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 HEALTH SCIENCES STANDARD 
 
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 QM451 .W581899 Anatomy of the brain 
 
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 5 iWftARlCS ^ 
 
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 HEALTH. 
 
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ANATOMY 
 
 OK THE 
 
 BRAIN AND SPINAL CORD. 
 
PRINTED BY 
 
 E. & S. LIVINGSTONE 
 
 4 MELBOURNE PLACE 
 
 EDINBURGH. 
 
ANATOMY 
 
 OF THE 
 
 BRAIN AND SPINAL COKD>* 
 
 BY 
 
 J. RYLAND WHITAKER, B.A, M.B.(Lond.) 
 
 FELLOW OF THE EOTAL COLLEGE OF PHTSICIAXS, EDIXBUBGH; 
 
 LECTCKEE OX iXilOUT, SCEGEOXS' HALL, EDIXBUEGH, AXD LADIES' SCHOOL OF 
 
 1IEDICIXE, 1IIXTO HOrSE, EDIXBUBGH; EXA3IIXEE IX AXATOMT, 
 
 EOTAL COLLEGE OF PHTSICIAXS, EDIXBCBGH. 
 
 SIXTH THOUSAND . 
 
 EDINBURGH: E. & S. LIVINGSTONE. 
 
 1899. 
 
 ("all eights eeserved] 
 

 
 ISV 
 
TO 
 
 Sir JAMES ALEXANDER RUSSELL, 
 
 LL.D., M.A., M.B., B.Sc, F.R.C.F.E., F. R.S.Ed., 
 Late Lord Provost of Edinburgh, 
 
 ®Ijis littk fttatmal is respsrtfulhr gauicat^u 
 
 IN TOKEN OF MANY KINDNESSES. 
 
 THE AUTHOR. 
 
PKEFACE TO THIED EDITION. 
 
 This little book, first written whilst a student at the 
 earnest request of students, has now reached a 
 third edition, and has become a favourite, perhaps 
 undeservedly, with those for whom it was originally 
 intended. Although fully conscious of its many defects, 
 I fear that my time, now so much occupied with teach- 
 ing, leaves me no chance of remodelling the book in 
 a way that more mature years and experience would 
 suggest. It must practically remain in the same garb, 
 however imperfect, in which it first appeared. This 
 the student, at least, will probably not regret. 
 
 In this edition my work has been confined to the 
 removal of the more glaring blemishes and errors, and 
 to the rewriting and bringing up to date some of the 
 sections. As the book is now much used by senior 
 students and by practitioners, a general summary, for 
 their special use, has been added at the end. 
 
 Though the actual number of pages has been slightly 
 increased, the matter has been shortened, for the 
 individual pages have been made smaller, more margin 
 
viii PREFACE. 
 
 having been allowed, so that the book reads more 
 easily and more room has been obtained for extra 
 plates. 
 
 To Dr W. F. Harvey, and to my other demon- 
 strators and students who have so kindly, more than 
 once, read over the proofs, I cannot sufficiently express 
 my gratitude. 
 
 Finally, it remains for me to thank Messrs M 'Lagan 
 & Cumming for the trouble they have taken in the 
 reproduction of the plates, and the Messrs Livingstone 
 and staff for their uniform courtesy and excellent execu- 
 tion of the work. 
 
 Surgeons' Hall, 
 Edinburgh, 1st May 1899. 
 
TABLE OF CONTENTS. 
 
 Dedication, 
 Preface, ... 
 List of Plates, 
 
 l'AGE 
 V 
 
 vii 
 
 xiii 
 
 SECTION I. 
 
 The Spinal Cord, its Membranes, and its Vessels, 
 
 Chapter I. 
 
 Membranes of the Spinal Cord, 
 I. Dttra Mater, 
 II. Pia Hater, 
 III. Arachnoid, 
 
 Cerebro-Spinal Fluid. 
 
 3 
 4 
 6 
 9 
 10 
 
 Spinal Vessels, 
 
 Chapter II. 
 
 11 
 
 Chapter III. 
 
 
 The Spinal Cord, 
 
 12 
 
 I. Fissures of the Cord, 
 
 14 
 
 II. Spinal Nerves, 
 
 16 
 
 III. White and Grey Matter of Cord, 
 
 17 
 
 1. White Matter, 
 
 IS 
 
 White Columns, 
 
 IS 
 
 White Commissure. 
 
 25 
 
 Structure of White Matter. 
 
 26 
 
 2. Grey Matter, 
 
 27 
 
 Cornua, 
 
 28 
 
 Grey Commissure, 
 
 i".' 
 
 Neuroglia, 
 
 30 
 
 Nervous Constituents, 
 
 31 
 
 Vesicular Columns, 
 
 32 
 
 IV. Deep Origins of Spinal Nerves, ... 
 
 37 
 
TABLE OF CONTENTS. 
 
 SECTION II. 
 
 The Brain, its Membranes, and its Vessels, 
 Dissection to Expose Membranes, 
 Dissection to Remote Brain, ... 
 
 PAGE 
 
 43 
 43 
 44 
 
 Chapter I. 
 
 Membranes of Brain, 
 
 
 45 
 
 I. Dura Mater, 
 
 
 45 
 
 Falx Cerebri, 
 
 
 46 
 
 Falx Cerebelli, 
 
 ... ... 
 
 47 
 
 Tentorium Cerebelli, 
 
 ... 47 
 
 II. Pia Mater, 
 
 
 49 
 
 III. Arachnoid, 
 
 ... 
 
 50 
 
 IV. Venous Sinuses, 
 
 Chapter II. 
 
 52 
 
 Vessels of the Brain, 
 
 ... 
 
 57 
 
 I. Arteries, ... 
 
 
 57 
 
 II. Veins, 
 
 
 61 
 
 Chapter III. 
 Sub-divisions of the Brain, 
 I. Medulla Oblongata, 
 
 1. Fissures of Medulla, 
 
 2. White Matter — Areas of Medulla, 
 
 3. Grey Matter of Medulla, 
 Recapitulation,... 
 
 II. Pons Varolii, 
 
 1. White Matter of the Pons, 
 _'. Grey Matter of the Pons, 
 
 III. Cerebellum, 
 
 1. Lobes of Cerebellum, ... 
 
 2. Peduncles of Cerebellum, 
 
 3. Medullary Vela, 
 
 I. Grey Matter of Cerebellum, 
 
 Minute Structure of Grey Matter, 
 5. White Matter of Cerebellum, 
 The 4th Ventricle, 
 
 63 
 65 
 66 
 
 67 
 
 77 
 85 
 
 87 
 89 
 91 
 
 92 
 95 
 97 
 100 
 101 
 102 
 105 
 106 
 
TABLE OF CONTENTS. 
 
 XI 
 
 
 
 PAGK 
 
 IV. Cerebkum, 
 
 ... 
 
 113 
 
 I. Exterior of Cerebrum, 
 
 114 
 
 1. 
 
 Fissures of Cerebral Hemispheres, 
 
 114 
 
 2. 
 
 Lobes and Convolutions 
 
 116 
 
 
 Structure of Cerebral Cortex, ... 
 
 128 
 
 II. Base 
 
 of Cerebrum, 
 
 132 
 
 III. Interior of Cerebrum, 
 
 138 
 
 1. 
 
 Ventricles, ... 
 
 141 
 
 
 Lateral Ventricle, 
 
 142 
 
 
 The 3rd Ventricle, .. 
 
 146 
 
 
 The 5th Ventricle and Septum Lucidum, 
 
 147 
 
 
 Velum Interpositum, 
 
 148 
 
 
 Choroid Plexus, 
 
 149 
 
 
 Veins of Galen, 
 
 150 
 
 
 Great Transverse Fissure, 
 
 150 
 
 2. 
 
 Basal Ganglia, 
 
 151 
 
 
 Corpora Striata, 
 
 151 
 
 
 ' Optic Thalami, 
 
 153 
 
 
 Corpora Geniculate, ... 
 
 155 
 
 
 Pineal Gland, 
 
 156 
 
 3. 
 
 White Strands, 
 
 157 
 
 
 Corpus Callosum, 
 
 157 
 
 
 Anterior Middle, and Posterior Com- 
 
 
 
 missures, 
 
 160 
 
 
 Fornix, 
 
 160 
 
 
 Internal and External Capsules, 
 
 163 
 
 IV. Crura Cerebri, &c, 
 
 165 
 
 1. 
 
 Crura, 
 
 165 
 
 2, 
 
 Corpora Quadrigemina, 
 
 169 
 
 3. 
 
 Aqueduct of Sylvius, ... 
 
 170 
 
 Origins of Cranial Nerves, 
 
 170 
 
 General Summary, 
 
 ... 
 
 180 
 
 SECTION III. 
 
 Outlines of Development or — 
 I. The Spinal Cord, 
 II. The Brain, 
 Index, 
 
 190 
 191 
 193 
 199 
 
LIST OF PLATES. 
 
 PLATE PAGE 
 
 I. — Fig. 1, General View of the Brain and Spinal Cord 
 (Hirschfeld and Leveille). Figs. 2 and 3, Mem- 
 branes of the Spinal Cord, ... ... ... 4 
 
 IJ. — Figs. 4, 5, and 6, Membranes of the Spinal Cord. 
 Fig. 7, Central Canal of Spinal Cord (Foster). 
 Fig. 8, Sections of Spinal Cord, ... ... 8 
 
 III. — Sections of Spinal Cord at various levels, ... 14 
 
 IV.— Fig. 13, Tracts of Spinal Cord. Fig. 14, Vesicular 
 Columns and Deep Origins of Spiual Nerves. 
 Fig. 15, Blood- Vessels, ... ... ... 22 
 
 V. — Various kinds of Nerve Cells of Spinal Cord, ... 28 
 
 VI.— Figs. 23, 24, 25, and 20, White Tracts of Spinal 
 Cord (Bristowe). Fig. 27, Pia Mater. Fig. 28, 
 White Nerve Matter of the Spinal Cord. Fig. 29, 
 Anterior Horn of the Spinal Cord, ... ... 32 
 
 VII.— Fig. 30, Different kinds of Cells of the Spinal Cord, 
 Neuroglia, &c. (Van Gehuchten). Figs. 31 and 32, 
 Collaterals (Edinger), ... ... ... ... 34 
 
 VIII.— Fig. 1, Collaterals. Fig. 2, Spiual Ganglion. Fig. 3, 
 Neuroglia Cells (Van Gehuchten). Fig. 4, Nerve 
 Cells,... ... 40 
 
 IX. — Fig. 33, Diagrammatic View of Parts of the Brain. 
 
 Fig. 34, Membranes of the Brain, ... ... 41 
 
 X. — Fig. 35, Membranes aud Vessels of the Brain 
 (H. & L.). Fig. 36, Venous Sinuses (Wilson's 
 Plates), ... ... ... ... ... 48 
 
 XL — Figs. 37 and 38, Venous Sinuses (Wilson), ... 52 
 
 XII.— Figs. 39 and 40, Blood- Vessels of the Brain (II. & L.), 58 
 
xiv LIST OF PLATES. 
 
 PLATE PAGE 
 
 XIII.— Blood- Vessels of the Brain, ... ... ... 60 
 
 XIV. — Blood- Vessels of the Brain, and Areas of Motion and 
 
 of Sensation, ... ... ... ... ... 62 
 
 XV.— Views of the Medulla, ... ... ... ... 66 
 
 XVI. — Fig. 50, Diagram of Course of Fibres in the Spinal 
 
 Cord,... ... ... ... ... ... 70 
 
 XVII.— Sections of the Medulla, ... ... ... ... 78 
 
 XVIII. — Figs. 57 and 58, Nuclei in the 4th Ventricle 
 
 (Edinger), ... ... ... ... ... 82 
 
 XIX.— Figs. 59 and 60, Pons. Fig. 61, Crura Cerebri, ... 90 
 
 XX— Figs. 62 and 63 (H. & L.), Figures of Cerebellum, 94 
 
 XXI.— Figs. 64 and 65, Cerebellum. Fig. 66 (Edinger), 
 
 and Fig. 67, Structure of Cerebellum (Ferrier), 98 
 
 XXII. — Structure of Cerebellum (Edinger) ... ... 102 
 
 XXIIa.— Figs. 68 and 69, Structure of Cerebellum (Van 
 
 Gehuchten), ... ... ... ... ... 104 
 
 XXIII. — Convolutions of the Brain, ... ... ... 118 
 
 XXIV. — Convolutions of the Brain, ... ... ... 124 
 
 XXV.— Figs. 74 and 75, Relation of Fissures, &c, to Skull 
 
 and Scalp, ... ... ... ... ... 128 
 
 XXVI. — Figs. 76, 77, and 78, Structure of Cerebrum (Ramon y 
 
 Cajal), — ••• ... ... ... 130 
 
 XXVIL— Fig. 79, Base of the Brain, ... ... ... 134 
 
 XXVIII.— Fig. 80, Side View of the Brain, ... ... 135 
 
 XXIX. — Diagram of Ventricles, ... ... ... ... 133 
 
 XXX. — Diagram of Ventricles, ... ... ... 142 
 
 XXXI. — Diagram of Ventricles, ... ... ... ... 144 
 
 XXXII. — Velum Interpositum, &c. ... ... ... 145 
 
 XXXIII. — Diagram of Ventricles, ... ... ... 143 
 
 XXXIIIa.— Fig. 1, Velum Interpositum, Fig. 2, Fornix, &c, ... 150 
 
 XXXIV.— Capsules, k ... 154 
 
LIST OF PLATES. xv 
 
 PLATE PAGE 
 
 XXX V— Fig. 87, Nuclei of 3rd and 4th Nerves (Edinger). 
 Fig. 88, Optic Nerves (Hill). Fig. 89, Fornix. 
 Fig. 90, Nucleus Oaudatus (Edinger). Fig. 91, 
 Fornix (own specimen, and Hill), ... ... 160 
 
 XXXVI.— Fig. 92, Blood- Vessels to Capsules. Fig. 93, Ver- 
 tical Section of the Cerebrum. Fig. 94, Diagram 
 of the 3rd Ventricle. Fig. 95, Fascia Dentata, &c, 164 
 
 XXXVII.— Fig. 96, Diagram of Tracts of Fibres (Hill). Fig. 97, 
 Tracts of Medulla (Edinger, Hill, Bruce). Fig. 98, 
 Inter-peduncular Space (Holden). Fig. 99, Eesti- 
 form Body (Edinger), ... ... ... ... 168 
 
 XXXVIII. — Nuclei of Origin of Cranial Nerves, ... ... 172 
 
 XXXIX. — Nuclei of Origin of Cranial Nerves, ... ... 176 
 
 XL.— Figs. 100 and 101, Tracts of Degeneration in the 
 
 Brain and Spinal Cord, ... ... ... 182 
 
 XL I. — Diagram of Course of Motor Fibres (Van Gehuchten), 184 
 
 XLII. — Diagram of Course of Sensory Fibres (Van Gehuchten), 186 
 
 XLIII. — Diagrams of Development of the Brain and Spinal 
 Cord (after Quain, Kolliker, Sclrsvalbe, and 
 Edinger), .. ... ... ... ... 192 
 
 XL IV. — Diagrams of the Vesicles of the Brain and the Parts 
 
 Developed therefrom (after Van Gehuchten), ... 194 
 
ANATOMY 
 
 OF THE 
 
 BRAIN AND SPINAL CORD. 
 
 THE nervous system of man comprises two por- 
 tions, the Sympathetic and the Cerebrospinal, 
 The latter, the cerebro-spinal, has two parts: a central, 
 which consists of the brain and spinal cord, and a 
 peripheral, which consists of the several nerves of 
 the body. 
 
 NERVOUS SYSTEM. 
 
 1. Sympathetic. 2. Cerebro-spinal. 
 
 I 
 
 I I 
 
 (i) Central Part- (2) Peripheral Part- 
 
 Brain and Spinal Cord. The Nerves of the Body. 
 
 The Central Nervous System of man, the only 
 part treated of in this hook, is, as we have just 
 seen, made up of the Brain and Spinal Cord. Sur- 
 rounded by the bony wall of the cranium in the 
 one case, and of the spinal canal in the other, these 
 two parts of the great cerebro-spinal nervous system 
 are continuous with each other through the foramen 
 magnum. They are each enveloped in three distinct 
 membranes, the Meninges, which form additional pro- 
 tective sheaths around them, and help to support 
 them in their respective cavities. 
 
 B 
 
2 THE SPINAL CORD 
 
 The Brain and Spinal Cord are, moreover, each 
 composed of two kinds of nervous substance, known 
 from their colour as the White and Grey Matter 
 respectively ; but with this difference in their 
 arrangement, namely, that in the Brain the grey 
 matter is situated chiefly on the outside, forming 
 the cortex ; whilst in the Spinal Cord the white 
 substance is external, and the orev matter forms 
 the central core or pith. 
 
 We shall describe, firstly, the Spinal Cord, with its 
 Vessels and Membranes; and, secondly, the Brain, 
 with its Vessels and Membranes. 
 
AND ITS MEMBRANES. 
 
 SECTION I. 
 
 SPINAL CORD AND MEMBRANES. 
 
 Dissection. — To see the spinal cord and its membranes it will 
 be necessary to open the vertebral canal. To do this, remove the 
 muscles from the vertebral grooves, and saw through the laminae 
 of the vertebras on each side, close to their union with the pedicles, 
 being careful, especially in the dorsal region, to direct the edge of 
 the saw inwards. Carry the incision downwards as far as the lower 
 end of the sacral canal, and upwards as high in the neck as may 
 be convenient. Break through with the chisel any partially sawn 
 arches, cut through the various ligaments, and remove the pieces 
 of bones thus detached. Carefully clear away the connective 
 tissue, veins, and fat covering the outer aspect'of the dura mater, 
 snip through the articular processes with the bone forceps, and 
 dissect out one or more of the processes of the dura mater which 
 pass through the inter-vertebral foramina. Examine the outer 
 surface of the dural sheath, and then slit it open in its entire 
 length, 
 
 CHAPTER I. 
 MEMBRANES OF SPINAL CORD. 
 
 (Plates I. and II.) 
 These membranes are identical in many respects 
 with those of the Brain, and are therefore simi- 
 larly named. They are the Dura Mater, the Pia 
 Mater, and the Arachnoid. The Dura Mater is the 
 most external, the Pia Mater is in close contact 
 with the cord, and the Arachnoid forms a vertical, 
 tubular partition between the others, dividing the 
 
4 THE SPINAL CORD 
 
 space between them into two — viz., the sub-dural 
 and the sub-arachnoid. Thus we speak of the sub- 
 dural space, meaning that between the dura mater 
 and the arachnoid, and of the sub-arachnoid, or that 
 between the arachnoid and the pia mater. For 
 convenience we shall describe (1) the Dura Mater; 
 (2) the Pia Mater ; (3) the Arachnoid. 
 
 I.— THE DURA MATER. 
 
 (Pigs. 2 to 6.) 
 
 The Dura Mater, the most external and the 
 strongest covering of the cord, is a firm fibrous mem- 
 brane, continuous at the foramen magnum with the 
 similar membrane which lines the cranial cavity. 
 Enclosed in the spinal canal, it does not, however, 
 form an endosteum to the bones, and in this respect 
 differs from the cranial dura mater. Its outer 
 surface has a shining, pearly-white appearance, and 
 is separated from the walls of the spinal canal by 
 loose areolar tissue with a little fat, and by a plexus, 
 of veins. Slender fibrous bands, especially at its 
 lower end, attach it closely to the posterior common 
 ligament of the vertebras. In extent the dural 
 sheath reaches from the foramen magnum to the 
 second or third piece of the sacrum, where it ends 
 in a conical cul-de-sac. As you will see upon open- 
 ing it, the cavity which it encloses is much longer 
 and wider than its contents — the spinal cord — for 
 this latter ends at the first or second lumbar 
 vertebra. Below the pointed termination of the 
 spinal marrow — conns meclullaris — the cavity of 
 
Fir,. I 
 
 Fig. 2. 
 
 ki/perior 
 I gin us. 
 
 iteral * 
 inus. 
 
 Subdural space 
 
 Plate I. 
 
 A interior median f. 
 
 j 'erebrum 
 
 Subarachnoid 
 space 
 
 ^Cerebellum 
 
 Spinal nerv 
 
 Medulla 
 
 . Dura mater. 
 
 irachno'ld. 
 Pia mater. 
 
 Spinal Cord 
 
 m terminale. 
 
 tda equina. M 
 
 Conns medullaris. 
 
 Spinal __ j 
 nerve roots. \ 
 
 Ligament um 
 dentieulatum.. i 
 
 Epithelium. 
 
 Posterior median f. 
 
 Fig. 3. 
 
 ira mater. 
 
 achnoid. 
 
 Via mater. 
 
 Linea 
 plendens 
 
AND ITS MEMBRANES. 5 
 
 the dural sheath is occupied by bundles of nerve 
 roots — cauda equina (Fig. 1) — in the midst of 
 which you will be able to pick out a slender, silvery- 
 looking thread, the filura terminate or central 
 ligament (Fig. 1, fil. ter.). Continuous with the 
 apex of the conus medullaris, this terminal filament 
 runs down the middle line amonsrst the nerve roots 
 to the lower end of the dural cavity. It there 
 pierces the dural sheath, receives an investment 
 from it, and passes along with this investment to be 
 attached to the back of the coccyx (filum dura? 
 matris spinalis, see page 13). Thus, we see that 
 the dura mater forms a very loose "covering to the 
 cord, and we find, moreover, that it has a greater 
 capacity in the neck and back than it has in the 
 loins. Smooth and glistening on its inner aspect, 
 it presents on each side a longitudinal series of 
 rounded openings arranged an pairs, one for each 
 spinal nerve root. These roots, as they pass out to 
 the inter-vertebral foramina, carry with them a 
 tubular prolongation of the dura mater which, in 
 part, ensheaths the spinal ganglia, and, in part, 
 blends with the periosteum of the neighbouring 
 bones (Figs. 4 and 6, page 8). 
 
 It is important to recollect that, although the 
 spinal cord itself ends at the spot indicated — viz., 
 the second lumbar vertebra, the dura mater, the 
 arachnoid, and the cerebro-spinal fluid, extend as 
 far as the second piece of the sacrum, so that injuries 
 inflicted upon the spine as low down as this latter 
 point may cause death by inducing inflammation 
 of the meninges. 
 
6 THE SPINAL CORD 
 
 Minute structure of the dura mater. — 
 Under the microscope the dura mater will be seen to 
 consist of white fibrous and elastic tissues, arranged 
 in longitudinal bands or lamellae, with flattened, 
 branched, connective tissue corpuscles, clasping the 
 bundles of fibrils. Both its inner and outer surfaces 
 are smooth and covered by epithelial plates. Many 
 lymphatics and blood-vessels, as well as slender 
 nerve filaments derived from both spinal and sym- 
 pathetic systems, are furnished to its substance. 
 
 II.— THE PIA MATER. 
 
 (Figs. 2 to 6.) 
 
 Disskotion, — After slitting open the dura mater, the first mem- 
 brane you will see is the delicate arachnoid. Pierce it with a 
 sharp-pointed blow-pipe and inflate, as far as you can, the sub- 
 arachnoid space. Next, to expose the pia mater, remove a small 
 piece of the arachnoid from any part of the cord, leaving it intact 
 elsewhere. 
 
 The Pia Mater is a delicate, highly - vascular, 
 fibrous membrane, which so closely surrounds the 
 spinal cord that it cannot easily be stripped off. It 
 also furnishes sheaths to the roots of the spinal 
 nerves. A distinct process or fold of it passes 
 into the anterior median fissure of the cord, and 
 other smaller septa penetrate the spinal marrow 
 at various points, carrying with them blood-vessels 
 and lymphatics for the nutrition of both its white 
 and grey matter. The largest of these septa is seen 
 at the posterior median fissure (Fig. 6, Plate II., 
 page 8). It is not, however, a fold of pia mater 
 like that in the anterior fissure, but consists of the 
 
AND ITS MEMBRANES. 7 
 
 supporting tissue of the cord called neuroglia (see 
 page 30). If you compare the pia mater of the 
 cord with that of the brain, you will find that the 
 former is thicker, less vascular and more adherent 
 to the subjacent nervous tissue. 
 
 The outer surface of the pia mater is compara- 
 tively rough, and has the three following structures 
 connected with it — the linea splendens, the liga- 
 mentum denticulatum, and the septum posticum. 
 
 1. The linea splendens (Fig. 3, page 4) is a 
 thickened fibrous band along its anterior aspect. 
 It is sometimes difficult to make out. 
 
 2. The ligamentum denticulatum is a well- 
 defined structure (Figs. 3 and 5, lig. dent.) which 
 runs longitudinally on each side of the cord in the 
 form of a toothed white band, having its serrated 
 edge turned outwards. It helps to support the 
 spinal marrow within its dural sheath. Internally, 
 it is attached to the pia mater, about midway 
 between the lines of origin of the anterior and 
 posterior nerve roots, reaching upwards as high as 
 the medulla oblongata, and ending below on the 
 pointed extremity of the cord, the conus medullaris. 
 Externally, its outer margin forms a series of tooth- 
 like processes, about twenty-one in number, which 
 are fixed to the inner surface of the dura mater, in 
 the intervals between the points of exit of successive 
 nerve roots. The highest of these denticulations is 
 attached opposite the margin of the foramen 
 magnum, between the last cranial and first spinal 
 nerve, and the lowest between the twelfth dorsal and 
 first lumbar nerves. The ligamentum denticulatum 
 
8 THE SPINAL CORD 
 
 thus partially divides the sub-arachnoid space into an 
 anterior and a posterior compartment. 
 
 3. At the back of the cord is another process or 
 partition — the sejrtum posticum (Figs. 4, 6, page 8, 
 sep. post.) — which crosses the sub-arachnoid space 
 and serves to connect the pia mater with the 
 arachnoid. 
 
 Below the end of the cord, the pia mater, though 
 at first retaining its tubular form, afterwards becomes 
 suddenly reduced in size, and is finally prolonged as 
 a sheath to the delicate thread-like continuation of 
 the spinal cord, the filum terminate or central 
 ligament (Fig. 1) ; the silvery hue of which will 
 enable you to distinguish it among the surrounding 
 bundles of nerve roots (cauda equina). 
 
 Lying between the pia mater on the one hand, 
 and the arachnoid on the other, but connected with 
 both, is a quantity of delicate connective tissue 
 arranged in the form of a spongy network, the 
 sub - arachnoid trabecular, which are clothed with 
 epithelial plates (Fig. 4, page 8, sub-arach. trab.). 
 The lacuna? or areola?, thus formed, contain the 
 greater part of the cerebro-spinal fluid. 
 
 Minute structure of the pia mater (Fig. 27, 
 Plate VI., page 32). — The pia mater consists of a 
 basis of white fibrous connective tissue, which is 
 arranged in interlacing bundles, and supports a 
 plexus of blood-vessels. Both its surfaces are 
 covered by epithelial cells. It possesses a com- 
 plete network of lymphatics ; and its nervous 
 supply is derived from the sympathetic system. 
 
Fig. 4. 
 
 "Epithelium 
 iganientu 
 
 racknoid train ■ 
 
 Dura mater. 
 Pia mater. 
 
 nal nerve. 
 
 nation. 
 
 Fig. 5. 
 
 Plate II. 
 
 I) lira 
 
 gamentwtn 
 dent 
 
 nerve. 
 
 Fig. 6. 
 
 Arachnoid. 
 
 interior median fissure. 
 Dura mater. 
 Pia mater. 
 
 Ligament . 
 • dent. 
 
 Fig. 7. 
 
 ibarachnoid space. 
 
 Subdural space. 
 
 Transverse section of lower part 
 of spinal canal. 
 
 Fig. 8. 
 Interior median fiss. Anterior nerve root. 
 
 Septum posticum. 
 Posterior median fissure. 
 
 rang/ion. ; 
 
 Spina! nerve. 
 Posterior median fins. Posterior nerve root. 
 
AND ITS MEMBRANES. 9 
 
 III.— THE ARACHNOID. 
 
 (Figs. 2 to 6.) 
 
 The Arachnoid is an extremely fine and delicate 
 membrane. It is non-vascular, and thus differs 
 materially from the other two. Many authors deny 
 that it is a special membrane, and consider it to be 
 one of the layers of the pia mater, describing the 
 two together as the pia-arachnoid (see pages 50 
 and 51). 
 
 Forming a cylindrical partition between the dura 
 mater and the pia mater, the arachnoid divides the 
 space between them into two — the sub-dural and 
 sub-arachnoid, previously referred to. The sub-dural 
 space is very narrow, for the outer surface of the 
 arachnoid is in more or less close contact with the dura 
 mater. The sub-arachnoid space is much larger and 
 contains the chief part of the cerebro-spinal fluid. 
 It is crossed by the sub-arachnoid trabecular which 
 connect the arachnoid with the pia mater. The arach- 
 noid, moreover, forms tubular prolongations around 
 both the nluni terminale and the teeth-like processes 
 of the ligamentum denticulatum ; and similar cover- 
 ings are furnished to the roots of the spinal nerves. 
 These sheaths enclose the nerve roots as they pass 
 outwards to the dura mater, but, when the roots 
 pierce that membrane, the epithelium of the outer 
 surface of the arachnoid becomes continuous with 
 the epithelium lining the inner surface of the dura 
 mater, whilst the rest of the arachnoidal sheath 
 blends with the perineurium of the nerves (Figs. 2 
 and 4. epith.). Thus we see that each spinal nerve 
 
io THE SPINAL CORD 
 
 root receives a covering from all tbree membranes 
 of the cord. It is stated, too, that the sub-dural and 
 sub-arachnoid spaces, though they do not directly 
 communicate with one another, are both continuous 
 with the lymphatic plexuses which surround the 
 spinal nerves. It may perhaps be well to mention 
 that the sub-dural space was formerly spoken of as 
 "the cavity of the arachnoid" — the arachnoid 
 membrane itself being then looked upon as a 
 serous membrane, enclosing a serous cavity, and 
 the epithelial lining of tbe deep surface of the 
 dura mater as one of its layers. 
 
 Minute structure of the arachnoid. — The 
 arachnoid consists of bundles of white fibrous tissue, 
 interlacing with one another, and arranged for the 
 most part longitudinally. Both its surfaces are 
 covered by epithelial cells. The source from which 
 it derives its nerve-supply is still very doubtful; 
 most probably it is the sympatbetic system. As 
 we have said, many authors regard the arachnoid 
 as one of the layers of the pia mater. 
 
 Cerebro-spinal Fluid. — The cerebro-spinal fluid, 
 about two fluid ounces in quantity, is a clear-looking, 
 alkaline liquid, containing little or no albumen. It 
 chiefly occupies the interstices of the sub-arachnoid 
 trabecular By its means, probably, an equality of 
 pressure is maintained upon the brain and cord ; 
 hence we find that any sudden disturbance of tbe 
 fluid, such as would be caused by pressure on a spina 
 bifida, at once gives rise to serious cerebral symptoms 
 — such as convulsions and loss of consciousness. 
 
AND ITS MEMBRANES. n 
 
 CHAPTER II. 
 
 SPINAL VESSELS. 
 
 (Fig. 15, Plate IV., page 22.) 
 
 Dissection. — Remove the cord with its sheaths from the spinal 
 canal, by cutting through the spinal nerves at their exit through 
 the inter- vertebral foramina, and snipping the bands of connective 
 tissue which attach it to the posterior common ligaments. 
 
 1. Arteries. — The arteries on the surface of the 
 spinal cord are the anterior and posterior spinal. 
 
 The anterior spinal artery, formed above by 
 the union of two branches, arising one from each 
 vertebral artery, runs along the front of the cord 
 underneath the linea splendens. As it passes down- 
 wards it is reinforced by a series of anastomotic 
 branches from arteries in the neck and back. It 
 gives off branches to the pia mater, to the roots of 
 the spinal nerves, to the anterior median fissure 
 (a cleft seen on the front of the cord), and ends 
 below upon the filum terminale. 
 
 The posterior SPINAL arteries, two in number, 
 run downwards, one on each side, behind the line 
 of origin of the posterior nerve roots. They are 
 derived from the same source as the anterior, and 
 are joined by small branches which enter the inter- 
 vertebral foramina along the roots of the spinal 
 nerves. They anastomose freely and send offsets 
 into the septum at the back of the cord — the 
 posterior median septum. 
 
12 THE SPINAL CORD 
 
 2. Yeins. — The veins of the spinal cord lie within 
 the pia mater, have an anterior, a posterior, and 
 right and left lateral trunks, and form a fine plexus 
 over the surface of the corcl. They are larger on the 
 back than on the front of the cord. Laterally, after 
 being joined by veins from the bodies of the verte- 
 brae, branches pass out with the spinal nerves through 
 the inter-vertebral foramina, and open into either 
 the vertebral, inter-costal, or lumbar veins, according 
 to the regions in which they occur. 
 
 3. Lymphatics. — There are no lymphatic vessels, 
 properly so-called, in the nervous system, but there 
 are lymph spaces round the nerve cells — peri-cellular, 
 and round the blood-vessels — peri-vascular. 
 
 CHAPTER III. 
 THE SPINAL CORD. 
 
 The Spinal Cord is the elongated cylindrical 
 column of nervous substance contained in the 
 vertebral canal. Composed of two kinds of nervous 
 matter — an outer cortical part, consisting princi- 
 pally of white nerve fibres, and an inner grey 
 core or pith, consisting chiefly of nerve cells and 
 their processes — it is invested by three membranes, 
 the meninges ; gives origin to thirty-one pairs of 
 spinal nerves ; and is partially divided by anterior 
 and posterior median fissures into two lateral seg- 
 ments, which are united across the middle line by 
 a band of fibres called a commissure. You have 
 
AND ITS MEMBRANES. 13 
 
 already seen that the spinal marrow is much 
 smaller than the capacity of its bony case, so much 
 so, that, in the adult, it occupies two-thirds only 
 of the length of the spinal canal. About eighteen 
 inches loner, it reaches from the foramen magnum 
 to the lower border of the first or second lumbar 
 vertebra. Above, it is continuous with the medulla 
 oblongata ; below, it ends in a pointed extremity, 
 the conus medullaris, from the apex of which it is 
 prolonged downwards as a delicate thread-like fila- 
 ment, the filum terminale. According to the regions 
 of the spine in which they are situated, different 
 portions of the cord have received special names ; 
 thus we speak of the cervical, dorsal, and lumbar 
 portions. The spinal cord, moreover, presents two 
 swellings or enlargements — an upper one, the cervical 
 enlargement, extending from about the third cervical 
 to the second dorsal vertebra, and a lower or lumbar 
 enlargement, which, beginning at the tenth dorsal 
 vertebra, is largest opposite the twelfth, and then 
 gradually tapers away to the pointed extremity of 
 the cord. The connection between the increase of 
 nervous substance in these two parts of the cord and 
 the origin of the large nerve bundles given off to 
 the upper and lower limbs respectively is sufficiently 
 obvious. 
 
 Filum terminale. — This filament is the atrophied 
 remnant of the embryonic spinal cord. In its upper 
 part it is composed of nervous matter surrounding 
 a central canal, but in its lower part it becomes 
 solid and consists of cells (the exact nature of which 
 
14 THE SPINAL CORD 
 
 is not decided), of blood-vessels, and ultimately of 
 mere prolongations of pia mater and of dura mater 
 (see page 5). 
 
 We shall now examine (1) the exterior of the cord 
 with its spinal nerves; then (2) the interior. 
 
 I.— FISSURES OF THE CORD. 
 
 On both the anterior and posterior aspects of the 
 spinal cord there is seen a median longitudinal cleft 
 or depression, which penetrates some distance into the 
 nervous substance, and partially divides it into two 
 lateral halves. These clefts are called the anterior 
 and the posterior median fissures (Fig. 10, Plate III., 
 page 14). The transverse band which connects the 
 two halves at the bottom of these fissures js called 
 the commissure of the spinal cord. 
 
 1. The anterior median fissure is the wider 
 of the two, though in depth it extends through only 
 one-third of the thickness of the cord. It contains 
 a distinct fold of the pia mater, which conveys blood- 
 vessels into the interior of the spinal marrow (Fig. 4, 
 Plate II., page 8; Fig. 15, Plate IV., page 22). At the 
 bottom of this fissure lies the transverse band of 
 nerve fibres, the anterior or white part of the com- 
 missural band (Fig. 14, Plate IV., page 22), which 
 unites together the two lateral halves of the cord. 
 
 2. The posterior MEDIAN FISSURE, narrower 
 but deeper than the anterior, is rather a septum 
 than an actual fissure, for it does not contain a fold 
 of the pia mater, but is filled up by blood-vessels 
 
Fig. 9 — Cervical Region— 
 
 Anterior commissure 
 
 Posterior commissure. 
 
 Plate III. 
 
 Anterior cornu. 
 
 Lateral cornu. 
 
 Posterior cornu. 
 
 Clarke's column. (.-_ 
 
 A nterior mes. fiss. 
 
 I- Lateral cornu. 
 
 V 
 
 f-Posteriov mes. fiss. 
 
 Anterior group of cells. 
 
 Anterior cornu. 
 
 Lateral group of cells. .1^ 
 
 Posterior group of cells. 
 
 \ 
 
 Lateral cornu. 
 
 'Posterior ccmu. 
 
 Fig. 12. —Sacral Region— 
 
 'Anterior cornu. 
 
 Posterior cornu. 
 Sections of the Spinal Cord in the regions of the different groups of nerves 
 
AND ITS MEMBRANES. 15 
 
 and connective tissue (ependyma and neuroglia 
 cells) attached closely to the deeper layer of the pia 
 mater. The 'posterior or grey commissure lies at 
 the bottom of this septum (Fig. 9, Plate III., page 
 14). About the middle of this grey band you will 
 find the central canal of the spinal cord. 
 
 In addition to these median fissures, we have yet 
 to describe, on each side of the cord, two lateral 
 longitudinal depressions, the positions of which are 
 indicated by the lines of origin of the anterior and 
 posterior nerve roots (Figs. 5 and 8, Plate II., page 8). 
 They are called the anterolateral and postero- 
 lateral grooves, though the antero-lateral is scarcely 
 a distinct groove. They mark off the surface of each 
 half of the cord into three columns — an anterior, a 
 lateral, and a posterior. The anterior column lies 
 between the anterior median fissure and the anterior 
 nerve roots ; the lateral column between the an- 
 terior and posterior nerve roots ; and the posterior 
 column between the posterior nerve roots and the 
 posterior median fissure (Fig. 15, Plate IV., page 22). 
 
 In the cervical region, close to the posterior median 
 fissure, two additional slightly marked clefts can be 
 made out, one on each side, which, with other minor 
 clefts, break up the cord into many tracts or columns, 
 to be described hereafter. 
 
 Some authors divide the cord thus — (1) A posterior 
 segment — between the posterior median fissure and 
 the posterior nerve roots. (2) An antero-lateral seg- 
 ment — between the anterior median fissure and the 
 posterior nerve roots. The antero-lateral segment 
 is again divided, by the line along which the anterior 
 
1 6 THE SPINAL CORD 
 
 nerve roots take origin, into (a) an anterior part, 
 between the anterior median fissure and the anterior 
 nerve roots ; and (6) a lateral part, between the 
 anterior and posterior nerve roots. From a develop- 
 mental point of view this sub-division is the more 
 correct. 
 
 II.— SPINAL NERVES. 
 
 (Figs. 5 and 8, Plate II., page 8 ; Fig. 15, Plate IV., page 22.) 
 
 Along the sides of the spinal cord arise, as we 
 have already seen, the several spinal nerves — 
 thirty-one pairs — eight cervical, twelve dorsal, five 
 lumbar, five sacral, and one coccygeal. Each nerve 
 takes origin, called its superficial origin, by two 
 roots — an anterior and a posterior — springing from 
 the antero-lateral and postero-lateral grooves 
 respectively. The roots are enclosed in sheaths 
 similar to those of the cord itself, and they pierce 
 the dura mater by two separate openings, one for 
 each root (Figs. 3 and 6). Sometimes each root, 
 especially the posterior one, consists of two bundles, 
 perforating the dura mater by two separate openings. 
 Except in the case of the first nerve, the posterior 
 roots are the larger, and their fasciculi more 
 numerous and thicker than those of the anterior 
 roots. Thev, moreover, become connected with a 
 ganglion, or collection of nerve cells (spinal ganglion, 
 Fig. 8, page 8 ; Fig. 14, page 22), before they join 
 the anterior roots to form a spinal nerve. The 
 anterior roots are motor, the posterior sensory in 
 function, whereas the spinal nerves themselves are 
 
AND ITS MEMBRANES. 17 
 
 mixed nerves, carrying both motor and sensory 
 impulses. These nerve roots, with the exception of 
 the first or highest, are not attached to the cord 
 opposite the vertebra below which they leave the 
 vertebral canal, but at a higher level. This differ- 
 ence between the points of origin and exit (a matter 
 of considerable clinical importance),* though slight 
 in the cervical region, increases as we descend the 
 cord, until, at its lower end, the nerve roots form an 
 almost vertical bundle, known as the cauda equina 
 (Fig. 1). In the upper part of the cervical region 
 of the cord, a little in front of the posterior roots 
 of the first four nerves, we see a series of nerve 
 filaments which are the twigs of origin of the spinal 
 part of the spinal accessory nerve. They soon unite 
 to form a single trunk, which ascends to the foramen 
 magnum. 
 
 III.— WHITE AND GREY MATTER 
 OF THE SPINAL CORD. 
 
 A transverse section of the spinal cord, such as 
 that represented in the Figures Plate III., page 14, 
 will demonstrate to you the interior of the cord 
 and its sub-division into two lateral halves. It 
 will show you distinctly (1) the existence of the 
 white cortex; (2) the central grey core; and (3) 
 the commissural band, composed of white matter 
 and grey matter, connecting together its lateral 
 segments. 
 
 * See Hilton's " Rest and Pain/' 5th Ed., 1892, page 86. 
 
 C 
 
iS THE SPINAL CORD 
 
 1. THE WHITE MATTER. 
 
 Taking up such a section of the spinal cord, and 
 examining it with the naked eye, you will see, as we 
 have just said, that the white matter forms the outer 
 or cortical part of the cord, and surrounds the grey 
 centre. This white matter, arranged in a series of 
 columns, gradually increases in amount from below 
 upwards, being specially augmented in the cervical 
 and lumbar enlargements. Compared with the grey 
 matter, it is more abundant in the neck and back, 
 but less so in the loins (Plate III., page 14). 
 
 1. White Columns of the Cord, and their 
 Sub-divisions.— Your attention, you will remember, 
 has already been called to the fact that the exit and 
 entrance of the nerve roots sub-divide each lateral 
 half of the cord into three longitudinal white seg- 
 ments or columns — namely, an anterior, a LATERAL, 
 and a posterior; each of which, however, can be 
 again sub-divided into smaller tracts or strands of 
 fibres w T hich have received special names and have 
 special functions (Fig. 13, Plate IV., page 22). 
 
 Tracts or Strands. — To determine by actual 
 dissection these various tracts or strands would be 
 impossible ; the task has, however, been accomplished 
 by the study of development and by the aid of ex- 
 perimental physiology and pathology; for "we may 
 learn as much of the course of nerve fibres by 
 studying them in their birth as in their death 
 — in their development as in their decay." The 
 development teaches us that different tracts or 
 
AND ITS MEMBRANES. 19 
 
 bundles of fibres acquire their white substance — 
 medullary sheath — at different periods of their 
 growth (see page 41), so that, in specially prepared 
 specimens, we are enabled to pick out and trace 
 these tracts or systems through successive sections 
 of the cord. On the other hand, the study of phy- 
 siology and the selective action exercised by disease 
 (so analogous to that exercised by certain poisons) 
 affords equally valuable information. For to phy- 
 siology and pathology are we indebted for the 
 knowledge that, when a nerve fibre degenerates in 
 consequence of injury or disease, the proper nerve 
 substance is replaced by connective tissue, which, 
 when treated with staining reagents, behaves differ- 
 ently from the surrounding undegenerated nerves. 
 
 By the above means, then, we can define with 
 more or less certainty the following tracts or systems 
 in the several white columns of the spinal cord 
 (see Table, page 25). 
 
 (a) Anterior Column. — In this column have been 
 mapped out a median and a lateral division. 
 
 1. The median division — the dieect PYRAMIDAL 
 tract — antero- internal tract— fasciculus of Turck 
 — is a well-marked bundle of fibres, situated close to 
 the anterior median fissure (Fig. 13, page 22). It 
 is a descending or motor tract, and is, as we shall 
 see hereafter, a continuation of that part of the 
 anterior pyramid of the medulla oblongata which 
 does not decussate in the medulla, hence its name, 
 direct pyramidal tract. It decreases in size from 
 above downwards, and can be traced as a distinct 
 
20 THE SPINAL CORD 
 
 fasciculus to the first lumbar nerve, though isolated 
 fibres have been followed as far as the fourth pair 
 of sacral nerves. Its fibres, as they descend in the 
 cord, cross over at lower levels to the opposite side, 
 and thence through the grey matter of the cord 
 become connected with the anterior nerve roots of 
 that side. 
 
 2. The lateral part of the anterior column, antero 
 EXTERNAL TRACT, forming by far the larger part of 
 the column, has also been called the anterior root 
 zone, basis bundle, or anterior ground tract. It is 
 mostly made up of short commissural fibres between 
 different segments of the cord. 
 
 (6) Lateral Column. — This well-defined column 
 marked off on the surface of the cord by the antero- 
 lateral and postero-lateral grooves, and limited inter- 
 nally by the grey matter, is composed of five distinct 
 strands of fibres (Fig. 13, page 22). 
 
 1. Thus occupying the posterior part of the 
 column, at a little distance from the surface of the 
 cord, is a bundle of fibres, known as the crossed 
 pyramidal tract (crossed pyram., Fig. 13). This, 
 as we shall afterwards see, is the continuation 
 downwards of the chief part of the anterior pyramid 
 of the medulla oblongata of the opposite side ; hence 
 the name, crossed pyramidal tract. This crossed 
 pyramidal tract exists in all regions of the cord. 
 It is the principal motor tract, and decreases in 
 sectional area as we descend the cord ; for its fibres 
 constantly turn into the grey matter (Fig. 23, &c, 
 Plate VI., page 32, and Plate XLL, page 184). 
 
AND ITS MEMBRANES. 21 
 
 2. The DIRECT CEREBELLAR TRACT. — The thin 
 lamina of white matter, which separates the crossed 
 pyramidal tract from the surface of the cord, con- 
 stitutes the direct lateral cerebellar tract, so called 
 from its connection with the cerebellum on the same 
 side (Fig. 13, page 22; and Plate VI., Fig. 23, &c, 
 page 32, lat. cereb.). It is an ascending tract, and 
 extends from the level of the second lumbar nerve 
 upwards to the restiform body. Its fibres are prob- 
 ably connected through a group of cells called 
 Clarke's column, with the posterior nerve roots on 
 the same side. It most likely carries visceral sensa- 
 tions and sensations from tendons, and is concerned 
 with the maintenance of equilibrium. 
 
 3. Ascending anterolateral tract (Hadden 
 and Gowers). — This area is situated in the anterior 
 part of the lateral column, in front of the direct 
 cerebellar tract (Fig. 13, page 22). It lies on the 
 surface of the cord and extends into the anterior 
 column nearly as far as the anterior median fissure. 
 It is called by Gowers the antero-lateral ascending 
 tract — comma-shaped tract — not, however, to be 
 confounded with the ill-defined descendinsr comma 
 tracts described in the posterior columns. Gowers' 
 tracts exist most likely in all regions of the cord, 
 but their lowest limits have not yet been defined. 
 Their fibres can be traced to the cerebellum. They 
 are sensory routes from the spinal cord to the brain. 
 
 4. Descending antero-lateral tract. — Closely 
 associated with Gowers' tract, and occupying about 
 three-fourths of the antero-lateral column (see Fig. 13) 
 
22 THE SPINAL CORD 
 
 is the descending antero- lateral tract (Lo wen thai 
 and Marchi). Its fibres mingle with those of Gowers' 
 tract and come from the cerebellum of the same 
 side. Some of them probably pass out by the 
 anterior nerve roots. It may be an indirect motor 
 tract, or may belong to the crossed pyramidal tract. 
 
 5. The rest of the lateral column is called the 
 
 MIXED ZONE or LATERAL GEOUND BUNDLE (Fig. 13), 
 
 though it is often divided into two parts — anterior 
 and posterior mixed strands — the latter being also 
 called the limiting layer (Fig. 13). It consists of 
 fibres with a short course — commissural fibres. 
 
 Thus we see that the lateral column contains in 
 all five tracts — the crossed pyramidal tract; the three 
 cerebellar tracts (two ascending and one descending); 
 and the mixed zone. 
 
 (c) Posterior Column. — The arrangement of the 
 strands in this column somewhat resembles that in 
 the anterior (Fig. 13). Thus, especially in the cervical 
 region, we find, close to the posterior median fissure, 
 (1) a narrow band called the postero - internal 
 tract — posterior median column, fasciculus of 
 Goll ; and (2) an external division named the 
 postero - external tract — cuneate fasciculus, 
 posterior root zone, fasciculus of Burdach. 
 
 The postero-internal tract, GolVs tract, in- 
 creases in size from below upwards. It is best seen 
 in the dorsal region, for at lower levels it is not 
 distinct from the next fasciculus, the fibres of the 
 two being intermingled. It is a direct tract from 
 
Plate IV. 
 
 Anterior median/. Fig. 13. Direct pyramidal tract. 
 
 Basis bundle, 
 es. antero-lateral tract 
 
 Limiting layer. - BB 
 Comma Tract 
 
 Ascending 
 antero-lateral tract. 
 
 Crossed 
 
 pyramidal tract. 
 
 Lateral cerebellar tract. 
 
 Lissauer's tract. 
 
 Postero-external .. 
 
 , . . ' / Postero-internal tract. 
 Posterior median j. '"\\/ 
 
 >K^ ( ' : 
 
 
 Anterior root. 
 
 Anterior vesicular column 
 
 Lateral fillet ... 
 
 Lateral 1 
 
 vesicular column. 
 
 Clarke's column. 
 
 Posterior 
 vesicular column 
 
 \_ Anterior cornu. 
 
 Anterior commissure. 
 
 Latend cornu. 
 '^Posterior commissure. 
 
 U0- Posterior cornu. 
 
 Ganglion 
 
 .interior column 
 
 — -Lateral column 
 
 -Posterior column 
 
 Diagram of tht vessels of the cord. 
 
 J. T MURRAY DELT 
 
AND ITS MEMBRANES. 23 
 
 the muscles to the brain, its fibres being derived 
 from the posterior roots of the spinal nerves. 
 
 The POSTERO - EXTERNAL STRAND, fasciculus of 
 
 Burdach, also increases in size as it ascends. Its 
 fibres, like those of the last bundle, are derived from 
 the posterior nerve roots. We shall presently trace 
 them to their ultimate destination (see " Posterior 
 Nerve Roots"). 
 
 The distinction between these two parts of the 
 posterior column (Goll and Burdach) is of considerable 
 importance in the pathology of locomotor ataxy, a 
 disease of the posterior nerve roots, in which there 
 is loss of muscular sense — sense of effort — and con- 
 sequently of co-ordination of muscular movements, 
 for in these tracts travel fibres which are closely 
 connected with that sense and with the mechanism 
 of co-ordination. That the columns of Goll and 
 Burdach conduct sensory impulses from the muscles 
 is also proved by the fact that in whales, where the 
 extremities are not developed, these columns — Goll 
 and Burdach — are rudimentary in comparison to 
 what they are in animals with well-developed limbs. 
 
 Another tract, the postero - marginal, is a 
 small zone which lies in this column round the tip 
 of the posterior horn, separating the horn from the 
 surface. It is often called Lissauer's tract (Fig. 13), 
 and its fibres, which come from the posterior roots, 
 run for a short distance upwards and downwards in 
 the tract, and then enter the grey matter. Lissauer's 
 tract is sometimes described with the lateral column. 
 (See below, " Posterior Roots.") 
 
i4 THE SPIN A l. CORD 
 
 Several other minor strands have been described 
 in the different columns of the cord, but are riot, 
 of sufficient Importance to detain as here, Some 
 of them — Unices tract, the lateral fillet, and the 
 comma tract — are figured in Figs. 13 and 14, Plate 
 IV., page 22. It is well, however, to remember that 
 
 the several tracts :ire not, so definite as the figure; 
 
 would indicate for with the ascending fibres we 
 find descending intermingled, and viae vered, 
 
 To Sinn up, then, the pyramidal t racts, direct and 
 
 crossed, and part of the anterolateral tract, are 
 descending or motor tracts; the posterior column, 
 the lateral cerebellar tract (spino-cerebellar), and 
 
 Gowers' tract are, on the other hand, ascending 
 
 or sensory tracts. The rest of the white matter 
 1 is chiefly commissural. 
 
