Book - The Nervous System of Vertebrates (1907)
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|1906 Textbook Review by Herrick|
|"The Nervous System of Vertebrates" by J. B. Johnston, Ph. D., Professor of Zoology in West Virginia University. With 180 illustrations. 12mo., 460 pp. Cloth, $3.00 net. P. Blakiston's Son & Co. (See advertising pages of this Journal.)
Among the contributions of American men of science to morphology, none is more distinctive than the recent elaboration of a functional analysis of the vertebrate nervous system. Beginning with a study of the components of the peripheral nerves, it soon extended to include the unravelling of the central connections of the functional systems found in the cranial nerves. The successful accomplishment of these results in a broad way in the lower vertebrates has made it possible to draw up an entirely new set of schemata for the plan of the vertebrate nervous system — schemata in which the unit is the functional system of neurones. The lower vertebrates are found to conform to a single type with remarkable fidelity, in spite of their great differences in organization. Howfar this type is applicable above the Amphibia has been a matter of speculation, for none of the higher forms have been examined from this point of view. The human brain furnishes a partial exception, though here the analysis has been only fairly successful on account of the bewildering complexity of structure.
Starting on the firm foundation of the functional analysis of the ichthyopsid type of brain, as already elaborated. Professor J. B. Johnston lias made an examination of the whole phyletic series from the lowest vertebrates upward and published his results in the form of a manual on the ' Nervous System of Vertebrates ' (see advertising pages of this Journal) which is more than an excellent text-book. It is an important positive contribution to vertebrate morphology and will unquestionablv have a large influence in shaping the course of research in vertebrate neurology, both human and comparative.
The earlier works on nerve components and functional divisions of the brain were hard reading. The first step in this work was the elaboration of a new nomenclature in which to clothe the new morphological ideas, and porhaps partly on this account, many neurologists have failed ontirely to get the point of view from which these researches have been undertaken, Johnston's book has opened up this field in a way which should be immediately iruitiul. lie has sketched in bold outlines a picture of the functional divisions of the vertebrate type of brain and of the evolutionary history of each system in detail. For the first time human and comparative neurology have been co-ordinated in a thoroughly practical way. The co-ordination is doubtless very imperfect and many of Johnston's homologies must be accepted merely as suggestions of a [program for future research. But as such they represent not only a pioneer endeavor, but a well thought-out and correlated system of principles which rest on the sure foundation of extensive and controlled study of the lower vertebrates, i'robably few morphologists not directly engaged in the study of the brains of the Ichthyopsida realize what an extensive literature has grown up within the past decade in fish neurology and how completely the functional analysis outlined by Strong in Ib'Jo has been confirmed and reinforced by these exceedingly laborious researches. The extension of this functional analysis into the central nervous system has given the key to many of the most baltiiug problems of comparative neurology.
Johnston's book has not only made the results of these researches available to morphologists in general, but he has given to physiologists and psychologists, especially comparative psychologists, and insight into the organization and phylogeny of the vertebrate nervous system which cannot fail to supplement in a helpful way their existing literature.
C. Judson Herrick.
The Nervous System of Vertebrates
By J. B. Johnston, Ph.D.
Professor Of Zoology In West Virginia University
With One Hundred And Eighty Illustrations
John Murray, Albemarle Street, W.
The attempt has been made in the following pages to give an account of the nervous system as a whole, to trace its phylogenetic history and to show the factors which have determined the course of evolution. This has been made possible by recent studies directed toward the analysis of the nervous system on the basis of function. The functional point of view, which is the chief characteristic of the present book, brings the treatment of the nervous system into close relation with the work of recent years on the behavior of animals. The study of behavior aims to give an account of the actions of animals in relation to the environment. The study of the nervous system aims to describe the mechanism by which actions are directed and adapted to the conditions of life.
