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DESCRIPTIVE AND ILLUSTRATED CATALOGUE 


OF 


THE PHYSIOLOGICAL SERIES 


OF 


COMPARATIVE ANATOMY 


CONTAINED IN 


THE MUSEUM 


OF 


THE ROYAL COLLEGE OF SURGEONS OF ENGLAND. 


VOL. Il. 
SECOND EDITION. 


LONDON: 


PRINTED FOR THE COLLEGE; 


AND SOLD BY 
TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 


MDCCCCII. 


ALERE b 


FLAMMAM, 


PRINTED BY TAYLOR AND FRANCIS, 
RED LION COURT, FLEET STRERT. 


PREFACE 


TO THE 


SECOND VOLUME. 


Tue second volume of the Physiological Catalogue comprises 
descriptions of the Nervous System of the Invertebrata (exclusive 
of sense-organs), and of the Brain and Spinal Cord, with their 
membranes and blood-vessels, of the Vertebrata. The descrip- 
tions of the Invertebrata have been intrusted to Mr. R. H. 
Burne, B.A. Oxon., Assistant in the Museum, who has so 
largely enriched this department of the Collection ; he has also 
described the Brain and Spinal Cord of Fishes, Amphibia, 
and Birds, also Spinal Cords and Membranes. 

Prof. G. Elliot Smith, M.D., Fellow of St. John’s College, 
Cambridge, who has contributed so much to our knowledge of 
the Brains of Mammals, has described those of Reptiles and the 
Mammalia, his work forming by far the largest and most 
important part of this volume ; he was assisted in the Primates 
by Mr. W. L. H. Duckworth, M.A. Cantab. 

The specimens of Mammalian Brains have all been re- 
- mounted on the improved plan devised by Mr. William Pearson, 
our Prosector, that enables all the convolutions to be seen. 

The generic and specific names used are those most recently 
adopted in the British Museum. 

The value of the work has been greatly enhanced by the 
admirable drawings made by Mr. J. Green with his accustomed 
skill. 

C. STEWART, 
Conservator. 
28 July, 1902. 


CONTENTS. 
VOL. Il. 


D. 
NERVOUS SYSTEM. 


INVERTEBRATA. 


ECHINODERMATA. 
OPHIUROIDEA . 
ECHINOIDEA 
HOLOTHUROIDEA . 

ANNELIDA. 
OHMTOPODA 
HIRUDINEA . 
GEPHYREA . 

ARTHROPODA. 
CRUSTACEA . 
ARACHNIDA . 
MYRIAPODA . 
INSECTA . 


MOLLUSCA. 
PELECYPODA 
AMPHINEURA Fa ea: 
GAMIGOPODA Soe sts ee he 
CEPHALOPODA . 


PROTOCHORDATA. 


TUNICATA 
CEPHALOCHORDA . 


Nos. 


vi 


CONTENTS OF VOL, I. 


VERTEBRATA. 


BRAIN. 
PISCES, 


CYCLOSTOMI . 
ELASMOBRANCHIL. 
Sqvaipa 
Rasrpa 
HOLOCEPHALI . 
GANOIDEL 
TELEOSTEA., 
ANACANTHINI 


ACANTHOPTERYGII . 
PHARYNGOGNATHI . 


Puysostomi . 
PLEeCTOGNATHI . 


DIPNOI 


AMPHIBIA, 


URODELA. 
ANURA 


REPTILIA. 


LACERTILIA . 
OPHIDIA . : 
ORNITHOSAURIA . 
DINOSAURIA . 
EMYDOSAURIA . 
CHELONIA 


AVES. 
STRUTHIONIFORMES . 


ANSERIFORMES 

FALOONIFORMES 
CORACIIFORMES 
PASSERIFORMES 


MAMMALIA. 


MONOTREMATA. 


Ornithorhynchide . 


Echidnida . 


87—96 

97—105 
106 
107—118 
119 


120—121 


122—125 
126 


127 
128—132 
133 
134 
135—139 
140—147 


148—157 
158—173 
174—182 
183 

184—188 


189—190 
191—196 


CONTENTS OF VOL. II. 


MARSUPIALIA. 
PoLYPROTODONTIA. 
Dasyuride . 
Peramelide . 
Didelphyide 
DIpRoroDonmTIA. 
Macropodide 

Phascolomyide . 
Phalangeride . 
INSECTIVORA. 
Erinaceide . 
Talpide . 
Tuparde 
Centetide . . 
DERMOPTERA. 
Galeopithecide . 
RODENTIA. 
ScruROMORPHA. 
Castoride 
Sciuride . 
HystRICOMORPHA. 
Octodontide 
Hystricide . 
Chinchillide 
Dasyproctide 
Caviide . 
MyomorpHa. 
Dipodide 
Muride , 
DUPLICIDENTATA, 
Leporidee 
CHIROPTERA 
EDENTATA. 
Dasypodidee 
Glyptodontide . 
Bradypodide 
Megatherude 
Myrmecophagide . 
Manide . 
Orycteropidee 


Vil 


Nos. 
197—203 
204—206 
207—208 


209—221 
222—224 
225—229 


230—231 
232 
233 
234 


235—236 


237—241 
242—244 


245 
246 —248 
249—251 


258 
259—260 


261—265 
266 


267—270 
271—272 
273—278 
279—280 
281—286 
287 

288—289 


CONTENTS OF VOL, II. 


Mustelide . 

Ursida . 
Poxntpepra. 

Phocide . 

UNGULATA. 

\ Hyracorpera 
AMBLYOPODA 
-Pronoscrra 
ToxoponTIA. . 
PERISsODACTYEA. 

Tapiride . 
Rhinocerotida 


CONTENTS OF VOL. II. 


Mysracocett. 
Balenide 


PRIMATES. 

ProsiMit. 
Chiromyide 
Lemuride 

ANTHROPOIDBA. 
Hapalide 
Cebide 
Cercopithende . 
Simiide . 
Hominide . 


Membranes of the Brain . 


Blood-vessels of the Brain . 


SPINAL CORD. . 


PISCES. 
CYCLOSTOMI 
ELASMOBRANOHII . 
TELEOSTEA 


AMPHIBIA 
REPTILIA . 
AVES 


MAMMALTA. 
MONOTREMATA 
INSEOTIVORA 
EDENTATA 
OARNIVORA . 
UNGULATA . 
OCETAOEKA . 

* PRIMATES 


Membranes of the Spinal Cord 


VOL. Il. 


ix 
Nos. 
523—530 


531—532 
533—548 


549—553 
554—593 
594— 643 
644—674 
675—728 


729—740 
741—748 


749 
750—752 
7538—755 


756—757 
758—-764 
765—771 


772—7173 
774 

775—776 
777—780 
781—790 
791—796 
797—805 


806—808 


DESCRIPTIVE CATALOGUE 


OF THE 


PHYSIOLOGICAL SERIES. 


D. 
NERVOUS SYSTEM *. 


Ae INVERTEBRATA. 
Loeb, Comparative Physiology of the Brain, 1901. 


ECHINODERMATA. 


Cuénot, Arch. de Biol., t. xi. 1891, p. 445 (Anat.). 
Romanes & Ewart, Phil. Trans., vol. clxxii. 1881, p. 836 
(Physiol.). 


In the Echinodermata there are three distinct systems of central 
nervous organs—superficial oral, deep oral, and apical—that 
occur, either in the form of a circumaxial ring (apical system of 
Echinids and Ophiurids), radial cords (apical system of Asterids 
and deep oral system of Holothurians), or more usually as a 
combination of the two (superficial oral system). All three 
are not invariably present, and there is also variation in their 
respective importance. The superficial oral system occurs in 
all and usually predominates over the others, but in Crinoids it is 
relatively weak and the chief place is taken by the enormously 
developed apical system. The apical and deep oral systems are 


* In this volume are included descriptions of the nervous system of 
Invertebrata and Protochordata and of the brain and spinal cord, with 
their membranes and blood-vessels, of Vertebrata. 


VOL, Il. B 


2 PHYSIOLOGICAL SERIES. 


sometimes absent. ‘The whole central system, whether it is 
continuous with the general body-epithelium (Asteroidea) or is 
comparatively deep-seated, always retains strong indications 
of its epithelial origin. Two kinds of nuclei lie in the super- 
ficial parts of the nerve-cords—some large and with distinct 
nucleoli, belonging apparently to ganglion-cells, others small 
and deeply staining. The latter belong to attenuated supporting 
epithelial cells that traverse the cord at right angles to its surface. 
The spaces between them are filled by nerve-fibrille. 


Ch. 
Transverse section through the Radial Cord of Echinus esculentus. x 700. 


O.L. Connective-tissue lamina, G.C. Nuclei of ganglion (?) cells. 
8.0, Supporting cells, N.F. Nerve-fibrils. 


Isolation of the several radial cords of the oral system from 
the cireumoral ring destroys all power of co-ordinated action 
between the different arms or segments, although the move- 
ments of the individual parts of each are still in perfect harmony 
amongst themselves. From this fact the circumoral ring might 
be thought to be a co-ordinating centre for the general body 


movements, and thus of somewhat higher functional value than si : 


the radial cords, but it is probably nearer the truth to consider 
all parts of the system of equal value and the cireumoral ring 


simply as the path along which stimuli may pass from one 
segment to another. 


OPHIUROIDEA. 
D. 1. Two specimens of the oral central nervous system of a 
Snake-armed Starfish (Ophiocoma echinata). 


The superficial oral system consists of a pentagonal 
ring that surrounds the mouth near its passage into the 


NERVOUS SYSTEM.—INVERTEBRATA. 3 


cesophagus, and of five radial cords. Each cord arises from 
the ring at a point opposite one of the radii and passes 
down the arm between the vertebral ossicles and the ven- 
tral plates (fig. 2). A cavity (epineural canal) lies between 


Fig. 2. 
V. AN. 


R.C. 


eR ® 
Diagrammatic transverse section of the Arm of Ophiocoma echinata. X40, 
A.V. Ambulacral vessel. E.C. Epineural canal. M. Intervertebral 
muscle. P. Median partition of epineural canal. P.V. Pseud- 

hemal vessel. R.C. Radial cord. T.F. Tube-foot. V. Vertebral 


ossicle. V.P. Ventral plate. 


the body-wall and the superficial surface of the oral ring 
and radial cords; it is usually single, but in Ophiocoma a 
partition of connective tissue divides it longitudinally into 
two separate channels. 

The superficial oral system is to a large extent sensory 
in function; it innervates the entire body surface, the 
ambulacra, the mouth, and alimentary canal. The deep 
oral system (not distinguishable in the specimen) forms a 
thin layer of nervous tissue upon the deep surface of the 
superficial system, separated from it by a delicate layer of 
connective tissue. Upon its deep surface lie the pseud- 
heemal and ambulacral vessels. The deep oral system is 
the motor centre for the intervertebral muscles of the arms, 
and probably also gives off fibres that accompany the peri- 
pheral and ambulacral nerves of the superficial system. 

The oral ring and proximal parts of the radial cords are 
shown in an isolated state in the upper specimen, and in 

B2 


4 . PHYSIOLOGICAL SERIES. 


their relations to the disc in the lower; in both cases only 
the most general features can be seen. ‘I'he apical system 
has been removed with the genital ring sinus in which it 
lies. 0.C.A1292C. Brit. Mus. 
Hamann, Jena. Zeitschr., Bd. xxiii. 1889, p. 235. 


ECHINOIDEA. 


D. 2. Part of the body-walls of a Sea-urchin (Zchinus esculentus) 
showing the oral nervous system. 

The superficial system corresponds in its main features 
to that of Ophiurids. The oral ring (indicated by black — 
paper) lies around the mouth-opening between the teeth 
and the pharyngeal wall, separated from the latter by an 
epineural canal. Opposite each of the five radii it gives 
off a cord that leaves the lantern of Aristotle between the 
pyramids, passes under the arch of the auricula, and runs 
along the mid-line of the radius, separated from the inner 
surface of the ambulacral plates by an ‘‘ epineural canal,” 
and from the general body-cavity by the radial canals 
of the pseudhemal, blood-vascular, and ambulacral systems. 
Near the apical pole the cords pass through the test and 
become lost in the general surface epithelium. From the 
oral ring a few fine nerves are given off to the alimentary 
canal, and from the radial cords arise a series of ambu- 
lacral and peripheral nerves. The latter perforate the test 
and form upon its outer surface an intricate plexus, by 
which the movements of the spines and pedicellarie are 
controlled. The deep oral system (not visible in the 
specimen) is in a reduced condition, and is only present 
upon the inner surface of the oral ring at the point of 
origin of the radial cords; it innervates the masticatory 
apparatus, and is entirely wanting in agnathous forms. 

In this specimen parts of the oral systems have been 
exposed, showing the circum-oral position of the nerve-ring 
and its relation to the radial cords. One of the latter with 
its ambulacral nerves has been isolated by the removal 
of the ambulacral plates of one radius. The apical system 
has been removed with the genital-ring sinus. 

Hamann, Jena. Zeitschr. Bd. xxi. 1887, p. 119. 


NERVOUS SYSTEM.—INVERTEBRATA, 5 


HOLOTHUROIDEA. 


D. 3. A Sea-cucumber (Holothuria nigra) with the nervous system 
shown by the removal of the bivial body-walls. 

The oral ring of the superficial system surrounds the 
mouth under cover of the calcareous ring and in close 
contact with the oral integument. The five radial cords 
given off from it pass beneath the radiai pieces of the cal- 
careous ring and along the radii; they are separated from 
the deep surface of the integument by an epineural canal. 

The deep oral system (not visible in the specimen) is 
confined to the inner surface of the radial cords, and is 
separated from the muscles of the body-wall by the pseud- 
heemal, blood-vascular, and ambulacral vessels. The re- 
spective share taken by the two systems in the innervation 
of the body has not been satisfactorily determined. There 
is noapical system. Black paper has been inserted beneath 
the oral ring at the points of origin of the radial cords and 
in various places beneath the cords. The calcareous ring 


has been removed. O.C. A 1292 b. 
Ludwig, Bronn’s Thier-reich, Bd. ii. Abth. 3, 1889- 
1892, p. 64. 
ANNELIDA., 


Retzius, Biol. Untersuch., N.F. Bd. ii. p. 1, iii. p. 1, iv. p. 1, 
vii. p. 6, ix. p. 83, 1891-1900. 


The central nervous system is bilaterally symmetrical ; it 

consists typically of a pair of preeoral (cerebral) ganglia situated 
in the prostomium, and of a series of post-oral ganglia, arranged 
segmentally in pairs.along the ventral mid-line of the body and 
united together by transverse commissures and longitudinal 
connectives. ‘l'his ventral chain of ganglia shows great diversity 
in the degree of concentration of its parts in a transverse direc- 
tion. Longitudinal concentration is rare and never extreme. 
Frequently the segmental ganglionation is absent, and the 
chain is then represented by a fibrous cord with a continuous 
layer of ganglion-cells on its ventral surface. The size and 
complexity of structure of the cerebral ganglia depend entirely 
upon the degree of development of the cephalic sense-organs. 
Apart from particular functions due to their connection with 


6 PHYSIOLOGICAL SERIES. 


~ 


these organs, they do not seem to differ in kind from the post- 
oral ganglia, and, except for a certain inhibitory power, cannot 
be regarded in any special way as controlling or co-ordinating 
centres for the rest of the nervous system. Hach pair of ventral 
chain ganglia constitutes a reflex centre for its innervation 
area. In the ventral chain of many Annelids there are a 
limited number (usually three) of medullated giant nerve- 
tubes ; in many instances connections have been seen between 
them and giant or medium-sized cells upon the ventral 
surface of the ganglia. Their function is still doubtful, but 
they are probably nerve-elements and not simply supporting 
structures. A definite visceral system is present connected 
with the cerebral or subcesophageal ganglia. In certain 
forms the central nervous system is still closely united to the 
epidermis (subcuticula), and in these cases the fibres of its 
supporting tissues can be traced directly to the elongated bases 
of the epidermal cells. 


CHAUTOPODA. 


Racovitza, Arch. Zool. Exp., sér. 3, t. iv. 1896, p. 183 
(Brain). 


D. 4. The anterior part of the body-walls of a Lug-worm 
(Arenicola marina) opened from the dorsal aspect. 

The nervous system, as might be expected from the 
sluggish habits of the worm, is poorly developed. The 
cerebral ganglion is a small lobulated body situated, as in 
other Polychwtes, in the prostomium (in the specimen the 
anterior part of the body-wall is turned inside out, so that 
the cerebral ganglion and inverted prostomium form a 
small excrescence above the cut edge of the pharynx). 
There are three distinct paired centres in the ganglion, 
constituting a fore-, mid-,and hind-brain; each is situated 
beneath and in close contact with a particular sensory 
area of the prostomial epithelium, upon which labial palps, 
tentacles and eyes, and a nuchal organ may respectively 
be developed in higher Polychwtes. ‘The cerebral ganglion 
is connected by a pair of long connectives (from which the 
nerves to the otocysts arise) to a ventral cord, that lies 
within the body-cavity internal to the circular muscles; 


NERVOUS SYSTEM.—-INVERTEBRATA.,. 7 


it shows no sign of metameric ganglionation, but on a 
level with each annular furrow gives off a delicate pair of 
nerves. 

Neuropile* appears to be mainly confined to the cerebral 
ganglion. The medulla of the cord consists of a dorsal 
strand of nerve-fibres, covered on its ventral surface 
by a continuous layer of unipolar ganglion-cells, mostly of 
small size (fig. 3). At the point of union of the cord with 


Fig. 3 
NL. P. GF. M 
‘ Hy a ¢ 
pasar uM, 
Pn 
i, 
x 


Transverse section through the Ventral Cord of Arenicola marina. x 50, 


C.M. Circular muscles. G.C. Ganglion- cells. G.F. Giant fibres. 
L.M. Longitudinal muscles. M. Medulla. N.L. Neurilemma. 
N.S. Neuroglia septum. P. Peritoneum. 


the cesophageal connectives and on a level with the anterior 
end of each setigerous segment, are a pair of giant ganglion- 
cells. In several instances a direct connection has been 
traced between these cells and three giant fibres that lie 
along the dorsal aspect of the cord. The distribution of 
the giant fibres is still doubtful. The cord is surrounded 
by a neurilemma, and is permeated by a considerable 
quantity of neuroglia fibres. These are specially concen- 
trated in the sagittal plane, and form a_ partial septum 
between the two halves of the cord. In the specimen the 
general form and position of the cerebral ganglion, circum- 
cesophageal connectives, and ventral chain can be seen, but 


* 


* The felt-work formed by the ultimate ramifications of ganglion-cell 
processes. 


hr Vie) es ae i oe es a, ee a is ieee) me y = = 
4 e a) YS i) r. ry a a a ; n a3 * a ss % 
. + 


PHYSIOLOGICAL SERIES. 


it is not possible to distinguish the nerves arising from 
them. 


1900, p. 468. 


D. 5. Two specimens of the anterior part of the nervous system % 
of a Polychwte (Marphysa sanguinea), shown respectively — 
in an isolated state and from the left side within the body, 
In this active worm, with definite cephalic sense-organs, 
the cerebral ganglia are well developed (fig. 4). ‘They lie 2 
in the prostomium at the base of the swollen palps, and — 
are clearly separable into two main regions—fore- and 

mid-brain—each of which consists of a pair of owcvonlg 

masses united by a transverse commissure, and coated with 


Wowte teens 


Brain of Marphysa sanguinea. x 25. 

A.N. Antennary nerves. E. Eye. F.B. Fore-brain. F.C. Its com-. 
mieeure, ELB. Hind-brain. LL.M. Longitudinal muscles — 
M.B. Mid-brain. M.C, Its commissure. O.N. Optic nerve — 
(ES.C. (Esophageal connective. P.L. Palp-lobules. V.N. Vis- — 
ceral nerve. 


small unipolar yanglion-cells. The fore-brain lies in front 
of and below the mid-brain, and is mainly concerned with 
the innervation of the palps, into which the anterior part ; 
of each of its lobes is prolonged as a bundle of arborescent _ 
ganglionic processes. , Each lobe also sends a root from its ” 

ventral surface to the. visceral nerve, and another from its 
lateral parts to the circumcesophageal connective. 


NERVOUS SYSTEM.—INVERTEBRATA. 9 


The mid-brain is the centre of origin for the nerves to 
the eyes and tentacles. Its postero-lateral parts are pro- 
longed backwards to form a pair of indistinct lobes, from 
which fibres extend to the nuchal region—they apparently 
represent the third area of the Polycheete brain (hind- 
brain). From each side of the mid-brain a second root is 
given off to the circumeesophageal connective; it unites 


Transverse section through a Ventral-chain Ganglion of Marphysa 
sanguinea. X 76. 


C.M. Central medulla. O.T. Connective tissue. G.C. Ganglion-cells, 
G.F. Giant fibre. L.M. Longitudinal muscles. N.R. Nerve- 
root. P.G. Pigment masses. 


with the first (derived from the fore-brain) immediately 
outside the ganglion. The ganglia of the ventral chain 
lie close together, one in each segment, and are united by 
definite though short fibrous connectives. A pair of para- 
podial nerves rises from each ganglion. Upon the ventral 
surface of the cord’runs a single large “ giant fibre.” 
Jourdan, Ann. Sci. Nat., sér. 7, t. ii. 1887, p. 250. 


D. 6. T'wo specimens of the nervous system of a Sea Mouse 
(Aphrodite aculeata). The cerebral ganglion is of large 
size and complicated structure ; it lies in the prostomium 
and consists of a central mass of neuropile, separable into 
two main centres—the fore- and mid- brain. Between the 
two, on their posterior surface, liesa third, very definite mass 
of neuropile, from which a pair of stalk-like processes project 
upwards towards the dorsal integument. Hach stalk 


10 


PHYSIOLOGICAL SERIES. 


Ld 


expands somewhat at its distal end and is capped by 
a number of closely packed nuclei, surrounded by a limited 
amount of protoplasm. Small ganglion-cells of a similar 
nature (ganglionic nuclei) are found in connection with 
the sensory centres in many Invertebrates, and in this 
instance they complete the striking resemblance that these 
stalked structures bear to the fungiform bodies of Insects. 
It is to be noticed that the neuropile at the base of the 
stalks is condensed here and there to form glomeruli similar 
to those found in the olfactory centres of Arthropods and 


Transverse section through the Brain of Aphrodite aculeata, x 50. 


©. Root of wsophageal connective. F.B. Fore-brain. G.C. Ganglion- 


cells. GL, Glomerali. G.N, Ganglionic nuclei. M.B, Mid- 
brain. S. Stalk of “fungiform body.” 8.T. Supporting tissue. 


Vertebrates. The relations of the “fungiform bodies” to 
the cephalic sense-organs is doubtful. The cerebral ganglion 
is enclosed in a thick capsule composed of large granular 
stellate cells lodged within a loose vacuolated connective 
tissue; a protecting and supporting layer of somewhat 
similar structure is present around the cerebral ganglion 
and ventral cord of Gephyrea. In the meshes of this 
tissue lie a number of moderate-sized ganglion-cells, 
forming a sparse layer around the brain. A pair of long 
slender connectives pass on either side of the pharynx to_ 
the anterior ganglion of the ventral chain. Each arises by 
two roots derived respectively from the fore- and mid- 


NERVOUS SYSTEM.—INVERTEBRATA, ll 


brain. The ganglia of the ventral chain are transversely 
concentrated and show no external sign of their paired 
nature ; they are metamerically disposed and united to one 
another by a pair of closely approximated connectives. 
Each ganglion gives off three pairs of nerves, the largest 
of which arises furthest back and innervates the parapodia, 
while the two anterior pairs supply the trunk muscles and 
skin of the segment in which the ganglion lies. All parts 
of the ventral chain are enclosed in a thick fibrous neuri- 
lemma (subcuticular fibrous tissue), on the outer surface 
of which there isa delicate homogeneous membrane (fig. 7). 


Fig. 7. 
S.F. 


a CM. 
Part of a Ventral-chain Ganglion of Aphrodite aculeata in transverse 
section. xX 150. 


C.M. Central medulla. G.C. Ganglion-cells. H.M. Homogeneous 
membrane. N.L. Neurilemma. S.F. Supporting fibres, 


Many delicate fibres derived from the neurilemma traverse 
the substance of the connectives and ganglia. Ganglion- 
cells are confined to the ventral surface of the ganglia; 
they are lodged in the meshes of the neurilemma. 

In the upper specimen the anterior portion of the nervous 
system including the brain and 7 ventral chain ganglia is 
shown in an isolated condition. Below is an entire animal 
in which the nervous system is displayed in situ by the 
removal of the ventral body-walls from the mid-line. 


Rohde, Zool. Beitr., Bd. ii. 1890, p. 1. 


12 PHYSIOLOGICAL SERIES. 


D. 7. Two specimens of the nervous system of an Earthworm 
(Lumbricus terrestris) showing the anterior part isolated and 
the whole system in situ. 

The cerebral ganglion issmall and bilobed. It is situated 
above the posterior part of the buccal cavity in the third 
body-segment, and is united by a pair of fibrous connectives 
to the ventral cord. 

The latter lies free in the body-cavity, and swells slightly 3 
within each segment to form a ganglion, from which three 
pairs of nerves are given off to the body-walls. Between oa 
the ganglia, the cord is almost, though not quite, free from 


Transverse section through a Ventral-chain Ganglion of Lumbricus 
terrestris, X 125, 


BL. Blood - vessel. ©.M. Central medulla, G.C. Ganglion - cells. 
G.F. Giant fibres. M. Muscle-fibres, NL', NL’, The two 
layers of neurilemma. S.T. Supporting tissue. 


ganglion-cells. The central nervous system is surrounded 
by a neurilemma, in which two layers are distinguishable : 
(i.) an outer layer largely composed of longitudinal musele- 
fibres, (ii.) an inner cuticular layer. Within the cuticle 
lie the connectives and ganglia embedded in a supporting 
fibrous tissue (? neuroglia) (fig. 8). Three medullated giant 
fibres run along the dorsal surface of the cord; their 
relations to the rest of the system are still obscure, but it is 
certain that at the hinder end of the cord the two lateral 


NERVOUS SYSTEM.—INVERTEBRATA. 13 


fibres are in connection with ganglion-cells that lie in pairs 
on the ventral surface of a certain number of the posterior 
ganglia of the chain. Anteriorly the lateral fibres are said 
to break up in the subcesophageal ganglion. The median 
fibre apparently arises from cells in the same ganglion. 
Branches from all three fibres have been seen to enter the 
lateral nerves. It is probable that the giant fibres act as a 
direct path of communication between all regions of the 
nervous system, and are particularly concerned in bringing 
about the simultaneous contraction of the whole body-wall, 
such as takes place when the worm shoots back into its 
burrow. In creeping, contraction occurs slowly segment 
by segment. The co-ordination of this segmental contrac- 
tion is apparently due, not so much to connections within 
the central nervous system as to an orderly sequence 
of independent stimuli, each of which is caused by the 
stretching of the integument of any one segment by the 
contraction of the longitudinal muscles of the segment 
in front. | 

Friedliinder, Zeits. wiss. Zool., Bd. xlvii. 1888, p. 47, & 

Bd. lviii. 1894, p. 661 (Anat.). 
Friedlander, Arch. ges. Physiol., Bd. lviii. 1894, p. 168 
(Physiol.). 


D. 8. An Harthworm (Lumbricus terrestris) with the ventral 
body-walls removed to show the nervous cords, their 
ganglia and lateral branches. O. C. 1296. Hunterian, 


HIRUDINEA. 


D. 9. The ventral body-walls of a Leech (Hirudo medicinalis) 
with the nervous system exposed from the dorsal aspect. 
The central system lies amongst the parenchyma internal 
to the body-walls. The cerebral ganglion is a small bilobed 
body situated close behind the jaws on the upper surface of 
the pharynx ; it is of very simple construction and probably, 
as its removal causes no appreciable difference in the actions 
of the animal, differs little if at all in function from the 
ganglia of the ventral chain. It innervates the cephalic 
sense-organs, and jaws. A pair of extremely short connec- 
tives unite the cerebral ganglion around the anterior part of 


PHYSIOLOGICAL SERIES. 


pharynx to a series of (apparently) 23 transversely 
la ventral-chain ganglia. The first of these 
(subesophageal ganglion) is of some size and represents 
the four anterior ganglia of the chain ; the following 21 are 
simple rounded masses, situated segmentally, and each 
giving off two pairs of nerves to the body-walls of its seg- 
ment. The terminal ganglion is a compound structure like 
the first, and represents a longitudinal concentration of at = 
least 7 pairs of ganglia ; it supplies the anal sucker. The a 
successive post-oral ganglia are united to one another by —__ 
three connectives—a lateral pair similar to those of other 
worms and a delicate median ventral cord (nerve of Faivre) 


Fig. 9. 


Transverse section through the Ventral-chain Connectives of Hirudo 
medicinalis, xX 200. 
BS. Blood-space. (©, Connectives. M. Muscle-fibres. N.F. Nerve 
of Paivre. NL’, NL*. The two neurilemma-sheaths. P.O, Pig- 
ment-cells, 8, Septa. 


that originates in the subeesophageal ganglion and extends 
throughout the length of the chain ; it is lost in the dorsal r 
parts of each ganglion (figs. 9 and 10). wg 

Each simple post-oral ganglion consists of a laterally 
paired mass of neuropile, invested on its lateral and ventral 
surfaces by unipolar ganglion-cells of different sizes. Two 
of these at the anterior end of the ventral surface of each 
ganglion are of colossal proportions (‘1 mm. diam.), and 
contribute fibres to the lateral nerves of the same side. 


NERVOUS SYSTEM.—INVERTEBRATA. 15 


There are no giant fibres in the connectives. The ventral 
cord is surrounded by a double neurilemma-sheath — 
(i.) an outer sheath that loosely envelopes the cord and 
extends for some distance along the lateral nerves : it forms 
the outer wall of the perineural blood-vessel; (ii.) an 
inner sheath, that closely invests the cord and binds the 
three connectives into a single strand. Offshoots from 


Fig. 10. 


Transverse section through a Ventral-chain Ganglion of Hirudo medicinalis, 
x 125. 


C.M. Central medulla. G.C. Ganglion-cells. G.GC. Giant ganglion-cells. 


this inner sheath penetrate amongst the fibres of the con- 
nectives and dip into the substance of the ganglia, where 
they separate the ganglion-cells into three definite groups 
and form an investment to the central medulla. 

Both sheaths contain many muscle-fibres. 

The outer neurilemma-sheath has been removed and 
black paper placed beneath the nerve-cord. OQ. C. 1295. 

Leuckart, Die Parasiten des Menschen, Bd. i. 1894, p. 579. 


GEPHYREA. 


‘ 


D. 10. The anterior and posterior parts of the body-walls of a 
Gephyrean (Sipunculus nudus) showing the nervous system. 
The cerebral ganglion is a rounded mass with slight lateral 
swellings, situated upon the dorsal surface of the cesophagus 
at the base of the tentacles, Nerves for the tentacles arise 


PHYSIOLOGICAL SERIES. 


- 


its postero-lateral surface, and upon its anterior face 
re number of finger-like processes of doubtful function 
(possibly sensory). It has been shown that a special reflex 
connection exists between the cerebral ganglion (a purely 
sensory centre?) and the motor centre that controls the 
retractors of the introvert. Two long (11 mm.) circum- 
cesophageal connectives (from which the nerves for the 
retractors of the introvert are given off) unite the cerebral 
ganglion to the ventral cord. The latter for the first part 
of its course lies loose in the body-cavity accompanied by 
a strand of muscle (mostly removed in the specimen) ; 
about 10 mm. in front of the nephridia it becomes closely 
applied to the body-wall, and runs in this position between 
two bundles of the longitudinal muscle-layer to the posterior 
extremity of the body, where it terminates in a spindle- 
shaped enlargement. 

So long as the ventral cord lies close to the body-wall it 
gives off, about the middle of each circular muscle-band, a 
pair of lateral nerves, that run between the circular and 
diagonal muscle-layers towards the dorsal mid-line, but do 
not meet to form a complete ring round the body. In front 
of the nephridia the nerves come off more irregularly and 
are enveloped in strands of muscle; they supply the anterior 
end of the trunk and the introvert. No nerves arise 
from the cord within the introvert. The cord is a mixed 
motor and sensory centre in which impulses are slowly 
propagated (100-200 mm. per second) in either direction. 
The cerebral ganglion consists of a central mass of neuro- 
pile surrounded by unipolar ganglion-cells varying in size 
from 4-55 mw, and arranged in fairly definite groups; a few 
bipolar cells occur in the neighbourhood of the digitiform 
processes, The substance of the ganglion is permeated by 
a network of neuroglia fibres, and it is enclosed in a pro- 
tective layer of large stellate cells (neuroglia cells ?). The 
cord is composed of a fibrous core covered on its ventral 
surface by ganglion-cells; it shows no sign of ganglionation 
or lateral duplicity. It is surrounded by a double sheath 
of neurilemma, the space between the two being filled with 
stellate cells similar to those around the cerebral ganglion. 
The posterior enlargement does not differ in structure from 


NERVOUS SYSTEM.—INVERTEBRATA. 17 


the rest of the cord ; its size is mainly due to an increase 
of the stellate cells between the neurilemma-sheaths. 

In the specimen the introvert is retracted. A red rod has 
been placed in the mouth and black paper beneath the 
different parts of the nervous system. 

Metalnikoff, Zeits. wiss. Zool., Bd. Ixviii. 1900, p. 293 

(Anat.). 
Uexkull, Zeits. Biol., N.F. Bd. xv. 1896, p. 1 (Physiol.). 


ARTHROPODA. 
Bethe, Arch. f. ges. Physiol., Bd. Ixviii. 1897, p. 449 
(Physiol.). 

The central nervous system agrees with that of Worms in its 
bilateral symmetry and general plan of construction, but is 
always entirely free from the integument. The cerebral ganglion 
is comparatively simple in many cases, but shows a gradual 
increase in size and complexity of structure as the cephalic sense 
organs become more perfect and the intelligence more pro- 
nounced. This brain development is noticeable in the increasing 
complication of the optic ganglia and in the development of 
glomerular condensations in the neuropile of the antennary 
lobes very similar to those in the olfactory lobes of Vertebrates, 
but is particularly marked by the appearance, among the higher 
orders, of peculiar cerebral organs (fungiform bodies) whose 
development seems to be linked in some obscure way with the 
growth of the intelligence. The visceral system is always 
clearly defined. Its centres of origin (cesophageal ganglia) show 
a gradual migration from their original post-oral position to- 
wards the cerebral ganglion, and finally fuse with it, although 
always united by a post-oral commissure. The ventral chain 
in all except the lowest groups shows a considerable degree of 
concentration laterally, but varies in longitudinal concentration 
within the widest limits—from the Phyllopods with a pair of 
ganglia to every pair of appendages, to the Brachyura, some 
Arachnids and Insects, in which it is represented by a single 
post-oral ganglionic mass. 

The segmental character of the nervous system is functional 
as well as structural, for each ganglion forms an independent 
reflex centre for the activities of its innervation area. Co- 


ordination is mainly due to transmission of stimuli from ganglion 
VOL. I. Cc 


18 PHYSIOLOGICAL SERIES, 


to ganglion, but also, at least as concerns locomotive movements, 
to the influence of a definite centre of co-ordination—the subceso-_ 
phageal ganglion. The cerebral ganglion exerts a higher 
controlling influence over the rest of the system than in Worms, 
owing to its increased inhibitory power and to the production of 
the general muscle tonus (state of constant partial contraction). 
It is hard to say whether any power of initiation should be 
assigned to the cerebral ganglion—its removal generally results 
in the cessation of spontaneous locomotion, but this may be due — ‘ “ 
to decrease in muscle-power following upon loss of tonus. ve 


ORUSTAOEA. 


D. it. The isolated nervous system of a ‘Phyllopod (Apus - 
produetus). The central system is in an essentially primitive ‘= 


Fig. 11. 
C.G. 


“(ES 6G. 


sS= sz a 
7) (* | ie 


Diagram of the anterior parts of the Nervous System of Apus, 
after Zaddach and Pelsencer, : ut 


A.C", A.C. Centres for antennary nerves’ 1. and 11. A.N}, A.N*, An-— 4 


tennary nerves. (ES.G. (Esophageal ganglion, O©.G. Cerebral 
ganglion. ©.N. Optic nerve. V.C. Visceral centre, = 


/ 


ss 


NERVOUS SYSTEM.—INVERTEBRATA. 19 


condition, and reminds one, in the ladder-like construc- 
tion of its ventral chain, of that of certain Tube-worms 
(e.g. Serpula). The cerebral ganglion is a small quadri- 
lateral body, situated in front of the cesophagus close 
beneath the eyes, and so placed that its proper ventral 
surface faces upwards and its anterior border backwards. 
It gives off a pair of nerves from the outer angles of its 
true anterior end to the eyes. The first pair of antennze 
are supplied by a pair of small nerves that seem to rise 
from the circumcesophageal connectives; their true centres 
of origin are, however, situated in the lateral parts of the 
cerebral ganglion. On a level with the posterior margin 
of the mouth, each circumcesophageal connective enlarges 
to form an cesophageal ganglion, which gives off two nerves 
—a small one from its outer aspect to the second antenna, 
and a visceral nerve from its inner surface ; the two ganglia 
are united by a double commissure. The condition of the 
antennary nerves in Apus suggests that the direct origin 
of these nerves in the higher Crustacea from the cerebral 
ganglion is the result of an anterior concentration of 
centres originally separate and post-oral in position. The 
ganglia of the ventral chain are paired and, in the anterior 
region of the body, widely separate. They are united to 
one another transversely by a double commissure and longi- 
tudinally by a pair of connectives. In the posterior part 
of the body the ladder-like appearance of the chain is lost 
owing to the shortening of the commissures and connectives, 
although the individuality of the ganglia is maintained. 
The ganglia correspond in number and position to the 
appendages, and are thus more numerous than the body 
segments. The second pair of maxille alone seem to have 
no corresponding ganglia; their nerves arise from the 
connectives.. The specimen is so small that only the most 
important of the above-mentioned characters are visible, 
such as the wide lateral separation of the ventral-chain 
ganglia and their gradual approximation to one another 
posteriorly. O. C. 1302 1. 

Pelseneer, Quart. Journ. Micro. Sci., vol. xxv. 1885, 

p- 433. 


o2 


20 


PHYSIOLOGICAL SERIES. 


D. 12. Two specimens of the nervous system of a Barnacle 


(Lepas anatifera). The small bilobed cerebral ganglion 
lies on the anterior wall of the cesophagus at its entry 
into the stomach; it gives off a large nerve on either side 
to the peduncle, and an extremely fine pair (not visible in 
the specimens) from its anterior surface to the vestigeal eye. 
The visceral nerves arise from the circumeesophageal 
connectives close behind the cerebral ganglion. The sub- 
m@sophageal ganglion is the largest and most important 
nerve-centre in the body; it sends a large pair of nerves 
from its dorsal surface to the adductor scutarum muscle, 
and also supplies the mouth-parts and first pair of cirri, It 
is followed by a chain of four segmentally placed ganglia, . 
each of which gives off a pair of nerves to the cirri of its 
segment; the terminal ganglion is slightly larger than the 


others, and represents a fusion of two, it innervates the 


last two pairs of cirri and the penis. The ganglia are 
moderately concentrated in a transverse direction, but the 
connectives—particularly at the anterior end of the chain— 
are distinctly separate. Between them runsa small median 
nerve (not visible in the specimens), that arises in the sub- 


msophageal ganglion and is ultimately distributed to the — 


rectum. In the upper specimen the nervous system is 

shown in an isolated state, and in the lower from the right 

side within the body. O, C. 1302 x. 
Gruvel, Arch. Zool. Exp., sér. 3, t. i. 1893, p. 489. 


D. 13. A Stomatopod (Lysiosquilla, sp.) with the nervous system 


displayed from above. The small quadrilateral cerebral 
ganglion lies in the second cephalic segment; it gives 
off three large pairs of nerves respectively to the eyes and 
to the two pairs of antennw, as well as a few delicate 
branches (not shown in the specimen) to the neighbouring 
muscles and integument. The circumosophageal con- 
nectives, owing to the extended character of the head- 
region, are remarkably long in front of the mouth; on 
either side of the asophagus they swell slightly to form a 
pair of small esophageal ganglia, that give off the visceral 
nerves and are united together behind the esophagus by a 
single commissure. A short distance behind the cesophagus 


NERVOUS SYSTEM.——-INVERTEBRATA. 21 


the connectives join the subesophageal ganglion—-an 
elongated mass formed by the longitudinal concentra- 
tion and fusion of eight pairs of ganglia; it innervates 
the mandibles, maxillze, and five anterior pairs of thoracic 
appendages. The last three thoracic and the six abdominal 
ganglia are segmental in position; each gives off three pairs 
of nerves, distributed respectively to the appendages and 
lateral muscles of the same segment and to.the flexor muscles 
of the one behind. The terminal ganglion supplies the 
sixth abdominal segment and the telson. All the ventral- 
chain ganglia show a high degree of transverse concen- 
tration, combined (except in the case of the subcesophageal 
ganglion) with well-marked longitudinal separation. The 
connectives are bound up in a common neurilemma-sheath. 

Bellonci, Ann. Mus. Civ. Stor. Nat. Genova, vol. xii. 

1878, p. 518. 


D. 14. Two specimens of the nervous system of a Lobster 
(Homarus vulgaris). The cerebral ganglion is lodged 
immediately below the bases of the eye-stalks; it is 
roughly quadrilateral in shape, with a pair of conspicuous 
rounded eminences (globuli) upon its lateral margins. 
Each of its upper angles is connected by a nervous tract 
to a rod-shaped optic ganglion that lies within the eye- 
stalk; from its lower angles arise the antennary and in- 
tegumentary nerves; the circumcesophageal connectives 
are given off from the middle of the ventral border. ‘The 
cerebral ganglion, as in other Decapods, has considerable 
structural complexity (fig. 12). Three regions can be 
traced in it, of which the anterior two correspond probably 
to the proto- and deuto-cerebrum of the Insect brain, while 
the third is a part of the tritocerebrum peculiar to Crus- 
tacea. The protocerebrum is the optic centre; it consists 
of the optic ganglia, and of a quadrilateral mass (proto- 
cerebral lobes) that forms the upper part of the cerebral 
ganglion. The protocerebral lobes are separated by a 
slight median furrow; they are traversed by numerous 
commissural fibres, and have in the middle of their sub- 
stance a transverse bar of dense neuropile that probably 
represents the corpus centrale of the Insect. 


22 : PHYSIOLOGICAL SERIES. 


Each optic ganglion contains four neuropile masses 
placed at intervals between the retina und the optic tract — 
and united together by decussating fibres ; upon the cae oe 
surface of the centre nearest the tract is a winiald excrescence ~ 
that may possibly represent the fungiform body of the Insect i a 
brain in a very rudimentary state. . “A , 

There are two pairs of centres in the deutocerebrum— i 
the lateral lobes (globuli) united by a stout commissure, 


Horizontal section through the Brain of Astacus fluviatilis. x 40. 


©.C. Corpus centrale. C.GB. Commissure of globuli, C©.PC.L. Com- 
missares of protocerebral lobes. D.C. Deutocerebrum. GB. 
Globulus. GL. Glomeruli. G.N. Ganglionic nuclei. O.D. 
Decuseating bundle of optic tract. 0.T, Optic tract. sles” aT 
Protecerebral lobe. T.C. Tritocerebrum. om 


and, internal to them, two smaller neuropile masses con 
tiguous in the mid-line ; each pair gives rise on either side 
to a root of the first antennary nerve. The nature of the § a 
globuli is obscure ; some compare them with the fone ; q 
bodies, others with the antennary lobes of Insects, In we 


NERVOUS SYSTEM.—INVERTEBRATA, 23 


of the latter view, it may be said that the globuli of Crusta- 
ceans agree with the antennary lobes of Insects in having 
glomerular condensations of their neuropile, in giving off 
a root to the antennary nerve, and in receiving a large 
decussating tract from the fungiform body of the opposite 
side, assuming such to be the nature of the protuberance 
on the optic ganglion of the Lobster. 

The tritocerebrum constitutes the centre for the second 
antennary and the tegumentary nerves. 

The complicated structure of the cerebral ganglion is 
apparently mainly due to its connection with highly 
developed sense-organs, yet the fact that its removal causes 
more disturbance to the normal activities of the creature 
than in Worms—particularly by destroying the capability 
of spontaneous locomotion—suggests that it possesses to 
some degree, at any rate, the power of controlling, or 
perhaps even of initiating, activities in the rest of the 
nervous system. 

A pair of small csophageal ganglia are situated upon 
the circumcesophageal connectives on a level with the 
cesophagus, but some distance in front of the post- 
cesophageal commissure by which they are united. 

Hach of them gives off, besides a few delicate filaments 
to the esophagus, two stout nerves. One of these runs 
forward, parallel to the cesophageal connectives, half-way 
to the cerebral ganglion, and at this point unites with its 
fellow of the opposite side and with a median nerve derived 
from the cerebral ganglion, to form the gastric nerve—a 
trunk that runs in the median plane along the anterior and 
dorsal surfaces of the stomach to the pylorus, at which 
point it forms a small ganglion and divides into two lateral 
branches which are distributed to the intestine. The second 
of the two nerves supplies the upper lip and is connected by 
a branch to the components of the gastric nerve where they 
unite to form the median trunk. The subcesophageal 
ganglion innervates the mouth appendages and gives off 
from its dorsal surface a few nerves to the body-muscles ; 
it is composed of six pairs of ganglia fused together. The 
removal of this ganglion occasions [in the Crayfish (Astacus 
fluviatilis) | the loss of all power of co-ordinated locomotion, 


24 


PHYSIOLOGICAL SERIES. 


although other co-ordinated movements of the limbs can 
still take place. The rest of the ventral-chain ganglia 
(five thoracic and six abdominal) are transversely con- 
centrated but longitudinally widely separated. They are 
situated segmentally, and each gives off a pair of nerves to 
the appendages of its segment and a second pair to the 
neighbouring trunk-muscles. In the abdominal region, a 
third pair of purely motor nerves arise from the connectives 
behind each ganglion and are distributed to the great 
abdominal flexor. The terminal ganglion innervates the 
6th abdominal segment and the telson; it also gives off a 
small rectal nerve, probably comparable to the median 
nerve in the ventral cord of Lepas. 

The connectives of the ventral chain share in the lateral 
concentration seen in the ganglia; in the thorax they lie 
side by side and (except between the third and fourth ganglia 
where the sternal artery passes between them) are bound up 
in acommon neurilemma-sheath. In the abdomen they are — 
closely contiguous. The ganglion-cells of the central system 
are mostly unipolar, and vary much in size, from large pear- 
shaped cells *2 mm. in diameter to ganglionic nuclei, in which 
the nucleus is surrounded by a mere film of protoplasm. 
The latter occur always in masses in connection with certain 
definite parts of the central system—e. g., the globuli and 
a restricted area of the subcesophageal ganglion. The 
nerve-fibres derived from ganglion-cells that lie within the 
central system are tubular, with a thick neuroglia-sheath 
(in which myelin may occur) containing a semifluid sub- 
stance. After leaving the ganglion-cell they give off a 
few lateral twigs, that break up in the neuropile and provide 
a means of communication between the difterent nerve- 
elements. The main fibre then passes either directly into 
one of the peripheral nerves and is distributed to the 
muscles, or runs within one of the connectives to a neigh- 
bouring or distant ganglion and there breaks up in the 
neuropile. The sensory fibres are very delicate; they 
arise, a8 in Worms, from cells in or close beneath the skin, 
and enter the ganglia as part of a peripheral nerve. 
Within the ganglion they divide into anterior and posterior 


NERVOUS SYSTEM.—INVERTEBRATA, 25 


branches, that run in the connectives to neighbouring or 
distant ganglia. 

The ganglion-cells cover the lateral and ventral surfaces 
of the neuropile masses of the ventral-chain ganglia; the 
connectives occupy the dorsal surface. In each connective 
there is a giant nerve-tube ; it originates in a large cell on 
the ventral surface of the cerebral ganglion and runs the 
whole length of the chain without apparently giving off 
lateral branches; it finally divides and passes into the 
nerves of the tail-fin (uropodites). The giant fibres in 
their origin and distribution present a striking parallel to 
Mauthner’s fibres in the spinal cord of Fishes, and it has 
been suggested in both cases that possibly they put the 
steering and balancing apparatus under the direct control 
of the brain. 

In the upper specimen the origin and course of the 
visceral nerves are seen from the left side, indicated by 
black paper; in the lower the nervous system is shown, as 
a whole, in its natural position from above. The left eye 
has been removed to expose the antennary nerves. 

O. C. 1302 1. 

Krieger, Zeits. wiss. Zool., Bd. xxxili. p. 527 (Anat.). 

Allen, Quart. Journ. Micr. Sci., vol. xxxvi. 1894, p. 483, 

& vol. xxxix. 1896, p. 33 (Histol.). 
Bethe, Arch. f. Phys., Bd. lxviii. 1897, p. 449 (Physiol.). 


D. 15. A Lobster (Homarus vulgaris), dissected to show from 
the ventral aspect the cerebral ganglion and ventral chain. 
The origins of the optic and antennary nerves are shown, 
also the divergence of the connectives for the passage of 
the cesophagus. 

The degree of transverse approximation of the con- 
nectives in the region of the thorax has been made apparent 
by the removal of the common neurilemma-sheath, by 
which they are naturally bound together. * O.C. 1301. 

Hunterian. 