 Of sensory impulses, those of tOUch and of 
 
 muscular sense travel along the posterior columns, 
 though there are reasons for thinking that common 
 
 seiisiliilit v not only ascends along I he posl<iiot 
 
 columns but also along the lateral columns of the 
 
 same and opposite sides. 
 
 Sensations of pa/in most likely travel along the 
 
 lateral columns of the opposite side to that, at which 
 thev enter the cord, tllOUgh their exact come ha:: 
 
 not yet, been worked out,. Some hold that sensa- 
 tions of pain pass through the grey matter. 
 
 Sensations of temperature heat and cold travel 
 in the anterolateral column, in the fasciculus of 
 
 ( lowers. 
 
 Vaso- motor impulses are conducted by the 
 
 lateral columns. 
 
AND ITS MEMBRANES. 
 
 25 
 
 Table of White Tracts of the Spinal Cord. 
 (Fig. 13, Plate IV., page 22.) 
 
 Anterior 
 cohimn. 
 
 Lateral 
 column. 
 
 Posterior 
 column. 
 
 ' 1. Direct pyramidal trad. Antero-internal — 
 Fasciculus of Tlirck. Uncrossed pyramidal 
 tract. 
 2. Antero-external — Basis bundle. Anterior 
 root zone. Anterior ground fibres. 
 
 1. Crossed pyramidal tract. 
 
 2. Direct lateral cerebellar tract. 
 
 3. Antero- lateral ascending tract or comma 
 
 tract (Gowers). Sensory zone. 
 
 4. Antero-lateral descending tract (Lowentbal 
 
 and Marchi). 
 
 5. Mixed zone — anterior mixed ; posterior 
 
 mixed or limiting layer. 
 
 Postero-internal — Fasciculus of Goll. 
 Posteroexternal — Fasciculus of Burdach. 
 
 Posterior root zone. Fasciculus cuneatus. 
 
 Posterior ground fibres. 
 Marginal zone — Lissauer's tract. 
 
 2. White Commissure. — The two anterior white 
 columns of opposite sides of the cord are united 
 across the middle line by a band of white fibres, the 
 anterior or white commissure, seen at the bottom 
 of the anterior median fissure (ant. com., Fig. 9, 
 page 14). Its constitution is too complex for an 
 elementary work of this kind. Suffice it to say that 
 it consists (1) of decussating fibres — axis-cylinder 
 processes and protoplasmic processes of the nerve 
 cells of the anterior horn (see "Grey Matter"); (2) 
 of collaterals from different sources (see below) ; 
 and (3) of neuroglia cells and their prolongations 
 (see " Neuroglia "). 
 
26 THE SPINAL CORD 
 
 Minute structure of the white matter. — 
 Besides blood-vessels and lymphatics, the white 
 matter of these various columns of the spinal cord 
 consists — (1) of a supporting framework of connec- 
 tive tissue called neuroglia, which will be fully 
 described under the grey matter (page 30) ; (2) of 
 medullated or white nerve fibres running for the 
 most part longitudinally; and (3) of non-medullated 
 nerve fibres which run with the white nerve fibres. 
 
 The white nerve fibres of the spinal cord are the 
 axis-cylinder processes of nerve cells, and have the 
 same structure as peripheral nerves, consisting of a 
 central core or axis-cylinder. In transverse section 
 this core, though made up of a number of fibrillse, 
 appears as a dark spot, surrounded by a laminated 
 white (medullary) sheath (Fig. 28, page 32). Usually, 
 however, neither neurilemma nor nodes of Ranvier 
 can be detected, though some hold that they are both 
 present. In their course along the spinal cord, the 
 axis-cylinder processes turn in at right angles to their 
 direction, and entering the grey matter, there break 
 up into brushlets of branches which end free. 
 
 Collaterals. — Moreover, the longitudinal fibres 
 of these columns give off at more or less right angles 
 to their course a series of side branches called 
 collaterals* which can be traced to different parts 
 of the grey matter, in which they end in tufts or 
 brushlets of fine varicose fibrillse. These brushlets 
 
 * For full account of Collaterals, see the able translation and 
 interesting summary of Kollikers' and other papers, by William 
 Aldren Turner, M.B. Edin.; M.ll.C.P. Lond. — Journal of Anatomy 
 and Physiology, Vol. xxv. 
 
AND ITS MEMBRANES. 27 
 
 ultimately end in little knobs, and do not anastomose 
 with each other, nor with the neighbouring fibrillse, 
 nor with the processes of nerve cells, but merely form 
 a beautiful plexus around the body of the cells. 
 Some authors hold that they do unite. At the 
 point where the collaterals are given off, the fibres 
 usually have a small triangular- shaped enlargement 
 (Fig. 31, page 34). 
 
 2. THE GREY MATTER. 
 
 The grey matter occupies the interior of the cord, 
 and is completely surrounded by the white substance. 
 It forms two columns extending through the entire 
 length of the cord, one in each half; and these two 
 columns are united across the middle line by a 
 vertical transverse grey band — the posterior or grey 
 commissure. In transverse section, therefore, the 
 grey matter presents more or less the appearance 
 of the capital letter H, for it is arranged in two 
 irregularly crescent-shaped masses — one in each 
 lateral half of the section (Plate III., page 14). 
 These two grey crescents are united across the 
 middle line by a transverse band of grey matter — 
 the cross-bar of the H — which represents the grey 
 commissure previously mentioned. Each grey cres- 
 cent is semi-lunar in shape, having its horns or 
 cornua pointing — the one forwards and outwards, 
 the other backwards and outwards — hence they are 
 known as the anterior and the 'posterior cornua. 
 The convexity of each grey mass looks inwards 
 towards the middle line, whereas the corresponding 
 concavity is directed outwards. 
 
28 THE SPINAL CORD 
 
 1. Cornua. — The anterior horn of each crescent, 
 irregular in outline, is, for the most part, shorter and 
 thicker than the posterior, and arches outwards 
 towards the place from which the anterior nerve 
 roots take their superficial origin. It does not, 
 however, quite reach the surface of the cord, some 
 white matter being interposed. It can be divided 
 into an enlarged anterior part or head, a narrow 
 part or neck, and a hinder part or base. 
 
 The posterior HORN, on the other hand, is 
 longer, more slender and more pointed than the 
 anterior, and almost reaches the surface of the cord 
 at the fissure along which the posterior nerve roots 
 take their superficial origin. Here it tapers to a 
 point called the apex cornu posterioris, which con- 
 tains a stratum of rather clear-looking connective 
 tissue, known from its gelatinous aspect as the 
 substantia gelatinosa of Rolando. Near its base 
 the posterior horn, like the anterior, is somewhat 
 constricted, forming the cervix or neck, while the 
 slightly enlarged part between the apex and neck 
 forms the caput cornu posterioris. 
 
 The outer concave side of each crescent, slightly 
 behind its centre, assumes the form of a network, 
 projecting outwards into the white substance. This 
 network, called the processus reticularis, is best 
 seen in the cervical region. Immediately in front 
 of this process, and about midway between the 
 anterior and posterior cornua, lies a collection 
 of grey matter — the inter medio -lateral tract — 
 lateral vesicular column — which may be regarded 
 
Plate V. 
 
 Fig. 17. 
 
 Fig. 16 
 
 Fig. 22.— Cell with long axis cylinder process. 
 Different Kinds of Nerve Cells. 
 
AND ITS MEMBRANES. 29 
 
 as a lateral horn (Fig. 14, page 22). Look for it, 
 especially in the dorsal region. 
 
 If, now, you take a series of transverse sections 
 from the different regions of the cord, and compare 
 them together, you will find that the grey matter is 
 relatively most abundant in the lumbar region, and 
 least so in the cervical. Again, if you notice the 
 respective sizes of the anterior and posterior horns of 
 each grey crescent, you will see that they differ in 
 different regions, for in the cervical region the 
 anterior horn is broad, the posterior narrow ; whilst 
 both are narrow in the dorsal, and both broad in 
 the lumbar (Plate III., page 14). 
 
 2. Grey Commissure (Plate IV). — We have already 
 seen that the convex sides of the two crescents are 
 united across the middle line by a band of grey 
 nerve substance, forming the posterior or grey part 
 of the commissure, which connects together the 
 lateral segments of the cord. This grey band is 
 placed nearer to the anterior than to the posterior 
 ends of the crescents, and consists of nerve cells, of 
 neuroglia cells, and of transverse nerve fibres. About 
 its centre may be seen a small opening — the central 
 canal or ventricle of the spinal cord. This canal 
 is the remains of the primitive medullary canal 
 of the embryo, and extends throughout the entire 
 length of the spinal marrow. Above, it expands 
 into the fourth ventricle of the brain, whilst below 
 it enlarges, becomes T shaped in section (Fig. 7), 
 and is prolonged into the filum terminale. It is 
 lined by a layer of columnar cells, ciliated in the 
 
30 THE SPINAL CORD 
 
 child, though it is doubtful whether such is the 
 case in the adult. 
 
 Minute structure of the grey matter. — 
 To examine the minute structure of the grev matter 
 you will require specially prepared microscopic sec- 
 tions. Such specimens will show you that there are 
 two chief constituents of the grey matter, namely — 
 (1) A ground substance or stroma, called NEUROGLIA 
 (nerve glue) ; and (2) NERVOUS ELEMENTS — nerve 
 cells and their processes — embedded in this stroma. 
 
 1. Neuroglia (Plates VII. and VIII, pages 34 
 and 40), already referred to under the structure of 
 the white matter, is a delicate and peculiar kind 
 of connective tissue which pervades both the grey 
 and white substance of the cord. It consists entirely 
 of cells, which are of two kinds — ependyma cells 
 and neuroglia cells (Fig. 30, page 34). 
 
 (1) Ependyma cells are epithelial cells which 
 line both the central canal of the cord and the 
 various spaces — ventricles —of the brain. In the 
 mid-line of the cord the processes of these cells 
 extend from the central canal to the deep aspect 
 of the pia mater, thus forming a mesial septum, 
 especially well seen on the posterior aspect of the 
 cord (Fig. 30, page 34). 
 
 (2) Neuroglia cells. — Cells of Deiters — Spider 
 cells — Astrocytes — vary much in size. They have 
 numberless processes, long or short, whicli usually do 
 not bifurcate, but which, after extending a variable 
 distance from the cell, end free without anastomosing. 
 
AND ITS MEMBRANES. 31 
 
 The processes of neighbouring cells cross and recross 
 each other, and form an intricate network through- 
 out both the grey and white matter. As shown by 
 the action of staining reagents, there is a distinct 
 chemical difference between the body of the neuroglia 
 cell and its processes, and as a consequence some have 
 described these processes as separate fibres, and not 
 as processes of the neuroglia cells. 
 
 Neuroglia is pretty evenly distributed throughout 
 the grey substance, but upon the surface of the cord 
 beneath the pia mater is a distinct layer, and around 
 the central canal will be found a considerable collec- 
 tion of it, which has been called the central grey 
 nucleus. 
 
 The substantia gelatin osa of Rolando, previously 
 
 referred to, was formerly regarded as a similar 
 
 accumulation of neuroglia, but is now known to 
 contain many nerve cells. 
 
 Neuroglia has for its function to support the deli- 
 cate nerve tissues and to protect them from injury 
 from without. It is of especial interest, clinically, 
 as being the probable seat of many of the inflam- 
 matory processes which affect the central nervous 
 system. 
 
 2. The Nervous Constituents of the grey matter 
 are of two kinds — (1) Multipolar nerve cells, the 
 cell-bodies of the neurones — occurring either singly 
 (Fig. 16, &c, page 28), or collected into groups — 
 called vesicular columns. (2) Non-medullated and 
 medullated nerve fibres, which are either strands 
 
32 THE SPINAL CORD 
 
 of fibres from various sources, or branched and 
 unbranched processes of nerve cells, which traverse 
 the grey matter in all directions. 
 
 Vesicular Columns (Fig. 11, page 14). We shall 
 consider (1) the groups of nerve cells; and (2) 
 their structure. The various groups of nerve cells 
 seen in transverse sections of the spinal cord are, 
 you will readily understand, sections of columns of 
 cells, which extend either through the whole length 
 of the grey matter, or only through certain regions 
 of it ; hence they are known as vesicular or gang- 
 lionic columns. They are best marked in the 
 cervical and lumbar regions. 
 
 (a) Anteeior. vesicular column. The largest 
 of these groups is that situated in the fore part of 
 the anterior cornu. It can be traced throughout 
 the entire length of the cord, and is known as 
 the anterior vesicular column — "motor ganglionic 
 column — though it can be sub-divided into two 
 groups — the one anterior or inner, the other lateral 
 (Fig. 11, page 14). In the lumbar region an 
 additional posterior group, which lies behind the 
 anterior, makes its appearance. 
 
 Since it is from these groups of cells of the anterior 
 cornu that the anterior or motor nerve roots spring, 
 the entire collection has been termed the " motor 
 vesicular column." 
 
 The cells of these columns exercise a trophic 
 influence on motor nerves and on muscles. As we 
 shall afterwards see, there are two strata of cells pre- 
 siding over the muscles: (a) an upper stratum — the 
 
rt p'yr. 
 
 Fig. 23. Ascending antero-lat. 
 
 Lateral 
 •erebellar. 
 
 dach's tract.. God's tract. 
 
 
 Fig. 27. 
 
 Plate VI. 
 
 Pla mater. 
 
 S \v ' j>. 
 
 Fig. 24. 
 
 Fig. 25. 
 
 -c. p. 
 
 G. B. 
 
 Fig. 26. 
 
 c. p. 
 
 ztions of tracts at various levels 
 
 Fig. 28. Neuroglia cells. 
 
 
 *- y <® ■/•to 
 
 : mm ' 
 
 Transverse section of white matter of 
 spinal cord. 
 
 Fig. 29. 
 
 
 -; 
 
 2$2 
 
 •'.•:-'\vr:::.*r-iij*ffl^^> 
 
 /t7i<«rtor coma of spinal cord. 
 
 MURRAY D E LT 
 
AND ITS MEMBRANES. 2>Z 
 
 first trophic realm* — situated in certain regions of 
 the brain surface; and (6) a lower stratum — the second 
 trophic realm — the nerve cells of the anterior horn. 
 Now, in any injury to the cells of the upper stratum 
 — -first trophic realm — the muscles are paralysed 
 and rigid, and any atrophy which follows is by no 
 means rapid, being due to disuse; whereas, if the 
 cells of the anterior vesicular column, second stratum 
 — second trophic realm — be injured, the paralysed 
 muscles are flaccid and degenerate rapidly. 
 
 (b) Posterior vesicular column. — The cells of 
 the posterior horn are for the most part not arranged 
 in distinct groups. At the base of the posterior horn, 
 however, near its inner angle, is a well-marked 
 collection of cells variously known as POSTERIOR 
 vesicular column, Clarke s column, Dorsal nu- 
 cleus (Fig. 10). Though it is found along only the 
 middle region of the cord, from the level of the 7th 
 cervical to that of the 2nd lumbar nerve, it probably 
 has representations in all regions of the cord, even 
 as far as the bulb. As we have seen, its cells are, on 
 the one hand, connected with the posterior or sensory 
 nerve roots, and, on the other, with the lateral cere- 
 bellar tracts, and through them with the cerebellum 
 of the same side. 
 
 Injury to the other cells of the posterior horn 
 causes sensory and trophic disturbances of the skin. 
 
 * These well-chosen terms we owe to John Wyllie, M.D., LL.D., 
 late Lecturer on Medicine, School of Medicine, Edinburgh, 
 
 D 
 
34 THE SPINAL CORD 
 
 (c) Lateral vesicular column. — A third group 
 
 of nerve cells — the nucleus of the intermedio- 
 lateral tract, often called the lateral horn (Fig. 14) 
 — lies at the base of the posterior corn a on its outer 
 side, within the column of grey matter of the same 
 name, and, like it, can be distinguished in the dorsal 
 region only. 
 
 Table op Vesicular Columns. 
 
 (See Figs. 10, 11, Plate III., page 14.) 
 
 ( Antero-internal group. 
 
 1. Anterior vesicular J Antero-external group. 
 
 column. ] Posterior group — found in lumbar 
 
 I region. 
 
 2. Lateral vesicular f Lateral horn — found in thoracic 
 
 column. \ and lumbar regions. 
 
 ( Clarke's column; dorsal nucleus — 
 
 3 ' column VeSiCUlar 1 found from the 7th or 8th cer " 
 
 v. vical to the 2nd lumbar nerve. 
 
 Structure of the nerve cells. — The nerve 
 cells of the grey matter of the spinal cord vary 
 considerably, in size, in shape, and in structure. 
 Firstly as to shape and size : — Most of the cells are 
 multipolar and stellate in transverse section, and 
 have two sets of processes — protoplasmic and axis- 
 cylinder processes. 
 
 The largest cells are found in the anterior vesicular 
 column, especially in its outer group, and similar 
 cells occur in Clarke's column. In the posterior horn 
 most of the cells are small and spindle-shaped, and 
 are called solitary cells ; others are larger, have long 
 curved processes, and are known as comet cells. 
 
Fig. 30. 
 
 Plate VII. 
 
 Collaterals. 
 
 J/t.-.c/ .* piii a. 
 
 Cells of 
 anterior 
 column. 
 
 Cells of 
 lateral column. 
 
 Commissural cells. 
 
 toot cell. 
 
 cylindd 
 rocess. 
 
 Fig. 32. 
 
 ommistural cell 
 
 Column cell. 
 
 Iscending 
 branch. 
 
 Porta >or root. 
 
 Descending 
 
 ' branch. 
 
 Cells of 
 posterior 
 
 horn. 
 
AND ITS MEMBRANES. 35 
 
 Secondly as to structure: — Each cell has a distinct 
 oval nucleus, and contains a network of fibrillge and 
 one or more nucleoli. The body of the cell is fibril- 
 lated and granular, and has no distinct nucleated 
 sheath, differing in this respect from the cells found 
 in the various ganglia throughout the body — e.g., 
 sympathetic and spinal ganglia, which have a dis- 
 tinct fibrous capsule, lined by epithelial cells. 
 
 According to their behaviour with methylene blue, 
 the cells are distinguished into those (a) in which 
 the nucleus only is stained, called Caryochromes, 
 and (b) into those in which both the body of the cell 
 and nucleus stain, Somatochromes. Two chemically 
 distinct substances, chromatic and achromatic, are 
 found in the Somatochromes. The chromatic mat- 
 ter when stained appears as granules, stripes, cones, 
 blocks and networks. (Fig. 4, Plate VIII., page 40.) 
 It is probably the nutritive material of the cell, 
 for it is used up during its activity. The achro- 
 matic matter, on the other hand, is the essential 
 protoplasmic constituent of the cell. On it tbe 
 life and activity of the cell depend — the activity 
 being accompanied by a swelling of the cell. 
 
 Processes of Nerve Cells are, as we have said, of 
 two kinds — (1) axis-cylinder processes ; (2) proto- 
 plasmic processes. 
 
 (1) The axis-cylinder processes are branched 
 or unbranched processes of nerve cells, and are con- 
 nected to the nerve cell either directly, as seen in 
 the motor type of cell, or indirectly through a plexus 
 of fibres, as seen in the sensory type. Composed 
 
36 THE SPINAL CORD 
 
 of many primitive fibrillse they, in many cases, soon 
 acquire a medullary sheath, and become the axis- 
 cylinders of nerve fibres, which, after a longer or 
 shorter course, end in the grey matter in fine brush- 
 lets of branches. They are centrifugal processes, 
 carrying impulses away from the cell. 
 
 (2) The protoplasmic or grey processes are a 
 series of delicate ramifying branches which cross and 
 recross each other in all directions (Figs. 17 and 19, 
 Plate V., page 28). They are centripetal processes, 
 carrying impulses to the cell, and may, through their 
 relation to neuroglia and to blood-vessels, subserve 
 the nutrition of the nerve elements. 
 
 At the cells the protoplasmic and axis-cylinder 
 processes are in most cases continuous with each 
 other ; passing through the cells without interruption : 
 their terminal processes, however, do not anastomose 
 with the processes of other nerve cells, but are 
 merely in contact with the nerve elements. Hence 
 it follows (1) that nerve cells, most likely, do not 
 generate nerve motion, but are nutritive only ; 
 and (2) that contact, and not actual continuity, is 
 sufficient for the conduction of motor, sensory, and 
 reflex impulses along the spinal cord. 
 
 Classification of the Nerve Cells. 
 
 1. Cells with short axis-cylinder processes. In these cells the 
 axone soon breaks up into branches which do not become encased 
 in a medullary sheath, but form a fine plexus of fibrillse. They are 
 the sensory type of cell, and are almost entirely confined in their 
 distribution to the posterior horns (Fig. 19, page 28). 
 
 2. Cells with long and distinct axis-cylinder processes (Fijr. 22, 
 page 28), which do not branch, or branch but slightly, and which 
 
AND ITS MEMBRANES. 37 
 
 ultimately become clothed with a medullary sheath. They are 
 regarded as the motor type of cell, and may be sub-divided into 
 two groups — 
 
 (a) Root Cells which occur in the anterior horn. Their axis- 
 cylinder process is continued into the anterior nerve roots; 
 and their protoplasmic processes pass in various directions 
 through the grey matter (Fig. 31, Plate VII., page 34). 
 (6) Column Cells which are met with in all parts of the grey 
 matter. They are so called because their axis-cylinder 
 processes pass into the antero-lateral white columns of the 
 same or of the opposite side (commissural cells) of the 
 cord (Fig. 32, Plate VII., page 34). 
 
 IV.— DEEP ORIGINS OF SPINAL 
 NERVES. 
 
 (Fig. 14, Plate IV., page 22.) 
 
 The several spinal nerves are, as you know, mixed 
 nerves, for they contain both motor and sensory 
 fibres. They each spring from the spinal cord by 
 two roots, an anterior — motor, coming from the 
 antero-lateral grooves, and a posterior — sensory, from 
 the postero-lateral grooves. These attachments to the 
 cord are called the superficial origins of the nerves. 
 The deep origins are the nerve cells in the grey matter, 
 to or from which the nerve roots can be traced. 
 
 (1) The Anterior Nerye Roots — motor roots. 
 Most of the fibres of these roots can be traced from 
 the nerve cells of the anterior horn. The cells from 
 which they spring are called root cells, and the 
 several bundles of white fibres which can be seen 
 passing through the peripheral white substance to 
 the antero-lateral grooves — their superficial origin — 
 are the axis-cylinder processes of these cells. Other 
 fibres of the anterior roots come from cells in the 
 opposite anterior and posterior horns (Fig. 14, page 22). 
 
3§ THE SPINAL CORD 
 
 (2) The Posterior Nerye Roots — sensory roots — 
 before reaching the spinal cord, pass through 
 the spinal ganglion, in which there are unipolar 
 nerve cells. At a little distance from these cells, the 
 pole, or axis-cylinder process, bifurcates in a T-shaped 
 manner, one limb of the T becoming the distal, the 
 other the central end of a nerve fibre of the posterior 
 root. The central processes enter the cord in two 
 sets — a lateral set which goes to the marginal zone 
 (Lissauer's tract), and a mesial set which enters the 
 postero-external strand. On entering the spinal cord, 
 all the fibres, mesial and lateral, at once divide into 
 ascending and descendiDg branches, which give off 
 collaterals to different parts of the grey matter. 
 (Figs. 31 and 32, Plate VII., page 34.) The de- 
 scending branches after a short course turn at right 
 angles into the grey matter and end free in little 
 tufts. Of the ascending fibres, those of Lissauer's 
 tract lose themselves in the substantia gelatinosa 
 of Rolando ; those of the rest of the column after a 
 long, short, or intermediate course enter the grey 
 matter. At first they occupy the postero-external 
 tract, but as they ascend they become more internal 
 and are found in the fasciculus of Goll, their 
 place in the postero-external strand being taken 
 by fibres of the nerve roots which enter the cord at 
 higher levels : hence it follows — 1st, that these two 
 columns of Goll and Burdach are not physiologically 
 distinct ; and, 2nd, that the greater part of the column 
 of Goll consists of fibres, which come from the legs, 
 whereas the fibres that constitute the column of 
 Burdach mostly come from the upper limbs and neck. 
 
AND ITS MEMBRANES. 39 
 
 The columns of Goll and Burdach ultimately end in 
 nuclei (nucleus gracilis and nucleus cuneatus) in the 
 medulla; from which fibres can be traced to the 
 opposite side of the brain, in what is known as 
 the superior pyramidal or sensory decussation. 
 
 Besides the fibres of the posterior roots which are 
 thus connected with the nerve cells of the ganglia, 
 there are others having no such connection, but which 
 merely pass through the ganglia on their way to 
 nerve cells in the spinal cord. On entering the cord 
 these fibres pass at once into the grey matter, 
 through which they can be followed in various 
 directions, even as far as the cells of the anterior 
 horn (Fig. 14, Plate IV., page 22). 
 
 Note. — Gaskell suggests that each spinal segment 
 has two sets of nerve roots : — 
 
 1. A somatic set. — The motor and sensory nerves usually 
 described — (a) the former, the motor, being aganglionic and 
 connected with the cells of the anterior horn ; and (b) the latter 
 the sensory, being ganglionic and connected with the cells of the 
 posterior horn. 
 
 2. The other set of nerve roots — the splanchnic set, or visceral 
 set — are distributed to blood-vessels, to the heart, and to other 
 hollow viscera. They consist of two groups— 
 
 (a) A ganglionic set, connected with the cells of Clarke's column 
 — their ganglia being the lateral ganglia of the sym- 
 pathetic trunk. They are the motor group, and pass to the 
 lateral ganglia of the sympathetic, thence to the walls of 
 blood-vessels and viscera. When stimulated, they cause 
 contraction of blood-vessels and viscera, and give rise to 
 increased activity and to increased waste. 
 
4 o THE SPINAL CORD 
 
 (h) An aganglionic set, connected with the cells of the lateral 
 horn. They are the inhibitory group, and do not pass to 
 the ganglia of the sympathetic, but run on as rnedullated 
 nerve fibres to ganglia situated in the tissues themselves, 
 Stimulation of this set causes dilatation of the vessels and 
 various inhibitory phenomena — such as cardio-inhibition. 
 They diminish activity and tend to promote repair. 
 
 Summary. — To sum up, then, we have the spinal 
 cord presented to us as an elongated mass of nervous 
 substance, consisting of white and grey matter; in- 
 vested by three membranes ; having two distinct 
 enlargements; giving origin to thirty-one pairs of 
 spinal nerves ; nourished by spinal vessels, and 
 divided by anterior and posterior fissures into two 
 lateral segments, each with three sub -divisions 
 which can be mapped out into numerous tracts, 
 or systems of varying significance. 
 
 We see, moreover, that our ideas in regard to the 
 constitution of the spinal cord must undergo at least 
 this modification, that whereas formerly the spinal 
 cord was regarded as made up of two distinct ele- 
 ments — nerve fibres and nerve cells — we must now 
 consider that there is only one nerve element 
 — the neurone — the nerve cell with its protoplasmic 
 and axis -cylinder prolongations. These neurones 
 are arranged in tiers, one above the other, and are 
 connected together by their protoplasmic and by 
 their axis-cylinder processes and collaterals. These 
 facts have important bearings on the physiology 
 of the spinal cord. 
 
 The following Tables will be found useful for 
 reference : — 
 
Fig. 1 
 'erve fibres with collaterals. 
 
 Plate VIII. 
 
 Ganglion of Ou posterior root 
 of a spinal nerve. 
 
AND ITS MEMBRANES. 41 
 
 -Long Tracts of Conduction to and from the 
 Brain. 
 
 TABLE OF ASCENDING AND DESCENDING DEGENERATIONS. 
 
 / 1. Lateral cerebellar tract, from visceral tract. 
 
 2. Postero- internal strand, Goll's tract, from 
 posterior roots. 
 
 3. Antero- lateral ascending tract of Gowers, 
 V from crossed sensory roots. 
 
 1. Crossed pyramidal tract—the chief motor 
 tract — contains 90 per cent, of the motor 
 fibres. It is often called the lateral 
 pyramidal tract. 
 
 2. Direct pyramidal tract, fasciculus of Tlirck, 
 usually contains only about 10 per cent, 
 of the motor fibres. 
 
 Tracts which 
 
 undergo 
 
 Ascending 
 
 Defeneration. 
 
 Tracts which 
 
 undergo 
 
 Descending 
 
 Defeneration, 
 
 II. — Short Commissural Tracts. 
 
 These neither undergo ascending nor descending degeneration, 
 or at least for no great distance, and are therefore considered to be 
 commissural fibres between different segments of the cord, 
 
 1. The posteroexternal strand — fasciculus of Burdach. 
 
 2. Antero-external column — anterior root zone. 
 
 3. Part of the lateral column — lateral limiting layer. 
 •4. Lissauer's tract— marginal zone. 
 
 Table of the Order in which the several Tracts of 
 White Matter receive their Medullary Sheaths. 
 
 1. Anterior and posterior root fibres. 
 
 2. Ground fibres of the antero-external column. 
 
 3. Ground fibres of the postero-external column. 
 i. Lateral mixed zone. 
 
 5. Limiting layer and anterolateral ascending tract. 
 
 6. Posteromedian column. 
 
 7. Direct lateral cerebellar tract. 
 
 8. Crossed and direct pyramidal tracts. In man these 
 
 tracts get their medullary sheath, for the first 
 time, at birth. 
 
42 
 
 THE SPINAL CORD. 
 GOWEES' TABLE. 
 
 SHOWING THE APPROXIMATE RELATION TO THE SPINAL NERVES OF 
 
 THE VARIOUS MOTOR, SENSORY, AND REFLEX FUNCTIONS 
 
 OF THE SPINAL CORD. 
 
 MOTOR. (Nerves. 
 
 MOTOR. 
 
 SENSORY. 
 
 Lower 11-ck 
 muscles, 
 
 Middle part 
 
 of 
 
 Trapezius 
 
 Lower part 
 of 
 Trapezius J 
 and dorsal 
 muscles 
 
 Lumbar 
 
 muscles 
 
 Peroneus, I. r 
 Flex, of J 
 
 ankle, Ext. "| 
 of aukle V. 
 
 J •*■ \ Small rotators of head 
 n i Depressors of liyoid 
 
 3 Lev. ang. scapulae 
 
 J Diaphragm ~\ fcj 
 
 ISerratus I ~' 
 
 /Flex, of elbow j o 
 
 n ~{ Supinators I ^ 
 
 _ / Ext. wrist and fingers 
 
 ) Ext. elbow 
 
 /" Flex, wrist and fingers 
 o J Prouators 
 
 I 
 
 -j -j f Muscles of hand 
 
 2\ 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10' 
 
 11 
 
 12 
 
 , 1 J 
 
 2 ^ Cremaster 
 o f Flexors of hip 
 
 I Extensors of knee 
 
 4 f Abductors of hip 
 
 k I Ext. and abduct, of hip 
 
 Scalp 
 
 Intercostals 
 
 .Abdominal muscles 
 
 S 1 
 
 ) Flexors of knee 
 
 Intrinsic muscles of foot 
 
 Perineal and 
 muscles 
 
 Co. 
 
 1} 
 
 Neck and upper part 
 
 of chest 
 j- Shoulder 
 
 -Arm, outer side 
 
 Radial side, fore- 
 arm and hand; 
 thumb 
 
 Arm, inner side 
 ulnar side of 
 forearm and 
 hand ; tips of 
 fingers 
 
 Front of thorax 
 > Ensiform area 
 
 Abdomen 
 (Umbilicus 10th) 
 
 |_ Buttock, 
 
 | upper part 
 
 Groin and Scrotum 
 (front) 
 
 C outer side 
 
 a front 
 V. inner 
 
 3 
 
 \ Thigh 
 
 [ 
 J pinner side 
 
 " \ Leg, inner side 
 
 1 I C Buttock, lower part 
 I J Back of thigh 
 
 2 T | Leg ) except inner 
 I v & foot j i^art 
 
 4 V Perinseum and anus 
 
 5, 
 
 (Skin from coccyx to 
 
 30 f :U1US 
 
 REFLEX. 
 
 *j y Scapular 
 
 8 
 
 1; 
 
 2 
 
 3 
 
 4" 
 
 5 
 
 a \. Epigastric 
 
 7 
 
 Abdominal 
 
 / 
 1 Cremasteric 
 
 Knee-jerk 
 
 I ure 
 
 I Gluteal 
 
 J \ Fcot- 
 ±\ J clonus 
 
 2 V Plantar 
 
43 
 
 SECTION II. 
 
 BRAIN AND ITS MEMBRANES. 
 
 The term Brain, or Encephalon, includes all that 
 part of the great central nervous system which is 
 enclosed within the cavity of the cranium. Invested 
 by three membranes or meninges, it presents, as you 
 will afterwards see, four distinct sub-divisions : — 
 (1) The Cerebrum, a large convoluted mass, or big 
 brain ; (2) the Cerebellum, or little brain ; (3) the 
 Pons Varolii, a white transverse band uniting the 
 two halves of the little brain ; and (4) the Medulla 
 Oblongata, or bulb, the enlarged upper end of the 
 spinal cord (Figs. 33 and 34, page 44). 
 
 From a developmental point of view, the brain is 
 divided into six parts : Telencephalon, Diencephalon, 
 Mesencephalon, Isthmus Rhombencephali, Meten- 
 cephalon, Myelencephalon ( see " Development, " 
 page 190). 
 
 We shall describe (1) the membranes and vessels 
 of the brain, and (2) the several parts of the brain ; 
 but before doing so we shall, for convenience, give 
 seriatim the following dissections : — 
 
 Dissection. — 1. To expose the Membranes of the Brain. — Make 
 an incision along the middle line through the entire thickness of 
 the scalp, from the root of the nose in front to the external occipital 
 protuberance behind. Turn back the pericranium to the level of 
 the ears, and then saw through the outer table of the skull-cap 
 along a line passing round the skull, about half-an-inch above the 
 
44 THE BRAIN 
 
 external occipital protuberance behind, and about the same distance 
 above the supra-orbital arch in front. Break through the inner 
 table with the chisel and forcibly raise the detached skull-cap, 
 which you will find more or less adherent to the subjacent mem- 
 brane, especially along the lines of the cranial sutures. Branches 
 of the meningeal arteries will be seen ramifying on the outer 
 surface of the exposed membrane, between it and the bone. 
 
 2. To Remove the Brain. — With a sharp pair of scissors cut 
 through the dura mater at the same level at which you have sawn 
 the bones, and reflect it upwards towards the top of the head. 
 Examine as far as you can the strong process, falx major, passing 
 down mesially between the cerebral hemispheres. Divide this pro- 
 cess in front where it is attached to the crista galli of the ethmoid, 
 and cut through the veins which enter the sinus contained within 
 its upper border. Eaising the falx out of the longitudinal fissure, 
 turn it back, but do not cut it behind. Now pass the fingers of the 
 left hand beneath the fore-part of the brain, and gently raise it from 
 the anterior cranial fossae, taking care to detach the small white 
 rounded bands, olfactory lobes, 1st pair of nerves, from the cribri- 
 form plate of the ethmoid. The optic nerves, 2nd pair, and the 
 two internal carotids will now be seen close to the anterior clinoid 
 processes, and should be divided. Piercing the dura mater, ex- 
 ternal to the carotid, are the round 3rd nerves, and in the free 
 margin of the tentorium cerebelli, now exposed, are seen the 
 slender lf.th nerves. Cut through these, and through the infundi- 
 bulum which passes down towards the sella turcica of the sphenoid. 
 Then with the point of the knife make an incision through the 
 margin of the tentorium on each side, just behind and parallel to 
 the upper margin of the petrous part of the temporal bone, carry- 
 ing the incision as far back as necessary, but being careful not to 
 injure the parts beneath. You will now see the following nerves, 
 which will require to be divided one after another. Just below the 
 anterior end of the tentorium will be found the large 5th nerves ; 
 nearer the middle line, the slender 6th nerves; below and external 
 to the 5th, the 7th or facial, and 8th or auditory nerves, and the 
 auditory artery ; immediately below the 8th are the 9th, 10th and 
 11th nerves. Cut the 9th, the glossopharyngeal, and the 10th, the 
 vagus, but leave intact the spinal part of the spinal accessory 
 nerve ; lower down near the middle line is the 12th or hypoglossal 
 nerve, consisting of two bundles, which pierce the dura mater by two 
 
Fig. 33. 
 
 Plate IX. 
 
 ( 'trrhrum. 
 
 Pom Varolii, 
 
 Superior 
 
 cerebellar p& 
 
 Middle, cerebellar peduncle. 
 
 Cerebellum. 
 
 '^Pf§Ef ' Inferior cerebellar ped'jailr. 
 
 Fia. 34. Cerebrum, 
 
 Dura mater. 
 
 knoid. 
 
 later. 
 
 I space N 
 
 5th ventricle, 
 
 3rd ventricle, 
 
 Subarachnoid space. 
 
 4th ventricle. 
 
 Medulla. 
 
 Isthmus 
 Rhombcncep 
 
 Ti ntorium cerebelli 
 y Cerebellum. 
 'Foramen Majendie. 
 
 URRAY OEC 
 
AND ITS MEMBRANES. 45 
 
 separate openings. Next pass the knife as far down the spinal 
 canal as possible, and divide the spinal cord, the nerve roots 
 attached to its sides, and the vertebral arteries as they wind round 
 from the back. Snip through the veins of Galen, and the brain 
 can now be easily removed from its bed, and should be at once 
 placed in spirit. Leave it there for a few days ; then examine it 
 and carefully remove the pia mater, except at the back of the brain 
 between the cerebrum and cerebellum, in order not to disturb a 
 process of pia mater — the velum interpositum — which passes into 
 the brain at this point. 
 
 CHAPTER I. 
 
 MEMBRANES OF THE BRAIN. 
 
 To examine the first of these membranes — the 
 cranial dura mater — replace, as far as you can, the 
 falx major and the tentorium cerebelli, and fasten 
 them in their places by a few stitches. It will, how- 
 ever, be far more satisfactory for you if you can 
 obtain a specimen specially prepared to show the 
 arrangement of the dura mater (Plate XL, page 52). 
 
 I.— THE DURA MATER. 
 
 The Cranial Dura Mater is a dense white fibrous 
 membrane, rough externally, but smooth and polished 
 within. It is lined by a layer of epithelial cells 
 similar to that which lines the spinal dura mater. 
 Composed of two layers (though these are not 
 distinct from each other) — an inner, which sends 
 processes between the parts of the brain, and an 
 outer, which forms the endosteum of the inner table 
 of the cranium — it adheres to the bones of the skull, 
 
46 THE BRAIN 
 
 in two places especially : (1) along the lines of the 
 cranial sutures, and (2) at the base of the cranium. 
 This latter fact accounts for the rare occurrence of 
 accumulations of pus or blood at the base of the 
 brain between the dura mater and the bone. The 
 dura mater, moreover, sends a tubular process along 
 each of the several cranial nerves as they leave 
 the skull through their various foramina; part of 
 this tubular process forms a sheath to the nerve, 
 part of it becomes attached to the pericranium. 
 The dura mater also passes into the orbital cavities, 
 and there blends with the periosteum. At the 
 lower margin of the foramen magnum the dura 
 mater is closely attached to the bones, and becomes 
 continuous with the spinal dura mater. Along 
 certain lines the two layers, of which the cranial 
 dura mater is composed, separate from each other, 
 leaving variously shaped channels, called VENOUS 
 sinuses, for the passage of the blood from the brain 
 into the venous system. 
 
 Of the partitions given off from its inner layer, 
 two — the FALX CEREBKI and the FALX CEREBELLI — 
 are vertical ; the third, the TENTORIUM CEREBELLI, 
 is usually said to be horizontal, though it is far more 
 vertical than horizontal, for it slopes downwards and 
 backwards. 
 
 1. The Falx Cerebri — so called from its sickle- 
 shaped form (Fig. 37, page 52) — is the vertical 
 mesial process of dura mater which is lodged in the 
 great longitudinal fissure, and separates the inner 
 surfaces of the cerebral hemispheres from each other. 
 
AND ITS MEMBRANES. 47 
 
 In front it is pointed, and is attached to the apex 
 and to the posterior margin of the crista galli. 
 Behind it widens out, and is fixed along the middle 
 line to the upper surface of the tentorium cerebelli. 
 Its upper convex margin contains the superior 
 longitudinal sinus, and adheres to the ridges seen 
 on each side of the median depression, on the inner 
 aspect of the vault of the skull. The lower margin 
 contains the inferior longitudinal sinus. It is 
 concave and free, and in front is in contact with 
 the upper surface of the corpus callosum, though 
 behind it is some distance from that body. 
 
 2. The Falx Cerebelli (Fig. 37) is the small 
 median vertical triangular partition attached behind 
 to the internal occipital crest, and above, at its widest 
 part, to the mid-line of the under surface of the ten- 
 torium cerebelli. Its free concave margin projects 
 forwards and fits into the notch between the halves 
 of the cerebellum. Its posterior attached margin 
 contains the occipital sinus, which is single above 
 but bifid below. 
 
 3. The Tentorium Cerebelli (Fig. 37), supporting 
 the posterior part of the cerebrum, slopes forwards and 
 upwards, somewhat horizontally, as an arched tent- 
 like partition between the big brain and the little 
 brain. The posterior convex margin is attached 
 behind to the transverse ridges on the inner aspects 
 of the occipital, parietal, and temporal bones, and 
 further forwards it is fixed to the upper margin of 
 the petrous part of the temporal bones. It ends in 
 front at the posterior clinoid processes. This margin 
 
4 8 THE BRAIN 
 
 contains the lateral sinuses behind and the superior 
 petrosal sinuses in front. The anterior concave 
 margin, free in the greater part of its extent, is 
 attached on each side by a narrow slip to the anterior 
 clinoid processes. Between this margin and the 
 dorsum sellse of the sphenoid is an oval opening 
 for the passage of the crura cerebri, the superior 
 peduncles of the cerebellum, and the posterior cere- 
 bral arteries. Along the middle line of the upper 
 surface of the tentorium runs the straight sinus, 
 which receives the veins of Galen from the interior 
 of the brain (Fig. 37, page 52). 
 
 The MINUTE structure of the dura mater of the 
 brain is similar to that of the spinal cord. It 
 consists of layers of fibrous tissue. The larger 
 arteries lie near the outer surface of the membrane, 
 whereas the veins are embedded in its midst or lie 
 between its layers where these exist. There are 
 few capillaries in its substance, but on its inner 
 aspect is a rich network of vessels covered by 
 epithelial cells and surrounded by peri - vascular 
 spaces which by means of stomata communicate 
 with the sub-dural space (Robertson). 
 
 The Agreements and Differences in the Arrangement 
 of the Cranial and Spinal Dura Mater may 
 be arranged as follows \ 
 
 (a) Agreements — 
 
 1. Both are fibrous membranes. 
 
 2. Both invest their respective organs. 
 
 3. Both form the outer boundary of the sub- 
 
 dural space. 
 
Fig. 35. 
 
 Plate X. 
 
 Dura mater. - 
 
 Middle 
 mugial artery 
 
 /'in mater. 
 
 A rachnoid. 
 
 Krcvlar sinus, 
 
 asverse sinus. 
 
 petrosal sinus 
 
 *V._ Veins of orbit. 
 
 S3 CarvenovA sinus. 
 
 Superior petrosal sinus. 
 
 Lateral sinus. 
 
 Occipital sinus. 
 
AND ITS MEMBRANES. 49 
 
 b) Differences — 
 
 1. The cranial dura mater forms the perios- 
 
 teum of the bones; the spinal does not, 
 though some authors hold that there 
 are two layers in the spinal dura mater 
 — the outer forming the periosteum of 
 the bones. 
 
 2. The cranial dura mater sends off processes 
 
 between the parts of the brain ; not so 
 the spinal dura mater — it gives off no 
 such processes. 
 
 3. The cranial dura mater, by the separation 
 
 of its constituent layers, encloses the 
 various venous sinuses; the spinal dura 
 mater does not form sinuses. 
 
 The cranial dura mater receives its nerve supply 
 from the 4th and 5th cranial nerves, and from the 
 sympathetic. 
 
 Pacchionian Bodies (or Glands) are small white 
 elevations, which indent the inner surface of the ver- 
 tex of the skull, along each side of the middle line. 
 They are said to be out-growths of the villi which 
 normally exist in the arachnoid. Their exact nature 
 and use is unknown. Some hold that they are mere 
 excretions, others that they are communications 
 between the sub-arachnoid space and the venous 
 sinuses of the dura mater, others that they are 
 ligaments which fix the pia mater to the dura 
 mater and help to suspend the brain. 
 
 II.— THE PIA MATER, 
 
 (Fig. 34, page 44, and Fig. 35, page 48.) 
 
 The Pia Mater of the brain, like that of the spinal 
 cord, is an extremely fine vascular membrane, com- 
 posed of a plexus of capillary blood-vessels held 
 
 E 
 
5o THE BRAIN 
 
 together by delicate connective tissue (Fig. 35, page 
 48). It is practically one layer with the arachnoid 
 (page 51). Covering the surface of the brain, it dips 
 into the various fissures between the convolutions; 
 and from its inner surface numberless blood-vessels 
 emerge for the nourishment of the substance of the 
 brain. Besides the septa between the convolutions, 
 the pia mater also sends into the brain through a 
 large fissure, called the great transverse fissure, a 
 special prolongation, the velum interpositum, the 
 margins of which are wrinkled and folded, forming 
 a vascular fringe, the choroid plexus ; and a similar 
 vascular process of pia mater, known as the tela 
 choroidea inferior, or choroid plexus of the 4th 
 ventricle, lies in the roof of that cavity (see " Ven- 
 tricles," page 141). 
 
 In structure the pia mater of the brain corre- 
 sponds to the inner of the two layers of the pia-arach- 
 noid described on the following page. It receives its 
 nerve supply from the 3rd, 5th, 6th, 7th, and 8th 
 nerves, as well as from the sympathetic. 
 
 III.— THE ARACHNOID. 
 
 The Arachnoid is a smooth, glistening, trans- 
 parent, colourless membrane, situated between the 
 dura mater and the pia mater (Fig. 35). Formed of 
 a single layer, it is, on the one hand, separated from 
 the dura mater by veins, and, on the other, envelops 
 the brain but does not pass into its fissures. It is 
 closely connected to the pia mater beneath by the 
 sub-arachnoid trabeculse, which are far more numer- 
 ous than those in the spinal cord. At certain spots, 
 
AND ITS MEMBRANES. 51 
 
 especially at the base of the brain, the pia mater and 
 the arachnoid are more widely separated from each 
 other, forming the SUB-ARACHNOID SPACE, which 
 contains most of the cerebro-spinal fluid. 
 
 Minute structure. — The arachnoid is not a dis- 
 tinct membrane from the pia mater, and the two are 
 often described together under the name pia-arach- 
 noid. This consists of two layers of epithelium — a 
 superficial and a deep — the latter being in contact 
 with the brain. The two layers are united by 
 numberless trabecular covered by epithelial cells. 
 The nerve supply to the arachnoid is probably the 
 5th, the facial, and the spinal accessory nerves. 
 
 Sub-dural and Sub-arachnoid Spaces (Fig. 34). — 
 The space between the dura mater and the arachnoid 
 is called the sub-dural space, and is lined by epi- 
 thelial cells. The space between the arachnoid and 
 pia mater is the sub-arachnoid space, and is crossed 
 by the sub-arachnoid trabecular. It contains cerebro- 
 spinal fluid. Both its inner and outer walls are 
 lined by epithelial cells, which also cover the 
 surfaces of the trabecular. The sub-arachnoid space 
 is most distinct in the following situations — (1) 
 at the great longitudinal fissure ; (2) at the base of 
 the brain, in the triangular interval, called the 
 inter-peduncular or opto-peduncular space; and (3) 
 posteriorly, between the cerebellum and the medulla 
 oblongata. 
 
 Cerebro-spinal Fluid. — Most of this fluid is 
 contained in the meshes of the sub-arachnoid tra- 
 becule, though a little is found in the sub-dural space. 
 
52 THE BRAIN 
 
 It communicates with the fluid in the central canal 
 of the spinal cord, and in the ventricles of the braiD, 
 through an opening — the foramen of Majendie — in 
 the roof of the 4th ventricle (Fig. 34, page 44), and 
 through two similar lateral openings in the ven- 
 tricular roof between the medulla and cerebellum. 
 Corresponding communications also exist at the 
 inferior horns of the lateral ventricles. The cerebro- 
 spinal fluid is not merely intended to fill the sub- 
 arachnoid space, but helps to protect the nerve 
 centres from sudden shocks ; acting, in fact, as a 
 water-bed (Hilton) on which the brain rests. 
 According to Foster it is probable that the cerebro- 
 spinal fluid, being of the nature of lymph, also 
 subserves the nutrition of the brain. 
 
 IV.— VENOUS SINUSES. 
 
 (Figs. 36, 37, Plates X., XL, pages 48 and 52.) 
 
 The sinuses of the brain, formed by the separation 
 of the two layers of the dura mater, are lined by 
 epithelial cells continuous with those lining the 
 interior of the veins. These sinuses are fifteen in 
 number — five paired and five single. The single sin- 
 uses are the superior and the inferior longitudinal, 
 the straight, the circular, and the transverse. The 
 paired set includes the two lateral, the two superior, 
 and the two inferior petrosals, the two cavernous 
 and the two occipital. Other smaller sinuses are 
 sometimes described. 
 
Plate XI. 
 
 Fio. 37. 
 
 Inferior longitudinal sinus. 
 
 Superior longitudinal sinus. 
 
 Falx major. 
 
 rramen caxumJj 
 
 M-i- Straight 
 
 sinus. 
 
 ' -Tentorium, 
 cerebeUi. 
 
 Lateral sinus. 
 
 Occipital sinus, 
 petrosal sinus. Superior petrosal sinus. 
 
 Fig. 38. 
 Parasinoidal- sinus. 
 
 Superior longitudinal sinus. 
 
 Pacchionia.n body, 
 Bone. 
 
 Dura mater. 
 
 Subarachnoid space. 
 
AND ITS MEMBRANES. 53 
 
 1. The Superior Longitudinal Sinus (Figs. 37, 
 38, page 52) begins in front at the foramen caecum 
 as a small vein, which often communicates with the 
 veins of the nose, and thence arches upwards and 
 backwards in the convex margin of the falx cerebri 
 to reach the internal occipital protuberance, where it 
 is joined by several other sinuses at the triangular 
 dilatation, called the torcular Herophili,* or the meet- 
 ing of the sinuses. Cut open the sinus in its entire 
 length and you will see that it is wider above than 
 below, being triangular in section, and that it in- 
 creases in size as it passes backwards, its cavity being 
 crossed by many slender bands — chordaa Willisii. 
 Many veins, from the substance of the brain, pour 
 their blood into this sinus. They run mostly from 
 behind forwards — that is, in the reverse direction to 
 the blood current in the sinus. They pierce the wall 
 of the sinus by slit-like openings, which act as valves, 
 and thus prevent regurgitation of the blood. Before 
 entering the sinus they pass through small spaces, 
 called the para-sinoidal spaces, which lie on each side 
 of the superior longitudinal sinus (Fig. 38, page 52). 
 Other smaller veins enter this sinus from the diploe 
 of the surrounding bones, and it receives an emissary 
 vein through the parietal foramen. 
 
 2. The Inferior Longitudinal Sinus (Fig. 37) is 
 really a small vein contained in the free concave 
 border of the falx major. It commences in front 
 
 * As HoUlen points out, the term torcular is a mistranslation of 
 the original word, (TcoKr]v— a canal or gutter. 
 
54 THE BRAIN 
 
 by minute venous radicles within the substance of 
 the falx, and ends behind in the straight sinus. 
 
