COLUMBIA LIBRARIES OFFSITE 
 
 HEALTH SCIENCES STANDARD 
 
 HX64058581 
 QM34 B91 1912 The anatomy of the b 
 
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 BURKHOIDER 
 
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 Anatomy of the Brain 
 
 A Manual for Students and 
 Practitioners of Medicine 
 
 THE BRAIN OF THE SHEEP (OVIS ARIES) BEING SELECTED 
 
 FOR DESCRIPTION AND ILLUSTRATION BECAUSE 
 
 OF ITS AVAILABILITY AND ITS PRACTICAL 
 
 IDENTITY WITH THE HUMAN BRAIN 
 
 FOR LABORATORY USE. 
 
 S}) J. F. BURKHOLDER, M. D. 
 
 Professor of Ophthalmology ir» the School of 
 Medicine of the Loyola University. 
 
 Q OGX) B 
 
 With an Introduction by 
 
 PROF. HENRY H. DONALDSON 
 
 B OGX) Q 
 
 WITH FORTY Pl'M. PAGE PI,ATKS (.SIX OP THEM COLORED) 
 FROM ORIGINAI- DRAWINGS BT THE AUTHOR. 
 
 C. P. ENGELHARD & COMPANY 
 Chicago 1912 
 
>/vqJ^ 
 
 Copyright, 1912. 
 G. P. Engelhard & Company. 
 
 
CONTENTS. 
 
 Pag.- 
 
 I'lcl'acf t;> First iMlition 7 !) 
 
 Prefaoi- to Second Edition ] l-]2 
 
 lutroduf'lioii l;)-14 
 
 CHAPTEPv I. — The Brain — Its Penioval and I'rcj) iration. . . 15-16 
 
 CHAPTEP IT.— Coverino-s of llie Brain 17-18 
 
 CHAPTEPv III.— Dura IMater Eneepliali 19-23 
 
 CHAPTER IV. — Araclinoidea Encepliali 24-25 
 
 CHAPTER v.— Pia Mator Encepliali 26-27 
 
 CHAPTER ^"I.— Blood Vessels at the Base of tlic P.rain 28-30 
 
 CHAPTER VIE— External Surface of the Brain 31-32 
 
 CHAPTER VIII.— Dorsal Snrface of the (V idiruin 33.37 
 
 CHAPTER IX.— Dorsal Surface of the Cerel.ruui 38-40 
 
 CHAPTER X. — Lateral Surface of the Cerehruni 41-42 
 
 CHAPTER XL— Ventral Surface of the Cen lirum 43-46 
 
 CHAPTER XII. —The Medulla Oblongata 47-48 
 
 CLTAPTER XIII. — Mesial Surface of Cereliruni and Cere- 
 bellum 49-54 
 
 CHAPTER XIV.-— Cerebral Substance and Corpus Callosuni. .i.l GO 
 
 CHAPTER XA'.- The Lateral Ventricles Ul-(i4 
 
 CHAPTKR XVI. —The Fornix 65-66 
 
 CHAPTER X^'rI.— The Hippocampus 67-61) 
 
 CHAPTER X\lir.— Tiie Optic Thalamus 70-74 
 
 CHAPTER XIX.— The Pineal Body *'.... 75-76 
 
 CHAPTER XX. — The .Viiterior Conunissure 77-7!t 
 
 CHAPTER XXL— The Tliird Ventricle 80-8! 
 
 CHAPTER XXIL-The ( orpora Quadrigemina 82-8M 
 
 CHAPTER XXUr.— Cerebral Peduncles 84-86 
 
 ( IIAPTER .\.\IV.— Tin- P.ms 87-89 
 
 ( IIAPTER XXV.— The Tra|)e/.inni 90-92 
 
 CHARTER XX VI.— Structure of llie .Medulla Oblongata— 
 
 Ventral Surface ' !i;!-l()] 
 
 CHAPTER XXVIL— The Medulla Oblongata- Lateral Sur- 
 face 102- 1(15 
 
 CIlAl'TKR XW'III.— 'J'li<. Medulla obl.ingafa- Dorsal Sur- 
 face ](),; 108 
 
 ( IIAI'TKR XXIX.-The K.-uilli \<ul ride lid II;! 
 
Digitized by the Internet Arciiive 
 
 in 2010 witii funding from 
 Columbia University Libraries 
 
 http://www.archive.org/details/anatomyofbrainmaOOburk 
 
LIST OF^ILLUSTRATIONS. 
 
 Page. 
 
 PLATE I.— Dorsal area of Sheep's Skull 119 
 
 PLATE II.— Lateral area of Sheep's Skull 121 
 
 PLATE III.— Dorsal Aspect of Dura Matei- 12:3 
 
 PLATE IV. — Arteries on Ventral Surface of the Brain 12.3 
 
 PLATE v.— Dorsal Surface of the Brain 127 
 
 PLATE VI.— Lateral Surface of the Brain 129 
 
 PLATE VII.— Ventral Surface of the Brain 131 
 
 PLATE VIIL— Mesial Surface of the Brain 13:5 
 
 PLATE IX.— Anterior Surface of the Briin 13.5 
 
 PLATE X — Extensioji of Cerebrum to Show iJr.iy and 
 
 White Matter 137 
 
 PLATE XL — Corpus Callosum — Dorsal Surface 139 
 
 PLATE XII. — Corinis Callosum — Showing Radiating Fibres 
 
 of the Splcnium 141 
 
 PLATE XIII. — Lateral Ventricles of the Brain 143 
 
 PLATE XIV.— Third Ventricle and Choroid Plexus 145 
 
 PLATE XV. — Lateral and Third Ventricles of the Brain... 149 
 
 PLATE XVI. — Fornix, Hippocampus, and Cingulum Inferior 14!» 
 PLATE XVII. — Fascia Dentata and Mesial Surface of the 
 
 Hippocampus 151 
 
 PLATE XVIIL— Corpus Striatum 150 
 
 PLATE XIX. — Anterior Commissure 155 
 
 PLATE XX.— Pillars of the Fornix 157 
 
 PLATE XXI. — Proximal Termination of Optic Tract 159 
 
 PLATE XXII.— The Corona Radiata 101 
 
 PLATE XXIII. — Ventral Surf ae • of Pons, Trapezium, and 
 
 Medulla Oblongata Hi3 
 
 PLATE XXIV.— Lateral Surfa-e of Cms Cerebri, Pons. 
 
 Trapezium, and ]\Iedulla Oblongata I«i5 
 
 PLATE XXV.— Dorsal Surface of Pons, and Medulla 
 
 Oblongata 167 
 
 I'lvA'i'J"] XXVI.— -Fig. 1. Coronal Section through Olfactory 
 
 Bulbs. Fig. 2. Section Througli Anterior Portion of 
 
 Lateral Ventricles 169 
 
 PLATE XXVri. — Fig. 1. Section .lust Posterior to Fissure 
 
 of Sylvius. Fig. 2. Section through Substantia Inter- 
 
 mrjilia 171 
 
6 ANATOMY OF THE BRAIN 
 
 PLATE XXVIII. — Fig. 1. Section tlirougli the Corpus Pine- 
 ale. Fig. 2. Section 2.-5 mm. Anterior to Posterior Ex- 
 trenrity of Cerebrum 1~3 
 
 PLATE XXIX. — Sections tlirougli the Collieulus Superior 
 
 and Crura Cerebri 175 
 
 PLATE XXX. — Sections through the Pons and Trapezium.. 177 
 
 PLATE XXXI. — Sections through the Medulla Oblongata . . 179 
 
 PLATE XXXII. — Sections througli the IMedulla Oblongata 
 
 and Spinal Cord 1^1 
 
 PLATE XXXIII. — Enlarged Section of Spinal Cord .5 cm., 
 
 Caudad to :\Iodulla Oblongata 183 
 
 PLATE XXXIV. — Section through tiie Lower Portion of 
 Medulla Oblongata Showing Decussation of Pyramidal 
 Fibres 185 
 
 PLATE XXXV. — Section through Xuclel Areuati 187 
 
 PLATE XXXVI.— Section througli Caudal Third of Fourth 
 
 Ventricle 189 
 
 PLATE XXXVII. — Section through Trapezium Cochlear and 
 
 Vestibular Nuclei 191 
 
 PLATE XXXVIII. — Section Ihroiigh Colliculi Superiores . . . 193 
 
 PLATE XXXIX. — Base of Skull Showing Dura Mater with 
 
 Exits of Cranial X'erves 195 
 
 PLATE XL.— Base of Skull 197 
 
ANATOMY OP THE BRAIN 
 
 PREFACE. 
 
 It may seem an unwarranted liberty to ask the student 
 to add this little volume to his already overcrowded 
 library, but after the contents have been carefully ex- 
 amined, I trust the intrusion will be pardoned. 
 
 I feel, as 1 think all teachers of anatomy do, that the 
 teaching of the architecture of the human brain has been 
 a failure for the average medical student, not because of 
 a want of many very admirable works on the subject, 
 both descriptive and practical, but on account of the 
 great scarcity of appropriate laboratory material, or per- 
 haps the proper appreciation of the material ready at 
 hand. That neurology can be intelligently taught by 
 any other than the laboratory inethod, no teacher has 
 the hardihood to affirm. 
 
 In looking up the matter of anatomical material suit- 
 able for the present requirements of laboratory work in 
 neurology, the sheep {ovis aries) was found to offer an 
 inexhaustible supply, and a source easily reached. This 
 material can be procured as fresh as need be, and at a 
 cost quite within the reach of anj^ institution or indi- 
 vidual. 
 
 Its adaptability for the teaching of the anatomy of the 
 brain to the medical student was ascertained by the dissec- 
 tion of a number of sheep brains, and by writing an out- 
 line of description as a guide to the student for laboratory 
 work. This outline was mimeographed and each student 
 was supplied with a copy and with three sheep brains, 
 two of which were removed while the third was left in 
 the brain case. The student then worked out each dis- 
 .section as outlined and made drawings of his preparations. 
 The experiment was an uncjualified success, and removed 
 all apprehension, so far as the neurological laboratory was 
 concerned, in the matter of working material. 
 
 At the suggestion of Professor Donaldson of the Uni- 
 versity of Chicago, I undertook the elaboration of my first 
 descriptifm, and the result is contained in the following 
 pages. 
 
8 ANATOMY OF THE BRAIN 
 
 This small effort is of necessity very imperfect, as little 
 literature is available for reference; but the writer trusts 
 that it may assist in some measure those who, like himself, 
 are compelled to conduct a course on the brain, and who 
 are in need of material or a laboratory guide. 
 
 The Basel association nomenclature (BNA) has been 
 followed as closely as possible. The association name, 
 where it is thought necessary, is followed by the common 
 or popular names in parenthesis ; this facilitates the con- 
 sultation of other works on the subject.; 
 
 For a like reason the following terms are employed: 
 
 Cephalad (anterior or toward the head). 
 
 Caudad (posterior or toward the tail). 
 
 Ventrad (ventral or toward the under parts). 
 
 Dorsad (dorsal or toward the upper). 
 
 Mediad (median or toward the middle line) and 
 
 Laterad (lateral or toward the side). 
 
 The terms ventral, dorsal, etc., are used as being more 
 in conformity with the spirit of the "BNA" than the 
 terms anterior, posterior, superior and inferior. 
 
 The drawings, with the exception of plates I and II, 
 which are photographs, are the work of the author ; they 
 were made from dissections, and unless otherwise indicated 
 represent the actual size of the structures under con- 
 sideration. 
 
 Perhaps the only inconsistency in the work is the sub- 
 division of the substantia alba and the substantia grisea 
 of the medulla spinalis (spinal cord) into tracts and col- 
 umns somewhat after the manner in which Toldt arranges 
 them in' the human medulla spinalis; and, furthermore, 
 this arrangement is illustrated by means of an histological 
 preparation, a departure from the original idea of the 
 work that could not well be obviated. Histology, path- 
 ology and embryology may prove this arrangement to be 
 at variance with the truth, but until such evidence is forth- 
 coming, the description here given will be helpful. 
 
 The close correspondence between the encephalon of the 
 sheep, and that of man, is a powerful argument in favor 
 of a like correspondence obtaining in the medullae spinal es 
 
ANATOMY OF THE BRAIN M 
 
 of the two Species. Even a microscopic examination of 
 some of the tracts of the medulla spinalis of the sheep 
 and their course eephalad reveals the fact that their courses 
 are not dissimilar to those taken by corresponding tracts 
 of the human medulla spinalis. 
 
 It has been deemed advisable to confine this work to 
 the consideration of such structures as can be identified 
 by gross dissection, using, as occasion may require, a 
 small hand magnifier or, preferably, an ordinary dissect- 
 ing microscope. There are no structures described or il- 
 lustrated, except the medulla spinalis, that cannot be 
 worked out by a first year student of ordinary intelligence. 
 
 The dissections from which the illustrations for this 
 book were made are now in the museum of the depart- 
 ment of neurology of the University of Chicago. 
 
 My thanks are due Professor Donaldson for many valu- 
 able suggestions in the selection of dissections for draw- 
 ing and for much assistance in properly naming various 
 tracts, fissures and gyri. Acknowledgment is also due Dr. 
 A. G. Wippern for assistance in arranging the nomencla- 
 ture. 
 
 Thanks are aspecially due the publishers of this vol- 
 ume for the great care they have exercised in its produc- 
 tion, particularly on account of the fidelity with which 
 they have reproduced the original drawings. The cuts, 
 as shown in the following pages, speak for themselves. 
 
 I wish to make special acknowledgment to Messrs. Ar- 
 mour & Co. for the very liberal manner in which they 
 supplied me with material and for permitting me to collect 
 such as best suited my purpose. 
 
 J. F. B. 
 
 108 N. State St., Chicago. 
 
ANATO-MY OP THE BRAIN H 
 
 PREFACE TO THE SECOND EDITION. 
 
 Iininediately aftei- the publication of the first edition of 
 this laboratory introduction to the study of neurological 
 anatomy, the author began the preparation of a serial sec- 
 tion of the bi'ain-steni of the sheep, stained by the Pal- 
 Weig'art method. This piece of research was due to the 
 desire on the part of the writer to substantiate his convic- 
 tion.s. that the i-ehitionships of the components of the brain- 
 stem of the sheep would prove as useful in teaching the 
 architecture of the corresponding region of the human 
 ])rain, as the grosser parts have been. That this is true 
 can be convincingly affirmed, by comparing i)lates XXXII 
 to XXXVIII, inclusive, of the present edition, with illustra- 
 tions of the analoLiiuis regions of the human brain, that 
 may be found in any authoi'itative work on descriptive 
 human anatom.w 
 
 The wonderfull\' siiiii)lc figure showing the cochlear and 
 vestil)ular nerves and their nuclei, as seen in plate 
 XXXVII, is positively diagi'amatic in its clearness, and 
 yet this comi)le.\ mechanism is thus perspicuously shown 
 in the space of a half dozen sections. 
 
 The original idea, that the book should contain the de- 
 scription of no sti'uctui-e tliat could not be seen by a hand 
 glass or dissecting iiiici'osco|)e, has been strictly followed 
 in the second edition. Most of tlie minute structures that 
 are mentioned, however, such as those that occur in the 
 stained .sections of the brain-stem, can be seen with the un- 
 aided eye. Moreover, many of these :;tructures can be 
 identified in unstained sections without an immoderate 
 exertion of the imagination. For demonsti-ations of this 
 character, sections should ])e cut as thin as i)0ssible under 
 water, using a sharj) thiu-bhide i-a/oi-, and placing the 
 specimen on parafined coi-lc or dissecting wa.x.* 
 
 One gratifying result that may, in a measure, be attrib- 
 uted to this laboratory guide, is the incentive it has given 
 to the study of iiustaiiicd se<'1ioiis of bi-iiu tissue. S])ecific 
 
12 ANATOMY OP THE BRAIN 
 
 directions, that will very materially facilitate tliis method 
 of study, are given in the text. 
 
 Furthermore, we cannot insist too forcibly upon the tear- 
 ing process, in facilitating the dissection of the brain. 
 The study of the larger bundles of fibres is greatly aided 
 by this method of work. When the sheep's brain is used 
 as a source of laboratory supply, there is no reasonable 
 necessity for being inordinately sparing of brains ; and the 
 student, if permitted to use the necessary material, will 
 very soon acquire a true and lasting perspective of this 
 intricate organ. 
 
 Henle made frequent use of this tearing process of dis- 
 secting the human brain as shown in Vol. 3 of his human 
 anatomy published in 1868. We are not paying sufficient 
 attention to these so-called primitive methods in this day 
 and age of complicated laboratory and often unsatisfactory 
 technie, and we and our students are the losers thereby. 
 
 Thanks are due Professor Herrick of the University of 
 Chicago for suggesting the introduction of figs. D. and E., 
 which show more clearly than the original plates the for- 
 amen interventriculare and the attachments of the pia and 
 arachnoid to the dorsal surface of the medulla oblongata. 
 Thanks are due Dr. Wippern for his care in correcting the 
 proofs. And again, my thanks are due to the publishers 
 for the accuracy with Avhich they have reproduced my 
 original drawings. 
 
 *Preparation of Dissecting Wax. Formula: 
 
 Bees wax (white or yeUow) 4 oz. 
 
 Parafin (50°) 4 oz. 
 
 Colophonium 1 oz. 
 
 Canada Balsam % oz. 
 
 mix. 
 Place the ingredients in the desired container and 
 melt. Stir while cooling until the mixture begins 
 tO' congeal on the sides of the vessel; then allow to 
 stand in a cool place. Do not allow the bottom 
 of the dish to get cold too quickly. Let the mass 
 get quite cold before using. 
 
 If a black mass is desired, add a tablespoonful 
 of lamp black. 
 
 Commercial rosin should not be substituted for 
 colophonium. 
 
 This mass does not shrink, crack, not get brittle; 
 neither is it effected by cold. It is very tenacious 
 to the dish and dissecting pins. 
 
ANATOMY OP THE BRAIN 13 
 
 INTRODUCTION. 
 
 During the last few years increasing emphasis has been 
 laid on the study of the brain as a part, of the anatomical 
 training of students preparing for medicine. 
 
 In many places where this preparatory work has been 
 introduced, human brains are difficult to obtain, and for 
 this reason mainly, the study of this organ is limited to a 
 few demonstrations. 
 
 It may be assumed that for some years, at least, it will 
 not be possible to relieve the difficulty arising from the 
 scarcity of human material. Under these circumstances, 
 it seemed desirable to prepare a description of a bram of 
 moderate size, which might be used in place of the human 
 brain, thus allowing the student to have the entire speci- 
 men under examination, and study it at his leisure. This, 
 of course, is by no means a new idea, since the work m the 
 Zoological Laboratory at Cornell University under Pro- 
 fessor Burt G. Wilder has for years been conducted on this 
 principle, and furthermore he has there used the sheep's 
 brain for the purposes of dissection. 
 
 All things considered, there is no more accessible mate- 
 rial of the proper size than the brain of the sheep, and 
 for the purpose of utilizing this, the present book has 
 
 been prepared. 
 
 The directions for the study of the specimen assume 
 that it is the purpose of the student to obtain a good 
 three-dimensional impression of the brain with which his 
 topographical terms may be associated. This is much 
 facilitated where the text and figures apply directly to the 
 specimen in hand, and it therefore seemed worth while 
 to brin- together the accompanying drawings, explained 
 by a brief text, in a form where they could be used in 
 connection with the laboratory work. 
 
 The chief dit¥erence between the brain of the sheep and 
 that of man is, apart from size, first in the cranial liex- 
 nvo which is much less developed in the sheep; second, 
 in the relative size of the cerebellar hemisphere ; and third, 
 in the propo.tional development and sculpturing of the 
 cerebral hemispheres. Ml of th.-se differences are readily 
 
14 ANATOMY OP THE BRAIN 
 
 appreciated by the inspection of demonstration specimens 
 or figures representing them. 
 
 On the other hand, the student's greater difficulties arise 
 in the attempt to understand the deeper lying parts rep- 
 resented by the inter-brain and mid-brain, together with 
 the ventricular cavities. To comprehend these, careful dis- 
 section is required, and this, fortunately, can be just as 
 well carried out on the brain of the sheep as on that of 
 man. 
 
 It will be seen from turning the pages, that most of 
 the appearances described in the text can be observed with 
 the unaided eye, and the statements have been so formu- 
 lated as to guide the student in making his own observa- 
 tions rather than to present him with a comprehensive ac- 
 count of the several structures. 
 
 This book meets a need that has been felt for some 
 years, and if at the same time arrangements can be made 
 with the firms dealing in sheep to remove the brains and 
 supply them to laboratories at reasonable prices, one me- 
 chanical difficulty standing in the way of the study of 
 the brain will have been removed. 
 
 It is as an aid to this end that Dr. Burkholder has pre- 
 pared the following description of the figures of the sheep's 
 brain, all of which were draAvn by himself from his own 
 careful dissections. 
 
 Henry H. Donaldson. 
 The Wistar Institute of Anatomy and Biology, Phila- 
 delphia, Pa. 
 
ANAT()^rV OF THE BRAIN 15 
 
 CHAPTER I. 
 THE BRAIN-ITS REMOVAL AND PREPARATION. 
 
 THE ENCEPHALON OF THE SHEEP {ovis (Ivies) . 
 
 The encephalon (brain) consists of four large subdi- 
 visions : 
 
 Cerebrum, 
 
 Cerebei.lum, 
 
 Pons, and 
 
 Medulla Oblongata; 
 all inclosed within the cranial cavity, the walls of which 
 in the adult are osseous, and the sutures of the calvarium 
 obliterated. 
 
 To remove the encephahm ^\'ith()ut iujuiy to its cover- 
 ings or the nervi cerebrales requires care, as laceration 
 of these structures may lead to erroneous conceptions, or 
 at least endanger a proi^er conception of the normal re- 
 lations. 
 
 The following instruments ai-e necessary for dissecting: 
 a large and a small bone forceps, a brain knife, small scis- 
 sors, scalpel, and a pair of dissecting forceps with sharp 
 points; all of which must be of good quality and in prime 
 condition. Nothing is more disastrous to good dissecting 
 than poor instruments in poor condition. 
 
 Begin with the bone forceps at the cephalic extremity of 
 the cranium just behind the frontal edge of the orbital 
 fossae (Plates I and II A). The first incisions will open 
 the large frontal sinuses, the inner walls of which form the 
 outer walls of the brain-case. 
 
 AVorking caudad, clip away small portions of bone until 
 an opening is made and the outer covering of the en- 
 cephalon is reached. Proceed now with the greatest care; 
 with the handle of the scalpel, pry the dense white mem- 
 brane "the dura mater" away from the skull before fur- 
 ther clipping away the bone, a small portion at a time. 
 Unless this precaution is taken this membrane will surely 
 be lacerated. 
 
16 ANATOMY OF THE BRAIN 
 
 It will be noticed that the dura mater is more firmly at- 
 tached to the inner surface of the skull along the middle 
 line than at the sides, while the locations where the at- 
 tachment is greatest will be seen to be at the sutures or 
 seams between the ossa cranii. 
 
 Remove the calvarium as far caudad as the sutura lamb- 
 doidea (Plate IB), which separates the os parietalis from 
 the OS occipitale; then proceed from the foramen occipitale 
 magnum — out of which passes the medulla spinalis — clip- 
 ping away the condyli occipitales, and finally the remain- 
 the portion of the os occipitale. Note how tightly the dura 
 clings to the cephalic portion of the bone, particularly at 
 the sutura lambdoidea. In clearing away the lateral walls 
 of the brain-case, caution must be exercised not to lacerate 
 the nervi cerebrales. 
 
 For the student of human anatomy preparing for the 
 study of medicine, a further use of the skull can be made 
 for the purpose of getting an idea of the arrangement of 
 the internasal bones, and the distribution of the Nn. 
 olfactorii. Remove the nasal bones by means of the bone 
 forceps, and a veritable labyrinth of convoluted bony struc- 
 tures will be exposed. These are the turhinal hones (con- 
 chae etJimoideales) or the ethmoturhinals. 
 
 The Nn. olfactorii can be traced for some distance, by 
 using a reasonable amount of care, showing their distribu- 
 tion to the Schneiderian membrane covering the superior 
 turbiual bones. This dissection requires very little skill, 
 and consumes a modicum of time. 
 
ANATOMY OP THE BRAIN 17 
 
 CHAPTER II. 
 
 THE COVERINGS OF THE BRAIN. 
 
 Having: removed the brain-case, a drawing should be 
 made of the exposed dura, of the Sinus Sagittalis (longi- 
 tudinal sinus), the Sinus Transversus (lateral sinus), and 
 the CoNFLUENS Sinuum (Torcular Herophilii), exposed as 
 directed in the description of the dura mater, and shown 
 in Plate III. 
 
 The student may now proceed in one of two ways ; either 
 the dura can be Avholly reflected and the encephalon re- 
 moved and placed in a ten per cent solution of formalin, or 
 a long incision may be made over each cerebral hemisphere 
 through the dura and the whole skull with the attached 
 brain placed in the solution. In either case it must remain 
 in a solution of this strength for four or five days, and 
 then be kept in a five per cent solution as long as required 
 for dissection and study. 
 
 In removing the encephalon, proceed from the caudal ex- 
 tremity, clipping away the nervi cerebrales close to the 
 foramina through Avhich they pass (Plates VII and 
 XXXIX), preserving at least 1 cm. of the nervi optici, and 
 taking care to remove the whole of the bulbi olfactorii from 
 their fossae; be particularly careful with the N. facialis and 
 the N. acusticus. 
 
 Each time the brain is to be studied it should be placed 
 in water for an hour to remove the formalin. This proced- 
 ure obviates the irritation of the conjunctiva and respira- 
 tory mucous membranes, which the vapor of formalin will 
 cause if allowed to circulate through the laboratory. 
 
 MENINGES. 
 
 These membranes surround the encephalon for its pro- 
 tection and partial nourishment. There are three of thein, 
 and from without inward are called: 
 
 Dura, 
 
 Arachnoid, and 
 
 1»IA. 
 
18 ANATOMY OF THE BRAIN 
 
 The dura is the first exposed on removing' the calvarium, 
 the pia is closely attached to the encephalon, and the 
 arachnoid lies between the two. 
 
ANATO:»[V OP THE BRAIN 19 
 
 CHAPTER III. 
 
 DURA MATER ENCEPHALI. 
 (dura, hard; mater, a mother.) 
 The dura (Plate III) is the strongest of the three mem- 
 branes, and not only protects the encephalon, but by send- 
 ing projections from its inner surface, between the hemi- 
 sphaeria cerebri and between the cerebrum and the cere- 
 bellum, acts as a support. This membrane consists of white 
 fibrous tissue arranged in bundles or strands that run in 
 many different directions. 
 
 Over the hemisphacria cerebri, vermis cerebelli and hemi- 
 sphaeria cerebelli, it is quite thin and cannot be separated 
 into distinct layers. The thickest and densest part of the 
 membrane, as previously mentioned, lies directly beneath the 
 sutura sagittal is and the sutura lambdoidea. At the cephalic 
 extremity there is a triangular thickening consisting of two 
 of three layers; the apex of this triangle points caudad in 
 the middle line, tlu^ base ccphalad and ventrad into the 
 cephalic extremities of the fos.sae olfactoriae. The gyri, 
 and sulci cerebri can be seen somewhat indistinctly through 
 the thinner parts of the membrane. 
 
 The dura consists, roughly speaking, of two layers, an 
 outer and an inner, the foi-mer, constituting the endosteum 
 of the ossa cranii, is very fii-mly attached to the inner sur- 
 faces of the cranium, and particularly so at the sutures, into 
 which fibrous bands <if dura pass. Between this layer and 
 the bone is a large number of arteries of various sizes, called 
 the arteriac meningeae, which supply the dura and the 
 inner table of the ossa cranii. This outer layer of the dura 
 also gives off tubuhn- prolongations which surround the 
 nervi cercbralcs as they pass through the various foramina ; 
 that accompanying the nervus opticus divides as the nerve 
 emerges from the foramen opticum, into its two primary 
 layers, the inner continuing as a sheath for the nerve form- 
 ing its cpincufium, while the outer unites with the peri- 
 osteum of the fossa orbitalis. 
 
20 ANATOMY OP THE BRAIN 
 
 The inner layer of the dura as it lies over the fissura 
 longitudinalis cerebri, and the fissura transversa cerebri, 
 leaves the outer layer and dips into these fissures. That 
 which rests in the fissura longitudinalis cerebri is called 
 the falx cerebri, very slightly developed in the sheep ; that 
 in the fissura transversa cerebri is the tentorium cerebelli. 
 Where the falx cerebri and the tentorium cerebelli leave the 
 outer layer, and in various locations on the base of the 
 cranium, the two layers of the dura separate and leave large 
 spaces of various shapes called sinuses, which convey venous 
 blood from the encephalon. These sinuses, like veins, are 
 lined with endothelial cells. 
 
 The Falx Cerebri has the shape of a sickle, hence its 
 name, and begins about 2 cm. caudad of the cephalic ex- 
 tremity of the encephalon where it is exceedingly narrow 
 and receives the vena frontalis. It widens as it proceeds 
 caudad, and is firmly attached to the sagittal centre of the 
 tentorium cerebelli. It is quite narrow even at its widest 
 portion and, really is suspended between the hemisphaeria 
 cerebri only at their caudal extremities. The long tri- 
 angular canal inclosed by the falx cerebri and the outer 
 layer of the dura is called the sinus sagittalis, analogous in 
 location to the sinus sagittalis superior (superior longi- 
 tudinal sinus) in man. The flow of blood in this sinus is 
 directed toward the caudal extremity of the encephalon. 
 
 As the falx proceeds caudad, numerous veins enter its 
 sharp concave border to empty blood into the sinus sagit- 
 talis. A large vein, the V. cerebri magna (vein of Galen), 
 enters the falx about & mm. cephalad to the tentorium. 
 This vein conveys blood from the plexus chorioideus of the 
 lateral and third ventricles and the lobi occipitales (caudal 
 extremities of the hemispheres). 
 
 The Tentorium CEREBELiii, the other reflection of the 
 inner layer of the dura, forms a partial roof over the fossa 
 cranii posterior. This layer or tent is membraneous in 
 the sheep and in man ; but is osseous in some species, as 
 the cat, dog, lion. As you follow the falx cerebri caudad 
 and ventrad it suggests the parting of the falx into halves 
 which gradually diverge, leaving a large, somewhat tri- 
 
ANATOMY OF THE BRAIN 
 
 21 
 
 angular opening, through which passes the mesencephalon, 
 composed of the structures connecting the cerebrum with 
 the cerebellum, pons, and medulla oblongata. 
 
 The inner margins of the tentorium are thus free, while 
 its outer borders are attached to the outer layer of the dura 
 lining the cranium. The free margin is thin, but where the 
 structure is attached to the outer dura it is very thick, and 
 at the point where the falx meets the tentorium will be 
 found a large triangular thickening in the outer portion of 
 which rests the confluens sinuum. 
 
 Traced cephalad along the basis cranii, the tentorium is 
 attached laterally to the external lip of the sulcus carotieus 
 and blends gradually with the dura lining the fossa cranii 
 media (Plate XXXIX). As the tentorium proceeds ce- 
 phalad it becomes greatly thickened, and almost tendonous 
 in character. 
 
 The sinuses, as previously stated, are spaces between the 
 two layers of the dura and convey venous blood. 
 
 The Sinus Sagittalis (Plate III). Make an incision 
 in the sagittal line of the dura mater about 4 cm. from the 
 cephalic extremity of the encephalon, and the sinus will be 
 exposed ; pass a bristle cephalad as far as possible without 
 using force, and then dissect it out, and the sinus will be 
 seen to end in the V. frontalis within about 2 cm. of the 
 cephalic extremities of the lobi frontales, which are drained 
 by this vein. Traced caudad, the sinus enters the con- 
 fluens sinuum. 
 
 The Confluens Sinuum is situated where the falx and 
 the tentorium meet, directly beneath the protuberantia oc- 
 cipitalis externa. Leading from the confluens sinuum at 
 each side is a sinus transversus which follows for some dis- 
 tance the attachment of the tentorium. 
 
 These sinuses finally enter the substance of the os oceipi- 
 tale, through which they run for a short distance and then 
 re-enter the cranial cavity close to the foramina condyli 
 anteriora where each enters a large sinus, the sinus hasilaris 
 magna resting on the os basilare (Plate XL). This 
 sinus is wide ventrad but gradually becomes smaller as it 
 passes dorsad, the two extremities not quite meeting in the 
 
22 ANATOMY OP THE BRAIN 
 
 dorsal midline. Pass a bristle along each sinus transversus 
 and dissect each out with the bone forceps. The sinus basi- 
 laris magna is drained by the two venae vertebrales that 
 leave the cranial cavity through the foramen occipitale 
 magnum, one on either side of the medulla spinalis. 
 
 The large V. ophthalmica enters the fossa cranii media 
 through the fissura sphenoidalis, bringing blood from the 
 orbit (Plate XL). This vein enters the sinus cavernosus. 
 Each sinus cavernosus rests in the sulcus caroticus on 
 either side of the corpus .sphenoidale. 
 
 Running almost completely around the hypophysis is the 
 sinus circularis; on each side this sinus communicates freely 
 with the sinus cavernosus. 
 
 The sinus circularis and the sinus cavernosi contain a fine 
 reticulum of connective tissue, arranged somewhat after the 
 manner of the cancellous tissue in bone. 
 
 In each sinus caverncsus will be seen a very dense plexus' 
 of small arteries, called the rete mirahile (Galen) which 
 will be described in connection with the arterial circulation 
 on the ventral surface of the encephalon. 
 
 As each sinus cavernosus passes caudad it lies mediad to 
 the N. trigeminus, the fibrous sheath (epineurium) of which 
 is firmly attached to the external wall of the sinus. 
 