D. 16. The cerebral ganglion with the eyes and the principal 
nerves given off from the ganglion, displayed in situ, from 
a Lobster (Homarus vulgaris). O.C. 1303. Hunterian. 


26 P PHYSIOLOGICAL SERIES. 


D. 17. Scyllarus arctus, with the nervous system exposed. The 
cerebral ganglion is remarkable for its relatively large size ; 
it gives off the usual nerves to the cephalic sense-organs, 
but the optic tracts and ganglia, owing to the great breadth 
of the head, are peculiarly long and slender. The sub- 
wsophageal and thoracic ganglia are longitudinally 
appproximated, but (with the exception of the components 
of the submsophageal ganglion) are not fused together. 
Between the 2nd and 3rd and 3rd and 4th thoracic ganglia 
the connectives are quite separate, leaving in the latter 
position a large opening between them for the passage of 
the sternal artery ; elsewhere they are bound together by a 
common neurilemma-sheath. The last thoracic ganglion — 
is connected with a chain of six segmentally placed 
ubdominal ganglia. They are transversely concentrated, 
und are connected together by an apparently single cord, 
the result of the transverse concentration of the paired 
connectives, | 

Bouvier, Ann. Sci. Nat., sér. 7, t. vii. 1889, p. 73. 


D. 18. The isolated nervous system of a Hermit Crab (Zupagurus 
bernhardus). The transverse and longitudinal concen- 
tration of the components of the subcesophageal-thoracic _ 
mass is greater than in Scyllarus, but posterior to the 
subeesophageal centre the outlines of four ganglia can be 
traced upon the ventral surface of the mass. Three of 
these are situated in front of the perforation for the sternal 
urtery, and respectively innervate the three anterior pairs 
of thoracic appendages. The fourth centre is formed by 
the fusion of the last two thoracic ganglia with the first 
abdominal, it innervates the two posterior pairs of thoracic 
limbs and the anterior part of the abdomen. The mass is 
perforated between the 3rd and 4th thoracic ganglia by the _ 
sternal artery, and has also two minute openings between 
the 2nd and 3rd and Ist and 2nd; beyond the indication 
afforded by these apertures, all external traces of connectives 
are lost. The abdominal chain consists of five pairs of 


transversely concentrated ganglia united by separate 
connectives. 


NERVOUS SYSTEM.—INVERTEBRATA. 27 


D.19. A Spider-Crab (Maia squinado) dissected from above. 
The cerebral and esophageal ganglia, with the nerves that 
arise from them, are essentially similar to those of the 
Lobster, except for the great development of the integu- 
mentary nerves given off from the posterior corners of the 
cerebral ganglion. The circumcesophageal connectives are 
remarkably long, owing to the position of the ganglia of 
the ventral chain. The latter are concentrated to the 
maximum degree in the longitudinal direction, and are 
fused together to form an oval mass in the middle of the 
cephalothorax, from which nerves radiate to the appendages 
and body. The large appendicular nerves are composed 
of bundles of small fibres without a common investment. 
From the dorsal surface of the central mass, at its anterior 
end, a pair of small nerves are given off to be distributed 
to the roof of the gill-chamber, and from the posterior 
end of the mass a bundle of nerves pass into the abdomen. 

O. C. 1303 ab. 
Audouin & Milne-Edwards, Ann. Sci. Nat., t. xiv. 1828, 
p. 92, 


D. 20. A* King-Crab (Limulus polyphemus) dissected from the 
dorsal aspect. The entire cephalothoracic part of the 
central nervous system is concentrated around the oral end 
of the cesophagus in the form of an oval ring. The pre- 
oral part of the ring represents the cerebral ganglion ; it 
projects anteriorly as a subconical, feebly bilobed mass 
(protocerebrum) from whose anterior end nerves are given 
off to the lateral and median eyes, and to a ventral integu- 
mentary pit otf unknown function situated in front of the 
mouth. | From its dorsal surface, near its union with the 
lateral parts of the ring, arise a pair of delicate integu- 
mentary nerves that innervate the ventral skin of the 
cephalothorax external to. the limbs. Between the 
protocerebrum ana the lateral parts of the ring are a 
pair of centres (indistinguishable superficially) united by 
a small pre-oral commissure ; they form part of the 
cerebral ganglion and give off nerves to the chelicer» 
and viscera. The protocerebrum is remarkable for an 


28 


PHYSIOLOGICAL SERIES. 


- 


excessive development of a pair of outgrowths similar 
in many respects to the fungiform bodies of the Insect- 
brain (fig. 13). Each of them consists of an arborescent 
mass of peculiarly dense neuropile coated by a thick layer 
of ganglionic nuclei; they cover the whole surface of the 
protocerebral lobes with the exception of a small area on 
the dorsal surface. Their function is entirely unknown. 


Fig, 13. 


From an enlarged model of the Brain of Limulus, after Viallanes, 


CH.N. Nerve to chelicerw. F.B. Fungiform body. O,G. Optic ganglion. 


O.N, Optic nerve. OOC.G, Ocellary ganglion. OC.N. Ocellary 
nerve. P.L. Protocerebral lobe. SN. Nerve to sensory pit. 
V.N. Visceral nerve. 


The lateral and posterior parts of the ring are composed 
of six pairs of ganglionic masses intimately fused together 
longitudinally and united transversely by a series of com- 
missures; the posterior pair are fused in the mid-line to 
form a single “ post-oral” ganglion. 

Seven pairs of integumentary nerves are given off 
from the dorso-lateral margins of the ring, and from its 


—— 


i 


NERVOUS SYSTEM.—INVERTEBRATA. 29 


ventro-lateral border six pairs of pedal nerves, distributed 
respectively to the five pairs of walking appendages 
and to the operculum. A pair of fine nerves for the chilaria 
arise from the ventral surface of the “‘ post-oral”’? ganglion. 
The ring is united posteriorly by connectives to a chain of 
six pairs of transversely concentrated ganglia, situated in 
the abdomen. From each of these, except the last, two 
pairs of nerves are given off—one to the appendages 
(gills) of the segment proper to the ganglion, the other to 
the integument. The latter are united on either side 
external to the bases of the limbs by a longitudinal con- 
necting cord, parts of which only are to be seen in the 
specimen. ‘The three posterior ganglia are fused together 
to form a single mass, which sends nerves to the last two 
pairs of gills, the hinder extremity of the abdomen, and 
the post-anal spine. . 

The central nervous system, together with the motor 
and some few sensory nerves, is enveloped by a large 
arterial blood-space; a pair of arteries—branches of the 
anterior aorta—open into the space on either side above 
the anterior part of the nerve-ring. Experiments upon 
this nervous system show that, although parts of it are 
much concentrated, each segmental centre is entirely inde- 
pendent in its actions, the regulation and orderly sequence 
of the movements of different segments being due to the 
transmission of stimuli from centre to centre, and not to 
the influence of any one specialized centre of co-ordination. 

Viallanes, Ann. Sci. Nat., sér. 7, t. xiv. p. 405 (Anat.). 

Hyde, Journ. Morph., vol. ix. 1894, p. 431 (Physiol.). 


ARACHNIDA. 
St. Remy, Arch. Zool. Exp., t. v dis, 1887, p. 1. 


D. 21. The nervous system of a Scorpion (Pandinus imperator), 
exposed from the dorsal aspect. The main part of the 
central system lies in the cephalothorax and is concentrated 
around the cesophagus in a compact mass that represents the 
cerebral and first nine ventral-chain ganglia. The cerebral 
part of the mass is bilobed ; it innervates the median 
and lateral eyes and the chelicerze. On either side of the 
cesophagus it is continuous with the anterior region of the 


30 ' PHYSIOLOGICAL SERIES. 


large oval subcesophageal ganglion—a composite mass from 
which nerves are given off to the mouth, the pedipalpi, the 
four pairs of walking-legs, and the first four segments of 
the abdomen. The cephalothoracic mass is united by a 
pair of delicate connectives to a chain of three abdominal 
and four post-abdominal ganglia, all of which are trans- 
versely concentrated but are united by separate connectives. 
The last abdominal and the first three post-abdominal 
ganglia lie severally in the segments that they innervate, 
but the first two free abdominal ganglia are approximated to 
the cephalothoracic mass, being respectively two segments 
and one segment in advance of their nerve distribution. The 
terminal ganglion of the chain lies in the 4th post-abdominal 
segment; it supplies the 4th and 5th segments of the 
post-abdomen and the post-anal spine.. The three posterior 
ganglia and their connectives show a marked increase in size 
compared with those in front of them, correlated no doubt 
with the great activity of the post-abdomen. O.C. 1297 B. 

Blanchard, L’organisation du Régne Animal (Arach- 

nides), 1852, p. 39. 


D. 22. A Spider (Avicularia avicularia) dissected from the dorsal 
aspect. The central nervous system is extremely concen- 
trated; it lies in the middle of the cephalothorax behind 
the mouth, encircling the horizontal part of the oesophagus 
and extending backwards beneath the stomach. The supra- 
cesophageal part of the system is small and feebly bilobed ; | 
it innervates the eyes and rostrum. On either side of the ; 
csophagus it is connected to the suboesophageal mass by a 
pair of ganglionic centres that give off nerves to the 
cheliceree and viscera, The third and largest part of the 
central system lies beneath the oesophagus and stomach, 
separated from them by the entosternite; it has an oval 
form and is composed of six pairs of fused ganglionic 
centres that represent the ganglia of the ventral chain, 
From this mass nerves are given off to the pedipalpi, to the 
four pairs of walking-legs, and to the abdomen. Fibrous 
partitions, derived from the neurilemma, penetrate to a 
certain extent between the several centres of the sub- 
cesophageal mass. O.C. 1300, 

Schimkewitsch, Ann. Sci. Nat., sér. 6, t. xvii. 1884, p. 15, 


NERVOUS SYSTEM.—INVERTEBRATA. 31 


D. 23. A Pentastomum tenioides, in which parts of the 
nervous system are shown from above (fig. 14). The 
central system is in a degenerate condition ; it consists of 
a bilobed ganglionic mass, situated behind the cesophagus. 
Its lateral parts are united in front of the ceesophagus by a 
delicate commissure, in which there is no sign of a pre- 
oral ganglion. The ganglionic mass gives rise from its 
posterior surface to a pair of longitudinal nerves of some 


Fig. 14. 


The Nervous System of Pentastomum tenioides, after Leuckart. 


©. Pree-oral commissure. G. Ganglion. L.C. Longitudinal cords. 
ES. Cisophagus. 


size that extend to the hinder part of the body; it also 
gives off from its anterior and lateral regions several small 
nerves to the alimentary canal, body-muscles, and cephalic 
hooks and papilla. The specimen shows little beyond the 


main ganglionic mass. O. C. 1294 ¢. 
Spencer, Quart. Journ. Micr. Sci, vol.xxxiv. 1893, 
p. 33. ; 
MYRIAPODA. 


D. 24. Two specimens of the nervous system of a Centipede 
(Ethmostigmus rubripes). The central system shows the 
Arthropod type in a very simple condition ; it consists of 


32 


PHYSIOLOGICAL SERIES. 


a bilobed cerebral ganglion of relatively uncomplicated 
structure, and of a chain of 22 transversely concentrated 
post-oral ganglia, united to one another by transversely 
separate connectives. The cerebral ganglion (fig. 15) is 
composed of two pyriform lobes on either side, situated one 
above the other with their long axes at right angles. 
The’ dorsal pair are set transversely to the axis of 
the body, and give off from their pointed outer ends a 
bundle of optic nerves. The ventral pair innervate the 
antenne ; they lie slightly in advance of the dorsal lobes 


The Brain of Scolopendra morsitans, after St. Remy (Ventral aspect). 
A.L, Antennary lobes. O.L. Optic lobes. V.N. Visceral nerves, 


with their axes longitudinal. In front they are continued 
into the antennary nerves, and behind into the circum- 
cesophageal connectives. Glomerulated condensations occur 
in their neuropile similar to those found in the antennary 
lobes of other Arthropods, and from their posterior parts 
nerves are given off to the viscera. The subcesophageal 
ganglion is larger than the rest of those in the ventral 
chain; it innervates the jaws and other mouth appendages, 
The succeeding 21 ganglia are similar to one another. 
They are arranged segmentally, and each gives off four 
pairs of nerves—one to the limbs and the rest to the body- 
wall and trachez of the same segment. 


a 


NERVOUS SYSTEM.——-INVERTEBRATA. 33 


In the lower specimen the nervous system has been ex- 
posed from the dorsal aspect, the isolated anterior part of 
another being mounted above. 


D, 25. A Centipede (Scolopendra morsitans) with the integument 
and muscles removed from the right side so as to give a 
lateral view of the nervous system. The Hunterian de- 
scription of this specimen is as follows :—“ Centipede—the 
brain a small roundish body laid bare: the two great 
nerves going to the tail with ganglions at the places where 
they give off nerves, as in the Lobster.”” The part above 
alluded to as the brain is the large subcesophageal ganglion; 
the union of the connectives above the oesophagus is not 
shown. ‘The ventral position of the ganglia and the nerves 
given off from them are well displayed in this preparation. 

O. C. 1298. Hunterian. 


D. 26. The isolated nervous system of a Centipede (Scolopendra 
sp.). Preserved in Goadby solution. 


INSEOTA. 


Viallanes, Ann. des Sci. Nat., sér. 7, t. xiv. p. 429. 
Binet; Jour. de |’Anat., t. xxx. 1894, p. 449. 
Brandt, Hore Soc. Entom. Ross., t. xv. 1879, p. 2. 


In the Insecta, apart from the complexity of the cerebral 
ganglion, one of the most noteworthy features is the variable 
degree of longitudinal concentration of the ganglia of the 
ventral chain, either when comparison is made between adults 
of different species or between the larva and imago of the same 
species. As a rule the nervous system of the adult is more 
concentrated than that of the larva. Concentration usually 
appears first amongst the abdominal ganglia, resulting in the 
fusion of some at the posterior end of the chain and the in- 
clusion of some in front in the metathoracic ganglion. The 
thoracic ganglia also fuse in various ways, though less fre- 
quently. The pro- and mesothoracic, meso- and metathoracic, 
or all three, may thus unite. 

Although in some Orders (e. g. Lepidoptera) a certain definite 
arrangement of the ganglia is fairly constant, in most it is not 


VOL e II . D 


34 i PHYSIOLOGICAL SERIES. 


so, and a variety of stages of concentration occur within the 
Order. In the embryo the nervous system is usually entirely 
unconcentrated, and the adult condition is attained by the suc- 
cessive fusion of ganglia in the embryonic and pupal stages. 
Some embryos, however, have a single unsegmented post-oral 
mass, from which the ganglia of the adult are produced by 
subsequent segmentation. 


D. 27. Models of the brain (cerebral ganglion) and right fungi- 
form body of a Black-beetle (Periplaneta orientalis) x 60, 
with a drawing of a transverse section through the left 
half of the ganglion, the position of which is indicated 
by a black line on the model. The cerebral ganglion 
in Insects consists to a large extent of a pair of proto- 
cerebral lobes in connection with the optic ganglia ; 
thus the size of the brain depends mainly upon the 
degree of development of the eyes, and need not 
necessarily afford an indication of the state of intelligence 
of the individual. The brain further comprises a second 
pair of centres (deutocerebrum), probably olfactory, in 
connection with the antenne; and a third pair (trito- 
cerebrum), situated in the roots of the cireumcsophageal 
connectives, that innervates the labium and gives rise to 
the visceral system. It apparently corresponds to the 
cesophageal ganglia of Crustaceans. 

The protocerebrum consists of the optic ganglia (not 
shown in the model) and of a pair of large protocerebral 
lobes, contiguous in the mid-line. The latter are united by 
commissures, and each contains several remarkable struc- 
tures. The most striking of these are the fungiform bodies 
—organs that are possibly indicated in Crustacea, but 
reach their full and characteristic development in Insects, ; 
One is lodged in each protocerebral lobe; it consists of 
two masses of dense neuropile (calyces, F) deeply concave 
from side to side, and situated near the dorsal surface of 
the brain with their concavities facing upwards. (The 
calyces are exposed on the right side of the model.) Their 
neuropile derives its fibres from a cap of ganglionic nuclei 
(coloured yellow), Hach calyx gives off from its lower 
(convex) surface a short pedicle, that unites with its fellow 


NERVOUS SYSTEM.—INVERTEBRATA. 35 


to form a common neuropile-stalk (peduncle, G). This 
stalk penetrates directly downwards through the substance 
of the protocerebral lobe till it reaches the mid-horizontal 
plane of the brain. Here it gives off two branches, 
one of which (cauliculus, H) curves forward and upward 
near the anterior surface of the brain to terminate in a 
rounded end close beneath the anterior lip of the outer 
calyx ; the other (trabecula, I) runs diagonally downwards 
and inwards, till it meets its fellow, without fusion, in 
the mid-line. The fungiform bodies do not directly give 
rise to any nerves, but they enter into close relations with 
all parts of the brain by means of fibrous tracts, the most 
important of which pass to the optic ganglion of the same 
side, to the opposite fungiform body, to the corpus centrale, 
and to the antennary lobe of the opposite side. Fibres 
belonging to this latter tract continue directly past the 
fungiform body into the optic ganglion, and constitute an 
optico-olfactory chiasma similar to that seen in Decapod 
Crustacea. 

In spite of the evident importance of these structures 
their function is still unknown, but it is noteworthy that 
within the same Order their size increases roughly in pro- 
portion to the intelligence of the Insect, and among social 
forms they may even vary in development between the 
persons of the society—being, for instance, proportionately 
larger in the Worker bee than in the Drone or Queen. 

The protocerebral lobes are united across the mid-line 
by two bands of deeply staining neuropile. One of these 
(the pons) lies immediately below the dorsal point of union 
of the two halves of the brain; it is in the form of a for- 
wardly directed horseshoe, and stands in close relation to 
the roots of the nerves to the white spots (vestigeal ocelli). 
A similar though backwardly directed horseshoe-shaped 
band gives origin to the ocellary nervesin Limulus, and 
there is a somewhat similar strand in the fore part of the 
brain in Decapod Crustacea. 

The second commissural band (corpus centrale) is larger 
and of more complicated structure ; it has the form of a 
erescentic plate hollowed below, and consists of two layers 
of neuropile. It lies approximately in the centre of the 


D2 


36 


PHYSIOLOGICAL SERIES, 


— 


‘brain, and apparently forms a nucleus to which fibres from 


all parts converge. The most important tracts in con- 
nection with it are derived from the fungiform bodies and 
optic and antennary lobes ; beneath it lie a pair of small 
neuropile masses—the tubercles of the corpus centrale. 
(The corpus centrale and tubercles are shown in the 
drawing directly above the trabecula.) A similar though 
simpler median band lies between the protocerebral lobes 
in the Decapod Crustacea. 

The antennary lobes (deutocerebrum) consist of two 
lobules on either side united by transverse commissures ; 
the ventral of the two gives off the larger part of the 
antennary nerve (probably olfactory) ; its neuropile is 
glomerulated. A second smaller root of the antennary 
nerve is derived from the dorsal lobule, it is chiefly motor 
in function. A small tegumentary nerve rises from the 
anterior face of the ventral lobule. 

Each half of the tritocerebrum gives off a nerve from its 
anterior surface that meets its fellow in the mid-line to 
form a triangular ganglion (frontal ganglion, E) from 
which a median nerve runs back along the alimentary 
canal, 

These models, which were cast from originals recon- 
structed from a series of transverse sections by Mr. B. T, 
Newton, have been diagrammatically painted and have 
certain parts and areas indicated by letters and numbers, 
the key to which is mounted below the models. 

Newton, Quart, Journ. Mier. Sci., vol. xix. 1879, p. 340. 


D. 28. Two specimens of a Cockroach (Blatta americana) dis- 


sected to show the nervous system from the dorsal and 
ventral aspects. The dorsal surface is shown in the left-hand 
specimen, the ventral in the right. The cerebral ganglion 
lies in the head, and is so placed that the optic lobes lie 
vertically above the antennary. The subsophageal 
ganglion for the innervation of the mouth-parts is also 
situated in the head close below the cerebral; it is united by 
a pair of connectives to a ventral chain composed of 
9 paired ganglia, The anterior three are larger than the 
rest, and lie one in each thoracic segment at equal distances 


NERVOUS SYSTEM.—INVERTEBRATA, 37 


apart. Hach gives off nerves (seen best in the right-hand 
specimen) to the legs and body muscles, and (in the case of 
the posterior two) to the wings. 

In the abdomen the ganglia of the chain are situated at 
irregular intervals—the first four fairly close together, the 
last three somewhat further apart. The terminal ganglion 
(6th) is larger than the rest and represents a fusion of the 
two posterior larval ganglia; it innervates the hinder end 
of the body, the rectum, the genital organs, and the cerci. 

Each of the other abdominal ganglia gives off a single 
pair of nerves to the body-walls and trachez. 

The ventral-chain ganglia are composed of definite 
dorsal and ventral masses of neuropile, from which the 
nerves arise by two or more independent roots, that appa- 
rently convey either motor or sensory impulses according 
as they spring from the dorsal or ventral mass. The pro- 
bability of a localisation of motor and sensory functions in 
opposite regions of the cord of Arthropods has been dis- 
cussed since the idea was brought forward by Newport. 
Later observations have tended to show that in the 
case of Crustacea such localisation does not occur, but 
that in Insects it most probably does. This latter con- 
clusion rests not only upon physiological experiments, but 
is also based upon anatomical grounds—more particularly 
upon a comparison of the alar nerve-roots in flying beetles 
with those of beetles whose wing-cases are present but 
immoveable. In the former case each alar nerve rises by 
two main roots, one from the dorsal mass of neuropile, the 
other from the ventral. In the beetles with purely pro- 
tective non-motile wing-cases (e.g. Blaps mortisaga) the 
dorsal root is entirely absent (Binet, /. c.). 

Preserved in Goadby solution. 

Miall & Denny, Life History and Structure of the 

Cockroach (Periplaneta orientalis), 1886, p. 86. 


D. 29. A large female Orthopterous Insect (Karabidion australe) 
with the nervous system shown from the dorsal aspect. 
The thoracic ganglia are nearly equal in size, and lie, 
widely separated, in the three thoracic segments. There 
are six free abdominal ganglia, situated respectively in 


38 


PHYSIOLOGICAL SERIES. 


successive abdominal segments from the 2nd to the 7th. 
Each of the anterior five innervates the segment in which 
it lies; the 6th gives off nerves to the hinder end of the 
body. The 1st abdominal segment is supplied by the 
metathoracic ganglion. O. C, 1299 k. 


D. 30. A Locust ( Tropidacris latreille:) dissected from the dorsal 


aspect. The cerebral ganglion is small compared with the 
size of the head, and is united to the subosophageal 
ganglion by relatively long connectives. The three thoracic 
ganglia are separate, although the meso- and metathoracic 
show a certain amount of approximation. The metathoracic 
ganglion is much larger than the other two; it sends a 
number of nerves to the anterior parts of the abdomen in 
addition to those to the metathorax, and probably repre- 
sents a fusion of the true metathoracic ganglion with a 
certain number of abdominal ganglia. Within the abdomen 
there is a chain composed of five separate ganglia situated 
respectively in the 2nd, 4th, 6th, 7th, and 8th segments. 
The first of them innervates the fourth segment; the 
last is larger than the others and is no doubt a compound 
mass, O. C. 1299 c. 


D. 31. A female Stick-insect (Pseudobacteria?) showing the 


nervous system from the dorsal aspect. The entire system 
is of the most delicate nature and, in conformity with the 
general structure of the insect, is greatly extended longi- 
tudinally. The cerebral and subcesophageal ganglia are 
not visible. The three thoracic ganglia are separate ; they 
are followed by a chain of five abdominal ganglia situated 
respectively in the 2nd to the 6th abdominal segments. 
The first of these free ganglia innervates the 2nd 
segment of the abdomen, so that presumably the first 
primitive abdominal ganglion is included in the meta- 
thoracic, The terminal ganglion innervates the posterior 
region of the body and the genitalia, 
The genital organs are also shown in this specimen. 


O. C, 1299 p. 
Miiller, Nov, Act. Nat, Curios., Bd, xii, 1825, p. 568. 


NERVOUS SYSTEM.—INVERTEBRATA. 39 


D. 32. An immature Water-Scorpion (Belostoma) showing the 
nervous system. In all the Hemiptera the post-oral part 
of the central nervous system shows a high degree of 
longitudinal concentration, and in none perhaps more so 
than in the Water-Scorpions. In this example the sub- 
cesophageal ganglion lies close to the cerebral, in the pro- 
thorax ; it is almost contiguous with the prothoracic 
ganglion, the approximation of the two being evidently 
due to the forward position of the 1st pair of legs. The meso- 
and metathoracic ganglia are fused with one another and 
with the abdominal chain to form a round central thoracic 
mass from which nerves are given off to the two posterior 
pair of thoracic limbs and to the abdomen. Owing to the 
half-macerated condition of the specimen, the component 
parts of the central thoracic mass are visible as three pairs 
of opaque centres representing respectively the meso- and 
metathoracic ganglia and the united ganglia of the 
abdominal chain. O. C. 1299 B. 


D. 33. Two specimens of the nervous system of another species 
of Water-Scorpion (Vepa cinerea). In its main features 
this system corresponds with that shown in the last speci- 
men, but the longitudinal concentration is even more 
marked. In this species the subcesophageal ganglion is 
completely fused with the prothoracic. In the upper 
specimén the nervous system is seen isolated ; in the lower 
in situ. QO. C. 1299 Ba. 


D. 34. The nervous system of a Lepidopterous larva exposed 
from the dorsal aspect. The cerebral ganglion consists of 
two small rounded lobes contiguous in the mid-line. It is 
united around the cesophagus by a pair of short connectives 
to a ventral chain, composed (as in the great majority of 
Lepidopterous larve) of 11 equal-sized ganglia—i.e., 
1 subeesophageal, 3 ‘thoracic, and 7 abdominal. The sub- 
cesophageal and prothoracic ganglia are approximated to 
one another ; but the remainder lie at about equal distances 
apart in successive segments of the body. The terminal 
ganglion is distinctly grooved transversely and represents 
a fusion of two embryonic ganglia. As in the adult, it 


40 


PHYSIOLOGICAL SERIES. 


innervates the reproductive organs in addition to the hinder 
region of the body-wall. The connectives of the ventral 
chain are very slender ; they lie close side by side, except 
between the three thoracic ganglia where they are trans- 
versely separated. O. C. 1299 a. 


D. 35. The larva of a Moth (Metura sawndersii) contained within 


its protective case and dissected from the ventral surface. 
The nervous system is of extreme delicacy. It does not 
differ in the number of its post-oral ganglia from that 
shown in the preceding specimen, but the altered positions 
of the ganglia relative to the body-segments and to one 
another suggest that those changes have begun, which 
finally, during the pupal stage, produce the longitudinal 
concentration of the nervous system found in the imago. — 
The first abdominal ganglion is for example markedly 
approximated to the metathoracic, and lies with it in the 
metathoracic segment. O. C. 1299 F. 


D. 36. Two specimens of the nervous system of the larva of a 


Goat Moth ( Cossus ligniperda) : one in situ seen from above, 
the other isolated. The cerebral and subwsophageal ganglia 
are moderately separate, but the prothoracic is almost 
confluent with the suboesophageal. It is followed by a 
chain of 10 ganglia (2 thoracic and 8 abdominal). Between 
the thoracic ganglia the connectives diverge laterally, 
leaving an oval space. In the anterior of these spaces, in 
the left specimen, a small median nerve can be seen, which 
arises from the prothoracic ganglion and ends in two 
lateral branches close in front of the mesothoracic. It 
belongs to a series of median sympathetic nerves, found 
commonly among insects ; as a rule each rises from one of 
the two connectives close behind a ganglion, or from the 
ganglion itself, runs to the succeeding ganglion and there 
divides into two lateral branches, each of which joins one 
of the peripheral nerves and is distributed to the respiratory 
organs. The abdominal ganglia are situated at equal 
distances apart, with the exception of the first which is 
approximated to the metathoracic, and the last two which 
are almost contiguous. 
Cattie, Zeits. wiss. Zool., Bd, xxxv. 1881, p. 304. 


NERVOUS SYSTEM.—INVERTEBRATA. 41 


D. 37. A Lamellicorn Beetle (Dynastes centaurus) dissected from 
above to show the nervous system. The cerebral ganglion 
is comparatively small; it is united to the subceesophageal 
by connectives of moderate length. In the thorax there 
are three ganglionic masses, of which the anterior two are 
simple and respectively constitute the pro- and meso- 
thoracic ganglia ; the posterior mass is elongated in shape, 
and consists of the true metathoracic ganglion fused with a 
short cylindrical appendage that represents a concentra- 
tion of the abdominal chain ganglia, and innervates the 
abdomen. This arrangement of the ganglia is the one 
usually found among Lamellicorns. 


D. 38. A male Longicorn Beetle (Macrotoma) showing the 
nervous system from above. The cerebral ganglion is 
small relative to the head, and is united to the subcesopha- 
geal ganglion by long connectives. The thoracic ganglia 
are separate, with approximation between the meso- and 
metathoracic. The latter innervates the anterior part of 
the abdomen, as well as the metathorax. There are four 
free abdominal ganglia, the first of which is situated on 
the boundary-line between the thorax and the abdomen, 
This number and arrangement of the ganglia is charac- 
teristic of this family of Beetles. “0. GC. 1299 a. 


D. 39. The nervous system of a Hornet ( Vespa crabro), isolated. 
The large size of the cerebral ganglion is due, partly to the 
bulk of the protocerebral lobes—the centres for the great 
compound eyes, and partly to the high degree of develop- 
ment of the fungiform bodies. The latter differ in 
many respects from those of the Black-beetle (D 27); 
their calyces are larger and arch to a considerable extent 
over the anterior and posterior surfaces of the proto- 
cerebral lobes; the peduncle and its two calycal branches 
are remarkably stout, but the cauliculus and trabecula are 
insignificant, and without definite outlines. The ocelli 
receive their nerves from three centres that lie directly 
beneath them. The cerebral ganglion is continuous around 
the cesophagus with the small subcesophageal ganglion. 
There are two ganglia in the thorax—the first is the pro- 


42 PHYSIOLOGICAL SERIES. 


thoracic, the second a compound mass that represents a 
fusion of the meso- and metathoracic ganglia with the first 
two abdominal. In the abdomen there are five separate 
ganglia, the last of which is double and is formed by the 
fusion of two larval ganglia. 

Viallanes, Ann. Sci. Nat., sér. 7, t. ii, 1887, p. 1 


(Brain). 
MOLLUSCA. 
v. Ihering, Anat. des Nervensystemes .... der Mollusken, 
1877. 


Garstang, ‘Science Progress,’ vol. v. 1896, p. 38. 


The central nervous system of the Mollusca may be compared 
with that of an Annelid or Arthropod in so far as it is essenti- 
ally bilaterally symmetrical and consists of a paired pree-oral 
centre united around the cesophagus to a ventral system below the 
gut. But in Molluses the ventral system, when longitudinally 
elongated, shows no true metameric segmentation, and thus differs 
fundamentally from the ventral chain system of Annelids and 
Arthropods, although it much resembles the ventral cords of a 
Turbellarian. In addition to the pre- and postoral centres 
common to most Invertebrates, there are present others peculiar 
to the Mollusca. The most important of these are certain 
pallio-visceral centres for the innervation of the mantle, gills, 
and parts of the viscera, They occur either as a simple ganglionic 
loop uniting the lateral parts of the circum-oral system, or as 
a number of isolated ganglia (pleural, branchial, abdominal) 
united together by a fibrous commissure and due apparently to 
the disintegration of some such generalised loop. Modification 
in the various groups of Molluses tends either towards the 
concentration of all the centres towards the head (Gastropods, 
Cephalopods), or—in the Peleeypods—towards the diminution 
and suppression of the cerebral and pedal ganglia owing respect- 
ively to the absence of the head with its sense-organs and to 
the degeneration in many forms of the foot or byssal apparatus. 
Besides this reduction of the anterior ganglia, there is, in the 


Pelecypods, a backward migration of the pallio-branchial centres — 


(visceral ganglia) and a progressive increase in their size, lateral 


f 
t 


NERVOUS SYSTEM.—INVERTEBRATA. 43 


concentration, and complexity of structure, depending upon 
the perfection of the mantle sense-organs or the formation of 
siphons. 


PELECYPODA. 
Rawitz, Jena. Zeits., Bd. xx. 1887, p. 384. 


D. 40. A wax model of the nervous system of Nucula nucleus, 
x 25. The central system, as in other Pelecypods, consists 
of three pairs of ganglia united to one another by com- 
missures and connectives. The cerebral ganglia lie in 
front of the mouth united by a short commissure ; each 
gives off three nerves that respectively innervate the 
anterior adductor, labial palps, and anterior part of the 
mantle. Posteriorly, the cerebral ganglia gradually di- 
minish in thickness and pass insensibly into a pair of long 
cerebro-visceral connectives, by which they are united to 
the visceral ganglia. The latter are small and laterally 
separate ; they lie ventral to the gut at some little distance 
in front of the posterior adductor united by a definite 
commissure, and innervate the gills, posterior adductor, 
and posterior part of the mantle. The cerebro-pedal 
connectives arise from the inner ventral surface of each 
cerebral ganglion by two roots, that remain separate for a 
fourth of the distance to the pedal ganglion. The double 
origin of these connectives from each cerebral ganglion 
has been thought to indicate that the latter is a compound 
structure consisting of two ganglia comparable to the 
cerebral and pleural of the Gastropod. But it may be, 
that the posterior root of the cerebro-pedal connective is 
the proximal part of the otocystic nerve running free for 
the first part of its course and not completely united with 
the cerebro-pedal connective as in most other Pelecypods. 
It is suggestive in this connection that in Solenomya (another 
of the Protobranchia) the otocystic nerve is entirely free 

_ from cerebral ganglion to otocyst. The pedal ganglia lie 
in the substance of the foot closely united together by a 
double commissure; they innervate the pedal muscles. The 
nervous system shows its low organisation by the diffuse 
distribution of ganglion-cells upon its surface (indicated by 


44 


PHYSIOLOGICAL SERIES. 


yellow in the specimen). They not only form a layer of 
some thickness upon the three pairs of ganglia and the 
root of the branchial nerve as in other Pelecypods, but cover 
the outer and dorsal surfaces of the cerebro-visceral 
connectives and the cerebral and visceral commissures. 
Pelseneer, Arch. de Biol., t. xi. 1891, p. 166. 
Drew, Quart. Journ. Micro. Soc., vol. xliv. 1901, p. 373. 


D. 41. The nervous system of an Edible Mussel (Mytilus edulis), 


isolated. The ganglia are small—the pedal and visceral 
of approximately equal size, the cerebral slightly smaller. 
The latter lie on either side of the mouth, united by a long 
preeoral commissure. From the posterior extremity of 
each a single cord is given off, which shortly divides to 
form the cerebro-pedal and cerebro-visceral connectives. 
The pedal ganglia lie between the viscera and the foot ; 
they are closely applied to one another, and each gives off 
two main nerves—a large one from its lateral border to the 
pedal muscles, and a smaller posterior one to the byssus 
gland. The visceral ganglia lie some distance apart upon 
the antero-ventral surface of the posterior adductor, united 
to one another by a slightly ganglionic commissure. Each 
ganglion gives off two principal nerves, an anterior 
ganglionic branchial nerve and a large posterior trunk that 
supplies the mantle and posterior adductor. 


D. 42. Two specimens of the nervous system of a Scallop 


(Pecten maximus)—one isolated, the other shown. within 
the body from the left side. The remarkable perfection of 
the sense-organs on the mantle-border of the Scallops, and 
the large size and energy of their adductor muscle, are 
accompanied by a corresponding development of the visceral 
ganglia, the centres from which these parts are mainly 
innervated. The ganglia are completely fused in the 
mid-line, and form a rectangular mass situated upon the 
ventral surface of the adductor, near the centre of the animal. 
Each anterior corner receives one of the cerebro-visceral 
connectives ; external to these arise the branchial nerves, 
followed, along each lateral margin of the ganglion, by 
a series of lateral mantle-nerves, distributed to the middle 


NERVOUS SYSTEM.—INVERTEBRATA. 45 


region of the mantle-border. From each posterior corner 
arises another bundle of nerves (posterior pallial), which 
innervates the posterior adductor and the hinder sixth 
of the mantle-border. The branches of the pallial nerves 
just before their final distribution are united by a ganglionic 
cord (not shown in the specimen) that runs completely 
round the mantle parallel to its edge. 

The cerebro-visceral connectives lie for their posterior 
third upon the surface of the adductor ; anterior to that 
point they traverse the superficial parts of the gonad to 
reach the small cerebral ganglia. The latter lie behind 
the mouth, united preorally by a very long and delicate 
commissure; they give off nerves to the anterior part of 
the mantle and labial palps. The pedal ganglia are small 
and contiguous in the mid-line ; they lie above the foot, 
between the cerebral ganglia. O. C. 1808 & 5. 


D. 43. Two specimens of the nervous system of a Pond-Mussel 
(Anodenta cygnea), shown respectively from the left side 
in situ, and isolated. The ganglia are more marked than 
in Mytilus, but show much the same relative proportions 
to one another. The cerebral lie at the postero-lateral 
margins of the mouth, and are united preeorally by a long 
commissure ; each gives off the usual nerves to the mantle, 
palps, and anterior adductor. The pedal ganglia are closely 
applied to one another, and are situated in the upper part 
of the foot embedded in the viscera; they give off 
numerous nerves to the pedal muscles and integument. 
The cerebro-visceral connectives run one on either side of 
the body on a level with the line of attachment of the gills; 
at their anterior end they lie far apart near the surface of 
the visceral mass, but towards the visceral ganglion run close 
together, between the organs of Bojanus. The visceral 
ganglia are larger than either cerebral or pedal; they are 
fused together to form a bilobed mass* situated on the 
ventral surface of the posterior adductor. They give off 
several small visceral filaments from their anterior surface, 
and two pairs of larger nerves from their lateral and 
posterior borders. The lateral pair supply the gills, and 
have at their origin a ganglionic area that underlies a 


46 


PHYSIOLOGICAL SERIES. 


special branchial sense-organ (osphradium). The posterior 
nerves are distributed to the mantle (particularly to the 
papille that surround the inhalent opening) and to the 
posterior adductor.. 

In the lower specimen black paper has been placed 
beneath the ganglia. 0. C. 1303 8 a, 


AMPHINEURA. 
Plate, Zool. Jahrb., Suppl.-Bd. iv. 1898, p. 151. 


D. 44. The central nervous system of a Chiton (Hanleya 


abyssorum), showing some of its more important features. 
The nervous system in this and other Amphineura consists: 
fundamentally of two pairs of longitudinal cords united 
anteriorly to a circumoral ring. An even layer of ganglion- 
cells covers all parts of the cords and ring, without local 
concentration to form special ganglia, except in the 
Aplacophora and one species of Chiton. The outermost 
pair of cords (lateral cords) lie in the body-walls above the 
branchial furrow, lodged between the main branchial 
vessels; they innervate the mantle with its sense-organs, 
and, from their slightly thickened posterior. fourth, the 
gills and probably also the renal organs and heart. They are 
continuous with another above the rectum, and thus form an 
elongated loop, comparable, apart from its relation to the 
rectum, to the visceral loop of Gastropods and Pelecypods. 
The ventral or pedal cords extend throughout nearly the 
whole length of the foot, buried in its substance. They 
are united together by a large number of very delicate and 
somewhat irregularly disposed commissures, and give off 
from their outer and ventral surfaces numerous pedal nerves, 
that unite to form a rich plexus in the muscles of the foot. 
The first and last of the series of pedai commissures are far 
stouter than the rest, (in the specimen these two are 
perfect, the roots only of the other commissures and of the 
pedal nerves are shown). The pedal and lateral cords of 
the same side unite together in front to form the band- 
like anterior part of the circumoral ring. Behind the 
mouth the ring is completed by a slender strand, that 
terminates on either side in a swelling at the anterior end 


NERVOUS SYSTEM.—INVERTEBRATA. 47 


of the pedal cord. From these swellings, which much 
resemble the labial lobes of Haliotis, two pairs of con- 
nectives are given off—one to the ganglia of the subradular 
organ (imperfect in the specimen), the other to the buccal 
ganglia, which lie as usual upon the posterior surface of 
the buccal mass, between the cesophagus and radular sac. 
The buccal system in this and certain other species forms a 
second complete ring around the gut: the buccal ganglia 
being united by commissures both below the cesophagus 
and above the roof of the buccal mass. The buccal ganglia 

probably innervate the whole alimentary canal. 
O. C. 1305 c. 

Burne, Proc. Malac. Soc., vol. ii. 1896, p. 4. 


D. 45. The anterior part of the nervous system of the same 
species of Chiton, isolated to show the two nervous rings 
(cireumoral and buccal) that surround the alimentary 
canal. QO. C. 1305 vb. 


GASTROPODA. 
Bouvier, Ann. Sci. Nat., sér. 7, t. iii. 1887, p. 1. 


D. 46. An isolated specimen of the nervous system of an Ormer 
(Haliotis tuberculata). The cerebral ganglia are small but 
fairly distinct, and are united in front of the mouth by a 
long ribbon-like commissure. From the lateral parts of each, 
two connectives pass beside the buccal mass to a compound 
pleuro-pedal ganglion beneath the gut. The greater part 
of this ganglion belongs to the pedal system, and extends 
backwards in the substance of the foot as a pair of flattened 
cords, fused to one another and to the pleural centres at their 
anterior end, and united at intervals by nine transverse 
commissures. Nerves are given off from this “ ladder-like ” 
pedal system to the foot and epipodium. The pleural 
ganglia form a pair of indefinite excrescences on the dorsal 
surface of the fused anterior ends of the pedal cords. 
They give off a pair of large mantle-nerves, and are united 
together, as in other Prosobranchs, by a commissural 
loop (visceral loop), that in its passage from ganglion to 
ganglion is twisted in the form of an 8. This twisted or 
-streptoneurous loop is characteristic of the Prosobranchs, 


48 


PHYSIOLOGICAL SERIES, 


- 
= 


and always bears in its different parts a definite relation to 
the gut. The arm of the visceral loop that rises from the 
left pleural ganglion passes beneath the gut to the opposite 
side of the body ; here, at a point slightly posterior to the 
free tip of the gill, it forms a ganglion (subintestinal 
ganglion) from which the gill and olfactory organ (osphra- 
dium) are innervated. The loop continues its course round 
the margin of the mantle-cavity, and at its hindermost 
extremity forms another ganglion (abdominal ganglion), 
from which several nerves are given off to the viscera. 
On the left side of the mantle-cavity, opposite the sub- 
intestinal ganglion, a third ganglion (supraintestinal) is 
formed for the innervation of the left gill and osphradium. 
After leaving this ganglion the loop turns to the right over 
the dorsal surface of the intestine, and finally enters the 
right pleural ganglion. 

Nerves are given off from the cerebral ganglia to the 
sense-organs and integument of the head ; those to the lips 
take their origin, in common with the buccal connectives, 
from a prominence on the antero-ventral surface of each 
ganglion (labial lobe). The buccal ganglia form a single 
horseshoe-shaped band, situated on the posterior wall of the 
buccal mass between the radular sac and cesophagus. 

O. C. 1305 F. 

Lacaze-Duthiers, Ann. Sci. Nat., sér. 4, t. xii, 1859, 

p. 247. 


D. 47. The nervous system of a Limpet (Patella vulgata), 


isolated. This nervous system agrees in its general features 
with that of Haliotis, but differs from it in the following 
important particulars :—The ganglia are more pronounced 
and independent: this difference is particularly marked in 
the separation of the pleural and pedal ganglia. The pedal 
cords are not fused at their anterior end, but form a pair 
of ganglionic enlargements united by a stout commissure. 
Posteriorly they gradually become purely fibrous. The 
pedal cords are united by two commissures only. The 
labial lobes are detached from the cerebral ganglia. A 
nerve of some length is interposed between the sub- and 
supraintestinal ganglia and the visceral loop. 0. C. 1305 x. 


NERVOUS SYSTEM.—INVERTEBRATA. 49 


D. 48. The nervous system of an Apple-Snail (Ampullaria urceus), 
isolated excepting the pedal nerves of the right side. The 
nervous system of this Prosobranch affords a striking 
example of a condition of the visceral loop, known as 
zygoneury ; by this is meant the presence of certain con- 
nections between the sub- and supra-intestinal ganglia and 
the pleural ganglion of the same side, whereby a kind of 
false orthoneury arises that to a greater or less extent 
masks the original streptoneurous condition of the loop. 
These connections occur commonly among Prosobranchs, 
and can be present on one or both sides constituting right, 
left, or double zygoneury according as the nervous union 
takes place between the right pleural and subintestinal 
ganglia, the left pleural and supra-intestinal, or both. In 
this specimen double zygoneury is shown in an extreme 
form. The visceral loop passes from the left pleural 
ganglion beneath the intestine to a small subintestinal 
ganglion partially fused to the right pleural ganglion-—this 
fusion constitutes the right zygoneurous connection. From 
the subintestinal ganglion the visceral loop runs round the 
margin of the mantle-cavity as usual, giving off a nerve to 
the mantle on the right side and several to the viscera from 
a bilobed abdominal ganglion situated at its posterior ex- 
tremity. The left arm of the loop, after giving off a few 
small nerves, enters an elongated supra-intestinal ganglion, 
which gives origin to a stout nerve for the osphradium 
and several smaller branches that are said to pass across 
the roof of the mantle-cavity to the gill, which in this 
molluse is displaced from the left to the right side by the 
development of the lung-sac. The supra-intestinal ganglion 
is connected by a large trunk to the left pleural ganglion 
(the left zygoneurous connection) and to the right pleural 
ganglion by a delicate filament that passes dorsal to the 
intestine and subintestinal ganglion, and represents the 
supra-intestinal arm of the streptoneurous loop in a very 
much reduced condition. 

The pleural ganglia are fused to the pedal to form a pair 
of subcesophageal masses, in each of which the constituent 
parts are separated by a shallow depression. They are 
connected by three commissures—one between the pleural 

VOL. Il. EK 


50 PHYSIOLOGICAL SERIES. 


centres, the other two between the pedal. The nerves from 
the pleural ganglia innervate the mantle ; one of those on 
the right side is of large size, and forms a considerable 
ganglion before breaking up to innervate the penis, rectum, 
and neighbouring parts. The pedal ganglia are continued 
backwards in the substance of the foot as a pair of longi- 
tudinal fibrous cords, connected together by 3 or 4 delicate 
commissures. From their outer sides a number of pedal 
nerves are given off, which towards the margin of the foot 
form a rich plexus with minute ganglia at the meeting- 
points of the nerve-filaments. The pedal system, except 
for the absence of ganglion-cells in the longitudinal cords, 
closely resembles the “ ladder-like” system of Vivipara 
[Paludina]. The cerebral ganglia are united by a long 
ribbon-like commissure; they innervate the cephalic sense- 
organs, and are united by a pair of long connectives to two 
small buccal ganglia situated in the usual place on the 
posterior surface of the buccal mass and connected by a 
subcesophageal commissure. O. C. 1305 a. 
Burne, Proc. Malac. Soe., vol. iii. 1899, p. 317. 


D. 49. A Heteropod (Carinaria mediterranea) with the nervous 
system displayed from the left side. The system, which is 
very delicate compared with the size of the animal, bears 
many resemblances to that of a Prosobranch, particularly 
in the possession of a crossed (streptoneurous) visceral 
loop. The ganglia are considerably lobulated. There are 
two main pairs—(i.) the cerebral (fig. 16), from which 
nerves are given off to the large and highly-organised eyes, 
the otocyst, tentacles, and labial region of the integument ; 
and (ii.) the pedal ganglia. The latter lie above the fin 
within the body ; each is bilobed, with the two lobes one 
above and slightly in front of the other. The upper lobe 
receives a stout connective from the cerebral ganglion, and 
gives off from its hinder end a connective to the visceral 
ganglion of the same side, and from its upper surface 
3 or 4 tine nerves that radiate to the body-wall. A large 
nerve for the penis rises from the upper lobe on the right 
side. .The lower lobe sends nerves to the body-wall and 
to the various regions of the foot, that to the fin being 


NERVOUS SYSTEM.—INVERTEBRATA. 51 


particularly large. A pair of long slender connectives arise 
from a lobe (fig. 16, PL.L.) on the posterior surface of each 
cerebral ganglion and accompany the alimentary canal ; 
near the visceral mass each crosses to the opposite side of 
the body—the left below the gut and the right above, 
and upon reaching the visceral mass is joined by the 
above-mentioned pedo-visceral connective, and swells to 
form a small visceral ganglion upon the surface of the 
gastric gland. These two visceral ganglia represent the 


Fig. 16. 


PL.V. C. 


Cerebral Ganglia of Carinaria mediterranea. 


C.P.C. Cerebro-pedal connective. O.N. Optic nerve. PL.L. Pleural lobe. 
PL.V.C, Pleuro-visceral connective. 


supra- and subintestinal of a Prosobranch ; each is united 
by a delicate filament to a large abdominal ganglion 
situated upon the gastric gland midway between the two. 
The gill is innervated from the supra-intestinal ganglion. 

Ganglia comparable to the pleural of other Gasteropods 
are not present as independent centres ; they are probably 
fused with the cerebral ganglia, forming the lobes from 
which the visceral loop arises. 

Pelseneer, OC. R. Acad. Sci., t. exiv. 1892, p. 775. 

: ™ 
D. 50. Two specimens of the nervous system of a Roman Snail 
(Helix pomatia), shown respectively in situ from the left 
side, and isolated. 