A text-book of comparative neurology at the present time must meet the needs of workers of all grades, students, investigators and instructors. Its descriptions should be intelligible to students who have had one year of work in zoology or medicine, including the anatomy and embryology of some vertebrate. On the other hand there should be included all facts which are important for the functional and phylogenetic mode of treatment. How far these difficult conditions have been met only the use of the book can show. Little space is given to mere descriptive anatomy and some descriptive matter which is well presented in the text-books of zoology, anatomy and histology in common use, is omitted. This accounts for the brief treatment of the eye, ear and other sense organs, the distribution of the spinal nerves, etc. On the other hand, every effort has been made to bring out clearly the functional significance and relationships of the structures described, and to interest and train the student in the interpretation of structure in terms of function, adaptation and evolution.
In the preparation of the text considerable time has been given to the review of the Author's earlier work and that of other writers, and to the study of many unsettled questions. In this way much material has been collected which is published here for the first time. The new observations, which are found in nearly every chapter, have to do chiefly with the brains of selachians, ganoids and amphibians, and with the origin of the organs of the sense of taste. The whole discussion of the phylogeny of the forebrain in chapter XVIII may be regarded as a new contribution to the subject, since the account given differs in essential respects from the earlier views of the author and from those of other writers. The proof that taste buds have their origin in the entodermal lining of the pharynx establishes an exception to the statement that all nervous structures are derived from ectoderm. It suggests the further possibility that some of the peripheral plexuses of the sympathetic system may form a second exception.
The nomenclature of the nervous system is in a very unsatisfactory state for want of a guiding principle. It is believed that a guiding principle is furnished by the mode of treatment here attempted. The usual description of the nervous system based upon mere structural relations is quite lacking in life and meaning, and no set of terms has any commanding force. Significance and essential fitness of terms can come only with the study of the nervous system from the point of view of functional relationships. It is not yet time for a general revision of nomenclature on this basis. Accordingly the BNA terms which are now the most generally familiar, have been employed as far as they are adequate. The few new terms that have been introduced are necessary for the description of the functional divisions of the nervous system. InTdescribing brain tracts compound names have been employed which indicate the origin and ending of the constituent fibers. Care has been taken to use as the first part of the compound name the name of the nucleus of origin of the fibers. For the sake of consistency and clearness it is necessary to put the names of most nerve centers and tracts into the Latin form. In many places, however, English equivalents have been used interchangeably with the Latin terms. The object has been to deviate as little as may be from common language in a subject in which technical terms must be so largely used.
The majority of the illustrations are made from original drawings. The drawings have been so constructed that in the case of a transverse section the reader looks at the caudal surface of the section, the dorsal border is uppermost and the right and left sides correspond to those of the reader. In the case of lateral views and sagittal sections the anterior end is placed at the reader's left. For the sake of the true illustration of the results of other workers and because of the peculiar value of good figures, a large number of illustrations have been copied. The author wishes to express his hearty thanks to the writers who have given permission for the use of their figures.
At the end of each chapter is a literature list giving the sources for the bulk of the facts contained in the chapter and the authorities for the facts which support at critical points the general views presented. At the end of each chapter there are given also suggestions for laboratory work. These do not constitute a systematic laboratory course, although they offer the material from which each instructor can arrange a course suited to his conditions. The primary intention of these suggestions is to indicate the best or most easily obtainable material for the illustration of the facts in the chapter. It is hoped that in the near future there may be sufficient demand for courses in comparative neurology to warrant the preparation of a systematic laboratory guide.
The first chapter is intended as a help to prospective investigators in the choice of material and methods for their studies. The beginning student may best pass over all but the last two paragraphs of the chapter.
The author wishes to acknowledge his indebtedness to the larger books on the nervous system of man and mammals, of which those of Barker and Cajal have been the most useful. The most cordial thanks are due to Professor C. Judson Herrick for many helps, including the loan of numerous books and papers and the engravings for Figures 4, 42, 43, 88, 89 and 90, and most of all for reading and criticizing the greater part of the manuscript.
Point of view; anatomical, experimental and physiological methods. Morphological terms; planes of sectioning; neurological terms.
Neural tube; neural crest; neuromeres; secondary brain segments; auditory and olfactory pits and optic vesicle; histogenesis of central nervous system; longitudinal zones. Development of peripheral nerves and sense organs; part played by the neural crest and by ectodermal placodes. Morphology of the head.