 3. The Lateral Sinuses (Fig. 36).— These are 
 two in number, right and left, the right being 
 usually the larger of the two. Through them most 
 of the venous blood from the brain reaches the 
 internal jugular veins. They commence at the 
 internal occipital protuberance, and running out- 
 wards and downwards in the attached margin of 
 the tentorium cerebelli, in the grooves on the inner 
 surface of the occipital, parietal, and temporal bones, 
 finally turn forwards to end in the bulb of the 
 internal jugular vein. Blood enters these sinuses 
 from the superior and inferior petrosal sinuses, 
 from the inferior cerebral and cerebellar veins, from 
 the diploe of the bones, and from the scalp by 
 emissary veins. 
 
 4. The Straight Sinus (Fig. 37) lies in the middle 
 line of the upper surface of the tentorium cerebelli, 
 where the falx major is attached. Behind, it ends 
 at the meeting of the sinuses; while in front it 
 receives the inferior longitudinal sinus and the veins 
 of Galen, the latter bringing blood from the third 
 and the lateral ventricles of the brain. Some cerebral 
 and cerebellar veins also open into this sinus. 
 
 5. The Cavernous Sinuses (Fig. 36), so called 
 from the spongy appearance of their interior, are 
 placed in the grooves on each side of the body of 
 the sphenoid. They are oval in vertical transverse 
 section, and contain, in their thickened outer wall, 
 
AXD ITS MEMBRANES. 55 
 
 the third, the fourth, and the ophthalmic division 
 of the fifth nerves ; while internally, and separated 
 from the blood of the sinus by a thin lining- 
 membrane, is the internal carotid artery, with the 
 sixth nerve on its outer side. These sinuses com- 
 municate with the circular sinus, and with the 
 superior and inferior petrosal sinuses; and receive 
 small cerebral veins and the veins from the orbit 
 (Fig. 36, page 48). 
 
 6. The Circular Sinus (Fig. 36) surrounds the 
 pituitary body in the sella turcica. At each side 
 it communicates with the cavernous sinuses. 
 
 7. The Petrosal Sinuses (Fig. 36) are two on 
 each side — the superior and the inferior. The 
 Superior Petrosal sinus lies along the upper 
 border of the petrous part of the temporal bone, 
 and connects the cavernous sinus with the lateral 
 sinus. The Inferior Petrosal sinus runs in the 
 groove between the occipital bone and the petrous 
 part of the temporal bone. It unites the cavernous 
 sinus to the lateral sinus after the latter has passed 
 out of the skull to become the internal jugular vein. 
 Cerebral, cerebellar, tympanic, and auditory veins 
 pour their blood into one or other of these sinuses. 
 
 8. The Transverse or Basilar Sinus (Fig. Bo), 
 sometimes double, is placed across the basilar process 
 of the occipital bone, and connects together the 
 inferior petrosal sinuses. It communicates below 
 with the anterior spinal veins. 
 
56 THE BRAIN 
 
 9. The Occipital Sinuses (Fig. 36) commence 
 near the foramen magnum as two small channels 
 which run upwards in the attached margin of the 
 falx cerebelli, and then join above to form a single 
 sinus which opens into the torcular Herophili. 
 
 Emissary Yeins are small vessels which pass 
 through foramina in the skull, and unite the veins 
 of the scalp with the cranial sinuses. If it were 
 not for these veins injuries to the scalp would lose 
 half their significance (Treves). 
 
 The Meningeal Arteries, which supply the dura 
 mater with blood, ramify in branching grooves on 
 the inner surface of the cranium, between it and the 
 outer surface of the dura mater (Fig. 35, page 48). 
 From the fossae in which they ramify they are called 
 the anterior, the middle, and the posterior meningeal 
 arteries, and they arise from the ethmoidal, ascend- 
 ing pharyngeal, internal maxillary, occipital, and 
 vertebral arteries. For the description of these 
 vessels see your dissecting manual. We shall now 
 pass on to examine the vessels of the brain. 
 
AND ITS MEMBRANES. 57 
 
 CHAPTER II. 
 
 VESSELS OF THE BRAIN. 
 
 (Figs. 39, 40, Plate XII., page 58.) 
 
 Dissection. — Remove with great care the pia mater, and in 
 doing so, at the under surface of the brain, dissect out the vessels 
 and the cranial nerves. 
 
 I.— ARTERIES. 
 
 The arteries of the brain are derived from the two 
 internal carotids and from the two vertebrals. 
 
 I. The Internal Carotid Arteries, when they 
 reach the anterior clinoid processes, give off the 
 ophthalmic branches, and then divide into anterior, 
 and middle cerebral, and posterior communicating. 
 
 1. The ANTERIOR cerebral arteries run for- 
 wards to the fore part of the great longitudinal 
 fissure, and curving round the anterior end of the 
 corpus callosum, pass backwards on its upper surface, 
 under the name of the arteries of the corpus callosum. 
 At their commencement they are joined by a short 
 transverse branch — the anterior communicating; 
 while behind they anastomose by small branches 
 with the posterior cerebral arteries. They supply 
 blood to the frontal and olfactory lobes, to the optic 
 nerves, to the corpus callosum, and to the anterior 
 perforated spots (Figs. 39, 40). 
 
 2. The MIDDLE CEREBRAL or SYLVIAN ARTERIES 
 
 are the largest branches of the internal carotid, and 
 
58 THE BRAIN 
 
 run upwards and outwards in the fissure of Sylvius 
 till they reach the surface of the island of Reil, 
 where they ramify in the pia mater, forming part of 
 the cortical system of arteries. They anastomose 
 with the anterior and posterior cerebral arteries, 
 and are distributed by four branches to part of 
 the frontal, parietal, and temporal lobes (Figs. 42, 
 43, page 60). Other branches of the Sylvian 
 artery are furnished through the anterior perforated 
 spot to the corpus striatum, and are all terminal 
 arteries, belonging to the " ganglionic system " of 
 branches. They are the lenticular, the lenticulo- 
 striate, the lenticulo-optic; and will be again re- 
 ferred to in describing the nuclei of the ventricles 
 of the hemispheres. The middle cerebral artery is 
 the one chiefly concerned in cerebral haemorrhage. 
 
 3. The ANTERIOE CHOROIDAL ARTERIES, one Or 
 
 two in number, are either branches of the internal 
 carotids or of the middle cerebrals. Entering the 
 fissure between the temporal lobe and the cms 
 cerebri (Fig. 40, page 58), they reach the descending 
 cornu of the lateral ventricle, and there form the 
 vascular fringe called the choroid plexus. 
 
 4. The POSTERIOR COMMUNICATING ARTERIES mn 
 backwards and join the posterior cerebral arteries 
 (branches of the basilar artery), and thus is established 
 a free anastomosis between the carotids and the 
 vertebral s. 
 
 IT. The Vertebral Arteries — branches of the sub- 
 clavian — enter the foramen magnum by perforating 
 the posterior occipito-atlantal ligament and the dura 
 
Fio. 39. 
 
 Plate XII. 
 
 Fori. 
 
 ,r cen hral. 
 
 Middle cerebral. 
 Carotid. 
 
 \-- Corpus callosum. 
 
 Postei ior cerebral. 
 
 Superior cerebellar. 
 Basilar. 
 
 Inferior cerebellar. 
 
 'Vertebral. 
 
 Fio.-40. 
 
 p?' communiccUiny. 
 
 Posteriorr 
 
 ■aiHiiumieating 
 
 ior cerebellar, 
 averse branch. - 
 
 Posterior 
 inferior cerebellar, 
 
 Anterior spinel, 
 
 A nterior cerebral. 
 
 Middle cerebral. 
 
 - Posterior cerebral. 
 
 - Basilar. 
 
 A nterior inferior . 
 cerebellar. 
 
 Vertebral. 
 
 Arteries of the Brain. 
 

 AND ITS MEMBRANES. 59 
 
 mater. They then curve round to the anterior 
 surface of the medulla between the 12th cranial nerve 
 and the anterior roots of the 1st cervical nerve. At 
 the lower border of the pons they unite to form a 
 single trunk — the basilar artery — which may be 
 seen running in the groove on the front of the pons, 
 till it reaches its upper margin, when it divides into 
 two branches — the posterior cerebral arteries 
 (Fig. 40, page 58). 
 
 1. BrAJsX'HES of the vertebral arteries. — 
 Only one branch, the posterior inferior cerebellar, 
 which may, however, sometimes be a branch of the 
 basilar, is given off by the vertebral artery to the 
 brain. It supplies the under surface of the cere- 
 bellum. 
 
 2. Branches of the basilar (Fig. 40): — 
 
 (1) Transverse branches, three or four in number, 
 run transversely outwards on the pons. One of 
 them, the internal auditory branch, enters the inter- 
 nal auditory meatus. 
 
 (2) The anterior inferior cerebellar arteries are 
 distributed to the anterior part of the lower surface 
 of the cerebellum, and anastomose with the other 
 cerebellar arteries. 
 
 (3) The superior cerebellar arteries, given off near 
 the termination of the basilar, supply the upper 
 surface of cerebellum, and send branches to the valve 
 of Yieussens, to the pineal gland, and to the velum 
 interpositum. 
 
60 THE BRAIN 
 
 (4) The posterior cerebral arteries — the terminal 
 branches of the basilar — curve outwards and back- 
 wards, round the crura cerebri, to the under surface 
 of the posterior cerebral lobes, supplying them and 
 anastomosing with the anterior and the middle cere- 
 bral arteries. They send branches to the posterior 
 perforated spot and to the velum interpositum 
 (posterior choroidal), and give three chief cortical 
 branches (Fig. 40). 
 
 Circle of Willis (Figs. 39, 40, page 58).— This 
 important arterial inosculation takes place at the 
 base of the brain between the internal carotids and 
 the vertebrals. In front the circle is formed by the 
 anterior communicating artery which joins together 
 the two anterior cerebral arteries ; behind by the 
 two posterior cerebral arteries, branches of the 
 basilar; and on each side by the internal carotids, 
 the anterior cerebrals, and the posterior communi- 
 cating. 
 
 CIRCLE OF WILLIS. 
 
 In Front : 
 Anterior Communicating. 
 
 On each Side : 
 Left. Right. 
 
 Anterior Cerebral. Anterior Cerebral. 
 
 Internal Carotid. Internal Carotid. 
 
 Posterior Communicating. Posterior Communicating. 
 
 Behind : 
 
 The Two Posterior Cerebrals, 
 
 branches of the 
 
 Basilar. 
 
Fid. 12, 
 
 Plate XIII. 
 
 Area of anterior cerebral. 
 
 Area, of 
 middle cerebral. 
 
 Area of poster tor cerebral. 
 
 Fig. 43. 
 
 „ A rea of anterior cerebral. 
 
 X A rea of 
 
 m id die cerebral. 
 
 A rea of posterior cerebral. 
 
 Diagram op Distribution of Arteries of Brain. 
 
AND ITS MEMBRANES. 61 
 
 II.— VEINS. 
 
 Cerebral Veins. — The veins of the brain do not 
 accompany the arteries, but open into the various 
 sinuses in the dura mater. In the cerebrum we 
 have two sets of veins — the one superficial, on the 
 surface of the brain, the other deep. Of the super- 
 ficial set those above open into the superior longi- 
 tudinal sinus ; those on the lateral and under aspect 
 of the brain open into the lateral, the cavernous and 
 the superior petrosal sinuses. The deep set of veins, 
 gathering the blood from the interior of the brain, 
 enters the veins of Galen, and thus pours its blood 
 into the straight sinus. 
 
 Cerebellar Yeins. — The veins on the upper 
 surface of the cerebellum enter the veins of Galen 
 and the straight sinus ; those on the under surface 
 end in the occipital, and in the lateral sinuses. 
 
 Special Characters of the Cerebral Circulation 
 
 are — 
 
 1. The free anastomosis at the circle of Willis, 
 which provides a ready supply of blood from other 
 vessels in case of the sudden blocking of any of the 
 more direct channels. 
 
 2. The tortuous course through bony canals of the 
 arteries as they enter the skull, thus mitigating the 
 force of the heart's beat. 
 
 3. Their ramifications in the pia mater before 
 entering the substance of the brain. 
 
62 THE BRAIN 
 
 4. The thinness of the arterial walls, and the 
 smallness of the capillaries. 
 
 5. Except at the circle of Willis, and at their 
 terminations by capillary vessels, there is little 
 communication between the branches of the cerebral 
 arteries, so that if any artery be obstructed, the 
 nutrition of the area to which it is supplied becomes 
 impaired. 
 
 6. The existence of venous sinuses which are 
 without valves, and which do not run with the 
 arteries — the larger arteries, in fact, having no 
 companion veins. 
 
 Plates XIII., page 60, and XIV., page 62, will 
 give you an idea of the distribution of the chief 
 arterial branches to the cerebral cortex. The 
 numbers 1, 2, 3, and 4 indicate the branches and 
 the parts to which they are distributed. 
 
Plate XIV. 
 
 nterior cerebral. 
 
 Vac, 
 
 fotor 
 
 Pig. 44. 
 
 II rii i ini . i /•///. Let/. 
 
 Hearing. 
 
 irea of posterior cerebral. 
 
 Area of middle 
 cerebral. 
 
 -- -Visual 
 
 \- - Vision. 
 
 Fig. 45. 
 A rm and shoulder. Trunk, 
 of anterior cerebral. 
 
 ea of middle cerebral 
 
 Smell and taste, 
 
 Touch. 
 
 Vision. 
 
 Area of posterior cerebral. 
 
 Diagram op Arteries and Chief 
 Centres in Brain. 
 
AND ITS MEMBRANES. 63 
 
 CHAPTER III 
 
 BRAIN AND ITS SUB-DIVISIONS. 
 
 (Figs. 33, 34, page 44.) 
 
 General Outline of the Brain. — Placing the 
 brain before you, you will see that it is an oval-shaped 
 mass of nervous substance, that has not inaptly been 
 likened to the kernel of a walnut ; for, says Wilks, 
 " one cannot but be forcibly struck with the resem- 
 blance between the human head and a walnut. 
 There is, first, the pericranium and the skin, then the 
 bone and the shell ; within a dura mater and a thick 
 membrane lining the shell of the fruit; then the pia 
 mater and the delicate membrane coverinsf the 
 kernel, which is again made up of convolutions into 
 two masses joined together by a commissure or 
 corpus callosum." 
 
 Viewed from above, the surface of the brain is seen 
 to be arched and convex, and presents many tortuous 
 folds or convolutions of nerve substance, with inter- 
 vening fissures or furrows, the whole giving to the 
 exterior of the organ a most characteristic appearance. 
 Along the middle line of this aspect of the brain 
 runs a deep longitudinal fissure, which, when the 
 brain is in situ, lodges the falx cerebri and divides 
 
64 THE BRAIN 
 
 the mass into two similar halves. These symmetrical 
 halves are called the cerebral hemispheres, and 
 they together form the first great division of the 
 Encephalon — the CEREBRUM — which is united to the 
 rest of the brain and to the spinal cord by two 
 masses of nerve substance known as the CRURA 
 CEREBRI. On separating the walls of this median 
 longitudinal fissure you will find that, in front and 
 behind, the cleft extends right through to the base 
 of the cerebrum ; but that, in the middle of its 
 extent, it is interrupted below by a transverse band 
 of nerve fibres, the CORPUS CALLOSUM, or great 
 commissure of the brain. 
 
 The under-surface or base of the brain, convo- 
 luted like the upper surface, is very irregular, for it 
 fits into the corresponding fossae at the l>ase of the 
 skull. On this aspect you will recognise the other 
 sub-divisions of the brain (Fig. 34, page 44), viz. : 
 
 (1) the cerebellum or little brain, lying behind and 
 below the posterior part of the cerebral hemispheres : 
 
 (2) the PONS varolii which, when viewed from 
 the front, appears as a broad white band, crossing 
 transversely between the two halves of the cere- 
 bellum ; (3) the MEDULLA OBLONGATA (Fig. 34), or 
 bulb, placed between the pons above and in front, 
 and the cerebellum behind, and serving to connect 
 these several parts of the brain with the spinal 
 marrow below. The sub-divisions of the brain, from 
 a developmental point of view, are given on page 194. 
 
 We shall describe (1) the MEDULLA; (2) the PONS; 
 
 (3) the cerebellum ; and (4) the cerebrum. 
 
AND ITS MEMBRANES. 65 
 
 I.— MEDULLA OBLONGATA. 
 
 (Figs. 46 to 49, Plate XV., page 66). 
 
 Dissection. — If you have only one brain to work upon it will be 
 best to pass on at once to the study of the cerebrum (page 113) and 
 afterwards return to the medulla. If you have more than one 
 brain, then cut through the crura cerebri, and begin the examina- 
 tion of the medulla. 
 
 The Medulla Oblongata — Myelencephalon — the 
 most complicated portion of the central nervous 
 system, is, as you already know, the expanded upper 
 end of the spinal cord, and, like it, is composed of 
 grey and white matter. It has anterior, posterior, 
 and lateral aspects. The anterior surface rests 
 upon the basilar process of the occipital bone ; 
 the posterior is hidden by the cerebellum. In 
 general outline it is more or less conical, with its 
 long axis nearly vertical, its base being directed 
 upwards and forwards towards the Pons Varolii, its 
 apex downwards and backwards, and continuous with 
 the spinal marrow at the lower border of the foramen 
 magnum. In length, the medulla measures about 
 one and-a-quarter inches; in breadth, at its widest 
 part, about one inch ; in thickness about half-an-inch. 
 On its ventral or anterior aspect it is convex, and is 
 limited above by the lower border of the pons ; below, 
 by what is known as the decussation of the pyramids 
 — several bands of fibres passing, at the bottom of 
 the anterior median fissure, from one side of the 
 medulla to the other. Behind, that is on its dorsal 
 aspect, the medulla, in its lower half, is convex, and 
 resembles the spinal cord, but, in its upper half, it 
 expands laterally and becomes flattened from before 
 
 F 
 
66 THE BRAIN 
 
 backwards, forming part of the rhomboida] depression 
 called the floor of the 4th ventricle. On this aspect, 
 the upper boundary of the medulla is marked by 
 several transverse lines — the strice acusticce — run- 
 ning across the widest part of the ventricular floor 
 (Fig. 47); the lower boundary is purely artificial, 
 corresponding with the lower margin of the foramen 
 magnum. The lateral aspect of the medulla sup- 
 ports an oval eminence, the olivary body, crossing 
 the lower part of which, as well as the surface of 
 the medulla just below it, you will be able to make 
 out several transverse streaks, the external arciform 
 fibres (Figs. 46, 49), the significance of which you 
 will understand hereafter. 
 
 1. FISSURES OF THE MEDULLA. 
 
 Like the spinal cord the medulla is a symmetrical 
 organ, being divided by superficial median clefts — 
 anterior and posterior — into two similar lateral seg- 
 ments, which are again sub-divided into anterior, 
 posterior, and lateral areas by the continuation up- 
 wards, though not in a direct line, of the place of 
 origin of the anterior and posterior spinal nerve 
 roots (Figs. 46 and 48, page 66). 
 
 1. The anterior median fissure of the medulla, 
 a direct continuation upwards of the anterior median 
 fissure of the spinal cord, ends above, at the lower 
 margin of the pons, in a slight recess, needlessly 
 named the foramen caecum. At the lower limit of 
 the medulla, this same fissure is interrupted by the 
 bands of fibres known as the decussation of the 
 pyramids (Fig. 46, page 66). 
 
Plate XV. 
 
 Fig. 46. 
 
 j)(ic nerve, 
 ic tract. 
 
 Optic commissure. 
 
 Crus cerebri. 
 
 Fig. 47. 
 
 Nates. 
 Testes. 
 
 fiddle cerebellar 
 . peduncle. 
 
 4th ventricle. 
 External , . . 
 
 eiform fibres. W"™ f™ 
 
 rrai area 
 
 Decussation 
 of pyramids. 
 
 Fasciculus teres 
 
 Locus c&ruleus. 
 
 Superior 
 cerebellar 
 peduncle. 
 
 Superior- 
 fovea 
 
 Stria; 
 usticve. 
 
 —Tuberculum 
 acusticam. 
 
 Inferior cerebellar 
 peduncle. 
 
 A la einerea. 
 
 Anterior median f. 
 
 Fig. 48. 
 
 Superior medullary vdmn 
 
 Fig. 49. 
 
 \la... 
 
 t tubercle 
 Claw 
 Calamus 
 
 criptorius 
 %nd obex. 
 
 mmedianf. 
 erttl. dorsal s 
 
 Superior cerebellar 
 ■ peduncle. 
 
 Pons. 
 
 "R >st if or >n body. 
 
 Olivary body 
 -7'i hervk of Rolando. 
 Fv/rwculus of Rolando. 
 
 -Funiculus cuneatus. 
 Funiculus gracilis. 
 
 Rostenor median f. 
 
 Crus cerebri. 
 
 Corpora geniculata 
 . _ externa. 
 
 ..-- interna. 
 
 Rulvinar. 
 \- Corpora 
 quadriyemina. 
 
 Middle pedunch 
 " of -cerebellum. 
 
 Olivary body. 
 
 External 
 arciform fibres. 
 
AND ITS MEMBRANES. 67 
 
 2. The POSTERIOR MEDTAN FISSURE, continuous 
 with the posterior median fissure of the spinal cord, 
 expands above into the shallow rhomboidal space 
 called the floor of the 4th ventricle, alons - the centre 
 of which runs a mesial groove, iu a line with the 
 median fissure of the cord. External to the pos- 
 terior median fissure of the medulla are two minor 
 sulci — the paramedian and lateral dorsal sulci (Figs. 
 47, 48). 
 
 3. The lateral fissures, continuous with the 
 lateral fissures of the cord, give origin to the roots of 
 the 9th, 10th, 11th and 12th pairs of cranial nerves — 
 the 9th, 10th and 11th pairs springing from the 
 continuation of the postero-lateral groove, and the 
 12th pair from the continuation of the antero- 
 lateral groove. 
 
 2. WHITE MATTER OF THE MEDULLA. 
 (Areas of the Medulla.) 
 
 By means of the above fissures the surface of 
 each half of the medulla is marked out into three 
 areas, viz.: an anterior area or pyramid, between 
 the anterior median fissure and the line of origin of 
 the 12th nerve ; a lateral area or pyramid, between 
 the 12th nerve in front and the 9th, 10th, and 11th 
 nerves behind ; and a posterior area or pyramid, 
 between the posterior median fissure and the 9th, 
 10th, and 11th pairs of nerve roots. It will be 
 convenient to begin with the description of the 
 posterior area (Figs. 46 to 49, page 66). 
 
 1. Posterior Area. — This area, lying between the 
 posterior median fissure and the line of origin of the 
 
68 THE BRAIN 
 
 9th, 10th, and 11th pairs of nerve roots, may be 
 divided into an upper or anterior part, and a lower 
 or posterior part. The upper portion of this area 
 enters into the formation of the floor of the 4th 
 ventricle, a cavity which should naturally be 
 described at this stage, but, owing to the fact that 
 many of its parts are connected with the pons and 
 cerebellum, its description must be deferred until 
 we have treated of that division of the brain. 
 
 The lower portion of the posterior area, very 
 similar in appearance to the spinal cord, is, for the 
 most part, formed by the upward prolongation of the 
 various white tracts of the posterior column of the 
 cord, the several strands there defined changing, 
 when they reach the medulla, their position, their 
 arrangement, and their names. These changes we 
 shall now describe. 
 
 In dealing with the white substance of the 
 posterior column of the cord, you will doubtless 
 remember that we called your attention to the 
 existence, in the cervical region, of a strand of 
 fibres close to the posterior median fissure, called 
 the postero-intemal strand — fasciculus of Ooll. 
 Now, traced into the medulla, this strand, which lies 
 between the posterior median and the paramedian 
 fissures, becomes more prominent, and at the point 
 where the central canal of the cord becomes the 
 cavity of the 4th ventricle, the fasciculus enlarges, 
 and is removed a little to one side. It is called 
 the FASCICULUS or FUNICULUS GRACILIS — slender, 
 and its enlarged upper end is known as the 
 clava — a club (Fig. 48, page 66). When followed 
 
AND ITS MEMBRANES. 69 
 
 upwards it tapers to a point and becomes gradually 
 lost, though we shall afterwards be able to trace its 
 fibres along with those of the next fasciculus, first 
 to collections of grey matter — nucleus gracilis and 
 nucleus cuneatus — in the medulla, and thence to 
 the cerebrum and cerebellum (see " Sensory Decus- 
 sation," page 83). 
 
 The outer division of the posterior column of the 
 spinal cord, the postero-external strand — fasciculus 
 of Burclach or cuneate fasciculus — passes into the 
 medulla under this latter name. It lies between 
 the paramedian and lateral dorsal sulci, and expand- 
 ing above into a tubercle — the CUNEATE TUBERCLE 
 (Figs. 48, 50) — reaches upwards beyond the clavn, 
 and forms one of the lateral boundaries of the lower 
 part of the 4th ventricle (Fig. 48, page 66). 
 
 Besides the tracts just described there are on this 
 aspect of the medulla two other strands, known 
 respectively as the funiculus of Rolando and the 
 RESTIFORM BODY. They are not represented on the 
 surface of the posterior column of the spinal cord; 
 for the former is chiefly grey matter, and the latter 
 belongs mainly to the lateral column. 
 
 (a) The funiculus of Rolando. — The first of 
 these tracts, the funiculus of Rolando, is of a 
 greyish colour, for there is little or no white matter 
 on its surface. It lies outside the funiculus cuneatus, 
 between it and the line of origin of the roots of the 
 9th, 10th, and 11th pairs of cranial nerves. Like the 
 two tracts previously mentioned, it expands above into 
 a tubercle — the tubercle of Rolando (Figs. 48, 50). 
 
70 THE BRAIN 
 
 The funiculus of Rolando is often very poorly de- 
 veloped in the adult brain, but in the medulla of 
 children it is always well marked. 
 
 (6) The RESTIFORM BODY. — The remaining prom- 
 inence, the largest and most conspicuous on this 
 surface of the medulla, is called the INFERIOR CERE- 
 BELLAR PEDUNCLE Or RESTIFORM BODY — Testis, a 
 rope (Figs. 47, 48). Placed behind, and to the 
 outer side of the lateral column of the cord, it lies 
 above the level of the clava, the cuneate tubercle 
 and the tubercle of Rolando, and, when looked at 
 from the surface, seems to be incorporated with these 
 fasciculi, though not so in reality; for, as we shall 
 presently see, it is composed of fibres derived, for 
 the most part, from the lateral columns of the spinal 
 cord (Fig. 50, page 70). 
 
 On this area of the medulla, then, we note four 
 strands : (a) the funiculus gracilis and its clava ; 
 (6) the funiculus cuneatus and its tubercle; (c) the 
 funiculus of Rolando ; and (d) the restiform body. 
 
 2. The Lateral Area of the medulla, continuous 
 with the lateral column of the cord, lies between the 
 roots of the hypoglossal nerve in front and those of 
 the 9th, 10th, and 11th nerves behind. It is wider 
 below than above, where it is partially hidden from 
 view by the oval eminence — the olivary body. To 
 determine the origin of its various strands we must 
 refer back to the constitution of the corresponding 
 column of the spinal cord. You will recollect that, 
 in that column, we traced five tracts — the crossed 
 pyramidal, the (ascending and descending) antero- 
 
Fiu. 50. 
 
 To cerebellum. 
 
 Restiform body. 
 
 -Mf Olivary body. 
 
 Plate XVI. 
 
 To motor areas. 
 
 / / < 
 
 Tubercle .— /---/-- -y""\ 
 
 liculus of Rolando. \- - 
 
 fasciculus of Goll. - 
 
 mculus of Burdock. ... 
 
 Mixed zone 
 of lateral column 
 
 kral cerebellar tract. \- - - 
 
 prior median fissure 
 
 Posterior columns. 
 
 External 
 rciform fibres. 
 
 - Mixed zone. 
 
 Crossed 
 ill pyramidal tract. 
 
 Direct 
 pyramidal tract. 
 
 Anterior 
 median fissure. 
 
 Lateral 
 column. 
 
 A nterior 
 columns. 
 
AND ITS MEMBRANES. 71 
 
 lateral tracts, the direct lateral cerebellar tract, and 
 the mixed zone. 
 
 The crossed pyramidal tract can be followed to 
 the anterior pyramid of the opposite side of the 
 medulla, The direct lettered cerebellar tract, on 
 passing up into the medulla, will be seen as a 
 superficial band of fibres (Figs. 49, 50), running 
 upwards and backwards across the line of origin 
 of the 9th, 10th, and 11th pairs of nerve 
 roots, over the funiculus of Rolando, above its 
 tubercle and across the cuneate funiculus. Then, 
 turning sharply upwards, it is joined by a set of 
 fibres — the external arciform fibres (Fig. 50, 
 page 70), which, together with it, form the main 
 mass of the restiform body or inferior peduncle 
 of the cerebellum (Figs. 48, 50). (For a full 
 account of the constitution of the restiform body or 
 inferior cerebellar peduncle, see page 99.) 
 
 The mixed zone of the lateral column, when traced 
 upwards to the bulb, is seen to dip under the olivary 
 body, so that only a small part of it is visible on 
 the surface of the medulla as a narrow white strand, 
 between the olivary body and the roots of the 9th. 
 10th, and 11th pairs of nerves. Most of the fibres 
 of this strand go to form part of a network of 
 fibres that will become familiar to us under the 
 name formatio reticularis. Some of them are, 
 however, commissural between different segments 
 of the cord. 
 
 Of the antero-lateral ascending and descending 
 tracts, the former is probably a crossed sensory tract 
 from the posterior roots, and passes most likely to 
 
72 THE BRAIN 
 
 the cerebellum ; the latter, the descending tract, 
 starts in the cerebellum, being part of the indirect 
 or secondary motor tract. 
 
 Thus, then, the fibres of the lateral column of the 
 spinal cord, on reaching the medulla, are disposed 
 of in three ways (see Fig. 50): (1) Some — crossed 
 pyramidal tract — go to the opposite anterior pyramid ; 
 (2) others — direct lateral cerebellar tract — to the 
 restiform body, and thence to the cerebellum of the 
 same side ; (3) others — antero-lateral tracts — to or 
 from the cerebellum ; (4) others — the mixed zone — 
 pass partly behind, and partly beneath the olive to 
 the formatio reticularis. The constitution and ulti- 
 mate destination of these strands of fibres will be 
 seen hereafter. They are figured on Plates XL., 
 XLL, XLIL, pages 182, 184, and 186. 
 
 Olivary Body. — The olivary body is an oval 
 prominence, about half-an-inch long, placed at the 
 upper end of the lateral area of the medulla. It is 
 bounded in front by the roots of the 12th nerve, 
 but is separated behind from those of the 9th, 10th 
 and 11th nerves by a narrow white tract, which, as 
 we have already seen, is part of the mixed zone of 
 the lateral column of the cord. Above, the olive 
 almost touches the lower border of the pons; below, 
 it is crossed transversely by delicate fibres— the 
 external arciform fibres — already referred to. If you 
 cut into it you will see that it contains a grey core 
 called the inferior olivary nucleus (see page 81). 
 
 3. The Anterior Area, also called the anterior 
 pyramid of the medulla (Fig. 46, page 66), lies 
 
AND ITS MEMBRANES. 73 
 
 between the anterior median fissure and the roots 
 of the hypoglossal nerve, which serve to separate it 
 from the olivary body. It is a pear-shaped prominence, 
 which is broader above than below, though it be- 
 comes slightly constricted before disappearing beneath 
 the transverse fibres of the pons. The pyramids of 
 the two sides will afterwards be traced through the 
 pons to the cerebral peduncles, and thence to the 
 cerebral cortex. To their constitution you will re- 
 quire to give your closest attention, for it is some- 
 what complicated and of the greatest importance 
 (Fig. 50, page 70). Note that although we are 
 tracing these pyramidal tracts upwards, they are in 
 reality descending or motor strands. 
 
 The anterior column of the spinal cord, you will 
 remember, had a median division, direct pyramidal 
 tract, and a lateral division, basis bundle or anterior 
 root zone. Now, the pyramids of the medulla are, 
 to a small extent only, made up of fibres derived from 
 this inner division — direct pyramidal tract — of their 
 own side of the cord; by far their greater part is 
 composed of fibres — crossed pyramidal tract — which 
 come from the opposite lateral column of the spinal 
 cord. This crossed tract, after leaving the opposite 
 lateral column, passes upwards and inwards through 
 the anterior commissure, across the bottom of the 
 anterior median fissure, where it decussates in a 
 series of bundles, with a similar set of fibres from the 
 other side, constituting together the decussation of 
 the 'pyramids. Turning upwards this crossed tract 
 then forms the inner and by far the larger part of 
 the opposite anterior pyramid (Fig. 50); the outer 
 
74 THE BRAIN 
 
 and smaller part of the same pyramid being formed 
 by the continuation upwards of the direct pyramidal 
 tract of the same side. Thus, for example, the LEFT 
 anterior pyramid of the medulla is chiefly made 
 up of the crossed pyramidal tract of the right 
 lateral COLUMN, and, to a much smaller extent 
 only, by the direct pyramidal tract of its own side. 
 We must note, however, that although the fibres of 
 the direct pyramidal tract do not decussate in 
 the medulla, they do decussate as they pass down 
 the spinal cord, and ultimately, through the nerve 
 cells of the anterior born, become connected, like the 
 crossed tracts, with the anterior nerve roots of the 
 opposite side to that at which they left the brain. 
 The pyramidal tracts are the chief motor tracts, and 
 their decussation explains the phenomena of certain 
 forms of paralysis, in which when one side of the 
 brain, say the left, is injured, loss of motion ensues, 
 not on that side but on the opposite side of the body. 
 " In cases, then, in which we find total or partial 
 paralysis of the muscles on one side, with increased 
 excitability to mechanical stimuli and a tendency to 
 contracture, we can justly conclude that the opposite 
 pyramidal tracts are affected " (Edinger). 
 
 The outer division of the anterior column of the 
 spinal cord — antero-extemal tract — will afterwards 
 be traced through the upper part of the medulla 
 (see "White Matter," floor of 4th ventricle, page 113) 
 to the following destinations — (1) to the formatio 
 reticularis, (2) to the posterior longitudinal bundle, 
 and (3) to the tract of the fillet. 
 
AND ITS MEMBRANES. 
 
 75 
 
 External arcifoem fibres (Fig. 49, page 66). — 
 These are a set of fibres which, as at present seen, 
 emerge from the anterior median fissure of the 
 medulla, cross over the surface of the anterior 
 pyramids, over the lower part of and below the 
 olives, and finally turn upwards, along with the 
 lateral cerebellar tract, to form, with it, part of the 
 restiform body. They will be again referred to in 
 treating of the grey matter of the medulla. 
 
 Table of Objects seen on Surface of Medulla. 
 
 Fissures. -> 
 
 Areas. 
 
 t Anterior median, with decussation of the pyramids. 
 | Posterior median. 
 
 I Two lateral, with nerve roots — the 12th from antero- 
 *■ lateral ; 9th, 10th, 11th from postero-lateral groove. 
 
 f Anterior pyramids. 
 
 \ Decussation of pyramids. 
 
 ( 1. Anterior area, 
 
 2. Lateral area. 
 
 ( Olive. 
 
 ( Lower 
 part. 
 
 Posterior 
 area. 
 
 >per f 
 art. \ 
 
 Upper 
 par 
 
 \ External arciform fibres. 
 (_ Tract of white matter. 
 Restiform body. 
 Funiculus of Eolando and 
 
 its tubercle. 
 Funiculus cuneatus and 
 
 its tubercle. 
 Funiculus gracilis and its 
 
 clava. 
 Lower half of the floor of 
 
 4th ventricle. 
 
 Summary. — Thus, then, we see that the surface 
 of the medulla oblongata presents four fissures — an 
 anterior, two lateral, and a posterior: three areas — 
 an anterior, with its pyramids and their decussation ; 
 a lateral, with its olive ; a posterior, with its funiculus 
 
7 6 
 
 THE BRAIN 
 
 gracilis, funiculus cuneatus, and funiculus of Rolando, 
 and their respective enlargements; and, finally, the 
 restiform body, or inferior cerebellar peduncle. 
 
 Table of Relations between White Tracts of Cord 
 and their representatives in the medulla. 
 
 Anterior 
 column. 
 
 Lateral 
 column. 
 
 Posterior 
 column. 
 
 Cord. 
 
 1. Direct pyramidal 
 tract 
 
 2. Mixed zone 
 
 1. Crossed pyramidal 
 
 tract 
 
 2. Direct lateral cere- 
 
 bellar tract 
 
 3. Mixed zone 
 
 4. A ntero- lateral 
 
 ascending tract 
 
 5. Antero-lateral de- 
 
 scending tract 
 [ 1. Postero-internal 
 strand (Goll) 
 
 2. Posteroexternal 
 
 strand (Burdach) 
 
 3. Lissauer's tract 
 
 Medulla. 
 
 to outer part of the an- 
 terior pyramid of the 
 medulla of the same 
 side. 
 
 to posterior longitudinal 
 bundle. 
 
 to olivary peduncle and 
 fillet. 
 
 to formatio reticularis. 
 
 to the inner part of the 
 pyramid of opposite 
 side; a few fibres go 
 to the pyramid of the 
 same side. 
 
 to restiform body and 
 thence to the cere- 
 bellum of same side. 
 
 to olivary fillet. 
 
 to formatio reticularis. 
 
 to the cerebellum — prob- 
 ably crossed sensory 
 tract. 
 
 from the cerebellum of 
 same side. 
 
 to funiculus gracilis, and 
 to its nucleus. 
 
 to funiculus cuneatus, 
 and to its nucleus. 
 
 to formatio reticularis. 
 
 to the grey matter of the 
 posterior horn. 
 
AND ITS MEMBRANES. 77 
 
 3. GREY MATTER OF THE MEDULLA. 
 
 From the white strands of the medulla, which 
 have so far occupied our attention, we next turn to 
 the consideration of the arrangement of its grey 
 substance. This is far more irregular than that of 
 the spinal cord, and for its satisfactory study you 
 will require a special series of preparations, though 
 tlie accompanying figures will no doubt give you 
 material assistance (Fig. 51, &c, Plate XVII., 
 page 78). 
 
 The grey matter of the medulla oblongata may 
 be described under two heads — (1) that represented 
 in the spinal cord, and derived from one or other of 
 its grey crescents ; (2) that not so represented, but 
 forming isolated collections or nuclei not obviously 
 connected with the grey matter of the spinal cord. 
 
 1. Grey Matter derived from the Grey Cres- 
 cents. — Transverse sections of the lower part of the 
 medulla will show you that the grey matter of the 
 medulla has an arrangement very similar to that of 
 the grey matter of the spinal cord; but that higher 
 up in the medulla the appearance of the grey 
 crescents becomes much changed. (Compare Figs., 
 Plate XVII, page 78, with Figs., Plate III., page 14.) 
 
 (a) The anterior cornu of the spinal cord, as 
 we trace it upwards, loses its characteristic shape, 
 for, owing to the fact that the fibres of the crossed 
 pyramidal tract cut their way through the neck of 
 the anterior horn, the head becomes separated from 
 the base, and the neck is replaced by a reticulum of 
 fibres, part of the formatio reticularis. The head 
 of the anterior horn, thus detached, enlarges, and, 
 
78 
 
 THE BRAIN 
 
 PLATE XVII. 
 
 Fia:. 53. 
 
 Fig. 56. 
 
 a. in. f. 
 
 Anterior median fissure. 
 
 a, m.f. 
 
 Anterior median fissure. 
 
 a. re. 
 
 Arciform nucleus. 
 
 a. n. 
 
 Arciform nucleus. 
 
 as. gloss. 
 
 Ascending root of the glosso- 
 
 a. 0. 
 
 Accessory olive. 
 
 
 pharyngeal nerve. 
 
 c. r. 
 
 Corpus restiforme. 
 
 e. a. f. 
 
 External arciform fibres. 
 
 e. a. f. 
 
 External arciform fibres. 
 
 h. n. 
 
 Hypoglossal nerve. 
 
 ij. n. 
 
 Glossopharyngeal nerve. 
 
 n. c. 
 
 Nucleus cuneatus. 
 
 l.orf. 
 
 Lemniscus or Fillet. 
 
 n. g. 
 
 Nucleus gracilis. 
 
 n. a. 
 
 Arciform nucleus. 
 
 n. 1. 
 
 Nucleus lateralis. 
 
 n. am. 
 
 Nucleus ambiguus. 
 
 n. v. b. 
 
 Nucleus of olivary body. 
 
 n.f. t. 
 
 Nucleus of fasciculus teres. 
 
 p. m. f. 
 
 Posterior median fissure. 
 
 n. o. b. 
 
 Nucleus of olivary body. 
 
 p.t. 
 
 Pyramidal tract. 
 
 p. 1. b. 
 
 Posterior longitudinal bundle. 
 
 s. g. R. 
 
 Gelatinous substance of Rolando. 
 
 p. t. 
 
 Pyramidal tract. 
 
 5th as. 
 
 Ascending root of 5th nerve. 
 
 v. 
 
 Vagus. 
 
 
 
 5th as. 
 
 Ascending root of the 5th nerve. 
 
 
 Fig. 52. 
 
 
 Fig. 55. 
 
 a. m. f. 
 
 Anterior median fissure. 
 
 a. m. f. 
 
 Anterior median fissure. 
 
 f.c. 
 
 Fasciculus cuneatus. 
 
 a. n. 
 
 Arciform nucleus. 
 
 f.'J. 
 
 Fasciculus gracilis. 
 
 a. o. 
 
 Accessory olive. 
 
 h. n. 
 
 Hypoglossal nerve. 
 
 e. a. f. 
 
 External arciform fibres. 
 
 ft. c. 
 
 Nucleus cuneatus. 
 
 /• r. 
 
 Formatio reticularis. 
 
 n. g. 
 
 Nucleus gracilis. 
 
 /. 8. 
 
 Fasciculus solitarius. 
 
 v. m. f. 
 
 Posterior median fissure. 
 
 h. n. 
 
 Hypoglossal nerve. 
 
 p. t. 
 
 Pyramidal tract. 
 
 n. am. 
 
 Nucleus ambignus. 
 
 s. g. R. 
 
 Substantia gelatinosa Rolando. 
 
 ft. c. 
 
 Nucleus cuneatus. 
 
 s. p. d. 
 
 Superior pyramidal decussation. 
 
 n. f. t. 
 
 Nucleus of fasciculus teres. 
 
 5th as. 
 
 Ascending root of the 5th nerve. 
 
 it. a. 
 
 Nucleus gracilis. 
 
 s. d. 
 
 Sensory decussation. 
 
 ft. h. 
 
 Nucleus of the hypoglossal nerve 
 
 
 
 ft. o. b. 
 
 Nucleus of olivary body. 
 
 
 
 p. t. 
 
 Pyramidal tract. 
 
 
 
 r. 
 
 Raphe. 
 
 
 
 v. 
 
 Vagus nerve. 
 
 
 
 v. re. 
 
 Vagus nucleus. 
 
 
 
 4th vent. 
 
 4th ventricle. 
 
 
 
 5th as. 
 
 Ascending root of the 5th nerve. 
 
 Fig. 51 
 
 Fig. 54. 
 
 a. c. 
 
 
 Anterior cornu. 
 
 a. m. f. 
 
 a-, m. 
 
 f. 
 
 Anterior median fissure. 
 
 a. n. 
 
 d. p. 
 
 
 Decussation of the pyramids. 
 
 a. o. 
 
 d. p. 
 
 t. 
 
 Direct pyramidal tract. 
 
 •:■ '••• / 
 
 f.B. 
 
 
 Fasciculus of Burdach. 
 
 f.c. 
 
 f.G. 
 
 
 Fasciculus of Goll. 
 
 f.Q. 
 
 m. z. 
 
 
 Mixed zone. 
 
 f. r. 
 
 p. c. 
 
 
 Posterior cornu. 
 
 i. a./. 
 
 p. m 
 
 /■ 
 
 Posterior median fissure. 
 
 n. c. 
 n. q. 
 n. 1. 
 ft. o. b. 
 p. m. /. 
 P . t. 
 s. (j. R. 
 t. R 
 5th as. 
 
 Anterior median fissure. 
 
 Arciform nucleus. 
 
 Accessory olive. 
 
 External arciform fibres. 
 
 Fasciculus cuneatus. 
 
 Fasciculus gracilis. 
 
 Formatio reticularis. 
 
 Internal arciform fibres. 
 
 Nucleus cuneatus. 
 
 Nucleus gracilis. 
 
 Nucleus lateralis. 
 
 Nucleus of olivary body. 
 
 Posterior median fissure. 
 
 Pyramidal tract. 
 
 Gelatinous substance of Rolando. 
 
 Tubercle of Rolando. 
 
 Ascending root of the 5th nerve. 
 
a.m./. 
 
 Plate XVII. 
 
 Fig. 53. 
 
 Pio. 56. 
 
 '■<(.?'. 
 
 
 *.g.R. 
 
 5th as. M^/^WL^.'^^ 
 
 p.vKf. ' as. gloss, 
 
 -n.y. 
 
 R^gp^ 
 
 / // ^v<-v ■■'■-■■Mm 
 
 r 
 
 iz.9"- 
 
 ) 
 f c.r. 
 
 & a. it. j / 
 n./.t. p.l.b. 5th{ 
 
 n.ai 
 
 p.m./, 
 
 v.n. 
 
 f.G. p.m./ 
 
 p-m./. 
 
AND ITS MEMBRANES. 79 
 
 by the interposition of the anterior pyramids between 
 it and the anterior median fissure, is pushed from 
 the antero-lateral aspect of the cord to the lateral 
 aspect of the medulla, where, in sections of the lower 
 part of the medulla, it may be seen as a distinct 
 grey collection, the nucleus lateralis (n. L, Fig. 
 54, page 78). 
 
 Again, when the central canal of the cord opens 
 out into the floor of the 4th ventricle, the grey 
 matter which surrounds that canal is brought to the 
 surface, and hence the base of the anterior horn 
 appears on the ventricular floor as a narrow grey tract 
 close to the median furrow (Fig. 57, page 82). It is 
 known as the nucleus of the hypoglossal nerve ; 
 and in sections of the medulla at this level the nerve 
 may be seen as a band of fibres running from the 
 nucleus towards the anterior surface of the medulla 
 (n. h., Fig. 55, page 78). Close to this nucleus is 
 another small collection of nerve cells — the nucleus 
 of the fasciculus teres (n.f. t., Fig. 55, page 78). 
 
 The greater part of the anterior horn — the neck — 
 is replaced, as above said, by a reticulum of cells and 
 fibres, part of these latter being the fibres of the 
 crossed tract on their way to the opposite side of 
 the medulla. This network constitutes the anterior 
 part of the formatio reticularis or grey reticulum 
 (Figs. 54, 55, /. v.). 
 
 (b) The grey matter of the posterior horn, on 
 reaching the medulla, also takes up a lateral position 
 and increases in amount. The head of the horn, 
 much enlarged, comes nearer to the surface, and 
 appears at about the middle of the medulla as a 
 
5c THE BRAIX 
 
 well-marked grey nucleus, the tubercle of Rolando 
 (t. JR.. Fig. 54). beneath the surface prominence of 
 the same name. To its outer side will be seen a 
 band of white fibres, the ASCENDING ROOT of the 
 
 FIFTH CRANIAL NERVE {5th OS., Fig. 54). 
 
 The grey matter of the base of this horn is also 
 much increased in amount, and, between the median 
 line and the grey nucleus of Rolando, grows out as 
 two superficial aggregations — the inner one into 
 the fasciculus gracilis to form the NUCLEUS of bbe 
 FASCICULUS gracilis, the outer into the fasciculus 
 cuneatus to form the nucleus cuneatus [Fig. 54). 
 Each nucleus thus lies beneath the corresponding 
 white tract on the surface, and causes the elevations 
 called the clava and the cuneate tubercle. To these 
 nuclei, as we have seen, can be traced most of the 
 fibres of the posterior column of the spinal cord. 
 The nuclei themselves may be followed as far as the 
 pons. From them start a set of fibres (internal 
 arciform fibres) which cross the middle line and go 
 t . form the sensory decussation (see page 83). 
 
 The neck of the posterior cornu, like that of the 
 anterior, is replaced by a network of fibres, the 
 white reticulum, which becomes continuous with 
 - e srey reticulum, constituting together the FOR- 
 MATio reticularis (Figs. 54 and 55), a network of 
 longitudinal, oblique, and transverse fibres (arciform 
 fibres), with nerve cells and neuroglia cells embedded 
 amongst them. The fibres of this reticulum are 
 chieflv commissural in nature, though there are 
 rea- - for thinking that sensory impulses, and im- 
 pulses wmich inhibit spinal reflexes, travel through 
 
AND ITS MEMBRANES. 81 
 
 it to the cerebrum (see "Sensory Decussation/' 
 8. d., Fig. 52, page 78). Some of its longitudinal 
 fibres are derived from the mixed zone — anterior 
 root zone — of the anterior column of the spinal cord. 
 
 2. Isolated Grey Masses or Nuclei of the 
 Medulla. — The chief of these nuclei are — 
 
 (1) The corpus dentatum or olivary nucleus. 
 
 (2) The accessory olives. 
 
 (3) The arciform nucleus. 
 
 (a) The corpus dentatum or olivary nucleus 
 (Fig. 55) is contained in the centre of the olivary 
 body, which must be cut into in order to see it. It 
 is covered superficially by the external arciform 
 fibres (Fig. 55). This ganglion consists of "flask - 
 shaped, multipolar nerve cells, and neuroglia cells 
 arranged as a zig-zag lamina or crumpled sheet of 
 grey matter, concave and open on its inner aspect. 
 Through this opening, called the hilum, enters the 
 olivary peduncle, a bundle of nerve fibres, which 
 passes into the centre of the olivary nucleus, to be 
 there distributed in different directions. 
 
 The corpus dentatum or olivary ganglion is 
 closely connected with a grey mass in the cerebellum 
 — the corpus dentatum of the cerebellum — for any 
 injury to this latter nucleus causes atrophy of the 
 opposite olivary ganglion (Fig. 99, Plate XXXVII., 
 page 168). 
 
 (b) Two other isolated nuclei — the ACCESSORY 
 olives (Fig. 55) — will be found, the one on the inner 
 
 G 
 
82 
 
 THE BRAIN 
 
 side of, the other behind, the corpus dentatum. 
 They are linear in shape, and are closely connected 
 with the olivary nucleus. 
 
 (c) The third nucleus — arciform nucleus ; 
 nucleus of the external arciform fibres (Fig. 54) — 
 is placed amongst these fibres as they cross over the 
 anterior pyramids of the medulla. The nucleus 
 itself is continuous above with the nucleus pontis 
 (See " Pons "). 
 
 The remainder of the grey matter — the nuclei of 
 the several cranial nerves — will be studied in re- 
 lation to the floor of the fourth ventricle (page 111). 
 
 Table of Grey Matter of the Medulla. 
 Cord. 
 
 Grey 
 Matter 
 of the 
 Spinal 
 
 Cord. 
 
 Anterior 
 Cornu. 
 
 Posterior 
 Cornu. 
 
 Medulla, 
 Head — Nucleus lateralis. 
 Neck— Anterior part of the formatio 
 reticularis. 
 , Base — Nucleus of the hypoglossal nerve. 
 ^ Head— Nucleus of Rolando. 
 Neck — Posterior part of the formatio 
 reticularis. 
 
 < 
 
 Base- 
 
 J 
 
 Nucleus gracilis. 
 , Nucleus cuneatus. 
 I Nuclei on floor of 4th ventricle. 
 
 T Nucleus of the olivary body. 
 
 (^ Nucleus of the external arciform fibres. 
 
 Isolated grey nuclei _, Accessory olivary nuclei 
 in the Medulla. 
 
 Raphe. — A transverse section of the medulla will 
 show you that above the level of the pyramidal decussa- 
 tionHheJmedulla is partially divided into two lateral 
 segments by a central median raphe* or partition, which 
 forms a thin membranous septum of nerve substance, 
 extending' from the anterior median fissure to beneath 
 
Fig. 57. 
 
 pora Qnadrigeinina ~ 
 3rd. 
 