The central system is much. concentrated. It consists of 
two main ganglionic masses—(i.) a paired oblong cerebral 
ganglion, united by two connectives on either side of the 

E2 


52 


- PHYSIOLOGICAL SERIES. 


cesophagus to (ii.) a large compound subcsophageal mass 
formed by the fusion of pedal and pleural ganglia with 
the four centres of the short untwisted (orthoneurous) 
visceral loop. 

The two halves of the cerebral ganglion are united by a 
short commissure ; each is indistinctly lobulated, the most 
conspicuous lobe forming a conical projection (tentacular 


Fig. 17. 


Diagrammatic reconstruction of the Pleuro-pedal mass of Helia pomatia. 


x 20. 


C.P.C. Cerebro-pedal connective. C.PL.C, Cerebro-pleural connective. 


P.G, Pedal ganglion. PL.G. Pleural ganglion. V.L. Visceral loop. 


lobe) on its anterior surface, from which arises a large 
nerve for the optic tentacle and eye and a smaller one for 
the otocyst. From the antero-lateral margins of the 
ganglion, nerves are given off to the lips and anterior 
tentacles, and from its ventral surface a pair of delicate 
buccal connectives. The substance of the subcsophageal 
mass (fig. 17) is traversed between the pleuro-visceral and 
pedal centres by the anterior aorta. The pleural ganglia 
give off no nerves. Four large nerves rise from the 
ganglia of the visceral loop; three of them innervate 


NERVOUS SYSTEM,—INVERTEBRATA. 53 


the mantle and respiratory organs, the fourth enters the 
visceral mass and is distributed to the genital organs. 
The pedal ganglia are united by two distinct commissures ; 
each gives off a large bundle of nerves to the foot. 

The entire central system is enclosed in a thick sheath 
of connective tissue (fig. 18). There are two distinct kinds 
of ganglion-cells—large unipolar cells, some of immense 
size (‘17 mm.) situated around the subcesophageal and 


Horizontal section through the right Cerebral Ganglion of Helix pomatia. 
x 40. 


C.T. Connective tissue. G.C. Large ganglion-cells. G.N. Ganglionic 
nuclei. T.L. Tentacular lobe. 


buccal ganglia and on the posterior surface of the cerebral, 
and small cells with a minimum of protoplasm, very similar 
to the ganglionic nuclei of Arthropods, crowded together 
upon the lateral surface of the tentacular lobes of the 
cerebral ganglia. The neuropile of the tentacular lobes 
derived from these cells is peculiarly dense. 

In the upper (isolated) specimen blue paper has been 
placed beneath the four nerves that rise from the visceral 
loop, and in the-lower specimen the main features of the 
nerve distribution have been indicated by black paper. 

O. C. 1305 A a. 


Nabias, Act. Soc. Linn. Bordeaux, sér. 5, t. vii. p. 10. 


PHYSIOLOGICAL SERIES. 


D. 51. A Slug (Limaz rufus), laid open longitudinally along the 


back, and with the viscera removed, to show the nervous 
system. The cerebral ganglia are pear-shaped and situated 
at some distance apart united by a commissure. They 
innervate the same organs as in the Snail. The esophageal 
nervous ring is completed below the gut by. a larger 
ganglionic mass from which nerves radiate to supply the 
body. The principal nerves are the two inferior ones which 
extend on either side of the mid-line of the ventral surface 
straight to the hinder end of the body, giving off branches 
from their outer sides to the muscular foot. A small 
asymmetrical ganglion is formed on the nerve that supplies 
the heart and respiratory apparatus. The subcesophageal 
ganglion is a compound body, formed, as in the Snail, by 
the fusion of the pedal, pleural, and visceral ganglia. 

O. C. 1304. Hunterian. 


D. 52. The same species of Slug laid open along the ventral 


aspect, and with the viscera removed to show more 
especially the suboeesophageal ganglion and its nerves. A 
bristle occupies the place of the esophagus. O.C. 1305. 

Hunterian. 


D. 53. A Slug (Limaz sp.) with the body-walls divided longi- 


tudinally along the ventral surface, and divaricated to show 
the nervous system in position. Preserved in Goadby 
solution. 


D. 54. Two isolated specimens of the nervous system of a Pond- 


Snail (Limnea stagnalis). The central nervous system 
although decidedly concentrated is much less so than in the 
Land-Snail. The three pairs of ganglia that form the 
circum-cesophageal ring (cerebral, pleural, and pedal) are 
independent and joined together by short commissures and 
connectives. The orthoneurous visceral loop is extremely 
short, yet its ganglia and the fibrous strands that unite 
them to one another and to the pleural ganglia can be 
clearly distinguished. The distribution of the nerves that 
arise from the various ganglia corresponds in the main with 
that seen in //elix, but it should be noticed that at the end 
of one of the terminal branches of the pallial nerve given 


NERVOUS SYSTEM.—INVERTEBRATA. 55 


off from the right visceral ganglion there is a small round 
ganglion ; this underlies a sensory pit (probably olfactory) 
situated close to the respiratory orifice. The cerebral 
ganglia are considerably lobulated. Blue paper has been 
placed beneath the visceral loop in both specimens. 
O. C. 13054 db. 
Lacaze-Duthiers, Arch. Zool. Exp., t. i. 1872, p. 437. 


D. 55. Two specimens of the nervous system of a Sea-Hare 
(Aplysia punctata), seen from the dorsal aspect, isolated 
(upper specimen), and in situ. The several ganglia of the 
circum-cesophageal ring are separate, definite in outline, 
and of moderate size. The cerebral ganglia lie close together 
above the cesophagus, on either side of which they are 
united by a pair of short connectives to the pedal and pleural 
ganglia. Hach pleural ganglion lies slightly behind and 
below the pedal ganglion of the same side, joined to it by 
a very short connective. The pedal ganglia are united by 
two commissures—one short and stout passing directly from 
ganglion to ganglion, the other longer and more delicate. 
The pleural ganglia give rise to a long untwisted (ortho- 
neurous) visceral loop, that extends backwards through the 
cavity of the body to the pericardium. Here it is completed 
by a large bilobed ganglion, from which nerves are given 
off to the body-wall, generative organs, and gill. The 
branchial nerve arises from the upper of the two lobes, and 
at the base of the gill forms a small round ganglion that 
underlies a special sense-organ (osphradium). The chief 
nerve given off from the lower lobe supplies the genital 
organs. Although the visceral loop is essentially ortho- 
neurous, it shows a variable but distinct tendency towards 
a streptoneurous twist. When seen from above its left arm 
appears in the posterior part of its course to lie directly 
beneath or even in some cases slightly to the right of the 
right arm. This partial streptoneury is interesting in view 
of the unmistakably twisted loop of another Opisthobranch 
(Actwon). The nerve distribution resembles that in other 
Gastropods ; the sense-organs of the head and the integu- 
ment around the mouth are supplied from the cerebral 
ganglia; the pleural nerves innervate the anterior parts of 


56 


PHYSIOLOGICAL SERIES. 


the lateral body-walls, while the ventral and posterior parts 
of the body receive nerves from the pedal ganglia. The 
buccal ganglia are contiguous in the mid-line ; they lie on 
the posterior surface of the buccal mass between the 
cesophagus and radula-sac, and give off nerves as usual 
to the buccal mass and alimentary canal. 


D. 56. A Sea-Hare (Aplysia sp.) opened longitudinally to the 


right of the dorsal mid-line, and with the body-walls spread 
to either side to show the nervous system in situ. The 
viscera have been removed with the exception of the buccal 
mass and part of the heart. The outlines of the ganglia 
are less distinct than in the previous specimen, as the 
connective-tissue sheath by which they are enveloped has 
not been removed. Preserved in Goadby solution. 


D. 57. Two specimens of the nervous system of a Nudibranch 


( Archidoris tuberculata). The central system is extremely 

concentrated. It consists of a single supra-cesophageal 
lobulated mass, in which can be traced three pairs of centres 
that apparently represent cerebral, pleural, and pedal ganglia. 
The cerebral, which form the anterior part of the mass as 
seen in the lower specimen, give off, as usual, buccal connec- 
tives and nerves to the cephalic sense-organs. The pleural 
and pedal centres supply the body-wall and generative 
organs. The lateral parts of the compound ganglion are 
united below the esophagus by a triple commissure ; two 
of its constituents arise in the pedal ganglia and correspond 
to the two pedal commissures of Tectibranchs (e.g. Aplysia), 
the third (marked by black paper in the upper specimen) 
unites the pleural centres and may be regarded as an 
orthoneurous visceral loop. QO. C. 1305 Ba, 


D. 58. A Nudibranch (7ritonia hombergii) with the nervous 


system exposed from above. The central system consists 
of four ganglionic masses concentrated in a transverse 
band above the anterior end of the msophagus. The 
inner pair are contiguous with one another in the dorsal 
mid-line ; each represents a fusion of a cerebral with 
a pleuro-visceral centre. From the anterior (cerebral) 


NERVOUS SYSTEM.—INVERTEBRATA. 57 


portion, nerves are given off to the integument and sense- 
organs of the head. The posterior (pleuro-visceral) part 
innervates the lateral and dorsal regions of the body-wall. 
The two outer centres represent the pedal ganglia; they 
are in contact with the lateral surfaces of the pleuro-visceral 
centres ; each sends several large nerves to the foot. As 
in Archedoris the lateral parts of the supra-cesophageal mass 
are united below the gut by a triple commissure enclosed 
in a common neurilemma-sheath. Preserved in Goadby 
solution. 

v. Ihering, Anat. des Nervensystemes... der Mollusken, 

1877, p. 174. 


CEPHALOPODA. 


Note.—In describing the Cephalopod nervous system it has been assumed 
for convenience’ sake that the funnel and mantle-cavity are situated on the 
ventral aspect of the animal, and the beak at the anterior end. 


D. 59. The anterior parts of a male Pearly Nautilus (Nautilus 
pomptlius) from which the viscera and left half of the 
body-walls and funnel have been removed to show the 
nervous system én situ. The central system shows no 
differentiation into separate ganglia, but is coated evenly 
in all parts by a continuous layer of ganglion-cells ; it is 
situated entirely within the head region, supported by the 
upper part of the large cephalic cartilages. Above the 
oesophagus lies a transverse cylindrical bar of nervous tissue 
directly continuous at either end with an antero-posteriorly 
flattened optic ganglion. The extremities of the supra- 
vesophageal bar are connected below the cesophagus by two 
semicircular nervous bands that rise by a common origin 
from either end of the bar and slant respectively for- 
wards and backwards towards the ventral surface of the 
csophagus. The anterior semicircular band is_ thick 
at either end, but rapidly tapers towards its middle, 
until beneath the osophagus it forms a narrow com- 
missural strand. It gives off on either side from the 
lower end of its thickened region a stout nerve for the 
funnel, and from its anterior surface, between this point 
and its junction with the supra-cesophageal bar, a large 
number of nerves for the outer and lateral series of tentacles. 


58 


PHYSIOLOGICAL SERIES. 


One of those on the left side is larger than the rest and 
innervates the spadix—an accessory sexual organ in the 
male formed by the modification of certain of the tentacles 
of the lateral series. The posterior semicircular band is of 
equal calibre throughout. From the hinder margin of its 
lateral parts a series of nerves are given off to the body- 
muscles, as well as a pair on either side to the posterior 
region of the funnel. From its postero-ventral border it 
gives rise to two large nerves that run backwards upon the 
ventral surface of the body to the neighbourhood of the 
gills ; here each gives off two branchial branches and is said 
to then continue onwards to terminate among the viscera 
(this continuation is not shown). Nerves from the supra- 
cesophageal bar supply the olfactory tentacles and pit, the 
otocyst, and parts of the hood. This centre also gives origin 
near either end to two strong connectives, that after a 
sinuous course join a ganglion (pharyngeal ganglion) upon 
the lateral surface of the buccal mass. The pharyngeal 
ganglia of opposite sides are united beneath the gut by two 
commissures, one of which passes anteriorly along the inner 
border of the lower beak, giving off two large nerves to the 
tissues within it, while the other passes transversely between 
the cesophagus and radula-sac and has upon its course a 
pair of buccal ganglia from which nerves are distributed to 
the buccal mass and esophagus. 

Although the central nervous system shows a certain 
degree of specialisation in being concentrated in the head, 
it is on the whole in a very simple and primitive condition, 
and reminds one, especially in the band-like form of its 
several parts and the diffuse distribution of ganglion-cells 
upon its surface, of the condition observed in the Amphi- 
neura, The three nervous bands of which it is composed 
probably represent the typical centres of the Mollusea in a 
state of great simplification, namely :—cerebral (supra- 
esophageal bar) for the innervation of the head region 
with its sense-organs, pedal (anterior semicircular band) 
innervating the tentacle complex and the funnel, and 
pleuro-visceral (posterior semicircular band) for the mantle, 
gills, and viscera. O. C. 1306 Aaa. 

Graham Kerr, Proc. Zool. Soc. 1895, p. 673. 


NERVOUS SYSTEM.—INVERTEBRATA. 59 


D. 60. The anterior or muscular part of the body of a female 
Pearly Nautilus (Nautilus pompilius) laid open longitudin- 
ally along the dorsal aspect, and with the sides divaricated 
to show the nervous system. 

In the female the inner ring of tentacles consists not 
only of two lateral groups, as in the male, but also of a 
ventral series located in two lobes that lie one on either 
side of the ventral mid-line. 

A pair of large nerves (the left one is indicated by black 
paper) for the innervation of these are given off from the 
anterior subcesophageal band on the outer side of the funnel- 
nerves. Hach enlarges as it nears the tentacular lobe to 
form a triangular ganglion, from which branches radiate 
to the individual tentacles. O. C. 1306 a. 

Owen, Memoir on the Pearly Nautilus (Nautilus 

pompilius), 1832, p. 36. 


D. 61. The head of a Cuttle-fish (Sepia officinalis) dissected from 
the dorsal aspect to show the form and position of the 
central nervous system. It is extremely concentrated, 
and forms a compact ring around the fore part of the 
cesophagus protected externally by a cartilaginous capsule. 
The ring is divisible into a pyriform supra-cesophageal 
mass (cerebral ganglion) and a larger oblong subcesophageal 
ganglion, united together on either side of the cesophagus 
by stout connectives. 

The cerebral ganglion is joined on either side by a short 
stalk to a large kidney-shaped optic ganglion, from whose 
distal margin a number of nerve-fibres arise and perforate 
the cartilaginous optic capsule to reach the retina. Upon 
the dorsal surface of each optic stalk there is a small 
rounded excrescence from which the olfactory nerve takes 
its origin (see Olfact. Organs, Section E). Upon the right 
side bristles have been placed beneath the superior ophthalmic 
nerve—a small nerve that rises from the hinder part of the 
subcesophageal mass close to the base of the circum- 
cesophageal connective, and innervates the globe of the eye 
and the integument on its dorsal surface. OQ. C. 1306 D. 


60 PHYSIOLOGICAL SERIES. 


D. 62. The central nervous system of a Cuttle-fish (Sepia officin- 
alis), isolated to show the relations of its parts, the origin 
of the main nerves, and the anterior portion of the visceral 
system. 

The pointed anterior extremity of the cerebral ganglion 
is joined by a pair of connectives to a small independent 
ganglion (supra-pharyngeal), which is probably a dis- 
connected piece of the cerebral ganglion and not a part of 
the visceral system. This ganglion is situated on the dorsal 
surface of the cesophagus close behind the buccal mass, and 
innervates the peristomial membrane by a number of nerves 
that radiate from its anterior margin. It is united to the 
anterior part of the suboesophageal mass by a pair of 
connectives, that rise from its posterior surface, and by a 
second pair from its outer extremities to a buccal ganglion 
that lies below the oesophagus on the posterior wall of the 
buccal mass. Nerves from this latter centre supply the 
buccal mass, radula, and alimentary canal. 

The cerebral ganglion is further united by connectives to 
the subceesophageal mass. ‘There are two on either side—a 
small one that arises from its anterior extremity and joins 
the suprapbaryngeo-subcesophageal connective close to the 
suboesophageal mass, and another, extremely short and 
stout, that forms the lateral part of the cireum-cesophageal 
ring below the optic stalk. This last is superficially single, 
but internally two fibrous strands can be distinguished that 
pass respectively to the anterior and posterior parts of the 
subasophageal mass, and represent cerebro-pedal «and 
cerebro-pleural connectives. The subcsophageal mass 
may be divided into an anterior and a posterior region. 
The anterior innervates the arms and fore part of the 
funnel, and may be regarded as a pedal ganglion. The 
posterior region contains the pallial and visceral centres; it 
projects backwards beyond the cerebral ganglion and gives 
off three large pairs of nerves respectively to the mantle, to 
the posterior part of the funnel, and to the viscera and gills; 
two smaller pairs arise from its dorsal and ventral surfaces 
and innervate the superficial parts of the eyes. 

O. C, 1306 ¥, 

Pelseneer, Arch. Biol., t. viii. 1888, p. 723. 


NERVOUS SYSTEM.—INVERTEBRATA. 61 


D. 63. The isolated nervous system of a Cuttle-fish (Sepia officin- 
alis) showing the origin and course of the main nerves. 

The innervation area of the cerebral ganglion includes 
the eyes (through the mediation of the optic ganglia), the 
olfactory pit, the otocyst (by nerves that perforate the 
subeesophageal mass), and, indirectly through the supra- 
pharyngeal ganglion, the lips. 

The anterior (pedal) region of the subcesophageal mass 
is composed of a brachial and an infundibular centre. The 
brachial nerves arise from the anterior margin of the 
former ; they are 10 in number—8 for the non-retractile 
arms and 2 for the tentacles. Just before the separation 
of the 8 arms from their common muscular base, their 
nerves are united together by a circular commissure, the 
main part of which enters a small ganglionic enlargement 
upon each brachial nerve, while a smaller strand leaves the 
commissure on one side of the ganglion, passes across its 
inner surface, and joins the commissure again on the other 
side. In the free part of each arm the nerve is central in 
position and ganglionic. The nerves for the anterior part 
of the funnel arise from the ventral surface of the in- 
fundibular centre—their extremities can be seen in the 
specimen projecting beyond the optic ganglia. 

A pair of large mantle-nerves are given off from the 
lateral posterior corners of the pleuro-visceral centre. 
Each of them runs diagonally backwards to the retractor 
capitis muscle ; at this point it gives off a branch from 
its inner margin, and then passes through the substance of 
the muscle to the dorsal wall of the mantle-cavity. Here 
it divides into two branches, one of which shortly enters a 
large round ganglion (g. stellatum), from which nerves 
radiate to all parts of the mantle; the other passes along 
the median surface of the stellate ganglion and is distri- 
buted to the lateral-fin fold. The posterior infundibular 
nerves arise slightly in front of the pallial, from the ventral 
surface of the pleuro-visceral centre. The visceral nerves 
are given off close side by side from its posterior border. 
They run backwards to the ventral surface of the gastric 
gland, perforate the subhepatic cartilage and continue close 
beneath the skin, one on either side of the cephalic vein to 


62 


PHYSIOLOGIOAL SERIES. 


* 


the external renal openings. Just posterior to the subhepatic 
cartilage, each nerve gives off a branch from its lateral 
surface to the retractor infundibuli, and a little further hack 
a second branch from its median side to the rectum and 
ink-sac, 

Dorsal to the external renal openings the two main 
trunks are united by a plexiform commissure, and from this 
point continue along the antero-lateral margin of the 
kidneys till they reach the bases of the gills. Here each 
forms a ganglion and passes forwards along the gill to its 
anterior end. Numerous delicate fibres from the plexiform 
commissure ramify amongst the viscera and establish con- 
nections with a large splanchnic ganglion situated upon 
the stomach. The splanchnic ganglion is further connected 
to the buccal ganglia by an extremely fine pair of nerves 
that lie upon the walls of the cesophagus, 

From the active predaceous habits of the Dibranch 
Cephalopods and the great concentration of their central 
nervous system, one may conclude that the latter is a 
highly-specialised and efficient organ, but as to its 
actual working little definite is known. It may be 
said, however, that:—The cerebral ganglion (in certain 
cases at any rate, though apparently not in all) exerts a 
general inhibitory influence over the rest of the system. 
In its anterior part is located a centre for the fixation 
of the arm-suckers, their relaxation depending on another 
centre in its posterior part. Each brachial nerve forms 
a reflex centre for the general movements of the arm in 
which it lies. The pleuro-visceral mass, and not as might 
be supposed the stellate ganglion, is the reflex centre for 
the respiratory movements of the mantle; it is also the 
controlling centre for the chromatophores. 

The action of the heart can take place independently 
of the cephalic central system, although its pulsations are 
regulated by the subcesophageal mass, O. C, 1306 B. 

Chéron, Ann. Sci. Nat., sér. 5, t. v. 1866, p. 41. 


D. 64. A section of the mantle of a large Cuttle-fish (Sepia 


officinalis) showing one of the pallial nerves with the 
ganglion stellatum. The branch of the pallial nerve that 


NERVOUS SYSTEM.—PROTOCHORDATA. 63 


passes without being implicated in the ganglion, through 
the substance of the mantle to the muscle-fibres of the 


lateral fin, is indicated by a black bristle. O. C. 1307. 
Hunterian. 
PROTOCHORDATA. 
TUNICATA. 


D. 65. A Simple Ascidian (Phallusia mammillata) from which 
the dorsal parts of the test have been removed to show 
the nervous system. In the adult this is in a much 
reduced condition ; it is minute compared with the bulk of 
the animal, and consists of a rod-like ganglion that lies on 
the muscular body-wall upon the dorsal surface between the 
oral and atrial apertures, close in front of the latter. From 
either end it gives off a pair of nerves that respectively 
innervate the integument and muscles of the oral and atrial 
siphons. A few small nerves for the general body-wall 
arise from its lateral parts. The hinder end of the ganglion 
is prolonged backwards as a fine ganglionic cord, that runs 
along the dorsal edge of the branchial sac and terminates 
upon the liver. This cord (visceral cord) apparently inner- 
vates the anterior region of the alimentary canal ; it has 
been shown to be the degenerate remains of the portion of 
the larval dorsal cord that lies between the cerebral vesicle 
and the tail. O.C, 1307 a. 

Presented by Prof. C. Stewart. 

Van Beneden & Julin, Arch. de Biol., t. v. 1884, pp. 317 

& 633. 

: CEPHALOCHORDA. 


D. 66. The isolated central nervous system of a Lancelet 
(Amphioxus lanceolatus) showing its general form and 
some few of the spinal nerve roots. The central nervous 
system in Amphiorus consists of an unsegmented tubular 
cord of roughly triangular cross section. At either end it 
narrows to a point, but otherwise is of approximately 
similar calibre throughout. It lies upon the dorsal surface 
of the notochord, extending from its hinder extremity to a 
point some little distance behind its anterior end. The 


64 PHYSIOLOGICAL SERIES. 


anterior pointed region terminates in a median eye-spot 
and gives off two pairs of purely sensory nerves to the 
snout. From the rest of the cord a series of mixed and 
motor nerves arise, that correspond in number and position 
to the septa sbetween the myotomes and consequently 
alternate on either side. The central canal is lined by a sup- 
porting epithelium. This is surrounded, as in Vertebrates, 
by a layer of ganglion-cells, while the outer parts of the 
cord consist of non-medullated nerve-fibres of different 
sizes. Some of these, which arise from giant ganglion-cells 
that lie across the canal in the anterior and posterior thirds 
of the cord, are of remarkably large size and remind one of 
Miiller’s fibres in Cyclostomes or of the giant fibres in 
_ Invertebrates. In front the canal broadens out to form a 
cerebral vesicle, that probably corresponds with the three 
primary vesicles of the vertebrate brain. A small evagina- 
tion of its dorso-anterior wall extends towards the olfactory 
pit and indicates the last closed connection of the central 
canal with the exterior (a similar excrescence occurs in the 
embryos of Vertebrates) ; while below, another median 
evagination apparently represents the infundibulum, As 
the walls of this “ brain”’ region are thinner than in other 
parts of the cord, there is no external sign of a cerebral 
enlargement. O. C. a, 1847. 
Willey, ‘ Amphioxus,’ 1894, p. 82. 


VERTEBRATA. 


BRAIN. 
Edinger, Anat. Central Nervous System, 5th ed. (Engl. 
trans.) 1899. 
Edinger, Abhandl. Senckenberg. Gesell., Bd. xv. 1890 
(Cerebrum). 


Haller, Morph. Jahrb., Bd. xxvi. 1898, p. 632 (Bibliog.). 
PISCES. 
OCYOLOSTOMI. 


D. 67. The brain of a Sea Lamprey (Petromyzon marinus). 
The Cyclostomes have an extremely simple brain, 


NERVOUS SYSTEM.—VERTEBRATA. 65 


similar in many respects to that of a low Urodele or to 
the embryonic stages of higher Vertebrates. It consists 
of a slight enlargement of the anterior end of the cord 
accompanied by a corresponding increase in the size of the 
central canal and its partial transverse division into three 


ventricles. Upon this foundation certain excrescences have 


been developed in connection with the senses of sight and 
smell. The dorsal wall is to a very large extent purely 
epithelial, nervous matter being mainly confined to the 
floor and side walls. The primitive condition of the brain 
is also shown by the relatively large size of the ventricles, 


Brain of Petromyzon marinus (enlarged). 


[For list of abbreviations, see page 508. ] 


and by the absence of any special thickenings of their 
nervous walls. 

The medulla forms nearly half the brain (fig. 19, A). It 
passes behind insensibly into the cord, and in front is 
laterally expanded with separation of its walls in the 
mid-dorsal line to enclose a large pyriform opening (fossa 
rhomboidalis) covered by a thin vascular membrane. This 
roof consists of an epithelium continuous with that lining 
the fourth ventricle, of pia mater and blood-vessels ; it is 
considerably larger than the fossa and in consequence 
projects in all directions into the cranial cavity, and in 

VOL. II. F 


PHYSIOLOGICAL SERIES. 


conjunction with the similar vascular roof of the optic 
lobes spreads out over a large part of the dorsal surface of 
the brain. These two choroid plexuses have been removed 
together and mounted at the side with their under surfaces 
exposed to show the complicated folding of their walls 
(fig. 19, B). 

The roof of the medulla behind the open rhomboid fossa is 
slightly thickened on either side of the mid-line, and here 
gives origin to the hinder roots of the vagus (the roots 
are not shown in the specimen). Similar thickenings in the 
lateral walls of the fossa give origin to the 7th and 8th 
cranial nerves, and another pair of swellings in the floor of 
the fourth ventricle, seen through the open rhomboid fossa, 
are the motor nuclei of the 5th pair of nerves. The floor of 
the fourth ventricle is indented in the mid-line by a sharp 
furrow, on either side of which is a slight thickening due 
to a pair of tracts (fasciculi longitudinales posteriores) that 
connect the thalamencephalon with the cord and on their 
way form connections with the motor nuclei of the cranial 
nerves. They are particularly well marked in Fishes, 

The rhomboid fossa is bounded in front by a narrow but 
slightly thickened lip—the cerebellum. The mid-brain con- 
sists above of a pair of very prominent rounded eminences 
—the optic lobes. They contain a common ventricle 
derived from the aqueduct of Sylvius and are superficially 
separated from one another in the dorsal mid-line by a 
groove. Their walls are composed for the most part of 
nervous tissue from the outer surface of which the optic 
nerves are given off, but this is replaced at the anterior end 
by an epithelial choroid plexus (the fore part of the speci- 
men at the side) similar to that covering the rhomboid fossa. 
The removal of this plexus has exposed a minute opening 
situated at the anterior end of the optic lobes and bounded 
in front by a band of commissural fibres (posterior com- 
missure)—not externally visible—that marks the boundary 
line between the mid-brain and thalamencephalon or 
primary fore-brain. 

The thalamencephalon is remarkably deep from above 
downwards. Its roof is epithelial in its anterior part and 


NERVOUS SYSTEM.—VERTEBRATA. 67 


projects beak-like above the cerebrum, but posteriorly it is 
nervous and swollen to form an asymmetrical pair of ganglia 
(ganglia habenulz), the smaller (left) of which is in con- 
nection with the pineal body. In the specimen these 
ganglia can only be distinguished as a single median 
thickening in front of the optic lobes. The ganglia habenule 
are one of the most constant parts of the vertebrate brain. 
They are always present on either side close in front of the 
epiphysial evagination, are united by a commissure, and 
are always in connection by tracts with the olfactory area 
of the cerebrum and with the corpus interpedunculare. 
The latter can be seen in the specimen as a small median 
protuberance close behind the origin of the oculo-motor 
nerves. The floor of the thalamencephalon is expanded 
ventrally to form a capacious infundibulum. Lobi inferiores 
and saccus vasculosus are absent, but there is said to bea 
well marked saccus infundibuli in the posterior wall of the 
infundibulum. A similar structure occurs in Elasmo- 
branchs and embryo Teleosts. The side walls consist 
mainly of tracts that connect the cerebrum with the more 
posterior regions of the brain. They are covered super- 
ficially by the optic tracts on their way downwards and 
forwards from the optic lobes to the chiasma in front of the 
infundibulum. The thalamencephalon is continuous at its 
anterior end, on either side of the mid-line, with a pair of 
hollow lobes—the secondary fore-brain—each consisting of 
two parts: a posterior lobe (the hemisphere), and a larger 
anterior lobe (the olfactory bulb) from which a nerve is 
given off to the nose. A slight lobulation observable upon 
the surface of the olfactory bulbs is due to a glomerular 
condensation of the neuropile close beneath the surface. 
The hemispheres are mesially united by a commissure 
(anterior commissure) that lies in the dorsal parts of the 
anterior wall of the thalamencephalon (lamina terminalis). 
They have ganglion-cells scattered irregularly throughout 
their walls and show no signs of cortical structure. 
Ahlborn, Zeits. wiss. Zool., Bd. xxxix. 1883, p. 191. 


F 2 


SE ae 


68 PHYSIOLOGICAL SERIES. 


ELASMOBRANOHII. 


Miklucho-Maclay, Beitriige z. verg]. Neurol. 1870. 
Edinger, Arch. mikr. Anat., Bd. lviii. 1901, p. 661 (Cere- 
bellum). 


The brain of the Elasmobranchs only partially fills the cranial 
cavity. It has generally an elongated narrow form, with the 
several regions lineally arranged and, except in the case of the 
cerebellum, with but little overlapping of parts. 

It is chiefly remarkable for the great development of the centres 
in connection with the sense of smell—olfactory bulbs and 
peduncles, and cerebrum. The lamina terminalis is more or less 
thickened—excessively so in Rays—and frequently is indented 
in the mid-line to form small lateral ventricles. The optic lobes 
are well marked, as are also the several parts of the hypo- 
thalamus (infundibulum, lobi inferiores, saccus vasculosus and 
saceus infundibuli). The cerebellum, asin Bony Fish and Birds, 
is strongly developed ; it overlaps the optic lobes and medulla to 
varying degrees and frequently shows complex transverse folding. 
Posteriorly it is continued into the convoluted margins of the 
rhomboid fossa (medullary auricles). In Sharks the medulla is 
usually long and without definite separation from the cord, but 
is much shortened in Rays. It owes its large size mainly to the 
great development of the nuclei of the cranial nerves, especially 
those in connection with the respiratory nerves (x.) and the 
sensory nerves of the skin (v. and the lateral-line nerves). 
It also contains great longitudinal motor tracts (fasciculi longi- 
tudinales posteriores) in its floor, besides less developed tracts in 
connection with the optic lobes (fillet) and cerebellum, The 
walls of the brain are nervous except for the vascular epithelial 
roof of the rhomboid fossa and third ventricle. There is no sign 
of cortical formation in the cerebrum, but its walls consist of a 
relatively thin outer molecular stratum anda thick cellular layer 
surrounding the ventricles. In its base definite cell-masses give 
rise to the anterior commissure and to longitudinal tracts that 
pass to a large ganglion (nucleus rotundus) in the thalamus, which 


‘in turn gives off fibres to the hinder parts of the brain. A 


second pair of tracts pass from the cerebral roof (pallium) into 
the base of the thalamencephalon, and decussate behind the optic 
chiasma in close contiguity with tracts from the base of the 


NERVOUS SYSTEM.—VERTEBRATA. 69 


mid-brain (decussatio post-optica). The thalamencephalon also 
contains in its dorsal parts a pair of ganglia habenule connected 
by tracts with the olfactory parts of the cerebrum, and with the 
tectum opticum, corpus interpedunculare (Meynert’s \bundle), 
and hypothalamus. In the lower parts of the thalamus lie 
another pair of ganglia (g. geniculata) situated under cover of 
the optic tracts. They are very constant throughout vertebrates 
and contribute fibres to the opticus. The hypothalamus, whose 
walls consist of a fibrous reticulum interspersed with numerous 
ganglion-cells, is the chief point of origin of the great fasciculi 
longitudinales posteriores ; it is also connected with the cere- 
bellum and tectum opticum. 

In the roof of the mid-brain (tectum opticum) there are two 
chief layers—an outer layer consisting of the roots of the opticus 
and containing numerous ganglion-cells in its deeper parts ; and 
a deep fibrous layer in which the fibres for the most part run 
transversely and constitute a tectal commissure, thickened in its 
anterior parts to form the posterior commissure. On either side 
the fibres pass backwards into the medulla (some crossing in the 
floor as the commissura ansulata), and constitute the anterior 
termination of a large sensory tract (fillet) that extends into the 
cord and is connected in the medulla with the sensory cranial- 
nerve nuclei. Part of this tract arises from a nucleus in the 
posterior part of the tectum—the homologue of the posterior 
corpora quadrigemina of Mammalia. A nucleus of large cells 
(roof nucleus) lies in the mid-line at the hinder extremity of 
the tectum beneath the transverse commissure ; its meaning is 
doubtful, though probably it is a nucleus of the trigeminal 
nerve. 

The cerebellum consists, as in all vertebrates, of four layers— 
molecular, intermediate (Purkinje’s cells), fibrous, and nuclear ; 
the fibrous being situated external to the nuclear, and not as in 
Teleosts, Birds, and Mammals, on its deep surface. The layers 
vary in thickness in different regions, the nuclear for instance 
being almost entirely concentrated in a pairsof ridges, one on 
either side of the mid-line (longitudinal zones). Tracts connect 
the cerebellum with the thalamencephalon, mesencephalon, and 
spinal cord, but the greater part of the fibrous layer is in direct 
connection with the sensory cranial nerves. 


70 PHYSIOLOGICAL SERIES. 


SQUALIDA. 


D. 68. The brain of Notidanus griseus exposed within the skull 
from the dorsal and ventral aspects. 

The Elasmobranch brain is found in its simplest and most 
primitive condition in the Notidanide, and presents in 
them many features that in other members of the class are 
transient, occurring only during certain developmental 
stages. The following characters should be particularly 
noticed as indications of primitive construction :—The rela- 
tively great length and narrowness of the brain; the absence 
of any marked local thickening of its walls; their general 
thinness and the consequent spaciousness of the ventricles 
(for these and other internal features see Maclay, t. ii. 
tig. 12) ; the simple unconvoluted cerebellum ; the great 
development of the medulla, its length, wide dorsal open- 
ing, and gradual passage into the cord. 

The fore-brain (cerebrum) is deeply cleft anteriorly 
(more so than in any other Elasmobranch) by an infolding 
of the lamina terminalis; its cavity is thus separable into 
a posterior unpaired chamber—the fore part of the third 
ventricle—passing in front into a pair of anteriorly directed 
pockets, or lateral ventricles. The latter are continuous at 
their anterior end with the cavities of the long olfactory 
peduncles, by means of which the olfactory bulbs, which are 
situated directly beneath the olfactory organ, are connected 
to the rest of the brain. The olfactory bulb has always 
in Elasmobranchs (except it seems in Eehinorhinus) this 
close relation to the olfactory organ, so that the length 
of the peduncle varies in different forms according to 
the position of the organ with regard to the brain. The 
peduncle is usually, as in this case, hollow, but sometimes 
when very long it is solid; it has the same structure as the 
olfactory bulb, and together with it is an outgrowth from 
the fore-brain. 

The thalamencephalon is comparatively short and wide. 
The fore part of its roof is membranous and forms a conical 
sac-like protrusion (paraphysis) between the hemispheres. 
The hinder part is concealed by the optic lobes; it contains 
the ganglia habenulw and gives origin to the thread-like 


NERVOUS SYSTEM.—VERTEBRATA. 71 


epiphysis. The floor is evaginated in the mid-line to form 
the infundibulum. This is hidden in the specimen by the 
hypophysis—an ectodermic glandular structure closely 
attached to its ventral surface. The lateral parts of a large 
vascular dilatation of the posterior wall of the infundibulum 
(saccus vasculosus) can be seen protruding beyond the 

lateral parts of the hypophysis. On either side of the 
_ infundibulum, in front of the saccus vasculosus, are a pair 
of globular enlargements—the lobi inferiores. Each of 
them contains a cavity (not shown) in connection with that 
of the infundibulum. 

The optic lobes are of considerable size, although neither 
here nor in any other member of the group do they reach 
the size and importance that they do in most Teleostean 
fishes. They are oval in form, separated dorsally by a 
superficial longitudinal groove, and contain a large com- 
mon cavity. Their posterior part is covered by the anterior 
lobe of the cerebellum. No part of the Hlasmobranch 
brain is subject to more variation than the cerebellum ; 
in this species it occurs in its simplest form, although well 
developed when compared with that of certain other 
Vertebrate groups (e. g. Cyclostomes, Amphibia). It is 
superficially perfectly smooth except for a slight median 
longitudinal furrow, and when seen from above is diamond- 
shaped with pointed anterior and posterior lobes, within 
each of which extends a part of the common cavity. A 
single median opening leads from the latter into the fourth 
ventricle. On either side of the posterior cerebellar lobe 
lies a convoluted portion of the thickened margin of the 
rhomboid fossa; this ridge (medullary auricle) is clearly 
seen on the left side; it passes to the mid-line under cover 
of the posterior lobe of the cerebellum; here meets with its 
fellow of the opposite side, without fusion, and then, 
turning abruptly upwards into the cavity of the cerebellum, 
forms a projecting longitudinal ridge (dorsal longitudinal 
zone of Burckhardt) that runs close beside the mid-line to 
its anterior extremity. From their microscopic structure 
the medullary auricles should be included in the cerebellum. 
The course of this pair of zones is not visible in the 
specimen after they pass under cover of the cerebellum. 


72 


PHYSIOLOGICAL SERIES. 


The medulla is large and remarkably long, with an exten- 
sive rhomboid fossa roofed over by a thin pleated vascular 
membrane (turned to one side in the specimen). Within 
the cavity certain ridges and swellings—due to tracts 
and nerve nuclei—show with great clearness. A. parti- 
cularly prominent pair on either side of the mid-ventral 
line are the fasciculi longitudinales posteriores. On the 
outer side of these lie a pair of lesser swellings—the motor 
nuclei of the vagus ; and outside these again, on the lateral 
walls of the ventricle, another very pronounced pair, re- 
markable for their beaded appearance. They are the 
sensory nuclei of the vagus. In front they pass under 
cover of the auricles. In the swollen border of the rhom- 
boid fossa, just before it bends to form the auricles, lie the 
nuclei of the acusticus and lateral line (tuberculum 
acusticum and lobus lines lateralis). O. C. 1311 Bd. 

Presented by Dr, Albert Ginther. 


D. 69. The brain of a Greenland Shark (Lemargus borealis). This 


brain differs little in its essential features from that of 
Notidanus. In detail the following differences are ap- 
parent :—The lamina terminalis is not so deeply indented, 
so that although the fore-brain is clearly separable into 
unpaired posterior and paired anterior regions, the latter 
are not so prominent. The optic lobes with their associated 
tracts and nerves are far less developed. The cerebellum 
is relatively larger and extends forward to the anterior 
border of the optic lobes. It shows upon its dorsal surface 
a shallow transverse indentation—the first indication of the 
transverse folding so strongly marked in some of the higher 
Elasmobranchs., 

The dorsal walls of the cerebrum and thalamencephalon 
have been turned to one side, exposing the cavities of these 
parts and showing in the floor of the third ventricle a long 
slit leading into the infundibulum, saccus vasculosus, and 
lobi inferiores. The latter are prominent and about equal 
in size to the optic lobes. The thalamencephalon roof is 
epithelial and vascular; it is much convoluted on its inner 
surface, and forms a choroid plexus that hangs within the 


NERVOUS SYSTEM.—VERTEBRATA. 73 


third ventricle and extends slightly into the lateral ven- 
tricles. 

The cerebellum has been divided in the mid-line, and the 
two halves have been separated to show the large cerebellar 
cavity and the course of the longitudinal zones along the 
roof on either side of the mid-line. The latter are specially 
well seen coursing backwards upon the ventral wall of the 
anterior lobe. 

The floor of the fourth ventricle has been exposed by 
turning the vascular roof to one side. Owing to the divi- 
sion of the cerebellum and to the somewhat unnatural 
separation of the side walls of the medulla, the fore parts 
of the fasciculi longitudinales and of the vagal lobes are 
brought into view. ‘The fine transverse strands visible at 
intervals on either side of the fasciculi posteriores are 
tracts connecting them with the motor nuclei of the cranial 
nerves. The motor nucleus of the vagus and the relation 
of the root of the superficial ophthalmic lateral-line nerve 
to the lobus lineze lateralis are particularly clear. 

O.C. 1311 Be. 
Presented by W. Cowan, Esq. 


D. 70. Parts of the cranium of a Spinous Shark (Hehinorhinus 
spinosus) with the brain shown from the dorsal aspect. 
This brain, like those of the two other representatives of 
the Spinacidee (Acantlias and Lemargus), is of an essen- 
tially simple type. This is particularly shown by the 
relatively large size of the medulla (it occupies about half 
the brain-length), its extensive rhomboid fossa and gradual 
passage into the cord. The cerebellum is rounded and, for 
that of an Elasmobranch, very poorly developed ; it shows 
a feeble transverse groove. The parts of the brain in front 
of the cerebellum are somewhat indefinite in outline owing 
to imperfect preservation, but it can be seen that the optic 
lobes and nerves are small, the thalamencephalon fairly 
long, and the cerebrum of medium size, without median 
division and apparently with a considerable cavity. 

From either side of the cerebrum is given off an 
immense solid olfactory nerve, without however any cor- 


| 
| 
. 
| 


74 


PHYSIOLOGICAL SERIES. 


. 


responding development either of the fore-brain or of an 
olfactory bulb; in fact it is stated that an olfactory bulb is 
absent. This marked disproportion in development between 
the olfactory nerves and the cerebrum, with the apparent 
absence of definite olfactory bulbs, suggests that the nerves, 
although evidently to a great extent fibrous, probably also 
have the nature of olfactory centres; it should be noticed 
in this connection that shortly before entering the cerebrum, 
‘each olfactory nerve undergoes a very perceptible enlarge- 
ment. The poor development of the optic parts of the 
brain are probably to be accounted for by the deep habitat 
of this Shark. The brain occupies only a small part of 
the spacious cranial cavity. . 
This preparation is from a fish caught off the coast of 
Cornwall. | O.C.1311B a. 
Presented by F. Buckland, Esq. 
Jackson & Clarke, Journ, Anat. & Physiol., vol. x. 1876, 
p. 76. 


D. 71. Part of the skull of a Spiny Dog-fish ( Acanthias vulgaris) 


with the brain exposed from the dorsal and ventral aspects. 
This is a simple brain like the preceding specimen, but 
shows certain differences that foreshadow more pronounced 
features in the relatively complex brains of higher Sharks; 
such are a pair of indistinct rounded eminences upon the 
dorsal surface of the fore-brain at its hinder end, and the 
deepening of the transverse cerebellar furrow. The median 
indentation of the fore part of the cerebrum is strongly 
marked and terminates on the dorsal surface in a rounded 
pit—a nutritive foramen of very constant occurrence among 
Elasmobranchs. The olfactory peduncles are slender and of 
moderate length with small olfactory bulbs; on the other 
hand, the visual organs and optic lobes are very strongly 
developed. The lobi inferiores are also well marked and 
oval in form. The medulla does not differ in any important 
way from that of previously described primitive forms. Its 
cavity is exposed on the right side. 


D. 72. Part of the cranium of a Spotted Dog-fish (Seylliwm 


catulus) with the brain in situ. This brain, in comparison 


NERVOUS SYSTEM.—VERTEBRATA. 75 


with those previously described, shows a noticeable increase 
in the size of the parts in connection with the olfactory 
organs (olfactory bulbs, peduncles, and cerebrum). On the 
other hand, the optic region is weak. The olfactory bulbs 
are each partially divided into a right and left half by a 
shallow groove—an indication of incipient duplicity, of 
interest in view of the complete separation of the olfactory 
bulbs into two parts in Carcharias. They are united by 
short thick peduncles to the lateral parts of the cerebrum. 
The latter is strongly convex in front and shows but slight 
indications externally of separation into lateral lobes ; its 
postero-dorsal parts are raised to form a pair of rounded 
eminences similar to those seen in Acanthias. The cerebrum 
is continuous behind with the remarkably long and narrow 
thalamencephalon. The tela choroidea forms a close-fitting 
membranous roof to this region, and shows very clearly 
between its posterior fourths an opaque band—the com- 
missura habenulw. The epiphysis, which rises close behind 
this commissure, is long and thread-like as in most Elasmo- 
branchs; it extends forwards over the cerebrum and 
terminates on a level with the olfactory bulbs in a thickened 
end. In this and most other genera it is said to be solid 
except close to the brain, and to consist of cells embedded 
in a finely granular intercellular substance. 

The cerebellum is quite simple, though of some size ; it 
has a median longitudinal furrow and slight lateral inden- 
tations. (The asymmetry noticeable in this cerebellum is 
probably unnatural, due to distortion during hardening.) 
The medulla is of a higher type than in the previous speci- 
mens ; it is shorter and broader and has a more definite 
limit towards the cord. The brain fills the greater part of 
the cranial cavity. 


D. 73. The brain of a Spotted Dog-fish (Scyllium catulus) opened 
to show its internal structure (fig.20). The roof of the cere- 
brum has been removed to show the direct continuity of the 
unpaired part of the cerebral cavity with the third ventricle 
behind, and with the lateral ventricles in front. The latter 
are separated by a thick median septum, and are continued 
from their postero-lateral parts through the olfactory 


76 


ae 


PHYSIOLOGICAL SERIES. 


. 


peduncles to the ventricles of the olfactory bulbs. The walls 
of the cerebrum are thick throughout, with no local swellings 
suggestive of corpora striata. On either side a choroid 
plexus projects downwards and forwards from the roof of the 
thalamencephalon into each lateral ventricle. Behind the 
cerebrum the brain has been longitudinally bisected and 
the two halves have been turned to either side. The saccus 
vasculosus has been opened from behind showing its cavity 


Fig. 20. 
LAT. se OLF BULB. 


Aa 


OLF. TR. ae “ot 
«" £ FOR. LOB. INF. 


Va : “ 
fi”. GANG. HAB. 


. 
. PF os 
fq 


Brain of Scyllium catulus (dissected), 


continuous with that of the infundibulum, as well as a 
pair of large oval apertures in the lateral walls of the 
infundibulum that communicate with the ventricles of the 
lobi inferiores. 

In the floor of the thalamencephalon in front of the 
chiasma there is a small median pit (recessus preopticus), 
and at the point of union between the wall of the saccus 
vasculosus and the floor of the mid-brain, another (saccus 
infundibuli) which is found also in Cyclostomes and embryo 
Teleosts. 


NERVOUS SYSTEM.—VERTEBRATA. 77 


Close behind the point of origin of the epiphysis, the cut 
edge of the roof of the brain is thickened by the presence 
of the posterior commissure. The mid-brain contains a 
considerable cavity (aqueduct of Sylvius) which sends 
lateral offshoots into the optic lobes. The roof (tectum 
opticum) of this region is moderately thick ; its division 
into outer and inner layers is very evident upon the section 
surface. 

In dividing the cerebellum the roof has been cut along 
its right lateral margin and turned aside entire with the 
left half of the brain. The thin simple character of its 
walls, and the complete course of the longitudinal zones from 
the medullary auricles to the boundary line between the 
cerebellum and mesencephalon are shown. 


D. 74. Part of the skull of a Basking Shark (Selache maxima) 
with the brain exposed from above. The brain is relatively 
small and somewhat shorter and broader than those pre- 
viously described ; it occupies a small part only of the 
spacious cranial cavity. The cerebrum is globular with 
thickened (?) walls, and is superficially without signs of 
lateral division. The olfactory bulbs and peduncles have been 
destroyed, but the root of the (apparently solid) right peduncle 
can be seen rising from a slight eminence at the antero-lateral 
corner of the cerebrum. The thalamencephalon is very 
short, and is completely hidden in dorsal view between the 
cerebrum and optic lobes. The latter are of considerable 
size and are covered by the anterior lobe of the cerebellum. 
The cerebellum is large, with a series of twelve or so deep 
transverse fissures. 

The fish from which this dissection was made was caught 
in the North Sea; it measured 12 feet in length. 
O. C. 1311 46. Presented by Dr. Albert Giinther. 


D. 75. A similar dissection of the hinder part of the skull of a 
somewhat larger Basking Shark (Selache maxima). The 
parts of the brain anterior to the optic lobes are absent. 
In this specimen the large size and convoluted structure of 
the cerebellum are very clearly shown ; it should be noticed 
that the median transverse furrow is more pronounced than 


78 


PHYSIOLOGICAL SERIES. 


the rest; it is the representative of the single furrow in such 
forms as Acanthias, The medulla is a good example of 
the elongated open type; in it, the several prominences 
are very clear, more particularly the arrangement of the 
convoluted auricles and the lobus lines lateralis. 

