jr., A.IM. (Queen's Univ., Can.), Ph.D. (Munich), Instructor in Anatomy, Cornell Medical College, Z8th Street and First Avenue, New York City. Chester, Wayland Morgan, A.B., A.M., (Colgate Univ.), Professor of Biology, Colgate University, Hamilton, N. Y. Child, Charles Mantjing, Ph.B., M.S. (Wesleyan), Ph.D. (Leipzig), Professor of Zoology, Hull Zoological Laboratory, University of Chicago, Chicago, HI. Churchill, Edward Perry, A.B. (Iowa), Ph.D. (Johns Hopkins), Field Assistant U. S. Bureau of Fisheries, Hampton, Va. Clapp, Cornelia Maria. Ph.B. (Syracuse), Ph.D. (Chicago), Professor of Zoology, Mount Holyoke College, South Hadley, Mass. Clark, Howard Walton, A.B., A.M. (Indiana), Scientific Assistant United States Bureau of Fisheries, United States Biological Station, Fairport, Iowa. CoE, Wesley R., Ph.D. (Yale), Professor of Biology, Yale University, New Haven, Conn. Coghill, George E., A.B., Ph.D. (Brown), Professor of Anatomy, University of Kansas, R. F. D. 9, Laivrence, Kan. Cole, Leon J., A.B. (Michigan), Ph.D. (Harvard), Professor of Experimental Breeding, College of Agriculture, University of Wisconsin, Madison, Wis. CoLTON, H.\rold Sellers, B.S., M.A., Ph.D. (Pennsylvania), Instructor in Zoology, University of Pennsylvania, Philadelphia, Pa. ' 110 AMERICAN SOCIETY OF ZOOLOGISTS CoNGDON, Edgar Davidson, A.B., A.M. (Syracuse), Ph.D. (Harvard), Leland Stanford Jr. University, 330 Coleridge Avenue, Palo Alto, Cal. CoxKLiN, Edwin Grant, Ph.D. (Johns Hopkins), Sc.D. (Pennsylvania), Professor of Biology, Princeton University, Princeton, N. J. Cook, Margaret Harris, B.S., Ph.D. (Pennsylvania), 122 West Linn Street, Bellefonte, Pa. CoPEL.AND, Manton, S.B., S.M., Ph.D. (Harvard), Professor of Biology, Bowdoin College, Brunswick, Maine. CoRT, William Walter, A.B. (Colorado College), A.M., Ph.D. (University of Illinois), Assistant Professor of Zoology, University of California, Department of Zoology, University of California, Berkeley, Calif. CowLEs, R. P., B.A. (Stanford), Ph.D. (Johns Hopkins), Professor of Zoology, University of the Philippines, Manila, Philippine Islands. Crampton, Guy Chester, B.A., (Princeton) M.A. (Cornell), Ph.D. (Univ. of Berlin), Associate Professor of Entomology, Massachusetts Agricultural College, Care of Department of Entomology, Amherst, Mass. Crampton, Henry Edward, A.B., Ph.D. (Columbia), Professor of Zoology, Barnard College, Columbia University; Curator of Invertebrate Zoology, American Museuyn of Natural History, New York City. Crozier, William John, B.S. (College of the City of New York), A.M., Ph.D. (Harvard). Resident Naturalist, Bermuda Biological Station for Research; Agar's Island, Bermuda. Curtis, Maynie Rose, A.B., A.M. Ph.D. (INIichigan), Assistant Biologist, Maine Agricultural Experiment Station, Orono, Maine. Curtis, Winterton Conway, A.B., A.M. (Williams), Ph.D. (Johns Hopkins), Professor of Zoologj', University of Missouri, 208 Hicks Avenue, Columbia, Mo. Dahlgren, Ulric, A.B., M.S. (Princeton), Professor of Biology, Princeton University, 204 Guyot Hall, Princeton, N. J. Daniel, J(ohn) F(ranklin), S.B. (University of Chicago), Ph.D. (Johns Hopkins), Assistant Professor of Zoology, University of California, 1421 Hawthorn Terrace, Berkeley, Cal. Davenport, Charles Benedict, Ph.D. (Harvard), Director of Department of Experimental Evolution, Carnegie Institution of Washington, Cold Spring Harbor, Long Island, A". Y. Davenport, Gertrude Crotty, B.S. (University of Kansas), Cold Spriiig Harbor, Long Island, N. Y. Davis, Herbert Spencer, Ph.B. (Wesleyan), Ph.D. (Harvard), Professor of Zoology, University of Florida, Gainesville, Fla. Day, Edward Carroll, A.B. (Hamilton), A.M., Ph.D. (Harvard), Dalton Hall, Bryn Mawr College, Bryn Mawr, Pa. Detlefsen, John A., A.B. (Dartmouth), A.M., Sc.D. (Harvard), Assistant Professor of Genetics, University of Illinois, College of Agriculture, 916 West N evada Avenue, Urbana, III. DoDDS, Gideon S., B.A., M..'V. (Colorado), Ph.D. (Pennsylvania), Assistant Professor of Zoology, University of Missouri, Biology Building, Columbia, Mo. MEAfBERS 111 DoiXET, Jr., William Lee, A.B., A.JSI. (Randolph-Macon), Ph.D. (Johns Hopkins), Professor of Biologj', Randolph-Macon College, Ashland. Va. Drew, Gilmax A., Ph.D. (Johns Hopkins), Assistant Director, Marine Biological Laboratory, Woods Hole, Maxf:. Edmoxdsox, Charles Howard, Ph.B., M.S., Ph.D. (Iowa University), Assistant Professor of Zoology, Universily of Oregon, Eugene, Ore. Edwards, Charles Lixxoln, B.S. (Lombard and Indiana), A.M. (Indiana), Ph.D. (University of Leipzig), Director, Dept. Nature Study, Los Angeles City Schools, 1032 West 39th Place, Los Angeles, Cal. EiGEXMAXx, Carl, H., Ph.D., A.M., A.B. (Indiana), Research Professor and Dean of the Graduate School, Indiana University, Bloomington, Indiana. Eleod, Morton Johx, B.A., M.A., M.S. (Simpson), Ph.D. (111. Wes. Univ.), Professor of Biology, University of Montana, Missoula, Mont, Enders, Howard Edwix, B.S. (Lebanon Valley College), M.S., B.S. (Michigan), Ph.D. (Johns Hopkins L'niversity), Associate Professor of Zoology and in charge of Biologj-, Purdue University, Summer School Staff, Dept. Zoology, Indiana University, 107 Fowler Avenue, West Lafayette, Ind. ERDM.ixx, Rhoda, Ph.D. (Munich), Lecturer in Biolog>-, Yale University and Associate, Rockefeller Institute; Yale Universily, New Haven, Conn. Etcleshymer, Albert C, B.S. (Michigan), Ph.D. (Chicago), M.D. (St. Louis), Professor and Head of Dept. of Anatomy, University of Illinois; University of Illinois Medical College, Honore and Congress Streets, Chicago, III. Fasten, Nathan, B.S. (College of City of New York), Ph.D. (Wisconsin), Instructor of Zoology, Science Hall, University of Washington, Seattle, Wash. Ferris, Harry Burr, B.A., M.D. (Yale), E. K. Hunt, Professor of Anatomy, Medical Department, Yale University, 395 St. Ronan, New Haven, Conn. Foot, Katharine, 9So Park Avenue, New York City. Fox, Henry, B.S., M.A., Ph.D. (Pennsylvania), Entomological Assistant, U. S. Entomological Laboratory, Clarkesville, Tenn. Gage, Simon Henry, B.S. (Cornell), Emeritus Professor of Histology and Embryology, Cornell University, 4 South Avenue, Ithaca, N. Y. Galloway, Thomas W., A.B., A.M., Ph.D. (Cumberland), A.M. (Harvard), Litt. D. (Missouri Valley) Professor Biology, Beloit College, Beloil, Wis. Gabman, Harrison, D.Sc. (Kentucky), Professor of Entomology and Zoology, Kentucky Agricultural Experiment Station; State 'Entomologist, Lexington Ky. Gee, Wilson,B.S. (Clemson),M.A. (University of South Carolina), Ph.D. (University of California), Professor of Biology, Emery University, Oxford, Ga. Gerotjld, John H., Litt.B. (Dartmouth), A.B., A.M., Ph.D. (Harvard), Associate Professor of Biology, Dartmouth College, Hanover, N. H. Glaser, Otto Charles, A.B., Ph.D. (Johns Hopkins), Junior Professor of Zoology, University of Michigan, Ann Arbor, Mich. Goldfarb, A. J., B.S. (College City of New York), Ph.D. (Columbia), Professor of Biology, College of City of New York, Convent Ave., New York City. GoldSchmidt, Richard B., Ph.D. (Heidelberg), In charge of the Department of Genetics, Kaiser Wilhelm Institut fur Biologic, Daalem bei Berlin, Germany (Present address. Zoological Laboratory, Yale University, Neio Haven, Conn.). 112 AMERICAN SOCIETY OP ZOOLOGISTS GooDALE, Hubert Dana, Ph.D. (Columbia), Research Biologist, Massachusetts Agricultural Experiment Station, North Amherst, Mass. GooDBiCH, Hubert Baker, B.S. (Amherst), M.A., Ph.D. (Columbia), Instructor in Zoology, Wesleyan University, Middletown, Conn. Graham, John You.\g, Ph.D. (Munich), Professor of Biology, University of Alabama, University, Ala. Grave, Benjamin H., B.S. (Earlham), M.S. (Carleton), Ph.D. (Johns Hopkins), Professor of Biology, Knox. College, Galesburg, III. Grave, Caswell, B.S. (Earlham College), Ph.D. (Johns Hopkins), Associate Professor of Zoology, Johns Hopkiris University, Baltimore, Md. Gregory, Emily Ray, A.B. (Wellesley), A.M. (Pennsylvania), Ph.D. (Chicago), Sweet Briar College, Sweet Briar, Va. Gregory, Louise H., A.B. (Vassar), A.M., Ph.D. (Columbia), Instructor in Zoology, Barnard College, New York City. Griffin, Lawrence Edmonds, A.B., Ph.B. (Hamline), Ph.D. (Johns Hopkins), Professor of Zoology, University of Pittsburgh, Pittsburgh, Pa. Gross, Alfred O., A.B., (Illinois), Ph.D. '(Harvard), Assistant Professor of Zoology, Bowdoin College, Brunswick, Maine. Guberlet, J. E., A.M., Ph.D. (Illinois), Professor of Biology, Carroll College, Waukesha, Wis. Gudger, E. W., B.S., M.S., (Nashville), Ph.D. (Johns Hopkins), Professor of Biology, State Normal School, Greensboro, N. C. GuLiCK, Addison, A.B. (Oberlin), A.M. (Harvard), Ph.D. (Wurzburg, Germany), Assistant Professor in Physiology, University of Missouri, Columbia. Mo. GuYER, Michael F., B.S. (Chicago), A.M. (Nebraska), Ph.D. (Chicago) Professor of Zoology, University of Wisconsin, Madison, Wis. H.\LL, Mauhice Crowther, S.B. (Colorado), M.A. (Nebraska), Ph.D. (George Washington), D.V.M. (George Washington), Parasitologist, iJesearc/i Laboratory, Parke, Davis & Co., Detroit, Mich. Hamaker, John Irvin, A.B. (Kansas), A.B., A.M., Ph.D. (Harvard), Professor of Biology, Randolph-Macon Woman's College, 12 Princeton Street, Lynchburg, Va. Hancb, R. T., A.B., M.A., Ph.D. (Pennsylvania), Assistant in Zoology, University of Pennsylvania, Zoological Laboratory, University of Pennsylvania, Philadelphia, Pa. Habgitt, Charles W., Ph.D. (Ohio University), Professor of Zoology, Director of Laboratories, Syracuse University, Syracuse, N. Y. Hargitt, George Thom.as, Ph.B. (Syracuse), A.M. (Nebraska), Ph.D. (Harvard), Associate Professor of Zoology, Syracuse University, 909 Walnut Avenue, Syracuse, N. Y. Harmon, M.\ry Theresa, A.B., M.A„ Ph.D. (Indiana), Assistant Professor of Zoology, Kansas Slate Agricultural College, Manhattan, Kan. Harper, Eugene Howard, A.B. (Oberlin), A.M. (Harvard), Ph.D. (Chicago), Bedford, Va. Harrison, Ross Granville, Ph.D. (Johns Hopkins), M.D. (Bonn), Bronson Professor of Comparative Anatomy, Yale University, US Huntington Street, New Haven, Conn. MEMBERS 113 Hart, Charles A., Systematic Entomologists, Illinois State Laboratory of Natural History, Univeririty of Illinois, Urbana, III. Haktmax, Carl G., Ph.D. (Texas), Associate Professor of Zoology, University of Texas, 1908 University Avenue, Austin, Tex. He.\th, Harold, A.B. (Ohio Wesleyan), Ph.D. (Pennsylvania), Professor of Invertebrate Zoology, Leland Stanford University, 231 Walnut Street, Pacific Grove, Cal. Hegxer, Robert W., B.S., M.S. (Chicago), Ph.D. (Wisconsin), Assistant Professor of Zoology, University of Michigan (on leave of absence), Johnson Fellow, Johns Hopkins University, Baltimore, Md. HEiLBRUXTf, L.V., Ph.D. (Chicago), University of Illinois Medical School, Congress and Honore Streets, Chicago, III. Henchmax, Ax-xie p.. Box 34, Jaffrey, N. H. Hebrick, Charles Jubsox, Ph.D. (Columbia), Professor of Neurology, Anatomi - cal Laboratory, University of Chicago, Chicago, III. Herrick, Fr.vxcis HoBART, A.B. (Dartmouth), Ph.D. (Johns Hopkins), Sc.D. (Pittsburgh), Professor of Biology, Western Reserve University, Adelbert College, Cleveland, Ohio. HicKERXELL, L. M., A.B., A.M., Ph.D. (Princeton), Assistant Professor of Zoology, .Syracuse University, 1052 Ackerman Avenue, Syracuse, N. Y. HiLTOx, William Atwood, B.S., Ph.D. (Cornell), Professor Zoology, Pomona College, Claremont, Cal.; Director Laguna Marine Laboratory; Editor Journal of Entomology and Zoology, Claremont, Cal. HoGE, Mildred Albro, A.B. (Goucher), A.M., Ph.D. (Columbia), Instructor in Zoology, Indiana University, Bloomington, Ind. HoGXTE, M.\RT Jaxe, A.B. (Goucher), Ph.D. (Wurzburg), Instructor in Zoology, Wellesley College, Wellesley, Mass. Holmes, Samtel J., B.S., ^I.S. (California), Ph.D. (Chicago), Associate Professor of Zoology, University of California, Berkeley, Cal. Hooker, Davexport, B.A., M.A.,.Ph.D. (Yale), Assistant Professor of Anatomy, Yale University, School of Medicine, 816 Orange Street, New Haven, Conn. Hocser, Gilbert Logax, B.S., M.S. (Iowa), Ph.D. (Johns Hopkins), Professor of Animal Biology and Director of the Laboratories of Animal Biology, State University of Iowa, Iowa City, Iowa. Howard, Arthub D., B.S. (Amherst). M.S. (Northwestern), Ph.D. (Harvard), Scientific .\ssistant. United States Bureau of Fisheries, Fairport Biological Laboratory, United States Biological Laboratory, Fairport, Iowa. Hu.NTSM.iX, Archibald Gowaxxock, B..\., M.D. (Toronto) Lecturer in Biology, Biology Department, University of Toronto, Toronto, Canada. Hcss.\KOF, Louis, B.S. (City College of New York), Ph.D. (Columbia), Curator of Ichthyology, American Museum of Natural History, 77th Street and Central Park West, New York City. HtrxLET, JcLiAX SoRELL, B..\. (Oxford), Assistant Professor of Biology, Rice In.^titute, Houston, Tex. Htde, Roscoe R.\tmoxd, A.B., A.il. (Indiana), Ph.D. (Columbia), Assistant Professor of Zoologj' and Ph3'siology, Indiana State Normal School, 83S Chestnut Street, Terre Haute, Ind. 114 AMERICAN SOCIETY OF ZOOLOGISTS Hymax, L. H., Ph.D. (Chicago), Research Assistant, Chicago University, Hull Zoological Laboratorij, Chicago University, Chicago, III. Ibsen, Heman Lawritz, B.S., M.S., Ph.D. (Wisconsin), Assistant in Experimental Breeding, University of Wisconsin, Madison, Wis. IsELT, Frederick B., B.S. (Fairmount), M.S. (Chicago), Professor of Biology, Central College, Fayette, Mo. Jacobs, Merkel Henry, A.B., Ph.D. (Pennsylvania), Assistant Professor of Zoology, University of Pennsylvania, Philadelphia, Pa. Jennings, Herberts., B.S. (Michigan), A.M., Ph.D. (Harvard), LL.D. (Clark), Henry Walters Professor of Zoology and Director of the Zoological Laboratory, the Johns Hopkins University, Baltimore, Md. JoHANNSEN, OsKAR AUGUSTUS, B.S. (IlHnois), A.M. (Cornell), Ph.D. (Cornell), Professor of Biology, Cornell University, College of Agriculture, Ithaca, N. Y. Johnston, John B., Ph.D. (Michigan), Professor Comparative Neurology, University of Minnesota, Minneapolis, Minn. Jones, Orben Lloyd, B.S., M.S., Ph.D. (Wisconsin), Associate Professor, Animal Husbandry, Iowa State College, Ames, Iowa. JoRD.iN, Harvey Ernest, B.A., M.A. (Lehigh), Ph.D. (Princeton), Professor of Histology and Embryology, University of Virginia, Charlottesville, Va. Juday, Chauncey, A.B. and A.M. (Indiana), Biologist, Wisconsin Geological and Natural History Survey; Lecturer in Zoology, University of Wisconsin, Madison, Wis. Kampmeier, Otto F., Ph.D., Instructor in Embryology and Comparative Anatomy, School of Medicine, University of Pittsburgh, Pittsburgh, Pa. Kellicott, Wm. E., Ph.B. (Ohio State University), Ph.D. (Columbia), Professor of Biology, Gaucher College, Baltimore, Md. Keener, William Allison, A.B., A.M. (Franklin and Marshall College, Lancaster, Pa.), Ph.D. (Virginia), Associate Professor of Biology, University of Virginia, University, Va. KiNCAiD, Trevor, B.S. LTniversity of Washington, 1899; M.A. University of ■ Washington, 1901 ; Head of Department of Zoology, University of Washington, Seattle, Wash. King, Helen Dean, A.B. (Vassar), A.M., Ph.D. (Bryn Mawr), Assistant Professor of Embryology, The Wistar Institute of Anatomy and Biology, The Wistar Institute, Thirty-si.zth and Woodland Avenue, West Philadelphia, Pa. Kingsbury, Benjamin Freeman, Ph.D. (Cornell), M.D. (Freiburg), Professor of Histology and Embryology, Cornell University, £ South Avemie, Ithaca, N. Y. Kingsley, John Sterling, A.B. (Williams), Sc.D. (Princeton), Pro-fessor of Zoology, University of Illinois, Urbana, III. Kirkham, William Barri, B.A., M.A., Ph.D. (Yale), Instructor in Biology, Sheffield Scientific School, Yale University, 103 Everit Street, iVew Haven, Conn. Knowbr, Henry McE., A.B., Ph.D. (Johns Hopkins), Professor of Anatomy, Medical Department, University of Cincinnati, Cincinnati, Ohio. KoFoiD, Charles Atwood, A.B., Sc.D. (Oberlin), A.M. (Harvard), Ph.D. (Harvard), Professor of Zoology, University of California, and Assistant Director Scripp's Institution of Biological Research, Berkeley, Cal. MEMBERS 115 KoRNHAUSER, SIDNEY I., Ph.D., A.M. (Harvard), A.B., (Pittsburgh), Assistant Professor of Zoology, Northwestern University, 71S Clark Street, Evanston, III. Krecker, Frederic H., A.B., Ph.D. (Princeton), A.M. (Cornell), Assistant Professor of Zoology, Ohio Slate University, Columbus, Ohio. Kribs, Herbert Gut, A.B. (Oberlin), Ph.D. (Pennsylvania), B.A. (Union), Assistant in Zoology, University of Pennsylvania, Philadelphia, Pa. Kc.NKEL, Beverly Waugh, Ph.B., Ph.D. (Yale), Professor of Biology, Lafayette College, Boston, Pa. Kdntz, Albert, B.A. (Morningside), Ph.D. (State University of Iowa), Asso. ciate Professor of Biology and Histology, St. Louis University School of Medicine, St. Louis, Mo. Lambert, Avery E., B.S., Ph.D. (Dartmouth), Burr Professor of Natural History, Middlebury College, Middlebury, Vt. Land.\cre, Francis Leroy, A.B. (Ohio), Ph.D. (Chicago) Professor of Anatomy, Ohio Stale University, Columbus, Ohio. Lane, Henry Higgins, Ph.B. (De Pauw), A.M. (Indiana), Ph.D. (Princeton), Professor of Zoology, University of Oklahoma, 4^5 South Lahoma Avenue, Norman, Okla. La Rue, George R., B.S. (Doane), A.M. (Nebraska), Ph.D. (Illinois), Assistant Professor of Zoology, University of Michigan, Ann Arbor, Mich. Lasiiley, Karl Spencer, A.B. (West Virginia), M.S. (Pittsburgh), Ph.D. (Johns Hopkins), Assistant Professor Psychology, University of Minnesota, Minneapolis, Minn. Laurens, Henry, A.M. (Charleston), Ph.D. (Harvard), Assistant Professor of Biology, Yale College, Osborn Zoological Laboratory, Yale University, New Haven, Conn. Lee, Thomas G., B.S., M.D. (Pennssdvania), Professor of Comparative Anatore^, University of Minnesota, Institute of Anatomy, Minneapolis, Minn. Lefevre, George, A.B., Ph.D. (Johns Jopkins), Professor of Zoology, University of Missouri, Columbia, Mo. LiLLiE, Frank R., B.A. (Toronto), Ph.D. (Chicago), Professor of Embryology and Chairman of the Department of Zoology, University of Chicago; Director, Marine Biological Laboratory, Woods Hole, Mass. University of Chicago, Chicago, III. Linton, Edwin, A.B., S.M. (Washington and Jefferson), Ph.D. (Yale), Professor of Biology, Washington and Jefferson College, 400 East Maiden Street, Washington, Pa. Little, C. C, A.B., S.D. (Harvard), Research Fellow, Cancer Commission of Harvard University, Boston, Mass. LocY, William Albert, Ph.D. (Chicago), Sc.D. (Hon.) (Michigan), Professor of Zoology and Director of the Zoological Laboratory, Northwestern University, Evanston, III. Long, Joseph A., S.B., A.M., Ph.D. (Harvard), Assistant Professor of Embryology, University of California, 1534 La Loma Avenue, Berkeley, Cal. Longley, William H., M.A.. Ph.D. (Yale), Professor of Botany, Gaucher College, Baltimore, Md. THE ANATO.MIC.\L RECORD, VOL. 14, NO. 1 116 AMERICAN SOCIETY OF ZOOLOGISTS Lund, Elmek J., Ph.D. (Johns Hopkias University), Assistant Professor of Zoology, University of Mitmesotn, Minneapolis, Minn. LuTZ, Frank E., A.B. (Haverford), A.M., Ph.D. (Chicago), Assistant Curator of Invertebrate Zoology, American Museum of Natural History, 77th Street and Central Park West, New York City. McClung, C. E., Ph.C, A.B., A.M., Ph.D. (Kansas), Professor of Zoology and Director of the Zoological Laboratory, University of Pennsylvania, Philadelphia, Pa. McClure, Charles F. W., A.B., A.M. (Princeton) D.Sc. (Columbia), Professor of Zoology, Princeton University, Princeton, N. J. MacCdrdt, Hansford M., A.B. (Ohio Wesleyan), A.M., Ph.D. (Harvard!, Professor of Biology, Alma, College, 701 Center Street, Alma, Mich. MacDowell, Edwi.n' Carleto.n, A.B. (Swartlunore), S.M. Zool. (Harvard), S.D. (Harvard), Research Investigator, Station Experimental Evolution, Carnegie Institution of Washington, Cold Spring Harbgr, Long Islajid, N. Y. MacGillivray, Alexander Dyer, Ph.D. (Cornell). Associate Professor Systematic Entomology, University of Illinois. 603 West Michigan Avenue, Urbana, III. McGregor, Jame.? Howard, B.S. (Ohio State University), A.M., Ph.D. (Columbia), Associate Professor of Zoology, Columbia University, New York City. McIndoo, Nokman Eugene, A.B., A.M. (Indiana), Ph.D. (Pennsylvania), Insect Physiologist, Bureau, of Entomology, Washington, D. C. Marchand, Grace B., 2S Mercer Street, Princeton, N. J. Mark, Edward L., A.B. (Michigan), Ph.D. (Leipzig), LL.D. (Michigan), LL.D. (Wisconsin), Hersey Professor of Anatomy and Director of the Zoological Laboratory, Harvard University, 109 Irving Street, Cambridge, Mass. Marshall, Ruth, B.S., M.S. (Wisconsin), Ph.D. (Nebraska), Lane Technical School, Chicago, III. Marshall, William Stanley, B.S. (Swarthpiore), Ph.D. (Leipzig), Associate Professor Entomology, University of Wisconsin, 139 East Oilman Street, Madison, Wis. Mast, Samuel Ott.mar, B.S. (Michigan), Ph.D. (Harvard), M.Pd. (Michigan Normal College), Associate Professor of Zoology, the Johns Hopkins University, Baltimore, Md. Mead, Albert Davis, A.B. (Middlebury), A.M. (Brown), Ph.D. (Chicago), Sc.D. (Pittsburgh), Professor of Biology, Brown University, 283 Wayland Avenue, Providence, R. I. Met?, Charles W., B.A. (Pomona), Ph.D. (Columbia), Station for Experimental Evolution, Carnegie Institution of Washington, Cold Spring Harbor, Long Island, N. Y. Meyer, Arthur William, B.S. (Wisconsin), M.D. (Johns Hopkins), Professor of Anatomy, Stanford Jr. University, 121 Waverley Street. Palo Alto, California. Michael, E. L., A.B., M.S. (California), Assistant Scripps Institution, La .lolla, Calif. Middleton, Austin Ralph, A.B., Ph.D. (Johns Hopkins), Assistant Professor of Biology, University of Lousiville, Lotdsville, Ky. MEMBERS 117 MoE-VKHAUS,. William J., A.B. (Indiana), Ph.D. (Chicago), Professor of Physiology, Indiana University, 501 Fess Avenue, Bloomington, Ind. MooDiE, Roy Lee, A.B. (Kansas), Ph.D. (Chicago), Instructor in Anatomy, University of Illinois, Chicago, Congress and Honore Streets, Chicago, III. Moody, Julia Eleanor, B.A., M.A. TMt. Holyoke), Ph.D. (Columbia), Associate Professor of Zoology, Wellesley College, Wellesley, Masfs. Morgan, Axx Haven, A.B., Ph.D. (Cornell), Professor of Zoology, Mi. Holyoke College, So. Hadley, Mass. Morgan, Thomas Hunt, B.S. (Kentucky), Ph.D. (Johns Hopkins), Professor of Experimental Zoology, Columbia University, Mew York City. MoRGtiLis, Sergius, A.M. (Columbia), Ph.D. (Harvard), Professor of Physiologj', Creighton University Medical School, Omaha, Neb. ' Morrill, Albro David, B.S., M.S. (Dartmouth), Professor of Biology, Hamilton College, Clinton, Oneida County, N. Y. Morrill, Charles V., A.M., Ph.D. (Columbia), Instructor in Anatomj-, Cornell University Medical College, ^Sth Street and First .Avenue, New York City. MosHER, Edna, B.S. (Cornell), Ph.D. (Illinois), Instructor in Entomology, University of Illinois, Natural History Building, Urbana, III. MuLLENix, RoLLiN Cl.^rke, A.B.. A.M. (Wheaton), Ph.D. (Harvard), Professor of Zoolog}', Lawrence College, 4^1 Washingtoti Street, Appleton, Wis. MtTLLER, Herman J., A.B., A.M., Ph.D. (Columbia), Instructor in Zoologj', Rice Institute, Houston, Texas. N'abocrs, Robert K., Ph.D. (Chicago), Professor of Zoology, Kansa/: Agricultural College, Manhattan, Kan. Xachtrieb, Henry Francis, B.S. (Minnesota), Professor of Animal Biology and Head of the Department, University of Minnesota, Minneapolis, Minn. Neal, Herbert Vincent, A.B., A.M., Ph.D. (Harvard), Professor of Zoology, Tufts College, Tufts College, Mass. Nelson, James Allen, Ph.D. (Kenyon College), Ph.D. (Pennsylvania), E.xpert Bee Culture Investigations, Bureau of Entomology, United States Department of Agriculture, Washington, D. C. Newman, Horatio Hackett, B.A. (McMaster), Ph.D. (Chicago), Associate Professor of Zoology, and Dean in College of Science, University of Chicago, 57 IS Dorchester Avenue, Chicago, III. NoRRis, Harry Waldo, A.B., A.M. (Grinnell), Professor of Zoology, Grinnell College, Grinnell, Iowa. OsBORN", Henry Fairfield, A.B., Sc.D. (Princeton), LL.D. (Hon.) (Trinity, Princeton. CoUunbia), D.Sc. (Hon.) (Cambridge University), Ph.D. (Hon.) (University of Christiania, Upsala), Research Professor of Zoology, Columbia; President Board of Trustees, American Museum Natural History; Curator Emeritus Dept. Vertebrate Paleontology, Vertebrate Paleontologist, LTnited States Geological Survej'. American Museum of Natural History, Seventy-seventh Street and Park West, New York City. OsBORN, Henry Leslie, A.B. (Wesleyan), Ph.D. (Johns Hopkins), Professor of Biology, Hamline University, 1500 Hewitt Avenue, St. Paul, Minn. O.SBORN, Herbert, B.Sc, M.Sc, D.Sc, (Iowa State College), Research Professor Ohio State University, Columbus, Ohio. ' 118 AMERICAN SOCIETY OF ZOOLOGISTS OsBURN, Raymond C, Ph.D. (Columbia), Professor of Biology, Connecticut College for Woynen, New London, Conn. Packard, Charles, M.S., Ph.D., Instructor in Zoology, Columbia University, Scheimerhorn Building, Columbia University, New York City. Painter, Theophilus Shickel, A.B. (Roanoke), A.M., Ph.D. (Yale), Adjunct Professor of Zoology, University of Texas, Austin, Texas. Parker, George Howard, S.B., S.D. (Harvard), Professor of Zoology, Harvard Universit)', 16 Berkeley Street, Cambridge, Mass. Parshley, H. M., A.m., Sc.D. (Harvard), Assistant Professor of Zoology, Smith College, 250 Elm Street, Northampton, Mass. Pattex, Br.^dley Merrill, A.B. (Dartmouth), A.M., Ph.D. (Harvard), Senior • Instructor Western Reserve Medical School, Cleveland, Ohio. Patte.v, William, B.S. (Harvard), M.A., Ph.D. (Leipzig), Professor of Zoology, Dartmouth College, Hanover, N. H. P.^tterson, John Thomas, B.S. (Wooster), Ph.D. (Chicago), Professor of Zoology, University of Te.xas, University Station, Austin, Texas. Payne, Fernandus, A.B., A.i\I. (Indiana), Ph.D. (Columbia), Associate Professor of Zoology, Indiana University, Bloomington, Ind. Pearl, Raymond, A.B (Dartmouth), Ph.D. (Michigan), Biologist and Head of Department of Biology, Maine Agricultural Experiment Station, Orono, Maine. Pearse, Arthur Sperry, B.S., A.M. (Nebraska), Ph.D. (Harvard), Associate Professor of Zoologj', University of .Wisconsin, Madison, Wis. Peebles, Florence, A.B. (Goucher), Ph.D. (Bryn Mawr), Associate Professor of Physiology, Bryii Mawr College, Bryn Mawr, Pa. Perkins, Henry F., A.B. (Vermont), Ph.D. (Johns Hopkins), Professor of Zoology, University of Vermont, 305 South Prospect Street, Burlington, Vt. Petrunkevitch, Alexander, Ph.D. (Freiburg), Assistant Professor of Zoology, Sheffield Scientific School, Zoological Laboratory, Yale University, New Haven, Conn. Phillips, Everett Franklin, A.B. (Allegheny), Ph.D. (Pennsylvania), Agriculturalist, Bureau of Entomology, United States Department of Agriculture, Washiiigton, D. C. PiERSOL, George Arthur, M.S. (Pennsylvania), Sc.D. (Pennsylvaina College), Professor of Anatomy, LTniversity of Pennsylvania, Jf72Jt Chester Avenue, Philadelphia, Pa. Pike, Frank H., A.B. (Indiana), Ph.D. (Chicago), Assistant Professor of Physiology, Columbia L^niversity, 437 West 59th Street, New York City. Pratt, Henry Sherring, A.B. (Michigan), A.M., Ph.D. (Leipzig), Professor of Biology, Haverford College, Haverford, Pa. Rand, Herbert Wilbur, A.B. (Allegheny, Harvard), A.M., Ph.D. (Harvard), Assistant Professor of Zoology, Harvard University; A/useu»! o/ Comparative Zoology, Cambridge, Mass. Ranso.m, Brayton Howard, B.Sc, !M.A., Ph.D. (Nebraska), Chief, Zoological Division, Bureau of Animal Industry, L'nited States Department of .Agriculture, Bureau of Animal Industry, Washington, D. C. Reed, Hugh Daniel, B.S., Ph.D. (Cornell), Assistant Professor of Zoology, Cornell, McGraw Hall, Ithaca, N. Y. MEjrBERS 119 Reese, Albert Moore, A.B.. Ph.D. (Johns Hopkins), Professor of Zoology, West Virginia University, Morgantown, W. Va. Reighard, Jacob Ellsworth, Ph.B. (Michigan), Professor of Zoology; Director of Zoological Laboratory and Biological Station, University of Michigan, Ann Arbor, Mich. Reixke, Edwin Eustace, M.A. (Lehigh), Ph.D. (Princeton), Assistant Professor of Biologj-, Vanderbilt University, Nashville, Tenn. Rice, Edward Loraxus, A.B. C^Vesleyan), Ph.D. (Munich), Professor of Zoology, Ohio WesUyan University, Delaware, Ohio. Richards, A., B.A. (Kansas), ^LA. (Wisconsin), Ph.D. (Princeton), Wabash College, Craicfordsville, Ind. Riddle, Oscar, A.B. (Indiana), Ph.D. (Chicago), Resident Investigator, Carnegie Institution of Washington, Cold Spring Harbor^ Long Island, X. 1". Rilet, William Albert. B.S. (DePauw), Ph.D. (Cornell), Professor of Insect Morphology and Parasitology. Cornell University, Ithaca, .V. Y. Ritter, William E., B.S. (California), Ph.D. (Harvard), Director of Scripps Institution for Biological Research of the L^niversity of California, Professor of Zoologj-, University of California, La Jolla, Cal. Robertson-, Alice, B.S., M.S., Ph.D. (California), Professor of Zoology, Wellesley College. Wellesley, Mass. Robertsox, William R. B., A.B. (Kansas), Ph.D. (Hanard), Assistant Professor of Zoologj-, University of Kansas, 1420 Ohio Street, Lawrence, Kans. Rogers, Charles Gardxer, A.B., A.M. (Syracuse), Ph.D. (California), Professor of Comparative Physiology, Oberlin College, Oberlin, Ohio. Rogers, Fred Terrt, A.B., Ph.D. (Chicago), Assistant Professor of Zoologj-, Baylor University, Waco, Texas. RuTHVEN. Alexander G., B.S. (Momingside), Ph.D. (Michigan), Director, Museum of Zoology, Assistant Professor of Zoology, University of Michigan, Museum of Zoology, Ann Arbor, Mich. ScHAEFFER, AsA Abthitr, A.B. (Franklin and Marshall), Ph.D., (Johns Hopkins) Associate Professor of Zoology, University of Tennessee, Knoxville, Tenn. ScHiEDT. Richard C. F., Ph.D. (Pennsylvania), Sc.D. (Hon.) (Franklin and Marshall), Professor of Biology and Geology, Franklin and Marshall College, lOJfS Wheatland Avenue, Lancaster, Pa. ScoTT, George G., A.B., A.M. (Williams), Ph.D. (Columbia), Chairman Department of Biology, College of the City of Xew York, Xew York City. ScoTT, John W., A.B., A.M. (Missouri), Ph.D. (Chicago), Professor of Zoology, University of Wyoming, Laramie, Wy. Scott, William, Ph.D. (Indiana), Assistant Professor of Zoologj-, Indiana University, Bloomington, Ind. Sheldon, Ralph Edward, A.B., A.M. (Cornell), S.M. (Harvard), Ph.D. (Chicago), Assistant Professor of Anatomy and Director of Anatomical Laboratories, University of Pittsburgh, School of Medicine, Pittsburgh, Pa. Shelford, Victor Erx-est, B.S., Ph D. (Chicago), Assistant Professor of Zoology, L'niversity of Illinois, and Biologist of Illinois State Laboratory, SOS West Iowa Street, Urbana, III. Shepherd, W. T., A.M., Ph.D., Professor of Zoology and Dean, Waynesburg College, Waynesburg, Pa. • 120 AMERICAN SOCIETY OF ZOOLOGISTS Shorey, Marian Lydia, A.M. Ph.B., (Brown), Ph.D. (Chicago), Hugenot College, Wellington, South Africa. Shull, Aaron Franklin, A.B. (Michigan), Ph.D. (Columbia), Associate Professor of Zoology, University of Michigan, 520 Linden Street, Ann Arbor, Mich. SiGERFOos, Charles P., B.S. (Ohio State), Ph.D. (Johns Hopkins), Professor of Zoology, University of Minnesota, Minneapolis, Minn. Smallwood, William Martin, Ph.D. (Harvard), Professor of Comparative Anatomy, Syracuse University, 525 Euclid Avenue, Syracuse, N. Y. Smith, Bertram Garner, A.B. (Michigan), Ph.D. (Columbia), Assistant Professor of Zoology, Michigan State Normal College, ISi College Place, Ypsilanli, Mich. Smith, Frank, Ph.B. (Hillsdale College), A.M. (Harvard), Professor of Systematic Zoology, University of Illinois, Urbana, III. Smith, Locy Wright, B.A. (Mt. Holyoke), M.A., Ph.D. (Cornell), Instructor in Zoology, Mt. Holyoke College, South Hadley, Mass. Spaeth, Reynold A., Ph.D. (Harvard), Instructor in Biology, Yale University, Osborn Zoological Laboratory, New Haven, Conn. Stockard, Charles Rupert, B.S., M.S. (Mississippi Agricultural and Mechanical College), Ph.D. (Columbia), Professor of Anatomy, Cornell University, Medical School, Cornell Medical College, First Avenue and Twentyeighth Street, New York City. Streeter, George L., A.M., M.D., Research Associate in Embryology, Carnegie Institution, Johns Hopkins Medical School, Baltimore, Md. Stromsten, Frank Albert, B.S., M.S. (Iowa), D.Sc. (Princeton), Assistant Professor of Animal Biology, State University of Iowa, 943 Iowa Avenue, Iowa City, Iowa. Strong, Oliver S., A.B., A.M. (Princeton), Ph.D. (Columbia), Instructor in Neurology, Columbia University, College of Physicians and Surgeons, 4^7 West Fifty-ninth Street, New York City. Strong, Re'uben Myron, A.B. (Oberlin), M.A., Ph.D. (Harvard), Associate Professor of Anatomy, Vanderbilt University Medical School, Nashville, Tenn. Sturtevant, Alfred H., A.B., Ph.D. (Columbia), Cutting Fellow, Columbia University, New York City. SuM.NER, Francis B., B.S. (Minnesota), Ph.D. (Columbia), Biologist, Scripps Institution for Biological Research, La .lolla, Cal. Surface, Frank M., A.B., A.M. (Ohio State), Ph.D. (Pennsylvania), Biologist, Maine Experiment Station, Orono, Maine. SwEZY, Olive, B.S., M.S., Ph.D., (California), Associate in Zoology, Assistant Zoologist, Scripps Institution for Biological Research, University of California, East Hall, University of California, Berkeley, Cal. Tannreuther, George W., A.B. (Manchester), A.M. (Antioch), Ph.D. (Chicago), Instructor in Zoology, University of Missouri, Columbia, Mo Tashiro, Shiro, B.S., Ph.D. (Chicago), Instructor in Physiological Chemistry, University of Chicago, Hull Bro. Chemical Laboratory, Chicago, III. Tennent, David Hilt, B.S. (Olivet), Ph.D. (.Johns Hopkins), Professor of Biology, Bryn Mawr College, Bryn Maxor, Pa. MEMBERS 121 Thompson, Caroline Burling, S.B., Ph.D. (Pennsylvania), Associate Professor of Zoology, Wellesley College, Leighton Road, Welleslej/, Mass. ToRREY, Harry Beal, B.S., M.S. (California), Ph.D. (Columbia), Professor of Biology, Reed College, Portland, Ore. Treadwell, Aaron L., B.S., M.S. (Wesleyan), Ph.D. (Chicago), Professor of Biology, Vassar College, Poughkeepsie, N. Y. Van Cleave, Harley' Jones, B.S. (Knox College), M.S., Ph.D. (Illinois), Associate in Zoology, 300 Natural Historij Building, University of Illinois, Urbana, III. Verrill, Addison E., S.B. (Harvard), A.M. (Yale), Professor of Zoology, Emeritus, Yale University, New Haven, Conn. Wagner, George, M.A. (Michigan), Assistant Professor of Zoology, University of Wisconsin, Biology Building, Madison, Wis. Waite, Frederick Clayton, Litt.B. (Adelbert), A.M. (Western Reserve), A.M., Ph.D. (Harvard), Professor of Histology and Embryology, School of Medicine, Western Reserve University, 135S East 9th Street, Cleveland, Ohio. Wallace, Lodise Baird, A.B. (Mount Holyoke), Ph.D. (Pennsylvania), Dean of Constantinople College, Constantinople, Turkey, South Hadley, Mass. Walter, Herbert Eugene, A.B. (Bates), A.M. (Brown), Ph.D. (Harvard), Assistant Professor of Biology, Brown University, Providence, R. I. Walton, Lee Barker, Ph.B. (Cornell), A.M. (Brown), Ph.D. (Cornell), Professor of Biology, Kenyan College, Gambier, Ohio. Ward, Henry Baldwin, A.B. (Williams), A.M., Ph.D. (Harvard), Professor of Zoology, University of Illinois, Urbana, III. Welch, Paul Smith, A.B. (James Millikin), A.M., Ph.D. (Illinois), Assistant Professor of Entomology, Ka7isas State Agricultural College, Manhattan, Kan. Wells, Morris Miller, B.S. (Chicago), Ph.D. (Illinois), Instructor Department of Zoolog}', University of Chicago, Chicago, III. Wenrich, David Henry, B.A., M.A., Ph.D., Instructor in Zoology, University of Pennsylvania, Zoological Laboratory, Philadelphia, Pa. Wentworth, Edward N., M.S. (Iowa), Professor of Animal Husbandry, Kansas State Agricultural College, Manhattan, Kans. Werber, Ernest I., Ph.D. (Vienna), Sessel Research Fellow, Yale University, Osborn Zoological Laboratory, New Haven, Conn. Wheeler, William Morton, Ph.D. (Clark), Professor of Economic Entomology, Bussey Institution, Forest Hills, Boston, Mass. Whiting, Phineas W., A.B., M.S., Ph.D., Harrison Research Fellow, University of Pennsylvania, Zoological Laboratory, Philadelphia, Pa. Whitney, David Day, B.A. (Wesleyan), M.A., Ph.D. (Columbia), Professor of Zoology, University of Nebraska, Lincoln, Neb. WiBMAN, Harry Lewis, A.B., A.M. (Cincinnati), Ph.D. (Chicago), Associate Professor of Zoology, Head of Department, University of Cincinnati, Cincinnati, Ohio. Wilder, Harris Hawthorne, A.B. (Amherst), Ph.D. (Freiburg), Professor of Zoology, Smith College, Northampton, Mass. 122 AMERICAN SOCIETY OF ZOOLOGISTS Wilder, Inez Whipple, Ph.B. (Brown), M.A. (Smith), Associate Professor of Zoology, Smith College, Northampton, Mass. WiLDMAN, Edward E., B.S., M.S., Ph.D. (Pennsylvania), Head Department of Science, West Philadelphia High School for Girls, 4331 Osage Avenue, Philadelphia, Pa. WiLLARD, W. A., Ph.B. (Grinnell), A.M. (Tufts and Harvard), Ph.D. (Harvard), Professor of Anatomy, University of Nebraska, College of Medicine, Omaha, Neb. Williams, Stephen Riggs, A.B., A.M. (Oberlin), A.M., Ph.D. (Harvard) Professor of Zoology and Geology, Miami University, 300 East Church Street, Oxford, Ohio. Wilson, Edmund B., Ph.B. (Yale), Ph.D. (Johns Hopkins). LL.D. (Yale, Chicago, Hopkins), M.D. (Hon.) (Leipzig), Sc.D. (Cambridge), Da Costa Professor of Zoology, Columbia University, New York City. Wilson, Henrt Van Peters, A.B., Ph.D. (Johns Hopkins), Professor of Zoology, University of North Carolina, Chapel Hill, N. C. Wodsedalek, Jerry Edward, Ph.D., M.Ph., Ph.D. (Wisconsin), Professor of Zoology and Head of the Department of Zoology and Entomology, University of Idaho, Moscow, Idaho. WoLCOTT, Robert Henry, B.S., M.D. (Michigan), A.M. (Nebraska), Professor and Head of the Department of Zoology, University of Nebraska, Lincoln, Neb. Woodroff, Lorande Loss, A.B., A.M., Ph.D. (Colmnbia), M.A. (Yale), Professor of Biology, Yale University, Osborn Zoological Laboratory, New Haven, Conn. Wright, Albert Hazen, A.B., A.M., Ph.D. (Cornell), Assistant Professor of Zoology, Cornell University, Upland Road, Ithaca, N. Y. Wright, Sewall G., S.B. (Lombard), S.M. (Illinois), S.D. (Harvard), Senior in Animal Breeding Investigation, Animal Husbandry Division, Bureau of Animal Industry, Department of Agriculture, Washington, D. C. Yerkes, Robert M., Ph.D. (Harvard), Assistant Professor of Comparative Psychology, Harvard University, Emerson Hall, Cambridge, Mass. YocuM, H. B., A.B. (Oberlin), M.A., Ph.D. (California), Professor of Zoology, Washburn College, 1815 Huntoon Street, Topeka, Kan. YooNG, Robert T., B.S. (Pennsylvania), Ph.D. (Nebraska), Professor of Zoology, University of North Dakota, University, N. D. Zelent, Charles, Ph.D. (Chicago), Professor of Zoology, University of Illinois, Urbana, III. author's abstract of this paper issced by the bibliographic service, december 1 PERSISTENCE OF THE POSTERIOR CARDINAL VEINS IN AN ADULT CATHERBERT E. METCALF AXD KATHARINE D. METCALF North Dakota Agricultural College ONE FIGURE During the spring of 1917 one of the students in a class in vertebrate dissection reported a cat possessed of a double vena cava. This cat was then carefully dissected by the authors and an attempt is here made to explain the structures found as remnants of a condition carried through from embryonic stages to the adult form without further change. The cat was one picked up in the street, was very hardy and evidently had been foraging for itself for some time. Physically it was in fairly good condition with a moderate amount of fat around the kidneys. Its coat was in a filthy condition, but otherwise it was practically physically fit. The veins of the head, neck and thorax were also carefully dissected but they showed no great variation from those of a normal cat. In the normal embryonic development of the cat the posterior cardinal veins run along the dorsal side of the mesonephros and enter the heart through the common cardinal veins. Each receives the internal iliac vein draining the posterior extremities, short branches from the mesonephros, and the segmental veins draining the body wall. The sub-cardinals are developed median and ventral to the mesonephros. These sub-cardinals are connected at intervals with the posterior cardinals by sinusoids, and with each other by anastomoses. Thus all of the blood from the mesonephroi and the posterior extremities is drained by the posterior cardinal veins alone during the earlj' embryonic stages. Likewise in the cat here reported the per ' Proceedings from the ZoologicaK Laboratory of the North Dakota Agricultural College, No. 1. 123 124 HERBERT E. METCALF AND KATHARINE D. METCALF sistent posterior cardinal ^'eins drain the posterior limbs and the most of the blood from the now developed true kidney or metanephros. The development of the unpaired vena cava inferior begins at the point where communication is established between the right hepatic vein of the Uver and the right sub-cardinal vein, developed on the opposite side of the mesonephros and which is in reality a tributary of the post cardinal vein. A branch of the posterior cardinal vein encircles the ureter of the pemaanent kidney and is called the supra-cardinal vein. This has persisted in the adult cat on the left side. The pemanent kidneys then take up their position opposite the large anastmoses between the posterior cardinal veins and sub-cardinals, and it is at this point that the renal veins are developed. In the specimen found, there are two separate and distinct main veins running from each leg as far forward as the region of the kidney with absolute!}' no anastomoses along their course. The condition is clearly one of arrested embryonic development. These two main trunks can easily be identified as persistent posterior cardinal veins, having lost, however, the caudal anastomosis which is present in the embryo. The right side differs from the left in one particular only, and that is that the loop through which the ureter passes occurs on the left side only (fig. 1, C). This may easily be explained. Both ureters pass underneath the post cardinals, then curve sharply to meet the spermatic artery and vein (fig. 1, B). The ureter on the left side passes through a loop exactly as the ureter passes through a loop composed of the posterior and supra-cardinals in the embryo. Therefore, the median vein of this loop is without doubt the supra-cardinal vein. This vein receives the veins from the region of the spinal cord which would empty into the unpaired vena cava in the normal cat. This vein has entirely disappeared on the right side. It is readily seen, however, that the persistence of this vein is necessary on one side or the other in order that the region beneath the spinal cord be drained. As we go further foward the right sub-cardinal has united with the right hepatic vein of the li\-er and a single vena cava is pros POSTERIOR CARDINAL VEIXS IX AX ADULT CAT 125 ent for a very short distance. The posterior cardinals converge and empty into this. Both renal veins instead of joining the unpaired portion empty into the right and left postcardinal veins respectively, although one branch from the right kidney enters the unpaired vena cava. The spermatic veins, which enter in different positions on each side of the normal cat, here enter the right and left post cardinals exactly as in the embryo. Hr %&rcAie^ E>T«MiTT I'e^io^ CjCTVtniTy This cat also shows very nicely the fact that the left spemiatic vein is made up at its proximal end of a portion of the left post cardinal vein (fig. 1, A). Functionally the end result of the system as here described must have been exactly as good as that of a normal cat, and there seems to be no reason why this particular cat should have noticed any physiological effect from its abnormal drainage system, which may be explained as the persistence of the right and left posterior cardinal veins and the left supra-cardinal veins. 126 ■ E. R. HOSKINS BIBLIOGRAPHY (1) Reighard and Jennings 1901 Anatomy of the Cat. Henry Holt & Co. (2) KiNGSLEY, J. S. 1912 Comparative Anatomy of Vertebrates. P. Blakis ton's Son & Co. (3) Prentiss, C. W. 1915 Textbook of Embryology. W. B. Saunders Co. (4) Bailey and Miller 1916 Te.xtbook of Embryology. VVm. Wood & Co . .author's abstract of this paper issued by the bibliographic service, december 8 MICROSCOPE LAMPS FOR STUDENTS E. R. HOSKINS Anatomical Department, New York University and Bellevue Hospital Medical College 1. The following method will ])rovide at very small cost microscope lamps which for ordinary student laboratories, are as satisfactory as the rather expensive lamps now on the market. 'Mazda' lamps of sixteen candle power with ground ('frosted') bulbs are dipped two or three times in a saturated solution of Bleu de Lyon in 50 per cent alcohol. After each dipping the lamp is permitted to dry. Wiring for the lamps is strung along the top of the table and protected by a metal strip one inch wide. Sockets are placed at the desired intervals. If students are seated on two sides of the tables, one such lamp will provide light for foin- persons. These lamps may be used effectively also for general illumination of the laboratories and offices. 2. Attention is called also to the new 'Mazda' lamps of higher power provided with a blue bulb, which are used commercially to illuminate show windows. These give a very strong nearly white light which is suitable for high-power microscopical work, but they are more expensive than the lamps described above. AUTHORS ABSTRACT OF THIS PAPER ISSUED BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 1 CONCERNING THE REXAL PORTAL SYSTEM IN CHRYSEiMYS .MARGINATA BYRON L. ROBINSON' Minneapolis, Minnesota TWO FIGURES The presence of a renal portal system in reptiles is still an unsettled question. ^Miatever the significance of such a system, its presence has been definitely proven in fishes and amphibians, and its absence quite as siu-ely shown in adult birds and mammals. But in the consideration of the question with respect to reptiles, one encounters contradictions, hazy statements, and lack of statement by various writers. The following table will indicate the position of authors on the subject: DATE AfTHOB ARTICLE OR BOOK pnB LISHED STATEilEN'T Owen "Anatomy of Vertebrates" "Elements of Comparative 1866 Hazy Present in reptiles except Gegenbauer . . . 1878 Anatomy" Chelonia Kingsley "Vertebrate Zoologj-" 1899 Present in reptiles except Chelonia' Kingsley "Comparative Anatomy of 1912 Persists to a greater or less Vertebrates extent in adult reptile Pratt "Vertebrate Zoology'" 1905 Present Stromstem .... Anatomy and Development 1905 Belief of connections. No ^'enous System of Che proof Ionia. Am. J. Anat.4:453 Wiedersheim . . "Comparative Anatomy 1907 Only indications retained of Vertebrates in adult Wilder "History of the Himian Body" 1909 Not present in adult reptile Agushi Renal and suprarenal veins 1911 Capillaries in Trionyx of Trionyx japonicus. japonicus Anat. Anz. .39, p. 18.3 Hegner "College Zoology." .1914 Absent'in turtle D. Lewis "The Circulator}' System of Chrj'semys marginata" Thesis U. of Wis. (unpublished) 1916 Present in -Ch.l marg. 127 128 BYROX L. ROBINSON There seems to be a' preponderance of statement among authorities that a renal portal system is not retained in reptiles, at least not in its entiretj'. We have Gegenbauer, Kingsley, and Hegner agreeing that there is none in turtles, and Wiedersheim and Wilder that it is not present in the adult reptile; while opposed to these statements there is Pratt who says that the renal portal system is present, in the turtle. As to original work on the problem, Stromstem believes that there are connections larger than capillaries between the posterior renal advehentes and the postcava in Chelydra serpentina, but he presented no evidence to prove it in his article. His work was general, including the anatomy and development of the entire venous system of several forms of Chelonia. The largest part of his work was on- the hepatic portal system. Agushi in working on the Japanese form used the metal corrosion method with India ink injections and sections for a control. He claims to have demonstrated capillary connections, but his work is not conclusive. His work was not confined to the kidney but included the suprarenals as well. Dorothy Lewis in working out the general circulation of Chrysemys marginata was unable to get a starch mass into the postcava by injecting through the renal portal vein. She concluded from this that there were no connections larger than capillaries between them, and therefore that there was a true renal portal system in this form. The author tried several injections through the renal portal vein, none with success. The injection is difficult, and the results not at all conclusive. This, then, is the status of the problem: the predominant note among writers on the subject seems to be that there is not a true renal portal system in the Chelonia at least, but there is no definite e\'idence to support this point of view nor is there any conclusive evidence given by those who hold that a renal portal system is present in the Chelonia. The need for specific work on the problem is evident. It is in the hope of giving some definite evidence that the author brings forward the results of his work on Chrysemys marginata. The attempt was, by means of a proper injection, suitable clearing of tissue, and careful THE RENAL PORTAL SYSTEM 129 dissection, to demonstrate a connection larger than capillarj' between the renal portal vein and the postcava. Specimens of Chrysemys marginata were readily obtained from the lakes about Madison. In presenting the results of the work, the author wishes to thank Professor George Wagner for suggesting the problem and for other aid, and he desires to acknowledge to ^Ir. George Bishop not only many helpful suggestions but also time and effort spent b}^ him in a large part of -the injection work. Before proceeding to the problem itself, it is advisable to give a brief description of the veins in the vicinitj'^ of the kidney of Chi-j-semys marginata. Running along the ventral side of the Fig. 1. Drawing of entire terrapin, ca, carapace; v, vertebral; r/j. renal portal; i, stub of intercostal; cl. cloacal; h. hypogastric; hi, branches to hind limb; ci, common intercostal; pc. postcava; ab, right abdominal. body between the plastron and the peritoneum are to be found the paired abdominal veins, extending from the region of the liver posteriorly to the sides of the pelvic girdle (fig. 1). In the latter position they pass dorsally and join the circumflex iliac veins. The circumflex iliac vein also receives the common intercostal vein from the lateral part of the carapace, veins from the hind limbs, and veins from the cloacal region. It is continued as the renal portal vein through a notch on the dorsolateral edge of the kidnej-; and it divides into an anterior and a posterior branch on the lateral .surface of the kidney. The anterior branch joins the vertebral vein, while the posterior forms the hypogastric draining the pelvic region. This differs from the description of ^liss Lewis, for- she says that the renal portal vein does not connect with the vertebral and that the 130 BYRON L. ROBINSON hypogastric is a branch of the circumflex iliac. The postcava is attached to the medic-ventral edge of each kidney, is unpaired, and forms a thin-walled sinus between the kidneys. The postcava runs anteriorly through the liver and opens into the sinus venosus. Most of the time spent on the problem was used in discovering a proper manner of injecting and' in experimenting with injection masses. It is not, therefore, out of place to review here the steps taken in developing a suitable technique and to give the results of the experimentation. The first injection was done with a simple raw starch mass. Injections were made into the postcava, into the renal portal ^•ein, and into the abdominal vein, each in a separate specmien. They were all made with a sjrringS. Injection into the postca\'a resulted in getting none of the mass through the kidney into the renal portal veins. In spite of this fact, connections larger than capillaries might exist between the veins, for valves might be present. The flow of blood is in the direction opposite to the injection, that is from the renal portal veins to the postcava. Several injections were tried into the renal portal veins themselves, but without success. These veins are hard to find when uninjected, are short, and are easily injured. Injections into the abdominal vein (preferably the left which is larger) resulted in finding the starch mass in the postcava. This indicated that there might be found a connection between the renal portal vein and the postcava. This preliminary work with a starch mass was followed by double injections, gelatine mass followed by starch mass. And in this work of experimenting with \-arious masses the following difficulties were encountered: 1. The thinness of the walls of the veins which were injected into made the work difficult and uncertain. The postcava though a comparatively large vessel was hard to inject on account of the delicacy of its walls. The renal portal veins presented this difficulty also. The abdominal veins are less THE REXAL PORTAL SYSTEM 131 liable to injury, and yet some difficulty was found- in getting an injection thi'ough them at times. 2. The testis or ovary is attached to the lateral surface of the kidney by means of a mesentery in which black pigment is deposited. This obscured the vessels on the lateral sm-face, and great difficulty was experienced in removing this mesentery without injuring the delicate walls of the veins beneath. 3. The question of the proper masses to show up the ^'essels to the best advantage was a problem. To bring out the ^-essels it was necessary to have a sharp contrast between the colors of the two masses used. A blue gelatine obscured ever3i;hing in the kidney. The vessels injected with the starch mass must stand out against the kidney filled with the gelatine which goes into the finest capillaries. After many trials the following two masses were used with good results. A cold gelatine mass was made up according to the Tandberg method as given in Guj^er's "Animal ^licrology" except that carmine was used for the pigment instead of Berlin blue. It was made up as follows: 5 grams of gelatine were added to 100 cc. of tepid distilled water. Carmine dissolved in anunonia was then added to the gelatine solution to give a Ught red color. Acetic acid was added to neutralize the ammonia, neutralization being indicated by the disappearance of the anunoniacal odor and the change in color to a bright red. 5 to 6 grams of potassium iodide were then added slowly, and finally a few crystals of thymol as a preservative. The mass remains liquid at ordinary temperatures, but solidifies when the object injected is placed in formaldehyde. A starch mass was made up after experimentation in the following manner: 20 grams of starch were added to 550 cc. of water, and the starch cooked. 50 grams of Zinc oxide were added, and then enough 50 per cent potassium hj-droxide to hiake the mixture smooth. A trace of soap was put in, and finallj^ a few crystals of thjanol to preserve. The starch mass cannot be preserved with formaldehyde, for such a mass following the cold gelatine sets the gelatine and interferes with the injection. 132 BYRON L. ROBINSON Successful injections with these masses gave a light red kidney against which the branches of the renal portal vein filled with the white starch mass, showed up clearly. It was found best to use an air pressure apparatus in the injection in place of the syringe, for it gave a steady pressure and filled up the smallest branches with the starch mass. The injected terrapins were placed into 10 per cent formaldehyde to set the gelatine and then into 50 per cent alcohol to set the starch. The kidneys were dissected out and placed into 95 per cent alcohol. They were then cleared by running them through absolute alcohol, then benzol, and finally a mixture of oil of wintergreen and isosafrol (oil of wintergreen 5 parts and Fig. 2. Terrapin A, right kidney, rp, renal portal; v, vertebral; pc, postcava; A, hypogastric. isosafrol 3 parts) following the Spalteholz method for clearing. One kidney was then drawn entire to show the distribution of the blood vessels, and then thick sections were cut, arranged in series, and drawn to show the vessels in the kidney injected with starch. In two series of kidney sections indication was found that a connection larger than capillary existed between the renal portal and the postcava. In sections about midway between the anterior and the posterior ends the starch mass was found extending from the region of the renal portal to the postcava. For verification a nmnber of kidneys were dissected on the lateral surface to demonstrate the connection. Two dissections were successful. A right kidney is shown (fig. 2) with the vessel extending down from the renal portal to the postcava. THE RENAL PORTAL SYSTEM 133 It was found by dissecting off carefulh' the entire mesentery of the ovarj' or testis. A similar connection is clearly seen also in the dra\^"ing of the entire terrapin (fig. 1). These results show a connection between the renal portal vein and the postcava, a connection larger than capillary. While there may be capillaries present also between the two veins, yet the demonstration of a larger connection proves at least that the renal portal system is not complete. CONCLUSIONS The following results were obtained in this work on Chrysemys marginata : 1. Injection of a starch mass into the postcava resulted in finding none in the renal portal vein. This does not disprove a connection larger than capillary, for valves might be present. 2. Injection of starch into the renal portal vein was unsuccessful. 3. Injection of starch into an abdominal vein resulted in finding the mass in the postcava. 4. By means oi a double injection a connection was demonstrated between the renal portal vein and the postcava. This proves at least that a complete renal portal system does not exist in Chrysemys marginati. 134 BTKOX L. ROBINSON BIBLIOGRAPm' Agushi. K. 1911 I'eber die Xebennieren and Xierenpfortader des Trionyx japonicus Anat. Anz. Bd. 39, p. 183. Gegenbacer 1878 Elements of comparative anatomy, p. 594. Gxn-ER, M. F. 1906 .\niinal Micrologj', p. 86. Heg.ver 1914 College Zoologj-, p. 532. KiNGSLET 1899 Vertebrate Zoologj', p. 303. 1912 Comparative anatomy of vertebrates, p. 300. Lewis, D., 1916 The circulatory system of Chrysemys marginata. Bachelor thesis U. of Wis., p. 16 (mipublished). Owen 1866 Anatomy of Vertebrates, p. 505. Pratt 1905 Vertebrate Zoologj-, p. 159. Stromstem, F. a. 1905 A contribution to the anatomy and development of the venous sj-stem of Chelonia. Am. Jour. Anat. vol. 4, p. 453. Taxdler 1901 Mikroskopische Injectionen mit Kaltfiussiger gelatin. Review in Journal of Applied Microscopy, vol. 5, p. 1625. WiEDEKSHEi.M 1907 Comparative Anatomy of Vertebrates, p. 429. Wilder 1909 History of the Human Body, p. 324. WooDL.vxD, W. 1906 A suggestion concerning the origin and significance of the 'Renal Portal' sj-stem. Proceedings Zoological Society of London, vol. 2, p. 886. aithor's abstract of this paper issced bv the bibliographic service, december 15. OBSERVATIONS ON THE SHAPE OE THE ERYTHROPLASTID IN THE ^TNG OF THE BAT LESLIE B. AREY From the Anatomical Laboralory of the Northwestern University Medical School^ In previous publications ('16, '17) there has been presented in detail the evidence derived from the study of drawn blood, circulating blood, and fixed preparations which has led the writer to conclude, contrary to certain recent investigations, that the biconcave disc represents the normal shape of the mammalian erythroplastid — the concavo-convex 'cup' being merely an occasional constituent of the blood. For reasons that are obvious the inspection of. blood circulating in the transparent parts of mammals should furnish reliable information upon this topic. There are, nevertheless, certain sources of error to be avoided: only vessels of greater calibre than a red corpuscle are suitable for study; the effect of pressure upon small vessels must be ehminated or controlled ; the possible influence of the anesthetizing agent carried in the plasma upon the circulating corpuscles (similar to its demonstrable effect in modif jdng the shape of drawn corpuscles) must be shown not to exist or else non-anesthetized animals used. In the studies upon circulating blood, the omenum and mesentery have largely been employed. It is hardly reasonable to urge that the necessary exposure of these parts during the examination, inviting though it does drying, stasis, and inflammation, need militate against the validity of the results, j^et if these abnormal conditions can be avoided a valuable check is thereb}' gained. The onlj- situation which might appear a priori to be more favorable than the omentum or mesentery is such an one as is furnished by the wing of the bat. In the present communication it is proposed to present evidence derived from this source. ' Contribution Xo. 51, October 1, 1917. 13.) 136 LESLIE B. AREY Since an extended review of the literature has been published recently by the writer ('17) only those contributions bearing directly upon the subject at hand need be mentioned. Weidenreich ('03) recommended for study the wing of the hibernating bat, evidently intending to infer that cup-shaped corpuscles would.be found. Jolly '05) also reported observations upon the bat's wing* He asserts that rouleaux occur normally in the capillary circulation, these breaking into short segments which persist in the veins, only to reform long rows if the current slackens; in support of this claim a similar finding by Weber and Souchard ('80) on curarized dogs is cited. In rouleaux he found the separating lines to be transverse, the terminal corpuscles of short trunks discoid, while corpuscles free in the plasma likewise had the disc configuration. Exceptionally cup shapes were seen at the end of rouleaux or free. Weidenreich ('05) denied that rouleaux exist in the normal circulation and suggested that Jolly must have observed capillaries in which the flow had almost or wholly ceased. He adds that in the bat's wing he has repeatedly seen only cups. Again in 1906 Weidenreich reiterates these points, objecting that Jolly saw corpuscles compressed into rouleaux by incipient stasis, whence their true fomi vanishes; cc . . . . da ich wiederholt schonste Napfformen und zwar nur Napfformen sah, besteht fiir mich kein Grund von meiner Deutung abzugehen." Jolly ('06 a) denied that stasis influenced his results and this and later publications ('06 b ; '09) simply re-emphasize his former contentions. My own observations have been made during the preceding summer upon a number of bats' of two species.* The animals • From a footnote in a later communication ('09) it appears that many of the animals used in his experiments were prematurely aroused from hibernation; this he believes neither involves complications nor introduces a source of error. ' For the procural of these animals I am indebted to the persistent efforts of Mr. J. R. Reuling of Muscatine, Iowa. • Lasionyctcris noctivagans Le Conte: Vespertilio gryphus lucifugus Le Conte. SBLVPE OF BRTTHROPLASTID IX THE WING OF BAT 137 were held by an assistant' and the wing spread on a glass plate over the microscope stage; various lens combinations were employed both with and \A-ithout the aid of a cover glass. The keratinized and pigmented epidermal cells make observation less simple then in the inspection of a mesentery. Xevertheless a thorough search usually re^'eals a favorable location, and experience soon enables one to overcome surprisingly the early observational difficulties. Small vessels branching off from larger ones in a reciurent manner often afford a favorable site. ^Minute capillaries merely large enough to allow corpuscles to pass in single file are to be avoided for here crowding and distortion are ine\'itable ; stretching of the wing also flattens small vessels by increasing their lateral diameter, whence corpuscles pass through more or less on the flat thereby producing a deceptive picture of innumerable cups (vide infra) . It is often possible to control the blood flow by applying pressure of the finger to large vessels in more remote regions of the" wing; such manipulation may induce a rythmical flow of a halting or pulsating nature, whereby individual corpuscles can easily be watched and made to revolve; in other instances corpuscles pass by continuously, a few at a time. The normal circulation, with a minimiun of interference, was, however, given the preponderance of attention. I do not beheve that the occurrence of rouleaux ^\^thin the normal circulation, as maintained by Jolly, is in accord with the facts. When corpuscles pass under pressure in single file through capillaries, temporary piles of approximated elements undoubtedly form. In va,rying abundance they may also be found in larger vessels, but I feel confident that this is correlated with some artificial restriction to the usual flow; I hold it probable that this condition can be induced or aggravated by inhibiting the current distad of the spot vmder inspection. It is significant that Jolly neither describes nor figures rouleaux in the ' It is a pleasure to acknowledge the valuable assistance rendered bj- Mr. F. H. Reuling during the course of these experiments. In several instances he has checked my observations and with identical results. 138 LESLIE B. AEEY arterial circulation where he states ('09, p. 101) ". . . . la rapidite du courant empeche de distinguer nettement les globules." The explanation of Jolly's contention may exist in the circumstance that manj- (or most?) of his experimental animals had been recently in their dormant winter state where the circulatory condition is presumably that of essentia' stasis. Eliminating the deceptive simulations of cups afforded by corpuscles viewed obliquely on the flat/ I was able to convince myself of the normality of the disc shape. I do not believe that, in the bat at least, an opinion concerning the shape of a corpuscle carries weight unless that particular corpuscle is seen on both faces, or at least in perfect profile. Blood drawn from a cut between two opposed cover glasses, fused at one point and separated by a hair, confirmed this opinion; many corpuscles were seen which appeared as veritable cups until rotation presented an edge \'iew. This illusion I do not remember having seen so strikingly before in the blood of other manmaals (cf. '17, p. 469); the impression was gained that in these co>rpuscles the excavated faces were especially deep, this perhaps being due to thicker rims. The foregoing observations on the iring of the living bat support the contention that the mammalian erythroplasiid is correctly described as a biconcave di^c. ' David ('08) and Lohner (10) have emphasized the importance of this illusion and have constructed elaborate models to demonstrate its actuality. SHAPE OF ERTTHROPLASTID IX THE WING OF BAT 139 LITERATURE CITED Aret, L. B. 1916 The mammalian erythrocyte — a biconcave disc. Science n.s., vol. 44, no. 1133, pp. 392-395. 1917 The normal shape of the mammalian red blood corpuscle. .\iii Jom-. Anat., vol. 22, no. 3, pp. 439-474. V. D.wiD, C. 190S Ueber optische Einstellungsbilder kreisscheibenformigej Erythrozyten. .\rch. f. mik. Anat.. Bd. 71, pp. 159-163. Jolly, J. 1905 Sur la forme des globules rouges de's ^Mammiferes Comp. rend. see. biol., T. 58, pp. 4S1-4S3. 1906a Quelques remarques a propos de la forme, de la structure et de la fixation des globules rouges des Mammiferes. Folia haematol., Jahrg. 3, no. 4, pp. 183-186. 1906b Courte response a la note precendente de M. Weidenreich. Folia haematol., Jahrg. 3, no. 5, p. 244. 1909 Sur quelques points de la morphologie du sang etudies par Tob servation de la circulation dans I'aile de la chauve-souris. Arch. d'Anat. microscopique. T. 11, pp. 94-109. LoHXER, L. 1907 tjber die Glockenformen von Saugererythrocyteu und ihre Ursachen. Arch. f. d. gesam. Physiol., Bd. 131, pp. 408—424. Weber E. et Souchard, E. 1880 De la disposition en piles qu'effectent les globules rouges du sang, Archiv de Physiol., Annee 1880, pp. 521-531. Weidenreich, F. 1903 Die roten Blutkorperchen. Ergeb. d. Anat. und Ent wickl., Bd. 13, pp. 1-94. 1905 Einige Bermerkungen iiber die roten Blutkorperchen. Anat. Anz., Bd. 27, no. 24, pp. 583-596. 1906 Einige Bermerkungen zu dem Aufsatze J. Jolly's iiber die Form, Strukture, und Fi.xation der roten Blutkorperchen der Saugethiere. Folia haematol., Jahrg. 3, no. 5, pp. 241-244. H) ACTHOBS ABSTRACT OF THIS PAPER ISSUED BT THE BIBLIOGELVPHIC SERVICE, DECEMBER 8 A SEASONAL STUDY OF THE KIDNEY OF THE FIVE SPINED STICKLEBACK, EUCALIA INCONSTANS CAYUGA JORDAN WALTER X. HESS Zoological Laboratory, Cornell University TEX FIGURES CONTENTS Introduction 141 Materials and methods 143 History 144 General morphology of the stickleback kidney 145 Histological structure of the different kidney cells during the resting, or winter stage 148 Histological structure of the different kidney cells at the breeding season. . 149 Nature of the exuded secretion 153 Regeneration of the granular cytoplasm within the slime-secreting cells... . 153 Comparisons with the kidneys of other fishes 154 Kidney parasites 155 Summary and conclusion 156 Bibliography 157 INTRODUCTION It is a matter of general knowledge among Zoologists that the sticklebacks, family Gasterasteidae, constitute a group of fishes in which the nest-building instinct is very pronounced. The nest varies with the species since that of the five-spined stickleback (text fig. Ij is constructed largely of algae and other small water plants, while certain of the larger marine species build their nest chiefly by drawing together the vegetation close at hand, though sometimes leaves and other debris, found in the water, are used. This material is shaped into form by the male, and fastened together by means of a substance secreted by the kidneys. The secretion has been mentioned by many authors as silk, and is described and figured in connection with 141 THE ASATOMIC.4L RECORD, VOL. 14, NO. 2 FEBRUARY, 191S 142 WALTER N. HESS several species, as slender, thread-like strands similar in appearance to spider's silk. The present study was undertaken with a view to demonstrating what portion of the urinary tract functions in this rt ^vl r Text fig. 1 A drawing of a nest of the finc-spined stickleback, Euoalia inconstans cayuga Jordan. Drawn from photographs by Dr. E. E. Barker, and a nest in the collection of the Zoological laboratory. process, what changes the various cells undergo at different seasons of the year, and finally to determine if possible the nature and kinds of secretions. KIDNEY OF FI^'E-SPINED STICKLEBACK 143 The writer is sincerely indebted to Dr. H. D. Reed for suggestions and criticisms throughout the progress of this work; also to Dr. R. J. Gihnore for material which he kindly donated. MATERIALS AND METHODS Material for this work was collected monthly throughout the year, except for about two months during the middle of winter. Since previous workers disagree as to whether the females function in producing the secretion, both males and females were preserved for study. The majority of the fishes were killed in the fixing fluids with the abdominal cavity opened. The kidneys of several were removed and preserved separately. The chief fixers used were: Zenker's fluid; mercuric chloride; 10 per cent formalin; Flemming's (strong formula); Benda's; and Zenker's fluid with the acetic acid used in the proportion of one drop to ten cubic centimeters. In order to detennine the seasonal changes in the kidneys, serial sections, varying in thickness from three to ten microns, were made of the kidneys of both males and females, taken at the different seasons. For general staining, Delafield's haematoxylin and eosin were very satisfactory. For more detailed study those killed in Flemming's solution, and stained in Heidenhain's iron haematoxylin proved most satisfactory, though eosin was often used as a counter-stain. FlemmiAg's triple stain was used but with little success. Ehrlich's triple stain proved very satisfactory in showing secretion granules after fixation with Zenker's fluid. For cytoplasmic structures, and to clearly differentiate certain protozoan parasites present, copper haematoxylin proved an excellent stain after fixation with Zenker's fluid in which the acetic acid was used in the proportion of one drop to ten cubic centimeters. In order to demonstrate the portions of the kidney which form the secretion, a wax model, as a reference aid, was constructed from serial sections of the kidney of a male taken at the end of the active period. 