 Passing through the sinus cavernosus are the N. oculomo- 
 torius, N. trochlearis, and the N. abducens on their way to 
 the fissura sphenoidalis; the sinus cavernosus empties into 
 the sinus petrosiis inferior which runs along the ventral 
 border of the pars petrosa of the os temporale and ends at 
 the foramen jugulare by entering the V. jugularis interna. 
 A bristle should be passed along the sinus petrosus inferior 
 and dissected out by means of the bone forceps. 
 
 In this connection a very nice dissection can be made of 
 the ganglion semilunare (Gasseri) showing the origins of 
 the N. ophthalmicus, N. maxillaris, and the N. mandibularis. 
 The dissection should begin at the fossa temporalis and be 
 carried mediad, proceeding carefully when the region of 
 the sinus cavernosus is reached. 
 
 At this stage the student must cease operations on the 
 basis cranii, which are to be resumed when working out the 
 
ANATOMY OF TlIK BRAIN 23 
 
 exit of the iiervi cerebrales from the cranial cavity. Per- 
 haps the better way to make this latter preparation would 
 be to decalcify the basis cranii by immersing it in a ten per 
 cent solution of commercial nitric acid in water, after which 
 the nervi cerebrales can be easily removed with the dural 
 processes surrounding them. 
 
24 ANATOMY OF THE BRAIN 
 
 CHAPTER IV. 
 ARACHNOIDEA ENCEPHALI. 
 
 (ARACHNE, spider's WEB; EIDOS, LIKE.) 
 
 The arachnoid is a membrane of very uncertain quantity 
 and variable in its character and distribution. As a rule it 
 covers the entire encephalon and lies immediately beneath 
 the dura, and the space between it and the dura is called the 
 cavum subdurale. 
 
 This membrane is most easily identitied in the region im- 
 mediately caudad to the cerebellum, where the dura and 
 the arachnoid are reflected from the vermis to the dorsal 
 surface of the medulla oblongata; as a rule the membrane 
 is continued as a tubular prolongation over the medulla ob- 
 longata thence to the medulla spinalis. 
 
 The space beneath the arachnoid is the cavum suharach- 
 noideale, and at certain places this space is quite deep, as in 
 the angle made by the cerebellum with the medulla. 
 
 At the fossa interpeduncularis, and other limited places, 
 these deep spaces are called the cisternae subarachnoideales, 
 and are filled with a very delicate reticulum of tissue which, 
 like all the spaces between the arachnoid and the pia, con- 
 tains the cerebro-spinal fluid. 
 
 The reticulum forms the trabeculae subarachnoidealae. 
 Place a small quantity on a slide in glycerine and water; 
 tease under a dissection microscope, and study. Clip a 
 small piece of arachnoid from that covering the hemisphae- 
 rium cerebri ; mount in glycerine ; it will present, mingled 
 with a few elastic fibres, a very fine reticulum of white 
 fibres which, under a dissecting microscope, looks like 
 ground glass. Under a higher power a very beautiful 
 plexus of capillaries and arterioles can be seen, many of 
 them containing blood. A large number of arteries can 
 be seen passing through the trabeculae subarachnoidealae, 
 but the tissue itself is nonvascular. The trabeculae are 
 most abundant on the ventral surface of the encephalon 
 and contain much fluid which acts as a water-bed for the 
 
ANATOilY OP THE BRAIN 25 
 
 organ it supports; while over the convexities of the hemis- 
 phaeria cerebri the flnid is very scarce, thouj^rh more abun- 
 dant beneath the portions of arachnoid that lie over the 
 sulci cerebri. 
 
2G ANATOMY OF THE BRAIN 
 
 CHAPTER V. 
 PIA MATER ENCEPHALI. 
 
 (PIA^ TENDER; MATER, A MOTHER.) 
 
 The pia mater is an exceedingly thin membrane in con- 
 tact with the encephalon; and containing vessels in large 
 quantity, it provides nutrition for the entire substance of 
 the brain cortex. 
 
 This delicate membrane dips to the bottom of the various 
 sulci and during the development of the organ is pushed 
 through the fissura transversa cerebri (great transverse 
 fissure) into the ventricular cavities of the encephalon, 
 where it will be further studied, when describing those 
 spaces. 
 
 At the cephalic extremity of the encephalon there is in the 
 cells of the pia a deposit of pigment granules which in some 
 instances assumes the form of a large triangular patch, ly- 
 ing beneath the similarly-shaped thickening of the dura. 
 This deposit of pigment is black and may be scattered in 
 various other locations, notably on the ventral surfaces of 
 the lobi frontales. In some encephala this pigment will 
 be found as far caudad as the medulla spinalis. Animals 
 killed at different seasons of the year do not show any 
 regular variation in the quantity or the extent of dis- 
 tribution of this pigment; but from the limited number 
 of specimens examined, it appears to be much less in 
 lambs under one year than in adult sheep. 
 
 Toward the caudal extremity of the medulla oblongata, 
 the pia is greatly increased in density and thickness as 
 it becomes the pia of the medulla spinalis. In this location 
 two distinct layers can be distinguished ; an external, whose 
 fibres run longitudinally, and an inner with transverse 
 fibres, the latter appearing to be the more numerous. Ex- 
 amine a small portion under the dissecting microscope. 
 
 In the region of the medulla spinalis, and the caudal 
 portion of the medulla oblongata this thickened pia is 
 furthermore greatly increased laterally, forming the liga- 
 
ANATOMY OF THE BRAIN 27 
 
 inottutn dniticitldliui} ; lying between the dorsal and ventral 
 roots of the Nn. cerebrales, and passing eephalad, ventral 
 to the roots of the N. aceessoriiis. 
 
 The lateral border of this liganieutuni denticulatmn 
 occasionally takes the form of a white fibrous cord, which 
 runs parallel to the spinal portion of the N. accessorioiis. 
 This cord may be mistaken for a part of- the nerve, which 
 in this neighborhood, is occasionally divided into two well- 
 defined fasciculi, quite similar in color and consistency to 
 the ligamentous cord. 
 
 These ligaments on each side appear to blend with the 
 dura, as it forms the tubes for the exit of the Nn. glosso- 
 pharyngei, Nn. vagi, and Nn. accessorii. 
 
 At the point where the pia is reflected from the caudal 
 surface of the cerebellum to the dorsal surface of the me- 
 dulla oblongata, there is occasionally, a median foramen, 
 called the apertura mediana ventriculi quarti (foramen o* 
 Magendie). 
 
 If we trace the pia a short distance caudad on the medulla 
 spinalis, it will be seen to lose its excessive thickness, and 
 becomes the delicate fibro-vascular membrane usually de- 
 scribed. 
 
28 ANATOMY OF THE BRAIN 
 
 CHAPTER VI. 
 
 BLOOD VESSELS AT THE BASE OF THE BRAIN. 
 
 The blood supply (Plate IV) to the encephalon is almost 
 entirely derived through the arterid carotis interna on either 
 side. The internal carotid artery, after it is given off from 
 the common carotid, enters the cranial cavity through the 
 foramen ovale, passing ventrad to the proximal extremity of 
 the N. mandibularis which leaves the cranial cavity 
 through the same opening. As the artery enters the cran- 
 ial cavity it lies opposite the caudal extremity of the fossa 
 hypophyseos, where it immediately divides into a plexus of 
 small arterioles, the rete mirabile, which in their turn simi- 
 larly divide, and so on until the whole of the sinus cavern- 
 osus is completely filled with small arteries in a manner 
 similar to the arrangement of the vas aft'erens in the kid- 
 ney forming the glomerulus inside the capusula renis. This 
 plexus of vessels also invades the fossa hypophyseos occu- 
 pying all the space not taken by the hypophysis and sinus 
 circularis. 
 
 The vessels from the two sides come very close together 
 caudad to the hypophysis, but the arteries of one side do 
 not anastomose with those of the other. The small ar- 
 teries are finally gathered together, opposite the centre of 
 the hypophysis and form one large artery on each side, the 
 arteria propria cerebri. 
 
 These pierce the dura which forms the roof of the sinus 
 cavernosus on either side of the foramen diaphragmatis 
 sellae and at once divide into two rami nearly opposite the 
 infundibulum, the ramus anterior passing cephalad, and the 
 ramus posterior, caudad. The former nins cephalad in the 
 sulcus between the tractus opticus and the lobus hippo- 
 campi ; it then turns sharply mediad, and in some cases runs 
 almost parallel with the tractus opticus. 
 
 When this anterior ramus reaches the nervus opticus it 
 divides into two branches, the a. cerebri anterior, con- 
 tinuing on as the apparent extension of the ramus anterior 
 
ANATOMi' OF THE BRAIN 29 
 
 to the fissura longitudinalis cerebri, and the a. cerebri 
 MEDIA passing directly laterad in the fissura cerebri later- 
 alis (fissure of Sylvius). The latter artery is widely and 
 irregularly distributed to the lateral aspect of the hemi- 
 sphaerium cerebri, passing dorsally in some instances as far 
 as the fissura longitudinalis cerebri, supplying also a 
 considerable portion of the external surface of the lobus 
 frontalis and the lobus parietalis. 
 
 The A. cerebri anterior passes cephalad usually on the 
 ventral surface of the lobus frontalis, and is distributed 
 to the facies ventralis and the facies medialis of this por- 
 tion of the encephalon. As the Aa. cerebri anteriores pass 
 cephalad they anastomose at one or more points, permitting 
 a free communication between the vascular systems of the 
 two sides. At the bifurcation of the A. propria cerebri, a 
 large branch is usually seen, the A. cerebri posterior, which 
 may arise either from the ramus anterior or the ramus pos- 
 terior. It passes laterad and caudad across the pedunculus 
 cerebri and is soon hidden by the lobus hippocampi. It is 
 distributed to the facies medialis and the facies ventralis of 
 the lobus occipitalis. 
 
 The rami posteriores pass caudad and converge to meet 
 beneath the fossa interpenduncularis, where the nervi oculo- 
 motorii (third pair of cranial nerves) emerge from the 
 pedunculi cerebri (crura cerel)ri), forming the arteria basi- 
 laris; this artery runs directly caudad in the middle line on 
 the ventral surface of the pons, and the medulla oblongata. 
 
 As the ramus posterior reaches the N. oculomotorius it 
 gives off a branch, the A. basilaris gangliaformis posterior 
 that passes laterad, cephalad to the root of the nerve, winds 
 around the pedunculus cerebri, and is distributed to the 
 pulvinar, corpora geniculata, and the corpora quadrigemina. 
 
 Just before the rami unite, a large branch, the A. cerebelli 
 anterior passes laterad and is distributed to the facies dor- 
 salis and thei facies lateralis of the cerebellum ; it runs 
 caudad in the sulcus between the vermis and the hemi- 
 sphaerium cerebelli, to anastomose with the artery next to 
 be described, the A. cerebelli posterior. 
 
 This artery ai'ises fniin the A. hasilai-is as it passes over 
 
30 ANATOMY OF THE BRAIN 
 
 the groove between the pons and the medulla oblongata. 
 It lies dorsad to the N. abdueens, supplies the dorsal and 
 lateral surfaces of the medulla oblongata as well as the 
 neighboring parts of the cerebellum ; it then passes dorsad 
 and cephalad to meet the A. cerebelli anterior. 
 
 On proceeding caudad the A. basilaris gives off small 
 branches from either side which are distributed to the ven- 
 tral surface and sides of the medulla oblongata. In the 
 region where the medulla oblongata merges into the medulla 
 spinalis, the A. basilaris breaks up into a spray of little 
 branches which are distributed to the adjacent parts; at 
 its caudal extremity the artery can be seen anastomosing 
 with the A. spinalis ventralis, which passes caudad through- 
 out the entire length of the medulla spinalis. 
 
 There is a very peculiar and useful arrangement of the 
 larger arteries on the ventral surface of the central portion 
 of the encephalon called the circulus arteriosus (circle of 
 AVillis). As the Aa. cerebri anteriores approach the mid- 
 line, just cephalad to the chiasma opticum, they are con- 
 nected directly or indirectly by one or more small arteries 
 called the Aa. communicantes anteriores, thus completing 
 the cephalic portion of the circle, while the caudal part 
 is formed by the union of the rami posteriores. 
 
 A drawing should be made of the ventral surface of the 
 encephalon showing the circle, the proximal portion of its 
 branches, and the other structures of interest. The obvious 
 functions of this circle formed by the anastomosis are to 
 supply a constant quantity of blood to the encephalon in an 
 even stream, with a like degree of pressure in every direc- 
 tion, and to insure a free supply to the whole encephalon, 
 should one or the other of the sources of blood to the circle 
 be obliterated. 
 
 The student should bear in mind that the formation of 
 the circulus arteriosus of the sheep differs from that of the 
 human brain, where there is an additional supply of blood 
 supplied by the large A a. vertebrales. 
 
ANATOMY OF THE BRAIN 31 
 
 CHAPTER VII. 
 THE EXTERNAL SURFACE OF THE BRAIN. 
 
 THE HEMISPHAERIA CEREBRI. 
 
 The heiiiisphaeria cerebri are two symmetrically arranged 
 portions of the encephalon, separated by the pissura longi- 
 TUDiNALis cerebri, Constituting its largest subdivisions. 
 
 The outermost or ectal portion of each hemisphaeriura, 
 that which is seen after the encephalon is cleared of its 
 meninges, is the pai,lium. It is characterized by a series 
 of long, narrow folds, much convoluted, which have a some- 
 what definite and regular arrangement. 
 
 The sagittal diameter of the cerebrum is about 7 cm., the 
 greatest transverse diameter about 6 cm., while the dorso- 
 ventral will average about 4 cm. ; these measurements vary 
 somewhat in difiPerent specimens. 
 
 The external layers of the pallium consists of the cell 
 bodies of myriads of neurones (nerve cells) which consti- 
 tute a Dart of the substantia grisea or cortex of each hemi- 
 sphaerium. Internal to this substantia grisea is the sub- 
 stantia alba, composed principally of medullated fibres of . 
 the neurones (axones with their sheaths). Make a small 
 wedge-shaped incision into' one of the gyri cerebri, and 
 the differentiation of the cerebral matter into substantia 
 grisea and substantia alba can be easily verified. 
 
 The following short method of staining the substantia 
 grisea to show its constituent neurones can be easily carried 
 out. A small quantity of substantia grisea is placed on a 
 coverglass, and a second cover glass placed directly on it 
 and squeezed down so that the nerve substance is smeared 
 evenly over both glasses. The covers are then separated 
 and floated for two hours, film downward, on a saturated 
 aqueous solution of methylene blue. They are then washed 
 in distilled water and dried; finally, after exposure to a 
 gentle heat to thoroughly dry them, they are mounted in 
 bfilsam.* 
 
 ♦H. L. Osborn, Journal of Applied Microscopy, Vol. 1, p. 7. 
 
32 ANATOMY OF THE BRAIN 
 
 The irregular depressions on the surface divide each 
 hemisphaerium into gross subdivisions called lobi cerebri, 
 and these again into gyri cerebri (cerebral convolutions). 
 The larger depressions are called fissures; those separating 
 the gyri, which are smaller are called sulci. 
 
 The layer of substantia grisea constituting the cortex is 
 not an homogeneous mass of matter with the neuron bodies 
 arranged in a heterogeneous manner. These neuron or 
 cell bodies are arranged in definite stratae, which in some 
 specimens prepared by the Kaiserling method, can be faintly 
 seen by the unaided eye. 
 
ANATOMY OP THE BRAIN 33 
 
 CHAPTER VIII. 
 
 DORSAL SURFACE OF THE CEREBRUM. 
 
 On the fades dorsalis cerebri (Plates V and IX) of 
 each hemisphaerium is a transverse fissure called the fissura 
 cruciata. It lies about 2.5 cm. caudad to the cephalic ex- 
 tremity of the encephalon, is inclined slightly cephalad as it 
 passes laterad and separates the lobus frontalis from the 
 lobus parietalis. 
 
 The fissura cruciata in some specimens does not reach 
 
 the lateral border of the dorsal surface, but rests between 
 
 the caudal extremity of the gyrus frontalis medialis and 
 
 the cephalic extremity of the gyrus parietalis externus 
 
 (gyrus lateralis). 
 
 The facies dorsalis of the lobus frontalis is divided into 
 too well-defined gyri : a mesial, called the gyrus frontalis 
 superior, and a lateral, the gyrus frontalis medialis. 
 
 These gyri are separated from each other by the sulcus 
 coronalis which is really a prolongation of the fissura cru- 
 ciata ; this fissure passes cephalad in the sagittal plane and 
 terminates in a bifurcation near the polus anterior. The 
 gyrus frontalis superior is in most cases somcAvhat de- 
 pressed, particularly at its caudal extremity, where a well 
 marked notch appears which is the cephalic termination of 
 the sulcus splenialis (Plate IX). In many specimens the 
 A. cerebri media leaves the fissura cerebri lateralis and con- 
 tinues its course in the fissura cruciata to reach the neigh- 
 borhood of the fissura longltudinalis cerebri. 
 
 There is another very important and well marked fissure 
 situated on the facies dorsalis called the fissura suprasylvia. 
 This fissure begins on the facies lateralis cerebri about 1 cm. 
 cephalad to the middle of the fissura cerebri lateralis; it 
 then passes caudad and dorsad winding around the summit 
 of the fissura cerebri lateralis lying about 2.5 cm. laterad to 
 the fissura longltudinalis. The further course of the fissure 
 runs in a caudo-laterad direction, reaching in some in- 
 stances the tentorial surface of the lobus occipitalis. The 
 
34 ANATOMY OP THE BRAIN 
 
 caudal two-thirds of the fissura suprasylvia separates the 
 parietal from the temporal lobie. 
 
 Occasionally the lateral extremity of the fissura cruciata 
 appears to pass directly into the fissura suprasylvia, but if 
 the student takes the trouble to open the fissure he will see 
 that this condition is only apparently so. At this point 
 there is a more or less well developed gyrus hidden from 
 view. 
 
 The facies dorsalis of the lobus parietalis is divided, in 
 the adult specimen, by three well developed sulci, that may 
 be named, sulcus lateralis, sulcus medialis and sulcus inter- 
 media, which run in a caudo-laterad direction, parallel with 
 the caudal portion of the fissura suprasylvia. 
 
 These sulci divide the lobi into four gyri, an external, an 
 internal and two mesial. These gyri become larger and 
 longer from the fissura longitudinalis, laterad. They run 
 to the polus posticus, and at irregular intervals are divided 
 by transverse depressions that form shallow sulci. These 
 four parietal gyri are very constant, and in no instance was 
 there observed any evidence of the separation of a lobus oc- 
 cipitalis. The gyrus lateralis, in many instances, extends 
 cephalad to the fissura cruciata, and, winding around the 
 extremity of this fissure, forms a connection with the lobus 
 frontalis. This arrangement is nicely shown in the right 
 hemisphere as seen in Plate V. 
 
 In most cases the fissura cruciata lies beneath the os pari- 
 etale, but occasionally it lies directly beneath the sutura 
 eoronalis, and thus the parietal lobe is alm.ost wholly cov- 
 ered by the parietal bone. 
 
 Slight variations in the manner of the arrangement of 
 some of the gyri and sulci are seen in most specimens. In 
 fact, the arrangement is not always the same, even in the 
 two hemispheres of the same brain. The gyri and sulci 
 of the human enaphalon are not exempt from such varia- 
 tions. The fissura cerebri lateralis (Sylvius), however, 
 never varies ; it is invariably in the same relative position. 
 
 Professors Simpson and King of Cornell University* 
 
 ♦Quarterly Journal of Experimental Physiology, Vol. IV, No. 1, 
 1911. 
 
ANATOMY OP THE BRAIN 
 
 35 
 
 have done a splendid piece of research on the motor areas 
 of the cerebrum of the sheep, which must be mentioned in 
 this connection and which we have illustrated by three 
 figures : A. B. C. taken from plates V, VIII and IX. 
 These phj'siologists place these centres in the laryrus fron- 
 
 FIG. A. 
 
 'riii.s fiirure illnstrates the dorsal surface of the l)rain. The 
 lines and dots on the super fi-ontal convolntion of the 
 left cerebral hemisphere show the motor areas. 
 
 talis superior of the left hemispherium. They occupy the 
 exposed surface of the gyrus to within a short distance 
 of its vt'ntral border. Tliis excitable area winds over the 
 
36 
 
 ANATOMY OF THE BRAIN 
 
 free border of the gyrus onto its mesial surface for a 
 distance of 1 mm. 
 
 They have not only shown where the motor area is lo- 
 
 FIG. B. 
 
 Frontal elevation of the cerebrum showing* the motor areas 
 and their relations to each other. 
 
 FIG. C. 
 
 Showing the mesial surface of the left cerebral hemisphere 
 with motor areas. 
 
ANATOMY OP THE BRAIN 37 
 
 Gated, but they have worked out the location of the specific 
 centres of the various groups of muscles. 
 
 These figures show the positions of the four different 
 centres numbered 1, 2, 3 and 4. 
 
 1. Muscles of the face, mouth and tongue. 
 
 2. Muscles of the head and eye. 
 
 3. Muscles of the fore limbs. 
 
 4. Muscles of the hind limbs. 
 
 Their locations should be marked in on the drawings 
 that are made of the cerebral gyri and sulci, not for- 
 getting the area involved on the facies medialis cerebri. 
 
38 ANATOMY OF THE BRAIN 
 
 CHAPTER IX. 
 
 DORSAL SURFACE OF THE CEREBELLUM. 
 
 As the heraisphaeria cerebri diverge (Plate V) by the 
 opening of the caudal extremity of the fissura longitudinalis 
 cerebri, we see the cephalic elevation of the fades cerebelli 
 dorsalis. 
 
 In the centre will be seen a large and more or less inter- 
 rupted ridge called the vermis cerebelli with its surface 
 marked by numerous transverse sulci situated quite close 
 together and separating the narrow folia cerebelli. 
 
 The vermis cerebelli, as viewed from the dorsal aspect, 
 appears to run in a caudal direction, reaching a plane al- 
 most as high as the faeies cerebri dorsalis; it then turns 
 suddenly ventrad to reach the dorsal surface of the medulla 
 oblongata, where it turns again and takes a cephalic direc- 
 tion, where the convexities of the folia lie against the dorsal 
 surface of the medulla oblongata. 
 
 These folia are very flat portions of the cerebellar sub- 
 stance, and are composed, like other parts of' the brain, 
 of substantia grisea and substantia alba. The former lies 
 on the two surfaces and the convexity of each folium. 
 Deep fissures extend down between the several folia carry- 
 ing the substantia grisea with them to the bottom. When 
 these folia are cut transversely, as in the sagittal section 
 of the vermis, a very beautiful tree-like arrangement of 
 grey and white matter is seen, called the arbor vitae, as 
 shown in Plate VIII, and described in this and in Chapter 
 XIII. The large thick limbs can be seen diverging from 
 the central white substance, the corpus medullare cerebelli ; 
 and from these limbs smaller branches spring like the 
 branching of a tree. 
 
 If the cerebellum be detached from the rest of the en- 
 cephalon the cephalic portion of the vermis will also turn 
 ventrad and then eaudad; the apices of the vermis thus 
 come close together, and in many specimens touch, as they 
 lie suspended in the cavity of the ventriculus quartus. 
 
ANATOMY OF THE BRAIN 39 
 
 The vermis can be divided into five lobes by four fissures. 
 According to Bradley* the fissures enumerated in a cephalo- 
 caudad direction may be called, fissure I, fissure II, fissure 
 III and fissure IV, and the lobes A, B, C, D and E (Plate 
 VIII). 
 
 In the ventral part of the concavity on the cephalic sur- 
 face of the vermis will be seen a distinct horizontal fissure 
 called fissure I, Plate VIII. That portion of the ver- 
 mis vertral to this fissure is lobe A ; the major part of 
 which is characterized by such short folia that it may be 
 called the vermis cerebelli minor; furthermore, this par- 
 ticular part is separated from the remainder of lobe A 
 by quite a distinct fissure. Near the centre of the oblique 
 cephalic surface will be observed a well marked and sharply 
 curved fissure with its convexity directed dorsad; this is 
 fissure II. 
 
 Lobe B lies between fissures I and II. About 5 cm. from 
 the dorsal extremity of the caudal surface is fissure III. 
 
 Lobe C occupies the space between fis.sures II and III. 
 On the ventral surface of the remaining portion of the 
 vermis is fissure IV, separating lobes D, and E (Plate 
 VIII). 
 
 A section of the vermis cerebelli minor is ver^- clearly 
 shown in Plate XXX, in Fig. 3. The caudal extremity of 
 this portion of the vermis can be seen by depressing the 
 medulla oblongata. 
 
 On either side of the vermis are the hemisphaeria cere- 
 belli; on an ordinary inspection the facies cerebelli lateralis 
 (Plate VI) might be said to j) resent for examination three 
 well marked lobes separated by two fissures. These lobes, 
 in a general way, follow the same general arcuate course 
 as the vermis, arching dorso-caudad and then ventrad, and 
 may be named, iobus superior, lobus medial is, and lobus 
 inferior. This simple arrangement, however, will be found 
 greatly modified on a closer inspection and no small degree 
 
 *0n the development and homology of the mammalian cerebellar 
 tissues. By O. Charnock Bradley, M. B., Professor of Anatomy, 
 Royal Veterinary College, I'^dinburgh. Journal of Anatomy and 
 Physiology Vol. XXXVII, 1903. 
 
40 ANATOMY OF THE BRAIN 
 
 of complexity exists, particularly in the ventral portion 
 of the hemisphere. 
 
 At the extreme ventral part of each hemisphere is 
 a small lobule made up of six or seven folia, called the floc- 
 culus (Plate VI). Between the flocculus and the lobus su- 
 perior is a long serpentine lobe called the paraflocculus. 
 The paraflocculus is said to be separated from the lobus su- 
 perior by a distinct fissure, but there are many instances in 
 the mature specimen where the caudal extremity of the lobus 
 superior appears to be continuous with the paraflocculus. 
 The three or four cephalic folia of the iobi superiores are in 
 direct continuity across the vermis. 
 
 m 
 
ANATOMY OF THE BRAIN 4:1 
 
 CHAPTER X. 
 
 LATERAL SURFACE OF THE CEREBRUM. 
 The fades lateralis cerebri (Plate VI) of the hemisphae- 
 rium cerebri does not present the same regularity in the ar- 
 rangement of its gyri and sulci, as is found on the facies 
 dorsalis. In fact there are only two, the fissura cerebri 
 lateralis (Sylvii), and the fissura rhinalis (fissura limbica 
 of Turner), that are constant. 
 
 About 3.5 cm. caudad to the polus frontalis will be seen 
 the fissura cerebri lateralis beginning on the facies dorsalis 
 about 2 cm. laterad to the fissura longitudinalis, and, run- 
 ning directly ventrad for about 2 cm., divides into a ramus 
 posterior and ramus anterior; the former runs caudad only 
 a short distance and, turning sharply ventrad, ends in the 
 fissura rhinalis where the tractus olfactorius unites with the 
 lobus hippocampi. The ramus anterior is in most instances 
 carried cephalad in a zig-zag manner, somewhat parallel 
 with the external border of the tractus olfactorius. 
 
 The fissura rhinalis separates the tractus olfactorius and 
 the lobus hippocampi from the cerebrum, and forms the 
 dividing line between the facies lateralis cerebri, and the 
 facies ventralis cerebri. 
 
 The cephalic extremity of this fissure ends in the sulcus 
 olfactorius, not shown in Plate VI; the caudal termination 
 is on the mesial surface of the cerebrum near the polus 
 
 posticus. . 
 
 Between the diverging rami of the fissura lateralis cerebri 
 and the fissura rhinalis is a very constant lobe, called the 
 lobus centralis (the insula, or the island of Reil). This 
 lobus centralis at its caudal extremity very frequently pre- 
 sents three well-marked small convolutions, the central one 
 of which rests in the antrle formed by the diverging rami of 
 the fissura lateralis cerebri. These convolutions extend into 
 the substance of the hemisphere and can be easily shown by 
 slightly elevating the ventral extremities of the gyrus syl- 
 viacus. In fact, the lo})US centralis may be so depressed 
 
42 ANATOMY OF THE BRAIN 
 
 that the ventral extremities of the gyrus sylviacus appear to 
 hang over it, suggesting its partial occlusion ; it is only in 
 the older specimens that this overlapping is so well marked. 
 In all cases, however, the rami of the fissura lateralis 
 cerebri dip well in toward the centre of the hemisphaerium, 
 thus cutting off the insula as a separate lobe. 
 
 The lower projecting ends of the gyrus sylviacus suggest 
 very strongly the operculum in man; the ventral extremi- 
 ties of this gyrus might well be called the operculum, 
 in the sheep. 
 
 There will be seen in almost all encephala a large gyrus 
 that has been mentioned several times already; this is the 
 gyrus sylviacus (arcuatus). This gyrus arches over the 
 dorsal extremity of the fissura lateralis cerebri. There is in 
 many cases a well-marked gyrus lying parallel with and 
 dorsal to the tractus olfactorius, the gyrus orbit alis; this 
 gyrus is in some cases quite distinctly separated from the 
 lobus centralis. Just dorsad to the cephalic ramus of the 
 fissura lateralis, lies the gyrus frontalis inferior; these two 
 gyri, are, however, generally broken up into a number of 
 small irregular convolutions. • 
 
 The arrangement of the sulci and gyri on the faeies later- 
 alis of the lobus temporalis follow no definite order that 
 could be ascertained from a careful study and comparison 
 of the limited number of encephala examined, and will not 
 be further discussed at the present. 
 
ANATOMY OP THE BRAIN 
 
 43 
 
 CHAPTER XI. 
 
 VENTRAL SURFACE OF THE CEREBRUM. 
 
 The fades ventralis cerebri (Plate VII) of the encephalon 
 exhibits a large number of very important structures. 
 That part of the cerebrum lying: between the two sulci 
 rhinales should be considered as the ventral surface of the 
 encephalon. 
 
 At the cephalic extremity will be seen two large oval 
 masses of matter placed obliquely; these are the hulhi olfac- 
 torii, very large in macrosmatic animals. These bulbs lie 
 in the deep sulci olfactorii; their cephalic extremities turn 
 slightly dorsad in front of the lobi frontales. Each bulbus 
 olfactorius is attached to the cerebrum by three radices. 
 
 The radix medial is passes caudad and mediad to the facies 
 medialis and unites with the subcallosal extremity of the 
 gyrus cinguli; it is composed of substantia grisea, and is 
 always well marked. 
 
 The radix lateralis passes laterad and caudad to unite 
 with the cephalic extremity of the lobus hippocampi at its 
 outer part; the lateral margin of the radix lateralis is di- 
 rectly continuous with the external border of the lobus hip- 
 pocampi. These borders form the internal or ventral lip 
 of the fissura rhinalis. 
 
 The radix lateralis is always well marked and much 
 larger than the radix medialis; it consists of an external 
 larger portion of substantia grisea, and an internal part of 
 substantia alba much less in quantity than the substantia 
 
 grisea. 
 
 The radix intermedia is composed entirely of substantia 
 alba, derived principally from the commissura anterior, to 
 be subsequently traced and described. This so-called radix 
 does not appear on the surface of the encephalon but, on 
 slightly elevating the bulbus olfactorius, or by dissecting 
 away the substantia grisea which constitutes the locus per- 
 foratus anterior, as described in a later dissection the cor- 
 responding extremity of the commissura or radix is plainly 
 .seen f Plate XIX). 
 
44 ANATOMY OP THE BRAIN 
 
 Between the sulcus olfactorius and the fissura longitudi- 
 nalis cerebri is seen the gyrus rectus, which winds around 
 the cephalic extremity of the sulcus olfactorius and then 
 takes a course directly eaudad, parallel with the gyrus orbi- 
 talis. 
 
 The large triangular or quadrilateral space (espace quad- 
 rilatiere of Broca) formed by the diverging radices olfac- 
 toriae, is called the locus perforatus anterior. It consists of 
 substantia grisea marked by a large number of perforations, 
 through which pass the antro-mesial and the antro-lateral 
 arteries arising from the A. cerebri anterior and the A. 
 cerebri media respectively to be distributed to the corpus 
 striatum. 
 
 After a specimen has been taken from formalin and 
 placed in water for twenty-four hours, examine the ventral 
 surface just cephalad to the tractus opticus. In this re- 
 gion, a small band of substantia grisea may be seen ex- 
 tending from the mesial border of the lobus hippocampi 
 near its cephalic extremity, to, and bending around onto 
 the facies medialis cerebri. Here it blends with the sub- 
 callosal extremity of the gyrus cinguli. 
 
 Just eaudad to the loci perforati anteriores is seen a 
 crucial arrangement of substantia alba, the chiasma opti- 
 cum. 
 
 Passing cephalad from the lateral extremities of the 
 chiasma opticum (optic commissure) are two large nerves 
 the nervi optici that have been cut in removing the 
 encephalon. 
 
 Passing latero-caudad from the chiasma, are two large 
 bands of substantia alba called the tracti optici; these tracts 
 soon disappear dorsad to the lobi hippocampi, and will be 
 traced to their destination in a subsequent dissection. 
 
 Immediately behind the chiasma opticum is a projection 
 of substantia grisea, the infundihulum, which connects with 
 the hypophysis (pituitary body, not shown in Plate VII, 
 but drawn in Plate XIX) , The hypophysis can be liberated 
 from the fossa hypophyseos (sella turcica), when freeing 
 the encephalon from the basis cranii interna, by making an 
 incision through the dura at its attachments to the margins 
 
ANATOMY OF THE BRAIN 
 
 45 
 
 ol: the fossa, then, by gently rupturing the bands of connect- 
 ive tissue that attach the hj'pophysis to the fossa, it can be 
 removed without injury. 
 
 In the centre of the infundibulum is a large opening lead- 
 ing into the ventriculus tertius. The infundibulum appears 
 to rest upon a triangular eminence of substantia grisea, the 
 tiiher cinereum, in the inverted specimen. 
 
 The caudal extremity of the tuber cinereimi presents in 
 most cases an eminence more or less bilobed, called the 
 corpora mamillaria (corpora albicantia, bulbi fornicis). In 
 some instances there is apparently but one corpus mamil- 
 lare, as superficially, in these cases, there is only one emi- 
 nence. 
 