O0.0.1311 4. Presented by Sir E. Home, Bart. 


D. 76. The brain of a Porbeagle (Zamna cornubica) divided in 


the median sagittal plane, and with the halves so mounted 
as to show the lateral and median surfaces. alate 

This brain (fig. 21) reaches a comparatively high state of 
development; itis distinguished by its antero-posterior con- 
centration, the large size of the fore-brain and optic lobes, 
and the excessive development and structural complication of 
the cerebellum, The fore-brain is globular and, owing to the 


— 
- SOW . 
Ws 


Brain of Lamna cornubica, in sagittal section, 


immense thickening of the lamina terminalis, almost solid, 
its ventricle (best seen at the back of the left-hand specimen) 
being all but obliterated. The olfactory peduncles are narrow 
at their origin from the antero-lateral parts of the cerebrum 
and gradually become inflated as they approach the small 
olfactory bulbs. In this part their walls are extremely thin 
(see the cut edges of a square window in the figure). It 
seems likely that the small size of the olfactory bulbs is 
compensated by the great development of the cerebrum. 
The thalamencephalon is very short—compressed between 
the cerebrum and the large optic lobes. The latter are com- 
pletely covered dorsally by the cerebellum, The structure 
of the cerebellum is well shown in the right-hand specimen: 


NERVOUS SYSTEM.—VERTEBRATA. 79 


although to all appearance nearly solid it will be seen to 
‘be formed of a single sheet of nervous tissue thrown into a 
complex series of transverse folds, between each of which 
penetrates a part of the general cavity of the organ. This 
complex folding is manifestly only a further extension of 
the simple transverse grooves seen in Acanthias or Caleus. 
The position of the original median transverse furrow is 
marked by the deepest and most complex fold. 
The lobi inferiores are small and open widely into the 
infundibulum. 
The medulla is considerably shortened antero-posteriorly. 
O. C. 1811 Bb. 


D. 77. The cranium of a Tope (Galeus communis) showing the 
_ prain in stéu. The brain affords in its general construction 
and proportions an excellent example of that of an Elasmo- 
branch, in which all the typical features are strongly marked 
without any excessive specialisation of any one part. Thus 
itis long and narrow, though not so much soas in low types 
like Wotidanus ; the optic and more especially the olfactory 
centres are highly developed ; the cerebellum is large and 
transversely furrowed, though not so complex as, for instance, 
in Zamna; the medulla is of some length, though far shorter 
than in primitive forms. Beyond these more general 
features, in which this brain occupies a central position 
among those of Hlasmobranchs, it should be noticed that 
the olfactory bulbs, although not double as in Carcharias, 
are very distinctly bilobed. They are united to the cere- 
brum by short, thick, hollow peduncles. 

The cerebrum is of the massive type with strongly 
thickened lamina terminalis, and has upon its dorsal surface 
two pairs of rounded eminences in place of the single pair 
noted in Acanthias ; it shows no other external sign of 
lateral separation. The cerebellum has four main transverse 
fissures besides a few somewhat more partial and indistinct. 
The lobi inferiores, hypophysis, and saccus vasculosus are 
prominent, and very typical in form and arrangement. 


D. 78. The brain of a Tope (Galeus communis) isolated. The 
vascular roof has been removed from the rhomboid fossa. 
O,C. 1311. Hunterian. 


80 


PHYSIOLOGICAL SERIES. 


D. 79. The brain of a Shark, probably a species of Carcharias. 


The fore-part of this brain agrees in all important 
particulars with the published descriptions of that of the 
Blue Shark (Carcharias glaucus). The olfactory bulbs are 
completely double, each part being attached to the olfactory 
peduncle bya short separate stalk. The peduncles are long 
and apparently solid, and terminate on either side in an oval 
swelling upon the lateral parts of the cerebrum, far back 
towards the ventral surface. The large and massive cere- 
brum shows no external sign of division upon its dorsal 
aspect, but beneath there is a slight median furrow. Pos- 
teriorly it overhangs the thalamencephalon and mevts the 
anterior surface of the optic lobes. In other respects this 
brain closely resembles that of Galeus. O. C. 1311 B. 


D. 80. A specimen of the brain of a Shark, with the medulla 


removed. It is probable from the general form of the 
cerebrum, and more particularly from the characteristic 
method of origin of the olfactory peduncle (seen on the right), 
that this is the brain of a Carcharias. It is strongly bent 
artificially towards the ventral aspect, and a piece has 
been removed from the left side of the cerebrum by trans- 
verse and sagittal incisions, to show the immense thickness 
of the dorsal cerebral wall and the relatively small size of the 
ventricle. Upon the transverse sectional surface, a portion 
of the choroid plexus can be seen protruding from the 
ventricular cavity. The method of apposition of the medul- 
lary auricles in the mid-line can be clearly seen beneath the 
posterior lobe of the cerebellum. O. C. 1311 aa, 


D. 81. The cranium of a Monk-fish (Rhina squatina), with the 


brain in situ exposed from the dorsal and ventral aspects. 
The brain in this fish is remarkable for the slight develop- 
ment of the olfactory centres, for not only are the bulbs 
and peduncles peculiarly small for an Elasmobranch, but the 
cerebrum is also feeble. The latter is thin-walled (so that 
its apparent size is deceptive), with a pair of rounded 
swellings on its dorsal aspect, and is deeply cleft anteriorly 
as in some of the lower Sharks. The low type of the brain 
is further shown by its long narrow form; and by the 


NERVOUS SYSTEM.—VERTEBRATA. 81 


relatively great development of the medulla, its gradual 
passage into the cord, and widely open rhomboid fossa. In 
contrast to the large medulla, the cerebellum is small, its 
greater part consisting (asin the Rays) of the posterior lobe. 
Its sides are somewhat swollen to form a pair of lateral lobes 
(peduncles) close in front of the medullary auricles. The 
optic lobes are oval and of moderate size ; the lobi inferiores 
scarcely distinguishable ; the hypophysis small; and the 
saccus vasculosus and infundibulum very large. It should 
be particularly noticed that the brain combines features 
characteristic respectively of the Sharks and Rays—the 
cerebrum and medulla conforming to the former type, the 
cerebellum to the latter. The brain occupies only a small 
part of the spacious cranial cavity. 


RAJIDA. 


D. 82. The cranium of a Skate (Raja batis) with the brain 
exposed. The brain occupies only a small part of the 
cranial cavity, and is chiefly remarkable for the strong 
development of the olfactory centres and for the antero- 
posterior shortening of the medulla and the prominence 
of the auricles and lobi linez lateralis. 

The olfactory bulbs are solid and differ considerably in 
shape from those of Sharks ; each is laterally lengthened 
and bears a somewhat similar relation to its peduncle that 
the foot of a stocking does to the leg, the heel being repre- 
sented by the swelling at the end of the peduncle, and the 
foot by the part of the bulb that extends outwards along the 
posterior surface of the olfactory capsule. The peduncles 
are solid and very long; each terminates in a strongly pro- 
nounced swelling on the lateral surface of the cerebrum. 
Owing to the presence of these the cerebrum is remarkably 
broad ; it is convex anteriorly, but has no median groove; 
upon its dorsal surface are a pair of indistinct eminences. 
The thalamencephalon and mid-brain are well developed 
but in no way remarkable. The former is somewhai 
longer and narrower than in many Rays. The optic lobes, 
although dwarfed by the great size of the fore-brain, are 
in reality well-developed; the lobi inferiores, infundibulum, 

VOL. II, G 


82 


PHYSIOLOGICAL SERIES. 


saccus vasculosus, and hypophysis are also strongly 
marked, The latter is connected (as in other Elasmo- 
branchs) by a blood-vessel to a transverse bar of vascular 
connective tissue closely adherent to the perichondrium. 
The cerebellum differs from that of a Shark in the slight 
development of its anterior lobe. Its surface is smooth 
except for a single transverse furrow and slight lateral 
indentations. At the sides of the posterior lobe lie the 
strongly developed auricles and lobi line lateralis ; the 
latter apparently owe their size to the peculiarly large nerve- 
supply necessary for the lateral-line organs and ampulla. 

The medulla shows a very high degree of antero-posterior 
concentration, the rhomboid fossa extending only a short 
way beyond the cerebellum. 


D.83. The brain of a Skate (Raja batis) dissected to show its 


internal structure. The dorsal parts of the cerebrum have 
been removed to show the solidity of its walls and the 
extremely small size of the ventricle. The latter, although 
of some little extent in the horizontal plane, is reduced to 


Fig. 22. 


OLF.TR. 4 
VENT. CER. gr 


. Ase 
Se 
SiTees 


Cerebrum of Raja batis (horizontal section), 


a mere slit dorso-ventrally. Its outline can be traced with 
difficulty in the specimen; it is clearest towards the 
extremities of the lateral ventricles. 

Behind the cerebrum, the brain has been divided by a 
mid-sagittal incision and its two halves have been separated. 
Its internal structure differs in several particulars from 


NERVOUS SYSTEM.—VERTEBRATA. 83 


that of Seyllium (D. 73), the most noteworthy being the 
relatively small size of the cavities of the optic lobes, the 
more massive structure of the cerebellum, and the absence 
of a cavity in its anterior lobe. 

Upon the right side, the posterior lobe of the cerebellum 
has been removed to show the complicated folding of the 
medullary auricle and its passage into the longitudinal zone 
of the cerebellum. The olfactory bulbs and the greater 
part of the peduncles have been removed. Transverse 
sections of them are mounted above to show that they 
do not contain a cavity. 


D. 84. The cranium of a Torpedo (Torpedo galvanii) opened 
from above to expose the brain. A pair of immense 
electric lobes form the most striking and important feature 
of the brain; they are developed in the floor of the medulla, 
and apparently represent the motor vagal lobes of other 
Elasmobranchs in a state of excessive hypertrophy. Pro- 
jecting upwards, they entirely fill and obliterate the rhomboid 
fossa and are bounded anteriorly by the auricles and 
cerebellum. Hach gives rise to two large bundles of 
nerves for the electric organ. The electric lobes contain a 
number of gigantic ganglion-cells, the axis-cylinders of 
which pass directly into the electric nerves. The brain, 
with the exception of the electric lobes, is poorly developed. 
The cerebellum is very small, diamond-shaped, and, but 
for a cruciform furrow, smooth. The optic lobes are of 
moderate size, although the nerves are remarkably slender. 
The cerebrum is globular, with slight prominences on its 
dorsal surface ; it receives at its antero-lateral corners a pair 
of fine solid olfactory peduncles. O.©.1310. Hunterian. 

Rohon, Arb. Zool. Inst. Wien, t. i. 1878, p. 151. 


HOLOCEPHALI. 


D. 85. Two specimens of the brain of a Sea-Cat (Chimera 
monstrosa). In the lower specimen the brain is seen én situ 
from above, the hypothalamus and neighbouring parts being 
also exposed through a window cut in the cranial floor. 


In the upper specimen the internal structure is shown by 
| @ 2 


84 PHYSIOLOGICAL SERIES. 


the removal of the roof of the thalamencephalon and 
the upper part of the left hemisphere, and by the sagittal 
division of the hinder parts of the brain and the turning 
to one side of the left half (fig. 23). 

Fig. 23. 
LONG. ZONE 


GANG. HAB. 


- 
- 
- 
”* 
- 
wee” 
* 
- 


; ‘ 
TUB.ACOUS. * 
LOB.LIN. LAT. : HEM. 
MED. AUR. OLF. BULB. 


Brain of Chimera monstrosa (dissected). 


The brain is divisible into three well-defined regions :— 
(i.) A large anterior mass composed of two pairs of con- 
tiguous lobes, the anterior of which are small and in 
connection with the olfactory organs and the posterior 
united together in the mid-line ; they are the olfactory 
bulbs and cerebral hemispheres. (ii.) A remarkably long 
and slender thalamencephalon. (iii.) The mid-brain, 
cerebellum, and medulla—a considerable mass, remarkable 
for its great dorso-ventral depth. This hinder part, owing 
to the resemblance that the sides of the thalamencephalon 
bear to olfactory peduncles, was formerly supposed to include 
the cerebrum, A more detailed examination will show that 
this brain, in spite of its obvious peculiarities, is, apart from 
the cerebrum, essentially that of an Elasmobranch. The 
olfactory bulbs are small and rounded in form; each is 
feebly bilobed. They are separated from the hemispheres 
byafarrow. Each hemisphere is fusiform, and is attached to 
its fellow near the middle of its median surface by a delicate 
lamina terminalis continuous above and below with the roof 
and the floor of the thalamencephalon. Slightly behind 
the lamina a large semicircular opening (foramen of Monro) 
leads on each side from the 3rd ventricle into a cavity that 


_ NERVOUS SYSTEM.—VERTEBRATA. 85 


extends within the hemisphere to the olfactory bulb. The 
posterior part of this cavity is mainly occupied by a 
prominent swelling on the lateral wall of the hemisphere, 
that probably represents the corpus striatum. 

The thalamencephalon forms a tube 25 mm. long ; its 
sides are ribbon-like and fairly thick, but the floor and roof 
are composed only of epithelium and pia mater. The 
roof is more extensive than the space between the lateral 
walls and thus bulges upwards, particularly in front, in a sac- 
like manner. It is infolded in the mid-line in its anterior 
two-thirds to form a choroid plexus, small processes of 
which project into the lateral ventricles. At its hinder end 
it forms a conical projection that accompanies the epi- 
physis. In front of the epiphysis the roof of the thalamen- 
cephalon is swollen to form a pair of prominent ganglia 
habenule which, as in the Amphibia, form a projecting 
lip when the tela choroidea is removed (upper specimen). 
Behind the epiphysis, the anterior border of the optic 
tectum is thickened to form the posterior commissure. 
The optic lobes are of considerable size, and contain a large 
ventricle, the lower half of which is partly filled bya swelling 
of the lateral walls. The cerebellum is simple, though well 
developed: it is diamond-shaped, with anterior and posterior 
lobes each containing an offshoot from the common ventricle; 
its surface is smooth with the exception of a longitudinal 
furrow and a feeble transverse indentation. The inner 
surface of the cerebellum is marked by a pair of prominent 
longitudinal ridges similar to those of Elasmobranchs, and, 
like them, continuous with the medullary auricles. 

The medulla is strongly concentrated antero-posteriorly, 
and is remarkable for the great development of two pairs 
of lobes. One pair (lobus linex lateralis) is continuous 
with the auricles and gives origin on either side to the 
dorsal root of the ophthalmicus superficialis vu. The 
second pair (tuberculum acusticum) lie below them, and 
give rise to the lateralis and the lower roots of the lateral- 
line branches of the vil. nerve. The lobus vagi is nodulated 
as in Blasmobranchs. The lobi inferiores, though small, 
are remarkably prominent. The saccus vasculosus is well- 
developed. 


86 


PHYSIOLOGICAL SERIES. 


From the above it will be seen that the hinder part of 
the brain is closely similar to that of an Elasmobranch, parti- 
cularly in the conformation of the cerebellum and medulla. 
The optic lobes show a slight tendency towards the Teleostean 
type in having an enlargement on their lateral walls 
suggestive of the torus semicircularis, but the hypothalamus 
is essentially that of an Elasmobranch. The cerebrum in 
its relation to the olfactory bulbs, in the considorable separa- 
tion of the hemispheres and the relative thickness of their 
dorsal and ventro-lateral walls, is closely similar to that of 
a Dipnoan or low Amphibian. 

Wilder, Proc. Ac. Sci. Philad. 1877, p. 219. 


GANOIDEL. 


D.86. Part of the skull of a Sturgeon (Acipenser sturio) with 


the brain exposed from the dorsal and ventral aspects. In 
comparison with the size of the fish (this individual weighed 
154 lbs., and measured 6 ft. 4 in.) the central nervous 
system is peculiarly small. The brain occupies only a part 
of the spacious cranial cavity, and in its superficial features 
combines characters found in Elasmobranchs, Amphibia, 
and Teleostea: for example, the medulla resembles that 
of a low Shark or Amphibian, whereas the cerebellum is 
very similar to that of Ceratodus but is provided with a 
valvula as in Teleosts. Or, again, the mid-brain and 
thalamencephalon have a strong superficial likeness to 
those .of Ceratodus, whereas the cerebrum resembles that 
of a Teleostean in having an epithelial pallium. 

The medulla broadens gradually from the cord towards 
the cerebellum, and has a very widely-open rhomboid fossa 
covered by a strongly pleated vascular roof (removed and 
mounted on the left in the specimen). In its floor are a 
pair of well-marked fasciculi longitudinales, each of which 
sends a strong offshoot to the motor root of vit. In the 
hinder part of the rhomboid fossa on either side lie the 
sensory vagal lobes, nodulated as in Sharks. To the side 
and in front of the vagal lobes, the margin of the rhomboid 
fossa swells to form a conspicuous lobe on either side (lobus 
linewe lateralis) that gives origin to certain nerves of the 


NERVOUS SYSTEM.—VERTEBRATA. 87 


lateral line. In front of the lobus linew lateralis the 
margins of the rhomboid fossa bend upwards and slightly 
outwards to form the posterior crura of the cerebellum. 
The cerebellum forms an upstanding recurved anterior 
border to the rhomboid fossa. Its anterior parts (not 
shown in the specimen) project within the optic lobes, 
forming a valvula cerebelli as in Teleosts. Molecular, 
nuclear, and intermediate layers are present in the cere- 
bellum, but, as in Elasmobranchs, the distribution of the 
nuclear layer is very partial, and Purkinje’s cells are 
irregularly disposed. The optic lobes are very small and, 
as in Dipnoi and Urodeles, form a single globular enlarge- 
ment without a distinct median furrow. They are said to 
contain small tori longitudinales and semicirculares similar 
to those of Teleosts. 

The thalamencephalon is narrow and fairly long, with a 
well-developed hypothalamus. The sides of the infundi- 
bulum are swollen to form a pair of small lobi inferiores. 
The saccus vasculosus is well-developed. As in most 
Elasmobranchs and many Teleostea, the epiphysis is long 
and thread-like ; towards its base it is in close contact with 
the roof of a large conical paraphysis. The cerebrum is of 
relatively small size, and consists of basal ganglia (striatum 
and epistriatum) covered by an epithelial roof, in which a 
few nerve-elements have been observed. The olfactory 
bulbs are sessile on the cerebrum; each contains a cavity 
in connection with the cerebral ventricle, and receives a 
large olfactory nerve indistinctly separable into two bundles, 


Johnstone, Zool. Jahrb., Bd. xv. 1901, p. 59. 


TELEOSTEA. 


Rabl Ruckhard, Arch. Anat. u. Phys. 1898, p. 345 (Pallium). 
Haller, Morph. Jahrb., Bd. xxvi. 1898, p. 632 (Histol., 
Bibliogr.). : 


The brain of Bony Fishes differs from that of Elasmobranchs 
in many important features. It is far more concentrated longi- 
tudinally, and is remarkable for the strong development of 
the optic lobes, which in some cases completely dominate the 
rest of the brain and render it nearly globular in form. On 


88 PHYSIOLOGICAL SERIES. 


the other hand the olfactory region, whose great development. 
forms one of the most striking features of the Elasmobranch 
brain, is peculiarly feeble in the Teleostea. The olfactory bulbs 
are small, either sessile upon the cerebrum or connected with it 
by long peduncles, and the cerebrum itself is represented by a 
pair of rounded basal ganglia roofed over by an epithelial non- 
nervous pallium (fig. 24). 

The thalamencephalon shows essentially the same features in 
both groups, although much compressed antero-posteriorly in 
the Teleostea. The cerebellum is large, except in some sluggish 
bottom fish (e. g., Lophius, Cyclopterus), but is usually solid 
and not hollow as in the Elasmobranchs. Its anterior parts 


Fig. 24. 


also are strongly developed, and protrude forward beneath the 
tectum opticum into the cavity of the optic lobes, forming the 
highly characteristic Teleostean valvula cerebelli. The medulla 
is in most cases much concentrated and often shows remarkably 
well-developed facial and vagal lobes. The basal ganglia of the 
cerebrum have much the same minute structure as in Elasmo- 
branchs; they are united by commissural strands (c. interlobu- 
laris) that occupy a thickening of the floor of the common 
ventricle. These commissures are derived partly from the 
olfactory areas and partly from the striatum. Their relation 
to the anterior commissure of Mammals is doubtful. 

The thalamencephalon, in minute structure and arrange- 
ment of tracts and nuclei, is approximately similar to that in 
Elasmobranchs, the cerebro-hypothalamic tracts being, however, 


: 
; 


Ss 
i 


ee 


ee or a aa 


. 


NERVOUS SYSTEM.—VERTEBRATA, 89 


specially strong. The tectum opticum has also essentially the 
same structure in both groups, although its elements are in 
Teleostea arranged somewhat more definitely in layers. The 
ependyma and nervous tissue also are greatly developed on 
either side of the mid-dorsal line of the tectum forming a pair of 
longitudinal ridges (tori longitudinales), traces of which are also 
found in Reptiles and Birds. The lateral parts of the optic 
lobes contain a pair of large nuclei (n. laterales), from which 
a considerable proportion of the fillet-—a particularly well- 
developed tract in Teleosts—takes its origin. They are super- 
ficially visible as a pair of bulgings into the cavity of the optic 
lobes (tori semicirculares). The cerebellum and valvula show 
the structure common to the cerebellum of all Vertebrates ; 
Purkinje’s cells are, however, somewhat irregularly disposed. 
The valvula is connected by tracts to the lobi inferiores. 


ANACANTHINI, 


D. 87. The cranium of a Cod (Gadus morrhua) in sagittal section, 
showing the brain from the left side. The cranial cavity is 
very extensive, and is only partially occupied by the relatively 
small brain. The latter shows well the main Teleostean 
characters. The olfactory bulbs are small round bodies 
lying close beneath the olfactory capsules; they are con- 
nected by long delicate tubular peduncles (the ventral parts 
of which only are nervous) to the basal region of the cere- 
brum. The peduncles lie close side by side for the posterior 
two-thirds of their course; in front they diverge towards 
the olfactory capsules and gradually increase in calibre. 
The basal ganglia of the cerebrum form two pronounced 
swellings of the cerebral floor; they are separated from 
one another dorsally by a deep sagittal fissure and are 
ventrally united by a transverse commissure. Lach is dis- 
tinctly lobulated, the two main lobules (striatum and 
epistriatum) lying respectively antero-lateral and postero- 
mesial. The roof of the cerebrum (pallium) is entirely 
non-nervous and consists of a continuation of the ependyma 
that lines the brain-cavities, in conjunction with the pia 
mater. In front it is continuous with the epithelial roof 
of the olfactory tracts, and behind with that of the thalamen- 


90 


4 


PHYSIOLOGICAL SERIES. 


cephalon. ‘The dorsal and lateral parts of the thalamen- 
cephalon are much restricted, being buried to a considerable 
extent by the optic lobes ; but the hypothalamus is strongly 
developed, the lobi inferiores in particular being large and 
prominent: they lie almost directly below the optic lobes. 
The latter are of great size, of almost globular form, and 
are separated in the mid-line by a sharp furrow. The 
optic tracts arise mainly from their superficial parts, and 
pass forward on either side of the thalamus to the ventral 
surface of the cerebrum; here they leave the brain and 
cross—the right below the left—to form the optic nerves. 
The cerebellum is tongue-shaped with its free end over- 
hanging the rhomboid fossa. It is connected with the basal 
parts of the brain by a pair of prominent anterior crura 
that give passage to the cerebellar tracts and contain the 
nuclei of part of the trigemino-facial nerve complex. The 
medulla, in comparison with that of a Shark, is much 
concentrated. The rhomboid fossa is consequently small. 
Its borders show definite swellings, due to the posterior 
crura of the cerebellum and to the nuclei of the posterior 
cranial nerves. 


D. 88. Parts of the head of a Cod (Gadus morrhua) with the brain 


exposed from the lower surface. The optic nerves, before 
entering the brain, cross one another, the left beneath the 
right. Behind this crossing lies the large spherical pituitary 
body attached to the antero-ventral surface of the infun- 
dibulum. It covers the anterior parts of the lobi inferiores., 
Behind it in the mid-line, separating tlie posterior parts of 
the lobi inferiores, is a small saccus vasculosus continuous 
with the distal end of the infundibulum. 

In this specimen the distribution of the third pair of 
cranial nerves is shown. It sends branches to the inferior, 
superior, and internal recti and to the inferior oblique, as 
well as a ciliary branch to the eyeball. A bristle is placed 
beneath the branch to the inferior oblique. 
O. C, 1380 A. 8. 


D. 89. A sagittal section of the cranium and brain ofa Cod ( Gadus 


morrhua). Black paper, inserted behind the pallium, brings 
out clearly the relations of this membrane to the basal 


NERVOUS SYSTEM.—VERTEBRATA. 91 


ganglia and olfactory tracts. At the root of the olfactory 
tract can be seen the cut edge of the commissura inter- 
lobularis (fig. 25, ant. comm.). The common cavity of 
the infundibulum and saccus vasculosus is clearly shown ; 
in the side wall of the former isa minute opening that leads 
into the ventricle of the right lobus inferior. 

At the anterior end of the tectum opticum lies the 
section surface of the small posterior commissure. 

A narrow passage leads from the aqueduct of Sylvius 
into the cavity of the optic lobes *. In the section this cavity 
is largely obliterated by one of a pair of longitudinal ridges 
(tori longitudinales) that lie on either side of the mid-dorsal 


Fig. 25. 


TECT. OPT. AQ. SYL. CER. 
TORUS. LONGIT. / 


CORP.STR.. POST COMM. 
PALL. : 
™~ 


bs 


/ * 
3 SR VENT. “ SAC. VASC. 
ANT. COMM. FOR. LOB. INF. VALV.CER. 


Brain of Gadus morrhua in sagittal section. 


line of the tectum. The torus is thickest anteriorly where 
it abuts on the posterior commissure, and gradually fades 
away posteriorly. 

The hinder part of the optic ventricle is occupied by a 
forwardly projecting process of the cerebellum (valvula 
cerebelli). This structure is formed by the invagination of 
the anterior parts of the cerebellum into the cavity of the 
mid-brain, and thus in sagittal section shows two superposed 
layers—the lower one continuous behind with the cere- 
bellum and passing in front by reduplication into the dorsal 
layer. The latter is closely applied to the first, and is 
continuous posteriorly with the hinder margin of the tectum 
opticum. Beneath the posterior lobe of the cerebellum can 


* In fig. 25 the leading line from aq.s¥L. points somewhat too far back. 


92 PHYSIOLOGICAL SERIES. 


be seen the cut surface of the nervous bridge that unites 
the two posterior crura of the cerebellum, and behind this 
the lobus facialis and lobus vagi. O. C. 1308 0. 


D. 90. A similar specimen in which the structure of the optic 
lobes and valvyula cerebelli is more clearly visible. 

In this specimen the left optic nerve crosses above the 
right. 

D. 91. The brain of a Cod (Gadus morrhua) dissected from above. 

The posterior lobe of the cerebellum and the tectum 
opticum with the exception of the torus longitudinalis 
have been remoyed, thus exposing the medulla and the 
cavity of the mid-brain. Within the optic ventricle are 
certain marked prominences: on either side a large semi- 
lunar excrescence (torus semicircularis) due to the presence 
at this spot within the latero-ventral walls of the mid-brain 
of a nucleus in connection with the fillet : in the central 
mid-line at the hinder end of the ventricle a subconical 
projection (valvula cerebelli), the structure and relations 
of which are shown in the previous specimens: and in the 
dorsal mid-line a pointed tongue-like process that extends 
from the posterior commissure to the hinder end of the 
tectum opticum. This structure, composed of the two 
tori longitudinales, consists of nerve elements and a local 
thickening of the ependyma that lines the brain-cavities. 
Beneath its broad anterior end lies the narrow opening 
by which the optic ventricle communicates with the 
aqueduct of Sylvius. 

The dorsal surface of the medulla is occupied by a series 
of swellings that almost entirely close the rhomboid fossa, 
and are due mainly to the sensory nuclei of the cranial 
nerves (fig. 26). Judging by Goronowitsch’s account of 
these structures in Lota, their relation to the several cranial 
nerves should be approximately as follows :—The prominent 
lateral crura of the cerebellum contain besides cerebellar 
tracts, a pair of large nuclei from which arise the acoustic 
and lateral-line nerves. These lobes apparently represent 
the tuberculum acusticum of Elasmobranchs (Johnstone, 
Zool. Jahrb, 1901, p. 159) or the Sturgeon shifted forward 
owing to the concentration of the medulla. Close behind 


~—" 


NERVOUS SYSTEM.—VERTEBRATA. 93 


the cerebellum and exposed by the removal of its free 
extremity, are a pair of prominent lobes (posterior crura 
of cerebellum); they are united above the fourth ventricle 
by a commissure, but otherwise are very similar in aspect 
to the lobi lines lateralis of Elasmobranchs. They must, 
however, be compared with the medullary auricles as they 
consist entirely of a backward prolongation of the cere- 
bellum. Behind these, on a level with the exit of the 


Fig. 26, 
OLF.TR, 


CORP.STR. ~~ PALL. 


TECT. OPT. 
TOR. LONG, on 


VALV.CER.” 
CER. 


ers 
*. 


LOB. FAC. LOB. VAG. 


Brain of Gadus morrhua (dissected). 


vagus from the brain, are a pair of lobes almost contiguous 
in the mid-line and each indistinctly divided by a longi- 
tudinal furrow. They give origin to the sensory roots of 
the facial and glosso-pharyngeal and represent a dis- 
membered portion of the lobus vagi of Elasmobranchs. 

Behind and to the sides of these lobes are elongated and 
somewhat irregular excrescences from which arise the 
sensory roots of the vagus. 

Goronowitsch, Festschr. fiir Gegenbaur, Bd. iii. 1897, 

p. 14 (Lota). 


7 


94 PHYSIOLOGIOAL SERIES. 


D. 92. The brain of a Bib (Gadus luscus) exposed from the left 
and ventral aspects. 

In comparison with the brain of the Cod, there are 
noticeable differences in the relative proportions of the 
parts—the cerebral basal ganglia and optic lobes being 
much more nearly equal in size. ‘This is due partly to an 
increase in the size of the basal ganglia, and partly 
to a decrease in the optic lobes relative to the brain as a 
whole. The right optic nerve crosses below the left. The 
saccus vasculosus is more prominent than in the Cod, and 
the pituitary body very much smaller. The lobi inferiores 
meet in the mid-line behind the saccus vasculosus. 


O. C. 13880 a 5. 


D. 93. The head of a Five-bearded Rockling (Motella mustela) 
with the ventral surface of the brain exposed. The optic 
nerves cross—the right below the left—at a considerable 
distance in front of the brain. In this specimen parts of 
the trigeminal nerve are also shown. O. C. 1380 A 7. 


D. 94. The head of a Sole (Solea vulgaris) with the brain exposed. 
Owing to the torsion of the skull the fore’ part of the 
brain is rotated to the right, but the region behind the 
optic lobes is quite similar to that of other fishes except for 
a hardly perceptible tendency to bend towards the right. 
The medulla is fairly long, with a pair of very prominent 
lobes (facial ?) upon its dorsal surface. The cerebellum is 
small, nearly globular in shape, and projects slightly back- 
wards over the rhomboid fossa. The optic lobes are also 
of moderate dimensions, and give off equal-sized optic 
nerves. ‘The left nerve passes above the right and twists 
round above the sphenoid bone to reach the left eye which 
is displaced to the right side of the fish. 

The thalamencephalon is remarkably elongated for a 
Teleostean, and forms a conspicuous neck between the 
optic lobes and corpora striata. 

The olfactory bulbs are large and are separated from the 
basal ganglia by a considerable constriction. The parts 


NERVOUS SYSTEM.—VERTEBRATA. 95 


of the fore-brain show a distinct tendency towards a linear 
arrangement, the olfactory bulb and corpus striatum of the 
left side being thrust to amarked degree behind the corre- 
sponding parts on the right. 

The lobi inferiores are globular and prominent. 


D. 95. The head of a Brill (Rhombus levis) with the brain exposed 
from the right (blind) side. The brain is perfectly sym- 
metrical. The optic lobes are relatively somewhat larger 
than in the Sole, The corpora striata are very small, with 
sessile olfactory bulbs at their anterior end. The left optic 
nerve passes below the right. O. C. 1380 a 11. 


D. 96. A similar specimen of the brain of a Hallibut (Hippoglossus 
vulgaris) exposed from the right (ocular) side. It closely 
resembles that of the Brill except for its larger size. The 
infundibulum and saccus vasculosus are very prominent. 
The right optic nerve is slightly smaller than the left, it 
crosses beneath it ; both are of immense size. 


ACANTHOPTERYGII. 


D. 97. Part of the cranium of a Gilt-Head (Chrysophrys aurata) 
with the brain exposed from the right side. The small 
olfactory bulbs are sessile on the cerebrum ; each gives 
rise to a stout olfactory nerve. The basal ganglia are 
immensely developed ; each is a lobulated globular body 
slightly larger than one of the optic lobes. The latter are 
of moderate dimensions ; the lobi inferiores are large and 
longitudinally elongated. The cerebellum is small, quadri- 
lateral in outline, and of considerable dorso-ventral depth. 

The right optic nerve crosses beneath the left; its distal 
part has been opened out to show its flat ribbon-like form 
and pleated folding. O. C. 1380 A 20. 

D. 98. The brain of a Mackerel (Scomber scombrus) exposed 
from the right and dorsal aspects. The olfactory bulbs 
and corpora striata are small and closely contiguous, form- 
ing together a pyramidal anterior extremity to the brain. 
The lobi inferiores are small, but the optic lobes are of 


96 


PHYSIOLOGICAL SERIES. 


* 


remarkable size, pressing in front against the corpora 
striata and overhung posteriorly by the cerebellum ; they 
are globular in shape, separated in the mid-dorsal line by 
a shallow groove. Upon the antero-lateral surface of each 
is an indentation from which emerges the main part of 
the optic tract. The lobule that lies postero-ventral to the 
indentation is due to an overlapping of the tectum opticum. 
The right optic nerve crosses below the left ; both are of 
great size, although the eyes in this fish are comparatively 
small. The cerebellum is of moderate size; it is egg- 
shaped, with its narrow end projecting forwards over the 
hinder half of the optic lobes. The crura cerebelli are 
strongly pronounced. The medulla is much shortened 
antero-posteriorly, O. C. 1380 a 18. 


D. 99. The cranium of a Mackerel (Scomber scombrus) with the 


brain exposed from above. The roof of the optic lobes and 
the anterior free end of the cerebellum have been removed 
to show the valvula cerebelli. This organ occupies the 


Fig. 27. 


Valvula cerebelli of Scomber scombrus. 


major part of the cavity of the optic lobes and is to a great 
extent responsible for their size. It consists of a central 
lobe directly continuous with the cerebellum, and of two 
lateral lobes or wings formed by the reduplication of the 
anterior ends of the central lobe. 

This relation of the lobes to each other is shown in the 
diagram (fig. 27). 


D. 100. The skull of a Fishing-Frog (Lophius piscatorius) with 


the brain exposed from the dorsal and ventral aspects, and 
with the origins, and in some cases the peripheral parts, of 
the cranial nerves shown. 


NERVOUS SYSTEM.—VERTEBRATA, . OF 


The brain is feebly developed and occupies only a small 
part of the spacious cranial cavity. The fore-brain is re- 
markably small ; it forms a pyramidal eminence in front of 
the optic lobes. The bulbi olfactorii are sessile on the 
basal ganglia, but in this specimen are hardly to be distin- 
guished. They give off delicate olfactory nerves. The optic 
lobes are large in comparison with the feeble development 
of the rest of the brain, but are not in reality particularly 
strong. They are separated in the mid-dorsal line by a 
shallow groove. The cerebellum is extremely small for a 
Teleostean, forming merely a little rounded excrescence 
between the hinder margins of the optic lobes. The 
medulla is followed by a swollen region of the cord with 
a single pair of eminences upon its dorsal surface. This 
enlargement is by some included in the medulla, and 
homologized with the vagal lobes, but from its micro- 
scopic character (Ussow, Arch. Biol. t. iii. p. 642) it 
seems that it more likely is a modified part of the cord, 
comparable to the metameric swellings found in this region 
in the Gurnard. It should be noticed that in both cases 
the anterior spinal nerves are strongly developed. 

The pituitary body is a remarkable structure both for 
its enormous size and its position a centimetre or more 
in front of the brain. It is spherical and connected to the 
infundibulum by a long delicate pedicle. The pineal 
gland is situated in a similar way beneath the cranial roof 
far in front of its point of origin upon the roof of the 
thalamencephalon, The same forward shifting is noticeable 
to a less degree in the eyes, in the position of the optic 
chiasma, and in the point of exit from the brain of the 
trigeminal complex of nerves. Possibly in all cases it is 
due to the great development of the anterior face-region. 
The lobi inferiores are peculiarly small ; they lie one on 
either side of a prominent saccus vasculosus. 

In this specimen the spinal cord is*‘also shown (for 
description see D. 754). O. C, 1308 n. 


D. 101. The isolated brain of a Fishing-Frog (Lophius pisea- 
torius), This specimen shows the features mentioned in 


VOL, Il. H 


98 _ PHYSIOLOGICAL SERIES. 


the description of the previous specimen, but with greater 
clearness. The pedicle of the pituitary body is nearly 
20 mm, long. O. C, 1308 M. 


D. 102. The brain of a Gurnard (T'rigla hirundo) exposed in 
situ from above. The olfactory bulbs are of some size ; 
they are sessile on the cerebrum, and each gives origin to a 
stout olfactory nerve. The basal ganglia are globular, 
smooth, and very large; the optic lobes are also well 
developed and somewhat flattened antero-posteriorly. The 
small cerebellum projects slightly backwards; it has 
prominent crura. ‘The medulla is short, with well marked 
vagal lobes on either side of the rhomboid fossa, The 
anterior part of the cord is much thickened, and shows 
upon its dorsal surface a series of 5 pairs of metameric 
enlargements, which are fully described in the section 
devoted to the spinal cord. O. C. 1308 a. 


D.103. A young Lump-Fish ( Cyclopterus lumpus), 3°5 em. long, : 
with the brain and spinal cord exposed from above. The 
brain is similar in all essentials to that of the adult, but is 
shorter and broader in outline, larger relatively to the size 
of the body, and more nearly fills the cranial cavity. The 
latter feature is common to the young of many Teleosts. 

O. C. 1308 La, 


D. 104, The head of a Lump-Fish (Cyclopterus lumpus) with the 
brain exposed from the dorsal and ventral aspects, The 
brain is poorly developed in every part. The minute 
olfactory bulbs are sessile upon the cerebrum. The optic 
lobes are oval in outline, and, although they form the 
largest region of the brain, are very small in comparison 
with those of most other Teleosteans. The cerebellum 
hangs backwards over the front part of the rhomboid fossa; 
it is oval, quite small, and without prominent crura. The 
medulla is remarkably long and narrow, and merges 
gradually into the cord much as in the lower Sharks. 
It shows no definite superficial eminences, and no doubt 
owes its simple unmodified character to the peculiarly 
feeble development of the cranial nerves. 

Presented by W. B. Tegetmeier, Esq. 


NERVOUS SYSTEM.—VERTEBRATA. 99 


D. 105. A Dragonet (Callionymus lyra) with the brain and spinal 
cord exposed from above. The optic lobes are very strongly 
developed. The cerebellum very closely resembles that of 
Lophius ; it is a small rounded eminence lodged between 
the hinder margins of the optic lobes, and protrudes slightly 
over the rhomboid fossa, The medulla is small and shows 
no clear separation from the cord. In this specimen the 
corpora striata have been removed. O. C, 1308 1. 


PHARYNGOGNATHI. 


D.106. The head of a Wrasse (Labrus sp.) with the brain 
shown in situ from above. The brain occupies the greater 
part of the cranial cayity. 1t is remarkable for the great 
development of the basal ganglia, which equal, if they do 
not exceed, the optic lobes in size. Each is roughly 
triangular when seen from above, and is contiguous in the 
mid-line with its fellow by one of its sides. Their surface 
is distinctly lobulated. The cerebellum is tongue-shaped ; 
its greater part hangs backwards over the rhomboid fossa 
but there is also a small anterior lobe. Its surface is 
crinkled, probably by shrinkage. The crura cerebelli are 
well-marked. O. C. 1308 a. 


PHYSOSTOMI. 
Mayser, Zeits. wiss. Zool. Bd. xxxvi. 1882, p. 259. 


-D.107. The brain of a Carp (Cyprinus carpio) shown in situ from 
above (fig. 28). In the Carp family the brain is distin- 
guished by the great development of the vagal and facial 
lobes. This development renders the medulla unusually 
broad and defines it abruptly from the cord. The vagal 
lobes form a pair of large wing-like swellings on either 
side of the rhomboid fossa, and embrace between their 
anterior ends the unpaired facial lobe—a rounded body 
situated in the dorsal mid-line behind the cerebellum. 
This “lobus impar” represents apparently a fusion of 
the two .small facial lobes seen in the Cod (Goronowitch, 
l.c. p. 23). The cerebellum, though much elevated, is of 
moderate size; it hangs slightly backwards over the 
medulla, The optic lobes are superficially very large, but 

H2 


100 


D.108. The head of a Tench ( Tinca vulgaris) exposed from above. 


PHYSIOLOGICAL SERIES, 


. 


owe their size mainly to the great development of the 
valvula cerebelli. Their roof is composed as usual of two 
chief layers—an outer cellular and fibrous layer from 
which the optic tracts arise, and an inner commissural 
layer; but the outer layer is deficient over a large triangular 
area in the mid-dorsal parts, leaving a semitransparent 
membrane (the commissural layer) through which the 
wings of the valvula cerebelli can be seen (upon the right 


Fig. 28. 


Brain of Cyprinus carpio. 


side black paper has been inserted beneath a part of this 
exposed commissural layer), The epiphysis is small and 
pear-shaped. The olfactory bulbs are situated close to the 
olfactory organs. The olfactory peduncles are somewhat 
widely separate, but are connected, as far as the bulbs, both 
dorsally and ventrally by a delicate membrane (black 
paper is inserted beneath its anterior end), the upper layer 
of which is a forward extension of the pallium. 


This brain has the same general characters as that of the 
Carp, but differs from it in the smaller size and more 
globular form of the cerebellum. The tectum opticum 
also has only a small median area deficient in the outer 
layer, from which—as this deficiency is apparently due to 
the thrusting aside of the lateral parts of the tectum by 
the contained valvula cerebelli—one may infer that the 
valvula is less developed. 

Presented by T. W. H. Burne, Esq. 


D. 109, The isolated brain of a smaller Tench (Tinca vulgaris), 


This specimen is similar to the last, but, in addition, shows 


"4 So 


NERVOUS SYSTEM.—VERTEBRATA. 101 


the crossing of the optic nerves—the left below the right— 
as well as the union of the lobi inferiores in the mid-line 
behind the saccus vasculosus. The olfactory bulbs and 
peduncles have been removed. O. C, 1880 4 15. 


D.110. The head of a Barbel (Barbus vulgaris) with the brain 
exposed from above. The cerebellum is considerably larger 

_ than in the Tench; it is oblong and overhangs the anterior 
part of the medulla. The optic lobes are well-developed. 
In the mid-line the outer layers of the tectum are deficient, 
exposing a transparent commissural area of triangular 
outline through which the valvula cerebelli is indistinctly 
visible as in the Carp. The left basal ganglion has been 
removed, exposing the short thalamencephalon with the 
ganglia habenulee—two small whitish excrescences on the 
dorsal margins of the thalamus. The crossing of the optic 
nerves—the left above the right—can also be seen. From 
the anterior end of the corpora striata delicate olfactory 
peduncles are given off. The olfactory bulbs in this and 
other Carps lie close to the olfactory capsules: they are not 
shown. | O. C. 1308 z. 


D.111. Brain of a Bleak (Alburnus alburnus). It closely re- 
sembles that of the Tench (D. 108), except in the somewhat 
smaller relative size of the “ lobus impar.” 


D. 112. The brain of a Roach (Leuciscus rutilus) exposed from 
above. The “lobus impar” and lobi vagi, though dis- 
tinctly visible, are far less developed than in the other 
specimens of Cyprinoid brains. 

Presented by Mr. S. Epprett. 


D.113. The head of a Pike (Lsoa lucius) with the brain exposed 
fromabove. For that of a Teleostean, the brain is long and 
narrow, with tapering medulla and open rhomboid fossa. 
The cerebellum and optic lobes are considerably developed, 
the latter having a long oval shape. The epiphysis is 
saccular and pear-shaped ; it overhangs the small basal 
ganglia and extends forward to the anterior extremity of 
the olfactory bulbs, which are sessile on the cerebrum. 


PHYSIOLOGICAL SERIES. 


D.114. The head of Mormyrus jubelini with the brain exposed 


from the left side. In the Mormyride the brain is re- 
markable for the immense development of the valvula 
cerébelli. This organ does not lie as in other Teleosts 
completely within the optic lobes, but projects through the 
tectum opticum, thrusting its lateral parts downwards to 
either side, and spreads out in three pairs of lobes or wings 
over the surface of the brain, completely concealing it from 
view when looked at from above, and extending so far down 
on either side as to leave exposed only the lower parts of 
the hemispheres and optic lobes. This unusual relation of 
the valvula cerebelli to the tectum opticum appears to be a 
further extension of some such process as that seen in the 
Carp (D. 107), in which the lateral parts of the tectum are 
divaricated and the central area much thinned out, but 
without extrusion of the valvula. The wings of the valvula 
are called from their position anterior, lateral or middle, 
and posterior. Their deep surface is occupied by a layer 
of small cells (nuclear layer) covered superficially by a 
number of parallel ridges each composed of molecular, 
nuclear, intermediate, and fibrous layers. In the specimen 
the exposed surface of the posterior wings has a finely 
corrugated appearance due to these ridges, but the anterior 
and lateral wings are smooth, because, by folding, the deep 
nuclear layer has become superficial in position. 

The olfactory bulbs are small and are situated close to 
the olfactory organs. They are connected by delicate 
peduncles to the cerebrum. The left basal ganglion can be 
seen below the anterior wing of the valvula; it has a 
somewhat oblong shape. Close behind it, below the anterior 
part of the lateral wing of the valvula, lie two narrow 
masses of brain-substance. The anterior of the two is the 
laterally depressed left half of the tectum opticum ; the 
other is part of the torus semicircularis, . 


Presented by J. 8. Budgett, Esq. 


D.115. The brain of Mormyrus kannume exposed in situ from 


above. The wings of the valvula cerebelli have been re- 


moved from the left side to expose the underlying parts of 
the brain. 


NERVOUS SYSTEM.—VERTEBRATA. 103 


The basal ganglion is well developed and is clearly 
divided into two lobes, an outer and anterior, and a median 
and posterior—the striatum and epistriatum. The cavity 
of the optic lobe is bounded in front by the displaced 
tectum opticum and is occupied by the large torus semi- 
circularis. Fig. 29. 


».---OLF. BULB 


CORP. STR: 1 a... ANT. WING. 
e. 


4 
TECT.OPT. 


_-POST. WING. 
ROOT VALV. CER. ~* 
cen 


LOB. IMPAR.-~ 


Brain of Mormyrus kannume. 


The cerebellum is small and tongue-shaped, with its 
pointed apex directed forwards. Its base is separated in 
front by a transverse groove from a small rounded emi- 
nence—the posterior part of the root of the valvula. Behind, 
a similar but shallower groove divides it from a small lobe 
(fig. 29, x.) said to resemble in microscopical features the 


104 £ PHYSIOLOGICAL SERIES. 


lobus impar of the medulla, although superficially it 
apparently forms part of the cerebellum. The medulla is 
remarkable for the immense development of a lobe upon 
its lateral and dorsal parts. This lobe (lobus impar) 
probably represents a fusion of a large median facial lobe, 
such as that seen in the Carps, with a pair of vagal lobes. 
The latter envelope the sides of the facial lobe and bound 
with their upper swollen borders a depressed central area— 
the median parts of the facial lobe. 

Presented by G'. A. Boulenger, Esq, 

Saunders, Phil. Trans. vol. elxxiii. 1882, p. 927. 3 


D.116. The brain of a Herring (Clupea harengus) shown in situ 
from above. It is remarkable for the great size of the 
optic lobes and the shortness of the medulla. The optic lobes 
are oval with a slight lateral depression about the middle. 
The outer layers of the tectum are deficient in the mid- 
line at the posterior end, leaving a small triangular area of 
commissural fibres exposed, 

The basal ganglia are very closely applied to one 
another in the mid-line, forming an apparently single 
globular mass ; they are continuous anteriorly with a pair 
of conical olfactory bulbs. The cerebellum is oblong 
and very deep from above downwards. The medulla is 
much concentrated, and has a well-marked facial lobe 


behind the cerebellum. O. C. 1308 c. 


D.117. The fore part of an Eel (Anguilla vulgaris) with the 
brain exposed from the dorsal aspect. In front of the 
medulla the several regions of the brain are of approxi- 
mately equal size, and as each is more or less clearly 
bilobed, the brain appears to consist of four pairs of 
rounded equal-sized nodules situated one behind the other. 
The anterior pair (olfactory bulbs) are slightly pointed in 
front and give off two large olfactory nerves, The optic 
lobes and cerebellum are divided down the middle by 
a shallow groove. The cerebellum is considerably broader 
than long, with its anterior and posterior borders parallel. 
The medulla is small and much shortened. 