Functions of nerve elements; stimuli and impulses; polar differentiation; parts of a nerve cell and course of impulses. Receptive and excitatory cells and reflex actions. The Neurone Theory.
The work of the nervous system in relation to soma and viscera; four kinds of nervous activity and the corresponding divisions of the nervous system.
General cutaneous endings and general cutaneous components in the spinal and cranial nerves; general cutaneous centers in spinal cord and brain; general survey.
Sense organs, morphology and physiology; special cutaneous components; special cutaneous centers; differentiation of cutaneous and auditory centers and cerebellum.
Organism sensitive to light; development of special light percipient organ, the retina; optic tracts; structure of tectum opticum; origin and morphological position of the eyes. Pineal eyes.
General Visceral Subdivision. Visceral afferent components; visceral sensory centers. Special Visceral or Gustatory System. Organs of the sense of taste, origin, structure and distribution; innervation; gustatory centers; change of function . in higher vertebrates.
Sense organ; nerve; olfactory centers. Relations to other systems.
Ventral nerves; roots wanting in cranial region; origin, arrangement and distribution of components; plexuses; "hypoglossus"; eye muscle nerves; relations of the somatic motor column in the brain.
Origin, arrangement and distribution of the components; fibers to the sympathetic; nerves of mastication; of expression; vagus and spinal accessory complex; relations of the visceral efferent column.
Development of ganglia and nerves; structure of the system; general constitution and relations.
General constitution of central system; four chief zones; substantia reticularis; functions and organization of; centers of correlation; their relation to complex activities; materials for study of these centers. Region of the myelencephalon.
Phylogenetic history. Mammalian cerebellum; hemispheres and vermis; subdivisions and fissures; structure; review of vertebrate cerebellum. Structure of cerebellar cortex; fiber tracts of cortex. Deep gray masses and their fiber connections. Evolution of structure and function, general suryey; function in mammals.
1. The Cutaneous Apparatus. The lemniscus system; the differentiation of centers in the tectum mesencephali.
2. The Optic Apparatus. Tectum opticum; development of optic centers in the thalamus; division of function between centers.
3. Centers related to the posterior commissure.
4. The Olfactory and Gustatory Apparatus. The hypothalamus; its limits, relations, structure and fiber tracts. The nucleus habenulae; structure, relations and fiber tracts. The hypothalamus and nucleus habenulae as derivatives of the visceral sensory zone of the brain.
5. The nucleus of the tractus strio-thalamicus and the sub stantia reticularis thalami.
6. The Saccus Apparatus.
Survey of the forebrain of lower vertebrates. The archipallium and neopallium of mammals.
Structure of the cortex. Cerebral localization. Evolution of the neopallium.
List of Illustrations
1. Outlines of the spinal cord with the dorsal and ventral roots in Petromyzon and in a mammal 14
2. The brain of Heptanchus 15
3. The medulla oblongata of the lake sturgeon (Acipenser rubi cundus), to show the longitudinal zones 16
4. Two views of the brain of the buffalo fish, Carpiodes velifer (Raf.); (i) from above; (2) from the right side. From C. Judson Herrick after C. L. Herrick 17
5. Simple diagrams of the branchial nerves of lower vertebrates as seen from the left side 19
6. A diagram of the lateral line canals and pit organs together with the nerves which supply them, in a ganoid fish (Amia calva). After E. Phelps Allis. 21
7. A sketch of the brain of Chimaera monstrosa from the left side to show especially the position of the nerve roots 23
8. The outline of the brain ventricles as seen from above; A, of a cyclostome fish, Lampetra Wilderi; B, of a selachian, Mustelus canis; C, of a young specimen of a bony fish, Coregonus albus; D, of a tailed amphibian, Necturus maculatus 25
9. A diagram of one side of the forebrain in Mustelus to show what is believed to be the primitive relations of the wall and ventricle 26
10. The outline of the ventricles in man 26
11 . The mesial surface of the right half of the brain of a selachian, Squalus acanthias ' ' 29
