Talk:Book - Human Embryology (1945) 16

CHAPTER XVI COMPARATIVE VERTEBRATE DEVELOPMENT

ConsidiTtd objKtnely and samt^aU} the embr^olog} of man has

no more interest than that of any other mammal or lerttbrale and from this standpoint special tndeaiours to noth out human embrjologj by t*self may to be misplaced — Keibet {iQio )

INTRODUCTION

The study of human dcNcIopment has been greatly influenced by the knosvlcdt^e obtained as the result of imestigations on other vertebrate types This has been in part due to the greater ease with which closely sta ed embryos of kno^n age can be obtained m animals and to tlic absence of limitation of expenmcnl Further, in order to explain certain peculiar structural and functional phenomena occurring tn human development a knowledge of comparauve embryology is imperative Thus the presence of the notochord, the visceral arches, the sequence of kidnevs, the functional differentiation of the nervous system and the foetal metabolism can best be understood on the assumption that they arc at least in part features inherited from ancestral stages in the development of the human race Since many ancestral organs seem to have disappeared entirely, it may be assumed that during the course of evolution features have persisted when they are functionally necessary during development as for example the mammalian mesonephiw or when they provide a scaffolding for some essential structure of the later embrvo or adult, as for example, Meckel s cartilage

Fifty years ago most competent zoologists vvere satisfied to explain embryonic development mainly in the terms of the so called Law of Reeapitulalton or Law of Biogenesu This law stated that embryonic development repeats m order the adult stages through which the race has passed during its evolution This is often expressed by the statement Ontogeny repeats phylogenv While there is nothing in the known facts of embryology evolution or genetics to show that ancestral adult features arc handed down by heredity to the embryos of more advanced forms yet there arc a multitude of characters appearing temporarily during the development of an individual that arc known to be primitive and can be explained only in the light of the evolutionaiy past of the speaes Most modem embryologists therefore, would restate the Law of Recapitulation in the highly modified form that Ontogeny repeats funda mental steps in the ontogenies of ancestral forms especially when these steps are of structural or functional importance to the indindual (de Beer 1940)

Although the original law especially as expressed by Haeckel (1874), has been replaced by a more tenable modem version the general idea of recapitulation has been of the utmost importance m the stimulation and imerpretation of investigations in the field of comparative embryology For one fact which does not seem tofit in with the modern thcorvof recapitulation a thousand can be cited which arc meaningless without it No matter how inadequate the modern theory may be regarded as an explanation of the reason for the developmental course taken by a species the general pnncjple wiH always be found of value in embryological study With few exceptions, the younger the stage of development of an embryo of a particular species the lower is the animal group which it resembles both morphologically and physiologically The value of this pnnaple for (he correlauon of facts is far greater for the student than the question of its worth as a philosophical explanation of ontogenies

It must be staled that the authors are under no illusion that the subject of comparauve vertebrate development can be adequately presented in a book of this character However some of the more fundamental facts especially those relating to early stages of development

377

378

HUMAN EMBRYOLOGY

will be given. It is hoped that the brief presentation of these facts will help to make more clear and meaningful many otherwise uncorrelated phenomena of human development, and that they will at the same time stimulate interest in the general field of embryology,

THE GERM CELLS

There are significant differences in the morphology and physiology of the germ cells of various vertebrate species just as there are differences between adults of the species. But as the germ cells are relatively simple structural and functional units compared with adults, the apparent differences are neither as numerous nor as extensive. Both male and female germ cells are nevertheless highly specialized and their structure is adapted to, or determined by, the functions they perform The sperm cells are more likely to possess visible distinctive characters than are the ova , but most of these sperm peculiarities are of no known significance It IS generally believed that their morphological traits are chiefly adaptations to the particular problems which they must solve in reaching and penetrating the ova. In order to accomplish this function the amount of cytoplasm in a sperm is reduced to a minimum, a flagellum is oes^loped tvhich renders it highly motile and the sperm head frequently possesses a special mechanism for the perforation of the ovum and its membranes. After fertilization, sperm morphology does not appear to be concerned with the further development of the embryo, although the genetic structure of the male gametes is of fundamental importance.

Ova, on the other hand, are always distinctly larger cells than the normal somatic cells of the organism from which they are derived. Further their increased cytoplasmic mass is frequently enormously enlarged by the accumulation of yolk oi deutoplasm (Fig. 410). They frequently possess protective envelopes, or egg membranes, and owing to the absence of motile organs they can only be moved passively. The size of ripe vertebrate ova, excluding their membranes, range from a diameter of about loop. in Amphtoxus and eutherian mammals (range 80-150/i) to about 85 mm. m the ostrich. The structure of an ovum, especially the degree to which nutrient material is included in its cytoplasm, has a marked effect on early development. Yolk-rich (megaleathal — mega = muc , lecithal = yolk) eggs support embryonic development of a vegetative sort to a relatively late stage; yolk-poor (mwlecithal ^m(e)io — less) eggs can do this only for a very short time, after which the embryo must acquire means 0 obtaining its nourishment from outside itself be that from sea water, soil, the tissue of a ost or the mammalian uterine mucous membrane.

The primitive Metazoan reproductive method appears to have been one in which a large number of miolecithal eggs ivere produced and widely dispersed. With little stored materia an early larval, or free-living embryonic stage, was necessary. In vertebrate evolution t tendency was to increase egg size and reduce the number of eggs laid. This tendency was associated ^v'lth the prolongation of the developmental period as in reptiles and birds w ere a larval stage is suppressed. In the mammalian class the evolution of specialized viviparo mechanisms has resulted in egg size being secondarily reduced, only slightly in Monotrem but markedly in Euthena. . r

Ov'a can be classified, therefore, on the basis of the relative amounts and distnbution 0 yolk and cytoplasm within them Table IV is designed to present this classification and correlate vertebrate ovum types with cleavage types Like all classifications this is for co • venience, and there are intermediate ova and cleavage types which do not quite con 0 to any compartment in the scheme. The most complete intergradation is miolecithal and medialecithal types. A fairly well marked gap exists between the medialcc and megalecithal eggs, but even here a few transitional types are kno^cn (eggs o P Lepidosteidae ) .

Fig. 410 — Schematic section of mature amphibian egg

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CLEAVAGE

\s has been described on paijc fa deisn^c i* the process wJjerebt the protoplasmic rnass of the fertilized efc,t, is pirlitioncd (either completel) or mcomplctel> ) into cells of il)out the size normal for the particular species Ostini, to the hrge size it is Iikcl> tint the unfertilized egg IS in an ibnonmJ metabolic state As clctsage progresses tlic diminution m cell size ol the successisc generations ofbhstomcrcs establishes gncluallj normal metabolic conditions ^ncomitant with tlic diminution in cell size greater mobilit) is conferred on the mdisidual hlastomeres thus facihnting liter morphogenetic mosements (see gastnihtion page 383) and

HUMAN EMBRYOLOGY

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m those eggs with gross accumulation of deutoplasm this material is gradually extruded from the effective protoplasmic mass.

Cleavage may be classified either in relation to the fate of the resulting blastomeres in subsequent development or, descriptively, in accord with the actual pattern of the cellular divisions Utilizing the former method cleavage is either determinate or indeterminate. Ova ■with determinate cleavage are those (mosaic eggs) in which the organ-forming regions are already predelineated m the fertilized egg. Indeterminate ova, which are usual in vertebrates, are those in ^vhlch there is no obvious mosaic structure at the time of fertilization and it is only after a certain, and generally quite late, stage of cleavage that presumptive organ regions are established. Up to this stage the blastomeres are pluripotent and are not yet “determined” (see page 121) so that, unlike the blastomeres in determinate cleavage, their prospective potency IS not necessarily identical with their actual developmental fate This implies that such

blastomeres possess certain poweis of adaptation to changes in their cellular environment, and consequently, eggs showing this type of cleavage are often called regulative eggs.

purely descriptive classification of cleavage is 1 elated to ^ actual pattern of the cell divisions. This pattern is largely

Ll .5 y dependent on the amount and distribution of the stored

JrC deutoplasm and thus the type of cleavage is related to the initial

size of the egg and varies according to ^vhether the eggs are niiolecithal, medialecithal or megalecithal (Table IV).

J CLEAVAGE IN MIOLECITHAL EGGS

^ ^ In these eggs the first cleavage spindle forms near the centie

of the egg so that two equal-sized blastomeres are formed

• (complete (holoblastic) and equal cleavage). These blastomeres

/' in turn divide equally and successive equivalent divisions of the

^ daughter cells result in the formation of a morula made up 0

many cells of nearly equal size and containing neaily equa ( ^ amounts of yolk and cytoplasm. In practically all these

Vsi ’■‘tl miolecithal eggs, however, there is a slight difference in blasto mere size and quality after the third cleavage. In Amphioxus after this third (equatorial) cleavage the four cells at the so-ca e

“animal” pole are slightly smaller than the four at the

n pole. Subsequent divisions emphasize this difference so t at t e „ , morula (Fig. 411) possesses an “animal” pole with smaller ce s

tion of mature'"^cgg **^0? ^ “vegetal pole” "wnth larger cells. Even P f

Amphtoxus B Early blastula mammals some difference m blastomere size is usually detecta

early in cleavage (Figs 28 and 412)

CLEAVAGE IN MEDIALECITHAL EGGS

In these eggs with a moderate amount of yolk the first two cleavages ordinarily ^ our equa astomeres, but the third cuts off animal pole cells which are much sma er ose e t at the vegetal pole (complete and unequal cleavage) Moreover, the sma con am itt e yolk, while the vegetal cells are loaded with it. This inert nutritive ma 'eeps ^ e metabolic rate of these vegetal pole cells relatively lower than that of the anima p’oup, e ^tter, therefore, divide much more rapidly and so assume the „igte

formation of the embryo The most familiar examples of medialecithal ova with complete u unequa c eavage are amphibian eggs, especially those of frogs and toads (Fig- 4 U

CLEAVAGE IN MEGALECITHAL EGGS j

tb ^ megalecithal eggs of reptiles, birds and the egg-laying mammals {Monotremata) ^^P the greatest development of yolk storage. Sharks and Lyt {Euselaehn) have almost as mu

I'lG 411 — A Schematic section of mature egg of Amphtoxus B Early blastula of Amphtoxus

COMPARATINE VERTEBRATE DEVELOPMENT 381

^olW, while the bon> fishes {T<Uostei) have notice ^

abh less but still enoutjh to limit cleavage to the | ,

mcomplece type In megalccithal eggs the active ( ^

egg cytoplasm with Us nucleus is a relatively ’

minute mass at the animal pole of the heavily ‘ F )\ 1

yolked egg Cleavage is at first equal but only f ^

involves the active cytoplasmic region The yolk j f \ '1

mass does not divide but is graduallv used as ^ I 1 I*

pabulum for the embryo and the extra embryonic ‘ ^ i ‘

membranes derived from the cells of the animal , j^r * jj ^

pole This incomplete partial or discotdal type of j

cleavage (meroblastic) results m a disc shaped \ ' j

morula and blastula instead of the essentialK v •* /

spherical structures seen in all the previously n.

mentioned types (cf Figs 415 417 and 419) ^ ^ TT % ^

In the phylum Chordata the miolecithal ^ ^ ^ ^

medialecithal and megalccithal types are all

found although the latter two are the more Fic 412 —A living morula of sheep killed five ° _ , , , , ^ ... days after mating x 380 (Reproduced

common The (^ephalochordata possess miolccitnal from Physiology of Reproduction by per

eggs with nearly equal complete cleavage In the mission of Messrs Longmans Green & Co

C}closlemala the pelr<}iin.,onU have medialecithal ova vvith unequal complete cleavage while the

mytinoids have megalecithal eggs wath incomplete cleavage Among the fishes the sharks and rays {Eusilachi) have megalecithal eggs unth incomplete cleavage The Poljplertdae the CkondrosUt the holostean Imia (i e , the group formerly called the ganoids) the Dipnoi (lung fishes) and the Holoeepkali have medialecithal eggs with unequal compleic cleavage The eggs of the holostean Lepidosteus (also a ganoid form) are transitional m type having so much yolk that cleavage is never complete yet m general pattern 1$ more like the unequal complete type than the discoid The true bony fishes (formerly grouped together as TtUostei) have relativclv small megalecithal eggs with defimtelv discoid cleavage Amphibia are characterized by

Frc 413— Section of an early blastocyst of the golden ham ster Cruttus au alus The outer cells are developing to form the trophoblast which is more darkly jtained than the cen trally placed cells x 640

(Reproduced from Physiology of Reproduction bv per

mission of NIessrs Longmans Green &, Co Ltd )

medialecithal eggs and complete but unequal cleavage Here the Apoda (Gjmnophionia) arc exceptions having so much yolk that their eggs should be classed as megalecithal with incom pletc cleavage AU reptiles and birds have large megalccithal eggs with incomplete cleavage All marsupials (Mctalhena) and placental mammals (Euthcria) have miolecithal eggs with complete and almost equal cleavage The reJalive ahscnce of yolk in both Metathena and Euthena is considered by some to represent a revcoal m evolution from the ^gs of ancestral oviparous reptile like mammals which undoubtedly possessed megalccithal ova The eggs of marsupials contain rather more yolk than do those of placental mammals, and yolk bearing fragments are commonly eliminated during cleavage {deutoplasmolysu) This phenomenon may represent a stage in adapution to viviparity The rare egg laying mammals (Monotremata or Protothena) have megalecithal ova with discoid cleavage (Caldwell, 1884 Flymn and Hill 1939 1947) There is now an extensive literature concerning the mechanism of cleavage the rates of cleavage in different animal groups and the effects of cbcimca! substances, especivlly mitotic poisons on cleavage This has been summarized by Boyd and Hamilton (19^2)

HUMAN EMBRYOLOGY

BLASTULA FORMATION

- c:

Fig 414 A Section of sheep blastocyst 10 days post insemination The endoderm can be seen lining the upper half of the blastocyst cavity X 230

B Section through inner cell mass region of another sheep blastocyst at the 10th day The inner cell mass is becoming intercalated into the trophoblast x 230.

C Section of embryonic disc of a sheep blastoc%st 12 days post insemination The embryonic formative ectoderm is now bulging above the lc\el of the adjacent trophoblast x 280

(Reproduced from “Physiology of Reproducnon,” by permission of Messrs Longmans Green & Co , Ltd )

In miolecithal eggs the blaslula is the hollow sphere of cells which results from the process of cleavage. The cavity of the blastula {blastocode) IS enclosed by cells which are slightly smaller m the animal than in the vegetal hemisphere (Fig. 41 7A), In medialecithal eggs the blastocoele is relatively small and, since the animal pole cells are definitely smaller than those in the vegetal portion of the sphere, the blastocoele cavity is much nearei the animal pole (Fig. 417®)* no longer speak of animal and vegetal hemispheres, but rather of an animal portion (usually about one-third) and a much larger vegetal portion. In megalecithal eggs the blastula is merely' a thin flattened disc of cells resting on the yolk mass, but separated from the yolk, except at its margin, by a shallmv cleft-like blastocoele (Fig. 419).

Although the mammalian egg is relatively yolk-poor and cleavage is at first complete and nearly equal, the late morula and blastula are distinctly different from those of lower vertebrates with miolecithal ova (e.g., Amphioxus). In the mammalian moiula an outei layer of small, slightly flattened cells can be distinguished from the larger polyhedral ce s of the inner cell mass This outer layer is t e trophoblast or trophoblastic ectoderm (

33i 34i 35i 56 and 4i3)- The blastula caw^^^ appears between the trophoblast and t cell mass and separates them side where they remain m contact. This yp of blastula, which is peculiar to the eutberia mammals, is probably not quite compara e the blastulae of lower forms, and part y or reason it has long been called a '^1^ *„ei The eggs of marsupials are slightly la g and more yolk-laden than those o p «  mammals and they diffeientiate more ra so that blastocyst formation is not qui same. Hill (1918), Hartman (1920), (1934) and McCrady 'SjS an ,,,

shown that in several of these ( Dasyurus, Macropus and Perameles) true morula, for, after the second blastomeres arrange themselves 1 layer around the inner surace „ ^12) pellucida, forming a hollow sphe ( g- j Lh eliminated yolk-fra^ents m the cc" cavity. This is a typical blastula and

CO\IP\R\TI\E VLRTrBR\Tr DE.\ tLOPME^T 383

blaslocjst for ihrro ,s no inner cell mas Certain largercells at the animal |»le (formatne area) m,™ie innards to form the endodem. (n)-nn and Hill 19(0) In the insectirores HmictnleUs stmtspinosus (Goetz, 1938) and Btphanlulus Jamesonu (van der Horst 1942)

a smeic lavered blastula ( mammalian blastula ) is formed without an intervening morula stage and at first without an inner cell mass \toncpolc however, a thickening resembling an inner cell mass, soon appears This is perhaps caused b> dehmination of an

inner cell mass in the true sense It is conceivable therefore that the **

marsupials and certain inscciivorcs show some of the transitional steps leading up to the typical mammalian blastocyst / ra-V

There is considerable variation in the relation of the trophoblast "f> to the mner cell mass ( formative cells ) in the stages immcdiatclv following the formation of the blastocyst m the different cuthenan groups In some e g , pnmates (probably including man) bats and a .

most rodents the trophoblast at first complcieK covets the tnner cell <

mass (Figs 56 58 and 428) In others like the pn, and probablv most of the ruminants and carnivores, the trophoblastic cells (Raubtr s laitr) covering the inner cell mass soon disappear exposing on the surface the cmbrvonic ectodermal portion of the inner cell mass This remains exposed until the amniotic folds form at a later stage

GASTRULATION

The Metazoan embryo at the end of cleavage (1 c in the blasiula B stage) undergoes a rapid change m shape due to a complex rearrange ment of the constituent cells This arrangement results in the establishment of the germ layers and is essentially a process enabling presumptive organs to reach (iieir correct position (RabI 1915 \ ogt 1929 Lehmann 1945) It is called ^af/ri/fa/ion The nature extent ^ and chronology of the gasiruiation movements IS different m different J species but thev always precede by a little the appearance of the 5 us ii

primordial organs In the mammals the process is delayed and when It occurs IS restricted to the formative cells of the inner cell mass The simplest form of gastrula is an embryo with only tvvo germ layers ^ an outer xhe ectoderm and an inner the rniAx/rm (Pig 415) The term gastrulation is often defined as the process by which the single lavered ^

blastula IS converted into a two-layered gastrula Tins is an adequate ' n.ir TT S

definition for a stage m many invertebrate types eg the miolecithal eggs of CoelenUrata and Cchnodermata as it desenbes a liurlv definite r'

period m development for these eggs owing to their complete and ::

nearly equal cleavage produce blastulac which are hollow spheres ^

with the cells of the vegetal hemisphere only slightly larger and more yolk laden than those of the animal hemisphere Xmphioxus possesses a q "■Xr?— t_i-J^ similar blastula (Fig 415)

vC::^

4'5 — Semi schemaiic drawings lo sho» gasiruiation and chorda mesoderm lormation in Imphtorus (Based partly on Conklin 1933 ) Ectoderm and neural tube in section in blue Endoderm in yellow Chorda mesoderm and oelinitvc chorda in reverse red sCipple Unsectioned mesodermal cells are shown with red stipple

' Late blastula stage (longitudinal seclionl B Earl) gastrula stage (longitudinal section)

^ Late gastrula stage (longitudinal s ction;

U Early mesodermal diverticula stage (transverse section)

h Definitive coclomic pouch stage (transverse section)

the arrow in A represents the future amcro posterior ams of the embrvo

384

HUMAN EMBRYOLOGY

In order to understand the morphogenetic movements occurring at gastrulation it is necessary to know the position of the presumptive organ-forming areas in the late blastula stage. Maps (Fig. 418) showing these areas have been provided for amphibian eggs by a number of investigators who have applied coloured marks to portions of such eggs and followed the fate of the stained regions in subsequent development (Vogt, 1925 and 1929)

GASTRULATION IN MIOLECITHAL EGGS

The blastulae derived from miolecithal eggs gastrulate by invagination of the vegetal hemisphere into the animal hemisphere, thus obliterating the blastocoele and forming a new

INTRACMBRYONiC

Fig 416 — Schemes to shotv the relation of the amnion and chorion to the somatopleure

A — Cross section of a typical vertebrate embryo in the region of the fore or the (q

B — Cross section of a typical mediolecithal vertebrate embryo in the region of the yo m show the potential “yolk sac ” gj

C Cross section of a typical anamniote vertebrate embryo of the megalecithal group, of a teleost, to show the trilaminar yolk sac. tvpic^^

D, E and F — Cross sections of successive stages in the development of the nsing

ammote vertebrate such as a reptile In these three schemes the amniotic folds are s from the extra-embryonic somatopleure

• ted

cavity, the gastrocoele (also called the archenteron or primitive gut), lined by the ^ q’jje cells which constitute the primary endoderm. The outer layer of cells is now the ^ blastopof^ circular opening, where the latter is continuous with the mvaginated endoderm, is tn In the Coelenterata the gastrula develops into the adult without any fundament in its morphology Even in the Echinodermata and Amphioxus the embryo retains i gastrula form for an appreciable time, becoming motile and feeding during ^ .jefly at was formerly held that these simple gastrulae grow in length by cell multiplication the nm of the blastopore. This rim was regarded as an undifferentiated area, an cells believed to arise there were considered to become ectoderm if they happenea

CO\irAIl^\TIVI VIRllBRAin DLVLLOPMLNT

385

cMcrmI to the nm or cnclodcrm if just intcmil to it More recent work howescr ind especiall> the results of mappint, has shown tint the cells of the bhstuh ln\e a prospectisc su’nific'ince licforc Ristnihtion I he chaOsCs it the hlxstoporic hp therefore in%ol\c extensive migratory movements nlhcr than simple proliferation Indeed in \wphtovus a.s subsequent development showa (Conklin 1932) the invat,inated inatcria! includes more than the primary endoderm (I ig 415) as it also gives oni.in to the third germ lajer (tlie mesoderm and notochord) In all vertebrates inv agination of the primary endoderm precedes bv onlv a bncf penod the invagination of mesoderm and notochord m fact the three processes occur more or less concurrently In verte brales then there is no clear distinction between the period or the process of formation of cnthxlcrm mesotlcrm and notochord there fore It IS liecoming common practice for vertebrate embryologists to include as gastrulation not onlv the process of endoderm formation but also that of the early formation of mesoderm and notochord for the sake of continuity the origin of the somites coelom and neural plate will lie discussed here although these processes arc not even in a general seme a part of gastrulalion

Careful study of the growing gastnila of Impktotus reveals that the invaginated vegetal hemisphere cells form onlv that endoderm which lines the floor and approximately the lower lsvo.tJurds of the lateral sides of the elongating gasirocoelc or primitive gut 1 his primarv endoderm is augmented by secondaty endoderm or thorda mtsodem consisting of small yolk free cells (Pig 4J5) which migrate in through and proliferate from the region of the blastopore ami form the roof and upper tliird of the sides of the primitive gut This chorda mesoderm is not considered to contribute much to the definitive gut It is really a stage m tlic denvalion of the mesoderm and notochord from the cctodenn In this process the chorda rneso* derm along the midline of the roof of the gastrocoeic cvaginalcs dorsal ward forming a ridge wliicli soon separates from the gut l>eginning at the cephalic end and forms a solid rod of tissue the notoihord At the same time lateral diverticula (the mesodemie or totlomic pouches) ansc in consecutive pairs from the lateral part of the chorda mesoderm on either side of the notochord cv agination The first pair

appear at the anterior (head) end and the succeeding ones, m sequence back towards the blastopore I he pouches enlarge, separating the ectoderm from tlic primitive gut and finally sever their own connection with the gut cavity and endoderm Thus a senes of isolated paired mesodermal sacs enclosing paired cocinmic cavities arc formed throughout the length of the embryo (Pig 4i5r) Phev expand ventrally and dorsally separating the cndodcrmal gut completely from the ectoderm Along the mid sagittal plane where the adjacent portions of right and left mesodermal pouches come into contact

ventral and dorsal to the gut they form the temporary ventral and permanent dorsal mesentery Tig 416) The lateral portion of the

Fio 417 — Semi schemaiic drawings to show Kastnilation and chorda mesoderm formation in Amphibia The same conventions are adopted as m I ig 415 \ Cleavage stage B Section of cleavage stage C Tarly gastrula stage (longitudinal section)

D Intermediate gastrula stage (longiludinal section)

E Late gastrula stage (longitudinal section)

386

HUMAN EMBRYOLOGY

mesoderm of each pouch comes into contact with the ectoderm and becomes mainly translormed into a segment of the body musculature, the medial portion, m contact with the endoderm, forms the smooth muscle and connective tissue of the alimentary tract and mesenteries Probably relatively little of the chorda-mesoderm remains after formation of the notochord and mesoderm.

any which persists is found as a median strip m the roof of the definitive gut cavity. The processes just described constitute the fundamental steps in the segregation and differentiation of ectoderm, endoderm, mesoderm and notochord.