D.118. The head of a Conger Eel (Conger vulgaris) with the 
brain exposed from above. The brain is more elongated 


NERVOUS SYSTEM.—VERTEBRATA. 105 


than in Anguilla. It is remarkable for the large size of 
its olfactory centres and the linear arrangement of its 
several parts. It also shows a very decided right-handed 
rotation of its anterior end. 

The olfactory bulbs are of great size and are separated 
from the cerebrum by short peduncles. Each receives an 
immense nerve from the olfactory organ. The right bulb 
lies partly below the left, much as in the Sole. The basal 
ganglia of the cerebrum are considerably lobulated, and 
with the olfactory peduncles can be seen to be covered by 
a relatively close-fitting pallium. The thalamencephalon is 
remarkably long for a Teleostean, forming a narrow neck 
between the cerebrum and the moderately developed optic 
lobes. The cerebellum is quadrilateral with a marked 
longitudinal groove on either side. The medulla is small 
and much concentrated. 

The fish from which this specimen was made measured 
5 ft. 7 in. in length. 


PLECTOGNATHI. 


D.119. A Globe Fish (Dzodon sp.) opened along the dorsal 
surface to show the brain and spinal cord. The brain lies 
in a capacious cranial cavity, and in dorsal view has an 
outline very similar to the conventional club on a playing 
ecard; this is due mainly to the great development of the 
optic lobes. The basal ganglia are also large; each is 
distinctly divided by a furrow into a lateral and a median 
lobe. The olfactory bulbs are not shown. The cerebellum 
is oblong and overhangs the medulla and anterior part of 
the cord. 

The spinal cord is remarkably short, ending in a fine 
filament less than 10 mm. behind the posterior border of 
the cerebellum. ‘The remainder of the neural canal is 
occupied by a cauda equina, indicated on a level with the 


pectoral fins by black paper. ~ QO. C, 1808 kK. 
DIPNOI. 
_D.120. Parts of the skull of Ceratodus forsteri with the brain 
exposed. 


In most characters the brain is very primitive and closely 


106 


PHYSIOLOGICAL SERIES. 


eo 


resembles that of a Urodele Amphibian. It is, for instance, 
very long and narrow, with spacious ventricles enclosed 
by thin or, in parts, epithelial walls. 

The medulla is very like that of a low Shark—long, and 
very broad in front with a widely open rhomboid fossa and 
well marked medullary auricles. It gradually merges into 
the cord behind. The highest development is shown by 
the cerebral hemispheres, which are large, like those of 
Amphibia, and greatly expanded in their ventral parts. 
They are separated from one another in the mid-line as far 
back as the anterior commissure. Their walls are thin and 
even purely epithelial in their dorso-median parts, where 
they are closely attached to a large glandular paraphysis 
that projects from the roof of the thalamencephalon wedge- 
like between them. In front, the lateral ventricles are 
continued by a narrow passage into the cavities of a pair 
of strong olfactory bulbs. In the pussession of definite 
olfactory bulbs Ceratodus differs markedly trom Protopterus 
or the Amphibia, and shows more resemblance to Elasmo- 
branchs. A window has been cut in the left hemisphere 
and olfactory bulb to show the continuity of their cavities 
and the relation of the glandular paraphysis to the mesial 
wall of the hemisphere. 

The thalamencephalon a::d mesencephalon, as in Urodeles, 
are very long and narrow. The former shows a pair 
of strongly marked ganglia habenule. - The epiphysis, 
which is not shown in the specimen, is small. The optic 
lobes form a single prominence of small size between the 
thalamencephalon and the cerebellum. It is narrower in 
front than behind, and is divided mesially by a conspicuous 
but narrow dark band due to a local thinning of the roof. 
The cerebellum is slightly damaged ; it is more strongly 
developed than in Amphibia, though less so than in Fishes, 
and forms a broad transverse band behind the optic lobes, 
continuous laterally with the medullary auricles. 

In the floor of the fourth ventricle lie a pair of small 
fasciculi longitudinales posteriores, and in the lateral walls, 
rather far back, a pair of longitudinal ridges—the vagal 
lobes, which in position resemble those of Sharks but are 
without their characteristic nodulation. 


q 
j 
a 


a! a 


ee 


oe 


— a = ee oe 


NERVOUS SYSTEM.—VERTEBRATA. 107 


The epithelial roof of the rhomboid fossa is much 
pleated ; it has been longitudinally bisected and turned 
to either side. Upon the lower surface of the brain, the 
great ventral expansion of the hemispheres and _ their 
clearly defined median separation can be seen. The 
hypophysis has been removed and mounted on the left, 
thus uncovering the large funnel-like infundibulum. 

In this specimen the olfactory organs are also shown. 
On the left, the floor of the narial chamber has been 
removed to show the transversely pleated character of the 
roof. A red rod has been inserted into the anterior and 


posterior nares on the right. O. C. 1309 B. 
Saunders, Ann. Mag. Nat. Hist. ser. 6, vol. iii. 1889, 
p. 157. 


D.121. The brain of a Mud-fish (Protopterus annectens). It 
chiefly differs from that of Ceratodus in being shorter and 
more compact, in the absence of separate olfactory bulbs, 
and in the feeble development of the cerebellum. In all 
these features it also more nearly resembles the brain of 

an Amphibian. 

The cerebral hemispheres are remarkably deep dorso- 
ventrally, they are united at their posterior end by an 
anterior commissure situated in the lamina terminalis (this 
is not shown). 

In front of the ganglia habenule the epithelial roof of 
the thalamencephalon is prolonged forwards as a conical 
paraphysis. The medulla is shorter than in Ceratodus, 
with the borders of the rhomboid fossa swollen and, half 
way between the calamus scriptorius and the cerebellum, 
curved inwards towards the mid-line. There are no de- 
finite lobi inferiores, but they are possibly represented by 
the slightly swollen lateral walls of the infundibulum. 


Burckhardt, Centralnervensystem v. Protopterus, Berlin, 
1892. 


a 


AMPHIBIA. 
Osborn, Jour. Morph. vol. ii. 1889, p. 51. 
In the Amphibia, and especially among the Urodeles, the 


brain is of a remarkably low type and closely resembles that of 
a Dipnoan. 


108 PHYSIOLOGICAL SERIES. 


With the exception of the medulla and cerebrum, all parts 
are very poorly developed. The medulla is similar in form to 
that of a low Shark, with wide open fossa rhomboidalis and 
no sharp boundary towards the cord. ‘The hemispheres, in- 
cluding the olfactory bulbs which are at the best only slightly 
indicated, form the largest part of the brain, and show signs of 
incipient pseudo-occipital lobes. But their size is somewhat 
deceptive, as the walls are relatively thin throughout. They 
consist of an outer molecular and an inner cellular layer, and 
show no signs of cortical formation, unless possibly a small 
aggregation of cells in the outer layer of the median wall should 
be regarded as a rudimentary hippocampal cortex. 

The hemispheres are united by an anterior commissure, in 
which two portions can be distinguished: one between the basal 
parts—the true anterior commissure; and the other connecting 
the olfactory regions of the pallium—a hippocampal commissure. 

The hemispheres are connected to the thalamencephalon by a 
large basal tract on either side. The ganglia habenule are 
always well marked and externally visible, though not so strong 
as in the Cyclostomi and Dipnoi. The pineal gland is ves- 
tigeal. The optic lobes are only developed to any extent in the 
Anura, and in them have a many-layered tectum. The roof 
nucleus, in connection with the trigeminal nerve, is particularly 
strong in Urodeles. The cerebellum, although small, is com- 
posed of three layers—nuclear, intermediate and molecular, but 
an internal fibrous layer, owing to the small size of the cerebellar 
tracts, is not differentiated. 


URODELA, 


D, 122. A Menopoma (Menopoma alleghaniensis) with the brain 
and spinal cord exposed from above. This specimen, although 
somewhat damaged, shows clearly the chief superficial cha- 
racters of the Urodele brain. The cerebral hemispheres are 
separate in the mid-line nearly to their posterior extremities. 
Each is large and oval in shape, and projects backwards to 
some exent over the lateral parts of the thalamencephalon, 
forming a rudimentary pseudo-oecipital lobe. Independent 
olfactory bulbs are absent, but two strong double olfac- 
tory nerves arise from the antero-ventral parts of each 
hemisphere. 


NERVOUS SYSTEM.—VERTEBRATA, 109 


The thalamencephalon and mesencephalon differ little from 
one another in diameter, and form together a narrow cylin- 
drical neck between the hemispheres and the broad anterior 
end of the medulla. A large hole between the hinder extre- 
mities of the hemispheres indicates the spot from which the 
conical vascular paraphysis has been removed ; its posterior 
border is formed by two slight thickenings, the ganglia and 
commissura habenule. The optic lobes are very weak, and 
do not differ materially from those of Protopterus. The 
cerebellum is quite rudimentary—a mere narrow band of 
nervous tissue forming the anterior border of the rhomboid 
fossa. The medulla is flattened from above downwards. 
In front it is broad, but gradually narrows posteriorly, and 
merges imperceptibly into the cord. Its lateral walls 
diverge widely in front and bound an extensive rhomboid 
fossa. O. C. 1311 F. 


D. 123. The, head of a larval Axolotl (Amblystoma tigrinum) 
showing the brain. It differs little from that of Meno- 
poma except for the stronger development of the optic lobes. 
In this specimen the paraphysis and ganglia habenule 
are very clear.: 


Stieda, Zeits. wiss. Zool., Bd, xxv. 1875, p. 285. 


D.124. A Menobranchus lateralis with the brain exposed from 
above. It agrees in all essentials with that of Menopoma. 
QO. C. 13115. 


D.125. The head of a Proteus anguinus showing the brain. The 

__ olfactory bulbs are separated from the hemispheres by a 
slight constriction. The ganglia habenulee are remarkably 
large; close behind them lies the minute epiphysis. The 
optic lobes, as might be expected in a blind creature, are 
scarcely differentiated. 


ANURA. 
D.126. The head of a Bull Frog (Rana ee) with the brain 
exposed from above. 
This brain, though formed on a ies plan to that of 
a Urodele, differs from it in the relatively greater breadth 


110 PHYSIOLOGICAL SERIES. 


- 


of the thalamencephalon, in the larger size of the optic 
lobes, and in the stronger development of the cerebellum, 
The olfactory bulbs are separated from the hemispheres by 
a shallow constriction and are fused together in the mid- 
line. Behind this union the hemispheres are separate as 
far back as the anterior commissure. Between their 
posterior extremities there is, in the specimen, an oval 
aperture in the roof of the thalamencephalon caused by 
the removal of the paraphysis ; its hinder margin is 
formed by the slightly protuberant ganglia habenule and 
their commissure. 

The optic lobes form the broadest part of the brain. 
They are prominent oval bodies separated in the mid-line 
by a deep gutter. In front they diverge and expose a 
part of the tectal commissure. Between this and the 
thalamencephalon is a small crescentic pit at the base of 
which lies the posterior commissure. A deep furrow sepa- 
rates the optic lobes from the cerebellum. ‘ 

The medulla is somewhat shorter than in the Urodeles. 
The epithelial and vascular roof of the rhomboid fossa has 
been removed and mounted at the side to show its pleated 
under surface. 


Keker, Anat. of the Frog (Engl. trans.), 1889, p. 141. 


REPTILIA. 


Edinger, Senckenberg. naturf. Gesell., Bd. xix. 1896 (Cere- 
brum) & Bd. xxii. 1899 (Thalamencephalon). 
Haller, Morph. Jahrb., Bd. xxviii. 1900, p. 252. 


The Reptilian brain is narrow and of considerable length, 
with moderately developed optic lobes and, except in swimming 
forms, with insignificant cerebellum, The medulla oblongata 
shows astrong longitudinal dorso-ventral curvature, convex below, 
In this class the brain differs most markedly from that of a lower 
Vertebrate in the great structural advance of the cerebrum, 
notably in the presence, for the first time in the Vertebrate 
series, of an undoubted cerebral cortex (fig. 80). The condition 
of the pallium is of special importance. It is not only much larger 
than that of an Amphibian, but is also much more highly 


NERVOUS SYSTEM.—VERTEBRATA. 111 


differentiated. The mesial wall of the hemisphere is composed 
of a large dorsal area—the hippocampus, and a ventral spindle- 
shaped area—the tuberculum olfactorium (see fig. 31). A re- 
latively narrow strip of thick ganglionic matter extending from 
the lamina terminalis behind to the olfactory peduncle in front 
separates these two areas; this body may be called para- 
terminal, because its most distinctive feature in the adult is 
that it lies alongside the lamina terminalis, and in the foetal 
brain is developed from those parts of the walls of the neural 
tube which are placed alongside the end or terminal plate. Its 


Fig. 30. 


Section of pallium of Tropidonotus natrix, x 150. 


surface forms the precommissural area, and in Mammals its 
upper part becomes stretched and otherwise modified to form 
the septum lucidum (vide Journ. of Anat. & Phys. vol. xxxii. 


_p. 411). 


In Reptiles and Monotremes the peculiar cortex, of which the 
tuberculum olfactorium is formed in Meta- and Hutherian 
mammals, although present, is ill-defined; so that the corpus 
striatum seems to extend to the surface of the ventral half of 
the brain. : 

A comparison with the condition found in the Monotremes 
(vide infra) and in the feetal state of all mammals, clearly 
demonstrates that the whole of the mesial surface of the cerebral 
hemisphere of the reptilian brain, which is not precommissural 
area nor tuberculum olfactorium, represents and is homologous 


4 


112 PHYSIOLOGICAL SERIES. 


with the hippocampus of the mammalian brain (figs. 31, 32, 
& 33). This hippocampal formation also extends beyond the 
dorso-mesial edge of the hemisphere, and forms in different 
reptiles and birds a variable area of the dorsal surface (see 
“ Further Observations on the Fornix,” Journ. Anat. & Phys. 
vol. xxxii. p. 245). 

The hippocampal formation presents a very different appear- 
ance to its mammalian homologue because that peculiar modifi- 
cation of the edge of the hippocampus which in Mammals 
produces the fascia dentata, has not yet occurred in the 
Sauropsida, although in many Sauria the first stage in the 
development of the fascia dentata, viz., a formation of numerous 
small cells at the ventral edge of the flat hippocampal plate, is 
distinctly recognizable. 

Two simple rounded commissures are placed close together in’ 
the lamina terminalis. The dorsal of these represents the 
psalterium of Mammals, being derived from the hippocampus. 
In many Reptiles such as Sphenodon and the Lacertilia, the 
caudal half of this commissure is separated from the rest and 
crosses the middle line not in the lamina terminalis but in a fold 
of the roof between the paraphysis and dorsal sac. This “ com- 
missura aberrans hippocampi” (usually known by the misleading 
title “‘commissura pallii posterior”) is probably a modified in- 
heritance from the Amphibia, in which certain fibres from the 
caudal part of the cerebral hemisphere cross the mesial plane 
along with the fibres of the superior commissure (commissura 
habenulz). 

That part of the pallium which forms the bulk of the whole 
nervous system in Mammals is represented in Reptiles by a 
small insignificant area on the dorso-lateral aspect of the 
hemisphere, which is not sharply differentiated from the pyri- 
form lobe below it. The neopallium (as I have called this part 
of the palliam (Journ, Anat, & Phys. vol. xxxv. 1901, p. 431) 
is so poorly developed that the fibre-systems to which it gives 
rise—internal capsule, pes pedunculi, and pyramidal system, are 
absent in the reptilian brain. The chief cerebral tracts are in 
connection with the olfactory centres, and include some between 
the olfactory areas and the hippocampal cortex that are of 
special importance, as they are the first cortico-sensory connec- 
tions to appear in the Vertebrate series. 


‘ NERVOUS SYSTEM.—VERTEBRATA. 113 


In the thalamencephalon the tracts and nuclei are larger and 
more numerous than in lower forms, indicating a greater com- 
plexity of connection between the fore and hind parts of the 
brain, due mainly to the presence of cortical tracts. The 
nuclei rotundi, in which the main part of the strio-thalamic 
tracts terminate, are particularly large and form the greater 
part of the protuberant thalami. There are also two end nuclei 
of some of the optic fibres which are supposed to represent the 
lateral geniculate bodies. On the other hand, the connection 
between the hypothalamus and cerebellum is usually very weak. 
The fasciculus longitudinalis posterior rises partly from the 
hypothalamus, but mainly from a large-celled nucleus in the 
floor of the mid-brain. 

The epiphysis is in most cases strongly developed, and in 
Lacertilia is in connection by its distal end with a median 
veetigial eye lodged in a foramen in the cranial roof. 

The infundibulum shows scarcely any signs of a saccus vas- 
eulosus except in the swimming forms. The cerebellum, as in 
Amphibia, owing to the small size of the tracts that enter it, 
has no clearly defined inner fibrous layer. In the Reptiles there 
is an increase in the number of acoustic nuclei, corresponding 
to the development of a rudimentary cochlea (lagena). 


LACERTILIA. 


D. 127. The brain of a Monitor Lizard ( Varanus varius). 

In general form this is a typical example of the brain of 
a Reptile. The olfactory bulbs are long and narrow, and are 
united by short peduncles to the pear-shaped hemispheres. 
The hemispheres form the broadest part of the brain, and 
parts of them, representing the pyriform lobes, bulge down- 
ward behind the tuberculum olfactorium to form pseudo- 
temporal lobes. Posteriorly they are contiguous with the 
anterior face of the optic lobes and completely cover the 
thalamencephalon. In the dorsal mid-hne, between the 
cerebrum and optic lobes lies the club-shaped epiphysis, 
with a small vestigial eye in connection with its distal end. 
The optic lobes are well developed, and form a pair of 
rounded eminences separated from one another in the mid- 
line by a deep furrow. 

VOL. I. I 


114 


PHYSIOLOGICAL SERIES. ‘ 


eo 


The cerebellum is of moderate dimensions and has the 
plate-like form usual among Reptiles. It is concave in 
front and arches forward slightly over the optic lobes. The 
medulla shows well the characteristic Reptilian flexure. Its 
fourth ventricle (rhomboid fossa) is considerably restricted. 


OPHIDIA. 


D. 128. A Ringed Snake (Tropidonotus natrix), shortly before 


hatching, with the brain exposed from above, showing in 


linear succession the olfactory bulbs, cerebral hemispheres, 


optic lobes, and medulla. The thalamencephalon and cere- 
bellum are respectively covered by the caudal poles of the 
hemispheres and the hinder part of the optic lobes. The 
epiphysis forms a minute protuberance between the cere- 
brum and optic lobes. 

Preserved in Goadby solution. 

Rathke, Entwicklungsgesch. der Natter (Coluber natriz), 
1839, pp. 36, 80, 180, 199. 


D. 129. A similar specimen with the brain exposed from below. 


Preserved in Goadby solution. 


D. 130. A similar specimen with the left side of the brain laid 


bare. The flexure of the medulla oblongata is very marked. 

The relation between the form of the cerebral hemisphere 

and the developing globe of the eye is well shown. 
Preserved in Goadby solution. 


D. 131. The brain of a Python (Python seba). The brain is very 


long and narrow and peculiarly flat from above downwards. 
(In this specimen a certain amount of this flatness is due to 
artificial pressure during preservation.) The hemispheres 
are pear-shaped, moderately broad behind with well marked 
caudal (pseudo-occipital) and ventral (pseudo-temporal) 
lobes, and terminate in front in olfactory bulbs, each of 
which receives a stout bundle of nerves. Posteriorly they 
abut against the optic lobes. The cerebellum is poorly 
developed and forms a flat, almost horizontal, sheet of 
neryous tissue overlying the fore part of the fourth ventricle. 


a 


eee 


: 7 | 2) 


NERVOUS SYSTEM.—VERTEBRATA. 115 


A small epiphysis lies between the hinder ends of the 
hemispheres. The infundibulum is prominent and gives 
attachment to a large spherical hypophysis. O.C. 1318 a. 


D. 132. The brain of an Indian Python (Python molurus) in 
sagittal section seen from the left. The dorso-ventral 
flattening of the brain is well seen. The right olfactory 
bulb and peduncle and the cerebral hemisphere have been 
sagittally divided to show their cavities. That of the 
olfactory bulb is capacious and is connected with the lateral 
ventricle by an extremely delicate lumen in the ventral 
part of the peduncle. From the outer wall of the hemisphere 
a pair of lineally arranged eminences (corpus striatum) 
project into the ventricle. Beneath them can be seen the 
cut surface of the lower part of the striatum. The mesial 
wall of the hemisphere has been mounted on the right 
side to show the paraterminal body—a longitudinal ridge- 
like thickening of the wall that fits into a depression 
along the lower border of the striatum. 

The flattened tectum opticum is separated into corpora 
quadrigemina by a longitudinal fissure (shown in the pre- 
vious specimen) and by a shallower transverse groove, 
visible in this specimen as an indentation upon the cut 
edge between the posterior two thirds. The posterior 
eminences are formed by a pair of nuclei that contribute 
fibres to the fillet. In the Snakes the large trigeminal 
roof-nucleus situated along the mesial area of the tectum 
beneath the commissural layer is seen to advantage. The 
openings from the aqueduct of Sylvius into the lateral 
optic ventricles are small and situated far forward. The 
cerebellum, although small, is relatively thick. The rhom- 
boid fossa is covered by a delicate membranous roof, the 
anterior part only of which, as in the Turtles, is pleated 
and vascular. 

The hypophysis is mounted on the léft, below the in- 
fundibulum ; it shows well the two parts of which it is 
composed. 

The Snake from which this specimen was obtained 
measured 15 feet in length. 

Rabl-Ruckhard, Zeits. wiss. Zool., Bd. lviii. 1894, p. 694. 

3 12 


PHYSIOLOGICAL SERIES. 


ORNITHOSAURIA. 


D. 133. A cast of the cranium and parts of the cranial cavity of a 


Pterodactyl (Seaphognathus purdoni). 'The brain in this 
creature appears to have entirely filled the cranial cavity. 
It was of an essentially Avian type. The hemispheres 
were large and oval—longer and narrower than in most 
Birds, but rounder anteriorly than in recent Reptiles. 
They extended well back over the thalamencephalon and 
partially covered the optic lobes. The latter were enor- 
mously developed forming the broadest part of the brain, 
and occupied the usual Avian position upon the latero- 
ventral parts of the mesencephalon. . In Birds this position 
is due to the thrusting aside of the optic lobes by the 
great forward development of the cerebellum. Thus it is 
legitimate to infer from the position of the optic lobes that 
in this creature the cerebellam was strongly developed, 
although it is not represented in this cast. 


DINOSAUBIA. 


D. 134. The cast of the cranial cavity of a Dinosaur (Jguanodon 


mantelli). The description of the brain from such a cast 
as this must of necessity be to a large extent a matter of 
inference; for although the anterior and lateral parts of 
the cranial cavity seem to have approximately followed 
the contours of the brain, such was evidently not the case 
in the mid-dorsal region. 

The brain as a whole was long and narrow, with no very 
marked ventral flexure of the medulla. The hemispheres 
were peculiarly short and broad, and remind one more of 
those of a Bird than of a Reptile, being shorter and more 
abruptly tapering in front than even in the Crocodiles, 
They were strongly arched above, extremely prominent in 
their lateral parts, and flattish below. In the mid-line in 
front they were prolonged into either olfactory peduncles 
or bulbs, it is not apparent which. 

The optic chiasma and infundibulum are strongly marked. 
The space between the dorsal parts of the cerebrum and 
the crest of the cerebellum shows no brain contours, as 
evidently here the brain did not reach the cranial roof. 


NERVOUS SYSTEM.—VERTEBRATA. 117 


The optic lobes, which apparently occupied this space (for 
no signs of them are visible in the Avian position upon the 
lateral or ventral surface) were probably of some size, to 
judge by the magnitude of the optic nerves. The cerebellum 
was of considerable extent in transverse and dorso-ventral 
directions, but whether it was also antero-posteriorly ex- 
panded as in Crocodiles, Chelonians, and Birds, or a mere 
transverse plate as in other Reptiles, it is difficult to say. 
The form of the projecting lateral parts favours the latter 
supposition, 
Andrews, Ann. Mag. Nat. Hist. ser. 6, vol. xix. 1897, 
p- 585. 


EMYDOSAURIA. 


D. 185. The head of a young Sharp-nosed Crocodile (Crocodilus 
americanus) with the brain exposed from above. The 
hemispheres form by far the largest part of the brain. 
They are short and broad with a strongly arched dorsal 
surface, and in general features much resemble those of a 
Bird. Anteriorly they abruptly taper to form a pair of 
long olfactory peduncles, by which they are connected with 
two strong fusiform olfactory bulbs that lie side by side 
close behind the nasal chamber on a level with the anterior 
margin of the eyes. The optic lobes are moderately 
developed, and lie upon tke dorsal surface of the brain 
between the hemispheres and the cerebellum. The cere- 
bellum is very large for that of a Reptile and superficially 
bears some resemblance to that of a low Shark, being 
a smooth rounded protuberance above the anterior end of 
the fourth ventricle and showing upon its surface a feeble 
transverse furrow. O. 0. 1817 a. 

Rabl-Riickhard, Zeits. wiss. Zool., Bd. xxx. 1878, p. 336. 


D. 186. “ The brain of a Crocodile six feet long” *. This brain 
measures only 40 mm. in length, and does not equal 25 mm. 


* This, in all probability, is the Crocodile alluded to in the following 
passage from a Hunterian MS. obtained from the executors of Sir Everard 
Home, and entitled ‘Modern History of the Absorbing System ’:— 

“Tn the beginning of the winter 1764-5 I got a Crocodile which had been 
in a show for several years in London before it died.” 


118 PHYSIOLOGICAL SERIES. 


. 


in breadth at the broadest part. The specimen is still 
largely covered by the dura and pia mater. The Bird- 
like form of the hemispheres is very striking. Upon the 
left side, part of the pallium has been removed to expose 
the lateral ventricle, which is reduced to a narrow slit by 
the great development of the corpus striatum. Openings 
have been also made through the walls of the left optic 
lobe and the cerebellum. The olfactory bulbs and tracts 
have been removed. O. C. 1318. Hunterian. 


D.137. The brain of a young Crocodile divested of its membranes. 
The original description states that the brain is, “to ap- 
pearance, made up of five parts; two, anterior, answering 
to the cerebrum; two behind these which answer to the 
‘nates and testes’; the posterior, the cerebellum.” The 
transverse furrow upon the latter is very strongly marked. 
The left half of the medulla has been removed. 

O.C. 1317. Hunterian. 


' 
i 
a 
* 
I 


D.138. A longitudinal section of the head of a young Crocodile, 
showing the brain in sagittal section from the left. The 
brain is too small to show the anterior and posterior com- 
missures, but upon the inner wall of the thalamencephalon, 
towards the dorsal aspect, a roughened area is probably 
the cut surface of the median (soft) “ commissure,” which is 
found in certain Reptiles. The cavities of the right optic 
lobe and of the cerebellum and their connections with the 
aqueduct of Sylvius and the fourth ventricle are very 
clearly shown. A marked protuberance into the optic 
ventricle from the posterior wall of the lobe is due to the 
presence at this spot of a large lateral nucleus, similar to 
that found in Teleosts. The medullary flexure is strongly 
marked. O.C. 1315, Hunterian. 


a_i eer 


D. 139. The left half of the same head. The section in this case 
passes slightly to the left of the mid-line. By this means, 
although the olfactory peduncle is unavoidably removed, the 
ventricles of the hemisphere and olfactory bulb, and the 
relation of the latter to the nasal cavity are very clearly 


NERVOUS SYSTEM.—VERTEBRATA. 119 


shown. The pallium is quite thin and the lateral ventricle 
is to a great extent occupied by the corpus striatum, though 
apparently not so much so as in the adult. O. C. 1316. 
FHunterian. 

CHELONIA. 

D. 140. The cranium of a Turtle (Chelone mydas) with the brain 
exposed from above. The Turtle’s brain is very instructive, 
because it readily lends itself to comparison with the 
corresponding organ in the Amphibia and the lower 
Ichthyopsida on the one hand, and with that of the diver- 
gent Avian and Mammalian phyla on the other. 

The brain does not fill the roomy cranial cavity, in which 
respect it resembles the condition found in Ichthyopsida 
and differs from birds, mammals, and many other reptiles. 
In this specimen, the olfactory nerves (not peduncles), the 
olfactory bulbs, the cerebral hemispheres, the mesen- 
cephalic roof, the cerebellum, and the medulla oblongata. 
are visible in linear succession. 

The true olfactory nerves (which are such short and 
insignificant filaments in most Vertebrates, and in man 
and all mammals have practically no intra-cranial course, 
because they enter the bulb as soon as they perforate the 
ethmoid bone) are collected into greatly elongated (40 mm.) 
rounded cords, that arise anteriorly from the mucous mem- 
brane of the nasal fossee and end by being inserted inio the 
olfactory bulbs. The fibres during their course are collected 
into three bundles—dorsal, ventral, and lateral—which end 
respectively in the dorsal, ventral, and lateral surfaces of 
the olfactory bulb. The latter is a hollow, laterally com- 
pressed vesicle, attached to the anterior extremity of the 
cerebral hemisphere by a cylindrical peduncle, which is so 
short that without close examination the bulb appears sessile. 

The cerebral hemisphere is also a hollow, laterally com- 
pressed vesicle, more than thrice as long as, and propor- 
tionately deeper than, the olfactory bulb. It completely 
overlaps the thalamus, but does not cover the roof of the 
mesencephalon. The epiphysis, together with the dorsal 
sac and paraphysis, forms a large pyriform mass projecting 
upwards from between the hinder parts of the two hemi- 
spheres. 


120 PHYSIOLOGIOAL SERIES. 


The optic lobes are rounded, of moderate size and sharply 
defined. They lie upon the dorsal surface of the brain in 
the depression between the cerebrum and cerebellum and 
are separated mesially by a sharp furrow. The cerebellum 
is a large hollow hemispherical protuberance hanging like 
a hood over the anterior end of the rhomboid fossa. Its 
walls are relatively thin. The fourth ventricle (rhomboid 
fossa) is spacious ; it is covered by a membranous roof, the 
lateral parts of which are extensively pleated and highly 
vascular (this vascular membrane has been removed and 
mounted on the left). In the floor of the fourth ventricle 
lie a pair of well marked fasciculi longitudinales. 

Stieda, Zeits. wiss. Zool., Bd. xxv. 1875, p. 361. 


7. 
- 


le ei 


D. 141. The brain of a Turtle (Chelone mydas) isolated and seen 
from the left side. The olfactory peduncle is continuous 
posteriorly upon the ventral surface with a rounded hemi- 
spherical boss, known as the tuberculum olfactorium, which 
extends backwards at the base of the brain almost to the 
optic chiasma, and includes also part of the lateral and mesial 
walls of the hemisphere. The hemisphere is relatively very 
deep dorso-ventrally, and is thus in striking contrast to that 
of Testudo or the Ophidia. The dorsal parts of the hemi- 
spheres extend back-nearly to the optic lobes, but laterally 
leave a considerable area of the thalamencephalon, covered 
by the optic tracts, exposed. The infundibulum is very 
prominent. The ventral curvature of the medulla oblongata 
is well seen. 0. 0.1312 p. 8 


—— a PS 


D.142. The brain of a Turtle (Chelone mydas). The dura mater 
has been removed from the left side, and the vessels of the 
pia mater minutely injected, ‘The partial removal of the dura 
shows how loosely it envelopes the brain and atthe sametime 
displays the form and disposition of the cerebral organs. A  __ 
white bristle has been inserted into the infundibulum, and 
a black bristle into the ruptured distal extremity of the 
epiphysis. The sac-like membranous roof of the medulla 
is shown, with a bristle placed beneath its non-vaseular 
inedian part. Black thread has been tied round the 6th, 


NERVOUS SYSTEM.—VERTEBRATA. 121 


9th, 10th, 11th, and 12th cranial nerves. The forward 
course of the accessorius roots to join the vagus are 
particularly clearly seen. O. C. 13812. Hunterian. 


D. 143. The brain of a Turtle (Chelone mydas) in sagittal section 
seen from the left side. In this section the thin mesial wall 
of the right hemisphere has been exposed showing a tract 
of fibres radiating over the precommissural area. A similar 
though far more strongly marked tract (tr. hippocampo- 


Fig. 31. 


PARAPHY. 
MONRO FOR, DORS: SAC 


PAR. STALK MESEN. 
/ comm. sup.” COMM. POST, 
A f SGU 


HIP. 
ie 


OLF. BULB. 


OLF. NERVE 
RAMUS 0. 


j 
OLF NERVE 
RAMUS V. 


AREA PRECOM. ” : 
”” COMM. D” 
OLF. TUBER. 


SOF T COMM. 


\ 
CORP. MAM. MED. OBLs 
XN 


iX& . 
COMM. V. “THIRD VENT. 


OPT. CHI. “CORP. PIT. 


Brain of Chelone mydas, in sagittal section. 


mesencephalicus) is found in Birds; it forms a direct con- 
nection between the hippocampus and the tectum opticum. 
The anterior commissure and psalterium can be seen close 
together in front of and below the foramen of Monro. The 
optic thalamus is small ; it is joined to its fellow across the 
cavity of the third ventricle, as in the Mammalia, by a large 
soft “commissure” in which is situated a central nucleus 
of considerable size. The roof of the third ventricle is 
evaginated to form a group of three successive elongated 
outgrowths, constituting together the club-shaped promi- 
nence seen in the previous specimen between the hinder 
parts of the hemispheres. The foremost outgrowth is the 
paraphysis, the intermediate and largest the dorsal sac, 
and the most caudal the epiphysis. The specimen also 
shows very clearly the large cavities of the optic lobes and 


122 PHYSIOLOGICAL SERIES. 


. 


cerebellum, in open communication respectively with the 
aqueduct of Sylvius and the fourth ventricle. The limits of 
the vascular and non-vascular portions of the membranous 
roof of the fourth ventricle are also very clearly shown. 


D. 144. The left cerebral hemisphere of the previous specimen 
divided by a longitudinal vertical section and with the twa 
halves mounted to show the internal surface. 


Fig. 32. 


OLF. BULB. 


The lateral wall. The mesial wall. 
Chelone mydas, left hemisphere. 


The corpus striatum (which is seen in the lower part of 
the lateral and ventral walls of the ventricle) is relatively 
very small. It consists of a narrow and thin band of grey 
matter that extends, in the floor of the ventricle, from the 
olfactory peduncle in front to the anterior end of the optic 
thalamus behind, and fuses with the latter body beneath 
the foramen of Monro. In its slenderness and general 
relations it resembles the corpus striatum of Amphibia and 
Sphenodon, and differs in these respects markedly from 
that of Ophidia, Lacertilia, and Mammalia. 


NERVOUS SYSTEM.—VERTEBRATA. 123 


From the lateral wall of the hemisphere an enormous 
bulging extends into the ventricle and almost obliterates it. 
This has been called the epistriatum by Edinger ; its nature 
is best demonstrated in Sphenodon (fig. 33), in which it is 
clearly seen to be a large invaginate fold of the pallium 
(probably the homologue of the pyriform lobe of Mammals). 

This eminence is prolonged further in the caudal direction 
than the corpus striatum and becomes continuous with a 


Fig. 33. 


NON. HIP PAL. 


 EPISTRI. 


EPISTRI. 


ane 
SESS MRR AR SH SH 


Ti 
BRR E 
arenes 


PERRIER SHER ATE 
HOM aeRO MS wie 
7 


‘ 
CORP. STRI. 


Diagrammatic transverse section through the hemisphere of Sphenodon. 


mass of grey matter, which represents the nucleus amygdalz 
of Mammals. This nucleus consists of a thickening of the 
lateral wall of the small descending cornu of the lateral 
ventricle just behind the caudal extremity of the corpus 
striatum. On the lateral surface of the brain there is a 
triangular flattened area corresponding to this body, just as 
there is on the ventral surface in many mammals (e. g. 
Erinaceus, Perameles). 


D.145. The brain of a large Turtle (Chelone mrydas). The dura 
mater is reflected from the right side, showing its extensive 
development and the loose trabecular tissue by which the 
space between it and the pia mater is occupied. A par- 
ticular development of this tissue consisting of parallel 
vertical strands occurs above the optic lobes; they give 


124 


PHYSIOLOGICAL SERIES. 


passage to numerous blood-vessels (not seen in the specimen). 
The ventricle of the right hemisphere has been opened 
showing the thinness of the pallium, the spaciousness of the 
cavity, and the prominence of the epistriatum. Part 
of the right side of the cerebellum has also been cut away 
to show its remarkably thin walls and large cavity 
continuous with the fourth ventricle. The epiphysis is 
well shown. The arteries in this specimen have been 
injected. O. C. 1813. Hunterian. 


D. 146. The brain of a Turtle, with the ventricles of the cere- 


bellum, optic lobes, and cerebral hemispheres laid open. 
The following is Mr. Hunter’s description of this prepara- 
tion :—“ In the first or superior ventricle is an eminence 
which extends a little way into the olfactory nerve and 
runs through the whole length of the ventricle. The 
plexus choroideus is also seen in the ventricle. The ven- 
tricle of the nates is exposed, and a white bristle is placed 
in it, as is the ventricle of the cerebellum with a black 
bristle lying in it. At the lower part of the ventricle is a 
continuation of the tunica arachnoides, which shuts up or 
makes part of the ventricle. In the angle or quadrangle 
made by the cerebrum and nates, &., is a duct or canal 
like the infundibulum leading from the upper part of the 
skull to the last ventricle.” 

In the above description the “ first ventricle” is that 
of the right cerebral hemisphere with the epistriatum 
(‘an eminence”) exposed. The “nates” (optic lobes) 
include both nates and testes of Mammalia. The “ conti- 
nuation of the tunica arachnoides” is the non-vascular 
epithelial roof of the fourth ventricle; a small part of it can 
be seen at the hinder margin of the cerebellum on the right. 
The “canal” is the basal part of the epiphysis. 

O. C. 1314. Hunterian. 


D. 147. The brain of a Tortoise (Testudo tabulata). Relative to 


the size of the creature (the shell measured 280 mm. in 
length) the brain is extremely small. Its most highly 
developed parts are in connection with the olfactory organs ; 
the olfactory bulbs in particular being very large—quite 


NERVOUS SYSTEM.—VERTEBRATA. 125 


two thirds the size of the hemispheres. The main part of 
the hemispheres lies behind the foramen of Monro, forming 
extensive pseudo-occipital lobes that reach backwards on 
either side to the hinder margin of the mid-brain. The 
anterior parts of the hemispheres are very short. The epi- 
physis is remarkably well developed. The optic lobes and 
cerebellum do not essentially differ from those of the Turtle. 

The roof has been removed from the left hemisphere 
and olfactory bulb showing the continuity of their ventricles, 
and in the case of the former the relatively slight promi- 
‘nence of the corpus striatum and the position of the choroid 
plexus. Upon the left side, the cavities of the optic lobe 
and cerebellum have been opened showing the thinness of 
their walls and the forward protrusion of the choroid plexus 
from the roof of the rhomboid fossa into the cavity of the 
cerebellum. 


AVES. 


Bumm, Zeits.wiss. Zool., Bd. xxxviii. 1883, p. 480 (Cerebrum). 

Brandis, Arch. mikr. Anat., Bd. xli. 1893, p. 623; xliii. 
1894, p. 96; xliv. 1895, p. 534. 

Boyce & Warrington, Phil. Trans., vol exci B. 1899, p. 293. 


The brain is remarkably constant in form throughout the 
class of Birds, and may be readily distinguished by its form, and 
more particularly by the position of the optic lobes, from that of 
any other living vertebrate. It differs from the brain of lower 
forms mainly in its relatively greater breadth and in the 
shortening of its base. Its most characteristic features are the 
great development of the cerebrum, optic lobes, and cerebellum. 
The cerebrum is usually broader than long ; its size is due almost 
entirely to the development of the corpora striata. The hemi- 
spheres cover the thalamus and frequently also the greater 
part of the optic lobes, and in addition to well-marked pseudo- 
occipital lobes usually have definite though rudimentary pseudo- 
temporal lobes. By the forward projection of the cerebellum, 
the optic lobes are always more or less depressed laterally towards 
the ventral surface. The olfactory bulbs and hypothalamus 
are weak ; the medulla is flexed as in Reptiles though not so 
strongly. 


126 PHYSIOLOGICAL SERIES. 


The corpora striata are structurally separable into several 
areas, comparable apparently to the putamen, nucleus caudatus, 
and globus pallidus of Mammalia. They are connected with 
the nuclei of the thalamus by large and complex basal tracts. 
The pallium, except for an extension of its cortical area, is 
essentially the same as in Reptiles; it is in parts extremely thin. 
The cortico-thalamic tracts are, however, stronger and more 
numerous than in lower forms, and an important connection first 
appears in this group between the cortex of the pseudo-occipital 
lobe and the tectum opticum. Injury to this tract has been 
shown to interfere with the vision of the opposite eye. Another 
connection between the cerebrum and tectum opticum (traces 
of which occur in Reptiles) attains a strong development, in 
Birds. This tract (tractus hippocampo-mesencephalicus) arises 
from the surface of the median wall of the hemisphere, coils 
round the cerebral peduncle and terminates in the tectum. Its 
function is not known. 

The geniculate bodies are enormously developed. The tectum 
opticum is also highly differentiated, and shows many alternating 
layers of ganglion-cells and neuropile. The fillet is particularly 
large, and rises to a great extent as in Fish from a prominent 
lateral nucleus. The cerebellum is relatively greater than in 
any vertebrates other than Fish and Mammals, It corresponds, 
as in the lower groups, with the mammalian vermis. The tract 
of fibres connecting the cerebellum with the acoustic centre is 
particularly strong. 


STRUTHIONIFORMES. 


D. 148. The cast of the cranial cavity of a Moa (Dinornis mazi- 
mus). This, which is probably a trustworthy representation 
of the brain, differs in several particulars from the brain of 
living Ratite Birds. It is as a whole somewhat more 
elongated, owing mainly to the greater length between 
the anterior extremities of the hemispheres and the optic 
chiasma. The hemispheres are less arched above, broader in 
front, and show more marked mesial eminences on either 
side of the dorsal mid-line. The olfactory bulbs are rela- 
tively large. The optic lobes and nerves are smaller actually 
than in the Ostrich. The cerebellum has the usual Avian 


he 


NERVOUS SYSTEM.—VERTEBRATA. 127 


form, but its apex seems to lie further forward than is 
usually the case. The medulla is only slightly flexed. The 
hypophysis is very large. 


D.149. The brain of an Ostrich (Struthio camelus). This specimen 


shows well the chief superficial characters of a Bird’s brain : 
great longitudinal compression of the basal parts; minute 
olfactory bulbs sessile on the anterior extremities of the 
hemispheres; strong development of the cerebrum and 
optic lobes; depression of the latter towards the ventral 
surface, and great size of the cerebellum. These characters 
taken together at once distinguish this brain from that of 


any lower vertebrate, although the development of the 


optic lobes is equalled in many Teleosts and that of the 
cerebellum in the higher Sharks. Each cerebral hemi- 
sphere is short, and very broad behind, with an indentation 
on the base in the position of the mammalian Sylvian 
fissure, forming the anterior boundary of a small pseudo- 
temporal lobe, and with indications upon the dorsal surface 
of a longitudinal furrow that extends forwards to the base 
of the olfactory bulb and forms the lateral boundary of 
a mesial eminence. 

The hemispheres are strongly arched above, contiguous 
in the mid-line, slightly concave below and bluntly pointed 
in front, with the points lying close side by side and termi- 
nating in a pair of small olfactory bulbs. The hemispheres 
extend backwards over the roof of the thalamencephalon 


and conceal the greater part of the optic lobes. The latter 


are a pair-of oval prominences situated on the latero-ventral 
aspect of the mesencephalon with their long diameter 
directed downwards and forwards. At their anterior ends 
they pass directly into the optic tracts, which form a complete 
chiasma in front of the infundibulum. The chiasma has 
been partly dissected to show the crossing of the nerve- 
fibres. The cerebellum represents the Mammalian vermis ; 
it is remarkably large, and forms an upstanding rounded 
or sub-conical eminence that projects forwards between the 
hemispheres above the roof of the mesencephalon, and 
backwards over the rhomboid fossa. It is slightly flattened 
from side to side and convex in front and behind, with a 


128 PHYSIOLOGICAL SERIES. 


slight concavity in its anterior face where it abuts against 
the pseudo-occipital lobes of the cerebrum. It is deeply 
fissured transversely, as in higher’ Sharks and Mammals. 
The medulla is short and passes into the cord by a some- 
what abrupt constriction. O. C. 1321s. 


D. 150. A similar specimen seen from the ventral surface. The 
optic lobes, tracts, and chiasma are well shown, as is also 


the sharp ventral flexure of the medulla. O.C. 1321s a. 


D. 151. The brain of an Ostrich (Struthio camelus) injected. 
The right lateral ventricle has been exposed by the removal 
of the lateral wall. It shows clearly the foramen of Monro, 
with a choroid plexus —an offshoot of the vascular epithelial 
roof of the thalamencephalon—projecting through it into 
the ventricle. On the left an opening has been made in 
the dorsal wall (pallium) of the hemisphere to show the 
natural position of the plexus. The outer wall of the right 
optic lobe has been removed by a tangential section to 
expose its cavity—a lateral diverticulum of the aqueduct of 
Sylvius. The thickness of its walls is somewhat exagge- 
rated by the direction of the section. The dorsal parts of 
the cerebellum have also been cut away, showing the 
transverse folding of the organ, and laying bare the apex of 
the cerebellar ventricle—an offshoot of the fourth ventricle. 
A black bristle has been inserted into the ruptured end of 
the left olfactory bulb and others mark the positions of the 
chief cranial nerves. A brown bristle is placed in the cavity 
of the infundibulum. O. C. 1822. Hunterian. 


D. 152. Part of the section of cerebellum removed from’ the 
preceding specimen. QO. C. 1823. Hunterian. 


D. 153. The brain of an Ostrich (Struthio camelus) with several 
of its cavities exposed from the right side. The corpus 
striatum has been entirely removed, showing the extent of 
the lateral ventricle in a sagittal plane, and the foramen of 
Monro (indicated by a blue rod). The right optic lobe has 
also been mostly cut away, to show the thickness of the mid- 
brain floor and the relatively thin teetum—here upon the 


a 


NERVOUS SYSTEM.—VERTEBRATA. 129 


point of merging into the tectal commissure. The cerebellum 
is in sagittal section, showing its cavity and the depth of 
its transverse folding. 


D. 154. Parts of the brain of an Ostrich (Struthio camelus). The 
anterior half of the cerebellum and the valve of Vieussens 
have been removed, exposing the anterior part of the fourth 
ventricle and the optic lobes. The latter are widely divari- 
cated and are united by a broad commissural sheet (tectal 
commissure), which is slightly thickened on the boundary 
line between mid-brain and thalamencephalon to form the 
posterior commissure. 

The dorsal parts of the thalamencephalon are also shown 
by the removal of the pseudo-occipital lobes of the hemi- 
spheres. The roof (tela choroidea) is epithelial and vascular ; 
it is evaginated. towards the anterior end to form the 
epiphysis (somewhat damaged), and in front sends a 
vascular offshoot into each of the lateral ventricles (on the 
right side the hemisphere has been cut through the middle 
of the foramen of Monro to show the continuity of this 
plexus with the tela choroidea). The side walls of the 
thalamencephalon are thick and appear, when seen from 
above, as two rounded eminences (optic thalami) covered 
laterally by the optic tracts. In the left hemisphere the 
relatively immense proportions of the corpora striata and 
the delicacy of the pallium are shown. O. C. 1321s. 


D. 155. A cast of the cranial cavity of an Ostrich (Struthio 
camelus). 


D. 156. Brain of a Rhea (Rhea americana). Upon the left side 
part of the pallium has been removed, exposing the corpus 
striatum. A small excrescence can be seen upon the right 
peduncle of the cerebellum, at the point towards which 
the ends of the transverse fissures converge. This pro- 
minence is not present in the specimens of Struthio 
(cf. especially D. 149), but is found in most other birds ; 

it probably corresponds with the flocculus cerebelli of 
Mammals. O. C. 1821 R. 
VOL. Il. K 


PHYSIOLOGICAL SERIES. 


D. 157. Three transverse sections through the fore-brain of a 


Ki-wi (Apteryx) in front of the foramen of Monro. The 
uppermost section is taken close behind the olfactory bulbs; 
the middle one slightly in front of the lamina terminalis, 
and the lower through the anterior commissure. They 
show the relatively immense development of the corpora 
striata and the extreme thinness of the median walls of the 
hemispheres. The termination of the anterior commissure 
in the corpora striata and its relation to the anterior 
extremity of the third ventricle are also well displayed. 

QO. C. 1821 Q. 

ANSERIFORMES, 


D. 158. The head of a Wattled Brush-Turkey ( Catheturus lathamit) 


with the brain exposed from above. The cerebral hemi- 
spheres are slightly longer and more sharply pointed in 
front than in the preceding specimens. They show clearly 
the longitudinal dorsal furrows meeting in the mid-line 
close behind the olfactory bulbs. The small clavate epi- 
physis can be seen wedged in between the anterior end of 


the cerebellum and the cerebral hemispheres. 
O. C. 1321 0. 


D. 159. The brain of a Honduras Turkey (Meleagris ocellata) 


showing the small size and rounded form of the hemispheres. 
The longitudinal dorsal furrows are conspicuous at their 
anterior end. The cerebellum is well developed. 