12. A sketch of the brain of a cyclostome fish, Lampetra Wilderi, as seen from the left side 3
13. Sections of the neural plate and folds in amphibia, Amblystoma tigrinum and A. punctatum 35
14. Transverse section of the neural tube of Amblystoma puncta tum just after closing 36
15. Transverse section through the neural tube, neural crest and ectoderm of Amblystoma at a later stage than that shown in Fig. 14 3 6
16. Same as Fig. 15, later stage 37
17. A part of the spinal cord of an i8-day Catostomus embryo, showing the giant ganglion cells 38
18. Figures of the brain of a selachian embryo (Squalus acanthias) to show the history of the neuromeres. After Locy. ... 39
19. Figures to show the history of the neuromeres in a bony fish and in the chick. After Hill 40
20. The brain of a pig embryo of 12 mm. from the right side. From Minot as drawn and revised by Dr. F. T. Lewis. . . 41
21. Transverse sections through the region of the optic vesicle in embryos of: A, Torpedo ocellata; B, Gallus domesticus; C, Cavia cobaya. After Froriep 42
22. The development of the optic vesicles in Amblystoma punc tatum 43
23. A part of a transverse section of the inferior lobe of the stur geon, stained by the Golgi method 47
24. A horizontal section of the nucleus praeopticus of the sturgeon, by the Golgi method 48
25. A part of a transverse section of the optic lobe of the sturgeon, by the Golgi method 49
26. The ganglion of the IX nerve in Amblystoma punctatum at the time of formation of the central processes 51
27. A few cells of the trigeminal ganglion of Amblystoma puncta tum with the fibers of the ramus mandibularis growing out from them 51
28. A, a diagram of the head of Petromyzon at a stage when the neural crest is segmented into the anlages of the cranial ganglia. B, a similar diagram at a later stage when all the cranial nerves are to be recognized. After Koltzoff. 52
29. Three diagrams of the head of Squalus acanthias to show the differentiation of the neural crest into the cranial ganglia. After Neal 53
30. A reconstruction of the peripheral nerves in a four weeks human embryo, 6.9 mm. long. From Streeter 54
31. Reconstruction of peripheral nerves in four weeks human embryo, 7.0 mm. long. From Streeter 55
32. Reconstruction of peripheral nerves in six weeks human em bryo, 17.5 mm. long. From Streeter 56
33. Three stages in the development of the acustico-lateral system in the sea bass. From H. V. Wilson 57
34. A transverse section through the nasal sac of an embryo of a bony fish at about the time of hatching, to show the origin of the fibers of the olfactory nerve 61
35. Two figures representing the formation of unipolar cells in the spinal ganglion of the dog embryo. After Van Gehuchten 62
36. A median sagittal section of the head of an embryo Ambly stoma punctatum 67
37. Diagrams representing the development of the buccal cavity, hypophysis and nasal pit in Amphioxus and Petromyzon. After Legros 68
38. A diagram representing the segmentation in a generalized vertebrate head 71
39. Several types of nerve cells from the central and peripheral nervous system of vertebrates 78
40. A unipolar nerve cell from the brain of Carcinas to illustrate Bethe's experiment 80
41. Diagrams intended to show several forms of reflex chains in the nervous system of vertebrates 83
42. A portion of the subepithelial nervous network in the palate of the frog. From Prentiss 86
43. A portion of the nervous network about the walls of a small vessel in the palate of the frog. From Prentiss 87
44. Two ganglion cells of the nervous network in the intestinal wall of the leech Pontobdella, showing neurofibrillae passing through the cells. From Bethe after Apathy 88
45. A diagram of the component elements in the spinal cord and the nerve roots of a trunk segment, to illustrate the relations of the four functional divisions of the nervous system 97
46. Diagrams to represent the extent and arrangement of the functional divisions in the brain of a selachian 100
47. A diagram to show the arrangement of the two afferent divis ions in the brain of man 101
48. General cutaneous endings in the skin of a cyclostome, Lam petra Wilderi 105
49. A diagrammatic representation of the general cutaneous com ponents of a trunk segment 106
50. A simple diagram of the general cutaneous components in the cranial and spinal nerves of a fish 107