GASTRULATION IN MEDIALECITHAL EGGS

Gastrulation in the medialecithal ova of the lampreys {Petromyzontidae), certain of the “ganoid” fishes (Polyptendae, Chondrosiei, Atniidae) and the Amphibia is typified by that of the frog although, of course, there are variations in detail. In the frog

D

Fig 418 — Scmi-schematic drawing to show primiU\c streak stages

.\ Late gastrula

stage through pnmiUve

streak (trans\ ersc sec tion)

B Farlj ncurula

(trans\ersc section)

C Formation of neural folds (surface vnew) D. Prcsumptite regions on the surface of the hlastula

(Fig. 417) the relatively great size and slow cleavage rate of the yolkladen blastomeres in the vegetal two-thirds of the blastula is the chief cause of differences in its gastrulation from that of such forms as Amphioxus. As the large cells form too bulky a mass to be mvagmated within the fewer and smaller cells of the animal pole, gastrulation is effected by the proliferation and spreading of the smaller animal pole cells downwards and over those of the vegetal pole while, at the same time, the animal pole cells of the advancing margin are progressively mvagmated so that a new cavity (the gastrocoele) which communicates with the exterior is formed, and the original segmentation cavity is obhteiated The gastrocoele is partially lined by animal pole cells (chorda-mesoderm or secondary endoderm) in addition to the heavily yolked cells of the original vegetal pole (primary endoderm) The former will give origin to the mesoderm and notochord. Those animal pole cells which are never mvagmated (1 e , those furthest from the area of invagination) will in later stages form the definitive ectoderm and neural plate The process of spreading, or overgrowth, by the smaller animal pole cells, is called epiboly It commences at the margin of the animal hemisphere and from the first shows a bilateral symmetry, the- overgrowth is more rapid at the future cephalic margin [dorsal lip) of the blastopore and slower at the future caudal margin [ventral lip) , the marginal regions joining the dorsal and ventral lips are the lateral lips and they show a dorso-ventral gradient in the degree of overgrowth. The entire margin of overgrowth is the blastopore As epiboly nears completion the blastopore becomes a small circular opening plugged with buried endoderm cells. This is known as the yolk plug and is of little significance except as a characteristic condition at one period in the gastrulation of most medialecithal eggs of vertebrates The original yolk-laden cells of the vegetal two-thirds of the blastula now form a mass within the ectodermal shell and beneath the sht-hke gastrocoele which lies between the mvagmated chorda-mesoderm and the primary endoderm The chorda-mesoderm is continuous with this primary endoderm cranially, and temporarily forms the roof and upper lateral portions of the gastrocoele or primitive gut cavity With continued development the periphery of the mvagmated chorda-mesoderm extends ventrally on the lateral side of the primary endoderm At the same time the upper edges of t e latter extend medially and eventually fuse in the mid-hne an

CO\IPAR.\TI\E NFRTEBRATE DEVELOPMENT

387

undemcith the axial portion of the chorda mesoderm This axial portion is the notochordal plate and as it is separated from the roof of the I'astrocoelc it becomes the notochord The fused edges of the primary endoderm underlnni, the notochord form the permanent roof of the enteron or gut Lnlike Im/Aiono mesodermal pouches are not formed b> csagination from the chorda mesoderm The mesodermal sheet mcrcl> extends \entrall} between the endoderm and the o\crl\ing ectoderm Mesoderm formation begins in the late >olk plug stage as the blastopore is constricting to form a \erucal dumb bell shaped slit The lower end of this slit remains open as the definitive anus the upper end persists tcmporanl) as a duct xhc neurenltrie eanat leading from the caudal end of the ectodermal neural groove into the gut just caudal to the point where the secondarv endoderm and notocliordal plate are still con iinuous Between these two openings tlic lateral lips of the blastopore fuse and from this fusion line or e streak the mesodermal sliect

continues to be proliferated from the ectoderm and extends laterally and anteriorly on each side of the notochord As each sheet grows laterally it separates the ectoderm from the cndoticrm until finally as in Imp/uoxus the sheets meet ventral to the gut (Fig ji8\andB)

The further differentiation of the mesodermal somites lateral plate mesoderm and coelom is typical of that of most vertebrates

GASTRULATION IN MEGALECtTIlAL EGGS Fishes The process of gasinilation in vertebrate mcgalecithal eggs vanes with the amount of yolk relative to the cytoplasm In the Teleostet (bony fishes) the cytoplasmic area is relatively large compared w ilh that of sauropstdan (reptiles and birds) eggs After early cleav age in the telcosts the blastoderm usually covers about one fifth of the surface of the egg \t the margins of the blastodtse the deeper cells separate (by delamination) from the outer thus forming a circular zone of primary or yolk endoderm \t about the same lime liouever a definite inturning (invagination) of the surface cells begins at the caudal margin of the disc to form a layer of secondary endoderm (chorda mesoderm) corresponding to that of Amphtoxur and the \mphibia This spreads rapidlv over the upper surface of the yolk separating it from the overly ing ectoderm and fusing on all sides with the marginal yolk endoderm As this overgrowth continues its rim passes the equator of the egg and constricts on the caudal side of the vegetal pole to form a somewhat circular opening which is readily recognized as the blastopore \Nhen this process is ncarlv complclcd the two layered blastoderm grows downwards and envelops the yolk mass to form the bilaminar yolk sac which is part of the primitive gut and characteristic of all mcgalecithal vcrlcbrales Tlie invagination

Flo 419 — Srmi schematic dras mgs in shos gasinilation and chorda mesoderm formation in the asian egg

\ Germinal d sc \ ith w o polar bodies B Lateral surface lies of early biaslixlisc C Longitudinal section through early I lastodisc

D Longitu I nal section through later blastodi c (The arrows in the inset show the direction of migration of the mesoderm )

E Farlv gastrula stage {longitudinal section^

F I resumptiie regions in the surface of Ihe blastoderm (superior view)

G Presumptiie regions in the surface of the blasiodeim (lateral vies )

H Transverse section through late gastrula stage in region of notochordal plate

I Transverse section at level of primitive streak

388

HUMAN EMBRYOLOGY

at the blastopore is much more marked, and the primitive streak persists for a longer time than in the frog. The process of primitive streak formation is still active and the blastopore is still open even after the formation of the head fold and many somites. The notochord and mesodeim arise much as in the frog, the former by invagination of the chorda-mesoderm through the doisal hp of the blastopore (primitive node) and the latter by invagination of surface cells thiough the primitive streak (fused lateral lips of the blastopore).

Reptilia. Owing to the still greater proportion of yolk m the reptilian egg, gastrulation IS even less like that of the frog than is that of the Teleostei The blastodisc is a relatively small aiea on the huge yolk mass, and the segmentation cavity is insignificant. Under the entire blastoderm yolk endoderm cells separate from the surface cells (ectoderm) and orgamze to form a complete sheet of primary endoderm. The two-layered disc now begins to overgrow the yolk, as in the fishes, and at the same time a small depression forms on its surface near the ( audal margin. This is an area of invagination, the dorsal hp of the blastopore. There is a convergence of surface cells towards this area and a short primitive streak or “plate” is formed, ■d though apparently no such movement of the actual edge of the bilaminar disc occurs, as ,n the fishes From this the notochord and mesoderm arise as in the Fishes and Amphibia.

Peter (1935), however, considers that in the chameleon and lizard most of the notochord and gut endoderm is formed from the delaminated yolk endoderm, only the caudal portions of each arising from the invaginated chorda-mesoderm (see also Pasteels, 1937 and 1940).

Aves. Cleavage and blastoderm formation in birds are almost identical with these processes in reptiles. There is a blastula stage in which the cleavage cells form a blastoderm three or four cells thick, separated by a shallow “segmentation” or “subgerminal” cavity from the centrally placed yolk and continuous with it at the periphery. The central, unattached region is the area pellucida, the attached margin, the area opaca. Around the margin, yolk endoderm delaminates from the overlying ectoderm as m reptiles. According to the usual description, based largely on Patterson’s (1909) investigation of the pigeon, the caudal margin of the blastoderm invaginates to form secondary endoderm much as in the bony fishes. Convergence of the blastoporic lips gives rise to a distinct primitive streak, and it is during the initiation of this process that the blastopore is closed (Fig 419). Jacobson (1938) believes that much of the foregoing description of gastrulation m birds requires modification He states that there is practically no segmentation cavity and that there is a very brief period when the area pellucida of the blastula is made up of a single cell layer He considers that there is no invagination of the caudal edge of the blastoderm to form a temporary blastopore Instead, there IS an o\'al area of the caudal region of the area pellucida, not involving the margin of the disc, from which individual cells migrate beneath the blastoderm, proliferate, and organize to form a sheet of secondary endoderm which soon spreads out like that of the reptiles and bony fishes to fuse with the marginal yolk endoderm This area is the primitive blastoporal plate and coriesponds to the dorsal lip of the blastopore, although there is no invagination. There follows a movement of surface cells toivards the plate, and the area caudal to it, which is comparable to convergence in the t^qies previously described. These cells form a definite primitive streak from the lower surface of which, for a short time, endoderm continues to be budded Soon, however, all the cells proliferated laterally from the streak he between the ectoderm and endoderm and are, therefore, mesoderm (Fig. 420). From the cephalic end of the streak the notochord arises m the usual manner, being first included, as a notochordal plate, in the roof of the primitive gut, and later separating from it to assume its typical position between the gut and the central

Fro 420 — Schematic representation of the surface view of the developing blastoderm in the chick embrj’o The area vasculosa IS represented in red dots.

COMPARATIVL VERTEBRATE DEVELOPMENT

389

nen'ous system (Fig 42 1) More recently Pasleels (1945) Has rein\ estigated the origin of the avaan endoderm In the duck he found the primary cndoderm to arise as the result of the progressive delamination of the dealing blastodisc into a superficial and a deep layer between which a cleft appears He homologizes this cleft with the blastococle and considers that the sub germinal cavity IS not a blastococle being infact only theresuk of theprogressiveliquefaction of the yolk acted upon by enzymes produced by the yolk syncytium and perhaps the blastoderm itself

GASTRULATION IN MAMMALS

Up to the present it has not been possible to make an adequate experimental analysis of the process of gastrulation m the mammals The precocious segregation of tissue regarded as ectodermal to form the trophoblast limits the formation of the endoderm and the intra embryome mesoderm to a restncied group of cells in the typical euthenan blastocyst Earlier investigators (e g Keihel 1889 and Hubrecht, 1890) thought that mammalian gastrulation occurred m two stages The first of these is the formation of primary endoderm by delamma lion of cells from the inner cell mass or ils equivalent and the second the imagination of embry oruc disc cells to form secondary endoderm mesoderm and notochord Most modern investigators necessarily basing tbeir conclusions on morphological findings regard both the processes as essentially part of gastrulation though invagination is much modified and reduced Endoderm formation in all mammals IS basically similar to that m the avian egg in that cells migrate or are delaminated from the deep surface of the inner cell mass (Fig 414) These endodermal cells may in part become intimately related to the trophoblast in the formation of the yolk sac but there is no reason to doubt that their initial formation is an integral part of gastrulation In the second stage of gastrulation there is a migration of surface ectodermal disc cells to a limited axial region of the posterior portion of the embryonic disc to form the primitive streak From tins streak cells come to he between the embryonic disc ectoderm and the endoderm to form the intra embryonic mesoderm (and in many species by later extension the extra embryonic) The anterior extrcmitv of the pnmuive streak is specialized to form the primitive or Hensen s node Some of the cells of this node form an invagination which gives origin to the notochordal or head process as described in human development (page 49I This notochordal process becomes temporarily intercalated in the axial region of the endoderm hut later separates from it to form the notochord In addition to the formation of mesoderm from the primitive streak as an integral part of gastrulation mesoderm can also arise from the trophoblast (extra embryonic mesoderm) from the prochordal plate (cephalic mesoderm) and from the neural crest (page 270) The theoretical consequences of these additional methods of mesoderm formation on our conception of gastrulation are not vet clearly understood For details of gastrulation in marsupials the reader is referred to I Ivnn and Hill (1942) and McCrady (1938 and 1944)

VERTEBRATE EMBRYONIC OR EOETAL MEMBRANES

As has been stated earlier (page 69) a structure or tissue developed from the fertilized egg that does not enter into the formation of the embryonic body is called an (extra )embryonic or foetal membrane These membranes are of functional importance during embryonic hfe being concerned with the supply or storage of nutriment respiratory txchange and protection oftheembryo They arelargely shed or absorbed at hatching or birth The foetal membranes include the_job sac the chorion (or serosa) the amnion, the allantois the trophohlasl (m mammals) the piacinia and the orn6jfif<3l cord Certain of them are not necessarily membranous m character

Flo 431 — Section of somite stage of (he de veloping chick embryo to show formation of amniotic caviw and formation of >oIk sac and extra embryonic coelom

390

HUMAN EMBRYOLOGY

(e.g. many placentae and the umbilical cord). In many mammals (deciduate types) the uterine tissues come to be intimately connected with the outermost embryonic membranes (page 67).

FOETAL MEMBRANES IN ANAMNIOTA

The cyclostomes, fishes and amphibia do not possess an amnion and are consequently known as the Anamniota, In the embryos of these vertebrates the only embryonic membrane developed is the yolk sac This sac, whether in the form of a definitive yolk sac (e g., m the megalecithal eggs of the hag-fish, the sharks and the bony fishes, Fig 41 6G) or of a mass of heavily yolked cells (e.g , in frog, Fig 416B), is enclosed within the ventral wall of the body In theforms with a definitive yolk sac during orsoon after gastrulation the ectoderm, mesoderm and endoderm of the embryonic disc grow down over the yolk mass, thus enclosing it within the primitive gut and body wall. This three-layered (trilaminar) yolk sac wall has exactly the same fundamental structure as the gut and abdominal wmll of the frog embryo at about the time of closure of the neural groove The only difference is that in the frog the yolk material is intracellular, within the endoderm cells of the gut (Fig. 416B), whereas in the megalecithal species it is in the form of a relatively large non-cellular mass lying within the gut cavity and distending the whole “abdomen” far beyond the normal body contours (Fig. 41 6C) In these trilaminar yolk sacs the mesoderm becomes very vascular and gradually transports the nutritive material, absorbed from the yolk by the endoderm, to the growing tissues of the embryo proper. Thus the yolk sac shrinks as the body grows, and finally becomes incorporated into the ventral abdominal w^all and gut Its tissues are not only homologous with those of the gut wall and body ^vall, but they actually become part of these structures.

Some Euselachii are viviparous, and in these the yolk sac wall functions both to absorb the yolk through the endoderm and to absorb oxygen and nutriment through its ectoderm from the uterine wall of the mother This is a type of yolk sac placentation, and in some species It consists of a fairly close apposition of the yolk sac wall to the uterine lining (Gate-Hoedemaker, ’^933)* III the relatively rare viviparous bony fishes the yolk sac is usually very small as the eggs themselves approach the medialecithal type In these, therefore, no yolk sac placenta is formed, but absorption from the maternal tissues is carried on by vessels of an excessively enlarged pericardium or by special modifications of gill or anal filaments (Turner, 1940)

EMBRYONIC AND FOETAL MEMBRANES OF AMNIOTA

Most of the anamniota discussed above deposit their eggs in water, but there are other groups of megalecithal vertebrates {Reptiha, Aves and Monotrematd) which lay their eggs on land These are all characterized by the presence of an amnion, a modification of the extraembryonic body wall (somatopleure) to form a liquid-filled cavity, surrounding the embryo (Figs 416E and F and 422). The most obvious purpose of the amniotic cavity is to provide a local aquatic habitat for the embryo in eggs laid in non-aquatic surroundings The amnion develops before the embryonic body is definitely formed and persists, in these types, until hatching. The ev'olution of the amnion is uncertain, but its probable primitive manner of formation is showm in Fig. 41 6E and F. The chorion, or serosa, is formed during the closure of the amniotic folds from that part of the extra-embryonic body wall which does not contribute to the amnion (Fig. 423) • The development of the extra-embryonic coelom completely or incompletely separates the non-amniotic somatopleure, consisting of extra-embryomc ectoderm and its lining of (somatoplcuric) mesoderm from the splanchnopleure formed by the extra-embryonic endoderm and its covering of (splanchnopleuric) mesoderm This portion of the extra-embryonic somatopleure is the chorion The extra-embryonic endoderm and its covering splanchnopleuric mesoderm form the bilaminar splanchnopleuric yolk sac The chorion and the splanchnopleuric yolk sac are structures not found as such in the aquatic egg types, but nevertheless they are represente in the latter by the somatopleuric and splanchnopleuric layers of the anammote yolk sac (Fig. 41 6C).

CO\IP\R\TIVr VERTEBR.\TF DEVELOPMENT

39« 

TROPIIOBLAST

This structure is a special precocious!} dcselopcd embr\omc membnne found m the desclopmenl of Metathcna (marsupials) and Emhcna The primara object of this membrane

392

HUMAN EMBRYOLOGY

CHORION

(SEROSA)

CX7RACMBRYONIC

AMNIOTIC OUCT

ACtANTOIS

IS the formation of a vesicle capable of absorbing nutritive material and, by its rapid growth, the provision of a space m which the embryo can grow and differentiate

AMNION

In viviparous mammals an amnion is always developed and in its definitive stage of development is essentially similar in all metathenan and eutherian groups although it originates

m different ways. The most primitive method of amniogenesis would seem to be by folding of the extra-embryonic somatopleure, as has been described above for the megalecithal amniotes. There are all gradations from this method of amniogenesis to that of such species as the monkey or man, m which the amniotic cavity arises by a cavitation of the inner cell mass as a result of the confluence of intercellular spaces in that part of it related to the covering trophoblast. In some mammals, e.g., carnivores and ungulates (Fig 422), showing amnion formation by folding, the trophoblast over the embryonic disc becomes a thin membrane (known as Rauber’s layer) and disappears, leaving the embryonic disc secondarily intercalated in the wall of the blastocyst and thus exposed until the amnion is formed In many bats (Fig. 422) an ectotrophoblastic cavity appears between the trophoblast and the embryonic disc ectoderm, the definitive amnion IS formed later by folding within this space. In many rodents (Fig. 422) the trophoblast covering the inner cell mass proliferates an , at the same time, the inner cell mass is invaginated into the yolk sac This condition, especially when it occurs at the embryonic isc stage, IS known as “inversion” or entypy 0 the germ layers. The proliferating column o trophoblast is called the “carrier, or rager. The space enclosed by the embryonic disc and the cells of the Trager is the pro-ammotic space. This space is divided by the development o amniotic folds, into a lower amniotic ^ and an upper epamniotic (ectoplacental) cavi y.

In rodents with superficial implantation only partially interstitial implantation

formation IS by simple folding. Thus m with partially interstitial (intramural) imp a tion of a large blastocyst where the uteri epithelium does not grow over disc at the site of penetration, the a develops by folding (Figs 428 an 433 h

The later htstory of the amn,on ar « 

tOtK SAC VILLUS

VITELLINE MEMBRANE

CXTRAEMBRVONIC COELOM

ALLA ITOIS

Fig. 423 embryonic

/ -- |Vlossman

■Three stages in the development of the considerably as ^as een ® ^ independent

ic membranes of the chick. (l937)' remain. G/

393

COMPARATINE VERTEBRAfE DEVI- LOPMENT

non \ascubr membrane until fuW term as tn roost mammals twth a small or no allantois (a) it mat expand to obliterate almost coTnpleta> the extra emhT>oroc coeloro the mesodetin coveting the ammon fusme nith that of the chorion, (3) »t ma\ become surrounded b% the allantois thus becoming x asculanzed as in Artiodactyh Pmssodactyla ind Cami^^ra These dificrcnt conditions of the amnion are more hheU dependent upon the degree of development of the allantois than on mtnnsjc functional difTcrcnces in the ammon itself

There ma> be some correlation between the t>pe of ammon formation m mammals and the time and the method of implantation of the blastocvst Early implantation seems to favour ammon formation by cavitation, late implantation is associated with ammon formation by folding

YOLK SAC

In the development of reptiles, birds and monotremes all of which have mcgalcciihal eggs the first foetal membrane to appear is |he yolk sac It vs formt d vmtiaUy by the extension of blastodermic endoderro round the >olk mass Later the roesodetm becomes interposed between this endodetm and the overlying ectoderm \Nhcn the extra embryonvc coelom appears U splits the mesoderm into an outer somatopleunc layer and an inner splanchno pleunc layer ^Flg 423) The former tot ether with the ectoderm constitutes the Jema or ehrn It while the inner splanchnopkuric layer and the endoderm form the definitive yolk

sac

Metatheria (Marsuptalta) Jnspite of the iact that these mammals have miolecithal eggs they develop a yolk sac soon aficr the falastula stae-e In us fundamental structure this sac resembles very closely that found m the reptiles birds and monotremes After the formation of the endoderm (page 389) this embryonic layer by its own growth extends gradually round the inner surface of the ucutammac ectoderm Eventually the endoderm iQtms a complete lining for the blastocyst wall vvhich thus becomes bilanumr Hill (rgio) from hw study of the development of £)as>unu concluded that the marsupial bilammar blaslo cyst consists of embryonal and extra cmbrvonal

Ftc 424 — Otagrami comparing th^ stager ik early development of a primiUve rod nt of the sijuirrel family [CilrUuj /rtdnmhnealtis) with riniiUr stages in a specialized rodent (laboratory mouse) A B and C — C trtdtCimlintatus (after

Mossman and Weiifeldi 1939) D E and F

Ifw rear a?tir (from Snell 1941)

leyona The fermer is constituted b\ an outer lajer of embf>onic ectoderm tvith an underlying poitionotendodenn (seiiig 40^) these tno lajm ntll form the future embryo The ectra ewhrytinal region separated from the other area by a junctional line is formed bs the Kophohlastic ectodenn (Iroph ectodenn) together nilh the underlying portion of endoderm The tuo layers ectodermal and endodermal of the cetra embryonal region constitute a buatnmar omphalopleurc (or yolh sac) Later In eleielopmetit e-ctension of mesoderm beyond the margin of the embryonal area forms a tnhinunar omphalopicure Since tins mesodermal extension does not usually reach more than a third of the distance to the abembryonic pole of the b asiocyst the b.lammar omphalopleurc preatsts in the abembryomc hemisphere thromhout gestatton and the endoderm of the yolk sac in marsuptals remains ,n permanent contact yyoth the outer nail of the chonomc sac oter a considerable part of m extent (see II, nn 1923 and

^^ove, th,

tije v^T ^ Pericarw ^ ^espiraf dev^, ’ -fJence an ^ f exch^n ^

£S~ ~S- '$?&rs*sz*«Ss^

5f^;S?‘33s '5:5.-S£= t aZ »?5H

an ^'"^mense^ f'^ncZ^- '^^us ,n /r envl^^'T'"^

a storage

a^iantojs varilc “^^ae dur,n 1”^^ indeed, in

appearance and

COMPARATIVE VlRTbBRATE BEYFLOPMENT 39 j

m the s.ze of endodcrmal component It is iE%a'5 a highW vascular structure -md from us mesoderm is derived the foetal blood svstem to the mam placenta (Figs and 43BI The fused aJhncoic mesoderm (with us vessels) and the chonon Vvsilh us trophoblast) « the foetal portion of all definitive (or chom aUanlou) placentae in mammals The cmlodcrmal portion of the allantois is nell developed in primitive tvpcs (Fig 42B) while in the more specialized species U ma> be either excccdingl) large (Figs 427 and 428) or more often \cr> much reduced (mart) or absent as in some rodents (Ca la)

PLACESTATION IN AMNIOTA

\s has been stated earlier certam viviparous fishes have developed a t>pe of >olk sac placenta In the amniotes placental mechanisms are found in a slight!) developed condition in certain reptiles and marsupials In the emhcnari mammals placentae are univ ersall) present though as Will be indicated later there is a veo consider able range of variation shown in their nngin histological structure and superficial appearance

Reptilia A few reptiles eg, ccriam snaves, and lizards imfaia and I i/>efO fceno)

arc ovoviviparous that is to sa) the eggs although esscntiall) like those of oviparous forms are heW in the female leproduetive tract until the) hatch The foetal membranes of these species ate not din’erent from those species who c eggs develop outside the bod) Ihere are however a still smaller number of U/ards which are truls vivt parous that is their eg^s have poorl) developed shell and albumen W)ers and their membranes form a rather close union for respirator) and nutritive purposes with the uterine lining of the mother Usuall) it is the )Cilk sic and thr inUf venmg chonon vshich form this placental contact with the maierna.1 tissue but vn one or tv\o species the allantois and the intervening chonon acmallv fuse with tlie uterine lining to form a fairly complex chorjo allantoic placenta (Wcekes 1930 and >935)

Placentatson in Marsupials Like the viviparous lizards the membranes of these lower mammals vary m the degree lo which the )oIk sac and allantois are developed as nutritive, respiratory and excrctor) organs Those with shorter gestation periods like the opossum {Didelphys) and kangaroo {\factopus) seem to depend chiefly upon the )olk sac for nutnijonal relations with the uterus although m all types which have been studied the allantois 1 at least of respiratory significance As has been explained earlier (page 393} the wall of the embryonic vesicle m the opossum eventually shows three different regent '/) an abcmbryonic non vascular portion (hilaminar yolk sac or omphalopleure) (2} a broad vascular zone formed where the mesoderm of the yolk sac remains in contact with the somatopleurc (trilaminar omphalopleure) and (3) the non vascular serosa or chorion Of these three regions though some fluids and substances from the uterine cavity may pass through the first and the third it is the tnfaminar omphalopleure which constitutes the important orpan of nutrition and respiration It can be regarded as constituting a chorjo Mtellme placenta Those marsupials with longer gestaUon periods like Perameles (the bandicoot)

fv - ^ vh- '/%. /5

Fio 425 — Trans\erse sreuon of the aniiin«c>meirial porlion of the uterine cavity m the goJden hamster C 1 e ut aurafus vo jhjw earb atlachment of the blastocMC <30 LRe potlufdfrom Phyiiology ofReprcxluction hy perinisiitn of Messrs Longmans Green 6 . Co Ltd '

HUMAN EMBRYOLOGY

have a chorio-allantoic placenta of about the same complexity as the most highly specialized placenta of lizards. (For details of marsupial placentation see Hill and Fraser, 1925, Flynn, 1923 and 1930, Pearson, 1949.)