O. C. 1821 . 


D. 160. The brain of a Fowl (Gallus ferrugineus v. domesticus). 


The hemispheres have much the same proportions as in 
Catheturus, but do not extend so far back. The olfactory 
bulbs are clearly shown, The cerebellum has well marked 
floceuli. In this specimen also the strong ventral convexity 
of the medulla, characteristic of Birds and Reptiles, and 
the large size of the optic lobes, tracts and nerves are 
well marked. The hypophysis has been removed, exposing ~ 
the open end of the infundibulum. 

Presented by W. B. Tegetmeier, Esq. 


D.161. A sagittal section of the head and brain of a Polish Fowl 


(Gallus ferrugineus vy. domesticus), showing the modified 
form of the brain correlated with the cranial protuberance 


NERVOUS SYSTEM.—VERTEBRATA. 131 


characteristic of this breed. The entire brain is much 
lengthened. The cerebrum is pushed strongly forward and 
upward to occupy the cavity of the cranial protuberance, 
and is separated from the somewhat depressed cerebellum 
bya waist-like constricted region consisting of the thalam- 
encephalon and mesencephalon. The distortion of the brain 
in this breed does not seem to entail any noticeable change 
in habits or intelligence. 

This specimen also shows well the structure of the optic 
chiasma. Upon its section surface a number of stripes are 
visible, successively dark and light. This appearance is 
due to the cut edges of a series of band-like bundles of 
nerve-fibres derived alternately from either optic nerve. 

O. C, 1321 5. 
Presented by W. B. Tegetmeier, Esq. 
Tegetmeier, Proc. Zool. Soc. 1856, p. 366. 


D. 162. The brain of a Bustard (Otis sp.). The specimen, 
although in a bad state of preservation, shows the general 
form of the brain. 

The cerebral hemispheres are remarkably short and broad 
and almost globular in contour. They leave most of the 
thalamencephalon exposed and cover no part of the optic 
lobes. (This may be due partly to artificial displacement. ) 

The tectal commissure is overhung posteriorly for about 
one-third of its extent by the anterior lobe of the cere- 
bellum. In front it is separated by a transverse groove— 
the infolded posterior commissure—from the thalamen- 
cephalon. The roof of the third ventricle has been removed 
exposing its slit-like cavity bordered by the prominent optic 
thalami. Between the postero-median margins of the 
cerebral hemispheres lies the epiphysis. Its stalk originates 
from the thalamencephalon roof in front of the optic 
thalami. O. C. 1321 8. 

D.163. The brain of a Wattled Crane (Grus carunculatus). The 
cerebral hemispheres are strongly arched above, flat below, 
and from the dorsal aspect have an almost quadrangular 
outline. Their anterior ends are rounded and give attach- 
ment to the olfactory bulbs on their ventral surface. The 

K 2 


132 


PHYSIOLOGICAL SERIES. 


dorsal furrows are well marked and bound a pair of strong 
median prominences. They meet in the mid-line behind the 
anterior border of the hemispheres. The hinder parts of 
the brain call for no remark. O. C. 1821 Bb. 


D. 164. Brain of a Stone-Curlew (Gidicnemus bistriatus). The 


bad condition of this specimen has apparently led to a 
certain amount of distortion (e.g. the large interval between 
the hemispheres and optic lobes is probably unnatural). 
The hemispheres are markedly globular with well-defined 
pseudo-temporal lobes. O. C. 1321 Ba. 


D. 165. The brain and spinal cord of a Goose (Anser ferus) at 


about the twelfth day of incubation. At this stage the 
brain shows much resemblance in its hinder parts to that 
of anadult Lizard, and in its hemispheres to that of an Am- 
phibian or low Shark, e. g. Notidanus. The optic lobes are 
large, and occupy a dorsal position immediately in front of 
the cerebellum. The latter is as yet remarkably small, as 
in adult Amphibia or Reptilia. The medulla is strongly 
flexed, and the rhomboid fossa is lengthened and widely 
open in front, as in Urodeles. The thalamencephalon forms 
a distinct segment between the optic lobes and the elongated 
hemispheres. O.C. 1319. Hunterian. 


D. 166. Median sagittal section of the brain of a Goose (Anser 


ferus). In this section the brain-cavities are shown. In 
front, the spacious third ventricle communicating by the 
foramen of Monro with the ventricle of the right hemi- 
sphere and prolonged ventrally behind the optic chiasma 
into the infundibulum. The anterior wall of this ventricle 
(lamina terminalis) gives passage to the double anterior 
commissure. Note the protuberant optic thalami in the 
upper part of the ventricle and the cut edge of the delicate 
tela choroidea. 

Posteriorly the third ventricle is connected with the 
fourth by a narrow passage, the aqueduct of Sylvius, roofed 
over by the posterior and tectal commissures, and prolonged 
laterally to form the cavity of the optic lobes. In this 


NERVOUS SYSTEM.—VERTEBRATA. 133 


specimen the large size of the cerebellum, its small cavity 
continuous with the fourth ventricle, and its composition of 
layers of white and grey matter are also clearly visible. 


D. 167. The brain of a Goose (Anser ferus). The hemispheres 
have been pressed to either side to show the lamina terminalis 
and the anterior commissure. This method of treatment 
has also uncovered the dorsal surface of the thalamen- 
cephalon, the tectal commissure, and anterior lobe of the 
cerebellum. The origin of the tractus hippocampo-mesen- 


cephalicus can be clearly seen upon the surface of the median 
walls of the hemispheres. O.C. 1321 a. 


D. 168. The brain of a Goose (Anser ferus) partially divided from 
above by a median sagittal incision and with the two halves 
turned aside to show the diverticulum of the fourth ventricle 
within the cerebellum and the arrangement of the layers 
of white and grey matter that form the arbor vite. The 
outer surface of the left optic lobe has been removed to 
expose its ventricle, and a bristle has been passed from it 
into the aqueduct of Sylvius to demonstrate the continuity 
of the two cavities. The right lateral ventricle has been 
opened by section of its thin mesial wall. Its extent and 
continuation into the olfactory bulb are thus shown, as well 
as the great disproportion in bulk between the corpus 
striatum and pallium. O. C. 1821. Hunterian. 


D. 169. The brain of a Duck (Anas boscas) from which the greater 
part of the left side has been removed. The superficial 
appearance of the brain is very similar to that of the Goose. 
In taking away the left hemisphere the anterior commissure 
has been isolated and kept intact from its termination in the 
left corpus striatum to its entry into the right hemisphere. 
The optic tracts and chiasma have also been dissected, 
showing in the latter the interlacing of six large independent 
bundles of fibres (three belonging to each optic nerve) as 
they pass from one side to the other. All the fibres of the 
optic nerves cross to the opposite side of the brain in the 
chiasma. ‘The course of the ascending root of the tri- 
geminal nerve has also been dissected. out, and a bristle 


134 PHYSIOLOGICAL SERIES. 


is placed beneath the 4th nerve. The relation of the 
concave anterior surface of the cerebellum to the cerebrum 
is very clearly shown. The flocculus is strongly marked. 


O. C. 1380 15. 


D. 170. The brain of a White Stork (Ciconia alba) from which 
the right, hemisphere has been removed to show the optic 
tract upon that side. The optic lobes are peculiarly pro- 
minent. The emergence of the fourth pair of nerves from 
the valve of Vieussens is clearly shown. The great interval 
between the hemispheres and cerebellum is probably arti- 
ficial, O. C. 1380 A 33. 


D. 171. The brain of a Saddle-billed Stork (phippiorhynchus 
senegalensis). This specimen is badly preserved, but shows 
the rounded form of the hemispheres and their relations to 
the optic lobes and cerebellum. O.C. 13821 Be. 


D. 172. The brain of a Brazilian Cormorant (Phalacrocorax 
brasiliensis) showing its 1 Flange form and long oval 
hemispheres. O. C, 1821 a a. 


D. 173. The brain of a Heron (Ardea cinerea). 


FALOCONIFORMES. 


D. 174. The brain of a Sulphur-crested Cockatoo (Cacatua sul- 
phurea). The hemispheres are remarkably large, extending 
back so as to completely cover the dorsal surface of the 
optic lobes. They are oval in shape, and have a strongly 
marked “Sylvian” fissure upon their ventral surface, 
behind which the hemisphere expands to form a very 
definite pseudo-temporal lobe. Dorsal longitudinal furrows 
are present, but in this specimen are indistinct. The 
Parrots are among the few Birds in which the cerebrum is 
longer than broad. The cerebellum and optic lobes are 
relatively rather small. O. C, 1821 a. 


D. 175. The brain of a Cockatoo (Cacatua triton). This 
specimen shows similar features to the last, but owing to 
its better state of preservation the cerebral furrows are 
more pronounced, O. C. 1321 aa. 


 —— ———— mT 


NERVOUS SYSTEM.—VERTEBRATA. 135 


D. 176. The brain of a Great Horned Owl (Bubo maximus). 
This remarkable brain is distinguished by an immense 
lateral development of the hemispheres accompanied by a 
marked approximation of their anterior extremities to the 
optic chiasma. The enlargement chiefly affects the median 
part of each hemisphere between the dorsal longitudinal 
furrow and the mid-dorsal line. By the great development 
of this area the parts of the hemisphere external to, and 
including the anterior half of the dorsal longitudinal furrow 
have been thrust outwards and downwards, so that what 
under typical conditions would be the lateral parts of the 
hemisphere occupy a ventral position, and what in other 
birds would be its dorsal vault forms here its anterior and 
lateral border. This transformation of parts, accompanied 
by a marked shortening of the distance between the olfac- 
tory bulbs and the chiasma, gives to the long axis of the 
fore part of each hemisphere a nearly transverse direction. 
The ventral surface of this brain compares well with that 
of the Goose (D. 167), in which the dorsal parts of the 
hemispheres have been artificially thrust to either side. 
In other features, except for the strong development of 
the optic lobes, the brain is quite typical. O. C. 1321 kK. 


D. 177. A similar specimen, in which the upper part of the left 
hemisphere has been removed to show that the great lateral 
expansion of the cerebrum is due to an immense enlarge- 
ment of the corpus striatum. QO. C. 1321 Kk a. 


D.178. The hinder parts of the brain of an Owl (Séria sp.) 
showing the strong development of the optic lobes and 
thalami in this keen-sighted bird, and the relatively com- 
plex formation of the chiasma. In place of the half dozen 
large interlacing bundles seen in the chiasma of the Duck 
(D. 169), each optic nerve here splits into five delicate 
laminze that interlace and alternate with one another as 
they pass through the chiasma to the optic tract of the 
opposite side. A certain number of fibres are said aiso to 
pass direct from each optic nerve to the tract of tae same 
side—a condition apparently correlated with the frontal 
position of the eyes. O. C. 1380 10. 


7 


D. 179. The brain of a White-tailed Eagle (Haliaétus albicilla). 
The hemispheres are very broad. The dorsal parts of the 
right one have been removed to’ show the ventricle, the 
large corpus striatum, and the narrow cut edge of the 
pallium. The lateral parts of the corpus striatum have 
been cut away on the left. The large optic lobes have 
been treated in a similar way on either side, showing in 
each the narrow slit-like ventricle and the thickness of the 
walls. The postero-ventral wall, owing to the presence 
of the large lateral nucleus, is peculiarly massive. The 
cerebellum is well developed; its right half has been 
remoyed. This specimen also shows very clearly the 
club-shaped epiphysis and the origin of its stalk from the 
roof of the thalamencephalon between the optic thalami. 

0. 0. 18211, 


136 PHYSIOLOGICAL SERIES. 


D. 180. The brain of a Sparrow Hawk ( Accipiter fringillarius). 
The hemispheres are broad and somewhat’globular in shape. 
They cover only the anterior parts of the optic lobes. The 
latter, as in all birds of prey, are very strongly developed. 

0. C, 1321 m. 


D. 181. The head of a Griffon Vulture (Gyps sp.), with the 
brain exposed from above. The hemispheres are strongly 
developed; they are remarkably broad in their posterior 
part, but much more pointed in front than in the previously 
described Falconiformes. O. C. 1821 0. 


D. 182. Two parts of the brain of a Vulture (Vultur) in 
transverse section. The upper specimen is the anterior 
extremity of the cerebrum, seen from behind. In the 
lower specimen the section has also been made through 
the hemispheres, but somewhat further back, just in front 
of the optic chiasma, through the anterior commissure. 
The section surface faces to the front ; it shows clearly the 
position and relations of the anterior commissure, as well 
as the lateral ventricles, corpora striata, and pallium. | 

0.0. 1321p, 


NERVOUS SYSTEM.—VERTEBRATA, 137 


CORACIIFORMES 


D.183. The brain of a Condor (Sarcorhamphus gryphus). The 
hemispheres are much narrower and longer than in the 
Falconiformes. They extend backwards so as nearly to 
cover the optic lobes. The cerebellum and a great part of 
the left hemisphere have been removed exposing the left 
optic lobe and thalamus and the tectal commissure. 

O. C. 1821 N. 


PASSERIFORMES. 


D.184. The brain of a Touraco ( Zuracus sp.). This specimen 
is not well preserved, but shows that the hemispheres are 
globular and very moderate in size, extending back only 
over the anterior third of the optic lobes. The latter are 
somewhat exceptionally large. QO. C. 1321 4. 


D. 185. The brain of a Crowned Pigeon (Goura coronata). This 
specimen differs little from the last. The hemispheres are 
small and globular. They do not cover any part of the 
well-developed optic lobes. O. C. 1321 F. 


D.186. A cast of the cranial cavity of a Solitaire (Pezophaps 
solitarius), giving without doubt a trustworthy representation 
of the brain. The hemispheres are of moderate size with 
but slight indications of dorsal longitudinal furrows. They 
are widely separated mesially, especially in their posterior 
parts, and extend back over the anterior half of the optic 
lobes. The latter are well developed and strongly depressed 
towards the ventral surface. The cerebellum is of some 
size; its peduncles lie about midway between the anterior 
and posterior extremities. In front it extends between the 
hinder ends of the hemispheres. The hypophysis is small 
and narrow. 


‘D. 187. The brain of a Lyre-bird (Menura ated): The hemi- 
spheres are of very large size. The area between each dorsal 
longitudinal fissure and the mid-line is strongly developed 
somewhat as in the Owl (D.176). But instead of 
the hemispheres being short, as in that case, they are re- 


138 PHYSIOLOGICAL SERIES. 


markably long—the distance between the olfactory bulbs ; 
and the chiasma being very considerable, and the hinder ~ 
parts being prolonged backwards over the entire dorsal i“ 
surface of the optic lobes. As these parts are also very a 
deep dorso-ventrally the optic lobes are more depressed 
than usual, and lie entirely upon the ventral surface. a 


O. C. 18211. 


~ D.188. The brain of a Bower-bird (Ptylonorhynchus violaceus). 
The hemispheres are well developed, and completely cover 
the dorsal surface of the optic lobes. They are relatively 
broader and rounder than in the preceding specimen. No 
furrows are visible upon their surface. The cerebellum is _ 
~ comparatively small. 0. C. 132114. — 


MAMMALIA. 
Orper MONOTREMATA. 


Family OrniTHORHYNCHIDA. 


D. 189. The brain of a Duck-billed Platypus (Ornithorhynchus 
anatinus); also a right cerebral hemisphere, dissected to 
show the fascia dentata in the mesial wall. : 

This brain, in common with that of the Spiny Anteater, — 
exhibits in the relative proportions of its various constituent 
parts and in their degree of histological differentiation un- — 
mistakeable evidence of its conformity to the mammalian — 
type. But, on the other hand, the structural plan of several — 
important regions of the brain (notably of the cerebral — 
commissures and the neighbouring parts) differs in a very _ 
pronounced manner from that which obtains elsewhere — 
among mammals (excluding the Marsupials in regard to — 
certain of these features). It is significant that the general 
arrangement of the “commissural region,” which is so — 
peculiar in the Monotremes, essentially agrees with the — 
structural plan which is common to most non-mammalian — 
vertebrates. 3 

Many of these peculiarities can be satisfactorily studied — 
only by histological examination, and hence do not come — 


NERVOUS SYSTEM.—VERTEBRATA. 139 


within the scope of this account, but others may be appre- 
ciated by the naked eye even in specimens so imperfect as 
these. 

The elliptical olfactory bulb (figs. 34, 35, 36, and 37) 
projects well beyond the anterior end of each cerebral hemi- 
sphere, and appears to have a pointed anterior pole. This 
is due to the fact that the true olfactory nerves are collected 
into a compact bundle (compare specimen 13801 [O. ©.]), 
which is inserted into the anterior pole of the olfactory bulb 
(fig. 35). Such an arrangement is commonly found among 


Fig. 34. (Nat. size.) 


aN CER. HEM. 


Fig. 35. (Nat. size.) 


PYR.L._ : 
OLF. TUBER-4...7-| 


Tuser.V. ‘Ly 


the Sauropsida and Ichthyopsida, and occurs nowhere else 
in the Mammalia, not even in the Spiny Anteater. The 
lateral wall of the olfactory bulb is peculiar in being deeply 
invaginated so as to practically obliterate the olfactory 
ventricle. On the left bulb, an oblique furrow indicates 
the situation of this invagination (fig. 34). 

The pyriform lobe is seen upon the ventral surface of the 
hemisphere (fig. 35) as a very narrow, sinuous band pro- 
longed backward from the peduncle of the olfactory bulb. 
In the separated hemisphere (fig. 36) its posterior extremity 


140 


PHYSIOLOGICAL SERIES. 


is seen to extend on to the mesial surface of the hemisphere, — 
where it expands to form a pyriform tubercle, which is 
placed immediately below the “tail” of the hippocampus 
(fascia dentata). The pyriform lobe is separated from the 
rest of the “pallium” by an exceptionally deep rhinal fissure, _ 
which is seen in the specimen (fig. 35) as a mere line bi 4 
the ventral surface. 

To the mesial side of the anterior half of the pyriform 
lobe there is a deep endorhinal fissure separating it from — 


Fig. 36. (Nat. size.) 


Fig. 37. (Nat. size.) 


an elliptical projection of peculiar cortex, commonly known ” 
as the tuberculum olfactorium. The presence of a definite 
endorhinal fissure is peculiar to the Monotremes; in other 
mammals there is merely a shallow furrow in the corre= | 
sponding situation lodging the compact (external) olfactory — 
tract. In the Monotremes there is no such compact tract, 
because the fibres which proceed from the olfactory bulb — 
to the pyriform lobe are scattered diffusely over the surface 
of the latter. 

In comparison with the brains of most other mammals #4 
will be found that these regions of the brain—olfactorjeall 
bulb, olfactory tubercle, and pyriform lobe—are relatively — 


NERVOUS SYSTEM.—VERTEBRATA. 14] 


small in the Platypus. This fact, which is especially note- 
worthy in a lowly-organised mammal, is readily explained 
by the lessened importance and value of the sense of smell 
to an animal whose active life is chiefly aquatic. 

The optic and oculo-motor nerves and the associated 
parts of the brain are exceedingly small, because the sense 
of sight is of limited value to an animal which spends much 
of its time in dark burrows. Under such circumstances 
the sense of touch is a much more serviceable guide, and 
hence it is not surprising to find the organs of this sense 
highly developed. The chief tactile organ is the broadly 
expanded snout, covered with an extremely delicate soft 
skin.. The latter is most richly supplied with numerous 
branches of the trigeminal nerve (see specimens 1380 H 
and 13801 [O. C.]), which terminate in peculiarly modified 
end-organs (Wilson & Martin, Proc. Linn. Soc. N.S.W. 
1895, p. 660). 

The enormous development of the fifth nerves exercises 
a most marked influence upon the configuration of the 
region of the pons Varolii and medulla oblongata. The 
sensory nerves coming from the snout are inserted (wholly 
in front of the pons) as two large strands on each side—a 
mesial nerve coming from the maxillary region (representing 
the conjoint ophthalmic and superior maxillary divisions of 
Human Anatomy), and a lateral nerve from the mandibular 
_ region, At their insertion a huge mass of nerve-cells is 
developed as a receptive organ, so as to produce a great 
swelling, the tuberculum quinti, upon each side of the 
ventral surface of the hind-brain (fig. 35). The small 
narrow band of pontine fibres is stretched across this pro- 
minence at the situation of its greatest breadth. In the 
caudal direction, the tuberculum quinti tapers to a point 
upon the lateral aspect of the upper part of the spinal cord. 
The post-pontal part of the tuberculum quinti corresponds 
to the tubercle of Rolando in the brain of other mammals. 

The motor root of the fifth nerve emerges on the deep 
aspect of the cephalic projection of the tuberculum quinti 
and, after extending around the mesial edge of the latter, 
extends transversely outward in front of the pons to join 
the mandibular root, Owen committed the peculiar error 


| 


142 PHYSIOLOGICAL SERIES. 


of mistaking it for the pons. On the left side of the 
specimen (fig. 35, v.M.) this motor root has been cut short. — 
The other cranial nerves conform to the usual mammalian 
plan, which is seen to better advantage in the brains * 7 
other animals (vide infra). > 
Perhaps the most inexplicable feature of the brain of then 
Platypus (as also of the Spiny Anteater) is the relatively 
large size of the so-called “ palliam ” of the cerebral hemi- — 
sphere. The term “ pallium” is at the present time used 
in a perplexing variety of ways by different writers, and — 
all of these applications of the term are strangely at vazlanil 4 
with that which Reichert intended to convey when he in- — 
troduced the word “mantle” or “ pallium.” There are 
three distinct varieties of mantle in all mammalian hemi-— 
spheres:—a basal pallium or pyriform lobe, a marginal — 
pallium or hippocampus, and a more variable area inter- — 
calated between these two regions, which has hitherto — 
received no exclusive title. To indicate this region I shall 
employ the distinctive, if hybrid, name “ neopallium” *. 
Among lowly-organised mammals there is, according to 
Dubois, a more or less intimate relationship between the — 
size of this cortical area and the extent of the. variou 
sensory surfaces of the body. In the case of the Piatra 
in which the visual apparatus is very poorly represented — 
and the auditory nerve is not remarkable for its large — 
size, one naturally looks to the enormous trigeminal nerve — 
for the explanation of the large neopallium. But that this — 
cannot be regarded as the full explanation is shown by the 
still more obtrusive greatness of the neopallium in the — 
Spiny Anteater, in which the trigeminal nerves are not 
extraordinarily large and none of the other cranial nerves — 
attain to exceptionally great dimensions, As one is 
naturally loathe to explain this large neopallium as ana-_ 
logous to that of the Primates, in which the neop: m 
becomes enlarged and elaborated out of all proportion t 
the extent of the sensory areas in association with the 
development of the higher psychical faculties, a satisfactory — 


* Journ, Anat, & Phys, 1901, p. 431. 


NERVOUS SYSTEM.—VERTEBRATA.,. 143 


explanation of the large size of the neopallium in the 
Monotremes (and in Tachyglossus more especially) cannot 
be offered at present. Professor C. J. Martin has shown that 
stimulation of the cerebral cortex of Platypus in the situa- 
tions shown in figures 34 and 37 gives rise to definite 
muscular actions: thus stimulation of the “ arm-area” 
(1) produces a digging movement in the opposite fore- 
limb, of areas (2) and (8) produces movements of the 
eyelids, and of (4) retraction of the head (Journ. of Phys. 
vol. xxiii. 1898, p. 383). This shows that physiologically 
the cerebral cortex of Platypus reacts in a manner analogous 
to that of lowly placental mammals. 

In striking contrast to the relatively large size of the 
cerebral cortex, is the smallness of the efferent tracts which 
pass from it to other regions of the central nervous system. 
The pes pedunculi and the pyramidal tract are so insigni- 
ficant, that they give rise to no projection upon the surface. 
of the brain. The pyramidal decussation is very diffuse. 

With the exception of the hippocampal and rhinal 
fissures, which subdivide the pallium into its three funda- 
mental constituent parts, the hemisphere of the Platypus is 
devoid of true fissures or sulci. The general smoothness 
of the neopallium is, however, disturbed by depressions for 
the bony capsules of the floccular lobes of the cerebellum 
_ (compare figs. 34 & 35) and by aseries of vascular furrows. 
The most noteworthy of the latter consist of-a series of 
large shallow channels produced by very large veins, which 
converge towards the apex of the hemisphere (fig. 37). 
The large size of these veins is due to the fact that the 
longitudinal venous sinus is practically, if not completely, 
obliterated (because the falx cerebri is bony), and the 
general cerebral veins enlarge to replace them. The 
spurious resemblance of the brain of Platypus to the avian 
type is thus considerably accentuated, because in many 
birds an analogous arrangement of the cerebral veins is 
found. — 

Several well-marked transverse furrows are produced by 
the branches of the middle and anterior cerebral arteries. 

The cerebellum of Ornithorhynchus is a slightly simplified 


144 PHYSIOLOGICAL SERIES. 


form of that of Tachyglossus (vide infra). The only marked — 
difference, and that of no systematic significance, is the 
projection of the floccular lobes [which are lacking in this 
specimen]: in the Spiny Anteater’s brain they are flattened 
and sessile. 4 
In the separated cerebral hemisphere (fig. 36) part of the 
overhanging neopallium has been removed in order to 
expose the fascia dentata lying in the mesial wall of the a 
hemisphere. . 
The peculiar position of this specialised fringe of the 
hippocampus and its relations to the commissures ee 4 
with the condition seen to much better advantage in the — 
specimen of the Spiny Anteater’s hemisphere (D.191). In — 
the Platypus, however, the caudo-ventral part of the hippo- 
campal are dwindles to much more insignificant proportions — 
than is the case in Tachyglossus. 3s 
It thus happens that that (caudo-ventral) part of the are, 
which alone persists in an undisturbed condition in the — 
Eutherian brain, is here an exceedingly diminutive tail-_ 
like appendage of the chief mass of the hippocampus, which — 
is placed further forward in the hemisphere on the dorsal 
aspect of the commissures. It is, moreover, a very signi-— 
ficant fact that this, the most bulky part of the hippo- 
campus in the Monotreme, occupies this cephalic (anterior) — 
position in the mesial wall, which its representative in the — 
Sauropsida and many Ichthyopsida occupies. 4 
Presented by Prof. G. Elliot Smith. — 
Elliot Smith, Jour. Anat. & Phys., vol. xxxiii. 1899, p. 310. 
D. 190. A cast of the cranial cavity of a Duck-billed Platy 0 ~ 
(Ornithorhynchus anatinus). j 
This shows the actual size and shape (when viewed from — 
the dorsal aspect) of the brain of Platypus. The configu- 
ration of the base of the brain cannot be accurately es, | 
because the casts of the huge maxillary parts of the t 
geminal nerve are superposed. The most prominent pa i ’ 
of the mesial ridge between these nerves indicates the si 
and shape of the pituitary body. 
Gervais, Nouv. Arch, Mus., t. v. 1869, p. 248. 


NERVOUS SYSTEM.—VERTEBRATA, 145 


Family Ecurpnip~z. 


D. 191. The brain of a Spiny Anteater (Tachyglossus [ Echidna] 
aculeatus), in which the greater part of the lateral and 
dorsal walls of the left cerebral hemisphere have been dis- 
sected away so as to expose the hippocampus in the lateral 
ventricle. 

In spite of the marked contrast between the general 
appearance of this brain and that of the Platypus, there is 
the closest structural agreement in most of the essential 
features of the two. 

The most obtrusive feature of this brain is the relatively 
enormous development of the cerebral hemispheres, which 
are much larger, both actually and relatively, than those 
of the Platypus. In addition the extent of the cortex is 
very considerably increased by numerous deep sulci. The 
meaning of this large neopallium is quite incomprehensible. 
The factors which the study of other mammalian brains 
has shown to be the determinants of the extent of the 
cortex, fail completely to explain how it is that a sma'l 
animal of the lowliest status in the mammalian series comes 
to possess this large cortical apparatus. In other small, 
terrestrial, insect-eating mammals such as the Pangolins 
and the Anteaters, and in the fossorial Bandicoots, Hed ge- 
hogs, and Armadillos, we find highly macrosmatic brains 
with small neopallia: and yet in Tachyglossus, whose mode 

of life is not dissimilar to many of these mammals, we 
find alongside the large olfactory bulb and great pyriform 
Jobe of the highly macrosmatic brain a huge complicated 
neopallium. 

In the remarks concerning the brain of the Platypus 
(D. 189), it was tentatively suggested that the enormous 
development of the trigeminal nerves might explain to some 
extent the large size of the receptive organ and “storehouse,” 
so to speak, for tactile impressions. But sucha suggestion 
does not help us in the case of the Spiny Anteater, because 
the trigeminal nerves are much smaller than they are in the 
Platypus, and yet the neopallium is much larger. The 
eyes and optic tracts are still very small, as in the Platypus, 
so that another factor in determining a large pallial area is 
lacking. . 

VOL. II, L 


146 


chief determinants of the extent of the neopallium. 


PHYSIOLOGICAL SERIES, 


The auditory nerves are indeed large, but the me al 
geniculate body, which it is customary to regard as_ an 
integral part of the cortical acoustic path, cannot even be — 
recognised as a projection behind the optic thalamus lon 
specimen D, 193] ; ; so that it is unlikely that the cortical — 
auditory tract is sufficiently largely developed to exple ing 
the large neopallium. Nor is the extent of the surface 0 
the body, the tactile acuteness of which can hardly be 
heightened by its covering of spines, sufficient to ayaa 
large tactile area in the cortex. Yet these are the factors” 
which in lowly organised mammals are supposed to be the] 


b= 


Fig. 38. (Nat. size.) © - 
OLF. BULB_ < 


Dubois has clearly demonstrated that among the more — 
lowly organised Mammalia the size of the cerebral ie 
varies with the extent of the various sensory curhenee 
the body, and that the lowlier the position of the cre; : 
in the Mammalian phylum the smaller this cortical ron . 
sentation becomes. But in the Spiny Anteater all these 
generalisations are upset: for this small animal, with n 
specially acute sense except that of smell—and a high 
degree of macrosmatism is usually associated with a small — 
neopallium—occupies the lowliest status in the Mammalian — 
hierarchy, and hence should have the feeblest cortical 
presentation for its sense-organs. f 

The cerebral hemispheres are short and broad (fig. 38). q 
Their growth in the antero-posterior direction appears to” ¢ 


NERVOUS SYSTEM.—VERTEBRATA, 147 


have been restrained by the resistance of the cranium, and 
they have extended chiefly in the lateral direction. This 
lateral extension has been carried to an extreme degree in 
the postero-ventral region of the neopallium, which has 
grown downward and then mesially so as to produce a 
peculiar bending of the pyriform lobe (fig. 39). 


Fig. 39. (Nat. size.) 


In all ant-eating mammals the snout is prolonged to 
form a long tubular structure which lodges the vermiform 
tongue. This elongation of the skull may involve the 
cranial cavity, and in that case the brain assumes an elon- 
gated form in adaptation to the shape of its bony case. 
The Great Anteater (Myrmecophaga, D. 282) and the Aard- 
vark (Orycteropus, D. 288) afford instances of this, On the 
other hand, the elongation may be restricted to the beak, 
and the brain then becomes packed away, so to speak, in 
a short cranial cavity lying entirely behind the maxiilary 
region. The brain of the Pangolin (Manis, D. 287) and that 
under consideration exemplify this type, in which the brain 
develops in a cavity which restricts its antero-posterior 
growth. The hemispheres thus expand chiefly in the lateral 
direction, and the restriction to elongation expresses itself 
in a series of transverse sulci, the disposition of which is 
re-described in the account of the next specimen. 

The olfactory bulb is a large, flattened, foot-like mass 
partly overlapped by the anterior pole of the hemispnere. 

L 2 


148 


- 


PHYSIOLOGICAL SERIES, 


* 


It rests in the cranium upon a broad cribriform plate, 

through the namerous foramina of which small bundles of — 
olfactory nerve-fibres proceed to the ventral surface of the — 
olfactory bulb. A short peduncle connects the bulb to the 
cephalic extremity of the pyriform lobe, The latter is a — 
peculiar, sinuously curved band of cortex, which extends 
along the whole length of the base of the hemispheres. 
The extraordinarily twisted form of the pyriform lobe is’ 
quite distinctive of this brain. This is seen to advan tage c 
on the left side, in which the neopallium has in great p 

been removed and the pyriform lobe left (fig. 40). 


Fig. 40. (Nat. size.) 


The olfactory bulb slightly overlaps the tuberculum 
olfactorium posteriorly. The olfactory tubercles are = 4 
Jarge, bat are so placed in the floor of a deep depressiot 
the prominent lips of which are formed by the pyrifoll 
lobes, that their greatness is not apparent. + 
Behind this fossa the latter almost meet, so much are 
they bent towards the mesial plane (fig. 39). In the 7 2p 
cleft between them the delicate optic nerves may be seems 
Emerging between the posterior part of the py orm 
lobes and the pons Varolii are the ribbon-like iipetatal oe 
nerves. It is a peculiarity of the Monotremata that the 
trigeminal nerves are inserted into the brain-stem wholly 
in front of the pons. ‘4 
Note the large size of the auditory nerve, which is placed 
immediately behind the point where the pontine fibre: 
enter the cerebelium. ‘The other cranial nerves call for no 
special comment, ; 
In spite of the great size of the pallium, the pyramic 1 al 
tracts are so insignificant that they form no prominence on 


NERVOUS SYSTEM.—VERTEBRATA., 149 


the surface. The roots of the hypoglossal nerve, however, 
serve to indicate the lateral limit of each pyramid. There 
is a diffuse crossing of the fibres of the pyramids, instead 
of the compact decussations found in most mammals. 

The trapezoid body, which is such an obtrusive feature 
of most mammalian brains, is not recognisable as such by 
the naked eye in the Monotremes. 

The cerebellum is noteworthy for the small dimensions 
of its lateral parts, and from the fact that its structural 
plan cannot be certainly brought into harmony with that 
which is common to all the Meta- and Eutheria. It, how- 
ever, closely agrees with that of the Platypus. But there 
is a large sessile floccular lobe, in marked contrast to the 
pedunculated, encapsuled flocculus of the Platypus. 

In the left cerebral hemisphere the lateral ventricle has 
been opened so as to expose the hippocampus. The latter 
presents an appearance which is characteristic of the 
Monotremes. For, although the hippocampus also extends 
through the whole length of the lateral ventricle in the 
Marsupials, as it does here, it is only in the Monotremes 
that we find the largest and plumpest part of the hippo- 
campal arc occupying the dorsal and cephalic position. 
The caudo-ventral part of the hippocampal are rapidly 
tapers to a point in Tachyglossus, and even to a more 
marked degree in Ornithorhynchus. O. C. 13823*. 

Ziehen, Semon’s Forschunygsreise, Jena. Denkschr. Bd. vi. 
1897, p. 4. 


D.192. The left cerebral hemisphere of a Spiny Anteater ( Tachy- 
glossus [Echidna] aculeatus): also a coronal section of 
another left hemisphere. 

A rough area in the centre of the mesial surface of the 
hemisphere indicates the place from which the optic 
thalamus was detached (fig. 41). In front of this area the 
elliptical sections of two commissural bands are to be seen 
The lower or ventral commissure (comM.v.) is much the 
larger of the two and contains nerve-fibres corresponding to 
the anterior commissure of other mammalian brains. But, 
as the coronal section (fig. 42) [which passes through the 
two commissures] clearly shows, the ventral commissure 


150 PHYSIOLOGICAL SERIES. 


* 


has a much wider distribution than the anterior com- 
missure of most Eutheria, for it connects the whole of — 
the two cerebral hemispheres, excepting the hippocampal 
formations only. Now in all Eutheria part of the neopal- 
lium is connected to the other hemisphere by means of the 
corpus callosum, so that the ventral commissure of the Spiny 
Anteater represents not only the anterior commissure, but — 
also the corpus callosum of the Eutheria. , 


Fig. 41. (Nat. size.) 


FASC . DENT. COMM.D. 


a! 


OLF. BULB 


PYR.L. 


Fig. 42. (Nat. size.) 


The dorsal or hippocampal commissure (comM.D.) is 
much smaller. It was erroneously believed by Flower 
(Phil. Trans. 1865) to represent the corpus callosum ; but 
as it is wholly derived from the hippocampal formation — 
by means of the fornix, it cannot be strictly regarded as — 
the representative of a commissure (the corpus callosum) — 
which is derived from cortical areas (neopallium) other than — 
the hippocampus (Elliot Smith, Proc. Linn. Soc. N.S. wa 
vol. ix. 1895, p. 635) *. 


* This view, which was originally stated by Owen in 1837, and conclu- 
sively demonstrated by modern methods by Symington (Journ. Asad & 
Phys. 1892), has recently been called in question by several writers, without 
a tittle of evidence to justify their irrational refusal to recognise a fact which — 
is unquestionable and so easily demonstrable. 


NERVOUS SYSTEM.—VERTEBRATA. TSI 


Upon the upper surface of the dorsal commissure there 
is a narrow band of cortical substance, which is obviously 
the cephalic prolongation of the fascia dentata. A study 
of the mesial surface of the hemisphere shows this at a 
glance, and an examination of the coronal section confirms 
the opinion that the structure in question is really the 
fascia dentata. 

The caudal portion of this structure may be seen (behind 
the rough area on the corpus striatum) occupying the 
position in which we are accustomed to look for it in 
the Hutherian brain. It appears to be depressed below the 
level of the rest of the surface, because the neopallium 
tends to bulge over the marginal hippocampal region. 
The clearly-defined hippocampal fissure separates the fascia 
dentata from the neopallium. But, unlike the arrangement 
found in the higher mammals, the fascia dentata (with the 
hippocampal fissure bounding it on its dorsal or peripheral 
side) extends far forward above the dorsal commissure. 
This explains the presence of the hippocampal formation in 
the peculiar position in which it is seen in the coronal 
section. There (fig. 42) we see the fibres of the small 
dorsal commissure spreading out to form the ventricular 
covering (or alveus) of the hippocampus, from which they 
are wholly derived. By means of this section, it is easy to 
correlate the appearance of the ventricular surface of the 
hippocampus (seen in the last specimen, fig. 40) with the 
mesial distribution of the fascia dentata (which is merely a 
specialised marginal fringe of the hippocampal formation) 
in the hemisphere of this specimen. It is now also possible 
to understand how it is that the dorsal commissure is 
derived from the hippocampus. (Hlliot Smith, Journ. 
Anat. & Phys. vol. xxxii. 1897, p. 32.) 

The hippocampal fissure extends only a short distance 
beyond (2. e. in front of) the dorsal commissure, so that the 
fascia dentata (of which it forms the uorsal boundary) 
appears [in a spirit-preserved specimen] to blend with the 
neopallium above it, and also with the precommissural area 
below it. Ina fresh brain the fascia dentata may, however, 
be readily distinguished by its colour, and may be traced 
forward into close proximity to the olfactory peduncle. 


152 


PHYSIOLOGICAL SERIES. 


[In this specimen the olfactory bulb has been removed, and 
the irregular cut surface of its peduncle can be seen upon 
the ventral surface of the anterior pole of the hemisphere. | 

At the concave margin of the postcommissural part of 
the fascia dentata there is a strand of white fibres—the 
fimbria or fornix. This consists of a group of fibres 
collected from or going to the hippocampus. In all 
Marsupials and placental mammals the fimbria projects as 
a prominent crest; but in both Monotremes it consists 
merely of a slight thickening of the edge of the alveus, 
which does not project to form a ridge. Anteriorly 
its fibres appear in this specimen to pass bodily into 
the dorsal commissure, but many of them do not do 
so. A considerable proportion of the fibres of the 
fornix bend downward behind the ventral commissure as a 
compact bundle (the anterior pillar or column of the 
fornix), which enters the optic thalamus and proceeds 
toward the corpus mammillare: others again enter the 
precommissural area, and are known as the precommissural 
fibres (of Huxley). These fibres can be satisfactorily seen 
only in fresh specimens or in histological preparations 
(compare Journ. of Anat. & Phys. vol. xxxii. fig. 6, p. 36). 

In this specimen the fissures and sulci may be studied 
with advantage. 

The rhinal fissure is ockreonitamaly deep in the Mono- 
tremes, and especially in Tachyglossus, as the coronal section 
(fig. 42) shows. ,It pursues a very tortuous course on the 
lateral, ventral, and caudo-mesial surfaces of the hemisphere. 


Just before it leaves the lateral to reach the basal surface a 
of the hemisphere, it gives off a short horizontal branch as 


deep as itself. This branch is probably produced by factors 
analogous to those which cause the so-called ‘“ Sylvian 


fissure” in other mammals ; it is, in other words, a kink a 
produced by the downward growth of the neopallium 


behind it, and, as such, has a claim to be called the © f 
“Sylvian fissure” equal to that of, say, the Cat’s brain. — 


At the same time there is no reason for regarding it as 


a strict homologue of the similarly-named fissure of other 
mammals. The same term is used simply as a matter of con- 
venience in the same way that it is applied to the Edentate, 


NERVOUS SYSTEM.—VERTEBRATA. 153 


Carnivore, Ungulate, and Primate brain respectively, in 
which no exact correspondence exists. We know-from the 
distribution of the claustrum that the exact cortical areas 
from which the lips of the Sylvian fissure are formed in 
different higher Orders [or even Suborders and Families— 
compare the Cynoid, Arctoid, and Pinniped Carnivores and 
the progressive modifications in their various families] are 
not strictly homologous in different mammals ; so that if 
we use the term ‘‘ Sylvian” for all these various types of 
fissure, we are also justified in using it for the fissure of the 
Spiny Anteater’s brain, which is clearly caused by analo- 
gous factors of growth, without thereby implying any 
strict homology in the cortical areas which form its lips. 
It will avoid much confusion, however, if we call this 
sulcus (fig. 43, syL.F.) “ pseudosylvian.” 


Fig. 43. (Nat. size.) 


OLF. BULB. 


elaoo-) 


The sulci of the neopallium of the Spiny Anteater. vary 
very considerably in different individuals, and there is no 
clue to indicate whether any of them should be regarded 
as the representative of a sulcus of other mammalian brains. 
On the other hand, the arrangement of the sulci suggests 
that they might be due to purely mechanical factors 
operating in an uniformly growing pallium, the longi- 
tudinal expansion of which is restricted. 

The most constant of all the sulci are three distinguished 
as a, 8, and ¥ in the diagrams (figs. 38 and 43). 

[The figures (38, 39, and 43) illustrating this account are 
drawn from the preceding specimen (D. 191) in order that 
both hemispheres might be represented. The description, 
however, applies more especially to this specimen (D. 192), 


154 


PHYSIOLOGICAL SERIES. 


in order that the arrangement of the sulci on the cranial — 
surface may be compared with ‘that of the mesial surface 
(fig. 41).] 

The suleus « begins immediately behind the pseudo- 
sylvian, and pursues a course upward, 7. e. mesially, to 
terminate just in front of the caudo-mesial angle of the 
dorsal surface. F 

The sulcus y is the deepest and most constant of the — 
radiating sulci on the mesial surface of the hemisphere, — 
It appears to spring from the hippocampal fissure at a 
short distance behind the supracommissural exposed portion _ 


of the fascia dentata. In most brains it crosses the dorsal 


edge and joins the sulcus 8 on the dorsal surface. The latter 
pursues a course for a variable distance in front and parallel 


to the suleus a. Its mode of termination is variable. In 


this specimen it bends forward opposite the mid-point of 
the sulcus a, and, after a short oblique course, ends in a 
bifid extremity. In the other specimen (D.191) it behaves 
in a different manner (fig. 43, 8). In specimen D.192 — 
there is a short sulcus below 8, which may be regarded as — 


a part of the same sulcus, as the two are commonly united 


as in specimen D. 191. ; 
On the dorsal surface of the hemisphere there are 
commonly two oblique or sagittal sulci (fig. 38, 8 and e), — 
and behind them a short sulcus y, parallel to # and £. 
Behind 8 there are two sulci, { and », and behind these 
again two others, o and p. . 
The greater part of the hemisphere is thus divided intoa _ 


series of slightly oblique transverse bands by the series of _ 
sulci, y, 8, a, €+, and o+p. The shallow sulcus 7 on ~ 


the mesial surface (fig. 41) is placed above and parallel to 
the anterior part of the hippocampal fissure *. , 

It is very significant that the most constant and primitive 
sulci of the Meta- and Eutherian neopallium, such as the — 
calearine (splenial), orbital (presylvian), and suprasylvian — 
sulci, are absent. This is one of the many manifestations — 
of the great gap which separates the Monotremes from all — 
other mammals. Presented by Prof. G. Elliot Smith. 

Waldeyer (Review only), Merkel and Bonnet’s Ergeb- — 


* The indicating letter has been omitted in the figure, 


NERVOUS SYSTEM.—VERTEBRATA. 155 


nisse, Bd. viii. 1898, p. 372. (The more recent work by 
Bela Haller [ Morph. Jahrb. 1900, p. 463] is quite mis- 
leading.) 

D.193. The left cerebral hemisphere of a Spiny Anteater (Tachy- 
glossus | Echidna] aculeatus), dissected to show the hippo- 
campus in the lateral ventricle. 

In this specimen parts of the mesial wall have heen torn 
asunder, and as a result the exact shape of the hippocampus 
can be seen to better advantage than in specimen D. 191. 
The latter specimen shows the same structures, however, 
in situ. . 

D.194. A cast of the cranial cavity of a Spiny Anteater (Tachy- 
glossus aculeatus). 

Gervais, Nouv. Arch. d. Mus., t. v. 1870, p. 247. 


D.195. The optic thalami, mid-brain, cerebellum, and medulla 
oblongata of a Spiny Anteater (Zachyglossus [| Echidna] 
aculeatus). 

Fig. 44. (x 2.) 


S, OPT. THAL. 


PINEAL. _ 


. ANT. QUAD. CORP 


-POST. QUAD. CORP 


This specimen was prepared by the late Sir William 
(then Professor) Flower (see Proc. Zool. Soc. 1864, p. 18) 
to demonstrate the corpora quadrigemiina, concerning 
the existence of the posterior pair of which some doubt 
had been raised by the writings of his predecessor, 
Sir Richard Owen. 

On the dorsal aspect (fig. 44) the small oval masses of 
the optic thalami will be observed in front, separated by 


156 


PHYSIOLOGICAL SERIES. 


. 


the narrow mesial slit-like third ventricle. At its caudal 
extremity a blunt rounded sac is found representing the 
pineal body, and in front of this the ganglion habenule 
and teenia thalami are found on each side of the ventricle, as 
in all other vertebrate brains. Perhaps the most significant 
feature of this specimen is the absence of any protuberance 


corresponding to the mesial geniculate body. In this a 


respect the Monotreme brain differs most markedly from 
that of all other mammals. The absence of any markedly 
projecting lateral geniculate body is not so peculiar, not 
only because this body is not prominent among the lowlier 
mammals, but also because the visual apparatus, of which 
it forms an important part, is poorly developed in the 
Monotremes. 

The quadrigeminal bodies are comparatively small and 
flat as comparedwith those of other mammals. 

The pons Varolii is prolonged into a forwardly-projecting 
process or rostrum in the mesial plane, probably because 
the nuclei pontis are scattered throughout a much greater 
antero-posterior extent than the narrow lateral parts of the 
pons occupy. This peculiar rostrum is distinctive of the 
Monotremes, since it is also found in the Platypus. Im- 
mediately in front of the rostrum note the interpeduncular 
body, one of the oldest parts of the brain in the phylogenetic 
sense. The rounded knob formed by the corpora mam- 
inillaria, the oculo-motor nerves, and the delicate optic 
tracts conform to the usual mammalian type. 

In comparison with the corresponding organ in other 
mammals, the cerebellum in the Monotremes presents — 
features so peculiar that no exact comparisons with that of 
other mammals can be instituted with any degree of 
certainty. The fissura prima (preclivalis of Human — 
Anatomy) is apparently placed very far back, so that the 
greater part of the cerebellum, including the whole of the — 
anterior and the greater part of the dorsal surface, corre- 
sponds to the anterior lobe of other mammals (the combined 
lobus centralis and lobus culminis of Human Anatomy). 
Thus the whole of the postclival region, which in the higher 
mammals becomes so greatly expanded that it forms the bulk 
of the organ, becomes relegated to the caudo-ventral region 


NERVOUS SYSTEM.—VERTEBRATA. 157 


of the cerebellum and is a narrow insignificant strip, which 
is expanded laterally only to a very slight degree. ‘The 
region of the nodulus agrees with that of other mammals. 
The floccular lobe is sessile in Tachyglossus, but projects for 
a considerable distance in Ormthorhynchus. It is a simply 
foliated appendage, and is not divisible into flocculus and 
parafloceulus ; nor can a ventral and dorsal segment be 
recognised as in other mammals, although the radiating 
feather-like arrangement of the folia in Tachyglossus is a 
simplified form of the two-layered type of paraflocculus. 

The cerebellum differs in a most marked manner from 
that of other mammals, and seems to be a highly specialised 
modification of the primitive mammalian type. Its most 
significant feature is the relatively small size of its lateral 
parts. Seeing that most of its exposed part probably 
represents the anterior lobe of the mammalian cerebellum, 
in which there is no clear line of demarcation between 
vermis and lateral hemispheres, such distinctions are also 
lacking in the Monotreme. QO. C. 1823**. 

Ziehen, Semon’s Forschungsreise, Jena. Denkschr. 1897, 
p. 23. 


D.196. The cranial cast of a.so-called “ Proechidna” (Proechidna 
The brain is distinctly larger than it is in 7. aculeatus ; 

the olfactory bulbs project much further beyond the hemi- 
spheres ; the hemispheres are proportionately much longer 
than in the other species and are extremely large and 


richly convoluted for so lowly a mammal. 
Gervais, Nouv. Arch. Mus., t. v. 1869, pl. xiv. 