51. A reconstruction of the cranial nerves of Petromyzon dorsatus to show the arrangement and distribution of the several systems of nerve components 108
52. The principal sensory collaterals in the spinal cord of the new-born rat. From Cajal 109
53. Some cells of the dorsal horn in the chick embryo of five days. From Cajal in
54. Transverse section of the substance of Rolando of the cervical cord in the new-born cat. From Cajal 112
55. Cells in the dorsal horn of the cord in a chick embryo of nineteen days incubation. From Cajal 113
56. Transverse section through the spinal V tract and the sub stance of Rolando in a new-born rabbit. From Cajal 114
57. A, transverse section of the spinal cord of Lampetra to show the ceils of the dorsal horn 115
58. A, transverse section of the tuberculum acusticum of Lam petra; B, a sagittal section of the cerebellum of the same animal 116
59. A diagram representing the centers and fiber tracts related to the general cutaneous components in fishes 118
60. A diagram representing the general cutaneous centers and fiber tracts in the human brain 120
61. A large and a small neuromast from a sucker embryo at about the time of hatching 124
62. A diagram of the lateral line canals and nerves in Amia. After E. Phelps Allis 125
63. A reconstruction of the chief rami of the cranial nerves in a bony fish, Menidia, to show the arrangement of the several systems of components. After C. Judson Herrick 129
64. Transverse section of the brain of the sturgeon at the level of the VII and VIII nerves 131
65. Transverse section of the brain of the sturgeon at the level of the V nerve 132
66. Transverse section of the brain of Scy Ilium to show the fold ing of the cerebellar crest and tuberculum acusticum 133
67. Transverse section of the acusticum of the sturgeon to show acusticum cells and a Purkinje cell 134
68. A section through the same region as in Fig. 67, to show cell forms intermediate between the acusticum and Purkinje cells. 136
69. A diagram to show the central endings of the special cutaneous components in fishes 138
70. A diagram to show the central ending of the vestibular and cochlear nerves and of the optic tract in man and the chief secondary tracts related to them 140
71. A, a section through the retina of a mouse embryo of 15 mm.;
B, a section through the retina of a chick embryo of fourteen days incubation; C, a section of the retina of a dog. From Cajal 144
72. Cells from the retina of the chicken. From Cajal 145
73. The tectum opticum of the sturgeon 147
74. A section of the optic lobe of a bird. From Cajal 149
75. A series of diagrams intended to illustrate the origin and mode of formation of the optic vesicle in vertebrates 151
76. A sketch showing the relations of the two epiphyses in verte brates 152
77. A diagrammatic representation of the general visceral sensory components in a trunk segment 155
78. A transverse section through the region of Clarke's column of the thoracic cord of a new-born dog. From Cajal 156
79. A reconstruction of the cranial nerve components in a tailed amphibian, Amblystoma. After Coghill 158
80. A simple diagram of the visceral nerves of the head in fishes. 159
81. Four transverse sections through the medulla oblongata of the frog to show the position and ending of the fasciculus communis and nucleus commissuralis 160
82. Transverse section through the medulla oblongata of a mouse at the level of the nucleus commissuralis. From Cajal . . 161
83. Transverse section through the medulla oblongata of a mouse four days old. From Cajal 162
84. A, a transverse section through the medulla oblongata of the sturgeon at the level of the X nerve; B, at the level of the IX nerve 163
85. Sense organs of bony fishes. A, a taste bud from the oesopha gus of Catostomus at the time of hatching; B, a taste bud from the pharynx of the same embryo; C, two neuromasts from the skin of the same embryo 165
86. A taste organ from the pharynx of the ammocoetes of Petro myzon dorsatus 166
87. A taste bud from the skin of an adult Lampetra 167
88. A projection of the cutaneous branches of the communis root of the right facial nerve in a bony fish, Ameiurus. From C. Judson Herrick 168
89. A parasagittal section through the brain of the spotted sucker, Minytrema melanops, to show the gustatory centers and tracts. From C. Judson Herrick 170