Implantation in Eutherian Mammals. Before placentation in this sub-order can be described, it is necessary briefly to refer to implantation. In some eutherian mammals S ) P^S) sheep, cow, horse, dog, cat) the chorionic sac remains in the uterine lumen where it expands to fill the greater part of the cavity (Fig 427). This is called central, or circumferential and superficial, implantation. In other eutherian mammals (e.g , mouse, rat, hamster) the blastocyst comes to he in a recess of the uterine cavity which becomes closed off from the remainder of the cavity and in which the blastocyst becomes implanted (Figs. 425 and 426) This is eccentric implantation which later becomes partly interstitial. In still other euthenan mammals (e g , man,

chimpanzee, certain bats) the blastocyst comes to • he in a sub-epithelial position within the decidua

427)* This IS complete interstitial implantation usually occurs at a much earlier stage in development of the embryo than either eccentric or superficial The site of implantation of a blastouterus shows species differences. In many animals (e.g., most rodents and msectivora) on the antimesometrial side of the uterus, in ^ bat, and in Tarsius) li IS on the mesometrial side. In a few species the f implantation is orthomesometrial or lateral, that is,

approximately half-way betw'een the mesometrial antimesometrial positions. This occurs m the

> tenrecs [Centetes and Hemicentetes) where the sites ol

implantation of a litter tend to alternate, every other embryo implanting on the same side (Goetz, igs?)*

Placentation in Bnthetian Man.mals. Part of the explanation of the differences the eutherian placenta lies in the extreme variability of the foetal membranes themse ves, and in the manner and extent of their ^eve op ment. In general, the more primitive groups a membranef more nearly like those of the reptiles. Fig 426 — Transverse section through complete while the higher forms have much more specia ize

uterine cavity of the golden hamster, Cncetus membranes This is true for the developmeniai

r history of the membranes as f ^on

of Reproduction,” by permission of Messrs mature condition Since membrane Longmans Green & Co , Ltd ) have evolved independently in each group

after it began to diverge from the

mammalian stock, orders such as the Insectivora and Rodentia show a wide range m mem morpholog)' entirely within the group Because of this the resemblance between the mem of the primitive members of two orders is greater than that between the more specialize is clear, how ever, that there has been much less variation in the structure of the foetal ^

than in the adult morphology of the various groups For example, it would be \ ’-^ee

for an expert on placental morphology, to distinguish between the membranes of a c *'^P gorilla and man, or betw^een those of a sheep and a goat. In fact, even those o a sea-lion (both Carnivora, but of very different body structure) are very similar. .jy

such as these it can be argued that the characters of foetal membranes have changed m evolution than have the adult body chaiacters and that, there.ore, in general, they are

39 ?

COMPARATIVE VERTEBRATE DEVELOPMENT

criteria for determining phNlogenetic rdationsbips joammals— particularly affinities between the larger groups such as orders and families , , , v

It w not practicable here to give a detailed account of the great v arietv of methods whereby the foetal membranes of evttheriarv mammals dctclop or even to describe their mature structure Reference to Figs 427 and 428 tvhich illusiratt ihc development of the membranes in the pig dog Tarsius rhesus monkey ground squirrel hedgehog and man eives a general idea of repre senutive types of membranes and placentae These figures should be compared with Figs f2q and 430, and Table ^ to correlate the finer structure of the placentae

The chorion is relatively larpc m relation to the embryo m early stages of development but at term m all < utherian mammals the chononic cavity is practically filled by the amnion which in turn has its cavity ocrupted nevrly completely by the foetus In general the earlv chorion is relatively extensiv e m those forms (pig sheep) which develop thm or scattered areas of placentation at a rather late stage whereas in those which rapidly develop a thick and concentrated placental area (man r^ents) it is relatively small from the beginning A large allantoic vesicle is always a concomitant of a large chorion and of a thin or scattered placental «r“a like that of the pig and sheep

yolk sac PLACENTATIOV IV EUTHERIA

The \a cnUrization of the interposed mesodenw vn the trilaminar omphalopleure of many carnivores rodents and msectivores may give rise to a temporary rhono vitelline placentation (Figs 427 and 428) similar to that found mr’awupiah This serves the important function of ciQurtvIuni the embryo until the somewhat tardilv developing allantois has time to reach and v'vseulariitt the chonon

An entirely dilTerent type of volk sac placentation both structurally and physjologicallv develops m the mammals which show some /brm and degree of so called inversion of germ layer or entypy This is called inverted yolk sac placentation and occurs m Rodentva Lagomorpha (rabbits) many Nlicrochitoptcra (bats) andlnvectivora.andmthe Dasypodidae (armadillos) As de enbed on page 394 and illustrated in Figs fj?? and 498 no mesoderm develops m the abembryonic hemisphere of the blasiocvst or bdammar omphalopleure which therefore remains a very thin, membrane m contact with the uterine w all may disappear com pletcly ormavevennever develop asm the guinea pig In any case the embryonic hemisphere of the volk sac is very vascular and inverts into the abembrvonJc area thus bringing us lining rndodeiTn mio very dose relation to the utenne mucosa over a mde area The relative extent nf this inverted volk sac increases as gestation progresses, and m RodenUa and LagomorpfiQ at term it iv attached almost directly on all sides to (he placenta often in a ring very close to the attachment of the umbilical cord In most sprcics part or aF of (he outer or endodermal surface of the inverted volk sac is covered with well formed and often elaborately branched vascular vilU which are in intimate contact with the utenne mucosa These vilh arc usually longest near the chono allantoic placenta and in roam species they fit into crypts m the foetal surface of the placenta In some rodents (eg, Jamtus) endodermal vilh of the inverted yolk sac become so intermingled wuh the true (chono allantoic) placenta thit they form an integral part of it Its elaborate specialuation and the fact that it persists in a functional condition till term indicate that the inverted volk sac placcma « undoubtedly of great physiological significance and a major factor to be corjvjdered m laboratorv experiments concerning placental function m the*e animals

CHORIO ALLANTOIC PLACENTATION IN EUTHERIAN MAMMALS ^^am^lahan placentation may be defined as an apposition or fusion of the foetal membranes ^ the uterine mucosa (o permit of phvstolo^cal exchange between the foetus and the mother I he most tspical of the structures ind the defimtivc one m all Fmhcna is the chono allantoic

placenta However other placental mechanisms exist dunng the development of each euihenan

mammal Of these the chono vilelline and inverted yolk sac placentae of .ome tvpes have

398

HUMAN EMBRYOLOGY

402

HUMAN EMBRYOLOGY

been described above. Other accessor)'^ placental adaptations are illustrated and explained in Figs. 427 and 428. Further discussion of eutherian placentation here is confined to the chorioallantoic type The variety of gross forms of chorio-allantoic placentae has excited interest out of all proportion to its significance. Fig. 430 give some idea of the appearance of the better known varieties

A summary of the finer structure of the main types of chorio-allantoic placentae is given m Table V This is based on Grosser’s (iQsy) classification of them according to the intimacy of the union between the foetal and maternal tissues, or in other words, according to the structure of the membranes separating the maternal and foetal blood in the functional parts of the placenta Grosser rightly maintained that this “placental membrane” is the structure of greatest physiological significance in any form of placentation. The terms which he applied appear S'jrnewhat complicated at first sight, but will be seen to be appropriate, being lormed

TAB; r V THE TISSUES MAKING UP THE SEPARATION MEMBRANE IN THE FOUR

PRINCIPAL TYPES OF PLACENTATION

Type oj ‘ c 1

1 Epitkeliochonal

Endotheltochonal

Haemochonal

HaemoendotheUal

Maternal ti,su

Endotlie >

+

—

Epithelii 'j

Foetal tissue

+ :

—

—

Chorion

'h 1

+

—

Endothei' ,

+ 1

+

“f

Familiar exari- \

Horse, pig, cattle

Cat, dog

Man, monkey.

Rabbit, guinea pig, rat

Main zoological t'l '1

1

j

1

\niodactyla, Penssodactyla, Cetacea, f Manidae,

1 Leniuroidea, American mole.

Carnivora,

Bradypodidae,

Tupaiidae,

European mole

Primates,

Tarsndae,

Sirenia,

Megachiroptera,

Most Microchiroptera, Hyracoidea, Myrmecophagidae, Dasypodidae,

Most Insectivora, Lower Rodentia (Sciundae, Myomorpha)

Higher Rodentia (Leporidae, Geomoidea, Hystricomorpha)

by a combination of the names of the maternal and foetal tissues which are in contact (Fig 4 ^ 9 ) For instance, if, as m the pig, the epithelium of the utei us persists and the trophoblast 0 t chorion meiely lies m contact with it, the placenta is spoken of as “epithelio-chortal ^

uterine epithelium disappears and the chorion comes into contact with the endothe mm the maternal vessels, as in the dog and other Carmvora, it is an “endothelto-chorial type considered that in many Ungulata the epithelium disappears leaving the chorion m mi with the connective tissue of the uterus. To this ty^ie he gave the name “syndesmo-chort^^^^ Since this condition occurs only in a very limited area of the bovine placenta, an is probably atrophic and non-functional, this type of placentation has been omitte ro table. There are accessory placental areas in other species which structurally syndesmo-chorial conditions, but there are no known cases where the main chorio p placentation is of this t^e. In many mammals (e g., Rodentia, most Insectivora, -yora,

and Cheiroptera) the invasive activity of the placental trophoblast is greater than in so that eventually even the endothelium of the maternal blood vessels is destroyed endothelio-chonal placenta becomes “ haemochorial” While Grosser’s classification ^00

considerable value in the study of different types of placentation, it cannot e app rigidly. Detailed study of the placentae of a number of species has shown

COMI'\RMl\I MRTIllRAll IIUIIOI’MIVI 4'U

rc^cnat.om ate nceexari m an anrmpi in place a Riarn platrma m one nr rllicr nfCttmtei i calcROtaea In manv Lnculaica ftt raample it ba. I>«n .bnnn ibal cap.Uanra ate fnumi in the iropliolilasl ... i

In connwtion >mUj pliccnial iinicturr it mmt Mi • !*■ rrTnpml>rroi ifnt inan\ cliorioMhntoic placcntir Ini e a th.cVrr pberntM infmbrmt m Minr f -iThrr jnqri than \i\cT Hmi m thp rahhit iihrn tlir athntmc circubiinn i» fint rital.hihn! tlirrc arc arraiishcrr llic trophni>bix of thf ciiorion » ju't vntU the ulcnnc cptllicimm an cpithrlirv-clinnal rondition

baler in tlm animal a Incmnchonal cnmliu.m it trachctl tthcrc the maternal hWl it m direct contact ttilh thr irnphrhhti Slill liter the tn>phn»>bit itvlf »rrmt to dioppear from much

Hsrrnwfei 9I Ubff

int«cti<eri (CKCpt H«1eil Ch fOpt«ri HjrriM tfei T»f to tfea and lower S <id«tt Rodentii

Dupl c dent «nd H (her S m pi cident Podtmla

Oeifpodo iei Ctftop e^e<o 4*t and Hoffiineidci are « Hoot Cefeo del New World Am eaten and Oertvioptera an (rabeeular

[ Cp iref o><^eool(An oduifla (S odea Cawitlodra Traxviodei) PeruodaetpU Cctacta Lemgrt New World Holet and 0*d World Am-etten)

tnd t*^l (Carnirorti SloiKt Old World Holei and S ten a)

e £p iNrl oKhonol (hjrpoihetlcal)

MORPHOLOGICAL TYPES OF CHORIO ALLANTOIC PLACENTATtON Atfinjed at 1 tree with ibe mott pilmrtWe tjrpe Lrtow T»ie ijnatl V»p ffurra ibow In 1 mpt fed form (he iiructurc «( (he placental membrane aeparat nj the maternal and foeui blood « A ' t 4^ m T pK«»l < «BW U .« f P •> I w 9 Iwl IV ■ Ql M I Vhi>I >a flooe

Iin Itkwe m* IM mS •« 4t>rc.e

1 10 ^29 — I)i3((raini illuit rating it e riain morpl t4oC‘c»l t>1‘n of cliorio-aUantoic placrnta

of the placenta so that onl) foetal endnihrliiiin separatee tJic luf> 1 ;Io<k 1 streams a hafmo tndotktUal condiuon (Motsman 1936 ) The frrvdom uith tthich sidattances pats from one blood stream 10 the other is correlated to some drv^rec \Mth the thieVness ami slruclure of the placental membrane Thick membranes are pmbab]> lot [lermeablc than thm ^tso the earlier thicker placental membranes of a Riven ipecics arc stated to l>e less permeable than m the later tlnnnrr stiRcs (I lexner tnd Gcihorn tgp see alto pai,c BO It should be stated houcser that estimations of placental permeabiht) on the apparent structure of the placental metnliranc ate still leniativc

A placenta n said to be non deciduous if there « no actual fusion of foetal cliorion to the uterine tissues thus at hirth these pheenne separate without teanne; maternal tissues and therefore without Joss of blood by the mother All epithclio-chnnal tlilTute and rotjlcdonart

404

HUMAN EMBRYOLOGY

placentae are of Jis variety In all other types fusion takes place and more or less maternal Hssue IS shed and maternal blood lost, at b.rth; hence these are deciduous. SpecSclcX cells, as found m human and many other uten, are often absent from decdLs pWentaf

eg., tn the dog placenta, which is considered deciduous only because the maternal da„£ tissues and blood vessels are torn at birth Sianauiar

an ” cp«heho-choriaI placentae are vdlous (Figs. 427, 428 and 420)

All endotheho-chonal, haemo-endothehal and most haemochorial types f re UnLue (Figs 42 ' 428, 429 and 43. A) Some haemochorial types, especially among the primates, exhibit Lin intcr-gradations between a labyrinthine and a villous structure (Fig 43.) Applrentlymanand

ZoRiLLA Brown Bear

of the placema^.^ie^i!^ chorionic sacs of a number of mammals to show the gross forms

zonarj’ or annular rar deer and cow, cotyledonary; monkey, btdiscoidal, dog, etc,

derivations of thr zonary, otter, polecat, ZoriUa and brown bear show special

carnivore zonary placenta

Fiff. 68 illu^rateiffb^ ^^present the maximum expression of the haemochorial villous condition, labyrinthine placenm”^^^if*^ of development of one of the more primitive types of haemochorial Ume seems to be b ' J j change over from the labyrinthine to the haemochorial villous rcsultins- first in a t coalescence of the trophoblastic tubules carrying maternal blood,

that in most labvrmfb'^^^ ^ definite villous condition. As a general rule it seems

directions in areas d I^acentae the maternal and the foetal blood streams flow in opposite UqsSl has desrribpVfi^^ ^ j enough to have functional interchange. Mossman

and there is a nnss.ivi ^ P|^y®*o^ogical advantage of this arrangement in the rabbit placenta placenta (Chapter V Ind a somewhat similar functional provision exists m the human

COMPARATIVE VERTEBRATE DEVELOPMENT 403

EXTRA EMBRYONIC MESODERM IN PRIMATES

One of the most puzzling problems of comparatisc morphogenesis of the foetal membranes has been raised h) the demonstration of the peculiar mesench>-niatous ewa embr)onic tissue in the earl> embryos of the primates generally (Hill 1932) of the lemurs (Gerard, i93'>) of man (Streeter 1926 and Hertig and Rock, 1941) and of the monke> (Heuscr and Streeter, 1941) and Its relation to the exocoelom and 4 oik sac From a stud> of comparative embryologv it would be expected that this mesoderm would be formed bj proliferation from the posterior (later pnmitne streak) region of the embrjo whence its cells would spread into the extra embryonic regions However, in both monkev and man the primary extra embryonic mesoderm develops before the appearance of the primitive streak (Figs 59 60 and 432) Hill (1932) and Florian (1933) are of the opinion that this mesoderm arises from the immotic ectoderm postenor to the site of the future tloacal membrane, Gerard (1932) believes that it arises from the endoderm of the volicsac Hertig (1935) Wislocki and Strcctei (1938) and Heuscr and Streeter (1941) have investigated the origin of this mesoderm in well fixed material from the monke> and are com meed that this pnmarv mesoderm IS derived at least in part, directl) from the tropho blavt Hertig and Rock (1941) found evidence of the same condition in their 8th-i2th da> human cmbr>os

— A sect on of a 12 day macac^u? blastocyst i^e yolk sac has now made us appearance between ihe mesoderm and the embryonic ectoderm I Vter Heuser and Stteettr 1941 ) x c 310 'Reproduced by the courtesy of the Carnegie Institution of Washinftol )

Fic 431 — Sections through the placenta of the New World monkey C/irysathn* m Kiialut \ labvnnihine portion E villous portion (After Hill 1932 }

Streeter and Hertig and Rock den> homolo gjcs between the earlv tissues and structure of the primates and those of other mammals and regard the precociousl> developed mesoderm and the cavnties in relation to it as special adaptations found only in higher primates If, however one recogmzes the value of comparative studies, as Heuser working upon the same matenal has done then an early primitive bilammar yolk sac can be recog mzed in the human and monkey with many resemblances to that of other mammals The recent work on the macaque has shown that the primary yolk sac which is essentially like that of all other mammals does not give nse directly to the secondary yolk sac The latter seems to arise by a rearrangement of

human embryology

COMPARATIVE VERTEBRATE DEVELOPMENT 4°?

the originally flat plate of disc endoderm to produce, adjacent to the embryo proper, a separate small cavity which qvnehly becomes surrounded by haematopoietic mesoderm The cavity of this secondary yolk sac seems to have no continuity with that of the pnmary sac (Fig 432) and as it enlarges the cavity of the latter recedes towards the vegetal or abembryomc hemisphere In man as has b«n described in Chapter V, the abcmbry'onic part of the pnmary yolk sac becomes separated completely from the remainder A surpns ingly comparable process is exhibited by the sloth Bradypus grisfus (Heuser and islocki, 1935), ^^here the exococlom extends around all except the abembryomc end of the primary yolk sac where the latter s original connexion with the trophoblasl is maintained A constriction develops between the abembryomc and embryonic portions of the sac which results in complete separation of the two portions There is then a small proximal haematopoietic, splanchno pleunc yolk sac homologous with the definitive yolk sac of man and the macaque, and a distal or abembryomc degenerating portion of the primary sac comparable with that part of the pnmary yolk sac of the monkey which is relegated to the abembryomc hemisphere of the chorionic vesicle It seems reasonable to assume therefore that the relatively direct and early method of separation of the two parts of the yolk sac m the macaque is merely an abbreviated and specialized method of pinching off of the distal portion seen m its more pnmitivc form in the sloth and possibly in man where the primitive abembryomc portion of the yolk sac is indicated in some embryos (Chapter V and Figs 75 and 76)

REFERFNCES

de Beer G R (i94o) Embryos and Ancestors Oxford Unn Press London

Boyd J D and Hamilton W J (igs'*) Cleavage of the egg and implantation In Press— Physiology of Reproduciion (Marshall) Longmans London

Caldwell H (1884) Telegram Monotremes oviparous ovaim meroblaslic Read at British Association Meeting Montreal '•nS Sept 1884 Brit Assoc Rep Montreal Meeting 1884 Cate Hoedemaker N J ten (1933} Beitrage zur Kenntniss der Plazeniaiion bei Haien und Reptilien Der Bau |der reifen Plazenta von Mustrlus hnis Risso und Srps ihalttdet Merr [Chaletda lridael)luj Laur ) ^tilt f u rnikr Anal 18 299-345

Flexner L B and Cellhorn A (t942) A comparative study of placenta permeability using radioactive sodium Anal Rtt 82 411-412

Flynn T T (1023) The yolk sac and allantoic placenta in Prr<i«r/« Quart J Micro Set 67 123-163 — (1930) The uterine cycle of pregnancy and pseudopregnancy as 11 is in the Diprotodont Marsupial Bdieneia runirufus Proe Unn Set Setv Sauth ttabs 50*^531

and Hill J P (1939) The development of the Monotremaia IV Growth of the ovarian ovum maiura

tion fertilization and early cleavage Trans ^eef Sec Lend 24 445-622 — (1942) The later stages of cleavage and the formation of the pnmary germ layers in the Mono tremata Free Z^al Sac Lend AIll 233— >53

— {1947) The development of the moooiremata PariVI The later stages of cleavage and the formation of the primary germ layers Tranj Sec 26 i-tjt Gerard P (1933) Etudes sur I ovogen^se el 1 onir^en^e chez les Lemuriens du genre Co/o 0 Arch de Biol _ « 9o-«5t

Ooetz R H {1937) Studien zur Placentauon der Centetiden II Die implantation und fruhetvtwicklung von HemicenteUs semiiptnosus (Cuvier) ^ f Anat u EntnGesch 107 274-318 ~ — (>938) On the early development of the Tenrecoidea (Hf»Mf*Bfel« jemupinofw) Bxomorbhosu 1 67-79 Grosser O (1927) Fruhentwicklung Eihautbildung und Placentation des Menschen und der Saueeuctc Bergman Munchen ^

Haeckel E (1874) Die Gastraca Theone die Pbylogcnelische Classification des Tierreichs und die Homoloeie der Keimblattcr Jenauehe Znls J'raturw 8 1-55 ®

Hariman C G (1920) Studies m the development of the opossum (Oi*//A>s u ginianu Z. ) W istar Institute Philadelphia

Hertig A T and Rock J (1941) Two human ova of the nre villous stage having an ovulation age of about el^en and tv eUe days respeeiivcly Coning Emh^et Ceamegie Inst Wash 29 i27-i>i6

^ ^ Development of the macaque embryo Contrib Embryol Carnegie

^d VSisl^k, G B (1935) Early dcvelopmem of the sloth (Brarfj-^Hr^rufw) and Its similarity to that of

Mil Gontrib Embryol Carne telnsi Wash 25 1-13 ’

j*’' ® f IJidf/pAys Quart J Micro Set 63 91-140

1,1932) The developmental history of the Pnmates PW Trans Roy Sec Land B221 a-t 1-78 Zeelfo^ Und the female urogenital organs of the Didclphy^dae Proc

vande^Hont C J (1942) Early stages in the embryonic devcVopmeni of Ele/iftantulur

5 Vr J Med Set

4o8

HUMAN EMBRYOLOGY

Hubrecht, A \V (i8go) Development of the germinal layers of Sorex vulgaris Quart J Micro Sci , 31 , 499-362

(1908) Early ontogenetic phenomena m mammals and their bearing on our interpretation of the

phylogeny of the vertebrates Quart J Micro Sci,^ 3 , 1-181 Jacobson, W (1938) The early development of the avian embryo I Endoderm formation II Mesoderm formation and the distribution of presumptive embryonic material J Morph , 62 , 415-443 and

Kcibel F (1889) Zur Entivicklungsgeschichte der Chorda bei Saugern (Meerschivemchen und Kanmchen). Arch Anat Physiol , Anatom Aht , 329-388

Kerr, T (1934)- Notes on the development of the germ layers in diprotodont marsupials Quart J Micro

Sci,n, 305-315

Lehman F E (1945) Emfuhrung m die physiologische Embryologie Basel McCrad), E, Jnr (1938) The embryology of the opossum Amer Anat, Mem, No 16

(1944) The evolution and significance of the germ layers J Tenn Acad , Set , 19 , 240-251

Mossman, H VV (1926) The rabbit placenta and the problem of placental transmission Am J Anal,

37 , 433-497 ^ ,

(* 937 ) Comparative morphogenesis of the foetal membranes and accessory uterine structures Contrib

Embryol , Carnegie Inst Wash , 26 , 129-246

and Weisfeldt, L A (1939) The foetal membranes of a primitive rodent, the 13-striped ground squirrel

"im J Anal, 64 , 59-109

\ I Lon, P L V 1 940) The foetal membranes of the kangaroo rat, Dipodomys, with a consideration of the phylogen)

of lie Geomyoidea Anat Rec , 77 , 103-127

P.t‘tefia J .1937 fitude sur la gastrulation des vertebres meroblastiques II Reptiles Arch Biol, Pans, 48 105-184

(1940 I n aper^u comparatif de la gastrulation chez les chordes Biol Rev, 15 , 59-106

(1940 On the formation of the primary entoderm of the duck [Anas domesltca) and on the significance

ui tin Ijj'jr/inar embryo in birds Anat Rec, 93 , 5-14 Patti. rson J 1 ’Mjg') Gastrulation m the pigeon’s egg — a morphological and experimental study J Morph,

20 ti I ;

Pearson J o oo Placentation of the marsupialia Proc Linn Soc Lond , 161 , 1-9 Prttr K 10 ’p Die erste Entwicklung des Chamaeleons, verghchen mit der Eidechse Z, f I”* Ot 0 103 , 147-188

(■933) ■‘ 3 ic )' rere Entwicklung des Chamaeleonkeimes nach der Furchung bis zum Durchbruch des

Lrdarms [[ / Anat u EntwGesch , 104 , 1-60 , .

Rabl C ^1915 r Jouard van Beneden und der gegenwartige Stand der wichtigsten von ihm behandelten Probleme Arih Mikr Anal , 88 , 1-470

Snell, G D (igii) Biology of the laboratory mouse Blakiston Co, Philadelphia .

Streeter G L 11926' The “Miller” ovum — the youngest normal human embryo thus far known Conlrt Embryol , Carnegie Inst Wash, 18 , 31-48 ^

Turner, C L 11940) Pericardial sac, trophotaeniae and alimentary tract m embryos of goodeid fishes J H/or/y/i , 67 , 271-289 c

Vogt tv (1925) Gestaltungsanalyse am Amphibienkeim mit ortlicher Vitalfarbung Rom’s Arch, 1 542-610

(1929) Gestaltungsanalyse am Amphibienkeim mit ortlicher Vitalfarbung Gastrulation und eso i.c dermlnldung beim Urodelen und Anuren Arch Entwmech Org , 120 , 384-706 ^

Weekes, H C (1930) On placentation m reptiles II Proc Linn Soc New South Wales, 55 , 55 ^- 57 .