 About two per cent of all the specimens studied show a 
 distinct bilobed corpora mamillaria; quite as marked as 
 that which obtains in the human brain, and in those of the 
 primates. In class work, when a specimen of well-defined 
 bilobed mamillary body is found, it should be shown to 
 each student and then preserved in the neurological 
 laboratory for demonstration purposes. 
 
 In the median line caudad to the corpora mamillaria is 
 a very marked depression, the fossa inter peduncular is 
 (locus perforatus posterior, pons Tarini), at the bottom of 
 which is the substantia perforata posterior. The fossa is 
 bounded on each side by large masses of white matter, the 
 pedunculi cerebri (crura cerebri) composed of fibres which 
 convey impulses to and from the cerebrum. 
 
 Rising from the ventral surface of the pedunculi cerebri 
 and close to their internal border will be seen the N7i. oculo- 
 motorii (third pair of cerebral nerves). Winding cephalad 
 from the dorsal surfaces of the pedunculi will be seen two 
 nerves, much smaller than the Nn. oculomotorii ; these are 
 the Nn. Irochleares (pathetici, fourth pair of nervi eere- 
 brales). Lying between the pedunculi cerebri, close to the 
 cephalic border of the pons, is a small quantity of grey 
 matter, very marked in some cases; this is the nucleus 
 interpeduncularis. 
 
 Tracing the pedunculi cerebri caudad they appear to pass 
 under a thick transverse band of tissue, the pons (Varolii) ; 
 
4'6 ANATOMY OP THE BRAIN 
 
 and at each extremity of the pons is a very large nerve, the 
 N. trigeminus (fifth pair, trifacial). 
 
 Caudad to the pons is another, but somewhat indistinct 
 transverse band of fibres, the trapezium, which in some en- 
 cephala is scarcely perceptible, while in others it is very 
 readily identified. 
 
 Arising from the ventral surface of the trapezium near 
 the middle lino are the Nn. ahducentes (sixth pair) about 
 the size of the Nn. trochleares. 
 
 Coming apparently from the lateral aspect of the tra- 
 pezium are two nerves, about the size of the oculomotorii ; 
 the cephalic nerve is the N. facialis (seventh pair, portia 
 dura) ; the caudal nerve is the N. acusticus (eighth pair, 
 portio mollis). 
 
ANATOMY OP THE BRAIN 47 
 
 CHAPTER XII. 
 
 THE MEDULLA OBLONGATA. 
 
 The medulla oblongata forms the large club-like body 
 directly caudad to the trapezium ; it gradually decreases in 
 size until it reaches the neighborhood of the medulla spin- 
 alis, at the level of the first cervical nerve. At this point 
 the decrease! in size is very abrupt, until it attains the 
 dimensions of the latter structure. The central nervous 
 system is prolonged caudad as the medulla spinalis, a long 
 cylindrical mass of nervous matter which gives off the nervi 
 spinal es. 
 
 From the sides of the medulla oblongata, beginning just 
 caudad to the trapezium there spring the roots of three 
 large nerves, N. glossopharyngeus (ninth pair), N. vagus 
 (tenth pair, par vagum, pneumogastric) and the N. acces- 
 sorius (eleventh pair, spinal accessory). From the ventral 
 surface of the medulla oblongata about 5 mm. from the 
 midline, there arise eight of ten roots, which unite to form 
 the N. Jiypoglossus (twelfth pair). 
 
 If the instructions to cut the nervi cerebrales close to 
 their foramina of exit have been followed, there will be no 
 difficulty in identifying the twelve pairs of cranial nerves 
 just enumerated. 
 
 The encephalon should now be placed under water and 
 the ventral surface carefully cleaned, removing all vessels 
 and the trabeculae subarachnoideales. 
 
 Care must be taken NOT to remove the pia mater in 
 making this dissection, for in so doing the attachments of 
 the filaments, as they emerge to form the nervi cerebrales 
 would be ruptured; thus very materially reducing the 
 value of the preparation. 
 
 One who has removed the medulla spinalis for the first 
 time will surely be impressed with the apparently num- 
 berless nerve filaments that attach the nervi spinales to 
 the cord, parti(!ularly in the case of those that go to njake 
 tlie Cauda equina. This same arrangement obtains on the 
 
48 ANATOMY OF THE BRAIN 
 
 ventral and lateral surfaces of the brain stem. In this 
 connection, note the N. oculomotorius, N. glosso-pharyn- 
 genus, N. vagus, N. accessorius and N. hypoglossus. 
 
 A very beautiful preparation can be made if the work 
 is carefully done, particularly so if the low power of a 
 good dissecting microscope is brought into requisition. 
 Make drawings of the dorsal and lateral surfaces. 
 
ANATOMY OF THE BRAIN 
 
 CHAPTER XIII. 
 
 49 
 
 MESIAL SURFACE OF THE CEREBRUM AND 
 CEREBELLUM. 
 
 FACIES MEDIALB3 CEREBRI. 
 
 [See Plate VIII. ] 
 Gently pull apart the hemispliaeria cerebri until the dor- 
 sal surface of the corpus callosum (a large band of trans- 
 verse fibres uniting the cerebral hemispheres) is seen; place 
 the heel of the brain-knife in the fissura longitudinalis 
 cerebri, resting the edge of the knife on the corpus callo- 
 sum. AVith one sweep of the Imife, cut the encephalou 
 completely through and the facies medialis cerebri is ex- 
 posed. 
 
 This surface is of special interest to the medical student 
 as its general appearance and construction more closely 
 resembles that of the corresponding area of the human 
 encephalon than any other of the regions that have been 
 studied. 
 
 The corpus callosum is the elongated mass of white mat- 
 ter lying about the centre of the exposed surface and pass- 
 ing cephalo-ventrad. The cephalic extremity, the genu 
 corporis callosi (knee), approaches to within about 2 cm. 
 of the polus frontalis, then bending ventrad and caudad 
 ends in the rostrum corporis callosi. The caudal extremity 
 ends in a blunt club-like enlai-gement, called the splenium 
 corporis callosi. 
 
 The mesial surface of the cerebrum very largely sur- 
 rounds the corpus callosum as the central structure, and, 
 like the other surfaces of the cerebrum, is for the most 
 part subdivided by a number of fissures into gyri. The 
 selection of the proper names for the various fissures and 
 gyri expased to view on this surface, caused considerable 
 anxiety; and if proper I'espect has not been paid to the 
 homologies, the censure must be laid to a perhaps excessive 
 desire to pave the way for the student in medicine to grasp 
 
50 ANATOIMY OF THE BRAIN 
 
 the complex arrangement obtaining on the mesial surface 
 of the encephalon of man. The various names have been 
 selected that appear to describe in the clearest and shortest 
 manner the conditions found on the part under considera- 
 tion, and little regard has been paid to their significance 
 from the standpoint of comparative anatomy, with the ex- 
 ception of some few terms selected from the anatomy of 
 the human brain. 
 
 The well marked gyrus lying immediately dorsad to 
 the corpus callosum is the gyrus cinguli. This gyrus ex- 
 tends through the entire length of the corpus callosum, Avith 
 its cephalic extremity turning sharply around the genu 
 corporis callosi, and proceeding caudad, follows the course 
 of the rostrum corporis callosi, and ending on the facies 
 medialis cerebri near its ventral border. 
 
 Frequently the radix medialis bulbi olfactorii can be 
 very distinctly seen passing to the cephalic extremity of 
 this gyrus. The caudal extremity of the gyrus cinguli 
 passes around the splenium corporis callosi and unites 
 with the caudal extremity of the lobus hippocampi.. 
 
 The sulcus corporis callosi lies between the gyrus cinguli 
 and the corpus callosum. 
 
 Dorsal to the gyrus cinguli there is seen a large gyrus 
 intermedins, marked off from the gyrus cinguli by the 
 sulcus cinguli. Occasionally this sulcus is poorly de- 
 veloped or it may be absent dorsal to the caudad third 
 of the corpus callosum, and then the gyrus cinguli and 
 the gyrus intermedins appear to fuse and form one very 
 large convolution which occupies the major portion of 
 the facies medialis, constituting the gyrus fornicatus of 
 comparative anatomists. 
 
 That portion of the gyrus intermedia lying dorsad to 
 the central third of the corpus callosum is usually very 
 wide and in the majority of instances reaches to the dorsal 
 margin of the facies medialis cerebri. 
 
 The gyrus marginalis posterior is separated from the 
 caudal half of the gyrus intermedins by the sulcus sple- 
 nialis (fissura limbiea of Broca) ; this fissure is very con- 
 stant in all mammals, even occurring in the Lissencephala 
 
ANATOMY OF THE BRAIN 51 
 
 (smooth-brained). It can be traced, in abnost all speci- 
 mens, to the dorsal surface of the gyrus frontalis superior 
 as a small fissure or notch, about 4 mm. cephalad to the 
 fissura cruciata ; Figs, a, b, and c and plate IX. The gyrus 
 passes well cephalad in the sheep's brain and ends about 
 the centre of the dorsal margin of the facies medialis. 
 
 The sulcus parolfaclorius lies between the cephalic por- 
 tion of the gyrus intermedins and the corresponding 
 margin of the facies medialis, marking off the gyrus mar- 
 giiialis anterior. In a number of instances the sulcus 
 parolfaetorius is not well developed, but is broken up into 
 numerous straight sulci, having a tangentical relation to 
 the sulcus cinguli. 
 
 The sulcus splenialis, the sulcus cinguli, the sulcus cor- 
 poris callosi and the fissura rhinalis end on the tentorial 
 surface of the hemisphere. 
 
 The facies medialis cerebelli can be nicely seen while 
 studying the corresponding surface of the cerebrum, show- 
 ing the lobes of the vermis cerebelli as indicated in Plate 
 VIII by the letters a, h, c, d, e. This lissection also shows 
 the cut surfaces of those structures that lie ventral to the 
 pallium. 
 
 As before noted, the radix medialis bulbi olfactorii can 
 be seen approaching the gyrus cinguli. About 1 cm. caudad 
 to the tip of the rostrum corporis callosi and a little 
 ventrad, is the commissura anterior composed of substantia 
 alba, cut across. This commissure is easily identified, and 
 can be traced to the corresponding bulbus olfactorius if 
 desired, as shown in Plate XIX. The dissection of the en- 
 tire commissure will be described in a later part of the 
 work. 
 
 Caudad to the eomiiiissure is the pars tecta columnae 
 fornicis, the dissection of which will be described later. 
 
 This will be a convenient place to describe the cephalic 
 and ventral walls of the ventriculus tertius, as formed by 
 the lamina terininalis and the tuber cinereum. If the 
 facies medialis cerebri be carefully examined, an indistinct 
 layer of tis.sue can be demonstrated, extending caudad in 
 a zig-zag manner from the terminal extremity of the 
 
52 
 
 ANATOMY OF THE BRAIN 
 
 rostum corporis eallosi to the comissura anterior. This 
 layer of tissue is called the lamina rostralis, and is semi- 
 diagramatically shown in Fig. D. It is difficult to demon- 
 strate in most specimens. 
 
 FIG. D. 
 
 A. The arrow passing through the foramen interven- 
 triculare (Monroe) accompanying the plexus chorioideus 
 ventrieulari lateralis. 
 
 B. Lamina rostralis. 
 
 C. Lamina terminalis. 
 
 D. Chiasma opticum. 
 
 E. Tuber cinereum. 
 
 F. Recessus infundibuli. 
 
 G. Arrow pointing to the aperatura mediana ventric- 
 uli quarti (Magendie). 
 
 H. Arachnoidea. 
 
 As the lamina rostralis reaches the cephalic border of 
 the commissura anterior, it blends with the dorsal portion 
 of the lamina terminalis {lamina cinerea), a structure of 
 considerable importance. The lamina terminalis is carried 
 almost perpendicularly ventrad to the region of the 
 chiasma opticum, passing some little distance cephalad to 
 the chiasma. It is then reflected backward, attached closely 
 
ANATOMY OF THE BRAIN 53 
 
 to the ventral and caudal surfaces of the chiasma, forming 
 a little cavity or diverticulum called the recessus opticus 
 ventriculi tertii. 
 
 After the lamina leaves the chiasma it is continued 
 caudo-ventrad as the tuber cinerea to reach the corpus 
 maraillare. The tuber cinerea dips ventrad, carrying with 
 it a diverticulum from the ventriculus tertius called the 
 recessus infundibuli, to reach the hypophysis as it lies in 
 the fossa hypophyseos. The portion of nerve tissue that 
 passes ventrad to reach the hypophysis is the infundib- 
 ulum; it, together with the tuber forms part of the floor 
 of the ventriculus tertius. 
 
 Ventral to the splenium corporis callosi rests the caudal 
 extremity of the fornix and beneath this, the fasciola cin- 
 erea; beneath the fasciola is the central portion of the fis- 
 sura transversa cerebri, containing the pia and the V. 
 magna cerebri. 
 
 Just ventrad to the fissura transversa cerebri are two 
 small structures, the trigona hahenulae and caudad to this 
 the corpus pineale ; ventrad from this latter structure is 
 the lamina pineale. 
 
 Directly caudad to the corpus pineale are two pairs of 
 bodies of unequal size, the corpora quadrigemina, resting 
 on the lamina quadrigemina, cephalad to which is seen very 
 indistinctly the commissura posterior. 
 
 Ventral to the lamina is a canal leading from the ven- 
 triculus tertius to the ventriculus quartns; this is the 
 aquaeductus cerebri (aqueduct of Sylvius, iter a tertio ad 
 quartum ventriculum). 
 
 Filling in the space which separates the commissura an- 
 terior from the commissura posterior is a large round sur- 
 face of substantia grisea, the mesial surface of the thalamus 
 opticus of the corresponding hemisphere. This structure 
 forms a considerable portion of the lateral wall of the 
 ventriculus tertius. A small quantity of the substantia 
 grisea of one thalamus stretches across the cavity of the 
 ventriculus tertiu.s and is attached to a corresponding por- 
 tion of the opposite thalamus forming the massa intermedia 
 
54 ANxVTOMY OF THE BRAIN 
 
 (commissura medialis) ; the cut surface of the massa is 
 almost circular in outline and about 1 cm. in diameter. 
 
 Posterior to the corpora quadrigemina and the pallium 
 is seen the cut surface of the vermis cerebelli showing the 
 arrangement of the substantia alba and the substantia 
 grisea called the, arhor vitae. The central portion, con- 
 sisting of substantia alba, has been named the corpus 
 medullare cerebelli. 
 
 Connecting the corpora quadrigemina with the corpus 
 medullare cerebelli is a delicate layer of tissue, the velum 
 medullare anterior (tegmentum ventriculi quarti, superior 
 medullary velum, valve of Vieussens). 
 
 The ventricidus quartus is a large space lying ventrad 
 to the velum medullare anterior and the cerebellum. 
 
 Leading from the caudal extremity of the ventricle will 
 be seen a small opening the canalis centralis of the medulla 
 spinalis ; this canal is sometimes called the ventriculus me- 
 dullae spinalis, and it extends throughout the entire length 
 of the cord. 
 
 Lying ventrad to the ventriculus quartus are the follow- 
 ing structures cut sagittally, in order cephalo-caudad ; cau- 
 dalic extremity of the pendunculus cerebri, together with 
 the pons, and the medulla oblongata. 
 
 The structures enumerated as pertaining to the facies 
 medialis cerebri must be identified and a drawing made 
 that will embrace all of them. A comparison with the cor- 
 responding surface of the human encephalon should also 
 be made. 
 
ANATOMY OF THE BRAIN 
 
 CHAPTER XIV. 
 
 55 
 
 CEREBRAL SUBSTANCE AND THE CORPUS CAL- 
 
 LOSTOI. 
 
 The internal architecture of the encephalon of the sheep 
 in a large number of parts is surprisingly similar to the 
 encephalon of man. 
 
 Make an horizontal section across both hemisphaeria 
 cerebri on a level with the highest point of the vermis 
 cerebelli. A very beautiful arrangement of the substantia 
 alba and the substantia grisea is presented and illustrated 
 in Plate X. 
 
 The depth to which some of the fissures and sulci sink 
 into the substantia hemisphaeria cerebri should be care- 
 fully noted, as well as the thickness of the substantia 
 grisea which is quite uniform throughout. 
 
 Study the fissura cerebri lateralis, the fissure coronalis, 
 and the sulcus splenialis which runs in an irregular man- 
 ner well cephalad into the lobus frontalis, almost parallel 
 with the fissura longitudinalis cerebri. 
 
 Examine also the long band of substantia alba that runs 
 from the lobus frontalis to the polus occipitalis; this 
 band is very irregular in outline, and becomes larger as 
 it passes caudad. This appearance is formed by cutting 
 oft' transversely the ventral layer of fibres of the corpus 
 callosum and a large number of fibres of the corona 
 radiata. These two structures will be again referred to. 
 
 Owing to these gyri and sulci the total quantity of the 
 cortex is nuich greater than that appearing on the surface. 
 It will also be noticed that leading into each gyrus there 
 is a band of substantia alba. This substantia alba consists 
 of medullated nerve fibres that carry impulses to and from 
 the cortical cells which lie in the substantia grisea. 
 
 Take one of the portions of the cerebral substance that 
 has been cut off and tear through the exposed substantia 
 alba toward the convexity of the gyrus, and the white sub- 
 stance will split in the direction in which the fibres run. 
 
• 56 ANATOMY OF THE BRAIN 
 
 This shows very plainly how the nerve fibres, as they en- 
 ter a gyrus, are distributed to its cortex. 
 
 In the further dissection of the eneephalon, frequent use 
 of this tearing process should be made for the purpose of 
 showing the direction taken, or the ultimate termination 
 of many definite strands of fibres, where the scalpel would 
 imperil the success of the dissection. 
 
 When a drawing of the horizontal section has been 
 made, the fissura longitudinalis cerebri should b^ gently 
 opened. At its cephalic extremity, the fissure will be seen 
 to pass completely through between the hemisphaeria 
 cerebri to the ventral surface of the eneephalon; likewise, 
 at the caudal extremity, the fissure will pass completely 
 through the cerebrum. 
 
 In the central portion, however, the fissure is interrupted 
 by a very large band of transverse fibres of substantia 
 alba, already mentioned, called the corpus callosum. A 
 section of this structure has been noticed on the facies 
 medialis encephali. The corpus callosum is the great 
 commissure of the cerebrum. 
 
 Tear away as carefully as possible the gyrusi cinguli, ly- 
 ing dorsad to the corpus callosum and examine its exposed 
 surface (Plates VIII, XI, XII, XIII). The transverse di- 
 rection of its fibres can be clearly seen after the gyri cinguli 
 have been removed, yet all the fibres do not run trans- 
 versely; for in the centre of the corpus callosum, passing 
 in a sagittal direction will be observed two strands, the 
 striae longitudinales mediales (nerves of Lancisi). 
 - Between these longitudinal striations is a very distinct 
 furrow running parallel with them called the raphe. Ex- 
 ternal to the stria longitudinalis medialis on either side, 
 there is another striation, the stria longitudinalis lateralis 
 lying directly ventral to the gyrus cinguli. This latter 
 stria fades out before reaching the genu corporis callosi, 
 and on its backward extension fuses with the caudal ex- 
 tremity of the lobus hippocampi. The stria longitudinalis 
 medialis can be traced cephalad around the genu corporis 
 callosi to the crura corporis callosi; traced caudad they 
 pass over to the ventral surface of the splenium corporis 
 
ANATOMY OF THE BRAIN 57 
 
 callosi and become continuous with the fascia dentata by 
 way of the fasciol« einerea. 
 
 In the central portion of the corpus callosmn, its fibres 
 assume the transverse direction, but as they proceed laterad 
 they diverge quite acutely and form what is called the 
 radiaUo corporis callosi. Those fibres constituting the 
 genu, and many adjacent fibres, bend in a latero-cephalad 
 direction toward the polus frontalis forming what is called 
 the forceps anterior or minor, which together constitute 
 about three-fifths of a circle. 
 
 The fibres of the rostrum radiate ventrad and are di- 
 rected toward the corresponding border of the faeies 
 medialis of the lobus frontalis. The fibres constituting the 
 splenium (Plates XI and XII) take a curved caudad di- 
 rection to reach the polus occipitalis, forming the forceps 
 posterior or major, following very closely the radiating 
 distribution assumed by the fibres of the genu in the lobus 
 frontalis; some fibres of the corpus callosum are seen 
 to pass dorsally to the lateral side of the cornu posterius 
 ventriculi lateralis, and then proceed cephalad to the ex- 
 tremity of the lobus hippocampi as shown in Plates XII 
 and XVI. This arrangement appears to be similar on 
 the two sides, though it is somewhat difficult to follow. 
 The direction of these various bands of fibres of the corpus 
 callosum can be demonstrated by tearing in the direction 
 in which they run. Trace carefully, and describe the ar- 
 rangement of the fibres of the genu and the rostrum by 
 drawings. 
 
 The tapetum is a layer of tissue forming the roof of the 
 cornu inferius ventriculi lateralis, and the cornu posterius 
 ventriculi lateralis when present. It is derived from the 
 corpus callosum, and is described in the human encephalon. 
 In the angle where the gyrus cinguli fuses with the ven- 
 tral surface of the corpus callosum, will be found a longi- 
 tudinal band of association fibres, called the cimjulum 
 superius (cingulum, a girdle). 
 
 This cingulum lies within the cortex, dorsal to the corpus 
 callosum and can be easily distinguished from the stria 
 longitudinalis lateralis; it is most readily found where the 
 
58 ANATOMY OF THE BRAIN 
 
 gyrus cinguli meets the corpus callosum. This tract is 
 quite narrow where it rests upon the (Corpus callosum, but 
 increases in size as it passes cephalad and caudad. Traced 
 cephalad it spreads out like an open fan, and, following 
 the fibres of the genu, is distributed to the region of the 
 apex of the lobus frontalis. Following the tract caudad, 
 it can be traced around the caudal border of the splenium, 
 passing ventrad, and then cephalad to end apparently in 
 the substantia alba of the lobus hippocampi. 
 
 The strand should be dissected out before completing 
 the study of the fibres of the splenium, the fibres of which 
 tear very nicely to their termination in the cortex of the 
 gyri at the caudal extremity of the pallium. 
 
 A drawing is to be made showing the general shape of 
 the corpus callosum, with the central longitudinal fibres ; 
 the drawing to likewise show on one side the lateral fibres, 
 and on the opposite side the cingulum superius. 
 
 Make a sagittal incision through the cephalic two-thirds 
 of the corpus callosum just to one side of the stria longi- 
 tudinalis medialis; the knife will be found to enter a large 
 cavity, the ventriculus lateralis (Plate XIII). The corpus 
 callosum will be seen to form the roof of this portion of 
 the ventricle. The genu corporis callosi, and the rostrum 
 corporis callosi as they turn ventrad and caudad, form 
 respectively the cephalic boundary and the extreme cephalic 
 portion of the floor of the ventricle. A portion of this 
 arrangement is shown in Plate VIII. 
 
 Pull away in an outward direction the cut fibres of the 
 corpus callosum, and expose the cavity of the ventricle. 
 At the outer angle of the ventricle, and attached to the 
 ventral surface of the corpus callosum, is another band of 
 longitudinal fibres called the fasciculus suhcallosus (cingu- 
 lum inferius). 
 
 The fasciculus subcallosus (Plates XII and XVI) is 
 very distinct from any of the other structures found in the 
 ventriculus lateralis. The fibres of this fasciculus, more- 
 over, are very closely attached to the ventral surface of 
 the corpus callosum, but the fibres of the two structures 
 do not in any way intermingle. 
 
ANATOMY OF THE BRAIN 59 
 
 The structure is exposed by very o^ently elevating the 
 fibres of the corpus callosum with a pair of bhmt pointed 
 forceps; this operation had better be commenced in the 
 region of the caudal extremity of the ventricle, where the 
 fasciculus is quite distinct and well developed. This fascic- 
 ulus begins at the cornu anterius ventriculi lateralis as a 
 very slender band of substantia alba, which in some in- 
 stances can with difficulty be traced — attached to the 
 nucleus caudatus— cephalad and ventrad to the substantia 
 perforata anterior ; or it may run into the radix olf actorius 
 intermedia. 
 
 An earnest effort should be made to accomplish this 
 dissection, as some variation in the cephalic termination of 
 the fasciculus subcallosus may be ascertained. As the fascic- 
 ulus is traced caudad it becomes wider and thicker, form- 
 ing a very graceful band having the shape of the italic 
 letter /; passing dorsad to the caudal extremity of the 
 corpus striatum, the plexus chorioideus ventriculi lateralis, 
 the hippocampus, and the dorsal portion of the cornu in- 
 lerius ventriculi lateralis. Traced farther caudad, it 
 passes between the fibres of the splenium, and those of the 
 cingulum superius, and finally spreads out in a radiating 
 manner to be distributed to the caudal extremity of the 
 pallium. 
 
 Particular attention must be given to the manner in 
 which the caudal extremities of the cingulum superior, 
 the splenium, and the fasciculus subcallosus are related to 
 each other. The fasciculus subcallosus forms a very small 
 portion of the roof of the ventriculus lateralis along its 
 lateral aspect; and as it passes cephalad it winds around 
 the nucleus caudatus. Traced caudad it forms more of 
 the roof of the ventricle and when it arches over the cornu 
 inferius ventriculi lateralis it is quite wide and easily 
 identified. 
 
 The ventral surface of the fasciculus subcallosus is cov- 
 ered by the ependyma which lines the general ventricular 
 cavity of the encephalon, while its dorsal surface is in con- 
 tact with the substance of the corpus callosum, and the 
 substantia filba of the overlying pallium. 
 
60 ANATOMY OF THE BRAIN 
 
 The cinguluin superior and the fasciculus subcallosus, 
 are structures that may be called association bundles, be- 
 cause they connect different regions of the same hemi- 
 sphere. Some of these bundles are quite long, connect- 
 ing for example, the polus anticus with the polus posticus ; 
 while other bundles may be very short, connecting contigu- 
 ous gyri. These association bundles contain both cortici- 
 fugal and corticipetal axones. 
 
 Make another incision in the corpus callosum, parallel 
 to that already made, exposing the one ventricle and 2 mm. 
 to the opposite side, leaving a small strip of corpus callosum 
 in the middle line; carefully reflect the corpus callosum 
 just cut through, from over the remaining ventriculus 
 lateralis, and the two ventricles will be clearly exposed to 
 view. Now proceed to open the whole of the body of the 
 ventricle, by removing the remaining portions of the corpus 
 callosum except the central sagittal strip, the genu, and 
 above 4 mm. of the splenium. 
 
ANATOMY OF THE BRAIN 61 
 
 CHAPTER XV. 
 
 THE LATERAL VENTRICLES. 
 
 The ventriculi laterales (Plates XIII, XIV, XV, XVI, 
 XVII, XXVI fig. 2, XXVII, and XXVIII figs. 1 and 2) 
 are two symmetrically arranged cavities, one for each 
 hemisphferium. These ventricles are large irregular cavi- 
 ties lined -with ependyma. a species of epithelimn derived 
 from the original cell layer of the embryonic neural tube. 
 This epend%nna lines all the ventricles of the eneephalon 
 and is reflected over the pia mater and the plexus chor- 
 ioideus that lie in these cavities, and, at the caudal ex- 
 tremity of the ventriculus quartus. it becomes continuous 
 with the ependyma lining the canalis centralis of the 
 medulla spinalis. 
 
 Each ventriculus lateralis is about 3 cm. long, 8 mm. 
 wide, and about 6 mm. at its greatest depth. The roof is 
 formed principally by the transverse fibres of the corpus 
 eallosum : the fasciculus subeallosus. however, as previously 
 stated, enters in a small measure into the formation of the 
 roof of the ventricle at its caudo-lateral portion. Its 
 cephalic wall is formed by the genu. The mesial portion 
 of the caudal extremity of the ventricle in the middle line 
 is lost in the angle formed by the union of the fornix with 
 the corpus eallosum. while the lateral portion is carried 
 ventro-laterad as the cornu inferius ventriculi lateralis. 
 
 The floor of the ventricle is very irregular and is formed 
 by the following structures: Caput nuclei caudaii, plexus 
 chorioideus veniricidi lateralis, corpus fornicis, and hip- 
 pocampus. 
 
 Filling in the concavity of the genu corporis callosi, is 
 a thin membrane, the septum pellucidum, which separates 
 the two ventriculi laterales toward their cephalic extremi- 
 ties. The septum pellucidum is thin and translucent, and 
 extends from the inner concave surface of the corpus cal- 
 lorum to the columnae fornicis anterior es. 
 
 In an occasional specimen the two layers which go to 
 
62 ANATOMY OF THE BRAIN 
 
 make the septum pelliicidum, can be demonstrated, with 
 a very narroAv space intervening; the so-called fifth ven- 
 tricle or pseudocode. This cavum septi pelludici is located 
 in the cephalic part of the septum close to the colulnnae 
 fornicis. A small vessel can be seen in this cavity, which is 
 derived from the vessels on the ventral surface of the 
 encephalon. 
 
 In most instances, however, the septum is so thin that 
 it appears to consist only of the double layer of the epen- 
 dyma. In} several specimens, however, the ventral part 
 of the septum pellucidum could be seen to consist of two 
 layers of tissue, between which was a very narrow slit-like 
 space, that extended for some distance caudad. 
 
 Leading from the main cavity of each ventriculus later- 
 alis are two quite large prolongations called the cornua. 
 
 The cornu anterius ventriculi lateralis projects ceph- 
 alad, ventrad, and somewhat laterad around the cephalic 
 extremity of the caput nuclei caudati to its ventral ex- 
 tremity, where, turning sharply cephalad, it enters the 
 tractus, and passes thence to the bulbus oifactorius to form 
 the ventriculus hulhi olfactorii. 
 
 The cornu inferius ventriculi lateralis is in reality the 
 continuation, ventrad and cephalad, of the caudo-laterad 
 extremity of the ventricle. This cornu toward its termina- 
 tion bends mediad, and terminates opposite a point on the 
 ventral surface of the encephalon where the tractus opticus 
 passes dorsad to the lobus hippocampi. 
 
 Passing into this cornu are seen the hippocampus, fim- 
 bria hippocampi (tania hippocampi), fascia dentata, and 
 the plexus chorioideus ventriculi lateralis (Plate XVI). 
 
 The portion of the encephalon forming the outer wall of 
 the descending cornu should be removed from one side, 
 exposing the entire cavity and its contents, care being 
 taken not to disturb the hippocampus and the plexus. 
 
 At the caudal extremity of the ventriculus lateralis, 
 where the hippocampus takes a sharp turn ventrad, there 
 can be seen in most instances, a shallow cavity pointing 
 caudad; this depression is, in all probability, a poorly de- 
 
ANATOMY OF THE BRAIN 63 
 
 veloped coruu posterius ventriculi lateralis, so well de- 
 veloped in the human eneephalon. 
 
 In the further consideration of the ventrieulus lateralis, 
 it would be well to study the structures lying in, or form- 
 ing the floor of the cavity. 
 
 The intraventricular portion of the corpus striatum 
 called the nucleus caudatus, is the large pear-shaped pro- 
 jection more readily seen in the cephalic extremity of the 
 cavity. It is composed of substantia grisea covered by the 
 ependyma lining of the ventricle. Over its convex surface 
 are seen quite a number of large veins that meet near the 
 union of the middle and caudal thirds of its inner border, 
 forming one large vena terminalis, into which empties the 
 V. chorioidea. 
 
 The V. terminalis leaves the ventrieulus lateralis through 
 the foramen interventriculare (foramen of Monro, porta) 
 (Plates XIII, XIV, XV and Fig D), and enters the ven- 
 trieulus tertius where it becomes the V. cerehri interna. 
 
 The further course of this vein will be followed when 
 the structures of the ventrieulus tertius are considered. 
 
 The internal arrangement and relationships of the struc- 
 tures forming the corpus striatum will be exposed and 
 studied after the other prominent features of the ventrie- 
 ulus lateralis have been considered. 
 
 At the point Avhere the V, terminalis dips ventrad to 
 reach the foramen interventriculare will be seen a tri- 
 angular space called the recessus triangularis ; this space 
 is very apparent if the corpus fornicis and the nucleus 
 caudatus be slightly separated. 
 
 Lying against the caudal two-thirds of the internal sur- 
 face of the nucleus caudatus is the plexns ckorioideus ven- 
 triculi lateralis, a very dense vascular fringe formed on 
 the margin of that portion of pia mater which pushes 
 the very thin wall of the ventricle before it during devel- 
 opment, and finally occupies the fissura transversa. On 
 superficial examination this plexus appears to lie within 
 the ventricular cavity of the eneephalon though morpho- 
 logically it is outside of it. 
 
 This process of pia as it rests over the third ventricle is 
 
64 ANATOMY OF THE BRAIN 
 
 called the tela chorioidea ventriculi tertii (velum inter- 
 positum). 
 
 The plexus ehorioideus ventriculi lateralis, traced 
 cephalad, apparently leaves the ventriculus lateralis pass- 
 ing into the ventriculus tertius by way of the foramen 
 interventriculare ; then proceeding caudad on the ventral 
 surface of the tela, it forms the plexus ehorioideus ven- 
 triculi tertii. 
 
 Now note particularly, that at every point in its course, 
 the plexus ehorioideus is always covered by the thin ven- 
 tricular wall which is not visible to the naked eye, and al- 
 ways morphologically outside of both the foramen inter- 
 ventriculare and the ventricle. 
 
 Reflect the sagittal strip of corpus callosum remaining 
 after exposing the ventriculi laterales, and the fornix will 
 be seen; in removing this strip, do not in any way molest 
 the genu. The septum pellucidum can now be very nicely 
 seen (Plate XIV), stretching between the genu corporis 
 callosi and the columnae f ornicis ; examine the septum care- 
 fully at this stage and see if two laminas can be demon- 
 strated. Tracing the plexus ehorioideus ventriculi lateralis 
 caudad and laterad, it will be seen to pass ventrad, accom- 
 panying the cornu inferius ventriculi lateralis and follow- 
 ing the concave border of the hippocampus almost to the 
 extremity of the cornu. 
 