1-14 WALTER N. HESS HISTORY Though many observations have been made on the biology of this pecuhar group of fishes, no extensive observations have been made on the histology of the organs, which form the secretion used in constructing the nest. As early as 1828, according to Mobius ('85), David Milne observed the ten-spined stickleback (Spinachia vulgaris Flem.), building its nest at the breeding season. Since that time many authors have reported similar observations. Coste ('48) described in detail the building of the nest by the sticklebacks. He found that the material of the nest was shaped into position by the fish, and thought that the intensive rubbing of the fish's body against this material caused it to remain in position in the nest. He does not seem to have discovered the secretion. Couch ('65) described the method by which the fifteen-spined stickleback builds its nest. He found that the fish secreted a material in the form of a thread which was used in binding the material of the nest together. This thread resembled silk, was elastic, and under magnification, appeared to be composed of several smaller threads glued together. Though he does not directly maintain that he traced the origin of the secretion, he states that there is no doubt but that the substance is obtained from the animal's own body. Ranson ('65) described very interestingly the biology of the ten-spined stickleback (Gasterosteus pungitius). He showed that the male alone constructs the nest in which he then actually forces a successive nuniber of females to deposit eggs. He seems to have overlooked the secretion entirely, for he refers to the building of the nest as an interlacing of fibers of small water plants. Heincke ('82) was apparently the first to discover the true source of the secretion; namely, the kidneys. He maintained that the male and female together constructed the nest, and stated that the secretion, as it passed from the fish, was in the form of a white slimy thread. KIDNEY OF FIVE-SPINED STICKLEBACK 145 Prince ('85) described the thread-like material which binds the nest together, as a colorless, tenacious substance, of the consistency of mucilage when fresh. It exhibits a delicate blue opalescence, which disappears in two or three days, leaving the threads of a transparent gray or a soiled-white color. ]\Idbius ('85) first definitelj' pointed out by histological study that the kidneys of the male stickleback produced the secretion for constructing the nest at the breeding season. He claimed to have found two kinds of secretion, which he designated respectively as mucigen and mucous. Most of the epithelial cells secreted the mucigen as a thread-like material, the finer strands of which were formed in the coiled kidney tubules, the coarser ones in the collecting tubules. The mucous-secreting cells were found interspersed between the other kidne}^ cells. Their nuclei disappeared duri^g the process of mucous secretion, while the nuclei of the mucigen forming cells became flattened and ridged. Following this period of active secretion the mucous secreting cells became slender, and the nuclei passed into the lumen with the last of the mucous substance. ^lobius did not say whether the urinary ducts function in forming the secretion, but he stated that the bladder took no part in this process. Like Couch ('65), Mobius described the thread as composed of a mass of smaller threads glued together. GENERAL MORPHOLOGY OF THE STICKLEBACK KIDNEY Since it has been claimed by certain authors that both the male and female fishes construct the nest, sections of both sexes were cut at different periods during the breeding season. It was readily seen that only the male forms the secretion, for the kidneys of the female showed no signs of the special glandular activity so characteristic of the male at this period. Mobius ('85), in his work on the sticklebacks, maintained that the entire kidney functions in producing the secretion, but since the histological preparations showed distinctly that only a portion of the kidney was functional in this respect, a wax model was constructed, from drawings of serial sections, in order 146 WALTER N. HESS to demonstrate what portions were involved. In making sections for this purpose, fish were taken at the end of the breeding Text fig. 2 A diagrammatic drawing, made from a model of the nephridial tubules of a male stickleback at the breeding season, showing the regions which form the different secretions. The portion shown in stipple secretes urine. The unshaded portions produce the slime-like secretion. B, bladder; BC, Bowman's capsule; BS, body segment; CUD, common urinary duct; VT, uriniparous tubule; KTA, kidney tube attachment; MT, muciparous tubule; UD, urinary duct. season when the cells, specialized for forming this secretion, were entirely vacuolated. Text figure 2 is a drawing of the model referred to above. No attempt was made to show the kidney tubules of the dif KIDNEY OF FIVE-SPINED STICKLEBACK 147 ferent segments, except in one, where an entire kidnej^ tubule is represented. It will be seen that the tubule consists of eight branches which unite a short distance from the urinary duct to form a single tubule. The tubule, shown in stipple with a Bowman's capsule at its end, consists of columnar epithelium and is subservient to the usual excretory function. Those portions of the tubules which are urinary in function, the writer has designated as the uriniparous tubules {UT), while the portions which secrete slime form the muciparous tubules (MT). The uriniparous tubules are of about the same diameter as the muciparous tubules for a short distance when they suddenly become constricted and much coiled. Unlike the muciparous tubules, they were never found branched. At the end of each uriniparous tubule is a Bo^Tnan's capsule. The portions of the kidney which secrete the slime are termed the muciparous tubules, the urinary ducts, the bladder and the common urinary duct. At the height of the slime secreting period the epithelial cells of all these regions are vacuolated throughout their entire extent. In the remaining body segments only the kidney tubule attachments are shown, since the general condition of each is the same as the one figured. The caudal three-fourths of the kidney has, as a rule, only one set of tubules attaching to the urinary duct in each segment, though one segment was found in which no tubule was present. On the other hand, towards the cephalic end of the kidney the tubules were very numerous. Here, together with the lymphatic tissue so characteristic of the anterior part of the fish kidney, they cause a conspicuous enlargement. Following the breeding season, the kidneys of the male are of about the same volume as those of the female. This condition lasts imtil late in January or February, when those of the male again increase in size preparatory to glandular activity. It seems rather peculiar that the first signs of glandular activity in the earlj' spring occur in the distal ends of the muciparous tubules. These become functional before there appears to be any evidence of activity elsewhere. Though it seems 148 WALTER N. HESS probable that all the muciparous tubules become active about the same time, the earliest signs of activity appeared to be in the cephalic region of the kidneys. From the appearance of the cells at different periods during activity, it is clearly evident that there is a difference in the amount of secretion produced in different regions. The cells of the muciparous tubules become active first and secrete the greatest amount of slime. The cells of the urinary duct anterior to the bladder, next, then those of the bladder, and finalh^ those of the common urinary duct, whose cells seemingly secrete the least of all. Thus it is obvious, that the male only produces the secretion, and that the epithelium of the muciparous tubules, urinary ducts, bladder and conmion urinary duct are active in producing the special secl-etion. The bladder is especially large in this species, and serves as a reservoir for the secretion, as well as contributing to its production. HISTOLOGICAL STRUCTURE OF THE DIFFERENT KIDNEY CELLS DURING THE RESTING, OR \\'IXTER STAGE From the first of July until the following February, the cells of the kidney show no signs of acti\'ity other than that of ordinary kidney cells, and hence this period can be spoken of as the resting stage as regards slime secretion. The cells of the muciparous tubules during the month of Deceniber (fig. Ij appear considerably different from those of the uriniparous tubules (fig. 2), though less differentiated than at the breeding season. The nuclei are nearly round, containing one large nucleolus, and a fine network of chromatin. The cytoplasm is of a fine granular character, though somewhat irregularlj' grouped, which appearance, however, may be due to fixation. The cells are very similar in histological structure to those of the urinarj- ducts (fig. 3), except that they are not as large and less columnar. The cells of the bladder and conmion urinary duct are similar to those of the urinarj^ ducts. The condition of the uriniparous tubules, at this season, is rather peculiar, in that the nuclei are very much enlarged, though the cells themselves are smaller (fig. 2) than during the KIDXEY OF FnE-SPIXED STICKLEBACK 149 spring (fig. 7). At this time, as at other seasons, these nuclei usually possess two large nucleoli about which can be seen an irregular chromatin network. ■ No attempt was made to study the cells of the smaller portion of the uriniparous tubule, other than to note that at this season, and also in the spring, they resembled the other lu^iniparous tubule cells, except that they are smaller and less columnar. It cannot be stated that the cells of the male and female kidneys at this stage are ahke histologically. In the female all the ceUs of the kidnej' are of a similar histological structure, there being no difference beween the cells of the different regions, such as has been described above for the male. HISTOLOGICAL STRUCTURE OF THE DIFFERENT KIDNEY CELLS AT THE BREEDIXG .SEASON" In the region of central New York, about the first of February the cells of the muciparous tubules, urinary ducts, bladder and common urinary duct of the male stickleback first begin to show signs of acti\ity. The cytoplasm stains lighter in these cells than in those of the urinipprous tubules, while their nuclei stain sUghtly darker, due to a rather denser granular content. About the middle of February, the cells of the proximal kidnej' tubules begin to secrete the slime. By the first to the middle of ^larch, all the other portions, including the urinarj' ducts, bladder, and common urinarj' duct become functional. Schiefferdecker ('84) found a somewhat similar condition in the bladder of Rana esculenta and Bufo \'ulgaris diu-ing the breeding season. Heidenhain ('90) working on the Tritons, found a similar condition in the cloacal region at this period. Among the first signs of glandular activity is the appearance, between the nuclei and the ends of the cells next to the lumen, of rather large granules, called here, secretion graniiles. Granules somewhat similar in appearance may be seen within the nuclei. The nuclei, however, at this stage appear very similar to their earlier condition. ^laziarski ('11) in a study of the silk glands of lepidopterous larvae, states that the nucleoli migrate out into the cell body loO WALTER N. HESS where they participate directly in the formation of the secretion. Xakahara ('17) claims that in the silk glands of certain insects, portions of the nucleoli migrate into the cell body and form, at least, a part of the secretion products of the cell. While the kidney cells in the stickleback are much different from those that secrete silk in insects, there is, however, some similarity in the methods of secretion. Garnier COO) from a study of the salivary gland of the rat, and ]\Iaxinow ('01) working on the same gland of the dog, claim that the migrated 'nucleolekorper' are metabolized into secretion products. On the contrarj-, Carlier ('99, '05) working on the stomach and liver cells of the newt, opposes the view that the nucleolar material can be considered as playing a role in the formation of the secretion substance. He maintains that the nuclei gi^'e up prez>anogen, which is produced from chromatin, that this is changed to zymogen in the cytoplasm, and finally into the secretion. Another observation important in this connection is the more recent view of glandular secretion upheld by Arnold ('05), Hoven ('10, '11) and Schultze ('11), which has grown out of the discovery of mitochondria or chondrisomes, wideh' distributed in the cj-toplasm of glandular cells, and supposed to give rise to the secretion granules. Of the tliree views, the last seems the least probable in the case of slime secretion in the stickleback-kidney. The dehcate fixers and stains to distinguish mitochondria were used, but in no instance was there any evidence that such was the source of the secretion granules. On the other hand, the \\Titer was unable to find the nucleoli dividing, or to observe the secretion products passing out of the nucleus. As the process of secretion progresses the nuclei appear to cave in on the side toward the free ends of the cells, indicating that the nuclear substance is diminished. The nucleoli in these cells are rather small at all stages, unlike the condition of true silk gland cells. It is pos sible that these nucleoli function directly in producing the secretion granules but it seems more plausible that certain products of the karj'oplasm pass into the cytoplasm forming the secretion KIDXEY OF FIVE-SPINED STICKLEBACK 151 granules. Whatever may be the origin of these granules they appear to function in breaking down the granular cytoplasm of the cell, thus forming the secretion. As the cell becomes active the granular protoplasm in the center of the cell, in a direct path between the nucleus and the free margin of the cell breaks down gi^'ing rise to the sUme (fig. 4 ^4). In this region the cells begin to appear vacuolated. This vacuolated area gradually enlarges until it occupies practically the entire area between the nucleus and the free end of the cell. The secretion granules appear to be rather evenly arranged, usually h'ing near the center of the cj'toplasmic vacuoles where these have appeared. As the distal part of the cell becomes well vacuolated, due to the continued formation of the secretion, the side of the nucleus towards the free end of the cell seems to cave in toward the base of the cell (fig. 4 B). Secretion granules continue to be formed but not as rapidly as in earUer stages. The nucleus, as shown in the figures, migrates to the base of the cell, where it becomes more and more flattened, until finally it lies at the base of the cell as a flat dark-staining irregular mass (fig. 4 C). While this is taking place the granular protoplasm at the base of the cell is being gradually broken down, imtil finally the entire granular protoplasm of the cell has disappeared (fig. 6). Even after the granular protoplasm has disappeared, the cell vacuoles often remained full of secretion for some time (fig. 5) and take a deep blue stain with Delafield's haematoxyhn. As the last of the secretion passes into the lunien of the kidney tubule, the cell becomes a non-staining vacuolated structure except for the small shrunken nucleus and the network of the vacuoles (fig. 6). Since the muciparous tubules are the first to become active, it is only natural that they shoiild first become exhausted in forming the secretion. As the cells become active and produce secretion they have a tendency to become broader and shorter than earUer in the season. The transition, between the slime secreting portions of the kidnej' tubules and the urinarj- portions, is rather abrupt, as 152 WALTER N. HESS is shown in figure 7. The sUme secreting cells are broad and rather flat, while those urinar\' in function are long and slender. Since this preparation, shown in figure 7, was made towards the end of the active season, the ^slime cells contain little or no secretion. As can be readily seen, the nuclei of the urinary cells adjacent to those producing slime, are relatively small. These cells and their nuclei, however, increase gradually in size until at about the third cell from the last muciparous cell they assume the characteristic appearance of the normal urinary cells. Normal m-inary cells at this season of the year show no marked changes. The nuclei are nearly round, and lie a short distance from the base of the cells. They may contain one, two or three nucleoli, but usually two, while the cells of the slmie secreting tjT^e were never found with more than one nucleolus. The cytoplasm of these cells was very granular and irregularly grouped. With such fixing fluids as Flemming's (strong formula) or one per cent osmic acid, and with Heidenhain's iron haematoxylin staining, the urinary cells were found to contain rather large granules, resembling those of the slime secreting cells. Some of the cells seemed to take up more of the osmic acid than others, and hence appeared dark and structureless. Mobius ('85) described these cells as forming a second kind of secretion. By destaining, however, they were found to be ordinary urinarj'^ cells. All of these cells were pouring into the lumen of the tubule, a substance which appeared to be an irregular granular mass. After a careful studj' of the kidneys of this and other species of fishes, the author is convinced that these are normal urinary secreting cells. XATURE OF THE EXUDED SECRETION Since it is often difficult to judge the nature of a secretion from its histological structure before being exuded, the structure of the substance after it has been used by the fish in constructing its nest will be considered briefly. Couch ('62), Mobius ('85), and Prince ('85), working on European forms, each described the structure of the material as being composed of threads KIDNEY OF FIVE-SPINED STICKLEBACK 153 resembling silk. The threads were elastic and under a microscope appeared to be composed of several smaller threads glued together. Heincke ('82), on the contrary, referred to the secretion as consisting of a white slime-like substance. The writer's observations on the natiu-e of this secretion confirms the work of Heincke, since no evidence of a fibrillated nature was to be distinguished, even with a high magnification. The fish often deposits the secretion in ribbon-like masses as maj' be seen in among the plant substance of the nest (text fig. 1). This secretion, upon histological examination, appears to consist of a very fine granular shme-Uke substance. It may function somewhat as a string in binding the material of the nest together, but probably is more in the nature of an adhesive substance. REGEXERATIOX OF THE GRANULAR CYTOPLASM WITHIX THE SLLME-SECRETIXG CELLS The process of secretion which reaches its maximum early in April continues late into Maj', and sometimes to a very slight extent into June. Early in June there takes place within the slmae secreting cells, a process whereby the granular c3rtoplasm is again restored so that the cells present an appearance similar to^that of the cells before the secretion began to be fonned. SchiefTerdecker ('84), working on the sublingual glands of the dog, found that new gland cells are formed at the base of the secreting cells, and gradually the old vacuolated cells were sloughed off. There is no evidence of any such process in the sticklebacks. Heidenhain ('90), in his work on the cloacal glands of the Triton, maintained that the protoplasmic granules regenerate themselves. This, in the kidney cells of the stickleback, seems impossible since at the end of secretory activity all the protoplasmic granules have disappeared. Moreover, at the time of regeneration, the granules are not uniformly distributed throughout the cell, but always found about the nucleus. The first change observed in the regeneration of these kidney cells was an enlargement and rounding of the nucleus. At the same time, in fact, as soon as the nucleus began to show signs 154 _ WALTER N. HESS of activit}^ there were observed inside the nucleus, numerous acid staining granules. In the body of the cell the cytoplasmic granules appeared first at the base, around the nucleus, and gradually came to occupy the entire cell. In most cells, as these granules began to be formed, the nucleus migrated some distance towards the middle of the cell. In every case the cytoplasmic granules were most numerous about the nucleus during their early stages of regeneration. Since the granules first form about the nucleus it seems that the nucleus must be discharging certain substances into the cytoplasm, which act upon the protoplasm of the cell restoring the granular condition. It does not seem probable, however, that these granules are formed within the nucleus and discharged into the cytoplasm. At any rate, it seems that the nucleus must play an important part in this regeneration. If these cytoplasmic granules are the products of mitochondia or similar cytoplasmic components, why do they form just around the nucleus and not evenly, or at least scattered, throughout the cell? COMPARISONS WITH THE KIDNEYS OF OTHER FISHES In order to obtain a more definite idea of the typical fish kidney, sections were made at the breeding season of the kidneys of the male bullhead (.Ajneiurus nebulosus LeSueur), the blacknosed dace (Rhinichthj^s atronasus Mitchill), and the gold fish (Carassius auratus L.). It was readily seen that no special secretion of any kind was formed by their kidneys, and that the cells of the kidney tubules, urinary ducts, bladder and common urinary duct resembled in general those of the female stickleback. The cells of certain tubules in the gold fish kidney were found to contain cytoplasmic granules only at their lumen end, in which region was found a rather shrunken, often irregularly-shaped nucleus. The basal portion of the cells appeared as large clear areas. In some cells the granular cytoplasm appeared to be practically' absent, and the nucleus was ^•ery much reduced. The exact significance of this condition is doubtful. It may represent a degeneration. This particular KIDNEY OF FIV-E-SPINED STICKLEBACK . 155 fish had been kept in the laboratorj^ under artificial conditions for about a j'ear, and it is possible that this would account for the above described condition. The other kidney tubules . appeared normal. KIDNEY PARASITES The habits of these little fishes are very peculiar and no doubt are conducive to parasitic infestation. The ^^Titer has found them living in various places, and under varying conditions, but usuall}^ in shallow, slowly flowing water in which plants are abundant. Some were collected in pools which were so nearly dry that they consisted of a rather blackish muck, from which other species had disappeared, while these were apparently inconvenienced in no way. They were found abundant in meadow streams in among the water plants, in swamps and among the water plants along the shores of Lake Cajoiga, New York. Nearly all specimens collected showed, upon histological examination, an abnormal condition of the kidneys. Scattered among the cells of the various tubules and ducts of the kidneys of both male and female at all seasons of the year, were .foimd nmnerous protozoan parasites. No attempt was made to study their life history. When mature the spores and finally the body of the old parasite, are discharged into the limien of the kidney tubules. What apparently is the same organism was described bj^ Thelohan ('92) as a Coccidian. He found the parasite widelj^ distributed among fishes, and in various tissues. Though black-nosed dace were taken in the same places as the sticklebacks, which possessed the kidney parasites, these fish showed no signs of any such infestation. SUMMARY AND CONCLUSION The secretion by means of which the five-spined stickleback builds its nest is produced by the male alone, and only at the breeding season. During the greater part of the year, the male kidney is an excretory organ. At the breeding season, however, only what 156 . WALTER N. HESS we term here the uriniparous tubules and glomeruU function thus, while the cells of the muciparous tubules, urinary ducts^ bladder, and common urinary duct become modified for the purpose of producing slime. In the process of slime secretion, the behavior of the nuclei is such, that they evidently pour into the cell bodies certain products, in the form of secretion granules, which function in breaking down the granular cytoplasm of the cells, and thus form the secretion. These secretion granules appear to be produced from certain products of the karyoplasm, as this substance gradually diminishes in amount during this process. It is possible that the nucleolus functions in this process. Only one kind of secretion is produced for constructing the nest. This material is not silk, nor is it composed of fine fibrils, but appears as a fine granular slime-like substance. It is sometimes exuded in ribbon-like masses, but it probabl,y functions more as an adhesive substance, than as a string, in binding the material of the nest together. The exact process by means of which the c.^'toplasmic granules are regenerated, following the process of slime secretion, is uncertain, but it seems evident that the nucleus is the active agent. During the resting or winter stage, the cells which form the slime during the spring appear much like those of the uriniparous tubules, except that their nuclei are smaller. At this season the nuclei of the uriniparous tubule cells are very large, often occupying at least half of the cell contents. The investigation justifies the conclusion that the whole kidney is not transformed periodically into a silk or slime producing gland as one is led to infer from other published accounts but that the process of slime secretion is due to the activity of the epitheUal cells of various ducts and tubes of the system not engaged in the excretory function. It is comparable to the secretion of slime by the genital ducts of Amphibia during the breeding season. From a comparison with fishes of diverse habits and affinities, it would seem that the formation of this slime seci-etion by the kidneys of the sticklebacks is probably unique among fresh water forms. KIDXEY OF Fn-E-SPINED STICKLEBACK 157 BIBLIOGRAPHY Abnold, J. 1905 Uber Bau und Sekretion der Driisen der Froschhaut; zugleich ein Beitrag zur Plasmosomen-Granulalehre. Arch. f. Mikr. Anat., Bd. 65, pp. 649-665. Brock, J. 1887 tjber Anhangsgebilde des Urogenitalapparates von Knochen fischen. Zeit. f. Wiss. Zool., Bd. 45, pp. 532-541. Carlier, E. W. 1899 Changes that occur in some cells of the Newt's stomach during digestion. La Cellule, vol. 16, pp. 405-454. 1905 Concerning the secretion of ferments by the liver cells and some of the changes observable in them during digestion. La Cellule, vol. 22, pp. 432-456. CosTE, il. 1848 Nidification des 6pinoches et des epinochettes. ^lem. a I'Acad. des Sci. T. 10, pp. 575-588. CoccH, J. 1862 A historj' of the fishes of the British Isles, vol. 1, pp. 167-184 Gaknier, C. 1900 Contribution k I'^tude de la structure et du fonctionne ment des cellules Glandulaires S^reuses. Du role de I'ergastoplasme dans la secretion. Journ. de I'Anat. et de la Physiol. T. 36, pp. 22-98. Geist, S. H. 1913 Untersuchungen iiber die Histologie der Uteruschleimhaut. Arch. f. Mikr. Anat. Bd. 81 pp. 196-219. Heidenhain, M. 1890 Beitrage zur Kenntniss der Topographie und Histologie der Kloake und ihrer driisigen adne.xa bei den einheimischen Tritonen. Arch. f. Mikr. Anat. Bd. 35, pp. 17.3-274. Hbnicke, F. 1882 Die Fische. Illustrirte Naturgeschichte der Thiere. Bd. 2, pp. 399-404. He vex, H. 1910 Contribution a I'etude du fonctionnement des cellules glandulaires. Du role du Chrondriome dans la secretion. Anat. Anz. T. 37, pp. 343-351. M.^xi.vow, A. 1901 Beitrage zur Histologie und Physiologie der Speichel drusen. Arch. f. Mikr. Anat. Bd. 58: pp. 1-134. M.\zi.\RSKi, S. 1911 Recherches cjtologiques sur les phenomenes secretoires dans les glandes filieres des larves des Lepideopteres. Arch. f. Zell forschung. T. 6 pp. 397-442. MoBius, K. 1865 The nest of the fifteen-spined stickleback. Ann. and Mag. Natl. Hist. vol. 16, p. 153. 1885 Ueber die Eigenschaften und den Ursprung der Schleimfaden des Seestichlingnestes. Arch. f. Mikr. Anat. Bd. 25, pp. 554-563. X.\K,iHARA, W. 1917 On the physiology of the nucleoli as seen in the silk gland cells of certain insects. Jour. Morph. vol. 29, pp. 55-68. Price, E. E. 1885 On the nest and development of Gastrosteus spinachia at the St. Andrew's Marine Laboratory. Ann. and Mag. Natl. Hist. vol. 16, 5th ser pp. 487-496. Raxsom, W. H. 1865 On the nest of the ten-spined stickleback. Ann. and Mag. Natl. Hist. vol. 16, 3rd ser: pp. 449-451. Retzius, G. 1905 t'ber den Bau der Haut von My.\ine Glutinosa. Biol. Untersuchungen. Neue folge Bd. 12 pp. 6.5-74. THE AXATOMICAI. RECORD, VOL. U, NO. 2 158 WALTER N. HESS Ryder, J. A. 1881 Notes on the development, spinning habits, and structure of the four-spined stickleback Apeltes quadracus. U. S. Fish. Comm., Bui. vol. 1, pp. 24-29. ScHiEFf ERDECKER, P. 1884 Zur Kenntniss des Baues der Schleimdriisen. Arch. f. Mikr. Anat. Bd. 23: pp. 382-412. ScHULTZE, A. 1911 tJber die Genese der Granula in den Driisenzellen. Anat. Anz. Bd. 38: pp. 257-265. Smith, E. 1897 The fishes of the fresh and brackish waters in the vicinity of New York City. Abs. Proc. Linn. Soc. New York, no. 9, pp. 12, 38-39. Thelohan, p. p. 1892 Sur des sporozoaires indetermines parasites des pois .sons. Jour, de I'Anat. et de La Phys. T. 28, pp. 163-171. WiD.^KOwicH, V. 1907 liber den Uterus von Squalus acanthias. Bemerkungen zur Entwicklungsgeschickte der Haie. Zeit. f. Wiss. Zool. Bd. 88, pp. 499-544. PLATES 159 PLATE 1 EXPLANATION OF FIGURES 1 Cells of the muciparous tubules, taken December 8. (A'), nucleus. 2 Cells of the uriniparous tubules, taken December 8. (A'^), nucleus. 3 Cells of the urinary duct, taken December 8. (GC), granular cytoplasm; {N), nucleus. 4 Cells of a pro.ximal collecting tubule showing different stages in the early process of secretion. Cell A, a rather early stage of cellular secretion. Between the nucleus (A^) and the free end of the cell the normal cytoplasmic granules are disappearing. Scattered about in the cytoplasm are many secretion granules {SG). At the base of the cell the normal cytoplasmic granules are unmodified. Cell B, a little more advanced stage of secretion than cell A. The nucleus (A') appears a?if fallen in on the side towards the free end of the cell. Secretion granules (SG) are abundant. The vacuoles {V) so characteristic of later stages are becoming prominent. Cell C, a rather late stage in the process of secretion. The nucleus (A') is very much flattened and shows a tendency to wander towards the base of the cell. The vacuoles (l) are very prominent tho'ugh at this stage they are full of secretion. Fish taken February 16. 160 KIDNEY OF FIVE-SPINED STICKLEBACK W.VLTER X. HESS PLATE 1 B C SG 161 PLATE 2 EXPLANATION OF FIGURES 5 Cells filled with secretion, the nuclei (^V) have wandered to the base of the cells. The normal cytoplasmic granules have disappeared. The vacuoles (V), filled with secretion, are very prominent. Fish taken April 1. 6 Cells at the end of the secreting period. The vacuoles now appear empty of secretion. There is no evidence of the normal cytoplasmic granules. Fish taken May 1. 7 A few cells to illustrate the transition between the proximal collecting tubules and distal collecting tubules at the end of the active period. The distal collecting tubules contain granular cytoplasm (GC), while those of the proximal collecting tubules are vacuolated (T). J^ish taken May 1. 8 Cells of the urinary duct to illustrate stages in the regeneration of the granular cytoplasm (GC) after the breeding season. Cell A, shows the nucleus in the early stage of activity. Cytoplasmic granules are forming about the nucleus at the base of the cell. The nucleus is wandering towards the center of the cell. Vacuoles are now indistinct where protopla.smic granules have formed. Cell B, a more advanced stage than Cell A. The nucleus (N) has enlarged and wandered farther towards the center of the cell. Cytoplasmic granules are increasing. Cell C, cytoplasmic granules now nearly fill the cell. The nucleus (N) appears nearly normal. The vacuolation is rapidly disappearing. Fish taken June 20. 162 KIDNEY OF FIVE-SPINED STICKLEBACK WALTER N. HESS PLATE 2 163 AUTHOR S ABSTRACT OF THIS PAPER ISSUED BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 15 HISTOLOGY OF THE SENSORY ROOT OF THE TRIGEMINAL NERVE OF THE RAT (MUS NORVEGICUS)' LYNN ARTHUR HOAG Department of Anatomy, University of Michigan During the course of a general study of the structure of medullated nerve fibers, a Weigert stained longitudinal section of the sensory root of the trigeminal nerve from a vrild rat (Mus norvegicus) was examined. It presented, about 1 mm. from the brain stem, a sharph' defined line of transition between the structure of the peripheral nerve trunk and the central nervous tissue, which change was revealed particularly by a difference in the intensitj' of staining. This change occurred along a regularh' curved transverse line which was sUghtly convex peripheralward. A cursor\' examination of similarly prepared sections from the same and other animals showed that this condition was normal and not an artifact. This picture has been described by a number of observers, more from the standpoint of microscopic relations than from the detailed histologic standpoint. A brief re\'iew of the most important communications will be both valuable and interesting. R. Thomsen ('87) observed, in cross-sections of the human abducens and oculomotor nerves from a case of multiple alcohoHc neuritis, that there were small, round, glistening placques or 'Herde' lying in the normal nerve tissue of the trunk and sharply delimited from it. They consisted of a hornj^ substance staining readily in carmine. Oppenheim ('87) found similar placques in cross-sections of the human facial and hj-poglossal nerves and designated them as the 'Herde' of Thomsen. The latter, having recognized that these 'Herde' were not specific ' In partial fulfilment of the requirements for the degree of Master in Science, Major in Anatomy, University of Michigan. 165 166 LYNN ARTHUR HO AG for any disease, sought to explain them as degenerating ganghon cells. Oppenheim, on the other hand, considered them as normal structures but gave no clear explanation of their significance. Staderini ('90) found the 'Herde' of Thomsen in the human oculomotor, trochlear, abducens, facial, and vagus nerves, and showed that these placques were not to be considered as degenerating ganglion cells but as processes of neuroglia from the brain stem out into the nerve trunk. This he proved in serial cross-sections by tracing the continuity of the placques with the central neuroglia. A. Hoche ('91) referring to the neuroglia, mentioned tooth-shaped processes extending from the surface of the spinal cord in company \^ith the ner\'e fiber bundles and ending abruptly a little distance peripherally. Lavdowsky ('91) in his communication on the neuroglia of the spinal cord, referred to the same arrangement and pictiu-ed such a condition in figure 7 of plate 16 accompanying his article. E. Redlich ('92), in describing the lesions occurring in the spinal cord and posterior nerve roots in tabes dorsalis, said that the degeneration begaii in those fibers of the iJosterior root which were of the intramedullar}^ type, thus intimating the presence of two essentially different types of nerve fibers, the intrameduliary and the extramedullar}-. Both KiiUiker ('93) and Edinger ('93) agreed with Lavdowsky in describing processes of neuroglia extending from the spinal cord out into the posterior roots of the spinal nerves. J. Schaffer (worked in '90, published in '94) found that the neuroglia in the nerve trunks ended in a pointed cone-shaped termination, convex peripheralward. Obersteiner and Redlich ('95), completing their work in '94, observed, during the course of their study of tabes dorsalis, a constriction and pial ring on the posterior nerve roots at their entrance into the spinal cord, and that a short distance peripherally the medullary sheaths lost their staining property over a small zone, resulting in a narrow clear space, a transverse 'Aufhellung,' which was bow-shaped with its convexity outwards. Obersteiner ('95) and E. Redlich ('97) defended and added details to their observations, urging especially the importance of the change from extramedullary to intramedullary SENSORY ROOT OF THE TRIGEMINAL — RAT 167 fibers in its relation to the primary lesions of tabes dorsalis in the spinal nerves. K. Schaffer ('01) added the observation that the myelin sheaths of the extramedullary part of the root stained darker but less sharply than those of the intramedullary portion, the two being separated bj^ the convex, non-staining line which had already been described as the 'AufheUung.' Obersteiner ('01) reviewed all the previous observations on the structure of the posterior roots of spinal nerves. E. Levi ("06) published the results of a comparative study of the sensory root's of all the spinal nerves, dealing especially with the transition from peripheral to central nerve fibers. E. Hulles ('06) extended the work of Levi to the human ^•agus, acoustic, and trigeminal nerves, finding there very much the same relations as in the posterior roots of the spinal nerves. Bikeles ('07) substantiated these histological findings from a phj-siological point of view bj* finding a difference between the reaction to secondarj' degeneration in the fibers peripheral to and central to the change. J. Bauer ('08) reported the results of a careful study of the posterior roots of spinal nerves in many annuals; Primates, L^ngulata, Carnivora, Insectivora, Rodentia, Edentata and j\Iarsupalia. He found in all classes the same structures that had been described for the human spinal nerves. MATERIAL AND METHODS The brown rat (Mus norvegicus) was selected to fm-nish material bfecause of the ease with which it could be handled and the readiness with which perfectly fresh nervous material could be removed. The trigeminal nerve root was selected primarily because of the fact that the feature under consideration is there particularly well shown; also because it is easily exposed and readily removed. Each root used was taken out in such a manner that a portion of the semilunar ganglion and a portion of the pons were included for landmarks and orientation. Similarly obtained nerves from the laboratory white rat, guineapig, rabbit, and dog furnished a series for a brief comparative study. 168 LYNN ARTHUR HO AG Standard laboratory methods were used in differentiating the histological elements studied. The general appearance was observed in formalin fixed sections stained in hematoxylin and one of the following counterstains — eosin, acid fuchsin, congo red, and Van Gieson's mixture (picro-fuchsin). The axones were studied in sections stained by Ranson's p3Tidine-silver method, and in a few Weigert myelin sheath preparations which showed a peculiar differential staining of the axis-cylinders.^ The myelin sheaths were stained by Streeter's paraffin modification of the Weigert-Pal method, by osmium tetroxide, and by Haidenhain's iron-alum hematoxylin, following fixation in Bouin's and Yoshii's fluids. The neurolemma, pia mater, and connective tissue sheaths were studied in sections and teased preparations stained by Van Gieson's method and the common protoplasmic stains. Huber's modification of Benda's first method and Kingerj^'s modification of the same were used to demonstrate the neuroglia. The neuroglia sections were cut at a thickness of 4^ and 5ix. while all others were either 8yu or 10/i. For the more intimate study of the myelin sheaths and neurolemma, nerve fibers which had been separated by teasi"ng were studied. An attempt was always made to obtain both the peripheral and central types of fibers in the teased preparations, and they were examined in the fresh condition or following fixation and one of the stains eniunerated above. The embryology was studied from a set of serially-cut, sagittal sections of sixteen rat embryos, the use of which was granted through the courtesy of Professor G. Carl Huber. PERSONAL OBSERVATIONS Rat — Mus norvegicus The sensory root of the trigeminal nerve averages about 4 mm. in length in fixed material. The motor root crosses the ventral surface of the sensory root obliquely from the median to the = Smith and Mair state that diffuse staining of the myelin and deep staining of the axone in Weigert preparations is due to too long 'chromation.' SENSORY ROOT OF THE TRIGEMINAL — R.\T 169 lateral side, the two being quite closely bound together. At a distance averaging from 1 mm. to l.o mm. from the brain stem the combined roots are apparently very slightly constricted, the diameter central to this zone being slightly less than the diameter peripheral to the constriction. In nerves which are brittle from fixation or dehj-dration there is a great tendency to fracture along the plane of this constriction,' transverse to the long axis of the root. In favorable longitudinal sections of the trigeminal uer\-e roots stained by a myelin method, there is, along a transverse line corresponding to the plane of the constriction, a distinct demarcation between a central lightly staining portion and a peripheral darkly staining portion. Between the two there is often • a verj^ narrow unstained zone extending transversely across the roots. This line of demarcation is usually somewhat saucer-shaped, appearing, in a longitudinal section of the root, as a curved line XNith the convexity peripheralward. The nerve fibers may be grouped in fairly distinct bundles which, in crossing this transition, project unequal distances beyond it, thus making of the change a serrate transverse line. The root distal to this abrupt change shows the structure which by comparison is seen to be tj^pical of peripheral nerve trunks, with the exception that the fibers are not found in definite funiculi each surrounded by perineurium. The component tissues of the trunk are definitely arranged, and in fixed and stained sections show good preservation of relations and structirre. The root proximal to this abrupt change is more characteristic of central nervous system tissue in that the myelin stains less intensely, the nerve fibers are not so firmlj^ bound together, and in otherwise well preserved material often show distortion forms and are separated by spaces due to shrinkage. Because of this abrupt change from the tj'pe of fiber found in the peripheral nerve trunk to the type found in the central nervous system, this region is particularly favorable for a detailed study of the comparative histology of central and peripheral meduUated nerve fibers. Both types, which have been 170 LlTvN -UlTHUK HOAG subjected to identical fixation, sectioning, and staining, can be observed together in the same high power microscopic field. It is generally difficult to trace in section the continuity of single nerve fibers across this transition line because of their tendenc}^ to suddenly change direction and thus disappear from the plane of section, and because of the fact that for a short distance the myelin sheaths often fail to stain, leaving a narrow clear zone between the central and peripheral areas. Our knowledge of the function of nerve fibers gives us the right to assume the continuity of these fibers, and actual proof may be obtained bj' teasing them through the line of transition. The abruijt line of change in the motor root does not always correspond with that in the sensory root, and it maj' be either slightly central or shghth' peripheral to the latter. The greater size of the sensory root as compared to the motor root so facilitates the sectioning of the desired region that most of the preparations were made from, and all the descriptions will be confined to, the sensor}^ root of the trigeminal. The supporting tissues bear a very important relation to the transition line. The pia mater forms a delicate fibrous sheath for the brain stem and extends outward along the nerve trunks for a short distance, becoming continuous with the epineurium which, farther peripherall.y, fuses with the denser dura mater. The junction between pia mater and ejiineurimn is soniewhat indefinite but maj^ be arbitrarily placed at the constriction marking the line of change from peripheral to central nerve fibers. In the living condition the only constriction of which one can truly speak is a decrease in the diameter of the trunk central to the line of change as compared to the diameter peripheral to the transition. At the junction of the pia mater and epineurium there is often a ring of thickened connective tissue which slu-inks dui'ing fixation and causes an annular constriction which is really an ai'tifact. From this ring, fine trabeculae and bundles of white fibrous tissue pass through the nerve parallel to the line of transition, and together with the neuroglia form a very delicate frame-work for the support of the ner\'e fiber bundles. In the human these inward prolongations have SENSORY ROOT OF THE TRIGEMIN^AL — RAT 171 been described as forming a lamina cribrosa through which the nerve fiber bundles pass, but in the rat such a structure is not visible. ^linute blood vessels often accompany these septae toward the interior of the nerve trunk. The neuroglia can be traced from the brain stem out into the sensory root of the trigeminal as far as the transition line but never beyond. In the same manner that the neuroglia is more dense around the periphery of the brain stem just under the pia mater, so it forms a cortical or 'bark' layer around the trigeminal trunk. It is less extensiveh' found in the center of the root. The general direction of the neurogUa fibers is at right angles to the ner^'e fibers, especiallj^ in the periphery of the trunk and in the lamina cribrosa region, but as obser\'ed in 4;u or oyu sections the neurogha tissue is not dense in any portion and takes less part in the formation of the supporting framework in the rat trigeminal than credited with in the hmnan trigeminal. As pre\aously indicated, the nem'ogha and bundles of pia mater here and there extend distally from the transition line as pointed processes, and confer a distinctly serrated appearance upon this line. These prolongations rarely intermingle with the supporting tissue of the peripheral trunk, and processes of the latter extending centrally do not fuse with the pia mater and neiiroglia. Upon this fact probably depends the tendencj^ of the root to fracture along the line of change. The supporting tissue of the peripheral nerve fibers consists of endoneurium; since there are no funiculi between the pons and semilunar ganglion in the trigeminal of the rat, there is no true perineurium. The neurolemma must be considered as a part of the framework and although it is an integral part of the peripheral nerve fibers it ^\•ill be considered here. In sections it is usually difficult to differentiate between the endoneurium and neurolenmia, and the most satisfactory^ method of studying them is in teased preparations. A variety of stains were applied to the teased nerve fibers, the most important being Weigert's myeUn sheath, stain, hematoxjdin and \'an Gieson's mixture, and osmium tetroxide. In teased specimens the endoneurium is seen to consist of delicate fibrils running close to and parallel 172 LYNN ARTHUR HOAG with the nerve fibers. White connective tissue fibrils are present to the exclusion of the yellow elastic. Even the white fibrils appear wavy after teasing operations in which thej^ are stretched. The fibrils are accompanied by cells which are chiefly of the fixed or fibroljlastic type. The protoplasm is rarely seen, and the nuclei ^•ary in shape according to their position and the pressure of surrounding fibers. Their apparent shape varies with the angle at which they are viewed. In general they are oval or flattened, staining fairly intensively and possessing distinct cliromatin granules. The neurolemma forms a close investing sheath for the peripheral nerve fibers, and can be seen as a membrane onh' where the fiber is broken, or over a neurolemma nucleus, or sometimes at the nodes of Ranvier. The neurolemma nucleus is oval and has even larger chromatin granules than the nuclei of the endoneurium. It can be readilj^ differentiated from the latter only when seen in profile, when it appears to lie on the side of the nerve fiber in an indentation in the myelin, between two nodes of Ranvier. The neurolemma is seen as a thin membrane covering it. In osmium tetroxide stains these nuclei are frequentlj^ surrounded by dark gray or black granules, called Elzholz granules.' As mentioned before, the neurolemma and endoneurimn stop abruptly at the transition line and do not intermingle with the pia mater and neuroglia. It is interesting to compare the relative number of nuclei of all tj^pes found on the central and on the peripheral sides of the transition line. For this purpose lOyu sections stained in hematoxyUn and eosin or acid fuchsin were used and the total number of nuclei in the same size microscopic fields each side of, and equally distant from, the transition line were counted by the aid of a ruled ocular. Using the number counted in a definite microscopic field central and adjacent to the transition line as unity, then the proportionate number in the same size field, adjacent to the transition peripherally, is expressed as a simple ratio. The table below, which gives the result of onl}' four counts, » For a complete description of the cells found in peripheral nerve trunks see the article by Doinikow. SENSORY ROOT OF THE TRIGEMINAL — RAT 173 TABLE I Shounng the proportionate number of nuclei on the central and peripheral sides of the line of change in the sensory root of the trigeminal nerve of the rat FIXATION STAIN THICKNESS PROPORTION- OF NUCLEI Central Peripheral Formol ^ .Mueller | Hematoxylin and eosin Hematoxylin and eosin Hematoxj-lin acid fuchsin Hematoxylin and eosin 10 10 10 10 1 1 1 1 7.0 8.3 6.2 5.9 shows that the nuclei are more numerous on the peripheral side. The- figures gi^•en are topically average. The axones were first studied in differentialh' stained sections, but this was unsatisfactory because of the difficult}' encountered in tracing them through the transition because of their abrupt change in course at that region. Their continuity can best be determined in fresh teased fibers or in teased material stained by osmium tetroxide. The axones pass through with no perceptible change in size and without exhibiting varicosities or constrictions. They show no characteristic difference in staining reaction on the two sides of the change. The structure which presents the most interesting differences and variations in passing through the transition is the medullary sheath. Text-book descriptions give as the main morphological difference between peripheral and central nerve fibers, the absence of the neurolemma from the latter. It is true that this plays a role in their differentiation, but it is inconceivable that the presence or absence of neurolemma should determine all the differential features between central and peripheral fibers as observed in the rat trigeminal. . In the search for other morphological distinctions it is necessary to consider what is known as the 'neuro-keratin network.' This term has called forth much discussion. One group of ^Titers maintains that the keratin-like network, insoluble in alcohol, which is seen in many Weigert myelin sheath preparations, is a preformed meshwork which serves as a support for the myelin during life. Another group contends that the network is purely an artifact, the result of the precipitation, from THF ANATOMICAL RECORD, VOL. 14. NO. 174 LYNN jVKTHUR HOAG colloidal suspension, of a certain chemical constituent which may be called neuro-keratin. A reasonable middle-ground, supported by the facts brieflj- mentioned belo\A, is to assume the presence of a framework for the mj'elin and to consider the variations in size and arrangement of this framework to be artifacts dependent upon the methods of preparation. Although unable to substantiate anj^ claim upon purely morphological studies, we must recognize that variations in the appearance of this framework in fixed ner\'e fillers may depend upon a varying chemical reaction, the result of differences in the fundamental arrangement of the substance in question, or the result of varying precipitation pictures due to the reaction of different reagents upon a uniform substance. In fixing trigeminal nerves previous to the application of Weigert's myelin sheath stain, it was found that the neurokeratin figure ^-aried with the chemicals used or even with varying strengths of the same fixative. Hy rough handling or a long wait before fixation a verj' coarse network was secured, which in some cases presented the characteristic funnel-shaped bodies described by various authors. In the same wa.v that Fischer ('99) worked out fixation pictures for many chemicals in their action upon protoplasm, definite pictures can be determined for the more characteristic fixatives in their action upon mj'elin. Converseh', the appearance of this network varies in fibers from the central and peripheral nervous systems when subjected to identical treatment. The best place to compare the two types of fibers is in a region showing an abrupt change from one to the other. In the sensory root of the trigeminal, where both the central and peripheral fibers ha^'e been handled identically in staining, the neuro-keratin network shows definite and rather uniform differences on the two sides of the transition. In the peripheral fibers there is usually a pronounced, regularl}' arranged, and fairly coarse meshed network. Because of this effective support the mj'elin sheath usually retains its tubular shape and is rather infrequently collapsed. The fibers therefore lie in quite close contact leaving few interstices in the peripheral root. On the other hand, the central fibers usuallj^ contain a loose, frail, irregularly arranged meshwork of neurokeratin which does not prevent many of the fibers from collapsing. The resulting distorted fibers leave shrinkage spaces in the root central to the transition A slight difference in the diameter of the peripheral and the central fibers exists. This is emphasized beyond the normal proportion in Weigert myelin sheath stains, but is better represented in osmium tetroxide preparations in which the myelin is well preserved. In carefully teased specimens stained by the latter method, central and peripheral fibers from the same nerve were measured bj' means of camera lucida projection and a ratio determined between the measurements. From a series of such counts the average diameter of the central fibers in the nerves examined was found to be 8.2/x, with a range from 1.2;u to 12.5)u, while the average diameter of the peripheral fibers was 9.2ju, the range being from 1.2^ to 13m- Taking the measurement of the central fibers as unity, the ratio of theu- diameter to that of the peripheral fibers is 1: 1.12. This may be an exaggeration of their normal ratio during life, because we cannot state exactl}^ the relative shrinkage effect of osmium tetroxide upon the two tj'pes. Further, these figures do not mean that there are no fibers smaller than 1.2^, but rather that those were the smallest fibers which took the stain enough to be visible. The relatively deeper staining of the peripheral nu'elin sheaths as compared with the central is well revealed in osmium tetroxide, Weigert myelin sheath, and Haidenhain's iron-alum hematoxylin preparations. This is the factor which really confers upon the sections the sharply defined line of change. A region such as we have under consideration is the most suitable place to demonstrate this difference because here it is possible to treat the two nerve fiber tj^^es bj- identical processes, thus ruling out the variations due to ine^■itable differences in method when treating two pieces of tissue separately. The difference in staining reaction in such sections is not one of quality so much as of degree or intensity. In osmium tetroxide both the central and peripheral myehn are stained brownishblack, but the peripheral is of an appreciabh' deeper shade. Of the possible explanations of this condition at least two naturally suggest themselves. First, in mass staining the two different kinds of supporting tissue surrounding the fibers may so influence the penetration or bleaching of the stain as to bring about the result above noted. Second, the two shades may be the phj'sical expression of actual chemical differences between central and peri]3heral mj-elin. When we remember that the reagent is identical, this explanation seems more possible. ^Moreover, in tissue which has been sectioned, the myelin is fully exposed to the action of the chemical, thus partialh- escaping the protective influence of the supporting tissues upon the reaction. The view that mj-elin in the central nervous system is deposited by a different agencj' than that in the peripheral sj'stem also lends support to the second explanation; but if myelin is e\'er\-where deposited by the axones, it would be difficult to assign it a varj-ing chemical constitution in different parts of the nervous S3'stem. In many preparations there is a narrow clear space between the central and peripheral portions of the root, which is apparently due to an interruption of the myelin, the hea\ily staining peripheral sheath ending as a rounded cone through which the axone projects, passing tlirough the narrow clear zone uncovered bj- m3'elin. In a few fa\-orably cut fibers, myehn was seen to be reacquired on the central side at a distance of about SO/j. from its interruption. A suggested explanation of this apparent lack of myelin in stained sections is that the supporting tissue of the lamina cribrosa region prevents the penetration of the stain to the mj'elin. This maj^ be true in mass staining, such as with osmium tetroxide, but is less convincing when the same condition is found in preparations stained on the slide after sectioning. The view that myelin is deposited through the agency of different structures in the peripheral and central fibers and that there is a gap between these structures at the place under consideration might be advanced as an explanation of the phenomenon. If we accept the statement that all myelin is deposited through the agency of the axones, this explanation is less plausible. The fact that Bauer ('08) found this clear space to be inconstant in a large comparative series of the posterior roots of spinal nerves, makes its significance very obscure. COMPARATIVE HISTOLOGY The sensory roots of the trigeminal nerves of a short series of mammals were examined in order to gain an idea of the extent and character of this transition in the more common laboratory animals. The sections from the white rat (^lus norvegicus albinus) show exactly the same features as those from the brown rat described above, and outside the variations normalh- incident to a series of sections from one animal, there are no peculiarities to distinguish it from the wild ^•ariety. In the guinea-pig preparations the only constant difference noticeable is the slightly greater cur%-e of the transitio'n hue, which forms a peripherally directed cone with rounded apex. This animal furnishes good nerve material for the application of the neurogUa staining technique as modified by Huber for use with manmials other than human. In the rabbit trigeminal the connective tissue lamina cribrosa is more pronounced and bundles of fibrous tissue can often be seen running at right angles to the nerve fibers. The transition forms more nearh' a straight Ime. The nerve fibers are grouped into bundles which are more definite than those of the rat. The line of change is relatively the same distance from the brain stem as in the wild rat. The dog shows a ver}- distinct and abrupt change from peripheral to central t\-pe of fibers. The transition line is relatively near the brain when its position is compared with the diameter of the trunk. Instead of always showing a simple outwardly convex line, the curve is often doubly convex or bow-shaped with both convexities directed peripherally. The contrast in staining on the two sides is very pronounced. EMBRYOLOGY The work of Harrison and others has taught us that the nerve fibers grow out from their neuroblast cell bodies by direct extension, and become anchored in their permanent position at an early stage of development. The sensory roots of all nerves develop from the neural crest, the neuroblasts in the latter sending processes centrally to the spinal cord and peripherally to the region of the future sensory ending. Harrison ('04) has showed us that the extension of these processes is accompanied by the migration of certain cells from the crest which give rise to the neurolemma sheath cells or Schwann cells. In sections of the neural tube and semilunar ganglion anlage in a rat embryo of 6 mm. length (crown-breech) the centrally directed processes of the neural crest cells can be traced into the marginal layer of the neural tube, passing through the external limiting membrane. Accompanying this definite embryonic nerve trunk are numerous cells with small, oval, lightly staining nuclei interspersed between the fibers. These extend only as far as the anlage of the pia mater and to the external limiting membrane which lies closely adherent to the marginal layer and is formed by the interweaving of the peripheral process of the spongioblasts. Along this line these cells cease abruptly in a curve corresponding to the normal surface curve of the brain stem. These nuclei belong chiefly to the developing sheath cells which apply themselves to the sides of the growing axones. In a 6 mm. rat embryo they are fairly evenly distributed in the trunk and in a 10 mm. embryo they have surrounded all the fibers, but together with the ingrowing mesodermal cells have also gathered into rows in many parts of the trunk, marking the development of fiber bundles. In distinction to the peripheral trunk, the marginal layer of the neural tube shows a less intense staining reaction. This is primarily due to the almost complete absence of nuclei and cannot be assigned at this time to different types of myelin, because such a chemical substance is not present. Its acquisition at a later stage accentuates the differential staining. This early line of change from i:)eripheral to central fibers corresponds to the pia mater anlage and external limiting membrane, both of which must be pierced by the developing axones in their exit or entrance, and which act as a barrier to the ingress of the sheath cells. These relations persist and may be demonstrated in sections of increasingly old(>r embryos. During the further development, the nerve trunk becomes better differentiated from the surrounding mesenchyme, the sensory root is relatively longer compared with its diameter, and the ner^-e fibers become more definitely grouped in bundles as the supporting tissue assumes definite arrangement. In an IS mm. rat embryo the pia mater is a definite membrane and is separated from the denser aniage of the dura mater by a slight amount of loose-meshed tissue, the arachnoid aniage. At this stage the semilunar ganglion lies close to the pons on the one side and to the bony foramina for its divisions on the other so the whole trunk is relatively short. During the development of the skull, when the distance from the foramina for the trigeminal di^•isions to the attachment of the sensory root on the pons is gradually increasing, it is conceivable that enough tension is put upon the roots to cause the line of change, representing the original line of pia mater and external limiting membrane, to be drawn slightly away from the surface of the brain in an outwardly convex bow. This view is substantiated when we examine sections of a 23 mm. rat embrvo in which the arachnoid tissue surrounding the trigeminal root is relatively much increased because of the greater distance between the pia mater and dura mater along the course of the nerve. The effect is seen in a section of a 30 mm. rat embryo where the transition line, even before birth, is slightly external to the brain surface. The migration of this line, due to inequality between growth in the nerve roots and in the skull, takes place chieflj' in the early post-natal period, because it is sUghtly established in a 30 mm. embryo and shows well in a young rat about four weeks after birth. The position of this line of change may be regarded as the result of varying degrees of, or the lack of, traction upon the trunks during the rapid development of the body which causes separation of the attached ends of the nerve at a slighth' greater rate than compensated by the growth of the fibers themselves. For the practical importance attached to this transition line in its relation to the etiology of tabes dorsalis, the reader is referred to the articles b}^ Nageotte, Obersteiner and Redlich, Le\'i, and the authors cited by them. I wish to thank Prof. G. L. Streeter for advice and direction in beginning thiswork. Profs. G. C. Huber and R. E. McCotter for encouragement and advice in its continuation and completion, and Prof. G. ^1. Curtis, in whose laboratory at ^'anderbilt University I was permitted to prepare much of the material used in this study. CONCLUSIONS 1. In the sensory root of the trigeminal nerve of the rat (Mus norvegicus), about 1 mm. from the pons, is an outwardly con\'ex line which marks an aljrupt change from the peripheral to the central type of ner\-e fibers. 2. The peripheral supporting tissues, endoneurium and epineurium, together with the neurolemma, meet, without intermingling, the central supporting tissues, neuroglia and pia mater, to form an' indefinite lamina cribrosa through which the bundles of nerve fibers pass. 3. The axones extend through this change uninterruptedly and unaffected morphologically. 4. The peripheral myelin shows — a. A deeper coloration than the central when both are identicall}" treated with myelin stains. b. A 'neuro-keratin network' which is more prominent and more regular than that in the central fibers when both are identically treated. These facts may be interpreted as showing distinct chemical and physical differences between the central and peripheral myelin. 5. A number of other mammals show a similar or identical picture in the sensory roots of their trigeminal nerves. (). This change may be considered as occurring at the line where the pia mater and external limiting membrane surrounding the embryonic nervous tube were pierced by the growing processes of neuroblasts, these membranes acting as barriers against the entrance of sheath cells into the neural tube. The position of this line depends upon the amount of tension to which the root is subjected during development. SENSORY ROOT OF THE TRIGE>UNAL — RAT 181 LITERATURE CITED Bai-er, Jrurs 190S Vergleichend-anatomische Untersuchungen der hinteren Riickenniarkswurzeln der Sdugetiere nebst Bemerkungen zur tabis chen Hinterwurzelerkrankungen. Arbeit, a. d. neurolog. Inst, an d. Wien. Univ., Bd. 17, Hft. I, s. 98-117. BiKELES, G. 1907 Ueber das Verhalten des proximalisten Teiles der hinteren Wurzeln bei Degeneration und Regeneration. Xeurolog. Centralbl., Bd. 26, s. 951. DoixiKOW, B. 1911 Beitriige zur Histologic und Histopathologie des peri pheren Xerven. Xissl und Alzheimer, Histologische und Histopath ologische Arbeiten uber die Grosshirnrinde, Bd. 4, Hft. 3, Jena 1911. Edixger, L. 1893 ^'orlesungen Uber den Bau der nervosen Centralorgane des Mensehen und der Thiere. Leipzig, 1S93. Fischer, Alfred 1899 Fi.xirung, Fiirbung, und Bau des Protoplasmas. G. Fischer, Jena 1899. Harrison, R. G. 1904 X'eue Versuche und Beobachtungen iiber die Entwick lung der peripheren X'erven der Wirbeltiere. Sitzungsber. d. Xiederr heinischen Gesellsch. f. Xatur und Heilkunde zu Bonn. Sitzung II Juli 1904. 1906 Further experiments on the deveJopment of the peripheral nerves. Am. Jour. Anat., vol. 5, p. 121. SocHE, A. 1891 Beitrage zur Kenntnis des anatomischen Verhaltens der menschlichen Rtickenmarkswurzeln im normalen und in krankhaft veranderten Zustande, Heidelb. 1891. HcBER, G. C.\HL 1901 Studies on the neuroglia. .Am. Jour. Anat., vol. 1, no. 1, p. 45. 1903 Studies on neuroglia tissue. Contributions to medical research, (dedicated to Victor Clarence Vaughan by colleagues and former students of the Department of Medicine and Surgery of the L'ni versity of Michigan). Wahr, Ann Arbor, Michigan, June 1903, pp. 578-620. HcLLES, Edcard 1906 Beitr?ge zur Kenntnis der sensiblen Wurzeln der Medulla Oblongata beim Menschen. Arbeit, aus d. neurolog. Inst. a. d. Wien. Univ., Bd. 13, s. 392. KixGERY, H. M. 1917 The application of Benda's neuroglia stain. Anat. Rec, vol. 11, no. 5, p. 289. KoLLiKER, A. 1893 Ge-n-ebelehre. 6 Aufl., Bd. 2, Th. I, s. 151.. Lavdowsky, M. 1891 Vom Aufbau des Ruckensmarks. Archiv. f. mikr. Anat., Bd. 38, s. 264. Levi, Ettore 1906 Studien zur normalen und pathologischen Anatomie der hinteren Riickenmarkswurzeln. Arbeit, aus d. neurolog. Inst, an d. Wien. Univ., Bd. 13, s. 62. Marburg, Otto 1902 Die absteigenden Hinterstrangsbahnen. Jahrbuch. f. Psychiat. und Xeurol., Bd. 22, s. 243. Nageotte, J. 1894 La lesion primitiv du tabes. Bulletins de la Society de Paris, Series .5, Tome 8, Xov. 16. 182 LYNN ARTHUR HO AG Obersteixer, H. 1895 Bemerkungen zur tabischen Hintenvurzelerkrankung. Arbeit, aus d. neurolog. Inst, an d. Wien. Univ., Bd. 3, s. 192. 1901 Anieitung beim Studium des Baues der nervosen Centralorgane. Leipzig und Wien. 1896 und 1901. Obersteixer, H. u.\d Redlich. E. 1895 Ueber Wesen und Pathogenese der tabischen Hinterstrangsdegeneration. Arbeit, aus d. neurolog. Inst, an d. Wien. Univ., Bd. 2, s. 158. Oppexheim, Herm.\xx 1887 Ueber einen Fall von chronischer progressiver Bulbiirparalyse ohne anatomisehen Befund. Virchow's Archiv, Bd. 108, s. 522 or Mendel's Centralbl., 1887. Redlich, E. 1892 Die hinteren Wurzeln des Rtickemnarkes und die patho logische Anatomie der Tabes dorsalis. Arbeit, aus d. neurolog. Inst, an d. Wien. Univ., Bd. I. 1897 Die Pathologie der tabischen Hinterstrangserkrankungen. Jena 1897. ScHAPFER, J. 1894 Beitriige zur Kenntnis des Stiitzgeriistes in menschlichen Ruckenmark. Archiv. f. mikr. Anat., Bd. 44, s. 26. ScH.^FFER, K.\Ri, 1901 Anatomisch-klinische Vortrage aus dem Gebiete der Nervenpathologie. Fischer, Jena. SiEBERT, F. 1895 Die Eintrittsstellen der hinteren Wurzeln in Ruckenmark und ihr Verhalten bei Tabes dorsalis. Dissertat. an Miinchen. Smith, J. L. .\xd M.\ir, W. . 1908 An investigation of the principles underlying Weigert's method of staining medullated nerve. Jour, of Path, and Bact., vol. 13, 1908. St.\derixi, R. 1890 Contributo alio studio dell tessuto interstitiale di alcuni nervi cranieasi dell" nonio. Monitore Zoologico italiano, anno I, no. 12, p. 232. Streeter, G. L. 1903 Ueber die Verwendung der ParafEneinbettung bei Mark scheidenfarbung. Archiv. f. mikr. Anat., Bd. 62, p. 734. Thomsen', R. 1887 Ueber eigentumliehe, aus veranderten Ganglienzellen hervorgegangene Gebilde in den Stammen der Hirnnerven des Menschen. Virchow's Archiv. f. path. Anat. u. Physiolog., Bd. 109. g3 author's abstract of this paper issued by the bibliographic service, decembers ADVANTAGES OF SAGITTAL SECTIONS OF PIG EMBRYOS FOR A :\IEDICAL EMBRYOLOGY COURSE' WILLI.UI F. ALLEN From the Department of Anatomy of the University of Oregon Medical School, Portland, Oregon EIGHT FIGURES The "nriter has recently been impressed with the superiority of sagittal sections over transverse sections for most of the laboratory work of medical students in embrj'ologj'. Bj^ the time the ordinary student has familiarized himself with the various turns found in a transverse series and has determined the direction required to follow forward or backward one of the three or four sections of the same organ found in a single transverse section, a considerable portion of the short time allotted for this course has elapsed. Since the time is insufficient for the student making graphic or wax reconstructions of the various sj^stems, the little knowledge obtained by student, when only transverse sections are supplied, is usually acquired from a study ' It is assumed in most medical embr3'ological laboratories that pre-medical students have had work in maturation, fertilization, segmentation and the early development of the main systems in some vertebrate. The aim of a medical course then is to obtain in as short time as possible a fairly comprehensive understanding of the formation of the various structures and organs of the body. To accomplish this the student should have access to a number of different stages of human embryos and their placenta, and to a collection of cleared embrjos that will show the formation of the skeleton. In our laboratorj' every two students are supplied with a slide box containing a longitudinal and a transverse series of a 6 mm. pig embryo, a transverse section of a 12 mm. pig, twelve specially selected transverse sections of a 25 mm. pig and two 15 mm. pigs for dissection of the viscera, central nervous sjstem and the cranial nerves. The writer is an advocate of the method of taking up the laboratory work from the standpoint of one system at a time, rather than attempting the study of all systems simultaneously. 183 THE AXArOMICAL RECORD. VOL. 14, NO. 3 UARCH, 19iS 184 WILLIAM F. ALLEX of the laboratory models or from his general didactic instruction rather than from a study of his transverse sections. It must be admitted, however, that for certain special studies, as for example, the origin and distribution of the cranial and spinal nerves, the organs arising from the branchial arches, certain relationships of the heart chambers and the formation of the vertebrae, transverse sections should be consulted. To amplify further, a transverse section through the otocyst of a 6 or 12 mm. pig embrvo, which is a more or less frontal section through the rhombencephalon, affords an excellent view of the cranial nerves and their ganglia. Likewise certain transverse sections in the trunk region, especially of 20 and 25 mm. embryos, will give excellent pictures of the spinal nerve components and the various elements that go to make up a vertebra. All of the illustrations for this paper were taken from a single sagittal series of a 6 mm. pig embryo, belonging to a student's loan set. • ALIMENTARY CANAL A study of the development of the alimentary canal and the formation of its appendages is one of the first studies that can be made satisfactorily from an examination of a sagittal series of a 6 mm. pig. If the student wiU examine a median sagittal section through the pharynx region he will be able to follow the course of the digestive tract from the oral ca^'ity to the branching off of the lung bud, and from especially favorable sections (fig. 1) this tube can be seen in section from the oral cavity to the outbudding of the dorsal pancreas. From its dorsal wall the following protuberances have appeared, enumerated from before backward: Rathke's pocket (R.P.) and its relationship to the infundibulum, Sessel's pocket (S.P.) and the dorsal pancreas (D.Pan.) The following ventral evaginations are shown: Thyroid gland (Thyr.) situated near the external carotid artery, the trachea bud (Tr.) from its origin to its separation into the two bronchi, the gall bladder (G.Bl.) and the hepatic portion of the liver (Liv.). The student should make an outline sketch of this section, incorporating in it the above mentioned portions of the alimentary canal. .Vn examination of a few following sec ADVANTAGES OF SAGITTAL SECTIOXS 185 tions brings us to the section from which figure 2 was drawn. From such a section the student can supply the cephahc arm of the intestinal loop (Int.) to his drawing of the digestive tract, and a few sections more (fig. 3) will supplj" a large portion of the caudal arm of the intestinal loop and the caudal end of the intestine ilut.) nearly to the cloaca. This section (fig. 3) also shows the position of the distal end of the ventral pancreas (T'.Po??.), which can be readily followed from adjacent sections to its origin from the intestine at the point of the budding off of the gall bladder. When the caudal portion of the intestine has been added to the drawing of the digestive tract, the student has obtained a very satisfactory picture of the embryonic digestive tube and a number of its appendages from a study of three sagittal sections of a 6 mm. pig embryo. The cloaca end of the alimentary canal can also be studied from this series but will be taken up under the next subdi\-ision. URIXARY SYSTEM Anj' of the lateral sections of this G mm. sagittal pig series will show the extent and structure of the mesonephros. From figure 4, which is a sagittal section through the cephalic end of the mesonephros, it is clear that the mesonephros (Meson.) is composed of collecting tubules, glomeruli and a mass of undifferentiated mesenchyme. In most sagittal series of pig embryos the extreme lateral sections are almost as perfect transverse sections through the tail or cloaca region as those from a frontal series and are far superior to corresponding sections from a transverse series. It is apparent that a few perfectly true transverse sections through the cloaca region will give the student a very clear conception of the relationship of the various ducts of the embryonic kidney; while it is equall.y true that nothing can be more confusing than an equal number of oblique transverse sections through this region. In figure o, which is a more lateral section of the same sagittal series as figures 1 to 4 we have a nearh' transverse section through the cephalic end of the cloacal (CI.) expansion of the intestine. In this section both of the mesonephric or 186 WILLIAM F. ALLEN Wolffian ducts are cut transversely and the left one (L.W.D.) is about to empty into the cloaca. It is from this region in a 7 mm. pig that the metanepliric ducts or ureters bud off from the mesonephric or Wolffian ducts. Ventrally the allantois (Al.) is leaving the cloaca to enter the umbilicus. A more lateral section (fig. 6), which is through a more caudal region of the cloaca than figure 5, shows the left mesonephric or \A'olffian duct L.W. D.) emptying into the cloaca. In a still more lateral section (fig. 7) the right mesonephric or Wolffian duct (R.W.D.) will be seen terminating in the cloaca, which is rapidly diminishing in size to become the postgut in figure 8 (P.G.). In figirres 6 to 8 the allantois (..4^) has entered the miibilicus with the mnbilical blood vessels and is situated midwaj- between the two umbilical arteries. BLOOD VESSEL.S Sagittal sections are especiaUj' useful for a study of the general arrangement of the principal blood vessels, which in general run for long distances in a longitudinal direction. Ferns A shghtly lateral sagittal section (fig. 4) furnishes an excellent view of the main v'enous trunks of a 6 mm. pig. The right atrium (R.At.), ventricle iR.Ven.) and the conus or bulbus arteriosus are seen in their correct position. This section is a little to the right of the atrio-ventricular opening. The sinus venosus (SA'.) will be seen opening into the right atrium, its orifice being partly guarded bj- the sinu-atrial valves (S.AA^.) The endotheUal lining of the heart chambers is clearly shown and the cardiac muscle is in an earl}' stage of its histogenesis. From figure 4 it is clear that the sinus v-enosus receives the entire venous blood from the embryo and the entire arterial supply from the fetal placenta. Entering the sinus venosus from abo\'e, the short right ductus Cuvieri or common cardinal vein (R.D.C.) is formed from the union of the right anterior cardinal vein (R.A.CA^.), with the right posterior cardinal vein R.P.C.y.). ^he former comes from the head and neck and the ADV.\XTAGES OF SAGITT.^L SECTIOXS 1S7 latter collects the intersegmental veins (/«/s.T'.) from the bodj^ walls, themesonephric veins from the mesonephros and a sub-cardinal vein {$ub. C.V.) traversing the ventral surface of the mesonephros. From below the left ductus Cu^•ieri or common cardinal vein (L.D.C.) joins the sinus venosus, and after curving around the lower and left side of the pharynx it takes origin from the union, of anterior and posterior cardinal veins from the left side of the bod}'. Xot far from its termination in the sinus venosus the left ductus Cuvieri receives the left umbilical vein (fig. 1, L. Umb.V.), The terminal portion of this vein probabh' represents the terminal portion of the original omphalo-mesenteric vein. From the rear the sinus venosus is continuous with a large sinusoid (S), which might be designated as a part of the ductus venosus, but which probably represents an enlargement of the original proximal or terminal portion of the right omphalomesenteric vein. Sinusoid (.S) collects the portal or common omphalo-mesenteric vein (P.V.) and the right umbilical \-ein {E. Umb.V.) from the rear, the former being somewhat more dorsal in position. Toward the median line sinusoid (S) is continuous with a large transverse sinusoid, the ductus venosus, which extends transverselj^ through the cephalic end of the liver to communicate with the left umbilical vein. The position of the ductus \-enosus is shown in figures 2 and 3 (D.V) to be more dorsal on the right side than on the left, which has doubtless been brought about by the difference in level of its two terminal connections, sinusoid (S) and the sinus venosus on the right side and the left umbilical ^-ein and left ductus Cu\'ieri on the left side. A comparison of the two umbilical veins reveals the left one to be slighth' the larger. After entering the lower left corner of the liver the left umbilical, pursues a fairl}^ straight course through the first half of the liver, to finally bend dorsad and cephaladto terminate in the left ductus Cuvieri (fig. I, L.D.C). As previously stated the left umbilical vein is also in direct communication with the sinus venosus through the ductus venosus. The opening of the left umbilical vein into the left ductus Cuvieri is fullj^ as large as its communication with the ductus venosus, so that the blood in the left umbilical vein would have an option