(1935) review of placentation among reptiles with particular regard to the function and eio of the placenta Proc Zool Soc Lond , 625-646

APPENDIX

Presumed I Dimensions of Dimensions of

Author and a?e m blastocvsl embryonic mass

embryo ‘^*1* (in mm) (in mm )

Reference to publication

STAGZ i — Tht Eatlj Blastotysl Stage up M the appeaiante oj the talk

Heuser and Streeter

«94» ,

-8

0 f87Xo 166 1

' 0 108x0 to8

(macaque’)

(approx )

(approx )

Uertig and Rock

«945

n

0 12x0 306x033

0036 XO 078 XO 09

(Cam no 82 5' Hertig and Rock

■ 94

?i

0I2 jX 03X045

0 o8j X 0 o8j

(Cam no 8oao)

(approx )

Wertig and Rock (Cam no 8155) Hemg and Rock i

1949 1

8

1 0 150X0 210X030G 1

[ 0030x0050x0090

t949

f938

9

from 9

0 56x0404x0422

0 046 X 0 088 X 0 ] 1 4

1

(Cam no 817:)

\\ islocki and Streeter

1

(Tn&caq'i«\ '

1

1

Hertig and Rock |

(Carn no 8 15) '

Hertig and Rock )

'943

9-to

^ 0 07xO498xo52j 1

1 005x005x008

1944

9lt

1 031x045x058

1

1 oryorj-r

(Cam no 8004)

Heuser (chimpanzee) . Ham Iton el ei 1

(Barnes) 1

Danes

■ 940 .

' 1943 '

10}

lOt-ll

1

0931 XO 77 XO 727

0 133x0 iiS

' »944

9-10

1 t 18x055

0 117X003C

(Davies Harding)

Hertig and Rock .

(Cam no 7699} 1

'94'

1 07«305‘SXto 6

j 0 138x0089x0 tjS

Streeter (Miller) 1

1926 1

' ^4

. 0093

Hert g and Rock (Carn no 7700) 1

1 ig^t '

i

1 0835x0540x0948

0 165x0 045x0 -*04

Dible and West

1941

047x028

1 0 t X 0 02

Sticte (Uerner)

193G

tt

0 78 X 1 36 X 0 7

1

1 0 tSxo 12

I Contr Emb Cam ' init 29 inat Pec 91

Caitr £•"}> Cent

I f«f 31

I Contr Emb Cam

] Inst 33

Conlr Emb Corn

fnsi 33

Contr Emb Cam

. /«! 27

I inat Rec 91

Contr Emb Cern Inst 31

J Morph 66 J Obst CiB Brit I Emp SO

I Trans Rot ioe I Edin 61

1 CoHr £m6 Cam

Inst 29

' Contr Emb Cam

ful 10

Contr Emb Cam

I Inst 29

I y Anal Land 75 ^eits / Mtk anat

40

STAGE 3 —-The Amniotu and Talk Sac I estcles a

Scipiades

1938

1.-12

099 1 018x0048

Bryce and "1

Teacher 1

' 1

1908

1

Bryce V TB i

1 '934

■I

j 077X063X05'* about 015

Teacher J

1 1924 1

1 1

I are nst detelot>ed I Contr Emb Cam

• Inst 27

I ^IacIehose I Glasgoi

I Trans Roy Soc

I Edin 53

. J Obsl Cyn Brit < Emp 31

Marchetti (Cam no 8139) l> nzenmeier (Stoeckel)

Peters

KtafVa (Torpm)

I «9-Jj i 1914

o 706 y o 700 075 ^ 061 x 052 I 6x08x09

»3Xs ixi-o

O I 2 f XQ 048x0 t 0 IXj Oj

O leXO 24X0 0. XO 2 i 6

Conlr Emb Cam

Inst 31

■I'ch / Gynak 102

Leip 1 u Item / Gynak 124

Contr £fn6 Corn

Inst 29

409

4o8 HUAIAN EMBRYOLOGY

Hubrecht, A W (1890) Development of the germinal layers of Sorex vulgaru Quart J Micro Set, 31 , 499-562

(1908) Early ontogenetic phenomena in mammals and their bearing on our interpretation of the

phylogeny of the vertebrates Quart J Micro Set, 53 , 1-181 Jacobson, \V (1938) The early development of the avian embryo I Endoderm formation II. Mesoderm formation and the distribution of presumptive embryonic material J Morph, 62 , 415-443 and

445-501

Kcibel, F (1889) Zur Entwicklungsgeschichte der Chorda bei Saugern (Meerschweinchen und Kaninchen) Arch Anat Physiol , Anatom Abt , 329-388

Kerr, T (1934) Notes on the development of the germ layers in diprotodont marsupials Qjiart J Micro Sci , 77 , 305-315

Lehman, F E (1945) Einfuhrung in die physiologische Embryologie Basel McCrady, E, Jnr (1938) The embryology of the opossum Amer Anat, Mem, No 16

(1944) The evolution and significance of the germ layers J Tenn Acad , Set , 19 , 240-251

Mossman, H W (1926) The rabbit placenta and the problem of placental transmission Am J Anat, 37 , 433-497

(1937) Comparative morphogenesis of the foetal membranes and accessory uterine structures Contrib

Embryol , Carnegie Inst Wash , 26 , 1 29-246

and \Vcisfeldt, L A (1939) The foetal membranes of a primitive rodent, the 13-striped ground squirrel

Am J Anat, 64 , 59-109

N If Ison, P E (1940) Thefoetalmembranesofthekangaroorat, Di/iof/omyr, withaconsiderationofthephylogeny

of the Geomyoidea Anat Rec , 77 , 103-127

Pacteels, J 11937' fitude sur la gastrulation des vertebras meroblastiques II Reptiles Arch Biol., Pans, 48 105-184

(1940^ Un aper9u comparatif de la gastrulation chez les chordes Biol Rev, 15 , 59-106

(^ 94 j/ F)n the formation of the primary entoderm of the duck (Anas domestica) and on the significance

of the bilarninar embryo in birds Anat Rec, 93 , 5-14 Patterson J T '1909) Gastrulation in the pigeon’s egg — a morphological and experimental study J Morph,

20, 65-1. r

Pearson J .1049 Placentation of the marsupiaha Proc Linn Soc Land, 161 , 1-9 Peter K Jiqf, 5' Die erste Entwicklung des Ghamaeleons, verglichen mit der Eidechse Z f EntujGescr 103 , 147-188

{’935) riere Entwicklung des Chamaeleonkeimes nach der Furchung bis zum Durchbruch des

Urdarms ^ f Anat u EntwGesch , 104 , i-6o

Rabl C (1915 (iJouard van Beneden und der gegenwartige Stand der wichtigsten von ihm behandelten Problemc Arch Mikr Anat , 88, 1-470

Snell, G D (1941) Biology of the laboratory mouse Blakiston Co, Philadelphia Strectei. G L (1926) The “Miller” ovum — the youngest normal human embryo thus far known Contrw Embiyol , Carnegie Inst Wash , 18 , 31-48

Turner, C L ("1940) Pericardial sac, trophotaeniae and alimentary tract m embryos of goodeid fishes j Morph 67 , 271-289

Vogt, ^V (19251 Gestaltungsanalyse am Amphibienkeim mit orthcher Vitalfarbung Roux’s Arch, 10 j 542-610

(*929) Gestaltungsanalyse am Amphibienkeim mit orthcher Vitalfarbung Gastrulation und Mesodcrmlnldung bcim Urodelen und Anuren Arch Entwmech Org , 120 , 384-706 Wcekes, D C (1930) On placentation in reptiles II Proc Linn Soc New South Wales, 55 , 550-57 (’ 935 / A review of placentation among reptiles with particular regard to the function and evo u of the placenta Proc Z^ol Soc Land , 625—646

APPENDIX

I rnutned

Dim mioni of

Dimensions of

\uthor and

at;e m

1 laslocMl

embnomc mats

cmbr> 0

Due da\-»

(in mm )

(m mm )

Uefctfnce to j ublication

ST jrr I ~Thi raih Sue< efp<a ant! ef iht U!k

Heusrr and Stre ter

1941

7 0

0 187 X 0 16P

0 108 xo infl

(macaque'

Herti? and Rock

t9\5

.{

(approx )

0 i*xo3f/ X033

(approx )

oojf xo 0,8 X 0 00

(Cam no 81*51 Herii^ and Rock

•91

A

0 iijV03xii4a

008^x0083

iCarfi no 8020 Heriig and Rock

>919

8

0 1^0x0*10x0306

(approx )

0030 oOjOXoriqo

Cam no 8153! Hetiig and Rock

«919

9

0 3.,l XO 404 XO 421

0046 XO oS3 XD 1S4

(Cam no 8171) Wislocki and Streeter (.macaque'

Hertig and Rock

1938

«945

9-10

0*07x0492x05*^

0 03 X 0 Oj X 0 ofl

iCarn no Siijl llrrt g and Rock

1914

9i

03IX04J 058*

otxo I3« 

(Cam no 8004) Heuter (ehimnanaee) Hamilton el at

«91<»

>913

V*

lol-i c

0931/0 7x07*7

0 t33XD it8

( names)

Oaties

<911

0-10

t lOxo jj

0 »i7XD03f

(DaMCS Hardin;^ Hertig and 1 ock

<9)1

It

0 7i30 515X 1 0*6

ft i3ftxoft89XO 138

Cam no ,69^ Streeter (Miller)

19*0

It

<*4

009*

Hertig and Rock

'91<

I*

0835x0510x0048

ft if 3 x 0 045x0 S04

Cam no 7700; Dible and West

Siieve (Werner)

'94« 

<936

ti

047x0*8

078 t 36x07*

ft 1 xo D* ft t8xo I*

iilC

Conir ffni) Ca ’

/■Lit 29

inat Rtc 91

Conir trrb Cart

Inst 2t

Cot// Fnb Corn

Insi 33

Cant I mb Ca n

Inst 33

Conir prrrb Cern

Inst 27

iral RiC 91

Conir / mb Corn

Inst 31

J Morfh 66 J Obst C\n Rnl rnp 50 Trans Roy Sot him 61

Conir Pmb Cettt

hit 29

Conir Cmb Cam

InsI 18

Co If hnb Cam

Inst 29

J ttal l^nd 75 fCtits S onot

40

STlCEs-^The imntoli 1 Scipiades 1938

in ( Talk Sac I enf/r» ate ^or 1 p tsent bi t the Mrsodermic I j//» 0 e not dr Roped 11-12 Oft) 018x0048 Csnl Imb

Corn

Brtce and "1 Teacher Brtce ‘

1908

> TD 1 1924

It 0 77 /o f3 xo }*

h,t 27 Maclehose Glasgot

tboiil 0 ij Trans R y

Soe

Teacher

1 19 4

Idin 53

3 Obsi Cm r mp 31

Dnt

5T/CC 3 — Tht Amntol e and Talk Soc I fsielri Enlarge ihs \ lUt ate in Streak has not jet appeared

Marrhflli

(Cam no B130) i-inzenttieier (Stoeckcl)

Peters

1 rafka (Torptn)

a

0X0 706x0 , 075x061x05a i OxoSxog

I 3Xt t xt o

I the Protest 0/ formalist but the Primiti e

1*6x0048x0116 Conir Fmb Cam

Inst 31

o'-tXiOj JffA f Cjtnak 102

118x0*4X004 ' Leip t u Mfin Arch

I / Crna* 124

D2IXd*i6 ! Cont Emb Cart I Inst 29

409

410

HUMAN EMBRYOLOGY

Presumed

Dimensions of

Dimensions of

Author and

age m

chorionic vesicle

embryonic mass

Reference to

embryo

Date

days

(in mm )

(in mm.)

publication

STAGE 4 — The Ammoltc and Talk Sac Vesicles Enlarge Funher, the Villi Branch, the Embryonic Disc becomes Oval, the Primitive Streak and Knot and, in the later part of the Stage, the Cloacal Membrane appear

Heuser, Rock and Hertig

1945

i 3 i

14x19x26

0 04X0 22 XO 253

Contr Emb , Cam Inst , 31

(Cam no 7801)

J Anat Lond , 83

Morton (Biggart)

1949

i3H'‘)

2 53x2 10 XI 68

0 27x0 027x0 16

Brewer (EdwardsJones-Brewei)

1937

and

. 1938

15

I 85 X I 71 X I 01

0 209 XO 177

Am J Anat, 61 Contr Emb , Cam Inst , 27

von Mollendorff

(OP)

1921

15

I 5 X I 15 X I 0

019X018

Zeits f Anat u Ent ,

62

Scblagenhaufer and

1916

15

20X1 6x1 0

0 24x0 28 XO 04

Arch f Gynak, 105

Verocay

Anat Anz , 37

Zeits f Mil Anat,

21

Fetzer "1

Fetzer and Floiiin 1

1910

1930

15

1

I 56 X I 048

0 26 XO 215

von Mollendorff (WO )

i 1925

1

j !

2 52 X 2 16 X 2 06

0 25 XO 22

Zeds f Anat u Ent , 76

Teacher J

^ TB II Bryce J

1 1924

1024

1

28x26x2 25

0 2 X 01

J Obst Gyn Brit Emp , 31

Trans Roy Soc , Edin , 53

Jung

' 1908

15

25X22X1 0

0 25

Karger, Berlin

Wilson (Rochester)

i 1945

1

16

23X22X20

0313X0220

Contr Emb , Cam Inst , 31

Strahl and Benecke \ Flonan and Benecke J

j 1910

ii 930 -i

16

32X22X12

0375X023

! Bergmann, Wiesbaden Anat Anz Erg , 71

Falkiner

1 1932

15

15X14

0 23 XO 3 XO 06

J Obst Brd Emp ,39

Flonan (Bi 1)

1927

16

2 13 X 2 12 X 2 13

0 35x0 34

Anat Anz Erg, 63

von Spec (von H )

1896

17

4 0

0 37x0 23

Arch f Anat u Phys

STAGE 5 Heuser, RocL and Hertig

(Cam No 7802) Meyer

Johnson (HR i) Jones and Brewer

Stieve (Hugo)

Flonan (Bi 24) Flonan and Hill (Manchester) Thompson and Brash Streeter (Mateer)

Gladstone and Hamilton (Shaw) Grosser (\Va 17)

Hill and Flonan (Dobbin)

Rossenbeck (PehlHochstetter) Grosser (K 1 13) Heuser

(Cam. no 5960) George

Ingalls

The Primitive Streak Elongates, the Notochordal {Head) Process and Archenteric Canal develop, and the Villi become branched

.. ft I I — I Jf mf

1245

i6i

2 2 X 2 35 X 3 75

0 35 X 0 05 X 0 42

1924

18

26x2 1x2 72

0 41 XO 4

1940

i 5 i(’)

0 55 X 0 43

1941

18J

60x50x25 (before fixation)

0 58 X 0 782

1926

17

44x47x3 8

0 57 X 0 63

1934

3 05X3 036x3 029

0 62 XO 41

J935

17

4 28x3 28

0 87 XO 625

1923

19

10 0x75X40

09X09

1920

17

61x56x25

0 92 X 0 78

' 94 '

18

80x30

I 05

1931

18

85x85x75

0*98x0 7

1931

16 (2)

90x55x25

0 96x0 59

1923

19

68x53

I 77 X I 02

i 1913

19

8 0X6 0

0 83 X 0 50

1932

18

15 0 X 14 0X9 0 (external)

I 53X0 75

i >942

i

18-19

I 01 XO 83

1 >918

21

76x67x47

2 00x0 75

Contr Emb , Corn Inst , 31

Arch f Gynak , 122 J Anat , 75 Contr Emb , Cam Inst ,29

Zeds f Mik Anat,

7 ,4

Bralisl lekar " J Anat Land , d 9 .

7 Anat Land , 58 Contr Emb, Corn Inst ,9

J Anat Lond, 7 b.

Zeds f “

Ent , 94 .

Phil- Trans RoySoc , B 219 Zeus f Aoat u Ent , 68 Anat 7 /r >.47 Contr Emb , Cam Inst , 23

Contr, Emb , Cam Inst ,30

Contr Emb , Cam

\PPENDI\

411

Presumed

' DimelMions of

Dimemiont of

t

Author and

a(*e in

1 chononic \mcle

embryonic man

Reference to

rmbr^o

Dale

da^i

i (in mm )

(in mm )

publicalior

STACE G . flu \eliKhardil Plali breemts nHtnolaltd in llu Roef

of llu Jolk Sae iht

NfuvnfrrK Ca'ial

U Prisinl

tht Srur<i{ Platt oitd faUt enJ the Eaih

Rfftegul bfgit li drttlaft

Fraisi

1907

ifl-i9 j

54x3a 1

1 17x06

1 Ireh f \ltk Inal

a Jnl -JO

Bryce (M Int\re>

1034

1

14 0x13 oxSo

1 4x05

' Ttafu Rtr Sot

^on Spec (Clae)

1PQ9

(external)

1 Fdiit 53

19*20 1

100x85x65

‘ 54

^ irch / Inal a

1

1 Phjt

INDEX

104.

'hon, 310. 323

‘ A’ disc, 367

Abdomen, muscles of, 359, 363 Abdominal

paraganglia, 329 pregnancy, 69 Abduccns

ner\c, 279, 288, 306, 308 puclfus, 285

\burant ductules of epididymis,

230, 231. 259

■^'1 iniinal development, 125 '’1' >iinalities

cidleientiation, 126

ft' environmental influences,

, 1 246 303

M ^ .1,-s ; 127, 244, 303

u 1 ni o 126, 245

d \ riopni' I 1 of gut, 214

' ' Mu’ u ! lb -,3 1 iSSOi se\ "I 1

ctrtiiunaiv . l \c 'ondroplavi '

\cf JStIt

canghon 3 5 nerve 270 \coustico-i 'Id \crosomi \dcnoidv I'lf)

\dipi ' >1^ f ,1 d \dit V I 1 \dru il gland 320 \drfnalin ^28, 329 Advchcntcv vena. 164 \fTcrtnt

nerve fibres. 283, 306 neurons, 273 Age, 104

determination of, 105 Agenesis, 126, 304 Agglutinins, 129 Ala

orbitalis, 343 temporalis, 343 .Alar lamina, 272, 283, 285 Alimentary system, 176 .Alisphcnoid, 343 Allanto-entcnc diverticulum, 70, 76, 176 vessels, 76

.\llantois, 76, 77, 80, 234, 389, 394 blood vessels of, 158, 394 duct of, 76 function of, 394 in man, 76, 176 .Alveolar phagocjtes, 201 \Kcoli of lung, 198, 200 Amastia, 373 .Ambiguus nucleus, 284 \mbK stoma, ancurogcnic limbs in. 306

.\mcloblasiic layer, 374 .Amcloblasts, 374 .Xmnto-cctodermal junction, 79 .Amniogcncsis, 392 in man, 45

.\mnion, 45, 78, 389, 392

Amniota

foetal membranes in, 390 placentation in, 395 Amniotic bands, 126 cavity, 45, 70, 78 duct, 79 fluid, 78, 81 v'olume of, 81 Amoebocytes, 97 Ampulla

of semicircular canal (Fig 353), 322

of vas deferens, 241 of Vater, 209 Amylase, 216 Anal

canal, 211, 250 filaments, 390

membrane, 58, 212, 235, 250 pit, 250 sphincter, 360

Anamniota, foetal membranes in, 390 Anastomoses

mtersubcardmal, 166 post-costal, 159 post-transverse, 159 pre-costal, 159 vitello-umbilical, 162 Anencephaly, 303 Aneurogemc limbs, 306 Angioblastic theory, 136 tissue, 136

Animal pole of ovum, 380 Annular artery, 319 Annulus ovahs, 145 Anoestrus, 33 Anomalies

of cardio-vascular system, 1 72 of eye, 317 of face, 1 1 5 of genitalia, 260 of gut, 214 of heart, 1 72 of kidney, 233 of mammary gland, 372 of neural tube, 303 of placenta, 82 of umbilical cord, 83 of urogenital system, 258 of uterus, 243 of veins, 1 72 Anterior

cardinal vein, 139, 164 chamber of eye, 32 r commissure, 301 lobe of hypophysis, 292 nans, 114 nerve roots, 304 Antigens, 129 Antrum, tympanic, 326 Anus, 215, 387 imperforate, 215, 250, 260 Aorta

aoriico-pulmonary septum, 149

Aorta

coarctation ol, 173 dorsal, 152, 154 branches of, 158 double, 173 ventral, 152 Aortic

arches, 152

persistence of, 173 bodies, 330 sac, 152-154 Aperture, median, 289 Aponeurosis, 368 Appendicular skeleton, 349 Appendix

of epididymis, 241, 259 of testis, 243, 259 v'ermiform, 211 Aqueduct cerebral, 288 of cochlea, 324 Aqueous chamber, 320, 321 Arachnoid, 320 reticulum, 287 Archenteric canal, 49

Archenteron, 384 Arches aortic, 152 branchial, 153, 17S hyoid, 153

mandibular, 109, 153 pharyngeal, log, 153, t?" visceral, 178 Area

opaca, 388 peliucida, 388 Arm

arteries of, 161 development of, no, 349 muscles of, 362 Areolae, secondary, 337

Arteriosus

patent ductus, 173 truncus, 149, i 5 ^> *73 Arteno-v’enous shunt, 173

Artery, or Arteries, 152 annular, 319 anomalies, 1 72 aortic arch, 139,

xial, 160 lasilar, I 57 ) *00 irachiai, 162 iranchial arch, i 53 > * 7 ° ironchial, 158 arotid, i 54 ~* 5 ® erebral, 157

ervical, 161

oeliac, 158, 218

ohc, middle, 218

omes nervi ischiadici, ommumcating

lorso-lateral segmental, i59

[ucius caroticus, 150 r»mrvraL xGs

412

IM)I \

' a{piraiu 312

acfn%. n part ff 3 ij rin{;l n M I t^n)(anum 3>

\uftfiilat »{

Nut rt mir 11 nri « ») t n I Nut rtllr IJI

Nut I

. iR

,nf f r 1^ Ml Ml

. ir--f> f 7 IjH >Mi Ml

an n i 1

j anrfratif •-<{ ! nil Ml

IW, n al 10 (lannc al \il |)r n II im, 1 . il U

j >«t I tarvehiil nl » 1 1 1

lult nan artf 15. ailiat M r tal Mil frnal ISa rriinal 31'> tarral tn Ml Ml fiffn nul tnmai 15 1 iprrtiniif IjI p nal iji •tlanrlni IjR pirn in alapr {ill lai 3 j iiilirlaiian IjC K I urrar nal |j > iilial 1C' ill tnr nical iGi ulnar iCj

uml ilifal r I 1 ij« 

Nfit i ral iCo nifal ijO

iiirllin 77 ijfl 310 Nrt fcial paril ms; nmt 41 Nn-rpijl iiic f Id tgo Nr>tet id carlilatje 3jn lucl^ini;! 190 N c ndinc

Aitroc^ifi aC*"

Aslro<r)toblaili afr Aiynvax a doml 1 31 3 Ntlas (Iig 37i) 3,0 Airnia of gill at5 of on phagH aoj of < varian 1 Hide

bundl 2 ^ 7 canal 140 143 diiiJionof ijf endocardial cuilii 11 141 lal vahes 151

Ntrium of heart 140 143 171 abjoTpiion of veinj inio I4f

Niitel.c Rt wll f l‘ 1 Nio

R irulati n in 3 f Nx al

an n if

1 filam nl f primal / it iVd t n I nl irai lal 33 1

llj

lU

Dan I

, an»n 1 r iM

r lenii n < f cui :

Darn r | la nial f Dan ti rnal 341 Dan! In clan I 3^3 I Daul

I lamina a i »• 3 I ,, 3»»

' Da liar

art r> » U I lam ra llic 3 , 3J3 I Da 1 (>e iumuli Datil t le I lac ! D lamtnxr et> 1 rx

‘Die

| ca( dlaiiet 3 )

duel “ill

D Iiarv api aratu 1 a D C fte»i» « f 3<

Il nil I f Niet 11 rill

I ci ancm m r.rculaii i> ai

• Irtictl I I

mull pie 13 > 131 W icll I3« 

Iliad 1 r

an tiiiali 1 4 f 31"^ incrn if 34*1 urman 347 I Dla I Ria mrianei I nr 331 IllaiKK irj 41 3na I Dla I <>ii 7 44 Cl 3na I I ilanusiar 70

Slages ( Np|irn lix> 40!! Dla loit r 3H7 ■ 111 m ir ^ 43 Cn 3 I p< irnliaiiiie* of 43 i-*i DIatic poral plat 3UIS Dlaii jifir 4) y 3D1 iipi t 3ni Dlatiufa 7 3U3 Dlomi 99 aoB 235

devfl pmrnt of 99 forinalion iheonrs f 11 saUntix 71 7G pol)ph>lrliC llieor) 103

[.bd""'’ '■

aoriic 330

D- f

carotid 14 cl rt maDm 1J »

' geniculale 3 (I mamillan '*e ) cfpanctra 1 i jineal s' r ?*: I j luiiarx 3 fl - d {«tat III 4 I trxTi iitali ri of 3 tialV I ‘ iifiin nl rant! lal I t

wall rl»iire / 3j /urLrrlan I! • 3 i le If D. nm m

4^ 4

JV

rartdag ti{ cell 33' t mjatl 33^ lerti al 314 141 <i 1 I I Ml ni ol 334 f tl nifi Ij3 er. I <1 n Iral 314 jnifatariilac 11 in 334 snira i er I ran 1334 lacuna 33'

I nc 3J

marn h k i 33* m ml ran 114 13' l--nnt al 31’ jiimary 33j

• loll 340

»I ’’C' 3/

D.t;ella I x.r 34'

raftiiil jt

Drachial

• tiery ifa pi *ui 3 J

Dram a* i 97^

ihi malifi^^il 3 3

nrttiluti ntaniir> iin(hc 3 1 9 A

external f nn of a?" llexuret |lc> 371 3 J internal f nn of sDi I 311 I myrt.naii n sC*) auin (fig lai) 3 /I \ritlrirlei sDi xexiclei I riinary 3f3 Dranci lal

arch 1^3 I «  arirtiei 153 i,0 c>»i4(liK 115) l<)7 rcunl nitxl i»( 137

Rri^vex emit lerfinl i^rj iiiraoilerm 57 ptuche* 173 Dranchiomeri'in 369 Dreajt ire Nlammar) Cland Drt ad livamrni of iiierui jjf Drt ncliial ancriei 15^

I udi 19II 109 miiiclei 3 Gj D rnnchui sot)