 The plexus receives its arterial supply from the ramus 
 posticus of the A. cerebri propria and from the A. cerebri 
 posterior. 
 
ANATOMY OF THE BRAIN 65 
 
 CHAPTER XVI. 
 
 THE FORNIX. 
 
 The corpus fornicis (L., fornix, an arch) (Plates XIII, 
 XIV, XVI, XX, XXVII) is a large body of substantia 
 alba, triangular in shape, and attached to the ventral sur- 
 face of the caudal half of the corpus callosum. 
 
 Stretching along either side of the fornix is tho plexus 
 chorioideus ventriculi lateralis. 
 
 At its cephalic extremity the fornix is continued as two 
 large cords of tissue called the columnae fornicis which 
 dip ventrad and then caudad to end in the corpora mamil- 
 laria, as shown in Plate XX. 
 
 The course of these columnae will be shown when work- 
 ing out the structures on the facies medialis cerebri. 
 
 The central portion of the corpus fornicis runs caudad 
 between the dorsal extremities of the hippocampi, forming 
 the commissura hippocampi. Some fibres at the cephalic 
 extremity of the commissura hippocampi run in a sagittal 
 direction, filling in the angle formed by the diverging crura 
 fornicis posterioria (posterior pillars of the fornix) as they 
 approach the hippocampi. These sagittal fibres, on reach- 
 ing the caudal border of the splenium, divide into two 
 bundles, one proceeding toward each polus occipitalis cere- 
 bri. 
 
 Pick up some of these mesial sagittal fibres of the fornix 
 and tracing them caudad, they will be seen to diverge, and 
 run with the transverse fibres of the splenium. 
 
 No little difficulty will be experienced in tracing the 
 fibres of the various fasciculi of the fornix even if great 
 care is exercised in making the dissection. Furthermore, 
 some fibres will be found to unite with the substantia alba 
 of the hippocampi. 
 
 The marginal strands pass latero-caudad to reach the 
 concave borders of the hippocampi, where they are called 
 the fimhria hippocampi CfOJ'pus fimbriatum, taenia hip- 
 pocampi), along which they can be traced almost to the 
 
66 ANATOMY OF THE BRAIN 
 
 extremity of the ventricle (Plates XIV, XVI, XXVIII). 
 As each timbria runs into the cornu inferius ventriculi 
 lateralis, it gradually diminishes in size and is finally lost 
 on the free concave border of the hippocampus. 
 
 The student should take ample time to study the rela- 
 tionship of the fornix to the surrounding structures, as 
 well as its attachments with the hippocampi and the cor- 
 pora mamillaria. Note the exact position of the columnae 
 fornicis in their relations to the commissura anterior, the 
 ventriculus tertius, the foramen interventriculare and the 
 ventriculi laterales. 
 
 The continuity of the columnae fornicis with the cor- 
 pora mamillaria will be worked out in a later dissection. 
 
 Make special note of the relative position of the fol- 
 lowing structures; corpus callosum, fornix and velum 
 interpositum, and their proximity to the ventricles. 
 
ANATO]\IY OF THE BRAIN 67 
 
 CHAPTER XVII. 
 
 THE HIPPOCAMPUS. 
 (Plates XIII, XIV, XVI, XXI, XXII, XXVIII) 
 
 The hippocampus is a large curved cylindrical body 
 formed by the fissura defitata (Plate XVII) projecting 
 into the caudal portion of the ventriculus lateralis and 
 its cornu inf erius ; it begins in the caudal third of the floor 
 of the ventricle, and at once passes into the cornu. Its 
 direction at its beginning is latero-caudad, but it changes 
 its course very abruptly and dips into the cornu inferius al- 
 most vertically ; toward its termination it changes its course 
 again, running in a cephalo-mediad direction, and ends at 
 the extremity of the cornu inferius ventriculi lateralis, at 
 about the cephalic pole of the lobus hippocampi. 
 
 The substantia grisea of the lobus hippocampi can now 
 be traced around the ventro-mesial border of the lobe to its 
 inner surface. 
 
 At this stage of the dissection make a transverse incision 
 through the cephalic extremity of the corpus fornicis just 
 at the dorsal end of the forajiien interventriculare. Make 
 another incision through the tractus olfactorius where it 
 joins the lobus hippocampi using the side of the eneephalon 
 where the external wall of the cornu inferius has already 
 been removed in a previous stage. Now proceed to ele- 
 vate the corpus fornicis and the hippocampus which is 
 cut loose from its tractus olfactorius, avoiding injury to 
 the delicate tela chorioidea ventriculi tertii, and its plexus. 
 
 The tela will be seen to pass laterad, ventrad and 
 cephalad, and rests in the fissura transversa cerebri. This 
 fissure will be seen between the following structures, viz., 
 the fornix, splenium and hippocampus dorsad and laterad, 
 and the corpora quadrigemina, pendunculi cerebri and the 
 thalami, ventrad and mesiad. The fissure is horseshoe- 
 shaped and lies in a plane which cuts the horizontal at 
 about 70°. 
 
 As previously staterl, the pia mater invaginates the cavity 
 
68 ANATOMY OF THE BEAIN 
 
 of the encephalon through the flssura transversa cerebri 
 where it forms the tela chorioidea ventriculi tertii. Care 
 should be exercised so that the" location and relations of this 
 fissure are clearly understood. If the thin wall of the 
 encephalon, which is pushed into the ventricular cavity 
 during development, were visible, there would be little 
 difficulty in understanding the true relationship of the 
 various structures in this neighborhood ; and how it is that 
 the choroid plexus is not inside the cavity of the ventricles, 
 nor the foramen interventriculare a true foramen nor the 
 fissura transversa a true fissure, in the sense that they open 
 into the ventricular cavities. 
 
 In turning again to the substantia grisea of the lobus 
 olfactorius (hippocampi) it will be seen to pass to the con- 
 cave surface of the hippocampus where the fissura hippo- 
 campi (fissura dentata) lies parallel to the margin of the 
 fimbria hippocampi; the fold of substantia grisea lying be- 
 tween the fissura hippocampi and the fimjbia is the fascia 
 dentata hippocampi (Plates XVII, XXVIII, figs. 1 and 2). 
 
 The substantia grisea which surrounds the fissura hippo- 
 campi can be traced dorsad, mediad and cephalad where it 
 finally ends in the fasciola cinerea. (Plates VIII, XVIII, 
 XXVIII, fig. 1) close to the middle line where only a nar- 
 row slit separates it from the fasciola of the opposite hip- 
 pocampus. The fissura hippocampi can be distinctly traced 
 to, and around the dorsal extremity of the fasciola to its 
 mesial surface where it ends. Each fasciola is thus divided 
 into a dorsal part continuous with the fascia dentata, and 
 a ventral part continuous with the substantia grisea of the 
 hippocampus. None of the fibres of the fimbria can be 
 traced to the ventral portion of the fasciola. Pick up some 
 of the fibres of the ventral surface of the fornix, and many 
 can be traced very nicely, to the fasciola cinerea and the 
 substantia grisea of the fascia dentata; while the fibres of 
 the fimbria hippocampi are distinctly distributed to the 
 fascia dentata only. 
 
 Turn the severed hippocampus over to the opposite side 
 together with the fornix ; this will expose the tela chorioidea 
 
ANATOMY OF THE BRAIN 69 
 
 ventrieiili tertii lying dorsad to the caudal half of the ven- 
 triculus tertiiis. 
 
 At the cephalic extremity "of the tela the Vv. cerebri in- 
 temae unite to form a large central vein, the V. cerebri 
 magna (vein of Galen) (Plates III, XIV) which runs di- 
 rectly caudad to the middle line of the tela, over the corpus 
 pineale, ventral to the central line of the splenium corporis 
 callosi. 
 
 At this point the vein rests in the sulcus separating the 
 fasciolae cinereae, then passing caudad about 1.5 cm. it en- 
 ters the sinus sagittalis as described when studying the 
 sinuses. 
 
 Grasp the cephalic extremity of the V. cerebri magna 
 and pull it and the tela, caudad, in order to expose the ven- 
 tral surface of the tela. On each side of this vein will be 
 seen the plexus chorioideus ventriculi tertii. 
 
 Now replace the vena magna with the tela, and note the 
 following structures. Mediad to the place occupied by the 
 plexus chorioideus ventriculi lateralis on either side, will 
 be found a large oval eminence, the thalamus; between the 
 caudal extremities of the thai ami there lies a small conical 
 body, the corpus pineale (Plates XV and XXVII, fig. 2). 
 Caudad to the thalami and the corpus pineale are four 
 eminences or collieuli called the corpora quadrigennina 
 (Plates XV, XXI, XXIV, and XXV). Reflect the tela 
 from these four bodies and its continuation with the pia 
 that is attached to the outer aspect of the eneephalon can 
 be easily understod. 
 
 The large V. cerebri posterior will be seen in the groove 
 between the thalamus and the corpora quadrigemina ; it 
 runs dorsad and empties into the V. cerebri magna as it lies 
 between the caudal extremities of the hemisphseria cerebri. 
 
 By gently separating the corpus striatum (nucleus cau- 
 datiLs) from the thalamus, the stria temiinalis (taenia semi- 
 circularis) (Plate XVI) will be seen at the bottom of the 
 sulcus separating these two structures. It consists of white 
 fibres that end cephalad in the caput of the corresponding 
 nucleus candatus and caudad they follow the cauda of the 
 nucleus caudatus to its end. 
 
70 ANATOMY OF THE BRAIN 
 
 CHAPTER XVIII. 
 
 THE OPTIC THALAMUS. 
 
 The thalamus opticus (for illustrations see Plate XV) is 
 not seen when the corpus callosum is removed to expose 
 the ventriculus lateralis. In order to see it, the plexus 
 ehorioideus lateralis must be pulled toward the fornix, and 
 the edge of the latter structure somewhat elevated; this 
 maneuver will expose the thalamus very clearly, and show 
 at a glance its relations to the corpus striatum, fornix and 
 plexus ehorioideus. 
 
 In the human encephalon, the thalamub is exposed to 
 view as soon as the corpus callosum is removed. 
 
 At the present stage of the dissection, however, the free 
 surfaces of the thalami are nicely exposed, with the excep- 
 tion of the mesial ; which, however," was identified and 
 briefly described when studying the facies mediaMs cerebri 
 (Plate VIII). 
 
 As can readily be seen, a large pavt of the cephalo-mesial 
 surface of one thalamus is attached to the corresponding 
 part of the mesial surface of the opposite thalamus, form- 
 ing a bridge across the cavity of the ventriculus tertius ; 
 this can be the better seen if a very slight effort, not suf- 
 ficiently violent to rupture the connection, be made to sep- 
 arate the two thalami. This bridge consists of substantia 
 grisea, and is called the massa intermedia, the so-called 
 middle commissure— a misuse of the term commissure. 
 
 Near the mesial border of the dorsal surface of each 
 thalamus will be seen the stria medullaris thalami to be de- 
 scribed later. The thalamus appears to terminate caudad 
 in a large projection or tubercle called the j^ulvinar (tuber- 
 culum thalami posterius). A similar protuberance, though 
 smaller and much less prominent can usually be seen on 
 the cephalic extremity of the thalamus which has been 
 named the tiiherculum thalami anterius, to which can be 
 traced the fasciculus thalamomamillare at its dorsal ex- 
 tremity. 
 
AXATOMY OF THE BRAIX 71 
 
 Just beneath the pulvinar and a little laterad is the cor- 
 pus geniculatum internum. The corpus genicidatum ex- 
 ternum (Plate XXXVIII) will be noticed in close relation 
 with the corpus geniculatum internum lying directly 
 cephalad and a little dorsad, the point of the line (Plate 
 XXI) shows the location of this body which is very in- 
 distinct in fresh specimens. 
 
 In a subsequent dissection, after the structures exposed 
 in Plate XXI have been studied, cut deeply into the tractus 
 opticus and the corpora geniculata at right angles to the 
 surface, the direction of the incision to pass through the 
 tips of the lines G and F. This section will expose the 
 substance of the two geniculate bodies and show them sep- 
 arated by only a very thin layer of substantia alba. This 
 substantia alba appears to form more or less of a capsule 
 that in many instances can be observed to completely sur- 
 round the substantia grisea of the external geniculate 
 bodies. 
 
 Later, the tractus opticus will be traced to the pulvinar. 
 the corpus geniculatum externum and to one of the cephalic 
 pair of the corpora quadrigemina (colliculus superior). We 
 may now revert to a brief consideration of the corpus 
 striatum together with a short study of some of the ar- 
 rangements of the constituents of the thalamus. 
 
 Make a horizontal section through the entire hemi- 
 sphaerium cerebri to which the lobus olfactorius is still at- 
 tached, just dorsad to the sulcus rhinalis, carrying the in- 
 cision to the middle line with one sweep of the brain-knife 
 and study the structures exposed as shown in Plate XVIII. 
 
 The substantia grisea of the nucleus caudatus is easily 
 identified ; external to this is a more or less interrupted band 
 of substantia alba, the capsula interna. 
 
 Beginning at its cephalic extremity this capsule is di- 
 rected mediad and caudad, until it reaches the sulcus lying 
 between the thalamus and the nucleus caudatus; at this 
 point it makes a bend called the ge7iu capsuloE internee and 
 then proceeds laterad and caudad as a dense white band 
 ending finally in the substantia alba of the occipital ex- 
 tremity of the hemisphere. 
 
72 ANATOMY OF THE BRAIN 
 
 That part of the capsule lying- cephalad to the genu is 
 called the pars frontalis (anterior limb), while that portion 
 caudad to the genu is the pars postica (posterior limb). 
 
 Lying directly external to the capsula interna is the 
 nucleus lentiformis (nucleus lenticularis). In many cases 
 this nucleus lentiformis can be seen to be composed of an 
 external dark portion, the putamen, and an internal part, 
 lighter in color, called the globus pallidus. 
 
 External to the nucleus lentiformis is seen a very thin 
 band of substantia alba, the capsula, externa, connecting 
 the substantia alba of the lobus frontalis with the substantia 
 alba of the lobus occipitalis. 
 
 Laterad to the capsula externa is the claustrum (clau- 
 DEBE, to shut), an irregular band of substantia grisea; 
 varying in amount and in some specimens difficult to 
 demonstrate. 
 
 Lying immediately outside the claustrum is the substantia 
 alba, very small in quantity, and the substantia grisea, very 
 considerable in quantity, of the insula. The substantia 
 grisea of the insula is cortical matter, and is directly con- 
 tinuous with the general cortical substance of the ence- 
 phalon. 
 
 The surface lying internal to the pars postica of the 
 capsula interna, is the cut surface of the thalamus, con- 
 sisting of substantia alba and substantia grisea arranged in 
 a very interesting manner as follows: 
 
 The substantia alba is centrally located, shaped like a tri- 
 angle, the sides of which are slightly concave, and which 
 might be called the pars centi^alis thalami. The pars cen- 
 tralis divides the substantia grisea of the thalamus into 
 three distinct areas; the area medialis thalami, the largest 
 of the three portions of the substantia grisea, which lies 
 between the pars centralis thalami and the mesial surface 
 of the thalamus ; the area lateralis thalami is between 
 the pars centralis thalami and the pars postica of the cap- 
 sula interna; the area posterior thalami is located di- 
 rectly caudad to the pars centralis thalami, forming the 
 caudal extremity of the thalamus and enters largely into 
 the formation of the pulvinar. 
 
ANATOMY OF IHE BRAIN 73 
 
 The area posterior thalami is occasionally very plainly 
 divided into two portions of nearly equal size by a sagittally 
 directed process of substantia alba derived from the pars 
 centralis and extending eaudad. 
 
 The arrangement of the substantia alba and the substan- 
 tia grisea just described can be very nicely seen if the en- 
 eephalon be prepai-ed by the Kaiserling method.* 
 
 In this description of the gray and white masses of the 
 thalamus, no attempt is made to homologize them with the 
 several nuclei of the thalamus opticus of man.* (**) 
 
 The instructor should prepare a number of encephala 
 
 *The Kaiserling Method. — A method for "wet preparations" of the central 
 neiTous system for museum and demonstration specimens. It results in a speci- 
 men tough enough to resist much handling, and at the same time one in which 
 both the normal size and especially the color are retained to aj remarkable degree. 
 It is well adapted for pathological specimens, whether of nervous or other tissue. 
 
 Special Reagents Required. 
 
 A. Fixing and hardening fluid — 
 
 Formalin (40 per cent formaldehyde) cc. 200 
 
 Distilled water cc. 1000 
 
 Potassium nitrate (saltpetre) grama 15 
 
 Potassium acetate grams 30 
 
 B. Preserving fluid — - 
 
 Potassium acetate grams 200 
 
 Glycerine cc. 400 
 
 Distilled water cc. 2000 
 
 The formulae as given will result in fluids sufficient in amount for a 
 human brain, provided the vessels used are small enough. 
 
 Procedure. 
 
 1. The brain or spinal cord is removed and placed in a vessel containing 
 enough of the fixing fluid A to cover it well, keeping it in the dark for from 
 six to eight days. 
 
 It Ib advisable to inject about 400 cc. of the fluid through the internal 
 carotid artery before removing the brain, especially if there is reason to be- 
 lieve that post-mortem softening has begun. Do not inject too much, lest 
 the blood, and consequentlv the color, be washed out of the blood-vessels. 
 
 The bottom of the vessel should be padded with absorbent cotton, and 
 during the period of fixation, the position of the specimen, should be changed 
 from time to time to prevent flattening or distortion. 
 
 2. Drain the specimen for 2 or 3 minutes, and place in 95 per cent alco- 
 hol for 5 or hours. 
 
 3. Then place in a glass vessel containing the preserving fluid B, where it 
 will keep indefinitely. 
 
 Even in the preserving fluid it is advised to keep the preparation in the 
 dark as much as possible, since the long exposure to light seems to cause it to 
 lose its natural color. 
 
 When on exhibition or in use for study or demonstration, the preparation 
 may be improved in appearance by placing it in 80 per cent alcohol for the 
 time being. This seems to brighten the color to a certain extent. Too long 
 duration in alcohol, however, will extract the color. 
 
 ThiH process is well adapted for the preparation of specimens for dissec- 
 tion. If dissection is made, it is suggested that it should be delayed until 
 aft«;r the specimen has been in the preserving fluid for about two wccks.^ — 
 "Virchow'B Archiv." Bd. 147, Heft. 3, p. 389. 1897. 
 
 • (**) A very conci.se iiiid dear ilfscripi ion nf (lie hnrnnn th:il:itiuis is givni \>y 
 GuBtav Mann, M. D. Kdin., B. So. Oxon., in The British Medical Journal 
 Feb. 11, 1905. 
 
74 ANATOMY OF THE BRAIN 
 
 by the Kaiserling process and make the necessary dis- 
 section^ to show these structures for verifying the text; 
 as brains prepared simply in formalin occasionally do not 
 show the differentiation, or at best, somewhat indistinctly. 
 
ANATOMY OF THE BRAIN 75 
 
 CHAPTER XIX. 
 
 THE PINEAL BODY. 
 
 The corpus pineale (L. Pinus, a pine-cone, conarium, 
 pineal gland, epiphysis). Descartes considered this struc- 
 ture the seat of the soul. (Plates VIII, XV, XXV, 
 XXVIII, hg. 1.) It is situated in the fossa formed by the 
 eoUiculi superiores and the thai ami. 
 
 The corpus pineale is said to contain neither neuron ele- 
 ments nor nerve fibres. It does contain, however, a vari- 
 able amount of hard, gritty, calcareous grains or particles. 
 Beware of this material if sectioning this oi-gan with a fine 
 microtome knife. 
 
 Beneath the corpus pineale will be observed quite an 
 acute triangular depression which may be called the fossa 
 suhpinealis, the floor of which is formed by the lamina 
 pinealis. Dorsal to the corpus passes the tela chorioidea 
 ventriculi tertii and the V. cerebri magna. It is retained 
 in position by a duplicate of pia, derived from the ventral 
 surface of the tela. It lies dorsal to the commissura pos- 
 terior. 
 
 Leaving the ventral surface of the epiphysis is a layer 
 of substantia alba called the lamma pinealis (Plate XX) 
 which passes caudad, ventral to the commissura posterior 
 and ends in the lamina quadrigemina. 
 
 Passing across the dorsal border of the cephalic surface 
 of the corpus pineale is a short transverse band of tissue, 
 called the commissura liahemdarum (habena, a rein or bit) 
 ending at either extremity in the trigomim liahenutiB. 
 
 The trigonum habenulse is a small depression. It marks 
 the position of a collection of cells called the ganglion 
 kahenulce. Extending from this ganglion, making a grace- 
 ful curve in a caudo-ventral direction to reach the nucleus 
 interpeduncularis, is a large and important bundle of 
 fibres called the fasciculus retrofexus of Meynert. This 
 fasciculus can be traced very easily in a serial section, 
 stained by Pal-Weigert process; see Plate XXXVIII. 
 
76 ANATOMY OF THE BRAIN 
 
 Running cephalad from the trigonum habenulai on either 
 side are the strice medullares thalami (habenulae) ; these 
 striffi pass cephalad, resting on the dorsal border of the 
 mesial aspect of the thalamus, then ventrad until they reach 
 the neighborhood of the foramen interventriculare. Their 
 further course is obscure. Between the trigonum habenula 
 and the lamina pinealis will be seen a small space called tht 
 recessus pinealis ventriculi tertii. 
 
ANATOMY OF THE BRAIN 77 
 
 CHAPTER XX. 
 
 THE ANTERIOR COMMISSURE. 
 
 Press the columnaB fornicis gently cephalad and you will 
 see just in front of them, as they diverge in their course 
 ventrad, toward the ventral part of ventriculus tertius, 
 a large transverse cord of substantia alba, the commissura 
 anterior cerebri (Plate VIII, XVII, XIX, XX, XXVII.) 
 Take a lateral half of the eneephalon and scrape away 
 the substantia grisea of the lobus frontalis in the region of 
 the ventro-raesial border, and that of the nucleus caudatus, 
 taking care not to injure the columnas fornicis, and expose 
 the lateral prolongation of the commissure. 
 
 By keeping to the ventro-niesial border of the commissure 
 as the student proceeds cephalad there Avill be no fear of 
 injuring any important structure in making this dissection. 
 A special dissection is necessary to show the whole of the 
 commissura anterior and to show its relations to the bulbi 
 olfactorii. The requisite dissection can be made before the 
 eneephalon has been cut sagittally, without unduly mutilat- 
 ing the lobi f rontales, as follows . 
 
 After the ventral surface of the brain has been studied 
 and a drawing made, including the chiasma opticum Math 
 its traeti optici and the nervi optici, the search for the com- 
 missura can be undertaken. With a sharp scalpel make an 
 incision through the centre of the chiasma in a coronal direc- 
 tion, as illustrated in Plate XIX. Now proceed with some 
 blunt instrument to scrape away the substantia grisea from 
 the loci perforati anteriores to the extent of 1 cm. on each 
 side of the fissura longitudinalis cerebri, carrying the ex- 
 cavation toward the dorsal surface of the eneephalon until 
 a cord of substantia alba about 2 mm. in diameter is 
 reached ; this is the commissura anterior. The further dis- 
 section is carried on very easily when once this point is 
 reached, for all the student has to do is to clear away the 
 substantia grisea that surrounds the remainder of the struc- 
 
78 ANATOMY OF THE BRAIN 
 
 ture, until it can be clearly traced from one bulbus olfac- 
 torius to the other. 
 
 The commissura is horse-shoe-shaped, with its centre 
 about 1 cm. immediately dorsal to the chiasma optieum, 
 while the limbs run cephalad, parallel to the fissura longi- 
 tudinalis, and enter their respective bulbi olfactorii. 
 
 As far as could be observed from gross dissections, the 
 commissure distributes very few fibres to any structures 
 except the bulbi ; a few, however, appear to radiate to the 
 lobi frontales and the lobi temporales. This arrangement 
 seems to be quite different from that obtaining in the brain 
 of man where the major portion of the commissura anterior 
 is distributed to the lobi temporales, and only a few fibres 
 to the bulbi olfactorii. On no account should the study of 
 this commissure be neglected. 
 
 With a sharp knife cut the columna fornicis, on the 
 mesial surface of a lateral half of an encephalon, at the for- 
 amen interventrieulare, and gently trace it cephalad and 
 ventrad. At the point where the columna approaches to 
 within about .5 cm. of the commissura anterior, it is called 
 the pars libera columnm fornicis as shown in Plate XX. 
 
 When it reaches the level of the commissura it becomes 
 imbedded in a quantity of substantia grisea, where it is 
 called the pars tecta columnce fornicis. The columna is 
 tough and is composed entirely of substantia alba. It 
 passes caudad to the commissura anterior along the mesial 
 border of the thalamus to its ventral surface to reach the 
 corpus mamillare, where it is distributed to the substantia 
 grisea of that body. A very nice dissection of the columna 
 fornicis can be made by simply scraping away the sub- 
 stantia grisea from the mesial surface that covers the col- 
 umna without cutting it. 
 
 From the substantia grisea of the corpus mamillare there 
 rises a cord of white fibres which takes a course cephalad, 
 dorsad and then slightly caudad, ending in the nucleus 
 of the tuberculum anterius thalami, where it appears to 
 end in a dense spray of white fibres that spread out and 
 run caudad and are finally lost in the substance of the 
 thalamus. The strand that connects the corpus mamillare 
 
A.NATOMY OF THE BRAIN 79 
 
 with the thalamus is called the fasciculus thalomomcmiil- 
 laris (tract of Yicq d'Azyr). 
 
 The pars teeta columns fornieis and the fasciculus thala- 
 momaraillaris are quite large and can be readily exposed if 
 the substantia grisea be removed as directed. To show the 
 fasciculus thalamomamillaris the excavation must be car- 
 ried caudad until a large part of the surface of the thala- 
 mus has been removed. In no ease was the fasciculus thala- 
 momamillaris seen to be directly continuous with the pars 
 tecta columns fornieis, in the substance of the corpus 
 raamillare. In making the incision dividing the encephalon 
 into two equal parts, the knife Avill occasionally deviate 
 from the middle line as it approaches the ventral surface, 
 and pass down through the ventral portions of the pars 
 teeta columnae fornieis and fasciculus thalamomamillaris, 
 and thus expose their fibres and make identification easy. 
 
80 I ANATOMY OF THE BRAIN 
 
 CHAPTER XXI. 
 
 THE THIRD VENTRICLE. 
 
 The ventriculus tertius (diacoele) (Plates XV, XXV, 
 XXVII, XXVIII) is a slit-like space in the central region 
 of the encephalon, lying in the sagittal plane. Overlying 
 it is its thin roof of velum interpositum and adherent to 
 this is the tela chorioidea ventriculi tertii. 
 
 In removing the brain from the skull the V. magna 
 cerebri is pulled upon and this in turn pulls in a caudad 
 direction the tela and the plexus, and gives the impression 
 that the ventricle is not entirely covered by this membrane 
 as shown in Plate XIV; this, however, is not the case as 
 the tela covers the ventricle completely. 
 
 The floor of the ventricle is formed by those structures 
 found in the locus interpeduncularis ; the frontal boundary 
 consists of the columnge fornicis, the commissura anterior, 
 lamina terminalis and the caudal extremity of the septum 
 peducidum. 
 
 Examine carefully to see whether the cavity of the ven- 
 triculus tertius extends between the two laminae of the 
 septum pellucidum. 
 
 The caudal wall is formed by the corpus pineale, the 
 lamina pinealis and the cephalic orifice of the aquaeductus 
 cerebri. 
 
 The lateral walls are formed on either side by the thalami 
 and the trigona habenulge. The central part of the ven- 
 tricle is bridged across by the massa intermedia, and at the 
 extreme caudal extremity it is crossed by the commissura 
 posterior. That part of the ventriculus tertius lying cephal- 
 ad to the massa intermedia is occasionally called the aula. 
 The ventriculus tertius communicates with each ventricu- 
 lus lateralis by means of the foramen interventriculare, and 
 with the ventriculus quartus through the aquaeductus cere- 
 bri. (Plate XX.) 
 
 There is a hollow projection composed of substantia 
 grisea protruding ventrad from the floor of the ventricle, 
 
AXATOMY OF THE BRAIN 81 
 
 the infundibiilum. This structure is about 3 mm. in 
 length and 2 mm. in diameter, very friable and invariably 
 injured when any effort is made to remove the hypophysis 
 and at the same time retain its connection with the en- 
 cephalon. 
 
 The hypophysis (pituitary body) rests in the fossa hy- 
 pophyscos (sella turcica), and when the structures are in 
 their normal position it is joined to the encephalon by 
 means of the infundibulum. That portion of the infundib- 
 ulum which remains attached to the encephalon after the 
 removal of the hypophysis can be plainly seen on the 
 ventral surface, Plate VII. 
 
 Reflect the pia mater from one of the thalami and from 
 the ventral surface of the encephalon; then cut off one 
 tractus opticus close to the chiasma opticum, and gradually 
 tease the tractus away from its attachment to the peduncu- 
 lus cerebri, and note its distribution to the pulvinar, col- 
 liculus superior of the corpora quadrigemina, and the cor- 
 pus geniculatum externum. 
 
82 ANATOMY OF THE BRAIN 
 
 CHAPTER XXII. 
 
 THE CORPORA QUADRIGEMINA. 
 
 The corpora quadrigemina (Plates VIII, XV, XXI, 
 XXV and XXXVIII) are four rounded eminences lying 
 between the thalami and the cerebellum. 
 
 The CoLLicuLi SuPERioRES (anterior pair, nates) are two 
 quite large bodies, hemispherical in shape and in the 
 sheep much greater in size than those lying directly ventral 
 called the colliculi inf&riores (posterior pair, testes.)' 
 
 They are exposed by gently separating the cerebrum 
 from the cerebellum. The structure of the colliculi s\j 
 periores is quite complicated and difficult to demonstrate 
 in unstained sections; much patience will therefore be re- 
 quired for their dissection. The cortex of these bodies is 
 about 1 mm. in thickness, is composed largely of substantia 
 grisea, and serves for the termination of a large number 
 of the fibres of the tractus opticus. The deep portions of 
 these colliculi consist mostly of transverse fibres that pass 
 between the colliculi, forming a sharp dip ventrad beneath 
 the sulcus inter-collicularis superior. 
 
 In sections of the mesencephalon of the sheep's brain 
 through the colliculus superior and stained by the Pal- 
 Weigert process and contrasted with Upson's carmine, four 
 stratae can be distinguished with the naked eye. Accord- 
 ing to the description of the human colliculus superior, 
 these layers would be called : 
 
 1. Stratum zonale. 
 
 2. Stratum cinereum. 
 
 3. Stratum opticum. 
 
 4. Stratum lemnisci. 
 
 The stratum opticum is largely composed of modulated 
 fibres from the tractus opticus. If the same section is 
 studied with the low power of a dissecting microscope, at 
 least six distinct layers can be seen lying between the 
 surface of the colliculus and the central grey substance. 
 
 Transverse fibres run laterad and ventrad, and pass be- 
 
ANATOMY OF THE BRAIN 83 
 
 Death the librse poutis superticialis and finally caudad to 
 end in nuclei situated beneath the ventral surface of the 
 caudal extremity of the medulla oblongata. This strand 
 of fibres can be readily teased out if the fibrje pontis super- 
 ficiales have been previously removed. The colliculi su- 
 periores are separated by the sulcus inter-collicularis supe- 
 rior at the bottom of which are found two bundles of 
 white fibres running in the direction of the sulcus, and 
 dorsal to the transverse fibres just referred to ; these sagit- 
 tally directed fibres will be discussed when considering the 
 remaining colliculi. 
 
 The Colliculi Inferiores are much smaller in the 
 sheep than the colliculi superiores and are composed almost 
 wholly of substantia alba. Their relations are very peculiar 
 and interesting ; to each colliculus fibres can be traced from 
 the pars centralis thalami, passing caudad through the 
 sulcus inter-collicularis superior, around the caudal border 
 of the colliculus superior, where they join the substantia 
 grisea which forms the colliculus inferior. From the lateral 
 extremity of the colliculus inferior, fibres constituting the 
 hrachium quadrigeminum inferius (Plate XXIV) can be 
 traced cephalad, resting in the sulcus between the dorsal 
 border of the pedunculus cerebri and the colliculus su- 
 perior; they then take a curved dorso-caudad direction and 
 help to form the caudal portion of the corona radiata, and 
 eventually are distributed to the substantia grisea of the 
 caudal extremity of the hemisphasrium. 
 
 This tract can be clearly seen if the tractus opticus be 
 cut off close to the chiasma, and then carefully raised 
 from the pedunculus cerebri. 
 
 In .stained sections of the colliculi inferiores, the nucleus 
 of each can be clearly seen as a round mass of matter, 
 surrounded by medulated nerve fibres. These fibres are 
 derived from the lemniscus lateralis of both sides of the 
 mesencephalon. Many of the fibres can be traced dorsal 
 to the colliculus inferior and across to the opposite side. 
 
 The fibres of the lemniscus lateralis from the floor of 
 the trij.'-fiiuiii Iciiinisci }is described on page 102 and shown 
 in Plate XXTT. 
 
84 ANATOMY OF THE BRAIN 
 
 CHAPTER XXIII. 
 
 CEREBRAL PEDUNCLES. 
 
 Leading caudacl and ventrad from the hemisphgeria are 
 the pedmiculi cerebri (Plate VII), emerging from the ven- 
 tral surface of the encephalon between the lobi hippocampi. 
 These pedunculi converge as they pass caudad, and meet 
 just before they reach the cephalic border of the pons, 
 where they disappear beneath the fibraB pontis superficiales. 
 On their ventral surface is seen the caudal portion of the 
 circulus arteriosus. From the ventral surface of each pe- 
 dunculus, close to its mesial border will be seen arising the 
 N. oculomotorius, from a well marked groove called the 
 sulcus oculomotorius. Winding around the external border 
 from the dorsal aspect, comes the N. trochlearis. 
 