 Plate XVIII. 
 
 Descending root of 5th nerve. 
 Locus cxruleus. 
 ■'.fth nerve. 
 
 - St/i nerve 
 
 Nucleus of 
 6th nerve. 
 
 Facial nerve. 
 Auditory nerve. 
 
 - - - hiferiov fovea. 
 --Vagus nerve 
 
 Ascending root 
 of 5th nerve. 
 
 Ascending root of 
 glnxsop- pharyngeal 
 
 Nuclei in 4th Ventricle 
 
 fcending root of 5th. 
 nerve. 
 
 12th. 10th. -9th 
 
 Fig. 58. 
 
 Uth. 
 Olivary body 
 
 A ud.itory. $ tfl - 
 Nuclei of the cranial nerves. 
 
AND ITS MEMBRANES. 83 
 
 the central groove on the floor of the 4th ventricle. 
 It consists of numerous fibres running in various 
 directions, and interspersed with small collections of 
 multipolar nerve cells. 
 
 Sensory Decussation. — The superior pyramidal 
 
 decussation, which has so often been referred to, 
 must not be confused with the inferior or motor 
 decussation (page 73). You will remember that 
 fibres can be traced from the posterior spinal nerve 
 roots through the posterior columns of the spinal cord 
 to their primary stations, the nucleus gracilis and 
 cuneatus of the medulla. From the cells of these 
 nuclei, fibres travel towards the anterior aspect of 
 the medulla until they come to lie in front of the 
 central canal, and there decussating in the raphe, 
 above and behind the pyramidal decussation, cross to 
 the opposite side of the bulb. Becoming longitudinal, 
 they form a considerable bundle of fibres just behind 
 the pyramids (motor fibres), and ascend to the 
 cerebrum in what is known as the tract of the fillet, 
 or lemniscus. They are crossed sensory tracts to the 
 brain (Fig. 96, Plate XXXVIL, page 168, fillet). 
 
 Thus we see that we have in the medulla two sets 
 of decussating fibres : — (1) The inferior pyramidal or 
 motor decussation ; and (2), behind and above this, 
 the superior pyramidal or sensory decussation. 
 
 The Arciform Fibres have already been several 
 times alluded to, so that w T e shall now merely collect 
 together, for the sake of clearness, the several state- 
 ments previously made. These fibres are divided 
 
84 THE BRAIN 
 
 into a superficial or external set, and a deep or 
 internal set. 
 
 1. The SUPERFICIAL ARCIFORM FIBRES form two 
 
 groups : — 
 
 (a) The anterior external arciform fibres, which 
 spring, you will remember, from the anterior median 
 fissure, through which they can be traced to the 
 central raphe, where they probably cross over to the 
 posterior column of the opposite side of the medulla, 
 to the nucleus gracilis and cuneatus. Emerging from 
 the fissure, they wind round the anterior pyramids 
 below, and over the outer surface of the olives, across 
 the line of origin of the 9th, 10th, and 11th pairs of 
 nerves. Turning upwards, they then blend with the 
 fibres of the direct lateral cerebellar tract, and with 
 them form the chief part of the restiform body 
 (Fig. 50, page 70). 
 
 (6) The other group — the posterior external arci- 
 form fibres — passes from the posterior column of one 
 side to the restiform body of the same side (Fig. 99, 
 Plate XXXVII., page 168). 
 
 2. The DEEP arciform FIBRES are a delicate net- 
 work of fibres found between the olives and behind 
 the pyramids. The exact course and origin of these 
 fibres are not yet known with certainty. Many of 
 them are derived from the nuclei of the pos- 
 terior columns before mentioned (superior pyramidal 
 decussation). Others enter the centre of the olivary 
 nucleus through its hilum, and either join the 
 cells of that nucleus or pass through the nucleus to 
 the restiform body directly, or first make for the 
 
AND ITS MEMBRANES. 85 
 
 surface, and then, along with the external arcifonn 
 ribres, go to the restiform body. 
 
 Recapitulation. — Since the constitution of the 
 medulla is so complicated, it will be well to sum- 
 marise the above facts in a somewhat different order. 
 Commencing at the anterior median fissure, we meet 
 on each side of that fissure — 
 
 1. The ANTERIOR PYRAMIDS OF THE MEDULLA, 
 composed of longitudinal fibres, derived chiefly from 
 the crossed pyramidal tracts of the opposite lateral 
 columns, and to a small extent from the direct 
 pyramidal tracts of the same side. Most of the 
 motor fibres coming from the brain are contained 
 in these pyramids, though others, as we shall 
 afterwards see, first go to the pons, thence to the 
 cerebellum, thence to spinal cord (secondary motor 
 tract). 
 
 2. Superficial to the anterior pyramids are a set 
 of fibres, which, having their origin in the nucleus 
 gracilis and nucleus cuneatus of the one side of the 
 medulla, and having decussated in the middle line, 
 emerge from the anterior median fissure, cross over 
 the surface of the anterior pyramids and the olives of 
 the opposite side to that from which they started, and 
 go to join the restiform body. They are the superficial 
 arcifonn fibres (Figs. 55, 56,e.«./.), and amongst them 
 is a mass of grey matter, the ARCIFORM NUCLEUS. 
 
 3. In the middle line behind the pyramids, 
 between them and the central canal, are thick white 
 bundles of fibres arranged in concentric curves. They 
 spring from the region of the posterior columns, 
 
86 THE BRAIN 
 
 nucleus gracilis and cuneatus, and form the SUPERIOR 
 PYRAMIDAL DECUSSATION, or decussation of the fillet. 
 Higher up in the medulla this same region is occupied 
 by fibres which traverse the medulla in all directions 
 — formatio reticularis. Neuroglia cells, and a few 
 nerve cells are scattered amongst the fibres, many of 
 which are known as the deep arciform fibres. 
 
 4. Outside the formatio reticularis, between it 
 and the surface, but behind the pyramids, is the 
 olivary nucleus (n.o.K, Fig. 56) with the olivary 
 PEDUNCLES. This nucleus is covered superficially by 
 the external arciform fibres (Fig. 56). Close to it are 
 the accessory olives (Figs. 55, 56, a.o., page 78). 
 
 5. Behind the olives you will see the nucleus 
 LATERALIS (n.L, Fig. 54), the upward continuation 
 of the anterior cornu of the spinal cord. 
 
 6. Posterior to the nucleus lateralis appears the 
 grey tubercle of Rolando (Figs. 53, 54, t.R.) — the 
 enlarged head of the posterior horn of the spinal 
 cord. On its outer side will be seen the ascending 
 root of the 5th nerve (5th as., Fig. 54). Superficial to 
 the tubercle of Rolando are the fibres of the DIRECT 
 LATERAL CEREBELLAR TRACT, which are on their 
 way, along with the arciform fibres, to the inferior 
 cerebellar peduncles or restiform body. 
 
 7. Posterior and internal to the nucleus of Rolando 
 is a mass of grey matter— the NUCLEUS CUNEATUS 
 (n.c, Fig. 54) — lying beneath the cuneate tubercle ; 
 and still nearer the middle line is another grey 
 collection, the nucleus of the funiculus gracilis 
 (Figs. 54, 55, n.g.). 
 
AND ITS MEMBRANES. 87 
 
 In front of the nucleus cuneatus will be seen a 
 special white rounded fasciculus, known as the 
 FASCICULUS SOLITARIUS {f.s., Fig. 55), the ascending 
 root of the glosso-pharyngeal nerve. 
 
 Close to the middle line, internal to the nucleus 
 cuneatus, lies the nucleus of the hypoglossal nerve, 
 from which the nerve itself may be seen running 
 forwards to its superficial origin. 
 
 The rest of the grey matter, internal to the 
 nucleus of the funiculus gracilis, and on each side of 
 the posterior median groove, belongs to the floor of 
 the 4th ventricle (Fig. 57, page 82), and will be fully 
 described with that cavity. 
 
 The next division of the brain to be considered is the 
 metencephalon, comprising the pons and cerebellum. 
 
 II.— PONS VAROLII. 
 
 General Outline. — The Pons Varolii — part of 
 the metencephalon, the other part being the cerebel- 
 lum — is a broad white band which crosses transversely 
 between the two halves of the cerebellum above the 
 level of the anterior aspect of the medulla oblongata. 
 It rests on the body of the sphenoid. Composed of 
 grey and white matter, it presents an upper and a 
 lower border — an anterior and a posterior surface 
 (Fig. 46, page 66, and Figs. 59, 60, Plate XIX., 
 page 90). 
 
 The UPPER BORDER is arched, being higher in 
 the middle than at the sides, and from it spring 
 the crura cerebri, or cerebral peduncles. Two 
 cranial nerves, the 3rd and 4th, are seen at this 
 border, the former being near the middle line. 
 
88 THE BRAIN 
 
 The LOWER BORDER, which marks the upper limit 
 of the medulla in front, is horizontal, and is almost 
 in contact with the upper margin of the pyramids 
 and the olives (Figs. 46, 49, page 66). At this 
 border are seen, from within out, the 6th, 7th, and 
 8th cranial nerves. 
 
 The anterior SURFACE of the pons is convex, 
 and rests on the dorsum sellse of the sphenoid bone. 
 Along the middle line it presents a shallow groove, 
 which lodges the basilar artery. On each side of 
 this groove is a longitudinal elevation caused by the 
 continuation upwards of the pyramids of the medulla. 
 At the sides, the pons becomes narrowed, and passes 
 as two rounded bundles, one on each side, into the 
 cerebellum, forming its "middle 'peduncles. From 
 the lateral part of this aspect of the pons springs 
 the 5th cranial nerve. 
 
 The posterior surface of the pons has ill-defined 
 limits, being continuous below with the medulla, above 
 with the cerebral peduncles. Flattened from before 
 backwards it forms the upper part of the floor of 
 the 4th ventricle, and will be described with that 
 cavity (page 106). 
 
 When we examine transverse sections of the pons, 
 we find that it can be divided into two portions, a 
 ventral portion and a dorsal portion. The latter, 
 called the tegmentum, is a continuation upwards 
 of the constituents of the spinal cord and medulla, 
 with the exception of the pyramidal tracts. The 
 former, the ventral part, contains, besides the proper 
 fibres of the pons, the upward continuation of the 
 pyramids of the medulla. 
 
AND ITS MEMBRANES. 89 
 
 It is interesting to note that in mammalia the 
 size of the pons bears a direct relation to the size 
 of the lateral lobes of the cerebellum; and that 
 in birds, reptiles, and fishes, where we have no 
 cerebellar hemispheres, the pons also is wanting. 
 
 We shall consider the constitution of the Pons 
 according to the folio wins: table: — 
 
 Table of the Structure of the Pons Varolii. 
 
 I. WHITE MATTER OF THE PONS. 
 
 1. Transverse fibres. 
 
 (1) Superficial. 
 
 (2) Deep. 
 
 2. Longitudinal fibres. 
 
 (1) Superficial. 
 
 Anterior pyramids. 
 
 (2) Deep. 
 
 (a) Lemniscus, or fillet. 
 
 (6) Posterior longitudinal bundle. 
 
 (c) Fasciculus teres. 
 
 3. Fibres of the 5th, 6th, 7th and Sth cranial nerves. 
 
 4. Formatio reticularis. 
 
 5. Raphe. 
 
 II. GREY MATTER OF THE PONS. 
 
 1. Nucleus pontis. 
 
 2. Superior olive. 
 
 3. Nuclei of origin of 5th, 6th, 7th and 8th cranial nerves. 
 
 4. Locus caeruleus. 
 
 1. WHITE MATTER OF THE PONS. 
 
 Dissection. — To see the arrangement of the white fibres of the 
 pons, you will require to dissect down on each side of the middle line, 
 through the superficial transverse fibres, until you reach a longitudinal 
 set passing upwards from the medulla. Reflect the longitudinal 
 fibres, when a still deeper transverse group will come into view. 
 
9 o THE BRAIN 
 
 The white or medullated nerve fibres of the 
 pons are arranged in two sets, a transverse and a 
 longitudinal, each being again divisible into a 
 superficial and a deep group. 
 
 1. TransYerse fibres. — (1) The superficial 
 transverse fibres appear on the surface of the pons, 
 and (2) the deep transverse fibres lie behind the 
 superficial longitudinal ones (Figs. 59, 60, page 90). 
 At the lower part of the pons, near the medulla, 
 the deep set of transverse fibres forms a special 
 collection, called, from its peculiar arrangement, 
 the trapezium (Fig. 59). Traced laterally, all the 
 transverse fibres of the pons pass into the middle 
 peduncle of the cerebellum. Some of these fibres 
 are commissural between the two halves of the 
 cerebellum; others are connected with the nucleus 
 pontis of the same side or of the opposite side. 
 
 2. Longitudinal fibres. — (1) The superficial 
 LONGITUDINAL fibres (Figs. 59, 60) are mostly the 
 upward continuation of the anterior pyramids of 
 the medulla, and in transverse sections are seen as 
 two rounded bundles behind the superficial trans- 
 verse fibres, though many of them are intersected by 
 these latter. (2) The deep longitudinal bundles 
 (Figs. 59, 60) are placed near the dorsal aspect of the 
 pons, which is chiefly made up of the formatio retic- 
 ularis, and of a prolongation of the grey matter of 
 the medulla. Three distinct sets of longitudinal 
 fibres can, however, be recognised — viz., (a) the 
 lemniscus, or fillet, the continuation of the sensory 
 decussation ; (b) the posterior longitudinal bundle, 
 
Fig. 59. 
 
 Plate XIX. 
 
 . Nucleus of Nucleus of Pars intermedia. 
 
 '■■ ''" • <-*^L 8 ffinerv *- 6th, /nerve. ..--' v 
 
 s--- 7<A (facial) 
 
 mamidal 
 
 Trapezium. 
 
 Transverse fibre* of Pons. 
 
 T . . Fig. 60. 
 
 L/ingula..- .___ 
 
 Superior medullary velum. - 
 
 Formatto reticularis. - - 
 
 Posterior 
 
 fivdinal bundle. M 
 
 5th nerve. 
 
 Superior cerebellar peduncle. 
 Descending root of 5th nerve. 
 - Suftstcmtia ferruginea. 
 
 \— Fillet. 
 
 longitudinal fibres 
 
 Pyramidal fif/res. 
 
 Fig. 61. 
 
 Corpora quadrigeiicitui, 
 Aqueduct of Sylvius, 
 trior longitudinal bundle. ~ A 
 
 Red nucleus. 
 Fac. lateralis. 
 
 Pyraviidul tract 
 
 Geniculate fac. 
 
 Transverse fibres of Pons. 
 
 .Superior cerebellar peduncle 
 
 Nucleus of 3rd nerve. 
 
 Fillet. 
 
 Substantia nigra. 
 
 Ca;udaie 
 cerebellar tract. 
 
 3rd nerve. 
 
 c^' 
 
AND ITS MEMBRANES. 91 
 
 made up of fibres traced from antero-lateral column 
 of the spinal cord; and (c) the fasciculus teres, a 
 bundle of fibres seen in the floor of the 4th ven- 
 tricle, and containing fibres of the facial nerve (see 
 " Cranial Nerves," page 170). 
 
 3. Transverse sections of the pons will further 
 show you the following additional fibres (Fig. 59) : — 
 The ascending root of the 5th nerve, fibres of the 
 6th nerve, of the facial nerve and of the pars 
 intermedia of the facial, and finally, fibres of the 
 8th nerve. 
 
 4. The formatio reticularis is a network of fibres 
 occupying the tegmental part of the pons. 
 
 5. The raphe is a mesial septum which lies 
 behind the trapezium, beneath the median groove 
 on the floor of the 4th ventricle. It is a contin- 
 uation of the raphe of the medulla, and, like it, 
 is composed of fibres, partly nervous and partly 
 neuroglia, which cross each other in every direction 
 (Fig. 59). 
 
 2. GREY MATTER OF THE PONS. 
 
 Dissection.— To see the grey matter of the pons you will require 
 a series of transverse sections similar to those represented in 
 Plate XIX., page 90. 
 
 The grey matter of the pons consists of multipolar 
 and stellate nerve cells, either scattered or arranged 
 in more or less definite groups. Thus we have — 
 
 1. The nucleus pontis, situated on the ventral 
 aspect of the pons, amongst the superficial transverse 
 fibres. It consists of many scattered nerve cells, to 
 
92 THE BRAIN 
 
 which can be traced fibres from the cerebrum — 
 cortico-pontine fibres; and fibres from the cerebellum 
 — ponto-cerebellar fibres. 
 
 2. The superior olivary nucleus (Fig. 59), 
 placed on the dorsal part of the pons, behind the 
 trapezium, at some little distance from the middle 
 line, in a region which would correspond to the 
 prolongation of the lateral area of the medulla. 
 
 3. The nuclei of origin of the 5th, 6th, 7th, and 
 8th cranial nerves. 
 
 4. The locus caeruleus — a bluish spot, which 
 will be described with the upper part of the floor 
 of the 4th ventricle (page 106). 
 
 III.— CEREBELLUM. 
 (Plates XX., XXL, XXII., XXIIa., page 94, &c.) 
 
 The Cerebellum, or Little Brain, the second 
 division of the metencephalon, is placed behind the 
 pons and medulla, and, like the rest of the brain, is 
 composed of grey and white matter. It occupies the 
 two lower fossae of the occipital bone, lying beneath 
 the level of the tentorium cerebelli, which separates 
 it from the posterior part of the cerebral hemispheres. 
 Ellipsoidal in shape, with its long diameter trans- 
 verse, it will be seen to consist of a median division, 
 called, from its worm-like appearance, the VERMI- 
 FORM process, of two lateral divisions, the cere- 
 bellar hemispheres, and of the three peduncles — 
 superior, middle, and inferior — by means of which it 
 is brought into relation with the cerebrum, with the 
 
AND ITS MEMBRANES. 93 
 
 pons, and with the medulla. The median division, 
 the vermiform process, though incorporated with the 
 rest of the cerebellum, is quite a separate division of 
 the little brain. This is shown by the fact that it is 
 the only part of the cerebellum which is developed 
 in birds, in reptiles, and in fishes. Even in many 
 mammals the central lobe is much larger than the 
 lateral lobes. 
 
 We shall consider the several parts of the cere- 
 bellum in the following order — (1) The lobes ; (2) 
 the peduncles; (3) the medullary vela; (4) the 
 grey matter; and (5) the white matter (see Fig. 62, 
 &c, Plate XX., page 94). 
 
 CEREBELLAR HEMISPHERES. 
 
 (Figs. 62, 63, page 94.) 
 
 The Cerebellar Hemispheres present three sur- 
 faces — an anterior, a superior, and an inferior — the 
 last two being separated from each other by a definite 
 margin, in which runs a well-marked cleft, the GREAT 
 horizontal fissure. The hemispheres are darker 
 in colour than those of the cerebrum, and consist of 
 a central white core and of numerous crescentic 
 laminae of grey matter with their convexities back- 
 wards (Fig. 62, page 94). 
 
 1. The upper surfaces of the cerebellar hemi- 
 sphere are concave, and are separated from each other 
 along the middle line by a slightly raised ridge, with 
 a shallow groove on each side. This raised portion is 
 the superior vermiform process, and across it the 
 two cerebellar hemispheres are continuous with each 
 
94 THE BRAIN 
 
 other, there being no definite line of demarcation 
 between them (Fig. 62, page 94). 
 
 2. The under surface of each hemisphere is, 
 on the other hand, convex, and is divided from its 
 fellow by a wide median groove or hollow, the 
 VALLECULA, in which you will see a definite division 
 of the cerebellum, the inferior vermiform pro- 
 cess. Posteriorly, the hemispheres are separated 
 by a mesial notch — incisura cerebelli posterior 
 — which receives the free anterior margin of the 
 falx cerebelli. 
 
 3. The anterior surface of the cerebellum 
 presents in the middle line a wide notch — the 
 incisura cerebelli anterior — which lodges the 
 Pons Varolii and Medulla, and in which, when these 
 are removed, we see from above downwards — 
 
 (a) Anterior end of superior vermiform process. 
 (6) Valve of Vieussens, or superior medullary velum. 
 
 (c) Cavity of the 4th ventricle. 
 
 (d) Anterior end of inferior vermiform process, 
 and anterior part of mesial fissure of under surface. 
 
 At the sides are the cerebellar hemispheres, with — 
 
 (a) The three peduncles — superior, middle, and 
 inferior. 
 
 (b) Outside the middle peduncle is the longi- 
 tudinal sulcus which separates the upper from the 
 lower lobes. In this sulcus, near the middle ped- 
 uncle, is lodged the flocculus, from the inner end of 
 
Plate XX. 
 
 Fig. 62. 
 
 L and ant. crescentic. 
 
 Anterior 
 oerior lobe^ 
 
 r - Central lobe. 
 
 Superior 
 
 •vermiform process. 
 
 Posterior superior lol 
 
 ^Qg/g^^^-- Horizontal jis. 
 Posterior inferior lobe. 
 Upper Aspect of Cerebellum. 
 
 Fig. 63. 
 
 Flocculus, 
 nygdaloid lobe.^ 
 
 ntral lobe, 
 'ender lobe.- 
 
 trior inferior lobe. 
 
 Nodule. 
 " %^«<^ ofjlocculus. 
 
 Inferior 
 
 medullary 
 
 velum. 
 
 Uvula. 
 
 Pyramid. "■ Tuber valvuke 
 
 Incisvra cerebelli posterior. 
 Loweb Aspect of the Cerebellum. 
 
 Furrowed band. 
 
AND ITS MEMBRANES. 95 
 
 which passes the inferior medullary velum, a thin 
 white lamina, which extends to the anterior end of 
 the inferior vermiform process (Fig. 63, page 94). 
 
 1. LOBES OF THE CEREBELLUM. 
 
 The surfaces of the cerebellar hemispheres have 
 a laminated appearance, for they are broken up 
 by numerous transverse furrows, varying in depth, 
 into crescent-shaped folia, which have been grouped 
 together under special names, though it must be 
 confessed that the lobes thus formed are often 
 exceedingly ill-defined, and, in the present state of 
 our knowledge, are of little or no practical import- 
 ance. A tabular list of them is given for the 
 purpose of reference. 
 
 1. On the upper surface of the cerebellar hemi- 
 spheres the lobes are (Fig. 62, page 94) : — 
 
 (1) The central lobe (Fig. 62), situated near 
 the centre of the anterior margin, and consisting of 
 a few folia, which are continued upwards on to the 
 superior medullary velum, to be presently described 
 (Fig. 48, page 66). 
 
 (2) The anterior superior, and (3) the pos- 
 terior superior lobes (Fig. 62). These lobes are 
 separated from each other by a more or less distinct 
 sulcus, which arches transversely across the surface of 
 each hemisphere. The anterior superior lobe is often 
 called the quadrate lobe, and is divided into an 
 anterior portion, named the anterior crescentic, and 
 a posterior portion, the posterior crescentic (Fig. 62). 
 Each of the lobes on the upper surface is continuous 
 
96 THE BRAIN 
 
 across the superior vermiform process with the cor- 
 responding one on the opposite side. 
 
 2. On the under surface of the hemispheres 
 the lobes are better marked, and more easily dis- 
 tinguished from each other than they are on the 
 upper surface (Fig. 63). Enumerated from behind 
 forwards we find — (1) a few folia, the posterior 
 
 INFERIOR LOBE ; (2) the SLENDER LOBE ; (3) the BI- 
 
 ventral lobe; (4) an oval mass, the amygdaloid 
 lobe or tonsil ; and, finally (5), a fringe-like lobe, 
 the FLOCCULUS. 
 
 3. On the superior vermiform 'process the lobes 
 are — an anterior, the lobulus centralis ; a middle, 
 the MONTICULUS CEREBELLi; and a posterior, or 
 COMMISSURA SIMPLEX, 
 
 4. On the inferior vermiform process the lobes 
 are : — 
 
 (1) The tuber valvule (Fig. 63), placed be- 
 tween the posterior inferior and the slender lobes 
 of opposite sides. 
 
 (2) The pyramid (Fig. 63), between the bi-ventral 
 lobes. 
 
 (3) The UVULA (Fig. 63), between the amygdaloid 
 lobes, and connected with them by a grey band, 
 called, from its ridged appearance, the furrowed 
 bamd (Fig. 63). 
 
 (4) The nodule (Fig. 63), or laminated tubercle, 
 the pointed anterior end of the inferior vermiform 
 process. It is placed between the flocculi, projects 
 into the roof of the 4th ventricle, and is continuous 
 with the inferior medullary velum (page 101). 
 
AND ITS MEMBRANES. 97 
 
 2. PEDUNCLES OF THE CEREBELLUM. 
 
 The Peduncles of the Cerebellum are three for 
 each hemisphere — the superior, the middle, and 
 the inferior. They severally connect the cerebellum 
 {I) to the pons — crura ad pontem; (2) to the 
 medulla — crura ad medulla m : and (3) to the cere- 
 brum — crura ad cerebrum. 
 
 1. The Superior Peduncles (part of the Isthmus 
 Rhombencephali) are two white bands, right 
 and left (Fig. 47, page 66), hidden beneath the 
 anterior part of the cerebellum, and to see them 
 you will require to divide the cerebellum by a 
 vertical median incision, and to draw the parts 
 asunder. The crura ad cerebrum, or superior ped- 
 uncles, arise in the middle of the white substance 
 of the hemispheres, behind the inferior cerebellar 
 peduncles, and, running upwards and forwards from 
 the anterior aspect of the cerebellum to the under 
 surface of the corpora quadrigemina, pass to the 
 dorsal or tegmental part of the cerebral peduncles. 
 At first the superior peduncles form the lateral walls 
 of the upper part of the 4th ventricle, and leave 
 between them a triangular interval which is bridged 
 over by a lamina of nerve substance, the superior 
 medullary velum (Fig. 48, page 66). As they 
 ascend the peduncles meet in the middle line, and 
 form part of the roof of the 4th ventricle. The fibres 
 of which they are composed come from the corpus 
 dentatum of the cerebellum and from the cerebellar 
 
 H 
 
98 THE BRAIN 
 
 PLATE XXL 
 
 (Page 98.) 
 
 Fig. 66. — Section through the Cerebellum of a dog, showing 
 arrangement of the different layers. 
 
 A. Layer of superficial epithelial cells. 
 
 B. Horizontal bipolar cells. 
 G. Molecular layer. 
 
 D. Granular layer. 
 
 a. Epithelial cells. 
 
 b. Horizontal bipolar cells. 
 
 c. Triangular cells. 
 
 e. Vertical bipolar cells. 
 
 J' >f >) 
 
 0- » ii 
 
 h. Purkinje's cells, on the axis-cylinder of which is 
 
 a collateral (i), which ascends to the molecular 
 layer and breaks up into branches. 
 
 j.n.o.s. Fibres from the medullary layer, ramifying like 
 
 trees amongst Purkinje's cells. 
 p. Moss fibres. 
 
Plate XXI. 
 
 Fig. 64. 
 
 Tegmentum. 
 
 ('rvs( a. 
 
 LOCUS n nit r 
 
 Miildli cerehelUu 
 peduncle. \^t 
 
 or aspect <>/ cerebellum 
 
 Corpus den to turn. 
 
 
 Grus cerebri 
 
 Pons. 
 
 Medulla. 
 
 lrf>or ctto-, 
 
 ". Flo. 66. 
 
 
 
 Fio. 67. 
 ^ *"\ Molecular laver. 
 
 '. 
 ,:i ^ \ N \ Purki/ijt s 
 
 ' <*■* \'c\ \/ cells. 
 
 \ 
 
 \ 
 
 - 
 
 
 • i »-> 3v > 
 
 Medullary white substance, 
 
 Granulat 
 layer. 
 
 >•*.,/* > 
 
 
AND ITS MEMBRANES. 99 
 
 convolutions. Most of them decussate with the 
 fibres of the peduncle of the opposite side, and then 
 pass up as a distinct bundle, with those that do 
 not decussate, to the higher parts of the brain — to 
 the red nucleus, to the optic thalamus, and to the 
 cerebral cortex (Fig. 99, page 168). 
 
 The superior peduncles are separated from the 
 middle peduncles by an oblique sulcus from which 
 proceeds a delicate lamina — the band of Reil — 
 lemniscus lateralis (see " Auditory Nerve " ). 
 
 2. The Middle Peduncles (Figs. 47, 49, page 66) 
 of the cerebellum — crura ad pontem — are best seen 
 in front. They are merely the continuation into 
 the cerebellum of the lateral part of the pons, that 
 part which lies beyond the superficial origin of the 
 fifth nerve. Emerging from the lateral part of the 
 white centre of the hemispheres, in front of the 
 inferior peduncles, the middle peduncles pass towards 
 the middle line, and, becoming incorporated with 
 the pons, form its superficial and deep transverse 
 fibres. Some of these fibres — inter-cerebellar — go 
 from one half of the cerebellum to the other ; others 
 become connected with a nucleus in the pons — 
 nucleus pontis — of the same side or of the oppo- 
 site side, and can thence be traced to the opposite 
 cerebral hemisphere. Others go to the posterior 
 longitudinal bundle and to the fillet. 
 
 3. The Inferior Peduncles (Fig. 47, page 66) of the 
 cerebellum — crura ad medullam, or restiform bodies 
 — constitute one of the lateral boundaries of the lower 
 part of the 4th ventricle, and then pass upwards 
 
ioo THE BRAIN 
 
 between the superior and middle peduncles into the 
 white matter of the cerebellar hemispheres. Their 
 constitution is somewhat complex, for they consist 
 (1) Of a spinal part, composed of fibres from (a) 
 the lateral column of the same side — direct lateral 
 cerebellar tract already described ; (b) from the 
 posterior column of the same side — the posterior 
 external arciform fibres (Fig. 99, Plate XXXVII., 
 page 168); (c) from the posterior column of the 
 opposite side — the anterior external arciform fibres 
 (Fig. 99). (2) Of an olivary part, composed of 
 fibres from the opposite olives — cerebello - olivary 
 fibres (Fig. 99, page 168). (3) Of fibres uniting 
 the roof nuclei of the cerebellum with the nuclei of 
 origin of the 5th. 8th, 9th and 10th cranial nerves. 
 
 3. MEDULLARY VELA. 
 
 1. The Superior Medullary Yelum — valve of 
 Vieussens (Figs. 48, 60, pages 66, 90) — is a delicate 
 sheet of nerve substance placed across the triangular 
 interval left between the superior cerebellar peduncles 
 before they meet in the middle line. Triangular 
 in shape, with its apex forwards, it forms part of the 
 roof of the upper division of the 4th ventricle, and 
 consists of a white lamina crossed on its upper 
 surface by several transverse grey ridges, with in- 
 tervening furrows, called the lingtjla (Fig. 60, 
 page 90), not to be confounded with the ligula 
 (Fig. 48, page 66), the epithelial thickening along 
 the lower margin of the 4th ventricle. The white 
 and grey matter of the superior medullary velum 
 
AXD ITS MEMBRANES. 101 
 
 are continuous at the sides with the white and grey 
 matter of the cerebellar hemispheres. 
 
 •2. The Inferior Medullary Vela — valves of 
 Tarini — consist of two thin delicate semilunar 
 folds or lamina? of nerve substance, one on each side, 
 hidden beneath the amygdaloid lobes of the cere- 
 bellum, which must be removed with great care to 
 see them. By their inferior (or posterior) convex 
 border, each of these semilunar folds blends with 
 the white substance of the inferior vermiform pro- 
 cess and with the furrowed band ; their anterior 
 concave semilunar edge is free, or rather continu- 
 ous with the layer of epithelium which lines the 
 under surface of the pia mater roofing over the 
 4th ventricle. Externally these two semilunar folds 
 are attached by a white band or peduncle to the 
 flocculus ; internally, a central part, very thin, 
 continues the lateral portions across the middle 
 line in front of the nodule (Fig. 63, page 94). 
 
 4. GREY MATTER OF THE CEREBELLUM. 
 
 The Grey Matter of the cerebellum consists of 
 two parts : that on the surface — the cortex cerebelli; 
 that in its interior — the grey nuclei. 
 
 1. The grey matter of the cortex of the cerebellum 
 not only covers its surface, but lines the sides and 
 passes across the bottom of its various fissures or 
 sulci, so that in reality it forms a thin lamina folded 
 on itself in a series of leaves or plates. A mesial 
 vertical section will enable you to see this arrange- 
 ment, and will show you the beautiful tree-like 
 
io2 THE BRAIN 
 
 appearance — ARBOR VIT.E — of the grey and white 
 matter (Fig. 34, page 44 ; and Fig. 65, page 98). 
 
 2. The chief masses of grey matter in the interior 
 of the cerebellar hemispheres are the corpora 
 dentata, placed one in each hemisphere. In 
 structure they are similar to the corpus dentatum 
 of the olivary body, and are, as you will remember, 
 closely connected with it. They each consist of a 
 wavy band of brown coloured nerve substance, en- 
 closing white matter, the whole forming a pouch-like 
 wavy lamina or capsule, open at its upper and inner 
 side (Fig. 65). Through this opening bundles of 
 white nerve 'fibres pass into the centre of the corpus 
 dentatum, and can be traced from the superior cere- 
 bellar peduncles, from the superior medullary velum, 
 and from the restiform body. 
 
 The other nuclei found in the white centre of the 
 cerebellum are the nucleus globosus, the nucleus 
 emboliformis, and the nucleus fastigii. They are 
 situated near the middle line, internal to the corpus 
 dentatum. 
 
 Minute Structure of the Grey Matter. 
 
 In the Figs., Plate XXIIa., page 104, Van Gehuchten, the various 
 elements are, for clearness sake, separated from each other. 
 The circles represent the free surface. 
 
 The grey cortex of the cerebellum consists of three 
 layers (Plate XXIL, page 102 ; Fig. 68, page 104 ; 
 and Figs. 66, 67, page 98) : — 
 
 (1) An outer— the molecular layer. 
 
 (2) A middle — the layer of Purkinje's cells. 
 
 (3) An inner — the granular layer. 
 
Plate XXII. 
 
 Purkinjes- cells 
 
 Fibres ending in a pltiras 
 
 Basket cells 
 
 ixls cylinders 
 
 Large 
 
 granular 
 
 cells 
 
 Small 
 granular 
 
 cells 
 
 8 fibres Small molecular cells Zona granularis 
 
 Zona molecularis 
 
AND ITS MEMBRANES. 103 
 
 1. The outer layer — molecular layer — forms a 
 clear grey stratum on the surface of the cerebellum. 
 It is composed of a delicate matrix of neuroglia, 
 and of nerve cells and nerve cell processes. The 
 nerve cells are of two kinds (Fig. 68, page 104) : — 
 
 (1) Small molecular cells, multipolar, with many 
 protoplasmic processes, but no axis-cylinder process. 
 
 (2) Large molecular cells — placed at the deeper 
 part of the molecular layer. They are transversely 
 elongated, and have — 
 
 (a) Protoplasmic processes, which ramify towards 
 the surface of the cortex ; and 
 
 (6) An axis -cylinder process, which runs trans- 
 versely between the molecular and granular 
 layers, and which, at right angles to its 
 direction, gives off branches which encircle 
 the bodies of the cells of Purkinje, in a 
 basket-like network; hence they are called 
 basket cells (Fig. 68, page 104). 
 
 2. The middle layer is formed of cells which 
 are characteristic of the grey matter of the cere- 
 bellum. They are called the cells oe Purkinje' 
 (Fig. 68), or from their shape antler cells. Large 
 flask-shaped cells, they are set at right angles to 
 the surface of the cerebellum. Their larger ends are 
 the deeper, and give off a single process — the axis- 
 cylinder process — which sends off lateral branches 
 and ultimately passes into the white matter. Of 
 the lateral branches some pass into the molecular 
 layer, some spread out in the granular layer. 
 The outer process of the cells is much larger, and 
 
104 THE BRAIN 
 
 breaks up into leaf-like branches, like the horns of a 
 deer, hence the name antler cells. These branches, 
 called protoplasmic processes, spread out in planes 
 across the laminae, and form a rich plexus, ramifying 
 towards the surface. Their ramifications end free, 
 and do not anastomose with each other, nor with the 
 processes of neighbouring cells, though some of 
 them are said to be attached to the connective 
 tissue, and to the blood-vessels, at the margin of 
 the molecular layer. 
 
 3. The inner or granular layer — rust-coloured 
 layer of Turner — consists of nerve cells and neuroglia 
 cells embedded in a delicate matrix of fine interlacing 
 fibrillae. 
 
 Its nerve cells are of two kinds — small granular 
 and large granular (Plate XXII., page 102). 
 
 (1) The small granular cells are polyhedral in 
 shape. Their protoplasmic processes end in little 
 tufts of short thick branches (Fig. 68), and their 
 axis -cylinder process is very slender, and arises 
 either from the body of the cell or from one of the 
 protoplasmic processes. Passing with an undulating 
 course towards the molecular layer, the axis-cylinder 
 process ends in two branches which run parallel 
 with the laminae of the cerebellum. 
 
 (2) The second kind of cells — the large granular 
 cells — are found throughout the. thickness of the 
 granular layer; they have axis-cylinder and proto- 
 plasmic processes, the former giving off collaterals 
 (Fig. 68). 
 
Plate XXII a. 
 
 Fibres ending 
 in a plexus 
 
 •ye granular 
 cells 
 
 Small 
 } granular cells 
 
 cells 
 
AND ITS MEMBRANES. 105 
 
 5. WHITE MATTER OF THE CEREBELLUM. 
 (Plates, pages 102 and 104.) 
 
 The fibres of the several peduncles of the cere- 
 bellum; along with commissural bands, passing from 
 one hemisphere to the other, and from one convo- 
 lution to another, constitute the entire white core 
 of the cerebellum. 
 
 This white matter consists of three kinds of fibres 
 (Fig. 69, page 104):— 
 
 (1) The axis-cylinder processes of the cells of 
 Purkinje already described. 
 
 (2) Fibres which, on reaching the grey matter, 
 divide frequently, and at this point, or at some other 
 part of their course, form little mossy tufts of short, 
 thick branches — hence they are called moss fibres 
 <Fig. 69). 
 
 (3) A set of fibres which end in a plexus in the 
 molecular layer, and appear to be prolongations of 
 Purkinje's cells, though not so in reality (Fig. 69). 
 
 Throughout the white matter, moreover, there are 
 many neuroglia cells with their prolongations. 
 
 The functions of the cerebellum are as yet 
 unknown. It probably contains psychical centres 
 like the cerebrum. The classical experiments of 
 Flourens point to the fact that it is a centre for 
 the co-ordination of muscular movements, such as 
 walking. Others hold that it is a centre which pre- 
 sides over equilibrium. Later experiments published 
 in Dr Courmont's thoughtful and interesting work 
 on the Cerebellum and its Functions show that the 
 
io6 THE BRAIN 
 
 cerebellum is also an organ connected with the 
 emotions. He produces many facts of comparative 
 anatomy in support of his theory, and adduces a 
 formidable mass of clinical evidence, showing that, 
 in cases of disease (tuberculosis, &c.) of the cere- 
 bellum, the emotional side of the patient's character 
 is markedly affected, w T hereas the intellectual aspect 
 remains intact. 
 
 THE 4th VENTRICLE. 
 
 ITS POSITION, FLOOB, EOOF, WALLS, AND NUCLEI. 
 
 In describing the posterior aspect of the medulla 
 oblongata, on page 68, you will remember w r e treated 
 of its lower or posterior division only ; we now pro- 
 ceed to consider its anterior or upper half, that 
 half which is connected with the 4th ventricle. 
 
 The 4th Ventricle is a conical - shaped space 
 placed between the medulla and pons in front and 
 the cerebellum behind. It is lodged in the fore- 
 part of the vallecula on the under surface of the 
 cerebellum, and has a quadrilateral floor and a tent- 
 like roof. We shall require to examine (1) its floor, 
 (2) its lateral boundaries, (3) its roof, (4) its lining, 
 (5) the openings into it, (6) its choroid plexus, and 
 (7) the various collections of grey matter or nuclei 
 beneath the floor. 
 
 I. The Floor, or Anterior Wall of the 4th 
 Ventricle (Fig. 47, page QQ), is a diamond-shaped 
 depression of the figure of an heraldic lozenge, and 
 resembles two triangles placed base to base. It 
 
AND ITS MEMBRANES. 107 
 
 looks backwards and upwards, and its lower or 
 posterior part occupies the back of the medulla; its 
 upper or anterior part the back of the pons. Its; 
 formation is due to the separation from each other 
 of the walls of the posterior median fissure of the 
 spinal cord, and the consequent opening out of the 
 central canal of the cord, thus bringing the grey 
 matter round that canal to the surface. Of its four 
 angles, two are lateral — right and left — and mark the 
 widest transverse diameter of the ventricular floor ; 
 of the other two angles, the superior is on a level 
 with the upper border of the pons, the inferior on 
 a level with the lower border of the olivary body. 
 From some supposed likeness to a writing pen, the 
 apex of the lower part of the ventricular floor has 
 been called the calamus scriptorius. At the lateral 
 angles the space is prolonged for a short distance 
 between the cerebellum and medulla, the prolonga- 
 tions being called lateral recesses. Running across 
 the widest part of the ventricular floor, opposite the 
 lateral angles, are the STRIDE ACUSTICJE (Fig. 47, 
 page 66), which join the auditory nerve, and which, 
 you will remember, mark the upper limit of the 
 medulla on this aspect. They also serve to divide 
 the ventricular floor into two divisions, a lower 
 portion belonging to the medulla, and an upper 
 portion belonging to the pons (Figs. 47, 50, pages 
 66, 70), both of which are again sub-divided, by the 
 vertical median groove that runs from the superior 
 to the inferior angle, into two lateral segments. 
 Thus we get the entire ventricular floor marked out 
 into four divisions — two above and two below the 
 
108 THE BRAIN 
 
 striae acusticae (Fig. 47). On examining each of the 
 lower divisions you will see, at about their centre, 
 a small triangular depression called the inferior 
 or posterior fovea (Fig. 47), the base of which is 
 directed downwards, the apex upwards, in close con- 
 tact with the striae ; while its inner and outer margins 
 are prolonged downwards, as two grooves, the inner 
 until it meets the central median furrow near the 
 lower angle of the ventricle, and the outer until it 
 reaches the lateral wall of the cavity. Thus we find 
 that each part of the lower division of the ven- 
 tricular floor can be mapped out into the following 
 four distinct areas : — 
 
 1. The inferior fovea (Figs. 47, 50), the space en- 
 closed within the sides of the triangular depression 
 just described. 
 
 2. A raised area, which lies between the median 
 furrow and the inner margin of the fovea. It 
 forms the lower part of the fasciculus or eminentia 
 teres, and is often called the trigonum hypoglossi 
 (Fig. 47). 
 
 3. The tuberculum acustictvm, enclosed between 
 the lateral wall and the outer margin of the fovea 
 (Fig. 47). It is a part of a larger area, situated 
 above the striae acusticae which cross it superficially- 
 
 4. The ala cinerea with the eminentia cinerea, 
 placed below the base of the inferior fovea (Fig. 47). 
 
 In like manner each of the two upper segments 
 of the ventricular floor, which differ from those of 
 the lower half in being covered by a thin layer of 
 white matter, has a similar triangular depression 
 
AND ITS MEMBRANES. 109 
 
 (Figs. 47, 50), the superior or anterior fovea, be- 
 tween which and the central furrow is a prolongation 
 of the fasciculus teres (Fig. 47). Extending from the 
 apex of this fovea to the upper angle of the ventricle 
 is a shallow depression, which, from its dark aspect, is 
 called the locus ccvruleus (Fig. 47), the colour being 
 due to a mass of pigmented nerve cells (substantia 
 ferruginea) lying beneath. 
 
 II. Lateral Walls of the 4th Ventricle.— The 
 
 lateral boundaries of the lower half of the ventric- 
 ular cavity are formed from below upwards by (a) the 
 funiculus gracilis and its clava (Figs. 48, 50, 
 pages 66, 70); (b) higher up, by the tapering end 
 of the funiculus cuneatus (Figs. 48, 50) ; and (c) 
 highest of all by the restiform body or inferior 
 peduncle of the cerebellum (Figs. 48, 50). The 
 boundary of the upper division of the floor is the 
 
 SUPERIOR CEREBELLAR PEDUNCLE (Fig. 48) of either 
 
 side. 
 
 III. The Roof of the 4th Ventricle.— The roof 
 of the 4th ventricle is tent-like in shape — its apex 
 projecting backwards towards the cerebellum. The 
 lower half of the roof is formed by pia mater which 
 at this point is reflected from the cerebellum to the 
 back of the medulla. It is, however, deficient in the 
 middle line — a hole, called the foramen of Majendie, 
 being left in the roof. Its under surface is lined by 
 a layer of flattened epithelial cells, and a thickening 
 of this epithelium at the lower angle of the ventricle 
 is called the obex (Fig. 48, page 66). A similar 
 thickening, with the addition of a little white nervous 
 
no THE BRAIN 
 
 matter, skirting the side of the lower half of the 
 floor, is called the ligula or taenia (Fig. 48). The 
 roof of the upper portion of the ventricle is formed 
 partly by the SUPERIOR CEREBELLAR PEDUNCLES 
 after they meet in the middle line, and partly by 
 the superior and inferior medullary vela, 
 laminse of grey and white matter already described 
 (page 100). 
 
 IV. Ependyma Yentriculorum. — The floor of the 
 4th ventricle is covered by a layer of grey matter — 
 the ependyma ventricwlorum — consisting of neu : 
 roglia derived from the central grey nucleus round 
 the canal of the spinal cord. Upon this ependyma 
 lies a layer of ciliated epithelial cells continuous 
 with the epithelium lining the central canal of the 
 spinal marrow, and with that which lines the cavities 
 of the third and lateral ventricles of the brain. 
 
 V. Openings into the 4th Ventricle. — At the 
 
 superior angle, the 4th ventricle communicates by 
 a narrow channel, aqueduct of Sylvius (iter a 
 tertio ad quartum ventriculum), with the third 
 ventricle (Fig. 80, page 136) ; below, at the in- 
 ferior angle, the cavity is continuous with the 
 central canal of the spinal CORD; behind, at 
 the lower part of the roof, just above the inferior 
 angle, a small rounded opening, the foramen of 
 Majendie, puts the ventricle in communication with 
 the sub-arachnoid SPACE (Fig. 34, page 44) ; while 
 at each side, near the lateral angles, are similar 
 openings in the roof, between the cerebellum and 
 
AND ITS MEMBRANES. in 
 
 medulla. Through these openings the cerebro-spinal 
 fluid can find its way from the sub-arachnoid space 
 into the cavities of the brain and spinal cord. 
 
 VI. Choroid Plexus. — The choroid plexus of the 
 4th ventricle consists of two longitudinal vascular 
 folds of the pia mater which forms the roof of the 
 4th ventricle. These vascular fringes run along each 
 side of the middle line of the roof, projecting into 
 the ventricle, though covered everywhere by the epi- 
 thelium which follows all their windings and folds, 
 and separates them from the cavity of the ventricle. 
 Part of this plexus passes, as a vascular tuft, into 
 each lateral recess. 
 
 VIT. Grey Matter or Nuclei beneath the Floor of 
 the $th Ventricle. — Connected with the grey matter 
 of the floor of the 4th ventricle we have the nuclei 
 of origin of most of the cranial nerves. This grey 
 matter is also the site of certain physiological centres 
 — such as the vaso-motor, respiratory, and cardiac. 
 
 1. Nuclei beneath the lower division of the ven- 
 tricular floor (Figs. 57, 58, page 82) : — 
 
 (1) The first of these nerve nuclei lies beneath 
 the lower part of the surface prominence known as 
 the fasciculus teres, which skirts the median furrow 
 on the ventricular floor. This prominence, which 
 not only occupies the lower part of this area, but 
 also passes up under the striae acusticae, gives origin 
 in its lower part to the 12th or hypoglossal nerve, 
 and is hence called the hypoglossal nucleus: 
 
ii2 THE BRAIN 
 
 and in sections of the medulla at this level the 
 fibres of the nerve may be seen running out from 
 this nucleus towards the periphery (Figs. 55, h.n., 57, 
 pages 78, 82). 
 
 (2) The tubercidv/ni acwsticum, corresponding in 
 position to the tubercle of Rolando, covers the 
 PRINCIPAL auditory nucleus (Figs. 57, 58, page 82). 
 It extends beneath the striae into the upper division 
 of the ventricular floor (Figs. 57, 58). 
 
 (3) The ala cinerea and its eminentia contain the 
 nuclei of origin of several nerves : thus, in its lower 
 part, we have the nucleus of the spinal accessory 
 nerve (Fig 57); in its upper part, and extending 
 into the inferior fovea, are the nucleus of the 
 vagus below (Fig. 57), and of the glosso-pharyn- 
 geal above (Fig. 57). 
 
 2. The nuclei beneath the upper division of the 
 ventricular floor are the following : — 
 
 Close to the lateral recesses are the SENSORY and 
 motor nuclei of the 5th nerve, the motor being- 
 internal, the sensory external (Fig. 57). The nucleus 
 of the 6th nerve (Figs. 57, 58) lies under the fore- 
 part of the fasciculus teres, superficial to, but higher 
 up and nearer the middle line than the nucleus of 
 the 7th ; the nucleus of the 7th or facial nerve 
 is placed deeper, and internal to the 5th, but ex- 
 ternal to the nucleus of the 6th nerve (Fig. 57). 
 The outer or accessory nucleus of the auditory or 
 8th nerve lies external to the facial nucleus. 
 
 These various nuclei will be again referred to in 
 the section on the " Superficial and Deep Origins of 
 the Cranial Nerves" (page 170). 
 
AND ITS MEMBRANES. 113 
 
 The White Matter of this part of the medulla 
 consists of the continuation of the pyramids, and. 
 behind these, of the formatio reticularis, and of two 
 longitudinal bands — the fillet, and the posterior 
 longitudinal bundle. The former is derived from 
 the posterior column, being in part a continuation 
 of the sensory decussation. The latter is derived 
 from the antero-lateral column of the spinal cord, 
 and can be traced up under the grey matter of the 
 rloor of the 4th ventricle to the crura cerebri. 
 The posterior longitudinal bundle is connected with 
 the nuclei of origin of the 3rd, 4th, and 6th cranial 
 nerves. 
 
 IV.— THE CEREBRUM. 
 
 General Outline. — In man the cerebrum is by 
 far the largest division of the brain, and weighs on 
 an average from 46 to 53 oz. Above, it occupies the 
 vault of the cranium : below, at its base, it is lodged, 
 in front, within the anterior and middle cranial 
 fossa?, but behind, it rests on the upper surface of 
 the tentorium cere belli. An egg-shaped mass cf 
 nervous substance, it is larger behind than in front, 
 and is partly separated by the great longitudinal or 
 iutf. :r-lu'n\i spherical fissure into two halves — the 
 cerebral hemispheres — which are united across the 
 middle line by a thick band of white matter, called 
 the corpus callosum. Each hemisphere is ovoid 
 in shape and is composed of a white stalk or 
 peduncle — the crus cerebri — surmounted by a 
 convoluted grey crust, mapped out by furrows or 
 
 I 
 
ii 4 THE BRAIN 
 
 sulci into a series of larger or smaller folds called 
 
 CONVOLUTIONS. 
 
 Internally, the cerebrum consists of strands of 
 white nerve fibres; of masses of grey matter — 
 ganglionic masses; of connecting bands — com- 
 missures; and its centre is hollowed out into a 
 large cavity, sub-divided into smaller spaces called 
 VENTRICLES. 
 
 We shall describe — (1) the exterior or cortex of 
 the cerebrum, with its fissures, lobes, and con- 
 volutions ; (2) the base; (3) the interior, with 
 its ventricles, ganglia, and white strands : and 
 (4) the peduncles or crura cerebri. 
 
 I.— EXTERIOR OF THE CEREBRUM. 
 
 The Grey Matter of the outer surface of the 
 cerebrum is known as the great hemispherical gang- 
 lion, cortex, or bark of the brain. It is divisible 
 into an upper part, called the mantle or pallium ; 
 and a basal part, the rhinencephalon (see page 125). 
 
 Each hemisphere is a triangular pyramid, and 
 presents three borders and three surfaces — an outer 
 surface, convex ; a mesial, plane and vertical ; and an 
 irregular under surface or base. Examine — (1) the 
 fissures, and (2) the lobes and convolutions. 
 