Duccinator inutcle 363 Durcopliar^ngeal membnne 4P 53 log 176

INDEX

414

Bud

limb, 1 10 taste, 184 ureteric, 231

Bulb, olfactory, 279, 314 Bulbar

legion of heart, 147 ndges, 148 septum, 148

Bulbo-urethral glands, 251 Bulboventricular loop, 140 sulcus, 140 Bulbus cordis, 140 Bursa

mfracardiac, 222 synovial, 352

Caecum, 2 1 1 Calcified cartilage, 334 Calyces of metanephros, 232 Canal

alimentary, 176 archenteric. 49 atrio-ventncular, 140, 143 central, of spinal cord, 274 incisive, 18 1 inguinal, 255 irruption, 337 of Kurstcmer, 193 naso-palatine, 18 1 neural, 265

neurentenc, 78, 265, 387 notochordal, 49 pencardio-pentoneal, 56, 176 pericardio-pleural, 56, 220 pleuro-peritoneal, 56, 221 semicircular, 323 utero-vaginal, 241 Cancellous bone, 336 Capillaries, bile, 207 Capsularis, decidua, 68 Capsule Bowman’s, 230 Ghsson’s (of liver), 208 internal, 296 joint, 352 Jens, 318 optic, 344 otic, 344 sclerotic, 344 Cardiac, see also Heart

muscles, 138, 151, 355, 366 tube, 139 valves, 15 1

Cardinal veins, 139, 162 anterior, 139, 164 common, 139, 165 posterior, 139, 165 Cardiogenic area, 137

mesoderm, 52, 137 plate, 53

Cardio-v ascular system, iok C arotid arteries

common, 156 cMcrnal, 155. 156 internal, 154, 156

330

sinus, 158

Carpus, 338, 350 Cartilage, 97, 334 arytenoid, 348 bones, 334 calcified, 334 cells, 97

corniculate, 348 cricoid, 348 cuneiform, 348 differentiation of, 97 elastic, 334 epiphyseal, 338 fibro-, 350 fibrous, 334 hyaline, 334 hypophyseal, 343 Meckel’s, 345 otic, 324 parachordal, 342 Reichert’s, 346 thyroid, 348

Caseosa, vernix, 119, 370 Castrate cells, 34 '

Cataract, 319 Caudate

lobe of liver, 207 nucleus, 296 Caul, 80

Causal embryology, 124 Cavity

amniotic, 45, 70, 78 brain, 281 joint, 352

nasal, 115, 179, 180 pericardial, 56, 137, 176, 218 peritoneal, 56, 176, 221 pleural, 56, 176, 220 primitive buccal, 179 subgerminal, 388 tympanic, 189, 326 uterine, 61

yolk sac, 45, 75, 176, 389, 393 Cavum septi lucidi, 301 Cell, or Cells angioblastic, 136 blood, 99 cartilage, 97 castrate, 34

chromaffin, 270, 328, 329 decidual, 68 dendritic, 99, 371 endodermal, 45 endothelial, 99 ependymal, 266 fat, 99

formative, 383 ganglion, 270 germ, 6, 9, 378 germinal, 266 hepatic, 206 of hypophysis, 292 interstitial, of testis, 10 Kupffer, 208 luteal, 22 mast, 99

mesenchymal, 07, qo mesothelial, 96 muscle, 366

myo-epithelial, 355, 366 nerv'c, 267, 270 neuroglia, 266 neurolemma, 268

Cell, or Cells olfactory, 314 oligodendroglia, 266 oxyntic, 217 paraganglionic, 328 parathyroid gland, 191 parietal, 217 pigment, 99 plasma, 99 pregranulosa, 238 primordial germ, 236, 238 reticulo-endothelial, 99 retinal, 317 Sertoli, 10 sperm, 9

sympathetic nerve, 327 Cell islets of Langerhans, 210 Central

implantation, 60, 396 nervous system, 263-333 tendon of diaphragm, 221 Centre

diaphyseal, 337 ossific, 336 ossificaUon, 335, 337 of chondrocranium, 342 of viscerocranium, 342 Centriole of spermatozoon, 1 2 Centrosome of ovum, 41 Cephalic flexure, no, 277 Cerebellar cortex, 286 hemispheres, 285 peduncles, 286 Cerebellum, 264, 279, 285 differentiation of, 286 folia of, 286 Golgi cells of, 286 nodule of, 285 Purkinje cells of, 286 Tentorium, 279 Cerebral

aqueduct, 263 artery, 157 commissures, 300 cortex, 294, 297 histogenesis of, 298 fissures (Figs 321, 322), 298 flexures, no, 277 hemispheres, 279, 294 external form of, 294 internal orm of, 295 nerves, 306 peduncles, 288 sympathetic ganglia, 32° veins, 164 vesicle, 278 Cerebro-spinal fluid, 287 ganglia, 305 nerves, 304, 306 Cerebrum, 294 Cervical artery, 161 cysts (Fig 195)} t97 fistula (Fig tgs), 197 flexure, no, 271, 278 plexus, 305 sinus, no, n6, 197 vesicles, 197 Cervix uten, 242 Chambers of eye, 321

INOI N.

6 lot

C3if«-ki d'^rl pmrni o( II5 It'S Dietno-rfTfptnr* ijfl 330 Cli uma optic afli ay' 3f>a Chick y

Chic'iti » orean j(W Chontinficati n

ofaVulI 340

o(\riw»ta 33f)

aooJrohlat 07 Chofi jfocla't 337 Chooirocranuim 341 ChonlrocM p7 Q omlro^ nciii 334 Chof lai* i nJ n ar 151 Chofija tncjol la»t 13

mrvwl nil 3t5j

CJ on n Co -« 3^3

froniMum 4 lac\ 4

xaicul-iriiaiion ( r ,1 Chonon-^j Uh h ma C Chononic tar 71 ,0 mU 1

Cfion'>'\iiclhri plat nu 304 ClofoiJ 3* » plea ii 3il7

Chnruiialf luir 3)17 334 ofnc 3U ChromafTn hr«l> 333 cflli j « 3 f! 3:3 air m^rn.rt ai tjearcn of ) 4

<3

chiarma ( rmadon of 19 dipt d numl>er of ill iiapi id numfier of 13 m d ( rntinaii n of tn in r rtil ration 41 in man 18 in maturation tli'i ion oru'uni

a a'ac

tn Jctrfrmnai 3W«  in Maracut fl etu 44 mcfollauc 3^1 un«4 i»t 3I • a ft patai la iPa OrfU

cnnt^r ital Canal 187

e 11 I R 1 *1

inter n urotp tir 3»l

, 3lt 937 951

938

957

n reduction 1

’ 357

t8

in iprrmi igrnrtu 1 1 \and\ 1 1! 33r 937 Ciliary txxly 31b 3311 Circl of \\ dill lOo CirruJj tion

f)ian?e» m at hnti 171 cliorionif 71 foelaJ If j intemllous 71 pJarertaJ 83 portal 3i'9 Mtelhn 77

Circumferential tmplaniaii'in 3 Cijierna ch'li 1C8 Cijterna a8

Ciatsificaiion nf ner\e fibrra af8 Ciamirum 237 Clavicle 34J Lleavae 7 37 42 373 classiricai onj of 31 o determinate 3O0 d coidal 381 luration of iiagei 44 equal 380 lolollavuc 380

i en in! tmal 234 rat tna) 934 I u aea!

it> ml ran 4 t o J a ac 33 j C afcvK al

myotome* 3 3

V r1 Ira 3U C»el I a 333 iC«M ar rluci 33 4

n 'Y ^ ’

t CaieUae art rv ijR 3ifl Oie! m

I eatra-ernlry me 47 .

• tntra^ml r> me jj 3

mic

lay 93C

{looeler 38^

Coital tc tu| a nor 37

C« K»« (lour f I ftU 37 I C> II enne I iluct of pn nrphr tul uler of kiiney 938

Cm 11 cull 88

Oitolioma 317 a Ion 9»i Calotiruin 198 Commitiurai plate 30» Ooinmi nire •ni n r 701 f mtr 938 ioi 1 alH-nular ijii v t hippocampal 908 joi porterior 303 Ciimmon

cardinal \ein« 131 ifj rjaculatory duel 10 excretory duel 940 947 I I aiic duct 907 ' Comtnuniratinit raiiii 398 Ct mpael bone 33*’

Caimp lence i'»3 127 ' Comj lexily 0 Conchae naral iBa Cone crib of retina 317 Congenital cataract 3tg derormiiy

and malnuinin n I9g and maternal inrctli n

• 197 facta! cCeA 113 hvdrocephaliu 303 •aiocy 303 inguinal h rnia 935

CVinceniial pal v 3 14

poivcyrtic li ine> 33 3j8

,( >n3vsi\ctiv*l *»« 71*

' ( nn etifig iialV *n

(> nn etive linue /

Convo! Iletl lol der 333 933 C pula iPj t pulati n 3 Cor

I 1 -culare t 3 Iril irulafe i 2 l^rd

nepl roc m'" *

»eX 9J

ipnal '■3

timl I eal jf* n I* 3^0

vrlairenio junveft n rd ttj

C rl»

ImjIW 140 ret J a 1^3 9 I 0 l»n im 3 Cl a m a 7ici

iinu I4J ifT iileiii 9^1 a fpiH

all leant 7r talUuin -jR 1 t eav fft Ttiim iiietl ra jl lut urn 0 91 91 9I en 1 icrine funeti n of 93 livTierarmia < f 94 maiurtiy of 94 if ineniiruaii n 34 9 f paraluiral relit tf ■•4 ifpresnanoy 94 0

irgret inn ti 33 >|urium 94 vatcutariraiinn of 4 vervni 94

rtiiaium *■81 >4 995

fa r|i iKlrt

Matnig) lan 330 renal ••jo

cereliellar 2 t cercl ral 2 it aO? of luprarenal glaml 3 9 of ihymut gland irjj Curti organ • f 3 4 Cortici fugal fd res 29O Cornet petal filires 39O Cotyledoni of I lac nia 83 41x4 Louche Mirll gene 16 Cranial n rver 300 (raniopagut 132 Craniurn 310 Crest neural aCj 2C0 drnvaiivr* of 970 Cretinism 127 Cribriform plates 314 Cncoid canilaRe 348 Crista

INDEX

416

Crown-heel length of embryos 105 Crown-rump length of embryos, 105 Crus commune, 323 Cryptomenorrhoea, 260 Cryptorchism, 256 Cumulus oophoncus, 16 Cuneate nucleus, 283 Cup, optic, 278, 289, 316 Curvatures of stomach, 204 Cushions, endocardial, 144, 146 Cutis, 370 plate, 371

Cuvier, duct of. 138, 164 Cycle

menstrual, 23 26 oogenetic, 23 ovarian, 23 prcgnani v, 22 uterine ..3 26 Cyclops, I ; 315 C% Stic due .o'"

C tst, or C\

branchial ■ 195), 197 ceivical (F y '93), 197 of kidnes - 238

thstoglossa IT urachal, 2O0 Mtclline {F‘g 2it , 216 C\toreticu!uin i C> totrophobl I'l 71

Decidua, bj, 67

relation of chi u i” mc to, 68 topograph ’ca’ ^ of 68 Decidual celts bli Deciduate placent Uion 69 Defects, congenital, 127 Dendrites, 267 Dendritic cells, 99, 371 Dental

cuticle, 375 lamina, 374 papilla, 374 pulp, 374 sac, 374 Dentate

g>'rus, 298, 301 nucleus, 286 Dentine, 373 Derivatives

branchial arch, 363 of diencephalon, 290 of ectoderm, 95 of endoderm, 96 of mesencephalon, 289 of mesoderm, 96 of rhombencephalon, 283 Dermal bones, 334, 341 Dermatome, 339, 355 Dermis, 370

Dermo-mvotomc, g6, 356 Descending colon, 211 Descent of testis, 254 anomalies of, 256 Determinate cleavage, 380 Determination, 121 of scK. 20, 237

Deutoplasm of o\um, 3, 37, 378 Dcutoplasmol>sis, 381 Development abnormal, 123

Development of bone, 334

Comparative Vertebrate, 377 and embryology, i experimental, 121 of external form, 107 factors in, 4 functional period of, 7 fundamental processes m, 6 heredity and environment in, 4 postnatal, 2

pre-functional period of, 7 prenatal, 2, 105 Developmental adaptation, 3 Dextrocardia, 173 Diaphragm, 221, 364 central tendon of, 221 muscles of, 222 Diaphyseal centre, 337 Diaphysis, 338 Diarthroses, 350 Dichorial twins, 131 Diencephalic gland, 293 Diencephalon, 263, 281, 290 glands of, 292 roof plate of, 291 Differentiation, 6, 122 auxano-, 122 de-, 122 histo-, 122 invisible, 6, 121, 122 of neural mechanisms, 312 visible. 6

Digestive system, 1 76 Digits, 1 14

absence of, 126 Dioestrus, 33 Dionne quintuplets, 132 Disc

“A,” 367

bilaminar embryonic, 46, 48

“I,” 367

intervertebral, 339 optic, 320

trilaminar embryonic, 48

“Z,” 367

Discus proligerus, 1 7 Diseases

congenital, 127

in production of anomalies, 127 Diverticulum

allanto-enteric, 70, 76, 176 Meckel’s, 215 pineal, 293 thvroid, 196

Division, reduction, ii, 18 Dizygotic twins, 13 1 Dorsal

aorta, 152, 154 double, 173 hp of blastopore, 386 mesentery, 204, 223, 385 mesocardium, 139, 218, 220 mesogastnum, 204 pancreas, 208 sacral ligament, 35c Double

dorsal aorta, 173 monsters, 132 penis, 260 Duct, or Ducts

allanto-entenc, 70, 76, 176

Duct, or Ducts amniottc, 79 cochlear, 324 of Cuvier, 138, 164 cystic, 206

ejaculatory, 10, 241, 259 endolymphatic, 323 of epididymis, 241, 259 excretory, common, 240, 247 Gartner’s, 241 hepatic, 207 lactiferous, 372 mesonephric, 228, 236, 240 Mullerian, 227, 236, 240 transformation of, 240 naso-lacnmal, 115, 182, 322 paramesonephric, 227, 236, 240 of Santorini, 209 thoracic, 168 thyro-glossal, 196 utnculo-saccular, 323 vitelline, 215 Wirsung’s, 209 Wolffian, 236 Ductuli

aberrantes, 230, 231 efferentia, 13 Ductus

arteriosus, 156 persistent, 173 caroticus, i‘j 6 endolymphaticus, 323 pharyngo-branchiahs III, 19° pharyngo-branchialis IV, 194 reuniens, 323 venosus, 140, 169 Duodenum, 202, 204

mesenterial fixation of, 163, 205 suspensory muscle of, 205 veins of, 163 Duplex monster, 132 Dura mater, 320

Ear, 1 14, 322

external, 114, no, 325 internal, histogenesis ol, 323

middle, 189, 325

muscles of, Table HI) 3^3 )7r*^#»n#Tir imnlantation. 6o, 39

Ectoblast, 125 Ectocardia, 365 Ectoderm, 7, 45, 3°3 derivatives of, 95 formation of, 45 neural, 266

Ectodermal placode, 263, 3

Ectopia

cordis, I73> 219 vesicae, 252, 260, 305 Ectopic gestation, 69 Efferent

nerve fibres, 284, 3*2

irons, 274 ree Ovum

Elastic

cartilage, 334 fibrils, 97

LNPI \

4«7

due 4G 48

roembranej Embryo orlttibt^tH

oUbU^i^ent m niucma C2 I pippricAT^iaJ ruJ?*- no

estimation of atje of lo^ 1 piphwal

eilemal form oi human 107 cariita?e JS*)

foetal Jtas of 1I7

gro\»th changes in 104 rpiph>ti* 338

implantation in ectopic sites 69 Epiploic foramen (riTWinsIm ) 2}3 m asufem nt of 105 Lpuna has 35* aw»

preparation of uterus for a6 1 pUhaUmu aOj 3y»

presomiie 107 f pithelio-chsnal plaeenia C<» 4»J

somite 107 LpithelioCMri 97

sveighl of io| fptileJium

mlrjDlosy ofUadder a 47

I pidid^tnts

sasaefrerenluof ic* 330 341 250 r pitjenesis 6 rpiglsitis 183 iD| 109

1 piloia 137

presomiie 107 somite 107 weight of io| Eml T4 olosy causal 134

descnpii'e ”• experimental a scope of a stages of 6 suUiMsions of 3 \afue of a Embr>otrop'he Ci Enamel la)er 373 orijan 3?4 Endocardial eushiorti 144 146 tiHue 149 Endocardium 133

coelsroic 336 ofrorriea 319 germinal I4 of lens 31O meiltillar) aGf mrsench> mal of inner car 324 ofifis 331 of oesoptiai^us 303 olfa<tor> 314 Tespvr»tor> 300 of retina 317 leniory aCj of tioinacli 3iC of uterus 93 i piirichium 370 Ipoophoton ducts of 341

Endoenne I riihroblastcnis (beialis 129

fartors in faulty drselopment isO I rytlirolilasts <>9 3o8 333 function of corpus luteum 23 Trsthrocyles 99 308 335 Endodertn 7 383 Fihmoid bone 314

Endoderm 7 383 denistitejof i

formation of 4$ 384 primary 45 3U4 |

secondary 383 Endolymphatic duct 323 Endometrium 33 changes in aG

m menstruation 37 I

phases of 6 strata of 37 EndoslieJfion 334 Endothelial cells 99

heart tube 54 137 Endothelio-chonal placenta Go 403 Endothelium 135 EntoUast 1 5 Entwickslungsmeehanik a Eniypy 392 397 Environment heredity and 4 Eosinophil cells 99 Epartenal bronchus aoo Ependyma]

Cells 38r layer 267 Epibolv 386

Epibranchial placodes 263 310 Epicardium 138 Epidermis 370 Epididymis 4s

appendix of 341 359 efferent ductules of 10

Fihmoid bone 314 Fustachisn lube 190 325 32G Futhcfia 391 implantation in 39G ptaeentaiinn of yolk sac of 391 FsocatioP 134 I locator I2| r volution of sex 9 Exoeorlom 4C

I xocorlomic membrane 4O 75 I xomphaios 314 Fxperimenial development 132 Implantation 3 I xtemai

auditory meatus no tSq 333 ear 114 it6 335 factors m dev clop ment 4 genitalia 347 349 female 232 male 351 glomerulus 338

Exira'cmbryonic coelom 47 53 310 membranes ^ mesoderm 45 46 r stra uienne pregnancy 69 Eye 315

accessory structures of 331 chambers of 330 331 intraocular vessels of 319 median 137 315 muscles 331 3C0

Eyelaihfs 31C 317 'Lychds 114 331

Facial

cl ft congenital 115 tr7 gangl on •’Gg nerve 15 3,0 3of jio

nucleus 2B5

Valciform I gamrnt "04 Fallopian tulie 340 lalx cerebri 370 ■’0}

Fa'fia 3 j 5 3b!

lumbar 358 Fat 99 308 Fauces ani Faucial tonsil 190 lemale

external genitalia 2j2 gona I 238 pronucleus 3, 40 lemoral artery 1G3 Fenestra vestil uli 32G Fertility 40

Feriilizati nib o 32 3/ 40 age 104

derinilinn of 37 40

optimum time for in menstrual

lens 318 inusrlr ^GC nerve 3WJ neuroglia 2GG Fibrils eiasiir 97 muscle aCG nerve 267 Fibroblast 97 Fibro*cariilage 350 Fibrocyte 97 Filiroui cartilage 334 Field Forces 124 Fifth ventricle 301 Filaments of ipermaiozoon I3 Fihfoim papillae of tongue 1B4 Filum terminate 372 Fimbria

ofliippocampus 398 301 of uterine tube 39 241 Fingtn

anomalies of 126

antero-median 274 central 298 choroidal 287 294 of eye jiG foetal 316

hippocampal 295 398 lateral (I ig 321) 298 lung 200 ^ rhinal 398 301

cervical (Fig 195) 197 urachal sGo urinary (Fig 25?) 348 vitelline (Fig atG) 3t6

INDEX

418

Flagellum of spermatozoon, 1 2 Flexure, or Flexures cephalic, no, 277 cervical, no, 271, 278 midbrain, 273, 275, 278 pontine, no, 277, 278 telencephalic, 277 Flocculus cerebelli, 285 Fluid

amnio tic, 78, 81 cerebro-spinal, 287 seminal, 38 Foetal age, 105 circulation, 169 development, 117 fissure, 316 gut, histogenesis, 216 membranes, 69, 389 bilaminar, 70 unilaminar, 70 in amniota, 390 in anamniota, 390 movements, 119 Foetus, 117

external forni of establishment of, 117

groivth chanc;'=’s of 119 Fold amniotic genital. ->3glosso-' , 1“ lue 185 head, m inguinal 23- ,

lateral bod> 79 lateral nasal, 114 179 medial nasal 114, 179 neural, 108 269 pericardio-pleural, I42 tail. 76, 79

Foliate papillae of tongue, 184 Follicle

Graafian, 16 ovaiian, i^i, 16 atresia of, 23 polyovular, 13 1 primary, 15 rupture of, 17 thyroid, 197 Follicle cells, 15, 22 Follicular

epithelium, 15 fluid, 17, 22

phase of endometrium, 26 Foot, 114 Foramen

caecum 183

epiploic (of Winslow), 223 interv cntncular of brain, 281 of heart, 148, 172 ugular, 344 ■ magnum, 343 optic, 343

ovale, of heart, 145, 170 closure of, 145 patent, 172 valve of. 145 ovale, of skull, 344 pnmum, 144 roiundum, 344

Foramen

secundum, 144 Forebram, 109, 263, 278, 289 Foregut, 55, 77, 176, 177 caudal portion of, 202 cranial portion of, 1 78 Forehead, development of, 117 Formative cells, 45, 383 Fornix, 298, 301

commissure, 298, 301 system, 298 Fossa, ovalis, 145 Fourth ventricle, 280, 281, 287 Fraternal twins, 5 Free-martin, 245 Friedman’s test, 90 Frontal bone, 344 lobe, 280, 295

Fronto-nasal process, 114, 180 Froriep’s ganglion, 307 Functional period of development, 7 Fundamental concepts, i— 8

processes in development, 6 Fundus of uterus, 242 Fungiform papillae of tongue, 184

Gall bladder, 246

Gametes, i, 9 Ganglion, or Ganglia acoustic, 323

acoustico-facialis, 310, 323 auditory, 269 cells, 270

cells layer, of retina, 317 development, 270 facial, 269, 310 Fronep’s, 307 geniculate, 310 glossopharyngeal, 269, 31 1 intermediate, 328 nodosum, 31 1 occipital, 269 spinal, 269 superius, 31 1 sympathetic, 327 terminate, 314 trigeminal, 269, 309 vagus, 269, 31 1 vestibulo-cochlear, 323 Gartner’s duct, 241 Gastrocoele, 384

Gastro-hepatic omentum, 204, 208 Gastrula, 7, 383 Gastrulation, 7, 383 in Aves, 388

double, as cause of twins, 1 3 1 in Fishes, 387 in Mammals, 389 in medialecithal eggs, 386 in megalecithal eggs, 387 in miolecithal eggs, 384 in Reptiha, 388 Genes

abnormality due to, 126 autonomous, 126 dominant, 126

environment and heredity, 4, 126

Genes

heteronomous, 5, 126 homozygous, 5, 126 recessive, 126 role of, 4 Genetic

relationships, i variations, 5 Genic balance, 257 Geniculate bodies, 291 ganglion, 310 Genital

blastema, 236 ducts, 240 fold, 234 organs, 227 ridge, 236 swellings, 250 system, 235 tubercle, 250 Gemtalia

anomalies of, 257, 2 '58 derivatives, 259 external, 247, 249 homologies of, 259 internal, 236

Gemto-urmary system, 211. 227-202

Genotype, 5

Germ

cells, 6, 9, 378 female, 14 male, ii

primordial, 236, 238 layers, 7, 44, 330 derivatives of, 95, 96 in development, 124 inversion of, 392, 397 Germinal cells, 266 epithelium, 14 Gestation, 26

extra-uterine, 69 period m man, 104 Gill clefts, 178, 179 Gland, or Glands Bartholin’s, 253 bulbo-urethral (of Cowperj, 251 diencephalic, 293 lacrimal, 321 lymph, 169 mammary, 372 parathyroid, 189, 19I) *94 parotid, 188 pituitary, 34, 278, 292 prostate, 249 salivary, 183, 187 sebaceous, 119, 372 Skene’s, 249 sublingual, 183, too

submandibular, 183) to7

suprarenal, 329 sweat, 372 tarsal, 321) 372 thymus, 189, 192 thyroid, 183, 189, 19° vesUbular (of Bartholin), 253 Gians

clitoridis, 252 penis, 251

Ghsson’s capsule, 208 Globus paUidus, 297

INDEX

4»9

Ciomfru)us 258 niwonfphne 230 mrtanephric 232 proncpfinc 29 Glomus coco 5fum iCi Glosso-cpiglottic folJ Glossophaongpal nerie f57 2/3 3^ 310 ganglion 311 Golgi apparatus ofo'um tC of sperm t2

Gonadotrophic hormones Gonads 1 Q 52 236 245 descent of 254 histogenesis of 237 ovary 238 2j6 testss 337 35*

Graafian follicle 16 Gracile nucleus 283 Granular layer of cerebellum aSG Grey matter of spinal cord 2G8 274 Groove

branchial lyq tinguo-gingival iQ^ neural 51 108 264 pharyngeal 109 173 tSg ectodermal 109

endoderm^) tfff first 190 second 190 tliird 190 fourth iqi fifth 194

_ uacheo^bronehtal igi iSi GroMth G

accretionary 6 104 auxeiic 6 104 ehang s loi intussu cepiive C multtphcative 6 10^ postnatal 3 p enaral 2 J04 m weight 1 04 Gubcrnaculum dentis 375 of ovary 56 of teeth 375