188 AVILLIAM F. ALLEN

of two ways of reaching the sinus venosus and the heart. Also the blood in the right side of the liver, collected in sinusoid (<S) could easily find its way into the sinus venosus by way of the ductus venosus and the left ductus Cuvieri. The right umbilical vein will be seen in the lateral sagittal sections 5 and 6 (R. ■TJmh.V.) to traverse the lateral wall of the abdomen a little below the level of the mesonephros and to enter the umbilicus in the region of the cloaca. Likewise corresponding sections on the left side of this embryo would show a similar distribution of the left umbiUcal vein. Upon entering the umbilicus the umbilical veins are situated laterally to their corresponding arteries (figs. 5 and 6), but soon assimie a caudal position (fig. 7, R.Umb. V. and R.Umb. A.). A still more lateral section (fig. 8 shows the umbilical veins have united more distally in the umbilicus to form a conimon umbilical vein (Umb.V.).

In addition to the connection between the two umbilical veins through the liver, the ductus venosus, there is a smaller anastomosing vein between the two umbilicals behind the liver. It appears (figs. 2 and 3, A.V.) in the mesenchyme directly below the pancreas, midway between the liver and the cephalic arm of the intestinal loop.

The portal vein (fig. 3, P.V.), representing in part the combined omphalo-mesenteric veins, occupies a general median position a little to the right of the digestive tract. In figure 3 it will be seen passing between the dorsal and the ventral pancreas to enter the caudal surface of the liver slightly median and dorsal to the right umbilical vein. These two veins are portrayed in figure 4 as anastomosing inside the liver, the common trunk after expanding into sinusoid (5) enters the sinus venosus from the rear. A short distance behind the dorsal pancreas (fig. 1) the portal vein takes origin from the union of the superior mesenteric vein with the omphalo-mesenteric vein. The former (Mes.V.) comes from the caudal region and the latter (fig. 2, 0.^1/. 1'.) passes dorsad in front of the cephalic arm of the intestinal loop and represents the original right omphalomesenteric vein. At the junction of the omphalo-mesenteric vein with the superior mesenteric vein to forn; the joortal vein,

a small branch is received from the region of the pancreas. It likely represents a persisting portion of the original left omphalomesenteric \-ein. There is a communicating vein between the portal and subcardinal veins.

Arteries

Excepting in the extreme cephalic and caudal extremities of a 6 mm. pig embryo the originally paired dorsal aortae have fused and formed a median longitudinal trunk of considerable size, the aorta. ^lost any median sagittal section of this series (fig. 3) will show long stretches of the aorta (Ao.) situated below the notochord and extending out laterall\' bej'ond the limits of the spinal cord. In figure 4 a portion of the original right dorsal aorta, now the right internal carotid artery (Ao.), is present in connection with the third branchial artery. Figures 1 and 2 show the intersegmental arteries (Ints.A.) to be well-advanced. It wiU be seen from figures 2 and 3 that the omphalo-mesenteric artery (O.M.A.) takes origin from the aorta from three stems, which soon unite in a single trunk that passes ventrally between the two arms of the intestinal loop. The bulbus or conus arteriosus (C.A.) and the ventral aorta (V.Ao.) are cut more or less longitudinally in figiu-es 1, 2 and

3. In figure 2 the basal portion of the third, fourth and the sixth or fifth right branchial arteries are present in connection with the ^"entral aorta, and nearly the entire course of the right sixth or fifth branchial arterj- (Br. A . 5) can be followed from the ventral aorta to the right dorsal aorta. In figure 3 a considerable of the right fourth branchial artery {Br. A. 4), especially the distal portion terminating in the right dorsal aorta, is seen between the third and fourth branchial clefts. A similar portion of the right third branchial artery {Br. A. 3) empties into the right dorsal aorta or external carotid artery {Ao.) in figure

4. In figure 1 a small portion of the right external carotid artery {E.Car.A.) appears in the region of the thjToid gland. The puhnonarj' and subcla\aan arteries are not shown in any of the sections figured. They are best followed in transverse sections.

190 WILLIAM F. ALLEN

CENTRAL NERVOUS SYSTEM

III most any median sagittal section of a 6 mm. pig embr3'o, as figure 1, the primary, secondary and tertiarj- segmentation of the neural tube can be readily distinguished. The neuromeres (Neuro.) or primary segments are clearly defined in the medulla region. Concerning the secondary segments of the brain region, the forebrain occupies all the space in front of the dotted line between the cavities (Dien.) and (Mes.), the midbrain corresponds to the division (Mes.) and the remaining portion of the brain behind the mesencephalon (Met. and My.) represents the hindbrain. The tertiary segments- telencephalon (Tel.) , diencephalon (Dien.), mesencephalon (Mes.), metencephalon (Met.) and myelencephalon (My) are well-differentiated in this section. The boundry line between the diencephalic and telencephalic segments, as determined by Johnston for early embryos, is a line between the velum transversum (V.T.) and the postoptic recess (P.OM.) or between the caudal borders of the interventricular foramen and the optic chiasma for later stages. The following diverticula appear in the basal plate of the diencephalon- mamillary recess (M.R.), infundibular recess (I.R.), postoptic recess (P.O.R.) and the preoptic recess (shown in front of the postoptic recess and the optic chiasma thickening). In the telencephalon the expansion of the hemispheres (C.H.) is apparent, but is more conspicuous in more lateral sections (fig. 3). The roof plate of the rhombencephalon (metencephalon and myelencepha'on) is for the most part reduced to one layer of flattened cells, the mesoderm outside is vascular and there is considerable stained coagulum within ' the fourth ventricle, giving every indication that the roof plate (tela chorioidea) has attained the function of producing cerebro-spinal fluid. The cervical (Cer.F.) and cephalic (Ceph.F.) flexures are prominent in this section, but the pontine flexure (Pon.F.) is barely visible. Concerning the histogenesis of the central nervous system (figs. 1 to 4) show an early differentiation of the neural tube into ependymal, mantle and marginal layers, and the germinal cells are proliferating rapidly about the ventricles and the central canal.

.\DV.WrAGES OF SAGITTAL SECTIOXS 191

SO.MITES

To illustrate the earh' differentiation of the somites into mj'otome and sclerotome, the extreme lateral sections of this series, which are nearly transverse sections through the tail, are especially valuable, for the reason that the caudal somites are in a much more elementarj- state than the cephalic somites. In such a section (fig. 8) the central ca\'ity of the right somite is filled with spindle-shaped cells that migrated from the walls of the somite. From the somite on the opposite or left side of this section it will be seen that this migration took place mainly from the median and ventral walls of the somite. These diffuse spindleshaped cells, the future sclerotome (ScL). are about to migrate medially to envelop the notochord and the spinal cord to form the skeletal axis. The outer or more dense portion, the myotome (Myo.) has differentiated into myoblasts and muscle fibrils in a more cephalic region (fig. .3, Myo.). Also the neighboring sclerotomes (Sd.) have differentiated into dense and diffuse portions, preparatory to the formation of the membranous vertebrae. It is obvious that later stages are necessary for the further stud}- of the development of the vertebrae and trunk muscles.

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THE ASAIOUICiL RECOED, VOL. U, NO. 3

PLATE 5

EXPLAXATIO.V OF THE FIGURE

5 Sagittal section considerably lateral to those from which figures 1 to 4 were drawn. This section is a sagittal section through the right mesonephros and the right umbilical vein, but a nearly transverse section through the tail region at the level of the beginning of the umbilicus and cloaca. Note that the left umbilical artery and Vein have entered the umbilicus and the right artery and vein are entering it. Observe that the cloaca, mesonephric or Wolffian ducts are cut in transverse section and the allantois is in connection with the cloaca. X 26

6 Sagittal section but 50 microns to the right of figure 5. Observe that the allantois has lost its connection with the cloaca and is situated midway between the umbilical arteries in the umbilicus; also that the left mesonephric or Wolffian duet has joined the cloaca. X 26

ABBREVI.4TI0.\S

Al., allantois

CI., cloaca

L.Umb.A., left umbilical artery

L.L'mh.V., left umbilical vein

Zy.Il'.D., left Wolffian or mesonephric

duct Meson., mesonephros Myo., myotomes

Nc, notochord

R.Vmb.A., right umbilical artery R.Umb.V., right umbilical vein li.W.D., right Wolffian or mesonephric

duct Sp.Cd., spinal cord Umb., umbilicus

200

WILLIAM F. ALLEN

PL.\TE 5

2U1

PLATE a

EXPLAXATIOX OP THE FIGCRES

7 Sagittal seotion 200 microns to the right of figure 6, a more caudal section through the embryo and a more ventral or distal section through the umbilicus. Observe that the umbilicus has nearly lost connection with the embryo, that the umbilical veins are situated behind their corresponding arteries and are about to anastomose. The right mesonephric or Wolffian duct will be seen terminating in the cloaca, which has become much reduced in caliber. X 26.

8 Sagittal section 220 microns lateral to figure 7, a more caudal transverse section of the embryo and a more distal transverse section of the umbilicus. Xote that the umbilical veins have united in a common vein and the reduction in size of the digestive tract from the cloaca to a small postgut. X 26

ABBRE\1ATI0XS

Al., allantois R.l'mb.V., right umbilical vein

CI., cloaca R.W.D., right mesonephric or Wolflian

L.l'mb.A., left umbilical artery duct

L.Umb.V., left umbilical vein Scl., sclerotome

Myo., myotome I'mb.. umbilicus

P.G., postgut Umb.V., umbilical vein (in umbilicus)

R.l'mb.A., right umbilical artery

202

■»T1_L1AM F. AIXEX

PL^TE 6

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ATTTHOR'S ABSTRACr OF THIS PAPER ISSUED BT THE BIBUOGHAPHIC SERVICE, JAXUART 5

OX THE BRANCHIAL EPITHELIUM OF AM:M0C0ETES'

IVAX E. WALLIX Department of Anatomy, Marquette University School of Medicine

EIGHT FIGCRES (tWO PLATEs)

In a recent investigation of the thymus in Ammocoetes ('17) it occurred to the author that the branchial epitheUum of the advanced larva does not represent a pure endodennal epithelium. The characters that suggested this hypothesis may be enumerated as follows: The epithelium in the young larva (5 mm.) is represented by a distinct single laj'er of cells which is- sharply marked off from the underlying mesench\Tna (fig. 1). In shghtl}' older larvae the epithelium of the gill arches has acquired a somewhat stratified character resembling transitional epithelium as found in the bladder of mammals (fig. 8). In still later stages the epithehumof the gill lamellae is composed of a mass of cells which are not arranged in stratified layers (figs. 6 and 7). Alesenchj-ma is not present in the gills of larvae bej'ond 6 to 7 mm. in length. Lymphocytes (and probablj- erythrocj-tes) and the cells of the primitive thj-mus placodes are formed from the cells of this epithelium which does not contain a basement membrane. The cells of the epithehmai have an intimate relationship to the blood channels of the gills and appear to enter into the formation of the endothelial lining when such a lining is present.

The importance of determining the character of this epithelium is obvious in the light of its relationship to lymphocj-te and thymus formation. While the acceptance of an endodermal character of this tissue would lend additional proof of the endodermal origin of blood in the ammocoetes according to the researches of Goette ('90), Wlieeler ('99) and Mollier ('06) and to the conten ' I am greatly indebted to Mr. Peter Okkelberg of .\nn Arbor, Mich., for supplying me with j'oung developmental stages of lamprey larvae some of which were used in this investigation.

205

206 IXAS E. WALLIX

tion of various investigators that the phylogenetically oldest blood is endodennal, the character of the eijitheliuin in the developing Jarva is such that one can not leave its purely endodennal character unchallenged.

The rapid change of the epithelium from a single layer of cells in the 5 mm. larva (fig. 1) to a multi-layered or massed condition in the 6 mm. larva is apparently not associated with mitotic division of the cells. In the comparatively few mitotic cells which have been observed the spindle was never so directed that the daughter cells would form a stratified epithehum.

In seeking an explanation of the increase in thickness of this epithelium one specimen measuring 5 mm. in length was found which displayed an apparent mingling of mesenchyma with endoderm in various parts of the branchial epithelium. Figure 5 represents a camera lucida drawing of one of these regions. In the lower right-hand part of the figure the endoderm is present as a single layer of cells sharply marked off from the underhang mesenchjTiia by a basement membrane. Above this portion the basement membrane is missing and the mesenchjanal cells appear to be mingling with the endodermal cells. In the upper left-hand part of the figure a basement membrane is again present. The basement membrane in the upper part of the figure lies next to developing muscle cells; in the lower part of the figure mesenchymal cells are present between the developing muscle cells and the basement membrane.

A transverse section of the branchial region of a 5 mm. larva .would show a more or less irregular outline of the endodermal lining. The gill arches are just beginning to form in this stage of development with a consequent complication of the endodermal lining. The question arises whether this apparent mingling of the two tissues as represented in figure 5 is not an artifact, the result of a tangential section through a part of the specimen. A reconstruction of a few sections of this region was made in the hope of determining this point. The reconstruction demonstrated that the epithelium is cut tangentially at this place, but it also shows a tangential plane of section in other parts of the branchial epithelium where the basement membrane is distinctly

BRAXCHIAL EPITHELIUM OF AMMOCOETES 207

visible. The degree of deviation of the section from the transverse plane is not an}' greater at the point of apparent mingling than it is in some other parts of the section where the basement membrane is visible. The angle of the plane of the section in relation to the plane of the basement membrane does not satisfy an explanation of the absence of the basement membrane at the apparent point of mingling.

The apparent mingling of the two tissues is further suggested in the character of the branchial epithelium in later developmental stages.

Figure 7 represents a frontal section through the entire gill and gill arch of a 6 mm. larva. In this stage of development the primitive gill pouches have enlarged producing an approximation of the two hemibranchs in the formation of the gill septa. The constriction at the left of the figure represents the point of attachment of the branchial septum to the lateral wall. The primary gill lamellae are in the early stages of formation, indicated at gl. 1 and 2 in the figure. It is evident from an examination of .the figure that a single layered-epithehum is not present in the greater part of the section. The cells form a continuous mass from the exterior to the interior. In places, for example end in the figure, the single layered condition still persists. This patch may represent one of the patches which in later developmental stages contains cilia.

• A single section as represented in figure 7 may be misleading when considered alone and apart from the sections preceding and following. The apparent continuity of the cells from the exterior to the interior may be due in part to the folding of the epithelium in the formation of the gill lamellae. However, this is not true of all parts of the section for the continuit}' of the massed condition of the cells in some places will persist through a number of sections.

Figure 6 represents a camera lucida drawing of a frontal section through a gill arch and a part of the gill septum of a 9.5 mm. larva. In tlus stage of development the cells are approacliing the stage at which they transform into lymphocjrtes. At the surface of the part which represents a gill arch a layer of thin cells have formed (s.c. fig. 6). Such a layer of cells in this situation is appar

208 IVAN E. WALLIX

entlj' in the process of foniiation in the younger hirva as represented in figure 8 (longitudinal section through a gill arch of a 7.5 mm. larva). The cell at X in the figure appears a-s if it were migrating from the deeper part of the cell mass in the formation of the surface or cuticular layer.

In the growth of the larva the mass of cells is gradually depleted so that in the full-grown larvae the secondary- lamellae contain onlj' a layer of thin cells lying next to the blood channels. The massed condition of cells is retained longest in the angles between the secondary lamellae.

A product of this epithelium which, it seems to me, demands more than a passing interest are the cells represented at d.c. in figures 3 and 4. So far as I can learn this type of cell was first described by Graf von Spee ('96). More recentlj^ the cell has been encountered in the blood work of Stockard ('15), Emmel ('16) and others. Stockard considers these cells of a 'questionabh' degenerate type' while Emmel speaks of them as 'phagocytic inclusions.' In the lamprey larva these cells are especially numerous in the branchial epithelium of the 15 mm. stage. AVhile an occasional one may be found in slightly younger and older stages the branchial epithelium of the 15 mm. larva is literally filled with these cells. There is apparently a limitation of this process to a definite de^•elopmental stage.

The cells in question appear to form as a final product of a breaking down process as represented at e.d. in figure 3. Thisfigure illustrates only one step of the process. The next step is a vacuohzation of the entire cell and the gathering together of the chromatin and the cytoplasmic remains into a cell-hke body within the hollow original cell. These cells are ver}^ characteristic in appearance. The cytoplasm has a homogeneous structure and with eosin stains a deep pink. The chromatin material is generally present as a single globular bodj^ ver}^ compact and darkly stained. The chromatin may be represented by a number of such bodies, however, and sometimes they stain a very pale blue.

What is the significance of the formation of this apparently degenerate type of cell? The answer to this question can, of necessity, only be made in the nature of hypothesis.

BRANXHIAL EPITHELIUM OF AMMOCOETES 209

In the consideration of these cells the results of Shiplej-'s ('16) work on the de^•elopment of en-tlirocytes iti vitro is suggestive. Shipley found that some of the eni:hrocytes in the culture developed into cells with pyknotic nuclei and suggests . that the strange environment niaj- be the cause of the degeneration. So far as I can judge the cells that Shipley describes resemble very closeh" the apparently degenerate cells found in the branchial epithelium of the lamprey larva.

Is it probable that the degenerate cells in the branchial epitheUum of the lamprey larva are cells which have become lodged in an unfavorable environment? In support of such a possibiUty there is a tj-pe of cell found in this epithelium which has the appearance of erythrocytes. Such cells are represented at ery in figure 2. These cells have a more or less vesicular nucleus and the c\i:oplasm is not .so homogenous as in the degenerate tj-pe of cell. The nucleus is not as vesicular, however, as it is in the developing erj-throcytes in other parts of the body. These erythrocyte-Uke cells are apparently fomied in this epithelial mass. It is, however, quite impossible to say with certainty that they are formed here, for vascular channels are forming in the mass of cells simultaneously. From this consideration it might be suggested that cells with erythrocyte potentialitie.s are present in the branchial epithelial cell mass; that some of these cells have environments approximating the conditions which are essential for erythrocyte development while others are apparently in an unfavorable environment and degenerate.

Another possibility suggests itself in the explanation of these cells. Their formation in connection with hematopoetic anlagen (not onlj- in the lamprey, but also in other forms where thej' have been described) may be essential to blood formation. Thej' may possibly have chemotactic properties in the nature of hormones ser\ang as a stimulus to blood formation.

The e\'idence submitted in the foregoing pages, it seems to me, warrants a conclusion that the branchial epithelium of the advanced lamprej' larva is a compound tissue composed of endoderm

210 IVAN E. WALLIN

and mesenchjaiia. "\Miile the one specimen represented in figure 5 maj- possibly be an artifact, the character of the epitheUum in the older larvae suggests a mingling of the two tissues. Such a mingling of tissues, however, is not a newly discovered histogenetic process. In the development of the thjTnus in higher animals mesenchjanal and endodennal cells mingle in the formation of the organ. The process in higher animals is fundamentally the same as it is in the lamprej' larva, but it differs in the amount of the tissue involved. In the thj^mus formation of higher animals the mingling is limited to localized areas; the minghng of the tissues in the lamprey larva occurs throughout the general branchial epithelium.