 1. FISSURES OF CEREBRAL HEMISPHERES. 
 
 Of the Fissures of the hemispheres the largest 
 and most evident sub-divide the surface of the 
 cerebrum into lobes, and may be called inter- 
 lobular; the smaller fissures — intra-lobular — 
 
AND ITS MEMBRANES. 115 
 
 divide the lobes into convolutions, which, in most 
 cases, have received definite designations. 
 
 1. The Inter-lobular Fissures are the fissure of 
 Sylvius ; the fissure of Rolando ; and the parieto- 
 occipital fissure (Fig. 70, page 118). 
 
 (1) The Fissure of Sylvius, unlike the other sulci 
 of the hemispheres, is not a mere indentation of the 
 cerebral cortex, but is formed by the folding upon 
 itself of the entire brain substance. It is a deep 
 cleft which begins on the under surface of the hemi- 
 sphere, at a point called the anterior perforated spot, 
 and then runs transversely upwards and outwards on 
 the base of the brain to the lateral aspect of the 
 hemisphere, where it divides into two limbs — an 
 anterior, short, vertical, ascending limb, and a pos- 
 terior, which runs horizontally backwards on the 
 surface of the hemisphere — hence called the hori- 
 zontal limb (Fig. 70, page 118). Sometimes there 
 are two short limbs — the one being then called 
 anterior, the other vertical. 
 
 (2) The Fissure of Rolando (Fig. 70), found only in 
 man and in apes, is one of the first fissures to appear 
 in the development of the brain. It commences above 
 at the median longitudinal cleft, or close to it, and in 
 some cases even appears on the inner surface of the 
 hemisphere. Descending obliquely forwards across 
 the outer surface of the hemisphere, it ends below, 
 near the anterior part of the horizontal limb of the 
 fissure of Sylvius, but in most cases falls short of 
 that fissure. It is not of uniform depth throughout, 
 being deeper below than it is in its upper part 
 (Cunningham). 
 
n6 THE BRAIN 
 
 (3) The Parieto - occipital Fissure appears on 
 both the outer and inner surfaces of the hemisphere. 
 The EXTERNAL PARIETO-OCCIPITAL FISSURE is a short 
 cleft on the outer aspect of the hemisphere near its 
 hinder end (Figs. 70, 71); the internal parieto- 
 occipital FISSURE, continuous above with the ex- 
 ternal, is a very constant fissure, and descends 
 vertically on the mesial aspect of the hemisphere 
 (Fig. 72, page 124). It will be noticed with that 
 surface. 
 
 2. The Intra-lobular Fissures separate indi- 
 vidual convolutions from each other, and will be 
 described with the convolutions which they serve to 
 map out. Those which have received special names 
 are — 
 
 1. Praecentral (Fig. 71), 
 
 2. Intra-parietal (Fig. 70). 
 
 3. Parallel (Fig. 70). 
 
 4. Triradiate (Fig. 73). 
 
 5. Collateral (Fig. 72). 
 
 6. Callosal (Fig. 72). 
 
 7. Calloso-marginal (Fig. 72). 
 
 8. Calcarine (Fig. 72). 
 
 9. Dentate (Fig. 72). 
 
 2. LOBES AND CONVOLUTIONS OF CERE- 
 BRAL HEMISPHERES. 
 
 The cerebral hemispheres are at first perfectly 
 smooth and without convolutions, and this develop- 
 mental type is retained in the case of many animals 
 — e.g., the insectivora. In the adult brain each 
 cerebral hemisphere has five principal lobes. Of 
 these, four are bounded by the inter-lobular fissures, 
 and take their names from the bones of the skull 
 in relation to which they lie : they are the frontal, 
 the parietal, the occipital, and the temporal. The 
 
AND ITS MEMBRANES. 117 
 
 fifth lobe — the central lobe, insula, or Isle of Reil — 
 is not in contact with the bones of the skull, but 
 is hidden within the fissure of Sylvius, the margins 
 of which must be separated in order to see it. Two 
 other lobes are sometimes described — the olfactory 
 lobe (see page 119) and the limbic lobe (see page 125). 
 
 I. The Frontal Lobe (Figs. 70, 71, page 118) is 
 pyramidal in shape, and is bounded behind by the 
 fissure of Rolando, which separates it from the 
 parietal lobe: below, by the fissure of Sylvius, 
 which separates it from the temporal lobe; internally, 
 by the GREAT LONGITUDINAL FISSURE, which sepa- 
 rates it from its fellow of the opposite side. It has 
 three surfaces — an outer, an inner or mesial, and 
 an inferior or orbital. 
 
 The outer surface has four convolutions: one, the 
 ASCENDING FRONTAL CONVOLUTION (Figs. 70, 71), 
 runs parallel to and in front of the fissure of Rolando, 
 and is limited in front by the praecentral sulcus 
 (Figs. 70, 71) ; behind by the fissure of Rolando. 
 The rest of the surface in front of this gyrus is 
 mapped out by two horizontal parallel sulci into 
 three antero - posterior gyri — the SUPERIOR, the 
 -MIDDLE, and the INFERIOR FRONTAL CONVOLUTIONS 
 (Figs. 70, 71), which are sometimes classed together 
 under the term pre-frontal lobe. The posterior part 
 of the. left inferior frontal convolution is called 
 Broca's convolution, and contains the centre for 
 speech (Fig. 4-i, page 62). It deserves special 
 notice. It curves round the anterior and vertical 
 limbs of the fissure of Sylvius, by which means it 
 
n8 THE BRAIN 
 
 can be sub-divided into three parts — (1) an anterior 
 part, pars orbitalis; (2) a middle part, pars triangu- 
 laris ; and (3) a posterior part, pars opercularis, or 
 basilaris (Fig. 70, Nos. 1, 2, 3, page 118). This last 
 is the part that contains the centre for speech (see 
 Fig. 44, page 62). 
 
 The orbital surface of the frontal lobe, bounded 
 on the inner side by the longitudinal fissure, and 
 behind by the -fissure of Sylvius, passes in the rest 
 of its extent into the outer aspect of the hemisphere. 
 At about its centre it has a three-legged sulcus — 
 the TRIRADIATE Or INTRA-ORBITAL FISSURE — which 
 sub-divides the surface into three gyri, an INTERNAL 
 
 ORBITAL, an ANTERIOR ORBITAL, and a POSTERIOR 
 
 orbital (Fig. 73, page 124), all of which are mere 
 prolongations, into this surface, though not directly, 
 of the convolutions of the outer surface. Thus the 
 superior frontal convolution becomes continuous with 
 the internal orbital, the middle with the anterior 
 orbital, and the inferior with the external orbital. 
 
 On the surface of the internal orbital convolution, 
 lodged in a triangular sulcus — the OLFACTORY GROOVE 
 — is a club-shaped body, the olfactory bulb and 
 its PEDUNCLE, sometimes regarded as a separate 
 lobe. Traced backwards, the olfactory peduncle bifur- 
 cates behind into two white bands, the outer passing 
 backwards towards the fissure of Sylvius, where it is 
 lost, the inner running to the side of the great longi- 
 tudinal fissure (Fig. 79, page 134). The small 
 conical elevation between these two limbs is called 
 the OLFACTORY TUBERCLE, or trigonum olfactorium, 
 often regarded as the middle root of the olfactory 
 
Fig. 70. 
 
 Plate XXIII. 
 
 F. of Rolando. 
 
 in < i limb 
 
 F. of Sylvius 
 
 ■ , ■ Parelld /'. / 
 
 i talis 
 
 Occi^ TiVL 
 
 traparietal 
 ■ sulcus. 
 
 ,' External 
 parieto~occipital f. 
 
 '-Superior ' 
 -Middle 
 -Inferior 
 occipital. 
 
 LOBE- 
 
 Horizontal limb 
 'jalaris Temporal Lobe. ff f $ 
 
 xris 
 
 Pig 71. 
 
 Prcece/dral s. 
 F. of Rolando. 
 
 ' Intraparietal sulcus. 
 
 Parieto-occipital f. c\Cf^ 
 
 Diagrams of Convolutions, 
 
AND ITS MEMBRANES. 119 
 
 peduncle. The area internal to the inner limb is 
 known as the olfactory area of Broca. The portion 
 of the internal orbital convolution internal to the 
 olfactory groove is called the gyrus rectus. It is 
 separated behind by a slight fissure from the area of 
 Broca. 
 
 The Olfactory Lobe. — The olfactory bulb and the 
 parts connected with it are, as we have said, often 
 regarded as a separate lobe. This lobe comprises the 
 following parts — (1) An anterior division, consisting 
 of (a) the olfactory bulb and its peduncle ; (6) of the 
 olfactory area of Broca ; (c) of the trigonum olfac- 
 torium : and (2) a posterior division, consisting of 
 the grey matter at the base of the brain, called the 
 anterior perforated spot, crossed by the outer limb 
 of the olfactory peduncle. 
 
 The mesial surface of the frontal lobe will be 
 described with the corresponding surface of the 
 hemisphere. (See " Table of Convolutions.") 
 
 Table of the Frontal Convolutions. 
 
 ( Ascending" frontal. 
 r J Superior frontal. 
 
 Outer surface 1 Middle frontal. 
 ^Inferior frontal. 
 
 T , | See mesial surface of hemi- 
 
 i lontal lobe * Inner surface -{ 
 
 I spheres. 
 
 f Internal orbital. 
 Anterior orbital. 
 Posterior orbital. 
 
 II. The Parietal Lobe has an inner surface 
 belonging to the inner aspect of the hemisphere 
 
120 THE BRAIN 
 
 (see " Mesial Surface "), and an outer surface, lateral 
 and convex, which is bounded in front by the FISSURE 
 of Rolando, separating it from the frontal lobe ; 
 
 behind by the EXTERNAL PARIETO-OCCIPITAL FISSURE, 
 separating it from the occipital lobe ; and below by 
 the HORIZONTAL LIMB of the FISSURE of SYLVIUS, 
 separating it from the temporal lobe. 
 
 This surface is furrowed by two sulci — the one is 
 directed downwards parallel to and behind the fissure 
 of Rolando, and forms the posterior limit of the 
 ASCENDING PARIETAL CONVOLUTION (post-central) ; 
 
 the other, the intra-parietal sulcus, often con- 
 tinuous with the last-named sulcus (Fig. 71), arches 
 from before backwards through the centre of the 
 surface, and sub-divides it into an upper division— 
 the SUPERIOR PARIETAL LOBULE (Fig. 71, page 118) ; 
 and a lower division — the INFERIOR PARIETAL LOBULE 
 (Fig. 71, page 118). The inferior parietal lobule is 
 again divisible into three parts — an anterior part arch- 
 ing round the posterior end of the horizontal limb of 
 the fissure of Sylvius, and called the SUPRA-MARGINAL 
 GYRUS or CONVOLUTION of the PARIETAL EMINENCE 
 (Turner) ; a middle part, the ANGULAR GYRUS, be- 
 hind the horizontal limb of the fissure of Sylvius, 
 and continuous round the hinder end of the parallel 
 sulcus with the middle temporal convolution ; and a 
 posterior, behind the angular gyrus, and called the 
 POST-PARIETAL CONVOLUTION (Fig. 71, page 118). 
 
 The angular gyrus probably contains the centre 
 for sight, though the occipital lobes are the chief 
 centres connected with this function. The ascending 
 
AND ITS MEMBRANES. 121 
 
 frontal and ascending parietal convolutions contain 
 the motor centres (Fig. 44, page 62). 
 
 Table of Convolutions of Parietal Lobe. 
 
 / Ascending parietal fg upra _ 
 
 I Outer surface ' Superior parietal marginal 
 
 Parietal lobe -} I Inferior parietal I Angular, 
 
 tinner surface (See mesial surface _ 
 
 \ of hemispheres I Post-parietal. 
 
 III. The Occipital Lobe. — This lobe presents a 
 greater number of individual variations in the 
 arrangement of its convolutions than any of the 
 other lobes. Pyramidal in shape, with the apex 
 backwards, it has three surfaces — an external, in 
 contact with the parietal and occipital bones; an 
 internal, forming part of the mesial surface of the 
 hemisphere; and an inferior, continuous with the 
 under surface of the temporal lobe. At present we 
 shall notice the external surface only ; the others 
 will be described with the corresponding surfaces of 
 the hemispheres. The external s urface is bounded 
 in front by the external parietooccipital 
 FISSURE, and by a line drawn downwards from this 
 fissure across the surface of the hemisphere to its 
 lower margin (Fig. 70, page 118, dotted line). The 
 other boundaries of the external surface are the 
 margins of the hemisphere. Two longitudinal sulci 
 divide the surface into three antero-posterior 
 convolutions — a superior, a middle, and an in- 
 ferior occipital (Fig. 70) — but these convolutions 
 are bv no means constant. 
 
122 THE BRAIN 
 
 The inner aspect of the occipital lobes contains 
 the centre connected with sight (Fig. 44, page 62). 
 
 Table of Convolutions of Occipital Lobe. 
 
 Occipital lobe -j 
 
 f Superior. 
 'Outer surface i Middle. 
 I Inferior. 
 
 Inner surface See inner surface. 
 
 ..Under surface See next section. 
 
 IV. The Temporal Lobe (Fig. 70, page 118), 
 occupying the middle fossa at the base of the skull, 
 is conical in shape and has three surfaces — an upper, 
 a lower, and an external or lateral. 
 
 The external surface is bounded above by the 
 
 HORIZONTAL LIMB of the FISSURE of SYLVIUS, which 
 
 separates it from the parietal lobe; below, by the 
 inferior temporal sulcus, which separates it 
 from the under surface. Behind, there is no definite 
 line of demarcation between it and the outer surface 
 of the occipital lobe — the line prolonged downwards 
 from the external parietooccipital fissure serving as 
 its limit. This surface has three antero-posterior 
 fissures — the superior (or parallel), the middle, 
 and the inferior temporal — the upper two sulci 
 separate from each other the SUPERIOR, the MIDDLE, 
 and the inferior temporal convolutions. The 
 inferior fissure is, as we have said, the boundary 
 between the outer and the lower surfaces. 
 
 The upper surface of this lobe is hidden within 
 the fissure of Sylvius, and is marked out by some- 
 what inconstant sulci into two or three indefinite 
 gyri- 
 
AND ITS MEMBRANES. 123 
 
 The inferior surface presents a transverse depres- 
 sion caused by the upper margin of the petrous 
 part of the temporal bone, and this may be taken 
 as the limit between the temporal and the occipital 
 lobes — the part in front of the groove being convex, 
 and belonging to the temporal lobe ; the part behind 
 the groove being concave., and belonging to the 
 occipital lobe. These two parts are taken together 
 under the term occipito-temporal, and their con- 
 volutions are two in number — a SUPEEIOR and an 
 inferior occipitotemporal convolution, separ- 
 ated from each other by the COLLATERAL FISSURE 
 (see Fig. 72, page 124). 
 
 Table of Convolutions of Temporal Lobe. 
 
 {Superior temporal. 
 Middle temporal. 
 Inferior temporal. 
 
 Temporal lobeJ T _„ „„„,_. /Superior and inferior 
 
 Lower surface 
 
 ^ occipitotemporal. 
 
 f Two or three indefinite 
 L pper surface \ 
 
 V. The Central Lobe — insula, Isle of Reil — the 
 first to be developed, lies deeply within the fissure 
 of Sylvius, and cannot be seen unless you separate 
 the sides of that fissure. Triangular in shape, it 
 consists of five or six convolutions, called GYRI 
 OPERTI (Fig. 73, page 124), which are limited exter- 
 nally by a deep sulcus separating them from the 
 adjacent convolutions collectively known as the OPER- 
 CULUM (Fig. 73), and formed by the contiguous ends 
 of the ascending frontal, ascending parietal, and the 
 
i2 4 THE BRAIN 
 
 inferior frontal convolutions. In front and behind, 
 the Isle of Reil is separated by well-marked sulci 
 from the frontal and temporal lobes respectively. 
 
 VI. Fissures and Convolutions of the Median 
 Surface of the Hemispheres (Fig. 72, page 124). — 
 
 Most of the convolutions of this surface are parts of 
 lobes already described, but it will be well to group 
 them together under the above heading. To examine 
 them you will require a mesial vertical section of the 
 hemispheres. 
 
 Arching through this aspect of each hemisphere 
 is seen the cut surface of the corpus callosum 
 (Fig. 72, page 124), which we shall take as our 
 guide to the study of the gyri and sulci. 
 
 The CALLOSAL FISSURE — ventricle of the corpus 
 callosum (Fig. 72). This fissure commences in front 
 below the anterior end of the corpus callosum. It 
 runs along the upper margin of the corpus callosum, 
 and then turns round its posterior extremity, and, 
 skirting the inner border of the temporal lobe, ends 
 in the notch of the uncus (Fig. 72). Between the 
 callosal fissure and the upper margin of the hemi- 
 sphere lies the calloso-marginal fissure (Fig. 72), 
 which, commencing in front beneath the anterior 
 end of the corpus callosum, extends backwards, 
 parallel to the margin of the hemisphere, to a 
 level with the hinder end of the corpus callosum, 
 where it turns upwards to the mesial border of the 
 hemisphere, a little behind the fissure of Rolando 
 (Fig. 72). The original direction of the calloso- 
 marginal fissure is continued by a small sulcus 
 
Fig. 72. 
 Callosal/. Paracentral lobe. 
 
 Plate XXIV. 
 
 Internal 
 arxeto-occipital /. 
 
 sill VI IIS 
 
 Calcarinef. 
 
 d of Giacomini- - 
 Collateral/. 
 
 Dentate 'conwlution. 
 
 Fig. 73. 
 
 Dentate/. 
 
 Anterior orbital c. 
 Frontal Lobe 
 Triradiate/. 
 
 terior orbital c. 
 
 - Gyrus rectus. 
 
 Internal orbital. 
 
 W&&. --Insula. 
 
 Operculum. 
 
 Diagrams of Convolutions. 
 
AND ITS MEMBRANES. 125 
 
 which, along with the calloso - marginal, separates 
 the gyrus fornicatus below from the marginal 
 convolution and the quadrate lobe above. 
 
 The gyrus fornicatus — convolution of the 
 corpus callosum (Fig. 72) — commences in front 
 below the anterior end of the corpus callosum, and 
 arching upwards and backwards over the body and 
 round the posterior end of the corpus callosum, it 
 becomes slightly constricted — the isthmus — and then 
 runs downwards and forwards, on the mesial edge 
 of the temporal lobe, as the superior occipito- 
 temporal convolution, gyrus hippocampi. It is 
 also called the uncinate gyrus, from the hook-like 
 process — uncus gyri fornicati — in which it ends 
 in front (Fig. 72). This group of convolutions, 
 together with the septum lucidum, fornix, cornu 
 ammonis, fascia dentata, fasciola cinerea, median 
 and lateral longitudinal striae and the peduncles of 
 the corpus callosum, forms the limbic lobe referred 
 to on page 117. The limbic lobe and the olfactory 
 lobe together constitute the Rhinencephalon. 
 
 N.B. — There is no little confusion in the naming of the above 
 convolutions. Thus the superior occipito -temporal is often called 
 the uncinate gyrus. Again, either the whole convolution, or only 
 the posterior part of it — viz., that near the hinder end of the corpus 
 callosum — is known as the hippocampal convolution; while the 
 part beneath the calcarine fissure — or at other times the whole 
 gyrus — is called the lingual lobe. The inferior occipito-temporal 
 convolution is often called the fusiform lobe, though this name is 
 sometimes confined to the posterior part of that gyrus. 
 
 The marginal convolution (Fig. 72), belonging 
 to the mesial surface of the frontal lobe, begins at 
 
i 2 6 THE BRAIN 
 
 the anterior perforated spot, and, running along the 
 upper edge of the hemisphere above the calloso- 
 marginal sulcus, becomes continuous above with the 
 superior frontal convolution. Inferiorlv, it passes 
 into the gyrus rectus of the orbital surface, and 
 posteriorly it is limited by the vertical part of the 
 calloso-marginal fissure (Fig. 72). The hinder part 
 of the marginal gyrus is called the paracentral 
 lobule (Fig. 72); it is the mesial aspect of the 
 ascending frontal convolution. 
 
 The INTERNAL PARIETO-OCCIPITAL FISSURE (Fig. 
 72) lies behind the vertical part of the CALLOSO- 
 MARGINAL fissure, the two enclosing between them 
 the mesial surface of the parietal lobe, called the 
 QUADRATE LOBE or PRECUNEUS (Fig. 72). 
 
 Below the internal parieto-occipital fissure will be 
 seen the calcarine sulcus (Fig. 72), which runs 
 forwards from the posterior border of the hemisphere 
 to join the internal parieto-occipital sulcus. They 
 together enclose the wedge-shaped mesial aspect of 
 the occipital lobe, called the CUNEATE LOBE or 
 cuneus (Fig. 72). 
 
 The dentate (hippocampal) FISSURE (Fig. 72), 
 continuous behind with the callosal sulcus, ends in 
 front, as we have already seen, in the notch of the 
 uncus. This fissure separates the hippocampal 
 gyrus from the fimbria or tamia hippocampi, 
 which will be seen in the descending horn of the 
 lateral ventricle. 
 
 The DENTATE CONVOLUTION or FASCIA DENTATA is 
 
 a notched gyrus, the free edge of the superficial grey 
 
AND ITS MEMBRANES. 127 
 
 matter of the hemisphere (Fig. 72). It lies at the 
 bottom of the dentate fissure, and is continuous in 
 front with a small band — band of Giacomini — which 
 crosses the uncus of the gyrus fornicatus, and behind 
 with a thin grey lamina, the fasciola cinerea, and 
 through it with the mesial and lateral longitudinal 
 striae of the corpus callosum. It is part of an abortive 
 convolution which can be seen on opening up the 
 fissure of the corpus callosum (see " Corp. Call.," 
 page 157), and its continuation, the dentate fissure. 
 
 Passing into the lateral ventricles, above the fim- 
 bria, through a fissure called the great transverse 
 fissure (described on page 150), is a vascular 
 inflection of pia mater known as the choroid 
 plexus of the lateral ventricles. These structures 
 will be better seen when we dissect the lateral 
 ventricles (see page 141). 
 
 Table of the Convolutions of the Mesial Surface. 
 
 [■Gyrus fornicatus. 
 Marginal. 
 
 Hippocampal (uncinate). 
 Dentate. 
 
 Quadrate (precuneus). 
 Cuneus. 
 Paracentral lobule. 
 
 Convolutions of Mesial 
 surface 
 
 It may be well to note that besides the motor 
 and sensorial areas named above, the cerebral 
 convolutions also contain other areas, areas of 
 association — the intellectual areas. These com- 
 prise most of the frontal, parietal, temporal, and 
 occipital lobes (see pages 157 and 181). 
 
i 2 8 THE BRAIN 
 
 The figures in Plate XXV., opposite, will show 
 you the relations of the fissures and convolutions to 
 the scalp and to the cranial bones. The various 
 methods for locating these fissures and convolutions 
 will be found in your surgical works. 
 
 Structure of the Cortex of the Brain. 
 
 (Fig. 78, Plate XXVI., page 130.) 
 
 The Grey Matter of the cerebral cortex is arranged 
 in several more or less distinct layers, composed of 
 nerve cells and nerve fibres, of neuroglia, blood- 
 vessels, and lymphatics. 
 
 Seen with the naked eye a vertical transverse 
 section of the cerebral cortex shows six strata, alter- 
 nately white and grey — three white and three grey. 
 The white layers correspond to regions in which 
 there are many nerve fibres gathered into trans- 
 verse bundles ; the grey layers to parts in which 
 there are few or no fibres. 
 
 With the microscope, four layers of the cortex are 
 usually described according to the kinds of nerve 
 cells met with in the various layers. Enumerated 
 from without inwards they are — (1) the molecular 
 or superficial layer ; (2) the layer of small pyramidal 
 cells ; (3) the layer of large "pyramidal cells ; and 
 (4) the layer of polymorphous cells. 
 
 1. The Molecular Layer. — The nerve cells of 
 this layer are of three kinds : — 
 
 (1) Polygonal Cells, which are scattered through- 
 out the layer. They have several protoplasmic 
 
Plate XXV. 
 
 Ascending limb 
 off. of Sylvius 
 
 Horizontal livib 
 off of Sylvius. 
 
 Fig. ?4- 
 
 F. of Rolando. 
 
 Parelldf. 
 
 Relations of Fissures of Cerebrum 
 to Skull. 
 
 Parieto-occip. f. 
 
 Fig. 75. 
 
 F. of Sylvius. 
 
 F. of Rolando. 
 
 Parielo-occ. f. 
 
 Relations of Fissures of Cerebrum 
 to Scalp. 
 
AND ITS MEMBRANES. 129 
 
 processes, and an axis-cylinder process ; this last 
 having a horizontal or an ascending direction, and 
 ending free in this layer. 
 
 (2) Fusiform Cells — ovoid in shape, with their 
 long axis horizontal. They are bipolar, and have 
 protoplasmic processes passing from each end of the 
 cell. At some distance from the cell one of these 
 processes gives rise to an axis-cylinder process, which 
 ends free in this layer. 
 
 (3) Triangular Cells, with usually three proto- 
 plasmic processes and several axis-c}dinder processes, 
 which ascend and end in the molecular layer. 
 
 2. Layer of Small Pyramidal Cells. — The cells 
 of this layer are, as indicated by their names, mostly 
 pyramidal in shape, though those situated next to 
 the molecular layer are polyhedral or star-shaped. 
 The pyramidal cells have their apices directed 
 towards the surface, and in structure resemble the 
 pyramidal cells of the next layer. 
 
 3. Layer of Large Pyramidal Cells. — The cells 
 of this layer are much larger than those of the last 
 layer. They are pyramidal or polyhedral in shape, 
 with their apices towards the surface and their bases 
 towards the white substance. Each cell has axis- 
 cylinder and protoplasmic processes. 
 
 The axis-cylinder process descends from the centre 
 of the base of the cell towards the subjacent white sub- 
 stance. In the upper part of its course this process 
 gives off at right angles to its direction many side 
 
 K 
 
i 3 o THE BRAIN 
 
 PLATE XXVI. 
 
 (page 130.) 
 
 Fig. 78. — M.L. Molecular layer. 
 
 p. Polygonal cell. 
 
 m. Fusiform cell. 
 
 n. Triangular cell. 
 
 S.P. Layer of small pyramidal cells, 
 
 L.P. Layer of large pyramidal cells. 
 P.C, Layer of polymorphous cells. 
 W.S, White substance. 
 
 a. Bunches of fibres of the pyramidal cells. 
 
 b. Small pyramidal cell. 
 
 c. Axis-cylinder of small pyramidal cell. 
 
 d. Large pyramidal cell. 
 
 e. Axis-cylinder of large pyramidal cell. 
 
 /. Cell with ascending axis-cylinder process. 
 g. Sensitive cells of Golgi. 
 
 Fig. 77. — Pyramidal cell with axis-cylinder process and col- 
 laterals, and their terminal swellings. 
 
 Fig. 76.— Terminal branches of the apical process of a pyramidal 
 cell. 
 
Plate XXVI. 
 
 Fig. 78. 
 
 Fig. 76. 
 
 Pyramidal cell. 
 
 W.S. 
 
AND ITS MEMBRANES. 131 
 
 branches — collaterals — which run horizontally and 
 branch dichotomously. The branches are granular, 
 and end free in little knobs (Fig. 77, page 130). In 
 the lower part of its course the axis-cylinder process 
 becomes tortuous, and gives off no collaterals. It 
 ultimately ends in little tufts of branches in the 
 grey matter at lower levels of the cerebro-spinal 
 axis. 
 
 The protoplasmic processes arise from the apex 
 and from the lateral angles of the cells. They are 
 beset with short thick spines (Fig. 76, page 130). 
 The horizontal branches cross and recross each other, 
 and form a dense network. All the branches end 
 free in little knobs or thickenings. 
 
 4. Layer of Polymorphous Cells. — In this layer 
 the cells vary much in size and in shape, being 
 fusiform, ovoid, triangular and star-shaped. They 
 have ascending and descending protoplasmic pro- 
 cesses. The axis- cylinder process, sinuous in its 
 course, gives off collaterals, and ends in the white 
 substance, either by bending at right angles to its 
 original direction, or by T or Y shaped junctions 
 with the fibres of the white matter (W.S., Fig. 78, 
 page 130). 
 
 Besides the several kinds of nerve cells just 
 described, there are throughout the last three layers 
 of the cortex two other kinds of cells : — 
 
 1. Cells with short axis-cylinder processes — cells of Golgi — star- 
 shaped, with branching protoplasmic processes, and with an 
 axis-cylinder process, which, after a short course, ends free in 
 dense tree-like branches. 
 
1 32 THE BRAIN 
 
 2. Cells with ascending axis-cylinder processes. — These cells are 
 fusiform or globular in shape, and are mostly met with in the 
 polymorphous layer. Besides their protoplasmic processes, they 
 have an axis-cylinder process, which ascends from the apex of 
 the cell towards the cortex, giving off collaterals on its way 
 (Fig. 78). Ultimately this process ends in tree-like branches beset 
 with small spines, knobbed at their extremities. 
 
 The white and grey nerve fibres found in the 
 grey cortex are the protoplasmic and axis-cylinder 
 processes of the nerve cells of the cortex, or of those 
 at lower levels of the nervous system. In structure 
 they are like the fibres of the spinal cord. 
 
 Neuroglia pervades the entire cortex, passing 
 especially along the line of its vessels. In structure 
 it is similar to the neuroglia of the spinal cord 
 described on page 30. It forms a superficial stratum 
 under the pia mater, being known as the super- 
 ficial stratum of the molecular layer. 
 
 The blood-vessels and lymphatics have already 
 been described (page 57). 
 
 The above may be regarded as the typical structure 
 of the chief part of the cerebral cortex, but there 
 are differences in different regions which space will 
 not allow us to describe. 
 
 II.— BASE OF THE CEREBRUM. 
 
 Though the heading of this section is " Base of the 
 Cerebrum," it will be as well to consider the base of 
 the entire brain, and not confine ourselves merely to 
 the under surface of the cerebrum (Fig. 79, Plate 
 XXVII, page 134). 
 
AND ITS MEMBRANES. 133 
 
 The Base or under aspect of the brain is, as we 
 have already seen, very irregular in shape. In con- 
 nection with it we recognise the following structures : 
 (1) the medulla, (2) the cerebellum, (3) the pons 
 Varolii, (4) the crura cerebri, (5) the under aspect 
 of the frontal, temporal, and occipital lobes, (6) part 
 of the great longitudinal fissure and of the fissure of 
 Sylvius, (7) the anastomosing circle of blood-vessels 
 — the circle of Willis — and (8) the superficial origins 
 of the cranial nerves. 
 
 If we now examine more particularly that part of 
 the base of the brain which lies between the great 
 longitudinal fissure in front, the under surface of the 
 frontal and temporal lobes on each side, and the 
 crura cerebri behind (Fig. 79), we shall find an 
 irregular shaped interval which consists of grey and 
 white matter stretching across the middle line and 
 uniting the under aspect of the hemispheres. In 
 this space, called the inter-peduncular, or opto- 
 peduncular space, are the following structures : — 
 
 Commencing in front, at the longitudinal fissure, 
 we see (a) the anterior end of the corpus cal- 
 losum — the rostrum. Hidden within the fissure, 
 and passing backwards and outwards from it, towards 
 the fissure of Sylvius, are two narrow white bands, 
 (b) the peduncles of the corpus callosum, between 
 which lies a thin grey lamina, (V) the LAMINA 
 CINEREA — lamina terminalis. Passing across the 
 middle line, behind the median fissure, is a white 
 band of nerve fibres, (d) the optic commissure, 
 which is prolonged forwards at the sides into two 
 
134 THE BRAIN 
 
 rounded bundles, (e) the optic nerves ; and back- 
 wards as flattened white strands, (/) the optic 
 tracts, which curve round the outer sides of the 
 crura cerebri. 
 
 External to the optic commissure, at the root of 
 the fissure of Sylvius, and behind the olfactory 
 peduncles, are two triangular shallow depressions, 
 one on each side — the anterior perforated spots 
 (Fig. 79), greyish laminae, perforated for the passage 
 of blood-vessels into the interior of the brain. These 
 perforated grey laminae are continuous internally 
 with the lamina cinerea; externally, with the hemi- 
 sphere. Across them run the external roots of the 
 olfactory peduncles, and the peduncles of the corpus 
 callosum. In the middle line, behind the optic 
 commissure, is a small grey elevation — (g) the TUBER 
 cinereum (Figs. 79, 80) — which is continuous, above 
 the optic commissure, with the lamina cinerea. 
 
 Projecting downwards from the tuber cinereum is 
 a funnel - shaped process, (h) the iNFUNDiBULvn 
 (Figs. 79, 80), to the apex of which is attached (in 
 the entire brain) the posterior of the two lobes of 
 the (i) pituitary body (Fig. 80, page 136). 
 
 Behind the tuber cinereum. between it and the 
 crura cerebri, are two small rounded pea-shaped 
 nodules, (j) the corpora albicantia (Figs. 79, 80), 
 which we shall afterwards see are closely connected 
 with the anterior pillars of the fornix (Fig. 80). 
 Between the corpora albicantia and the tuber 
 cinereum is a small vascular, trefoil-shaped emin- 
 ence — the EMINENTIA vascularis — homologous with 
 
Plate XXVII. 
 
 callosu 
 
 Olfactory bu 
 and pedunci 
 
 (o(k 
 
 Fig. 79. 
 Great Zong-ilwlimd fissvn 
 
 Cerebellun 
 
 Fronted lobe. 
 1^ Olfactory groove, 
 
 H|' Ldhii.ni 
 
 H|g||^ y-V.s-.w//-- tif ,Sylt ins. 
 
 Anlt • 
 
 cUed spot. 
 
 commissure. 
 
 Infundibulum. 
 
 Tuber 
 
 jpttc trod. 
 
 Corpora 
 
 albicanlia. 
 
 Posterior 
 
 perforated 
 spot. 
 
 - Pons. 
 
 Middle 
 cerebellar 
 
 peduncle. 
 
 OUvary 
 body. 
 
 Anterior 
 
 pyramid. 
 
 A ulterior 
 
 median jissure 
 
 Base of Bkain 
 
 MURRAY DECT 
 
AND ITS MEMBRANES. 135 
 
 the saccus vasculosus of lower vertebra ta. Behind 
 the corpora albicantia, between the diverging cere- 
 bral peduncles, lies the posterior perforated 
 spot — pons Tarini (Fig 79) — a grey lamina similar 
 to the anterior perforated spot, and, like it, perfor- 
 ated for the passage of blood-vessels into the interior 
 of the cerebrum. 
 
 Of these several structures the only ones requir- 
 ing further notice are the pituitary body and the 
 lamina cinerea. 
 
 1. The Pituitary body. — This body is usually 
 left in the sella turcica when removing the brain. 
 It is of a reddish colour, and consists of two lobes, 
 an anterior and a posterior. The anterior lobe, which 
 in structure resembles the thyroid body, was origin- 
 ally a hollow prolongation from the pharynx, but 
 subsequently becomes solid. The posterior lobe 
 is a downward tubular prolongation of the cavity 
 — diencephalon — from which the 3rd ventricle is 
 formed. The pituitary body in some way modifies 
 the nutrition of the body. 
 
 2. The Lamina cinerea is a triangular- shaped 
 membrane, composed of two lateral grey layers, 
 separated from each other in the mid-line by a 
 very thin portion, almost transparent — lamina 
 terminalis — which closes the 3rd ventricle below 
 and in front. Placed between and attached to the 
 peduncles of the corpus callosum in front, the lamina 
 cinerea is continuous behind with the tuber cinereum, 
 and at the sides with the anterior perforated spots. 
 
136 THE BRAIN 
 
 We may now turn our attention to the superficial 
 origins of the cranial nerves : — 
 
 1. On the under aspect of the frontal lobe, lying 
 in the olfactory groove, is the olfactory bulb, often 
 called the 1st nerve. From it arise the olfactory 
 nerves. 
 
 2. Springing from the fore and outer part of the 
 optic commissure on each side are the optic nerves. 
 
 3. At the upper or anterior border of the pons, 
 internal to the crura cerebri, are the 3rd nerves. 
 
 4. At this same border, but external to the crura 
 cerebri, are the 4th nerves. 
 
 5. At the side of the pons, where it becomes the 
 middle peduncle of the cerebellum, are the 5th 
 nerves. 
 
 6. At the lower border of the pons, near the 
 middle line, are the 6th nerves. 
 
 7. At a little distance from the middle line are 
 the 7th and 8th nerves. 
 
 8. On the side of the medulla, behind the olivary 
 body, are the 9th, 10th, and 11th nerves in this order 
 from above downwards. 
 
 9. In front of the olivary body arises the 12th 
 nerve. 
 
 Table of Cranial Nerves. 
 
 ENGLISH METHOD. 
 
 NAMES. 
 
 Olfactory, 
 
 
 
 GERMAN METHOD 
 
 1st pair, 
 
 1st nerve. 
 
 2nd pair, 
 
 Optic, 
 
 
 
 2nd nerve. 
 
 3rd pair, 
 
 Oculomotor, 
 
 
 
 3rd nerve. 
 
 4th pair, 
 
 Patheticus or T 
 
 rochlearis 
 
 , 4th nerve. 
 
 5th pair, 
 
 Trigeminus 
 
 or 
 
 Trifacial, 
 
 5th nerve. 
 
 6 tli pair, 
 
 Abducens, 
 
 
 
 6th nerve. 
 
AND ITS MEMBRANES. 137 
 
 ENGLISH METHOD. 
 
 NAMES, 
 
 t 1. Facial. 
 t 2. Auditory, 
 
 
 GERMAN METHOD. 
 
 7th pair. 
 
 7th nerve. 
 8 th nerve. 
 
 
 ( 1. Glossopharyngeal, 
 
 9th nerve. 
 
 Sth pair, 
 
 \ 2. Vagus, 
 
 
 10th nerve. 
 
 
 V3. Spinal Accessory, 
 
 11th nerve. 
 
 9 th pair, 
 
 Hypoglossal. 
 
 
 12th nerve. 
 
 (For the farther account of these nerves, see 
 " Superficial and Deep Origins of the Cranial 
 Nerves," page 170.) 
 
 Table of Objects seen on the Base of the Brain. 
 
 1. The Medulla. 
 
 2. The Cerebellum. 
 
 3. The Pons. 
 
 4. The Crura Cerebri. 
 
 5. Inter-peduncular space. 
 
 6. Posterior perforated spot. 
 
 7. Corpora albicantia. 
 
 8. Eminentia vascularis. 
 
 9. Pituitary body. 
 
 10. Infundibulum. 
 
 11. Tuber cinerexrm. 
 
 12. Anterior perforated spots. 
 
 13. Optic commissure. 
 
 14. Optic tracts. 
 
 15. Optic nerves. 
 
 16. Lamina cinerea — lamina terminal is. 
 
 17. Peduncles of the corpus callosum. 
 
 18. Rostrum of the corpus callosum. 
 
 19. The Cranial Nerves (see Table, above). 
 
 20. Under aspects of Frontal and Temporal Lobes. 
 
 21. Sylvian, and part of great longitudinal fissures. 
 
 22. Blood vessels — Circle of Willis. 
 
138 THE BRAIN 
 
 III.— INTERIOR OF THE CEREBRUM. 
 
 General Outline. — We now proceed to examine 
 the interior of the cerebrum. This we do by a series 
 of horizontal and vertical sections (see " Dissection," 
 page 140). 
 
 Above the level of the corpus callosum, each 
 hemisphere consists of a solid white central core — 
 centrum ovale, composed of strands of fibres, sur- 
 rounded externally by a wavy edge of grey matter — 
 the cerebral cortex. 
 
 Ventricles. — Below the level of the corpus cal- 
 losum, however, the centre of the cerebrum is 
 occupied by an irregular cavity, the remains of the 
 original cerebro-spinal embryonic canal (see "Develop- 
 ment"). This cavity, somewhat T-shaped in coronal 
 section (Figs. 93, 94, page 164), is sub-divided by 
 partitions or septa into smaller spaces called VEN- 
 TRICLES. Thus we have (1) the 3rd ventricle, a 
 vertical mesial longitudinal cleft-like space — repre- 
 sented by the upright part of the T — lying beneath 
 the corpus callosum, and extending below to the 
 base of the brain ; and (2) the lateral ventricles, 
 two lateral diverticula — the cross stroke of the T — 
 hollowed out in the substance of the hemispheres. 
 Uniting these various ventricles with each other are 
 narrow passages or channels, constricted portions of 
 the tube from which the brain and spinal cord were 
 developed. Thus, in front, as we shall afterwards 
 
Plate XXIX. 
 
 Fig. 81. 
 
 **-:*. 
 
 
 Corpus ccUlosum. 
 
 ( '. & 
 
 Corpus striatum (nucleus 
 caudaius). 
 
 0. T. 
 
 Optic thai am us. 
 
 T. & 
 
 T<en ia sem iciradarix. 
 
 r.P. 
 F. 
 
 Choroid plexus 
 
 Posterior port of fornix. 
 
AND ITS MEMBRANES. 139 
 
 see, are the foramina of Monro, which connect the 
 lateral ventricles with the 3rd ventricle and with 
 each other (Fig. 80, page 136); and behind is the 
 passage called the aqueduct of Sylvius, or iter a 
 tertio ad quartura ventriculum (Fig. 80). 
 
 Basal ganglia. — Besides the white nerve matter 
 and the central cavity, the interior of the cerebrum 
 is occupied by large masses of grey matter — gang- 
 lionic masses — basal ganglia — the chief of which are 
 the corpora striata, which belong to the telen- 
 cephalon ; the OPTIC THALAMI and the CORPORA 
 GENICULATA, which belong to the diencephalon; and 
 the corpora quadrigemina, which belong to the 
 mesencephalon (see "Development"). Each hemi- 
 sphere, therefore, forms a kind of shell enclosing 
 and overlapping the basal ganglia. 
 
 Commissures. — Finally, uniting together the cere- 
 bral hemispheres and their ganglia are longitudinal 
 and transverse bands or commissures — the CORPUS 
 CALLOSUM, the ANTERIOR, POSTERIOR, and MIDDLE 
 
 commissures, and the fornix. 
 
 We shall describe — (1) The ventricles, with 
 their communications and septa ; (2) the basal 
 ganglia ; (3) the commissures and other strands of 
 fibres ; but before doing so we shall give seriatim 
 the dissections required to expose these several 
 parts, so that the subsequent description of them 
 may be less disconnected and more easily under- 
 stood. 
 
i 4 o THE BRAIN 
 
 Dissection : — 
 
 A. To expose the Corpus Callosum. 
 
 Place the brain upon its base with the convex surface upper- 
 most. Take a large sharp knife, moistened in spirit, and cut from 
 the right hemisphere a horizontal slice about half-an-inch in 
 thickness. This will expose an oval-shaped central white mass of 
 nervous substance in the hemisphere — the centrum ovale minus, 
 studded here and there with small red spots — puncta vasculosa — 
 the cut ends of the blood-vessels. Surrounding the white centre 
 is the wavy grey edge, about one-eighth of an inch thick, the 
 cerebral cortex before referred to. 
 
 Kemove a series of slices similar to the first, until you reach the 
 level of the upper surface of the corpus callosum, then, with one 
 sweep of the knife, cut off the opposite hemisphere to this same 
 level, when you will see the centrum ovale majus, under which 
 term is included the whole area now exposed. The upper surface 
 of the corpus callosum is marked by a mesial groove, the raphe, 
 and by median and lateral longitudinal stria?. Procure, if possible, 
 a second brain, and make a mesial section of it, to enable you the 
 better to examine the corpus callosum and the parts beneath. 
 
 B. To expose the Lateral Ventricles. 
 
 1. The Body. — Cut through the corpus callosum a little on each 
 side of and parallel to the middle line, and with the back of the 
 knife raise its fibres, being careful not to injure the parts seen in 
 the floor of the cavity beneath. Enumerated from before back- 
 wards, these parts are — 
 
 (1) The nucleus caudatus (Fig. 81, page 138). 
 
 (2) The taenia semi-circularis, ,, „ 
 
 (3) The optic thalamus, h m 
 
 (4) The choroid plexus, » M 
 
 (5) The edge of the fornix, i. » 
 
 2. Cornua. — Next trace the cavity, forwards and outwards, as it 
 winds round the front of the caudate nucleus into the frontal lobe — 
 this is the anterior horn ; then follow it backwards into the 
 occipital lobes — the posterior horn; and downwards and outwards 
 into the temporal lobe — the descending or lateral horn. 
 
AND ITS MEMBRANES. 141 
 
 In the posterior horn you will .see the hippocampus minor (Fig. 
 82, &c.) ; in the descending horn, the hippocampus major, the pes 
 hippocampi (Fig. 82), the taenia hippocampi, and part of the 
 choroid plexus of the lateral ventricles (Fig. 82, page 142). 
 
 C. To expose the Fornix, the Septum Lucidum, 
 
 and the 5th Ventricle (Fig. 8-1, page 146). 
 
 Make a transverse incision through the centre of the corpus 
 callosum, and turn its ends backwards and forwards. Pass a sharp 
 knife along the fore part of the under aspect of the corpus callosum, 
 and sever its attachment to the septum lucidum. Lift up the 
 anterior part of the corpus callosum, when you will expose the septum 
 lucidum, and the cavity enclosed between its two layers— the 5th 
 ventricle. Next reflect the posterior half of the corpus callosum, 
 detaching it with the greatest care from the subjacent fornix where 
 they are blended together. This will expose the body of the fornix. 
 
 D. To expose the Velum Interpositum and the 
 3rd Ventricle (Figs. 84, 85, pages 146 and 148). 
 
 Cut transversely through the middle of the fornix, and turn 
 back the cut ends; the velum interpositum, a delicate process of 
 pia mater, will thus be brought into view. Examine this velum, 
 and then detach it in front and throw it back, so that it may be 
 again replaced if needed. The 3rd Ventricle will be seen beneath 
 it, extending to the base of the brain between the optic thalami. In 
 front are the anterior commissure, the anterior pillars of the fornix, 
 and the foramina of Monro ; behind are the pineal gland and its 
 peduncles; the posterior commissure, the corpora quadrigemina, 
 and the aqueduct of Sylvius ; while crossing the space transversely 
 is the middle commissure. 
 
 I.— VENTRICLES OF THE BRAIN. 
 
 The Ventricles of the Brain are five in number — 
 four, viz., the two lateral (1st and 2nd), the third 
 and the fourth ventricles are the remnants of the 
 cerebro- spinal embryonic canal, and are continuous 
 with each other and with the ventricle or central 
 
142 THE BRAIN 
 
 canal of the spinal cord. The 5th ventricle, on the 
 other hand, belongs to a different category from the 
 rest, and the term ventricle as applied to it is some- 
 what misleading, for it has none of the characters of 
 the other ventricles, being neither a part of the 
 original medullary canal, nor lined by the same 
 epithelium as the rest, nor in any way connected 
 with them in the adult. It will be noticed along 
 with the septum lucidum. The 4th ventricle has 
 already been described (page 106). 
 
 THE LATERAL VENTRICLES 
 (1st and 2nd). 
 
 The lateral ventricles, or ventricles of the 
 hemispheres (right and left), are two irregular 
 crescent-shaped cavities hollowed out in the sub- 
 stance of the cerebral hemispheres (Figs. 81, 82). 
 Placed back to back, each ventricle consists of a 
 central part or body, and of three prolongations or 
 recesses — the anterior, the posterior, and the 
 descending or lateral horns (Fig. 82, page 142). 
 
 The Body of the Ventricle is the highest and 
 largest portion, and, whether looked at from above 
 or in coronal section, is triangular in shape. It is 
 deeper in front than behind, and deeper near the 
 middle line than at the sides, where the roof and 
 sloping floor meet and blend with the substance 
 of the hemispheres. 
 
 1. The roof of the lateral ventricles is formed by 
 the CORPUS CALLOSUM. 
 
Plate XXX. 
 
 Fig. 82. 
 
 a a - 
 
 y-r. 
 
 K„ 
 
 V 
 
 ^4 
 
 
 i > 
 
 4 
 
 c. c. 
 
 C'.P. 
 
 H.Mi. 
 
 P.O. 
 
 A nterior a/rnu. 
 
 C 'orpus callosum. 
 
 Choroid plexus. 
 Hippocampus minor. 
 Posterior corna. 
 
 C. S. Corpus striatum (nucleus 
 
 caudatm). 
 T. S. Taenia semicircular is. 
 L. C. Lateral cornu. 
 0. T. Optic tlialamus. 
 H. Ma. Hippocampus major. 
 F. Fornix. 
 
 E. t '. Em in entia col lateralis. 
 
AND ITS MEMBRANES. 143 
 
 2. The floor presents from before backwards — 
 (a) a small part of the CORPUS CALLOSUM where it 
 turns down in the longitudinal fissure ; (6) a club- 
 shaped eminence — the NUCLEUS CAUDATUS of the 
 corpus striatum ; (c) an oval grey mass — the upper 
 surface of the optic thalamus, which is separated 
 from the nucleus caudatus by a shallow groove in 
 which lies (d) the taenia semi-circulaeis. Resting 
 on the optic thalamus is (e) the vascular fringe — 
 the CHOROID PLEXUS of the lateral ventricles ; and, 
 finally, close to this fringe, nearer the middle line, is 
 (/) the thin sickle-shaped free edge of the BODY of 
 the FORNIX. 
 
 3. The inner wall of the ventricle is formed in 
 front by a thin double vertical triangular mesial 
 partition — the septum lucidum — which extends 
 between the corpus callosum and the fornix. Behind 
 the septum lucidum, the floor, formed by the fornix, 
 and the roof, formed by the corpus callosum, blend 
 together in the middle line, so that there is no inner 
 wall. 
 
 4. Externally, the floor and roof meet, as we have 
 seen, in the mass of the hemispheres. 
 
 The Cornua of the Ventricles are three in 
 number — anterior, posterior, and lateral or descend- 
 ing (Fig. 82, &c, page 142). 
 
 1. The Anterior Cornu is a short triangular 
 horn-shaped cavity, which turns forwards and 
 outwards from the fore part of the body of the 
 
i 4 4 THE BRAIN 
 
 ventricle round the anterior end of the nucleus 
 caudatus into the substance of the frontal lobe. 
 
 Its roof and anterior ivall are formed by the 
 corpus callosum ; its floor by the substance of the 
 frontal lobe ; its inner wall by the septum 
 lucidum ; while, both behind and beloiv, is the 
 
 NUCLEUS CAUDATUS. 
 
 2, The Posterior Horn is a similar recess, passing 
 outwards, backwards, then inwards into the sub- 
 stance of the occipital lobe. 
 
 Its roof is formed by the corpus callosum ; its 
 floor by an oval prominence — the HIPPOCAMPUS 
 minor (Fig. 86, page 154), caused by the calcarine 
 sulcus seen on the mesial surface of the hemisphere. 
 
 3. The Lateral Horn — descending horn — curves 
 round the posterior end of the optic thalamus as a 
 bent finger-like passage with its convexity outwards. 
 It runs first backwards and outwards, then down- 
 wards, forwards, and finally inwards (b.o.d.f.i.) in 
 the substance of the temporal lobe (Fig. 82, &c, 
 page 142). 
 
 In its roof are — the corpus callosum ; the 
 posterior extremity of the optic thalamus: the 
 taenia semi-circularis ; and, finally, the taper- 
 ing end of the nucleus caudatus, which, at the 
 anterior part of the horn, swells out and passes 
 into the nucleus amygdalae. 
 
 In the floor of the passage lies a curved elongated 
 projection following the bend of the horn, and called 
 the hippocampus major (cornu ammonis). This 
 prominence is caused by the hippocampal (dentate) 
 
Plate XXXI. 
 
 Fig. 83. 
 
 — as. 
 
 -T.S. 
 
 - p.h: 
 
 - O.T. 
 
 -H.Ma. 
 
 T.H. 
 
 m—E.c. 
 
 } - HMi. 
 
 -a a 
 
 Corpus callosum 
 
 a. a 
 
 Anterior cornu. 
 
 5th V. 
 
 5th ventricle. 
 
 F. 
 
 Forn i.e. 
 
 a p. 
 