 The N. oculomotorius in most animals does not emerge 
 from its sulcus as a firm round solid fasciculus, as one 
 would suppose from the illustrations shown in most works 
 on human and comparative anatomy, but is formed by the 
 union o^ a large number of individual fibres similar in 
 manner to the formation of the N. hypoglossus as de- 
 scribed on page 45. 
 
 Passing transversely across the ventral surface of the 
 pedunculus is a very small and generally indistinct band 
 of nerve matter called the tractus peduncularis trans- 
 versus. This tract passes laterad about 3 mm. cephalad to 
 the superficial origin of the N. oculomotorius, until it 
 reaches the sulcus between the corpus geniculatum internum 
 and the colliculus superior and thence in some rare eases 
 can be apparently traced to the trigonum habenulge as de- 
 scribed in a subsequent study of the lateral area of the 
 medulla oblongata. 
 
 On the ventral surface of the pedunculus near its mesial 
 line is also seen a conical bundle of fibres lying in a direc- 
 tion parallel to the general course of the peduncle, with 
 its apex pointing toward the pons. This mass contains the 
 fibres of the tractus pyramidalis. which, traced caudad, 
 
ANATOMY OF THE BRAIN 85 
 
 pass dorsal to the fibrae poutis superficiales, and emerge at 
 the caudal border of the pons as the pyramis ventralis as 
 shown in Plates XXIII, XXX, XXXV, XXXVI, 
 XXXVII. Tracing this mass cephalad it will be seen to 
 form a considerable part of the corona radiata ; this corres- 
 ponds to the genu, and the cephalic part of the pars postiea 
 capsulge internse, on its way to the cerebral cortex. 
 
 The apparently rapid diminution in the size of the 
 tractus pyramidalis as it approaches the pons, is due part- 
 ly to its increased thickness, dorso-ventrally, and in part 
 to the large number of its fibres and collaterals that are 
 distributed to the motor nuclei of the Nn. cerebrales. 
 
 A very simple procedure will show the formation of the 
 corona radiata as shown in Plate XXII. Take the side of 
 the encephalon from which the tractus opticus has been 
 removed, and tear away the lobus hippocampi with that 
 portion of the cerebrum lying immediately ventral to it. 
 
 In order to ascertain the direction and distribution of 
 such fibres as those constituting in part the pyramis ven- 
 tralis, pick up a small bundle and pull or tease them gently, 
 and they will be lifted from their course very distinctly. 
 
 Make an incision passing transversely through the crura 
 at the level of the exit of the N. oculomotorius, which in- 
 cision also passes through the corpus genieulatum internum 
 and the cephalic portion of the colliculus superior, and note 
 the nucleus ruber. 
 
 No tissue resembling the substantia nigra of the pedun- 
 euli cerebri of the human encephalon can be found in 
 the peduncles of the sheep's brain. In contrasted Pal- 
 Weigert sections, groups of small ill-defined cells can be 
 seen ventro-laterad to the nucleus ruber, where the sub- 
 stantia nigra would be looked for, but no pigment, gran- 
 ular or otherwi.se, could be discerned. 
 
 There are some large cells in this locality, resembling 
 those found in the nuflcus ruber, but none of these con- 
 tained pigmctit. 
 
 Consult J'lates XXIX, XXXVIII, ;ind note how the 
 constituent elements after- they emerge from its nucleus, 
 converge to form the N. oculomotfti-ius and the course of the 
 nerve fibrils from the substantia grisea ventral to the 
 
86 ANATOMY OF THE BRAIN 
 
 aquaaductus cerebri ; also that on its way to the mesial sur- 
 face of the crus it passes through a large collection of sub- 
 stantia grisea, the nucleus ruber. 
 
 Note the aquseductus cerebri with a comparatively thick 
 wall of substantia grisea, and that the aqugeduct is not 
 circular. Observe also that the transverse band of sub- 
 stantia alba 2 mm. dorsal to the aqueduct ; this band is 
 composed of the transverse fibres of the colliculus superior. 
 On the lateral border of this section (Plate XXIX, fig. 
 1, Plate XXXyill) will be noticed a slight elevation, 
 which is the corpa geniculatum internum and externum, 
 and ventral to this is a much smaller elevation, very 
 slight in some instances, representing a section of the 
 tractus peduncularis transversus. Dorsal to the corpus 
 geniculatum externum in the same figure is another quite 
 small projection, a section of the brachium quadrigeminum 
 inferius. 
 
 A section of the pedunculi, intermediate between the 
 exit of the N. oculomotorius and the cephalic extremity of 
 the pons is very nicely shown in Plate XXIX, fig. 2, illus- 
 trating the brachia eonjunctivai and the tractus pyramidalis 
 pedunculi as well as the caudal extremity of the aquse- 
 ductus cerebri about which are arranged four bundles of 
 longitudinal fibres. 
 
 Plate XXIX, fig. 3, represents a section immediately 
 cephalad to the pons showing the cephalic extremity of 
 the ventriculus quartus and the various structures enumer- 
 ated in the preceding section. 
 
 These sections are very helpful in making clear the rela- 
 tions of these various tracts, as well as showing clearly the 
 composite nature of the crura cerebri. These sections 
 should be carefully studied and drawings made. Coronal 
 or transverse sections will be found to assist the student 
 greatly in understanding the dissections showing the vari- 
 ous strands and tracts. 
 
 Students should be given stained sections, through the 
 nucleus ruber, showing the nucleus and efferent fibres of 
 the N. oculomotorius. These should be studied and com- 
 pared with the gross preparation, as shown in Plate 
 XXXVIII. 
 
ANATOMV OK TlIK BRAIN 87 
 
 CHAPTEU XXIV. 
 
 jPt 
 
 THE PONS. 
 
 The pons (pons Varolii, cerebellar bridge), Plates XXIII, 
 XXIV, and XXV, is a large band of substantia alba, lying 
 in a coronal plane of the eneephalon. Its greatest longi- 
 tudinal diameter, is a little to each side of the median line 
 where it will average about 1 cm.; at its extremities, just 
 as it is about to enter the cerebellar hemispheres it will 
 measure about 8 mm. The central portion of the pons is 
 marked by a well developed sulcus hasilaris in which rests 
 the A. basilaris. 
 
 At the caudal extremity of this sulcus Avill be observed 
 a small triangular depression, with its apex cephalad oc- 
 cupied by the Aa. eerebelli posteriores. The prominent 
 convexities on either side of the sulcus basilaris mark the 
 location of the pontal nuclei and the tibres of the tracti 
 pyramidales. As the pyramidal tracts pass through the 
 pons they are called the fasciculi longitudinales super- 
 ficiales pontis (pyramidales). and can be plainly seen by 
 making an incision in the course of the sulcus basilaris 
 and reflecting the fibrae pontis superficialis ; sections of 
 these fibra^ are shown in Plate XXX, fig. 1. This dissection, 
 however, should be deferred until the ventral and lateral 
 surfaces of the medulla oblongata have been studied. It 
 will, of course, be noted that the caudal margin of the 
 pons is quite straight while the convexity of the cephalic 
 margin is veiy marked. 
 
 As the pons passes laterad on either side it takes a sharp 
 turn dorsad and passes directly to the hemisphaeria eere- 
 belli forming the hrachia pontis (the middle cerebellar 
 peduncles). Rising from the lateral portions of the pons 
 are the Nn. trigemini which are situated near the caudal 
 margin ; if the nerve be pressed caudad the fibres can be 
 plainly seen passing between the various strands of the 
 fibrae pontis superficiales. 
 
 Examine the nerve clo.sely and it will be seen to consist 
 of two bundles; that placed laterad is sensory and much 
 
88 ANATOMY 01'' THE BRAIN 
 
 larger than the smaller or motor fasciculus placed mediad. 
 The further dissection of this nerve will be undertaken at 
 a later stage. 
 
 Just dorsad to the N. trigeminus is a well developed and 
 distinct mass of cerebellar tissue, the flocculus (Plate 
 XXIII). 
 
 If a specimen be prepared by the Kaiserling method it 
 Avill be well to make some sections through the entire sub- 
 stance of the pons parallel with the transverse fibres. 
 
 This dissection will show quite plainly a deep set of 
 transverse fibres the fibrae pontis profmidae (Plate XXX, 
 fig. 1) about 4 mm. from the ventral surface. These 
 transverse fibres are quite white in color and readily dis- 
 tinguishable from the longitudinal fibres that have the ap- 
 pearance of substantia grisea. The fibrge pontis pro- 
 fundge must not be mistaken for the deep transverse fibres 
 so often mentioned as the trapeziums in works on human 
 anatomy. In Weigert-staiu^d sections of the sheep's brain 
 the fibrae pontis profundae jan be clearly traced to the 
 brachia pontis. 
 
 Besides these two groups there exist a ^"^itral group 
 of longitudinal fibres, the fasciculi lon^^i^ jdintu^venL'^upGi'- 
 ficiales pontis previously mentioned; and the fascicu\ ongi- 
 tudinaies profundis pontis that occupy a minor poicio^ of 
 the dorsal two-thirds of the pons. This fasciculus is ai. ^t 
 2 mm. ventrad to the surface of the eminentia mediaiis 
 and close to the mesial line ; it is often called the fasciculus 
 longitudi^ialis mediaiis; this fasciculus is very distinctly 
 seen when the section is held up to the light. 
 
 If the sectioning be made through the cephalic margin 
 of the pons, the hrachia conjunctiva (superior cerebellar 
 peduncles) are very plainly seen as two pronounced folds 
 of substantia alba at the dorso-lateral borders (Plate XXX, 
 fig. 1). 
 
 In the midline will also be seen a distinct septum divid- 
 ing the white matter of the pons into two symmetrical 
 halves ; this septum is called the raphe pontis. The dorsal 
 concave surface of the pons forms part of the cephalic 
 half of the floor of the ventriculus quartus, and the sharp 
 
ANATOMY OF THE BRAIN 89 
 
 dip 111 the centre of this surface is the sulcus longitudiualis 
 fo«sae rhomboideic, the elevation laterad to this sulcus is 
 the eminentia luedialis; these structures will ]ye further 
 considered in the study of the ventriculus quartus (see 
 Plate XXX, fig. 2). 
 
 If another transverse incision be made at the level of 
 the exit of the N. trigeminus the two transverse fibrous 
 masses will be seen to unite on either side and form the 
 brachium pontis. 
 
 In sections of this region of the encephalon, the large 
 area dorsal to the fibras pontis, has a very irregular con- 
 struction, and to the naked eye, appears to be perfectly 
 homogeneous, except for the fasciculi longitudiualis pro- 
 f undis pontis. This area is the formatio reticularis ; a most 
 beautiful picture in the stained section, and a fascinating 
 hunting ground for the neurologist. 
 
 In this connection students should be given stained trans- 
 verse sections of the pons, to ?piDress upoii them a right 
 idea of the wide distribution ^f tne nuclei pontis. These 
 nuclei are very exte^isive and have always been inade- 
 quately illuvtrated and described in works on human and 
 compPxC t9-e an'Jt-^iny. 
 If 
 
 'V 
 
90 ANATOMY OF THE BRAIN 
 
 CHAPTER XXV. 
 
 THE TRAPEZIUM. 
 
 The trapezium (Plates XXIII, XXX, fig. 3, and Plate 
 XXXVII) is a transverse band of fibres, the borders of 
 which are nearly parallel. It occupies the space between 
 the medulla oblongata and the pons. Its Madth is nearly 
 4 mm. and it extends completely across this portion of the 
 encephalon. 
 
 About midway between its borders and 3 mm. from the 
 middle line will be seen the exit of the N. abducens (sixth 
 pair). At its lateral extremities are two large nerves, the 
 N. facialis and the N. acusticus. The N. facialis (seventh 
 pair, portio dura of Willis) is easily identified and arises 
 superficially, from the cephalic half of the lateral portion 
 of the trapezium. Its appearance is distinctly fibrillar and 
 it passes laterad in a plane parallel with the ventral sur- 
 face of the trapezium after its exit ; the nerve can be readily 
 dissected centrally toAvard its genu (knee) which forms 
 the eminentia facialis situated in the floor of theVentricuIus 
 quartus, if the tissue be carefully cleared away from the 
 lateral side of the nerve. Or, still better, make an incision 
 through the centre of the trapezium parallel with its long 
 diameter or parallel to the caudad border of the brac^hium 
 pontis, thus making a section as shown in Plate XXX, fig. 
 3, and the course of the nerve can be very distinctly seen. 
 
 If the section be fortunately made along the caudal bor- 
 der of the nerve, it can be elevated from the surrounding 
 tissue and traced directly to the genu. In the same section 
 will be shown some fibres of the N. abducens passing ven- 
 trad a few mm. from the middle line. This section also 
 clearly illustrates the large portion of the ventriculus 
 quartus that is occupied by the vermis cerebelli minor, 
 as well as showing the radix ascendens, N. trigemini 
 (tractus spinalis N. trigemini) and the corpus restiforme; 
 the two latter lying laterad to the N. facialis. 
 
 The N. acusticus (eighth pair, portio mollis of Willis) 
 
AXAT():\IY OF THE BRAIX 91 
 
 is seen immGcliately caudad to the N. facialis and it can 
 be traced from the tnberciilnm aeusticnm in the recessus 
 lateralis ventriciili quarti, around the corpus restiforme ly- 
 ing ventrad to the floeciihis. This nerve is very soft and 
 easily torn so that considerable care must be taken in its 
 study or it will be spoiled and the usefulness of the dis- 
 section destroyed. The course of the N. aciLsticus as it 
 winds around the corpus restiforme is clearly displayed in 
 Plates XXIII. XXIV and XXV. An elevation! well 
 marked in most specimens, is seen on each side of the 
 middle line of the trapezium ; this is caused by the pyramis 
 medulla^ oblongata? at the pyramis pa.sses caudad, ventrad 
 to the fibres constituting the trapezium, to reach the 
 medulla oblongata. 
 
 Sections through the trapeziurti, cut in the direction of 
 the long diameter of the nucleus dorsalis N. coclilearis {N. 
 acusticus) and stained by Pal-Weigert process should be 
 supplied to the student for study and drawing. (See 
 Plate XXXVII.) 
 
 Fibres of the N. coclilearis should be traced to the nu- 
 cleus dorsalis N. cochlearis, and from this nucleus other 
 fibres are to be traced into the area acustica of the fourth 
 ventricle, and on toward the sulcus longitudinalis fossae 
 rhomboideje as the stricc medullares (stricc acusticece) . 
 
 Another fasciculus from the X^. coclilearis can be traced 
 into the nucleus ventralis N. cochlearis, which lies just 
 ventrad to the corpus restiforme and from which latter 
 nucleus, fibres can be seen entering the corresponding ex- 
 tremity of the trapezium. 
 
 The A'', vestibularis (N. acusticus) is distinctly seen 
 passing in a dorso-mesial direction, through the substance 
 of the brain-stem, toward the nucleus N. vestibularis which 
 lies toward the floor of the fourth ventricle. This nucleus 
 is sometimes called the "principal vestibular nucleus'' or 
 the nucleus dorsalis N. vestibula/ris. 
 
 Just mediad to the dorsal vestibular nucleus is the I'adix 
 df'seendens N. vestibularia. Scattered amidst these descend- 
 ing fibres are large multipolar cells, easily seen with the 
 dissecting microscope in contrasted sections. Those of 
 
92 ANATOMY OF THE BRAIN 
 
 these cells that lie caudacl in the radix descendens N. ves- 
 tibularis, constitute what is called Deiter's nucleus, while 
 those that are located in the caudal portion of the radix 
 for the nucleus of Bechterew. 
 
 In each lateral half of the trapezium, 5 mm. from the 
 raphe and quite close to the ventral surface, is a circular 
 light area about 1 mm. in diameter, the nucleus olivaB in- 
 ferior; see Plate XXX, XXXI and XXXVII. Immedi- 
 ately laterad to the olive nucleus is another light area, of 
 slightly larger dimensions, containing large multipolar 
 cells, seen in contrasted sections with the dissecting 
 microscope, constituting the nucleus facialis. A wide 
 spray of fibres visible to the naked eye in Pal-Wei- 
 gert sections can be seen converging toward the emi- 
 nentia facialis on the floor of the fourth ventricle, 
 close to the sulcus longitudinalis. These fibres form 
 the pars prima N. facialis (radicular part), and as 
 they reach the floor of the ventricle just dorsad to the 
 nucleus N. ahducentis (Pi te XXXVII), they assume a 
 fascicular form. This fasciculus then passes cephalad for 
 a short distance, lying mediad to u. i nucleus of the abdu- 
 cens nerve forming the genu N. facialis (ascending part). 
 The nerve then turns sharply ventro-laterad to reach the 
 surface ; this is the pars secunda N. facialis or emerging 
 part (fig. 3, Plate XXX). 
 
ANATOMY OP THE BRAIN 93 
 
 CHAI'IER XXVI. 
 
 STRUCTURE OF THE MEDULLA OBLONGATA. 
 VENTRAL SURFACE. 
 
 The medulla oblongata {medulla, marrow; ohlongus, 
 greater in length than in bi-eadth; cerebral protuberance 
 of Goll). The lower extremity is called the "tail or rachi- 
 dian bulb;" bulbns medullae spinalis seu rachidicus; 
 French, bulbe rachidian— Dunglison; see Plates XXIII, 
 XXIV and XXV. 
 
 In order to obtain the best results from a microscopic 
 examination of the encephalon, the specimen should be 
 hardened in a large quantity of a ten per cent solution 
 of formalin for at least a month. Take the specimen from 
 the formalin solution and place it in water for a week or 
 two, changing the water several times; the preparation 
 will then be in the best possiV'^ condition for inspection. 
 In fact, the longer the material remains in the hardening 
 solution the better. It ..as oeen found that medullae pre- 
 pared by tnis simple method present the superficial mark- 
 ings much more distinctly than when they are examined 
 immediately after removal from the skull or after a shorter 
 imme.'jion in formalin. The myelin sheaths of the nerve 
 fibres swell from the absorption of Avater, while the con- 
 nective tissue which is apparently in greater quantity be- 
 tween the various fasciculi, does not. This in all probabil- 
 ity, explains the prominence assumed by the various tracts, 
 after immersion in water, that previously were very in- 
 distinct or absolutely invisible to the naked eye. 
 
 The student will find several tracts located in the me- 
 dulla oblongata very difficult to identify unless some care 
 is exercised in preparing the specimen, but with applica- 
 tion, and a good specimen the tracts to be enumerated can 
 be found and named. 
 
 That portion of the encephalon under consideration is 
 perhaps the most difficult of any of the subdivisions of the 
 central nervous system to analyze, and nothing is at- 
 
94 ANATOMY OF THE BRAIN 
 
 tempted in the present connection except the superficial 
 markings, and those structures that are apparent in the 
 ventriculus quartus. The nuclei of origin of the nei-vi 
 cerebrales, the central nuclei, and the deep lying tracts, 
 will not be now considered to any great extent. 
 
 It is of great assistance, however, to the student in medi- 
 cine, while studying the medulla oblongata, to have several 
 Pal-Weigert sections at hand as when studying the me- 
 sencephalon, pons and trapezium. In these stained sec- 
 tions many important structures can be identified with- 
 out the aid, even of a hand glass, viz. : N. hypoglossus, 
 nucleus N. hypoglossus, nucleus olivae, N. vagus, nucleus 
 N. vagi, nucleus tractus spinalis N. trigemini, traetus soli- 
 tarius, nuclei arcuati, substantia reticularis alba, substan- 
 tia reticularis grisea &c. 
 
 Sections to be studied in this manner should be about 
 30 to 40 microns thick, thoroughly differentiated and not 
 counterstained. If the structure of the various nuclei 
 is to be studied the contrasted sections should be supplied 
 as well. See Plates XXXIV, XXXV and XXXVI. 
 
 The medulla oblongata measures 21 mm. in width, 17 
 mm. in length and 23 mm. in thickness; those measure- 
 ments will vary to a limited extent, but they are the aver- 
 age dimensions computed after the examination of about 
 fifty medullae. 
 
 Before removing the pia, some attention must be de- 
 voted to the consideration of the arrangement of this mem- 
 brane near the caudal extremity of the vermis cerebelli 
 and the cephalic portion of the medulla oblongata in the 
 region of the flocculus. Look for the aperaturae ventric- 
 uli quarti (foramen of Magendie), and examine the plexus 
 chorioideus ventriculi quarti on either side, and note the 
 close relation that these plexuses bear to the nervi acustici, 
 and how they appear to follow the nerves ventrad. (Figs. 
 D and E.) 
 
 "When separating the cerebellum from the rest of the 
 encephalon, care must be taken, not to injure the valve of 
 Vieussens. If the valve be closely examined, a thick trans- 
 verse band about 1 mm. broad can be seen within 1 mm. 
 
ANATOMY OF THE BRAIN 95 
 
 of its cephalic extremity. This is the decussation of the 
 Nn. troehleares. Grasp one of these nerves with the for- 
 ceps and gently pull ; it can be traced onto the margin 
 of the valve without much difficulty. The fibres of these 
 ner\'es, as they decussate, form an interlocking plait in 
 the substance of the valve so that it is impossible to trace 
 the nerves for any distance in the substance of the valve. 
 
 The tela chorioidca ventriculi quarti deserves more than 
 a passing notice at this time. If a specimen is examined 
 after it has been in vs'ater for a short time, and before any 
 dissection has been attempted or before it has been handled 
 to any extent, a clear idea of the attachments of 
 the tela can be ascertained. 
 
 Examine the angle formed by the caudal surface of 
 the vermis cerebelli and the dorsal surface of the medul- 
 la oblongata. Slightly depress the medulla oblongata and 
 a comparatively dense miembrane comes into view. This 
 is a portion of the arachnoid, and is reflected from the 
 caudal surface of the vermis and hemispheria cerebelli to 
 the dorsal surface of the medulla oblongata where it is, in 
 some specimens very firmly attached, as indicated by the 
 large curved red line in fig. E, page 107. In the neighbor- 
 hood of the flocculus this part of the arachnoid becomes 
 adherent to the pia. The tela, an altogether different 
 structure, is not at all effected by the foregoing manipula- 
 tion, and cannot be studied until the caudal part of the 
 vermis at least, has been removed, when it can be seen 
 sagging down into the cavity of the ventricle. It forms 
 the roof of the caudal portion of that cavity, is firmly 
 attached to its walls, and extends cephalad as far as, and 
 into the fissure separating the vermis major from the 
 caudal extremity of the vermis minor. 
 
 The attachments of the tela to the walls of the ventricle 
 are shown by the smaller curved red line in fig. E. In the 
 immediate neighborhood of the ventricular wall it is very 
 much thickened as shown in transverse section in Plates 
 XXXV and XXXVI. This thickened portion of the tela 
 is called the lifjnla. 
 
 The plexus of the tela skirts its cephalic border, and is 
 
96 ANATOMY OF THE BRAIN 
 
 particularly abundant in each extremity of this border, 
 close to the flocculus; completely filling in the angle formed 
 by the hemispheriuni eerebelli^ the flocculus and the cor- 
 pus restiforme. The red convoluted line in fig. E shows 
 this arrangement, A process of this same plexus passes 
 caudad, attached to the ventral surface of the tela ven- 
 trieuli quarti, hanging suspended in the cavity of the 
 ventricle as seen in section in Plate XXXVI. 
 
 In the region where the tela is attached to the rami obicis 
 as they form the lateral wall of the caudal third of the 
 ventricle, they spread out into broad oval masses in sec- 
 tion, so closely attached tq the eminentia vagi (ala cinerea) 
 that they are distinguishable only when stained. This par- 
 ticular arrangement will be further considered in a sub- 
 sequent chapter. 
 
 Now remove the pia completely from the medulla ob- 
 longata, and in so doing the nerves will be detached, but 
 as they have already been studied this will do no harm. 
 In this procedure be very 'careful not to injure the delicate 
 tissues that lie in the vicinity of the ventriculus quartus. 
 
 As already described the pia begins to thicken into a de- 
 cidedly tough and fibrous sheath as it is tra> ed toward the 
 caudal extremity of the medulla oblongata, anc iheres 
 very tenaciously to the tissues inclosed. It is specially 
 difficult to remove it from the fissura mediana ventr^lis of 
 the medulla spinalis, where this structure joins the medulla 
 oblongata. 
 
 Make an incision through the pia, parallel with, and on 
 each side of the fissura mediana ventralis, extending to the 
 caudal extremity of the specimen, and gradually detach 
 the membrane towards the dorsal surface ; lastly pull away 
 the part left in the fissura ventralis. If this operation be 
 carefully done, none of the delicate lines separating the 
 fasciculi on the surfaces of the medulla oblongata and the 
 medulla spinalis will be obliterated. 
 
 In Plate XXIII the pia is enlarged out of proportion, 
 and a diagramatie space shown between the cord and pia, 
 that does not exist in nature. 
 
 In the median line of the ventral surface is seen the 
 
ANATOMY OF THE BRAIN 97 
 
 fissitra media na ventralis, extending from tlie caudal ex- 
 tremity of the sulcus basilaris to the cephalic ending of 
 the fissura mediana ventralis medullae spinalis. 
 
 This so-called fissure of the medulla oblongata is really 
 not a fissure, but a sulcus, the fissure having been obliterat- 
 ed by the decussation of the fibres of the pyramides medul- 
 lae oblongatae passing from one side of the medulla to the 
 other; clearly shown in Plate XXXIV. 
 
 On examining the medullae of nearly a hundred en- 
 cephala, it was impossible to find any large bundles of 
 fibres passing from one. side of the medulla to the opposite 
 side of the cord, a condition contrary to what we find in 
 the human brain, where the decussating bundles are so 
 clearly seen by the naked eye. 
 
 On either side of the sulcus ventralis is a well marked 
 band of tissue called the pyramis (the anterior or ventral 
 pyramids) which is separated from the remaining portion 
 of the lateral half of the medulla oblongata by the sulcus 
 ventralis lateralis (antero-later^l fissure) ; this sulcus is 
 very distinct ceyjhalad, but becomes very indistinct as it 
 is traced caudad. 
 
 The p"'"^ im Is ar. at their greatest width as they lie in 
 the c al part of the medulla, but as they are traced 
 cephalaa they become gradually narrower and more dis- 
 tinct j each tract appears to break up into strands of fibres. 
 The median bundles reach the caudal border of the pons, 
 superficial to the trapezium, Avhile the lateral bundles pass 
 dorsad to the superficial fibres of the trapezium prior to 
 reaching the pons, constituting the fasciculus longitudina- 
 lis superficialis pontis (see Plate XXX), where transverse 
 sections of these bundles of fibres are nicely shown. By 
 reflecting the fibrae pontis superficialis the longitudinal 
 course of the fibrae pyramidales can be clearly demon- 
 strated by tearing the fibrae in the direction in which they 
 run. Traced caudad, the fibres of the pyramis take a 
 dorsal direction skirting the walls of the fissura ventralis. 
 As these fibres reach the bottom of the fissure they turn 
 abruptly toward the opposite si(l<\ cuttJTig across the base 
 of the colum;na ventralis to reach the j)roc('ssiis reticularis 
 
98 ANATOMY OF THE BRAIN 
 
 and the region of the fasciculi longitudinales dorsales as 
 outlined in Plate XXXIV. These decussating fibres are 
 sometimes collected into comparatively large fasciculi or 
 loose bundles, that can be seen with the low power of the 
 dissecting microscope even in unstained sections. These 
 decussating bundles are nothing in size compared to the 
 huge bunches that cross in the human medulla oblongata. 
 
 Sections that are cut .5 mm. in thickness, when placed 
 on the glass stage of the dissecting microscope over the 
 black diaphragm and flooded with water, show these de- 
 cussating fasciculi plainly. Or a better way is to place 
 the freshly cut sections on dark blue glass resting on white 
 paper and flooding with water. Now by using a focusing 
 lense to illuminate the sections the medullated fibres be- 
 come quite brilliant, and even very small fasciculi becomie 
 visible. 
 
 Immediately laterad to the cephalic third of the pyramis 
 can be found a very delicate and sometimes indistinct strip 
 of white substance, here called the fasciculus lateralis 
 miliar. The cephalic extremity of this tract is first ob- 
 served as it apparently emerges from the sulcus separating 
 the pons from the trapezium; look for it just mediad to 
 the exit of the nervus facialis from the trapezium. Occa- 
 sionally considerable persistence must be exercised to iden- 
 tify it, but a careful search will invariably be rewarded. 
 Traced eaudo-niediad to the caudal border of the trape- 
 zium, it is seen to approach the lateral margin of the py- 
 ramis from which it is separated by a distinct depression, 
 the cephalic extremity of the sulcus ventralis lateralis. 
 Traced caudad it runs for a short distance nearly parallel 
 with the fissura mediana ventralis; it then takes a gradual 
 bend laterad to reach the lateral aspect of the medulla 
 spinalis. In passing obliquely across the medulla oblon- 
 gata it lies laterad to the exit of the fibres which unite to 
 form the nervus hypogiossus. As the fasciculus reaches 
 the miedulla spinalis it becomes quite distinct and easily 
 distinguishable from the adjacent tissues; it can be finally 
 traced to the superficial area of the medulla spinalis, about 
 
ANATOilY OF THE BRAIN 99 
 
 the centre ot the funieiihis lateralis as shown in Plate 
 XXXIIl. 
 
 There can scarcely be any question, but that the fasci- 
 culus lateralis minor is the homologue of the fasciculus 
 ventrolateralis superficialis, commonly called Gower's tract 
 in the human medulla spinalis. Authorities on human 
 anatomy place this fasciculus jiLst ventrad to the centre 
 of the funiculus lateralis on or near the surface ; but when 
 it reaches the medulla oblongata, they bury it somewhere 
 in the recticulai formation of the medulla and pons on its 
 way to reach the brachium conjunctivum, in the substance 
 of which it passes to the vermis cerebelli. In the encepha- 
 lou of the sheep it can be traced to the trapezium over 
 which it passes, directing its course the cerebellum. In 
 Pal-Weigert sections it can be seen as a compact bundle of 
 fibres on the ventral surface just mediad to the region of 
 the nucleus olivae. See Plates XXXV, XXXVI, and 
 XXXVII. 
 
 Another very interesting feature of the medulla oblon- 
 gata is the oliva, so conspicuous in the human encephalon. 
 Lying one on each side, the olivae are to be seen immedi- 
 ately caudad to the trapezium, resting in the obtuse angle 
 formed by the caudal border of the trapezium and the 
 lateral border of the fasciculus lateralis minor. The olivae 
 are very indistinct in some specimens, but in others again 
 they are easily seen, and their superficial relations clearly 
 evident. 
 
 In a transverse section of the medulla oblongata passing 
 through the olivae, a distinct round nucleus can be seen 
 close to the surface of the structure, Plate XXX. fig. 3, 
 and Plate XXXT. fig. 1. also Plate XXXVT. 
 
 Laterad to the olivae on each side will be seen a longi- 
 tudinal tract of considerable size traceable in some instances 
 to the caudal extremity of the medulla oblongata. This 
 lartre bundle is the trarhts spinalis N. triiicmini {radix 
 asrrndens N. trif/rwini) of the medulla o])longata and 
 by reflecting the superficial transverse fibres of the 
 li-apczin'ii. and Ihf adjoining fibres of tlie pons, and then 
 
100 ANATOMY OF THE BRAIN 
 
 teasing the nerve caudad, the fibres of this radix can be 
 traced nicely. This radix rapidly diminishes as it is 
 traced caadad, and toward its termination the superficial 
 boundaries become very indistinct if not quite obliterated. 
 
 As the pia is carefully removed from this eminence a 
 number of the radices forming the Nn. glossopharyngeus 
 et vagus will be seen passing from the medulla between 
 the fibres constituting the tractus spinalis N. trigemini ; 
 the direction of the line of exit of these root fibres is caudo- 
 laterad, and they appear to be in line with those bundles 
 of fibres that constitute the radix cerebralis N. accessorii. 
 
 Another feature of interest is the presence of a large 
 number of arching fibres that appear to emerge from the 
 deep tissue of the medulla oblongata by way of the sulcus 
 ventralis lateralis. They are found on the cephalic half of 
 the medulla, covering the caudal part of the oliva; they 
 pass caudo-laterad then gracefully change their course to 
 cephalo-dorsad and are lost on the surface of the corpus 
 restiforme (Plate XXIII, Plate XXXV). 
 
 These fibres no doubt are the fihrae arcvatae externae, 
 and in all probability are analogous to the striations found 
 in the corresponding location on the human encephalon. 
 These fibrae are somewhat difficult to find in some speci- 
 mens, but they are there and a determined search will in- 
 variably reveal them. In other encephala, large numbers 
 of these fibres reach the surface and cover a large area 
 of the ventral and lateral surfaces, extending in some 
 instances almost to the caudal extremity of the medulla 
 oblongata. The fibres that are exposed on the surface form 
 only a small part of the arciform system of fibres, as those 
 that pass from the nuclei areuati to the corpus restiforme 
 beneath the surface, far exceed in number those that are 
 on the surface. In stained sections of the medulla ob- 
 longata, just cephalad to the pyramlidal decussation, great 
 bundles of these arcuate fibres can be seen in the ventro- 
 lateral part of the section, converging to unite with the 
 fasciculus cerebellospinalis to form the corpus restiforme. 
 These fibres can be seen in sections almost as far sephalad 
 as the olivae. If sections are made through the central 
 
ANATOMY OF THE BRAIN 101 
 
 third of the medulla oblongata as shown in Plate XXXV, 
 and examined, stained or unstained, a wavy mass of ap- 
 parently structureless material is seen immediately dorsad 
 to the pyramis. These are the nuclei arcuati, extending 
 for about 5 mm. on either side of the raphe where they 
 are most extensive. 
 