Such a tissue mingling is obviously a normal process so far as the thymus is concerned in the lamprey larva. It is only a small part of the entire epithelium, however, that enters into thymus fonnation. The cells of the greater portion of this mixed tissue are transformed into lymphocytes.

With the staining methods that I have emploj^ed it has been impossible to follow the further historj- of either tissue as an individual element in the mixed tissue. The cells appear to be all alike, i.e. in the early indifferent stage. It is consequently impossible at this time to determine whether the h'mphocytes are formed from the endodemial element or the mesenchj-mal element or the product of the two tissues combined.

The 'formation of a thin cuticular layer at the surface of the mass of cells in the developing larva is likewise difficult of explanation. The cells forming this laj'er were earlier a part of the general mass of cells.

The outstanding feature of this mingling or fusion process is the indicated histogenetic relationship of lymphocyte fonnation (and probabh' erythrocj-te formation) to thjaiius formation in this primitive animal. While the thymus in higher animals has retained the process of endodemial and mesenchymal fusion or mingling as essential to the formation of the organ, lymphocyte formation in higher animals has apparently dispensed with the endoderm.

BRAXCHIAL EPITHELIUM OF AMMOCOETES 211

LITERATURE CITED

E.MMEL, V. E. 1916 The cell clusters in the dorsal aorta of mammalian embryos.

Am. Jour. Anat., vol. 19, Xo. 3, pp. 401H122. GoETTE 1890 Entwickelungsgeschichte des Flussneunauges. Hamberg and

Leipzig. MoLLiER. S. 1906 Die Entwickelung von Blut und Gefa.ssen. In Hertwig's

Handbuch der vergl. u. exp. Entwickelungsgeschichte der Wirbeltiere.

Jena. Wheeler 1899 The development of the urogenital organs of the lamprey. Zool.

Jahrb.. Bd. 13. W.\LLIN', I. E. 1917 The relationships and histogenesis of thymus-like structures in ammocoetes. Am. Jour. Anat., vol. 22, Xo. 1, pp. 127-167. Shipley, P. G. 1916 The development of erythrocytes from hemoglobin-free

cells and the differentiation of heart muscle fibres in tissue cultivated

in plasma. Anat. Rec. vol. 10, Xo. i. pp. 347-354. Von Spee, Gr.\f 1896 Arch. f. Anat. u. Entwickelungsgeschichte. Stock.\rd, C. R. 191.5 The origin of blood and vascular endothelium in embryos

without a circulation of the blood and in normal embryos. Am. Jour.

Anat., vol. 18, Xo. 2, pp. 227-327.

PLATE 1

EXPLAXATIOX OF FIGURES

1 Frontal section of gill of a 5 mm. larva, b.a., blood vessel; end., endoderm; mes., mesenchjina; v.c, endothelial cells (?). (,V, oil immersion obj., comp. oc. No. 12.)

2 Small portion of the branchial epithelium of a 15 mm. larva, ery., young erythrocj-tes (?). (/; oil immer. obj.. comp. oc. Xo. 12 X 2.)

3 Portion of branchial epitheliimi of 15 mm. larva, d.c. degenerate cell; e.d., cell in which the degeneration process has just begun. (jV oil immersion, obj.. comp. oc. Xo. 12 X 2.)

4 Portion of the branchial epithelium of a 15 mm. larva, d.c. degenerate t\-pe of cell, lower one apparentlj- in a young blood vessel. i,\ oil immer. obj., comp. oc. Xo. 12 X 2.)

212

ON THE BRAXCHU.L EPITHELllM OF AMMOCOETES

irAX E. WALLIX

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PLATE 2

EXPLA.VATION OF FIGURES

5 Part of a transverse section of the branchial region of a .5 nun. larva, dm.. developing muscle cells; end., endoderm; mes., mesenchynia. (,V oil imnicr. ohj., comp. oc. No. 12.)

6 Frontal section of gill arch and jiart of gill ,'._. septum of a 0..5 nun. larva, b.a., hlood vessel containing erythrocytes; s.e., surface or cuticular layer of cells. (,":> oil immer. obj., oc. Xo. 10.)

7 Frontal section of gill of a 6 mm. larva, end., patch of cells which still retain endodermal characters; ql.l and 2, gill lamellae in process of formation. (,^> oil immer. obj., oc. Xo. 10.)

8 Longitudinal section through a gill arch of a 7.o mm. larva, en., endothelium of blood vessel; x, cell which appears to be migrating from deeper part to the surface. (,'.. oil immer. obj.. comj). oc. Xo 12.)

214

ox THE BRAXCHL\L EPITHEUrM OF AMMOCOETES

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## On the Anlage and Morphogenesis of the Chordates Dorsalis in Mammalia, in Particular the Guinea Pig (Cavia Cobaya)

G. Carl Huber Department of Anatomy, University of Michigan

Fourteen Figures

The discussion here undertaken is one which is in no sense foreign to anatomic and morphologic Uterature; indeed it may be stated that there is perhaps no single subject in vertebrate embryology which has been so frequentlj* and so ably investigated and has formed the basis of such extensive and fundamental speculation, as the subject here under consideration. The discussion of the anlage of the mammalian chorda dorsalis, involves a consideration of the anlage and homologies of the primar}' germ layers, the question of blastulation and gastrulation, considered ontogenetically and phylogenetically: in a word, the consideration of the embryologic stages immediateh' followmg the stages of segmentation. A full consideration of this broad question is beyond the limits of this communication. Xeither is it possible to consider here at all coni]3letely the extensive hterature involved. This seems the less necessary since relatively recently a goodly number of investigators have given extensive and critical reviews of the literature deaHng with this question as may be learned on study of certain of the contributions of O. Hertwig, Keibel, ^'an Beneden, Bonnet. Rabl Hubrecht and others. I shall, therefore at the outset, limit the .scope of this communication by stating that it is the purpose at this time to present observations dealing with the anlage of the mesoderm and chorda dorsalis as noted in the guinea pig, a form especially adapted for the investigation of these problems; as may be learned from the studies of Carius, Liederkiihn, Keibel, Graf Spee and others, documenting these observations by a series of figures, showing successive stages of development, taken from cross-cut and sagittal series, and to dispense verjlargely with a consideration of the enticing problems of blastulation and gastrulation as concerns the mammalian ovum, problems and questions which have influenced very greatly the interpretations given by certain in-\"estigators to the actual observations as recorded by them. Only a small portion of the hterature reviewed, and more especially that relating to mammalia, shall here receive notice, and only as the successive stages discussed by me are given special consideration.

Material And Method

The embryological material on which this investigation is based consists of many uninterrupted .series, cut in the cross and in the sagittal plane, of develojimental stages of the guinea pig, ranging from about the 10th daj- to the 15th day of development. The material is all of it 'tmied' ; the ages given extending from tune of observed insemination to the time of killing. For fixation I have used almost wholly Carnoy's fluid. After fixation and embedding in paraffine, the .sections were cut either by means of the ^linot rotary microtome or on a sliding microtome with the aid of the water-on-the-knife method. The sections of the great majority of the series have a thickness of either 5 yu or of 7 m; some few a tliickness of 10 n. After sectioning, the series were fixed to .slides bj^ means of the wateralbumen method and stained on the slide by means of hemalum antl Congo-red. Everj' embrj'ologist of experience knows that socalled 'timed' embr3ologic material of mammalia does not insure succession of stages; however, I believe all will agree that a nmch more complete series of stages is assured by this method, than when a chance collection is made. My own series though fairly complete lacks preparations covering as completely as might be desired certain stages of de\el()pmpnt, while other critical stages are covered by an abundance of material. The figures here presented were all drawn at relatively high magnification, with the aid of the camera hicida, and greatly reduced in reproduction. It has seemed to me desirable to present, so far as the size of the preparation permits, for each stage, figures showing cross and sagittal sections of the entire germ disc. A comparison of successive stages is thus greatly facilitated, and it is hoped extensive description obviated. Certain of the germ discs here considered ha^'e been reconstructed by Doctor Worcester, JNIiss Helen L. B. Gage and myself for another study now in progress. These reconstructions have been of great aid in determining respecti^'e stages and in determining the relations and relative size of the structures primarily mider consideration.

TWO LAYERED GERM DISC OF GUIXEA PIG AXD AXLAGE OF THE MESODERM

As is well known, the guinea pig belongs to that type of rodents presenting an inversion of germ layers. The phenomenon of .segmentation and implantation of the ovum of the guinea pig have been carefully studied by Graf Spec; the question of the inversion of the germ layers, as concerns the guinea pig, bj- Selenka. From Selenka's account, A^liich concerns us here most particularly, it is learned that the early stages of the blastocyst formation are not unlike similar stages as described bj' me for the albino rat. It is further learned that for the guinea pig, after the formation of a blastocyst with ectodermal node, visceral layer of entoderm, parietal or transitory ectoderm and ectoplacental cone, a stage corresponding in many respects to a 6 day, 16 hour stage of the albino rat (Huber, fig. 2-4), the further steps in the inversion differ somewhat from that observed in the albino rat. In the latter the egg cj'linder elongates through growth of the extra-embryonic ectoderm, resulting in a solid egg cyhnder in which a proamniotic cavity develops secondarily; while in the guinea pig the ectodermal node separates early from its close relation to the base of the ectoplacental cone and there is developed an interamniotic space separating tragerectoderm and ectodermal node, and bounded on the sides by a layer of visceral entoderm. The guinea pig egg cylinder thus elongates rajiidly. It encloses in its free end, which is the antiniesometrial end, a solitl nodule of cells, which is here known as the ectodermal node, surrounded almost completely by visceral entoderm, which layer extends to the base of the trager, enclosing the interamniotic cavity. Such as are not familiar with the egg cylinder of the guinea pig of this stage of development I would refer to figure 13, plate XII, of Selenka's studies, copied as figure 590 by O. Hertwig. In the series of figures given by me (fig. 1, A to E) covering the ectodermal node and vesicle stages, only the antimesometrial end of the egg cylinder is figlU'cd. The relations of the ])ortion of the egg cylinder here figured (o Ihc enl ire egg cylinder of the respective stage, may I'eadily be ascertained by comparing this series of figures Avith those gi\-en by Sclenka, to Avhich reference has been made.

Fig. 1 A lo E. A, 10 days, IS hours stage of egg cylinder of the guinea pig with ectodermal node showing the very beginning of the amniotic cavity; B, 10 days, 18 hours stage, with ectodermal vesicle with small amniotic cavity; C, 11 days, 18 hours stage, with ectodermal vesicle and amniotic cavity; D, 11 days, 18 hours stage, with differentiation of wall of ectodermal vesicle into primary embryonic ectoderm and amniotic ectoderm; E, 10 days, 18 hours stage, final bilammelar stage. X 200. enl., entoderm; cin.ccl., embryonic ectoderm; am.c, amiiidf ic (ivily: inn. ((., amniotic ectoilerni.

In figure 1. A to E, are presented a series of developmental stages of the guinea pig, giving in close sequence successive stages in the development of the ectodermal node and ectodermal vesicle with closed amniotic cavity and with embryonic and amniotic ectoderm differentiated. In A, of figure 1 — 10 day, IS hour stage — the entoderm, ent., is found in a single layer abnost completely surrounding a nodule consisting of radially arranged cells, the ectodermal nodule, presenting the very beginning of a central cavity. Only in one section of this series was this cavity clearly defined. It represents the anlage of a closed amniotic cavity. This ectodermal nodule occupies the antunesometrial end of the entodermal egg cylinder, much as a marble might occup}' the end of the finger of a glove. The space beneath the ectodermal nodule and between the entodermal layer, so far as sketched, in this and in the following four figures of this series, is the interamniotic space, not especially labelled here. Figure 1, B — 10 day, 18 hour stage — and figure 1, C — 11 day, 18 hour stage — follow in close succession of stages, presenting successively a slightly larger amniotic cavity. In figure 1, D — 11 day, 18 hour stage — a slight advance in morphogenesis may be observed. The increase in the size of the amniotic cavity is to be noted, more especially the differentiation in the wall of the ectodermal vesicle. That portion of the ectodermal vesicle which is in apposition with the entoderm, presents an ectoderm composed of tall colunmar cells with nuclei in several strata, and is recognized as the ectoderm of the embryonic disc, em.ect.; while that portion of the wall of the ectodermal vesicle which separates the amniotic from the interamniotic cavity, consists of relatively thick, flattened cells with nuclei in one layer and is recognized as the amniotic ectoderm, am.ect. The embryonic ectoderm has the form of an in\-erted watch crystal, and is throughout in close relation to the visceral entoderm. In figure 1, E, there is presented the 23d of a series of 50 sections, having a thickness of 5 /j, passing through the antimesometrial end of an egg cylinder of the guinea pig of a 10 day, 18 hour stage. This series appears to me to represent cross sections of the embryonic disc, though I am unable to as certain with any degree of certaint.v any definite bilateral symmetry. This stage is readily deduced from the preceding one. The larger amniotic cavity is evident. The embryonic ectoderm forms a thick laj'er, with nuclei arranged in four to five strata, becoming abruptly thinner as the amniotic ectoderm is readied, which consists of a single layer of thick flattened cells. The embryonic ectoderm is throughout in close relation with the laj'er of visceral entoderm. This stage maj'^ be regarded as pre.senting the final stage of the bilammelar condition of the germ disc of the guinea pig, the area forming a cup-or-saucer-shaped structure with concavity toward the ectoderm. There is at this stage no trace of mesoderm, ectoderm and entoderm being throughout in close relation.

As concerns the anlage of the mesoderm in the germ disc of the guinea pig, my own series do not give an answer which is not open to question in that none of the germ discs sectioned by me, covering the stages immediatelj' following the bilammelar stage, present the very beginning of mesoderm differentiation. The several germ discs of mj- series, covering this stage, though ranging over a day in difference of ages, all present a stage of mesoderm development which I can not regard as showing the first appearance of the mesoderm. I am led to believe that the anlage and early spread of the mesoderm in the germ disc of the guinea pig. occupies onh- a very brief period of time and that it would seem necessary to collect a large series of stages, from the end of the 11th to the beginning of the 12th daj^ of development, to chance on the desired prejiarations. In the material of the white rat, covering the period of the anlage of the mesoderm, I was more fortunate, in that a number of my preparations cover this stage very satisfactorily. In figures 31 and 32 (Huber) the anlage of the mesoderm in the albino rat is shown in a stage which is slighth' younger than the j'oungest stage showing mesoderm in my guinea pig series. The question of the anlage of the mesoderm in the albino rat was only incidentally touched upon in that publication and will be discussed more fully in a forthcoming monograph in which the development of the albino rat from the 10th to the 12th dav will be considered. In the albino rat, as I have stated on a former occasion, "The anlage of the mesoderm is from the sagittal portion of the caudal region of the primary embryonic ectoderm, the caudal part of the future primitive streak." This statement, in so far as my own series enable me to reach conclusions, is equally applicable to the germ disc of the guinea pig. In figure 2, there is pre ent

Fig. 2 Germ disc and amniotic ve.sicle of guinea pig, 12 days and 12 hours after insemination; earh' stage of mesoderm formation; anlage of head process. X 200. eiiL, entoderm; hd.pr., head process, in anlage; pr.str.. primitive streak, in anlage with formation of mesoderm; am.ect., amniotic ectoderm; am.m., amniotic mesoderm.

sented practically the middle section of a series of 58 sections, having 5 ii thickness, and passing appro.ximately through the sagittal plane of a germ disc and amniotic vesicle of a guinea pig of 12 day, 12 hours. Another germ disc, of 11 day and 18 hours, cut in the sagittal plane, though slightly obliquely - to the mid axis shows essentially the same stage of development, and stiU another, having an age of 12 days and 7 hours, is in a stag of development which is between that shown in stages D and E, of figure 1, and is distinctly younger than E, of figure 1, (10 days, 18 hours). The genu disc and amniotic vesicle shown in figure 2, is slightly compressed from right to left, as shown in this figure, due to a shght folding of the wall of the interamniotic cavity; hoAvever, this, so far as I am able to ascertain, has in no way influenced the relation of its parts, but gives this vesicle a slightly more elongated form than is normal, judging from the appearances presented by several other vesicles or germ discs of essentially the same stage, included in my series. From a study of figure 2, it may be observed that the outer layer of visceral entoderm forms a continuous layer, consisting of a single layer of short cuboidal or slightly flattened cells, distinctly separated as an uninteiTupted antl continuous layer over the entire extent of the primary embryonic ectoderm and continues into the entodermal layer forming the wall of the interamniotic cavity. Very few mitotic figures are observed in the entodermal layer; one is shown to the left in this figure. The primary embryonic ectoderm is relatively thinner than in the preceding stage described (E, fig. 1), showing two or three strata of nuclei, reduced to a single stratum of nuclei at its transition to the amniotic ectoderm, which latter extends as a single layer of flattened cells over the inner face of the amnion. Especial attention is drawn to the embryonic ectoderm of the future caudal region of this germ disc, the future primitive streak region, pr.str., to the left of this figure, ^'ery active mitosis is observed in this region and it will be noted that the sharp contour of the outer surface of the ectoderm is here lost. A migration of ectodermal cells is here noted, evidenced by the arrangement of the nuclei. The migrating cells constitute the primary mesodermal cells. As clearly seen in this section through the mid sagittal plane, certain of the cells derived from the ectoderm wander cephalad betwcM'n the primary embryonic ectoderm and viscei'al entoderm, and are tlislinctly and easily separable, from both ectoderm and entoderm. This group or i)rocess of cells, deri\'ed from the ectoderm, is regarded as the anlage of the head process. If the .series of .sections is traced in both directions from the mid sagittal section drawn in figure 2, it will be noted that the primary mesodermal cells liave spread out on both sides of the mid axis to a little o\'er half the circumference of this vesicle. The future head region and to the extent of about half of the spread of the primary embryonic ectoderm, is at this stage still free from the invasion of the mesodermal cells. The mesoderm of the germ disc of the guinea pig, as this series seems to indicate, though a slightly younger stage would perhaps present more conclusive evidence, has its anlage in the sagittal portion of the primary embryonic ectoderm and is clearly a deri^•ati^•e of the primary embryonic ectoderm of this region. The rapid spread of the mesodeiTn over the interamniotic cavity face of the amniotic ectoderm, is clearly shown in these preparations. In this vesicle the entire amnion consists of two layers of cells, one amniotic ectoderm, the other mesoderm, both in single laj'er. That the spread of the mesoderm o^'er the amniotic ectoderm is from the caudal region of the germ disc is perhaps evidenced by the fact that the cephalic end of the germ disc is as yet free from mesoderm, see to the right of figure 2. The mesoderm extends also along the inner face of the entoderm bounding the interamniotic cavity, to approximately half the lengtli of this ca\'ity. There is no indication that the entoderm bounding the interamniotic space contributes to the formation of the mesoderm. At this stage, the mesodermal cells of the interamniotic space are in a single layer.

On comparison of my own account of the anlage of the germ disc of the guinea pig with that given by Selenka. it will be observed that the two accounts differ very materialh-. Selenka's account of the anlage of the primitive groove reads as follows :

Was zunjichst die Primitivrinne selbst anbelangt, so tritt dieselbe aus als napfartige, randstandige Aussackung der Ektodennblase; sie wiichst sodann zu eineiii langpn uiid l)rciten abgeplatteten Blindsacke aus, welcher sich an der Wand des Entodennniantels hinabzieht. Sehr bald verkiirzt .sich dieser BLindsack, dessen Lumen der Primitivrinne der iibrigen Amnioten entspricht, imi am 13 Tage, also etwa zwei Tage nach seiner Entstehung, sich wieder zu ciner napfformigen Grube zu verkiirzen und bald daraiif ganzlich ziiverstreichen

Xoch ehe die bUndsackfonnige ■"Primitivrinne" ihre maximale Grosse erreicht hat, beginnt die Bildung des ^lesoderms. Hirer ganzen Liingo iiach treteii aus dcm deni Ento(it'rmniantol zuniichst gelegenen Thcile ihrer Waiuluiiii verciiizclte Mcsotlennzellen aus, von dencn etliche, in nieincn Priipaiaten mit AusliiufcM-n vcrsehene, in der Richtung nach der Basis des Keinicyliiiders zu sich fortschieben, wahrend vereinzelte andere rechts und links an der Innenseite des Entoderms fortwandern, wie ich aus Quer-und Langsschnittcn mit gcnligender Sicherheit erschliesse.

It is possible that I have missed this transitory outpocketing of the amniotic ca\-ity which gives rise to the primitive groove and the primary mesoderm. However, in the stage described in figure 2, no distinct primiti\'e groove is as yet recognizable, the primitive groove developing at a much later stage. The region of the primitive streak I have recognized in the stage described. It is possible that Selenka was led astraj' by reason of hmited material, and has interpreted an artefact, due to folding of the vesicle, as a structure of consequence. Selenka's figures are difficult to judge critically in that they all appear to be more or less diagrammatic. Figure 20, plate XIII, for instance, may represent a stage which is comparable to that given in my own figure 2, however, in Selenka's figure there is no indication of the participation of the ectoderm of the caudal region in mesoderm formation; no anlage of head process and the cephalic end (?) of the embryonic disc is well invaded by mesoderm. This figure of Selenka's suggests that he has drawn a frontal section of this stage as a sagittal section, viewed in this light, it becomes intelligible. Neither Lieberkiihn nor Keibel consider especially stages of the development of the mesoderm in the guinea pig of as early a stage as shown in figure 2.

A study of the literature, comprising both original sources and tlie more recent comprehensive reviews, reveals the fact that the majority of the more recent observers are agreed, so far as concerns mammalia, in regarding the mesoderm as a derivative of the embryonic ectoderm. O. Hertwig after discussing this question \-ery fully in liis account of the germ layers, expresses hiins(>lf as follows;

Hiusichtlich des Ursprunges des mittleren Keimlilattes bei den Siiugetieicn stinimciis jetzt wohl, von einzelnen Ausnahmen abgesehen, alle Heoliachter der Darstellung bei, welelie zuerst Ivolliker gegeben hat. Danach ist die Bildungsstatte des mittlereii Keimblattes, wie bei den ^'ogelu. einzig uiid allein iler Hcnsen'sfhe Knoten, der Primitivstreifen iind der Caudahvulst, also der Bezirk. in dessen Bereich ein Zusanimenhang: mit dem ausseren Keinililatt stattfinded und, wie leicht festziistellen ist, sich avicli zahlreiche Teilungsfiguren nacliweisen lassen, welclie ein Riickschluss auf eine sehr lebhafte Zellvermehrung an diesem Orte zulassen.

INIy o^'n \-iews concerning this question are expressed in one of the summaries found in Keibel's article on the development of the pig. This reads as follows and summarizes my own observations on the origin of the mesoderm in the guinea pig:

"Eine andere Quelle des Alesoderms als der Primitivstreifen liess sich beim Schweine nicht nachweisen; von einem peripheren Mesoblastkeim konnten trotz genauer Xachforschung k ine Spuren entdeckt werden."

"1. am Schildrande, 2. am Primitivstreifen, 3. hochst wahrscheinlich im mittleren Schildbczirk zerstreut."

The section here figured (B, fig. 3), seems to confirm this conclusion. We differ in the interpretation of the appearances present in our respective sections. The ectoderm and entoderm of this figure are as described in the former figure. Attention is callcil to the two mitotic figures founil in the entoderm; one immediately under the cells of the head process. Mitotic figures in the cntodermal cells are rare. There is no evidence that they contribute to mesoderm formation. C (fig. 3) reproduces a drawing of the 39th section of this series. In the axial region of the embryonic area there may be obser\-ed a spindle shaped group of cells constituting a well developed head process. This group of cells is still distinctly separated from the ectoderm by an unbroken membrana prima, or basement membrane, and is only in contiguity with the entoderm of this region and is as yet not in distinct continuity- with the lateral wings of the mesoderm, although these now encroach on the more central portion of the embryonic area. The cells of the head process present as yet no definite grouping and mitotic figures amongst them are not infrequently met with. In the fourth section further caudalward the cells of the head process become continuous with the ectoderm in the mid sagittal plane, as may be observed on a study of D (fig. 3), which reproduces the 49th section of this series and may be regarded as passing through the center of Hensen's node or the primitive node region. In the mid axial plane region of this area the ectoderm presents unusual growth activity as evidenced b}^ the number of the mitotic figures. The membrana prima or basement membrane is in this region absent, the cells of the head process being in direct continuity with the cells of the ectoderm. The direction of the long axis of the nuclei of this region indicates an outwandering of the ectodermal cells into the head process. The deri\-ation of the cells of the head process from the ectodermal cells of the cephalic portion of the primitive streak region, the region known as Hensen's node or primitive node is thus evidenced. It will be noted that there is here no indication of an infolding of the ectoderm to form the head process, but evidence of cell migration from the under surface of the ectoderm. The cells of the head process are in this region continuous with the mesodermal cells, this continuity is attained in the 43d section of this series. A few sections more caudal than that shown in D, of this figure, a shallow primitive groove becomes evident, which extends to near the caudal border of this area, .llong its entire length the mesoderm and the ectodern are in continuity, the membrana prima becoming evident a little to each side of the primitive groove. Active participation of the ectoderm of the primitive streak region in mesoderm formation is to be noted.

Fig. 4 The 40th section of a series of 87 sagittal sections of 7 m thickness of an embryonic disc of the guinea pig removed 13 days and 1 hour after insemination. X 100. Cephalic end of embryonic shield directed toward the right. The crosses placed beneath the figure indicate the appro.ximate level of the sections drawn for A to D of figure 3. /«-..s(r., primitive streak region ; pr.n., primitive node; hd.pr.. head process.

^"oln Henschen'schen Knoten aus wiichst nun cranialwiirts der Kopffortsatz. Dcr Kopffortsatz abcr liegt hicr zunilchst vollkomincn frei zwischen Ectoblast und I']ntol)last, wic dcnu iu dieseni Stacliiiin tiberhaupt an keiner Stelle des ^Icerschweinchonoies cin Zusaininenhaug von Mesoblast und Entoblast anni'hmbar erscheint. Die Bilder sprechen hier so deutlich, dass man jeden Gedanken daran sofort von sich wcisen kann Der Kopffortsatz ist aussehliessllch vom Mesoblast gebildet. und obwohl nianche Forschen angeben, dass derselbe mit dcni Entoblast innig verlothct sei und an dieser Stelle der Entoblast wirklich inosoblastischc Zellen Inldet, so konnte ich mich doeh nicht iiberzeugen, dass die platten Entolilastzellen die passive Kolle einer Bekleidung des mesoblastischen Kopffortsatzes aufgaben, urn active an seineni Wachsthum sich zu betheiligen.

Keibel states here very correcth' the origin and the relations of the head process, but speaks of it as developed from the mesoderm. I would consider the head process as also the mesoderm as a direct derivative of the ectoderm, a view which ^\ill receive further discussion in subsequent pages.

The stage of a free head process is followed by one in ^\hich the entoderm comes in very close relations with the under or ventral surface of this process and the under surface of the cell mass constituting the primiti\'e node region. An actual fusion of the head process and the mesoderm of the primitive node region with the entoderm, in the sense that the caudal end of the head process and the mesoderm are fused with the ectoderm of this region, does not obtain; the entoderm extending as a continuous membrane, composed of very much flattened cells, along the axial portion of the embryonic area, readily distinguished from the overlying cells in all sections passing through this region, whether cut in the cross or sagittal planes. At this stage, the cells of the caudal end of the head process present an important rearrangement. Those dorsally placed assume a more regular arrangement and an epithelioid character and a narrow space is differentiated beneath them; the caudal end of the head process assuming the form of a compressed coknnn of cells, its cells presenting radial arrangement about a narrow central lumen. This differentiation leads to the formation of a structure long known as the chordal canal, which constitutes an important phase in the anlage and morphogenesis of the chorda dorsahs. In figure 6, A to D, there are reproduced a series of drawings of sections of an embryonic area of guinea pig, re

Fig. 6 A to D, from cross sections of an embryonic shield of ttie guinea nis removed 13 days and 12 hours after insemination; showing early stages of chordal T,t TolT embraces 160 sections having 7 m thickness. X -OO- A, 3oth section, through head process, B, 53rd section, through chordal canal, L, 84th section, through region of the primitive node, D, 106th section through primitive streak and primitive groove, hd.pr., head process; ch.c chordal canal; pr.,,., primitive node; pr.str.gr., region of primitive streak and primitive groove.

nio\'ed 13 days and IH hours after insemination, showing early stages in the development and differentiation of the chordal canal. This series, cut cross-wise, embraces 160 sections of 7 ^ thickness, extending from anniion attachment of the cephalic border to amnion attachment at the caudal border. This embrj'onic area presents a very well de\-eloped ])rimiti\'e streak and groove, extending a little over half the length of the embrj^onic area as also a well developed primitive node. The mesoderm is spread over the entire extent of the embryonic area except in the region of the chordal canal and the head process and the oral plate region. In the ectoderm the medullary plate has obtained outline in approximately the cephalic half of the area. On tracing this series from the cephalic amnion attachment, it will be observed that a definite thickening of the ectoderm in the more central portion of the sections appears in the 16th section and the first trace of the cephalic end of the head process are to be noted in the 22d section. In A (fig. 6) is reproduced a drawing of the 35th section of this series. In the region through which this section passes, the head process consists of two la.yers of compactly arranged cells, occupying the axial region of the embryonic area, and situated between ectoderm and entoderm, readily separable from each of these layers. The mesoderm of this region apjjroaches the borders of this plate of process cells. The entoderm extends as a continuous layer, consisting of very flat and thin cells, ventral to this plate of head process cells. In the ectoderm the medullary plate is recognized as consisting of a thickened layer of ectodermal cells, with nuclei in three strata, and bounded on its \'eiitral surface by a distinct limiting membrane. As this series is traced caudalward the first traces of a chordal canal are to be observed in the 46th section, the head process being in this section somewhat thicker than that shown in A, of this figure, though as yet presenting the form of a flat, spindle shaped structm'e. In B (fig. 6) is reproduced a di'awing of the 53d section of this series. In this section the cells of the head process present a distineth' radial arrangement about a mall centrally placed lumen, tlie structure constituting a chordal canal, not as yet distinctly separated from the bordering mesoderm, which extends as a well developed layer to the borders of the embryonic area. This section — as other sections — ^^vas drawn by aid of camera lucida at a magnification of 600; reduced in reproduction. This magnification was sufficient to enable determining clearly the relations of the structures sketched; the figure ma}' thus serve to show that the chordal canal is at this stage distinctly separable from both ectoderm and entoderm. A distinct chordal canal is traced through 24 sections of this series. In certain of these sections the lumen appears double, again fusing to a single lumen; a phenomenon previously observed. In the 76th section, the distinct limiting membrane separating chordal canal and ectoderm disappears and the wall of the chordal canal which is directed toward the ectoderm fuses with the ectoderm the lumen of the canal, however, is still evident. The region of the Avell dcA'eloped primitive node found in this series is shown in C (fig. 6), reproducing a drawing of the 84th section. In this primitive node region the caudal end of the chordal canal and the mesoderm are fused with the ectoderm, as this drawing clearly portrays; the mesoderm extending as a massi\'e layer to the limits of the embrj'onic area. In this series it is impossible to trace the lumen of the chordal canal to the surface of the ectoderm ; neither is there observed a distinct infolding of the ectoderm of this region. A slight protrusion of cells in the center of the node region is noted, though this is not as pronounced as that figured by Carius for the rabbit. In D (fig. 6) is reproduced a drawing of the 106th section of this series, inserted to show a typical section of the primitive streak and groove region as presented in this series. The relations of the mesoderm to the ectoderm of the primitive streak region is here clearly shown, the direction of the long axis of the nuclei of ectodermal cells of this region evidencing a proliferation and migration of ectodermal cells to the mesoderm.

The chordal canal is a structure well recognized in embryologic literature and has been described for a number of mammals and other amniotes. Almost immediately after its aniage, its ventral surface comes into verv intimate relation with the under lying entoderm, though in all of the series of section of embryonic shields of the guinea pig, showing chorda! canal, the entoderm extends as an uninterrupted layer of flattened cells along the ventral — entodermal — surface of the chordal canal and head process. Soon after the anlage of the chordal canal, there may be noted in its caudal portion a dehiscence along its ventral wall, including underlying entoderm, so that the chordal canal assumes the form of an inverted trough, opening into the subentodermal space. The caudal end of the chordal canal, in certain of the mammalian embryonic shields carefully studied, extends to the dorsal surface of the ectoderm in the region of the primitive node, its lumen thus extending to the amniotic cavitj', forming the neurenteric canal. The metamorphosis of the head process into chordal canal and the opening of this into the entoderm is described as follows by O. Hertwig:

Der Kopfifortsatz bekommt in seincm Inncrn pine Hohlung, die meist als C'hordakanal, zuweilen auch als Canalis neurentericus bezeichnet wird; seine untcro Wand, nach dem sie mit dem innern Keimblatt eine Verschmclziing eingegaiigen ist, reisst langs dieser Naht ein; dadurch wird jetzt der ('hordakanal seiner Lange nach in den unter dem iniiorn Koiniblatt gclegen Raum eroffnet.

As is also noted by O. Hertwig, slight variations in the detail of formation of the chordal canal in mammalia has been observed, to the extent, that two main types are recognized. In the one type the chordal canal is relatively short, opening almost immediately after its anlage into the entoderm as observed in the rabbit, sheep and pig. In the other type the chordal canal forms a much more definite structure, extending for a relatively long distance cephalad, as in the guinea pig and the bat (Vespertilio murinus) and according to the recent account of Grosser. in the human embryo. Particularly in the guinea pig may there be observed a relatively long and well developed chordal canal, known to literature through the studies of Lieberkiihn, Keibel and Graf Spec.

In figure 7, there is presented a drawing of the 74th .section of a series of 150 sections, each of 7 ^ thickness, of the embryonic area of a guinea pig removed from the uterus 13 days and 12 hours after insemination, and cut in the sagittal plane. This series was very fortunateh' cut, the line of sectioning being almost exactly parallel to the mid axis of the embryonic shield. The figure reproduced is drawn from a single section. The caudal end of the section reproduced is readily recognized by means of the prominent allantoic anlage and which in the figure is directed toward the top of the page. For about the upper half of the length of the figure, the section passes through the primitive groove. The region of the primitive node with shallow primitive pit is indicated by figure legend, pr.n. From the caudal end of the embryonic area to the region of the primitive node the ectoderm shows no definite ventral boundary, but is continuous with the mesoderm of the primitive streak region. Cephalad to the primitive node region the ectoderm is bounded on its under surface by a distinct limiting membrane. Beneath the ectoderm of this region, and in close relation to it, there may be observed a long chordal canal, cut nearly through its whole length so as to include its lumen. The extent of the chordal canal is indicated by two crosses placed in the figure just beneath the entoderm. Beneath the chordal canal, the entoderm may in places be observed as a thin cuticular layer, with nuclei here and there evident. In this preparation, the chordal canal opens into the entoderm for a short distance, as is clearly seen in the figure. The chordal canal, in this preparation, does not reach the cephalic limit of the head process, this extending for a short distance cephalad, beyond the region in which a distinct chordal canal lumen can be determined. The anterior limit of the head process is not clearly defined in the series from which figure 7 was drawn. In another embryonic shield of about the same stages of development and taken from the same uterus also cut in the sagittal plane, but not in such favorable direction, the head process can be traced fairly distinctly over a continuous layer of entoderm, to near the region of the future pharyngeal membrane, though the head process cells appear as firmly fused to the entoderm. Figure 8, which is drawn from the same series from which figure 7 was taken, reproduces a portion of the 7()th section and was drawn at a higher magnification and embraces the primitive node region and the caudal end of the cliordal canal. This section, for this region, passes more nearly through the mid plane of the embryonic shield than does section 74, the basis of figure 7. A distinct primitive pit, pr.pt., is to be noticed in the primitive node region. The relation of the caudal end of the chordal canal to the ectoderm of the primiti\'e node region is to be noted; the direction of the long axis of the nuclei of the ectodermal cells evidencing a growth zone for the chordal canal in the ectoderm of this region. The distinct separation of the ectoderm from the definitive chordal canal is to be observed. The relation of the entoderm to the caudal end of the chordal canal and the ectoderm-mesoderm mass of the primitive node region, is clearly shown in this figure ; the entoderm extending as an uninterrupted continuous layer, consisting of flattened cells, beneath nearly the Avhole extent of the region figured. An extension of the lumen of the chordal canal to the surface of the ectoderm is not observed.

In none of my series, whether sectioned in the cross or the sagittal plane have I been able to determine a patent nuerenteric canal. This agrees with the observations of Lieberkiihn, who states, referring to the chordal canal:

"Auch ist es mir nie gelungen eine ausmiindung desselben an der Oberflache des Ectoblast wahrzunehmen,"

Graf -Spee in discussing this point describes a neurenteric cord — ' Neurenterischen Strang' — with cell nuclei radialh^ arranged, but having no lumen, and extending obliquely from ectoderm to entoderm, however, not distinctly separated from the cells of the primitive node region. This I have observed in a number of my series, cut in cross sections.

Grosser's account of a human embryo with chordal canal, is of interest in this connection. In the human embrj-o in question, with probable age of 18 days, the embryonic shield measured 670 M, with well developed chordal canal, having a length of 190 n. The chordal canal was found to open into the entoderm with two openings and on to the ectoderm by means of one small opening. As has been known for some time, the human embryonic shield of the pertinent stage, presents a patent neurenteric canal, well known through Graf Spee's description and figures of embryo G.le., and other more recentl.v described embryos, inchiding this of Grosser. So far as I am able to judge from a study of figures, the chordal canal of the human embryo described by Grosser presents many points of similarity to that found in the embryonic shield of the guinea pig presented in figure 7, the ]ii-imitive streak region, however, being distinctly longer in the guinea jiig. (irosser has called attention to the resemblance of the chordal canal in human and guinea pig embryos, stating:

"Am niichsten kommen noch die Bilder, die Lieberklihn \'om Meerschweinchen giebt."

Figure 7, in its main features is comparable with the well known figures given by Van Beneden, giving mid sagittal sections of embryonic shields . of Vespertilio murinus. In the embryonic sliield of this bat there is present a patent and very distinct neurenteric canal. Van Beneden described two kinds of openings of the chordal canal into the entoderm. 1 . An anterior opening consisting of a broad transverse slit. 2. Several smaller openings which soon fuse to form a single longitudinally directed slit. I am in accord with Keibel, when he states, referring to the two kinds of openings of the chordal canal into entoderm:

"Bei Kaninchen erscheint mir dieselbe durchaus nicht zutreffend, und wie schon gesagt, finde ich sie auch flir Meerschweinchen nicht bestatigt."

Lieberklihn was the first to call attention to the fact that the choi'dal canal does not open ventrally, primarily, by means of a single longitudinally directed slit, but usually by means of a series of smaller openings. This is clearly seen in his figure .'50 of jilate 20, giving a ventral surface view of an embryonic shield, also his figures 25 to 29 of the same plate. This fact is also clearly shown in the series of ten drawings grouped under figiu'e 0. These drawings ai'c fi-om representative sections of an eiiii)i\\()nic shield of a guinea jiig removed from the uterus Hi days and 12 liours after insemination, and taken from the same uterus from wliich the embryonic shield, a section of which was reproduced in figure 7 was taken, though that shield is of slightly younger stage of (kn-elopment. Tlie series of sections of the

Fig. 9 A to J. Drawings of representative cross section of an ambryonic shield of the guinea pig, removed 13 days and 1 hour after insemination. The series embraces 188 sections of 7 m thickness. X 200. A, .33rd section, through chordal plate with entoderm extending beneath; B, 43rd section, with arched chordal plate, entoderm extending under borders of chordal plate; C, 53rd section, flattened chordal plate incorporated in entoderm; D, 66th section, with flattened chordal plate with entoderm extending beneath; F, 79th section, arched chordal plate with entoderm extending beneath; G, 107th section, arched chordal plate, entoderm extending under the borders of chordal jjlate; H, 114th section, chordal canal reaches into ectoderm; I, 120th section, iirimitivo node region; J, looth .section, primitive streak region.

embryonic shi(4d from which figure 9 is drawn, numbers 188 cross sections having a thickness of 7 /z. Each of the several drawings of this figure inchides the axial portion of the embr\'onic shield as seen in cross section, with the ectoderm of the medullary plate, the primitive node and the primitive streak directed upward and with mesoderm and entoderm in normal relations. The chordal canal or metamorphosed chordal canal structures are to be found in the middle and under side of each drawing, either as a closed chordal canal or showing various degrees of ventral dehiscence and socalled incorporation into the entoderm. A (fig. 9) is of a drawing of the 33d section, counting from the cephalad border of the embryonic shield. This section falls to the region slightly caudal to the region of the future pharyngeal, membrane, a region in which it is believed a chordal canal with ])atent lumen does not develop, instead, the cells of the head process differentiate to form a chordal plate composed of short columnar cells, as indicated in the draAving. It will be observed that the entoderm extends beneath this chordal i)late, in the drawing from right to left, for nearly the entire extent of the chordal plate. B of this series reproduces a drawing of the 43d section. In this region the chordal canal has oi)ened ventrally, presenting in cross section the form of an inverted trough. It is further to be noted that the dehiscence extends through the entoderm, but that the edges of the entoderm extend beneath the borders of the arched chordal plate. C of this series is a drawing of the 53d section. The borders of the chordal plate are in this region spread out so as to bring the plate into a plane, seemingly incorporated between the edges of the cleft entoderm. However, by reason of the staining reaction of the protoplasm of the cells of the chordal plate and their short columnar shape, they are readily differentiated from the entodermal cells. D, of this series is of a drawing of the 66th section. In this region the chordal canal through ventral dehiscence and spreading has assumed the form of a jilate, howexi'r the splitting did not in\-olve the entoderm, this extending as a cuticular layer beneath the plate of chordal cells. E, of this series is of a drawing of th(> Tfith section. In this region there may be obsei-\'ed a ^'ery distinet chordal canal, with slit like lumen, the entoderm extending as an uninterrupted layer of flattened cells beneath the chordal canal. In F, of this series there is reproduced a drawing of the 79th section, and is of a region in which the entoderm extends as a cuticular layer beneath an arched chordal plate. G, of the series, is of a drawing of the 107th section. The region from which this section was taken approaches the primitive node region. The ventrally opened chordal canal presents in cross section the form of an arch the lips of the split entoderm extending under the borders of the arched chordal plate. Throughout this portion of this series of drawings, A to G, the chordal canal or plate is distinctly separated from the ectoderm, this presenting a definite limiting membrane on its under or ventral side. In H, of this series, reproducing a drawing of the 114th section, the chordal canal reaches into the ectoderm of the primitive node region and is no longer distincth^ separated from the ectoderm, although the fusion with the ectoderm is not as yet as complete as shown in the following drawing. Ventrally the chordal canal opens into the entoderm through a narrow slit. I, of this series reproduces a drawing of the 120th section, which passes through the primitive node region. In this region the caudal extension of the chordal canal is distinctly fused with the ectoderm, the direction of the long axis of the nuclei and the active mitosis indicating an ectodermal growth zone for the chordal canal. J (fig. 9) reproduces a drawing of the 15oth section, which passes through the anterior portion of the primitive streak and groove, and is added to show the active participation of the ectoderm of the primitive streak region in the formation of mesoderm. Throughout the primiti\'e node the entoderm extends as an uninterrupted layer of cells.

This series of drawings may ser\-e to illustrate how difficult it would be to portray adequately by means of a single illustration the dehiscence of the ventral wall of the chordal canal and its incorporation in the entoderm of the axial portion of the embryonic shield. A definite incorporation of the chordal plate into the entoderm, it would appear to me, does not obtain, and as concerns the guinea pig, there is at hand no evidence that the entoderm in an.y way contributes to the histogenesis of the chordal canal or chordal plate. In corroboration of this conclusion two further series of drawings are here added: they are of cross sections of slightly older stages than that discussed under figure 9.

In figure 10, drawings A to F, there are presented a series of six drawings of cross sections of an embryonic shield of the guinea pig removed from the utersu 14 daj's and 11 hours after insemination. This series included 188 cross sections of 7 ^ thickness. Measured as to age, reckoned from time of insemination to time of killing, this embryonic shield is nearly a day older than that discussed under figure 9. In actuality it presents only a slight advance in development ; both as to general development and specifically as concerns chordal structures and their relations. Drawing A (fig. 10) is of the 30th section counting from the cephalic border of the embryonic shield, and is from the region slightly caudal to the future pharyngeal membranes. A chordal plate is here ()bser^•ed with the entoderm extending as an uninterrupted layer ventral to it. B, of this series is of a drawing of the 44th section. Here also the entoderm extends ventral to the chordal plate. C\ of this series is of a drawing of the 57th section. In this region there is observed a slit in the entodermal layer, the edges of the split entoderm extending under the borders of the chordal plate. D, of this series reproduces a drawing of the 86th section. In this region the chordal plate is relati\'eh' ^^'ide, and as seen in cross section, of the form of a broad arch, with the edges of the separated entoderm extending under the borders of the chordal plate. E, of this series reproduces a drawing of the 107th section, which approaches the region of the primitive node. The ventrally open chordal canal presents in cross section the form of an arch, beneath which extends the entoderm as a thin but continuous layer. In the several drawings of this series, A to E, thus far considered, the ectoderm is separated from the chordal plate by a distinct, basal limiting membrane. F, of this series is of a drawing of the 119th •section, wliicli passes through the jiriniitive node region, in which region the caudal end of the chordal canal is continuous with the ectoderm with total disappearance of the basal limiting membrane. The active mitosis of the ectoderm and deeper cells indicate a region of growth activity. Ventrally the mesodern is in continuity with the cells of the primitive node. The entoderm passes uninterruptedly ventral to this area. In no por

Kig. 10 A to F. Drawings o' representative cross sections of iuit)ryonic shield of the guinea pig, removed 14 days and 11 hours after insemination. The series embraces 188 sections shavingT^ thickness, and shows relations of the chordal plate. X 200. A, 30th section, with flattened chordal plate with entoderm extending beneath; B. 44th .section, with flattened chordal plate with entoderm extending beneath: C, 57th section, chordal plate incorporated in entoderm; D, 86th section, wide arched chordal plate incorporated in entoderm; E, 107th section distinctly arched chordal plate with entoderm extending beneath; F, 119th section, primitive node region.

tion of this series, from region of the primiti\e node to cephahc end of head process was there observed a closed chordal canal, though in several regions the entoderm extends beneath the chordal plate, which results from dehiscence of the ventral wall of the chordal canal. In the regions in which the entoderm presents a cleft under the chordal plate, the edges of the cleft entoderm extend slightly under the borders of the chordal plate.

In figure 11, A to F, are reproduced a series of six drawings of respective cross sections of an embryonic shield of a guinea pig removed from the uterus 14 days and 7 hours after insemination. This embryonic shield was cut in cross sections having 5 n thickness; 327 sections fall to the embryonic shield. As measured by age this embryonic shield is slightly younger than that discussed under figure 10; as judged by stage of development, it is slightl,y older, as indicated in general by the presence of a well developed medullary groove in the cephalic portion of the embryonic shield. In A (fig. 11) is reproduced a drawing of the 42nd section, counting from the front part of the embryonic shield. This section passes just caudal to the forming foregut, so that the entoderm is cut slightly tangential, this accounting for its apparent thickness as seen in the figure. In this region the chordal plate is relatively wide, with the entoderm, left side of the figure, extending beneath the chordal plate. In B, of this series is reproduced a drawing of the 67th section. In this region the chordal plate is relati\ely narrow, with the edges of the cleft entoderm extending distinctly under the borders of the chordal plate. In C, of this series is reproduced a drawing of the 123rd section and gives a conventional figure of a flat chordal plate a])parently incorporated into the entoderm, though on closer study it may be observed that the edges of the cleft entoderm extend slightly under the borders of the chordal plate. D, of this series is of a drawing of the 223d section. In this region the chordal plate is again relatively wide, appearing in cross sections slightly arched, and especially on the left side, definitely incorporated in the entoderm; the edge of the entoderm extending under the border of the chordal plate on the right side. In E, of this series there is reproduced a drawing of the 234th section ; this approaching the region of the primitive node. In this sectiiin, as may be observed from the figure, the chordal plate is not completely separated from the ectoderm, but in the middle of the chordal plate, it is continuous with the ectoderm; the rather distinct radial grouping of the nuclei in the region of fusion of the chordal plate and ectoderm indicating the region of the neurenteric cord as described by (iraf Sjiee. In F, of this series there is reproduced a drawing of the 23Sth section, wliich jiasses just cephalad of the anterior border of tlie priiniti\e node, antl i)resents the caudal end of the definitive chonhd canal and its extension into and fusion with the ectoderm of the primitive node

Fig. 11 A to F. Drawings of representative cross sections of an embryonic shield of the guinea pig removed 14 da^-s and 7 hours after insemination. The entire series embraces 327 sections having .5 m thickness ; neural groove in cephalic portion of embryonic shield; as yet no somites; final stage of chordal plate. X 200. X. -12nd section, just caudal to foregut, chordal plate with entoderm extending beneath; B, 67th section, flattened chordal plate with entoderm extending under the borders of the chordal plate; C, 123d section, flattened chordal plate beginning to fuse with the ectoderm; D, 223d section, relativeh" wide and slightly arched chordal plate incorporated into the entoderm; E. 234th section, approaches primitive node region, chordal plate beginning to fuse with ectoderm; F. 2.3Sth section, just cephalad to border of primitive node.

region. The narrow ventral cleft extends through the entoderm, the edges of the cleft entoderm passing beneath the borders of the ventrally open chordal canal. Throughout this series the chordal plate is only in part incorporated in the entoderm. In figure 12, is presented a drawing of amid sagittal section of an embryonic shield of practically the same stage of development as that discussed under figure 1 1 . This series is of an embryonic shield of a guinea pig removed from the uterus 14 days and 12 hours after insemination, and includes 156 sections having 7ju thickness. The figure reproduces a draAving of the 79th section, and is drawn from a single section, the line of sectioning in this series being almost exactly parallel to the mid axis. The caudal end of the section is directed toward the top of the page, as evidenced by the prominent allantoic aniage. A study of the series reveals that the stage of development is that just prior to the formation of the first somite, this being indicated but not completely formed. The primitive streak region extends for a little more than a third of the length of the embryonic shield. The first indication of the pericardial space is to be noted. The chordal plate of this shield extends from the region of the primitive node, pr.n., to approximately the region of the future pharyngeal membrane, and is m close relation to the ectoderm, being separated from it by the distinct basal limiting membrane of the ectoderm. Here and there entodermal cells are to be observed beneath the chordal plate. The chordal canal is still evident for a short distance at the caudal end of the chordal plate, which becomes continuous with the ectoderm of the primitive node region. At this stage the ectoderm and mesoderm are still continuous in the primitive streak region, the entoderm extending beneath this region as an uninterrupted layer. In order to reproduce in one section, reduced to page length, the entire embryonic shield in a mid sagittal section, the reduction necessary obviates a clear presentation of details. It is hoped the figure is sufficiently clear to enable orientation. It may also be stated that cross sections gi\-e clearer pictures of the relations of the chordal i)late at this stage than do sagittal sections. These two series, figures 11 and 12, it may be stated, represent approximately the final stage in chordal plate morphogenesis and its incorporation into the entoderm. This stage is followed by one in ^^■hich the chordal ])late again separates from the entoderm and differentiates to form th(> definiti\'e choi'dal tlorsalis.

O. Hertwig's endeavor to find support for liis ' Celometheorie' in manunalian embryonic discs with vent rally open chordal canal, it would seem to me, is not sustained. Hertwig finds support for his contention in the accounts and figures of Heape — mole, and Van Beneden — rabbit. In his discussion of these figures (figs. 618 and ()19) he states:

"Links und rechts geht das Chordaepithel Kontinuierlich in das parietale Blatt des Mesoblasts liber, das aus mehr abgeblatteten Zellen besteht."

As my own figures may serve to show (figs. 8, 9, and lUj, the mesoderm is not directly continuous with the borders of the chordal plate, from the region just cephalad of the primitive node to its anterior limits.

The se]iaration of the chordal plate from the entoderm has been carefully studied by a number of investigators; first by Lieberkiihn, in the guinea pig, later by Keibel, in the guinea pig and rabbit. Keibel formulates his conclusions as follows:

Die Chorda kann sich aus dem Vcrbande des Entohlasts sovvohl dui'ch einfache Unterwachsung, als (lurch directc Einfaltungsprocesse auschalten. In crsteren Fallo crlialteii wir cine platte Chorda, wie sie Z. B. aus dem Kollikerseheii Handl)uch hckannt genug ist; iin zvveiten hat die Chorda alsl)akl eiiie Gestalt, wclche ihrere definitiven gleich ist oder ihr doch nahe koimnt. In den Fallon, in welchcn die Chorda zunachst cinfach aus dem Entoderm ausgesclialtet wird, erfolgt nachtraglich eine Umordnung der Chordazcllen, wolche einem Einfaltungsvorgang gleich zu setzen ist. In beiden Fallen kann nachtraglich noch ('in ('anal im Inncren der Chorda auftrcten, welchen ich als "secundiiren Cliorda canal" bezeichnen will.