 Choroid plexus. 
 
 p. a 
 
 Posterior cornu. 
 
 C. S. Corpus striatum (nucleus 
 
 caudatus). 
 
 T.S. Taenia semicircular is. 
 
 P. H Pes hippocampi. 
 
 0. T. Opticus thalamus. 
 
 H.Ma. Hippocampus major. 
 
 T.H. Tcenia hippocampi. 
 
 E.C. Eminent ia collateral is. 
 
 H. Mi. Hippocampus minor. 
 
AND ITS MEMBRANES. 145 
 
 fissure on the surface of the brain. Below, at the 
 apex of the horn, the hippocampus ends in an 
 enlarged, grooved, paw-like, extremity — the pes 
 hippocampi ; while along its inner concave margin 
 lies a thin, white, tapering band of fibres — the 
 taenia hippocampi or fimbria, the prolongation of 
 the posterior pillars of the fornix. Above and 
 interna] to the fimbria is the CHOROID PLEXUS of 
 the lateral ventricles, which at this point projects 
 into the ventricular cavities through the lateral part 
 of what is known as the great transverse fissure 
 (see page 150). Below the fimbria is the free edge 
 of the grey matter of the cortex, which, from the 
 notched appearance caused by the entrance over 
 its free edge of the choroidal artery, receives the 
 name fascia dentata. The choroidal artery carries 
 with it into the lateral ventricles a process of pia 
 mater called the velum interpositum, in the free 
 margin of which the artery breaks up into the 
 choroid plexus of the lateral ventricles (see "Velum 
 Interpositum"). 
 
 At the point where the lateral and posterior 
 horns diverge from each other you will see a slight 
 eminence — the EMINENTIA COLLATERALS — varv- 
 ing in size in different subjects. It is caused 
 by the collateral fissure on the surface of the 
 brain (Figs. 82, 83, 86, pages 142, 144, 154). 
 
 Ependyma Yentriculorum. — The lateral ven- 
 tricles are lined by a layer of neuroglia covered on 
 the surface by columnar ciliated epithelium, con- 
 tinuous with the epithelium of the other ventricles. 
 
 L 
 
146 THE BRAIN 
 
 Communications. — Between the anterior pillars 
 of the fornix and the optic thalami are two slit-like 
 openings, one on each side — the FORAMINA of MONRO 
 (Fig. 80, page 136). By means of these openings 
 the two lateral ventricles communicate directly with 
 the 3rd ventricle and indirectly with each other. 
 Through these same foramina, as we shall afterwards 
 see, the choroid plexuses of the lateral ventricles are 
 continuous with those of the 3rd ventricle. 
 
 THE 3rd VENTRICLE. 
 
 The 3rd ventricle (Fig. 85, page 148 ; Fig. 93, 
 page 164) is the narrow, vertical, cleft- like space, 
 situated in the middle line between, the optic 
 thalami. It lies beneath the body of the fornix, and 
 extends down to the base of the brain, being deeper 
 in front than behind. 
 
 Boundaries. — The roof is formed by a layer of 
 flattened epithelial cells, which covers the under 
 surface of the velum interposltum. 
 
 In its floor are the structures contained within 
 the inter-peduncular space at the base of the brain 
 (Fig. 98, page 168) — viz., the locus perforatus 
 
 POSTICUS, the CORPORA ALBICANTIA, EMINENTIA 
 VASCULARIS, the TUBER CINEREUM, the INFUNDI- 
 BULUM, the OPTIC COMMISSURE, the LAMINA CINEREA 
 and LAMINA TERMINALIS. 
 
 In front, the ventricle is limited by the ANTERIOR 
 PILLARS of the FORNIX, the ANTERIOR COMMISSURE, 
 
 and by the lamina cinerea and terminalis; behind, 
 by the aqueduct of Sylvius, and the posterior 
 
Plate XXXII. 
 
 Velum Interposithm 
 
 Fig. 84. 
 
 •S. Corpus striatum (nucleus 
 
 caudatus). 
 L. Septum lucidum. 
 V. 5th ventricle. 
 
 T. Optic I 'huh I hi 'is. 
 
 H. Pes hippocampi. 
 Ma. Hippocampus major. 
 C. Eminentia collateralis. 
 
 Mi. Hippocampus minor. 
 
 Fornix cut. 
 Q. Pineal gland. 
 
 a a 
 
 Corpus callosum. 
 
 F. 
 
 T.S. 
 
 Fornix (anterior pillars) cut 
 Tien ia sem ir ircu la ris. 
 
 P. II. 
 H.Ma. 
 T.H. 
 F. I). 
 
 Pes hippocampi. 
 Hippoca mpus major. 
 Taenia hippocampi. 
 Fascia dentata. 
 
 C.P. 
 V.I. 
 V.G. 
 
 a 
 
 Choroid plexus. 
 Velum interposit a in. 
 Veins of Galen. 
 Cerebellum. 
 
AND ITS MEMBRANES. 147 
 
 commissure, above which is the base of the pineal 
 gland. At the sides the walls of the cavity are 
 formed by the inner or vertical faces of the optic 
 THALAMI, along each of which runs a bundle of 
 white fibres — the peduncles of the pineal gland. 
 Crossing the centre of this space, between the optic 
 thalami, is a broad, grey band — the middle, soft, or 
 GKEY COMMISSURE. 
 
 The 3rd ventricle is lined by epithelium similar to, 
 and continuous with that of the other ventricles. 
 On the roof, however, the epithelium is flattened, 
 and follows all the folds of the vascular fringes — the 
 choroid plexuses — which hang down along the 
 middle line from the under surface of the velum 
 interpositum (Fig. 94, page 164). The lateral walls 
 of bhe ventricle are covered by a layer of ependyma, 
 and the floor consists of grey matter continuous 
 with the grey matter of the aqueduct of Sylvius. 
 This grey matter comes to the surface of the 
 brain, at the posterior perforated spot, at the tuber 
 cinereum and at the lamina cinerea. 
 
 Communications. — The 3rd ventricle communi- 
 cates in front, through the foramina of Monro, with 
 the lateral ventricles; behind, through a narrow 
 passage — the aqueduct of Sylvius — with the 4th 
 ventricle ; and below, at the fore part of the floor, by 
 a conical-shaped passage with the infundibulum — 
 
 ITER AD INFUNDIBULUM. 
 
 The 4th ventricle was described at page 106. 
 
 The 5th Ventricle and the Septum Lucidum 
 
 (Dissection, page 141). — The Septum Lucidum is 
 
148 THE BRAIN 
 
 the thin, double, vertical, mesial partition which 
 separates the lateral ventricles from each other in 
 front (Fig. 85; Fig. 80, page 136; Fig. 93, page 164). 
 Triangular in shape, it fills up the interval between 
 the concavity of the knee-shaped bend of the corpus 
 callosum and the anterior pillars of the fornix. 
 Broader in front than behind, it gradually tapers 
 to a point where the corpus callosum and fornix 
 come in contact with each other. Between the two 
 layers of which it is composed it encloses a narrow 
 slit-like cavity, the 5th ventricle, or ventricle of 
 the septum. Internally, next the cavity of the 5th 
 ventricle, each lamina of the septum is composed of 
 a thin layer of grey matter, derived originally from 
 the grey matter of the cortex. Externally, next the 
 cavity of the lateral ventricles, each lamina of the 
 septum consists of white matter representing the 
 medullary or white matter of the hemispheres, and, 
 like the rest of the lateral ventricles, is covered by a 
 layer of ependyma and epithelium. The cavity of 
 the 5th ventricle itself is not lined by epithelium 
 like the other ventricles, nor, does it in any way 
 communicate with them. 
 
 As we shall see in the section on " Development," 
 the septum lucidum was originally part of the wall 
 of the hemispherical vesicle which became cut off 
 from the general surface by the development of 
 the corpus callosum and fornix. 
 
 The Yelum Interpositum (Dissection, page 141) 
 is a thin horizontal partition, which you have already 
 seen in the roof of the 3rd ventricle, and in the 
 
Third Ventricle 
 
 Plate XXXIII. 
 
 Fig. 85. 
 
 #/< r. 
 
 r.N 
 
 .4.6'. 
 
 C. S. 
 
 S.L. 
 
 T.S. 
 
 O.T. 
 
 C.Q 
 
 A. V. 
 
 Anterior cornv. 
 
 Corpus striatum (nucleus 
 
 caudatus). 
 Septum lucid urn. 
 Taenia sem icircularis. 
 Optic thalamus. 
 Corpora quadrigemina. 
 n. Nates. 
 t. Testes. 
 Arbor vitte. 
 
 C.C. 
 5th T 
 A. P. 
 C.A. 
 M.C. 
 3rd T 
 P. P. 
 P.G. 
 S.M. 
 4th V 
 P.O. 
 
 Corpus callosum (act). 
 r . 5th ventricle. 
 F. Anterior pillars of fornix. 
 
 Anterior commissure. 
 
 Middle commissure. 
 
 3rd ventricle. 
 
 Peduncles of pineal (/land. 
 
 Pineal gland. 
 
 Superior medullary velum. 
 
 4th cent rich:. 
 
 Posterior cornu. 
 
AND ITS MEMBRANES. 149 
 
 floor of the lateral ventricles (Plate XXXTIIa., page 
 150). It is a double fold of pia mater, which enters the 
 brain through what is known as the great transverse 
 fissure of the cerebrum, thus appearing in the 3rd 
 and lateral ventricles, though separated from their 
 cavities by the epithelium of the ependyma. Tri- 
 angular in shape, with the apex forwards and its 
 base backwards, the velum infcerpositum has the 
 same extent as the body of the fornix, so that 
 ix> reaches from the foramina of Monro in front 
 to the splenium of the corpus callosum behind, 
 beneath which, after investing the pineal gland, 
 it will be seen to be continuous with the rest 
 of the pia mater on the cerebrum and cerebellum 
 (Fig. 84, page 146). At the sides, the free edges of 
 the velum interpositum project into the floor of the 
 lateral ventricles, and rest on the upper surfaces of 
 the optic thalami, round the hinder ends of which 
 they pass down the descending horns of the lateral 
 ventricles, being still continuous with the pia mater 
 of the rest of the brain. 
 
 Choroid Plexus (Plate XXXII., page 146 ; Plate 
 XXXIIa., page 150). — The choroid plexus consists 
 of tortuous ramifications of small blood-vessels, 
 covered with vascular papillae, over which is a layer 
 of epithelium. Projecting downwards along the 
 middle line of the under aspect of the velum 
 interpositum are two of these vascular fringes — the 
 choroid plexuses of the 3rd ventricle — covered every- 
 where, however, by the epithelium which forms the 
 roof of that cavity. In each lateral margin of the 
 
150 THE BRAIN 
 
 velum interpositum are similar vascular fringes — the 
 choroid plexuses of the lateral ventricles, which 
 extend from the foramina of Monro in front (through 
 which they are continuous with the plexuses of the 
 3rd ventricle) to the apex of the descending cornu 
 of the lateral ventricles, where the velum inter- 
 positum, as we have just seen, becomes continuous 
 with the rest of the pia mater through the great 
 transverse fissure. As the vascular fringes pass down 
 the lateral horns they give a prolongation into the 
 posterior horn. 
 
 The Yeins of Galen (Plate XXXILl, page 150) 
 are two veins which gather the blood from the 
 corpora striata and choroid plexuses, and run back- 
 wards, side by side, between the layers of the velum 
 interpositum. Ultimately uniting to form a single 
 vein, they discharge their blood into the straight 
 sinus. 
 
 The Great Transverse Fissure of the cerebrum 
 (Fig. 84, page 146) is the large artificial cleft which 
 is made into the lateral ventricles when the pia 
 mater and choroid plexuses, with the epithelium 
 covering them, are torn away from the posterior 
 part of the brain beneath the fornix, and from the 
 descending cornua of the lateral ventricles. The 
 fissure thus formed is horse-shoe shaped : its central 
 part corresponds to the base of the fornix, its lateral 
 parts to the descending horns of the lateral ventricles. 
 Through this fissure the pia mater and choroid 
 plexuses project into the ventricles, though, as we 
 
Plate XXX 1 1 1. a 
 
 5th Ventrt 
 
 Form. 
 
 Fig. 1 
 Velum Tnteupositum 
 
 ucleus e'midatus. 
 J 
 
 yro id plexus, 
 
 r w&n\ interpositnm, 
 
 Veins of Galen 
 
 Fig. 2 
 Fascia dentata and Fornix 
 
 *|w of Lancisi 
 
 'orittx-,\- _: 
 
 {Band of QiacominL 
 
 Fascia dentata 
 
 Fasciola cinerea 
 
AND ITS MEMBRANES. 151 
 
 have before noted, everywhere separated from their 
 cavity by the epithelium which covers them. 
 
 The convex or posterior lip of the fissure is 
 bounded (a) near the middle line by the posterior 
 part of the corpus callosum and fornix; (b) on 
 each side by the free margins of the hemisphere 
 — viz., the fimbria and the fascia dentata, 
 
 The concave or anterior lip of the fissure is bounded 
 (a) near the middle line by the corpora quadrige- 
 mina and cerebral peduncles; (b) on each side by 
 the posterior part of the optic thalami. 
 
 II.— BASAL GANGLIA. 
 
 Under this heading are usually described the two 
 large grey masses at the base of the brain — the 
 corpora striata and the optic thalami. They are, 
 however, quite distinct in their origin. The term 
 moreover, is often made to include the corpora 
 quadrigemina, the corpora geniculata, and the locus 
 niger. The corpora geniculata will be described 
 witli optic thalami, and the corpora quadrigemina 
 with the crura cerebri (page 165). The locus niger 
 was described with the 4th ventricle (page 106). 
 
 1. The Corpora Striata are two in number, one 
 in each hemisphere, and are each sub-divided into two 
 parts — an intra-ventricidar portion, which appears 
 in the floor of the lateral ventricles ; and an extra- 
 ventricular portion, hidden in the white substance 
 of the hemisphere (Fig. 86, page 154). 
 
152 THE BRAIN 
 
 The Nucleus Caudatus — the intra-ventricular 
 portion of the corpus striatum — so called from its 
 shape, has been described as a pear-shaped, kite- 
 shaped, pyriform or pyramidal eminence, of a pinkish 
 grey colour, which appears in the fore part of 
 the floor of the lateral ventricles. Covered on the 
 surface by a layer of white substance, each nucleus 
 consists of a grey core streaked with white fibres, 
 hence the name corpus striatum. Its larger end or 
 head is directed forwards, and its posterior end or 
 tail, gradually tapering to a point, passes backwards 
 outside the optic thalamus, where it turns downwards, 
 forwards, and outwards, into the roof of the descend- 
 ing horn of the lateral ventricle, and can be traced 
 as far as the tip of the temporal lobe. It may thus 
 be said to form an arch with its concavity forwards, 
 one end of the arch being formed by the head of the 
 nucleus, the other end by its tail (Fig. 90, page 160). 
 
 The Nucleus Lenticularis — the extra-ventricu- 
 lar part of the corpus striatum — can only be seen 
 in sections of the hemispheres (Fig. 86, page 154; 
 Fig. 93, page 164). In horizontal sections it appears 
 as a longitudinal grey mass, shaped like a double 
 convex lens (lenticularis). It is placed external 
 to the nucleus caudatus, and is separated from it 
 by a strand of white nerve fibres, called the inner 
 capsule (Fig. 86, page 154 ; Fig. 93, page 164). In ver- 
 tical transverse section it is triangular in shape, and 
 is intersected by two white laminae, which divide it 
 into three parallel strands — internal, middle, and 
 externa], of a somewhat different colour (Figs. 86, 93). 
 
AND ITS MEMBRANES. 153 
 
 The internal and middle are pale in colour, hence 
 the name globus pallidas applied to them ; the ex- 
 ternal segment is darker, and is called the putamen 
 — clippings, shells (Fig. 93). The nucleus caudatus 
 and the nucleus lenticularis are continuous with 
 each other in front and below. 
 
 Claustrum. — External to the nucleus lenticularis 
 will be seen a narrow band or streak of grey matter — 
 the claustrum — separated from the nucleus lenticu- 
 laris by a white strand of fibres, the outer capsule 
 (Fig. 86), and from the contiguous grey matter of the 
 isle of Reil by a second white strand. Thus, enumer- 
 ated from within outwards we have : — 
 
 1. The nucleus caudatus. 
 
 2. The inner capsule. 
 
 3 The nucleus lenticularis. 
 
 4. The outer capsule. 
 
 5. The claustrum. 
 
 6. A strand of white fibres — white matter of the 
 isle of Reil. 
 
 7. The grey matter of the surface — grey matter of 
 the isle of Reil. 
 
 The nucleus lenticularis, the claustrum, and the 
 tail of the caudate nucleus are continuous below and 
 in front with the amygdaloid nucleus, which is a 
 thickened part of the cortex of the temporal lobe. 
 It is seen at the anterior end of the descending horn 
 of the lateral ventricles. 
 
 2. The Optic Thalami are two large, oval, convex 
 prominences placed above the crura cerebri, but 
 behind and internal to the corpora striata, from which 
 
154 THE BRAIN 
 
 they are separated by the taenia semicircularis. 
 Forming 1 part of the floor of the lateral ventricle 
 and the walls of the 3rd ventricle, each optic thala- 
 mus consists of a central grey core, covered on the 
 surface by a stratum of white matter. They have 
 four surfaces and two ends, and, where they enter 
 into the formation of the ventricular cavities, they 
 are clothed by ependyma and epithelium. Their 
 anterior end is rounded — anterior tubercle — and 
 their posterior and external end swells out into a 
 prominence — the posterior tubercle or pulvinar , 
 which overhangs the brachia of the corpora quad- 
 rigemina (Fig. 98, page 168); and the two oval 
 nodules called the corpora geniculates interna and 
 externa (Fig. 98). The pulvinar, where it is free, 
 also forms part of the roof of the descending horn 
 of the lateral ventricle. 
 
 The upper surface of the thalami optici appears in 
 the floor of the lateral ventricles, and resting upon 
 it are the velum interpositum, the choroid plexus, and 
 the edge of the fornix. The under surface, in its 
 hinder part, is placed above the crus cerebri (teg- 
 mentum, Fig. 98), while more in front it lies over 
 the c >rpus albicans and the tuber cinereum. 
 
 The inner (mesial) surfaces of the optic thalami 
 are vertical and form the lateral walls of the 3rd 
 ventricle. Along them run the peduncles of the 
 pineal gland, and above these we see a shallow groove, 
 the sulcus of Monro, which marks the upper limit of 
 this surface. Passing transversely between the 
 optic thalami is the grey or soft commissure. Exter- 
 nally the optic thalami blend with the substance of 
 
Plate XXXIV. 
 
 c'ai'sules 
 Fig. 86. 
 
 o.r. 
 
 H.Mi. 
 
 i 
 
 a 
 
 T. 
 0. 
 
 IF. 
 V. 
 T. 
 K. 
 /'. 
 
 .0. 
 
 s. 
 
 a 
 
 s. 
 
 T. 
 Ma. 
 P. 
 H. 
 
 a 
 
 - m 
 
 Anterior^cornu. 
 
 Corpus vt> iatum (nucleus 
 
 candatus). 
 Corpus callosum. 
 Taenia semicircidaris. 
 Optic thalamus. 
 Hippocampus major. 
 Choroid plexus. 
 Teen ia It ippocampi. 
 Em i n en t ia collatera I is. 
 Posterior cornu. 
 
 N.L. 
 E.G. 
 
 a 
 
 w. I. 
 Gl 
 
 p. 
 
 o.r. 
 
 H.Mi. 
 
 Nucleus candatus. 
 Interior capsule. 
 
 a. Anterior limb. 
 
 (/. Genu. 
 
 p. Posterior limb. 
 Nucleus lenticularis. 
 External capsule. 
 Claustrum. 
 
 White matter of hie of Rt il. 
 Grey matter of Isle of Reil. 
 Putai 
 
 Optic thalamus. 
 Hippocampus min or. 
 
AND ITS MEMBRANES. 155 
 
 the hemispheres, their outer limit being the posterior 
 part of the inner capsule and the nucleus caudatus. 
 
 In front of the optic thalami are the nucleus 
 caudatus and the anterior pillars of the fornix (Fig. 
 80, page 136; and Fig. 85, page 148), the latter 
 passing to the base of the brain. Between the optic 
 thalami and the pillars of the fornix are the slit-like 
 clefts — the foramina of Monro (Figs. 80, 85). 
 
 Behind the optic thalami are the posterior pillars 
 of the fornix, winding down the descending horn of 
 the lateral ventricle (Fig. 83, page 144). 
 
 Structure. — The optic thalami are chiefly com- 
 posed of grey matter arranged as three nuclei — 
 anterior, outer, and inner (Fig. 86, page 154). The 
 course and relations of its white tracts are not yet 
 understood. 
 
 Both the functions and the morphology of the 
 basal ganglia are undecided. Anatomical appear- 
 ances seem to be in harmony with the view that 
 these ganglia are terminal stations of certain tracts 
 of the cerebral peduncles. In man they may prob- 
 ably take the place of the corpora quadrigemina 
 in the frog, and, like them, exercise a restraining 
 influence on the reflex centres of the spinal cord. 
 
 Corpora Geniculata. — Below and external to 
 the pulvinar are, as we have said, two pairs of oval 
 eminences — the corpora geniculata interna, and 
 externa — the internal being below and mesial to 
 the external, and separated from it by a band of 
 white flbres, one of the roots of the optic tract 
 (Fig. 98, page 168). 
 
156 THE BRAIN 
 
 These geniculate bodies consist of a grey core, 
 and a white cortex. From each proceeds a white 
 band which joins the optic tracts. The band from 
 the internal pair has, however, nothing to do with 
 sight. Similar bands connect the external bodies 
 to the anterior, and the internal to the posterior 
 pairs of corpora quadrigemina. 
 
 The Pineal Gland (or body) is a reddish, vascular, 
 oval body, situated in the middle line above the 
 orifice of the aqueduct of Sylvius, in the longi- 
 tudinal groove between the corpora quadrigemina. 
 Firmly attached to the velum interpositum, which 
 gives it a special covering (Fig. 84, page 146), this 
 so-called gland is a backward prolongation of the 3rd 
 ventricle and is connected to the cerebrum by two 
 white bands — the 'peduncles — which, as we have 
 already seen, run one along the inner surface of each 
 optic thalamus. The peduncles end in front by 
 joining the anterior pillars of the fornix. On its 
 ventral aspect, the pineal gland is connected with 
 the posterior commissure. 
 
 In Structure the pineal gland is composed of 
 follicles, separated by connective tissue, and filled 
 with cells (neuroglia- cells), calcareous particles 
 (brain sand), and corpora amylacea. It is probably 
 a rudimentary eye. 
 
AND ITS MEMBRANES. 157 
 
 IH._WHITE STRANDS. 
 
 White Matter. — Beneath the grey matter lies 
 the white nerve substance of the brain, which, like 
 that of the spinal cord, is composed both of grey and 
 of white or medullated nerve fibres. The medullated 
 fibres are transverse and longitudinal, the latter pre- 
 dominating. They are the axis-cylinder processes of 
 the nerve cells of the various layers of the cortex, or 
 of cells at lower levels of the cerebro-spinal system. 
 
 They are divisible into three groups. 
 
 (1) Commissural fibres, which connect identical 
 parts of the two hemispheres. 
 
 (2) Association fibres, which connect different parts 
 of the same hemisphere. 
 
 (3) Projection fibres, which connect the grey 
 matter of the hemispheres with the lower parts of 
 the cerebro-spinal axis. 
 
 I. The COMMISSURES of the brain are the corpus 
 callosum, the anterior, middle, and posterior com- 
 missures. 
 
 CORPUS CALLOSUM. 
 (Fig. 80, Plate XXVII [., page 136.) 
 
 The Corpus Callosum. — As you already know, 
 the corpus callosum is the white transverse band of 
 nerve fibres which arches from before backwards, in 
 the middle line, between the cerebral hemispheres, 
 and connects them together. About four inches 
 long, it forms the floor of the great longitudinal 
 fissure and the roof of the lateral ventricles, and 
 
158 THE BRAIN 
 
 reaches further forwards than backwards. It is 
 thicker afc the ends than in the middle of its 
 extent, and is thickest and widest behind. 
 
 Anteriorly, it turns downwards and backwards 
 upon itself in the great longitudinal fissure, making 
 a knee-shaped bend — the genu (Fig. 80, page 136). 
 Becoming gradually smaller it then forms a narrow 
 median band — the rostrum (Fig. 80) — which ends 
 below at the base of the brain by bifurcating into 
 two tapering processes — the peduncles — which, you 
 will remember, could be traced to the anterior per- 
 forated spot at the root of the fissure of Sylvius, and 
 were there lost. Between them lies the lamina 
 cinerea. 
 
 Posteriorly, on the other hand, the corpus 
 callosum ends in a thickened, free, rounded border 
 or base — the splenium (Fig. 80). From the outer 
 ends of the splenium two horn-shaped bundles of 
 fibres, the forceps major, diverge into the occipital 
 lobes ; and two similar bands, the forceps minor, can 
 be traced from the genu into the frontal lobes. 
 
 The upper surface of the corpus callosum is 
 marked along the middle line by a longitudinal 
 groove — the raphe— parallel to which, on each side, 
 you will see two or more faint lines — the median 
 longitudinal strice (nerves of Lancisi). Exter- 
 nally, under cover of the overhanging edge of the 
 gyrus fornicatus, are similar longitudinal striae — 
 lateral longitudinal strice (taeniae tectae, covered 
 bands). The median striae, when traced forwards, 
 are joined in iront by a prolongation of the lateral 
 striae, and pass with them round the anterior end 
 
AND ITS MEMBRANES. 159 
 
 of the corpus callosum to the peduncles of the corpus 
 callosum ; behind, on the other hand, the striae can 
 be traced into a fine grey lamina — the fasciola cin- 
 erea — and then into the fascia dentata (Fig 2, 
 page 150). The striae longitudinales, the fasciola 
 cinerea, and the fascia dentata form the abortive 
 convolution (connected with the sense of smell), 
 and referred to on page 127. 
 
 The under surface of the corpus callosum rests, 
 in the posterior half of its extent, upon the upper 
 surface of the body of the fornix, to which it is closely 
 adherent, especially near the splenium. In its 
 anterior half, it is connected below with the vertical 
 mesial partition — the septum lucid um — filling up, 
 as we have seen, the space left between the fornix 
 and concavity of the knee-shaped bend of the corpus 
 callosum (Fig. 89, page 160). 
 
 Laterally, the transverse fibres of the corpus 
 callosum form the roof of the lateral ventricles, and 
 diverge into the white substance of fche hemispheres. 
 
 Structure. — The corpus callosum consists of 
 white nerve fibres, which are in the main transverse, 
 a few only being longitudinal. As they pass into 
 the hemispheres they diverge in all directions, and 
 probably go, along with the fibres of the corona 
 radiata, to the grey matter of the cortex. They 
 start from some of the pyramidal cells of the one or 
 other side of the cortex, and end in ramifications in 
 the pyramidal and molecular cell layers of the 
 opposite hemisphere. Many of them are collaterals 
 of the projection systems of fibres. 
 
160 THE BRAIN 
 
 It is worthy of note that the corpus callosum may 
 be absent without any ill effect (Holden). 
 
 The anterior, middle, and posterior commissures 
 are connected with the 3rd ventricle (Fig. 80, page 
 136). 
 
 The Anterior Commissure is a round white cord 
 which passes transversely across the middle line in 
 front of the anterior pillars of the fornix, between 
 them and the lamina terminalis. It connects 
 together the limbic lobes of the two sides. 
 
 The Middle (Grey) Commissure crosses the 3rd 
 ventricle between the optic thalami. It is a delicate 
 band of grey matter connected with the grey matter 
 of the thalami optici. 
 
 The Posterior Commissure, situated in front of 
 and below the pineal gland, but above the com- 
 mencement of the passage into the 4th ventricle, is 
 a rounded band which stretches between the optic 
 thalami. It is not known whence its fibres come 
 nor where they end. 
 
 II. The association fibres (see page 157). — Of 
 these the chief is the fornix (Figs. 89, 91, page 160; 
 Plate XXXIIIa., Fig. 2, page 150). 
 
 THE FORNIX. 
 
 Beneath the corpus callosum, and more or less 
 blended with it, especially behind, is a longitudinal 
 system of association fibres — the FORNIX. It is an 
 arched white band, which can be traced from the 
 
Plate XXXV. 
 
 Fio. 87. 
 
 Retina. 
 
 Fig. 88. 
 
 A ntertor nucleus. 
 
 Eding^rs nucleus. 
 
 A K ^- Posterior nucleus. 
 
 Optic 
 yimmissure. 
 
 Optic tract. 
 /Optic thalamux. 
 
 .Corpora geniculata. 
 
 Corpora 
 auadriger,nina. 
 
 Part of fillet. 
 
 Nucleus of 4th rurve. DlAGBA * ° F °PTIC NBBVB8 AND 
 i J Optic Tract. 
 
 i 
 
 | Septum lucidum 
 
 Anterior 
 commissure. 
 
 Diagram of Nuclei of 3rd 
 a*jd 4th Nerve. 
 
 Corpus albicans. 
 
 Fornix. 
 Bundle of Vioq a" Azt/r . 
 
 Fig. 90. 
 
 Gyrus fornicatus. 
 
 Genu. 
 
 5tk vent-ride 
 Fornix. 
 
 Uncus. 
 
 Fig. 91. 
 
 Splenium. 
 
 <us caudatas 
 
 g. of the shape of the nucleus 
 caudatns. 
 
 Fimbria. -' 
 
 Fascia dentata. 
 
 Tvberculum 
 fasciae dentata. 
 
 Fio. of Fornix— the Optic 
 Thalamus removed. 
 
AND ITS MEMBRANES. 161 
 
 hippocampus major to the corpora albicantia. The 
 fibres of whicli it is composed spring as two riband- 
 like bands — the posterior pillars of the fornix or 
 fimbrle — one on each side, from the free surface 
 of the hippocampus major, in the descending horn 
 of the lateral ventricles (Fig. 91). Ascending from 
 the concave edge of the hippocampus the two pillars 
 pass round the posterior ends of the optic thalamic 
 and, converging towards each other, meet in the 
 middle line to form a wide, flattened, triangular- 
 shaped band — the body of the fornix — which has 
 its apex directed forwards and its base backwards 
 towards the splenium. 
 
 Superiorly, the body of the fornix is in contact 
 with the under surface of the corpus callosum ; 
 inferiorly, it lies on the delicate lamina — the velum 
 interpositum. Behind, by its -base it blends with 
 the splenium. In front, its fibres diverge and pass 
 downwards and forwards from the apex of the body, 
 as two cylindrical processes — lying side by side — the 
 anterior pillars of the fornix, which can be traced 
 to the base of the brain, to the corpora albicantia. 
 In this course they lie first in front of, then in the 
 substance of, the optic thalami, but behind the an- 
 terior commissure which separates them from the 
 lamina terminalis. At the base of the brain, the 
 pillars make an 8-shaped twist on themselves, form 
 the cortex of the corpora albicantia, and end in the 
 grey core of these white bodies, from which fibres 
 re-ascend, as the bundle of Vicq d' Azyr, to the optic 
 thalami (Fig. 89, page 160). As they descend in front 
 of the optic thalami, the anterior pillars of the fornix 
 
 M 
 
1 62 THE BRAIN 
 
 form, as already explained, one of the boundaries of 
 the small circular foramina — the foramina of Monro. 
 
 At the sides, the fornix appears as a thin, free, 
 sickle-shaped edge, which rests upon the velum 
 interpositum and the optic thalamus, and enters into 
 the formation of the floor of the lateral ventricles. 
 
 Originally the fornix consisted of two separate 
 divisions, right and left, but these ultimately fuse 
 in the middle line to form the body, their ends 
 remaining free as the anterior and the posterior 
 pillars of the fornix. 
 
 Where the posterior pillars of the fornix diverge 
 from each other, there will be found a triangular 
 space filled up by transverse fibres of white matter. 
 It is called the lyra. Sometimes the fornix is 
 entirely blended with the posterior part of the under 
 surface of the corpus callosum: at other times a 
 small interval, called the ventricle of Verga, is left 
 between them. 
 
 The Taenia Semicircularis is the narrow white 
 band which lies in the groove between the nucleus 
 caudatus and the optic thalamus. In front, it joins 
 the corresponding pillar of the fornix ; behind, it 
 passes into the substance of the roof of the 
 descending horn of the lateral ventricle (nucleus 
 amygdala?). 
 
 III. Projection fibres (see page 157). — The 
 chief projection systems of fibres are contained in 
 the internal and external capsules. 
 
AND ITS MEMBRANES. 163 
 
 INTERNAL AND EXTERNAL CAPSULES. 
 
 (Fig. 86, Plate XXXIV, page 154). 
 
 In treating of the Basal Ganglia you will re- 
 member we referred to two strands of white fibres, 
 the INNER and outer CAPSULES, the former lying- 
 internal to, the latter external to the nucleus len- 
 ticularis. Of these so-called capsules, the internal is 
 of the greatest clinical importance, for through it 
 pass the chief motor and sensory tracts. 
 
 The Internal Capsules (Fig. 86, page 154).— 
 Seen in horizontal section each internal capsule 
 appears as a longitudinal semi-lunar shaped band of 
 white matter with its convexity directed towards 
 the middle line. It can be divided into three 
 portions — an anterior, a middle, and a posterior. 
 The anterior division lies between the nucleus 
 caudatus and the nucleus lenticularis; the posterior 
 DIVISION lies between the optic thalamus and the 
 nucleus lenticularis, and forms with the anterior 
 division a sharp angle, or knee-shaped bend — the 
 middle portion, called the genu. The inner capsule 
 therefore has three parts — (1) a knee-shaped bend, 
 the genu; (2) a part in front of the knee; and (3) 
 a part behind the knee. This capsule contains all 
 the fibres of the crusta of the cms cerebri of the same 
 side except those that go to the nucleus lenticularis. 
 Emeroioq- from between the nucleus lenticularis and 
 the tail of the caudate nucleus, and reinforced by 
 fibres from the optic thalamus and the region below 
 
1 64 THE BRAIN 
 
 it, the fibres of the crusta form a radiating, hollow, 
 fan-shaped mass of nerve fibres — the COROXA RADI- 
 ATA — which spread out into the cerebral cortex. 
 
 In the internal capsule there are four sets of 
 fibres. 
 
 (1) The tracts forming the knee, and the anterior 
 two-thirds of the posterior limb of the inner capsule 
 are motor in function, and are in relation respec- 
 tively, from before backwards, with the centres for 
 the ocular, oro-lingual, facial, brachial, trunk, and 
 crural muscles. Injury to this portion of the inner 
 capsule results in loss of motion on the opposite side 
 of the bodv. 
 
 (2) Mingled with the motor fibres are others 
 which connect the central convolutions (ascending 
 frontal and parietal) with the nucleus pontis, and, 
 through this nucleus, with the cerebellum of the 
 opposite side. This tract is called the secondary 
 motor tract, or cortico-pontine tract (Plate XLL, 
 page 184). It is ultimately connected, though the 
 exact route is unknown, with the anterior spinal 
 nerve roots of the opposite side to that at which 
 it left the brain. 
 
 (3) The posterior third or more of the hinder 
 division of the inner capsule contains sensory 
 strands ; for, when injured or diseased, there ensues 
 loss of sensation, general and special, on the opposite 
 side of the body, the motor powers not being affected, 
 unless the lesion implicates the motor tracts also. 
 
 (4) The anterior limb of the internal capsule, in 
 front of the knee-shaped bend, carries fibres from 
 
Fio. 92. 
 
 Lateral ventricle. 
 
 Corpus callomm. 
 
 Isle of Hell. - 
 
 Arteries - - 
 nun striatum 
 
 •ten cerebral. 
 
 Plate XXXVI. 
 
 Nucleus caudattu. 
 
 Internal capsule. 
 
 Nucleus lenlicularis. 
 External capsule. 
 
 Claustrum. 
 3rd ventricle. 
 
 Sylvian artery 
 (middle cerebral). 
 
 Internal carotid. 
 Fig. 93. 
 
 nrpus callosum 
 
 Font ix 
 
 Pvtamen 
 
 Globus 
 pall id u. 
 
 }ptic thalamu 
 
 Septum lucidum. 
 
 Nucleus caudatus. 
 
 Lateral ventricle, 
 ivterior capsule 
 
 Nucleus 
 lenlicularis. 
 -Claustrum. 
 . Isle of Rett. 
 
 - Anterior 
 commissure. 
 
 mens caudatus. 
 
 Fig ^4. 
 Fornix. ' Corpus callosum. 
 
 Choroid 
 ^^ - : Wk~ plexus. 
 
 f Fimbria. 
 
 Fascia den tata . • 
 
 Fig. 95. 
 
 iptic thalamus 
 
 Crura cerebri. 
 
 3rd ventricle. 
 
 Gyrus hipptocampi 
 
 Choroid plexus. 
 
AND ITS MEMBRANES. 165 
 
 the sensorial areas — tactile, visual, auditory, and 
 olfactory — to the optic thalamus: they are called 
 the eortico-thalamic fibres. 
 
 The External Capsule lies between the nucleus 
 lenticularis and the claustrum. The tracts which 
 compose it, and their functions, are undecided. 
 
 Fig. 92, Plate XXXVI, page 164, will give you an 
 idea of the relations of the Sylvian artery, and the 
 distribution of its branches to the capsules, and to 
 the contiguous nuclei. When describing the middle 
 cerebral artery, page 58, we saw that it gave 
 off a ganglionic system of arteries — the lenticular, 
 lenticulo-striate, and the lenticulo-optic. The len- 
 ticular artery supplies the inner and middle parts of 
 the lenticular nucleus and the internal capsule ; the 
 lenticido -striate artery is distributed to the outer 
 part of the lenticular nucleus, to the external 
 capsule, and to the caudate nucleus ; the lenticulo- 
 optic artery goes to the outer and posterior part of 
 the lenticular nucleus and to the outer part of the 
 optic thalamus. The lenticulo-striate artery is called 
 the artery of cerebral haemorrhage. 
 
 IV— CRURA CEREBRI. 
 
 The crura cerebri belongs to that sub-division of 
 the brain called the mesencephalon. This sub- 
 division also comprises the corpora quadrigemina 
 and the aqueduct of Sylvius. 
 
 I. The Crura Cerebri, or Cerebral Peduncles 
 
 (Fig.- 46, page 66), are the two cylindrical masses 
 
1 66 THE BRAIN 
 
 which you see springing in front from the upper 
 margin of the pons. Diverging from each other, 
 and enlarging as they ascend, they soon enter the 
 base of the cerebral hemispheres, burying themselves 
 in the optic thalami. 
 
 Between the peduncles, where they diverge from 
 each other, will be found the posterior perforated 
 spot and two little white bodies, the corpora 
 albicantia (Fig. 98, page 168) ; winding round the 
 outer side of the crura are the optic tracts above, 
 and the 4th nerves below; on their inner side is 
 a groove, the oculomotor groove, from which the 
 3rd nerve takes its superficial origin ; and on their 
 dorsal aspect are four rounded tubercles — the cor- 
 pora quadrigemina — with the lamina quadrigemina, 
 beneath which runs the aqueduct of Sylvius. 
 
 Structure. — A section at right angles to the 
 crura cerebri will show you that they each consist 
 of two portions, a posterior or dorsal, called the 
 tegmentum, and an anterior or ventral, called 
 the crusta, pes or basis. These two parts of the 
 crura are separated from each other by a narrow 
 stratum of grey matter, called, from its dark colour, 
 the LOCUS NIGER (substantia nigra), the position of 
 which is indicated on the surface by the oculomotor 
 groove internally, and by another slight groove, the 
 lateral sulcus, externally (Fig. 61, page 90). 
 
 (1) The Tegmentum (Fig. 61, page 90), is the larger 
 division of the crus, and, like the formatio reticularis 
 of the medulla and pons, is composed of a reticulum 
 of longitudinal and transverse fibres interspersed with 
 
AND ITS MEMBRANES. 167 
 
 grey matter. We shall study, first, the grey, then the 
 white matter of the tegmentum. 
 
 (a) The grey matter of the tegmentum consists 
 of scattered cells, and of two definite collections, the 
 one being the grey matter of the aqueduct of 
 Sylvius, the other lying beneath the anterior pair 
 of corpora quadrigemina, and known as the RED 
 nucleus or nucleus tegmenti (Fig, 61, page 90). 
 This latter nucleus consists of multipolar nerve 
 cells, and is probably the primary termination of 
 the superior cerebellar peduncles. 
 
 (6) The white matter. — The longitudinal fibres 
 come from the anterior and lateral columns of the 
 spinal cord, and form the superior cerebellar ped- 
 uncles. The best marked tracts are the posterior 
 LONGITUDINAL BUNDLE and the TRACT OF THE 
 FILLET; the former appearing in sections of the 
 crura as two well marked strands, one on each side 
 of the aqueduct of Sylvius ; the latter, the fillet, 
 appearing as a tract of oblique white fibres on the 
 outside of the red nucleus (Fig. 61). The transverse 
 fibres are as yet little understood. 
 
 (2) The Crusta, Pes or Basis — the ventral part of 
 the peduncles — lies in front of the locus niger, and 
 is chiefly composed of the pyramidal tracts of the 
 medulla, though other strands are superadded, for 
 transverse sections of the crusta are much larger 
 than those of the pyramids. The following are the 
 various tracts of fibres of the crusta : — 
 
 (1) The pyramidal tracts, motor strands from the 
 cortex, occupy the middle and inner part of the 
 
1 68 THE BRAIN 
 
 crusta. They are divisible into two parts — an ex- 
 ternal, the pyramidal tracts proper; an internal, the 
 geniculate fascicuhis. The latter comes from the 
 genu of the internal capsule, and contains fibres 
 connected with the motor part of the 5th nerve, 
 with the 7th and 12th nerves, and hence with the 
 muscles of mastication, of the face and of the 
 tongue. (See Fig. 61, Plate XIX., page 90). 
 
 (b) The cortico -pontine tract, which passes from 
 the cerebral cortex to the nucleus pontis, and then 
 to the opposite half of the cerebellum. As they 
 travel through the cms, these cortico-pontine fibres 
 form two groups ; the one occupies the posterior 
 external part of the crusta, and is called the 
 fasciculus lateralis ; the other group mingles 
 with the geniculate and pyramidal fibres. 
 
 (c) The caudate cerebellar fibres, or boundary 
 layer of the pes, probably come from the caudate 
 nucleus. 
 
 The relative positions of these tracts to each other 
 will be understood by reference to Fig. 61, page 90. 
 
 (3) The Substantia Nigra is a semi-lunar band 
 of grey matter placed between the two divisions of 
 the crus. It is characterised by darkly pigmented 
 cells — hence the name. Through it pass the roots of 
 the 3rd nerve before they emerge at the oculomotor 
 groove (Fig. 61). Its connections and uses are un- 
 known. 
 
 The two pedes are quite distinct from each other, 
 whereas the two tegmenta are merely separated by 
 the median raphe. 
 
Hex cerebri. Fj<:. 96. 
 
 •-— Optic thalamus, 
 
 Plate XXXVII. 
 
 Fig. 97. 
 
 Lateral fill let/ 
 
 uperinr olive. ■'* 
 Fillet 
 
 Inferior olive. 
 
 ucleus gracili 
 
 .Corpora Quadrigemina 
 
 3rd nerve 
 
 Cerebellum. 
 
 Inferior peduncles 
 of cerebellum. 
 
 Vucleus euneA'Ms. 
 
 Clarke's column. . 
 
 vctory bulb 
 
 Crossed 
 pyramidal tract 
 
 —\ Fasciculus of Gott. 
 
 Lateral cerebellar tract. 
 Fasciculus of Burdock. 
 
 rpora \ 
 
 \nilata externa. \ 
 
 Mra gejiiculata interna. 
 
 ^Posterior root. 
 
 f\ n ,t Cerebellum. 
 
 Corpus callosum. 
 
 Corpus dentatum. 
 
 mi Anterior perforated spot. 
 
 Corpora albieantia. 
 
 Crura cerebri. 
 
 Lateral - 
 cerebellar tract 
 
 Anterior external 
 arciform fibres. " 
 '\ Pulvinar. 
 
 Corpora quadrigemina. 
 and brachia 
 
 -Fillet. 
 
 ~ Posterior 
 longitudinal 
 bundle. 
 
 Funiculus 
 gracilis. 
 
 Fig. 99. 
 
 \ Superior 
 cerebellar peduncle 
 
 Restiforni body. 
 Cevebello-olivary tract. 
 
 Inferior olive. 
 
 "Posterior external 
 
 arciform fibres. 
 
 Pyramids. 
 
AND ITS MEMBRANES. 169 
 
 II. The Corpora Quadrigemina (Fig. 85, page 148) 
 are four rounded tubercles, separated from each other 
 by two grooves, the one longitudinal, the other trans- 
 verse. They are placed in pairs, on each side of the 
 middle line, below and behind the pineal gland and 
 above the aqueduct of Sylvius. The anterior pair, 
 the larger, are called the nates, the posterior pair, 
 the smaller, the testes, and they rest upon a thin 
 lamina — the lamina quadrigemina — beneath which 
 runs the aqueduct of Sylvius. Laterally, each pair 
 is prolonged into two white bands or cords — the an- 
 terior and posterior brachia (Fig. 98, page 168). 
 The anterior brachium passes between the pul- 
 vinar and the corpus geniculatum internum, thence 
 to the external geniculate body and to the optic 
 tract, of which it is the direct root; the posterior 
 brachium runs forwards and outwards, and in part 
 penetrates the corpus geniculatum internum, and 
 in part passes into the lateral sulcus, a groove by 
 which the corpora quadrigemina are separated from 
 the crura cerebri. 
 
 Structure. — The anterior pair of corpora quad- 
 rigemina consist of several layers of grey and white 
 matter ; the posterior pair of a central grey core and 
 of a white cortex. Homologues of the corpora 
 quadrigemina exist in all vertebrata. They invari- 
 ably give origin to the optic nerves, and in size bear 
 a direct relation to the animal's power of sight. 
 
 In birds there are only two corpora, but they are 
 very large, especially in those birds which have 
 great powers of sight. In the mole the posterior 
 
170 THE BRAIN 
 
 pair are well developed; the anterior pair are 
 rudimentary. 
 
 Injury to the optic nerves causes the anterior pair 
 to waste, but leaves the posterior pair unaltered. 
 
 III. The Aqueduct of Sylvius is the narrow pas- 
 sage between the 3rd and 4th ventricles (Fig. 80, page 
 136). Above, it is roofed over by a thin lamina — 
 lamina quadrigemina — so called because it supports 
 the corpora quadrigemina. Its floor and lateral 
 walls are formed by the dorsal part of the cerebral 
 peduncles. Internally it is lined by ciliated co- 
 lumnar epithelium, outside which is a thick layer 
 of grey matter continuous with the grey matter — 
 (locus casruleus) — of the 4th ventricle. From this 
 grey matter arise the 3rd, the 4th, and part of the 
 5th nerves. 
 
 Summary. — Thus we see that the cerebrum con- 
 sists of a convoluted cortex, of basal ganglia, of 
 ventricles united by narrow passages, and of white 
 strands formed of commissural, projection, and 
 association fibres. 
 
 ORIGINS OF THE CRANIAL NERVES. 
 
 The Cranial Nerves have superficial and deep 
 origins. 
 
 By the term superficial origins is meant the 
 points at which the nerves are attached to the 
 surface of the brain. Their deep origins (sub- 
 cortical) are the several deep-seated nuclei to or 
 from which they can ultimately be traced. Each 
 
AND ITS MEMBRANES. 171 
 
 nerve has, moreover, a cortical representation (cortical 
 origin). 
 
 1. The Olfactory Nerves — 1st pair — spring from 
 the olfactory bulbs, and pass through the holes in 
 the cribriform plate of the ethmoid, to be distributed 
 to the upper part of the olfactory mucous membrane. 
 The roots of the olfactory peduncles have already 
 been noticed (page 118). They are two in number, 
 a mesial root and a lateral root. The mesial root 
 passes in part to the callosal gyrus (gyrus of the 
 corpus callosum), in part to the area of Broca : the 
 lateral or outer root can be traced to the extremity of 
 the temporal lobe, where it blends with the anterior 
 end of the gyrus hippocampi. By means of these two 
 roots the olfactory peduncle is connected with the 
 two ends of the limbic lobe. The trigonum olfac- 
 torium is sometimes regarded as a third root, and a 
 well-marked bundle of fibres can be traced to it from 
 the peduncle. Besides the above distinct roots, some 
 of the fibres of the olfactory tract go to the anterior 
 end of the thalamus, others pass through the anterior 
 commissure to the opposite cerebral cortex, and to 
 the opposite olfactory bulb. 
 
 It is worthy of note that in animals with well- 
 developed organs of smell, the gyrus hippocampi, 
 the stria? longitudinales, and the fascia dentata are 
 well marked ; whereas in man, with small olfactory 
 lobes, they are relatively small. Injury to the 
 olfactory bulb causes atrophy of the uncinate 
 gyrus of the same side. This gyrus, therefore, is 
 the cortical centre. 
 
1 72 THE BRAIN 
 
 2. The Optic Nerves — 2nd pair — can be traced 
 back from the eyeballs, through the optic foramina 
 to the outer sides of a mesial band — the optic com- 
 missure — in which they partially decussate. From 
 this commissure they run backwards as the optic 
 tracts round the outer sides of the crura cerebri, 
 and then bifurcate into an internal limb which 
 goes to the corpora geniculata interna, and an 
 external limb which can be traced to the pulvinar, 
 to' the corpora geniculata externa, and to the 
 anterior pair of corpora quadrigemina (Fig. 98, 
 page 168). In the optic tracts and commissure there 
 are four sets of fibres — (1) an outer set, the direct 
 fasciculus, to the eyeballs of the same side ; (2) a 
 middle set, which come from the macula lutea, 
 and are partly crossed and partly uncrossed — 
 fasciculus macular is ; (3) a crossed set, which 
 decussate with the fibres of the opposite side, 
 e.g., those of the right tract going to the left eye, 
 and those of the left tract going to the right eye ; 
 (4) an internal set, which pass from one tract to 
 the other and then back to the brain without 
 entering the eye ; this set is known as the com- 
 missure of Gudden. 
 
 The deep origins of the optic nerves are two-folcl 
 — sub-cortical or ganglionic, and the cortical. 
 
 (1) The ganglionic centres were named above, 
 and are the pulvinar of the optic thalamus, the 
 corpora geniculata externa, and the anterior pair 
 of corpora quadrigemina (Fig. 88, page 160). These 
 several nuclei degenerate when the eye of a young 
 animal is destroyed. 
 
Fig. 1 
 
 Tegmentum / $£ '•.-':- 
 
 *S/ A <J "?<("<< of Sylt 
 \ 
 
 Plate XXXVIII. 
 
 Nuclei of 3rd 
 
 \\ ■'' and 4th nerres 
 
 3 | 
 
 Crusta. 
 
 Nucleus 3rd nerve. 
 Red nuc. 
 
 4th newe 
 
 Super cerebellar V 1 '«&« f Vieussens. 
 
 peduncle. . 
 
 Sue. of 3rd n.- 
 
 3 rd Ncrae 
 
 -Aqueduct of Sylvius 
 >*^^ Sue. of 6th n. 
 
 Fig. 4 
 
 Fig. 5 
 
 Super root, of oth n, 
 
 son/ pf. 5th. y j. j 
 
 Sensory pf 
 
 Motor 
 ac. of oth h 
 
 Motor pt. 5t 
 
AND ITS MEMBRANES. 173 
 
 (2) The cortical centres are situated in the 
 occipital lobes — cuneate lobe — and are connected 
 with the ganglionic centres by means of a bundle 
 of fibres, the optic radiation, which passes from these 
 ganglionic centres backwards behind the internal 
 capsule to the cuneate and lingual lobes. 
 
 " The roots of the optic tracts which spring from 
 the corpora geniculata interna (the internal set of 
 fibres named above) have no real connection with 
 vision, as they do not undergo atrophy like the other 
 roots when the eyes are destroyed " (Ferrier). 
 