90. A diagram of the gustatory paths in the brain of the carp as seen from the left side. From C. Judson Herrick . . . . 172
91. Part of a sagittal section of the brain of a newly hatched bony fish 173
92. A diagram representing the centers and tracts related to the visceral sensory components in fishes 174
93. A transverse section through the olfactory epithelium of a bony fish at the time of hatching 177
94. An oblique section through the forebrain of Lampetra . . . 178
95. A horizontal section through the olfactory bulb of the sturgeon 179
96. A spindle cell and two granules from the olfactory bulb of the sturgeon 180
97. An olfactory glomerulus from the brain of the sturgeon . . 181
98. Cells with short neurites in the olfactory bulb. From Cajal. 182
99. A transverse section of the forebrain of the sturgeon at the level of the anterior commissure 184
100. An outline of the median sagittal section of the forebrain of Lampetra 185
101. A diagram of the olfactory conduction paths in the sturgeon. 187
102. A diagrammatic representation of the somatic motor compo nents of a trunk segment 191
103. An early stage in the formation of the pectoral fin and brachial plexus in a selachian, Spinax. After Braus ... 192
104. The formation of the cervical plexus in a selachian, Hexan chus. After Fiirbringer 193
105. A transverse section through the nucleus of origin of the III nerve in Lampetra 195
106. A diagrammatic representation of the visceral efferent com ponents in a trunk segment 199
107. Diagram to show the central relations of the IX, X and XI nerves in mammals according to Onuf and Collins . . . 201
108. A diagram of the sympathetic system and the arrangement of its neurones in a mammal. Chiefly after Huber . . . 209
109. Diagram illustrating the spinal representation of the sympa thetic nerve in a mammal. From Onuf and Collins ... 210 no. A diagram to illustrate Langley J s " axone reflex " .... 213 in. Tract cells in the spinal cord of the trout. After Van Ge huchten 219
112. The relations of the cerebellum, brachium conjunctivum and gustatory tracts in selachians (Scyllium) 226
113. Transverse section through the cerebellum of the sturgeon . 227
114. Transverse section through the cerebellum and secondary gustatory nucleus of the sturgeon 228
115. Transverse section of the brain of the sturgeon at the junc tion of cerebellum and midbrain 229
116. Transverse section through the midbrain of the sturgeon . . 230
117. The relations of the cerebellum, brachium conjunctivum and gustatory tracts in a ganoid fish (Acipenser) . . . . 231
118. A, the left lateral aspect of the brain of a pouch specimen of Dasyurus viverrinus; B, median sagittal section through the cerebellum of the same brain. After G. Elliot Smith . 232
119. A diagram representing the fundamental and more constant secondary fissures of the mammalian cerebellum spread out in one plane. After G. Elliot Smith 234
120. The mesial surface of the right half of the brain of Squalus acanthias 236
121. A diagrammatic transverse section of one fold of the cere bellum. From Koelliker 238
122. Net-like fiber ending in the human cerebellum. After Cajal. 241
123. Two schemes to show the course of impulses in the cerebellar cortex. From Cajal 242
124. Two transverse sections through the cerebellum of Scyllium. 244
125. A transverse section through the cerebellum of Necturus . . 246
126. A transverse section through the deep gray nuclei of the cerebellum of man 2 47
127. Outline transverse sections through the mesencephalon of a cyclostome, a 'selachian, a ganoid, a bony fish, an amphibian and a mammal 255
128. Transverse section of the diencephalon of the rat at the level of the body of Luys. From Cajal 257
129. Transverse section of the dorso-mesial portion of the posterior corpus quadrigeminum of the new-born dog. From Cajal. 259
130. Transverse section of the anterior corpus quadrigeminum of the rabbit of eight days. From Cajal 260
131. Lower part of the corpus geniculatum laterale of a new-born cat. From Cajal 262
132. Nucleus of posterior commissure in Lampetra 266
133. Transverse section through the corpora mammillaria of the sturgeon 270
134. Transverse section through the inferior lobes of the sturgeon. 272
135. Transverse section through the posterior commissure of the sturgeon 273