These two methods of chordal plate separation, it seems to me, are exemplified in the figures presented in figure 13. The series forming the basis for this figure are of an embryonic shield removed from the uterus 14 days, 11 hours after insemination, and are from the same uterus from which the embryonic shield described under figure 10, was taken. The series includes 340 sections of 7m thickness. There are present five pairs of .somites with a sixth pair forming. In A (fig. 13) is reproduced a drawing of the 170th section. The line of sectioning is not quite at right angles to the mid axis, as evidenced by the difference in

Fig. 1.3 A to C. Drawings of cross sections of an embrj-onic shield of the guinea pig removed 14 days and 11 hours after insemination. The entire series embraces 342 sections haWng 7 ix thickness. This embryonic shield possesses five pairs of somites with a si.\th pair forming and presents early stages in separation of chordal plate from the entoderm. X 200. A, 170th section, flattened chordal plate found between closed neural tube and entoderm; B, 2.52nd section, to the left border of chordal plate folded ventrally; C, .300th section, primitive streak region, chorda dorsalis in the act of separating from the primitive streak, region.

structure presented in the drawing by the two opposed somites, the one cut through its middle, the other not. The chordal structure appears as a flattened plate, situated between the closed neural tube and the continuous entoderm. It would appear that in this region the borders of the split entoderm had grown toward the midline and fused. In B, of this series is reproduced a drawing of the 252nd section. This section approaches the region of the primitive node. There is present in this region an open neural groove. The chordal plate was fixed in the act of being rolled under, seen clearly only on the left side of the figure. These two figures, it would appear to me, e^'idence the two methods of separation of the chordal plate, from the entoderm — undergrowth of entoderm ventral to the chordal plate and infolding of the borders of the chordal plate. Especial attention has been given to the manner of the caudal extension of the chordal structures, caudal to the primitive node region, and, to the relative and absolute shortening of the primitive streak; by Lieberkiihn in the guinea pig, Bonnet in the sheep and Keibel in the guinea pig and the pig. Exact measurements are presented which show that the primitive streak becomes relatively and absolutely shorter as development progresses. Though I present here no exact measurements, my own observations corroborate this, as may readily be ascertained on study of figures 4, 5, and 7, and on comparing these with figure 12, all of drawings of mid sagittal sections of progressive stages of development. The morphogenesis of the chorda dorsalis in the region caudal to the primitive node, namely in the primitive streak region, it would seem to me is well shown in C (fig. 13) the 300th section of this series. As is well known, in the axial portion of the primitive streak the ectoderm presents no basal limiting membrane. From the time of mesoderm anlage, ectoderm and mesoderm are in this region inseparably fused; the ectoderm here constituting the primary source of the mesoderm. With the stage when the chordal plate begins to separate from the entoderm, the ventral cells of the ectoderm-mesoderm mass in the primitive streak region begins to separate from the lateral mesoderm and from the overlying ectoderm proper, the latter differentiating to form the neural plates, the sides of the neural groove and later neural canal, a definite basal Imiiting membrane separating the ectoderm of the neural plate and canal from the chordal structures developing. This it seems to me is in process of attainment in the region of the section sketched in C ffig. 13) the section passing through the caudal portion oi the primitive node, no longer clearh' defined. As may be obser\-ed on study of this section the chorda dorsalis is only in part differentiated, dorsalty it is still in direct continuity- with the floor of the neural groove. So far as ray observations go, no definite chordal canal is to be observed in the primitive streak region and the term head process seems to be inappropriately applied to this structure in this region. From the region of the primitive node caudahvard, the entoderm of the axial portion of this region at no time presents a ventral cleft, but at all stages in development passes as an uninterrupted laj'er, in close relation to the overh'ing mesoderm, but in no sense fused with it in the way that the ectoderm and mesoderm are fused in the primitive streak region. So far as I have been able to determine entoderm of this region takes no part in the morphogenesis of the chorda dorsalis and the latter can not be said at any time to be incorporated in the entoderm of this region. The two drawings reproduced in figure 14, are from a slightly older stage than that shown in figure 13. Thej' are made from cross sections of an embryonic shield removed 14 days 12 hours after insemination. The series includes 300 sections of 10m thickness. A (fig. 14) reproduces a drawing of the 132nd section. \'entral to the closed neural canal and between this and the continuous layer of entoderm, there may be observed a chordal plate in process of transformation to definite chorda dorsalis; the borders of the chordal plate appear in the act of turning in to form a chordal structure. B, of this series, reproduces a drawing of the 236th section, taken from the region of the anterior part of the primitive streak in which the chorda dorsalis is completely separated from both the ectoderm and entoderm, a completion of the process shown in its inception in C (fig. 13). The mode of the separation of the chorda dorsaUs as here described is not quite the same as that given by Keibel. Fri)m his studies on the embryonic shield of the pig, he is led to the following conclusion, given here in his own words:

Der KopfTortsatz muss :uif Kosten des Priinitivstrcifens gewachscn sein. Dies Wachsthum miissten wir uns so vorstellen, dass immer der vorderste Theile des Primitivstreifens sich in dem Kopffortsatz unibildst, und damit dem entsprechend das vordere Ende des Primitivsti'eifens zin-iickweicht.

Fig. 14 A :uid B. Drawiiiss of cross sections of ;in embryonic shield of the guinea pig removed 14 days, 12 hours after insemination. The entire series embraces 300 sections of 10 n thickness. Chordal i)hite nearly separated from entoderm, to form the chorda dorsalis. X 200. A, 132nd section, arched chordal iilate, in the act of folding in to form chorda dorsalis, situated between neural tube and closed entoderm; B, 23Gth section, chorda dorsalis .separated from ectoderm of neural i)lates and the enttxlerm in the i)riniitive streak region.

It has here been contended tliat the licad pnicess is a derivative of the primitive node and grows cephalad between ectoderm and entoderm and from its anlage is separated from the ectoderm by means of a distinct basal Hmiting membrane. Keibel's conchision seems to me appHcable only to that part of the chorda which develops caudal to the primitive node, in particular to the primitive streak region, the process resulting in an absolute shortening of the primitive streak and in the formation of a chorda dorsalis.

The development and relations of the anterior end of the chorda dorsalis have been the subject of special considerations in several investigations. In the guinea pig, as has previously been stated, the anterior end of the head process can be traced to the region of the future primary pharj^ngeal membrane. This is clearly shown in figure 5, and this question was discussed in connection with this figure. A definite chordal canal, so far as my material enables me to determine, does not develop to the anterior limits of the head process. The cells of the cephalic end of the head process, with nuclei arranged in one or two strata, come in ^■ery close relation with the underl^-ing entoderm, so that at times it becomes difficult or quite impossible to differentiate clearly between cells of the head process and the underlying entoderm. I am led to conclude that the entoderm of this region at no time develops a distinct cleft, admitting of incorporation of head process in the entoderm. These observations are in the main in accord with those of Keibel, with reference to the cephalic end of the chorda anlage; his words read as follows :

.\in schwierigsten liegeii die Verhiiltnisse jedenfalls am A'orderen Ende des Embrj'os. Dort ist das Entoderm schon vor der Einschaltung der Chorda verdiekt und, nachdem die Einschaltung gescheheii ist, lasst sich beim besteii Willen kciiie Circnze mehr zwischeii den eingeschalteten Zellen und deni Entohlast crkennen.

Notwithstanding, Keibel is of the opinion, that the entire chorda dorsalis is developed from cell material derived from the head process. On further development, the cells of the head process, for a tune intimately blended with the underlying entoderm, separate again from the entoderm; the two structures are then readily differentiated. Bonnet in his contributions to the embryologj^ of the sheep contends that the anterior end of the chorda dorsahs is derived directly from the entoderm, the 'chordaentoblast.' This idea is developed and modified in his studies on the embryologj^ of the dog. In this contribution he speaks of an ' Erganzungsplatte des Urdarmstrangs' out of which develops the mesoderm of the anterior part of the head, the chorda of the anterior part of the head and a 'priimandibulares Darmrudiment." In the guinea pig, as also previously determined by Keiiiel, such an 'Erganzungsplatte' can not be differentiated, and I question its existence in other mammalia. In Grosser's preparation of a human embryo with chordal canal it was also impossible to determine definitely the anlage of the cranial end of the head process, his own words, omitting references to plates, read as follows:

"Ganz am cranialen Ende des Kopffortzatzes findet sich eine Region, in der die Abgabe von Material aus dem Entodenn an das ^Mesoderm nich auszuschliessen ist (Protochordal — oder Erganzungsplatte); doch ist die Konsservierung gerade dieser Stelle wenigen giinstig."

It has been the aim in this communication to present in successive stages, illustrated by figures drawn of sagittal and cross sections, the anlage and morphogenesis of the chorda dorsaUs in the guinea pig, a form in which the successive stages of chordal development are relatively easily determined, by reason of size of structure and definition of stages, if suitable material is at hand. It is recognized that a comprehensive discussion of this fundamental jiroblem, even so far as concerns only the amniotes, requires a comparison of results here obtained with observations made on other mammalian forms as also avian and reptilian forms. It is lioped that further study will admit of this. The observations pertaining to the guinea pig, as here briefly recorded, seem to me to warrant the following summary and conclusions: —

SUMMARY AND CONCLUSIONS

1. In the guinea pig, the head process has its anlage in the cranial border of the primitive node, an area of ectodermal proliferation, forming the cranial end of the primitive streak; by accretion of cells and proliferation of its own cells, the head process grows cephalad in the axial portion of the embryonic shield, primarilj- independent of the later wings of the mesoderm, to reach approximately the seat of the future primary pharyngeal membrane. At the caudal end of the head process, the cells of the head process are in direct continuation with the cells of the ectoderm of the primitive node region. Cranial to the primitive node the head process grows between ectoderm and entoderm, independent of each.

2. Soon after the anlage of the head process, its caudal end through rearrangement and growth of cells, acquires a lumen. The head process of this region differentiates to form the chordal canal. The chordal canal at no time in development extends to the cranial limit of the head process. The cranial end of the head process retains the character of a plate of cells, which fuse intimately with the underlying entoderm, so that its delimitation is for a time uncertain.

3. The chordal canal soon after its formation, through dediscence of the ventral wall spreads out to form a chordal plate. With the dehiscence of the ventral wall of the chordal canal and the formation of a chordal plate, a cleft or split develops in the axial portion of the entoderm in the region of the chordal plate so that the lumen of the chordal canal becomes continuous with the cavity enclosed by the entoderm. This splitting of the ventral wall of the chordal canal and the underlying entoderm, in the guinea pig, takes place primarily in several regions, so that a series of discrete openings are formed, "\\'hich fuse to form a longitudinally directed slit. The chordal plate is at no time definite^ incorporated in the entoderm, the edges of the split entoderm, extending at all times to a greater or less degree under the borders of the chordal plate.

4. The churdal plate is then again separated from tlie entoderm to form the definitive chorda dorsaUs, this either by a simple undergrowth of the edges of the cleft entoderm, the edges approximating and fusing, or by undergrowth of the entoderm accompanied l)y a ventral folding of the borders of the chordal plate. Both of the methods of separation of the chordal plate from the entoderm may be observed in different regions of the same embryonic shield.

5. In the primitive streak region the chorda dorsalis differentiates directly finm tlie ventral part of the ectoderm-mesoderm mass of the axial j)art of the primitive streak, by separation from the lateral mesoderm and from the ventral part of the neural plates; this leads to a relative and absolute shortening of the primitive streak. In the region of the primitive streak, the entoderm, in all stages of development, retains its character as an uninterrupted layer.

6. An open neurenteric canal is not developed in the guinea pig; instead a neurenteric cord, not clearly defined, leading from the ectoderm to the entoderm, in the primitive node region.

7. This final conclusion seems warranted : Since the entoderm takes no active part in the histogenesis of the head process, chordal canal, and chordal plate and since the chordal .plate becomes only jiartially and temporarily incorporated in the entoderm; there seems no justification for classing the chorda dorsalis as an entodermal derivative. And since the head process, the anlage of the chordal canal and derived structures, has its anlage in the cranial portion of the primitive node, a region of active ectodermal cell proliferation; and since the chordal canal and plate retain their contiiuiity with the primitive node, which serves as a growth zon(>: there seems justification in regarding head process — chorda! canal, and derived structures, chordal plate and chorda dorsalis — as a derivative of the ectoderm in the sense that the mesoderm is derived from the ectoderm of the primitive streak region of the embryonic shield.

LITERATURE CITED

VON" Be.vedex. Ed. ISSS Untersuchungen iibei' die Bliittei'bildung. den Chordo kanal unci die Gastrulation bei den Siiugetieren. Kaninchen und Ves pertilio murinus. ^'el■handlung. Anat. GesscUseh., Anat. Anz., vol. 3. Box-XET, R. 1884 Beitriige zur Embryologie der Wiederkiiuer, gewonnen am

Sehafei. Arch. f. Anat. u. Phys., Anat. Abtli.

1897 Beitrage zur Embryologie des Hundes. Anat. Hefte, vol. 9.

1901 Beitrage zur Embryologie des Hundes. Anat. Hefte, vol. 16. CiRius, F. ISSS a Ueber die Entwickelung der Chorda und der primitiven

Rachenhaut bei Meerschwoinchen und Kaninchen, Dissertation.

1S8S b Ueber den Kopffort.satz des Kaninchens. Sitzungrbr. d. Ges.

z. Bef. d. Nat.. Marburg. Quoted here from O. Hertwig. Grosser, O. 1913 Ein menschlichen Embryo rait Chordokanal. Anat. Hefte,

vol. 47. He.^pe, W. 1883 The development of the mole. Quart. .Jr. Micro.scop. Sc,

vol. 23. Hertwig. O. 190(5 Die Lehre von den Keimblattern. Handbuch der ver gleichenden und experimentelleii Entwickelungslehre der Wirljcltiere,

vol. 1. Gustav Fischer, .Jena. Huber, G. C-\rl 1915 The development of the Albino rat (Mas norvegicus

albinus). Memoirs of the Wistar Institute, no. .'). Hubrecht, a. a. W. 1890 Studie.s in mamma ian embryologj'. II. The development of the germ layers of Sorex vulgaris. Quart. Jr. INIicro scop. Sc, vol. 31. KoELLiKER, A. 1883 Ueber die Chordahohle und die Bildung der Chorda

beira Kaninchen. Sitzungsbr. d. Ph}'sical. med. Gesellsch., Wurzburg. Keibel, F. 1889 Zur Entwickelungsgeschichte der Chorda bei Siiugern (Meer schweinchen und Kaninchen). Arch. f. Anat. u. Phys., Anat. Abth.

1894 Studien zur Entwickelungsgeschichte des .Schweines (Sus scropa

domesticus). Morphol. Arlieiten, vol. 3.

1900 Die Gastrulation und die Keimblattbildung der Wirbeltiere. Ergebnisse d. Anat. u. Entwickl. vol. 10.

LiEBERKUHN, M. 1882 and 1884 Ueber die Chorda bei Saiigethieren. Arch, f. Anat. u. Phys., Anat. Abth.

R.\BL, C. 1889 Theorie des Mesoderms. Morphol. .Jahrbuch. vol. 15.

1893 Theorie des Mesoderms (Fortsetzung). Morjihol. .Jahrbuch, vol. 19.

Selen'K.\, E. 18S4 Studien iiber Entwickelungsgeschichte der Thiere. Drittes Heft. Die Bliitterumkehrung ira Ei der Xagethiere, Ivreidel, Wiesbaden.

Spee, F. Gr.\f. ISSS Ueber die Entuickclungsvorgange vom Knoten in .Siiugetierkeimscheiben. Anat. Anz., vol. 3.

1896 Neue Beobachtungen tiber sehr friihe Entwickelungsstufen des Menschen Eies. Arch. f. Anat. u. Phys., Anat. Abth.

1901 Die Imjilatation des Meerschweinchoneies in die Uteruswand. Zeitschrift. f. Morph. u. Anthrop., vol. 3.

Strahl, H. ISSS Durehschnitte des Area embryoiuili.s bci Siiugetierembryoneii. Verhand. del' Anat. Gesellsch., Anat. Anz., vol. 3.

Triepbl, H. 191-1 Chorda dorsalis und Keimbliitter. Anat. Hefte, vol. 50.

TsuKAGUCHi, R. 1912 Zur Entwickelungsgeschichte der Ziege (Capra Hircus). Anat. Hefte, vol. 46.

## SOME CONSIDERATIONS REGARDING MICROSCOPICAL TECHNIQUE

C. E. McCLUXG From the Zoological Laboratory of the University of Pennsylvania

It has been said that the discoveiy of a new method maj' do more to advance science than the enunciation of a new principle. If this may, with any truth, be asserted of one method how really significant must be the comprehension of the technical aggregate upon which a science rests! ^Microscopical technique is variousty regarded by biologists. To some it is an end in itseK-^a sufficient field for the exercise of all the powers of the investigator; to others it is a necessary evil to be endured only so far as it makes apparently satisfactory returns for the time spent. An exclusive acceptance of either position is a mistake leading to indifferent results. Technique is a tool, but an indispensable one, and, as j^et, but imperfecth' developed. It needs most careful study and merits all the care and attention we can devote to it. Progress in microscopic anatomy is largely dependent upon the refinement of present methods and the invention of new ones. Each serious student in this field of biology owes it to his chosen science to contribute something that is new or to suggest means for bettering the methods now in use. Rigid attention to all details of procedure is absolute^ required in cytological investigations, and we may rightfully demand this of each worker as a prerec}uisite to the acceptance of his results. So much is the least we may ask — bej'ond this we can reasonably expect contributions to our present technical armamentarium. This expectation will be realized when the fundamental importance of the technical side of our work is appreciated and better means for its development are provided.

' An evening lecture delivered at the Mirine Biological Laboratory, Woods Hole, July 27, 1917.

PROTOPLASMIC CONDITIONS

A consideration of the reaction between living protoplasm and chemical or physical agents must involve both members of the combination. Nothing is more obvious than the specificity of protoplasm, but changes which any particular variety may undergo are much less understood and appreciated. That there should be such a condition of variable reaction is no cause of surprise when the seasonal peculiarities of eggs under the same experimental conditions are recalled. Despite these facts there is little attention paid to the physiological condition of material submitted to the action of fixing fluids and stains, it being too generally assumed that the resulting differences in appearance are occasioned by the technique. Doubtless all experienced investigators can recall instances of inexplicable perversity on the part of apparently well understood materials and processes, resulting in such departures from the expected results as to raise grave doubts concerning the adequacy of our methods. Rarely, however, is the fault ascribed to the material and yet, as I hope to show, even the slightest modification of the protoplasmic element may markedly change the end result.

VALIDITY OF PHENOMENA

The importance of an exact knowledge of cell morphology increases from year to year as the conviction grows that in this structural unit are presented, in the most simple, available terms, the varied biological problems which engage our attention. In view of the fact that we rarely see a cell in its normal living condition the question becomes acutely serious regarding the adequacy of the phenomena we study in prepared material. This is a consideration to which thoughtful microscopists have given careful attention, and from many lines of evidence the conclusion has been reached that, in most respects, the product of our technique is representative of the living cell. It is hardly necessary to indicate the basis of this belief more than cursorily. Perhaps the most weighty evidence of this concordance is the high degree of uniformity in appearance obtained by the most

varied processes. Such variation as appears, in its major aspects, is clearly due to shrinkage, tearing, expansion or other physical changes which can reasonably be accounted for or predicted. Added to this is the close agreement in appearance between such details as are visible in the living cell and the same structures in fixed material. There is nowhere, in the variations under different systems of treatment, any suggestion of indefinite or unrestricted change, but only modifications of limited order involving a common series of elements everywhere recognizable.

SCOPE AND METHODS OF THE PROBLEM

T\Tiile this uniformity exists, and is most encouraging, there is an accompanying variability in details which is often most annoying and puzzhng. ^\Tiere the purpose is to ascertain, down to the hmit of vision, the exact architecture of the cell parts, this uncertainty of appearance may prevent the attainment of a confident judgment regarding some of the most significant cellular conditions. Since our effort should always be to reduce to their lowest limits the unknown variables in our problems the occurrence of these unpredictable changes in our materials is a constant challenge to the conscientious investigator.

So far our only method of attack has been largely through modifications of our empirical methods, but it has seemed possible to add to them some more reasonable means for determining the causes of our variables. Knowing the great interest all biologists must have in these fundamentals of our methods and realizing the insuperable difficulties in the way of the individual worker attacking alone the complexities of the problem, I am givmg the results of a series of investigations upon microscopical technique, extending over a number of years, in the hope of contributing something to our common store of knowledge concerning the most trying, difficult and essential part of our work. In obtaining these results I have had the invaluable help of many of my students, among whom I am particularly indebted to Doctors Sutton, Carothers, Allen, Whiting and Hance. Without the thoughtful, efficient and discriminating help of Aliss Ca

268 C. E. McCLUXG

rothers particularly it would have been impossible for me to have accomplished any large m'easure of the results so far obtained. Even with all this assistance my experience comprehends a relativel}' small range of materials and touches chiefly nuclear structures. Fortunatety, from other sources, much information has been gained about cytosomic conditions, especially relating to mitochondria.

FRESHNESS OF MATERIAL

Some of the conditions involving protoplasm in its passage through technical treatment are fairlj- well understood and appreciated. The necessity for immediate fixation, for instance, appeals to most workers, but it is surprising to find the laxity which prevails even here. It is seriously advocated by some that a delay in fixation is desii'able for the 'improvement' of the cell. Nothing is more certain however than that changes occurring after the death of the organism are, from the beginning, destructive. There is a possibility that some of these ma^' favor the demonstration of certain structural details, but the inherent chance of error is so great that results obtained by this method could receive credence only when confirmed by more reasonable means. The extent to which post-mortem changes occur in a given period vary much with the nature of the material and the attendant physical conditions. In general there is a progressive liquefaction of the protoplasmic gels which eventualh' manifests itself in the prepared objects by vacuoUzation and loss of fine detail.

AGE OF SPECIMEN

In plant cells the changes incident to age are clearly marked and do not escape notice, but in animals these are less obvious and often fail to receive consideration. It is true that cleavage phenomena have been studied and the relation of nucleus to cj^tosome determined, together with the distribution of certain physically distinguishable substances, and ^linot has given us a con

MICROSCOPICAL TECHNIQUE 269

ception of the nucleo-c3-to,some relation in adult cells, but we are yet lacking an understanding of the \ariations which must be ascribed to the age conditions of our prepared material. Without having made anj- careful study of this subject I have come to reaUze certain conditions in Orthopteran germ cells which must be due to the age of the organism. Among these are a greater density of the protoplasm, more of a tendency toward degeneration, and less precision in response to reagents. Hartman beheves that there is an increase in size of the chromosomes with age. This is a subject which should receive careful attention.

METABOLIC COXblTIOX OF THE ORGANISM •

At any given period in the life history of an organism the reaction of its cells to physical agents varies with metabohc conditions. This fact has been demonstrated in our experience with Orthopteran cells through changes resulting from the use of different food plants and through the invasion of the body by fimgi. If Chortophaga is fed upon grass its reaction to fixation in Flemming, and to staining in haematoxylin, is such as to produce a pure nuclear stain after appropriate handhng. Other animals of the same species, fed upon clover and subjected to the same technical treatment, show a reversed staining reaction. A similar reversal occurs in the cells of animals whose bodies are invaded by the myceUa of a fungus which not infrequently attacks grasshoppers. So profound is the change thus produced that it is practically impossible to secure a normal nuclear stain with haematoxjdin.

METHOD OF KILLING

At first thought it would seem absurd to consider that the method of killing an animal would have any effect upon its cells, and yet it has been clearly proven that certain well marked differences obtain between the cytological details of animals killed by cyanide or by xylol. Ever since the beginning of my work

270 C. E. McCLUNG

upon the Orthoptera I have been familiar with two contrasting conditions in the first spermatocyte metaphase. In one case the spindle is long and clean, the chromosomes extended and well distributed, and the cytoplasm clear and bright. Under the other condition the spindle is short and restricted, the chromosomes are contracted and crowded, and the cytoplasm is granular and hazy. Notwithstanding numerous efforts to produce these appearances at will by modifications of the different steps in the technical processes thej' remained unaccounted for. By exclusion and fortunate circumstance it was finally determined that killing the animal by dropping xylol upon it would eventuate in the extended spindle while animals killed by cyanide fumes would show cells with the contracted spindle. Experiments now under way have shown that like changes may foUow other killing agents.

It has of course long been recognized that various animals require very careful treatment before they are subjected to the action of killing and fixing fluids. Unless they are narcotized they contract so strongly that their cells are useless for stud}'. Some marine flat worms reduce themseh'es almost to the state of unorganized jelly under the action of ordinary fixing agents. That the relatively stable cells of the grasshopper could be influenced bj' the almost instantaneous process . of killing did not occur to me, and in this respect I do not find myself alone, judging by the lack of pubhshed observations on this point. After the discovery of the actual facts and a careful consideration of the case the variations thus produced did not, after all, seem so strange. An animal, after death by cyanide, is limp and flaccid and there is no tendency for the jumping legs to break off. On the contrary, an animal killed by xylol is stiff and rigid and the jumping legs are either cast off or easily break from theii' attachment. If these lethal agents so differently affect the muscular and connective tissue cells it is not at all strange that other cellular complexes, including the germ cells, should manifest differential results. AMiether the action upon the muscle fibers is the same as upon the spindle fibers is another matter.

MICROSCOPICAL TECHXIQUE 271

but it would not be strange to find it so. Although experiments have not yet been carried far they indicate that the action of anaesthetics, Hke chloroform and ether, is sunilar to that of xylol, while decapitation produces the same result as cyanide. It is possible that the disturbances resulting from decapitation are due to alterations in the pressure of the bodj- fiuids but we do not have any definite information upon the final cause of any of these changes.

METHOD OF TREATMENT IX FIXING

While it is generally admitted that the tissue must be so exposed to the action of the fixative that ready penetration can be effected it is not so clearly appreciated that shght variations in the conditions existing at the time of fixation can produce extensive differences in the finished product. One of the most striking instances of this appears when the same form of material is treated with the same fixative, in one case being in a reasonable sized mass and iu the other a smeared fihn. A fixative which gives atrocious results in the former case maj- produce good smear preparations. ^ly experience has been that, with Orthopteran cells, almost any fixative wUl produce a good smear preparation. It must not be assumed that this is because no fLxing agent is requu-ed, for this material, unlike the Hemipteran, cannot be fixed by drying but requires the immediate application of a fixative.

The size of the mass alone wUl not determine the character of fixation — immediate penetration and ready exchange of fiuids must be provided for. In the study of Culex cells, as has been described by Whiting, Hance and Holt, although what appeared to be a good preservation was obtained by removing the abdomen and fixing the gonads in situ, when a careful study of the chromosomes was made this was found to be very poor. Indeed this method seemed to indicate that the diploid chromosome number is three, as has been asserted by two European observers, when, as a matter of fact, it is six. This is easily demonstrated by removing the gonad, freeing it of adherent fat and fixing in Flemming. Under these conditions the paired elements remain

'll'l C. E. McCLUNG

entirely separate and distinct, whereas without these precautions the members fuse together and the number of chromosomes is apparently one half what it really is. In Drosophila the first spermatocj^te metaphases are rarely seen unless the testis is freed of fat and trachea.

Similar difficulties arise in the treatment of the mammalian testis where clumping of the chromosomes invariably results unless the seminiferous tubules are teased out or otherwise exposed to the direct action of the fixative, as has been shown by Allen and Hance. It maj' safe!}' be said that almost all the .work done on mammals is worthless largely because of neglect at this period in the technical process. The more fluid the chromosomes are the greater the difficulty in preserving them as separate and distinct entities. Under faultj^ treatment they tend strongly to flow together, with apparent numerical reductioii, and this may go so far as to show metaphase plates as flattened masses of chromatin with occasional openings through it. Even a casual inspection of published figures will show the prevalence of this condition.

LENGTH OF FIXATION

It is not enough to choose an appropriate fixing agent and to apply it properh' — the time of its action is important. This varies with the character of the tissue, its size and with the fixing agent used. A familiar result with most cytologists is the glassy and more or less homogeneous appearance of Amphibian testis cells treated with osmic mixtures. The same kind of cells ma\^ be immersed in picro-formal-acetic mixtures for an indefinite period without harm, while grasshopper cells exposed to osmic mixtures for days will not be injured. On the other hand if the period of immersion be too brief the preservation is incomplete and faulty. Drosophila spermatocytes in metaphase, if given insufficient treatment with Flemming, are reduced to amorphous masses.

MICROSCOPICAL TECHNIQUE 273

CHARACTER OF FIXATI\-E

Of all the steps in the technical processes that involving the character of the fixative has received most adequate attention. It is generalh' recognized that the agent must be adapted to the material, and emphasis can not be too stronglj^ laid upon the importance of this fact. At the same time, as can be seen bj^ reference to other statements I have made, the character of a fixation can not be judged properly unless it is known how the material has been affected by other agents in the process. It is also true that some combinations are, under proper conditions, generally applicable to a large range of materials, and this is more true of all fixatives than has been reaUzed. Combinations of acetic acid, picric acid and formalin may be said to constitute a universal fixative because the,v can be applied to so many kinds of materials to preserve the finest details of structure without detrimental effects. It is however necessary to realize that even with accurate preservation of structures their full demonstration may require a special fixation. Thus while the picro-formal-acetic mixture may show the presence of mitochondrial structures they can not be made evident by specific stains. It is therefore required that we not onh' choose an appropriate fixati^'e for the type of cell we wish to studj^ but we must also make the selection in view of the particular cell structure to be investigated. Having decided upon the substances required it yet remains to be determined in what relative strengths thej' should be combined and with what adjuvants. To do this properly an extensive and time consuming series of experiments is necessary and the advantage of cooperation becomes apparent. It is possible that after a number of such series has been completed some better general principles will be developed to guide new investigations.

Such a cooperative and extended studj' of the action of certain chemical fixatives has been undertaken at the LTniversity of Pennsylvania by Doctors Carothers, Allen, Whiting and Hance with very encouraging results. The details of these have been published in part and will not be repeated here, but it should be noted that the relative strengths of the dift'erent members

274 C. E. McCLL'XG

of the combination are important. It also appears evident that the presence of certain adjuvants contributes materially to the perfection of action in any given case. Thus the addition of urea to the picro-formal-acetic mixtures or to Flemming produces well marked and characteristic effects upon both plant and animal cells. Various sugars and mahc acid correspondingly improve the action of fixatives upon plant cells, each producing a distinctive reaction. In general the action of these inert substances is to preser\-e the more fluid parts of the nucleus, so that othen\'ise empty spaces are shown in sections to be filled with a dehcate reticulum. Increased concentration or specific action maj- however result in vacuolization of the cytoplasm. The great advantage of these additions to the fixing fluid for chromosome studies is in preventing the somewhat liquid chromatin of certain cells from flowing together with the consequent loss of chromosome outlines.

PHYSICAL CONDITIONS DURING FDL\TION

Little attention, relatively, has been paid to the physical conditions under which the protoplasm and its coagulant are brought together, and yet this is far from being an unimportant matter. Temperature, concentration of the reagents, method of application, the presence of adjuvants and many other circumstances are significant. I wish here to speak particularly of the relation of temperature to the fixation process. The optimum conditions appear to vary both with the material and with the fixative. It seems generally true that for mammal tissues a temperature of 0°C. with Flemming, and 38°C. with picro-formal-acetic is best. There seems to be less difference in the case of invertebrates but this is dependent somewhat upon the rapidity of penetration. Our experience so far would seem to indicate that if immediate action is secured, as in a film, the temperature is not important, but that if time is required to bring the cell and reagent together it should be considered. The explanation for the variation in temperature required to produce equallj' good results would seem to be that a low temperature holds the tissue

MICROSCOPICAL TECHXIQUE 275

unchanged during the period required for the penetration of a slow!}- mo^•ing reagent, while the higher temperature raises the rate of penetration of the fixative which is thus brought to the cell before it can undergo alteration. Of course with so high a temperature as 100"C. the action is directly that of the heat.

WASHING

Once the protoplasm is coagulated by fixation we are then dealing with a soUd instead of with a semi-fluid substance, but this does not signify that the object can be treated with any less care. In fact mam* of the poor preparations which we see are the result of neglect in after-fixation stages. Without exaggeration it can be said that the best of fixed material ma3' be spoiled at almost any period of its subsequent treatment. I should like to give some examples of these changes which have appeared during the course of our experiments, beginning with the next step of washing out the unused fLxative from the cell. According to all directions this should be thorough, but apparently the principal object sought is to remove an extraneous substance for physical reasons. It seems certain, however, that marked differences in a fundamental staining reaction Taay foUow in tissues which would commonly be regarded as weU washed, due to the further extraction of chemical substances. Haematoxj-lin. while not a test for chromatin, nevertheless, under ordinar}- concfitions, gives a pure nuclear stain -nith sufficient extraction. This was the universal result in all my own Flemming preparations, but every year when students in my c^-tologj^ class made sUdes from fresh material they secured a reversed staining reaction, the nucleus being unstained and the cytoplasmic structures darkly tinged. Finally the j-eUow color of the nucleus in these latter cases, together with the amount of color in the alcohol which had stood for some months on my o^ti unsectioned material, suggested that possibly insufficient washing was responsible for the reversal of stain. To test this out paraffin sections were made of recently fixed material, which had been washed as usual for twenty-four hours, and the ribbon

276 C. E. McCLUNG

spread and dried. The paraffin was remo\-ed with xylol from the sections at one end of the slide and left protecting the other half. Thus prepared the slide was soaked in seventy per cent alcohol for three days, after which the paraffin was dissolved from the remaining sections and the whole slide stained in iron-haematoxyhn. Upon differentiation a very peculiar slide resulted, one end showing cells with a pure nuclear stain, the other exhib"iting excellent mitochondria but no stained chromatin. The length of washing is thus shown to be the means of securing a mitochondrial stain or a chromatic stain with the same material and the same reagents. With other fixatives no such results might follow and, in some, washing can be omitted completely. This part of the procedure must be dictated bj^ the character of the material, the nature of the fixative and the object sought.

DEHYDRATING

In dehydrating extensive shrinkage, distortion and tearing ma J' result. The gross differences thus produced have been considered by Allen in a recent paper, where it is stated that the major portion of shrinkage in the whole series of technical processes comes during dehydration. Besides these more general eflfects upon the whole tissue there are possible local changes within the cell which are significant. There has been extended discussion of the phenomenon of synizesis, much of it being fruitless and uncalled for. In an earlj^ paper I stated that this condition in the Orthoptera is an artifact and suggested that possiblj' it might be of similar character in other cases. This incidental remark has been more quoted and discussed than man}' of my most important statements. In this case synizesis is purely an artifact resulting from the too sudden passage of the material from one fluic^ to another. It ne^■er occurs in properly dehj'drated material and, while it may not always result from sudden dehydration there is the possibility of it, which should be avoided by gradual remo\-al of water. Aside from this question of synizesis, which probably is not nearly so important as it has seemed to some, there are many other changes produced by alcohol Avhich need not be discussed here.

MICROSCOPICAL TECHXIQUE 277

CLEARIXG

Removal of alcohol by some agent miscible with it, on one hand, and with paraffin on the other, may be attended with some of the same difficulties connected with dehj'dration, which can be avoided in large part by the proper selection of the agent and by its careful application. Shrinkage and hardening are the worst evils which follow the use of clearing agents. Some j^ears ago I tested the shrinkage action of various substances upon young chick embryos and found that while some of them reduced the dimensions of the disc almost a half, others caused a contraction of less than ten per cent. The least injurious of these was cinnamic aldehj-de following eightj^-five per cent alcohol. Allen reports that aniline oil, after seventy-five per cent alcohol, produces no appreciable diminution in volume even after twentyfour hours' action. While we have no exact data on the subject it seems certain that the gradual transition from alcohol to ■ the clearing fluid results in distinct advantages.

INFILTRATION

One of the worst difficulties in the paraffin method is the shrinkage and distortion which comes from the application of the hot paraffin. So severe is this action that the method is entirely inapplicable after certain fixatives. I have already referred to the fact that good smears may be secured by almost any fixation, but material fixed in Vejdovsky's chrome-sublimate or with HeUy's modification of Zenker suffers such contraction in the hot paraffin as to be useless for study. That this shrinkage and distortion occurs during infiltration was demonstrated to me by Doctor Danchakoff who carried some of the same Zenker-formal material through the celloidin process with excellent results. Doubtless much condemnation of fixing methods is unjust because the other circumstances attending the technique have not been properly appraised. There are some tissues also which can not be carried through the paraffin method because they are either too hard or too soft to withstand its action.

278 C. E. McCLUNG

SECTIONING

During the process of sectioning changes of great moment may occur, many of which are familiar to all experienced workers. I need not speak of such effects' as compression, tearing, splitting, folding and cracking of paraffin sections because they are obvious to all. Less marked, but of great importance in chromosome studies, is the removal entire of chromosomes which are either lost or carried over into neighboring cells to cause double confusion. Extreme care is needed in sectioning — the knife must be perfectly sharp, it must be inclined to the plane of the section at exactly the right angle, the paraffin should be homogeneous and of a density suited to the material, and the room temperature must be adapted to the thickness of the sections required. The resulting ribbon should consist of sections little less in diameter than the face of the block from which they were cut — straight, free from scratches or breaks and of uniform thickness. Such can be obtained only by the most exacting care in detail but are essential to good results.

SMEARING

If the smear method is employed it should be carefully checked by a study of sections. Properly used it is a valuable method but there are many difficulties attending it. Some material, like blood or the germ cells of the Hemiptera, may be distributed over a glass surface and fixed by drying, but the same procedure applied to Orthopteran cells results in a featureless expanse of unorganized material. Such cells must be distributed between two covers with exactlj^ the right pressure, the covers separated just so and the fihns fixed at once. The covers should be of the correct diameter for the amount of material between them and the pressure applied adapted^. to the density of the cells of that particular species. With the utmost care the cell elements suffer various distortions which must be recognized by comparison with sections. Some cells can not be smeared at all because of their fluid character and it is not uncommon in the best smears to find apparent multinucleate cells resulting from the fusion of sepa

MICROSCOPICAL TECHNIQUE 279

rate cells before fixation. It is almost literally a fact that one may find nearly any condition imaginable in a smear. The need for great caution is therefore clearly manifest.

STAINING

Time will not suffice for any adequate consideration of the process of staining. The number of conditions to be demonstrated, the variety of the staining agents available and the complexities of the processes are too great for anything less than a monographic treatment. I wish merely to call attention to the adequacy of two or three well understood stains for all general purposes. Iron-haematoxylin alone will serve to demonstrate almost all nuclear and cytoplasmic structures which can be specifically distinguished by other agents. If to the use of this is added the safranin — gentian violet — orange G. combination the cytologist is prepared for almost any condition aside from the most special studies.

MOUNTING

It would seem to be the opinion of some cytologists, judging by their preparations, that once the sections are obtained any method of getting them on the glass will do. And yet, just at this point the greatest care is needed if any size comparisons are to be made. A .complete and uniform spreading of the ribbon is absolutely required and no pains should be spared to secure it. I do not hesitate to say that unless this step is properly taken conclusions regarding size and form of ceU structures are almost worthless. A matter of apparent small importance is the straightness of the ribbons on the slide, but this mole hill may well become a mountain of difficulty in an extended study and materially reduce the effectiveness of the observer. A little time expended during the preparation of the slide will save much, later, and may even be the determining factor between good and bad results.

CIUTERIA OF JUDGMENT

It may seem somewhat aside from a discussion of technical problems to consider the subject of criteria of judgment in micro

2S0 C. E. McCLUNG

scopic anatomy, and yet it is so intimately a part of the wliole problem of interpretation involved that I can not refrain from speaking of this most essential and neglected phase of the work. Under the microscope things are not what they seem — every image produced by the lenses must be interpreted in the light of the observer's experience. The microscopical appearance of a sphere of air in water is about as widely removed from that of the actual object as could well be imagined. Many cellular structures require the same translation by experience when studied microscopically. The literature of chromosome studies alone is filled with false interpretations and worthless theories because of the neglect of this elementary conception of microscopical images. In most instances we study colored images, but these are superimposed upon refraction images and the distinction is not always realized, with the result that there are descriptions of longitudinally split rods in which the split is really a refraction line or of divided threads which are only hollow tubes. Even more ob\'ious errors than these are frequently made. A glance at the figures of metaphase chromosomes in many papers will show them to vary in diameter strongly and to have pointed ends. Neither of these conditions normally obtains and their representation is due to the fact that the observer neglected to note that these apparent variations- are due to a failure to focus each region,at'its optical sectit)n. Thus the fundamental organization of the chromosome is misrepresented because the observer has not realized that a knowledge of the third dimension of his object must be gained by focusing the microscope. If such an elementary knowledge of microscopical conditions appears lacking in an observer's work the experienced investigator at once suspects graver defects and discounts both the observations and the conclusions. No one can afford to place himself in an unfavorable light at the very beginning of his presentation by the neglect of the fundamentals of the science.

COXniTTOXS OF MICROSCOPICAL OBSERVATION

There are many considerations involving the choice and use of tlie microscope and its accessories, the manipulation of the'

MICROSCOPICAL TECHNIQUE 281

light and the substage condenser, the comparison of images produced by high and low magnification, etc., which are of the utmost importance in exact microscopical observation, but which I have no time to discuss here. I can not refrain from saying, however, that every microscopist should understand thoroughly the instrument upon which he depends. Without such an understanding his results are sure to lack precision and accuracy..

THE PERSOXAL FACTOR

There is one matter upon which I should like to speak, but hesitate to do so for fear of being misunderstood. Since it is one of such fundamental importance however I shall venture to express myself freely, trusting to the good judgment of my readers to take what I say in the spirit of helpfulness in which it is intended. An experience, which I am surprised to find extending to twenty years, has taught me that cytologists, like poets and other specialized individuals, are born to their work and can with difficulty, or not at all, be diverted into it. There are certain qualities, the possession of which is no warrant for undue self esteem, that are demanded of the person who would devote himself to the investigation of the intricacies of cellular phenomena. Without these, disappointment is bound to come to the individual and trouble to his fellow workers. The literature is burdened with papers which were at best doomed to a fruitless existence because their authors were not qualified by nature or training for the work which they undertook. In full recognition that this same statement may with truth be made of many other lines of endeavor, I would still say that it is particularly true of the exacting work of cj^tological observations. It does not follow even that because a man is a good histologist or embryologist that he will make a successful cytologist. There is no other type of work with which I am familiar that calls into play so strongly the qualities of infinite patience and care, the nicety of manipulation, the exactness of observation, the discrimination of values, the judgment of relations, the exercise of good common sense together with the need of well balanced con TBE ANATOMICAL RECORD, VOL. 14, NO. 5

282 C. E. McCLUNG

structive imagination, as does the finest cytological work. Before any person should decide upon the career of a cytological investigator he ought to demonstrate to some experienced worker the possession of the necessary qualifications for it. Even then, only time and a long suffering scientific public will be able to tell whether in his case the eminent cytologist was as good a judge of men as of cells.

AUTHOR'S ABSTRACT OF THIS PaPER ISSUED BT THE BIBLIOGRAPHIC SERVICE, APRIL 20

FURTHER OBSERVATIONS ON THE RELATIVE SIZE

AND for:\i of the right and left testes of

PIGEONS IN health AND DISEASE AND AS INFLUENCED BY HYBRIDITY

OSCAR RIDDLE

Station for Experimental Evolution, Carnegie Institution of Washington

In an earlier paper in this Journal the writer' published data for the weights of the right and left testes of nearly 200 doves and pigeons, and measurements of the length and breadth of 78 pairs of these. In the present paper the weights for 300 additional pairs of testes are given and measurements are supplied for more than 500 additional pairs.= The earlier results based on relativel}" small numbers indicated (1) that among pigeons the right testis is larger than the left in a verj' high proportion of cases; (2) that the left testis, though smaller in size, is nevertheless usualty longer (and narrower) than the right; (3) that the testes suffer very pronounced atrophy in disease — particularly in tuberculosis ; and (4) that the normal size relation of the two testes is probably more often reversed in hj'brids; and further that the "nimiber of these reversals seems to increase with the degree of hybridization, that is, with the width of the cross." The results given in the present paper leave little or no doubt on any of these topics; an adequate demonstration of these four points, however, requires the detailed presentation of the new data.

The results now at hand, moreover, warrant a consideration not hitherto attempted of the changed or reversed normal size relation of the two testes of hybrids. The fact, and the significance of the fact, of the frequent reversal of the size and form of the

' Riddle, O. Size and length relations of the right and left testes of pigeons in health and disease. Anat. Rec, vol. 11, October, 1916.

- A classified summary of the weights of still another 102 pairs of testes is given (table 28) at the end of this paper.

283

28-4 OSCAR RIDDLE

testes of hybrids from widelj^ separated forms (genera) — as this may now be seen in the light of the control of sex obtained by Whitman^ and later by Riddle — is the chief new point for present consideration in this paper. But the data concerned with the several questions connected with the size and length relations of the two testes should be examined first.

We may here restate some of the reasons for interest in data on the size and form relations of the right and left testes of birds. In t he earlier report the following statement was made :

The light ovary undergoes an early and more or less complete atrophy in most species of birds. Erzold ('91) has shown that in the sparrow the left testis is larger than the right. Firkct ('14 and Swift ('15) have shown that in the chick embryo there were more primordial germ cells in the left gonad, and that this gonad is thei'e also distinctly larger than the right. Allen ('07) found that the sex cells were unequallj^ distributed to the two gonads of the turtle (Chryscmj's), the left receiving most. In this form only 24 to 70 per cent of the sex cells ever enter the gonads. Our own accumulation of data on the size and length relations of the two testes of young and adult pigeons show a very decided predominate number of larger right testes; and also a distinct difference in shape of tlie two glands — the left though actually smaller in size is usually absolutely longer than the right. Changes in the size relation in birds dead of certain diseases — particularly tuberculosis — and in hybi'ids, are als6 suggested by our data.

The meaning of this pronounced inequality in the distribution of the primordial germ cells which is plainly associated with a larger left embryonic gonad, and the finding in adults of two groups of birds of a nearly constantly larger gonad, but this a different gonad in the two cases, is by no means clear. But, whatever this may mean, it is probably a situation of importance to the theory of sex

An examination of our data has shown that the measurements of glands of healthy Ijirds should- be grouped apart from those dead of disease; and those of pure species should be separated from hybrids. The justification of these separate groupings will appear later (pp. 8788)

The testes of pigeons suffer great reduction of size in disease — parti cuarly tuberculosis. It is probable that the right gland suffers

' Posthumous Works, vol. 2, The Carnegie Institution of Washington (in press).

See Riddle, O. The control of the sex ratio. Proc. of the Wash. Acad, of Sci., vol. 7, no. 11, June, 1917; and several earlier papers.

^ Present data show that this statement should ho "longer than the adult right." The very young were not .separately classified or studied in the earlier paper, and measurements were reported for only a verj' few such individuals.

TESTES OF PIGEONS

285

TABLE 1 Summary of previous data

CLASS

STATE

WEIGHT RELATIONS LENGTH BELATIOXS

L +

I- =

h

L + 1 L =

L

Pure species <

Common pigeons <

Specific hybrids <

Healthy Diseased

Healthy Diseased

Healthy Diseased

Diseased

09=

5

2

6

10

7

6=

7 11

5 31

27

8

19 24

12

14

1

2

8

.

2

2

2

6

1

1

3 2

1

7

Generic hybrids. .

4

6

Total healthy

11

7

51 9

6

10

Total diseased

28

17

74 33

6

14

Grand total .

39

24

126 42

12

24

' The cases of larger left testis are grouped under L +; those of equal size under L = ; those with a smaller left testis under L — .

- Five of the (9), and 3 of the (6), are from 14 Sp. suratensis (earlier miscalled Sp. tigrina) — all dead at less than 9 months old.

greater reduction than the left. The left (persistent) gonad of the female does not undergo a similar reduction in tuberculosis (p. 102).

The very considerable significance of the reversal in hj'brid pigeons of the normal size relations of the two testes will be treated later.

A summary, of the data available for the earlier publication is reproduced here in table 1. The 'length relations' of the two testes are shown in the last three columns of the table. The results are as stated above. The details of these data were thought to indicate that the smaller left testis is longer and thinner than 'the right. In this connection it was observed (p. 99) that:

This difference in form is perhaps not without interest since the only persistent gonad in the female — that of the left side — is characteristically 'thin' and 'long.' The testis that develops on this side is similarly characterized as compared with its mate of the right side.

286 OSCAB KIDDLE

In order to obtain a quantitative expression of the form differences of the gonads in 3'oung birds of the two sexes table 2 has been prepared. For this purpose healthy males and females of similar age were killed. Young birds (.3 to 7 weeks) were chosen instead of mature ones because the functional ovary becomes much enlarged and distorted by the ripening of the follicles; and further, because such an investigation was not included in our earlier report. The figures for the females show the almost, or quite, complete atrophy of the right ovary in most of these young doves. Four of the 21 retained right ovaries of measurable length. Two other points of interest attach to these data. First, the single, persisteiat (left) ovary is fullj^ twice as long as is either of the double organs (testes) present in the male. Second, in these very, young males the two testes are not of markedly different length; but the slight differejice that exists, at this stage, indicates a shorter left testis — not the longer one which is normal for healthy adult birds of pure species. Observations on the testes of many hundreds of males at still younger stages than that represented by the birds of this chart has fully convinced the writer that in the just-hatched squab the right testis is normally longer and larger than the left. We do not know whether the right testis is proportionately longer at this time. Females at the hatching stage normally show, on the other hand, decidedly longer and larger left ovaries. It is not easy to measure breadth and thickness of these ovaries. All who have seen the ovary of the young dove know that it is a quite thin tongue-like organ with a broader anterior and a more tapering posterior extremity, and with a soniewhat roughened or irregular outline.

SIZE AXD for:\i of testes of healthy adult doves of pure

SPECIES

Weights and measurements for the testes of 24 doves are given in table 3. In only 2 of the 24 is the left testis the larger, and in both of these cases the size difference is shght (0.7 per cent and 4.5 per cent). The length relations of the right and left testes of this group is, however, quite different. Although 22 of the

TESTES OF PIGEON'S

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TESTES OF PIGEONS

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290 OSCAR RIDDLE

24 left testes are smaller than their associated testis, 17 of them have a greater length than their larger associates. A comparison of the figures for "per cent of difference" for size and for length shows, moreover, that in all cases, without exception, the left testis is relati\-ely more elongate than the right.

SIZE AND FOR.M OF TESTES OF DISEASED ADULT DOVES OF PURE

SPECIES

The 20 diseased adult doves of table 4 show 3 smaller right testes and 4 additional pairs in which the two testes were of equal size.^ The enormous reduction in size of the testes of diseased birds is made clear by a comparison of the figures given in tables 3 and 4. In health the right testis of most, probably all, of these birds weighed between 0.500-1.000 g. Weights of 0.016 or 0.025 g. in adult birds (e.g., 924, A335) dead of disease, but known earlier to have been fully functional and fertile, indicate that fully 95 per cent of the weight of the gland was lost under disease. An inspection of the figures in this table, and in the succeeding tables in which the cause of death is recorded, will make clear a further point, namely, that tuberculosis is the disease associated with the most extreme atrophy of the testes. It was noted in our earlier paper that probably no reduction whatever occurs in the ovary of tubercular females. A suppression of ovulation and a cessation of the growth and development of follicles' plainly occur in the ovary of the female, but the total size of the gland proper is not reduced.

The number of pairs of testes recorded as of 'equal size' is necessarily larger in those series (diseased and young) in which very small glands predominate. Weighings were usually made to milligrams only, and differences in the two gonads were recorded only in cases where the difference was beyond question.

' The largest follicles that can be found in the ovaries of doves (of most species) dead of very advanced tuberculosis are rarely more than L5 mm. in diameter; the number of smaller but |>lainly visible follicles in such ovaries is, however, usually quite large.

TESTES OF PIGEON'S

291

TABLE 4

Weights and measurements of adult doves of pure species^ dead of disease'

Alll

578

123

A165

A350

E416

B688

494

A335

990

A345

E204

182

July 23 August 13 October 8 October 10 October 22 November 7 December 6 December 16 December 29 January 8, 1917 January 21 January 27 January 30

(Cause ?) (Cause ?) Sp., li., lu. Sp.. li. Li., sp. Lu., sp. Intest. Li. (fighting) Lu., li.. sp. Sp., li. (Cause ?)(juv.?) | (Ascaris) Sp., li., hem.

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R =

L =

R =

L =

R =

L =

R =

L =

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R = 0. L = 0.

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R = L =

R L

R = L =

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164

148

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WIDTH

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7.4 8.4

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292

OSC.\R RIDDLE

TABLE i— Continued

924

A41

994

A332

B601

A861

Gs

February 22

March 20

March 23

March 31

April 3

April 7

AprU 16

L:., sp. Li. and sp. Sp. , liver Li., sp. Intestine (?) Weakling Sp., li.

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' Some young offspring of blond ring dove 'mutations' (?) are included in this list.

^ Abbreviations of the names of organs to their first two letters, implies that advanced and verj' evident tuberculosis was found' in those organs (lungs, spleen, liver, joints, mesentery, intestine). When more than one organ was affected the name of the organ (or organs) apparently most affected is written first. When the word is written out it denotes that this organ was abnormal, but not necessarily tubercular. Immature birds are designated (juv.). References to hemorrhage (hem.) and abdominal wall (abd.) are also given as here indicated.

TESTES OF PIGEONS 293

SIZE AND form' OF TESTES OF HEALTHY YOUXG DOVES OF PURE

SPECIES

In table 5 are gi^'en the measurements of 29 pairs of testes of healthy young doves of pure species (2 in table 2), and the weights of 4 of these pairs. These few pairs of testes show no reversals of size from the order usual for the adults. The measurements indicate that in 17 of the 29 pairs the left testis was the longer, in 3 pairs they were of equal length, and in 9 pairs the right was the longer. It should be noted that the birds of this series, and of succeeding tables of '3-oung doves,' were of somewhat more advanced age (5 to 12 weeks) than were those, taken for the special purposes of table 2.

SIZE AND FORM OF TESTES OF HEALTHY ADULT COMMON PIGEONS

In tables 6, 7 and S are given the weights of 49 pairs of testes of healthy adult common pigeons. In 12 of these pairs the left testis was larger than the right, in 36 pairs smaller, and in one case the two glands were of equal size. These figures indicate a higher proportion of 'reversals' of the normal size relations than was found in Columbidse of pure species; and there are good reasons for believing that more than one wild species has entered into the stock which has given rise to the several scores of races of domestic or fancy pigeons.

]Measurements for 53 pau-s of testes are given in these same tables. The left testis is the longer in 25 pairs, shorter in 27 pairs, and of equal length in one pair. Since the left testis was noted above to be larger in only 12 of 49 pairs it is evident that in this group, as in the group of pure species, there is a decided tendency for the left testis to be elongate in form as compared with the associated testis of the right side.

Four measurements on the relative length of the two testes of very young common pigeons are appended to table 8. All of these illustrate the point already mentioned in connection with table 2, nameh', that at the time of hatching and for a short period thereafter the right testis is usuallj^ longer than the left.

294

OSC-AJl RIDDLE

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~

S

■^

d

J

s

S

s

s

a

u

z

~X

oc

■M

I-

1

w

o

CO

T— 1

rf

o

ftr

~

O

o

^

_;

o

1

i:

1

1

2

o

CO

1^

lO

1-H

00

TT

CO

+

1

+

C'l o

o o

00 CO

o o

JC tj

L-: -^

^ X

x: X

X X

f;

~ —

— "

5C 2^

O w

QC O

O —

t^ o

1

o o

o o

o o

o ci

CC IC

L*; -T

— <~

is

l: i:

II 11

11 11

11 II,

11 II

1: il

II h

r^ ■•

1

~ -^

ci h^:

c^ 1^

-_

'^-^ '

^-s,

--— ^

-—

^-.^

-— ^

^

■?)

r>I

■Si

ii

>i

>■.

O)

o

M

?1

j

3

3

<

•^

'C

•r

■r^

s

-^

-f

<:

<

<

<■

,

•n

00

t~

00

ro

CO

00

cc

CO

CO

to

■o

6

lO

CO

■^

O

1

'*'

«— i

2

lO

CO

^ '^

> o

-3 bO

a

o

c

O

296

OSCAR RIDDLE

TABLE 6 Weights and measurements of testes of healthy adult common pigeons

A403

A492

A99

A57

B554

A485

B407

A276

B269

A58

A321

O

A319

B664

July 28, 1916 July 28 July 28 May 31 July 28 July 30 July 30 July 30 July 30 August 2 August 2 August 2 August 2 November 10 <

R = 0.975 L = 0.770

R = 1.215 L = 1.425

R = 0.825 L = 0.627

R = 0.840 L = 0.890

R L

R = 1 215 L = 1.010

R = 0.710 L = 0.900

R = 0.925 L = 0.815

R = 0.790 L = 0.692

R = 0.820 L = 0.690

R = 0.215 L = 930

R = 1.500 L = 0.980

R = 0.610 L = 0.685

R = 035 L = 0.029

PER CENT

OF

DIFFERENCE

-26.6

+ 17.3

-31.6

+ 5.9

-20.3

+26.7

-13.5

-14 2

-18.8

+332.5

-53.1

+ 12.3

-20.7

LENGTH AND WIDTH

19.0 20.3

20.0 22.0

20.0 17.8

18.2 X 10.4 21. Ox 9.8

7.5 7.4

20.3 20.3

16.2 21.1

18.0 16.8

19.3

17.9 17.8

7.8 20.7

20.4 20.0

17.0 16.8

8.3 X 2.7 8. Ox 2.7

DIFFEREXCK

+ 6.8

+ 10

-12.4

+15.4

- 1.3

= 0.0

+30.2

7.1

+ 6.2

5

+165.4

- 2.0

- 1.2

-3.8

TESTES OF PIGEOXS

297

TABLE 6-Cmtinutd

so.