Gut

abnormal development of 214 acres a of 215 blood supply of 217 enzymes of 216 fixation of 213 Jorc 55 ,77 17C 202 lunctional activities of 216 n'nd 77 t<6 211 234 histogenesis of 21b 77 177 2to

return of to abdominal cavity ■’i lotationof 163 212

Omaecora,S*3,3

Habeauto-pcduncular tract ->90

Haematopoicsis

tnnnophNleiic theory of 99 102 polyphylelic llwory of to Haemivchonal placenta Co Sj 402 404

llaemo^loblast 99 Haemo-cndoihclial placenta 60 402 Haemoglobin 101 HaemoKtnph glands 169 Ilaemolvtic durase of newborn 129 Haemorrhage mensirtial 23 29 /faemotrophe 71 Hair 117 372 follicle 37'’ lanugo 117 372 vibnssal 117 Hand 114

anomalies of (Fig 390; 352 Hard palate 181 Harelip 115 127 lO 1C6 Hassal s corpuscles iCj Head

foltl 54 76 muscles 360 of pancreas 209 pfoeesi 49 ofspermstoroon 13 vein primary 164 Heart /j? annulus ovahs 145 anomalies of 172 atrioveninculae canal 140 143 valves 151 atrium 140 143 »?s auricular appendage 143 bulbar ridges 148 bullio-ventncuiar loop and sulcus 140 changes at birth 171 ensta lermiftahs 14C deiecotof 154 173 duciut tenosus >40 rCo endocardial cushions 144 14G endocardium 139 external changes 140 foramen

interventricular 148 ovale 145 primuin 144 Secundum 144 fossa ovahs 143 histogenesis of ijl 353 36b innervation of 330 intersepto valvular space 143 miervenous tubercle 146 I mbic band 1^6 mesenteric relations (Fig 227; J25

mcsocardium 139 218 '>20 musculi peciinati 147 myocardium 138 151 3C6 niyo*rp cardial mantle 138 151 2t8

papillary muscle 151

pars membranacea septi 190

septum

interventricular 148 pnmutn 143 secundum 145 spurium 143

Heart

iinu atnal orifice 141 sinus venosus 138 I4f 145 t82 venous valves 141 ventncle 123 140 t47 wall differentiation oi 137 Heat penod of 22 Helicotrema 324 Jlcmwphercs cerebellar 283 cerebral 279 294 Henie s loop 233 Henren 1 lines 367 node 49 383 Hepatic artery 218 cells 206 circulation 209 duels 207 rudiment 20b sinusoids t{>3 207 trabeculae "OG Hepato-cardiac channels 163 Hereditary

malformations 127 relationships 1 Heredity and environment 4

as factors m faulty development, tsC

Hermaphroditism 237 Hernia

(iiaphragmatic 221 inguinal 255 Heierolaxis 173 H u rr s menibrane 46 Hillocks auricular iib 325 Hindbrain 110 aCj 83 Hindgut 77 17& 211 Hippocampal eomriimure 208 Fiuurr 9 j 298 Hippocampus 295 297 298 Htfschsprung s disease 2f5 Histiocytes 90 Hiviogcnesis b of blood 99 of hone 97 334 of cartilage 97 of cerebral cortex '•98 of connective tissue qj of corpus luteum 24 of digestive tube "16 of foetal gut 21C of gonads 237 of heart 151 355 36b ofinlcmalcar 323 of muscle 366 ofnervous ti sue 263 of piniliyroid 193 of retina 317 of skin 370

Holoblaslic cleavage of ov-um 380 Homol0(,ues of genital svvtcrns 259 Hormone 9 Cb anterior pituitary 34 corpus luteum 3 follicle stimulating 34 gonadotrophic 23 34 lutcalizing 34 morphogenetic 124 ovarian 23

INDEX

420

Horse-shoe kidney, 233 Human embryos, see Embryos Humour

aqueous, 321 vitreous, 319 Hyaline cartilage, 334 Hyaloid artery, 318 Hydatid

of epididymis, 241, 259 of testis, 243, 259 H^datidiform mole, 67 Hydramnios, 82, 92, 184 Hydrocephalus, 303 Hymen, 243 imperforate, 260 Hvoid

arch, 109, 153 bone, 347, 363 coinua, 347, 363 muscles, 363 H/perdactihsm, 126 Hypobranchial eminence, 182, 183 Hypoglossal

nen'e, 278, 306, 307 Hypomeie, 357 Hypophy’seal cai tilage, 343 Hypophysis cerebri, 34, 278, 292 cells of, 292 hormones of 34 lobes of, 290, 292

relationship of ivith sex cycle, 34 stalk of 292 Hypoplasia, 126 Hypospadias, '51, 260 Hypothalamus i;, 280, 282

“I” disc, 367 Identical twins 5, 130 Ileum, 210 Iliac

artery, 159 lymph sac, 168 vein (Fig 157), 166 Impar, tuberculum, 182 Imperforate anus, 215, 250, 260 Implantation

of blastocy St, 60, 62 comparative, 377 in Eutheria, 396 sites of, 69 types of

central, 60, 396 circumferential, 396 eccentric, 60, 396 interstitial, 60, 63, 396 orthomesometnal, 396 superficial, 61, 396 Inasivc canal, 181 Incisura temporalis, 301 Indeterminate cleavage, 380 Indinduation, 124 Incus, 325, 347 Induction, 123 Indusium gnseum, 301 Infcnor vtna cava, 145, 163 Infracardiac bursa, 222 Infundibulum

of hypothalamus, 290 of utenne tube, 39

Inguinal canal, 255 crest, 255 fold, 237, 254 hernia, 255

Inheritance, cytoplasmic, 4 Inner cell mass, 43, 70, 382 Innominate artery', 156 vein (Fig 157), 166 Insemination, 22, 37 Insula, 280, 295 Interatrial foramen, 144 septum, 143

Intercostal artery, 159, 161 Intermediate ganglion, 328 mesoderm, 52, 159, 227 Intermenstrual loss, 33 Internal

capsule, 296

carotid artery, 154, 156

ear, 322

factors in development, 4 jugfular vein, 165 Interneuromeric clefts, 281 Interosseous artery', 162 Intersepto- valvular space, 1 43 Intersex, 257

Interstitial implantation, 60, 63, 396 Interthalamic connexus, 291 Intervenous tubercle of Lower, 146 Interventricular foramen

of brain, 281 of heart, 149 septum, 148 sulcus, 147

Intervertebral ligaments, 339 Intervillous circulation, 71 space, of placenta, 71 Intracartilaginous ossification, 334,

336

Intra-embryomc

coelom, 53, 210, 218 mesoderm, 48, 50

Intramembranous ossification, 334, 335

Intraretinal space, 317 Intra-utenne

amputations, 126 infection, 127 Intussusceptive growth, 6 Inversion of germ layers, 392 Involuntary muscle, 355, 365 Ins, 316, 317, 355 epithelium of, 316 muscles of, 366 stroma of, 317 Irruption canal, 337 Islands, blood, 71, 76 Islets of pancreas, 210 Isthmus

of brain, 278

of thy roid gland, 1 90

Jacobson’s organ, 314 Jaw, 178, 344, 363

Jaw

lower, 185, 347 upper, 178, 180 Jejunum, 210 Jelly, Wharton’s, 80 Joint, or Joints, giyo capsule, 352 cavity, 352 disc, 351

synovial, 350, 351 Jugular

foramen, 344 lymph sac, 168 vein, 165

Kidney, 228

anomalies of, 233 calyces of, 232

congenital polycystic, 233, 258 horse-shoe, 233 pelvis of, 233 tubules of, 228 Knot, primitive, 49 Krause’s membrane, 367 Kupffer cells, 208 Kursteiner, canals of, 193

Labia, 253 Labial swellings, 253 Labio-dental lamina, 185 sulcus, 185 Labio-gingival lamina, 374 sulcus, 185

Labio-scrotal swellings, 250 Labour, onset of, 90 Labyrinth, membranous, 324 Lacrimal

bone, 344, 348 gland, 321 sac, 322 Lactation, 26 Lactiferous ducts, 372 Lacunae bone, 336

in trophoblast, 63, 7 ® Lamarckian, 5

ar, 272, 283, 285 isal, 272

loroidea epithehahs, 207

mtal, 374 ,

bio-gingival, 374

rmmahs, 277, 3°°

gerhans, islets of, 210

ghan’s layer, 62, 71

ugo hair, 117, 37^ _

mgeal nerves, recurrent, 57 '

158, 31 L 363 mx, 198, 199 irtilages of, 199 uscles of, 199 ' 383

rves of, 199 ) 3 **' 383

ral

iniculatc bodies, 29^ ey columns, 273 version, 132 isal folds (process), II 4 '

Lateral

plate mesoderm 5 th)roid 193 igj

'entnde of brain aSi ■'89 Uw biogenetic of recapitulation

ameloblastic 37^ enamel J73 ependymal 366 Mnglioncell of retma -tty Langhans 6 71 '

mantle 67 marginal 07 nertous of retina 317 odontoblastic 37^ pigment of retina iio Leg '

anenes 163 bones 349 daefopment of 310 muscle? 36

uS"

at birth 120 ofembrjo J03 115 317 c»t»ule 318 epitheLum of 318

«be« 3,8 Pl»c^e Its 3»fi

^rtflJureofitomaeh aoa ontentum 20J 323 ’

15:;“."?' “

««coc)topoiesu joi

wenorenal ligament 3J4

coronary 208 sacra! 3.9 i^lciform 204 ao3 8«trospl«nic 32«  intersertebral 330

i^nc^renal j 4-^^^

°[l'\er 203

S,e

triangular 208 urnbilcal 172 H?atienta flava 3,0

l™?”™ >7.

, muscles 362

i;»b.cb„d. ,,6 33»

INDEX

t Linea alba iC-i ^ Lingual

rpithebitm *84 pnmordia 182 I tonsil jpo Ltnguo-dmial sulcus 18,

I Ijnguo-gingival groo\c 16. Lip 182 ' rlefj »Cf

furrow band i8j 3-4 bare 115 ,27 ,81 ,£5 /"*««■

rhombic 28 j upper i8j Liquor

of amnion ,8 8c , follieub 17 ,8 Litter mates 130 Liter 20^ jo6 capsule of 208 tells ao6 cords 207 ducts 207

harmatopriesis in 100 02 Kupffer cells of 208 '

ligamenii of 208 lobes of 207 IIRUSOlds of 307 Lobes

of cerebellum aBj of cerebrum 20j ®5 *t>popbMu 2<K> ep offiser 207 I of lung 900

Libules of placenta 8» Longitudinal bundle medial 260 I sympathetic trunks 9 7 I I-®op '

ffenles 233

I intestinal limbs of 12 I Loi.er extremits blood sessets of 162 bones of 349 development of 340 muscles of 36-’

I nerses of 30,

Lumbar arteries 159 nerves 305 I veins 107

1 Lumbo-cosul Veins 16-.

I Lumbo^cral plerus 30^

t-ung 198 alveoli of 198 bud 199

changes at birth '*ot fissures of 200 lobes of 200 I weal

cells 22 24 hormone 32

phase of endometrium

. Lucem 94 I Lymph

gland 169 sac iliac 168

Mmphaiic rystcm 168 I Lymphoblast lot 160 Lymphocyte 99 ,0, Lymphocytopoies s 101

Lymphoid arra

“Miiimocytopoies s 101 j 6 o

L>-mphoid area of tongue 1^

Macaeua rhesus cleavage m 44 implantation in 6j Macrophages 90

'lacTostomia 187 Macula saccular 324 utncular 324 'fagma reticulare 47

CCS of kidney ->32

I external genitalia of 2,1 I gonad 237 I pronucleus 41 'falformatJons 13^ of^mto-urinary svstem 2,8 of heart 173 *'

,®f nervous svstem 302 Ma feu, 325 34G Malnutrition 129 I Malpighian corpuscle, 230 viammary arter\ internal 160 gland 372 alveoli of 373 lactiferous clucU of 372 rupernumenry 373

line, 37J 37 J

Mamiflarv bodies 998 Mandible 348 Mandibular acch tog 153 ntne 309 process 109 178 3.3

Mam). la>er 867 Manubnum sterm 340 ^larginal

imus of placenta 84 zone 267 +

I Marrow

borte tot 336 i cavuv 335 Manupialia 393 placentalion m sn,

^ >olksacor 393 ^lasi cells 99 Mastoid air cells 3 5 I antrum 3 6 Maternal

grey 374 irhife 274

Maturation 6 ofhuman ovum 14-20 ofoogonmm 18

I Maxilla 348 '

Maxillary nerve 309

process toq 178 34,

i sinus 18

«f l.™.« tmbrjo,

•external aud.toiy ,to ,80 ,2. tntemal auditory 344 ®

INDEX

422

Mechanical agencies in production of anomalies, 126 Mechanocytes, 97 Meckel’s

cartilage, 345 diverticulum of ileum, 215 Meconium, 208, 217 Medial

lemniscus, 269 nasal fold (process), 114, 179 Medialecithal ova, 378 cleavage in, 380 gastrulation in, 386 Median

aperture of IVth ventricle, 287 eye, 127

fissure of spinal cord, 274 postero-, septum, 274 Mediastinum ovarii, 238 testis, 10, 237 Medulla

oblongata, 264, 278, 282, 283 of suprarenal gland, 329 of thymus gland, 194 Medullary cords, 237 epithelium, 266 velum, 287, 288 Medulloblasts, 266 Megakaryocyte, i o i Megalecithal o%a, 378 cleavage in, 380 gastrulation in, 387 Megalocytc, loi Meiosis, 6 1 1 Melanin, 371 Melanoblasts, 99, 371 Membrana propiia, 17 Membrane or Membranes anal, 58, 212, 235, 250 bones, 334, 336

buccopharyngeal, 48, 52, 56 109, 176

cloacal, 49, 57 79, 21 1 egg, 379 embryonic, 389 e\tra-embry'onic, 6g, 389 foetal, 69, 389 granulosa, 16 Heuser’s, 46 Krause’s, 367 Nasmyth’s, 375 placental, 60, 85, 402 pleuro-peritoneal, 220, 222 pupillatv', 319, 321 persistent, 321 Rcissner’s, 324 rupture of, 80 synov'ial, 350, 352 tcctonal (Fig. 355), 323 Umpanic, 325

urogenital, 58, 212, 235, 250 vestibular, 324 v’ltelline, 16, 37 Membranous labynnth, 324 Meninges, 95, 270, 287, 342 Mcningocoele, 303 Mcninx, 342 ecto-, 342 endo-, 342 KIcnisci, 352

Menses, 26 Menstrual age, 104 cycle, 23, 26 length of, 19 phases of, 26 flow, 26

phase of endometrium, 26 source of, 30 Menstruation, 23, 26-28 in adolescence, 29 anovular, 29 cause of, 30

corpus luteum of, 24, 26 haemorrhage during, 26 histology of, 29 length of, 26 relation of oestrus to, 33 relation of ovulation to, 3 1 Meroblastic cleavage of ovum, 38 1 Mesectodermal cells, 95 Mesencephalon, 109, 263, 277, 287 differentiation of, 289 Mesenchyme, 71 derivatives, 96 Mesenchymal cells, 97, 99 Mesenteric

artery, 77, 158, 210, 218 lymph sac, 1 68 vein, 164 Mesentery

dorsal, 204, 385 fixation of, 213 ventral, 204, 223, 385 Mesoeardmm, dorsal, 139, 218, 220 Mesocolon pelvic, 212 transverse, 214, 225 Mesoderm, 7, 45, 99, 385 axial, 52 branchial, 57 cardiogenic, 52, 137 chorda-, 385 chorionic, 70, 71 derivatives of, 96 extra-embryonic, 45, 46, 405 formation of, 45 intermediate, 52, 159, 227 mtra-embryonic, 48, 50 lateral plate, 52, 227 paraxial, 52, 227, 339 parietal, 47 primary, 47, 405 somatopleuric, 47, 53, 364 splanchnic, 47, 53, 364 splanchnopleuric, 47, 53, 365 visceral, 47, 365 Mesodermal

somites, 52, 107, 339, 355 syndrome, 127 Mesodermic pouches, 385 Mesoduodenum, 205, 213 Mesogastrium

dorsal, 204, 223, 385 ventral, 204, 223, 385 Mesonephne corpuscle, 230 duct, 228, 236, 240 fate of, 236 fold, 230 glomerulus, 230 mesentery, 230

Mesonephric tubules, 228 vesicle, 230 Mesonephros, 227 differentiation of, 230 epigenital part of, 230 functional activity of, 231 in man, 230 paragenital part of, 230 phylogeny of, 227 Meso-oesophagus, 203, 222 Mesorchium, 237, 255 Mesothelium, 96 Mesov'arium, 237 Metabolism, 6 uricotelic, 4 Metamerism, 107 Metanephric artery, 159, 233 bud, 231

Metanephric blastema, 231 Metanephros, 228, 231 anomalies of, 233 calyces, of, 232 collecting tubules of, 232 functional activity of, 234 glomerulus of, 232 histogenesis of, 232 tubules of, 228 ureteric bud, 231 Metaplasia, 123, 253 Metathalamus, 291 Metatheria, 393 yolk sac of, 393 Metazoa, i

Metencephalon, 263, 278 Metoestrus, 33 Microglia, 266 Microstomia, 187 Midbrain, 109, 263, 287 Middle ear, 189, 325 Midgut, 77, 177, 210 Migration of ovum, 40 Milk

ducts, 372 line, 373 ridge, 373 Minor calyces, 232 Miolecithal ova, 37> 37^ cleavage in, 380 gastrulation m, 384 Mitochondria of ovum, 16 Mitosis

in oogenesis, 19 in spermatogenesis, 19 Iitral valve, 151 Iittelschmerz, 33 lole. hydatidiform, 67

Monochorial twins, 131 Monocytes, gg, loi

Monoestrus, 22 Monophyletic theory ol poiesis, 99, 102 Monoplegia, 303 Monozygotic twins, 131 Monro’s interventricular

281

Monsters, 125, 13*

organizing centres in, 1 Siamese, 13 1

haemato*

foraminaf

31

INDE-V

423

Niorphogenelic hormonw 124 movements 7 363 MoruU 43 6j 380 jije of bi

Mosaic ]»uetn I2t Motor

end p'ate 3t>6 nenes

somatic 274 30O viscera) 274 2^4 3 t)P nucleus

of Spina) nerves 3/4 of irigemma) nerve aOj of vagus nerve 284 Mouth

development of 181 floor of 162 primitive 57 115 roof of ! >9 Mucosa uterine 23

implantation of embrjo in 60 in pregnancy 63 67 penetration by embryo f2 Mullerian

ducb 227 2315 240 transformation of 240 tubercle 242 Multiparous uterus Gt Multiple births (tee Twtnnitvg Multiplication cell G Multiplicative growth 6 104 Muscle or Muscles 3 jj“ 368 of abdomen 3 G of auditory ossicles 363 JVKk 5,G 35B oTbUdd r 248 bronchia] 36^ buccinator 3P3 cardiac 131 355 361 ciliary jfti cotc)gevis 360 ofduphfajm 364 digavtnr 363 of duodenum 203 of expression 363 of eye 221 360 facial 363 fibres 36(1 fibrils 366 geniohyoid 360 ofhead 360 hisfogcncsia of 3C6 ilio-cosiahs 358 infrahyoid 360 intercostal 359 intervertebral 358 ofmtevtme 365 intracostal 359 involuntary 355 36^

355 36b levator am 360 of limbs 362 {onps imus 358 lumbar 359 masseter 363 of mastication 361 mulljfidus 358 mylohyoid 303 ofnecx 360

obliquus abdominis neo of palate 363

Muscle or Muscles

papillary *5*

penncaJ 360 pharyngeal 361 prcvertebral 360

pteoi?^*^ 3G3 pupillary 355 3®® quadratus iumborum 3^9 rectus abdominss 359 roiatores 358 sacrospirsalis 359 scaJenei 360 segments 355

semispinalw 358

skeletal 355-369

smooth 355 36* spindle 36f splenius 3jB superfial 363 iternatis 359 siernomastDid 363 sinate 35^ sivfobyoid 363 siylopharyngeus 3G3 temporal 3G3 tensor tympam 363 tongue 3Cn tracheal 3G5

traniveesus abdomims 359 tratuvenus ihoraeis 359 irapetius 3C3 of trunk, 359 of vertebral column 358 visceral 355-3G9 vulunrary 355 367 Muscular system 355-369 Musculature origin of segmental (Tabic 11; 356 ongiftotvisceral arch (Table 111) 363

hfusculi pecimati 147 MyeJencephalon 263 37B nuclei of 283 Myelm

developmeniof inspmalcord 2C8 sheath 2C8 Myelination 268 Myeloblasts 09 Myelocytes of Wood los Mvoblajts 138 356 Myocardium 138 s^t 3jj Myoeoele y'

Myoepicardial mantle 138 2|8

Myo-epiihelial cells 355 3(16 Myofibnls 366 Myotome 339 3,5 cervical 360 coccygeal 359 demo- 96 35G head 360 lumbar 359 occipital 184 360 sacral 359 thoracic 356

Nall 117 371 fields 37s Nares

anterior 114 1 posterior 180

Nasal

bone 344 3^8 capsule 314

cavities I" ' conchae 1 folds (processes) J *-1 * I placode U4 179 3«4 s ptum 180 sinuses tSz

Nasmyth 1 membrane 375 Naso-lacrimal

duct 115 182 322 furrovv 115

Naso-palatine canal t8» Nasopharynx 201

Neck 114 Netghbounvise 721 N oeoftex 297 298 Nco-Laroarcltian j Neopallium 295 297 302 Nephric system phylogeny of 227 Ntphrocoele 228 Nephrogenic cord '’27 Nephron 233 Nephrosionte 228 Nephrotome 228 Ncne or Nerves abducent 279 306 308 accessory 278 30C 312 acoustic 270 auditory 306 3a cells histogenesis of 67 2/0 cerebral 30C cerebro-spinal 304 306 cervical 303 chorda tympam 326 cochlear 3 3 crania) 209 306 elTerent

somaiir 30G 31a visceral

branchial 209 311 general 306 311 special 30G 31 1 facial J57 279 3°®

310

fibres 268

glossopharyngeal 157 278 306 310

hypoglossal 278 306 307 laryngeal 157 15O 3ti 363 lingual 310 mandibular 309 maxillary 309 motor somatic 274 308 oculomotor 306 308 olfactory 30b 314 ophthalmic 309 optic 269 306 315 317 petrosal 310 phrenic 222 304 pi xuses

cervieo brachial 303 lumbosacral 305 post irematic 178 pre cervical segmental 307 pre trcmauc 178 profundus 309 somatic

afferent 306 effer nt 3^ 312

INDEX

424

Nerve, or Nerves spinal, 304 accessory, 312 rami, 304 roots, 304

trigeminal, 157, 279, 306, 309 trochlear, 306, 308 vagus, 278, 306, 31 1 vestibular, 269, 323 visceral, 306, 309, 311 vomero-nasal, 314 Nervous system

autonomic, 327 central, 263

development of function in, 312 parasympathetic, 327 peripheral, 269, 304 sympathetic, 327 tissue, histogenesis of, 265 Nervus terminalis, 314 Neural canal, 265 crest, 263, 269 ectoderm, 266 fold, 108, 269 groove, 51, 108, 264 mechanisms, differentiation of, 312

plate, 109, 263 supporting elements, 266 tube, 109, 263, 265 anomalies, 303 derivatives of, 269 histogenesis, 265 Neurenteric canal, 78, 265, 387 Ncuroblasts, 267, 327 differentiation of, 267 of retina, 3 1 7 Neurocranium, 341, 342 cartilaginous, 342 membranous, 344 Neurocranium regions of, 342 sense capsules, 342 Neuro-ectodermal junction, 264 Neurofibrillae, 267 Neurogens, 124 Neuroglia, 266 Neurolemma, 268 Neuromercs, 278, 281 Neurons, 267, 273 Neuropores, 109, 265 Neuro-somatic junction, 264, 269 Neurula, 7 Nipple, 373 Nissl’s granules, 267 Node or Nodes Hensen’s, 49, 389 primitive, 49, 380 of Ranvicr, 268 Non-granular leucocytes, 101 Non-rotation of intestine, 214 Norm, 125 Normoblasts, 10 1 Norrooc>'te, 101 Normogcnesis, 125 Nose, 115, 182 Nostnls, 180 Notochord, 49, 340. 385 Notochordal canal, 49

Notochordal plate, 49, 387 process, 49

Nuchal flexure, no, 271, 278 Nucleus, or Nuclei abducens, 285 acoustic, 283 ambiguus, 284 caudate, 296 cochlear, 283 cuneate, 283 dentate, 286 facial, 285

glossopharyngeal, 283 gracile, 283 habenular, 290 hypoglossal, 284 lentiform, 296 motor

of facial nerve, 285 of trigeminal nerve, 285 of vagus nerve, 285 of myelencephalon, 283 olivary, 283 of ovum, 16, 18, 37, 40 pontine, 285 pulposus, 340 red, 289

of tractus solitarius, 283, 310 trigeminal, 285 trochlear, 289 vagus, 283 vestibular, 283 Nulhparous uterus, 61 Nutrition

embryotrophic, 62 haemotrophic, 71

Oblique vein of left atrium, 168

Occipital

bone, 343, 344 ganglia, 269 lobe, 280, 295 tectum, 342

Oculomotor nerve, 306, 308 Odontoblastic layer, 374 Odontoblasts, 374 Odontoid process, 339 Oesophageal arteries, 158 Oesophagus, 202, 203 Oestradiol, 17, 22 Oestrogens, 22, 90, 91 Oestrous cycle, 22, 33 Oestrus, 18, 22, 33

relation to ovulation, 18, 33 Olfactory

apparatus, 314 bulb, 279, 314 cells, 314 cortex, 298 epithehum, 314 fibres, 314 lobe, 314 nerve, 306, 314 pit, no, 114, 179, 314 placodes, 114, 182, 314 tract, 314 Oligamnios, 81