 These nuclei extend throughout the middle third of the 
 medulla oblongata, and traced cephalad they cease some 
 little distance eaudad to the olivae. It must be remem- 
 bered that the arcuate fibres join those of the fasciculus 
 cerebellospinalis and go to the corresponding cerebellar 
 hemisphere. They are much more numerous in the sheep 
 than in man ; the nuclei likewise, are infinitely more ex- 
 tensive than those of the human encephalon. 
 
 This system of fibres and nuclei, obviously, has greater 
 physiological significance in the sheep than in man ; per- 
 haps they are association centres of great complexity in 
 structure and function; presiding over complicated sys- 
 tems of co-ordination and reflex acts, taking the place of 
 the higher reflex centres in the cerebrum when thiese 
 become functionless. 
 
U)2 ANATOJMV OF THE BRAIN 
 
 CHAPTER XXVII. 
 
 THE MEDULLA OBLONGATA - LATERAL SUR 
 
 FACE. 
 
 There is nothing particularly striking to be found on 
 the lateral aspect of the medulla oblongata. At the caudal 
 extremity, if the specimen be viewed from the side, the 
 ventral surface will be seen to bend quite suddenly in a 
 dorsad direction, to reach the medulla spinalis (Plate 
 XXIV) . The fasciculus lateralis minor is plainly seen, and 
 will be found to be exceedingly well marked as it reaches 
 the cord. An earnest effort should be made to identify 
 this structure, and to determine if possible its cephalic 
 destination. Its relations as it is traced are to be care- 
 fully noted. 
 
 Perhaps the easiest way to begin the study of the direc- 
 tion of the tract would be to search for it at the cephalic 
 extremity of the medulla spinalis, whence it can be fol- 
 lowed with comparative ease. The sulcus lateralis ven- 
 tralis and the sulcus lateralis dorsalis are easily identified; 
 the latter sulcus must be followed cephalad, where '+ will 
 be seen lying between the tractus spinalis N. trigemini and 
 the corpus restiforme. Toward its cephalic extremity it 
 becomes very indistinct and finally ceases at the cephalic 
 border of the trapezium. 
 
 Lying between the fasciculus lateralis minor and the 
 sulcus lateralis dorsalis, is an important tract called the 
 fasciculus cereheUospinalis (fig. E), because it runs direct- 
 ly to the corresponding cerebellar hemisphere from the 
 medulla spinalis. This fasciculus is frequently called the 
 direct cerebellar tract and forms part of the inferior cere- 
 bellar peduncle or corpus restiforme. Traced to its ter- 
 mination it will be found to pass from the dorsal part 
 of the funiculus lateralis medullae spinalis to the medulla 
 oblongata, constituting its lateral border resting between 
 the tractus spinalis N. trigemini, and the cephalic termina- 
 tion of the fasciculus cuneatus (see Plate XXIV). Upon 
 
ANATOiMY OP THE BRAIN 103 
 
 reaching the lateral extremity of the trapezium, it bends 
 dorsad, winding around the cephalic border of the N. 
 acusticus, and then turns slightly caudad to enter the 
 cerebellum to which it may be easily traced. 
 
 Just dorsad to the cephalic extremity of the fasciculus 
 cuneatus will be seen a modest elevation called the dava, 
 to be again referred to, and mediad to the cephalic extrem- 
 ity of the clava, lying close against the N. acusticus, will 
 be observed a limited view of the area acustica. Note how 
 unmistakably the N. acusticus can be observed entering 
 the dorsal surface of the medulla oblongata. 
 
 While engaged in the study of this surface of the medul- 
 la oblongata, some very interesting structures can be in- 
 vestigated if the caudal third of the hemisphaerium cere- 
 bri be removed as shown in Plate XXI. 
 
 It would be well, perhaps, also to remove the hemisphae- 
 rium cerebelli and the flocculus from the side under con- 
 sideration ; this dissection is easily effected, and will ex- 
 pose the parts to be immediately enumerated as shown 
 slightly enlarged in Plate XXIV. 
 
 Lying against the convexity of the corpus restiforme as 
 it winds cephalad of the N. acusticus will be found a large 
 band of substantia alba, consisting of fibres that constitute 
 the .lajor portion of the pons. This bundle is the brach- 
 ium pontis (middle cerebellar peduncle) and these fibres 
 connect the two cerebellar hemispheres. Some of these 
 structures have been noted before but a recapitulation 
 showing their relations to the medulla oblongata from its 
 lateral aspect will do no harm. 
 
 A portion of these fibres may be separated from the un- 
 derlying strands and traced by teasing to the medullary 
 substance of the hemisphaerium cerebelli. 
 
 Passing caudad, beneath the cephalic border of the bra- 
 ehium pontis is a large band coming from beneath the 
 corpora quadrigcmina, called the brarhium conjunctivum 
 (superior cerebellar peduncle, anterior cerebellar peduncle, 
 crus cerebelli ad corpora quadrigemina) ; this structure 
 will be more fully described while considering the anatdiny 
 of the vf^ntriv'Mlus (|uartus. 
 
104 ANATOMY OF THE BRAIN 
 
 Winding from the dorsal to the lateral surface of the 
 brachium conjunctivum can be seen the N. patheticus ; this 
 nerve is very delicate and will be torn from its attachment 
 if the dissector is not careful, as described in Chapter 
 XXVI while discussing the roof of the ventriculus quar- 
 tus. The hrachimn quadrigeminum inferius is plainly 
 seen running along the dorsal border of a triangular area 
 called the trigonum lemnisci (Plate XXIV). The three 
 boundaries of this space are, the ventral border of the bra- 
 chium quadrigeminum inferius, the cephalic border of the 
 pons and the dorso-caudal border of the pedunculus. Pick 
 up some of these fibres of the leminiscus lateralis, and 
 tear them in a cephalo-dorsad direction. They wall be 
 seen to pass between the brachium conjunctivum and the 
 brachium pontis to the lateral extremity of the trapezium 
 with the fibres of which they seem to be continuous. This 
 connection between the trapezium and the lemniscus later- 
 alis leading to the colliculus inferior is easily demonstrated 
 in stained serial sections. 
 
 ■In a later dissection when the tractus opticus has been 
 removed, this brachium can be distinctly traced by Avay of 
 the internal capsule to the caudal extremity of the hemi- 
 sphaerium cerebri as shown in Plate XXII. The student 
 must endeavor to trace this brachium when he is demon- 
 strating the corona radiata. 
 
 At the point, where the brachium meets the pedunculus, 
 look for the tractus peduncularis transversus, resting in 
 the sulcus between the colliculus superior and the pulvi- 
 nar. In some specimens this tract appeared traceable to 
 the mesial surface of the colliculus superior into the sul- 
 cus intercollicularis, where it reaches the lamina quadrige- 
 mina; it then changes its course and passes directly to- 
 ward the trigonum habenulae. 
 
 This tract, together with the brachium quadrigeminum 
 inferius and the caudal border of the tractus opticus, forms 
 another triangle, trigonum geniculatum, which contains 
 the corpus geniculatum externum. As the tractus pedun- 
 cularis transversus lies in the most dorsal portion of the 
 
ANATOIMY OF THE BRAIN 105 
 
 sulcus, it is very indistinct, but in a few cncephala there 
 can be no doubt as to its existence and destination. 
 
 The tractus opticus is particularly well shown in this 
 dissection as it passes dorso-caudad to reach the pulvinar, 
 corpus greniculatum externum and the colliculus superior. 
 
 If the caudal portion of the hemisphere be cut away in 
 an oblifiue direction, and the dissection carefully done, the 
 structures lying- dorsad and caudad to the pulvinar will be 
 nicely exposed and the relations of the pulvinar. fascia 
 dentata, hippocampus, and the cornu inferius ventriculi 
 lateralis clearly shown (Plate XXI). 
 
106 ANATOMY OF THE BRAIN 
 
 CHAPTER XXVIII. 
 
 THE MEDULLA OBLONGATA-DORSAL SURFACE. 
 
 The dorsal aspect of the iriednlla oblongata (Plate XXV 
 and fig. E), is of more than ordinary interest, as it is 
 largely occupied by that interesting space called the ven- 
 triculus quartus. The caudal extremity of the medulla 
 oblongata passes into the cephalic portion of the medulla 
 spinalis quite abruptly. The greater difference will be 
 seen in the lateral diameters. The caudal third of the 
 medulla oblongata does not enter into the formation of 
 the ventriculus quartus, and the description of that por- 
 tion not entering into relation with the ventricle will be 
 completed prior to the consideration of those parts of the 
 medulla that are so intimately associated with this very 
 important ventricle. 
 
 In the mid-dorsal line will be noticed the sulcus dorsalis 
 continued cephalad from the cord. This sulcus is pre- 
 vented from reaching the ventricle by an arched band of 
 tissue, whose convexity is directed caudad, called the ohex, 
 beneath which there is a cavity called the "ventricle of 
 Arantius. ' ' 
 
 This obex is generally quite prominent, and little diffi- 
 culty will be experienced in finding it. As the sulcus 
 dorsalis reaches the obex it appears to divide into two 
 rami that pass latero-cephalad in opposite directions, em- 
 bracing the extremities of the obex, and finally to disap- 
 pear on the dorsal surface of the medulla oblongata at a 
 variable distance from their origin. 
 
 On either side of the little triangular space formed by 
 the obex and the diverging rami of the sulcus dorsalis, is 
 seen a very delicate fusiform tract of substantia alba, for 
 which I would suggest the name of fasciculus fusiformis. 
 The writer's attention was first called to the possibility of 
 a distinct tract in this region from the peculiar arrange- 
 ment of the white fibres noticed in an histological section 
 of the cord located about 5 mm. from the medulla oblon- 
 
ANATOMY OF THE BRAIN 107 
 
 gata and stained with haeniatoxylin. The position, form, 
 and relation of this fasciculus can be easily seen with the 
 naked eye in almost all stained sections of the cephalic 
 extremity of the medulla spinalis. 
 
 This tract in section is clearly shown in Plate XXXIII, 
 P, and in making sections that gradually approach the me- 
 dulla oblongata, the tract increases in size and finally 
 reaches the surface by way of the proximal extremity of 
 the sulcus dorsalis as illustrated in Plate XXV. 
 
 This fasciculus is scarcely perceptible in fresh encephala, 
 and in those specimens that are examined directly after re- 
 moval from the solution of formalin ; after macerating the 
 formalin-fixed brain in water for one or two weeks the 
 tract is easily found. 
 
 If the sulcus dorsalis be gently opened the dorsal edge 
 of the fasciculus fusiformis will be seen skirting the wall 
 of the sulcus dorsalis, diminishing in size as it passes 
 caudad; the dissector should not neglect to discover this 
 fasciculus. The tract can be seen in a transverse section of 
 the cephalic extremity of the medulla spinalis with the 
 naked eye if a very thin section be made with a sharp 
 knife and the section viewed while held up to the light, 
 but not direct sunlight. It possesses a well marked nucleus 
 that is easily identified in stained sections; see Plate 
 XXXIV. 
 
 The sulcus dorealis, Plate XXV, is bounded on each side 
 by the fasciculus gracilis (tract of Goll, postero-internal 
 tract), which passes cephalad and ends, when it reaches 
 the level of the obex, in the clava which assists in forming 
 in part the caudo-iateral boundary of the ventriculus 
 quartus. 
 
 Laterad to the fasciculus gracilis can be seen the fascicu- 
 lus cuneatus (tract of Burdach, postero-external tract). 
 These two fasciculi are separated by the sulcus intermedins 
 dorsalis. The fasciculus cuneatus traced cephalad ends in 
 a very indi^^tinct enlargement in some specimens called the 
 tuherculum cuneatum. The tuberculum cuneatum is 
 placed more caudad than the clava, as illustrated in fig. E. 
 Within the substance of the clava and the tuberculum 
 
108 ANATOMY OF THE BRAIN 
 
 ciineatum there are irregularly arranged masses of cells 
 forming nuclei. The substantia grisea that eventually de- 
 velops into the nucleus of the clava is derived from the 
 grey matter of the cord, as an exeresence growing dorsad 
 into the cephalic part of the fasciculus gracilis, in the 
 same manner as that of the nucleus cuneatus in the human 
 medulla oblongata; while the nucleus of the fasciculus 
 cuneatum develops independently. The three nuclei, viz., 
 nucleus fasciculi fusiformi, nucleus fasciculi gracilis and 
 the nucleus fasciculi cuneati can be seen in stained sections 
 just caudad to the entrance of the canalis centralis into 
 the fourth ventricle. 
 
 From these nuclei many strands of fibres, constituting 
 the deep arciform series, can be easily seen, passing in an 
 arched direction, ventro-mesiad across the raphe, where 
 they turn cephalad, forming the ventral portion of the 
 formatio reticularis alba. This band of fibres as it passes 
 toward the cerebrum forms the mesial lemniscus or fillet 
 as shown in Plates XXXVI and XXXVII. 
 
 These inner arching fibres can be seen in the unstained 
 section if sufficient care and persistence is exercised. 
 
 The sulcus intermedins dorsalis is lost on the lateral 
 aspect of the medulla oblongata. The sulcus lateralis dor- 
 salis runs along the lateral border of the fasciculus cu- 
 neatus, separating it from the corpus restiforme, and is 
 the line of origin of the dorsal nerve roots of the nervi 
 cervicales as well as some of those going to the N. vagus 
 and N. accessorius. Ventral to the sulcus lateralis dor- 
 salis lies the fasiculus cerebellospinalis passing to the 
 lateral area of the medulla oblongata, forming there, as 
 stated, the major part of the corpus restiforme. 
 
 DESCRIPTION OF FIG. E. 
 
 A. Striae inedullares (N. aciisticus). /. Clava (caudal exti'emity). 
 
 B. Plexus ehorioideus ventriculi quarti. J. Fasciculus gracilis. 
 
 C. Ranuis obicis. K. Tuberculum cuneatum. 
 
 D. Taenia ventriculi quarti. L. Fasciculus cuneatus. 
 
 E. Trigonum vagi. M. Sulcus lateralis dorsalis. 
 
 F. Trigonum hypoglossi. i\^ Fasciculus cerebellospinalis. 
 
 G. Fasciculus fusiformis. S. Nucleus dorsalis N. cochlearis. 
 //. Obex. 
 
™- '""'■""" ''™3r:ut.u/'(o;sH5i"s*s.H'?^;^i.r'' -■"" " "■• 
 
110 ANATOMY OF THE BRAIN 
 
 CHAPTER XXIX. 
 
 THE FOURTH VENTRICLE. 
 
 The ventriculus quart us (fig. E) is an irregular space 
 lying dorsal to the pons, the trapezium' and the cephalic 
 two-thirds of the medulla oblongata. Its length is about 
 17 mm., its greatest width about 8 mm., and its depth 1 
 m, to 3 mm. Its roof is formed cephalo-caudad by the 
 velum medullare anterius (valve of Vieussens), vermis 
 cerebelli minor, and the tela chorioidea ventriculi quarti. 
 A portion of the lateral wall at the cephalic extremity is 
 formed on either side by the brachium conjunctivum. 
 
 The distal extremities of the brachia approach the mesial 
 line as they pass caudad, and meet in the medullary sub- 
 stance of the cerebellum, forming almost a complete circle, 
 as shown by the dotted line in Plate XXV. This circle is 
 completely filled in or closed by the velum medullare an- 
 terius. Further caudad the lateral boundaries are formed 
 by the areae acusticeae, and lastly by the rami of the obex 
 and a small portion of the clava. 
 
 ' The sulcus longitudinalis fossae rhomboideae divides the 
 floor of the ventricle into two symmetrical halves; the 
 cephalic extremity of this sulcus leading to the caudal 
 opening of aquaeductus cerebri, and its caudal limitation 
 ending at the entrance of the canalis centralis into the 
 cord. 
 
 The fossa rhomboidea is limited on each side by the sid- 
 cus limitans fossae rhomboideae. Just caudad to the cen- 
 tral part of the floor of the ventricle will be seen a very 
 narrow bi-convex area called the eminentia medialis, with 
 an exceedingly shallow groove running longitudinally 
 through its centre, perhaps a continuation of the sulcus 
 longitudinalis fossae rhomboideae. The eminentia medialis 
 is formed by the stria longitudinalis profundis (posterior 
 longitudinal bundle) bending dorsad to reach the floor of 
 the ventricle. (Plates XXXVI and XXXVII.) 
 
 This eminence in some cases is markedly depressed be- 
 
ANATOMY OF THE BRAIN 111 
 
 low the floor of the ventricle and is inclosed on either side 
 by a delicate semilunar sulcus; it is in all probability the 
 homolo£i:ue of the eminentia niedialis found in the floor 
 of the ventriculus quartus in man. The eminence is clear- 
 ly illustrated in Plate XXV and Plate XXXI, figs. 2 
 and 3, and fig. E. 
 
 The cephalic portion of each lateral half of the ven- 
 tricular floor is marked by a distinct spherical elevation 
 called the colliculus facialis {eminentia facialis,) beneath 
 which is the genu nervi facialis and to which the N. 
 facialis can be easily traced, as shown in Plate XXX, fig. 3. 
 
 The student must not fail to make an incision parallel 
 to the cephalic border of the trapezium extending com- 
 pletely through the structure in order to demonstrate the 
 course of this nerve as it passes through the substance of 
 this part of the encephalon. 
 
 Lateral to the eminence that has just been studied, look 
 for a triangular depression called the fovea anterior. 
 Caudad to this fovea the sulcus limitans fossae rhom- 
 boideae bends toward the middle line along the mesial bor- 
 der of quite a large convex elevation, the area acustica; 
 note the N. acusticus leading down to it. (See Plate 
 XXXVII.) 
 
 At the caudad extremity of the ventricle note the large 
 mass of matter lying dorsad to the entrance of the canalis 
 centralis, the obex previously mentioned; with its convex- 
 ity directed caudad, while the rami obicis pass cephalad 
 and are lost to view as they reach the areae acusticae. 
 Where the inner margins of these rami meet the mesial 
 convex borders of the areae acusticae is another triangular 
 depression, the fovea posterior (ala cinerea). (See Plate 
 XXXV.) 
 
 On each side of the caudal portion of the floor of the 
 ventricle, lying between the sulcus longitudinalis fossae 
 rhoraboideae and the ramus obicis, is a longitudinally 
 placed eminence called the eminentia hypoglossi (trigonum 
 hypoglossi). The sulci limitantes fossae rhombuideae con- 
 verge to meet the sulcus longitudinalis fossae rhomboideae 
 at the caudal extremity of the v(uitriele to form the cala- 
 
112 AN ATOMZ OF THE BEAIN 
 
 mus scriptorius (named by Herophilus, 3rd Century 
 B. C). 
 
 The nucleus alae cinereae which embraces the nucleus 
 vagus and the nucleus giosso-pharyngeus is situated im- 
 mediately lateral to the fovea inferior and the caudal ex- 
 tremity of the sulcus limitans fossa rhomboideae, and also, 
 lies in part beneath the well marked elevation called the 
 trigonum vagi or ala cinerea. Fibres from the nucleus N. 
 glosso-pharyngeus and N. vagi can be traced to these 
 nuclei (Plate XXXVI). 
 
 The trigonum vagi lies ventrad and somewhat mediad to 
 the ramus obicis (fig. E). The line of demarcation be- 
 tween the trigonum vagi and the ramus obicis is often a 
 well marked ridge which is called the taenia ventriculi 
 quarti, or perhaps it is homologous with the fasciculus 
 separans of the human brain. 
 
 The tissue lying laterad to the fasciculus separans or 
 taenia is non-nervous ; and on section has a vascular or 
 cavernous appearance (Plate XXXV). The surface of 
 this tissue m)ay be called the area postrema of Retzius. 
 
 The nucleus alae cinereae, is the point of termina- 
 tion of the sensory fibres of the N. giossopharyngeus 
 and the N. vagus. The nucleus ambiguus is found 
 just laterad and ventrad to the fovea posterior, and from 
 this nucleus spring the motor roots of the same two nerves, 
 together with some of those of the N. accessorius. 
 
 The tractus spinalis N. trigemini can be seen 7 mm. 
 laterad to the sulcus longitudinalis fossae rhomboideae, 
 with its concavity, containing the nucleus tractus spinalis 
 N. trigemini, directed to the mesial line. Winding around 
 the ventral and lateral surfaces of the tractus spinalis N. 
 trigemini is a very thick layer of fibres running in a 
 cephalo-laterad direction to reach the corpus restiforme 
 as shown in Plates XXXVII and XXXVIII. These fibres 
 are plainly seen converging from the nuclei arcuati toward 
 the corpus restiforme which forms a very prominent struc- 
 ture on the lateral extremity of these sections. 
 
 About 3 mm. cephalad to the tip of the calamus scrip- 
 torius, as a very slight transverse depression the sulcus 
 
AXATO.MV (iK THK RKAIN 113 
 
 traitsi^ersus, extending across the trigonum hypoglossi, 
 mai'king off an area of tissue the shape of an isosceles 
 triangle with its apex pointing to the entrance of the 
 canalis centralis of the medulla spinalis. 
 
 Under no consideration must the student be permitted 
 to leave the work on the gross anatomy of the sheep's 
 brain without making a series of coronal sections of the 
 encephalon such as those illustrated in Plates XXVI to 
 XXXII, inclusive. 
 
 Drawings should be made and all the parts identified. 
 These preparations are of great value in fixing in the stu- 
 dent's mind the relationships of the ganglia, fasciculi and 
 other points of interest that he has been working out in 
 the foregoing pages. 
 
 It would be well worth the trouble to prepare a brain by 
 the Kaiserling method, from which to make these coronal 
 sections, for there will be difficulty in making out many of 
 the points of interest even with a brain that has been care- 
 fully prepared. 
 
PLATES I- XL. 
 [From Drawings {Excepting I and II) hy the Author] 
 
118 ANATOMY OP THE BRAIN 
 
 PLATES I AND II. 
 
 These plates represent the skull of the sheep one-half 
 the actual size of the preparation and reproduced by 
 photographs. 
 
 PLATE I represents the dorsal surface of the skull. 
 
 PLATE II shows very clearly the lateral elevation of 
 the entire skull. 
 
 These two plates will assist the student in removing 
 the brain from the cranium, by giving him some concep- 
 tion of the place to make the first incision, and how the 
 further operations are to be carried on. 
 
ANATOMY OF THE BRAIN 119 
 
 PLATE I -DORSAL AREA OF THE SKULL 
 
120 ANATOMY OF THE BRAIN 
 
 PLATE II. 
 
 Lateral Elevation of the Sknll. 
 
I'lwXTK II LATERAL AREA OF THE SKTILL 
 
122 ANATOMY OF THE BRAIN 
 
 PLATE III. 
 
 THE ENCEPHALON. 
 
 This illustration is designed to give an idea of the 
 appearance of the eneephalon, inclosed within the dura 
 mater, the calvarium having been removed. Two of the 
 sinuses have been opened, as they ought to be if the 
 directions for dissecting them are carried out. Note the 
 tubular process extending caudad over the medulla 
 spinalis. 
 
 A. Bulbi olfactorii. 
 
 B. Triangular thickening. 
 
 C. Vena frontalis. 
 
 D. Pissura cruciata. 
 
 E. Fissura cerebri lateralis. (Sylvius.) 
 
 F. Sinus sagittalis. 
 
 G. Vena cerebri magna. (Galen.) 
 H. Confiuens sinuum. 
 
 I. Sinus transversus. 
 
 J. Vermis cerebelli. 
 
 K. Hemisphaerium cerebelli. 
 
ANxVTO:\[V f)F lUK BRAIN 
 
 123 
 
 PLATE I IT- DORSAL A'^'ECT OF DURA MATER 
 
 (x 1 2/3). 
 
124 ANATOMY OP THE BRAIN 
 
 PLATE IV. 
 
 THE CIRCULUS ARTERIOSUS. 
 
 The eirculiis arteriosus (Willisii) as shown in this draw- 
 ing can be worked out on most encephala where the arter- 
 ies have not been injected. It is a little difficult some- 
 times to identify the arteria cerebri propria because it 
 divides immediately after entering- the brain cavity. 
 
 A. Arteria cerebri anterior. 
 
 B. Arteria communicans. r' 
 
 C. Arteria cerebri media. 
 
 D. Ramus anterior. 
 
 E. Ramus posterior. 
 
 F. Arteria cerebri posterior. 
 
 G. Arteria basalaris. 
 
 H. Arteria cerebelli anterior. 
 
 /. Arteria cerebelli posterior. 
 
 X. Arteria cerebri propria. 
 
 Z. Arteria basilaris gangliaformis posterior. 
 
ANATO^ilY OF THE BRAIN 
 
 125 
 
 PLATE IV— ARTEKIKS ON VENTRAL SURFACE 
 OF THE BRAIN (x 1 2/3). 
 
126 ANATOMY OP THE BRAIN 
 
 PLATE V. 
 
 FACIES DORSALIS CEREBRI ET CEREBELLI. 
 
 A. Fissura longitudinal] s. 
 
 B. Sulcus coronalis. 
 
 C. Fissura cruciata. 
 
 D. Fissura cerebri lateralis. (Sylvius.) 
 
 E. Fissura suprasylvia. 
 
 F. Sulcus lateralis. 
 
 G. Sulcus intermedia. 
 H. Sulcus medialis. 
 
 I. Fissura cerebelli superior. 
 /. Fissura cerebelli medialis. 
 K. Fissura cerebelli inferior. 
 L. Medulla oblongata. 
 
 M. Sulcus dorsalis. 
 
 Z. Polus posticus. 
 
 1. Gyrus frontalis superior. 
 
 5, Gyrus frontalis medialis. 
 
 3. Gyrus sylviacus (arcuatus). 
 
 4. Gyrus lateralis. 
 
 5. Gyri mediales. 
 
 6. Gyrus internus. 
 
 7. Vermis cerebelli. 
 
 8. Flocculus. 
 
 9. Parafiocculus. 
 
 10. Lobus superior (hemisphaerium cerebelli). 
 
 II. N. cervicalis I. 
 12. Medulla spinalis. 
 
PLATE V-DOKSAL SURFACE OF J'HE BRAIN 
 
 (X 1 2/8). 
 
128 ANATOMY OF THE BRAIN 
 
 PLATE VI. 
 
 FACIES LATERALIS CEREBRI ET CEREBELLI. 
 
 A. Gyrus frontalis inferior. 
 
 B. Gyrus orbitalis. 
 
 C. Tractus olfactorius. 
 G. Fissura rhinalis. 
 
 H. Gyri centrales (Island of Reil). 
 
 7. Fissura cerebri lateralis (Sylvii). 
 
 J. Ramus posterior fissurae cerebri lateralis. 
 
 W. Ramus anterior fissurae cerebri lateralis. 
 
 Z. Lobus hippocampi. 
 
 3. Gyrus sylviaeus (arcuatus). 
 
 7. Vermis cerebelli. 
 
 8. Lobus cerebelli inferior. 
 
 9. Lobus cerebelli medialis (paraflocculus). 
 
 10. Lobus cerebelli superior (hemisphaerium cerebelli). 
 
 11. Flocculus. 
 
ANATOMY OF THE BRAIX 
 
 129 
 
 PLATE VI-LATP:RAL SURFACE OF THE BRAIN. 
 
130 ANATOMY OF THE BRAIN 
 
 PLATE VII. 
 VENTRAL SURFACE OF THE ENCEPHALON. 
 
 A. Fissiira sagittalis. 
 
 B. Gyrus orbitalis. 
 
 C. Substantia g'risea radicis lateralis. 
 
 D. Radix medialis bulbi olfactorii. 
 
 E. Substantia alba radieis lateralis. 
 
 F. Locus perforatus anterior. 
 
 G. Fissura rhinalis. 
 H. Insula. 
 
 /. Fissura cerebri lateralis. 
 
 J. Infundibulum. 
 
 K. Chiasma opticum. 
 
 L. Traetus opticus. 
 
 M. Corpus mamillare. 
 
 N. Traetus peduncularis transversus. 
 
 0. Nucleus interpeduncularis. 
 
 P. Pedunculus cerebri. 
 
 Q. Pons. 
 
 R. Trapezium. 
 
 S. Oliva. 
 
 T. Fasciculus lateralis minor. 
 
 U. Medulla oblongata. 
 
 V. Radix spinalis nervi accessorii. 
 
 W. Ramus anterior fissura cerebri lateralis. 
 
 Y. Sulcus ventralis medullae oblongatae. 
 
 Z. Lobus hippocampi. 
 
 1. Bulbus olfactorius. 
 
 2. N. opticus. 
 
 3. N. oculomotorius. 
 
 4. N. trochlearis. 
 
 5. N. trigeminus. • : 
 
 6. N. abducens. ' 
 
 7. N. facialis. 
 
 8. N. acusticus. ' ■ -'' 
 
 9. N. giossopharyngeus. 
 10. N. vagus. 
 
 li. N. aceessorius. 
 
 12. N. hypoglossus. 
 
 13. Radix aseendens N. trigemini. 
 
ANATOMY OF THE BRAIN 
 
 131 
 
 PLATE VIT VENTRAL SUREACE OE THE BRAIN 
 
 (x 1 2/3). 
 
l!^2 ANATOMY OP THE BRAIN 
 
 PLATE VIII. 
 
 FACIES MEDIALIS CEREBRI. 
 
 A. Rostrum corporis callosi. 
 
 B. Genu corporis callosi. 
 
 C. Bulbus olfactorius. 
 
 D. Sulcus cinguli. 
 
 E. Gyrus intermedius. 
 
 F. Sulcus parolfactorius. 
 
 G. Gyrus marginalis anterior. 
 H. Gyrus cinguli. 
 
 /. Corpus callosum. 
 
 /. Sulcus corporis callosi. 
 
 K. Gyrus marginalis posterior. 
 
 L. Sulcus splenialis. 
 
 M. Splenium corporis callosi. 
 
 N. Colliculus superior. 
 
 0. Corpus medullare cerebelli. 
 
 P. Ventriculus quarti. 
 
 Q. Canalis centralis. 
 
 R. Lamina quadrigemina. 
 
 8. Corpus pineale. 
 
 T. Commissura posterior. 
 
 U. Fasciola cinerea. 
 
 V. Trigonum habenulae. 
 
 W. Corpus fornicis. 
 
 X. Massa intermedia (commissura media] is ; 
 
 Y. Tuber cinereum. 
 
 Z. Commissura anterior. 
 
 2. Radix medialis bulbi olfactorii. 
 
ANATOMY OF THE BRAIN 
 
 133 
 
 PLATE VIII-MESIAL SURFACE OF THE BRAIN. 
 
134 ANATOMY OF THE BRAIN 
 
 PLATE IX. 
 
 FASCIES ANTERIOR. 
 
 This figure represents the encephalon when it is looked 
 at from a point directly cephalad. This plate together 
 with Plates V, VI and VII, will give a very clear idea 
 of the general shape and detailed appearance of the ex- 
 terior of the encephalon. 
 
 A. Gyrus frontalis medialis. 
 
 B. Sulcus coronalis. 
 
 C. Fissura cerebri lateralis. 
 
 D. Gyrus sylviacus. 
 
 E. Fissura erueiata. 
 
 F. Fissura sagittal is. 
 
 G. ' Gyrus frontalis superior. 
 H. Fissura suprasylvia. 
 
 J. Insula. 
 
 L. Lobus hippocampi. 
 
 0. Lobus olfaetorius. 
 
ANATOMY OP THE BRAlN 
 
 135 
 
 PLATE IX-ANTERIOR SURFACE OF THE 
 BRAIN (x 1 2/3). 
 
136 ANATOMY OF THE BRAIN 
 
 PLATE X. 
 
 EXTENSION OF FISSURES AND SULCI INTO THE 
 HEMISPHERES. 
 
 This illustration is introduced to convey some idea of 
 the relatively great superficial area provided by the ex- 
 tension of fissures and sulci into the substance of the 
 hemispheres. It must also be noted that, wherever the 
 depressions go, there follows, a corresponding quantity 
 of substantia grisea, and that this substantia grisea is 
 composed of innum,erable nerve cells, the physiological 
 units of all nerve tissue. 
 
 It is self evident that the area thus provided affords 
 accommodation for a vastly greater number of cells than 
 would be possible were the surface of the cerebrum un- 
 convoluted. 
 
ANATOMY OF THE BRAIN 
 
 1:17 
 
 ATE X-SEC1'I0N OF CEREBRUM TO SHOW 
 OKAY AXO WIIITP: MA'nWOH (x 1 2/3). 
 
138 anatojMY of the brain 
 
 PLATE XI. 
 
 COURSE OF THE FIBRES OF THE CORPUS CAL- 
 
 LOSUM. 
 
 This dissection was made to convey to the student some 
 idea of the course taken by the fibres of the corpus eal- 
 losum in its various parts. 
 
 A. Genu corporis callosi. 
 
 B. Stria longitudinalis medialis. 
 
 C. Stria longitudinalis lateralis. 
 Z>, Corpus callosum. 
 
 E. Fibres of the caudal portion of the corpus cal- 
 losum after they have changed their course and proceed 
 cephalad toward the cephalic extremity of the lobus hip- 
 pocampi, covering the cornu inferius ventriculi lateralis. 
 
 F. Splenium corporis callosi. 
 
 G. Corpus pineale. 
 
 H. Colliculus superior. 
 
ANATO:\rY OF THE BRAiN 
 
 139 
 
 PLATE XI ("OKPUS CALLOSUM, DORSAL SUR 
 FACE fx 1 2/3). 
 
140 ANATOMY OF THE BEAIN 
 
 PLATE XII. 
 
 FIBRES OF THE CORPUS CALLOSUM AND STRI- 
 ATED CONSTRUCTION. 
 
 Represents many features that are similar to those 
 shown in the preceding cut, emphasizing more particu- 
 larly perhaps the striated construction of the corpus ca]- 
 losum. 
 
 A. The cephalic extremity of the transverse fibres of 
 the splenium corporis callosi, as they lie over the cephalic 
 extremity of the cornu inferius ventriculi lateralis. A 
 large opening is shown through that portion of the spleni- 
 um which covers in the caudalie portion of the ventriculus 
 lateralis, and the beginning of the cornu. 
 