DATE

I FEB CE.VT WEIGHT OF

j DITFEBEXCE

LE.VGTH AXD WIDTH

1

FEB CENT

OF

DIFFERENCE

B679

Xovember 10 {

R = 0.034

L = 0.036

+ 5.9

8.6x2.8 8.0x2.2

— 7.5

B648

Xovember 10 |

R = 0.631 L = 0.605

- 4.3

19.2x8.0 18.8x7.5

- 2.1

B637

Xovember 10 I

R = 0.035 L = 0.030

-16.6

8.4x2.3 8.0 1.8

- 5.0

B633

Xovember 10

R = 0.052 L = 0.052

= 0.0

8.8x3.0 7.5x2.8

-17.2

B641

Xovember 10 \

R = 0.045 L = 0.087

-21.6

10.0x2.6 8.5x2.4

-17.6

THE A.V-AIOMICAL BECOBD. VOL. 14, .NO.

298

OSCAR RIDDLE

TABLE 7 /, nf testes Of healthy adult or adolescent common pigeons Weights and measwremer^^ V^^^Z^.

„»™ 1 I PER CENT

B513

B642

A243

193

B658

B502

December 13 December 13 December 13 December 13 December 13 March 9, 1917

TESTES OE PIGEONS TABLE 7— Continued

299

R = 0.692 L = 0.650

R = 0.111 L = 0.075

R L

1.090 0.812

R = 0.820 L = 0.610

R = 0.248 L = 0.188

R = 1.370 L = 1.050

PER CENT

OF

DIFFERENCE

6.4

-48.0

LEXGTH AND WIDTH

-34.2

-34.4

-31.9

-30.5

18.0 X 9.0 19. 7x 8.3

11. 2x 4.4 10. 8x 3.4

19.2x10.5 19. 8x 8.8

19.1 X 8.6 16.0 X 8.9

12.2 X 6.6 11. Ix 5.3

23.2 X 10.8 22.8 X 8.0

PER CENT

OF

DIFFERENCE

-f 9.4

- 3.7

+ 3.1

-19.3

.-flO.O

- 1.8

300

OSCAR MIDDLE

TABLE 8

„i. n{ i>"<les of healthy adult common pigeons Weights and measurements ofteslesj]J>^ »

^ , PEB

TESTES OF PIGEON;

301

TABLE S— Continued

NO.

DATEl

LENGTH AXD WIDTH

PJEH CENT OP DITFEBENCE

E411

December 13

(

R = 6.3x 1.1 L = 5.6x 1.0

-12.5

£547

December 13

/ I

R = 6.1x0.8 L = 5.^x1.0

- 5.1

E577

December 13

(

R = 6.1x1.0 L = 5.6x1.0

- 8.9

Eo52

December 13

{

R = 7.0x1.0 L = 5. Ox 1.0

-40.0

• The four individuals of this list were verj- young birds. SIZE AND FOR-M OF TESTES OF DISEASED ADULT CO.MMOX PIGEOXS

Data can be supplied for only 6 individuals of this group. All of these (table 9) had smaller left testes. .\11 left testes were also shorter than their right associates, but a comparison of the amounts (in per cent) of their shortness with the amounts (in per cent) of their size deficiency will show — as in other cases — that the left testes are the more elongate in form.

SIZE AND FORM OF TESTES OF HEALTHY ADULT SPECIFIC

HYBRIDS

Complete weights and measurements for the testes of 18 indi\'iduals of this group are given ien table 10. The left was larger in 2 cases and smaller in 16 cases. The number of 'reversals' of the usual size is not wideh' different from that noted in table 3 for pure species (2 : 22), but the indicated difference is in the same sense as found and reported in our earUer paper.

Although only two left testes of this group of IS were as large as their associated rights, 14 of them were absolutely longer than their right associates. This group, therefore, like the two preceding groups, shows that the left testes of adults are decidedly more elongate than the right.

302

OSCAR RIDDLE

TABLE 9 Weights and measuremlnis of testes of adult common pigeons dead of disease

A3&4

C-B9

A266

A419

A42o

A404

September 19

November 22

November 22

December 13

January 28. 101'

December 13

Crop (?)

Liver

Sp., body wall

Liver

old age (?)

killed, jo., li.

R = 0.050 L = 0.037

R = 0.578 L = 0.496

R = 0.027 L = 0.019

R = 0.018 L = 0.014

R = 0.170 L = 0.068

R = — L = —

-35.1

-16.5

-42.1

-28.5

-150.0

-?■>

LENGTH AXD WIDTH

7.8x3.3 7.8x2.6

17.5 X 8.5 17.5 X 7.7

6.4x2.6 5.2x2.8

6.1x2.4 6.0x2.0

11.1x5.9 8.6x4.0

9.3x2.0 4.8x2.1

0.0

0.0

-23 1

-16.7

-29.1

-93 8

TESTES OF PIGEONS

303

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304 OSCAR RIDDLE

SIZE AND FORM OF TESTES OF DISEASED ADULT SPECIFIC

HYBRIDS

In tables 11 to 14 weights are given for 61 pairs of testes from diseased specific hybrids. Of this number 7 had larger left gonads; in 49 the right was the larger; and in 5 the two were of equal size. The number of larger lefts (reversals) is here hardly as large as in the group of pure species dead of disease. Touching this matter, however, is the fact that a very great majority of these hybrids were derived from two ^'ery closely related species — St. alba and St. risoria — and that the sex ratio is usually but little, if at all, affected by this cross. The very pronounced atrophy of both testes in disease — particularly in tuberculosis — is shown by these data to apply to this group equalfy with the groups previously examined.

The measurements of 58 pairs of testes show 38 longer and 18 shorter left testes. A comparison of the detailed measurements for the two testes of the birds hsted in these same tables (11 to 14) will make it clear that here, as in other groups, the left testis is usually longer and thinner* than the right.

THE FORM OF THE TWO TESTES IN HEALTHY YOUNG SPECIFIC

HYBRIDS

Measurements for 1 1 1 pairs of testes for birds of this group are given in tables 15, 16 and 17 (4 in table 2). At this immature stage (5 to 12 wks.) onty about one-third (35: 61) of the left testes have surpassed^ their right associates in length. In 19 of these 115 pairs a difference in length was not ascertainable.

' In measuring the 'width' of the right and left testes the glands were measured (with Vernier calipers) at the widest point (usually anteriorly in the left testis) in their cross-wise dimension. The measurement of a third dimension was not attempted.

' It was noted above that at the time of hatching the left testis is normally shorter than the right. It is only during post-natal development that tlie left becomes absolutely longer than the right. It is an interesting fact that the gonads of the male (ring doves) increase very little in size from the time of hatching to about the fourth month (compare tables 2 and 15 to 17). In the female, however, there is an early decrease in size (degeneration) of the right gonad, and a fairly steady increase in size of the left gonad.

TESTES OF PIGEONS

305

TABLE 11 Weights and measurements of testes of adult specific hybrids dead of disease^

514

109

A148

B235

190

529

A168

A389

749

551

921

107

A679

952

May 25, 1916

June 8

June 11

July 26

August 1

September 1

September 5

September 5

September 10

September 20

September 21

September 24

September 26

September 30

Sp., li.

Sp., li., me

Sp., li.

Liver, digest.

Sp., li.

Sp., lu., li.

Li. and sp.

Liver spleen

Sp., liver

Lungs

Li., sp., hem.

Sp. and li.

(Cause ?)

Sp., lu.; liver

R = 0.025 L = 0.255

R = 0.022 L = 0.018

R = 0.085 L = 0.069

R = 0.012 L = 0.012

R = 0.040 L = 0.028

R = 083 L = 0.065

R = 0.045 L = 0.041

R = 0.570 L = 0.437

R = 0.026 L = 0.024

R = 0.075 L = 0.054

R = 0.069 L = 0.065

R = 0.035 L = 0.033

R = 0.097 L = 0.073

R = 0.028 L = 0.021

PER CENT OF DIFFERENCE

+920.0

— 22.2

-23.2

0.0

-42.9

-27.

-30.4

- 8.3

-38.8

- 6.1

6.1

-32.8

-33.3

LENGTH.^ ND "WIDTH

7.2 7.4

9.1 X 4.2 10.7 X 3.9

6.4

7.4

8.2 7.8

9.0 X 4.5 10.3 X 3.6

8.4 X 3.3 9.4 X 2

8.3 8.6

9.7 X 3.8

9.9 X 2.9

10.3 3.5

11.4 X 3.4

8.5 X 2.7

8.0 X 2.7

11.0 X 4.5

12.3 X 3.3

PER CENT OF DIFFERENCE

+ 2.8

-H7.6

+15.6

-5.1

+ 14.4

+ 11.9

+3.6 + 2.0 + 10.7 - 6.3 +11.8

■60b

OSCAR RIDDLE

TABLE 11

Continued

NO.

DATE

' DlSE.tSE

WEIGHT

PER CENT

OF DIFFERENCE

LENGTH AND WIDTH

FEB CENT OP DIFFERENCE

134

September 30

Sp., liver I

R = 0.020 L = 019

- 5.3

6.9 X 2.4

8.4 X 2.1

+21.7

196

October 1

Sp., li., {

R = 0.030 L = 0.028

- 7.1

8.0 X 2.5

8.1 X 2.2

+ 1.3

930

October 5

Li. and sp. <

R = 0.031 L = 0.025

-24.0

8.7 X 2.8 9.0 X 2.7

+ 3.4

TESTES OF PIGEOXS

307

TABLE 12

Weights and measurements of testes of adult specific hybrids dead of disease

PER

PER

so.

D.\TE

DISEASE

WEIGHT

CENT OF DIFFERENCE

LE.VGTH AND WIDTH

CENT OP DIFFERENCE

A400

October 6

Sp.. l;lu.,

/

I

R = 0.045 L = 0.035

-28.6

9.2 X 3.0 10.5 .V 2.3

-1-14.1

77

October 7

digest. (?)

/ I

R = 321 L = 0.247

-29.9

15.4 X 6.3 15.3 X 5.1

- 0.7

A35

October 7

Li., sp., lu.

/ I

R = 0.050 L = 0.042

-19.0

9.4 X 2.9 12.1 X 2.6

-1-28.7

127

October 7

Sp.

'

R = 0.028 L = 0.020

-40.0

8.1 X 3.0 8.0 X 2.3

- 1.3

504

October 12

Old age

(

R = 0.057 L = 0,050

-14.0

9.9 X 3.5 11.4 X 3.4

-1-15.2

A520

October 13

Liver (?)

1

R = 0.236 L = 0.255

+ 8.1

15.9 X 5.5 14.9 X 5.6

- 6.7

A163

October 20

Sp., Ii.

R = 0.037

L = o.mi

-19.3

9.0 X 2.5 9.0 X 2.5

= 0.0

520

November 15

Sp., R. lu.. Ii.

/

R = 0.038 L = 0.035

- 8.6

8.4 X 3.0

9.5 X 2.6

-1-13.1

950

November 16

Sp., Ii., lu.

{

R = 0.036 L = 0.031

-16.1

9.2 X 3.0

8.6 .X 2.8

- 6.9

592

November 21

Sp.. Ii., lungs (?)

{

R = 0.377 L = 0.345

- 9.3

16.5 X 7.0 18.4 X 6.4

+11.5

A94

November 26

Sp., Ii., intes.

{

R = 0.022 L = 0.020

-10.0

7.8 X 2.5 8.0 X 2.2

+ 2.6

A42

December 6

Li., lu., sp.

/ I

R = 0.014 L = 0.014

= 0.0

6.4 X 2.0 5.4 X 2.2

-18.5

B264

December 10

Digest. (?)

{

R = 0.035 L = 0.027

-29.6

8.4 X 3.0 9.2 X 2.2

+ 9.5

102

December 13

Sp., Ii.

(

R = 0.020 L = 0.023

+15.0

6.7 X 2.3 8.4 X 2.4

+25.4

308

OSC.VR

RIDDLE

T.\BLE 12— Continued

PER

PER

NO.

D.WE

DISEASE

WEIGHT

CEXT OF

DIFFEH ENCE

LENGTH AND WIDTH

CENT OF DIFFERENCE

53^

December 17

Sp.

/

R = 0.031

9.0 X 2.4

I

L = 0.025

-24.0

7.7 X 2.6

-16.9

509

December 18

Sp. and li.

f

R = 0.028

7.1 X 2.9

I

L = 0.030

+ 7.1

6.4 X 3.2

-10.9

533

December 20

Lu., sp., me.

/

R = 0.028

6.0 X 2.7

I

L = 0.023

-21.7

7.4 2.5

+23.3

TESTES OF PIGEOXS

309

TABLE 13 Weights and measurements of testes of adult specific hybrids dead of disease

78

A133

200

957

92

928

A69o

953

A192

A189

A322

904

E551

December 26 December 29 December 29 January 2 January 2 January 6 January 10 January 19 February 3 February 17 February 24 February 27 March 4

Liver Sp. and li. Sp., lu., li. Sp., U. Li., sp. Sp., U. Li. sp. Sp., lu., li. Li., sp.. jo. Killed Sp., li., jo. Sp., li.

Hemorrh

Guv.) I

I CENT OF

DUTEB EXCE

PEH LENGTH AXO CXNT OP WIDTH DIFFER ENCE

R = 0.061 L = 0.052

R = 0.012 L = 0.012

R = 0.018 L = 0.017

R = 0.034 L = 0.026

R = 0.035 L = 0.030

R = 0.022 L = 0.018

R = 0.315 L = 0.279

R = 0.032 L = 0.024

R = 0.023 L = 0.018

R = 0.062 L = 0.048

R = 0.038 L = 0.035

R = 0.031 L = 0.025

R = 0.023 L = 0.019

-17.3

= 0.0

5.9

-30.8

-16.7

-22.2

-12.9

-33.3

-27.7

-29.1

8.6

-24.0

-21.0

10.0 X 3.0 9.7 X 2.9

3.0

7.3 X 2.0

6.4 X 2.1 -14.1

8.6 X 2.1

8.0 X 2.2|- 7.5

7.8 X 3.0

7.4 X 2.5- 5.4

8.3 X 2.9

8.7 X 2.8+ 4.8

7.3 X 2.4 8 X 2.4 (?)

15.1 X 6.8 15.6 X 5.

4- 9.6

3.3

7.5 X 3.0'

8.1 X 2.3 -i- 8.0

-7.6 X 2.4 6.8 X 2.2

-11.8

9.3 3.5

8.7 X 3.0- 6.9

7.8 X 3.2

7.9 X 2.5

8.2 X 2.5

8.2 X 2.3

1.3

0.0

5.9 1.8

4.8 X 1.5-20.8

310

OSCAR RIDDLE

T.\BLE 13— Continued

NO.

DATE

DISE.1SE

WEIGHT

PER

CENT OF

DIFFE R ENCE

LENGTH AND WIDTH

PEE CENT OF DIFFERENCE

/

R = 0.037

9.0 X 3.0

A181

March 8

Li., sp., lu. \

L = 0.025 R = 0.043

-48.0

7.4 X 2.3 10.4 X 3.6

-21.6

A141

March 10

Sp., lu., liver \

L = 0.042 R = 0.035

- 2.4

11.3 X 3.1

8.5 X 3.1

+ 8.6

A153

March 17

Li., sp. \

L = 0.035 R = 0.045

= 0.0

10.0 X 2.4 7.2 X 2.8

+17.6

536

March 18

Li., sp., lu., me. \

L = 0.039

-15.4

9.8 X 2.4

+36.1

TESTES OF PIGEOX;

311

TABLE 14

Weights and measurements of testes

PEB 1 1 PER

NO.

Date

DISEASE

WEIGHT

CE.NT OF

DtFFEB EXCE

LEXGTH AXD CENT OF WIDTH IDIFTEBEXCE

45

March 22

Throat

{

R = 0.394 L = 0.250

-49.6

16.0 X 6.4 15.3 X 5.2

- 4.5

B399

March 22

Too much salt (?)

R = 360 L = 0.377

+ 4.7

16.9 X 6.3 17.9 .X 6.0

+ 5.9

A284

-March 22

Too much salt (?)

{

R = 0.612 L = 0.565

- 8.2

18.2 X 7.9 21.1 x7.5

+15.9

126

March 22

Sp., li.

{

R = 0.043 L = 045

+ 4.6

8.9 s 3.0 9.3 X 3.4

+ 4.5

A568

March 23

(Cause ?)

{

R = 0.545 L = 0.423

-28.8

18.7 X 7.3

18.8 X 6.6

+ 0.5

526

March 27

-Sp., li.

{

R = 0.062 L = 0.050

-24.0

10.2 X 3.0 12.5 X 2.6

+22.5

E508

March 23

Healthy (?). salt

R = 0.067 L = 0.044

-52.3

8.9 X 3.5 9.2 X 2.8

+ 3.3

B322

AprO 8

Sp., li., hem

I

R = 0.052 L = 0.060

+15.4

10.3 2.6 12.3 X 3.1

+19.4

945

April S

Sp., U.

R = 0.034 L = 0.031

- 9.7

7.4 X 3.0 8.4 X 2.9

+13.5

A252«

April 23

Sp., U.

(

R = 0.025 L = 0.025

= 0.0

7.0 X 2.9

8.1 X 2.6

+15.7

312

OSC.\B RIDDLE

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318 OSC.\K RroDLE

SIZE AND FORM OF TESTES OF HEALTHY ADIXT TRI-SPECIFIC

HYBRIDS

The group of birds here described as tri-specific hybrids all involve the same three species — St. alba, St. risoria, St. douraca. The}' are rather closely related species. Alba and risoria have been considered as varieties onh* bj' several writers; and douraca seems to have been considered by Stejeneger as the wild representative of the semi-domesticated risoria. The tabulated data indicate — by the relativeh- few cases of larger left testes (sizereversals) — that this group more closelj' approximates to the conditions found in pure species than do the other groups (common pigeons, specific hybrids, generic hybrids) investigated.

Tables 18. 19 and 20 supply the data obtained from 69 pairs of testes. Onh' 6 left testes were the larger, 61 were smaller, and 2 were the size equivalents of the other member of the pair. On the other hand, 42 left testes were longer and onh' 24 were shorter than the right; in three cases the two organs were of equal length.

FORM OF TESTES IN HEALTHY YOLTNG TRI-SPECIFIC HYBRIDS

Measurements for 44 pairs of testes are given in table 21 (4 in table 2). The left was the longer in 20 pairs. The details of the table show further that the left testis is usually thinner — of less width (proportionately less wide) than the right.

SIZE AND FORM OF TESTES OF HEALTHY ADLT.T GENERIC

HYBRIDS

A group of 35 healthy generic h3'brids were killed for the purposes of this study.'" Here the left testis was larger in 10 eases, smaller in 24, and of equal size in 1 case (tables 22, 23). The number of larger left testes (reversals) is clearly quite out of proportion to that found in any of the preceding groups of birds;

'"The principal crosses involved here are: Streptopelia X Turtur; Spilopelia X Streptopelia; Zenaida X Zenaidura; Stigmatopelia X Streptopelia. Two or three individuals of a sub-family cross involving Zenaida-Zenaidura X Streptopelia are also included in the tabulated data. In the summarized data of table 28 (detailed weights and measurements not given), to be mentioned later, two family hybrids, Columba X Streptopelia, are included.

"TllStES OF PIGEOXS 319

in those groups the width of the cross involved was either less in extent or wholly absent. These figures, then, strongly confirm the impression {p^ 102) obtained from the "diseased generic hybrids" reported upon in our earUer paper. This impression being that "tie number of the exceptions (reversals) seems to increase with the degree of hybridization (width of the cross)."

The left testis is here longer than its associate in a very high proportion of cases — 24 : 8 ; in 2 cases the compared lengths wereequal.

The form of the testes of healthy young generic hybrids may be noted in this connection. The 19 pairs (1 is in table 2) of testes of table 24 show 8 longer and 9 shorter left testes and 2' pairs of equal length Of these, 5 are clearly larger ; 7 axe smaller..

FORM AND SIZE OF TESTES IN DISEASED ADULT GENERIC

HYBRIDS

The weights of 14 pairs of testes of diseased generic- hybrids •• are recorded in table 25. The left testis was larger, in; 9' oases,, smaller in 4, and of equivalent size in 1 case. The numbers are' not large, but it is clear that similar proportions of larger (reversed) left testes are found in none other of the groups considered — neither in the present nor in the earlier report on this sub^ject. The only group that approximates to these proportions isj this same group — diseased generic hybrids — of our earlier report.. The ratio there of larger lefts to larger rightswas 7': 12. In 10 of the 14 pairs of testes recorded here the left was theilonger; in, three pairs the left was shorter, and in one pair there-was noi difference in length.

After all of the data that has just been discussed had been gathered, tabulated and described (in the form fomid in the preceding pages) , it was decided to accumulate a third' set of data onthis subject. Since the number of weights obtained' for some of the bird groups is smaller — both in our earlier communication: and in the data thus far treated here — than is desirable, , iti was. thought well to learn whether similar proportions for the various groups would be found in a third collection of data. That the proportions found in the two earlier sets do reappear in thesQ.

320

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TABLE 20

Weights and measurements of testes of hcalthi/ adult or adolescent tri-specific hybrids

xo.

D.ITE

WEIGHT

PER CENT

OF

DIFFERENCE

LENGTH AND WIDTH

PER CENT

OF

DIFFERENCE

A865

March 9

R = 0.805 L = 0.740

- 8.8

23.5

24.3

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E189

March 9

R = 0.632 L = 0.542

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E329

March 9

R = 0.153 L = 0.130

-17.7

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+12.8

E376

March 9

R = 0.650 L = 0.457

-42.2

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+ 9.1

E340

March 9

R = 0.507 L = 0.616

+21.5

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E20

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R = 0.695 L = 0.557

-24.8

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E271

March 9

R = 0.295 L = 0.290

- 1.7

12.2

17.1

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E391

March 9

R = 0.571 L = 483

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E393

March 9

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+11.0

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Ell

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- 7.5

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E269

March 23

R = 0.520 L = 0.435

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E126

March 23

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B639

March 23

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+17.5

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X 7.6

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A801

March 23

R = 0.640 L = 0.620

- 3.2

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A868

March 23

R = 0.790 L = 0.655

-20.6

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E16

March 23

R = 0.410 L = 0.365

-12.3

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A705

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+ 3.9

A623

March 23

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18.2 20.6

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+ 13.2

323

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II II

II II

II II

II II

II II

II II

si^^

s; ►^

—J ^

=: -:

-sJ ^

-^ !_;

=:

~

-va ^

-%- ^

"^ 1-^

Si 1-^

o

w^

c;

c;

C2

CI

c:

M

CI

CI

S

j=

,r;

2

.—

o

t;

^

^

^

^

^

^

^

^

i;

— ^

s

s

%

S

«£;

s

«s

S

s

• s

S

<

^H

._

..

t^

..

>-T

o

°s

^j

?i

3C

C-.

X

^

Lt

B

a

a

— ■

■—

■—

■—

oc

o

— .

C;

.

■^

«

^

CI

«

~

o

o

tr;

c^i

CO

«

CI

o

CJ

t^

+

II

II

1

+

+

1

+

+

II

1

+

eo —

o c

— =

3C -r

X >

— C)

■X. —

rr =

c: C-

c o

OC 00

»-« ^H

C) C)

— —

— _

_ —

— —

— —

~ ~

— —

— —

CI o

K X

X •/:

X X

X X

X >1

X X

X X

X X

X X

X X

X X

X X

■* >a

c o

C) M

3C C:

C) o

M —

r o

-r O

re -^

■■c -^

t^ .=

n o

lO lO

irr ic

= ^

^ o

o I'

L— «-T

t» 1^

-r- >.-:

— ^

T ^

^ •<!•

00 00

II II

II II

II II

II .11

ll II

II II

It II

II II

II II

II II

II II

II II

tf iJ

s; J

Si ►^

'^ 1—^

^ -=

i^ i^

s; ^

f^ ^

Si J

'^ t-^

a >-3

'Vi ^

s;

■^

-^

■#

O)

c^

c^

c^

M

c^

b

>.

>-,

>-.

>-.

>^

>>

>v

o

~

o

S5

t

i

'

i

j

^

_i

_5

c

3

"~

■^

~

•—

■s

S

e5

s

^

C-)

tc

IC

^

X

s

X

r^

L"^

•a

K

"~

•~

a

•-*

■"■

H

^^

a

TABLE 22 Weights and measurements of testes of healthy adult generic hybrids

so.

KILLED

■n-EIGHT

PEE CENT

OF DIFFERENCE

LENGTH AND »■=« CENT

^■°™ DIFFERENCE

R = 0.496

17.2x8.1 •

265

June 2 I

L = 0.400

-24.0

18.2 6.4

+ 5.8

979

March 23 |

R = 0.402 L = 0.355

-13.2

16.3x6.7 18.8x6.5

+15.3

A229

March 23 |

R = 0.533 L = 0.695

+30.3

19.2x8.1 21.4 \ 8.0

+11.4

A172

March 23 I

R = 0.395 L = 0.395

= 0.0

15. 6x 7.0 18.1 x5.5

+16.0

A221

March 23 |

R = 0.643 L = 0.530

-21.3

19.2x7.8 19.8x7.2

+ 3.1

A25

March 23 |

R = 0.310 L = 340

+ 9.7

15.4 \ 6.6 broken

?

A327

March 23 |

R = 0.715 L = 0.660

- 8.3

15.4x7.8 14.6x6.8

- 5.5

B267

March 23 <

R = 0.660 L = 0.558

-18.2

20.6x7.8 22.4x7.3

+ 8.7

911

March 23 <

R = 053 L = 0.058

+ 9.4

8.0x3.0 9.0x3.2

+12.5

A232

March 23 I

R = 0.455 L = 0.477

+ 4.9

16.4x7.0 , 18.0x7.0

+ 9.7

A299

March 23 1

R = 0.395 L = 0.304

-29.9

16. 8x 6.6 17. 8x 6.3

+ 5.9

A 17.5

March 23 |

R = 0.440 L = 0.409

- 7.6

17.2x7.3 20.2x6.4

+ 17.4

A 170

March 23 I

R = 0.620 L = 0.518

-19.7

21.2x7.4 21.4x7.2

+ 0.9

B350

March 23 <

R = 0.464 L = 0.471

+ 1.5

18.5x7.2 22.3x5.8

+20.6

A375

April 12 1

R = 0.684 L = 0.471

-45.2

19.6 x 7.7 19.6 X 0.9

= 0.0

A682

April 12 1

R = 0.600 L = 0.480

-25.0

19.2 X 7.7 19.2x6.2

= 0.0

E423

April 20 1

R = 0.632 L + 0.638

+ 0.9

23.5x6.5 23.2x6.6

- 1.3

326

TESTES OF PIGEONS

327

9

z z

so

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rt

CO

CO

■*

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n

d

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t^

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+

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+

a

(N 10

«K CC

00

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t^ l-H

CO CO

en

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t^ «?

r- 00

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d 10

d CO

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05

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d d

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II II

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si iJ

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to to

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II II

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II II

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II II

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Pi hJ

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t^ to

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to d

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e

55

^

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rt ^

a hj

c; J

a h4

si >J

tf 1-1

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f— t

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V

o

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b.

u

u

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s

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p

o

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s

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W

TESTES OF PIGEOXS

329

TABLE 25 Weights and measurements of testes of adult generic hybrids dead of disease

PER 1

PER

so.

DATE

DISEASE

WEirm' "=" °*' I.EKGTH AXD "^"^^ DIFFEB-i WIDTH 1 EKCE I

CENT OP

DIFFEB EXCE

881

May 25

Liver and (

R = 0.36.5

17.2x6.2

spleen \

L = 0.310-17.7

14.9 X 6. 2

-15.4

443

June 8

Sp., li., me. <

R = 0.035

L = 0.037+ 5.7

7.1x3.1 7.1x3.1

= 0.0

888

September 16

Sp., li.. i)eri

R = 0.210

13.7x5.5

card. \

L = 0.215

+ 2.4

15.3x5.4

+11.6

375

October 6

Hemorrhage <

R = 0.324 L = 0.441

+ 3.6

17.2x6.0 21.5x5.7

+25.0

773

October 15

Sp., li. 1

R = 0.016 L = 0.019

+18.7

6.6x2.1 6.7x2.0

+ 1.5

253

October 15

Old age ? '

R = 063 L = 0.067

-f 6.3

9.0x3.8 10.0x3.8

+11.1

522

October 16

(Cause ?) 1

R = 0.018

L = 0.020+11.1

6.4x2.2 6.8x2.3

+ 6.3

207

November 9

Sp., liver i.

R = 0.090 L = 0.098

+ 8.9

8 8x5.5 10.0x4.8

+13.6

466

December 5

Li., lu., sp. ',

R = 015 L = 0.018

+20.0

5.5x2.4

4.4x2.8

-25.0

599

February 10

Sp., li. 1

R = 0.051

L = 0.050- 8.0

7.6x2.3 7.7x2.5

+ 1.3

A363

February 14

sp.,ii. 1

R = 0.377

L = 0.300-25.6

17.6x6.0 16.8x5.7

- 4.7

A88

February 25

Sp., Uver <

R = 0.027

L = 0.028+ 3.7

7.1x2.3 7.8x2.3

+ 9.8

B391

March 7

Sp. -[

R = 0.027

L = 0.027 = 0.0

6.6x1.9 7.6x1.8

+15.1

A17

March 25

Sp., lu. 1

R = 037

L = 0.031 -19.3

8.0x3.7 10.0x2.5

+25.0

THE AXATOUICAI- RZCOKD, VOL. 14, NO. 5

330 OSCAR RIDDLE

data, collected between May 1 and October 25, is shown by the summary" given in table 28.

The numbers concerned in this summary are smaller than those found m tables (summaries) 1 and 26. They include weighings of only 102 pairs of testes. But here, as in both of those groups of data, it is found that : (a) The healthy birds of pure species show fewest larger left testes (reversals); (b) the generic hybrids (widest cross) show most reversals ; and (c) specific hybrids and tri-specific hybrids show intermediate numbers of reversals. Of the birds dead of disease, the generic hybrids again show the greatest proportion of reversals. The common pigeons are second in this respect.

There are available, therefore, three separate accumulations of data on the effect of degree of hj^bridity — or width of cross — on the number of size reversals of the two testes ; these would seem to establish the fact that the number of these reversals increases with the width of the cross. This fact becomes of much significance when joined with two other facts. These are, first, that a male dove which bears testes 'reversed' in the order of their size, is like a female and unlike a normal male in this respect; for, in the female the left ovary is always the larger ovary, and is normally the only gonad to persist beyond an early point in life. The second fact is that it is in these same generic (and familjO crosses where, by the wide cross, males can be made to arise from female-producing eggs. Finally, the three facts stand in such relations as to give support to the conclusion elsewhere stated by the writer, that the sex of doves and pigeons has been experimentally controlled. The testes measurements of the generic hybrids indicate, as do other lines of study, that a bird whose sex has been reversed usually retains one or another identifiable characteristic of the opposite sex; that is to say, such an adult is likely in some manner to betray the initial sex tendency of the germ from which it arose. In the present case, the gonads of the male may assume the size relations of the female.

"It is thought that suflioipiit details of the weights and mca.siiremonts are supplied by the preceding tables. Measurements were made of only a part of this group of gonads and these too are omitted from the table.

TESTES OF PIGEONS

331

TABLE 26 Classified summary of weights and measurements of testes

CLASS

STATE

WEIGHT RELATIONS

LENGTH RELATIONS

L +

L =

1

4

5

2

' 5

5

1

1

1 1

2

4

10

15

L 3

22 13

38

61 61

16 49

65

36 6

4 28

159 72

34

L +

17 17 10

44

20

42

62

35

14 38

87

25

25 8

10

42 122

58 ?fiO

L =

4

1

5

5

S

8

19

2

21

1

■ 2

3

2 2 1

5

■ 6 9

42

L

Healthy (young)

s

3

5

6 6

7 9

12

12

10 9

19

10

■ 7

Pure species <

8

Total

■'5

Healthy (youne)

?3

?/,

Tri-specific hybrids' '

Total

47

Healthy (young)

fil

/,

Specific hybrids \

18

Total

83

Healthy (young)

4

i?7

Cnmrnnn pigeons

4

Total

35

Healthy (young)

q

H

Generic hybrids \

3

Total

?0

32 19 51

70

Total diseased adult . . .

33

Grand tota} (+ juv .)•

'>}0

Closely related species (see text).

332

OSCAK RIDDLE

TABLE 27 Condensed summary of previous and present data'

Pure species.

Common pigeons .

Specific hybrids.

Generic hybrid.s.

Total healthy.

Total diseased.

Grand total.

BATIO:

L+ :L

1: 15.0

1: 5.3 1: 3.7

1: 4.5 1: 4.4

1: 4.3 1: 2.4

1: 1.5

Healthy.. Diseased.

Total.

Healthy.. Diseased .

Total.

Healthy.. Diseased.

Total .

Healthy.. Diseased.

Total.

L+L= L-L+L=L

WEIGHT ! IXXGTH HELATIONS I BELATIONS

2 12

14

17 2

19

8 17

1 30 34 10 44 24

74 58

11

1

63 26 14 2

25

10 16

26

37

47

84

77 28

35 57 73, 52

22

1 1

2

10

26

36

21 10

31

31

14

45

72 22

108 109

24 32 16: 12

4o| 44

152 149

147 90

299 239

94

17 9

26

141 8| 55 43196

were

X yi weights and measurements for tri-specific hybrids are ""^^"^d' JJ^^^ not represented in the earlier data which are here comoined with the data not represente t^-specific hybrids data are available for

Of

of the present paper v.. .^.o. f' r^l i^ i."io2, while this ratio for pure brids) are very closely related ones (as noted elsewhere).

TESTES OF PIGEONS

333

TABLE 28

Additional classified weight relations of testes of pigeons, dead or killed between

May 1 and October 25, 1917 (after all the birds of the preceding tables;

the individual iveights and lengths are omitted)

Pure species.

Specific hybrids.

Tri-specific hybrids.

Common pigeons

Generic hj'brids

Totals (102 birds)

WEIGHT RELATIONS

L +

14

3 3

6 4

1

22

10 8

15 17

4 2

66

SUMMAEY

The conclusions of our earlier paper on the normal size relations of the right and left testes of pigeons are confirmed b}^ much more extensive data. In healthj^ adult doves and pigeons the right testis is larger than the left in a very high percentage of cases. The left testis, in a high percentage of cases, is absolutely longer and thinner — more nearlj' the shape of the single persistent (left) ovarj- of the female — than is the right testis; it is relatively longer and thinner in probably nearly all cases.

The other conclusions of the earher paper are also confirmed:

(a) The left testis more nearlj^ approaches the shape which is characteristic of the 'single' left ovary than does the right.

(b) In disease — particularly in tuberculosis — the testes undergo extreme atrophy (often 90 to 95 per cent); the reduction is greater in the right than in the left testis; the ovary probably suffers no reduction whatever.

334 OSCAR RIDDLE

Further investigation has shown that the right testis of veryyoung (embryo to few weeks) squabs, contrary to the situation in the adults, is normally longer than the left.

The single (persistent) left o^'ar^' of j'oung female squabs is twice or more than twice as long as is either testis borne by males of similar age (3 to 7 weeks).

In hybrids the normal size relations of the two testes is disturbed ; the sex ratio is also disturbed in hybrids (see first citation under note 4). Some hybrid males bear gonads whose size relations are those of normal females; and the disturbance of the sex ratio in hj'brid birds is knowTi to consist in the production of an excess of males. These facts are probably interrelated.

The number of h3-brid males wliich exliibit gonads with the size relations 'reversed' (or, as in the normal female) increases as the width of the cross from which the hybrids originate increases. The excess of males from such crosses in birds is known to increase similarly (see first citation under note 4).

Disproportionately large numbers of males with reversed size relations of the gonads have been found among generic hybrids of doves and pigeons. The generic crosses which produced these hybrids j'ield the greatest excess of males. The application of the principle stated here to the several individual cases of generic hybrids, whose origin from female-producing eggs is otherwise suspected, will be made in a full and complete account of our studies on the control of sex in pigeons. The results support the conclusion that sex has been controlled in these forms, and that a male which is forced to arise from a female-producing egg may show in the relative size of its gonads an approximation to the relative size of the gonads of a female.

ATTTHOB 3 ABSTBACT OF THIS PAPER ISSUED BT THE BtBUOGBAPHIC SEBTICE, MAT 4

n

A PROBABLE CASE OF SUPERFETATIOX IX THE COW

>LVRY T. H-AiliLVX

Department of Zoology, Kansas State Agricultural College

Recently the writer (Harman, '17) reported a case of superfetation in the cat.- Since that time a student of hers has called attention to a condition in the cow which may be interpreted as superfetation.' A brief account of it follows.

A cow owned bj- ^Ir. Reppert was mated on December 22, 1 917. -Aiter she was taken away from the bull, she was kept in a small lot, and there was certainly no opportunit}- for a second mating until ^Slay 15, 1917. when she was removed from the lot to the pasture. In fact, there was hardly a probabihtj- that copulation could have occurred. However, for a short time she was with a number of other cattle in a pasture, but no males were among them. On September 27. 1917. she gave birth to a heifer calf, normaUj- developed and slighth' above the average in size. On October 1. she gave birth to another calf, which, according to the decision of the veterinarian, was a little more . than a four months' fetus. This second calf was inclosed in the amnion and the placenta was in good condition. The calf was dead when it was born, but had the appearance of ha\*ing been dead for only a very short time, as there was no indication of decay. During pregnancy the cow seemed to be normal in everyway, having a normal ajjpetite and gave milk up untU about six weeks before the birth of the first calf, .\fter the birth of the

' Contribution from the Zoological Laboratory, Kansas State Agricult iral College, no. 21.

- Harman, Marj- T. A case of superfetation in the cat. Anat. Rec, vol. 13, no. 3.

' I wish to express my indebtedness to Mr. R. R. Reppert, a graduate student, for calling my attention to this case and for giving me the data concerning it.

335

336 MARY T. HARM AN

first calf the milk flow was good, and the birth of the second calf was a surprise to the man in charge.

Certainly there was in the uterus at the same time two embryos of widely different degrees of development. Whether or not the second embryo began its development after the first one or simultaneously with it is a problem. It seems, however, that if it should be a case of retardation of development the placenta would ha^'e given evidence of a lack of blood supply, or the embryo would ha\e shown some degree of decaj^ from ha\-ing been dead for a long time. The embryo seemed normal. If it was a case of superfetation, the only chance for a second copulation was at the time that the cow was removed to the pasture, which was a little more than four months from the time of the birth of the last calf. If a second copulation did not take place, and if the eggs were not fertilized at the same time, there must have been a retention of spermatozoa, in the female reproductive organs, as was suggested by Sumner.^ Also, there must have been «ither an ovulation during pregnancy, or, as was suggested by Harman, '17, the egg was retained in the reproductive organs of the female for a length of time before fertilization, ^^^lethe^ or not this case may be interpreted as a true case of superfetation, or as a case of retarded development, it adds another one to the list of mammals in which the uterus contained embrj^os of widelj' different degrees of development at the same time.

< Sumner, F. B. 1916 Notes on the superfetation and defertilization among jnice. Biol. Bull., vol.30.

acthoh's Ibstract of this paper issued by the bibliographic service may 11

SUPPLEMENT

TO THE PROCEEDINGS OF THE AMERICAN SOCIETY OF ZOOLOGISTS,

PUBLISHED IX THE ANATOMICAL RECORD, VOLUME 14,

NUMBER 1, JANUARY, 1918

DARWINISIM AND NATIONS*

MAYNARD yi. -METCALF

I had thought to ask your attention at this time to some new data which throw Kght upon the origin of the Ciliata, but the suggestion has been made that the various scientific societies, in their meetings, give some attention to problems connected with the great task the Nation has before it in the present war. I have therefore changed my plan and shall speak upon the theme Darwinism and Nations."

Standing as we do in the midst of this great war, we are too near it to see its issues in their true relation and in proper perspective. Yet a few things stand out so boldly that they may be seen without much danger of confusion and false estimate. They challenge our attention and must be faced and thoughtfulh' appraised. There is taking place before us a gigantic experimental demonstration in social life, and students of the evolution of society have such opportunitj^ as has rarely been presented to see great forces ii» strenuous action molding the future of mankind. The truth or falsity of certain claims as to human relations and the evolution of the life of man must surely be made more clear than ever before.

We as zoologists are still further challenged to consider the present phenomena by the strictly biological form in which the

Address of the President of the American Society of Zoologists at the Fifteenth Annual Meeting of that Society, December 27, 1917, Minneapolis, Minnesota. 1

I MAYXARD M. METCALF '

argument of the protagonists of the Central Powers is so often put. German students, more than any others, have carried Darwinism to its logical extreme, with an unhesitating, uncompromising qualitj' that is in itself admirable. The NageliWeismann conception of the continuity of the germ-plasm and the consequent non-heritabilit}- of acquired characters marked a decided advance in our thinking upon evolution and problems of human progress. It furnished a necessarj'^ foundation for studies in genetics and is vital in questions of eugenics which may in time be the central questions of hmnan society. The fact that German scholars are not now taking an important part in studies of genetics should not obscure for us the fact of the great debt geneticists owe to Weismann and his fellow countrj'men.

Human individuals in their endeavor to perpetuate themselves are subject to selection under three forms — natural selection, marriage selection, and social selection dependent upon castes or cliques. The latter two, marriage selection and social selection, are chiefly intranational and do not apply to rivalries between those groups of men we call nations. Natural selection, on the other hand, applies to nations as well as individuals, and German thinkers are right in emphasizing it, though not to the exclusion of all other considerations.

Germany's presentation of her national philosophy and her claims for herself among the nations is too complex for any brief adequate statement, but we may note a number of its salient features: —

Nations, like individuals, are subject to natural selection through the struggle for existence. This struggle must take in large measure the form of war.

In this struggle it is the strong that survive and only the strong deserve to survive.

A nation therefore should conserve and increase its strength in order to take its proper place upon the Earth.

The Germans arc the mightiest and the greatest race and nation, and no considerations should be allowed to stand in the way of their taking their rightful place as the dominant people. The struggle for existence between nations must not be ameliorated but must be allowed to take its full and natural course in order that Germany, mightiest

DARWINISM AND NATIONS 6

of nations, may reach undisputed dominance. Any considerations that would hamper the outworking of this most fundamental law of nature are contrary to natm-e and so immoral. It is natural and therefore is right that the most mighty should come to unrestricted, unhampered rule.

In order to thrust herself forward most effectively in the struggle for existence the nation must do whatever is best for the development of her might. Everj-thing that tends to this end is right; everj-thing that hinders is wrong. The state, perfect in her power, is the ultimate goal and no considerations beyond the state are to be entertained. The state is a law unto herself. She is the source of all law and so is above all law.

I have tried to give a very moderate statement of these items from Germany's presentation of her claims. Ba' quotations from Treitschke, Bernhardi, ^-on Billow, Harnack and many others I could have put each item in much more extreme form, but understatement will do little harm for our present purpose.

Several friends to whom I have read this paper urge me to include the actual citations without paraphrase, and after some consideration I have decided to do this at the close of the paper. The actual words are so vivid that I fear if they were introduced at tliis point thej' would render difficult dispassionate consideraof the ideas we are discussing.

The German argument is in general logical. It presents a philosoph}' of national life and relations which accepts the Darwinian principle to the full and applies it uncompromisingly. If the premises, are correct, I see no escape from the conclusions. But' logic has no necessary relation to truth. We have conspicuous examples of eminent logicians who have failed to convince. Herbert Spencer is such an one. His reasoning is keen, but he seems so to enjoy the processes of his argument that he hastens to them without taking time to scrutinize the premises upon which his reasoning is based, and he is not convincing. The zoologist may think him quite an astronomer; the astronomer may regard him as well founded in geologj*; the geologist maj' think him profound in his knowledge of biology; but few students have the highest regard for Spencer as a thinker in their own special fields. In his "Philosophy of Style," on the other hand, where his data seem sound, his conclusions are convincing.

4 MAYNARD M. METCALF

That logic and factual truth have no necessary relation is clearly shown in mathematics, the purest of pure logic. Mathematics, like all logic, is occupied solely with truth of relation and not at all with truth of fact. Indeed whole fields of mathematics confessedly deal with data falsely assumed. It seems strange that mathematics should ever be classed as a science. Science deals with phenomena, mathematics, and all logic, deal only with relation.

But pardon this digression. We started upon it, I believe, from the statement that the uncompromising logic of the German philosophy is no sufficient indication of its truth unless it be founded upon true data. Shall we examine from this point of view some of the statements and implications in the German argument, with the .purpose of bringing out some of the fundamental relations between groups in human society and some of the fundamental elements in national strength, all of course from the point of view of the evolution of mankind and of societj'?

"Nations, like individuals, are subject to natural selection through the struggle for existence." Yes, sureh^ But this is not a statement of the whole truth. Like individuals, nations can, if they wish, supercede natural selection in large measure by developing cooperation, the principle that obtains to a greater or less degree among all communal organisms.. Human communities, especiall}', have freed their members from much of the stress of the struggle for existence, by substituting cooperation for rivalry in a verj- large proportion of the individual relations within the group. Interdependence between the individuals of the group has been so developed, through cooperation and division of labor, that cooperation may perhaps fairly be said to transcend natural selection as an influence upon the life of highly civilized man. The higher the development of human society, the more dominant becomes the principle of cooperation. Only in the most primitive communities can there be an approach to unrestricted natural selection. Indeed we know today no such human societies, and it is probable that this stage of social evolution was already passed before man's ancestors became truly men.

DARWINISM AXD NATIONS O

Not only has human society toda}' substituted cooperation for natural selection, in large measure. We are beginning to see more clearly the biological and social possibilities in eugenics, and future human society is altogether likely to relegate into desuetude the laissez faire principle of unrestricted selection among men.

As between individuals, so also between groups, between nations, it is possible to substitute cooperation for selection to a very considerable degree, and the question of the desirable extent of such substitution is one of the most important of social problems.

"In the struggle for existence it is the strong that survive and only the strong deserve to survive." Again yes, but we must carefully' definite the word strong as here used. We need to remember not only the point just made, that rivalry is not the only principle and that cooperation and ri\'alry are coordinate principles in international relations. We must remember as well that national strength cannot be assumed to be only phj^sical might or such power as is useful in unrestricted rivalry. Other forms of strength, strength of character, moral strength, strong emotional sjTiipathies, a genuine sjTiipathetic kindly feeling toward all sorts and conditions and races of men and an ability to understand them and their points of view, may tend to promote cooperation and may well be the greatest assets of a nation phj^sicalh^ and intellectually sound. This may well be the type of national character toward which we must move in order to reach such international relations as will bring man to his fullest development. Humanness, with a degree of natural humility, an ingrained altruism, may be the culminating quality in that strength which is most real and effecti\-e.

"A nation should conserve and increase its might in order to take its proper place upon the Earth." Yes, but here again might nfeeds defining. Pln-sical and spiritual strength both need to be considered.

"The Germans are the mightiest and the greatest race and nation, and no consideration should be allowed to stand in the way of their taking their rightful place as the dominant people."

b MAYNARD M. METCALF

In developed power in a military way, including that organization of the people which is necessary to give the fullest support to the army and navy, Germany surely led the world. Of her potential power, compared to that of the British Empire, France, America, or Russia, we must speak with less confidence. But with all her developed military strength, German}^ has shown a surprising spiritual difference from other peoples, and this somewhat unique character needs scrutiny in making any estimate of her national power. To this point we will return.

Her philosophy of the state as the world unit, her teaching that the state is ultimate and that duty to the state is the final duty, her claim that the state is the source of all law and is therefore above all law and not subject to it, is based upon assumptions that need exanaination.

It might be possible to organize world society upon the basis of the nations as rival rather than cooperating units, but such a plan consistently carried out would give not world society but international anarchy, at least until such time as one state should have become sovereign for the whole world. Just as in all smaller social communities selection is ameliorated by cooperation, and as intracommunal society is possible only is so far as cooperation is developed, so between nations world society is possible only to the extent to which cooperation is developed. ^^'ithin the community rivalry has been restricted and controlled and the struggle between individuals restrained by the development of law. Cooperation between the individuals of the community, and not the dominance of a single individual, is the plan of organization that has developed in all human communities, and the degree of development of cooperation and restraint of struggle seems a fair measure of the advancement of the civilization of the community. It might be possible to have a group of human beings among whom the freedom of the struggle was unrestricted. This probably would lead to the complete dominance of one individual in each group. But human social evolution has not taken this direction. Communities of almost this type are found among some of the gregarious feral Ungulata, but not among men.

DARWINISM AXD XATIONS 7

It is difficult to see anj- reason for believing that such a relation between nations would be possible for the world as a whole and would work out for human welfare. The presumption seems to favor a world society organized upon much the same plan as that^ which has everj-nhere developed in and between lesser communities, that is, a community of nations, with highly developed cooperation and with the %'iolence of rivalry restricted by law founded upon sanctions of moral and physical force by the whole commimitj' of nations. The evolution of human society has been mo^Tng in this direction and recent events seem to be greatly accelerating such development. The German conception of the nation as the ultimate unit, with unrestricted struggle for sur\4val between these several national units, until one becomes dominant and absorbs the others, seems to be contrary to the whole current of social evolution, and its realization seems most improbable.

If a world commimitj', and not the indi\-idual state, is the ultimate unit of social cooperation, of course the German conception of the state as the ultimate source of all law is false, the ultimate source of all enacted law being really the world communit}' of nations, and the ultimate sanctions of such law being world sanctions, not national sanctions.

Let us further consider this point so frankly and so strongly lu-ged by recent German social philosophers, namely that the state, being the ultimate source of law, is itseK above all law. There are two great assumptions in this statement, and each deserves examination: — first, that the state is the ultimate source of law; second, that as it is itself the source of law it is above the law and not subject to it. Both statements I beUeve to be fallacious. Even leaving out of account the thought of a world communit}' and its laws, the German conception of the state as the source of law is partial and inadequate. The state is the mechanism for enacting law and might be called the source for legal enactments. But so much of law as has the sanction of truth and its final authority, rests not upon the state but upon the imderh'ing reaHties. There are phj'siological laws, if we mav so call them, whose authoritv transcends all state enact

8 MAYNARD M. METCALF

ments, there are similar economic laws, and there are moral laws far more vital in human relations than any national enactments. The state is not the source of fundamental law, that which the British name "the common law." Onlj^ the enacted forms for the outworking of the principles of this bcjdy of fundamental law are dependent upon the state. Truth itself is the ultimate source of all fundamental law, and human enactments will constantly change as men reach fuller appreciation of the realities of relation that underhe human intercourse. The state is but a means for assisting the citizen to conform to the fundamental reaUties. The statement of the Prussian cult, that govermnent is the source of all law and so is above all law, as President King has so well said.^ "cannot be thought through for the government of God himself," whatever definition we may take of the concept "God." God is not the source of moral law. The source of moral law is truth itself. Truth is. It is not derived. It exists not because of any enactment by God or man, but in itself, and it is the ultimate source and sanction for all law.

If it be true that there is this great bod}' of fundamental law, resting upon the realities in human character and human relations, there seems no distinction between individuals and nations in responsibility to this body of essential, self-enacted law. No man, and no group or association of men, industrial, social, political) national, or world-communal, is above such law or free in any degree from obligation to it. It seems, indeed, most strange that any group of men could e\'er' convince themselves that they were, as a group, free from this obligation, and it seems still more strange that they could declare this freedom in so shallow a formula as the statement that "the state is the source of law and so above the law."

Among the most important of the truths of human nature and affecting human relations are those that emphasize the human capacity for well-being and the privilege of promoting human welfare, a privilege and an obligation. These truths are as real as the phenomena of mass and mass attraction between

DARWINISM AXD NATIONS 9

material bodies, or any other physical natural phenomena and relations. They are an essential part of natural truth, and as such must be conformed to by anj- man of true scientific spirit. To disregard them is scientific dishonesty and dishonor. It is equally unscientific for an individual or for any group of individuals.

In view of these considerations can it truly be said that "the Germans are the mightiest and the greatest race and nation"? Is it not rather true that among the highly developed peoples they are somewhat unique in the degree of their failure to perceive that body of scientific truth which we commonh' call moral, that in reality they are in this regard either a naturallj' deficient people or an undeveloped people, a people mediaeval in their character as they are in their governmental institutions?

It is peculiarly difficult to determine whether national and indi^'idual qualities are, in any instance, due to inheritance or to education. Qualities due to nurture may become, after long training, so firmly established and so highly developed as to appear natural to the stock itself. One must always walk cautiously in this field and not condemn, as inherently defective, stock that is capable of restoration by reversing the evil education.

In this connection there is one consideration, to which I have elsewhere referred,- which merits attention. "A race, a nation, makes itself; it is not made or molded chiefly by outside influences. Nations are what they have made themselves." The Germans, while always much given to philosophy, have never shown interest in moral philosophy'. "German}' has never had a Carlyle, an Emerson, or a Lincoln, and this lack is no accident. John Knox, Carlyle and Lloyd-George are the product and the sign of the British fighting sense for justice. Bismarck and Goethe, with their marked lack of interest in the moral aspects of statecraft and philosoph}', seem as truly characteristic of the German people." One must speak with some hesitation, for such judgments are peculiarly liable to error, but it surel}^ seems that the somewhat unique German lack of interest in the philosophy of

THE ANATOMICAL RECORD. VOL. 14, NO. 5

10 MAYNARD M. METCALF

morals and the moral qualities of conduct, must be due to inherent racial character.*

But whatever its source, this deficiency makes imtrue the statement that ' ' the Germans are the mightiest and the greatest race and nation." They fail to conform to those fundamental scientific realities which we commonly call moral, and this failure renders them peculiarly unadapted in an environment in which there is a gradually increasing appreciation and realization of moral relation between nations. If it be true that cooperation is increasingly to replace unrestrained rivalry between nations, and that this cooperation is to conform to the moral realities, then Ciermany's deficiency makes her peculiarly unfitted for the life that is to be. Lack of adaptation to environment, unfitness for life as it has to be, is not strength but weakness. It seems, therefore, that the Germans, instead of being the "mightiest and greatest race," are really quite unique in their unfitness.

In general intellectual development the Germans stand among the stronger peoples. They have had one or more preeminent and several major musicians. They had in Goethe one of the world's great poets. Kant is one of the strongest of philosophers, but his mother was Scotch. In social philosophy they have not reached beyond the ideal of economic efficiency and so have given no world-leaders. In astronomy and physics they have no rivals of Galileo, Keppler and Newton, but show a number of strong men of second rank. In zoological science they cannot equal Darwin and Pasteur, but in chemistry they show many of the ablest scholars. In invention, of course, they do -not rival America, and in recent work in physics, biology and medicine Germany is hardly keeping pace with Britain and America. In general one may say (ierman scientists ha\-e shown great diligence, much talent and some genius. In music, painting and

Kant indeed emphasized the categorical imperative in his philosophy, but three things should be noted: 1) that Kant's philosophy was purely abstract; 2) that it has never registered in German social life, and 3) that Kant was himself half Scotch in descent and more than half Scotch in intellectual type. Luther placed his chief emphasis >ipon faith, and while he preached personal righteousness, it is not this part of his message that has passed into German life. His infiuoncc, as seen today, is more eclesiastical than vital.