Oligodendrocytes, 266 Olivary nucleus, 283 Omental

bursa, 204, 222 superior recess, 223 Omentum

gastrohepatic, 204, 208 greater, 225 lesser, 223 Omphalopleure ' bilaminar, 393 trilaminar, 393 Ontogeny, i Oocyte

maturation of, 18 primary, 16, 19 secondary, 16, 18, 19 Oogenesis, 9, 14 Oogenetic cycle, 23 Oogonia, 15, 16 . Oophoricus, cumulus, 16 Opercula, 295 Ophthalmic nerve, 309 Optic

capsule, 344 chiasma, 282, 290, 302 cup, 278, 289, 316 disc, 320 foramen, 343 nerve, 278, 315, 317 recess, 291

stalk, 278, 281, 289, 316 sulcus, 277, 315 „ vesicle, no, 277, 289, 310 Ora serrata, 317 Oral cavity, 179, 182 Orbital muscles, 360 Orbitosphenoid, 343 Organ, or Organs absence of, 126 Chievitz’s, 188 chromaffin, 329 enamel, 374 Jacobson’s, 314 region, presumptive, 7 sense, 314 sex

accessory, i primary, i, 9 spiral, 324

supernumerary, i 2 d vomero-nasal, 314 Zuckerkandl’s, 329 Organization, 6 Organizer, 123 head, 123 mechanism, 124 primary, 123 region, 123 second grade, 123 in Siamese monsters, 131 tail, 123

third grade, 123 trunk, 123 in twins, 13 1 Organogenesis, 6

Orgasm, 39 Oro-pharynx, 201 _ Orthomesometnal implantatio

Ossicles, auditory, 326, 340 Ossific centre, 336

INDEX

425

OssificaUon 334 centres 335 Osteoblasts 97 335 Osteoclasts 337 Osteocyte 97 33® Osteogenesis 334 Osteoid 335 Otic

capsule 344 tatvlage 324 depression 110 323 pit, 313

placode 109 277 322 \esicle no 323 Otoeyst 323 344 Ovarian cycle 23

folbcle 9 14 t6 23 pregnancy 6g Ovar

Ovary i q 14 238 anomalies of 257 258 cortex of 14 t? descent of 256 differentiation of 238 follicles of 15 16 germinal epithelium of 14 238

K ibemaculum of 256 gament of 56 medulla of 14 Pfluger I tubes of 15 stroma of 14 supernumerary ajB Oviparous 395 Ovoviviparous 393 Ovulation g 17 18 23 age 104

methods for determination of 32 multiple i3g

relation to menstruation 31 time of 31

Ovum or Ova t g 37 3,8 cleavage of 7 37 42 379 comparison with spermatozoon 18 cytoplasm of 37 diameter of 37 duraUon of fertility of 40 fertilizauon of 40 formation of 38 boloblastic cleavage of 380 human 37 238 implantation of 60 62 atiomahes of 69 site of 63 83 maturation of g 14-20 tnedialecithal 378 tnegalecithal 378 membranes 379 meroblasuc cleavage of 381

tmgrauon of 40 tmolecitbal 37 378 nucleus of 16 18 37 40 penviielbne space 37 primordial 15 238 ^lauve 380 structure of 37 ^»“Port of to uterus 30 types technical n»m« of {Table IV) 370 “nfertUieed 37 '

'labibiy and longevity before feru uration 40

Ovum or Ova yolk of 37 378 Oxyntic cells of stomach 217

Fabulam, 66

Palaeopallium '*93 297 302 Palatal process 181 Palate

anomabes of 182 bones 348 deft t86 formation of 179 hard 181 premaxillary tSi primitive 180 soft I&l Pallidum 297 Pallidus globus 297 Pallium 294 Palpiebral

conjunctiva 321 fissure 321 Pancreas -02 08 accessory duct of 09 acim of 210 ampulla of "09 anomalies of 209 body of “*09 cells of 210 dorsal 208 ducts of 2tO head of '’09 histogenesis of "09 islets (of Langerhans) 210 mesenterial fixation of 21a tail of 209 ventral 208 Papillae dental 374 dermal 371 filiform S84 foliate 184 fungiform 184 vallate 184 Papillary muscle 151 Parachordal cartilage 34-* region 342

Paracyclic ovulation 31 Paradidymis 197 Paraganglia 328 abdominal 329 parasympathetic 330 Paraganghomc celb Paraluleal cells 22 i‘>4 Paramesonephne duct 227 female 241 male ”43 Paranasal sinuses 182 Paraphysis 291 Parasy mpathcuc

nervous system 323 327 329 paragangba 330 Parathyroid gland s8g 191 194 histogenesis of 193 Paraurethral glands (of Skene) 4 Paraxial mesoderm 32 339 Parietal bone 344

Parietal celb "17 lobe 280

Paroophoron 231 "o9 Parotid gland 188 Pars

anterior of hypopbvsu 292 caeca retinae 317 cibarvs ictvnae 317 cystica 06 hcpauca 206

intermedia, of hypophysis 29'’

iridis retinae 317 merabranacca septi 150 nervosa

of hypophysis ■’90 292 retinae 317 optica retinae 317 pclvina 248 phalliea '*48

tuberalis ofhypophysis 29 Parthenogenesis 41 Parturition 26 80 89 P dancles

cerebellar -85 cerebral 85 Pelwc colon 21 1 mesocolon "la Pelvis

bones of 338 349 renal 33 Penile raphe 2^1 urethra a^jl Penis I 37 I double 260

clans '’at - o

Pericardial cavity 36 137 i/6 t8 Pericardio peritoneal canals 50 I/6 Pericardio-pleural canab 56 a'‘0 fold 14

membrane 2'*o opemngs 56

Pericardium 53 too 2t6 transverse sinus of 139 220

visceral 138 _

Perichondrial ossification 330 Perichondrium 334 33®

Periderm 370 Penlymph spaces 324 Penneum I2 235 muscles of 359 Period

as embryo 1 17 as foetus 1 1 7 gestation 104

Pcri^ontal membrane 37 1 Periosteal ossification 336 Penosleum 336 Penouc spaces 324

Penpheral nervous system 304

leristabu 216 Peritoneal

cavity 56 178 **

sac lesser 222

INDEX

426

Persistent cloaca, 260 ductus arteriosus, 173 foramen ovale, 1 72 Petrosal

nerve, greater superficial, 310 sinuses, 164 Petrous bone, 348 Pfluger’s tubes, 15 Phagocytes, alveolar, 201 Phallic portion of urethra, 251 of urogenital sinus, 249 Phallus, 251 Pharyngeal arch, 109, 178 aiteries, 153, 178 derivatives of, 135-226, 334-369 groove, 100, 179, 189 ectodermal, 100, 179 endodermal, 179, 190 muscles, 363 pouches, 179, 189, 190 Phaivngo-tympanic tube, 190, 325, 326

Pharynx, 189, 201 oro-, 201 Phenotype, 5 Philtrum, 186 Phrenic nerve, 222, 364 PhvsicO'Chemical factors in faulty development, 132 Pia

arachnoid, 270, 287, 342 mater 270, 287, 342 Pigment cells. 99

granules of skin, 371 layer of retina, 3 1 7 Pineal gland, 278 290, 293 Pinna, n6 Pit

olfactory, no, 114, 179, 314 otic, no, 323 pnmitiv'c, 49

Pituicjtcs, 293

Pituitarv gland {see also Hypophysi function of, 34, 90 hormones of, 23, 34, 90 in pregnancy, 34, 90 relation to sex cycle, 34

Placenta, or Placental, 82, 389 accessory, 83 annular, 404 anomalies of, 82 barrier, 60, 85, 125 battledore, 83 bidiscoidal, 83, 404 border sinus of, 84 chono-allantoic, 76, 85, 396, 39 chono-vitelhne, 394 circulation in, 83 classification, 85, 397 cotyledons, 82, 404 deciduate, 85. 404 diffuse, 82, 404 discoidal, 85

cndothelio-chonal, 60, 402 cpithclio-chonal, 60, 402 full term, 82 function of, 85 furcate, 83

Placenta, or Placental intervillous spaces of, 71 haemo-chorial, 60, 85, 402, 404 haemo-endothelial, 60, 402 labyrinthine, 73, 404 lobed, 83 in mammals, 397 membranacea, 82 membrane, 60, 85, 402 origin of, 60, 377-407 position of, 83 physiology, 85 praevia, 69, 83 septa, 82 shape of, 82 size of, 82 succenturiata, 83 syndesmochorial, 402 transmissability, 86 vessels, 83 villous, 73, 85, 404 weight of, 82 zonary, 83, 404

Placentation {see Table V), 402 comparative, 377-407 deciduate, 69 human, 60-94 Placodes

dorso-lateral, 31 1 ectodermal, 263, 310 epibranchial, 3 1 1 lens, 1 15, 316 nasal, 114, 179, 314 otic, 109, 277, 322 Plasma cells, 99 Plasmoditrophoblast, 62, 72 Plastic state, 121 Plate alar, 272 basal, 342 blastoporal, 388 cardiogenic, 53 commissural, 300 cribriform, 314 cutis, 371 neural, 109, 263 notochordal, 49, 387 prochordal, 46, 56 urethral, 250 Pleural

cavity, 56, 176, 220 membrane, 220 Pleuro-pericardial canal, 56, 220 membrane, 220 Pleuro-peritoneal canal, 56, 221 membrane, 220, 222 Plexus

brachial, 305 cervical, 305 choroid, 287 coeliac, 327 lumbo-sacral, 305 sympathetic, 327 Plica inguinalis, 237 Pluripotency, 51 Pluripotent state, 12 1 Pneumato-entenc recess, 222 Polar

body, 18, 20, 40 spindle, 18, 40, 41

Pole

ammal, of ovum, 380 vegetal, of ovum, 380 Poliomyelitis, 127 Polyembryony, 130 Polymastia, 126, 373 Polymorphonuclear leucocytes, loi Polyoestrus, 22

Polyovular ovarian follicles, 13 1 Polyphyletic theory of haematopoiesis, 102 Polythelia, 373 Polyzygotic twinning, 130 Pons, 264, 282, 283 Pontine flexure, no, 277, 278 Portal

anterior intestinal, 163, 177 posterior intestinal, 177 vein, 163, 209 Postanal gut, 21 1, 234 Postaxial muscle, 363 Postcardinal vein, 139, 165 Post-costal anastomoses, 159 Posterior

commissure, 290 rachischisis, 303 Postero-median septum, 274 Post-gangliomc ramus, 328 Postmaturity, 105 Post-menstrual phase of endometrium, 26

Postnatal development, 2 Post-transverse anastomoses, 159 Post-trematic nerve, 178 Potency 7

prospective, 12 1 Potential fate, 121 Potentiality of blastomeres, 43> Pouch or Pouches coelomic, 385 endodermal, 179, 189 first, 190 second, 190 third, 190 fourth, 194 fifth, 194

mesodermic, 385 pharyngeal, 179 Rathke’s, 177, 279, 292 Preaxial muscles, 363 Precardinal veins, I39 j P re-costal

anastomoses, 159 veins 1 65

Pre-^decidual phase of endometrium,

26

Preformation, 6 Pre-ganglionic ramus, 328 Pregnancy

abdominal, 69 corpus luteum of, 24 20 cycle, 22 duration of, 104 ectopic, 69 extra-uterine, 69 maintenance of, 89 multiple, 126, 129 ovarian, 69 termination of, QO tubal, 69

Pregranulosa cells, 230 Pre-implantation penod, oi

INDEX

427

Pre menjirual phase of c

jnewium *6

Prenatal dc\fIopmen! 2 gto' th changes 1O3

period of embr>o IOt period of foetus 117 Prepuce 23!

Pressor ceceptoC reg’oos >50 Presumpme organ regions 3 Pre Ircmaiic nerves 178

Pnmarv

abdominal pregnancy 69 areolae 337 chorionic vilU 7 * follicles 15 oocvte 15

ovarian prcgnancv 69 ramus 3^7 sex organs 1 9 \olksac 43 46 ,0 75

345

cleavage in 44 origin of mesoderm in Pnmitive blood e tls 99 bone narrow Joi fcnMMTit/ie 49 streak 47 48 387 vascular system 133 yolk sac 43 46 Ptitrotdval follicles ij 36 germ cells 236 238

eoilal 340

ironto nasal 114 180 bead 49

laiersl nasal 114 17a tnaniSbular 109 iy8 oj mwillary log 178 34, median nasal vu notochordal 49 Pi'ava’ 181 transverse 339 ■uphold 3io Processus ascendcns 343 ,’■'"•1; >33 336

tofurdus nerve 300 Pto?eMational p?ase s - mcinim jg Pmlact'rSI “3 27 89

>rolircrative\ duct 228

3 8

'^"“ephros 227 '■orr^rv us of a r “ man, 225

.n^phrostomeof 2 ‘^fonucleus

405

Prospective I potency lai significance 121 Prostate gland '’49 Prostatic uincle 243 Proteolytic enzymes of gut 216 Pseudohermaphrodibsm 257

Pseudopregnancy 33 Pterygoid lamina 348 'Pterygo-quadrate cartilage 343 343 ' Pubic bone 349 Pulrnonary I alveoh 198 aoo arches 150 arteries 155 primordia 198 veins 143 Pulvinar 291 Pupil 3 t Pupillary

membrane 319 32' persistent 321 muscles 355 366 Purkinje cells 86 tissue 367 Putamen 397 Pygopagus 13 Pyfonc stenosis 315 Pyramidal tracts •’69 Pyriform corict 29^

Quadrate lobe of bver, 307 Quadruplets 133 Quickening 119 313 Quintuplets Dionne 133

Racblscbisis posterior 303 Radial artery 162 Radius 349 Ramus

communicans 338 pre ganglionic 338 post ganglionic 338 primary 337

penile 251 233 scrota) 332

Rathke s poucb 177 279 29'* Rauber s layer 383 392 Recapitulation of 154 377 Receptors cfaemo 158 330 Recess

lateral of 1\ Oi ventricle 287 of lesser sac (omental bursa) 233 Rectum "’ll 234 maldevelopment of 260 Recurrent (inferior) laryngeal nerves »57 *58 3” 363 Red blood corpuscles differentiation of g6 208 2 5 in bone msrroyt Red nucleus 289 Reduction division 11 18

Rutosis 19

Reference taWe of human develop

Regulative ova 380 Reichert s cartilage 301 I Reissner 5 membrane 383 I Renal

I corpuscles 330 I pelvis 233 I unit 233 vein 167 Rennin 216 Reproduction i ' Reproductive system 227-26 Reptilia

gastculation in 388 placentation m 395 Respiratory epiiheliutn 300 I organ foetal 201 I system i/6-"26 I Rete

I ovarii 338 I testis to '*37 I Retention bands '’to 211 213 Reticular

fibrils 97 2'’4 tissue 97 194 374 Reticulo-spinal tract 269 Reticulo-endothelial system 99 223 Reticulocytes tot .Retina 316 317 I histogenesis of 317 Keunat I artery 319 I vein 319 I Retropentoneal I lymph sac 1S8 I Rhabdomyomata 173 I Rh factor in congenital disease i'’9 Rhinal fissure 298 301 I Rhombenctphalon 110 263 277 I 28

Rhombic lip 283 Ribs 339 338 Ridge

arytenoid 199 epjpericardial no Rod and cone cells 317 Roof plate 271 273 '>86 291 Roots nerve '>68 304 Rotation of intestines 209 of stomach 233 Round ligament of liver 2o8 of uterus 256 Rubella 5 128 Rupture of follicle 17 of membranes 80

Sac

aortic 1^2 154 conjunctival 321 dental 374 cndolymph 3'>3 lymph 168 peritoneal greater .33 lesser '>22

I Voll' 45 75 *76 389 393

4 s 6

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i:i‘“Sc;,:^‘‘jfs

log j^o ‘ '■'eries

Oovr » oi^ /Q- ^

^89 ’334~36q

- ' ""4 S’

.> -o'-rnes

■’ ' ■^-S/«9..go

i ^ i^6

■':c?-'A.7‘,.i%

/"fervjlioy/^^acenta/ L^^o-chr, ®P3ces of ^

Praevia 85 ®epfa, 82 %

'■^"smissaK 402

5S; %"'>'•«“

I ^ole

I ^oioia/ nr

h‘oiS‘“-'‘^°nS' 3®»

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• P£nd/e 7 o^°^ 40

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725

^^nan/eq ’ '^8 t'ibal,^ 6 g°^ Po

/p/‘'5a;r59 90

period, 61

INDEX

427

Pre menstrual phase of endo metrium 26 Prenatal

development 2

growth changes lo^

period of embr)o lOj period of foetus 1x7 Prepuce a'

Pressor receptor regions rso PresumpU e organ regions 3 Pre tremalic nerves x,8 Primary

abdotninal pregiianc> 69 aseolae 337 chononicvilli 7: follicles 15 ooc)te I3

ovanan pregnanq ug ramus 337 sex organs t 9 >olk$3C 43 46 ,0 75 Primates cleavage in 44 origin of mesoderm in 40^ Primitive Wood cells 95 bone marrow lot knot or node 49 ttreak 47 4^ 387 vascular s)steiti 133

irxv'

follicles 12 238 germ cells 236 938 ova 12 238 Process CDSUl, 340

froDto-nasal 114 180 head 49

lateral nasal 114 179 mandbular too x?fi gi,

<09 «r8 345 medianoaul ui 1,0 notochordal 40 palatal i8t transverse 339

• iphoid 340

Processus ascendens 343 vaginalis 233 j,6 Procho dal plate 46 56 P octodaeum 212 234 Profundus nerve 305 ‘^rogestai.onal phase of endt P meitiurn 2r •rogesterone 23 2, gq

Prolactin 34 ' ^

Proliferative phase of endomeif, or

Promvelocvte iqi Proivcpiitic •luct 228 tubules 228 Pronephros 227 I'omerulus of 220 w man 229 ^

p ^ 41

• ro-oestru3 3,

Prosencephalon

too 263 a,, a9g

Prospective

poiencv tai significance lat Prostate gland 249 Proslatic utricle 243 Proieol>tic ena>fnea ofgui 216 Pseudohermaphrodilisns 2o7 P$eudopregnanc> 33 Pter>goid lamina 348 Pter>et)-qv)adraie cartilage 343 34;, Pubic bone 349 Pulmonarv

alveoli 198 2CO arches 155 arteries S55 pnmordia 198 veins 143 Fulvinar 291 Pupil 321 Pupillarv

membrane 319 321 persistent 321 mu cles 3a5 3CC Purkinje cells 286 tissue 367 Putamen 297 P>R0pagm 13 Pyloric stenosis 21S Pyramidal Iraeis 2C0 Pyriform cortex 29^

Quadrate lobe of liver -'o? Quadruplets 132 Quickening 119 313 Quintuplets Dionne 132

Rachlschlolo pcvtrrmr 303 Radial artery 1G2 I Radius 349 ' Ramus

communteans 328 pre ganglionic 32O post g3ni>lionic 328 . primary 327 I Raphe

penile 251 2j2 scrotal 252

. Rathke s pouch 177 2,9 292 ] Rauber s layer 383 392 Recapitulation Tavv of 154 377 I Receptors chcnio- 158 330 I Recess

lateral of IV ih vrntneic 87 of lesser »ac (omental bursa) 2'>3 Rectum 21 1 234

maldcvcioptncnt ©f 360 Recurrent (inferior) laryngeal nerves

In j 3'« 363

Ked blood corpuscles difTereniiaiion of 96 2o8 225 in bone marrow 101 Red nucleus 289 Reduction division II 18 mitosis 19

Reference table of human develop ment (Appendix) 408 Henexes 313

Regulative ova 380 Reichert s cartilage 301 Reissnet s membrane 2O3 Renal

corpuscles 230 pelvis 233 unit 233 vein 167 Rennin 2tG Reproduction i Reproductive svstem 27-6 Reptiha

gastrulation in 388 plaeenlation in 39^

Respiratorv

epithelium 200 organ foetal '*01 svxtem 1,6-226 Retc

ovarii 238 testis IP 237

Retention bands 210 211 213 Reticular fibnls 97 224 tissue 97 194 3,4 Reticulo-spinal tract "Gg Rcticulo endothelial svstem 99 223 Reticulocytes 101 Retina 316 317 histogenesis of 317 Retinal arterv stg vein 319 Retroperjloneal lymph sac 168 Rhabdomvomata 173 Rh factor tn congenital disexte 1 9 Rhinal fissure 298 301 Rhombencephalon 110 263 277 282

Rhombic lip 283 Ribs 339 358 Ridge

arytenoid igg epipericardiaf 110 Roci and cone cells 317 Roof plate 271 "72 206 '*91 Roots nerve 268 304 Rotation of intestines 209 of stomach 223 Round ligament of liver 2o8 of uterus 256 Rubella 518 Rupture

of follicle 17 of membranes 80

aortic 152 154 conjunctival 321 dental 374 endolymph 323 lymph 168 peritoneal greater 223 lesser 222

yolk 45 75 176 389 393

INDEX

428

Saccula cisterna, 324 macula, 324 Saccule, 323

Sacral artery, middle, 16 1 Safe period, 33 Salivary glands, 183, 187 Santorini’s duct, 209 Scala

media, 324 tympani, 324 vesubuli, 324 Scapula, 338, 349 Sclera 319 Sclerotic capsule, 344 Sclerotome, 96, 339, 355 Scope of embr)'ology, 3 Scrotal swellings, 251 Scioium, 9, 10, 252, 259 Sebaceous glands, 119, 372 Sebum, 1 1 9, 372 Sc( ondarv cboi ionic villi, 71 oocyte, 16, 18, 19 '■et characters, i spermatocyte, 10, n ^ yolk sac, 7o, 176

Secretory phase of endometrium, 26 Segmentation of body, 52, 107, 355 cawty, 45, 388 of head, 342

Segments, mesodermal, 52, 107, 355 Scgiegation, 121 Selfwise, 121 Semen, 38

Semicircular canals, 323 Semilunar valves, 150 Seminal fluid, 38

vesicles, 10, 38, 241 Seminiferous tubules, 9, 10, 237 Sense capsules, 342 Sensorv'

cells, 263-333 epithelium, 263 fibres, 304 nerves, 263-333 neurons {see cells) root of spinal nen'e, 304 Septa, placental, 82 Septi, pars membranacea, 150 Septum, or Septa aortico-pulmonary, 149 atnal, 143

bulboventricular, 148 interatrial, 143 interventricular, 148 closure of, 149 incomplete, 172 lucidum, 301

median, of spinal cord, 274 nasal, 180

postero-median, 274 primum, 143 secundum, 145 Sinus, 145 spunum, 143

trans-versum, 55, 138, 219, 364 migrauon of, 364 urogenital, 237 urorectal, 58, 21 1, 234

Septum

ventricular, 147 Serosa, 389

Sertoli, sustentacular cells of, i o Sex, 9

characters, secondary, i chromosomes, 20, 257 cords, 237

determination of, 20, 257 deviations, 257

differentiation of, 236, 243, 246 ducts, 240, 241, 243, 244 factors determining, 244, 246 glands, 9-36, 227-262 hormones, 9, 23, 34, 66 influence of environment on, 245, 246 organs

accessory, i primary, i, 9 primordia, 237, 238 ratio, 20

reversal, in cattle, 245 Shaft of hair, 372 Shape of placenta, 82 Sheath

medullary, 268 myelin, 268 neurolemmal, 270 Siamese twins, 131, 132 Significance, prospective, 121 Sino-vaginal bulb, ^242 Sinu-atrial orifice, 141 Sinus

border, of placenta, 84 carotid, 158 cavernous, 164 cervical, 110, 116, 197 coronary, 145, i68 marginal, of placenta, 84 maxillary, 182

obhque, of pericardium, 220

paranasal, 182

petrosal, 164

sagittal, 165

septum, 145

sphenoidal, 182 "

straight, 165

transverse, of pericardium, 139, 220

urogenital, 247 definitive, 235 primitive, 21 1, 234, 240 venosus, 138, 141, 145, 162 venous, 164

Sinusoids, hepatic, 163, 207 Sitting height of embrj'o, 1 05 Situs inversus viscerum, 132, 173 Size of placenta, 82 Skeletal

muscle, 355-369 system, 334-354 Skeleton

appendicular, 349 axial, 339 histogenesis of, 334 visceral arch, 345 Skene’s glands, 249 Skin, 370

papillae of, 371 pigmentation of, 371

Skull, 340

chondrification of, 340 membrane bones of, 334, 336 ossification of, 340-349 Smell, organ of, 179, 314 Smooth muscle, 365 Soft palate, 181 Somatic

arteries, 159 nerves, 304, 306, 312 Somatopleure, 364 Somatopleunc mesoderm, 47, 53,

364

Somites, 52, 107, 355 cavities of, 52 number of, 52, 108 occipital, 52, 360 pre-otic, 361 Space or Spaces

intervillous, of placenta, 71 mtraretinal, 317 of septum pelucidum, 301 subphrenic, 208 Special sensory

nerves and organs, 314 Sperm cells, see Spermatozoon Spermatic

artery, internal, 159 vein, 167

Spermatids, 10, ii, 19 Spermatocytes primary, 10, ii secondary, 10, 11, 19 Spermatogenesis, 9, 10 Spermatogonia, 10, 19 Spermatozoon, or Spermatozoa, i, 9) 10

acrosomic cap 6f, 12, 13 of animals, 378 behaviour of, at coitus, 3° degeneration of, 13 fate of, 39 flagellum of, 12, 13 formation of, in human, 1 1 head, 1 1 life of, 39

maturation of, 12, 13 middle piece of, 1 1 , 1 3 mitochondrial granules 01, *3

K, 1 1

nber of, 38 t-nuclear cap of, 13 -acrosomic cap of, 12, 13 icture of, II, 13

isport of, through female genital tract, 37 ,

Dility of, within female genita

tract, 38 iiogenesis, 11,12 loid bone, 343 . loidal sinus, 182 „,R

10-mandibular ligament, 34° bifida, 303

essory nerve, 278, 306, 3°®

263, 268, 271 makes of, 3^3 „

ro-median groove of -74

INDEX

Spinal rord

rpcndymai layer of 273 external form of 271 filum terminate of 27 erey matter of 68 •’74 lamina 0/72 mantle layer of marginal layer of 273 m\elination of 268 postert^median septum of 274 sulcus limitans of 272 tracts of 27