136. Scheme of the connections of the mammillary tracts, nucleus habenulae and the nucleus dorsalis thalami. From Cajal. 274
137. Sagittal section of the tuber cinereum of a new-born rat. From Cajal 275
138. Sagittal section of the tuber cinereum of the rat of eight days. From Cajal 276
139. A scheme to show the embryological relations of the nucleus habenulae and the inferior lobes in fishes 277
140. Nucleus habenulae of the sturgeon 278
141. Transverse sections through the nucleus habenulae and the facial lobe of a young Amia . . . . 279
142. Transverse section of the habenular nuclei in the dog. From Cajal 280
143. The efferent tract to the saccus vasculosus in the sturgeon.. 283
144. A general scheme of the saccus apparatus 284
145. A diagram of the fiber tracts in the forebrain of a cyclostome (Lampetra) 294
146. An oblique section through the inferior lobes and forebrain of Lampetra 296
147. A diagram of the fiber tracts in the forebrain of a selachian (chiefly after Kappers) 299
148. A diagram of the fiber tracts in the forebrain of a bony fish (chiefly after Goldstein) 302
149. A transverse section of the brain of the sturgeon behind the anterior commissure 303
150. A diagram of the fiber tracts in the forebrain of a tailed amphibian (Necturus) 306
151. Simple diagrams to show the history of the epistriatum in fishes and amphibia 308
152. Sketches of transverse sections through (A) the caudal part of the epistriatum in amphibia and (B) the corresponding structure in Ornithorhynchus. B after G. Elliot Smith . 310
153. A sagittal section of the forebrain and interbrain of a chick embryo of 7.0 days. After Minot 312
154. Part of a transverse section of the cortex of a chameleon. After Cajal 313
155. Transverse section through the forebrain of Lacerta at the level of the anterior commissure. After Cajal 314
156. A transverse section through the right lateral lobe of the forebrain of Lacerta. After Cajal 315
157. A diagram of the mesial surface of the hemisphere of a reptile to show the extent of the hippocampus and related structures. 316
158. A mesial sagittal section of the brain of an embryo of Sphe nodon punctatum. From G. Elliot Smith 317
159. The mesial surface of the right half of the brain of Ornitho rhynchus. From G. Elliot Smith 318
1 60. The mesial surface of the cerebral hemisphere of a marsupial (Phascolarctos). From G. Elliot Smith 319
161. Portion of a transverse section through the brain of a Moni tor (Hydrosaurus). From G. Elliot Smith 320
162. Transverse section of the cerebral hemispheres of Ornitho rhynchus. From G. Elliot Smith 321
163. Plan of cerebral hemispheres, lamina terminalis and optic thalami in horizontal section. From G. Elliot Smith . . 322
164. Sagittal section of the commissural and precommissural regions of the hemisphere of Ornithorhynchus. From G. Elliot Smith 323
165. Ventral surface of the brain of Ornithorhynchus. After G. Elliot Smith 324
166. Transverse section of the brain of a rat of four days through
the anterior commissure. From Cajal 325
167. Diagram of the mesial surface of (A) the hemisphere of a monotreme and (B) that of a mammal to show the extent and relations of the hippocampus 326
168. Schemes to explain the expansion of the corpus callosum and the formation of the septum pellucidum. After figures by G. Elliot Smith 328
169. Scheme of cerebral commissures and the margin of the cor tex of the human brain. From G. Elliot Smith .... 330
170. Scheme of the structure and connections of the hippocampus. From Cajal 332
171. Structure of the cerebral cortex 339
172. Diagram showing the probable course of impulses in the cells of the cerebral cortex. After Cajal 340
173. Scheme of long association tracts in the cerebral cortex. After Cajal 342
174. Scheme of commissural and projection fibers of the cortex. After Cajal 343
175. The primordial areas in the cerebral hemispheres, lateral surface. From Flechsig 346
176. The primordial areas in the hemispheres, mesial surface. From Flechsig . . .' 347
177. The primordial areas and border zones of the association fields, lateral surface. From Flechsig 350
178. The primordial areas and border zones of the association fields, mesial surface. From Flechsig . . . 350
179. Diagram of lateral surface of hemisphere showing localiza tion of functions 351
180. Diagram of mesial surface of hemisphere showing localiza tion of functions 351