DARWINISM AND XATIONS 11

sculpture Germany now shows little inspiration. In the whole field of intellectual life she has had her full share of able men and has given the world a few great leaders. There is no marked intellectual lack in German}', except her failure properly to evaluate moral phenomena, and her self-centered qualit.v resulting in a remarkable inability to understand the psj'chology of other peoples.

Were there time it would be profitable to consider the historical evidence that the attempt to dominate the world by force, even when apparently successful, has not only always pro\-en abortive after a rather brief period, but has destroyed the people who followed the false hope. Judging by the past, this hope of forcible dominance might be taken as a sign of decadence and approaching elimination. In the opinion of the writer, German triumph in the present war would be the surest and probably the shortest road to the destruction of Germanj'.

Any thorough discussion of German racial qualities would be appropriate to a meeting of anthropologists and ethnologists rather than zoologists, and I shall not attempt to carry it much further. We may, though, note, before leaving this phase of the subject, that the German people seem to be of mixed stock. The South German is round-headed and of moderate stature; the North German is narrow-headed and of greater stature. If the word "Teuton" is to be applied at all, it cannot well cover both of these stocks. It seems better limited to the northern type, though in this northern stock there is admixture of Slavic blood.

There seem quite clear psychic differences, as well, between the two divisions of the German people. Dickinson writes:' — "It is significant evidence of the two Germanys that not one of the great German composers was a Prussian. Bach was a Thuringian; Mozart was Bavarian; Haydn an Austrian citizen, probably a Croat; Beethoven was born in Bonn of Flemish descent, on his father's side; Weber, although born in Holstein, was an Austrian; Schubert was an Austrian; Schumann was a Saxon; Mendelssohn was a Jew, born in Hamburg; Wagner was a Saxon; Brahms was born in Hamburg, of Saxon descent."

12 MAYNARD M. METCALF

Practically the same thing is true as to German painters, sculptors, men of letters and philosophers, and among German scientists there is great preponderance of men from South and ^^'est Germany. Indeed ex-chancellor von Billow writes:^ — "German intellect had already reached its zenith without the help of Prussia. German intellectual life is predominantly the work of the South and West, achieved under the protection of her princes, small states and free cities. But the people who lived in the sandy soil of the Mark, in the plains east of the Elbe and .the Oder, so scantily favored by nature, during the centuries which witnessed the growth of German culture in other parts of the country, prepared the future of Germany as a state in battles and privations under the rule of heroic and politic kings. German intellect was developed in the West and South, the German state in Prussia. The princes of the West were the patrons of German culture; the Hohenzollern were the political leaders ai^d taskmasters." And further — "Prussia this rude and thoroughly prosaic state of soldiers and officials." These quotations bear the more weight when we remember that von Billow is himself a Prussian Junker. All who have lived in Germany know that Gemulhlichkeit is a southern and western quality and not Prussian. Yes, the spiritual distinctions are probablj' more marked than the physical differences between the Northern and Southern Germans.

If cooperation is destined to come in larger and larger measure in the world-community, and national selfishness is to give way in considerable degree to international helpfulness, then the qualities von Billow emphasizes as most marked in the Prussian will be at a discount. IMilitary genius will have to turn to other channels for its exercise, and state-centered statecraft must give way to a broader-visioned recognition of general human welfare. Sympathetic realization of human needs, founded upon a kindly appreciation of human character, must underlie statesmanship in the world community. It seems that so much of contribution to the larger wcrld-life as is to be expected from Germany, is likely to come chiefly from the Southern and Western Germans. Freed from their present obsession

DARWINISM AXD NATIONS 13

with the Prussian cult of abnormal exaltation of the nation, maj- the}- not perhaps return to something of the mellowness evidenced in their music, in some of their philosophy and literature, and in the childlike beauty of their folk-life? But to gain their freedom from Prussian dominance may prove a most difficult thing. They have been long trained to obedience rather than manly independence, and they are of a stock to which such training has been possible. There is in the Prussian Junker a true devotion to an ideal, and the inadequacj' and utter unworthiness of this ideal should not blind us to the possible value of the quaUty of devotion. If the more human element among the Germans could be redeemed and developed and could bring Germany to more normal spiritual life, the long training in devotion to the nation might be utilized to energize the new and sounder purposes. But who can look with confidence to any such result?

Efficiency recently has been the German ideal and has been increasingly emphasized for more than a generation. But efficiency is in itself no worth}- goal. It is but a means to an end. I think the world is becoming a bit wearj- of that efficiency which is measured in manufactured products and stored wealth. That is true efficiency which makes for human well-being. That is real efficiency which promotes not abundance of goods, but abundant life, and the chief satisfaction in Ufe is not in comforts and ease, but in the fun of the game and the pleasure of fellowship in the plaj'ing of it.

Some of us look with a degree of hope to the time when those high and fine qualities which count in the game and its joy shall so appeal to the souls of men that marriage selection, both voluntary and under communal guidance, will gradual!}^ breed into humankind the strength and beauty that shall increasingly underUe the developing and perfecting world-community. In that day, if it comes, I think men will look back upon the German culture, or rather the Prussian cult, of the present generation, as a strange aberration.

But returning to the phenomena of the present war: — one thing seems to stand out most clearly, namely, that the moral

14 MATNABD M. METCALF

sense of mankind, if outraged, is a mighty factor in determining success in the struggle between nations. Germany's failure to realize this fact has cost her dear. She has failed to conform to this salient feature of her environment and must reap the result of her unfitness for life as it is in some of its most fundamental aspects. The awful demonstration of the inviolability of moral truth, as of all other truth, may prove in the end to be worth far more than even its fearful cost.

For our own nation and for all others, the lesson is emphasized that for the development of real national strength, conformity to natural law is essential, and of the categories within this great body of fundamental law that group which we call moral and spiritual is not of secondary importance. Conservation of our national resources must include promotion of moral strength and of understanding sJ^npath.y with humanitj'.

I will now read citations from different German writers, to show that ni}^ statement of the German position was very moderate.

First as to German preeminence: —

The present German emperor (1914), from a proclamation to the Armj^ of the East: "Remember that you are the chosen people." Again from the emperor:'* — "The greater Germany which some day must dominate all Europe."

From Professor Lasson: — "We are morally and intellectually superior to other nations: we are without equals."

Die Zukunft' (1901): — "After all, it is obviously the meaning of history' that the white race under the leadership of the Teutons, should attain a real and definite domination of the world,"

Fritz Bley** (1897): — "We are the most capable nation in everj^ field of science, in every branch of fine arts."

Ernst Haeckel'*: — "One single highly cultivated German warrior of those who are, alas, falling in thousands, represents a higher intellectual and moral life value than hundreds of the raw children of nature whom England and France, Russia and Italy oppose to them."

Adolf Grabowsky" (1914): — "Today nothing is more urgent than this — that the will to conquer the world should take possession of the whole German people."

DARWINISM AND NATIONS 15

Lud^-ig Woltmann, Politische Anthropologie" (1903): — "The most distinguished men in modern spiritual history were for the most part Teutons of the full blood, such as Diirer, Leonardo da ^'inci. Gahleo, Rembrandt, Rubens, ^'an Dyck, Voltaire, Kant, Wagner. Others show an intermixture of the brunette race .... as in the case of Dante, Raphael, Michael

Angelo, Shakespeare, Luther. Goethe, Beethoven

Dante, Raphael, Luther and the others were geniuses not because of, but in spite of their mixed blood. Their endowment

was an inheritance from the Teutonic race The

entire European ci\-ilization, even in Slav and Latin countries, is

the work of the Teutonic race The Teutons are the

aristocracy of humanity "\Mioever has the characteristics of the Teutonic race is superior The cultural

value of a nation is measured by the quantitj' of Teutonism it contains."

Lieutenant Karl A. Kuhn" (1914):— "Kultur must build its cathedrals on hills of corpses, seas of tears, and the death-rattle of the vanquished." The mixed metaphors do not hide the thought.

Natural selection among nations

Bismarck:'- — "Not bj^ speeches and resolutions of majorities are the great questions of the time decided, but by iron and blood."

Xietsche:" — '"Ye shall love peace as a means to new wars, and the short peace more than the long."

Lasson:'^ — "Separate states are therefore by nature in a state of war with each other. Conflict must be regarded as the essence of their relations and as the rule, friendship as accidental and exceptional."

Ernst Hasse'° (1908): — "The worst of hj^Docracies is the participation of Germany in the Hague conferences."

Treitschke :'" — "The erection of an international court of arbitration as a permanent institution is incompatible with the nature of the state. Only in questions of second or third importance could it in any case submit itself to such a court of arbitra

16 MAYNARD M. METCALF

tion The living Ciod ^Yill take care that war shall always return as a terrible medicine for the human race

We have learned the moral majesty of war precisely in those of its characteristics which to superficial observers seem bestial and inhuman."

Bernhardi (1914):" — "The efforts directed toward the abolition of war must be termed not only foolish, but absolutely immoral, and must be stigmatized as unworthy of the human race. The weak nation to have the same right to live as the powerful and vigorous nation! .... War is a biological necessity of the first importance. .... War gives a biologically just decision."

Otfried Nippold (1913) r'^—" .... war is not only from the biological and true kultural standpoint the best and noblest form of the struggle for existence, but . . . ."

Power the goal for a nation

Lasson:'^ — "Kultur exists for the purpose of making itself effective as power."

Treitschke:'^ — "The state is first of all power to assert itself. . . . . Hence the obvious element of the ridiculous that

attaches to the existence of small states The whole

development of our company of states [the five great powers] aims unmistakably at ousting the states of second rank."

From a petition by 352 German professors in favor or annexations (1917): — "No policy of kultur without a pohcy of power."

Daniel Frymann (1912):" a propos Belgium and Holland: — "For today only those states can assert a right to independence that can secure it sword in hand."

Germany above moral obligations

The present emperor, in a speech to the Chinese Expeditionary Force, July 27th, 1900: — "You know very well that you are to fight a cunning, brave, well armed and terrible enemy [the Boxers!]. If you come to grips with him, be assured quarter will not be given, no prisoners will be taken. Use your weapons

DARWINISM AND NATIONS 17

in such a way that for a thousand years no Chinese shall dare to look upon a German askance. Be as terrible as Attila's Huns."

Lasson:'^ "In the intercourse of state with state there are no

laws, and there can be none A war may be waged

for political interests, but never for an idea Between

states there is but one sort of right — the right of the stronger. . . In the relations between states this right of the

stronger may be said to be moral There is no legal

obligation upon a state to observe treaties. ... A state cannot commit a crime. Treaty rights, are governed wholly by considerations of advantage."

Pastor Baumgarten :'" — "Anyone who cannot bring himself to approve from the bottom of his heart the sinking of the Lusitania .... and give himself up to honest joy at this victorious exploit of German defensive power — such an one we deem no true German."

Professor Oswald Flamm (1917):-' — "If neutrals were destroyed so that they disappeared without leaving any traces, terror would keep seamen and travellers away from the danger zones."

Otto Richard von Tannenburg- (1911): — "A policy of sentiment is folly. Enthusiasm for humanity is idiocy. Charity should begin among one's compatriots. Politics is business. Right and wrong are notions needed in civil life only. The German people is always right, because it is the German people and because it numbers 87,000,000."

Maximilian Harden-' (1914), one of Germany's most independent thinkers: — "Germany is striking. Who gave her leave? Her right is in her might."

Karl Peters-^ (1915): — "It is foolish to talk of the rights of others."

Thomas Mann'* (1914): — "Kultur is above morality, reason, science."

Lieutenant Karl A. Kuhn (1914): — "The power of the conqueror becomes the supreme moral law to which the vanquished must submit."

Clausewitz," the great teacher of modern Germany: — In war

18 MAYXAED M. METCALF

"the errors which proceed from a spuit of benevolence are the worst."

General von Hartmann:"" — "Military action .... in

its procedure is completely ruthless Recognize no

other law than that of mUitarj- necessity.'"-'

Bernhardi:" — "Might is at once the supreme right."

M. Stirner:-' — "\^Tiat does right matter to me? I have no need of it. "\Miat I can acquire bj' force, that I possess and

enjoy I have the right to do what I have the power

to do."

Rudolf Theuden fl914) :'" — "In international relations magnanimity is wholly out of place For the will of the state

no other principle exists but that of expediency, . . .selfishness, .... farseeing, shrewdly calculating selfishness."

Also a number of quotations to shoiv that these conceptions are not merely academic, but are put into practice.

From an official placard in Belgium:" — "In case any of the inhabitants fire upon soldiers of the German army, one-third of the male population will be shot."

General von Biilow;^- Belgian proclamation: — "^Yith my authorization, the general commanding these troops has reduced the town to ashes and has had 110 persons shot."

General von der Goltz, in a proclamation in Brussels (1914) :" — "In future the inhabitants of places situated near railways and telegraph lines which have been destroyed will be punished without mercy, whether thej" are guilty of this destruction or

not The hostages "[that have been taken in all

such places]" will be shot unmediately."

From the orders of the day by General Stenger, commander of the 58th Brigade, August, 28, 1914, in France: — "Beginning with today, no more prisoners are to be taken. All prisoners are to be put to death. The wounded, whether armed or not, are to be put to death. Prisoners, even when they are organized in large units, are to be put to death. Xo living man is to remain behind us."

DARWINISM AXD XATIONS 19

Then two quotations to show that such orders were carried out

From a letter by a noncommissioned officer of the lo4th Infantrs'. published in a Silesian paper under date of October 1914, being an account of fighting in France:'^ — "No quarter is

given The wounded are hammered and stabbed.

^Miether they are slightly or mortall}^ wounded,

our brave musketeers save the fatherland the costly care of numerous enemies."

From a letter to his fiancee, by a Bavarian soldier, Johan Wenger (191.5):'° — "T have also bayonetted a good number of women. During the battle of BudonwiUer, I did away with four women and seven young girls in five minutes. The captain told me to shoot these French sows, but I preferred to run my bayonet through them." ^Miether this soldier did as described, or was only boasting of a noble deed to which he coiild not honestly lay claim, makes httle difference in its bearing upon the point under consideration.

I feel I almost should apologize for reading to you such citations, those from the emperor and all through the Ust, but the facts must be faced.

Finally in regard to racial qualities

A single quotation from the poet Goethe: — "The Prussians are cruel by nature; cixdlization will make them ferocious."

Thft Orchard Laboratory,

Oberlin. Ohio.

December 10, 1917

CITATIOXS

' Henry C. King: "'Grounds of Hope in the Changing world Order," 1917.

^ !Maynard M. Metcalf: 'The Problem of Germany," Xew York Times, Sunday, September 16, 1917.

'Edward Dickinson, quoted by John Burroughs: "A Dual Germany," New York Times, April 19, 1917.

^ "Imperial Germans."

' From a proclamation of June 5, 191.5.

'From a letter published in "The .\msterdammer, " October 11, 1914.

' September 7. 1901.

' "Die Weltstellung des Deutsehtums."

20 MAYNARD .M. METCALF

' "Ewigkeit: Weltkriegsgedanken," 1915.

'" "Das Xeue Deutschland." •

" "Die Wahren Ursachen des Weltkrieges."

'- Addressed to the military committee of the Prussian Chamber of Deputies, 1862.

"Thus Spake Zarathustra," translated by Common, 1911.

" "Das Kultur und der Krieg."

'* "Die Zukunft des deutschen Volkstums," 1918.

'« "Politik."

" "Germany and the Next War," translated by Powlcs, 1912.

" "Der deutsche Chauvinismus."

" "Wenn ich der Kaiser \V:ir." 1912.

-" "Deutsche Reden in schwerer Zeit," No. 25.

-' Die Woche, quoted in New York Times, May 15, 1917.

-- "Grossdeutschland: Die Aufgabe des zwanzigsten Jahrhunderts. '

23 Die Zukunft.

" "Not und Weg."

2' Neue Rundshau, November, 1914.

-« "On War."

" "Militarische Notwendigkeit und Humanitat, in "Deutsche Rundshau," xiii, 1877.

2« Idem, xiv, 1878.

-^ "Der Einzige und sein Eigentum."

'" "Was uns der Krieg bringen muss," 1914.

" Hasselt, Belgium, August 17, 1914.

'- Liege, Belgium, August 22, 1914.

" Brussels, Belgium October 5, 1914.

'* Jauersches Tageblatt. October 18, 1914.

'=■ Dated Peronne, March 16, 1915.

AUTHOR S ABSTRACT OF THIS PAPER ISSUED BT THE BIBLIOGRAPHIC SERVICE. MAY 4

SYMPOSIUM

THE TEACHING OF ANATO:\IY AND THE INCULCATION OF SCIENTIFIC METHODS AND INTEREST

Given during the thirty-fourth sessio7i of the American Association of Anatomists, University of Minnesota, December 27, 1917

the value of the roentgen-ray and the living

model in teaching and research in hu:\ian .\a'ato:\iy

C. R. BARDEEN

University of Wisconsin

The practical value of roentgenology in clinical work has led to extensive studies of the structure of the body as re\'ealed by variations in tissue density. New light has been thrown on the anatomy not only of the skeletal system, but also of other parts of the body especially of the thoracic and abdominal viscera. In the main, these studies have been made by clinicians who have had no highly trained technical knowledge of anatomy and no special facilities for comparing the anatomy of the living as revealed by variations in tissue density' with the anatom}- of the dead as revealed by technical preparation. On the other hand, few anatomists have made themselves familiar with the data revealed by the x-ray studies of clinicians or with the possibilities of correlating the anatomy of the dead with the anatomy of the li\'ing revealed by the x-rays. Roentgenology' offers an attractive field for research to the anatomist and a fertile field for \-ivifying his work as a teacher.

Of the various subjects of the medical curriculum, anatomy offers the best opportunity for training the student in habits of resourceful independence. The student can be allowed to wander

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• CXE. 191S

338 C. R. BARDEEN

from a straight and narrow path and to make mistakes until he acquires self-mastery, because the resulting loss is that of a little time and material. In the chemical laboratory, if allowed too much freedom, he may blow up himself and his fellows. In the physiological laboratory or the cUnic he may cause too much needless suffering. In the dissecting-room a student may wisely be allowed considerable freedom when held up strictly for results. The most important thing he can get from the dissecting-room is the habit of independent workmanship with constant aim at results that show skill.

When students are given this sort of training in human anatomy, for which we are largely indebted to the genius of the late Franklin P. ^lall, thej- gain self-mastery, which carries them far in their subsequent medical careers. But while they may acquire considerable manual dexterity and considerable skill in observation, they are apt to neglect the imaginative reflection which is necessary for translating observation into work of value. As a means of stimulating the imagination in gross human anatomy roentgenograms are of considerable value, especially when study of the roentgenograms is combined with fluoroscopic studies on the li\-ing. The use of the roentgenograms belongs in the realm of work in which students may be given a free hand, since the worst that can happen is injury to a few plates. The taking of the roentgenograms and the use of x-ray machines for fluoroscopj', on the other hand, has to be carried on under strict supervision and therefore is of little value as a general means of training in independent initiative, although of good value in adding interest to the study of anatomy.

At the University of Wisconsin we have made a beginning in the sj'stematic use of roentgenology in connection with anatomical stud}-, but I feel that a far more extensi\'e use might be made with advantage.

For the benefit of our first -year students who are beginning the study of human anatomy we have a set of x-ray plates displayed in a room conveniently situated near the dissecting-rooms, and the students are encouraged to study these plates in connection with their work in dissecting. So far as possible pairs of stereo

TEACHING OF AXATOMY 339

sfopic plates are used and prismatic stereoscopes are provided for the study of these plates. The skeleton is well illustrated with especial reference to the joints in various positions and to the air sinuses of the skull. Plates are proAided to display the anatomy of the heart and of the lungs. The abdominal viscera are shown both with and ^^•ithout the preceding ingestion of barimn meals. Most of the plates are made from the living, both children and adults, but some roentgenograms are pro\-ided of specimens especiall\- injected after death to show blood-vessels and other features. I beheve that this latter feature could wisely be extended. Our plates along these lines have come chiefly from the research work of Dr. ^liller and Dr. Dunham on the lungs.

On the whole, I have thus far been somewhat disappointed at the lack of free independent use of the plates by the majority of the students. They readily go into the room with an instructor and express great interest in what he points out, but comparatively few students stud}- the plates carefullj' on their own initiative. The same men later in private practice will study x-ray plates carefully in connection with suspected fracture cases because here the study is a means to a definite end. It is hard to make the student feel the same interest in plates that might help him to understand better the part he is dissecting. It is probable that a better arrangement of plates and more careful labeling than we have pro\-ided would help. The students can be made to study the plates by requesting outline drawings with parts labeled.

During the second semester of the first-year students are taken in small groups to the fluoroscopic room of the x-ray department of the medical school and are shown the action of the various joints, the expansion and contraction of the thoracic cavity, the beating of the heart, the ingestion of a barium meal, and other physiological activities of the bod}', the different members of the group taking turn as subjects. The students always show more interest in fluoroscopy of the hving than in roentgenograms. If it could only safeh' be done, a great deal of interest might be added to the study of anatomy by turning over an x-ray transformer and a fluoroscopic outfit freely for the use of the students during the study of anatomy. But the danger of x-ray bums

340 C. R. B.\RDEEN

precludes this. The supervised and therefore Umited use of fluoroscopy in teaching anatomj^ can wiseh* be combined with the study of structure in action as revealed by visual observation, palpation, and precussion of the nude living model. We have endeavored to do this by the employment of students as models for certain h,ours each week during the second semester of the first year, and I beUeve with profit. .Irtists' models trained for this special work would probably be better than the untrained models we make use of.

For many of the advanced students in human anatomy roentgenology has proved even more stimulating than for the beginning students. We make it a regular part of our work in topographical anatomy somewhat along the lines described above for beginning students but more extended. Seniors in the College of Letters and Science and graduate students who are candidates for a blaster's degree, while carrying on medical studies, are required to present a thesis. AMien this thesis is chosen in topographical anatomy the student is usuallj' assigned to some topic in which the recent work in the field of roentgenology' has added something to our knowledge and is encouraged to try to add something of his town. These students have all shown great interest in this work. Several papers embodying the results are now in course of revision for publication. Advanced students of this character can, of course, be given more latitude in the use of x-fay apparatus than can be given to beginners.

The ready willingness of students in the dissecting-room to aid members of the staff and advanced students b}- making special dissections which help to unravel the mysteries of light and shade in roentgenograms contributes to scientific research, to the interest in teaching, and to the interest in stud}-.

2. WAYS AND. :MEANS IN THE TEACHING OF GROSS

anato:my

A. G. POHLMAX St. Louis University

There are certain objections to the course in gross anatomy made by the average medical student which must be taken into consideration in a discussion of the pedagogy of the subject. It is not nw purpose to advise the adjustment of any course so that it will meet with the approval of the student, and in particular, with the medical student. It may be said that medical students have been so often exposed to or vaccinated by the various science courses in the required premedical curriculum that they appear to be relatively inmiune to the intrusion of new ideas, either as to subject matter or methods of presentation. This immunit}' to learning is rendered the more effective bj- the gratuitous advice of the successful practitioner, whose memory of the actual work of his student days is somewhat hazy, just as the quality of this said work has been somewhat enhanced in the telling, and by a halo of age. In defense, however, of our colleague, the practitioner, it must be noted that he uniformly advises the prospective medical student to 'know his anatomy.' I have made repeated efforts to run do^Ti exactly what this \'aluable suggestion may mean, but without success. The result is that the medical student comes to the dissecting-room with an interest which is not paralleled in any other subject of the elementary medical curriculum. In addition, the student has a certain amount of preparation in vertebrate anatomj' — more or less misbegotten because he has regarded the study of vertebrate zoology as one of the necessary evils of the premedic years. There are three of these evils like the 'Three Musketeers of Dumas; physics, chemistr}-, language, and biology; named, as nearlj- as I can figure them," in b'lgbcar order. It follows, therefore, that our novice in the course in gross anatomy

341

349 A. G. POHLMAN

comes to us nowadays with the interest he possessed some twenty years ago, with certain more or less fundamental conception, regarding vertebrate structure, and possibly with ideas concernm, the phylogenetic relations of the more important organs. He naturally expects from a hurried dissection of the chief vertebrate f omis that he is preparing to understand the relations m the human body the better. If his instructor does not materialize a comparative explanation or does not pitch the work on a plane which presupposes information the student has gleaned from actual contact with lower forms, the student is likely to ask himself an embarrassing question, "my is vertebrate zoology a requirement for the study of gross anatomy?" He^may also find a ready answer to the question by passmg the word down the line "Qet through somehow. You won't use^ it, anyway. f our premedical requirement is merely to furnish us with studen s two years older, and who have supplemented all of the bad habits of study in the high school with many of the vicious mental tricks of the college student, I, for one, would feel that the requirement has undergone a perversion in function.

\11 of us who have enjoyed a varied experience realize that all students may be divided into three classes .Those who are genuinely interested in the work and who take advantage of all of the opportunities because they really like the thmg they do; those who are interested because the subject is made interesting to them, and, finally, the spoon-fed, led-by-the-hand variety who must have the subject 'learned' to them and whose mam ambition in any subject is to outguess the instructor on exammation questions and get by with it. The first-named variety comprises the very desirable class of students who learn in spite of their teachers , the second learn because of their teachers, and the third and unfortunately large per cent should contribute to a mortality list even more than they do. Yet even with them we must temper justice with mercy because they are a result of a mind-improvmg educational system which places a premium on learning the thing for the thing itself. Given a student whose mind has been so thoroughly cultivated that he cannot see the woods for the trees, and you have a desperate pedagogic problem. Add to this the lack

TEACHING OF ANATOMY 343

of initiative which usually accompanies this serious condition, and j'ou have the pest who foUows one about the laboratory absorbing ideas like a sponge sops up laboratorj^ stains, and giving out these ideas under pressure with somewhat similarly mixed results.

It was my doubtful privilege, and one which I am sure the majority of you have not enjoyed, to put in my first course in anatomy under the old sj'-stem. Gray's Anatomy was the family bible, and I gained a horror of sj'stematic text-book recitation which has always stayed with me. The book was the thing and the body was merely an accessory after the fact, mutilated at night under the most sordid of conditions. It was at this time that the three-year medical course changed to four, and a laboratory method of teaching anatomj- began largely, as I recall it, through the efforts of the late Professor Mall. Then the pendulum swung to the other extreme. No longer did the surgeon hold opera-glass clinics on a dissected cadaver. No longer was the dissecting-room work a sort of black art. In place of this, lectures became conspicuous in their absence and dissection became a day-light laboratory subject, and professional anatomists began to move in polite society. The swing to the research worker was a direct protest of those who knew, that anatomy was being poorly taught, and I will hark back to this later.

If I were to translate myself back some twenty years ago what were my thoughts and criticisms of the course in gross anatomy. I resented being kicked out of the dissecting-room after fortyeight hours' dissection of the lower half of the bod}', and registered my resentment by putting in several weeks the following summer with Professor Kerr in working out the relations of superficial to deep lymphatics of the axiUa. The most successful as well as the most spinal piece of dissecting I accuse myself of. Successful in that Gray and I differed. I worked through the osteology with a skeleton nearby and wondered why it was so essential to know all of the wrinkles and dimples and foramina with which various bones were excruciatingly and inaccessibly beset. I went over a collection of joints and wondered what kind of eye the man had who drew those delightfully crisp ligament separations. I protested the systematic origin, insertion, innervation, and rela

344 A. G. POHLMAN

tions of the individual muscles and maintained it couldn't be done, especially when we tripped up our instructor at times. I recall memorizing anastomoses between various arteries because it seemed to me they were at one time considered important and therefore wished on to future generations. I figured the veins were easily as important and far more complicated than the arteries and why so little devoted to them in the text. The various plexuses of nerves were as nightmares, and so thoroughly did I bone their form that I could draw them upside down and backwards to prove that I reallj- knew something of them. The brain was a chamber of nomenclature horrors, and I shone in my fraternity as the individual who had actually dissected a brain and was held, next to Gray, as the last word on the subject. Please remember I came into this work younger than most students and therefore more pliable; brought up in a museum, which may account for some of my peculiarities, then and now, but extremely eager to work and learn.

This, then, leads us to the second point I would make. One does not expect a student to swallow, digest, and assimilate all of the data of gross anatomj', and therefore some of the matter must be filtered out as more important as opposed to certain matter which must logically be less important. Essentials of anatomy do not exist. All of them are de-horned species of text-books with fewer adjectives, verbs, and prepositions. Condensation does not make for digestibilitj' any more than bulk makes the matter more easily assimilated, and because of this we have a teacher. I take the liberty of contrasting the teacher with the research worker. Both of these individuals are a result of brains and application. Neither of them are bom. Both represent men whose receptive apparatus and analytical power is or should be better developed than their motor discharge. There are, however, two requirements in the teacher which need not be found in the research worker. The first of these is a personal interest in students, and the second, an interesting personalit}^ to his students. Personal interest in students is not .sy^lon3^nous with research worker, and the interesting personalitj' may make itself known in a vicarious inspiration which the student is supposed to obtain through fleeting

TEACHING OF ANATOMY 345

glimpses of a great man comparing the rotation of the extremitj^ joints of the grasshopper with similar appendages in the cousin cricket, or what you will. Therefore, we must teach our students well because we are interested in the teaching, or not at all because we are not interested: either method is excellent and between the two lies mediocrit}-. If we are to select for our positions as teachers .of gross anatomy those indi\'iduals whose greatest merit lies in the bulk of productive work or in the seduction of students to do a great amount of this work for them, we must not expect any marked increase in the efficiencj' of our teaching.

346 A. G. POHLMAN

one, as a representative medical student would get little information or inspiration from your work. I hark back, therefore, to the transition of anatomy as a didactic subject to one of purely laboratory experience and refer to the pendulimi coming to a more midway position. Because we have professional anatomists nowadays ; because we have men of experience ; because we have research workers — although prominent men in gross anatomical research are relatively infrequent ; therefore we give our students opportunity to profit by experience and learn through their ears as well as their eyes. The advantage of ear learning over eye is obvious. One can't strain one's ears.

Personally, I believe that if an instructor demands more, or as much, of his students than he himself can deliver after years of experience, of obser^'ation and review ; after viewing hundreds of dissections to the student's one, this individual in my opinion does not have a fundamental conception of the subject and his students will get farther through his neglect rather than his interference. How successful is each one of us as a teacher? How often do we take inventory as to exactly how good we are at it? One cannot measure the efficiency of one's teaching ability by a criterion of examination any more than one can gauge the productiveness of his research with a bibliographic calipers. It is the blissful privilege of the true teacher to be discouraged, and because of his discouragement to ever try anew. If, therefore, you are perfectly satisfied with your method of teaching or perfectly contented with the results of your research, it means you are slipping or have slipped. Personally, I teach anatomy because a student will forget it, and do not let us make the common mistake of confusing the forgetting of a thing with the neverhaving-known the thing.

I have thus far tried to tell something of the medical student and his resistance and his conferred or acquired immunity. I have also attempted in an impersonal sort of way to tell who is the teacher of gross anatomy. I shall next unscrew the inscrutable and tell you what we should teach, and finally camouflage the impo.ssible by telling you how to do it. I reserve the right to deal negatively with the problem if I so choose in the interests of brevity and universal peace.

TEACHING OF ANATOMY 347

TMiat shall we teach our students in gross anatomy? It is diftieult indeed to make categorical statements on what one must do and what one must not do. Perhaps our discussion of the pedagogy of a subject would not suffer if the essayists were less theoretical and more practical. There has always been a suspicion in so-called standardized courses that the standardization consists in ' 'not doing as I do, but doing as I tell you." Perhaps it may be a good idea and the easiest way out of the difficulty to make it a personal quantity even if the method shines negatively in contrast with your own excellent views on the problem. In the teaching of gross anatomy I attempt to do five things: I encourage dexterity in dissection : a purposeful dissection ; an independence in observation; a justification of facts, and, finally, a weaving together of some sort of plot to the story of the body.

The training of a digital dexterity is a valuable asset to the medical student and it is a good thing to emphasize that it represents a sort of spinal busy work, but much good comes of it in a profession where a man is supposed to use his hands as well as his brains. Please do not misunderstand that I hold excellent dissection as equivalent to good anatomical work. We have all had students who dissect beautifully and know little of what they do and, conversely, students who dissect very poorlj-, but know a great deal about it. The tendency on the part of the average student is to be in too great a hurry, and I do not encourage an}'one to save time any more than I stimulate them to improve their minds. It is also a bad plan to install into the heart of students that the cutting of this or the tearing of that is such a terrible offense. The only way I know to tell how much traction a nerve will stand is to pull a few of them in two. There is a very ar])itrarv line between poor dissection and mutilation of the dead and the essential difference is like that between falsehood and lying — the intention.

Students are supposed to be dissecting, inasmuch as the work is largely spinal, to some purpose, and this purpose, I take it, is to check on the structures as they find them in the text. The body after all is the thing and the text is merely accessory after the fact. It not infrequently happens that students see structures very

348 A. G. POHLMAN

well as evidenced from the dissection (superior colliculus), and they also at the same time see things very poorly as far as the lateral geniculates are concerned. A purposeful dissection demands more than merely doing a good dissection and checking the structures found in the book. It demands an independence of observation; an interest in similar structures on the other side of the body or in other bodies.

Too nmch guidance — too manj^ directions are probably worse than none at all, because the student is supposed to have some initiative. It is a good plan, I find, not to go into great detail, but let the student work it out for himself as nmch as possible. It is also an excellent idea to sit down with the student once in a while and show him you can do the work yourself as well as talk about it. The best way to encourage observation in a student is to observe with him and not at him or to him.

If you tell a man the earth is not an oblate spheroid, but a truncated tetrahedron, it is mereh^ a waste of words unless he reacts and wonders wh}\ Justifibation of facts to me means this: first, it leads to an understanding of the relation of structure to function: second, the information is essential to a comprehension of abnormal structure and function; third, it is of interest from a phylogenetic standpoint to one who should be a student of evolution; fourth, it bears on the fundamentals governing the developmental processes, and, lastly, certain data are important to the proper conception of cross-section anatomy.

There is no justification for the absolute divorce between anatomy and physiology or anatomy and pathology, and it may be the anatomist is not as good a general physiologist and pathologist as the latter two are anatomists. The instructor certainly cannot expect a student with less time, interest, and experience to weave a pattern out of a mass of facts when the instructor himself cannot do it. I, for one, am anxious to hear Professor Jackson's paper and Professor Huntington's paper, which ought to let no little light in on the problem, provided they tell us how and what they do. It is safe to sa.y that details must go, and whether this artery has fourteen named branches and yonder twenty-two is of little consequence if one does not know the general territory involved. It is a good thing to know that the internal carotid has most of its

TEACHING OF ANATOMY 349

distribution inside the skull and that the external carotid is mostly outside the skull. It is folly to make the student memorize the origin, insertion, innervation, and action of muscles because the phj^siologist proves to him that all a muscle can do is shorten and that no muscle contracts by itself — in fact, leads him into reciprocal innervations for an answer. So the militant student comes to us for a justification, and either we hand him the worn-out adage, "Learn the tiling for the thing itself," or we explain why it is important, or we agree with him. Personally, I agree with him. The most important thing about a muscle is the position of its tendon to the plane of action in a joint. The same holds true of the details of anastomosis except from an historical interest, and the peripheral communication of nerves which, according to the physiologist, do not communicate.

Whatever maj' have been the sins of the academic courses, let us make what we teach to our students of a kind that will make them more receptive to later study of subjects which comprise their life work; at least let us not contribute to their resistance.

How you shall teach gross anatomy is quite inseparable from what you teach, and therefore depends both on teacher and teachee. I have said that t e teacher must have an interesting personality and nmst be interested in the welfare of his students. The student must be receptive, and in order that he be receptive, he will expect action on the part of the teacher; accessibility of information; interpretation of importance from the teacher's standpoint, and, finally, interest and inspiration. Interpreted the other way around, the teacher must translate himself into the person of his students. The student is usually loyal and will apologize for a poor teacher by saying "there is little question but that he knows his subject." If, therefore, we, as teachers, maintain the right to analyze how much our students know by their motor discharge, it is only fair that the student applj^ the same rule because a good teacher is at the same time one of his own pupils.

Next to remoteness in the person of the instructor comes inaccessibility of information. Just as I stated, too much guidance in dissection develops mental lean-to's in the students just so too much stereopticon, too much microprojection, too manj

350 A. G. POHLMAN

charts and museum specimens contribute to making information inaccessible to the student because we tend to make what constitutes a perfectl}' obvious thing remote. It has been said that the college course in physics is greatlj- interfered with through the chicaner}' of appliances and apparatus. It is just like telling a story to illustrate a point. If the story is too well told the student will remember the storj' and forget what it was intended to explain. It is mj^ opinion, therefore, that the more offhand the information, the more schematic the idea, the less like the original, the better it will take; bearing in mind justification must underlie aU information, imparted or required.

The next point I made was in reference to interpretation of the importance of certain facts which does not mean spinning out in an hour's lecture what a student may read somewhere in fifteen minutes. It consists in the teacher's telling the results of his own observation from his own experience and is therefoi'e mainly matter which is not to be found in a text-book. This is a problem which requires a great amount of time and study, and this is the sort of thing that does more to inspire the student than anj' one other thing I know. Lectures of this kind require experience, confidence and a certain amount of philosoph}-, and are either to be classed as valuable adjuncts to teachmg or very bad. It is much better to convince the students by precept, by word of mouth, and by action that no subject of vital interest can be difficult to a man who has the brains, the application, the facilities, and the incentive to work, but without the incentive the results are ineffective.

The advice given in a symposium like this \yill not materially affect us— the older men whose mental and physical habits are well formed — too well formed perhaps to allow even a moderate elasticity. Rather this recital of admonitions and experiences will do much to steer the j'ounger men toward a more friendly personal interest in their respective flocks and perhaps for the same reason that thej"^ do their research work — because they like to do it. There is a great future ahead in this country for the man who will take the teaching of gross anatomy seriously, and will take it seriouslv because he likes it.

3. HOW CAX AXATOIVIY BE TAUGHT AS A SCIENCE AND

FULFILL ITS PURPOSE AS A FOL^NDATION

FOR MEDICINE?

C. M. JACKSON Institute of Anatomy, University of Minnesota, Minneapolis

It is now generally agreed that in medical schools the fundamental branches should be taught primarily as sciences, but at the same time with a view to their purpose as a foiuidation for medicine. Thus anatomy on the one hand must fiu"nish a comprehensive and rational explanation of the form and structure of the hiunan body, and on the other hand it must provide a 'working knowledge' as a basis for subsequent study in physiology, patholog3', and clinical medicine. This ideal with its twofold purpose is clear. The question is, can it be realized? And, if so, how is it to be done?

The primarj" purpose — to teach human anatomy- as a scie: ce — is, at least in theorj-, not an especially difficult problem. In general, the object is to study the human mechanism in the Ught of its indi%'idual and racial history: to explain the human bodjas a biological organism. Given a competent teacher, students familiar with the principles of animal morphology-, and the facilities of a modem anatomical laboratory, this task could readU}- be accomphshed. It would require merely a carefully planned lecture and laboratorj- course, including a brief dissection of the human body, with correlated work in histology and embrj'ologj'.

But this knowledge of the general principles of hvmian morphology-, while indispensable, is insufficient for the needs of the medical student. His training must include more. He needs in addition many specific details of human structure which are necessary to solve the problems of physiology, pathology-, and

352 C. M. JACKSON

clinical medicine. To teach anatomy as a science and at the same time to meet the requirement for specific knowledge in the brief time available is the difficult task which confronts us as teachers of anatomj'.

From the cUnical point of \iew, it is desirable that the medical student should know all about human anatom}^ since the exact details needed caimot be foreseen. Yet this is clearh' impossible. The student might easih' spend years in the stud}- of gross anatomy alone, without exhausting the subject.

It is e\'ident that there must be a selection of the subject matter to be taught. The best that can be done is in teaching anatomy as a science to use as illustrative material so far as possible those concrete details most likely to be of use later and to present them in such a way as to give the student a collateral training which will be of maximum value.

To make wisely this selection of subject matter with a \aew to its practical application later requires of the anatomist a knowledge of the subsequent work in medicine. ^Tiile it is not necesssLTy for him to be a graduate in medicine, he should at least have a sufficient comprehension of physiologj', pathology, and clinical medicine to judge as to what will probably constitute the most useful preparation for these subjects.

Even with the best possible selection of subject material, much anatomy which the student may need must necessarily be omitted. The situation is materially improved, however, if the elective principle is adopted in the medical curriculum. According to this principle, it is frankly recognized that no student can be expected to learn all about every useful subject in the curriculiun. He can hope at best merely to get a fair grasp of the fundamental principles in each subject, with such details and training in handling them as will serve his purpose in the more frequently met and important phases of medical science and practice.

By cutting down the various required courses to the bare essentials, the medical curriculum, now overcrowded in most schools, can be somewhat reduced so as to give room for electives. This will pennit the individual student to supplement his required courses by further elective work in the lines of his greatest needs,

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353

and thus give him a training better than is possible with an inflexible curriculum. "^Tiile the time which can thus be devoted to electives is necessarily limited, the system is a decided improvement. -AJthough but few medical schools have as yet adopted this principle, many more will doubtless do so when its advantages are better understood.

Our experience with the elective system in the ^ledical School of the University of ^linnesota may be of interest in this connection. In 1914 we reduced our overcrowded and inflexible medical cuiriculimi from a total of about 4,800 hours to 3,624 hours of required work. Throughout the sophomore, jimior, and senior years, on two half-days a week no required work is now scheduled, this time being left open for elective courses offered in the various departments. From these elective courses, each student must choose the equivalent of six hours a week, or a total of 576 hours in the three years. Thus about 14 per cent of the curriculum is made up of electives, which may be chosen in any line for which the student is prepared.

In general, the system has worked out well, and is very satisfactory- to both students and faculty. As in other departments, the amount of required work in anatomy had to be reduced, in order to give room for electives in the ciirriculum. By abbre\'iating some of the courses, and making topographic anatomy elective, the required work in the department of anatomy (including gross anatomy, histolog}', and embryology) was reduced from 832 hours to 688 hours. This required work is now distributed as follows :

BrBJECT

HODES

TEAR

Gross anatomy

336

160 96 96

First

Histology

First

EmbrN^olog^'

First

Xeurologv

Second

Total

688

THE ANATOMICAL RECORD, TOLCME 14, NUMBER 6

354 C. M. JACKSON

"S'arious electives are offered in the department of anatomy, with enrollment during the past year as follows:

Special dissections 32

Topographic anatomy 14

Applied anatomy 14

Anatomical drawings 3

Anatomical technique 13

Implantation and placentation 3

Fetal anatomy 13

Special embryology 8

Experimental neurology 5

Research in anatomy 10

Anatomical seminar 8

Total ennillment 164

These electives varj^ in time, the average occupying about 80 hours. Thus, the total of the electives taken in anatomy arnounts to an average of nearly 170 hours for each student in a class of 75. This would bring the total average per student up to about 858 hours (required and elective), or slightly more than that formerly required of every student. Even though the total amount of time devoted to anatomy were the same, the efficiency of the instruction would be increased, because the work is distributed more in accordance with the varying needs and capabilities of the individual student.

The elective system requires more work by the staff, for it is evident that to teach several shorter, more specialized courses to students in small groups will require more work than to teach an equi^'alent amount of routine class work to students in larger groups. But the results justify the increased work by the staff, and the elective courses are profitable to the teachers themselves as well as to the students.

The students who choose their elective work in anatomy do so for various reasons. A few (would there were more!) take advanced anatomy because they become interested in the subject for its own sake or as a possible career. The majority elect it because the}' realize the advantage of a more extensive training in

TEACHING OF ANATOMY 355

anatomy as a foundation for clinical work. Some have in mind a better preparation for definite clinical fields in which they hope later to specialize. Whatever their purpose, the elective system permits them to obtain a training in anatomy far better than would be possible under the inflexible required system.

Another phase of increasing importance in medical education which concerns anatomy is the graduate work. The modern uniA'ersity must meet the growing demand for trained specialists in the various fields. In this connection, anatomy is concerned, 1) in the training of anatomists themselves, as r.ecruits to the profession and, 2) in contributing to the training of specialists in other fields. As a major line of graduate work, anatomy should be open to candidates for the Master's or Doctor's (Ph.D.) degree in the graduate school on the same basis as any other scientific subject. Teaching fellowships should be provided which will help to defray the student's expenses, while the experience in teaching will probably be of great value to hun in his future career. The training of recruits for the profession of anatomical teaching and research is an important phase of our work which deserves careful consideration.

The most recent phase of graduate medical education is in the chnical branches. Even under the elective system it is a recognized impossibility to provide adequate training for specialists in the various departments of medicine and surgery in the undergraduate curriculum. For the adequate training of such specialists, at least three years of graduate work are now generalh' considered essential, and the universities are beginning to make definite provision for the establishment of such courses. In this new field of graduate medical education, anatomy is also directly concerned, as is evident when the requirements for adequate training in clinical subjects are considered.

In graduate clinical work, as in graduate work generally, no definite and fixed curriculum can be fonnulated, the work being advanced in character and adapted to the individual student. Certain general principles are self-evident, however, and should be kept clearly in mind in planning the work in each case. It must be remembered that in anatomy, as in the other funda

356 C. M. JACKSON

mental sciences, the training of the average medical student (as we have seen) has necessarily been Imiited to that which may suffice for purposes of general practice. If he desires to specialize in any clinical branch, he must strengthen his foundation by further work in the fundamentals, otherwise the clinical superstructure will be unsatisfactor}'. Just as anatomy, physiology, and pathology form the foundation upon which the undergraduate clinical training is supported, so must more extensive work in these fundamentals form the basis for any efficient system of graduate training in specialized clinical lines.

We have had considerable experience at ^Minnesota during the past few years in the development of graduate work in the clinical subjects, and it may be of interest to know how it works out with reference to anatomy. As might be expected, those specializing in the various phases of internal medicine require, as a rule, comparative!}'- little additional work in anatomy. In surgery and allied subjects, however, the graduate students find it profitable to spend a considerable amount of time on advanced work in anatomy. They frequently make anatomy their minor department in working for advanced clinical degrees.

In ophthalmology and oto-laryngology, for example, the graduate students usually take advanced work in anatom}^ for two halfdays a week during the first year. In the first semester this work is in gross anatomy, consisting of 1) a review of the skull, with intensive study of special preparations ; 2) topographic anatomy of the head and neck, studied especially by sections in the three planes, and, 3) special dissections for the regional anatomy of the eye, ear, nose, and throat. This is followed in the second semester by a similar study of the special histology and embryology of the eye, ear, nose, and throat, including grt)ss fetal dissections and histological preparations of these regions in the hmiian embrj'o and adult. Those making anatomy a minor are required to take additional work in some appropriate phase of the subject. For example, the wax-cast model of the adult nasal cavity and paranasal sinuses (which is demonstrated at this meeting) was con.structed by Dr. Connor as a part of his work for a minor in anatomy.

TEACHING OF AXATOMT 357

Thus it is e\-ident that anatomy must play a role of increasing importance in the development of graduate work, not only in the tr ainin g of professional anatomists, but also in the training of clinical specialists in the various branches. In these new fields of anatomical work, as well as in the older and more familiar lines, the question of methods of teaching is one of perennial interest. Lack of time prohibits me from considering pedagogical methods, aside from a few general principles which maj' be briefly mentioned.

In the first place, uniformity of methods in teaching anatomy is unnecessary and even undesirable. The methods would naturally var\- according to the preparation and ability of the students, the facilities available, and the individuality of the teacher. To be efficient, however, they should regard the past, the present, and the futm-e. As to the past, the instruction in anatomy should of course be closely related to the previous work in zoology'. As to the present, everj- effort should be made to correlate the work in gross anatomy with that in histology and embrj'olog}'. And the future applications should be kept constantly in mind, as has already been emphasized.

The physiological H-iew-point is one which is often verj' useful in teaching anatomy, even though we maj' not go so far as to admit that ' 'anatomy without physiology is like an old maid without a down*'." In reviewing the locomotor apparatus, for example, I have found it a stimulating exercise for the students to reason out what sjTiiptoms would be expected if a given nerve trunk were cut and to give a complete explanation of the various structiu"es involved. In the case of a mixed nerve, such as the femoral, this would involve both sensorj' and motor sjTnptoms. The explanation of the sensorj' SATnptoms would include the distribution of the various sensory branches to corresponding areas of partial or complete anesthesia in the integument, joints, .and muscles. The explanation of the motor sj-mptoms would include, in the first place, the posture of the part, due to the unopposed action of the unparah'zed muscles. In the second place, it would include the movements which would be weakened or lost, due to partial or complete paralysis of the muscle groups innervated by

358 C. M. JACJCSON

the various branches of the ner\-e. Such an explanation thus involves a review of the anatoniA" of the nerves, muscles, bones, and joints in considerable detail. But it does more in that it helps to organize that knowledge into a workable fonn of obvious value later not only for physiologj^, but also for clinical medicine. In general, in our methods of teaching we should alwaj's bear in mind that, as ex-President Eliot has said, professional training is primarily not for information, but for power.

To summarize brief!}': human anatomy can be taught as a science, and inust be if it is to be efficient. By a judicious choice of methods and selection of subject matter, it can also fulfill its purpose as a foundation for medicine. The difficulties due to the limitation of time may be largely overcome by the adoption in the medical curriculum of the elective principle, permitting students to take supplementary work in anatomy corresponding to their indi\'idual needs. Graduate courses in anatomy should also be provided for those desh'ing to specialize further, either in anatomy or in other medical subjects. The methods of instruction in anatomy may vary, but they should always haxe due regard for the preparation of the student, should correlate closely the various phases of the work, and should develop a 'working knowledge' which will serve as a basis for future application.

4. -MODERN PR0BLE:MS OF EVOLUTION, V.IRIATION

AND INHERITANCE IN THE ANATO.MICAL PART

OF THE -AIEDICAL CURRICULUM

GEORGE S. HUXTLNGTOX Columbia University

The questions assigned to this part of our discussion are becoming increasingly important froiti the standpoint both of general education and of the special training in medicine. To a large degree they and cognate topics are already recognized as necessary parts of a liberal education, and as such are incorporated in undergraduate teachmg. Theii- particular significance in the field of the medical sciences and study has led to important and farreaching changes in pedagogic methods. It would be difficjlt to overestimate the \alue of the biological pre-medical courses offered by our leading institutions in theii' departments of zoologj-, embrjolog}, histologj- and comparative anatomy. They afford an indispensible framework upon which the detailed consideration of the problems here under discussion can be based in their important and intimate relations to the study of ^ledicine. It is necessary that the modern medical curriculum should fuUy recognize the obligation placed upon it by the progress of scientific thought and method, and make formal pro\'ision for meeting the same.

The anatomical course is preeminently the proper place in which this teaching should be developed, because the material facts upon which it is based, and which furnish the necessary background of illustration and demonstration, fall to a large extent already within the province of Anatomy, and require relatively shght expenditure of teaching tune and effort in order to develop their bearing on the broader themes indicated in this section of our SjTnposium.

In modern anatomical teaching the historic distinction between

359

360 GEORGE S. HUNTINGTON

' 'gross" and ' 'minute" anatomy has effaced itself completely, and the structure of the adult human body is considered as a whole from the three standpoints of its development, its resulting form and its relation to general vertebrate organization. Embryology and Comparative Anatomy thus necessarily become the guiding lines employed concurrently by the student in the acquisition of his anatomical knowledge. It then becomes merely a question at what points in the course, and to what extent, the teacher, in following these already existing lines, will direct the student's attention to the problems here under discussion.

The following gives in outline a method of procedure which I believe to have demonstrated its value in practice. The general form of the exercise, in which instruction is imparted in the topics of Evolution, Heredity and Variation, deserves a brief consideration. In the teaching of Anatomy, the Laboratory has universally replaced the old-time Anatomical Lecture in the sense that the student's concrete knowledge of structure is fundanientally based on his own personal observation and study. With this alteration in method the lecture in anatomy has exchanged its former place for one occupying a much broader and higher plane. It serves primarily to bring the specialized efforts of the student into a coherent whole, in which the individual objects of his study are viewed from the standpoint of their interdependence, first within the framework of the system to which they belong, and then in the relation of the latter to the entire organism. The morphological detail is acquired by minute personal, and often prolonged and repeated, observation. The summing up of the facts thus acquired, their functional interpretation, their phases of adaptation to the environment of the whole organism, are properly within the domain of the lecture. Within this domain appropriate use can be made of unusual and special illustrative material ordinarily not accessible to the student, or of special methods of demonstrating material habitually used by him in his own laboratory work, such as corrosions, reconstructions, special sections, Roentgen plates, etc.

It is here likewise that the enormous value of the aid afforded to the medical student by Comparative Anatomy can best be

TEACHING OF ANATOMY 361

Utilized, in throwing its strong side-light on the difficult and often obscure details of human structure. The densely crowded medical curriculmn of the present day does not permit the student to engage in systematic and practical work in Comparative Anatomy. And yet there is no region or part of the human body which is not more readily and permanently comprehended through the comparison with the corresponding structures in other vertebrates. It is perhaps the most important single function of the anatomical lecture to bring the salient points of this general relationship of vertebrate organization clearly and succinctly before the student. In this sense I believe that the problems which we are considering this morning are also best presented at the proper point in the anatomical course in fullj- illustrated lectures to the entire class or to large sections thereof.

For practical reasons I find it advisable to deal with the subject matter of this instruction in two general di\'isions, as detennined b}' the character, distribution and use of the material emploj'ed by the student in his anatomical work. I hence correlate the more generalized considerations to two parts of the regular anatomical teaching, taking up first the subject of Inheritance and subsequently the problem of \'ariation and Evolution.

1. INHERIT ANCE

In the ordinary coiu-se in General EmbryologA^ the student is carried, to a large degree as a re\'iew of his undergraduate work, through the morphology of the cell, the mechanism of mitotic cell-di^■ision, the behavior of the chromosomes, the origin and differentiation of soma- and germ-cells, the maturation of the latter, and the processes of fertihzation and cleavage. These are all phases of cellular life and activity readily and abundantly accessible to each individual student, and mastered by him through close personal observation. This is the proper point in his course for the introduction of the more generalized interpretation of the processes observed. The purpose of this exercise is to translate m the student's mind the more pureh' mechanical concepts of the vital processes, obtained by his personal study, into terms of their broader significance, viewed from the stand

362 GEORGE S. HI'NTINGTON

point of the cells of the smgle organism in their phj'sico-chemical aspect and of the entire individual in relation to the race of which he is a unit. These considerations form the introduction to the studj' of Heredity. Thej' include such topics as the specificity and individuality of the chromosomes, the distribution of paternal and maternal chromatin in syngamy, the theoretical analysis of chromosonial organization in respect to inheritance, the significance of equational and reducing division, the duplex character of the zj-gote in contrast to the simplex character of the gamete, sex detennination. This leads directly to a concise but fairh'^ comprehensive consideration of the laws of j\Iendelian inheritance, based on the following principles:

1. The existence of unit-characters, interpreted on the factorial hypothesis.

2. Dominance and Recession, in cases where the parents differ in a single genetic factor.

3. Segregation of the contrasting characters in the gametes of the offspring.

4. Independent assortment of contrasting unit-characters in cases where the parents differ in two or more genetic characters.