'fntnculus lermmalis of 271 ?anglia 269 nerves

dorsal root 304 central root 304

anena 133

5pU,,h„„p| „„

‘Spleen 09 2a 1 anomalies of 2 5

naematopoiesi, n siojenni ©r 5

Splenic "*

art rv 2 4 vein 164

Spongioblast* of neural tube 266

Of retina 317 JPongv bone 376

Wy 71 76 79 ‘onnecting 70 ,0

Sternal t'on 340 , J^y 340 Oternopagus i,,

Senium 340 ^

I of ovarv 14 Stylo h\0id ligament 347 [Styloid process 34 Subarachnoid space 272 287 3'*o

|Spbc„d,„a|,„„, ,6 ,55' 3 o

Subcentral veins 16-,

' Subclavian

artery 156 ,61 V «ns j6j S ubgerminal cavity 388

Subrnaj)djbuJ_rg«and | 8 ^ ig Subphrenic spaces 208 Substance

gray of spinal cord ^ nigra 289

I propria oi cornea 320 I fdacenij 8 j

atrio-ventricular 143 bulbovenincular 140 central 298 cerebral 295 jQg coronary 231 epithalamic •*82 290 h^othalamic a 8 i labio dental *83 '

Ubio-gmgival igg limitans 27a linguo denial 185 I terrninalis of tongue 184

is?'™"" 3 !l« 

concha 18. mesenteric

artery 77 ,58 2,5

vein 164

vena cava 165 168

iSupportingcellsof retina 317

|Upracardm4l veins 167 ^ ' ®viprareful '

artery 159 gland 3 9^ vein 167

.0 .37

Sv'elhngs

orytenotd, jpg

| ^,..uciciio-cnorial oyndesmoscs 331 Synostosis 331 Synovial joints 3 jo 33,

[ membrane 2S0 ne I System 35

digestive t7&-2^G formv 2 q 8 genital 235 homologies of 259 genitourinary an integumentary 370 lymphatic j68 muscular 355-369

autonomic 327 central 63-333 peripheral 304 respiratory 176- 26

.tpicw 33,-354

urogenital ^■>7-262

../Dtaiion of a.f

57 .00 ,,6

e

3,„77 «7 ^“junctum 3,0

f«"’‘;>3liyum’ 3,0 ^nulosum , P

'“cidum 9 o"^'®

•Pmosuu, 37Q

bulbar 148 jabio-scrotol 250 lingual lateral jg

• >Jvian

aqueduct 288

I fissure 2p8

Sympathetic

Of/lj 3 7

chain 328 ganglia 327 nenc fibres nenous system 327 ncuroblasls a 0%' 7 _ Paragangba 328 ^ympathin 329 |>napse 267

SyncSidrMis^®,^* |>'nchor,alfu.,on 9 >ncy uo-trophoblaM 6a

• 'ficytmm 6a 366

Syn<<.c,,ly(r.j 350, 35,

> tag

109

fold 76 79 ,09 gut 11 234 I of pancreas og of ipermatotoon 1 1

Tarsal plates of evelid 3 1

buds 164 fibres 184 31J Tectorial membran (Fw 9

I Tfcto septal extension tbo

of midbram gg

I ocapiial 342 posierius 342 Tenh 183 1O5 373 milk 373 permanent 373 Tegmentum aS'v 288 Tela choroidea 287 204 Telencephalon 263 278 ->89 Commissures of 301 medium 281 striatal portions of 204

bone 444 348 ! lobe 280 95

Ternporo^mandibular arucu) Tendon central of diaphragm ] Tensor

tympani muscle 326

I veil palatini 3^6 ientoriuia cerebelli 270

T^au 125 127 132

leratogcnesis J25 Teratomata 127 Teres ligamentum 164 172 lenninale ganglion 314 icrminalis nervm tu T esUs 19 "f

anomalies of 2^8 appendix of 243

INDEX

428

Saccula

cisterna, 324 macula, 324 Saccule, 323

Sacral artery, middle, 161 Safe period, 33 Salivary glands, 183, 187 Santorini’s duct, 209 Scala

media, 324 tympani, 324 vestibuli, 324 Scapula, 338, 349 Sclera, 319 Sclerotic capsule, 344 Sclerotome, 96, 339, 355 Scope of embryology, 3 Scrotal swellings, 251 Sciotum, 9, 10, 252, 259 Sebaceous glands, 119, 372 S'^bum, 1 19, 372 Scrondaiv

chorionic villi, 71 oocyte, 16, 18, 19 se c characters, i spermatocyte, 10, ii yolk sac, 75, 1 76

Secretory phase of endometrium, 26 Segmentation

of body, 52, 107, 355 cavity, 45, 388 of head, 342

Segments, mesodeimal, 52, 107, 355 Segregation, 121 Selfwise, 121 Semen, 38

Semicircular canals, 323 Semilunar valves, 150 Semmal fluid, 38

vesicles, 10, 38, 241 Seminiferous tubules, 9, 10, 237 Sense capsules, 342 Sensory

cells, 263-333 epithelium, 263 fibres, 304 nen-es, 263-333 neurons {see cells) root of spinal nerve, 304 Septa, placental, 82 Septi, pars membranacea, 150 Septum, or Septa

aortico-pulmonary, 149 atrial, 143

bulboventncular, 148 interatrial, 143 interventricular, 148 closure of, 149 incomplete, 172 lucidum, 301

median, of spinal cord, 274 nasal, 180

postero-median, 274 primum, 143 secundum, 145 Sinus, 145 spunum, 143

transversum, 55, 138, 219, 364 migration of, 364 urogenital, 237 urorectal, 58, 211, 234

Septum

ventricular, 147 Serosa, 389

Sertoli, sustentacular cells of, i o Sex, 9

characters, secondary, i chromosomes, 20, 257 cords, 237

determination of, 20, 257 deviations, 257

differentiation of, 236, 243, 246 ducts, 240, 241, 243, 244 factors determining, 244, 246 glands, 9-36, 227-262 hormones, 9, 23, 34, 66 influence of environment on, 245, 246 organs

accessory, i primary, i, 9 primordia, 237, 238 ratio, 20

reversal, in cattle, 245 Shaft of hair, 372 Shape of placenta, 82 Sheath

medullary, 268 myelin, 268 neurolemmal, 270 Siamese twins, 131, 132 Significance, prospective, 121 Sino-vaginal bulb, 242 Sinu-atrial orifice, .141 Sinus

border, of placenta, 84 carotid, 158 cavernous, 164 cervical, no, 116, 197 coronary, 145, 168 marginal, of placenta, 84 maxillary, 182

oblique, of pericardium, 220

paranasal, 182

petrosal, 164

sagittal, 165

septum, 145

sphenoidal, 182 '

straight, 165

transverse, of pericardium, 139, 220

urogenital, 247 definitive, 235 primitive, 211, 234, 240 venosus, 138, 141, 145, 162 venous, 164

Sinusoids, hepatic, 163, 207 Sitting height of embryo, 105 Situs inversus viscerum, 132, 173 Size of placenta, 82 Skeletal

muscle, 355-369 system, 334-354 Skeleton

appendicular, 349 axial, 339 histogenesis of, 334 visceral arch, 345 Skene’s glands, 249 Skin, 370

papillae of, 371 pigmentation of, 371

Skull, 340

chondrification of, 340 membrane bones of, 334, 336 ossification of, 340-349 Smell, organ of, 179, 314 Smooth muscle, 365 Soft palate, 181 Somatic

arteries, 159 nerves, 304, 306, 312 Somatopleure, 364 Somatopleuric mesoderm, 47, 53, 364

Somites, 52, 107, 355 cavities of, 52 number of, 52, 108 occipital, 52, 360 pre-otic, 361 Space or Spaces

intervillous, of placenta, 71 mtraretinal, 317 of septum pelucidum, 301 subphrenic, 208 Special sensory

nerves and organs, 314 Sperm cells, see Spermatozoon Spermatic

artery, internal, 159 vein, 167

Spermatids, 10, ii, 19 Spermatocytes primary, 10, ii secondary, 10, ii, 19 Spermatogenesis, 9, 10 Spermatogonia, 10, 19 Spermatozoon, or Spermatozoa, i, 9> 10

acrosomic cap of, 12, 13 of animals, 378 behaviour of, at coitus, 3° degeneration of, 13 fate of, 39 flagellum of, 12, 13 formation of, in human, 1 1 head, ii life of, 39

maturation of, 12, 13 middle piece of, 1 1 , 1 3 mitochondrial granules of, 13

eck, II umber of, 38 ost-nuclear cap of, 13 re-acrosomic cap of, 12, 1 3 ructure of, n, 13

•anspoJt of, through female gemtal tract, 37

lability of, within female genital tract, 38

- 12

noidal sinus, 182 g

no-mandibular ligament, 340

a bifida, 303

cessory nerve, 278, 306, 3°^

teries, 159

lumn, 339 „

rd, 263, 268 271

anomalies of, 3^3 „ .

antero-median

cervical flexure of, 1 10, 27 , /

INDEV

429

cord

cpcnd mal la\erof 273 ficicrnal form of 271 filum lerminale of '’7'* grey matter of 2G8 274 lamina of -’7 mantle layer of 272 marzmal layer of "’73 m\elmation of 68 posiero median septum of 274 sulcus Iimitans of 2/ tracts of 7

tentnculm terminalis of 274 gangUa 269

dorsal root 304 \entralroot 304 Spiral organ (of Corn) 324 Splanchnic antnes >38 mesoderm 47 53 364 Splanchnocramum 341 SplantVinopltunc mwoderm 47 53 s 1 ^'5

Spleen 209 224 anomalies of ••aj haematopoiesis in too 223 hisioeenesa of "ai Splenic artery 224 tein 164 Spongioblasts of neural tube 266 of retina 317 Spongy bone 336

l^'jjn'ous temporal bone 314 348

body 71 76 79 connecting 70 79 optic 2;8 81 289 316 S«;&t «05

artery 153 333 muscle 326

is,,'?,’"

Sternal bars 340 bodv 340 otemopagus 133 sternum 340 anomalies of gjo « 340 365"

Siomach 202 204 cursayuTes of 204 fetation of 22'i

basal 2, 67 «>mpactum 27 g,

Wffitutn 370 '‘“junctum 370 germinativ-um 370 panulosutn, 370 iuadum 370 ’pinosum 370 ,, ‘rngiosuni ->7 67

endometrium 27

Stroma

Stylo-hyoid ligament 347 Styloid process 34,

Subarachnoid space 27 38y 3 o

Subcardinai seios 165 16C Subceniral \rin$ tS^

Subclavian

artery 156 161 veins 163

Subgerrmnal cavity 388 Submandibular gland >83 (87 Subphrenic spaces 208 Substance

gray of spinal cord 268 274 white of spinal cord 268 274 Substantia nigra 289

propna cf cornea 320 Succenturiate placenta 83

atrioventricular 143 bulbovenincular 140 central 298 cerebral 293 298 coronary ■»5i epithalainic 282 290 hypothalamic 281 290 labiodental 18^ labio^ingival i6j Iimitans 72 linguo-dcnial 185 terminalis of tongue 184 Superficial implantation 61 396 Superior concha t8 mesentcnc

artery 77 tj® 2JO 2t8 vein 164

vena cava 165 168 Supporting cells of retina 317 Supracardinal veins 167 Suprarenal arteij 159 gland

Susientacular cells of (cstis 10 237

Sweat glands 372

Svvellmgs

arytenoid, 199 bulbar 148 labio-scrotal 250 lingual lateral 183 Sylvian aqueduct '•88 fissure 298 Sympathetic cells 327 chain 3 8 ganglia S'*? nerve fibres 327 nervous system 327 netiroblasls 270 paragangba 328 Sympaihui 329 Synapse 267 Synarthroses 350 351 Synchondrosis 351 Synchorial fusion 245 Syncytio trophoblast 62 8^ 129 Syncytium 62 366 Syndactyly (Fig 390) 3^2

Syndcsmo-chonal placenta 40 Syndesmoses 33I Synostosu 33!

Svnovial joints 330 351 membrane 33O 35 System

digestive 176-'* 6 fornix "98 genital 233

homologies of 259 genito-unnarv '>11 7 b

integumentarv 3^0 lymphatic 168 muscular 355-369 nervous

autonomic 327 central 63-333 peripheral 304 respiratory iy6-‘'26 shrictai 334-354 urogenital 3 7-26

Tail ,6 79 109 I fold 76 /9 109 I gyt •’«> 34

I of pancreas '’09 of spermatozoon 1 1 Tarsal places of evclid 3 t Tarsus 338 330 Taste buds 184 fibres 184 3>t

Tectonal membrane (Fig 333 3 3 Tecto septal extension 160 Tecto-spmal tract 69 Tectum

of midbram 288 occipital 34 postenus 34 Teeth 1B3 183 373 milk 373 permanent 373 Tegmentum 282 288 Tela choroidea 87 294 Telencephalon 263 2,8 289 94

commissures of 301 medium 81 striatal portions of 294 suprastnatal portions of 294 Temporal

bone 344 348 lobe 280 293

! Temporo mandibular articulation

348

Tendon central of diaphragm 2 1

lympani muscle 326 veil palatini 326 Tentorium ccrcbelli 279 Terala 125 127 13

Teratogenesis 125 Teratomata 127 I Teres ligamentum 164 172 I Termmale ganglion 314 j Terminalis nervus 314

anomalies of 258 appendix of '’43 239

INDEX

430

Testis

cells of, 9, 237 cords of, 237 descent of, 9, 120, 254 development of, 237 germ celk of, 237 gubernaculum of, 237 histogenesis of, 237 interstitial cells of, 10, 237 ligament of, 254 mediastinum of, 10, 237 position of, 9 rete, 8, 202

seminiferous tubules of, 9, to, 237 spermatogenesis in, 9-13 sustentacular cells of, 10, 237 tunica

albuginea of, 10, 237 vaginalis, of, 9, 255 undescended, 256, 258 Testosterone, 10 Tetrad formation, 19 Thalamus, 277, 290 nuclei of, 291 pulvmar of, 291 Thebesian valve, 146 Theca

externa, 17 interna, 17 Thecal cone, 18

gland, 17, 22, 23 Theory

monophyletic, of haematopoiesis, 99 . 102

polyphyletic, of haematopoiesis, 102

recapitulation, 154, 377 Third ventricle, 281, 289 Thoracic duct, 168 Thoracopagus, 132 Thymic corpuscles (of Hassall), 194 Thymocytes, 194 Thymus gland, 189, 192 anomalies, of, 193 histogenesis of, 193 Thyro-glossal duct, ig6 persistent, 197 Thyroid

cartilage, 348 diverticulum, 196 gland, 183, 189, 196 anomalies of, 197 histogenesis of, 197 lateral, 195, 197 Tibia, 349 Tissue

haematopoietic, 99, 208, 225 ligamentous, 350

primary differentiation of, QS-102 Tongue, 181, 183 muscles of, 184, 360 nerves, of, 183 papillae of, 184 Tonsil, 189, 190 Tonsillar fossa, 190, 201 Trabeculae cranii, 343 of spleen, 224 Trabecular region, 342 Trachea, 198

Tracheo-bronchial groove, 182, 198 rudiment, 178 Tract, or Tracts of brain

myehnation of, 268 cortico-spinal, 269 habenulo-peduncular, 290 motor, 269 olfactory, 314 pyramidal, 269 reticulo-spinal 269 sensory, 269 of spinal cord

myehnation of, 268 tecto-spinal, 269 vestibulo-spmal, 269 Tractus solitarius, 283 Trager, 392 Tragus, 116

Transindividual action, 5 Transperitoneal migration, 40 Transplantation of tissue, 3 Transport of ovum, 39 of sperm, 37 Transverse colon, 211

mesocolon, 214, 255 process, 339, 357 Tree, bronchial, 181 Treitz, ligament of, 205, 210 Triangulai ligament of hvei, 208 Tricuspid valve, 151 Trigeminal

ganglion, 269, 309 nerve, 157, 279, 306, 309

non-branchial component of,

309

Trilaminar embryonic disc, 48, 377406

Triplets, 132

Trochlear nerve, 306, 308 Trophoblast, 43, 45, 70, 382, 389,

391

attaching, 62 cyto-, 62, 71

Langhan’s layer of, 62, 71 plasmodi-, 62, 72 Trophoblastic shell, 71 Truncus

arteriosus, 149, 152, 173 Trypsin, 217 Tubal pregnancy, 69 Tube, or Tubes digestive, 176-226 endothelial, 137 Eustachian, 190 Fallopian, 240 neural, 109, 263, 387 pharyngo-tympamc, 190, 325, 326 Pfluger’s, 15 uterme, 39, 240, 242 Tubercle genital, 250 Mullerian, 242 Tubeiculum impar, 182 Tubo-tympanic recess, 1 90, 325 Tubules

collecting, of kidney, 230, 232 convoluted, 232, 233 mesonephne, 228

Tubules

pronephric, 228 seminiferous, 9, 10, 237 Tunic, vascular, of lens, 319 Tunica

adventitia, 152 albuginea of ovary, 238 of testis, 10, 237 media, 152 vaginalis testis, 9, 255 vaginalis in female, 256 Twinning, or Twins, 126, 129 in cattle, 245 causes of, 126 conjoined, 13 1 in dasypodine armadillo, 130 dichorial, 131 in diovulatory species, 130 dizygotic, 131 experimental, 132 fraternal, 5, 130 frequency of, 1 3 1 hereditary, 131 human, 131 identical, 5, 130 like, 5, 130

mirror imaging in, 132 in monovulatory species, 130 monozygotic, 130 in polyovulatory species, 130 polyzygotic, 130 Siamese, 131, 132 synchorial fusion in, 131, 245 true, 130 uniovular 1 30 unlike, 5, 130 Tympanic antrum, 326 bone, 326 cavity, 189, 326 membrane, 325 Tympanum, 325

Ulnar artery, 162 Ultimobranchial bodies, 19 1 Umbilical

arteries, 76, 80, 158 coelom, 80, 364 cord, 58, 79, 80, no, 389 length of, 82 fistula, 215 hernia, 212, 214, 365 ligaments, 172 veins, 76, 80, 162, 164

Umbilicus! 56, 79, 80,1:0,364 Undescended testis, 256, 258 Undetermined fate, 121 Unfertilized ova, 37 Unicornuate uterus, 260 Unilaminar foetal membrane, 7*^ Uniovular twins, 130 Unmyelinated nerve fibres, 200 Upper extremity bones of, 349 muscles of, 315 Urachal cyst, 260 fistula, 260 sinus, 260

INDE'S.

UrachuJ 8o 348 anomalies of 260

Ureter 228 S3' 24° 247 anomalies of 258 double 116 233 epithelium of 253

Ureteric bud 231

Urethra 10 247 25' corpus catemosum of 25J female 242 252 male 251 penile 251 pninime 247 prosfatic aji

Urethral

folds

groo%e 251 plate 250

Uncotelic metabolism 4

Unnary bladder 247 awamaUes of 258 36a fistula of 248 Si stem 227

Unniferous tubules 330 232 Urogenital fold 236

membrane 58 3:9 233 SjO mesentery 238 orifice 230 septum 237 sinus 247 definitive 235 pelvic portion of 249 phallic portion of 349 primitive 91 1 234 <<40 vesico<ureihral puriion of 247 sulcus 93a •I'stem 937

Urorectal septum 58 91 1 234 Ltenne cicle 23 2G

endom trial changes in 2C fisiolog) of ”9 length of 26 phases of 26 glands 27 mucosa 22 tubes 39 240 42

fimbnae of 241 btero-vaginal canal Uterus j 4 anomalies of 243 My of 242 broad ligament of cervix of 242 d'delphvs 260 duplex 260 epithelium of 22 Gy

■mplanution of embryo in 60-oa masculmus 245 '

during menstrual cycle 26

'Musculature of 22 ege nulliparous 6t ^

““fing pregnancy 67 preparation of fat embi-sn [^^Mdhgamen.of 2^6 '

suV septus 260 c,nicorni5 260

I "“Wtovnmio 30

prostatic 943 Utricular macula 324 Utrieido-saccular duc« 3^3 Uvula i8t

\agina I 37 240 anomaties of 242 *0® masniliDc 243 V estibule of 24-*

\ agus

ganglia '>69 311 nerve 2,0 306 31S \ allate papillae of tongue 184

\ alleculae i8j \ alve or \alvei of aorta s 50 atrio-ventncular 15* bicuspid ijt tsC cotoevary swwis iffi Eustachian 146 ofheart 150

anomalies of 172 of infcnor vena cav* '4^ mitral 151 semilunar 130 of smus venosus 141 143 ■Hiebesian 146 tncuspid 151 venous 141 I43 \ anations abnormal I2t-t34 environmental 5 genetic 5 normal t2i-i34 \ as deferens so 240 2^5 \ asa elTerenua 230 237 \ asculae system I35i7$ changes in at bmh 17s primitive 151 \ ^etal pole of ovum 380

• cm or \eins 16

advehrnies 164 azvgos line 1C5 S67 cardinal 139 16 anterior 139 1G4 common 139 1G3 postenor 130 1C5 sub- 163 iGG supra 167 duodenal 163 head pnmary 1G4 hepatic 164 iliac (fie 157} iG 6 mnoRiinatc (fig 157) t6G intercostal 167 intersubcardinal anastomosis jugular 163 lumbo-costal 16;, mesentenc 164 oblique ofleft atrium t68 omphalo mesenteric, 162 ovarian 167 para ureteric 167 portal 163 209 prci-ostal 165 pulmonary 143 renal 167 retina) 319

\ etn or % eins revehentes 164 spermatic 167 splenic 164 subcentral 1G3 subclavian 1G3 suprarenal 167 sympathetic 163 167 thoraco-lumbar 165 167 umbilical 76 Bo ib2 1G4 vena cava

inferior 146 167 superior iG^ iG3 vitelline 162 163 \ riameniouf placenta 6;

\ elum mterpoiiium 301 \ cna or % enac advehenies 1C4 cava

inferior 146 167 superior iGj it>8 revehentes 164 \ ctiotum ligamenmni 1(14 ^\eno«us ductus 1G4 \ enous

sinuses 1G4 , 141 144

[ \ eniral aorta 152

hp ©r btasvopore 3 t> mesentery 204 2'’3 38^ pancreas 208 root of spinal nerve 304 Ventricle or \ eniricles of brain 281 fifth 301

fourth 280 981 87 ofheart 125 140 sepiaiinn of 147 lateral 281 989 third 981 289 \eniriculus lerminahs 974 \ ermiform appendix ati Vermis "83

I V emix caseosa 1 19 370 I V ertebrae 338 339 arch of 339 body of 339 centrum of 339 chondnfication of 339 membranous stage of 339 transvene process 339 337 V ertebral artery iCo column 271 339 Vcriebraies 377-407 I N esical nrtery 159 V'csicle

brain primary 2G3 cerebral "89 •'94 forebrain 277 hindbrain 977 lens 31G 317 midbrain 277 optic I IP 77 50() 3tG otic IIO 323 srinina! to 38 '•41 Vesico-urethral canil 233 \ estibular

glands (of liarihohn) 253 membrane (ofKeissner) 324

INDEX

432

Vestibular nerve, 323 nucleus, 283 of vagina, 242 Vestibulo-spmal tract, ’269 Viability, 1 19 of ovum, 40 of sperm, 38 Villi

chorionic, 71 definitive, 71 development of, 71 physiology of, 83 primary, 71 secondary, 71 tertiary, 71 Viscera

transposition of, 132 Visceral

arches, 176-226 nerves, 306 309, 31 1 pericardium, 138 Viscerocranium, 341, 344 cartilaginous, 345 membranous, 348 Visual apparatus, 315 Vitelline artenes, 77, 210 circulation, 77 duct, 77, 79, 80 membrane, 16, 37 sac, 77

veins, 77, 145, 209 Vitello-mtestmal duct, 77, 164, 210 Vitello-umbilical anastomoses, 162 Vitellus of ovum, 37

Vitreous

body, 319

humour, 319 Viviparity, 4 395 Vomer, 348

Vomero-nasal nerve, 314 Vulva, 252

Weight

at birth, i so growth in, 104 of human embryos, 1 04 of placenta, 82 Wharton’s jelly, 80 White

blood cells, loi matter

of brain, 268 of spinal cord, 268, 274 ramus, 328 Willis, circle of, 160 Winslow, foramen of, 223 Wirsung, duct of, 209 Witch’s milk, 373 Wolffian (mesonephric) body, 228 duct, 228

X-chromosome, 18, 236, 257 X-zone (of adrenal cortex), 329 Xenopus pregnancy test, 90 Xiphoid process, 340 Xiphopagus, 132

Y-chromosome, ig, 236, 257 Yolk, 3, 78, 378

effect on cleavage of ovum, 380 granules of ovum, 37, 378 plug, 386

sac, 45, 75/ 176, 389, 393 blood islands of, 71, 76 definitive, 77, 177 endoderm, 385 haematopoiesis in, 99 Heuser’s membrane, 46 placenta, 397 primary, 75 primiUve, 70, 75, 394 of Eutheria, 394 of Marsupialia, 393 of Metatheria, 393 secondary, 75, 176 size of, 77 tertiary, 77

Zone or Zona

ependymal, 267, 274 germinal, 267 mantle, 267 marginal, 267 pellucida, 16, 37, 45, 60 Zondek-Ascheim test, go Zuckerkandl’s bodies. 329 Zygomatic bone, 348 Zygote, I, 37> 41