Oxvnr MARSUPIALIA, 
Suborder POLYPROTODONTIA. * 


Family Dasyvuripz. 


D.197. The brain of a Tasmanian Devil (Sarcophilus [ Dasyurus] 
ursinus) (), in which the left cerebral hemisphere has 
been separated from the rest of the brain. 


158 


PHYSIOLOGICAL SERIES. 


This is one of the simplest and most generalised types of — 
the mammalian brain, and presents a marked contrast — 
to the specialised Monotreme organ. 

Its most obtrusive feature is the relatively enormous size _ 
of the olfactory bulbs, which are attached by short thick — 
peduncles to the front of the cerebral hemispheres. In — 
the great majority of mammals the olfactory apparatus — 
is largely developed ; and in the case of a terrestrial, offal-_ 
eating animal, like Sarcophilus, the importance of the 
sense of smell becomes enormously enhanced and it becomes 4 
the dominant sense. This finds expression (asin Perameles, 
vide fig. 52) in the huge development of the olfactory 
bulb, in the large elliptical olfactory tubercle on the base of — 
the brain, ina pyriform lobe which forms a large part of 7 
ventral surface and almost half of the lateral aspect of 


Fig. 45. (Nat. size.) 


x 
SULC.ORB. / Y 


4 \ 
RN 
bee 4 ~ RAIN FP, 


PYRLL. 
OLF.TUBER. * 


hemisphere, and in a large hippocampal formation which | 
forms a considerable part of the mesial wall. ) 
This brain shows very clearly the definite connections 
which the olfactory peduncle establishes with both the 
lateral and mesial walls of the cerebral hemisphere. ice. 
the lateral aspect (fig. 45) the peduncle is dire 
continued into the pyriform lobe, and a layer of medw 
fibres upon the latter becomes collected into a definite 
bundle—the olfactory tract or so-called “ external olfactory 
root ’—which proceeds backwards in the shallow gre 
between the pyriform lobe and the olfactory tubere 
distributing fibres over the surfaces of both. The tea 
finally ends in a little nodule behind the olfactory tubercle — 
(fig. 45, *), which may be called the tubercle of the olfé 
tract [Retzius calls it the “ gyrus intermedius ”]. 


NERVOUS SYSTEM.—VERTEBRATA. 159 


A well-defined rhinal fissure begins anteriorly in the 
cleft between the olfactory bulb and the apex of the 
hemisphere, and separates the pyriform lobe from the neo- 
pallium. 

Upon the mesial surface (fig. 46) the olfactory -bulb 
may be distinctly seen to be connected by a short cylindrical 
peduncle to the precommissural area of the mesial wall. 
The tuberculum olfactorium is seen immediately below the 
latter. | 

In the caudal region of the mesial wall the fascia dentata 
and fimbria are seen presenting features such as we find in 
most mammals. The prominent, broad fimbria at once 
distinguishes this hippocampal formation from that of the 
Monotremes. 

Fig. 46. (Nat. size.) 
HIP, F. SULG. CALC. 


FASC. DENT, 
sey, 


bo 


OLF. TUBER” ‘ comm.v. 


This fimbria is seen to pursue a regular arcuate course 
upward and forward to reach a point immediately above 
the large ventral (modified anterior) commissure; and 
many of its fibres then cross the middle line in close 
relation to the upper extremity of the lamina terminalis, so 
as to form a smaller dorsal commissure, which is thus 
derived by means of the fornix (fimbria) from the hippo- 
campus. Histological examination shows that the fibres 
of this dorsal commissure are not grouped irregularly to 
form a round bundle, as in the Monotremes, but are 
compactly arranged in a crescentic form. In some 
Marsupials this dorsal commissure becomes more acutely 
bent so as to be distinctly bilaminar. Some of the fibres 
of the fimbria do not enter the dorsal commissure and are 
divided into two groups, a scattered anterior group of pre- 
commissural fibres and a posterior group—the so-called 
anterior pillar of the fornix—which proceeds behind the 
ventral commissure and passes through the optic thalamus 
toward the corpora mammillaria. 


160 


PHYSIOLOGICAL SERIES. 


The fascia dentata (like the hippocampal fissure which 
marks its peripheral boundary) proceeds upward and 
forward alongside the fimbriaas far as the dorsal commissure; 
and thenit passes forward above the dorsal commissure and 
appears to lose itself in the precommissural area immediately 
above the attachment of the olfactory peduncle. Ina | 
fresh brain (or by means of histological examination) the — 
fascia dentata may be traced forward practically into — 
continuity with the oltactory peduncle (Trans. Linn. Soe., 
Zool. ser. 2, vol. vii. 1897, pl. 15. fig. 8). The hippocampal 
fissure accompanies the fascia dentata in the greater part 
of its course, but stops just as it approaches the neighbour- 
hood of the olfactory peduncle. The mesial surface of the 
olfactory peduncle passes backward into direct continuity 
with the precommissural area, which is separated above by 
the fascia dentatafrom the neopallium. This precommissural — 
area is continuous below with the tuberculum olfactorium, 
and is bounded posteriorly by the lamina terminalis — 
containing the dorsal and ventral commissures. 

The retention in an undisturbed state of the cephalic 
portions of this hippocampal formation is the most interesting 
feature in the brain of the Marsupial. In this it agrees — 
with the Monotreme, but is the more instructive because — 
the caudal parts of the hippocampus in the Marsupial have — 
assumed the configuration which is met with in other — 
mammals, : 

The cephalic parts of the hippocampal formation are — 
retained in the Marsupial because the dorsal commissure is _ 
derived from the hippocampus, and the great non-hippo-— 
campal commissure (corpus callosum) has not yet made its 
appearance to disturb the integrity of the hippocampal are, — 

It is the absence of the corpus callosum and the 7 ‘ q 
of the supracommissural and precommissural parts of 
hippocampus undisturbed that renders the cerebral hem 
sphere in the Monotremata and Marsupialia so pander 
to the student of the higher mammalian brains, For the 
corpus callosum consists of a series of fibres at first ; 
intermingled with those of the dorsal or hippocampal = 
commissure, but distinguished from them by the fact that 
they come from a cortical area (the neopallium) other than — 


NERVOUS SYSTEM.—VERTEBRATA., 161 


the hippocampus and do not form part of the fornix. But 
as this series of neopallial fibres increases in number in 
the Eutherian brain, the corpus callosum rapidly extends 
and assumes the large dimensions which we usually associate 
with this body. As it does so it naturally stretches a 
portion of the great hippocampus (of which the fascia 
dentata forms the only part visible upon the surface), and 
the hippocampus atrophies in the region of stretching. 
Thus in all mammals possessing a corpus callosum, the 
hippocampus persists in an unchanged state only so far 
forward (or so far up) as the splenium of the corpus 
callosum, but its anterior part is represented by vestiges 
upon the upper surface of the corpus callosum and along a 
_line joining the anterior extremity of the latter to the 
olfactory peduncle. In man these vestiges together with 
some longitudinal fibres in connection with them are 
generally known as the longitudinal stric of Lancisius. 
(For a fuller elucidation of these peculiarities see Journ. 
Anat. & Phys. vol. xxxii. 1898, p. 30.) 

The precommissural area is also of interest in the 
Marsupial, in view of the fact that in most other mammals 
the upper part of the corresponding region becomes 
stretched by the growing corpus callosum to form a folium 
of the septum lucidum in each hemisphere. 

Upon the postero-superior region of the mesial wall of 
the hemisphere, there is a short arcuate sulcus running 
parallel to the hippocampal fissure. The corresponding 
sulcus in the Ungulata was named the “‘ jissura splenialis ” 
by Krueg, from its relationship to the splenium of the 
corpus callosum. There can be little doubt that this sulcus 
represents the anterior calcarine sulcus [7. e. the true 
calcarine fissure, the stem of the Y-shaped complex] in 
the human brain, and hence we may call it “ calcarine ” 
in Sarcophilus (Elliot Smith, Proc. Anat. Society, 1899) *. 


* For the demonstration of this homology compare the conditions found 
in Manis, Choleepus, Daubentonia and the other Primates. 

The most diverse views are put forward by various writers as to the 
possibility of homologising the sulci of one brain with those of another. 
Some writers attempt to institute comparisons upon a purely topographical 
basis between the cerebral sulci of brains of even different Orders of 


VOL. Il. M 


162 PHYSIOLOGICAL SERIES. 


In the smaller Dasyuride this sulcus is not present. | 
The cranial surface of the hémisphere is not quite smooth, — 
The rhinal fissure separates the pyriform lobe from the — 


Fig. 47. (Nat. size.) 


neopallium, and in addition the latter is also marked D 
several shallow furrows (figs. 45 and 47). .Of these the 


mammals; whereas others go to the opposite extreme and deny in toto the 
possibility of homologising the sulci found in one Order of mammals with 
those of another. 4 
There can be little doubt that the fundamental constituents of manga 
the sulci found in the Metatheria and Eutheria are morphologically st 
elements which can be certainly homologised in many different Orders, 
The exact homology of the hippocampal and rhinal fissures in all mamm 
is beyoud question, because the peculiar histological features of the “7 
these fissures enable us to certainly identify them. The developme 
history and the behaviour of the fundamental constituents of the 
sulcus of Primates and the upper part of the vertical ramus of the su 
commonly called “splenial” in other mammals indicate their identity. — 
the same manner we can recognise the suprasylvian, lateral, coronal, and 
orbital (presylvian) sulci in the most diverse Orders of mammals. Moe - 
these names were originally applied to the Carnivora (vide infra). a 
By “fundamental constituent ” I mean the stable basis of a sulcus, whick 
seems to be produced (even when the mechanical conditions must be vastl: 
different) in various Orders of mammals in response to some factors other that 
the mere general expansion of the neopallium. The extending cortex may 
be accommodated in the neighbourhood of such a sulcus by the prolongation 
of the latter: or, again, the furrow in question may become confluent with 
various other sulci in different mammals. Thus the calcarine sulcus (sem 
stricto, i.e. the short post-splenial furrow, which indents the wall of the 


NERVUUS SYSTEM.—VERTEBRATA. 163 


deepest and most constant is a short oblique furrow situated 
just above the mid-point of the anterior rhinal sulcus 
(i. e., the anterior horizontal part of the rhinal). It 
represents the presylvian sulcus, which is one of the most 
constant features of the mammalian neopallium. There 
are many reasons for regarding this presylvian sulcus as 
the earliest form of the sulcus known in Human Anatomy 
by the name “orbital.” [Compare the account of the 
Prosimian brain. | 

Behind the upper extremity of this sulcus there is a 
shallow transverse depression (figs. 45 & 47, x), which is of 
interest because the brain of Thylacinus, the large relative 
of Sarcophilus, exhibits a deep sulcus in the corresponding 
position. 

Above and parallel to the posterior rhinal fissure there 
is a short horizontal sulcus, and in front of it a small 
triradiate sulcus (vy). These clearly represent the great 
sulcus, which I have distinguished as “ horizontal” in the 


ventricle and thus produces the calcar avis) is undoubtedly a definite 
morphological feature, which is the common property of the Meta- and 
Eutheria. Yet in the Carnivora, Ungulata, and many other mammals its 
ventral end may be prolonged almost or quite as far as the rhinal fissure, 
merely because the expanding cortex in this region is most readily accommo- 
dated by the extension of this already-existing sulcus. In the Carnivora 
and Ungulata the upper end of the calcarine stlcus becomes confluent 
with the intercalary sulcus, forming the so-called “splenial.” In the 
Primates the lower end of the calcarine sulcus does not become prolonged 
and the upper (posterior) end joins, not the intercalary, but the postcalcarine 
sulcus. Now, in such a catalogue as this, it is quite impossible to explain on 
every occasion whether it is the “ calcarine,” or the “ prolonged calcarine,” 
or a “calcarine complex” to which we refer, without endless confusing 
periphrases, which would make the accounts hopelessly involved. The same 
kind of misunderstanding might arise also in the case of the suprasylvian, 
lateral, or orbital sulcus. 

The reader must therefore bear in mind that the same names are employed 
in different Orders in order to indicateas concisely as possible where to look 
for the homologous sulci, rather than to suggest the identity of the whole of 
. any suleus called by any given name. 

It is also impossible to discuss in a catalogue of limited Siuoosions all the 
reasons which have led to the adoption of the views set forth in the brief 
accounts of the various specimens. 

The student who is not acquainted with the nomenclature used for the 
_ sulci is referred to the figures of the brain in the Carnivora (infra). 


M 2 


164 


‘ PHYSIOLOGICAL SERIES. 


Thylacine (fig. 50). It is not possible to suggest any — 
homology between this and ‘a named sulcus of any ore 
mammalian brain. 

The neopallium in the Tasmanian Devil thus exhibits 
features of interest as a connecting link between the smooth — 
hemispheres of the smaller Dasyurids and the deeply — 
fissured hemispheres of the Thylacine, the suleal pattern 
of which it so clearly foreshadows. 

The base of the brain (compare with Perameles, fig. 52) 
presents features which differ in a very marked manner 
from those of the Monotreme brain, and closely agree with — 
the characters of the vast majority of other mammals, — 
Thus the pons presents the appearance of an almost — 
uniform transverse band and lacks the peculiar rostrum of — 
the Monotreme ; moreover, the majority. of its fibres pass — 
in front of the trigeminal nerve ; the pyramidal tracts — 
appear as prominent bands which decussate in a more or 
less compact mass, and not as a diffuse crossing, as in 
the Monotremes: the trapezoid bodies, which are not. 
recognisable as such to the naked eye in the Platypus and 
the Spiny Anteater, are now very prominent and well- — 
defined features. Each half of the trapezoid body consists 
of a large strand of fibres which springs from the acoustic — 
tubercle (where the nerve-fibres from the cochlea end), — 
and, after pursuing a transverse course on the caudal side 
of the pons, dips into the medulla and passes chiefly into 
the lateral fillet of the opposite side. It constitutes the 
chief cerebral path for auditory impulses. 

The pituitary body has been torn away with the infun-— 
dibulum, so that the mesial slit-like third ventricle has been — 
opened up between the large optic chiasma and a a 
distinctly paired corpora mammillaria. In the depress nn 
behind the latter note the large interpeduncular body 
contact with the pons. a 

The cerebellum conforms to a simple type such as y mM 
find in the Insectivora, Rodentia, Chiroptera, and Dasy- 
podide (Edentata). Projecting upon each side there is a 
large irregular mass of folia resting upon the lateral aspect 
of the pons and medulla oblongata, and separated from the — 


NERVOUS SYSTEM.—VERTEBRATA. 165 


rest of the cerebellum by a deep fissure. This is the 
floccular lobe. In man the representative of this mass 
becomes reduced to very insignificant proportions and forms 
the flocculus. In this brain, however, the floccular lobe is 
almost, if not quite, equal in size to the whole of the rest 
of the so-called lateral lobe. Two shallow sagittal grooves 
separate the upper surface of the cerebellum into three 
projecting ridges, each of which is subdivided by a small 
series of transverse furrows. In each of these grooves a 
triangular area of medullary matter is exposed. The area 
seen in this specimen between the floccular lobes corresponds 
to that region of the human cerebellum which lies behind 
and below the preclival fissure and in front of the uvula. 
Part of the uvula in this specimen may be seen as a little 
tongue-like process extending backward and forming an 
operculum over the apex of the fourth ventricle. The 
most significant feature of this organ to the human anatomist 
is the extreme diminution of the lateral hemispheres; but 
when the intimate association existing between the cere- 
bellar hemisphere and the opposite cerebral hemisphere is 
‘remembered, it is not surprising to find these parts of the 
cerebellum so poorly developed in a brain in which the 
pallium as a whole, and especially the neopallium, is so 
diminutive. The anterior lobe, which is relatively so large 
in the Monotremes, is completely hidden in this brain by 
an overhanging hood formed by the region lying behind 
the fissura prima (vel preeclivalis). O. CO. 1823 Bob. 
R. Owen, Todd’s Cyclopzedia, 1847, vol. iii. p. 291. 


D.198. The brain of a Tasmanian Devii (Sarcophilus [Dasyurus] 
ursinus). 

This specimen shows the real proportions of the huge 
olfactory bulbs. The hemispheres have been drawn apart 
so that a much greater part of the corpora quadrigemina 
is exposed than when the parts are in their natural position. 
[Compare the casts D. 199 and fig. 47. | 

This specimen is represented in Owen’s ‘ Anatomy of 
Vertebrates,’ vol. iii. p. 104. O. C. 1823 o ff. 


166 PHYSIOLOGICAL SERIES. 


D. 199. Cast of the cranial cavity of a Tasmanian Devil (Sarco- 
philus (Dasyurus] ursinus). ~ [In duplicate. | 
This shows better than the actual specimen (which is 
liable to distortion) the large proportions of the olfactory 
bulbs and the relations of the cerebellum (the chief divisions 
of which are clearly seen) to the cerebral hemispheres. 
Note the orbital sulcus on the hemisphere (fig. 45). * 
P. Gervais, Nouv. Archiv. Mus,, t. v. 1869, Pl. xiv. fig. 8. 


D. 200. A young Australian “Native Cat” (Dasyurus viver- 
rinus), with the brain and spinal cord exposed én situ, ; 
Parts of the hemispheres have been removed so as to 
expose the hippocampi from above. O. C. 18230), — 


hs ae 
ee ee a eh 


D. 201. The right half of the brain of an Australian “Native 
Cat” (Dasyurus viverrinus), separated by a mesial sagittal — 
section. 

Two white bristles have been inserted into the hippo- — 
campal fissure just above the prominent fascia dentata — 
which rests upon the dorsal commissure. A black bristle — 
has been inserted just below the ventral (anterior) commis-_ 
sure and another in the centre of the large “soft” or 
‘‘ middle commissure ” (so-called). The cavity of the third — 
ventricle in which the latter is placed may be clearly seenin 
this specimen. Its communication with the lateral ventricle, 4 
viz., the foramen of Monro, may be distinctly seen in the — 
groove between the dorsal and soft commissures. : 

Note the large size of the aqueduct of Sylvius, whicht 
opens from the posterior extremity of the third ventricle 
into the mid-brain. The roominess of this canal is very 
suggestive when it is recalled that in most submammalian — 
forms a ventricle exists in this situation and extends into — 
the “‘ optic lobes.” 

Note further the simplicity of the cerebellum, Its — 
deepest fissure—the fissura prima—opens on the anterior 
surface near the apex of the organ: it is the homologue of — 
the preclival fissure of Human Anatomy. d 

All of these features (excepting the arrangement of the 
hippocampus and the commissures) are common to other 
lowly mammalian brains, such as those of the Insectivora. — 


OQ. UC, 1828 ¢. 


NERVOUS SYSTEM.—VERTEBRATA. 167 


D. 202. The right cerebral hemisphere, the caudal part of the left 
cerebral hemisphere, and the brain-stem and cerebellum 
of a Tasmanian ‘‘ Wolf” (Thylactnus cynocephalus). 

The mesial aspect of the hemisphere (fig. 48) presents 
the typical arrangement of the cerebral commissures and 
hippocampus ; and, as such, this identical specimen was 


figured by the late Sir William Flower (Phil. Trans. 1865). 


Fig. 48. (x2.) 


FASC. DENT 


OLF. BuLB 4 Uf J. FASC . DENT. 


COMM.V. 


He, however, erroneously regarded the dorsal commissure 
as a true corpus callosum. ‘There is a well-developed 
ealearine sulcus beginning just above the caudal extremity 
of the rhinal fissure. It is prolonged upward and forward 
after the manner of the splenial complex in many orders. 
An oblique section has been made through the left hemi- 
sphere (fig. 49) (in the plane indicated in fig. 48) in the 


Fig. 49. (x2.) 


 CALCAR 


SULE CALC...» 


region of the deepest part of the calcarine sulcus. The 
latter is thus shown to be “complete” or “total”; in 
other words it gives rise to a bulging—the calcar avis or 
so-called hippocampus minor—in the ventricle immediately 
to the peripheral side of the true hippocampus. 

There is a deep and sharply-defined rhinal fissure, acutely 
bent at the junction of its anterior and posterior parts 


168 PHYSIOLOGICAL SERIES. 


(fig. 50). A deep and extensive orbital (presylvian) sulcus 
springs from the rhinal a short distance in front of the 
angle and proceeds transversely across the hemisphere as & 
two conjoined arcs. The upper arc, the convexity of 


if 


a» 


As 


Fig. 50. (x3) ’ 


OLF.TR. 
which looks backward, was probably a distinct sulcus 


originally. Here it has fused with the orbital suleus (figs. 
-50 and 51). It extends on to the mesial wall of the hemi- 


Fig. 51. (x3.) 


a)\..OLF. BULB, 


\,_.- SULC. ORB, 


sulcus prolonged from the cephalic extremity of the hippo- — 
campal fissure. J 

A shor‘ kink-like depression extends upward from the — 
angle of the rhinal fissure for a short distance, and may | 


NERVOUS SYSTEM.—VERTEBRATA. 169 


be regarded as analogous to the “Sylvian fissure” of 
Oarnivores *. 

A deep sulcus (y) begins near the posterior margin of 
the hemisphere and pursues a course parallel to the posterior 
rhinal almost as fur forward as the “ Sylvian fissure.” Its 
anterior extremity is joined by a shallow oblique sulcus to 
a second deep furrow (x) which pursues the same direction 
as the posterior sulcus but on a slightly higher level. The 
whole complex forms a great sulcus crossing the hemisphere 
obliquely as far as the dorso-mesial edge, where it almost 
reaches the upper extremity of the prolongation of the 
calcarine sulcus (fig. 48). The determination of the homo- 
logies of these furrows is fraught with great difficulty ; but 
it will be found, I believe, that the sulcus y represents the 
suprasylvian and the furrow x the coronal sulci of other 
mammals. In the right hemisphere of a Thylacine described 
by Beddard the sulci x and yY overlap but do not join. In 
the left hemisphere of his specimen the condition described 
in this hemisphere is found. 

In front of the presylvian there is a short separate hori- 
zontal sulcus analogous to that called “prorean” in the 
Carnivora. On the left hemisphere it joins the presylvian. 
There is a shallow olfactory sulcus (i.e. the depression in 
the neopallium which lodges the olfactory bulb and 
peduncle.) 

There are also a few ill-defined punctate depressions 
below and above the x+y complex sulcus. 

The plan of the sulci isa more complete elaboration of 
that faintly foreshadowed in the Tasmanian Devil. It has 
undoubtedly considerably diverged from the plan found in 
most placental mammals, though not to such a marked 
extent as that of the Monotremes or even of the Diprotodont 
Marsupials. 

_ The optic tract may be seen spreading out on the lateral 
tubercle of the optic thalamus. Behind the latter note the 


* But this is a feature vastly different from the true Sylvian fissure of the 
Primates (vide infra). In the latter part of this work I have therefore dis- 
carded the erroneous name “Sylvian ” and called it “ pseudosylvian.” The 
earlier part was already in print before I fully appreciated the utterly mis- 
leading effects of calling this furrow “ Sylvian.” 


170 


7 


PHYSIOLOGICAL SERIES. 


large mesial (posterior) geniculate body and the great 
corpora quadrigemina of which the anterior pair are 
especially prominent. The cerebellum conforms to the same 
plan as that of Sarcophilus. But the mesial and lateral parts 
of the region behind the primary fissure are unusually 
prominent. They are separated the one from the other by 
exceedingly deep broad furrows in which large medullary 
areas are exposed. The mesial ‘ vermis” is twisted toward 
the right and the lateral areas are expanded in a feather- 
like pattern, such as is common in Carnivora, Edentata, and 
other Mammalian Orders. 
F. E. Beddard, Proc. Zool. Soc. 1891, pp. 140-145. 


D. 203. A cast of the cranial cavity of a Tasmanian Wolf 


(Thylacinus cynocephalus). 

This shows that the olfactory bulbs are laterally com- 
pressed and of large size ; they are borne on long peduncles 
so that they are placed almost wholly in front of the 
hemispheres. 

The peculiar shape of the cerebral hemispheres is clearly 
demonstrated, and the relatively small size of the pointed 
apices which constitute the presylvian part of the hemi- 
spheres is shown. The positions of the sulci described in 
the actual brain are clearly indicated. 

The peculiar configuration of the cerebellum is also shown 
in a very striking manner. 

Gervais, Nouv. Arch. Mus., t. v. 1869, p. 229. 


Family PeramMeLip”. 


D. 204. The brain of a Rabbit-Bandicoot (Thalacomys lagotis). 


[This specimen lacks the greater part of its olfactory bulbs 
and the projecting portions of the cerebellum. ] 

The general features of this brain are like those of the 
brain of asyurus, but the cerebral hemispheres are more 
distinctly conical. O. OC, 1823 oh, 


D. 205. The brain of a Bandicoot (probably Perameles nasuta). 


This specimen was labelled “Dasyurus ” in the old Cata- 
logue; but the pointed cerebral hemispheres, the pronounced 
lateral “ spreading ” of the caudal parts of the pyriform lobes, 


NERVOUS SYSTEM.—VERTEBRATA. 171 


thesimplicity of the cerebellum, and its markedly-projecting, 
pedunculated floccular lobes clearly show that it is the brain 
of Perameles. In fact, it exhibits the characteristic features 
of the genus in a much more distinctive manner than the 
specimen (D. 206) labelled ‘‘ Perameles.” In both speci- 
mens the large olfactory bulbs are damaged so that their 
great size is not properly shown. 

The brain of Perameles is even more generalised and 
simple than that of Dasyurus. Italso closely resembles the 
brain of that most generalised of all Hutherian brains—the 
Hedgehog’s—in all points except the arrangement of the 
commissures: for Hrinaceus, like all Hutheria, possesses a 
true corpus callosum. 


Fig. 52. (Nat. size.) 


/ 


...-- OLF. BULB. 


SOLE. TUB: 


Bat VIR be 

--. TUB. OLF TR. 
SORT. Tits 

%).... TUB.CIN, 


The rhinal fissure is shallower and shorter than it is in 
Sarcophilus : there is only a faint indication of the orbital 
(presylvian) sulcus, which closely resembles that of Hrina- 
ceus; the cerebellum is much simpler, and there are no 
exposed medullary areas between the mesial and lateral 
portions of the organ. 

The accompanying drawing (fig. 52) represents the 
characteristic features of the base of the brain in a fresh 
specimen. O. OC. 1323 cd. 

Gervais, Nouv. Arch. Mus., t. v. 1869, p. 242. 

[The reader is warned that Gervais’ figure 12 on Plate 
xiii. obviously represents the brain of some small Macro- 
pod, and not a Perameles as it is labelled. | 


172 PHYSIOLOGICAL SERIES. 


D. 206. The brain of a Bandicoot (Perameles sp.). 
The prominent floccular lobes (compare fig. 52) have been 
removed from this specimen. O. C. 1323 ci. 


Family Diperpuyip”. 


D. 207. The brain of a Virginian Opossum (Didelphys marsu- 
pialis). 

This closely resembles the brain of Perameles and the 
Dasyuride. Note the well-defined rhinal fissure which 
does not extend the whole length of the hemisphere, so that 
posteriorly the pyriform lobe and the neopallium become 
freely continuous. 

Note the shallow orbital (presylvian) sulcus, especially 
on the right hemisphere. 

The hemispheres have been separated in order to expose 
the dorsal (hippocampal) commissure placed in front of the 
third ventricle. 

The cerebellum is simple like that of Perameles. 

O. C. 1823 B. 

Herrick, Journ. Comp. Neurol. vol. ii. 1892, p. 1. 


D. 208. The brain of an Opossum (Didelphys), with the arachnoid 
and pia mater in situ, 

This shows the true proportions of the olfactory bulbs and 
also how much of the corpora quadrigemina is uncovered 
by the cerebellum and cerebral hemispheres. 

O. C. 1823 Ba. 

Owen, Todd’s Cyclopedia, 1847, vol. iii. p. 292. 


Suborder DiproTopONTIA. 


Family Macropopip”. 


D. 209. A series of five coronal sections of the cerebral hemi- e 


spheres of a Bennett’s Wallaby (Macropus rujicollis), 
These specimens serve to demonstrate a peculiar bundle — 
of fibres (seen in the second section), the presence of which 
is peculiarly distinctive of the Diprotodont Marsupials. 
The uppermost section passes in front of the cerebral 
commissures and shows the relations of the precommissural 


NERVOUS SYSTEM.—VERTEBRATA. 173 


part of the hippocampus to the neopallium above it and to the 
precommissural area below it. (These features are perhaps 
seen to better advantage on the back of the second slice.) 


(Fig. 53.) 


Fig. 58. (x13.) 


HIP, F. ,NEOPAL., 


HIP. 