The Mendelian examples can, of course, be selected from a wide range, according to the material available. In general it is desirable, in view of the student's collateral reading, to employ the cases quoted frequently m the most accessible literature. To illustrate the first three of the above principles any of the following crosses may be used to advantage:

Red and white ]\Iirabilis fCorrens).

YeUow and green peas (^lendel).

•Black and white guinea pig (Castle).

Vestigial and long-winged Drosophila (Morgan).

The fourth principle, the inheritance of two or more independent pairs of factors, may be conveniently illustrated by the Mendelian example of cross-fertilization of round yellow with wrinkled green peas, or Morgan's case in which a gray vestigial Drosophila is mated with a long-winged ebony fiy.

Sex-linked inheritance is illustrated by the tran.smission of the white eye in Drosophila (JVIorgan), or by the analysis of heredi

TEACHING OF AXATO.MY 363

tary color blindness in ^lan, through each of the parents. This leads to a brief discussion of ^lendelian inheritance in IMan, with particular reference to the constantly growing importance of ^lendehan teratological and pathological human characters, especially in the eye and nervous sj^stem.

The aim of the foregoing presentation is to emphasize the fact that the stud}' of the chromosomal assortment furnishes a mechanism which exactly fulfills the ^Nlendelian requirements of pairing in the zygote and subsequent segregation in the gamete, and that in the gametic coupling or linkage the factors carried by the same chromosome tend to remain associated and are hence inherited together.

In the teaching of medical students there is a certain advantage in drawing the illustrations as far as possible from mammalian sources, and for this reason it is desirable, in problems of heredit}', to use as fully as maj' be feasible the rodent examples of guinea pigs, rabbits and mice grouped by W. E. Castle in his book on "'Heredity in Relation to Evolution and Animal Breeding" ('13).

Recentl}' Dr. Helen King of The Wistar Institute of Anatomy has suggested to me the value of the teaching material furnished in this respect by the Rat Colony of the Institute.

2. VARIATION AXD EVOLUTION

Following the consideration of the topic of heredity and its physical basis, which occupies a place in the general embryological course, I consider it desirable, preparatory to the study of evolutionary theories, to next present somewhat thoroughly the general problem of adaptation, as illustrated by concrete examples presenting themselves to the class in the regular anatomical com-se. The choice of the topic or topics used for this purpose is of course an extremely wide one, depending largely upon the arrangement of the time and material in the anatomical com-se of individual institutions. In my own practice I find it useful to introduce a general con.sideration of the vertebrate shoulder girdle at a point where the student has worked through the development and structure of bone and the forms of ossification in the histological course.

364 GEORGE S. HUNTINGTON

I may here be permitted to give an outline of the groimd covered in this exercise for the purpose of affording an example of the range of the presentation and of the amount and kind of the illustrative material required. The accompanying figures are of preparations in the JNIorphological JMuseum of Columbia University used in the demonstrations. The topic connects organically with the subject matter of the histological course by beginning its consideration with the unique type of ossification found in the ontogeny of the mammalian clavicle and of the corresponding elements where they occur in the remaining vertebrate classes. This finds its explanation in the phjdogenetic history of the bone, originally an exoskeletal derivative introduced secondarily into the complex of the primordial pectoral girdle, in response to the latter's adaptation to definite functional and mechanical requirements. As such it is the first bone of the skeleton to ossify, its primary centre developing in Man during the sixth week, when, at a point corresponding to the middle of the shaft of the future clavicle, a bony nucleus develops directly from the indifferent embryonic mesenchymal skeletogenic tissue, without the appearance of a prefonned cartilaginous model. From this central ossific nucleus cartilage subsequently extends mesad and laterad, both toward the sternum and toward the acromion. In this cartilaginous rod, divided by the primary bony nucleus into a sternal and an acromial segment, the rest of the clavicle develops. Late in development (Man, 20th year) a secondary centre appears in the sternal extremity, joining the shaft in the 25th j^ear.

This ontogenetic historj' of the mammalian bone calls for the consideration, from the standpoint of adaptation and evolution, of three main facts, which bespeak the relation of the mammalian clavicle to homologous skeletal elements in the lower vertebrates :

1 . The early direct dermal type of development of the primary clavicular ossific centre.

2. The derivation of the cartilaginous bed in which the rest of the shaft of the bone develops.

TEACHING OF ANATOMY 365

3. The mechanical conditions estabUshed in the pectoral girdle by the introduction of the clavicle.

The consideration of these topics is based on a study of the following series of t^-pes:

1. The primordial A'ertebrate pectoral girdle is illustrated by the structure in the Elasniobranchs. Any one of our common and readily obtainable Dog-fish, Sharks or Rays will answer the purpose. The smiple horse-shoe shaped cartilaginous arch of the girdle in Squalus acanthias is shown in fig. 1. The division of the same in the higher forms into a dorsal scapular and ventral coracoid segment, meeting at the point of attachment of the anterior extremity, is foreshadowed in the figure by the use of the colour scheme adopted in the remainder of the series.

The coracoid portions of opposite sides are continuous across the ventral mid-line in a clear hyaline suture. The right and left dorsal or scapular segments of the prmiitive arch are separated from each other by an interval and their free termination is tipped by a hyaline zone suggesting the supra-scapular cartilage of the later types.

The Elasmobranch pectoral girdle furnishes the primordial fundament upon which all other ^-ertebrate modifications are built.

2. In the Dipnoeans, Ganoids and the modern Teleosts, the prunitive uniform cartilaginous ghdle begins to l)ecome altered in two directions.

1. It is divided into segments.

2. The cartilage is largely replaced by b(jne from two soiu'ces:

a. IntracartUaginous ossification of the primitive girdle segments.

b. Deposit of membrane bone of dennal origin forming the clavicles.

A Teleost girdle is shown in fig. 2.

The primary- continuous and single elasmobranch girdle is here divided into separate and distinct right and left pectoral arches, each composed of a dorsal scapular and ventral coracoid element. These ossify partly by intracartilaginous replacement, parth^ by a deposit of membrane bone deri^•ed from the dermal

THE AXATOMIC.VL RECORD, VOL. 14, NO. 6

366

GEOKGE S. HUNTINGTON

Figure 1. Shoulder-girdle of Sqxialus acanthias, the Dog fish. In the continuous and single pectoral arch of this form the division into dorsal scapular (sc) and ventral coracoid (co) segments of the higher types is foreshadowed on the right half of the girdle by the use of the following color scheme adopted in the rest of the series :

Scapula yellow

Coracoid blue

Epicoracoid brown

Clavicle red

Episternum green

Sternum white

Dr — Dermal horny rays. Prp, Msp, Mip, — the three basal pieces of the fin, Propterygium, Mesopterygium, Metapterygium. Ra — cartilaginous rays (radialia) of fin. Pet — continuous undivided pectoral arch.

TEACHIXG OF AXATO-MY

367

Figure 2. Right shoulder-girdle of Gadtis callarias, the Cod fish, lateral view. CI — Cla\'icle (Cleithrum'). Co — Coracoid. Mco — iNIesocoracoid. Pel — Postelavicle (Post-cleithrum'l. Pi — Post-temporal, articulating with epiotic and pterotic processes of skull. Sc. — Scapula. Set — Supra-claviele (Supra-cleithum). Ra 1-4 — Proximal RaViials (Pterj'giophores).

exoskeleton and forming the clavicular or cleithral complex (cleithruni. post- and supra-cleithrum) . These investing bones are highh' developed in the Teleosts and are connected by a branched bone, the post-temporal, with the epiotic and opisthotic regions of the craniimi. In the higher vertebrates they become reduced, furnishing the investing bone of the clavicle and the episternum.

The elasmobranch therefore visuahzesthe formation of the primitive cartilaginous vertebrate girdle, the teleost the secondary engrafting on a portion of the same of an investing element, the clavicle, dennal in origin. This furnishes the outline for the interpretation of the ontogeny of the mammalian clavicle, deA'eloping partly by direct, partly by replacing ossification. Thus in the degree to which in higher vertebrates the clavicle enters into direct and intimate relation with the primitive segments of the pectoral girdle, cartilage of coracoid origin becomes added to the prunary bonj- clavicle, enabhng it to assmne secondary and functionally

368

GEORGE S. HUNTINGTON

important relations to the earlier elements of the arch. The primitive coracoid responds in a very definite manner in making provision from its own substance for the cartilaginous matrix upon which the dermal investing bone of the clavicle is grafted. The primitive expanded single ventral coracoid plate divides, by the development of one or more fenestrae, into a caudal larger element, the coracoid proper, and a cephalic narrower bar, the procoracoid, which is invested and replaced by the clavicle. This process is beautifully illustrated in

3. THE ANURE AMPHIBIANS Example: Raiut cntesbiana, the Bull-frog.

Figures. Shoulder-girdle of i?o?(afa(csb?'nnn, Bull-frog. CI — Clavicle. Co — Coracoid. Epc — Epicoracoid. 67 — Glenoid cavity. Ost — Omosternum (Episternum — . Sc — Scapula. Ss — Suprascapula. St — Sternum.

The pectoral arch is here formed by two scapular segments, the ventral scapula proper and the more dorsally situated suprascapula, both ossified in cartilage, with the exception of the area along the vertebral margin of the dorsal suprascapular segment which remains in cartilage, frequently impregnated with lime

TEACHING OF ANATOMY 369

salts. The cartilaginous coracoid, which meets the scapula in the formation of the glenoid socket, is divided into a caudal element, the coracoid proper, and a cephalic bar, the procoracoid. The former ossifies, the cartilaginous precoracoid rod is replaced by the investing bone of the clavicle.

The amphibian further shows the first appearance of the sternal apparatus in association with the pectoral girdle, and of the epicoracoid. The latter represents the beginning of a loosening of the originally firm ventral connection of the coracoid, made possible, and of distinct functional advantage in swimming forms, such as the frog (vide infra) , by the mechanical substitution of the clavicle in place of a considerable segment of the coracoid. Just as the division of the original single and massive coracoid plate into a cephahc procoracoid and a caudal coracoid in the narrower sense occurred through a trans\'erse split or fenestration in the long axis of the arch, so a similar cleft, at right angles to the preceding, resulted in the separation of the primitive coracoid plate int o a lateral scapular coracoid and a medial sternal epicoracoid. In some forms fLacertilia, Chelonia) the epicoracoid remains cartilaginous or fibro-cartilaginous. It is probably represented in man by the sterno-clavicular fibro-cartilage. In the general significance of its development it may be interpreted as one of the preliminary stages in the detachment of the rigid coracoid from its firm ventral sternal connection and its functional replacement by the more mobile ventral clavicular component of the girdle, while the reduced lateral portion of the coracoid is necessarily retained as the coracoid process, since it forms, at its junction with the scapula, an essential element of the glenoid socket. (Cf. infra, p. 378 and Fig. 12.)

4. REPTILES

The pectoral arch defaults in the Ophidia with the total suppi:ession of the fore limb. In the remaining orders of the class it' is found in three forms:

A. The girdle in the Lacertilia is very fully developed.

Example: Iguana tuberculata, Iguana (Fig. 4). It is composed of scapula and suprascapula, multifenestrated coracoid and epi

370

GEORGE S. HUNTINGTON

coracoid and clavicles. The medial extremities of the latter are supported by a T-shaped Episternum, derived ontogeneticalh' by the direct ossification of a dermal anlage, without cartilaginous praeformation. The combination of these components is in direct line with the conditions obtaining in the JMonotremes. These, the most primitive manunals, possess among the other structural characters carried over from theii' reptilian ancestry, a pectoral girdle which conforms closely to the Lacertilian type of the modern saurian reptiles just described. The massive coracoid

Figure 4. Shoulder-girdle of Iguana luberciilata, the Iguana. ('/ — Clavicle. Co — Coracoid. Epc — Epicoracoid. Epsl — Episternum. Gl — Glenoid cavity. Sc — Scapula. Si — Sternum. Siipsc — Suprascapula.

TEACHING OF ANATOMY

371

extends to the lateral manubrial angle and carries a broad bony epicoracoid plate. The ventro-niedial portion of the epicoracoids is covered by the vertical branch of the strong episternum, whose horizontal divisions suppoi't the clavicles.

Example: Platypus anatinus, Duck-billed Platj'pus (Fig. o).

A comparison of figs. 4 and 5 will show at once the transmission of the reptilian character to the primitive mammalian girdle.

B. Within the profound modifications of the exoskeletal apparatus of the Chelonians resulting in the development of the carapace and plastron, the pectoral girdle of these reptiles consists

Figure .5. ShouUler-givdle i)f Philijpus annlinus, the Duck-billed Platypus. CI — Clavicle. Cu — Coracoid. F.()C. — Epicoracoid. EpU — Episternum. .S'c — Scapula. -S( — Sternum.

372

GEORGE S. HUNTINGTON

of the straight dorsal scapular bar joined at the humeral articulation to the ventral coracoid. This is divided by a single large fenestra into the caudal coracoid proper and the cranial procoracoid, whose ventral extremities are joined by the fibrocartilaginous epicoracoid.

Example: Chelydra serpentina, Snapping turtle. (Fig. 6.) C. In the Crocodilians a simple Coraco-scapular arch is developed, the two components meeting in the formation of a glenoid cavity. The coracoid forms a single plate, broadening ventrad and firmly connected to the lateral sternal margin.

%<

Figure (i. iShiiulder-girdlc of Chi'li/ilrd serpciiliua, Snapping Turtle. CoCoracoid. £pc— Epicoracoid. (11— VAcno'ul cavity. Pco— Procoracoid. ScScapula. K

TEACHING OF ANATOMY

373

Clavicles do not develop, but a ventral episterninn makes its appearance. With the additional introduction of a clavicular (furcal) apparatus the crocodilian girdle would connect directly with the avian type. [Cf. figs. 7 and 8]

Example: Alligator mississippiensis, American Alligator (fig. 7).

«r# ).■■■■■«! ~^j-^

C^-^4

\^'^#

/?:

Wf

■'■■'i

Figure 7. Shoulder-girdle of Alligalor mississippiensis, Alligator. Co — Coracoid. Epst — Episternum. G{ — Glenoid '■avity. Sc — Scapula. Si — Sternum. Supsc — Suprasoapula.

374 GEORGE S. HUNTINGTON

5. THE AVIAN GIRDLE

In the typical flying birds the slender sword-Iikc scapula is joined at the glenoid to a massive coracoid, which, expanding ventrally, is firmly in vaginated in the marginal groove of the broad and carinated sternum. The two clavicles form bj- fusion of their medial extremities the well-known arch of the Furcula or Wishbone. The bony Episternum is replaced, at least functionally, by the extensive clavi-sternal aponeurotic membranes. The entire apparatus speaks for two functional adaptations of the girdle structures:

1 . The high development of the coracoid in contrast to the comparatively insignificant and slender scapula indicates the preponderance which the \'entro-appendicular muscles have obgained over the dorsal musculature as the result of the specific adaptation of the former to the movements of flight. The clavicles (furcula) appear introduced as an additional thoraco-humeral brace against the adduction of the forelimb to the tliorax in the action of the pectoral group.

2. The reciuisite area for pectoral muscular attachment is obtained by the increase in breadth and length of the sternum and ]\v the development of the Carina from its \-entral surface. Additional surface or muscular attachment is further furnished by the furcula and the episternal apparatus of the interfurcular and sterno-furcular aponeuroses.

Altogethfer the pectoral girdle of the typical bird furnishes the clearest example of the modification in structure and relation of the components correlated to specific functional adaptation.

Examj^le: Oh)- bticcinator, the Trumpeter Swan. (Fig. S).

The primitive vertebrate shoulder-girdle, ccmiposed of its phylogenetically oldest elements, scapula and coracoid, is characterized by the great firmness of the ventral coracoid connection, and is from its construction rigid and nearly immobile. A girdle of (his tyi^e, combining great strength and rigidity, enaljles a ])i>\\('iful \-enti()-appendicular musculature to move the anterior liml) wipiin a limited range in a few directions with great force, but'is not adapted to a wider extent of more diversified motion.

TEACHING OF ANATOMY

375

It is chiefly of value in ]iermitting: in()\'ements of adduction and rotation with a free extremity, witliout carrj-ing the hmb against or across the thorax, as in the acts of swimming, flying or digging. In these a rigid pectoral girdle and firm coraco-sternal junction act as a supporting arc, keeping the shoulder and gleno-humeral articulation away from the thorax ami pre\'enting undue adduction of the extremity, while permitting the full unfolding of the pectoral muscle-action.

Figure 8. .Shoulder-girdle of Olor bucciiiatur, Trumpeter Swan. Ca — Carina of sternum. Co— Coracoi*!. /^//— Furcula (Clavicles). (7i— Glenoid cavity. Sc — Scapula. St — Sternum.

376 GEORGE S. HUNTINGTON

This type of shoulder girdle hence occurs in foniis in which the foreltinb is used in a limited number and range of forcible movements of ab- and adduction and rotation.

It occurs, with or without the introduction of the secondarj' clavicle, in Elasmobranchs, Teleosts, Reptiles, Birds and Monotremes, in the latter as a direct reptilian inheritance.

Examples used in the illustration of the coracoid element:

Squalus acanthias Figure 1

Rana eatesbiana Figure 3

Alligator mississippiensis Figure 7

Iguana tuberculata Figure 4

Chel ydra serpentina Figure 6

Olor buccinator Figure 8

Platypus anatinus . , Figure 5

MODIFICATIONS OF THE PRIMITIVE SCAPULO-CORACOID ARCH

1. The primary firm sternal connection of the coracoid is loosened in one or both of the following ways:

A. Axial fenestration of the coracoid, either multiple (Iguana, Monotremes) or single (Rana, Chelonia), resulting in its division into a posterior or caudal element, the Coracoid proper, and an anterior or cranial bar, the Procoracoid.

Examples: Rana, fig. 3, Iguana, fig. 4, Platypus, fig. 5, Chelydra, fig. 6.

B. Transverse division, at right angles to the preceding, of the primitive coracoid into a lateral scapular segment, entering into the gleno-humeral articulation, and a medial sternal element, the Epicoracoid. The latter may ossify as a separate bony element, of the girdle, or may remain as a fibro-cartilaginous plate, thus still further increasing the mobility of the coraco-sternal connection.

Examples of Epicoracoid cited:

Rana Figure 3

Iguana Figure 4

Chelydra Figure 6

Platypus Figure 5

TEACHING OF ANATOMY 377

2. The coracoid may be further reduced, losing its medial connection altogether and appearing as a relatively insignificant process of the scapula, but always retained in extant forms as the Coracoid Process (subcoraeoid centre) because the glenoid socket is always formed by both scapula and coracoid, no matter how far the reduction of the latter may be carried.

This reduction of the coracoid obtains in all mammals, except the Alonotremes, which retain the full development of the reptilian coracoid with sternal connection through the epicoracoid. In some Marsupials, the next order above the Monotremes, the strong coracoid reaches the sternum during the early ontogenetic stages, but becomes reduced in later developnient to the coracoid process. Thus in Trichosurus.

In some forms (Man) the original path of the sternal extension of the coracoid is indicated by bands of fibrous tissue, containing at times fibro-cartilaginous nodules, forming the Costo-coracoid ligament. (Cf. Plate I, tig. 1)

3. The primitive scapulo-coracoid arch may be further modified by the introduction of the clavicle, a bone derived from the tegmentary exoskeleton and secondarily added to the primary elements of the girdle by investing the cranial portion of the coracoid (procoracoid). This addition of the clavicle maj' occur in two forms:

A. The clavicle replaces the procoracoid in the ventral segment of the pectoral arch, while the remaining original components, viz. Caudal Coracoid, Epicoracoid, and Episternum are retained in their full development. In this case the clavicle is introducted for the purpose of adding to the strength of the ventral arch of the girdle and of increasing the surface for attachment' of the pectoral musculature by the development of extensive aponeurotic membranes between the clavicles and the other elements of the girdle and the sternum (Carinate Birds, Monotremes).

In the birds in which the wing muscles are relatively reduced the clavicles become diminished in size and strength, lose their direct sternal apposition and the union with the opposite bone in the furcular junction.

Example: Ramphastos ariel, theToucan. (Fig. 9).

378

GEORGE S. HUNTINGTON

In the Brevipennate flightless ostriches the bone defaults altogether, only the coracoid remaining in Struthio, Rhea and Casuarius. This speaks for a relatively late acquisition of the clavicle as a component of the Avian Girdle.

Examjile: Casuarius casuarias, the Cassowavy. (Fig. 10).

Figuve 9. Shoulder-girdle of Rtmipliaslox ariel, the Toucan. CI — Reduced clavicles. C<> — Coracoid. Gl — Glenoid cavity- 'Sp — Scapula. St — Sternum.

In one ostrich, Droinaiu>i, the Emu (Fig. 11) rudmients of (he separate clavicles remain as two small bony crescents loosely attached to the girdle.

In the South .\merican group of the C'rypturi, although the sternum is keeled and the wings are to a cei'tain extent functional, yet the shoulder girdle and sternum ha\-e a distinct struthious character. This, together with other anatomical features, places these small ground-birds with the Ostriches in the super-order of the Dromaeognathae.

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379

B. The clavicle, secondarily engrafted on the procoracoid element of the primitive girdle, functional!}' replaces the caudal coracoid jjroper, which liecomes reduced to the lateral portion entering, as the coracoid process of the scapula, into the construction of the glenoid socket for the humeral articulation.

Figure 10. Shoulder-girdle of Casiiariiis casnarius, the Cassowary. Co-^ Coracoid. Gl — Glenoid cavity. Pco — Procoracoid. Sc — Scapula. St — Sternum.

Thus in the unique ontogeny of the mammalian clavicle, the primary direct centre of ossification of the shaft, appearing without the preceding formation of cartilage, in the human embrj'o in the sLxth week, represents the dermal element of the bone, derived from the exoskeleton. The cartilage added to this pri

380

GEORGE S. HUXTIXGTOX

mary centre at both the sternal and scapular ends is derived from the cranial element of the primitive coracoid, the procoracoid, and forms the bed in which further ossification of the shaft of the bone proceeds in both directions. The acromio-clavicular fibrocartilage and the sternal epiphysis of the clavicle, whose secondary centre develops in ^Nlan between the 18th and 20th year and joins

Figure 11. Shou\deT-giTd\e of Dromai us novae-hollandiae, the Emu. CI — Rudimentary clavicles. Co — Coracoid. 01. — Glenoid cavity. Pco — Procoracoid. Sc. — Scapula. St — Sternum.

the shaft in the 25th j-ear, are likewise part of the cranial procoracoid element. The lateral portion of the caudal coracoid proper constitutes the coracoid process of the scapula, completing with its subcoracoid centre (10th year) the glenoid fossa. (Fig. 12.)

The rest of the mammalian caudal coracoid defaults, with the exception of the costo-coracoid ligament and its occasional fibrocartilaginous nodules. (Plate i, fig. 1.)

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381

The sterno-clavicular fibro-cartilage is also a derivative of the primitive coracoid, and may be interpreted as part of its medial or sternal extremity or as an epicoracoid (Lacertilia, ^lonotremes).

The human interclavicular ligament and the occasional ossicula superasternalia (fig. 13) are referable to persistent rudiments of the primitive episternum. The introduction of the clavicle,

Figure 12. Human scapula. 14th year. Co — Coracoid. Sco — Subcoracoid.

replacing in the mammalia above the Monotremes the larger ventral portion of the coracoid and forming the thoracic connection of the pectoral girdle, influences the disposition of the pectoral musculature. In the superficial ectopectoral sheet the clavicle affords origin to the clavicular portion of the PectoraUs major. The cephalic part of the deeper entopectoral layer furnishes in non-claviculates the generalized Sterno-chondro-scapularis, which, with the appearance of the cla\icle, becomes in its central segment the mammalian Subclavius, while its medial portion is converted into the costo-clavicular or rhomboid ligament, and its lateral fibres become the coraco-clavicular ligaments (conoid and trapezoid) (fig. 16).

382

GEORGE S. HUNTINGTON

Figure 13. Human adult, Sternum and Ossicula Suprasternalia, with Interclavicular and Suprasternal ligaments. CI — Clavicle. Id — Interclavicular ligament. M — ^Manubrium. Oss — Ossa suprasternalia. Sst — Suprasternal ligament.

A B

Figures 14 .4 and 14 B. Schema of evolutionary derivation of human pectoral girdle from the vertebrate ground-plan, as illustrated by the Anure Amphibian.

TEACHIXG OF AXATOMY

383

The analysis of the human pectoral girdle in reference to the deri\'ation of the component elements reads therefore in tabular form as follows:

Archeal Axlage:

Primordial cartilaginous Girdle of Elasmobranchs

Components of Humax Pectoral Girdle

\

/'

Scapula and Coracoid

Dermal Cleithrum and Clavicles of \ Primary direct centre of clavicular

/ ossification.

Teleosts

Cranial Procoracoid

Ventral (Medial) end of Procoracoid

Epicoracoid

Episternum

Dorsal (Lateral) end of Procoracoid.

Caudal coracoid proper

Cranial segment of entopectoral muscle sheet furnishing the sterno-chondroscapularis.

a. Lateral portion

b. Central portion

c. Medial portion

Cartilage rod on which dermal clavicle is engrafted.

/ Epiphyseal centre at sternal extremity \ of clavicle.

Sterno-clavicular fibro-cartilage.

Ossa suprasternalia Inter-clavicular and Suprasternal Ligaments.

Acromio-clavicular fibro-cartilage.

f Coracoid Process, Subcoracoid, Costocoracoid ligament and contained fibro-cartilaginous nodules.

Coraco-clavicidar conoid and trapezoid ligaments.

Subelavius.

Costo-clavicular rhomboid ligament.

Figure 14 .1. Plan of pectoral girdle of ,\nure .\mphibian based on the structure in Rana catcsbiana. Co — Coracoid. Dc — Investment of Procoracoid by dermal clavicle. Epc — Epicoracoid. OH — Omosternum. (Episternum). Pco — Procoracoid. Sc — Scapula. Ss — Suprascapula. St — Sternum.

Figure 14 B. Phylogenet,ic derivation of elements of the human pectoral girdle. The homologous structures are indicated in A and B by the corresponding colors. Ac — Acromio-clavicular fibro-cartilage. Cc — Costo-coracoid ligament and contained fibro-cartilaginous nodules. Dc — Primary ossific centre of dermal Clavicle. Ej) — Sternal epiphysis of Clavicle. Ic — Interclavicular ligament. Oss — Ossicula suprasternalia. Pco — Procoracoid cartilage. Sc — Sterno-clavicular fibro-cartilage.

384 GEORGE S. HUNTINGTON

The functional results of these adaptations in the mammalia is to substitute, for the nearly inunoliile ventral coracoid connection of the pectoral girdle with the sternmn, the clavicular apparatus with moveable articulation at both the sternal and scapular extremities. The clavicle acts as a sufficient thoraco-hmneral brace, maintaining the position of the glenoid cavity in movements of the anterior extremity against the thorax, while at the same time the articulations at either extremity greatly increase the range and variety of these movements. The clavicle acts as the radius of the arc in which circumduction of the arm takes place, with the centre placed at the mobile sterno-clavicular articulation, while at the same time the lateral claviculo-scapular joint enables the glenoid socket to alter its direction and the scapula as a whole to maintain contact with the curvature of the thoracic wall in different positions.

Both of these mechanical functions of the mammalian girdle would have been interdicted by the retention of the complete primiti^•e coracoid, with its firm ventral attachment to the sternum and the immobile lateral junction with the scapula in the glenoid articulation.

The replacing clavicle thus finds its full development in mammals above the Monotremes, especially in forms which habitually execute forcible movements of the anterior extremity against the thorax. The bone is hence especially strong in mammals using the anterior lunb for digging (Edentates), swunming (some Rodents), flying (Cheiroptera), or grasping (Prmiates).

When the anterior extremitj' habituall.y performs no or onlj' slight movements against the thorax, and is used solely as a supporting or progressional lunb, the clavicle is reduced or defaults altogether. The pectoral girdle then consists solely of the scapula and its coracoid process and is attached to the thorax only by the thoraco-appendicular muscle planes. The clavicle is thus absent in many Carnivores and in the Ungulates. It is rudimentary in some Rodents and Carnivores (Felidae), appearing as a slight bony or fibrous intersection in the ventral sheet of the cephalohumeral muscle.

TEACHING OF ANATOMY 385

It is significant, in reference to tlie ontogenetic derivation of the primary clavicular anlage, that in ]\Ian, in cases of congenital absence of some of the cranial membrane bones (Parietal), the clavicles, also derived from the investing skeletal tissue, usually likewise default.

The high development of the clavicle in the Primates is the expression of the greater freedom of action of the anterior extremity, especially in movements of ad- and abduction, circumduction and rotation, permitting of a wide range of diverse uses.

The presentation just outlined in the concrete example of the vertebrate shoulder girdle is intended to introduce the student to the consideration of the unity in groundplan of vertebrate organization and of its far-reaching modifications in response to environmental and functional adaptations, and to thus pave the way for his study of the e\'olutionary problem. The matter contained in the preceding pages can readily be handled within the period of a single anatomical lecture, and the illustrative material is for the most part universally accessible. The only examples used which are more difficult to obtain are the shoulder-girdles of the jVIonotremes and of the Ostriches, and these can be demonstrated by drawings or photographs. The remaining illustrations are all derived from the dissecting room, the market or the usual range of domestic or laboratory animals. The effort required for their suitable preparation and assembly is, in my judgment, not unwarranted in view of their value from the teaching standjxiint.

It goes without saying that practically any portion or region of the body may be selected, instead of the example here given, for the purposes of this presentation, according to the space occupied by it in the anatomical course and the material available. Excellent opportunities for this treatment are afforded by the alimentary canal, especially the gastric and ileo-colic regions, the heart and vascular system, the central nervous system, the phylogeny of the vertebrate respiratory system, the pelvic girdle, the genito-urinary tract, etc.

THE ANATOMICAL RECORD, VOL. 14, NO, 6

386 GEORGE S. HUNTINGTON

EVOLUTIOX AND VARIATION'

The general problem of evolution is best approached in the medical curriculum through the consideration of variation as forming the physical basis of structural evolutionary change.

The medical student confronts the problem of variation from the outset of his practical medical course and carries it with him throughout the remainder of his i:)rofessional career. He encounters it during his work in the Dissecting Room in more or less significant instances, which either come under his own personal examination, or under that of his fellow students. It is highlj' desirable that he should not be led to regard these as mere anatomical curiosities, or as examples of a lusus naturae which are inexplicable and devoid of a deep scientific meaning. He meets with variation again in his later, so-called "clinical" j-ears of the course, in his hospital service and in his subsequent practice, often in some of its miportant semi-pathological aspects. Variation, wherever found, always readilj^ chains his attention and arouses his close interest.

^'ariation in my experience forms therefore the portal through which the broader theme of evolution can best be approached bj' the medical student, and I find that he invariably re.sponds to the opportunity for clarifying his concepts of variation along the lines of evolutionary doctrine. I am therefore in the habit of dealing in the anatomical course in the first place with variation along the line of a simple working classification of variants encountered in the human body, to which the student can correlate his own observations, which serves him as a guide in his interpretation of the same, and which can be made the basis for the general theoretical consideration of evolution.

A presentation of this nature should be illustrated as fulh' as convenient, and I find that the a.ssembly of such material calls for relatively small expenditure of time and effort, considering its educational value. This material is naturally of three kinds and derived from three sources:

1. Human Variations. The average dissecting room yields in the course of a few years a surprisingly large harvest of significant and desirable human variants, if thev are svstematicallv

TEACHING OF ANATOMY 387

preserved. This is of course the main source of the annual increment and the resulting gradual growth of this class of illustrative material. Some of the records can be kept in the form of drawings, charts or photographs. I have, howe\er, found it desirable to make peniianent wet or drj' preparations of the structures, wherever possible. In the case of the large and miportant group of the muscular variants I have for many years almost uniformly taken casts, which are subsequently colored and yield admirable and durable teaching objects.

A few desirable illustrations can be obtained by photograph or cast from the living subject, such as hare-lip, hypospadias and other developmental arrests of the genito-urinary region, Polydactyly, etc.

2. Ontogenetic Material. The comparative embr3'ological collection furnishes an almost unlimited amount of material for the correlated illustration of courses in variation and evolution, and should be utilized to the fullest extent, in slides and particularly in reconstructions.

3. Comparative Anatomical Material. A very large number of excellent examples are offered by the domestic and laboratory animals, or bj' forms readily obtained in the market (fishes, reptiles) . The rarer forms are of course only to be obtained graduallj- and as occasion offers, but pending such acquisition very good use can be made of drawings and photographs.

388 GEORGE S. HUNTINGTON

A CLASSIFICATION OF HU.MAX \ARIATIOXS TO SERVE AS A GUIDE IN ANATOMICAL INSTRUCTION TO MEDICAL STUDENTS

A distinction is first drawn between two general groups of variants which can, with certain reservations to be subsequently considered, be provisionally defined as: 1. Ontogenetic Variation and 2. Phylogenelic Variation.

Awhile every variation is in one sense ontogenetic, as resulting from the atypical differentiation of the embryo leading to the development of the abnormal indi\'idual, the term is here used to designate those variations which base themselves upon the normal ontogenetic range of the species to which the individual belongs. Ontogenetic variants arise from material forming a noi-mal constituent of the embryt) but not carried typicalh" into the adult organization.

It is well-known that the embryo in the early stages contains many structures which disappear or become highlj* modified during subsequent development. The shift, for example, in the mammalian axial \enous system from the prhnitive bilaterally symmetrical groundplan to the dextral position occupied in the typical adult, affords a fruitful field for the development of variants of this category.

Phylogenetic variations on the other hand are in large part reversional reproductions of conditions not found normallj^ in the embrj^o, marking the hereditary reappearance of characters belonging to the ancestors of the species, but lost or altered in the modern descendants in the majority of the individuals composing the race to-day. A smaller number of phylogenetic variants are progressive, constituting examples of evolutionary changes active to-day. and as j^et e^•idenced only in a small minority of individuals.

The numerical disproportion of the progressional and reversional phylogenetic variations results naturally from the fact that the latter draw for their appearance upon the accumulation of the entire past phyletic history of tlie race, while the former are confined to the Imiited field in which the extremely slow structural reorganizations are preparing for the next evolutionary step of the future. The questions as to the influence of variation by nmtatioii in exolution is taken up in the subsequent general consideration.

TEACHING OF ANATOMY 389

1. Ontogeneiic Variants

A. Errors ix Deat:lofmext.

1. Arrest of normal development.

Examples: Harelip, Cleft palate, Hypospadias, Vesical extrophy, certain instances of Renal dystopia.

2. Failure of normal development.

Examples: Default of the pectoral muscle group; single kidne}-.

3. Atypical development of vestigial siructures of a transitory

character in normal development. Examples: Right Aortic Arch and other main Variations of the prinian,' aortal branches in Alan. 4- Atypical development of permanent vestigial structures. Example: Usual development of the muscles of the external ear. 5. Errors in definition of muscular integers.

a. In Cleavage into successive muscular planes. Examples: The group of the intermediate pectoral muscles.

Tensor semi-vaginae articulationis humeroscapularis, Pectoralis minnunus, Costo-coracoideus.

b. In Segmentation into components within the confines

of a smgle muscular plane. Examples: The deep .Axillary .Arches.

c. In Migration. E.rample: The Sternales.

d. In Metamorphosis.

E.tamples: ^Mutual relation between Ischio-coccygeus and Lesser Sacro-sciatic ligament, between Levator ani and Obturator fascia.

B. Reversional Oxtogexetic ^'ariaxts.

In these the variation possesses a phyletic significance, but appears in the normal ontogeny of the species and is lost typically in the course of later development. Example: 13 free ribs.

390 GEORGE S. HUXTIXGTOX

C. Progressive Oxtogenetic ^'ARIAXTs.

Normally developed structures lose their typical relations during later stages, in conformity with an advancing evolutionary process.

Example: Variability of 12th rib and its default as a free skeletal segment by sjTiostosis witli the 19th vertebra.

2. Phylogenetic Variants

A. Reversioxal Phylogenetic Variaxts.

1 . Archeal Group, signalized by the appearance of characters belonging to the mammalian ancestry, and hence occurring in fossil and extant reptilia and widely distributed throughout the mammaUan phylum. Example: The ent-epicondylar foramen and the associated skeletal, muscular, arterial and nervous modifications around the distal extremity of the humerus in ^lan. This constitutes a verj^ constant and characteristic complex of anatomical characters wherever it occurs.

It appears nearly uniformly in the fossil reptilia, and especially in the Permian promammalian forms, and lies clearly in the mammalian ancestral line. It is ^•ery generally present in extinct mammalia. In li^-ing reptiles the foramen is present in a single form, Hatteria punctata. It is absent in birds and variouslj' distributed in the manmialian order. In general it would appear that the arrangement has a functional significance in the use of the anterior extremity, protecting the mam brachial or ulnointerosseus arteiy of the limb and the brachial nerve, which pass through the foramen, agamst undue pressure in forcible flexion of the forearm on the brachium at the elbow. As .such it appears widely distributed among the active and powerful early reptiles, but has been lost, with the single exception of Hatteria, in their reduced and creeping modern descendants. It is absent in the bird, because in the single vital use of the forelimb in flight there is no flexion at the elbow. In the manmialia it appears especially

TEACHIXG OF ANATOMY 391

in those forms which use the anterior extremity not merely for progression, but also for the special movements of swmiming, digging, and grasping. Thus it has been transmitted to both extant monotremes from their reptilian ancestry, one a swimming form. Platypus, the other a digging ant-eater, Echidna.

In the Marsupalia the foramen is present with the exception of the aberrant pohTDrodont Xotoryctes, and the Dasyuridae, representing the insectivores and carnivores of the Australian and Papuan zones, (Cf. infra, placental caruivora).

In the Edentates the foramen is very generally present in all living fomis, with the exception of one species among the Pangolins, Manis temminkii, and in the genus Bradypiis among the Sloths, where, however, one species carries the structure {Bradypus torquatus).

The members of the order, which really comprises three nonrelated types of ordinal rank, the TubuUdcntata (Or3'cteropus), the Pholidota (Pangolins) and the Xenarthra (Ant eaters, Armadillos and Sloths), are characterized bj' the use of the anterior extremity for digging in the myrmecophagous fonns. or for arboreal suspen.sion in the Sloths, functions which appear to favor retention and wide distribution of the ent-epicondylar foramen.

In the aquatic mammals, which have modified the anterior extremity into a flipper (Sirenia, Cetacea, PInnipede Carnivora), the movements of the greatly modified bones of the forearm against the humerus are extremely limited, or interdicted by bony union. The ent-epicondylar foramen is uniformly wanting.

In all the subdivisions of the extensive group of the Ungulates, using the anterior extremity solely for jjrogression. the foramen is absent. In the Rodents, with great diversity of habit and structure, the humerus is equally variable. The ent-epicondylar foramen is wanting in the majority of the numerous types included in the order.

The Insectivora possess the foramen except in a few instances (Erinaceus).

In conformity with the adaptation of the anterior limb far flight (cf. supra, humerus of bird) the Cheiroptera do not carry the entepicondylar foramen.

392 GEORGE S. HUNTINGTON

Interesting conditions in respect to the development of the foramen occur in the fissipede carnivora. In the cynoid forms (dogs, jackals, foxes and wolves) and in the arctoid bears the foramen is not present. In the aeluroid cats and their alHes, on the other hand, the structm-e is unifonnlj- present. Hyaena, which in the palaeontological historj' of the fissipede carnivora appears linked through the eocene Amphictis to both the modern Felidae, and the Virerridae, usually does not carry the foramen. Occasionally traces of the structure appear as individual variation in this form. (Plate ii, figs. 1, 2).

Among the Primates the foramen is present in all extant Prosimians, with the exception of one Lemur, Perodicticus, and in the Platyrrhine monkeys of the New World, both groups being largeljarboreal in habit, with extensive adaptation of the anterior extremity to this mode of life. On the other hand, the foramen is absent in the Catnrrhine .suborder of the old world monkeys, in the Anthropomorph Apes and Man. In the latter it appears as an archeal type of reversional variation.

A plan of the vertebrate distribution of the ent-epicondylar foramen is shown in figure 15. plates iii and iv give a selection of comparative tj^pes used in the presentation, and its occurrence in Man is illustrated in figure 3 of plate ii and in plate v.

2. Progon.\l Group. The qualification 'progonal" is intended to designate a variant whose degree of phyletic relationship falls within the limits of the general mammalian organization, in contrast to the first or ' 'archeal" group in which the variant character appears as a heritage deri\ed from the promammalian reptilian ancestry. I have selected for illustration two such cases, in which a muscle forming part of the normal organization in many representati^■es throughout all manmialian orders, develops atypically in Man as a progonal reversional variation in the meaning above defined.

1. The M. Omo-cleido-transversarius, or Levator claviculae appears as a very widely distributed mj'ological character in the majority of the mammalia.

It arises from the ci'anial bas(>, or from the transverse processes of one or of several of the upper cervical \ertcbrae (especially the

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393

Figure 15. Plan of the phj-letic distribution of the ent-epicondylar foramen in vertebrates. The red line shows the presence of the structures involved.

394 GEORGE S. HUNTINGTON

Atlas), descends, usually under partial cover of Trapezius and Sterno-mastoid, and is inserted into the acromion process of the scapula and into the acromial end of the clavicle, when this bone is present. It is supplied by branches of the second to fourth cer\dcal nerves. It occurs as a single muscle, or more rarely divided into a ventral and dorsal slip, in the following mammalia:

Monotremata. Platypus, Echidna.

MarsupaJia. Phascogale, Myrinecobius, Dasyurus, Chironectes, Didelphis, Cuscus, Thalacinus.

Edentata. Dasypus, Orj'cteropus.

Insedivora. Chrysochloris, Gymnura, Erinaceus, Centetes, Solenodon, Mj'ogale, Tupaia, Galeopithecus.

Cheiroptera. Pteropus, Vesperugo noctula, \. mui'inus.

Rodentia. Dasyprocta, Erethizon, Sciurus, Lepus. Siphneus.

Carnivora. Canis, Felis, Hj'aena, Mverra, Genetta, Aeonyx, Cercoleptes, Paradoxurus, Phoca.

Ungidata. 8us, Bos, Ovis, HjTax, Hippopotamus.

Cetacea. Globiocephalus, arising from Atlas with insertion into fascia of Supra- and Infraspinatus.

Primates.

Prosi7niae: Loris, Xycticebus.

Simiae: ^lacacus, Cercopithecus, Innus, Cynoccphalus, Ateles Ant liropomorpha.

The muscle has been found wanting only in the following forms :

I nsectivora: Condylura, Talpa.

Chiroptera: Plecotus.

Prosimiae: Perodicticus.

It is therefore one of the most generalized of mammalian muscles, appearing in both extant Monotremes, in the ^larsupalia and in many representatives of all the ^lonodelphian orders, with the exception of the Sireiiia.

Plate (3 shows the muscle api)caring in ^lan as a phylogenetic reversional variant of progonal rank.

The normal occurrence of the muscle in one of the lower Primates is shown in plate vii, fig. 1.

2. M. Sterno-costo-scapularis. In mammalia the cranial portion of the entopectoral muscle sheet comes into relation with the

TEACHING OF ANATOMY 395

shoulder girdle. In its primitiAe form it appears as the Sternochontlro-scapularis or Sterno-costo-scapularis, extending from the manubrium of the sternmn and the cartilage or bone of the first rib to the coracoid process and the adjacent cranial border of the scapula. As such it occurs wideh' in the non-claviculate manunals, with the exception of the fonns adapted to aquatic life, Cetacea, Sirenia and Pinnipede carnivora.

With the introduction of the clavicle the sterno-scapularis gains an intermediate attachment to this component of the girdle and is thus divided into a proximal portion extending from the sternum to the clavicle, and a distal segment passing between the claWcle and the coraeo-scapula.

In the lower claviculate mammals this leads in all orders to a great diversitj' of the details in the arrangement of the muscle, as indicated by the terminology applied to the individual components, as Sterno-coracoideus, Costo-coracoideus, Scapuloclavicularis, Scapulo-costalis minor, Retroclavicularis. Supracoracoideus, Pectorahs longus, and, where the prhnitive hmneral insertion of the entopectoral layer, from which the muscle derives, is retained (Monotremes), Epicoraco-humeralis or ventral Deltoideus.

In many forms, and typicallj' so in ^lan and the Primates generally, the proximal portion of the generalized Sterno-scapularis, between the thoracic parietes and the clavicle becomes the Subclavius, while the distal segment passing from the clavicle to the coracoid process metamorphoses into the coraco-clavicular (conoid and trapezoid) ligaments.

At times in the human subject the original continuity of the two structures is revealed by the insertion of the lateral subclavian muscle fibres into the coraco-clavicular ligament. Occasionally they reach in this way the base of the coracoid or even the adjacent portion of the cranial scapular margin.

[Plate I, fig. 2. Coracoid insertion of Subclavius in ^lan.]

In some instances in ^lan tlie reversion is more complete, and the Sterno-scapularis appears in its primitive fomi, either replacing the typical human subclavius or occurring in conjunction with a more or less modified subclavian derivative froin the entopectoral la3'er. These latter cases are usually recorded in the

396

GEORGE S. HUNTINGTON

Figure 16. Schemata showiiif; the effect of the iiitroduct ion of the chivich' on the disposition of the M. 8terno-costo-scapuIaris.

J. Primitive condition. M. Sterno-costo-scaimhiris, as it occurs in nonchiviculate mammals and in the liuman variant, witliout attachment to the chivick'.

li. The central portion of the muscle acquires a secondary attachment to the clavicle, resulting in the establishment of two derived muscles, the Costo-clavicularis and Coraco-clavicularis.

C. Typical condition in Man. Some of the pro.ximal fibres of the Costo-clavicularis metamorphose into the Rhomboid ligament, the main portion of the muscle becomes the Subclavius and the C'oraco-clavicularis furnishes the Conoid an<l Trapezoid ligaments.

I). Human variant. The normal Subclavius aiul Clavicular liganu^nts are associated with a Costo-scapularis.

TEACHING OF AXATOMY 397

literature as instances of "reduplication of the subclavius." An example of the Sterno-scapularis replacing the subclavius in ^lan, asaprogonal reversional variant, isshown in plate viii. The muscle as it occurs normally in combination with the Omocleido-transversarius in one of the piatj-rrhine monkeys, Ateles akr, is shown in figure 2, of plate vii.

3. Ataval Group. The term ' 'ataval" is here used to designate a more direct ancestor, an "atavus" or grandfather, in contradistinction to a more distant forbear, the "progonus." The variants of this group derive from the common Primate stem, and, when they occur in ]\Ian, represent either reversions to the Proanthropoid ancestor common to ^lan and the Anthropomorph Apes, or more distantly to the general Primate organization. With the shortening of the e^■olutionary path between the human variants of this type and their phyletic source, their number and the frequencj' with which they appear naturally increases. Hence the majority of the human reversional variations naturally fall within this group. To instance only a few of the many examples the following may be cited:

Axillarj^ arches of pannicular derivation.

Pectoralis quartus.

Chondro-humeralis.

Scansorius.

Dorso-epitrochlearis.

Union of condylar head of Flexor sublimis with Flexor profundus digitorum.

Default of Peroneus tertius.

Arrest of pehic advance at 26th vertebra. From the mass of the available examples I have here selected two for more detailed consideration and illustration. 1 . Humeral Insertion of the Pectoralis Minor. With few exceptions, depending on individual variation, the Pectoralis minor and Pectoralis abdominalis of the Prosimiae and of both the catarrhine and platyrrhine groups of the lower monkeys insert into the capsule of the shoulder joint and through its fibres into the radial tuberosity and the adjacent lateral surface of the shaft of the humerus, under cover of the Pectoralis major

398 GEORGE S. HUNTIXGTON

(Cf. plate ■sii, fig. 2). With or without an associated axillary arch the tendon fomis part of the deep layer of the conunon pectoral tendon of insertion. In the anthropoid apes and in Man the insertion of the Pectorahs minor migrates cephalo-mesad, leaving its prunitive association with the Pectoralis abdominalis and gaining a secondary point of insertion into the medial border and part of the upper surface of the coracoid process, the distal portion of its original tendon remaining as the coraco-humeral ligament between the coracoid process and the hmueral capsule. As a reversional ataval variant in ^lan, and more frequently in the anthromorphs. especially the Chimpanzee, the muscle forms a rounded tendon of insertion which, in part or as a whole, passes outward above the coracoid and under cover of the coracoacromial ligament to reach the radial tuberosity of the himierus through fusion with the shoulder capsule, at times partly united with the supraspinatus tendon.

This variation is shown in plate ix.

In the case of the M. sterno-scapularis shown in plate viri the same individual presents another U'pe of this variant in which the caudal part of the Pectoralis minor has the normal coracoid insertion, while the cranial portion develops a tendon which passes over the coracoid process to reach its insertion in the scapulohumeral capsule.

2. Variations of the Peroneal Muscles. Extensor quinti digiti brevis.

The Peroneal group of muscles are to be regarded on comparative anatomical grounds as derivatives from the primitive extensor mass of the toes, modified in the service of the movements of the foot at the ankle-joint.

In the ^lonotremes the nearest approach to the original condition among extant forms is encountered.

In Plat\'pus the lateral grouji of muscles is composed of the Peroneus longus, an early anlage of the Peroneus brevis and the Extensor brevis digitorum, all three arising from the fibula. The tendons of all three descend on the ventral aspect of the ankle to the foot.

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1. The Peroneus longus in-;erts on the hiteral surface of the cuboid and the base of the 5th metatarsal. A continuation of its tendon, surrounded by an indistinct sheath, crosses the plantar surface of the foot from the lateral to the mesal border to insert into the plantar aspect of the 1st metatarsal. This represents the earliest stage among extant mamnialia of the characteristic oblique plantar course of the tendon of this muscle, in which it has not yet given up its primitive lateral insertion into cuboid and 5th metatarsal and its new extension to the mesal border has not yet acquired the freedom and independence of the structure familiar in ]Man.

2. The Extensor brevis digitonmi passes to the four inner toes. Its lateral portion separates incompletely from the remainder as

3. the Peroneus brevis. This muscle arises in common with the preceding from the proximal portion of the lateral fibular surface, under cover of the Peroneus longus, and might well be designated as the Extensor digiti quinti brevis. Its tendon descends over the ventral aspect of the distal epiphysis of the fibula and extends to the terminal phalanx of the 5th toe. Xear the middle of its course over the 5th metatarsal the tendon sends off a lateral branch which inserts into the lateral surface of the head of the 5th metatarsal and base of its 1st phalanx. This lateral portion of the Extensor digiti y. brevis forms the primitive anlage of the Peroneus bre\4s of the higher forms in which it gains greater individuality and independence. Its tendon shifts the prunitive distal insertion proximad to the base of the 5th metatarsal and at the same time the muscle separates as a well defined integer from the remaining medial portion of the Extensor digiti V. brevis.

The change from this primitive condition, retained in the IMonotremes, to that encountered in the placental mammals, and particularly in Man, involves the following fundamental modifications:

1. The medial portion of the Extensor brevis digitorum suppl}'ing the four medial toes, shifts its primitive origin from the fibula caudad, occupying a secondary attachment to the dorsmu of the foot.

400 GEORGE S. HUNTINGTON

2. The Peroiieus brevis separates more completely from the Extensor digit! V. brevis, as whose lateral derivative it originallj' arose, increases in volume and appears as an independent muscle.

3. With the development of the external malleolus the tendons of both the Peroneus longus and brevis become lodged behind that process.

.\Iready in the Marsupalia the Peroneus brevis has separated from the Extensor brevis and its tendon passes behind the malleolus.

4. The medial portion of the primitive Extensor digiti quint i bre^'is, from whose lateral part the Peroneus brevis originally differentiated, may follow the Peroneus brevis in part or in its entirety, forming a forward extension of its tendon to the little toe (cf . plate x) , or it may be retained as a short extensor of the little toe, arising from the fibula, in close association with the Extensor longus. In the lower Primates it thus appears widely distributed in the Prosimiae, as the Peroneus quinti digiti, a small muscle, arising from the fibula, whose long and slender tendon descends in company with the tendon of the Peroneus bre\'is and is inserted on the lateral side of the long extensor tendon to the 5th toe.

It is thus found in Lennu- catta, L. varius, L. nigrifrons, Galago crassicaudatus, G. garnettii, G. allenii, Nycticebus tardigradus, Tarsius s])ectrum, Cheiromys madagascariensis.

5. The extensive occurrence of this muscle in the lower primates has led to the differentiation of a muscle peculiar to man and principally responsible for his ability to raise and evert the lateral border of the foot which makes the upright posture and walk possible, while the failure of such differentiation is largely the cause why the anthropoid apes have been handicapped in following the same evolutionary path. This muscle is the human Peroneus tertius, which appears as a derivative of the long Extensor with insertion into the base of the 5th metatarsal, but occasionally betrays its primitive origin by contributing the short extensor tendon to the lateral toes.

Some of these variants of the peroneal group are remarkably well presented in right foot of the indi\'i(luai shown in plate x.

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The Peroneus bre\us before reaching its insertion into the base of the 5th metatarsal gives off a well developed tendon which passes to the terminal phalanx of the little toe laterad to its tendon from the long extensor. This in a large measure repeats the primiti\-e condition of Platj'pus in which the Peroneus brevis is derived from a lateral element of the Extensor digiti V. brevis. The medial portion of this muscle appears as the human Peroneus tertius, as.sociated in this instance with the Extensor quarti digiti brevis which has retained its primitive fibular origin and whose tendon in its passage to the 4th toe has contracted an intermediate connection to the base of the 5th metatarsal in close proximity to the insertion of the Peroneus tertius. The medial portion of the Extensor digitorum bre\'is has moved in the usual manner to the dorsum of the foot, supph'ing the three inner toes, the great toe receiving in addition to the typical Extensor hallucis brevis the tendon of an accessor}^ element.

A similar variation also is recorded among the anthropomorph Primates fOrang). It forms a very significant example of a structure normally present in the lower Primates (Prosimiae) reappearing in man and the higher members of the order as a reversional phyletic variant of the ataval value. B. Progressive Phylogenetic Variants.

Two examples may be taken as illustrating evolutionary processes at present active in human organization and looking toward their distant future inclusion in the normal structure of the body.

1. Variation in the vertebral level of the pelvic girdle. Pelvic advance and retardation. The normal adult praesacral portion of the vertebral column contains 7 cervical, 12 thoracic and 5 lumbar vertebrae, making a total of 24 praesacral and constituting the 25th verterbra normally the 1st sacral element.

On phylogenetic evidence the conclusion is justified that in Man and the higher Primates a shortening of the longitudinal body axis has taken place in the course of evolution. As one of the results of this process the present a\-erage vertebro-pelvic level has been acquired, both regressive and progressive variations occurring at the lumbo-sacral junction.

In general the phylogenetic evidence goes to show that the

THE ANATOMICAL RECORD, VOL. 14. NO.

4()2 GEORGE S. HUNTINGTON

le\'el of the attachment of the primitive pelvic girdle to the vertebral colmiin was placed further caudad than at present and that the trunk was originally longer. The acquisition of the bipedal upright posture, completely assumed by man and incompletely attained by the anthropomorpha, led to a progressive shortening of the vertical body measure by the shift of the pelvic arch craniad upon the -^-ertebral lino. At any stage in this process the vertebra forming the first sacral element is of course the last to be included within the domain of the advancing peMs and to become incorporated in the sacrum. Hence the synostosis of the sacral segments takes place caudo-craniad. In man the first sac