 B. Fasciculus subcallosus. 
 
 C. Hippocampus. 
 
anato:j[y of the brain 
 
 141 
 
 I^LATE XII -CORPUS CALLOSUM, SHOWING RAD- 
 IATING FIBRES OF THE SPLENIUM 
 
 (x 1 2/3). 
 
142 ANATOMY OF THE BRAIN 
 
 PLATE XIII. 
 
 DISSECTION FOR THE CAVITIES OF THE VEN- 
 TEICULI LATERALES. 
 
 Illustrating the necessary dissections that are to be 
 made to expose the cavities of the ventriculi laterales, and 
 the structures forming their floors. 
 
 A. Cornu anterius ventriculi lateralis. 
 
 B. Nucleus eaudatus. 
 
 C. Corpus callosum. Hanging from this portion of 
 the corpus callosum will be seen the septum pellucidum, 
 separating the two ventricular cavities; the septum pel- 
 lucidum hangs :from the ventral surface and is not shown 
 in this drawing. 
 
 D. "V. corporis striati. 
 
 E. Recessus triangularis. 
 
 F. Corpus fornicis. 
 
 G. Plexus chorioideus ventriculi lateralis. 
 H. Hippocampus. 
 
 I. Cingulum inferius (fasciculus subcallosus). 
 J. Cornu inferius ventriculi lateralis. 
 
ANATOMY OF THE BRAIN 
 
 143 
 
 PLATE XIIl-LATEl^AL VENTKICLES OF THE 
 BRAIN (x 1 2/3). 
 
144 ANATOMY OP THE BRAIN 
 
 PLATE XIV. 
 
 CONNECTIONS OF THE VENTRICULI LATERALES 
 AVITH VENTRICULUS TERTIUS. 
 
 This is designed for the purpose of shovang the passages 
 that apparently connect the ventriculi laterales with the 
 ventriculus tertius and the structures that pass through 
 them. The corpus callosum and the central portion of 
 the corpus fornicis have been removed. 
 
 A. Septum pellucidum. 
 
 B. Colurana fornicis. 
 
 C. V. terminalis. 
 
 D. Foramen interventriculare (foramen of Monroe) 
 containing the V. terminalis and the plexus chorioideus 
 ventriculi lateralis on its way from the ventriculus lat- 
 eralis to become the plexus chorioideus ventriculi tertii. 
 The margin of the corpus fornicis has been cut away on 
 the left side to expose the fissure. 
 
 E. V. cerebri interna. 
 
 F. Plexus chorioideus ventriculi lateralis. 
 
 G. Margo corporis fornicis. 
 H. V. cerebri magna (Galen). 
 
 I. Plexus chorioideus ventriculi tertii. 
 J. Hippocampus. 
 
ANATOMY OP THE BRAIN 
 
 145 
 
 PLATE XIV- THIRD VENTRICLE AND CHOROID 
 PLEXUS (x 1 2/3). 
 
146 ANATOMY OF THE BRAIN 
 
 PLATE XV. 
 
 THE VENTRICULUS TERTIUS AND THE VEN- 
 TRICULI LATERALES, 
 
 after the corpus fornicis and the tela ehorioideus ventrie- 
 uli lateralis with its plexus have been removed. 
 
 A. Columna fornicis. 
 
 B. Ventriculus tertius (corpus fornicis removed). 
 G. Thalamus. 
 
 D. Stria meduUaris thalami. 
 
 E. Fimbria hippocampi. 
 
 F. Pulvinar. 
 
 G. Corpus pineale. 
 
 H: Colliculus superior. 
 
ANATOMY OF THE BRAIN 
 
 147 
 
 PLATE XV-LATP:KAL AND THIRD VENTRICLES 
 OF THE BRAL\ (x 1 2/3). 
 
148 ANATOMY OF THE BRAIN 
 
 PLATE XVI. 
 
 ANOTHER STEP IN THE DISSECTION OF THE 
 
 VENTRICULUS LATERALIS, 
 exposing the hippocampus, fimbria hippocampi and the 
 plexus ehorioideus attached to the pia seen passing into 
 the cavity through the fissura transversa as they pass 
 ventrad into the cornu inferior ventriculi lateralis. 
 
 A. Septum pellucidum. 
 
 B. Columna fornieis. 
 
 C. Recessus triangularis. 
 
 D. Plexus ehorioideus ventriculi lateralis. 
 
 E. Corpus fornieis. 
 
 F. Hippocampus. 
 
 G. Fibres of the splenium. 
 
 H. Cingulum inferius (fasciculus subcallosus). 
 
 /. Fimbria hippocampi. 
 
 J. Plexus ehorioideus. 
 
 L. Stria terminalis. 
 
ANATOMY OF THE BRAIN 
 
 149 
 
 PLATE XVI-FORXIX, HIPPOCAMPUS AND CIN- 
 GULUM INFERIOR (x 1 2/3). 
 
150 ANATOMY OP THE BRAIN 
 
 PLATE XVII. 
 
 DISSECTION SHOWING THE MESIAL SURFACE 
 OF THE LOBUS HIPPOCAMPI AND THE 
 FASCIA DENTATA 
 as they wind around the crus cerebri. 
 
 A. Radix medialis bulbi olfactorii. 
 
 B. Commissura anterior. 
 
 C. Cephalic extremity of the lobus hippocampi. 
 
 D. Crus cerebri (transverse section). 
 
 E. Fascia dentata. 
 
 F. Fissura dentata. 
 
 G. Fasciola cinerea. 
 
 H. Stria medullaris thalami. 
 
 /. Thalamus. 
 
 J. Foramen interventriculare. 
 
 K. Ventriculus lateralis. 
 
 L. Nucleus eaudatus. 
 
 M. Gyrus cinguli. 
 
ANATOMY OF THE BRAIN 
 
 151 
 
 PLATP] XVII-FASCIA DENTATA AND MESIAL 
 ST'KFACE OF TWE HIPPOCAMPUS (x 1 2/3). 
 
152 ANATOMY OF THE BEAIN 
 
 PLATE XVIII. 
 
 SECTION OF THE CORPUS STRIATUM AND THAL- 
 AMUS. 
 
 A composite drawing- illustrating a horizontal section of 
 the corpus striatum and the thalamus. 
 
 A. Nucleus caudatus. 
 
 B. Substantia alba insulae. 
 
 C. Nucleus lentiformis. 
 
 D. Capsula externa. 
 
 E. Claustrum. 
 
 F. Capsula interna. 
 
 G. Substantia grisea insulae. 
 H. Area medialis thalami. 
 
 I. Ventriculus tertius. 
 
 J. Area lateralis thalami. 
 
 K. Pars centralis thalami. 
 
 L. Trigonum habenulae. 
 
 M. Area posterior thalami. 
 
 N. Corpus pineale. 
 
 0. Fascia dentata. 
 
 P. Fissura dentata. 
 
 Q. Colliculus superior. 
 
 R. Cornu inferius ventriculi lateralis. 
 
 ^. Genu capsulae internae. 
 
ANATOMY OF THE BRAIN 
 
 153 
 
 PLATE XVI J 1 rilK CORPUS STRIATUM 
 
 (X 1 2/3). 
 
154 ANATOMY OF THE BRAIN 
 
 PLATE XIX. 
 
 FIBRES OF THE COMMISSURA ANTERIOR. 
 
 This dissection shows particularly well the course taken 
 by the greater number of fibres that constitute the com- 
 missura anterior. The drawing represents the central por- 
 tion of the commissure located about 5 cm. dorsad to the 
 chiasma opticum. The hypophysis is also shown. 
 
 A. Radix medialis bulbi olfactorii. 
 
 B. Commissura anterior^ or commissura olfactoria. 
 H. Hypophysis. 
 
 J. Infundibulum. 
 
ANATOMY OF THE BRAIN 
 
 155 
 
 PLATK XiX-THE ANTEKiOK COMMISSURE 
 
 (x 1 2/3). 
 
156 ANATO]\rY OP THE BRAIN 
 
 PLATE XX. 
 
 THE DISSECTION OF THE COLUMNAE FORNICIS. 
 
 A. Pars libera columnie fornicis. 
 
 B. Septum pellucidum (in part). 
 
 C. Substantia grisea. 
 
 D. Commissura anterior. 
 
 E. Pars tecta columnae fornicis. 
 
 F. Fasciculus thalamomamillaris. 
 
 G. Corpus mamiliare. 
 H. Lamina pinealis. 
 
 J. Aquaeductus cerebri. 
 K. Commissura posterior. 
 
ANATOMV^ OF THE BRAIN 
 
 157 
 
 l^.BM. ^ 
 
 l^LATE XX-PILLARS OF THE FORNIX. 
 
158 ANATOMY OF THE BRAIN 
 
 PLATE XXI. 
 
 An oblique section of the caudalic portion of the cere- 
 brum has been removed to expose the following struc- 
 tures in situ. 
 
 A. Colliculus superior. 
 
 B. Cornu inferius ventrieuli lateralis. 
 
 C. Hippocampus. 
 
 D. Fascia dentata. 
 
 E. Pulvinar. 
 
 F. Tractus opticus. 
 
 G. Corpus geniculatum externum. 
 H. Tractus peduncularis transversus. 
 I. Brachium quadrigeminum inferius. 
 J. Colliculus inferior, 
 
 0. Corpus geniculatum externum. 
 
AXATOMY OP THE BRAIN 
 
 159 
 
 PLATE XXI-PROXIMAL TER:^nNATION OF OP- 
 TIC TRACT. 
 
160 ANATOMY OF THE BRAIN 
 
 PLATE XXII. 
 
 THE CORONA RADIATA. 
 
 A. Hippocampus. 
 
 B. Fimbria hippocampi. 
 
 C. Portion of corona formed in part by the brachium 
 quadrigeminum inferius. 
 
 D. Portion formed at the genu by the pyramis anterior. 
 
 E. Portion formed by the mesial fibres of the pyramis 
 anterior. 
 
 P. Infundibulum and corpus mamillare. 
 
 G. Tracticus opticus. 
 
 /. Brachium quadrigeminum inferius. 
 
 J. Lateral fibres of the crus cerebri, (trigonum lem- 
 nisci). 
 
 K. Brachium conjunctivum. 
 
 L. Pyramis anterior, some fibres of. 
 
ANATOMY OF THE BRAIN 
 
 161 
 
 PLAICE XXn~THP] CORONA RADIATA. 
 
162 ANATOIMY OP THE BRAIN 
 
 PLATE XXIII. 
 
 VENTRAL SURFACE OF THE PONS, TRAPEZIUM, 
 AND MEDULLA OBLONGATA. 
 
 A. Pons. 
 
 B. Sulcus basilaris. 
 G. Flocculus. 
 
 D. Trapezium. 
 
 E. Oliva. 
 
 F. Pyramis ventralis. 
 
 G. Ramus aseendens N. trigemini, (tractus spinalis N. 
 trigemini). 
 
 H. Fasciculus lateralis minor. 
 
 /. Sulcus ventralis lateralis. 
 
 J. Funiculus lateralis. 
 
 K. N. acccssorius (spinal portion). 
 
 L. Sulcus ventralis. 
 
 N. Ligamentum denticulatum. 
 
 0. Pia. 
 
 5. N. trigeminus (the larger is the sensory and the 
 smaller the motor portion). 
 
 6. N. abdueens. 
 
 7. N. facialis. 
 
 8. N. acusticus. 
 
 9. N. glossopharyngeus. 
 
 10. N. vagus. 
 
 11. N. accessorius. 
 
 12. N. hypoglossus. 
 
ANATOMY OF THE BRAIN 
 
 16.1 
 
 I ' I . A T 1 : X X I f [ - VENTRAL SUR l^^\CK OF PONS, 
 
 TKAI'IOZKIM ANJ) MEDULiiA OIUjON- 
 
 (JA^'A (x 2 2/3). 
 
164 ANATOMY OF THE BRAIN 
 
 PLATE XXIV. 
 
 LATERAL SURFACE OF THE CRUS CEREBRI, 
 PONS, TRAPEZIUM, AND THE MEDUL- 
 LA OBLONGATA. 
 
 A. Corpus geniciilatuin internum. 
 
 B. Tractus opticus. 
 
 C. Fascies medialis cruris cerebri. 
 
 D. N. oculomotorius. 
 
 E. Tractus peduncularis transversus. 
 
 F. Tractus pyramis pedunculi cerebri. 
 
 G. Braehium quadrigeminum inferius or tractus cere- 
 bro-thalmieus. 
 
 H. N. patheticus. 
 
 /. Pons. 
 
 J. N. trigeminus. 
 
 K. N. abducens. 
 
 L. Trapezium. 
 
 M. N. facialis. 
 
 N. Tractus lateralis minor. 
 
 0. Oliva. 
 
 P. Pyramis. 
 
 Q. Funiculus lateralis. 
 
 B. Sulcus lateralis ventralis. 
 
 S. Sulcus lateralis dorsal is. 
 
 T. Fasciculus euneatus. 
 
 V. Clava. 
 
 V. Corpus restiforme. 
 
 W. N. acusticus. 
 
 X. Portio motor N. trigemini. 
 
 Y. Braehium pontis. 
 
 Z. Braehium conjunctivum. 
 
 1. Colliculus inferior. 
 
 2. Colliculus superior. 
 
 3. Corpus pineale. 
 
 4. Pulvinar. . i 
 
 5. Tractus spinalis N. trigemini. 
 
 6. Trigonum lemnisci. 
 
IMiATPJ XXlV-l.A'J'KJiAL SURFACE OF CRUS 
 
 cerp:br[. pons, ^irapezium, and med- 
 ulla OBI.OXtiATA (x 2 2/3). 
 
16G ANATOMY OF THE BRAIN 
 
 PLATE XXV. 
 
 DORSAL SURFACE OF THE MEDULLA AND PONS, 
 
 WITH FLOOR OF THE VENTRIC- 
 
 ULUS QUARTUS. 
 
 A. Ventriculus tertius. 
 
 B. Stria medullaris thalami. 
 
 C. Piilvinar. 
 
 D. Corpus pineale. 
 
 E. Corpus geniculatum iuteruuin. 
 
 F. Sulcus intercollicularis, 
 
 G. Colliculus superior. 
 H. N. patheticus. 
 
 I-X. Sulcus limitans fossae rhomboideae. 
 
 J. Colliculus inferior. 
 
 K. N. trigeminus. 
 
 L. Colliculus facialis. 
 
 M. Fovea anterior. 
 
 N. Brachium conjunctivum. 
 
 0. Sulcus long'itudinalis fossae rhoiuboideae. 
 
 P. Brachium pontis. 
 
 Q. Tuberculuin acusticum. 
 
 R. Fossa rhomboidea. 
 
 ;S^. Sulctls semilunaris. 
 
 T. Corpus restiforme. 
 
 V. Area aeustica. 
 
 V. Fovea posterior. 
 
 W. Eminentia medialis. 
 
 Y. Clava. 
 
 Z. Canalis centralis medullae spinalis. 
 
 1. Obex. 
 
 2. Depressio interfusiformis. 
 
 3. Sulcus fusiformis. 
 
 4. Fasciculus fusiformis. 
 
 5. Sulcus intermedins dorsal is. 
 
 6. Fasciculus gracilis. 
 
 7. Sulcus dorsalis. 
 
 8. Fasciculus cuneatus. 
 
 9. Sulcus lateralis dorsalis. 
 
 10. Fasciculus eerebellospinalis. 
 
A 
 
 j^ai^fek'A ^fe, 
 
 M 
 
 
 i 
 
 KgH 
 
 G-V 
 
 R'li 
 
 
 PLATE XXV^-DOKSAh SURFACE ()K PONS AND 
 THE MEDULLA OBLONGATA (x 2 2/3). 
 
168 ANATOMY OF TIIE BRAIN 
 
 PLATE XXVI. 
 
 Fig. 1. A CORONAL SECTION THROUGH THE 
 BULBI OLFACTORII, 
 
 beginning on the dorsal surface of the encephalon near 
 the narrowest portion of the gyrus medialis anterior. 
 
 A. Fissura iongitudinalis. 
 
 B. Fissura coronalis. 
 
 C. Gyrus frontalis inferior. 
 
 D. Gyrus orbitalis. 
 
 F. Ventriculus bulbi olfactorii. 
 P. Bulbus olfactorius. 
 
 Fig. 2. A SECTION THROUGH THE CEPHALIC 
 PORTIONS OF THE VENTRICULI LATER- 
 ALES AND SEPTUM PELLUCIDUM, 
 
 beginning in the fissura coronalis. 
 A. Fissura Iongitudinalis. 
 G. Corpus callosum. 
 /. Septum pelluciduui. 
 /. Nucleus caudatus. 
 K. Capsula interna. 
 L. Tractus olfactorius. 
 M. Rostrum corporis callosi. 
 N. Capsula externa. 
 0. Ventriculus lateralis. 
 
Fi"-. l-Cdtoiial Section 'rhr()U«j:li the Olfactory Bulbs 
 
 Fi^- 2— Section Tliroutih Anterior Portion of tho Lateral 
 Ventricles (x 2). 
 PLATE XXVI. 
 
170 ANATOMY OF THE BRAIN 
 
 PLATE XXVII. 
 
 Fig. 1. CARRY THE SECTION THROUGH THE 
 ENCEPHALON, 
 
 parallel to and just cephalad to the fissura cerebri lat- 
 eralis. 
 
 A. Fissura longitudinalis. 
 
 E. Fissura suprasylvia. 
 
 F. Nucleus lentiformis. 
 
 G. Corpus callosum. 
 K. Insula. 
 
 /. Septum pellucidum. 
 
 K. Capsula interna. 
 
 iV. Capsula externa. 
 
 0. Ventriculus lateralis. 
 
 Q. Substantia alba insulae. 
 
 jR.' Ramus anterior fissurae lateralis cerebri. 
 
 B. Claustrum. 
 
 T. Commissura anterior. 
 
 3. Nucleus caudatus. 
 
 W. Stria terminalis. 
 
 77. Columna fornicis. 
 
 Fig. 2. BEGIN THE INCISION ON THE DORSAL 
 SURFACE OF THE ENCEPHALON 
 
 about midway between the fissura cruciata and polus pos- 
 ticus, completing the section cephalad to the opening in 
 the infundibulum. 
 
 A. Fissura longitudinalis. 
 
 E. Fissura suprasylvia. 
 
 G. Corpus callosum. 
 
 J. Ventriculus tertius. 
 
 K. Capsula interna. 
 
 L. Recessus opticus ventriculi tertii. 
 
 0. Ventriculus lateralis. 
 
 P. Thalamus. 
 
 R" . Ramus posterior fissurse lateralis cerebri. 
 ■ V. Corpus fornicis. 
 
 X. Fasciculus subcallosus. 
 
 Y. Plexus chorioideus ventriculi tertii. 
 
 Z. Substantia intermedia. 
 
 1. Tractus opticus. 
 
 2. Infundibulum. 
 
 4. Lobus hippocampi. 
 
 5. Fissura dentata. 
 
AXATO:\[A' OF THE BRAIN 
 
 171 
 
 Fig. 1 — Section -lust Posterior to tho Fissure of Svlviiis 
 
 (x 2). 
 
 i^U 
 
 Fij?. 2— Section Throu<>li Sub>stautia Iiitennedia (x 2;. 
 PLATE XXVII. 
 
172 ANATOMY OF THE BRAIN 
 
 PLATE XXVIII. 
 
 Fig. 1. BEGIN THE INCISION 6 MM. CAUDAD TO 
 
 THE LAST SECTION, 
 reaching the ventral surface just caudad to the infundib- 
 ulum. 
 
 A. Fissura longitudinal is. 
 
 C. Fasciola cinerea. 
 
 E. Fissura suprasylvia. 
 
 F. Fissura dentata. 
 
 G. Corpus callosum. 
 
 J . Ventriculus tertius. ' 
 
 0. Ventriculus lateralis. 
 
 P. Fimbria hippocampi. 
 
 1. Tractus opticus. 
 
 2. Infundibulum. 
 
 3. Hippocampus. 
 
 4. Substantia grisea fissurae dentatae. 
 .5. Cornu inferius.ventrieuli lateralis. 
 
 6. Lobus hippocampi.. 
 
 7. Pulvinar. 
 
 8. Lamina pinealis. 
 
 9. Columna fornicis. 
 10. Corpus mamillare. 
 15. Corpus pineale. 
 
 Fig. 2. MAKE THE INCISION ABOUT 2.5 CM. 
 
 CEPHALAD TO THE POLUS POSTICUS, 
 ending on the ventral surface about the tractus peduncu- 
 laris transversis. 
 
 A. Fissura longitudinalis. 
 
 E. Fissura suprasylvia. 
 
 3. Hippocampus. 
 
 5. Cornu inferius ventriculi lateralis. 
 
 6., Lobus hippocampi. 
 
 11. Aquaiductus cerebri. 
 
 12. Corpus geniculatum internum. 
 
 13. CoUieulus superior. 
 
 14. Tractus pyramidalis. 
 
ANATOMY OF THE BRAIN 
 
 173 
 
 Fig. 1 ►Section Through the Corpus Pineale. 
 
 Pig. 2— Seetion 2.5 mm. Anterior to Ihe Posterior Ex- 
 tremity of the Cerebrum (x 2). 
 PLATE XXVIII. 
 
174 ANATOMY OF THE BRAIN 
 
 PLATE XXIX. 
 
 Fig. 1. SECTION THROUGH THE CRURA AND 
 COLLICULI SUPERIORES. 
 
 Fig. 2. SECTION THROUGH THE CRURA 
 
 intermediate between the N. aeulomotorius and the cephalic 
 border of the pons. 
 
 Fig. 3. SECTION IMIMEDIATELY CEPHALAD TO 
 THE PONS. 
 
 A. Nu. oenlomotorii. 
 
 B. Traetus pyraniidalis peduncnli. 
 
 C. Striae longitudinales (sections of). 
 
 D. Aqiiaeductus cerebri. 
 
 E. Fibrae transversae colliculi superiores. 
 
 F. Traetus cerebro-thalannis. 
 
 G. Sulcus inter-collicuius. 
 H. Colliculus superior. 
 
 I. Traetus peduneularis transversus. 
 
 J. Corpus geniculatum internum. 
 
 K. Traetus colliculus iuferius. 
 
 L. (a^ Stratum opticum in fig. 2. 
 
 (b) Brachium conjunctivum in fig. 3. 
 
 A. Crus. 
 
 0. Ventriculus quartus. 
 
 7*. Colliculus inferior. 
 
 Q. Nucleus ruber. 
 
PLA'J'K 
 
 XXIX-SE(ri'l<)XS 'IIIROlUilf THE 
 LICULUS SUPERIOR AND (JKIKA 
 CEKEBKT fx 2 2/3). 
 
 COL- 
 
176 ANATOMY OF THE BRAIN 
 
 PLATE XXX. 
 
 Fig. 1. 2mm. CEPHALAD TO THE CAUDAL BOR- 
 DER OF THE PONS. 
 
 Fig. 2. THROUGH THE N. TRIGEMINUS. 
 
 Fig. 3. THROUGH THE CENTER OF THE TRA- 
 PEZIUM. 
 
 A. Bracliium pontis. 
 
 B. Pyramis anterior. Fasciculus longitudinalis super- 
 ficialis pontis. 
 
 C. Stria longitudinalis medialis. 
 L. Brachium conjunctivum. 
 
 0. Sulcus longitudinalis fossae rhomboideae ventriculi 
 ([uarti. 
 
 Q. Fibrae pontis superficiales ventrales. 
 
 E. Raphe pontis. 
 
 T. Corpus restiforme. 
 
 V. Velum medullare anterius. 
 
 y. Eminentia medialis. 
 
 W. Fibrae pontis superficiales laterales. 
 
 X. Eminentia facialis. 
 
 y. Vermis cerebelli minor. 
 
 Z. Nucleus olivaris inferior. 
 
 5. N. trigeminus. 
 
 6. N. abducens. 
 
 7. N. facialis. 
 
PLATJ: XXX-SECTIONS THROUGH MHE PONS 
 AND TRAPEZIUM (x 2 2/3). 
 
178 ANATOMY OF THE BRAIN 
 
 PLATE XXXI. 
 
 Fig. 1. THROUGH THE OLIVAE. 
 
 Fig. 2. THROUGH THE N. ACUSTICUS. 
 
 Fig. 3. THROUGH THE CAUDAL THIRD OF THE 
 THE VENTRICULUS QUARTUS. 
 
 B. Pyramis. 
 
 C: Stria longitudinalis profundis. 
 
 F. Sulcus limitans fossae rhomboideae. 
 
 /. Eminentia medialis. 
 
 0. Sulcus longitudinalis fossae rhomboideae. 
 
 F. Area acustica. 
 
 Q. Ventriculus quartus. 
 
 U. Raphe. 
 
 T. Corpus restiforme. 
 
 Z. Oliva (nucleus of). 
 
 5. Radix aseendens N. trigemini. 
 
 8. N. acusticus. 
 
anato:my of the brain 
 
 17 9 
 
 PLATK XXXI-.SECI10N8 THROUGH THE MEDUL- 
 LA OBLONGATA (x 2 2/3). 
 
180 ANATOMY OF THE BRAIN 
 
 PLATE XXXII. 
 
 Fig. 1. SECTION THROUGH THE CAUDAL FOURTH 
 OF THE VENTRICULUS QUARTUS. 
 
 Fig. 2. SECTION AT THE ENTRANCE OF THE 
 CANALIS CENTRALIS. 
 
 Fig. 3. SECTION THROUGH THE CAUDAL BOR- 
 DER OF THE OBEX. 
 
 Fig. 4. SECTION OF MEDULLA SPINALIS. 
 B. Pyramis. 
 D. Columna dorsalis. 
 G. Substantia gelatinosa. 
 
 11. Columna ventralis. 
 J. Canalis centralis. 
 
 K. Substantia gelatinosa centralis. 
 
 L. Fissura ventralis. 
 
 B. Raphe. 
 
 T. Corpus restiforine. 
 
 X. Obex. 
 
 5. Radix ascendens N. trigemini. 
 
 7. Sulcus dorsalis. 
 
 12. Eminentia hypoglossi. 
 
J>LATE XXXIT-SKCTTONS THROUGH THE MKD- 
 
 ULLA OBLONGATA AND SPINAL 
 
 COKD (x 2 2/3). 
 
182 ANATOMY OF THE BRAIN 
 
 PLATE XXXIII. : 
 
 ENLARGED SECTION OF THE MEDULLA 
 SPINALIS. 
 
 A. Fissura ventralis. 
 
 B. Funiculus ventralis. 
 
 C. Sulcus ventralis lateralis. 
 
 D. Columna lateralis. 
 
 E. Funiculus lateralis. 
 
 F. Fasciculus lateralis minor. 
 
 G. Processus reticularis. 
 H. Fasciculi longitudinales dorsales. 
 I. Fasciculus cerebellospinaiis. 
 J. Sulcus lateralis dorsalis. 
 K. Substantia gelatinosa. 
 L. Fasciculus cuneatus. 
 M. Sulcus intennedius dorsalis. 
 N. Fasciculus gracilis. 
 0. Sulcus dorsalis. 
 P. Fasciculus fusiformis.- 
 Q. Commissura dorsalis. 
 R. Columna dorsalis. 
 8. Radix dorsalis nervi spinalis. 
 T. Canalis centralis. 
 U. Commissura ventralis grisea. 
 V. Fasciculus intereommissuralis ( Dexel & 
 
 Margulies) ventralis. 
 
 W. Radix spinalis N. accessorii. 
 
 X. Commissura ventralis alba. 
 
 Y. Columna ventralis. 
 
 Z. Radix ventralis nervi spinalis. 
 
ANATOMY OF THE BKAIN 
 
 183 
 
 <?X 
 
 PLATE xxxiii-enlargp:d section of spinal 
 
 CORD .5 CM., CAUDAD TO MEDULLA 
 OBLONGATA. 
 
184 ANATOMY OP THE BRAIN 
 
 PLATE XXXIV. 
 
 SECTION THROUGH THE LOWER PORTION OF 
 THE MEDULLA OBLONGATA, SHOWING 
 THE DECUSSATION OF THE PYRA- 
 MIDAL FIBRES. 
 
 A. Fissura ventralis, 
 
 B. Pyramis, 
 
 C. Pyramis, decussation of, 
 
 D. Fasciculi longituclinales dorsales, 
 
 E. Fasciculus cuneatus, 
 
 F. Fasciculus Gracilis, 
 
 G. Fasciculus fusiformis, 
 
 H. Radix dorsalis N. spinales, 
 
 I. Substantia gelatinosa (Rolando), • 
 
 J. Fasciculus cerebellospinalis, 
 
 K. Forraatio reticularis, 
 
 L. N. hypoglossus (caudal extremity), 
 
 0. Fasciculus lateralis minor, 
 
ANATOMY OF THE BRAIN 
 
 185 
 
 A B 
 
 PLATE XXXIV. 
 
186 ANATOMY OP THE BRAIN 
 
 PLATE XXXV. 
 
 SECTION THROUGH THE NUCLEI ARCUAT.T. 
 
 A. Sulcus ventral is. 
 
 B. Pyramis. 
 
 C. Nuclei arcuati. 
 X>, N. hypogiossus. 
 
 E. Fasciculus lateralis minor. 
 
 F. Fibrae arcuatae externae. 
 
 G. N. Glossopharyngi. 
 H. Corpus restiforme. 
 ./. Nucleus cuneatus. 
 
 J. Nucleus gracilis. 
 
 K. Fasciculus fusiformis. 
 
 L. Nucleus hypogiossus. 
 
 M. Taenia ventriculi quarti. 
 
 N. Ventriculus quartus. 
 
 0. Ramus obiseis. 
 
 P. Nucleus glossopharyngeus. 
 
 Q. Fasciculus solitarius. 
 
 B. N. vagus. ' 
 
 S. Tractus spinalis N. trigcmini. 
 
 T. Nucleus tractus spinalis N. trigeiiiini. 
 
 JJ. Formatio reticularis grisea. 
 
 y. Formatio reticularis alba. 
 
akatomy of the brain 
 
 187 
 
188 ANATOMY OF THE BRAIN 
 
 PLATE XXXVI. 
 
 SECTION THROUGH THE CAUDAL THIRD OF THE 
 FOURTH VENTRICLE. 
 
 A. Pyramis ventralis. 
 
 B. Lemniscus meclialis. 
 
 C. Fasciculus lateralis minor (Gower). 
 
 D. Tractus spinalis N. tragemini. 
 
 E. Corpus restiforme. 
 
 F. Nucleus vagi, dorsal and ventral areas. 
 
 G. Plexus ehorioideus ventriculi quarti. 
 H. Taenia ventriculi quarti. 
 
 /. Tractus solitarius N. vagi. 
 
 J. Nervus vagus. 
 
 K. Fibrge arcuatce externa?. 
 
 L. Eminentia medialis. 
 
 M. Nucleus ambiguus N. vagi. 
 
 N. Fibras arcuatae internae. 
 
ANATOMY OF THE BRAIX 
 
 189 
 
190 ANATOMY OF THE BRAIN 
 
 PLATE XXXVII. ;: 
 
 SECTION THROUGH THE TRAPEZIUM, COCHLEAR 
 AND VESTIBULAR NUCLEI. 
 
 A. N. coehl*. 
 
 B. Nucleus dorsalis N. eochlearis. 
 
 C. Striae niedul lares. 
 
 D. Nucleus ventral is N. eochlearis. 
 
 E. Corpus restifonne. 
 
 F. Fibres from the nucleus ventral is N. eochlearis. 
 
 G. Fibres from the nucleus dorsalis N. eochlearis. 
 H. Nervous vestibuli. 
 
 7. Nucleus lateralus N. vestibuli (Deiter). 
 
 /. Radix descendens N. vestibuli. 
 
 K. Nucleus oliva:\ 
 
 L. Nucleus N. facialis. 
 
 M. Pars prima N. facialis. 
 
 N: Nucleus N. abducentis. 
 
 0. Genu N. facialis. 
 
 P. Fibres of the trapezium. 
 
 Q. Nucleus tractus spinalis N. trigemini. 
 
 R. Tractus spinalis N. trigemini. 
 
 S. Tractus pyramidalis. 
 
 T. N. abducens. 
 
 v. Fibrfp arcuata^ externae. 
 
 V. Decussation of the stritv medulla res from the dorsal 
 and ventral cochlear nuclei. 
 
 W. Formatio reticularis. 
 
 X. Fasciculus lateralis minor. 
 
 ¥. Nucleus dorsalis N. vestibuli. ^ 
 
 Z. Area aeustica. 
 
ANATOMY OP THE BRAIN 
 
 191 
 
 . my 
 
 
 
 CM 
 
192 ANATOMY OF THE BRAIN 
 
 PLATE XXXVIII. 
 
 SECTION THROUGH THE COLLICULI SUPE- 
 
 RIORES. 
 
 A. N. oculomotor-ins, fibres leading from its nncleus. 
 
 B. Pyramis. 
 
 C. Corpus genicnlatus externum. 
 
 D. Stratum opticum. 
 
 E. Colliculus superior. 
 
 F. Stratum griseum eentrale. 
 
 G. Corpus geniculatum internum. 
 H. Aquaeduetus cerebri. 
 
 /. Nucleus ruber. 
 
 J. Fasciculus retroflexus (Meynert). 
 
 L. Lamina quadrigemina. 
 
ANATOMY OF THE BRAIN 
 
 193 
 
 PLATE XXXVIII-SECTION THROUGH THE COLLICULI 
 
 ^;:'^ ''?:!! ' SUPERIOKES. 
 
194 ANATOMY OF THE BRAIN 
 
 PLATE XXXIX. 
 
 THE BASE OF THE SKULL 
 with the dura mater and the nervi cerebrales in position. 
 
 1. 
 
 N. olfaetorius. 
 
 2. 
 
 Tractus opticus. 
 