 The centres for sight are connected with the 
 centre for articulate language in the frontal lobe ; 
 with the auditory centre in the temporal lobe ; and 
 with the centre for visual memory in the parietal 
 lobe — angular gyrus. 
 
 The 3rd Nerves (Figs. 1, 2, 3, page 172) appear 
 at the oculomotor groove, on the inner side 
 of the crura cerebri, close to the pons Varolii. 
 They spring from a longitudinal column of cells, 
 on each side of the middle line, in the grey matter 
 of the floor of the aqueduct of Sylvius (Fig. 
 87, page 160). This collection of cells is called 
 the oculomotor nucleus, and is a continuation of 
 the anterior horn of the spinal cord. Traced from 
 the cells of this nucleus, the fibres of the nerve 
 pass through the posterior longitudinal bundle, 
 through the red nucleus and locus niger, to 
 the oculomotor groove, on the inner side of the 
 crus cerebri. The nuclei of the 3rd nerves are 
 closely connected with the nuclei of the 4th and 
 
174 THE BRAIN 
 
 6th nerves, the nucleus of the 6th nerve of the 
 one side being united by means of the posterior 
 longitudinal bundle with the opposite 3rd nerve 
 (Fig. 3, page 172, and Fig. 4. page 17(3). There is 
 probably a partial decussation of the fibres of the 
 3rd nerve. The nucleus of the 3rd nerve gives rise 
 to two sets of fibres — 
 
 (1) To the extrinsic muscles of the eyeball, except 
 the external rectus and the superior oblique. 
 
 (2) To the intrinsic muscles of eyeball, viz., the 
 sphincter pupillse, and the ciliary muscle. 
 
 The 4th Nerves will be seen on the outside of the 
 crura cerebri, between the cerebrum and cerebellum 
 (Fig. 79, page 134). They are small and slender, 
 and arise from a nucleus in the wall of the aqueduct 
 of Sylvius behind that of the 3rd nerve (Fig 2, 
 page 172). The 4th nerve is connected with the 
 nucleus of the 6th nerve of the opposite side. 
 After leaving their nuclei of origin the 4th nerves 
 pass backward and decussate in the superior medul- 
 lary velum (superficial origin), so that the left nerve 
 comes from the right nucleus, and vice versa (Fig. 2, 
 page 172). 
 
 The 5th Nerves spring from the sides of the pons, 
 near its upper margin, by two roots — a large one, sen- 
 sory (ganglionic), and a small, motor (aganglionic). 
 The small — motoe ROOT — is the higher of the two, 
 and is separated from the larger root by some of 
 the transverse fibres of the pons. Followed back- 
 wards, this smaller part is seen to arise from the 
 principal nucleus — motor nucleus — lying just below 
 
AND ITS MEMBRANES. 175 
 
 the LATERAL ANGLE of the 4TH VENTRICLE (Fig. 57, 
 
 page 82). It is joined by the superior or descending 
 root of the 5th nerve, which comes from the 
 accessory nucleus — a column of grey matter at the 
 sides of the aqueduct of Sylvius (Fig. 5, page 172). 
 Some of the motor fibres come from the opposite side. 
 The large or SENSORY ROOT. — The nucleus of this 
 root is the Gasserian ganglion, situated on the apex 
 of the petrous part of the temporal bone. The uni- 
 polar nerve cells of this ganglion give off two branches, 
 one of which passes into the peripheral nerve ; the 
 other enters the cerebro-spinal axis, and there divides 
 into ascending and descending branches. The ascend- 
 ing branches terminate amongst the cells forming the 
 sensory nucleus of the 5th nerve — ^a nucleus lying 
 close to the outer side of the motor nucleus (Fig. 
 5, page 172). The descending branches form the 
 descending or inferior root of the 5th nerve, and can 
 be traced down the spinal cord as far as the first 
 cervical nerve. 
 
 The 6th Nerves take their superficial origin near 
 the middle line from the groove between the anterior 
 pyramids of the medulla and the lower border of 
 the pons (Fig. 79, page 134). Their deep origin is 
 situated underneath the outer part of the fasciculus 
 TERES in the fore part of the floor of the 4th ventricle, 
 in front of the striae acusticse (Fig. 57, page 82). 
 The nucleus of the 6th nerve is connected by means 
 of the posterior longitudinal bundle with the fibres 
 of the third nerve of the opposite side (Fig. 3, 
 page 172, and Fig. 4, page 176). 
 
176 THE BRAIN 
 
 The 7th Nerve consists of two parts — the facial 
 nerve proper (portio dura) and the pars intermedia. 
 The facial nerve proper (7th) springs from the groove" 
 between the olivary body and the restiform body, 
 just below the pons (Fig. 79). Its deep origin is 
 the facial nucleus in the formatio reticularis of the 
 dorsal aspect of the pons, near the nucleus of the 6th 
 nerve, but external and deeper in beneath the floor 
 of the 4th ventricle (Figs. 1, 2, page 176). The 
 fibres leave the nerve cells of this nucleus, and are 
 at first directed backwards and inwards towards the 
 middle line, internal to the nucleus of the 6th nerve. 
 They then ascend for a short distance behind the 
 nucleus of the 6th nerve, close to the floor of the 4th 
 ventricle, forming part of the eminentia teres, and ; 
 bending down and out over the upper end of the 
 nucleus of the 6th nerve (Fig. 2, page 176), they 
 run forwards, outwards, and downwards to the lower 
 border of the pons — their superficial origin. In the 
 pons the facial nerve is joined, through the posterior 
 longitudinal bundle, by fibres from the nuclei of the 
 3rd and 12th nerves. 
 
 The pars intermedia of the facial nerve is a small 
 bundle of nerve fibres which lies between the facial 
 and auditory nerves, and is connected with both. It 
 probably carries taste fibres to the glosso-pharyngeal 
 nucleus, the sensory impulses travelling from the 
 tongue to that nucleus through the chorda tympani, 
 and through the pars intermedia of the facial nerve. 
 
 The Auditory Nerve — 8th nerve — takes its super- 
 ficial origin in the same groove with, but behind, the 
 
Plate XXXIX 
 
 Fig. 2 
 
 Ww. of 6th n. 
 
 V 
 
 Nor. of 7th n. 
 
 Fig. 3 
 lateralis ^s^^s^sss^^ Dorsal nuc. 
 
 Nuc. of 8th n. 
 
 Nuc. of Oth n. 
 
 Nuc. of 3rd u. 
 
 3rd Nero? 
 
 Nuc. of 12th n. 
 
 Sue. ambiguus 
 
 Nuc. vagus 
 
 10th nerve 
 Nuc. ambiguus 
 
 7th nerve 
 
 Fig. 4 
 
 Nuc. 3rd n. 
 
 Nuc. 6th n. 
 
 Fig. 6 
 
 Xuc. of 12th 
 
AND ITS MEMBRANES. 177 
 
 facial, and separated from it by the pars intermedia. 
 Its true origin is, as with all sensory nerves the 
 ganglia (vestibular and spiral) on the course of the 
 nerve. Traced from these ganglia the axis-cylinder 
 processes enter the medulla and divide into ascend- 
 ing and descending branches, which end in tufts at 
 the sub-cortical or so-called deep origin of the nerve. 
 The auditory nerve has two roots — a mesial and a 
 lateral root (Fig. 3, page 176). 
 
 (1) The mesial root — vestibular division — (an- 
 terior, ventral, upper root) passes backwards through 
 the substance of the pons internal to the restiform 
 body, and becomes connected with the dorsal auditory 
 nucleus beneath the lateral angle of the floor of the 
 4th ventricle (Fig. 3, page 176). Some fibres are 
 connected through the raphe with the cerebellum 
 (vermis cerebelli), and with the inferior olivary body 
 — acusti co-olivary tract of Bruce* This root is 
 concerned with the sense of equilibrium, not with 
 hearing. 
 
 (2) The lateral root — cochlear division — (lower 
 or posterior root) can be traced round the outer side 
 of the restiform body and through the auditory 
 striae across the middle line of the floor of the 4th 
 ventricle (Fig. 3, page 176). Its chief connections 
 are (1) with the accessory or ventral auditory nucleus 
 placed in front of the restiform body, between the 
 mesial and lateral roots of the nerve (Fig. 3, page 
 176), and (2) with the ganglion of the lateral root, 
 
 * See magnificent work on the Brain by Dr Bruce, Lecturer 
 Pathology, School of Medicine, Surgeons' Hall, Edinburgh. 
 
 N 
 
 ft 
 
178 THE BRAIN 
 
 a collection of cells found amidst the lateral root 
 as it winds round the outer side of the restiform 
 body (Fig. 3, page 176). This is the true nerve of 
 hearing, being alone distributed to the organ of 
 Corti. Some of the fibres of the accessory nucleus 
 can be traced to the opposite fillet, and through it to 
 the posterior pair of corpora quadrigemina ; others 
 go to the superior olive of the same and of the 
 opposite sides. 
 
 The Glosso - pharyngeal — 9th pair of nerves. 
 The motor part of this nerve takes its deep origin 
 from the nucleus ambiguus or accessory vagal nucleus 
 (Fig. 5, page 176). The sensory fibres start in the 
 ganglia on the nerve (the petrous and jugular- 
 ganglia), and on entering the medulla divide into 
 descending branches which join the fasciculus soli- 
 tarius, and ascending branches which end in a special 
 nucleus, common to this nerve and to the vagus, 
 beneath the inferior fovea of the lower half of the 
 floor of the 4th ventricle (ala cinerea). 
 
 The Yagus — 10th nerve. The motor portion of 
 this nerve springs from the nucleus ambiguus or 
 accessory vagal nucleus (Fig. 6, page 176) of the same 
 and opposite sides. The sensory fibres arise in the 
 ganglia of the root and of the trunk of the vagus, 
 and after entering the medulla divide into descending 
 branches which join the fasciculus solitarius, and 
 ascending branches which end in tufts in the vagal 
 nucleus beneath the ala cinerea. Its superficial 
 origin is the groove behind the olive. 
 
AND ITS MEMBRANES. 179 
 
 The Spinal Accessory — 11th nerve — is a pure 
 motor nerve. It has two parts — a spinal part and 
 an accessory part. 
 
 (1) The spinal part arises from a column of 
 cells in the spinal cord — the lateral horn — and 
 extends as far down as the oth cervical nerve. 
 
 (2) The accessory or bulbar part has a similar 
 origin to the vagus, viz., from the nucleus ambiguus, 
 and from the column of cells lying beneath the ala 
 cinerea of the 4th ventricle. This column of cells 
 is common to the glosso-pharyngeal, to the vagus, 
 and to the bulbar part of the spinal accessory. This 
 last should really be regarded as part of the vagus, 
 and not as a separate nerve. 
 
 The Hypoglossal — 12th nerve — springs by several 
 filaments from the groove between the anterior 
 pyramids and the olives (Fig. 79, page 134). Its 
 fibres can be traced backwards through the formatio 
 reticularis to its deep origin, a column of cells lying 
 near the middle line, close to the surface of the floor 
 of the 4th ventricle, beneath the lower part of the 
 FASCICULUS teres. This area is often called the 
 trigonum hypoglossi (Figs. 57, 58, page 82, and 
 Fig. 5, page 176). 
 
 It is worthy of note that the motor faculties occupy 
 the anterior part, the sensory the posterior part, of 
 the brain ; just as in the spinal cord and medulla the 
 motor tracts and nerves and their nuclei are anterior, 
 the sensory posterior. 
 
i8o GENERAL SUMMARY. 
 
 GENERAL SUMMARY. 
 
 In the preceding sections we have described the 
 several parts of the brain and spinal cord ; in this 
 chapter we shall, for the sake of clearness, take a 
 general survey of the whole system, both grey and 
 white matter. 
 
 T. Grey Matter. — The grey matter of the cerebro- 
 spinal nervous system is, as we know, composed of a 
 countless number of superimposed neurones — motor, 
 sensory and intellectual — with their cell bodies and 
 their protoplasmic (centripetal) and their axis-cylin- 
 der (centrifugal) processes, by means of which the 
 different parts of the nerve-axis are brought into 
 relation with each other and with every part of 
 the rest of the body. The several neurones are, 
 however, independent, their processes being con- 
 tiguous only, not continuous The cell bodies, 
 supported by neuroglia, and nutritive in function, 
 constitute the grey matter ; their processes, especially 
 their axis-cylinder processes, form the various white 
 strands. 
 
 (1) In the cerebrum the grey matter constitutes 
 the cortex and the sub-cortical ganglia (basal ganglia). 
 
 (a) The cortex cerebri can be mapped out into 
 specific areas — motor, sensory, and intellectual. 
 
GENERAL SUMMARY. 181 
 
 The motor areas are the paracentral lobule, the 
 ascending frontal, and the ascending parietal convolu- 
 tions. Figs. 44, 45, page 62, will give you an idea of 
 their several positions. 
 
 The sensorial areas are — 
 
 For common sensibility — the same regions as 
 
 for the motor faculties. 
 For the sense of sight — the cuneate lobe and the 
 
 angular gyrus. 
 For the sense of smell and of taste — the tip of 
 
 the temporal lobe (hippocampal and uncinate 
 
 gyrus). 
 For the sense of hearing — the upper temporal 
 
 convolution. 
 
 The association areas — the true intellectual 
 centres, holding in subjection the lower centres — 
 constitute two-thirds of the total cerebral cortex, 
 and occupy most of the frontal, temporal, parietal 
 and occipital lobes. They cannot be stimulated 
 from without. 
 
 (b) The basal ganglia occupy the interior of the 
 cerebrum. Their functions and connections are as 
 yet undecided. The pulvinar of the optic thalamus, 
 the corpora geniculata externa, and the anterior 
 pair of corpora quadrigemina, are the sub-cortical 
 centres for sight, and are by means of the optic 
 radiation connected with the cuneate lobes (cortical 
 centres). 
 
 The posterior pair of corpora quadrigemina, and the 
 corpora geniculata interna are probably associated 
 with hearing. 
 
i8 2 GENERAL SUMMARY. 
 
 (2) The grey matter of the cerebellum is united by 
 its several peduncles with the cerebrum, medulla, 
 pons, and most of the cranial nerves. Of its 
 functions we are as yet ignorant. The table below, 
 page 184, will give you the chief constituents of its 
 peduncles. 
 
 (3) The rest of the grey matter extending from the 
 aqueduct of Sylvius to the filum terminate — is 
 arranged in a dorsal part (sensory in function) 
 behind the central canal, and a ventral part (motor 
 in function) in front of the central canal. In the 
 pons, medulla, and crura cerebri, this grey matter 
 forms the nuclei of origin of most of the cranial 
 nerves ; thus from the grey matter of the aqueduct 
 of Sylvius arise the 3rd and 4th nerves: from the 
 pons the 5th, 6th, 7th, and part of the 8th : from 
 the medulla the 8th, 9th, 10th, 11th, and 12th 
 nerves ; finally at the lower part of the medulla are 
 the nuclei of the fasciculus gracilis and cuneatus, 
 the primary terminations of the long sensory tracts 
 of the posterior columns of the spinal cord. 
 
 In the spinal cord the grey matter assumes the 
 form of long columns of cells — vesicular columns — 
 connected with the deep origins — motor and sensory 
 — of the spinal nerves. 
 
 II. White Matter. — The white substance of the 
 central nervous system, consisting principally of the 
 axis-cylinder processes of the nerve cells which con- 
 stitute the grey matter, can be arranged in two 
 distinct strands of fibres — short strands and long 
 strands. 
 
Plate XL, 
 
 Corpus callosum. ' ' L 
 
 eg 
 
 1st trophic realm. 
 
 Fig. 101. 
 
 1. Motor wrtas. 
 
 Direct pyramidal tract. 
 
 4. Pyramidal tract of pons. 
 
 5. Anterior pyramid of medulla. 
 
 Diagram of Motor Tracts. 
 
 6. Crossed pyramidal tract. 
 
 Diagram op a Descending 
 Degeneration. 
 
GENERAL SUMMARY. 183 
 
 (1) The SHORT strands are mainly commissural 
 between different segments of the same divisions of the 
 nerve axis. In the brain they comprise the various 
 commissures, connecting different hemispheres with 
 each other ; and the strands of association fibres 
 uniting different parts of the same hemispheres. In 
 the spinal cord they connect segments at one level 
 with those at another, and occupy the regions of the 
 cord known as the mixed zones. Many of them are 
 concerned with reflex acts. 
 
 To this group of short strands belong the corpus 
 calloswm, the anterior and posterior commissures, 
 the fornix, the posterior longitudinal bundle, and 
 the cerebellar peduncles. 
 
 (a) The corpus callosum, the fornix, and other 
 minor commissures have already been fully described 
 (pages 157 and 160). 
 
 (b) The posterior longitudinal bundle starts in 
 the cells of the anterior pair of corpora quadri- 
 gemina, and descends beneath the floor of the 4th 
 ventricle to the anterior column of the spinal cord 
 (see Fig. 97, page 168, and Plate XLL, page 184). 
 It contains ascending and descending fibres which, 
 on their way, give off' collaterals to the motor cranial 
 nerves. By its means peripheral sensory nerves are 
 connected with the cells of origin of motor cranial 
 nerves. It also unites the cerebellum with the 
 nuclei of origin of the cranial nerves, and the cranial 
 nuclei w r ith each other ; especially the 3rd nerve of 
 the one side with the 6th nerve of the opposite side. 
 
1 84 GENERAL SUMMARY. 
 
 (c) The peduncles of the cerebellum are three 
 in number — the superior, the middle, and the 
 inferior. 
 
 The superior peduncles contain ascending and 
 descending fibres, most of which decussate. Their 
 ultimate destinations are the red nucleus, the 
 cortex of the cerebrum, the optic thalamus, and 
 the lenticular nucleus. 
 
 The middle peduncles pass to the nucleus 
 pontis, to the posterior longitudinal bundle, to the 
 fillet, to the corpora quadrigemina, to the antero- 
 lateral tract of the spinal cord, and to the pyramids 
 of the same and of the opposite side. 
 
 The inferior peduncles. — Their fibres can be 
 traced to the opposite olivary body, to the fillet, to 
 the posterior longitudinal bundle, and to the antero- 
 lateral column of the spinal cord. 
 
 (2) The long strands — 'projection fibres — connect 
 the motor-sensorial areas with lower centres. They 
 are arranged in two groups : the one motor, the other 
 sensory. 
 
 (a) The motor strands are twofold : the princi- 
 pal motor strand, — cortico-spinal ; and the secondary 
 motor strand — the cortico-cerebellar-spinal. Both 
 these motor strands consist of two sets of neurones, 
 the one central — crossed; the other peripheral — 
 uncrossed. 
 
 (1) The principal motor strand, starting as the 
 axis-cylinder processes of the nerve cells of the motor 
 regions of the brain cortex (first trophic realm), 
 descends through the corona radiata, through the 
 
Plate XL/. 
 
 Cerebrum 
 
 Motor areas - 
 
 Pyramidal tracts 
 
 Posterior longit. 
 bundle 
 
 Secondary motor true 
 
 Nuc. 9th, 10th, 11th, %.-' 
 
 Direct pyr. tracts- 
 
 -Crossed pyr. tract 
 
 Diagram (after Van Gehuchtbn) op Motor Tracts 
 
GENERAL SUMMARY. 185 
 
 knee-shaped bend (geniculate fasciculus), and through 
 the anterior two-thirds of the posterior limb of the 
 internal capsule, thence through the inner and middle 
 portion of the crusta of the crura cerebri to the 
 pyramidal tracts of the pons and medulla of the 
 same side. At the bottom of the anterior median 
 fissure of the medulla, 90 per cent, of the motor 
 fibres decussate (decussation of the pyramids) with 
 those of the opposite side, and then descend in the 
 crossed pyramidal tract of the opposite half of the 
 spinal cord to reach the peripheral neurones situated 
 in the anterior horns (second trophic realm). The 
 rest — 10 per cent. — pass down the anterior column 
 of the cord, as the direct pyramidal tract, to cross 
 over at lower levels, through the anterior commis- 
 sure, to the opposite side of the spinal cord. The 
 crossed pyramidal tracts, however, also receive a few 
 fibres from the cerebrum of their own side. 
 
 In the internal capsule the motor fibres are 
 grouped, from before backwards, as follows: — (1) in 
 the genu we have fibres for the eyes, head, tongue, 
 and mouth ; (2) in the anterior two-thirds of the 
 posterior limb we have, first, the fibres for the 
 shoulder, then those for the elbow, wrist, fingers, 
 thumb, trunk, hip, ankle, knee, and toes. 
 
 As they descend through the crura cerebri, pons, 
 and medulla, the axis-cylinder processes of these 
 motor strands cross over to the opposite side, 
 and, by means of their collaterals and terminals, 
 come into relation with the peripheral neurones 
 of the several motor cranial nerves, just as at 
 lower levels the fibres intended for the spinal nerves 
 
1 86 GENERAL SUMMARY. 
 
 decussate in the pyramids (Fig. 100, page 182, 
 and Plate XLL, page 184). The central neurones 
 therefore carry the impulses for the brain to the 
 cranial and spinal peripheral motor neurones of the 
 opposite side, which in turn transmit them to the 
 muscles. Thus, for example, the right side of the 
 face or arm is worked from the right facial or spinal 
 nucleus (sub-cortical origin), but from the left 
 cerebral cortex (cortical origin). 
 
 Hence it follows, as we have said, that all peri- 
 pheral motor neurones are uncrossed, whereas the 
 central ones are crossed. 
 
 The following cranial nerves are, however, excep- 
 tions to this rule : the 3rd, the 7th, the motor part 
 of the 5th, 9th, and 10th nerves are partially crossed ; 
 the 4th nerves are totally crossed, decussating in 
 the superior medullary velum; the 6th nerves are 
 direct, and, as far as we yet know, the same is true 
 of the 12th nerve and of the bulbar part of the 
 vagus, these also being uncrossed. 
 
 (2) Secondary motor strand. — The cells of the 
 central neurones of this strand are found in the same 
 areas as the cells of the principal motor tracts, and 
 their axis-cylinders descend mingled with those of 
 the chief motor tract through the internal capsule 
 and crura cerebri to the pons, where they leave that 
 strand and end in branches amidst the nerve cells of 
 the nucleus pontis. The axis-cylinders of the nerve 
 cells of this nucleus (nucleus pontis) then cross over 
 to the opposite half of the cerebellum, to terminate 
 at the neurones of the cerebellar cortex, which 
 transmit the impulses through the inferior peduncle 
 
Plate XL//. 
 
 Cerebrum 
 
 Sensory areas 
 
 Crux, cerebri. 
 
 - Super cerebellar peduncle 
 
 Red nuc. 
 J -Corpora qicad. 
 
 2nd nerve -^f 
 
 pu f n. vest 
 
 6th nerve < , 
 
 ( n. cock. 
 
 9th add 10th 
 Ascend, antero-lateral 
 
 | ,Gang. post, root 
 Des. fibre 
 
 Diagram (after Van Gehuchten) of Sensory Tracts, 
 
GENERAL SUMMARY. 187 
 
 of the cerebellum, by some unknown route, to the 
 spinal cord, thence to the grey matter of the 
 anterior cornu (the motor peripheral neurones), and 
 thus to the muscles. This, then, is also a crossed 
 tract, the crossing taking place in the upper set of 
 neurones (Plate XLL, page 184; second: motor tract). 
 
 (b) The sensory strands conduct impulses from 
 the periphery to the brain. Their exact course 
 cannot be traced, but they are known to consist of 
 a peripheral and of a central set of neurones. 
 
 The peripheral neurones are uncrossed and single. 
 Their cells are situated outside the cerebro-spinal axis, 
 in the spinal ganglia, for the spinal nerves, and in 
 the ganglia of the sensory nerves, for the cranial 
 nerves. The cells of these ganglia have a peripheral 
 process — the protoplasmic process — which places the 
 surface of the body and the various sense organs in 
 communication with the cells of these ganglia; and 
 a central process — the axis-cylinder process — con- 
 necting the cells of the ganglion with the central 
 axis. They are, as we have said, uncrossed. The 
 central neurones connect these peripheral neurones 
 with the higher nerve centres. They are situated 
 within the central nerve axis, and consist of at least 
 two sets of superimposed neurones. They are 
 crossed — the crossing taking place either in the 
 spinal cord, in the medulla (sensory decussation), or 
 in case of the cranial nerves, at higher levels. 
 
 The chief sensory strands are : — 
 
 1. The fasciculi of Goll and of Burdach, which 
 were traced into the medulla as the fasciculus 
 
188 GENERAL SUMMARY. 
 
 gracilis and the fasciculus cuneatus. They end in the 
 nuclei of these fasciculi. A second relay of cells, 
 situated in these nuclei, carry the impulse one of 
 two ways, either (1) through the inferior cerebellar 
 peduncle to the cerebellum of the same side or 
 opposite side, or (2) through the medulla (sensory 
 docussation), through the pons and crura cerebri 
 (fillet), and through the posterior part of the internal 
 capsule to the opposite cerebral hemispheres. Some 
 of these latter fibres go direct to the cerebral 
 cortex (to the ascending frontal and ascending 
 parietal convolutions); others first pass through the 
 optic thalamus. 
 
 The fillet, the constitution of which is given, for 
 reference, in the following table, is seen as a flat 
 band (Figs. 60 and 61, page 90), in the tegmental 
 part of the pons and crura cerebri. It consists of 
 three portions — (1) the lateral fillet, which receives 
 its fibres from the antero-lateral tract of the spinal 
 cord, and from the nucleus gracilis and cuneatus of 
 the opposite side (superior pyramidal decussation) ; 
 it ends in the posterior pair of corpora quadrigemina : 
 (2) the mesial fillet which goes into the crusta of the 
 crura cerebri and ends in the lenticular nucleus : (3) 
 the intermediate fillet which obtains its fibres from 
 the cerebellum, from the antero-lateral column of the 
 spinal cord of the same side, and from the nuclei 
 gracilis and cuneatus of the opposite side (superior 
 pyramidal decussation); it ends partly in the anterior 
 corpora quadrigemina and partly in the cerebral 
 cortex (Fig. 96, page 168). 
 
GENERAL SUMMARY. 189 
 
 (2) The ascending antero-lateral tract of Gowers, 
 lying, as you know, on the surface of the lateral 
 aspect of the cord in front of the direct cerebellar 
 tract, can be traced through the superior peduncles of 
 the cerebellum to the lingual lobe of the vermis of its 
 own side (Bruce). Other fibres go direct to the brain, 
 probably carrying sensations of temperature and of 
 pain. It is a crossed sensory tract, though the cells 
 of the cord from which it starts are undecided. 
 
 (3) The direct cerebellar tract (dorsal cerebellar) 
 ascends along the lateral margins of the cord and 
 medulla to the inferior peduncle of the cerebellum, 
 thence to the upper part of the superior vermis. 
 Most of its fibres end in the same side (Bruce). This 
 tract is connected, as we have seen, by means of the 
 cells of Clarke's column with the posterior spinal 
 nerve roots. 
 
 The course followed by the several nerves of special 
 sense is too complicated for any elementary work. 
 (See "Deep Origins of Cranial Nerves.") 
 
i 9 o OUTLINE OF 
 
 SECTION III. 
 
 OUTLINE OF DEVELOPMENT. 
 
 In this section we shall give an outline of the 
 development of the brain and spinal cord. 
 
 One of the earliest steps in the development of 
 the human embryo is, as you know, the formation 
 of the blastoderm or germinal membrane. This 
 membrane is composed of three distinct super- 
 imposed layers of cells, the epiblast, the mesoblast, 
 and the hypoblast. Of these, the epiblast is 
 the one from which the central nervous system 
 is developed. 
 
 Primitive groove. — On the dorsal aspect of the 
 embryo, at a very early date, appear two ridges, 
 separated from each other by an intervening furrow 
 — the primitive groove. Gradually increasing in 
 size, these two ridges grow upwards and ultimately 
 meet in the middle line on the dorsal aspect 
 of the embryo. Blending together they form a 
 closed cylindrical longitudinal tube — primitive 
 medullary tube — with walls composed of epiblastic 
 cells. From this primitive tube the brain and 
 
DEVELOPMENT. 191 
 
 spinal cord are formed ; the walls giving rise to 
 the solid parts, the cavity remaining as the central 
 canal of the spinal cord, and as the ventricles of 
 the brain. 
 
 I'.— THE SPINAL CORD. 
 
 (Fig. 103, &c, Plate XLIH., page 192.) 
 
 The spinal marrow is developed from the hinder 
 part of the primitive medullary tube. The lateral 
 walls of this portion of the tube increase in thick- 
 ness, so much so, that the cavity of the tube is 
 reduced to a mere slit. Its roof and floor, how- 
 ever, remain thin. The walls are at first composed 
 of columnar epithelial cells, their inner free ends 
 being ciliated, their attached ends resting on a base- 
 ment membrane. Soon, however, this layer of cells 
 differentiates, and gives rise to three different kinds 
 of cells. They are known as spongioblasts, germinal 
 cells, and neuroblasts. 
 
 1. The spongioblasts are branching cells, the 
 processes of which anastomose with those of neigh- 
 bouring cells, and thus form a network called 
 myelo-s-pongium. The inner part of the cells still 
 retains its columnar character. 
 
 2. Germinal Cells.— Between the deep ends of 
 the spongioblasts we find many rounded nucleated 
 cells with much clear protoplasm, and with their 
 nuclei in some stage or other of division. They give 
 origin to the next group of cells — the neuroblasts, 
 hence they are called germinal cells. 
 
1 92 OUTLINE OF 
 
 3. Neuroblasts. — These cells have a large 
 oval nucleus, and little protoplasm. They are 
 arranged in masses, which are transformed into 
 the grey matter of the spinal cord (nerve cells 
 and grey crescents). The cells have distinct pro- 
 longations towards that part of the surface of the 
 embryonic cord from which the future anterior 
 nerve roots spring. These prolongations are the 
 commencement of the axis -cylinder processes of 
 these nerve roots. The posterior roots are a 
 subsequent development from the spinal ganglia 
 connected with these roots. 
 
 Externally, on the surface of the cord, in the 
 region in which the ivhite matter of the cord (the 
 various columns) is developed, we find no nuclei, 
 this part of the embryonic cord being composed of 
 the reticular and radiating processes of the spongio- 
 blasts. The anterior columns are the first to appear, 
 then the posterior, then the lateral. 
 
 As we have already seen in the account of the 
 spinal cord, these white strands acquire their medul- 
 lary sheaths at different dates, thus enabling us to 
 map out the course they take through the spinal 
 marrow (see page 41). 
 
 At first there are no indications of the anterior 
 and posterior median fissures of the cord. The 
 former, the anterior median fissure, is the cleft left 
 between the enlarging lateral halves of the cord. 
 The anterior commissure is developed at the bottom 
 of the fissure, and thus separates it from the central 
 canal of the cord. The posterior fissure is probably 
 the constricted dorsal part of the original canal. It 
 
Plate XL///. 
 
 Cerebral hemispheres. FlG. 104. 
 Fig. 103. ^==*^g^ Pineal gland. 
 
 Foramen /^■^VW^ y™**^*^™ 7 "™ ^ uadri ^ emina ' 
 ^f Monro. II £& ■■■■''^\\ J^K^'r~^< fC ^ - Superior 
 
 medullary velum. 
 
 ■- - Cerebellum. 
 
 Tween 
 
 brain. Hr lateral 
 'veniricl.es. 
 Anterior commissure^ 
 Olfactory nerve* Pituitary body}^^^^ ^ —^- Choroid plexus. 
 
 Infundibulum. ' 4th ventrwle. 
 _. , , . Medulla. 
 
 Hind brain. 
 
 brain 
 
 Fig. 105. 
 
 Fig. 106. 
 
 Mesenceph. 
 Rhomb. 
 
 — Telencep. 
 Diencep. 
 
 InfundibulumTX^ #- Myelen. 
 
 Fig. 107. 
 
 | Hemispheres, pv Corpora quadrig. rj m 
 
 Fig. 108. 
 
 callosum 
 
 .--jf- Cerebellum. 
 Medulla. 
 
 Choroid plexus. 
 
 Optic thalamus. 
 Pineal gland. 
 
 Corpora quad. 
 
 3rd ventricle: ^&K <• "V Cerebellum. 
 Crura cerebri. " om - \. ' 
 
 Fig. 109. 
 
 Medulla. 
 
 Corpora quadrigemina. 
 
 Cerebellum. 
 
 Corpus striatum. 
 
 Infundibulum. 
 
DE VEL OPMENT. 1 9 3 
 
 becomes filled up by a growth of neuroglia, derived 
 from the spongioblast, and remains as a mere 
 septum. 
 
 At first the spinal cord fills the entire length of 
 the spinal canal, so that there is no cauda equina ; 
 but by the rapid growth of the canal, as compared 
 with the contained spinal marrow, the cord, at about 
 the 9th month, reaches only as low as the 3rd lumbar 
 vertebra. 
 
 II.— THE BRAIN. 
 
 (Plate XLIIL, page 192.) 
 
 The brain is formed from the fore part of the 
 primitive medullary tube. At the period of develop- 
 ment, when the posterior part of this tube is as yet 
 open, the anterior part dilates considerably, but at 
 first remains single. Its walls thicken, and the 
 cavity of the tube is sub-divicled by two constrictions 
 into the three segments known as the anterior, the 
 middle, and the "posterior primary cerebral vesicles. 
 The anterior and posterior primary vesicles soon 
 divide into two, one behind the other, whereas the 
 middle primary vesicle remains single. Thus we 
 get five secondary vesicles formed from the three 
 primary vesicles. 
 
 The following table will give you, enumerated from 
 
 before backwards, the names of these primary and 
 
 secondary vesicles and the parts developed from 
 
 each (Plate XLIV., page 194):— 
 
 o 
 
194 
 
 OUTLINE OF 
 
 Table of the Cerebral Vesicles and the Parts 
 Developed from Each. 
 
 PRIMARY 
 VESICLES. 
 
 1. Prosen- 
 cephalon 
 
 2. Mesen- 
 cephalon 
 
 Rhomben- 
 cephalon 
 
 SECOND ARV 
 
 VESICLES. 
 
 1. Telencephalon 
 
 PARTS DEVELOPED PROM THE 
 VARIOUS VESICLES. 
 
 Cerebral Hemispheres. Cor- 
 pora Striata. Corpus Cal- 
 losum. Fornix. Lateral 
 Ventricles. Optic Chi- 
 ^ asma. Olfactory Lobe, y 
 
 v 2. Diencephalon 
 
 Optic Thalami. Pineal Body. 
 Infundibulnm. Pituitary 
 Body. 3rd Ventricle. 
 CorporaAlbicantia. Optic 
 Tracts. 
 
 3. Mesencephalon ra Cerebri. Aqueduct of 
 
 r Corpora Quadrigemina. Cru- 
 
 (_ Sylvius. 
 
 f Superior Cerebellar Ped- 
 [ 4. Isthmus Rhomb- | 1iw . 1m y alve of T 
 
 uncles. 
 sens. 
 
 Cerebellum. Pons Varolii. 
 5. Metencephalon Anterior part of the 4th 
 
 encephali I 
 
 / 
 
 i 
 
 Ventricle. 
 
 Medulla Oblongata, Pos- 
 6. Myelencephalon J terior part of 4th Ven- 
 ( tricle. 
 
 / 
 
 The Isthmus Bhombencephali (Plate XLI V., page 
 194) is the constricted portion between the mesen- 
 cephalon and the rhombencephalon. Thus we get 
 six rings with epiblastic walls composed of histo- 
 logical elements similar to those which give origin 
 to the spinal cord. By subsequent changes in these 
 rings the brain and its sub-divisions are built up. 
 

DE VEL OPMENT. 195 
 
 1. The Posterior Cerebral Yesicle gives origin to 
 the medulla oblongata, to the pons Varolii, and to 
 the cerebellum. Bending forwards at the upper end 
 of the primitive spinal cord (Fig. 106, page 192), 
 the posterior vesicle makes a second bend, a knee- 
 shaped bend, backwards on itself. It is, as we have 
 seen, at first single, but soon becomes divided by a 
 constriction into two parts, a posterior division — 
 the myelencephalon, and an anterior division — the 
 rnetencephalon. 
 
 The hinder division of the vesicle — the myel- 
 encephalon forming the forward bend — becomes 
 developed into the medulla, and the lower part 
 of the 4th ventricle. 
 
 The backward fold, forming the fore part of the 
 original vesicle — the rnetencephalon — becomes the 
 cerebellum, of which the central lobe is first 
 formed, the lateral lobes being a subsequent de- 
 velopment. The knee-shaped bend gives rise to 
 the pons varolii ; hence it is often called the pons 
 curvature. 
 
 The isthmus rhombencephali — the constricted 
 part between the posterior and middle cerebral 
 vesicles — becomes the superior cerebellar peduncles 
 and the valve of Vieussens (Fig. 34, isthmus rhomb., 
 page 44, and Plate XLI V., page 194). 
 
 2. The Middle Cerebral Yesicle likewise bends 
 forwards on the posterior vesicle, but, unlike the 
 other primary vesicles, does not divide, but remains 
 single. Its roof becomes thickened, and in it are 
 formed the corpora quadrigemina. Its floor a*id 
 
196 OUTLINE OF 
 
 sides give rise to the crura cerebri, while the 
 original central canal, much narrowed by the 
 growth of these parts, remains as the AQUEDUCT of 
 Sylvius — iter a tertio ad quartum ventricnlum. 
 
 3. The Anterior Cerebral Yesicle, like the pos- 
 terior, becomes sub-divided into two portions — a 
 posterior, the diencephalon, and an anterior, the 
 telencephalon. The entire vesicle, at first straight, 
 bends forwards on the middle vesicle, which now 
 forms the most prominent part of the head. From 
 each side of its posterior segment are developed the 
 optic VESICLES, which ultimately become the optic 
 nerves. With the formation of the optic nerves 
 and the optic tracts, the stalk of the optic vesicles 
 becomes solid, and by the growth backwards of the 
 tracts becomes connected with the mid-brain. In 
 the lateral walls of this segment — diencephalon — are 
 developed the two optic thalami, separated from 
 each other by a median cleft — the 3rd ventricle 
 (Plate XLIV). Across this cavity subsequently 
 grows the middle or grey commissure. Anteriorly> 
 the floor of the ventricle is prolonged downwards 
 as a funnel-shaped tube — the infundibulum — 
 connected with the pituitary body ; behind, on the 
 other hand, the cavity communicates with the 4th 
 ventricle through a narrow channel, the continuation 
 backwards of the original cavity — the aqueduct of 
 Sylvius. The roof of the vesicle rapidly becomes 
 thinner and is reduced to a mere lamina of epi- 
 thelium connected with the pia mater and choroid 
 plexus in the roof of the 3rd ventricle. 
 
DE VEL OPMENT. 1 9 7 
 
 The posterior part of the roof, however, has a 
 transverse thickening — the posterior commissure ; 
 and in front of this the roof grows upwards and 
 forwards, then backwards as a hollow process — the 
 PINEAL gland — epiphysis cerebri — which is regarded 
 as a rudimentary third eye. 
 
 The fore part — telencephalon — of the original 
 anterior cerebral vesicle bulges forward as a median 
 mass, which is at first single, but soon becomes divided 
 by a longitudinal cleft into two lateral segments. 
 These lateral segments form the hemisjDherical vesi- 
 cles, and become the cerebral hemispheres. The 
 cavities within them remain as the lateral VEN- 
 TRICLES, which are connected with the 3rd ventricle, 
 and, through it, with each other, by a constantly 
 narrowing neck, the foramen of Monro (Fig. 103, 
 page 192). In the floor of the ventricles appears a grey 
 mass — the corpus striatum — streaked with white 
 matter, giving it the striated appearance from which 
 it takes its name. Outside this grey mass we find 
 the grey and white matter of the island of Reil. 
 The olfactory LOBES are hollow outgrowths of the 
 lower and lateral parts of the hemispherical vesicles. 
 
 The roof and walls of the hemispherical vesicles 
 are at first an evenly expanded mass of grey matter, 
 which, however, soon becomes convoluted and fur- 
 rowed, giving rise to the fissures, lobes, and gyri of 
 the cerebral hemispheres. Increasing rapidly in 
 size these hemispheres grow backwards, and, finally, 
 completely overlap and hide the other sub-divisions 
 of the brain. 
 
198 OUTLINE OF DEVELOPMENT. 
 
 In front and for some distance backwards the 
 mesial surfaces of the cerebral hemispheres come in 
 contact, and at certain places partly grow together. 
 The corpus callosum, the fornix, and the small 
 commissures are developed from these united parts 
 of the mesial aspect of the hemispherical vesicles. 
 The anterior commissure is the first formed, then 
 the fore part of the fornix, and afterwards its pos- 
 terior pillars. Finally, the corpus callosum appears, 
 the anterior part being the first developed, its growth 
 extending backwards with the growth of the hemi- 
 spheres. That portion, however, of the walls of the 
 hemispherical vesicles which lies between the fore 
 part of the corpus callosum and the fornix is left, 
 as the mesial walls unite, as a triangular interval, 
 bounded on each side by a layer of grey and white 
 matter derived from the hemispheres. These lamina? 
 form the septum lucidum, the vertical partition 
 separating the lateral ventricles. Between the two 
 layers of which this septum is composed is enclosed 
 the cavity of the 5th ventricle, or ventricle of the 
 septum, which you will readily understand is never 
 connected with the rest of the ventricles, and is not, 
 like them, part of the primitive medullary cavity. 
 It is merely a portion of the great longitudinal 
 fissure which has become enclosed in the process of 
 development. 
 
i 9 9 
 
 INDEX. 
 
 Ala cinerea (cinereus, ash- 
 coloured), 108, 112, 178 
 Eminentia, 108, 112 
 Amygdalae {amygdala, an al- 
 mond) of cerebellum, 96 
 Nucleus, 153, 162 
 Apex cornu posterioris, 28 
 Aqueduct (aquaeductus) of Syl- 
 vius, 110,139, 170 
 Arachnoid (apdxviov, a spider or 
 spider's web) membrane of — 
 Spinal Cord, 9 
 Brain, 50 
 Structure of, 10, 51 
 Arbor vitas (from resemblance to 
 the shrub so-called) of cere- 
 bellum, 102 
 Arcuate fibres, or arciform fibres 
 
 of medulla, 75, 83 
 Areas of brain, see also convol- 
 utions, 116, 117, 120, 122, 
 127, 181 
 Areas of medulla, 67 
 Arteries — 
 
 Auditory, internal, 59 
 Basilar, 59 
 Brain, 57 
 
 Carotid, internal, 57 
 Cerebellar, 59 
 Cerebral, anterior, 57 
 middle, 57 
 posterior, 60 
 Choroidal, anterior, 58 
 Circle of Willis, 60 
 Communicating, anterior, 57 
 
 posterior, 58 
 Meningeal, 56 
 
 Special characters of the cere- 
 bral circulation, 61 
 Spinal, 11 
 Vertebral, 58 
 Association areas, 181 
 fibres, 160 
 
 Astrocytes, 30 
 Ataxy, locomotor, 23 
 
 Band of Giacomini, 127 
 Basal ganglia, 139, 151 
 Basis bundle, 20 
 Basis pedunculi, 167 
 Blastoderm (l3\aa-rbs, a germ ; 
 
 depfxa, skin), 190 
 Brachia of corpora quadrige- 
 
 mina, 169 
 Brain, (See Cerebrum and Ence- 
 phalon), 43 
 
 Arteries of, 57 
 
 Base of, 132 
 
 Development of, 193 
 
 Membranes of, 45 
 
 Sub-divisions of, 63 
 
 Yeins, 61 
 Brain sand, 156 
 Broca's convolution, 117 
 Bundle of — 
 
 Posterior longitudinal, 113, 183 
 
 Vicq d'Azyr, 161 
 Burdach, fasciculus of, 22, 23, 69 
 
 Calamus scriptorius (a writing- 
 pen), 107 
 
 Canal, central, of Spinal Cord, 29 
 
 Capsule, external, 153, 165 
 internal, 153, 163 
 
 Caryochromes, 35 
 
 Cauda equina (a horse's tail), 5 
 
 Cells- 
 Brain, 128 
 Cerebellar, 102 
 Column, 37 
 Comet, 34 
 Deiters, 30 
 Germinal, 191 
 Golgi, 131 
 
 Molecular layer, cerebrum, 128 
 Nerve cells, Structure, 34, 102, 
 128 
 
200 
 
 INDEX. 
 
 Cells- 
 Polymorphous, 131 
 Processes, 35 
 
 Purkinjg, 103 
 
 Pyramidal, 129 
 Root, 37 
 
 Solitary, 34 
 
 Spider, 30 
 
 Spinal cord, 34 
 Centres — 
 
 Motor, 121 
 
 Sight, 120, 122 
 Centrum ovale, 138 
 minus, 110 
 magus, 140 
 Central lobe, 117, 123 
 Cerebellum (dim. of cerebrum, 
 the brain), 92 
 
 Development of, 195 
 
 Fissures of, 93 
 
 Great horizontal, 93 
 
 Folia of, 95 
 
 Functions, 105 
 
 Grey matter of, 101 
 
 Hemispheres of, 93 
 
 Lobes of, 95 
 
 Medullary vela, 100 
 
 Minute structure of, 102 
 
 Peduncles of, 97, 184 
 
 Position of, 92 
 
 Vallecula of, 94 
 
 Vermiform process of, 93, 96 
 
 White matter, 105 
 Cerebral vesicles, 193 
 Cerebro-spinal fluid, 5, 10 
 Cerebrum (the brain), 113 
 
 Base of, 132 
 
 Commissures of, 157 
 
 Convolutions of, 116 
 
 Crura of, 165 
 
 Development of, 193 
 
 Exterior of, 114 
 
 Fissures and furrows of, 114 
 
 Grey matter, 114 
 
 Ganglia of, 151 
 
 General outline, 113 
 
 Hemispheres of, 113 
 
 Interior of, 138 
 
 General outline of, 138 
 
 Cerebrum — 
 
 Layers of cells in cortex, 128 
 Lobes of, 116 
 
 Peduncles or crura of, 165 
 Relations of, to cranial sutures, 
 
 128 
 Structure of, 128 
 Ventricles of, 138, 141 
 White matter of, 157 
 Choroid plexuses of, 149 
 Fourth ventricle, 111 
 Lateral ventricle, 145, 149 
 Third ventricle, 149 
 Circulation, special characters of 
 
 cerebral, 61 
 Clarke's Column, 33 
 Claustrum (which shuts off), 153 
 Clava (a club), 68, 109 
 Collaterals, 26 
 Column or Columns — 
 Anterior, 19 
 Clarke's, 33 
 Ganglionic, 32 
 Inter-medio-lateral tract, 28 
 Lateral, 20 
 Posterior, 22 
 Spinal cord, 18 
 Vesicular, 32 
 White, 18 
 
 Anterior, 19 
 Lateral, 20 
 Posterior, 22 
 Column Cells, 37 
 Comet Cells, 34 
 Comma Tract, 24 
 Commissure (union) cerebral, 
 great (corpus callosum), 157 
 Commissure of — 
 Brain, 139, 157 
 Anterior, 160 
 Middle or soft, 160 
 Posterior, 160 
 Spinal Cord, grey, 29 
 white, 25 
 Conns medullaris, 4 
 Convolutions (con., together ; 
 volvo, 1 roll) — 
 Cerebellum, 95 
 Cerebrum, 116 
 
INDEX. 
 
 20I 
 
 Convolutions — 
 Angular, 120 
 Corpus callosum, 125 
 Dentate, 127 
 Frontal, 117 
 Hippocampal, 125 
 Tsland of Keil, 123 
 Marginal, 125, 126 
 Mesial surface, 124 
 Occipital, 121 
 Occipitotemporal, 123 
 Orbital, 118 
 Parietal, 119 
 Post-parietal, 120 
 Relations to Scalp, &c, 128 
 Supra-marginal, 120 
 Temporal, 122 
 
 Uncinate (hippocampal), 125 
 Cornu Ammonis (from its 
 resemblance to horns of 
 Zeus-Ammon), Hippocamp- 
 us major, 144 
 Cornu of lateral ventricles, 140, 
 
 143 
 Cornua of Spinal Cord, 28 
 
 Lateral, 34 
 Corona radiata, 164 
 Corpora albicantia (white 
 bodies), 134, 161 
 Formation of, 161 
 Corpora geniculata {genu, a 
 
 knee), 154, 155, 172 
 Corpora quadrigemina (four), 
 
 139, 169, 172 
 Corpora striata, 139, 151 
 Corpus callosum (callosus, thick 
 or hard), 113, 133, 142, 157 
 Development of, 198 
 Dissection to expose, 140 
 Peduncles of, 158 
 Structure of, 159 
 Corpus dentatum cerebelli, 102 
 
 Olivi, 81, 
 Corpus res ti forme (restis, rope), 
 
 70,99 
 Cortex of brain, structure of, 114, 
 
 128 
 Cortex of cerebellum, structure 
 of, 102 
 
 Course of nerve fibres, 105 
 Crura ad cerebrum, 97 
 ad medullam, 97 
 ad pontem, 97 
 Cerebri, 64, 113, 165 
 Crusta, Basis, Pes, 167 
 Fornicis, 161 
 Crusta of Crura Cerebri, 167 
 Cuneus, 126 
 
 Decussation (decvsso, I cut cross- 
 wise) of pyramids, 73 
 
 Sensory or superior pyra- 
 midal, 81, 83, 186 
 Deiters, Cells of, 30 
 Development of — 
 
 Brain, 193 
 
 Spinal Cord, 191 
 Diencephalon, 194 
 Dissection to expose — 
 
 Corpus callosum, 140 
 
 Fornix, 141 
 
 Interior of Brain, 140 
 
 Lateral ventricles, 140 
 
 Membranes of Brain, 43 
 
 Pia mater, 6 
 
 Septum lucidum, 141 
 
 Spinal Cord, 3 
 
 Velum interpositum, 141 
 
 3rd Ventricle, 141 
 
 5th Ventricle, 141 
 Dissection to remove — 
 
 Brain, 44 
 Dorsal ridges, 190 
 
 Nucleus, 33, 177 
 Dura mater of — 
 
 Brain, 45 
 
 Spinal Cord, 4 
 
 Structure of, 6 
 
 Eminentia collateralis, 145 
 Teres, 108, 176 
 Vascularis, 134 
 Encepbalon (eV, in ; KeQaA-f). the 
 head), 43, 64 
 Arteries of, 57 
 Development of, 193 
 
 (See Cerebrum, Cerebellum, 
 Medulla, and Pons) 
 
202 
 
 INDEX. 
 
 Enlargements — 
 
 Cervical, 13 
 
 Dorsal, 13 
 
 Lumbar, 13 
 Ependyma (evUvfia, clothing) of 
 Cells, 30 
 
 Ventricles of brain, 110, 145 
 
 Spinal Cord, 30 
 
 Falx Cerebelli, 47 
 
 Cerebri, 46 
 Fascia dentata, 127, 145 
 Fasciculus — 
 
 Cuneatus, 22, 69 
 
 Gracilis, 68 
 
 Geniculate, 168 
 
 Solitarius, 87, 178 
 
 Teres, 111, 179 
 Fasciculus of — 
 
 Biirdach, 23 
 
 Goll, 22, 68 
 
 Rolando, 69 
 
 Turck, 19 
 Fasciola cinerea, 127, 159 
 Fibres — 
 
 Association, 157, 160 
 
 Commissural, 157 
 
 Projection, 157, 162, 184 
 
 Arcuate, or arciform, 71, 75, 83 
 
 Moss, 105 
 Fillet, 83, 89, 90, 188 
 
 Lateral, 24 
 Filum durae matris spinalis, 5 
 Filum terminale, 5, 8, 13 
 Fimbria (a fringe), 126, 145 
 Fissures of — 
 
 Cerebellum, 95 
 
 Cerebrum, 114 
 
 Medulla oblongata, 66 
 
 Mesial surface, 124 
 
 Spinal Cord, 14 
 Fissures — 
 
 Callosal, 124 
 
 Calloso-marginal, 124 
 
 Calcarine, 126 
 
 Collateral, 123 
 
 Dentate, 126 
 
 Great horizontal of Cere- 
 bellum, 93 
 
 Fissures — 
 
 Great transverse, 150 
 
 Hippocampal, 126 
 
 Inter-lobular, 115 
 
 Intra-lobular, 116 
 
 Intra-orbital, 118 
 
 Intra-parietal, 120 
 
 Longitudinal, 63, 113 
 
 Parallel, 122 
 
 Parietooccipital, 116, 120, 121, 
 126 
 
 Relation of, to cranial sutures, 
 &c, 128 
 
 Rolando, 115 
 
 Sylvius, 115, 122 
 
 Transverse, great, 150 
 
 Triradiate, 118 
 
 (See also Sulci of Brain) 114 
 Flexures, cranial, of embryo, 
 
 195 
 Flocculus (dim. of floccus, a 
 
 flock of wool), 96 
 Folia of cerebellum, 93 
 Foramen caecum of medulla 
 
 oblongata, tSQ 
 Foramen of Majendie, 52, 109 
 
 Monro, 146, 147, 155, 197. 
 Fore-brain, 194 
 
 Formatio reticularis, 71, 77, 80 
 Fornix (an arch or vault), 143, 
 146, 160 
 
 Dissection to expose, 141 
 Fossa Rhomboidalis (4th ven- 
 tricle), 106 
 Fourth ventricle, 106 
 
 Nuclei of, 111 
 
 White matter of, 113 
 Fovea (a pit) — 
 
 Inferior of 4th ventricle, 108 
 
 Superior of 4th ventricle, 109 
 Funiculus — 
 
 Cuneatus (wedge-shaped), 69 
 
 Gracilis (slender), 68 
 
 Rolando, 69 
 
 Teres, 108 
 Furrowed band, 96 
 
 Galen, veins of, 150 
 Ganglia, basal, 139, 151 
 
INDEX. 
 
 203 
 
 Ganglionic columns of the 
 
 Spinal Cord, 32 
 Geniculate body, inner, 154, 155 
 outer, 154, 155 
 Genu (knee) of — 
 
 Corpus callosum, 15S 
 
 Facial nerve, 176 
 
 Internal capsule, 163 
 Gland Pineal, 156 
 Glandular Pacchionii, 49 
 Globus pallidus, 153 
 Goll, Fasciculus of, 68 
 Gowers' Table, 42 
 Granular layer of cerebellum, 
 
 104 
 Grey matter of — 
 
 Brain, 114, 128 
 
 Cerebellum, 93, 102 
 
 Cerebrum 114, 128 
 
 Medulla, 77 
 
 Spinal Cord, constituents of, 30 
 Groove, primitive, 190 
 Gyri (yvpos, a circle) of brain 
 (See Convolutions), 114 
 
 Operti, 123 
 Gyrus, angular, 120 
 
 Dentatus, 127 
 
 Fornicatus (arched), 125 
 
 Hippocampi, 125 
 
 Rectus, 119 
 
 Uncinate, 125 
 
 (See Convolutions) 
 
 Hippocampus (after the fish of 
 that name) — 
 Major, 141, 144 
 Minor, 141, 144 
 Horn — 
 Lateral, 34 
 Spinal Cord, 28 
 Ventricles — 
 Anterior, 143 
 Lateral, 144 
 Posterior, 144 
 
 Infundibulum (funnel), 134, 146, 
 
 196 
 Insula, 123 
 Island of Beil, 123 
 
 Isthmus, 125 
 
 Interior of cerebrum, 138 
 General outline, 138 
 
 Lamina — 
 
 Cinerea (grey layer), 133, 135 
 
 Quadrigemina, 169 
 
 Terminalis, 133, 135 
 Lateral recess of 4th ventricle, 
 
 107 
 Ligamentum denticulatum, 7 
 Ligula (dim. of linrjula), 110 
 Linea splendens, 7 
 Lingula (tongue), 100 
 Lissauer's Tract, 23 
 Lobes of — 
 
 Cerebellum, 95 
 
 Cerebrum, 116 
 
 Central (Reil). 123 
 
 Frontal, 117 
 
 Limbic, 125 
 
 Occipital, 121 
 
 Olfactory, 119 
 
 Parietal, 119 
 
 Temporal, 122 
 Lobules of — 
 
 Cerebrum, 116 
 
 Cuneate, 126 
 
 Lingual, 125 
 
 Paracentral, 126 
 
 Parietal, 120 
 
 Quadrate, 126 
 Locomotor ataxy, 23 
 Locus ceeruleus, 92 
 
 Perforatus anticus, 134 
 
 Perforatus posticus, 135 
 Lyra (a lute), 162 
 
 Majendie, foramen of, 52, 109 
 Marginal zone, 23 
 Matter — 
 
 Grey — Brain, 114 
 
 Spinal Cord, 27 
 
 White— Brain, 157 
 
 Spinal Cord, 18 
 Medulla oblongata, 65 
 
 Anterior area of, 72 
 
 Anterior columns of, 72 
 
 Development of, 195 
 
204 
 
 INDEX. 
 
 Medulla- 
 External characters of, 65 
 
 Fissures of, 66 
 
 Grey matter of, 77 
 
 Internal structure of, 77 
 
 Isolated nuclei of, 81 
 
 Lateral area of, 70 
 
 Posterior area of, 67 
 
 Pyramids of, 67 
 
 Raphe" of, 82 
 
 White matter of, 67 
 Fourth ventricle, 113 
 Medulla spinalis, 65 
 Medullary velum, 100 
 inferior, 101 
 superior, 100 
 Membranes of — 
 
 Brain, 43, 45 
 
 Spinal Cord, 3 
 Meninges (fj.7]uiy^, a membrane), 
 
 3, 43 
 Mesencephalon {jx^aos, middle; 
 
 ijKe(pa\ov, the brain), 194 
 Metencephalon, 194 
 Mid-brain, 194 
 Mixed zone, 22, 71 
 Monro, foramen of, 146, 147 
 Motor centres, 121 
 Myelencephalon, 194 
 
 Nerves — 
 Cranial, 136 
 
 Origins — deep, 170 
 
 superficial, 136, 
 170 
 Table of, 136 
 Fibres — white structure, 26 
 Roots, 16 
 Spinal, 
 
 Anterior spinal, 37 
 Posterior spinal, 38 
 Origins — deep, 37 
 
 superficial, 37 
 Nerve Cells — 
 
 Classification of, 36 
 Processes of, 35 
 Structure of, 34 
 Nerve Cells of — 
 Cerebellum, 102 
 
 Nerve Cells of — 
 Cerebrum, 128 
 Spinal Cord, 31 
 Neuroblasts, 192 
 Neuroglia {vtvpov, a nerve; 
 
 y\ia, glue), 26, 30, 132 
 Cells, 30 
 Fibres, 31 
 Neurones, 31, 40, 180 
 
 Spinal, 31, 40 
 Nodule of Cerebellum, 96 
 Nuclei of — 
 
 Arciform fibres, 82 
 Fourth ventricle, 111 
 Medulla, 67 
 
 Origin of nerves, 37, 1 70 
 Nuclei pontis, 91 
 Nucleus — 
 
 Accessory olivary, 81 
 Amygdalae, 162 
 Arciform, 82 
 Caudatus, 152 
 Cuneatus, 80 
 Dorsal, 33, 177 
 Gracilis, 80 
 
 Intermedio-lateral tract, 28 
 Lateralis of medulla oblon- 
 gata, 79 
 Lenticularis, 152 
 Of nerves — 
 
 Auditory, 112, 176 
 
 Fifth, 112, 174 
 
 Fourth, 174 
 
 Glosso - pharyngeal, 112, 
 178 
 
 Hypoglossal, 79, 111, 179 
 
 Olfactory, 171 
 
 Optic, 172 
 
 Seventh, 112, 176 
 
 Sixth, 112, 175 
 
 Spinal-accessory, 112, 179 
 
 Third, 173 
 
 Vagus, 112, 178 
 Olivary body, 72, 81 
 Optic thalamus, 153 
 Pontis, 91 
 Red, 167 
 
 Superior olivary, 92 
 Tegmenti, 167 
 
 
 
INDEX. 
 
 205 
 
 Obex (a bar), 109 
 Olfactorv bulb, 118 
 
 Groove, 118 
 
 Lobe, 119 
 
 Tubercle, 118 
 Olivary body (oliva, an olive), 72 
 
 Nucleus of, 72 
 
 Peduncle, 81 
 Olives, accessory, 81 
 Operculum (covering or lid) 
 
 of insula, 123 
 Optic Commissure, 133, 172 
 
 Thalami, 139, 153 
 
 Tract, 134, 172 
 Origins of Nerves — 
 
 Cranial, 170 
 
 Spinal, 37 
 
 Pacchionian bodies, 49 
 Pallium, 114 
 Paracentral lobule, 126 
 Parasinoidal sinus, 53 
 Pars Opercularis, 118 
 Orbi talis, 118 
 Triangularis, 118 
 Peduncles of — 
 
 Cerebellum, 97, 184 
 
 Cerebrum. 64, 113, 165 
 
 Corpus callosum, 15S 
 
 Pes of crura cerebri, 167 
 
 Pineal gland, 156 
 Perforated spot, anterior, 134 
 posterior, 135 
 Pia-arachnoid, 9, 51 
 Pia mater of — 
 
 Brain, 49 
 
 Septa, 6 
 
 Spinal Cord, 6 
 Dissection, 6 
 
 Structure of, 8 
 Pineal (pinea, a pine-cone) body 
 
 or gland, 156 
 Pituitary [jntvita, phlegm or 
 
 mucus) body, 134, 135 
 Plexus, choroid, 111, 145, 149 
 Pons Tarini, 135 
 Pons "Varolii, 87 
 
 Forniatio reticularis, 91 
 
 Grey matter of, 91 
 
 Pons — 
 
 Raphe of, 91 
 
 White matter of, 89 
 Precuneus, 126 
 Primitive groove, 190 
 Processes — 
 
 Axis-cylinder, 35 
 
 Protoplasmic, 36 
 
 Reticularis, 2S 
 Projection fibres, 157, 162, 184 
 Prosencephalon (-rrpos, before; 
 4yK€(pa\ou, the brain), 194 
 Puivinar (a couch), 154 
 Purkinje, cells of, 103 
 Putamen, 153 
 Pyramidal cells, 129 
 Pyramidal tracts of medulla 
 oblongata, 70, 71, 73 
 
 Tracts of Spinal Cord, 1 8 
 Crossed, 20 
 Direct, 19 
 Pyramid of cerebellum, 96 
 Pyramids, medulla oblongata, 67 
 Pyramids — 
 
 Anterior, 72 
 
 Inferior decussation of, 72 
 
 Posterior, 67 
 
 Superior decussation of, 81, 
 83, 187 
 
 Raphe (pa^Tj, a seam) of — 
 
 Corpus callosum, 158 
 
 Medulla, 82 
 
 Pons, 91 
 Realm, trophic, 33, 184 
 Recapitulation of medulla, 85 
 Recess, lateral, 107 
 Relations of fissures of cerebrum 
 
 to scalp, &c, 128 
 Removal of Brain, 44 
 Restiform (restis, a rope) bodies, 
 
 . 70, 99, 184 
 Rhinencephalon, 114, 125 
 Rhombencephalon, 194 
 Rolando, Funiculus of, 69 
 Tubercle of, 69 
 Root zone, 20 
 
 Ascending of 5 th nerve, 80 
 Rostrum of corpus callosum, 158 
 
206 
 
 INDEX. 
 
 Rust-coloured layer of cere- 
 bellum, 104 
 
 Senses — 
 
 Hearing, 181 
 
 Muscular, 24 
 
 Pain, 24 
 
 Smell, 181 
 
 Sight, 122 
 
 Taste, 181 
 
 Temperature, 24 
 
 Touch, 24 
 Sensory decussation, 81, 83, 187 
 Septum Lucidum, 147 
 
 Posticum of Spinal Cord, 8 
 Sinuses — 
 
 Basilar, 55 
 
 Cavernous, 54 
 
 Circular, 55 
 
 Lateral, 54 
 
 Longitudinal, inferior, 53 
 superior, 53 
 
 Occipital, 56 
 
 Parasinoidal, 53 
 
 Petrosal, inferior, 55 
 superior, 55 
 
 Straight, 54 
 
 Transverse, 55 
 
 Venous, 52 
 Solitary cells, 34 
 Somatochromes, 35 
 Spaces — 
 
 Inter-peduncular, 133 
 
 Perforated, anterior, 134 
 posterior, 135 
 
 Sub-arachnoid, 4, 9, 51 
 
 Sub-dural, 4, 9, 51 
 Spinal Cord, 12 
 
 Anatomy of, 12 
 
 Arachnoid, 9 
 
 Arteries of, 11 
 
 Central Canal, 29 
 
 Columns or Tracts of, 18 
 Anterior, 15, 19 
 Antero-external, 20 
 Antero-internal, 19 
 Antero-lateral — 
 ascending, 21 
 descending, 21 
 
 Spinal Cord — 
 
 Columns or Tracts of — 
 
 Basis bundle, 20 
 
 Bruce's, 24 
 
 Biirdach, 22 
 
 Crossed pyramidal, 20 
 
 Direct lateral cerebellar, 21 
 
 Direct pyramidal, 19 
 
 Goll's, 22 
 
 Intermedio-lateral, 28 
 
 Lateral, 15, 20 
 
 Limiting layer, 22 
 
 Lissauer's, 23 
 
 Mixed zones, 22, 71 
 
 Posterior, 15, 22 
 
 Postero-external, 23 
 
 Postero-internal, 22 
 
 Postero-marginal, 23 
 
 Pyramidal crossed, 20 
 direct, 19 
 Commissures of — 
 
 Grey, 15, 29 
 
 White, 14, 25 
 Cornua of, 28 
 Development of, 191 
 Dura mater, 4 
 Enlargement of, 13 
 External form of, 13 
 Filum terminal e, 8, 13 
 Fissures of, 14 
 Grey matter of, 17, 27 
 
 Structure of, 30 
 Ligamentum denticulatum, 7 
 Lymphatics, 1.2 
 Membranes of, 3 
 Nervous constituents of, 31 
 Neuroglia of, 30 
 Origin of nerves from — 
 
 Deep, 37 
 
 Superficial, 37 
 Parts of, 13 
 Pia mater, 6 
 Tracts of, 18 
 
 (see Columns), 18 
 Veins, 12 
 White matter of, 17, 18 
 
 Structure of, 26 
 Spinal — 
 Arteries, 11 
 
INDEX. 
 
 207 
 
 Spinal— 
 Nerves, 16 
 Veins, 12 
 Vessels, 11 
 Splenium (airXriuiov, a compress) 
 of the corpus callosum, 158 
 Spongioblasts, 191 
 Spot, perforated, 134, 135 
 Strands — 
 
 White, 157 
 Motor, 73, 18-4 
 Sensory, 187 
 Stria? acusticse, Q6. 107 
 
 Longitudinal, lateral, and 
 mesial of corpus callosum, 
 15S 
 Structure (minute) of — 
 Arachnoid of Brain, 51 
 
 of Spinal Cord, 10 
 Dura mater of Brain, 48 
 
 of Spinal Cord, 6 
 Grey matter of Brain, 128 
 
 of Cerebellum, 102 
 of Spinal Cord, 30 
 Nerve Cells, 34 
 Pia mater of Brain, 50 
 
 of Spinal Cord, 8 
 "White matter of Spinal Cord, 
 •>* 26 
 
 Sub-arachnoid fluid, 10, 51 
 Space, 4, 9, 51 
 Trabecule, 8, 9 
 Sub-divisions of Brain, 63 
 Sub-dural space, 4, 9, 51 
 Substantia gelatinosa, 28 
 
 Nigra. 168 
 Sulci (furrows) fissures of the 
 cerebral hemispheres, 114 
 Calloso-marginal, 1 24 
 Callosal, 124 
 Calcarine, 126 
 Inter-lobular, 115 
 Intralobular, 116 
 Intra-parietal, 120 
 Island of Reil, 123 
 Lateral dorsal, 67 
 Olfactory, 119 
 Paramedian, 67 
 Parieto-occipital, 116, 120, 126 
 
 Sulci— 
 
 Pracentral, 117 
 
 Temporal, 122 
 
 Tri radiate, 118 
 (see also Fissures) 
 Sulcus — 
 
 Lateral (crus cerebri), 166 
 
 Lateral dorsal, 69 
 
 Oculomotorii, 166, 173 
 
 Paramedian, 67 
 Summaries — 
 
 Brain, 170 
 
 General, 180 
 
 Medulla, 75 
 
 Spinal cord, 40 
 Sylvius, Aqueduct of, 170 
 
 Tables — 
 
 Ascending and Descending 
 
 Degenerations, 41 
 Cerel>ral Vesicles, 194 
 Convolutions of, 
 
 Frontal, 119 
 
 Mesial surface, 127 
 
 Occipital lobe, 122 
 
 Parietal lobe, 121 
 
 Temporal lobe, 123 
 Cranial nerves, 136 
 Dura Mater — Agreements and 
 
 Differences, 48 
 Gowers', 42 
 
 Grey Matter of Medulla, 82 
 Tracts of conduction, 41 
 Objects on base of Brain, 137 
 Objects on surface of Medulla, 
 
 75 
 Order in which Tracts get 
 
 their Medullary Sheath, 41 
 Relations of Tracts of Cord 
 
 and Medulla, 76 
 Superficial Origins of the 
 
 cranial nerves, 136 
 Vesicular Columns, 34 
 White tracts of Spinal Cord, 
 
 25 
 Ta?nia (Taiuia, a band), 110 
 Hippocampi, 126, 145 
 Semi-circularis, 144, 162 
 Tarini Pons, 135 
 
208 
 
 INDEX. 
 
 Tegmentum (covering) of crura 
 cerebri, 166 
 
 Nucleus of, 167 
 Telencephalon, 194 
 Tentorium (a tent) cerebelli, 47 
 Thalamus (bed) opticus, 153 
 Trabs (a beam) cerebri (corpus 
 
 callosum), 157 
 Trabecules sub-arachnoid, 8, 9 
 Tracts of Spinal Cord, 18 
 Tract— 
 
 Antero-external, 20 
 
 Antero-lateral ascend., 21, 71 
 descend., 21, 71 
 
 Goll's, 22, 68 
 
 Optic. 134, 172 
 
 Lateral Cerebellar, 21 
 
 Pyramidal, direct, 19, 73, 185 
 crossed, 20,71, 185 
 
 Spinal Cord, 18 
 
 Interna edio- lateral, 34 
 Trapezium of Pons Varolii, 90 
 Trophic realm, 33, 184 
 Tuber cinereum, 134 
 
 Olfactorium, 118 
 
 Valvule, 96 
 Tubercle — 
 
 Amygdaloid, 96 
 
 Cuneate, 69 
 
 Rolando, 69, 80 
 Tubercula quadrigemina, 169 
 
 (see Corpora Quadrigemina) 
 Tuberculum acusticum, 112 
 Tiirck, Fasciculus of, 19 
 
 Uvula (dim. of uva, a cluster of 
 grapes) of Cerebellum, 96 
 
 Vallecula of Cerebellum, 94 
 Valve of Vieussens, 100, 174 
 "Varolii, Pons, 87 
 Veins — 
 
 Cerebellar, 61 
 
 Cerebral, 61 
 
 Emissary, 56 
 
 Veins — 
 
 of Galen, 1 50 
 
 Spinal, 12 
 Velum, inferior or posterior 
 medullary, 1 00 
 
 Interposition, 148 
 
 Superior or anterior medul- 
 lary, 100 
 Venous Sinuses, 52 
 Ventricles {ventriculus , dim. of 
 venter, a belly)— 138, 141 
 
 Dissection to expose, 140 
 
 Epithelial lining of, 145 
 
 Fifth, 147 
 
 Fourth, 106 
 
 Lateral, 138, 142 
 
 Medullary portion of 4th, 107, 
 108 
 
 Nuclei of, 111 
 
 Third, 146 
 
 Upper portion of 4th, 107, 108 
 
 Verga, 162 
 Vermiform process, 93, 96 
 Vesicles — 
 
 Anterior Cerebral, 196 
 
 Middle Cerebral, 195 
 
 Posterior Cerebral, 195 
 Vesicular Columns, 32 
 
 Lateral, 28 
 
 Table of, 34 
 Vessels — 
 
 Spinal, 11 
 
 of Brain, 57 
 Vicq d'Azyr, bundle of, 161 
 Vieussens, Valve of, 100 
 
 White Matter - 
 
 Brain, 157 
 
 Cerebellum, 105 
 
 Medulla, 67, 113 
 
 Spinal Cord, 18 
 Willis, Circle of, 60, 132 
 Wyllie's Trophic realms, 33, 184 
 
 Zone, mixed, 22, 71 
 
 Printed by E. & S. Livingstone, 4 Melbourne Place, Edinburgh. 
 
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 THE 
 
 Topographical Anatomy 
 of the Child 
 
 By JOHNSON SYMINGTON, M.D., 
 
 F.R.S.E., P.R.C.S.E., 
 
 Professor of Anatomy, Queen's College, Belfast; formerly Lecturer 
 
 on Anatomy. School of Medicine, and Examiner in 
 
 Anatomy, University of Edinburgh. 
 
 Illustrated by 14 beautiful and correctly Coloured Plates (nearly 
 all of which are life size) and 33 Woodcuts. 
 
 ' 1 >r Johnson Symington has well filled a gap in our Topographical Anatomy. 
 This department of anatomical science has been worked at most extensively and 
 ably b v Pirogoff, Braune, Luschka, and others, in the adult ; but the method of frozen 
 sections has hitherto been systematically applied to the child, in one case only, by 
 Professor Dwight. Dr Symington has added to our knowledge by presenting 
 us in this work with fourteen coloured lithographic illustrations, all life-size, 
 and thirty -three woodcuts taken from sections of male and female children, aged 
 four years and a half, five years, six years, and thirteen years, and has given us 
 a large number of very accurate observations on the position of the various organs 
 and viscera, and the changes which they undergo in the earlier periods of life. The 
 horizontal sections have been taken from a girl six years of age, whilst the vertical 
 sections (both coronal and sagittal) are from children of both sexes and various 
 ages. In addition to the illustrations, the work is most valuable for excellent 
 letterpress, treating very fully and minutely of the position of structures at all 
 periods of early life, and it is evident that many of the views generally held in 
 regard thereto will have to undergo considerable alteration. For example, l>r 
 Symington shows that the external auditory meatus is relatively as long in the 
 child as in the adult, when examined in the fresh state in subjects with the entire 
 head frozen; that the spinal cord in the newly-born child ceases at much the 
 same point as in the adult ; that the child's neck is not relatively short, but that 
 it is higher in relation to the vertebral column than in the adult. The common 
 assumption that the position of the stomach in the child is vertical is also shown 
 to be erroneous, and is proved by figures taken from an infant four days old, and 
 from a girl six years of age. The portion of the book devoted to the position of 
 the pelvic viscera in male children is of great importance to surgeons, and will be 
 carefully studied in view of operations on the urinary organs in early life. Too 
 much praise cannot be bestowed upon the author for the obvious care and industry 
 with which he has pursued his investigation, and the accuracy and fidelity with 
 which he has reproduced its results. Its dedication to Professor Uraune is a most 
 graceful compliment to an anatomist who has done more to advance the knowledge 
 of Topographical Anatomy than any other worker in this special branch.'— 2'he 
 Lancet, 2'2nd October 1887. 
 
E. 6- S. LIVINGSTONES' 
 
 Just Published, price 15s. net. 
 
 Profuselj/ Illustrated. 
 
 A TEXT-BOOK 
 
 OF 
 
 Medical Jurisprudence, Toxicology, 
 
 AND 
 
 Public Health. 
 
 BY 
 
 JOHN GLAISTER, M.D., 
 
 D.P.H.(Camb.), F.E.S.E. 
 
 Professor of Forensic Medicine and Public Health in the University 
 
 of Glasgow. 
 
 ' Taking this work as a whole we can unhesitatingly pronounce it to be one of 
 the best text-books dealing with Medical Jurisprudence, Toxicology, and Public 
 Health which we have met with. It is well written throughout, the information 
 contained in it is full and accurate without being redundant, and the illustrations 
 are appropriate and well executed. We can cordially recommend it to medical 
 practitioners and students, and also to members of the legal profession who will 
 find therein a useful guide in a class of cases which are often perplexing to the 
 legal mind.'— Lancet. 
 
 'This text-book will add a welcome unit to those with which Professors of the 
 Faculty of Medicine in the University of Glasgow have enriched the literature of 
 the profession. ... A novel feature of this work, as compared with similar 
 works published in former years, is the description of the Bertillon method of 
 identification, and of Galton's finger print system. The illustrations are numerous, 
 many consisting of photo reproductions, and therefore giving life-like pictures 
 of the various objects or features detailed. Altogether, l)r Glaister may be 
 congratulated on having produced a very useful text-book, and one to which both 
 the medical student and practitioner may turn for information with all confidence.' 
 — Glasgow Herald. 
 
PUBLICATIONS. 
 
 Third Edition, in 2 vols., price 18s. 
 
 ILLUSTRATED WITH 238 USEFUL ENGRAVINGS. 
 
 Applied Anatomy 
 
 BY 
 
 JOHN M'LACHLAN, M.D., B.Sc, F.R.C.S.E., &c. 
 
 The Book includes what is usually known as— 
 
 1. SURGICAL ANATOMY. 2. MEDICAL ANATOMY. 
 3. OPERATIVE SURGERY. 
 
 USED AS A TEXT-BOOK IN THE PRINCIPAL UNIVERSITIES & MEDICAL COLLEGES. 
 
 1 It deserves every success.' — Sir Gkokge Macleod, Professor of Surgery, 
 University of Glasgow. 
 
 ' If the medical student of to day comes to an examination unprepared, and 
 retires without his diploma, he certainly cannot lay the blame of his failure on 
 want of instruction. To help the student in his difficulties, to guide him in the 
 waste wilderness of his poor lecture-room notes, and to give him a chance of 
 learning something, the student has to find for himself men that can really teach 
 him, and books that convey useful information, information that will bear not 
 only on the work of the examination, but also on his futme professional life. 
 Dr M'Lachlan is such a teacher, and his book is of the kind we mean. It is a 
 successful attempt to show how the facts of Anatomy are necessary as a ground- 
 work both of Surgery and Medicine. If mastered it will do the student more 
 good than acres of MSS. dealing with theory and fad, for it makes his 
 anatomy interesting, and the bedside or the operating theatre intelligible, and, 
 except where vested interests in fees come in, it is pretty generally acknowledged 
 now that the dissecting room, the laboratory, and the hospital are the real places 
 of study.' — Edinburgh Medial Journal. 
 
 'The text is copiously illustrated with well executed engravings, numbering 
 altogether 238 as against 74 in the former edition. The author has produced a 
 work which is more fitted to meet the wants of the student and the practising 
 surgeon in the application of anatomy to practice, than any other which has 
 come under our notice.'— Hospital Gazette. 
 
 'The book is written specially with a view to the requirements of students 
 preparing for the higher examinations; and its successive editions have, in this 
 regard, been each one more perfect than the last. In this issue much new 
 matter and many new illustrations have been added. The work may be cordially 
 recommended to students as a complete and practically useful text-book.' — 
 Scotsman. 
 
E. & S. LIVINGSTONES' 
 
 Just Published, Fifth Edition, price 10s. 6d. net. 
 
 The Students' Handbook 
 
 OF THE 
 
 PRACTICE of MEDICINE 
 
 Designed for the use of Students and 
 Junior Practitioners. 
 
 By H. AUBREY HUSBAND, M.B., CM., 
 
 B.Sc, P.R.C.S.E., M.R.C.S., L.S.A., 
 
 FORMERLY LECTURER ON MEDICAL JURISPRUDENCE AND PUBLIC HEALTH 
 
 IN THE EXTRA-ACADEMICAL SCHOOL. EDINBURGH. 
 
 MEMBER OF THE GENERAL COUNCIL OF THE UNIVERSITY OF EDINBURGH; 
 
 EXTRAORDINARY MEMBER OF THE ROYAL MEDICAL 
 
 SOCIETY, EDINBURGH; 
 
 AND CORRESPONDING FELLOW OF THE MEDICO-LEGAL SOCIETY 
 
 OF NEW YORK. 
 
 Illustrations, Tables, Prescriptions, and Glossary. 
 
 'The book before us is an excellent example of its class; the 
 whole of medicine is digested and tabulated, and in fact served up 
 ready prepared at infinite pains to render it easily assimilated.' — 
 Lancet. 
 
 ' The distinguishing features of Dr Husband's handbook are con- 
 densation and clearness of diction— qualities which are certain to 
 ensure for the book a favourable reception by those for whom it is 
 intended. We have pleasure in recommending it to our readers as 
 a most useful work to peruse immediately before presenting one's 
 self for a Medical Examination.' — Students' Journal. 
 
 'The book is not put forth as a systematic treatise upon diseases 
 and their treatment, but under each section will be found a brief 
 statement of the main points connected with all the diseases 
 enumerated in the nomenclature of the Royal College of Physicians, 
 London. From the point of view of the uses to which this Manual 
 is designed, we know of no work that can be put in comparison with 
 it.' — Provincial Medical Journal. 
 
 ' Whether as a handbook for use as an introduction to the 
 systematic study of disease, or for the purpose of refreshing the 
 memory on the eve of an examination, the work is equally to be 
 commended, and one may safely assert that it will retain its well- 
 earned popularity.' — Hospital Gazette. 
 
PUBLICATIONS. 
 
 Sixth Edition, Revised and considerably Enlarged. 
 
 Illustrated by Coloured Plates, price 10s. 6d. net. 
 
 THE STUDENTS 7 HANDBOOK 
 
 OF 
 
 Forensic Medicine, Toxicology, and 
 Public Health 
 
 By H. AUBREY HUSBAND, M.B., CM., 
 
 B.Sc, M.R.C.S., L.S.A., F.R.C.S.E., 
 Author of ' Student's Handbook of the Practice of Medicine,' 1 etc. 
 
 U«ed as a Text-book in the principal Universities and Medical Schools in 
 Great Britain, India, and the Colonies. 
 
 'It is intended for students, and is for them very convenient. 
 This edition fully sustains the acceptableness of the work.' — 
 Lancet. 
 
 'The work is an excellent epitome of the subjects on which it 
 treats, and contains all that the student need know to pass his 
 examinations, or that the ordinary practitioner will require in the 
 course of his practice. ... As a trustworthy and readable guide 
 to the study of forensic medicine, we can strongly recommend it to 
 both students and practitioners.' — Student's Journal. 
 
 'The book is one which can be commended, and will in the 
 future, as in the past, doubtless smooth the passage of many medical 
 students through the difficulties of the examination room.'— Public 
 Health. 
 
 'The work has long enjoyed a pre-eminent reputation as a book 
 useful to students about to proceed to examination in the subjects 
 of which it treats; and men have been known to boast of having 
 secured academic degrees by no more than a cursory perusal of its 
 pages. They toiled not; but, being possessed of this handbook, 
 neither were they spun. The new edition gives the book in an im- 
 proved shape. The text has been revised, new matter lias been 
 added; and some professionally beautiful illustrations now appear 
 in the work. For the rest, this edition keeps the handbook well 
 abreast of its reputation.' — Scotsman. 
 
E. 6- S. LIVINGSTONES' 
 
 Just Published, Second Edition, price 12 s. net. 
 
 Elementary Textbook of Zoology 
 
 BY 
 
 ARTHUR T. MASTERMAN, 
 
 M. A. (Cantab.); D.Sc.(Lond. and St A?id.); F.R.SE.j 
 
 LECTURER ON ZOOLOGY AND BIOLOGY IN THE 
 SCHOOL OF MEDICINE OF THE ROYAL COLLEGES, EDINBURGH; 
 
 JOINT-AUTHOR OF 
 
 'THE LIFE-HISTORIES OF THE BRITISH MARINE FOOD-FISHES "; 
 
 EXAMINER IN BIOLOGY TO THE 
 
 ROYAL COLLEGE OF PHYSICIANS, EDINBURGH, ETC. 
 
 Pr o fusel y III us tr a ted. 
 
 Just Published, price 4s. net. 
 
 HANDBOOK of PUBLIC HEALTH 
 
 BY 
 
 JOHN ORR, 
 
 M.D.j F.R.C.P.E.j M.R.C.S.(Eng.)j 
 
 4 The medical student in particular will be the gainer by the 
 publication of Dr Oil's manual, but the general reader also may 
 glean useful instruction from its pages.' — Glasgow Herald. 
 
PUBLICATIONS. 
 
 Just Published, price 2s. 6d. net. 
 
 Illustrated by numerous Woodcuts Plain 
 and in Colour, 
 
 Midwifery Notes 
 
 FOR THE USE OF STUDENTS. 
 
 By T. A. GLOVER, M.D.(Edin.) 
 
 Fellow, Obstetrical Society, London, fyc. 
 
 'The author distinctly states that the object of these Notes is to help the 
 student in liis Practical Midwifery Training; to this end only matter which is 
 likely to be exemplified in the ordinary run of cases is included and this in such 
 a manner as to be easily digested and as easily retained. This book will be found 
 to he a useful introduction to the Art of Midwifery.'— pity's Hospital Gazette. 
 
 Price Five Shillings. 
 
 THE STUDENTS' 
 
 Handbook of Gynecology 
 
 PROFUSELY ILLUSTRATED. 
 
 THE MOST PRACTICAL HANDBOOK EYEE, PUBLISHED. 
 
 Used as an Introductory Text-Book in all the 
 Universities and Medical Schools. 
 
 'Everything is stated in a most clear and concise way, and as the volume is 
 nicely illustrated, it should he of great assistance to final men especially.' — 
 Dispatch. 
 
 'It is clearly and concisely written, and it is surprising; to find that it has 
 succeeded so well, in the small space at its disposal, in covering the ground 
 necessary for an elementary knowledge of this progressive and important branch 
 of medical learning ' — Scotsman. 
 
io E. &> S. LIVINGSTONES' 
 
 Just Published, price 4s. 6d. net. 
 
 The Conservative Treatment 
 
 OF 
 
 Tubercular Joint Disease 
 and Cold Abscess 
 
 AS CARRIED OUT AT BRESLAU BY 
 
 Prof. J. von MIKULICZ, LL.D.Edin. 
 
 BY 
 
 Dr a. henle, 
 
 Chief Assistant at the Surgical Klinilc, Breslau. 
 With PREFACE by Professor J. von MIKULICZ. 
 
 TRANSLATED FROM THE GERMAN BY 
 
 CHARLES W. CATHCART, F.R.C.S., 
 Senior Assistant Surgeon, Royal Infirmary, Edinburgh. 
 
 ' We regard this as a most important contribution to the literature of a, 
 most important department of surgery. Every practising surgeon should 
 learn for himself what the modes of treatment are which find favour with 
 Professor Mikulicz in a domain wherein he ranks as an authority of no 
 undeniable weight. In this handsomely bound and well printed octavo, he 
 will find discussed the "congestion" treatment, the "orthopaedic" treat- 
 ment, ihe " iodoform" treatment, ai d all the other preliminary m> thods of 
 avoiding the more advanced procedures of erasion, excision, &c, which 
 may be employed before sacrificing a whole limb. We strongly recommend 
 this volume to the attention of every practitioner.' — The Medical Press, 
 
PUBLICATIONS. n 
 
 Demy 4to., price 7s. G<1. 
 
 Illustrated -with 10 Coloured Plates. 
 
 Nerves of the Human Body 
 
 By ALFRED W. HUGHES, M.B. & C.M.Edin.; 
 
 F.R.C.S.Edin.; M.R.C.S. Eng.; 
 
 Late Professor of Anatomy, King's College, London^ 
 
 'An excellent work of reference for students, quite in place in a Medical 
 School library. The drawings are large and bold, demonstrating the distributions 
 and connections of the cranial and spinal nerves with clearness and accuracy. 
 The cranial nerves in particular are well represented. . . . The preparation 
 of "Nerves <>f the Human Body" must have cost its author much trouble, and 
 Dr Hughes may be congratulated on the result of his labours.' — British Medical 
 Journal 
 
 • As regards the work little is left to be desired. As far as the diagrammatic 
 and literal description of the nerves goes, this work is undoubtedly good; and 
 there is no doubt that the anatomical details are an improvement on those usually 
 given. It will be found a help to students in their practical work, and of equal 
 help to the practitioner in his pathological and therapeutic investigations.' — 
 Provincial Medical Journal 
 
 Price 4s. 6d. net. 
 ILLUSTRATED WITH 8 COLOURED PLATES, 
 
 MANUAL OF 
 
 SURGICAL ANATOMY 
 
 By ALFRED W. HUGHES, M.B. & C.M.Edin.; 
 
 F.K.C.S.Edin. ; M.E.C.S.Eng. ; 
 
 Late Professor of Anatomy, King's College, London. Author of 
 ' Xerves of the Human Body,' Sec. 
 
 Used as a Handbook in all the Universities and Medical Colleges. 
 
 •This little book contains very terse descriptions of the anatomical facts most 
 important to students about to present themselves for their Final Examina- 
 tion in Surgery. Clearness sometimes, and elegance of diction often, have 
 been sacrificed to brevity. It will recommend itself to those for whom it is 
 specially prepared.' — Lancet. 
 
 ■ Or Hughes evidently possesses the faculty of condensing a large amount 
 of information into a small space in a clear and methodical manner. The student 
 will find it a very reliable guide. 'I he work contains a number of excellent 
 illustrations, which will greatly assist the student in learning the relative posiiions 
 of various structures which he would encounter in the ligature of the principal 
 arteries '—Edinburgh Medical Journal 
 
12 E. & S. LIVINGSTONES' 
 
 Second Edition, price 6s. 
 Revised and Enlarged, with 12 Tinted Plates and 40 Woodcuts. 
 
 MANUAL OF THE 
 
 Minor Gynecological Operations 
 and Appliances 
 
 By J. HALLIDAY CEOOM, M.D., 
 
 F.R.C.P.E., F.R.C.S.E., 
 
 Lecturer on Midwifery and Diseases of Women, School of Medicine ; 
 
 President of the Obstetrical Society, Edinburgh; and 
 
 Examiner in Midwifery in the University of Edinburgh and Royal College 
 
 of Physicians, Edinburgh, 
 
 ' she descriptions and recommendations of Dr Croom seem entirely familiar, 
 intelligible, and wholesome. A number of well- executed lithographic plates, 
 giving various relations of the pelvic organs, add to the value of the book.' — 
 American Journal of Obstetrics. 
 
 'We are glad to see that this valuable Manual has run into a Second Edition. 
 Its arrangement is such as will commend itself both to the student and busy 
 practitioner. We finish the perusal of this work impressed with its simplicity of 
 arrangement and lucidity of expression.' — Liverpool Medico-Chirurgicul Journal. 
 
 Price 10s. 6d. 
 THE STUDENTS' 
 
 Handbook of Medicine 
 
 AND 
 
 Therapeutics 
 
 By ALEXANDEE WHEELEE, 
 
 Clinical Assistant , Out-Patient Department, Edinburgh Eoyal Infirmary . 
 Author of "Our Unseen Foes," &c. 
 
 Used as a Text-Book in the principal Universities and Colleges. 
 
 ' It is distinctly designed to refresh the memory on salient points, as well as to 
 enunciate the leading principles of treatment. These aims have been faithfully 
 carried out, and that too with an originality for which it might be thought there 
 could be little scope. Clear, concise, and accurate.' — Lancet. 
 
PUBLICATIONS. 13 
 
 3rd Edition. 5th Thousand, price 5s. net. 
 Illustrated by about 40 Plates (many Coloured) or 109 Figures. 
 
 Anatomy of the Brain and 
 Spinal Cord 
 
 By J. RYLAND WHITAKER, B.A., M.B.(Lond.) 
 
 F.R.C.P., L.R.C.S.(Edin.); 
 
 Lecturer on Anatomy, Surgeons' Hall, Edinburgh; Examiner for tfie 
 
 Triple Qualification. 
 
 Used as a Text-Book in the principal Universities and Medical Colleges 
 in Great Britain, India, the Colonies, U.S.A., and Italy. 
 
 'The book is an excellent Manual for the use of Students and makes a good 
 introduction to the heavier text-books. This Edition is made more valuable by 
 the inclusion of some new matter in the text, and by the addition of many new 
 figures and tables.' — Scotsman. 
 
 Price 4s. 6d. net. 
 
 Notes on Pathology 
 
 By J. RYLAND WHITAKER, 
 
 B-A^M-B-iLond.), F.K.C.P., L.R.C.S.fEdin.); 
 
 Lecturer on Anatomy, Surgeons' Hall, Edinburgh; Examiner for the 
 Triple Qualification. 
 
 Vol. I.— GENERAL. 
 
 Used as a Handbook in the principal Universities and Colleges. 
 
 'These "Notes," which traverse the whole range of General Pathology, have 
 evidently been compiled with great care. Together, they form an outline of the 
 subject of which it will not be difficult for the student to fill in such details as he 
 gathers from his lecturer or his text-book. The author himself recognises this as 
 the main object of his publication, and we may say at once that he has done his 
 work well, and that it should prove of much utility. In these days of "compendia " 
 of knowledge, where the aim often seems to be to condense into as small a space 
 as possible the facts of science, so that the student may be saved the trouble of 
 learning them step by step, it is gratifying to find a writer who takes a higher 
 view of the kind of assistance that the student needs. The information he 
 convey* in his little work is considerable, and also accurate; in parts even — e.g., 
 in the sections dealing with Inflammation and the Parasites- -it is almost, if not 
 quite, as full as is to be found in many a text-book. But it would be difficult for 
 the student to use the work simply for the purpose of "cram." We believe, 
 moreover, that teachers also may be glad of so concise a summary of the subject 
 as Mr Whitaker has riven.' — Lancet. 
 
i 4 E. & S. LIVINGSTONES' 
 
 Demy 8vo, price 4s. 6d. net. 
 
 Vaccination Eruptions: 
 
 ORIGINAL RESEARCH. 
 By THOMAS DOBSON POOLE, M.D., 
 
 Master in Surgery, University of Edinburgh; Felloiu of the Obstetrical Society. 
 
 'The title of this very interesting work concisely indicates its contents. A 
 good acquaintance -with the literature of the subject is shown on every page, and 
 the cited cases are of great interest, especially those in connection with the 
 subject of generalised vaccine eruption {vaccine gineralisee) . The differential 
 diagnosis between vaccination, ulcers, and primary chancres, also between vac- 
 cination eruptions and secondary syphilitic manifestations, is given in extenso 
 from Portalier's summary of Founder's lectures. In conclusion, this work deserves 
 perusal by all who are interested in the subject of vaccination, therefore by all 
 medical practitioners.' — British Medical Journal. 
 
 Second Edition. Price Two Shillings net. 
 
 Revised in accordance with the British Pharmacopoeia, 1898. 
 96 po. Crown 8vo. Bound in Cape Morocco. 
 
 The Students' 
 Practicai Materia Medica 
 
 BY 
 
 G. HAXTON GIFFEN, 
 
 L.R.C.P.E., L.R.C.S.E., L.F.P.&S.G. ; 
 
 'Bathgate' Gold Medallist in Materia Medica, Royal College of Surgeons. 
 
 'We recommend this little book.' — Dublin Journal of Medical Science. 
 
 'It contains a vast amount of information in small compass and is likely to 
 become popular with students preparing for an examination.' — Edinburgh Medical 
 Journal. 
 
 'This is a very concise and practical manual, a summary and resume* of the 
 principles of pharmacology, and the nature and uses of drugs with their doses. 
 The method of the arrangement of tlie chapters is simple and intelligible and 
 the doses of officinal preparations are stated under a system of classification 
 which prevents reiteration and more readily impresses the memory.' — Glasgow 
 Herald. 
 
 'It is at present the most succinct, lucid, and suggestive of all the manuals on 
 the subject.' — Scotsman. 
 
 ' It contains much useful nformation.' — Medical Press. 
 
PUBLICATIONS. 15 
 
 Quarto. Price Sixpence net. 
 SCHEDULES FOR 
 
 PLANT DESCRIPTION 
 
 (ILLUSTRATED) 
 
 By JOHN WISHART, 
 
 Lecturer on Zoology and General Biology in Robert Gordon's College, Aberdeen ; 
 Herbarium Medallist of the Pharmaceutical Society of Great Britain. 
 
 USED IN ALL UNIVERSITIES AND COLLEGES. 
 
 1 The use of these Schedules by pupils will train their powers of observation 
 and reasoning, and prevent them from being contented with book knowledge.' 
 — Dublin Journal of Medical Science. 
 
 • These tables are admirably adapted and arranged on a scientific principle 
 for building up an instructive record of plant examination.' — Aberdeen Daily 
 Free Press. 
 
 B"2" THE SAME AUTHOR, 
 
 Price Two Shillings net. 
 THE 
 
 Botanists' Vade Mecum 
 
 ' A very handy little pocket guide to the classification of plants, intended for 
 use during botanical excursions. The matter is very concise and well arranged, 
 and the value of the book is very materially enhanced by an ingenious and 
 novel form of index.' — Guy's Hospital Gazette. 
 
 'This little manual, of a size suitable for the pocket, will form a useful com- 
 panion to students of botany in their tield-days. Its arrangement is concise, 
 and its information conveniently scheduled. A useful ledger-index adds to the 
 convenience of the manual.' — Glasgow Herald. 
 
 'We commend this Vade Mecum as a very useful guide to all botanical 
 excursion students, who will find it an invaluable aid to recognising the char- 
 acters of the various divisions and natural orders.' — British and Colonial Druggist. 
 
1 6 E. & S. LIVINGSTONES' 
 
 Price 2s. 6d. net. 
 THE ROTATORY MOVEMENTS 
 
 OF THE 
 
 HUMAN VERTEBRAL COLUMN 
 
 AND THE 
 
 SO-CALLED MUSCULI ROTATORES. 
 By ALFKED W. HUGHES, 
 
 M.B. & CM. Edin. ; F.R.C.S. Eng. ; F.R.C.S. Edin ; 
 
 Late Professor of Anatomy, King's College, London; Author 
 oj ' Nerves of the Human Body'' and '■Manual of Surgical Anatomy.' 1 
 
 'The entire work bears evidence of careful observation, and forms a useful con- 
 tribution to the mechanism of the human skeleton.'— Edinburgh Medical Journal. 
 
 NEW EDITION. 
 
 Revised in accordance with the British Pharmacopoeia, 1898. 
 Price One Shilling net. 
 
 POSOLOGICAL TABLES; 
 
 Appendix on Poisons; Index of Diseases; 
 and Medicines arranged according to their Actions. 
 
 By WILLIAM CRAIG, M.D., 
 
 CM., F.R.S.E., 
 
 Lecturer on Materia Medica, School of Medicine, Surgeons' Hall, Edinburgh 
 
 Late Examiner in Materia Medica, Edinburgh University ; 
 
 Examiner, Royal College of Surgeons. 
 
 Being a Tabular Arrangement of all the Medicines contained in the 
 British Pharmacopoeia, with Dose, &c. 
 
 ' This is a useful little book, containing; a tabular arrangement of all the Phar- 
 macopceial preparations, with their doses and methods of administration. A table 
 on Poisons and an Index of Diseases with Appropriate Remedies are included.' — 
 Lancet. 
 
PUB LIC A T10NS. 1 7 
 
 Price Is. 6d. net. 
 
 Materia Medica Tables. 
 
 Designed for the Use of Students. 
 
 By A. HERBERT BUTCHEK, 
 
 L.R.C.P., L.R.C.S. &L.M., 
 Honorary Surgeon to Birkenhead Borough Hospital. 
 
 ' This is a small work intended to supply a long-acknowledged want, and 
 will be found to contain muck information arranged in an admirably simple 
 manner.' — Pitblisher' s Circular. 
 
 Price 2s. 6d. net. 
 
 THE STUDENTS' HANDBOOK 
 
 OF 
 
 Diseases of the Skin 
 
 Illustrated bj) Colour**) |)lates ant) ffiloob (Engrabinqs. 
 
 ' It is clearly and systematically arranged, and the student who masters its 
 contents will have acquired a useful general knowledge of the pathological 
 classification, course, and methods of treatment of all but the rarest diseases of 
 the skin.' — Manchester Guardian. 
 
 1 It will prove of service to the young practitioner, and also to older men in 
 country practices, whose work leaves them but little time for the study of 
 books of greater pretensions. A number of well-executed illustrations increase 
 the working value of the book.' — The Publisher's Circular. 
 
 Second Edition. Price 6d. net. 
 
 Revised in accordance with the British Pharmacopoeia, 1898. 
 
 Dose Tables of Materia Medica 
 
 Containing all the Doses required for Examinations and 
 
 Prescribing. 
 
 By T. HOMER, L.R.C.S., L.R.C.P.Edin. 
 
 u 8/02. 
 
1 8 E. & S. LIVINGSTONES' 
 
 Price Is. 6d. in Paper Boards; or in Cloth, 2s. 
 
 THE CHILD-HOW TO ITJRSE IT; 
 
 Or the Management of Children and their Diseases. 
 By ALEXANDER MILNE, M.D. 
 
 ' Dr Milne not only describes how the Child should be managed 
 from the hour of birth, but he notes the distinctive characteristics of 
 all the ailments to which Children are liable, and gives instruction as 
 to their proper treatment. A great many works have been published 
 of late years, but there is certainly not one which is more likely to be 
 of use to inexperienced or conscientious parents.' — Scotsman. 
 
 ' This little work will be found to contain copious details on the 
 management of infancy, expressed in language singularly free from 
 technicalitie s. ' — Courant. 
 
 ' We heartily recommend the careful study of Dr Milne's invaluable 
 work.' — Ladies 1 Oion Journal. 
 
 ' To emigrants and others who are at a distance from medical aid, 
 we believe the book will be a "present help in time of trouble.'" — 
 North Metropolitan. 
 
 Price Threepence. 
 
 The Monthly Nurse: 
 
 A FEW HINTS ON NURSING. 
 By H. AUBREY HUSBAND, M.B., CM., B.Sc., &c. 
 
 ' It can scarcely be said that a handbook of this kind is not 
 required, and it is certain that a more clearly-arranged little work of 
 the kind could not be found.' — Scotsman. 
 
 1 A little Manual written in the simplest possible style, but contain- 
 ing invaluable advice and instruction for those who have to act as 
 midwives. District visitors who should distribute copies of this 
 pamphlet to poor mothers would save them much unnecessary misery.' 
 — Literary World. 
 
 1 We have very great pleasure in bearing testimony to this excellent 
 little pamphlet. Monthly nursing, as it at present exists, is not at all 
 in a satisfactory condition, and it is a relief to be able to get at some 
 sensible advice and suggestions — Dr Husband supplies them here.' — 
 Medical Review. 
 
 We supply the above two Works on special terms to District Visitors 
 and Institutions using quantities for distribution. 
 
PUBLICATIONS. 19 
 
 Fourth Edition. Price 2s. net. 
 
 BOTANY NOTES 
 
 Specially adapted for Students preparing for Professional 
 Examinations in Medicine and Science. The various divisions 
 considered in accordance with the several University Syllabuses. 
 
 By ALEXANDER JOHNSTONE, F.G.S., 
 
 AUTHOR OF 'ZOOLOGY NOTES,' 
 
 Lecturer on Botany, School of Medicine, Edinburgh; and Natural Science 
 Master, Blair Lodge. 
 
 In reviewing ' Bofcauy Notes,' and ' Botany— a Manual,' The Lancet says 
 'This little volume entitled " Botany Notes" traverses the same ground as 
 the other book, but is rather more suitable for use on the evening preceding 
 Exam. It is not too much to believe that, if the student does not receive 
 material aid from the "Botany Notes" now before us, he has but small 
 prospect of receiving assistance from any printed matter whatever.' 
 
 Price 3s. 6d. net. 
 
 ZOOLOGY NOTES 
 
 Specially" adapted for Students preparing for Professional 
 Examinations in Medicine and Science. The various divisions 
 considered in accordance with the several University Syllabuses. 
 
 By ALEXANDER JOHNSTONE, F.G.S., 
 
 AUTHOR OF 'BOTANY NOTES,' 
 
 Lecturer on Botany, School of Medicine, Edinburgh ; and Natural Science 
 Master, Blair Lodge. 
 
 'This useful little manual is divided into three parts. The first part is 
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2o JE. & S. LIVINGSTONES' 
 
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 Handbook of Deductive Logic: 
 
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 The Awful and Ethical Allegory 
 
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 EEUTEE0I0IY SMITH 
 
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