 3. 
 
 N. oculomotorius. 
 
 4. 
 
 N. pathetieus. 
 
 5. 
 
 N. trigeminus. 
 
 6. 
 
 N. abdueens. 
 
 7. 
 
 N. facialis. 
 
 8. 
 
 N. acusticus. 
 
 9. 
 
 N. Glosso-pharyngeus. 
 
 10. 
 
 N. vagus. 
 
 11. 
 
 N. accessorius. 
 
 12. 
 
 N. hypoglossus. 
 
 AA 
 
 . Sinus frontales. 
 
 B. 
 
 Crista galli. 
 
 C. 
 
 Fossa olfactoria. 
 
 D. 
 
 Fossa frontalis. 
 
 E. 
 
 Foramen opticum. 
 
 F. 
 
 Commissura optica. 
 
 G. 
 
 Recessus infundibuli. 
 
 H. 
 
 Infundibulum. 
 
 I. 
 
 Foramen diaphragmatis sellae. 
 
 J. 
 
 Arteria carotis interna. 
 
 K. 
 
 Fossa hippocampi. 
 
 L. 
 
 Tentorium cerebelli. 
 
 M. 
 
 Foramen magnum. 
 
 N. 
 
 Meatus acusticus internus. 
 
 P. 
 
 Foramen jugulare. 
 
 R. 
 
 Dura mater. 
 
 S. 
 
 Fossa parietalis. 
 
 T. 
 
 Condylus occipitalis. 
 
ANATOMY OF THE BRAIN 
 
 195 
 
 1^1 \TF XXXJX-HASE OF SKULL SHOWING DURA 
 
 MA'['FAi AVITII EXITS OF CRANIAL 
 
 NERVES (X 1 1/3). 
 
196 ANATOMY OF THE BRAIN 
 
 PLATE XL. 
 
 BASIS CRANII. 
 
 A. Sinus frontales. 
 
 B. Lamina cribrosa. 
 
 C. Crista galli. 
 
 D. Sulcus chiasmatis. 
 
 E. Fissura sphenoidalis. 
 
 F. Processus clinoideus anterior. 
 
 G. Fossa hypophyseos (sella turcica), 
 H. Sulcus caroticus. 
 
 /. Foramen ovale. 
 
 J. Processus clinoideus posterior. 
 
 K. Fossa jugularis. 
 
 L. Dorsum sellae. 
 
 M. Sulcus sigmoideus. 
 
 N. Meatus acusticus internus. 
 
 0. Condylus occipitalis. 
 
 P. Foramen eondyloideum. 
 
 B. Foramen occipitale magnum. 
 
 S. Pars petrosa. 
 
 T. Os basilare. 
 
ANATOMY OF TJIE BRAIN 
 
 197 
 
 PLATK XI-. IJASi: Ol-' 1'1IH SKUl.l. (x T l/:i}. 
 
INDEX . 
 
 Ala ciiRTca, !)(>, Ill 
 Anterior cerebellar artery, 29, 12o 
 Anterior cerebral artery, 28, 12o 
 Anterior column of spinal conl ( tiiiiicii 
 
 Ins ventralis), 185 
 Anterior commissure, 4.'5. 51, 77. 155 
 Anterior coininiinicating artery, 30 
 Anterior liinb of internal capsule, 72, 153 
 Anterior perforated space, 44 
 Anterior spinal artery, 30 
 Anterior pillars of fornix, 78 
 Antero-lateral fissure, 97 
 Aperatura mediana ventriculi ciuarti, 27, 
 
 52, 94 
 A<iufeduetus cerebri, 53, 103 
 Aqueduct of Sjdvius, 53 
 Araclinoidea encephali, 24 
 Arachnoid membrane, 24 
 Arbor vit*. 54, 133 
 Area acustica, 91, 103, 167 
 Area lateralis thalami, 72, 153 
 Area medialis thalami, 72, 153 
 Area posterior thalaiui, 72, 153 
 Area postrenia of Retzius, 112 
 Arteria basilaris, 29, 125 
 Arteria basilaris gaiigliforniis postcriijr, 
 
 29, 125 
 Arteria carotis interna, 28 
 Arteria cerebelli anteiior, 29, 125 
 Arteria cerebelli postericn', 29, 125 
 Arteria cerebri anterior, 28, 125 
 Arteria cerebri media, 29, 125 
 Arteria cerebri ])osterior, 29, 125 
 Arteria propria cerebri, 28, 125 
 Arteria spinalis ventralis. 30 
 Arteria; communicantes fndi'rioKs, 30 
 Arteria; meningese, 19 
 Arteriic vertebra les, 30 
 Ascending [)art (N". facialis), 92 
 Associiitioii bundles, (»0 
 Aula, 80 
 Axoncs, 31 
 
 Pmsiiar artery, 30 
 
 Basis cranii, 22, 197 
 
 Btchterew's nucleus, 92 
 
 Blood vessels, 28, 125 
 
 Bracliia pontis, 87, 165, 167 
 
 Bracliium conjunctivae, 86, 167 
 
 Bracluum quadrigeniiiiii iiiferius, 83, 
 
 104, 159 
 Broca's limbic fissure, 50 
 Broca's quadrilateral space, 44 
 Bulbe rachidian, 93 
 Bnlbi fornicis, 45, 131 
 Bulbi olfactorii, 17, 43, 131 
 Burdach's tract, 107 
 Calamus scriptorius, 112 
 Canalis centralis, 54, 183 
 Capsula externa, 52, 72, 153 
 Capsula interna, 71, 153 
 Caput nuclei caudati, 61, 143 
 Caudate nucleus, 63 
 Cavum septi pellucidi, 62 
 Cavum subaraehnoideale, 24 
 Cavum subdurale, 24 
 Cell staining, 31 
 
 Central canal of spinal cord, 110, 183 
 Cerebellar bridge (pons), 87 
 Cerebellar peduncles, inferior, 102 
 Cerebellar peduncles, middle, 87 
 Cerebellar penduncles, superior, 86 
 Cerebellar arteries, anterior, 29 
 Cerebellar arteries, posterior, 29 
 Cerebellar licinis|)li('res, 39, 127 
 < 'crebelluin, 15 
 
 Ciichral arteries, anterior, 28 
 (crchral a r1 cries, middle, 29 
 ( rrcbiai arteries, posterior, 29 
 Cerebral convolutions, 32 
 ('eicbral ])eduneles, 94, 131 
 Cerebral ])r<.t ni.eiance of (Joll, 93 
 Cei'ebrnMi, 15 
 ( liiasma, oj)! iciiin, 44. 131 
 Cinguluni, 57 
 
200 
 
 ANATOMY OF THE BRAIN 
 
 Cingulum inferius, 58 
 
 Cingulum super ius, 57 
 
 Circle of Willis, 30 
 
 Circulation at the base of the brain, 30 
 
 Circulus arteriosus, 30 
 
 Cisterna subarachnoidea, 24 
 
 Clava, 103, 167 
 
 Claustrum, 72, 153 
 
 Colliculus facialis, 167 
 
 Colliculus inferior, 82, 167 
 
 Colliculus superior, 71; 146. 193 
 
 Columna dorsalis, 183 
 
 Columna lateralis, 183 
 
 Columna ventralis, 97, 183 
 
 Columnae fornicis anteriores, 61, 147 
 
 Columnse fornicis posteriores, 65, 149 
 
 Commissura anterior, 43, 51, 77, 155 
 
 Commissura anterior (dissection of), 77 
 
 Commissura dorsalis, 183 
 
 Commissiira liabenulariun, 75 
 
 Commissura hij^pocampi, 65 
 
 Commissura medialis, 54, 133 
 
 Commissura posterior, 53, 133 
 
 Commissura optica, 44, 131 
 
 Commissura ventralis alba, 183 
 
 Commissura ventralis grisea, 183 
 
 Conarium, 75 
 
 Conchfe ethmoideales, 16 
 
 Condyli occipitales, 16, 197 
 
 Confluens sinuum, 21 
 
 Cornu anterius ventriculi lateralis, 02 
 
 Cornu inferius ventriculi lateralis, 57, 
 
 62, 143 
 Cornu posterior ventriculi lateralis, 57 
 Cornua, 62 
 
 Corona radiata, 85, 161 
 Corpora albicantia, 45, 131 
 Corpora mamillaria, 45, 131 
 Corpora quadrigemina, 53, 69, 82 
 Corpus callosum, 49, 133, 137, 139 
 Corpus fimbriatum, 65 
 Corpus fornicis, 61, 65, 149 
 Corpus geniculatum externum, 71, 193 
 Corpus geniculatum intei'num, 71, 193 
 Corpus medullare cercbelli, 38, 54, 133 
 Corpus pineale, 53, 75, 133, 147 
 Corpus restiforme, 90, 100, 187, 189 
 
 Corpus striatum, 44 
 
 Corpus trapezoideum, 90 
 
 Cortex, 31 
 
 Corticifugal fibres, 60 
 
 Corticipetal fibres, 60 
 
 Crista galli, 197 
 
 Crura cerebri, 45 
 
 Crura fornicis posterior, 65 
 
 Crus cerebelli ad corpora quadriguniiii 
 
 103 
 Decussation of the Nn. trochlear.'s. 95 
 Decussation of the pyramids, 97, U'5 
 Deiter's nucleus, 92 
 Dentate fassia, 57 
 Dentate fissure, 67 
 Depressio interfusiformis, 1(57 
 Diacoele, 80 
 
 Direct cerebellar tract, 102 
 Dissecting Wax, 12 
 Dorsum sellse, 197 
 Dura mater encephali, 19, 123 
 Eminentia facialis. 90. ] 1 1 
 Eminentia hj'poglossi. Ill 
 Eminentia medialis, 89, 110, 167, 187 
 Eminentia teres (facialis), 90 
 Eminentia vagi, 96 
 Encephalon, 15 
 Ependyma, 39 
 Ejjineurium, 22 
 Epiphysis, 75 
 
 Espace quadrilatiere of 15rt:ca. 44 
 Ethmoturbinals. 16 
 External capsule, 72 
 External geniculated body. 71 
 Facies dorsalis cerebelli, 38. 127 
 Faeies lateralis cerebelli, 39 
 Facies medialis cerebelli, 51, 133 
 Facies dorsalis cerebri, 33, 127 
 Facies lateralis cerebri, 41, 129 
 Facies medialis cerebri, 49. 133, 157 
 Facies ventralis cerebri, 43, 131 
 Falx cerebri, 20 
 Fascia dentata, 57, 62 
 Fasoia dentata hippocampi, 68. 151 
 Fasciculi longitiulinales dorsales, 98, 
 
 183 
 Fasciculus cerebellospiiialis, 100. 183 
 
ANATOMY OF THE BRAIN 
 
 201 
 
 Fa-icicuhis ciineatiis, 102. 107, 183 
 Fasciciilus fiisiformis, 106, 167, 183 
 Fasciculus gracilis, 107, 183 
 Fasciculus lateralis minor, 98, 183, 183, 
 
 187, 189, 191 
 Fasciculus longitudinalis nu'dialis, 88 
 Fasciculus longitudiiialis proliunlis pon- 
 
 tis, 88, 177 
 Fasciculus longitudiiialis suiuMticialis 
 
 pontis, 87 
 Fasciculus retrofle.ws, 73, 193 
 Fasciculus separans, 112 
 Fasciculus subcallosus, 58, 149 
 Fasciculus tlialamomaniillaris, 79, 137 
 Fasciculus ventralis intracoramissuralis 
 
 [longitudinalis] (Dtxid & Maigulies ) . 
 
 182 
 Fasciculus ventrolatoalis su[)crficialis. 
 
 99 
 Fasciola cinerea, 53, 68, 133 
 Fibrse arcuatai externip, 100, 187 
 Fibrae arcuatie intern.T, 189 
 Fibrse longitudinales, 85 
 Fibrae pontis profunda'. 88, 177 
 Fibrae pontis superficialos, 84 
 Fibrae transversae colliculi suijcriores, 
 
 175 
 Fifth ventricle, 62 
 Fillet, 108 
 
 Fimbria hi]>pocamj)i. 62, 149, 173 
 Fissura cerebelli medialis, 127 
 Fissura cerebelli inferior, 127 
 Fissura cerel)elli superior, 127 
 Fissura cerebri lateralis, 41, 129 
 Fissura cerebri intermedia dorsalis 
 
 (sulcus), 127 
 Fissura cerebri lalcialis dorsalis 
 
 (sulcus), 127 
 Fissura cerebri iiifdialis dorsalis 
 
 (sulcus), 127 
 Fissura coionalis (-ulcus), 33 
 Kissura cniciata, 33, 127 
 Fissura dentata, 67, 151 
 Fissura hippocampi, 68 
 Fissura limbica, of IJroca, 30 
 Fissura liird)icii, of Tiirnei-, 41 
 
 Fissura longitudinalis cerebri, 20, 31, 
 127 
 
 Fissura inediaiia dorsalis medullae spin- 
 alis, 97 
 
 Fissura mediana ventralis medullae ob- 
 longatae, 96 
 
 Fissura rhinalis, 41, 130 
 
 Fissura sagittalis, 130 
 
 Fissura sphenoidalis, 22, 197 
 
 Fissura suprasylvia, 33, 127 
 
 Fissura transversa ct-rebri. 20. :!3. 67 
 
 Fissura venti^alis, 183 
 
 FissunB lerebelli, 39, 133 
 
 Fissure of Sylvius, 41 
 
 Flocculus, 40, 88, 129 
 
 Floor, of ventriculus teitius, 53 
 
 Folia cerebelli, 38 
 
 Foramina condyli anteriora, 21 
 
 Foramen condyloideum, 197 
 
 Foramen diaphragmatis sella'. 28 
 
 Foramen jugulare, 22 
 
 Foramen interventriculaic, (>'.). 145 
 
 I'^oramen of Magendi, 27, 94 
 
 Foramen of Monroe, 63 
 
 I'inamen oeciiiitale maginim. 16 
 
 Foramen optieum, 195 
 
 Foramen ovale, 194 
 
 Forceps anterior, 37 
 
 J'\)rceps, major, 57 
 
 Forceps, minor, 57 
 
 Forceps posterior, 57 
 
 Formatio reticularis alba, 108, 187 
 
 Formatio reticularis grisca, 187 
 
 Fornix. 65. 143, 149 
 
 Fossa cranii anterior, 194 
 
 Fossa cranii media, 22 
 
 Fossa cranii poslciior, 197 
 
 Fossa frontalis, 194 
 
 ]"'ossa liippociunpi, 194 
 
 l''ossa by|)0]i]iyse()s, 28, 194 
 
 Fossa interpeduiiciilaris, 24, 45 
 
 Fossa olfactoria, 194 
 
 Fossa orbital lis, 15 
 
 Fcssa parielalis, 19 1 
 
 Fo.s.sa rlioiiilMiidca. 1 10. 106 
 
 Fossa suhpiiicalis, 75 
 
202 
 
 ANATOMY OF THE BRAIN 
 
 Fossa temporalis, 22 
 
 Fovea anterior, 111, 167 
 
 Fovea posterior, 111, 167 
 
 Frontal siniLses, 15, 197 
 
 Funiculus lateralis, 102, 183 
 
 Funiculus ventralis, 183 
 
 Galen, rete mirabile, 22 
 
 Galen, vein of, 20 
 
 Ganglion liabenulse, 75 
 
 Ganglion semilunare (Gasser), 22 
 
 Gasserian ganglion, 22 
 
 Genu capsulfe internse, 71, 153 
 
 Genu corporis callosi, 49, 133 
 
 Genu nervi facialis, 92, 191 
 
 Globus pallidus, 72 
 
 GoU's cerebral protuberance, 93 
 
 Goll's tract, 107 
 
 Gower's tract, 99 
 
 Great commissure, 56 
 
 Great longitudinal fissure, 31 
 
 Great tranverse fissure, 33 
 
 Gyri centrales, 129 
 
 Gyri cerebri, 32 
 
 Gyri mediales, 127 
 
 Gyrus arcuatus, 42 
 
 Gyrus cinguli, 50, 133 
 
 Gyrus dentatus, 57 
 
 Gyrus fornicatus, 50 
 
 Gyrus frontalis inferior, 42, 129 
 
 Gyrus frontalis medialis, 33 
 
 Gyrus frontalis superior, 33, 127 
 
 Gyrus intermedins, 50, 133 
 
 Gyrus internus, 127 
 
 Gyrus lateralis, 127 
 
 Gyrus marginalis anterior, 51, 133 
 
 Gyrus marginalis posterior, 50, 133 
 
 Gyrus orbitalis, 42, 129 
 
 Gyrus parietalis externalis, 34 
 
 Gyrus parietalis internalis, 34 
 
 Gyrus parietalis medialis. 34 
 
 Gyrus rectus, 44 
 
 Gyrus sylviacus, 41 
 
 Hebenulfe, 75 
 
 Hemisplieria cerebelli, 39, 127 
 
 Hemisphserium cerebri, 31 
 
 Hippocampus, 59, 61, 67, 143 
 
 Hypophysis, 44, 155 
 
 Inferior cerebellar peduncle, 102 
 
 Inferior frontal gyrus, 42 
 
 Infundibulum, 44, 53, 131 
 
 Insula, 41, 129 
 
 Internal capsule, 71 
 
 Internal carotid artery, 28 
 
 Internal geniculated body, 71 
 
 Internal parietal gyrus, 34 
 
 Interpeduncular nucleus, 34 
 
 Interpeduncular space, 24 
 
 Island of Reil, 41, 129 
 
 Iter a tertio ad quartum ventriculuiu. 
 
 53 
 Kaiserling method, 73 
 Lambdoid suture, 16 
 Lamina cinerea, 52 . . , 
 
 Lamina cribrosa, 197 
 Lamina pinealis, 53 . 
 
 Lamina quadrigemina, 55, 133, 193 
 Lamina rostralis, 52 
 Lamina terminalis, 51, 52 
 Lancisi, nerves of, 56 
 Lateral column of the spinal cord, 182. 
 Lateral sinus, 17 
 Lateral ventricule, 56 
 Lemniscus lateralis, 83 
 Lemniscus medialis, 108 
 Lenticular nucleus, 72 
 Ligamentum denticulatum, 27, 163 
 LigTila, 95 
 
 Limbic fissure of Broca, 50 
 Limbic fissure of Turner, 41 
 Lissencephala, 50 
 Lobi cerebelli, 39, 133 
 Lobi cerebri, 32 
 Lobus cerebelli inferior, 39, 129 
 Lobus cerebelli medialis, 39, 129 
 Lobus cerebelli superior, 39, 129 
 Lobus centralis, 41, 129 
 Lobus frontalis, 34 
 Lobus hippocampi, 43, 131 
 Lobus occipitalis, 33 
 Lobus parietalis, 34 
 Lobus superior, cerebelli, 39, 127 
 Lobus temporalis, 34 
 
ANATOMY OF THE BRAIN 
 
 •203 
 
 Locus inleipfduuculaiis, 80 
 
 Locus perforatiLs anterior, 44, 131 
 
 Locus perforatus posterior, 45 
 
 lx)ngitudinal sinus, 17 
 
 Magendi, foramen of, 27 
 
 ^largo corporis fornicis, 145 
 
 Massa intermedia, 132 
 
 Meatus acusticus interna, ]!Hi 
 
 Medulla oblongata. 15, 47. !>3, 163, 185, 
 
 187. 189. 
 Medulla spinalis, 47 
 ^feningeal arteries, 1!) 
 Meninges, 17 
 
 Meynert's facieulus, 75. 103 
 Middle cerebellar peduncle. 87. 103 
 Middle cerebral artery, 29 
 Middle commissure. 132 
 Monroo, foramen of. 02 
 Motor fasciculus, 5th nerve, 152 
 Motor areas, 35, 36 
 Xates, 82 
 
 Xenes of Lancissi, oi) 
 Xervi abducentes, 46, 131, 191 
 Xervi accessorii, 27, 47, 131 
 
 Xervi acustici, 46, 131. 191 
 
 Xervi cerebrales, 17 
 
 Xervi faciales, 46, 131. 191 
 
 Xervi glossopharyngei. 47, 131 
 
 Xervi hypoglossi, 47, 131. 185 
 
 Xervi oculomotoiii, 45 
 
 Xervi olfactorii, 45, 131, 193 
 
 Xervi optici, 17, 44, 131, 
 
 Xervi pathetici, 45 
 
 Nervi spinales, 47 
 
 Nervi trigemini, 45, 131, 177, 179, 187, 
 189 
 
 Xervi trochlearc.s, 45, 131 
 
 Xervi vagi, 47, 131 
 
 Nervus cochlearis, 91 
 
 Xervus mandibularis, 22 
 
 Xervus maxillaris. 22 
 
 Xervus ophthalmicus, 22 
 
 Nervus vestibularis, 91 
 
 Neurones, 31 
 
 Nuclei arcuati, 101, 187 
 
 Nuclei pontis, 87 
 
 Nucleus abdueenlis, 92, 19] 
 
 Nucleus ala; cinerete, 112 
 
 Xucleus ambiguus, 112, 189 
 
 Xucleus caudatus, 63 
 
 Xucleus cuneatus, 108, 187 
 
 Xucleus dorsalis X. cochlearis, 91, 191 
 
 Nucleus doi-salis N. vestibularis, 91 
 
 Nucleus facialis, 90, 92, 108. 191 
 
 Xucleus fasciculus fusiformis, 108 
 
 Xucleus glosso-pharyngeus, 112, 187 
 
 Xucleus gracilis, 108, 187 
 
 Nucleus interpeduneularis, 45, 131 
 
 Xucleus lenticularis, 72, 153 
 
 Xucleus lentiformis, 72, 153 
 
 Xucleiis Xervus Acstibularis. 91 
 
 Xucleus olivaris inferior, 92, 191 
 
 Xucleus ruber, 85, 193 
 
 Nucleus tractus spinalis X. trigemini, 
 
 112, 190 
 Nucleus vagus, 112. 189 
 Nucleus ventralis N. cochh'nris, 91, 191 
 Obex, 106, 167 
 
 Olfactory bulbs, 43 
 
 Olfactory tracts, 43 
 
 Oliva, 99, 163 
 
 Operculum, 42 
 
 Optic chiasm, 44 
 
 ( )])tic conunissiu'e, 44 
 
 Optic nerve, 17 
 
 Optic thalamus, 70, 147 
 
 Optic tracts, 44. 131 
 
 Orbital fossae, 15, 121 
 
 Os basilare, 21, 197 
 
 Os occipitale, 21 
 
 Os parietale, 34 
 
 Os sphenoidale, 22 
 
 Os temporalis, 22 
 
 Ossa cranii, 15 
 
 Pallium, 31 
 
 I'araflocculus, 40, 129 
 
 Par vagum, 47 
 
 Pars centralis thalami, 72, 153 
 
 Pars frontalis ca])sulifi interna', 72, 153 
 
 Pars libra columna? fornicis, 78 
 
 Pars petrosa ossis temporalis, 22, 197 
 
 Pars posticus capsula; interna, 72, 153 
 
 Pars prima N. facialis, 92, 191 
 
 Pars secunda N. facialis, 92, 177 
 
204 
 
 ANATOMY OF THE BRAIN 
 
 Pars tecta columnse fornicis, 51, 78, 157 
 
 Pedunculi cerebri, 45, 131 
 
 Pia mater encephali, 26 
 
 Pigment granules, 26 
 
 Pineal gland, 75 
 
 Pituitary body, 44, 155 
 
 Plexus chorioideus ventriculi lateralis, 
 
 61, 143 
 Plexus chorioideus ventriculi quarti, 94. 
 
 95, 108, 189 
 Plexus chorioideus ventriculi tertii, 59. 
 
 64, 69, 145 
 Pneumogastric nerve, 47 
 Polus anticus, 33 
 Polus frontalis, 41 
 Polus occipitalis cerebri, 65 
 Polus posticus, 34 
 Pons, 15, 45 
 Pons Tarini, 45 
 Pons Varolii, 45 
 Pontal nuclei, 87 
 Porta, 63 
 
 Portio dura of Willis, 90 
 Portio mollis of Willis, 90 
 Portio motor aST. trigemini, 152 
 Posterior cerebellar artery, 29 
 Posterior cerebral artery, 29 
 Posterior commissure, 133 
 Posterior limb of internal capsule, 72. 
 
 153 
 Posterior longitudinal bundle, 110 
 Posterior perforated space, 45 
 Posterior pillars of the fornix, 65 
 Postro-external tract (Goll), 107 
 Postro-internal tract (Burdach), 107 
 Principal vestibular nucleus, 91 
 Processus clinoideus anterior, 197 
 Processus clinoideus posterior, 197 
 Processus reticularis, 97, 183 
 Protuberantia occipitalis externa, 21 
 Pseudocoele, 62 
 Pulvinar, 70, 147 
 Putamen, 72, 153 
 Pyramidales, 87 
 Pyramis, N., 97, 179, 185, 187 
 Pyramis ventralis, 85, 189 
 Rachidian bulb, 93 
 
 iladiatio corporis callosi, 57 
 Piadicular part. (N. facialis), 92, 99 
 Radix ascendens N. trigemini, 90, 99, 
 
 179 
 Radix cerebralis N. accessorius, 47 
 Radix descendens N. vestibularis, 91, 
 
 191 
 Radix dorsalis nervi spinales, 182 
 Radix intermedia bulbi olfactorii, 43, 
 
 131 
 Radix lateralis bulbi olfactorii, 43, 131 
 Radix medialis bulbi olfactorii, 43, 131 
 Radix spinalis nervi accessorii, 182 
 Radix ventralis nervi spinalis, 182 
 Rami obicis, 110, 111 
 Ramus anterior arterise proprise, 28, 125 
 Ramus anterior fissurae lateralis cerebri, 
 
 41, 129 
 Ramus posterior arterije propriae, 28, 
 
 125 
 RamvLs posterior fissurae lateralis cere- 
 bri, 41, 129 
 Raphe corporis callosi, 56 
 Raphe pontis, 88 
 Recessus infundibuli, 53 
 Recessus lateralis ventriculi quarti, 81 
 Recessus opticus ventriculi tertii, 53 
 Recessus pinealis ventriculi tertii, 76 
 Recessus triangularis, 143 
 Reil, Island of, 41 
 Rete mirabile of Galen, 22, 28 
 Retzius, area postrema of, 112 
 Rostrum corporis callosi, 49, 133 
 Schneiderial membrane, 16 
 Sella turcica, 44 
 
 Sensory fasciculus, fifth nerve, 163 
 Septum pellucidum, 61, 145 
 Sinus basilaris magna, 21 
 Sinus cavernosus, 22 
 Sinus circularis, 22 
 Sinus frontalis, 197 
 Sinus petrosus inferior, 22 
 Sinus sagittalis, 20, 123 
 Sinus sagittalis superior, 17, 123 
 Sinus transversus, 17, 123 
 Smooth-brained animals, 50 
 Spinal accessory nerve, 47 
 
ANATOMY OF THE BRAIN 
 
 205 
 
 Spinal cord, Plate XXXIII, 183 
 
 Spinal nerves, 47 
 
 Splenii\ni corporis callosi, 49, l;33 
 
 Staining, substantia grisea, 31 
 
 Stratum cineneum, 82 
 
 Stratum griseum cent rale, 192 
 
 Stratum leninisei, 82 
 
 Stratum opticum, 82^ 193 
 
 Stratum zonale, 83 
 
 Stria longitudinalis lateralis, oO 
 
 Stria longitudinalis profiuuiis. 110 
 
 Stria terniinalis, 09 
 
 Striae aeusticae, 91 
 
 StriiK longitudinales, 175 
 
 Striae longitudinalis mediales, ofi 
 
 Striae medullares, 91. 191 
 
 Striae medullares thalanii. 7ii. 7ii. 147 
 
 Subarachnoid space, 24 
 
 Subdural space, 24 
 
 Substantia alba, 31 
 
 Substantia alba insula', ].)3 
 
 Substantia intermedia, 132 
 
 Substantia gelatinosa, 182 
 
 Substantia gelatinosa centralis, 182 
 
 Substantia grisea, 31, 53 
 
 Substantia grisea fissnrae dentatae. 173 
 
 Substantia grisea insulae. 153 
 
 Substantia nigra, 85 
 
 Substantia perforata anterior. 44 
 
 Substantia perforata po-^teriii)-. -15 
 
 Sulci cerebri, 32 
 
 Sulci olfactorii, 41 
 
 Sulci rhinales, 41 
 
 Sulcus basilaris, 87, 1(13 
 
 Sulcus caroticus, 21, 197 
 
 Sulcus cliiasniatis. 197 
 
 Sulcus cinguli, 59, 133 
 
 Sulcus foronalis, 33, 127 
 
 Sulcus corporis callosi, 5(». 133 
 
 Sulcus dorsalis, 106, 167 
 
 Sulcus fusiformis, 167 
 
 Sulcus intorcollicularis, 107 
 
 Sulcus inler-colliculus superior, 83 
 
 Sulcus intermedius, 34, 127 
 
 Sulcu.s intermedins dorsalis. 107, lii7 
 
 Sulcus lati-ralis, 34, 127 
 
 Sulcus lateralis dorsalis, 102, 185 
 
 Sulcus lateralis ventralis, 102, 185 
 
 Sulcus limitans fossae rhomboideae, 110, 
 167 
 
 Stilcus longitudinalis fossae rhomboideae, 
 89, 91, 110, 1G7 
 
 Sulcus medialis, 34, 127 
 
 Sulcus oculomotorius, 84 
 
 Sulcus olfactorius, 41 
 
 Sulcus parolfactorius, 51, 133 
 
 Sulcus semilunaris, 110, 1(57 
 
 Sulcus sigmoideus, 197 
 
 Sulcus splenialis, 33, 50, 133 
 
 Sulcus transversus, 112 
 
 Sulcus ventralis, 1()3 
 
 Sulcus ventralis lateralis, 97, 103 
 
 Sulcus ventralis mednlhe oblongatae, 10? 
 
 Superior cerebellar peduncle, 88, 103 
 
 Superior longitudinalis sinus, 20 
 
 Sujjerior medullary velum, 54 
 
 Sntnra coronalis, 34 
 
 Sutura lambdoidea, l!i 
 
 Sutura sagittalis, 19 
 
 Sylvius, aquaduct of. 53 
 
 Sylvius, fissure of, 41 
 
 Tapetum, 57 
 
 Tarini, pons, 45 
 
 Taenia hippocampi, 02. 05 
 
 Taenia seraicircnlaris, 09 
 
 Taeniae tcctae (striii^ longitudinales later- 
 ales), 50 
 
 Taenia ventricnli i|uai(i. 112 
 
 Tapetum, 57 
 
 Tegmentum ventricuJi rpiarti, 54 
 
 'I'ela chrioidcM \cnliiculi ipiarti. 95. 110, 
 189 
 
 T(da chorioidea \riiiriculi tertii, 04 
 
 Tentorium cerelM'Jli. 20 
 
 'I'estes, 82 
 
 Thalamus opticus, 09, 147 
 
 Torcular llerophili, 17 
 
 Trabecuhe subarailmoidealcs. 24 
 
 Tract of Burdacli, 107 
 
 Tract of fJoll, 107 
 
 Tract of (Jower, 99 
 
 Tract of Vicq d'A/.yr, 79 
 
206 
 
 ANATOMY OP THE BRAIN 
 
 Tractus cerebio-tlialaiims, 175 
 
 Tractus olfactoiuus, 67, 129 
 
 Tractus opticus, 44, 131, 191 
 
 Tractus peduncvilaris trans versus, 84, 
 
 159 
 Tractus pyrauiis pedunculi cerebri, 86 
 Tractus pyramidalis, 84 
 Trapezium, 46, 90, 131 
 Trifacial nerve, 46 
 Trigeminus, 46 
 Trigonum geniculatum, 104 
 Trigonum liabenulae, 53, 75, 133 
 Trigonum hypoglossi. 111 
 Trigonum lemnisci, 83, 104, 160 
 Trigonum vagi, 112 
 Tuber cinereum, 45, 51 
 Tuberculum acusticum, 91, 167 
 Tuberculum cuneatum, 107 
 Tuberculum gracile, 103 
 Tuberculum thalami anterius, 70 
 Tuberculum thalami posterius, 70, 147 
 Turbinal bones, 16 
 Turner's fissure, 41 
 Vagus nerve, 47 
 Valve of Vieussens, 54 
 Varoli, pons, 45 
 Vein of Galen. 20, 145 
 
 Vi'lum interpositum, 64 
 Velum medulhxre anterium, 54 
 Vena cerebri interna, 63 
 Vena cerebri magna, 20, 53, 69, 145 
 Vena cerebri posterior, 69 
 Vena cliorioidea, 63 
 Vena corporis striati, 142 
 Vena frontalis, 21, 123 
 Vena jugularis interna, 22 
 Vena oplithalmica, 22 
 Vena terminalis, 62, 145 
 Vense vertebrales, 22 
 Ventral pyramids, 97 
 Ventricle of Arantius, 106 
 Ventriculus bulbi olfactorii, 62, 169 
 Ventriculi laterales, 58, 61 
 Ventriculus medullse spinalis, 54 
 Ventriculus quartus, 54, 110 
 Ventriculus tertius, 53, 80, 173 
 Vermis cerebelli, 38, 127 
 Vermis cerebelli minor, 90, 177 
 Vicq d'Azyr, tract of, 79 
 Vieussens, valve of, 54 
 Willis, circle of, 30 
 Willis, portio, dura of, 90 
 Willis, portio, mollis of, 90 
 
 i 
 
Date Due 
 
 misn 
 
 149. 
 
 
 
 ' ^01 'fc^ 
 
 ... 
 
 , 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
Nov I 
 
 t9l? 
 
 COLUMBIA UNIVERSITY LIBRARIES (hsi.stx) " 
 
 QM 34 691 C.2 
 
 The anatomy of the brain: 
 
 2002156725 
 
 
 •V 
 
 
 JUL 1 3 1949 ^uily '^^vuli 
 
 HOV ^ 2 "^- /1>4A