FASC, DENT. 


~~~ CAP.INT. 


(--- PRECOM. AREA. 
“RHIAN. F- 


OLF . TUBER. 


The second section (fig. 54) passes through the two 
cerebral commissures. The dorsal commissure is seen 
passing into the alveus of the hippocampus on each side. 
From this section it is possible to appreciate how the pallial 
operculum descends on the mesial side of the hippocampus 
toward the dorsal commissure, so as to shut out the fascia 


Fig. 54. (x13.) 


FASC . DENT. 


COMM.V. COMM.D. 


dentata in a view of the mesial wall (compare the specimens 
of the Black-faced Kangaroo). . 

The ventral commissure is seen (in the second section) 

to split into two bundles in the corpus striatum. The 

ventral bundle, which includes about half the fibres of the 

commissure, passes transversely through the corpus striatum, 

and joins the external capsule. This is the manner in 


174 PHYSIOLOGICAL SERIES. 


which the whole of the neopallial fibres of the ventral 
commissure behave in the Monotremata (fig. 42), the Poly- 
protodont Marsupialia, and the Eutheria. But in aut the 
Diprotodont Marsupials the dorsal half of the ventral 
commissure bends upwards in the corpus striatum, as it does 
in this section, and ultimately reaches the neopallium by the 
same route as that pursued by the internal capsule. This 
dorsal bundle I have called the “ fasciculus aberrans.” It — 
was first represented in a figure by Flower (Phil. Trans. 
1865), and first described by Symington (Journ. of Anat. & 
Phys. 1892) in Macropus. 1 have recently examined the 
brain in every genus of the Marsupialia (excepting Caeno- 
lestes), and found this ‘“‘ aberrant bundle ” to be invariably 
present in the Diprotodontia, but never in the Polypro- 
todontia, nor in other mammals. [This fact is here recorded 
for the first time. ] 

The third section passes through the hemispheres a short 
distance behind the commissures, and the “ splenium ” 
of the hippocampal commissure is still seen in the depths of 
the slice above the slit-like third ventricle, which separates 
the optic thalami. This section passes through the optic 
chiasma. 

The fourth section has been cut still further back. It 
exhibits the fimbria on the hippocampal formation, and it 
is easy to understand by comparison with the third section 
how the fibres of the fimbria reach the dorsal commissure. 

: 0. C. 1823 a 1. 

Symington, Journ. of Anat. & Phys., vol. xxvii. 1892, 

p. 69. . 


hag | 
oe a 


D. 210. The left cerebral hemisphere of a Yellow-footed Rock- 
Wallaby (Petrogale xanthopus), from which the lateral 
wall of the ventricle has been removed in order to expose 
the hippocampus (fig. 55). 

The disposition of the hippocampus is the most character- 
istic feature of the brain in Marsupials, in all of which, — 
both Poly- and Diprotodont, it presents a constant arrange- 
ment such as this specimen exhibits. Instead of being 
restricted to the descending limb and posterior part of the 
body of the lateral ventricle, as is the case in most 


NERVOUS -‘SYSTEM.—VERTEBRATA. 175 


mammals, the hippocampus extends forward as a large 
arcuate bulging upon the mesial wall of the ventricle ; 
this proceeds above the cerebral commissures, and reaches 
a point near the cephalic extremity of the hemisphere. 

[Similar dissections have been made in brains of Hrin- 
aceus (vide infra, D. 230) and Lepus (vide infra, D. 264) in 
order to demonstrate the difference between the Meta- and 
HKutheria in regard to this feature.] 

The anterior extremity of this great hippocampal arc is 
narrower than the more caudal part, and tapers to a 
rounded extremity. The inferior or caudal extremity is 
large and plump, and does not taper. In the Monotremes, 
which are the only other mammals possessing this hippo- 
campal are in its undisturbed simplicity, its caudal portion 


Fig. 55. (Nat. size.) 


CUT SURFACE 
bee OF THE 
PALLIUM. 


is relatively small, and tapers to a point. In regard to 
these features, the Marsupial approaches much more nearly 
to the Eutherian plan than does the Monotreme. 

Upon close examination of the ventricular surface of the 
hippocampus a series of oblique fibres (alveus) may be seen 
proceeding from the hippocampus to form a fringe-like 
band at its concave margin. This is the fimbria or fornia, 
and is here seen in its most simple form. 

Elliot Smith, Journal of Anat. & Phys., vol. xxxii. 

1897, p. 30. 


D. 211. The two cerebral hemispheres and the left half of the 
brain-stem and cerebellum of a Black-faced Kangaroo 
(Macropus giganteus, var. melanops). 

_ Above the large elliptical ventral commissure, note the 
elongated, horizontally-placed, U-shaped dorsal (hippo- 
_ eampal) commissure, the shape of which is characteristic of 


176 


PHYSIOLOGICAL SERIES. 


the Macropodide. There is a typically complete hippo- 
campal are of the usual Marsupial type, but its dorsal part 
is hidden by a great pallial operculum which descends as 
far as the dorsal commissure, so as to produce a spurious 
resemblance to the Eutherian condition. Such a neopallial 
operculum is found in all large Marsupials, such, for in- 
stance, as the Thylacine. In the right hemisphere this _ 
pallial operculum has been removed by dissection (fig. 56), 

and the fascia dentata is thus seen to extend far forward — 
above and beyond the dorsal commissure, just as it does in 
the Tasmanian Devil (D. 197) and in all Marsupials. The 
arrangement of the hippocampus in the ventricle may 


7 
§ 
a 
* 


Fig. 56. (Nat. size.) 


cCOmmMm.0O. FASC DENT. 
‘, roa 
SULC GEN. ; 


thus be correlated with the distribution of its specialised — 
fringe (fascia dentata) in the mesial wall of the hemisphere. — 

Above the upturned .caudal extremity of the rhinal — 
fissure a deep calcarine sulcus is found: it is prolongs a 
obliquely upward and forward for a short distance so as to 
converge with an anterior oblique suleus toward the dorsal _ 
edge of the hemisphere. This anterior oblique sulcus is 
apparently analogous to the genual suleus of other mail . 
malian orders. Immediately in front of the genual suleus — 
and the anterior extremity of the hippocampal fissure there — 
is a short rostral sulcus extending obliquely upward and — 
slightly forward. On the right side it bifurcates and — 
becomes Y-shaped. a 

There is a deep and typically-bent rhinal fissure. From — 
the neighbourhood of the angle of this fissure on the left 
hemisphere three sulci diverge widely in the neopallium. — 


NERVOUS SYSTEM.—VERTEBRATA. 177 


The interpretation of these raises a question of great 
difficulty. There can be little doubt that the most anterior 
represents the orbital or presylvian sulcus of other mam- 
mals*, It does not actually open into the rhinal fissure, 
but begins near it, and proceeds obliquely upward and 
forward. In this course it is joined by the anterior ex- 
tremity of a great inverted V-shaped sulcus, which may 
possibly represent the suprasylvian sulcus. But upon this 
question it is impossible to express a decided opinion at 
present f. 

The other two sulci which diverge from the angle of the 
rhinal fissure are probably to be regarded as essentially 
“Sylvian ” (in the sense in which this term is applied, say, 
in speaking of the Cat’s brain). The more posterior, which 

» we may distinguish as sulcus B, freely communicates with 
the rhinal fissure and with the sulcus tentatively called 
suprasylvian in such a manner that the presylvian and 
suprasylvian sulci, the sulcus B, and a short basal piece of 
rhinal fissure form a pentagonal pattern. The deep ver- 
tical sulcus which springs from the rhinal fissure between 
the lower ends of the presylvian sulcus and sulcus B may 
be distinguished as a. It ascends almost as far as the 
angle of the so-called “ suprasylvian ” sulcus. 

The sulcus which it is customary to call ‘ Sylvian fissure ”’ 
in mammals other than the Primates is a feature of little 
morphological stability, and is to be regarded as essentially 
of the nature of a kink produced by the flexure of the 
hemisphere. Or perhaps it would be more accurate to 
speak of it as being developed in response to the stress 
produced in this region of the neopallium by the ventral 
extension of its ventro-caudal region. In the Kangaroo 
this stress seems to be relieved by the two sulci a and B 


* Not the orbital pure and simple, but the orbital joined to a second more 
dorsal (mesial) sulcus, the direction and situation of. which is probably 
determined by the bias given to the expanding cortex by the presence of the 
orbital sulcus. Compare the left hemisphere of specimen D. 216. 

~ Close examination shows that the anterior limb of the V—which is the 
smaller and more unstable element and may represent the coronal suleus—is 
not joined to the caudal limb, which is the supposed homologue of the 
suprasylvian. 

VOL. Il, N 


178 


PHYSIOLOGICAL SERIES. 


instead of the customary single sulcus, which is the so- 
called “ Sylvian fissure.”” On the right hemisphere of this 
brain a third sulcus, which may be distinguished as 0, 
shares the representation of the pseudosylvian furrow. The 
sulcus ¢ is divided into two parts, but neither of these, nor 
the sulcus B joins the so-called suprasylvian. The latter is 
not joined to the orbital sulcus on the right side. 

In each hemisphere there are two horizontal prorean sulei 
in front of the orbital sulcus. There is also an extensive 
vertical sulcus parallel to the sulcus B, near the posterior 
margin of the hemisphere. 

(Ziehen describes a brain of Macropus rufus. Jena. 
Denkschr., Bd. vi. 1897, p. 54.) © 


D. 212. The brain and the upper portion of the spinal cord of a 


Giant Kangaroo (Macrepus giganteus). 

This is the largest brain found in any existing Marsupial, 
although the extinct forms Thylacoleo and Diprotodon 
possessed brains of much greater size. 

In this specimen the large olfactory bulbs are missing, 
but the size and shape of these parts of the brain are well 
shown in the casts of the cranial cavity (D. 215). 

The orbital (presylvian) sulcus and the sulci a and B all 
spring from the rhinal fissure. The sulcus B on the left 
side joins the suprasylvian sulcus, and the latter extends 
almost as far forward as the orbital (presylvian). A 
prorean sulcus is present. On the right side there is an 
additional sulcus between the sulci A and B, and the orbital 
sulcus is small. 

It isa strange fact that the “ paramedial ”’ suleus (compare 


tig. 58), which is such a characteristic feature of all other — 
representatives of the Macropodide, is lacking in this, the — 


largest member of the family. 


Behind the suleus B there are a number of small sulci, 
which on the whole assume a vertical (transverse) direction. — 
The characteristic features of the base of the mammalian — 


brain are exceedingly clearly demonstrated in this specimen 


(fig. 57). Note especially the thin-walled pouch of the ~ 


infundibulum, from which the pituitary “si has been 
torn away. 


ae es 


NERVOUS SYSTEM.—VERTEBRATA, 179 


The cerebellum conforms to the type presented by the 
smaller Marsupials, but the folia are much more numerous. 
In most other Orders of mammals we find in the larger 
members that the cerebellum becomes more compact, and 
the region behind the primary (preclival) fissure ceases to 
assume the hood-like form covering the anterior lobe. As 
a result of the slighter degree of expansion of this part of 
the cerebellum in such mammals, the exposed medullary 
area becomes greatly reduced, or even disappears. But in 
the Kangaroo this does not happen. The type of the 


Fig. 57. (x 2) 


smaller members of the Order with a hood-like covering 
for the anterior lobe and exposed medullary areas is re- 
tained, as it is in the Thylacine ; and the only difference 
consists in the larger size of the organ and a richer supply 
of fissures, and consequently more numerous folia. 
O. C. 1323 aa. 
Ziehen, Jena. Denkschr., Bd. vi. 1897, p. 54. 


D. 213. The left cerebral hemisphere, optic thalamus, and part of 
the mid-brain of a Giant Kangaroo (Macropus giganteus). 
There is a typically prolonged calcarine ‘sulcus, and the 
genual and rostral sulci are joined. 
There is a well-developed sulcus a—the “‘ Sylvian fissure” 
of most writers. The sulcus B, the ‘“ suprasylvian ”’ sulcus, 
and the “ coronal ” sulcus are joined to form a large are. 


There is a large presylvian sulcus. 
N 2 


180 _ PHYSIOLOGICAL SERIES. 


The cephalic portion of the fascia dentata and the 
characteristically bilaminar dorsal commissure of the Macro- 
podidee are well demonstrated. O. ©. 1823 ai. 


D, 214, The right hemisphere of the same brain of the Giant 
Kangaroo (Macropus giganteus) as specimen D. 213, cut 
transversely through the two cerebral commissures. 7 

Upon the mesial surface of the hinder [lower in bottle] 4 
fragment the arrangement of fascia deniata and fornix 
typical of the Marsupialia, and already described in the 
Black-faced Kangaroo, may be seen. 

The features of a coronal section through the commissures _ 
are seen, perhaps, to better advantage than in speci- 
men D, 209. O. C. 1823 ak. 


~~ 


fs * 


D. 215. A cast of the cranial cavity of a Giant Kangaroo 
(Macropus giganteus). [In duplicate.] 

This cast shows the true shape and proportions of the 
largest brain of an existing Marsupial, and permits us to 
compare the impression of the interior of the cranium with 
actual brains of the same species. We are thus able to 
appreciate to how great an extent we can rely upon casts 
of the cranial cavity in the interpretation of the features of 
the brain in such extinct forms as Thylacoleo. 

The shape of the large projecting olfactory bulbs is shown 
more accurately than in the other specimens. This peculiar 
form of bulb occurs also in all the Lemuroidea and in — 
many Ungulates. Note also the pronounced ventral 
extension of the postsylvian area of neopallium and the — 
very marked tapering of the anterior poles of the hemi- 
spheres. The relation of the hemispheres to the cerebellum, 
olfactory bulbs, and the pituitary body is very ariking . 
demonstrated. Fs 

It will be seen that from such a cast as this it is possible 
to map out the pattern of the cerebral sulci with almost as 
much certainty as in the actual brain. 

Thus we see the deep orbital and the shallower prorean — 
sulci, just as clearly as in specimen D. 211. The two 
pseudosylvian sulci diverging from the angle of the rhinal 
are also clearly exposed. The great V-shaped sulcus which — 


NERVOUS SYSTEM.—VERTEBRATA. 181 


I tentatively called “‘ suprasylvian ”’ is also seen to consist of 
two limbs. Of these the posterior (as a study of this series 
of Macropod brains shows) is much the more stable and 
represents in all, probably, the suprasylvian sulcus of other 
Orders, in spite of the fact that its topographical relations 
are so peculiar. The anterior limb of the V may represent 
the coronal sulcus of the Carnivora and Ungulata. We 
can also see a transverse sulcus extending inward from the 
angle of the V, just as we sometimes find in the actual 
brain (see D. 211). It is interesting to note that there is a 
large shallow depression in the place of the lateral (‘ para- 
medial ”’) suleus—a fact which is not demonstrable in the 
actual brains. This is of great interest when the peculiar 
absence of this sulcus in the larger, and not in the smaller, 
Macropods is recalled. There isa deep, long, postlateral 
sulcus. 


D. 216. The brain of a Parry’s Wallaby (Macropus parry?). 
A short deep “ Sylvian fissure ’—suleus A—extends 
almost vertically upward from the bend of the rhinal 
fissure (figs. 58 and 59). 


Fig. 58. (Nat. size.) 


... OLF. BULB 
| ai ay 


The orbital (presylvian) sulcus and the sulcus B both 
spring from the rhinal fissure, and diverge widely as they 
ascend. On the left hemisphere the short extent of the 
true orbital sulcus is seen, because it is not joined to the 


182 PHYSIOLOGICAL SERIES. 


“ false orbital.” [This is not shown in fig. 59, which 
represents the condition found on the right hemisphere 
reversed. | 

The suprasylvian suleus is connected neither with the 
sulcus B nor with the orbital. 

As in the Thylacine, the prorean sulcus joins the orbital 
on the right side only. 


Fig. 59. (Nat. size.) 


SULC . ORB. SULC . SUPRAS. 


On the caudo-mesial angle of the dorsal surface the 
characteristically Macropod paramedial sulcus is found 
(fig. 58). It probably represents the earliest form of the 

- sulcus called “ lateral” in Carnivores and se Sra and 
“ intraparietal ” in Primates. 

There are two fragments (D and p’) of a vertical sulcus 

behind the sulcus B. O. C. 1823 Ac. 


D. 217. A rough dissection of the brain of a Macropus. On the 
right side almost the whole of the cerebral hemisphere has 
been removed. On the left side the roof of the hemisphere _ 
and the greater part of the hippocampus have been removed _ 
in order to expose the fornix (fimbria) proceeding obliquely i 
across the optic thalamus to the dorsal commissure. : 

The nucleus caudatus is also exposed in the left hemi- 
sphere. This dissection was made by the late Sir Richard 


(then Professor) Owen for bis memoir in the Phil. Trans. _ 


1837. O.C. 1323 ae. 


D. 218. The brain of a Bennett’s Wallaby (Macropus rujicollis). 
The general features of this brain resemble those of 
Parry’s Wallaby (D. 216). 

The arrangement of the sulci in this species is interesting — 
because it is intermediate between that of the Kangaroo 


NERVOUS SYSTEM.—VERTEBRATA. 183 


and the smaller Macropods. The arrangement of the three 
sulci which diverge from the region of the angle of the 
thinal fissure is identical with that of the Giant Kangaroo. 
But there is a sulcus, the “ paramedian,” springing from the 
postero-superior part of the great arc formed by the supra- 
sylvian and sulcus B, which is not represented in the 
Kangaroo’s brain. It proceeds obliquely backward to the 
postero-mesial corner of the upper surface. This sulcus 
is seen in its typical form on the left hemisphere only : 
on the right side two small sulci take its place. The 
interest attaching to the paramedian sulcus is that it is a 
very characteristic feature of the smaller Macropodide. 
QO. C. 1323 ab. 

Ziehen, Jena. Denkschr., Bd. vi. 1897, p. 71. 

[In Ziehen’s specimen the sulcus A, his yy, is much more 
imperfect than in this specimen. | 


D. 219. The brain of a Derbian Wallaby (Macropus derbianus). 

This is not unlike the brain of Bennett’s Wallaby. 

The cerebral hemispheres have been separated from 
above in order to expose the dorsal or hippocampal com- 
missure, which may be seen as a narrow transverse band in 
front of the third ventricle. O. CO. 1823 ah. 

Ziehen, Jena. Denkschr., Bd. vi. 1897, p. 71. 


D. 220. The brain of Rat-Kangaroo (Bettongia gamardt) (?). 

The pallium is almost devoid of sulci, and in shape not 

unlike that of the Phalangers. There is, however, on the 

caudo-mesial angle of the dorsal surface the characteristic 

paramedian sulcus of the Macropodide. This sulcus prob- 

ably represents the “lateral sulcus” of the Rodents, 

Ungulates, and Carnivores. O. C. 1323 4g. 
Gervais, Nouv. Arch. Mus., t. v. 1869, p. 240. 


_D. 221. The brain of a Tree-Kangaroo (Dendrolagus inustus) ( ? ), 
in which the left hemisphere has been separated from the 
rest of the brain. 

The olfactory bulbs have been removed. In shape the 
cerebral hemispheres and the cerebellum conform to the 
Macropod type. But the hemisphere is remarkable for 


184 


4 


PHYSIOLOGICAL SERIES. 


. 


the paucity of sulci. There is a short sulcus a (“ Sylvian 
fissure”) on the right side, but it is almost completely 
aborted on the left side. There is a short deep paramedian, 
the characteristic Macropod, suleus; and also a small 
prorean sulcus. No other sulci are found on the cranial 
surface. But there are a number of shallow ill-defined 
depressions which conform to no known pattern. 

On the mesial surface there is the characteristic, oblique, 
prolonged calearine sulcus and a more characteristic inter- 
calary sulcus than is usually found in Marsupials. The 
features of the cerebellum, and in fact of all parts of this 


- brain, are demonstrated with exceptional clearness. 


| O. C, 1323 Ap. 
Beddard, Proc. Zool. Soc. 1895, p. 136. 


Family Pazascotomyip”. 


D, 222. The brain of a Wombat (Phascolomys ursinus), in which 


the left hemisphere has been separated from the rest of the 
brain. 


The short, broad, blunt anterior extremities of the hemi- — 


spheres of this brain form a marked contrast to the pointed 


anterior poles of most other large Marsupials, such as the — 


Kangaroos and especially the Thylacine. 

The cerebral sulci are in many respects peculiar. Per- 
haps the most significant feature is the absence of a well- 
defined calcarine sulcus, which is such a constant feature 
in the Marsupialia, and also in the Eutheria with the ex- 
ception of the peculiar Order of Rodents. 


— 


A typical orbital (presylvian) sulcus, such as we findin 
_ the Carnivora, appears to spring from the rhinal fissure far 


forward near the olfactory bulb, It is prolonged back- , 
ward under a small operculum, which meets the lower 


(pyriform) lip of the rhinal fissure, and then appears to 
curve upward again in what may be called the Sylvian 


region (fig. 60,a). This apparent upturned caudal ex- — 
tremity of the orbital sulcus, which may be regarded as — 


the representative of the sulcus A of the Kangaroos, 
presents a close resemblance to the arrangement found in 
many Viverride (e.g. the Civet, vide infra). [A com- 


parison with the latter will indicate why the two sulci a and — 


NERVOUS SYSTEM.—VERTEBRATA. 185 


B of the Kangaroo were spoken of (supra) as representing 
the so-called ‘ Sylvian fissure ” of the Carnivora.] 

Behind the sulcus A there is a short deep sulcus B pro- 
ceeding obliquely upward and backward from a triangular 
depression at the bend of the rhinal fissure. 


Fig. 60. (Nat. size.) 


SULC.SUPRAS. 
SULC.LAT. / 
‘, 


SULC. P. LAT. 


Tih as 


ginleite. i car cheer: by 

RHIN.F, 
Above the sulcus a there is a long oblique suprasylvian 
sulcus (figs. 60 & 61). As this sulcus is directed upward 
and backward, it resembles the typical suprasylvian sulcus 


Fig. 61. (Nat. size.) 


~ 


SULG. P. LAT. 


(e. g. in the Carnivora) much more closely than that of the 
smaller Macropods (e.g. Parry’s Wallaby, fig. 59), the 
obliquity of which is upward and forward *. 


* This difference may possibly be associated with the pronounced dwindling 
of the anterior regions of the hemisphere in the Macropodide. 


186 PHYSIOLOGICAL SERIES. 


‘To the mesial side of this suprasylvian sulcus there is a _ 
“lateral ” sulcus placed midway between the anterior and — 
posterior extremities of the hemisphere. It is widely separ- _ 
ated from its morphological posterior extremity (fig. 61, 8), 
which is a notch on the caudo-mesial angle. The latter — 
may be regarded as the representative of the paramedian — 
suleus of the Kangaroos. On the right hemisphere it is 
joined to a long transverse “ post-lateral” sulcus. = 
small sulcus F (fig. 60) may represent the postsylvia 
(posterior suprasylvian) sulcus of other Orders. 

There is a small separate prorean sulcus (fig. 61), and 
behind it there is a short transverse sulcus @, which m 7 | 
represent the coronal sulcus of other Orders. 

On the mesial surface (fig. 62) the typically Marup e 
arrangement of commissures and hippocampal formation is 
Fig. 62. (Nat. size.) q 


comm .D. 
{ 


SULG. GEN. 


SULC. ROST. 
\ 


seen. The dorsal commissure is not elongated to the same 
extent as in the Kangaroos, so that it more closely resembles. 
that of the Polyprotodont Marsupials. The prolonged 
genual sulcus is like that of the Kangaroo, as is also th 
rostral suleus. There is also the most extraordinary ab 
sence of the calcarine sulcus, in place of which there 4 
merely a small irregular pit (u). Lower down we find a 
short horizontal sulcus above the rhinal fissure (fig. 62). 
eee O. C, 1323 Ai 

R. Owen, Todd’s Cyclopedia, 1847, vol. iii. p. 293. 
W. H. Flower, Phil. Trans. vol. clv. 1865, p. 646. 


D. 223. Two casts of the cranial cavity of a Wombat (Phas 
omys ursinus). a a 
These casts admirably show the broad flattened cerebral 


NERVOUS SYSTEM.—VERTEBRATA. 187 


hemispheres and the projecting olfactory bulbs, as in the 

Kangaroos. The cerebral sulci are very deep furrows, 

conforming to the same pattern as in the brain (D. 222). 
Gervais, Nouv. Archiv. Mus., t. v. 1869, p. 235. 


D. 224. The brain of a Wombat (Phascolomys ursinus), dissected 
to expose the dorsal or hippocampal commissure from 
above. 

This dissection was made by the late Sir Richard (then 
Professor) Owen to demonstrate that the dorsal commissure 
of the Marsupial is derived from the fornix, i.e. that it is a 
hippocampal commissure or psalterium (Phil. Trans. 1837, 
p- 90; also Todd’s Cyclopeedia, vol. iii. p. 294, fig. 117 ; also 
‘Anatomy of Vertebrates,’ vol. iii.). 

The greater part of the cerebral hemispheres has been 
removed so as to expose the upper surface of the dorsal 
commissure, which may be seen passing into the fimbria 
upon each side. 

On the right side the fascia dentata may be seen lying 
upon the fimbria and extending obliquely across the upper 
surface of the dorsal commissures so as to reach the mesial 
surface of the hemisphere in front of the commissure. 

The corpora striata have been exposed in the lateral 


ventricles. 
Part of the cerebellum has been removed so as to open 
up the fourth ventricle. O. C. 1323 ao. 


Family PHALANGERIDA. 


D.225. The brain of a Brown Phalanger ( Yrichosurus fuliginosus) . | 
In general appearance this brain is not unlike that of | 
the Rat-Kangyaroos. It exhibits a shallow depression in | 
the situation where the characteristic paramedian sulcus | 
occurs in the smaller Macropodidee. Traces of a prorean | 
sulcus and that called “‘ suprasylvian ”’ in the Kangaroo are | 
present. , 
Although the neopallium is much larger than that of 
many of the smaller Polyprotodont Marsupials which 
possess a well-defined orbital sulcus, the latter feature is 
not clearly defined. O. C. 1323 am. 
Ziehen, Jena. Denkschr., Bd. vi. 1897, p. 84. 


188 ’ PHYSIOLOGICAL SERIES. 


D. 226. The brain of a Flying Phalanger (Petaurus breviceps). 
In all respects like a small specimen of Trichosurus. 
[The olfactory bulbs are lacking in this specimen. ] 
O. C. 1323 Be. 
Gervais, Nouv. Arch. Mus., t. v. 1869, p. 243. 


D. 227. The brain of a Koala or Australian “ Native Bear” 
(Phascolarctus cinereus) (3). 

The most noteworthy feature of this brain, as in Dendro- 
lagus (D. 221), is the paucity of sulci in such a relatively 
large neopallium. 

The few sulci which are found are exceedingly variable, 
and it becomes very difficult to determine their homologies 
with any certainty. 

The most pronounced sulcus (in this specimen) ascends 
from about the mid-point of the rhinal fissure, and may 
possibly represent the Carnivore pseudosylvian sulcus. In 
many cases, however, it is quite insignificant and does 
not join the rhinal fissure. In such cases there is oftena 
much deeper sulcus behind it, which Ziehen calls “Sylvian.” — 

In front of these pseudosylvian sulci there is a very 
faintly marked orbital (presylvian) sulcus. ; ; 

In addition very shallow furrows traverse all parts of 
the neopallium. 

The dorsal commissure is very small. The hippocampus _ 
presents the typical Marsupial arrangement. 

There is a short calcarine (splenial) sulcus, which cannot 
be seen in this specimen. O. C. 1323 ar. 

Ziehen, Jenaische Denkschr., Bd. vi. 1897, p. 98. 

Elliot Smith, Journ. Anat, & Phys., vol, xxxiii, 1898, p. 30. 


D. 228. The brain of a Koala (Phascolarctus cinereus), ( ¢). 
The sulci are much more imperfectly developed in this 
specimen. There is a pseudosylvian sulcus on the left — 
hemisphere only. O, O. 1323 as. 


D, 229. Casts of the cranial cavities of two skulls of the extinct — 
Thylacoleo carnifex. | 

The same peculiar, broad, flattened ahene which charac- 
terises the brain of Phascalomgaa is also presented by these 


NERVOUS SYSTEM.—VERTEBRATA. 189 


two casts.. The brain, however, was much larger than that 
of any living Marsupial, being about as large as that of a 
Pig, Hyzena, or Entellus Monkey. 

It possessed very large olfactory bulbs lying almost 
wholly in front of the hemispheres. 

There was a very deep vertical “ orbital sulcus,” resem- 
bling in position that of Macropus or Phascolarctus rather 
than that of Phascolomys. A very deep prorean sulcus; a 
deep (single), oblique, pseudosylvian sulcus (such as that 
labelled B in Phascolomys) ; suprasylvian and lateral sulci 
resembling those of Phascolomys rather than those of 
Macropus, and a postlateral sulcus are the most striking 
features of these hemispheres. | 

Gervais, Nouv. Arch. de Mus., t. v. 1869, p. 236. 


Orprer INSECTIVORA., 


Family HRINACEID«. © 


D. 230. The left half of the brain of a Hedgehog (Hrinaceus 
europeus), which had been divided by a mesial sagittal 
section (figs. 63, 64, & 65). : 

Also the left half of another Hedgehog’s brain, dissected 
to show the hippocampus in the lateral ventricle. 


Fig. 63. (x 14.) 


NEOPAL. _ RHIN.F. 
$ “ 


2 


SULC. ORB. 
4 


OLF. BULB. 


This is one of the simplest and most generalised of mam- 
malian brains. It closely resembles the brain of the Poly- 
protodont Marsupials (and especially Perameles) in all 
points except the arrangement of the cerebral commissures 
and the hippocampus, because the Hedgehog possesses a 
small corpus callosum and the Marsupials have none in the 

_ true sense. The resemblance between the brains of the 


| ae ale PHYSIOLOGICAL SERIES. 


Hedgehog and the Bandicoot is, however, very close, asa 
glance at figs. 52 and 65 so clearly demonstrates. . 

In the Hedgehog the olfactory apparatus is extra- — 
ordinarily largely developed, as we might expect in such a — 
lowly mammal of fossorial habits. 


Fig. 64. (x14.) 


HIP, 
CORP. CALL ° 


ei sder comme ., 
The neopallium is reduced to exceedingly diminutive 
proportions, so that the rhinal fissure (fig. 63) is placed — 
very high up upon the lateral wall of the hemisphere. 
Thus the pyriform lobe forms the greater part of the lateral” 


wall, q 


Fig. 65. (x14.) 


OLF. BULB, 


6", 


There is a short, very shallow, transverse orbital (pre- 
sylvian) furrow on the dorsal surface, as in Perameles and 
Sarcophilus. Inthe nearly-related and larger Gymnura this 
shallow furrow becomes converted into a deep suleus. _ 

The fascia dentata makes its appearance upon the 


NERVOUS SYSTEM.—VERTEBRATA. 191 


ventral surface of the hemisphere, on the mesial side of a 
depressed area corresponding to the nucleus amygdale. 

The simple cerebellum is slightly more elaborated than 
that of Perameles, so that it comes to more closely resemble 
that of Sarcophilus. It has sessile flocculi (comp. figs. 65 
and 52). 

In the dissected specimen (fig. 66), the lateral ventricle is 
prolonged forward to communicate by a narrow channel with 
the large cavity in the olfactory bulb. The hippocampus is 
placed in the caudal part of the chief cavity, and does not 
extend so far forward as in the Marsupial (compare the 
Wallaby’s brain, D. 210). The meaning of this is that when 
the corpus callosum makes its appearance (as it does for the 
first time in the Eutheria), the cephalic extremity of the 


Fig. 66. (x12.) 


HIP, 


LAT, VENT. 


OLF. VENT. 


hippocampus becomes reduced to a mere vestige lying partly 
upon the upper surface of the corpus callosum and partly in 
front of the latter body. The existence of a corpus callosum 
and the vestigial nature of the anterior part of the hippo- 
campal are are the great distinguishing features of the 
Kutherian brain, when compared with that of Marsupials 
and Monotremes. 
Flatau and Jacobsohn, Vergl. Anat. d. Centralnerv. 
1900, p. 341). 
Ganser, Morph. Jahrb., Bd. vii. 1882, p. 591. 
Elliot Smith, Journ. Anat. & Phys., vol. xxxii. 1897, 
p. 44. 


D. 231. A cast of the cranial cavity of a Hedgehog (Erinaceus 
europeus) . 
Shows the exact size and shape of the cerebral hemi- 
spheres and olfactory bulbs, 


192 ‘ PHYSIOLOGICAL SERIES. 


Family T'cPipz. 


D.232. The brain of a Mole (Talpa europea) (2), exposed ) 
in situ. 
This simple, highly santencalt brain resembles that of 

the Hedgehog but shows signs of greater specialisation, . 

It is, however, smaller, more flattened, and the optic part 


of the brain are very poorly developed. 
Ganser, Morph. Jahrb., Bd. vii. 1882, p. 591. 


Family Tupaups. 
D. 233. A cast of the cranial cavity of a Tupaia (Tupaia tana) 


Family Canter: 


D. 234. The cast of the cranial cavity of a Tenrec (Centeter 
ecaudatus). ‘ 
The olfactory bulbs are even larger in proportion to the 
size of the brain than they are in the Hedgehog. 
Such brains as those of Centetes and Hrinaceus enable us 
to appreciate the characters of the earliest Hutheria, and 
such forms as the Eocene Ungulate Dinoceras. a 
In the case of Centetes, however, the small size of the 
hemispheres is largely a secondary retrogressive char ge 
which occurs in the development of each individual (Forsyth 
Major). 


Suborder DmeRmMoprTera, 


Family Gazzorrruecips. 4 


D. 235. The brain of a Colugo (Galeopithecus volans), which has 
been divided in the mesial sagittal plane; and the le 
cerebral hemisphere separated from the brain-stem (figs. 67 
68, 69, and 70). 2 

This brain is of great interest because it presents a § 
of well-defined cerebral sulci, and at the same time oxhibi 
features which justify the lowly status usually cone 
Galeopithecus in the mammalian series, j 


NERVOUS SYSTEM.—VERTEBRATA. 193 


Thus the small size of the cerebral hemispheres which 
leave the greater part of the corpora quadrigemina exposed ; 
the high degree of macrosmatism in an arboreal animal; 
the prominence of the hippocampus; the small dimensions 
of the corpus callosum; and the smallness and primitive 
simplicity of the cerebellum, all point to the lowly status 
of this peculiar mammal, not far removed from the 
Insectivora. 


Fig. 67. (Nat. size.) Fig. 68, (Nat. size.) 


~ ,OLF. BULB. 


OLF. BULB. bs 


i \ TRS, 
x RHIN.F. ACOU.TUB 


Fig. 69, (Nat. size.) Fig. 70. (Nat. size.) 


SULC.CALC. 


CORP. QUAD. 


SULC. ROS. 


OLF.puLe,-"% 


4 \ 
FI! FASC.DENT, 


The very definite series of deep sulci on the cerebral 
hemisphere, however, at once separates Galeopithecus from 
the Insectivores proper. 

On the mesial surface there is a relatively small and 
very obliquely-placed corpus callosum. The large fascia 
dentata is, to a great extent, exposed on the surface 
(fig. 69). 

There is a deep calcarine (splenial) sulcus, beginning, as 
is usual, near the termination of the rhinal fissure and 
pursuing a course approximately horizontally forward. Its 

VOL. II. 0 


ee 
i a Se 


e 
- 


194 


PHYSIOLOGICAL SERIES. 


- 


slightly upturned anterior extremity overlaps the posterior 
extremity of a sulcus curiously like the rostral sulcus of 
the Sloths (fig. 69). 

The peculiarly-sinuous rhinal fissure is placed high up 
on the lateral wall of the hemisphere. Its posterior ex- 
tremity rises to a much higher level than any other pirt of 
the fissure (fig. 68), as often happens also in the Eocene 
Mammalia. 

In the small neopallium we find short sulci corresponding 
to the orbital (presylvian) sulcus (x), and the so-called 
‘Sylvian fissure ” (y) of such mammals as the Three-toed 
Sloth and many Carnivores. 

Midway between these sulci and the interhemispheral 
cleft there is a longitudinal sulcus almost as long as the 
hemisphere, presenting a slight concavity toward the 
mesial plane (fig. 67, w). There is nothing to help us to 
decide whether it represents either the suprasylvian or the 
lateral sulcus, unless it be the fact that the former is the — 
more primitive and stable of the two sulci in mammals 
generally. But its resemblance to the conjoint suprasylvian 
and coronal sulci in such small Ungulates as Dorcatherium 
and 7ragulus seems to be more than a fortuitous likeness. 

The cerebellum is unusually small and presents all the 
primitive simplicity of the Insectivore organ. [The 
greatly-projecting floccular lobes have become knocked off 
in this specimen. | 

The anterior quadrigeminal bodies are extremely large 
and bulge upward between the cerebellum and the cerebral — 
hemispheres. The posterior quadrigeminal bodies and the — 
mesial geniculate bodies are of moderate dimensions, 

It is of interest to note that the tractus pedunculuris 
transversus, which is feebly developed or perhaps absent in 
Marsupials and certain of the Insectivora and Edentata, is — 
well-developed in Galeopithecus. 

Presented by Prof. G. Elliot Smith *, 

W. Leche, Kong]. Sv. Vet.-Akad. Handl., Bd. xxi. 1886, 

p. 48. 


* This is one of several specimens which had been extracted and care- 
fully preserved by Dr. Charles Hose, of Borneo, and generously given to the 
writer fur examination, . 


NERVOUS SYSTEM.—VERTEBRATA. 195 


D, 236. A cast of the cranial cavity of a Colugo (Galeopithecus 
volans). [In duplicate.] 

This cast shows the true shape and proportions of the 
olfactory bulbs, cerebral hemispheres, and the main mass 
of the cerebellum. It gives some idea as to the exact 
area of the quadrigeminal bodies exposed. 

The rhinal and “ modified suprasylvian” furrows are 
well shown. 

Gervais, Journ. de Zool., t. i. 1872, p. 445. 


Orper RODENTIA. 
Section ScruROMORPHA. 
Family CasTorRIDZz. 


D. 237. The brain of a Huropean Beaver ( Castor fiber). 

Most parts of the brain of the Rodents present features 
such as are common to most of the Eutheria; but in 
respect to the arrangement of the sulci of the cerebral 
hemispheres, the Rodentia are the most aberrant group of 
the Eutheria (excepting perhaps the peculiarly-modified 
Sirenia). 

The most noteworthy features in the brain of the 
Beaver are the obliteration of a great part of the rhinal 
fissure and the utter absence of sulci in the large pallium. 
The meaning of this is not altogether clear, but appearances 
suggest that the growth of the brain in a roomy cranial 
cavity which has exercised little restraint on the growing 
hemispheres may explain this absence of sulci and 
imperfection of the rhinal fissure. But even admitting 
this, the smoothness of such large hemispheres isa peculiar 
phenomenon, which is much rarer than is generally supposed. 
Thus even in the small Hrinaceus, among the primitive 
Insectivores, there is a well-developed rhinal fissure and 
distinct traces of at least one neopallial sulcus ; and in 
Gymnura and, especially, Galeopithecus there are deep sulci, 
in spite of the fact that these brains are much smaller than 
that of the Beaver and represent a more primitive type. 


Then, again, among the Hystricomorphine Rodents we find 
02 


196 PHYSIOLOGICAL SERIES. 


- 


cerebral hemispheres of the same dimensions as, or even 
smallerthan, the Sciuromorphine Castor, possessing numerous 
deep sulci. 

This is one of the enigmas of cerebral morphology 
which we are utterly unable to satisfactorily explain at 
present. QO. C. 1323 RB, 

Beddard, Proc. Zool. Soc. 1892, p. 597. 


D. 238. The brain of a Beaver (Castor jiber), dissected to show 
the distribution of the fibres of the corpus callosum. 
This dissection was made by Prof. Richard Owen for 
purposes of comparison with the brain of the Wombat 
(D. 224). Its object was to demonstrate by comparison 
the absence of the corpus callosum in the Marsupial. 
R. Owen, Phil. Trans. 1837, p. 89. O. C. 13823 Ba. 


D. 239. The brain of a Beaver (Castor fiber), dissected to show 
the hippocampus and fornix. 

This dissection was also made by the late Prof. Richard 
Owen. By comparison with D. 238, it will be seen that 
when the corpus callosum has been removed, as in this 
specimen, an arrangement of the fornix is exposed which 
is analogous to that which may be seen in the Marsupial 
(D. 224) without removing any such commissure. Hence, 
Owen argued, the corpus callosum is lacking in the — 

- Marsupial. ' 

This rough dissection does not clearly demonstrate the 
further fact that in the Rodent the hippocampus does not — 
extend forward so far as it does in the Marsupial. 


O. C. 1823 Bb. 


D. 240. The brain of an American Beaver (Castor canadensis), 
(od) 
There is a shallow sagittal furrow on the dorsal surface 

of each hemisphere, which. might represent either the 
corono-lateral or the suprasylvian sulcus. The latter is the 
more stable and precocious of the two sulci, and is rarely 
absent when the lateral sulcus exists. Yet we know for 
certain that this sometimes happens in the case of 
Tamanduas (Edentata). 


NERVOUS SYSTEM.—VERTEBRATA. 197 


From the position of the sulcus in this specimen and by 
_ comparison with the brains of Dolichotis and Tamanduas, it 
seems more likely to be a representative of the lateral (or 
combined lateral and coronary). 
Note that the corpus callosum is rather short and plump, 
such as is found in the more primitive Insectivora. 
O. C. 1323 wl. 
D. 241. Two casts of the cranial cavity of an American Beaver 
(Castor canadensis). 


Family Scrvrmz. 


D. 242. The right half of the brain of a Squirrel (Sciwrus vulgaris). 
No sulci are present in the pallium. 
The corpus callosum is long and narrow with a definite 
genual thickening. 
The anterior quadrigeminal bodies are very large, 
probably because an active arboreal animal needs a well- 
developed visual apparatus. O. C. 1323 F. 


D. 243. The brain of a Squirrel (Sciurus capistratus). 
In spite of the large size of the anterior quadrigeminal 
bodies, they are completely hidden by the cerebral hemi- 
spheres. : 3 O. C. 13823 Fa. 


D. 244. The left half of the brain of a Squirrel (Sciurus capis- 


tratus). 

Observe the large size of the optic nerve, with which 
the prominence of the anterior quadrigeminal bodies is 
associated. © | O.C. 1328 Fe. 


Section HystrRICOMORPHA. 


Family OcToponTIpZ. : 


D. 245. The brain of a Coypu (Myocastor coypus), (¢ ). 
This brain resembles that of the Beaver but is much 
‘smaller, The rhinal fissure however is well developed. 
The pallium is devoid of well-defined sulci, although there 
- is aslight furrow on the caudal surface, possibly representing 


198 PHYSIOLOGICAL SERIES. 


the calearine (splenial) sulcus. It extends upward so as to 

slightly notch the dorso-caudal margin of the hemisphere. 
The corpora quadrigemina are partially exposed. 
According to Beddard other sulci may be present in the 

pallium. O. C. 1323 Be. 
Gervais, Journ. de Zool., t. i. 1872, pl. xxiii. fig. 7. 

(In this memoir cranial casts of numerous Rodents 

are described.) 


Family Hysrricipz. 


D, 246. The brain of a Porcupine (Hystria sp.). 

The cerebral hemispheres are very broad. (Their 
posterior extremities do not diverge in the manner Beddard 
describes, and the corpora quadrigemina are quite hidden.) 

The base of the brain resembles in shape that of the 
Beaver, but the rhinal fissures are deep and well-defined. 
There are two chief sulci and several pit-like a tn on 
the pallium. 

A short shallow posterior furrow runs paratial to the 
interhemispheral cleft and resembles the paramedian 
sulcus of the Kangaroos. 

There is a longer oblique sulcus further forward which 
cannot be strictly compared to any sulcus in other 
mammalian brains. It is impossible to say with any degree 
of certainty whether it represents the suprasylvian or a 
lateral element of such a form as the Capybara. 

There is no Sylvian fissure, although Beddard describes 
‘such a fissure in his specimens. O. ©. 1323 Be. 

Beddard, Proc. Zool. Soc. 1892, p. 600. 


D. 247. The brain of a Canadian Porcupine (Lrithizon dorsatum). — 

This brain is much more like that of the Coypu than 

the Porcupine. Its pallium is quite devoid of sulci. 

O. OC. 1323 Bm. 

Presented by St. George Mivart, Esq. 

D. 248. The brain of a Mexican Tree-Porcupine (Canodon 
mexicanus). 

This brain resembles that of the Canadian Porcupine. — 

Its pallium is entirely free from sulci, but is grooved in all ; 

directions by vascular furrows, O. C. 1323 wh. 


NERVOUS SYSTEM.—VERTEBRATA. 199. 


Family CH#INCHILLIDZ. 


D. 249. The brain of a Viscacha (Viscaccia maxima), in which 
the right cerebral hemisphere has been dissected to expose 
the hippocampus from above. 

There is a vertically-placed, somewhat arched, deep 
sulcus above the mid-point of the rhinal fissure, but not 
communicating with it. It may be regarded as the repre- 
sentative of the sulcus in the brain of Dolichotis (figs. 74, 
75, 8), which has been called Sylvio-suprasylvian ; in 

- other words, it is the suprasylvian sulcus or the Prosimian 
Sylvian. 

In front of this suleus the hemisphere gradually tapers 
to a narrow anterior extremity, and behind the sulcus the 
hemisphere suddenly broadens. 

_ There are two well-marked sagittal sulci representing 
the corono-lateral complex. According to Beddard other 
sulci may occur. O.C. 1323 Bf. 

_ Beddard, Proc. Zool. Soc. 1892, p. 599. 


D. 250. The brain of a Viscacha (Viscaccia maxima). 
: O.C. 13823 4649. 


D. 251. The brain of a Common Chinchilla (Chinchilla lanigera). 
The pallium is apparently devoid of sulci. It is, 
however, hidden to some extent in this specimen by the 

_ membranes, in which the middle cerebral artery is very 
prominent. O. C. 1823 Eg. 


Family DasyProcripZé. 


D. 252. The brain of an Agouti (Dasyprocta agutt). 

In contradistinction to the flattening which charac- 
terizes the basal region of the hemispheres in many 
Rodents, the pyriform lobe and olfactory tubercle in 
this specimen present the plump, rounded features which 
distinguish these regions in macrosmatic brains of other 
Orders. 

A deep and well-defined sulcus indents almost the whole 
length of the hemisphere parallel to and a short distance 


200 _. PHYSIOLOGICAL SERIES. | 


from the interhemispheral cleft. A comparison with the 
brains of Orycteropus, the Anteaters, and Carnivores would 
lead us to call this the lateral or the conjoint corono-lateral 
sulcus. Yet it is very unusual to find the lateral suleus 
present, and the more precocious and fundamentally stable 
suprasylvian sulcus absent. If, for instance, we compare 
this brain with that of Galeopithecus and many of the 
smaller Ungulates, the possibility of it being the supra- — 
sylvian presents itself. B: 

Taking all its features into consideration, one is inclined _ 
to regard it as the analogue of the lateral sulcus of such — 
a form as Tamanduas. It is also clear that the anterior 
extremity of snch a sulcus takes the place of the prorean 
sulcus found in the Marsupialia and Carnivora. 

Two notch-like indentations in the upper lip of the 
rhinal fissure may represent the Carnivore pseudosylvian — 
sulcus and the orbital sulcus. 4g 

Other sulci have been described in the Agouti ; in this — 
specimen shallow depressions occupy the positions of all — 
these sulci. — O. C. 18286. — 

Beddard, Proc. Zool. Soc. 1892, p, 602. | 


D 253. The brain of the Paca (Agouti paca). 

This brain agrees with that of the Agouti in presenting 
notch-like representatives of the orbital and pseudosylvian 
sulci in the upper lip of the rhinal fissure. 

The longitudinal (“lateral”) sulcus of the Agouti is here — 

“broken up into two fragments—anterior and posterior — 
paramedian sulci respectively, and between them is a short — 
oblique sulcus (which I shall call “ambiguus”), such as — 
the Porcupine exhibits. 0. C. 1823 ab, — 

Beddard, Proc. Zool. Soc. 1892, p. 604. | ‘ 


Family Caviups«. 


D. 254. The brain of a Capybara (Hydrocherus capybara), in 
which the left cerebral hemisphere has been separated from : 

the rest of the brain (figures 71, 72, and 78). 7 
This brain is much the large tound in the Rodentia ;— 


NERVOUS SYSTEM.—VERTEBRATA., 201 


and in virtue of the great extent of the mantle of the 
cerebral hemispheres there are numerous sulci. The 
aberrant character of the Rodent brain is therefore more 


Fig. 71. (x3) 


SULC. COR. 
“ 


\ _. SULC. SUPRAS. 


strikingly exhibited than it is in the smaller and less-richly 

furrowed brains of the Order. 7 
When viewed from above or below the cerebral hemi- 

spheres present a peculiar lozenge-shape, the lateral edge 


Fig. 72. (x3.) 


SULC.CA Lc. 


SULE. CGR 


SULC.ROS.... 


RHIN. F. POST. 


of each hemisphere being so shaped as to form a projecting 
angle slightly behind its mid-point. The large olfactory 
bulbs project freely in front of the hemispheres. 


202 


PHYSIOLOGICAL SERIES, 


There is a well-formed corpus callosum with a particularly 
well-developed genu (fig. 72). 

The hippocampal formation conforms to the usual 
Eutherian type. | 

The rhinal fissure however presents peculiar features. — 
It consists of a deep, long horizontal anterior rhinal 
extending two-thirds of the length of the hemisphere and — 
ending blindly in a triangular depression posteriorly. — 
There is a shallow posterior rhinal fissure which is not 
joined to the anterior rhinal on the right hemisphere, and 
is connected to it only by a very shallow furrow on the — 
left (fig. 73). In the region of approximation of these — 
two fissures there is a deep triangular depression, in which — 


Fig. 73. (x #.) 


SULC. LAT. 
= sik COR. 


SULC. ORB. 


SULC.SUPRAS. RHIN.F. 


the anterior rhinal fissure terminates. Holl has shown that * 
this depression is formed by a suleus which he calls the 
ectosylvian. 

There is a typical presylvian (orbital) sulcus which is — 
placed very far forward and pursues a very oblique, almost — 
horizontal, course, to join Holl’s ectosylvian suleus, The ‘ 
upper lip of the latter suleus is opercular and meets the li 
of the rhinal fissure. 

The suprasylvian sulcus is deep and oblique, and is o ill 
supplemented by a second arcuate element. This second — 
element may be independent (see right hemisphere of this 
brain), or it may be fused to the true suprasylvian to form 
a triradiate sulcus (as in the left hemisphere of this and th 
right hemisphere of the next specimen). 

Two sagittal sulci, the longer one placed behind ae 
shorter, extend the whole length of the hemisphere parallel 
to the interhemispheral cleft. The anterior suleus probably 


NERVOUS SYSTEM.—VERTEBRATA. 203 


corresponds to the coronary, and the posterior to the lateral 
suleus of other Orders. The adjacent ends of both sulci 
are bifid. 
There are a number of other sulci on the cranial surface 
of the hemispheres, but they are so unstable that they 
differ considerably on the two hemispheres of the brain 
and to a much greater extent in different brains. 
It is the sulci (or rather the absence of sulci) on the 
mesial surface of the Rodent’s brain by which the aberrant 
character of this Order is indicated. The rhinal fissure 
extends high up on the mesial surface (of the Capybara’s 
brain) parallel to the hippocampal fissure. The most 
striking fact, however, is the insignificant representative of 
the calearine sulcus. There is only a small sulcus behind 
the splenium of the corpus callosum in the situation where 
we should expect the deep long calcarine sulcus. In most 
Rodents even this is missing, and in this brain the features 
of this small furrow are such as to render its homology 
somewhat questionable. But even granting that this 
sulcus in the Capybara is the true calcarine, its insig- 
ficance is very peculiar when we recall that in all other 
Kutherian Orders as well as in the Metatheria the deep, 
long calcarine sulcus is the most constant and best defined 
of all the sulci of the neopallium, 

In the Capybara again, as in all Rodents, Siar is no 
intercalary sulcus, if we except the insignificant furrow 
near the upper surface of the splenium. 

There is, however, a well-defined genual and also a 
large rostral sulcus. 

The cerebellum is remarkable for its small size and 
compactness (fig. 71). Its folia are arranged in a 
simple transverse pattern, and as a result there is a close 
resemblance to the type prevalent in the Ungulata, 
There is a large floccular lobe. O. C. 1323 ed. 

Beddard, Proc. Zool. Soc. 1899, p. 798. 

Holl, Arch. f. Anat. und Phys. (Anat. Abth.) 1900, p. 295. 


D, 255. The brain of a Capybara (Hydrochwrus capybara) (3), 


in which the left hemisphere has been dissected to show 
the corpus callosum, 


204 


PHYSIOLOGICAL SERIES. 


On the left hemisphere of this brain the peculiar 
characters of the rhinal fissure are very pronounced. The 
anterior part of the anterior rhinal fissure is so faintly 
marked, that the deep posterior part appears to be a back- 
ward extension of the orbital suleus. It is separated 
by a wide interval from the posterior rhinal fissure. 

Note the peculiar lozenge-shape of the brain. This is 
well shown in a figure of Retzius’s (Biolog. Untersuch., — 
Bd. viii. 1898, Taf. xii. fig. 1). 0.0. 1823 aa, 


D. 256. A cast of the cranial cavity of a Capybara (Aye | 2 


cherus capybara). [In duplicate.] 


This shows the true shape and ptoportions of the ana 1 


projecting olfactory bulbs: and the peculiar lozenge- 
shape of the brain as a whole, each cerebral hemisphere 
having a most pronounced lateral angle slightly behind a 
point midway between the anterior and posterior poles. 
Note also the exceedingly small relative size of the 
cerebellum, 
Gervais, Journ. de Zool., t. i. 1872, p. 456. 


D. 257. The brain of a Patagonian Cavy (Dolichotis magellanica) 


(2), from which the left cerebral hemisphere has been 
separated (figs. 74 & 75). 

This brain is not so strikingly aberrant as that of the 
Capybara. And yet the practical absence of well-defined 
sulci on the mesial surface shows that this peculiarity of 
the other Rodentia also occurs in this genus. There is 


however a faint trace of a genual suleus and a shallow 


depression where one would expect to find the calearine _ 


- sulcus. 


Unlike that of the Capybara, the brain of this Cavy 
presents a typical well-defined rhinal fissure, such as is 


seen elsewhere in the Rodentia, in the Rabbit for instance. 
There is an extensive sagittal sulcus parallel to and 
coextensive with almost the whole length of the inter- 


hemispheral cleft. This corresponds to the corono-lateral — 
suleus of the Carnivora and Ungulata, and possibly also 7 


.*, to the prorean sulcus fused to the coronary element. 


A great vertical sulcus (s) pursues a slightly arched course ; 
upward from the junction of the anterior and posterior 


NERVOUS SYSTEM.—VERTEBRATA. 205 


rhinal fissures. It probably represents a fusion of the 
so-called “*Sylvian fissure”? of most non-Primate orders 
and the suprasylvian sulcus. Such a fusion is found in the 
Great Anteater’s brain (vide infra) and also, in all 
probability, in the Primates, in which the complex forms 
the true Sylvian fissure. In this brain, so as to avoid 
confusion, we may call it the “Sylvio-suprasylvian 
complex.” 


There is a small horizontal presylvian (or orbital) sulcus, 
which is not joined to the rhinal fissure. 

There is also a short sulcus of doubtful significance on 
the external side of the caudal end of the lateral sulcus 


(figs. 74 & 75). 


an 


SULC.ORB.. 


The resemblance between the cerebral sulci of this brain 
and those of the Lemurs is very instructive (vide infra). 

There is a compact cerebellum, which is relatively larger 
and broader than that of the Capybara. — It also conforms 
to a more generalized type found in many other Rodents, 
Edentates, Insectivores, and Marsupials. 

The floccular lobes project like those of the Rabbit. 

O. C. 1323 Ha. 
Beddard, Proc. Zool. Soc. 1892, p. 608. ) 


206 PHYSIOLOGICAL SERIEs. 


Section MyomorpHa. 
Family Diropips. 
D. 258. The brain of a Jerboa (Dipus sagitta). 


A simple smooth brain presenting no distinctive features. — 
O. C. 1828 Bh, 4 | 


Family Muripz. 


D. 259. The brain of a Rat (Mus rattus), in which the ltt 
hemisphere has been in great part removed to show 
mid-brain, and the right hemisphere has been di 
show the hippocampus. 

The typical arrangement of the lowly — 
cerebellum is well shown. 0. C. 1823 rd. 


D. 260. The brain of a Rat (Mus decumanus). = q 


Suborder DupLicIDENTATA. 
Family Lzporipz. 


D. 261. The head of a foetal Hare (Lepus europeus) with the 
brain exposed in situ. 0. ©. 1023 | 


D. 262. The brain of a Hare (Lepus europorus). O. C. 1828 Gs ry 


D. 263. The brain of an English Wild: Rabbit (Lepus eid). 
The only trace of sulci in the pallium is a shallow | 
posterior paramedian (lateral) sulcus, . 0. C. 1323 ae 
Presented by H. Power, Esq. 

Flatau and Jacobsohn, Vergl. Anat. d. Cone 
1900, p. 351. ; 


D. 264, The left cerebral hemisphere of a Rabbit (Lepus cur te 
culus), dissected to show the hippocampus (fig. 76). 


Fig. 76. (Nat. size.) 


Being a larger bein this shows more clearly than the 
Hedgehog’s brain the difference between the Butherian and 


NERVOUS SYSTEM.—VERTEBRATA. 207 


Metatherian hippocampus. The Rabbit’s hippocampus is 
restricted to the caudal part of the ventricle and does not 
extend so far forward as that of the Wallaby (D. 210). 

Note the continuity of the lateral ventricle with the 
cavity in the olfactory bulb. 


D. 265. Two casts of the cranial cavity of a Rabbit (Lepus cuni- 
culus). 


Orpver CHIROPTERA. 


D. 266. A cast of the cranial cavity of a Rousette Bat (Pteropus 
vampyrus). 

The brain in the Chiroptera exhibits features which 
indicate its lowly status in the mammalian series. It does 
not show signs of any marked specialisation or divergence 
from the primitive type of the Insectivora. 

The hemisphere is peculiar in that the rhinal fissure is 
almost completely deficient, although the well-developed 
pyriform lobe and neopallium present typical features. In 
the small bats the minute cerebral hemispheres are separated 
by a wide gap from the cerebellum so that almost the whole 
of the corpora quadrigemina is exposed. These hemispheres 
are, of course, quite smooth. In the larger forms, such as 
Cynonycteris, there is a well-developed splenial complex of 
calcarine and intercalary sulci of the typical form. In the 
largest representatives, such as Pteropus, this splenial are 
becomes even more extensive. 

On the cranial surface there is in Cynonycteris a very 
short, deep suprasylvian sulcus and a small shallow lateral 
sulcus. The latter may in some cases become deeper and 
more extensive. In this cranial cast of Pteropus there 
is a short, deep, suprasylvian and a short, shallow, lateral 


sulcus. 
There is no orbital sulcus, nor is there any trace of a 
pseudosylvian sulcus. . 


In the larger Bats the cerebral commissures are well- 
developed and resemble those of Galeopithecus. But in 
many of the smallest Bats (e. g. Nyctophilus and Vespertilio) 
the corpus callosum becomes extremely reduced in size so 


208 PHYSIOLOGICAL SERIES. 


that. the commissures present a spurious resemblance to — 
those of the Marsupialia (Trans, Linn. Soe. vol. vii. pt. 3, — 
1897, p. 47). 3 
The cerebellum and the other parts of the brain closely — 
resemble the corresponding organs in Galeopithecus. " 
In the small Bats the enormous development of the — 
auditory tracts is specially noteworthy. 
Flatau and Jacobsohn, Vergl. Anat. d. Centralnery. — 
1900, p. 208. | 
Gervais, Journ. de Zool., t. i. 1872, p. 437. Also — 
Retzius, Leche, Elliot Smith, and others. 


Orver EDENTATA, 


Family Dasypopips. 


D. 267. The brain of a Six-banded Armadillo (Dasypus seacinctus). _ 
This is a simple, highly macrosmatic brain resembling — 
that of the generalised Insectivores in most of its features. 
The rhinal fissure, however, consists of two fragments — 
separated by a wide gap (fig. 77). The posterior of these _ 


Fig. 77. (Nat. size.) 


RHIN. F, POST, 


RHIN.F. ANT. 


OLF. BULB. 


{ . 
tus.o.r, TUB. OLF, TR. 


(RHIN.F.PosT.) is prolonged obliquely forward into con-— 
tinuity with a suleus (8) of the neopallium, which probably 
corresponds to the orbital or presylvian suleus of other 
mammalian brains. Above the posterior rhinal fissure there 
is a second oblique sulcus (6) in the neopallium, which may 
be regarded as the representative of the suprasylvian sulcus: : 
of the Carnivora or of the Myrmecophagide. | 


NERVOUS SYSTEM, 


VERTEBRATA. 209 


On the mesial surface of the hemisphere there is a sulcus 
which may possibly represent a highly placed calcarine, 
which has become prolonged forward after the manner of 
the so-called “splenial” sulcus of Krueg in most mammals. 

The appearance of the diminutive corpus callosum (c.c.) 
and the large hippocampal commissure (ps.D., Ps.v.) and 
anterior commissure (A.C.) are shown diagrammatically in 
the accompanying scheme (fig. 78), which also exhibits the 


Tig. 78. 


relations of the fornix or fimbria (F), the fascia dentata 

(F.D.), hippocampus nudus (N.H.), and vestigial hippo- 

campus (v.H.) to the commissures and precommissural 

area (P). ». Q,C. 18231. 

Elliot Smith, Trans. Linn. Soc. (2nd Series, Zool.) 
vol. vil. 1899, p. 297. 


D: 268. The brain of a Cabassou (Cabassous unicinctus). 

This is an excellent example of a simple, highly macros- 
matic brain essentially similar to that of the Six-banded 
Armadillo, but relatively much shorter and broader than 
the latter. na 

The large olfactory bulbs are flattened against the anterior 
surface of the short cerebral hemispheres (figs. 79, 80, 81). 

The posterior rhinal fissure is represented only by a very 
shallow depression (fig. 80), but the supposéd representative 
of the orbital sulcus is exceedingly well developed (figs. 79 
and 80). 

The representative of the sulcus 8 of Dasypus is much 
more insignificant in Cabassous (figs. 79 and 80) thai it is 
in the former. 

VOL, I. P 


210 


PHYSIOLOGICAL SERIES. 


. 


There is a small corpus callosum and large psalterium 
(fig. 81), as in Dasypus (compare fig. 78) ; and the vestiges 
of the supracallosal and precallosal parts of the hippocampal 


Fig. 79. 


Fig. 80, (Nat. size.) 


SULC, ORB. 
RHIN.F. ANT f 


{ 
OLF.TuB. 


Fig. 81. (Nat. size.) 


HIP. VESTS. 
HIP. VEST, "é 


AREA PRECOM, HIP. INV, 


are are exceptionally clearly demonstrated (fig. 81). The 
arrangement of these parts agrees with that sho 
diagrammatically for Dasypus in fig. 78. “i 


NERVOUS SYSTEM.—VERTEBRATA. 211 


There is a very well-developed “ splenial ” sulcus, pro- 
bably representing the conjoint calcarine, intercalary and 
genual sulci of other mammals. It extends much further 
forward than the analogous sulcus in other Armadillos. 

The features of the typical, primitively simple mamma- 
lian cerebellum are unusually clearly shown in that of 


Cabassous (figs. 82, 83, 84, & 85). It closely resembles 
Fig. 82. (Nat. size.) Fig. 83. (Nat. size.) 


LOB. CENT. 


LOB. CENT.-- 


SECUN.F...- 


LOB. POST. ..- 


4 ‘FLO 
LOB. POST. 


Y 
CORP. QUAD. 


LOB. ANT.=Lobus centralis+-Lobus AREA C=Lobus tuberis. 

culminis. x= Lobus biventralis+ Amygdala. 
AREA A=Lobus clivi. | LOB. Post.= Uvula+nodulus. 
AREA B=Lobus cacuminis. 


that of the Rabbit except! that the large cake-like floccular 
lobe (composed of flocculus and paraflocculus) is here sessile 
and flattened against the rest of the cerebellum. 
O. C. 1323 1a. 
Elliot Smith, Trans. Linn. Soc., vol. vii. 1899, pp. 321 & 
371. . 


D. 269. The brain of a Three-banded Armadillo (Tolypeutes 
tricinctus). 
This brain is like that of Cabassous, but is smaller. The 
suprasylvian sulcus is absent, the orbital (presylvian) sulcus 
P 2 


212 PHYSIOLOGICAL SERIES. 


a 


is shorter. There is no pallial sulcus on the mesial surface of — 

the left hemisphere, but a faintly marked furrow is present — 

above the corpus callosum in the right side. O.C. 1823 1. 
Elliot Smith, Trans. Linn. Soc. loc. cit. 


D. 270. The brains of two Pebas ( Tatu novemeineta). 
In most of their features these brains closely resemble 
that of Cabassous. 
Fig. 86. (Nat. size.) ie 


RHIN, F. POST. _ 


RHIN,F, ANT, 


OLF.BULB - 


OLF, TUBER. 


The posterior rhinal fissure is very small and the anterior — 
rhinal is also very short. There is a well-defined presylvian — 
(8) but no suprasylvian sulcus. E 
The most noteworthy feature is the large size of the corpus” 
callosum in comparison with that of other Armadillos, : 
O. C. 1323 re, 
Elliot Smith, Trans. Linn. Soe. loc. cit. 


Family GrypProponTips. 


D. 271. A cast of the cranial cavity of Glyptodon claviceps. 

This is a replica of Gervais’s model. It shows the 
extraordinarily small size of the brain in comparison with 
that of the body of the animal ; the enormous dimensions — 
of the large, pedunculated and projecting olfactory bulbs 3 
the diminutive size of the cerebral hemispheres ; and th 
extraordinary greatness (especially in breadth) of th 
cerebellum. ; 

The cerebral hemispheres are flattened, and the only trace 
of a sulcus is one in the “ Sylvian region,” which probabl: 
represents the so-called suprasylvian sulcus of the Arm 
dillos, unless, after the analogy of Galeopithceus and mz 
Eocene Mammals, it is a phenomenally high rhinai fissure. 

Gervais, Nouv.’ Arch. Mus., t. v. 1869, p. 42. 


NERVOUS SYSTEM.—VERTEBRATA. 213 


D. 272. A cast of the cranial cavity of Glyptodon claviceps (two 
specimens). 
This is a less perfect cast of a larger brain than D. 271. 


Family BraDYPopIDZé. 


D. 273. The brain of a Three-toed Sloth (Bradypus tridactylus). 
[This specimen, having been preserved zz situ in the 
cranium, exactly retains its normal shape, but is unfortu- 
nately too soft to permit the arachnoid and pia membranes 
to be removed. The latter, however, are sufficiently thin 
to permit the sulci to be distinctly seen. | 


Fig. 87. (Nat. size.) 


SULC .DIAG.., 


OLF. BULB 


é 
OLF.. TUBER 


‘3 ‘“t 
H 
i PARAFLOC. 
PYP.L, -RHIN-F. 


Fig. 88. (Nat. size.) 


\_.---OLF. BULB 


The contrast between this brain and that of an Armadillo 
is almost as pronounced as are the differences exhibited in 
a comparison of the brains of the Cat and the Hedgehog. 
The contrast between the habits of the fossorial, terrestrial 


214 PHYSIOLOGICAL SERIES, 


Arniadillo and the arboreal herbivorous Sloth sufficiently 
explain the fact that the former is much more highly a 
macrosmatic than the latter. ~~ 

In the Sloth the neopallium is, in comparison with that : 
of the Armadillo, very large, although it is considerably 
smaller than that of Carnivores of the same size. It : 


Fig. 89. (x 2.) 


corp.ca.. ©& 


“ee 
- 


~ 
te. 

Tee, . ran 

i 


OLF.TUBER. / * 
COMM, ANT, 


is moreover richly supplied with deep sulci, which con- 
form to a pattern curiously like that which prevails among 
the Carnivora. 

The cerebral hemispianantd are sufficiently large to hide 
the corpora quadrigemina and to overlap the cerebellum to 
some slight extent ; it also partly overhangs the olfactory 
bulbs (fig. 87) but no olfactory suleus is developed. 

On the ventral surface the posterior part of the pyriform 
Jobe forms a very pronounced protuberance, commonly 


NERVOUS SYSTEM.—VERTEBRATA. 215 


known as the “ natiform eminence,” and as a result of this 
prominence there is a deep vallecula Sylvii separating the 
latter from the anterior part of the pyriform lobe and the 
olfactory tubercle. 

In profile the brain presents a general resemblance to the 
Feline type, although there are many differences. The 
cerebral hemispheres of the Sloth are, in comparison with 
those of the Cat, much more highly macrosmatic ; or, to 
express the same fact more accurately, the neopallium is 
relatively smaller in the Sloth. 

The anterior and posterior rhinal fissures meet in an 
upwardly-directed arc, and the resultant conjoint fissure is 
placed wholly upon the lateral aspect of the hemisphere 
and on a much higher plane than the corresponding fissure 
in the Cat’s brain. 

A distinctive ‘‘ Sylvian fissure” of the Feline type springs 
from the apex of the rhinal arch and ascends with a slight 
backward inclination for a short distance (fig. 87, »). 

There is a deep sulcus (8) which clearly corresponds to 
the presylvian (or orbital) sulcus of the Carnivora. It 
pursues a horizontal course across the blunt cephalic pole 
of the hemisphere. Its mesial:extremity (fig. 89, 8) is pro- 
longed on to the inner face ; this mesial prolongation may 
possibly represent a rostral sulcus. Its lateral extremity 
does not quite reach the rhinal fissure in this specimen 
(fig. 87, 8), but in some cases it joins the rhinal fissure and 
presents relations to the latter and to the Sylvian fissure not 
unlike the arrangement found in the brain of Galeopithecus. 

There can be little doubt as to the homology of the 
-arcuate sulcus 6 (figs. 87 & 88) with the combined supra- 
sylvian and postsylvian sulci of the Carnivora. The 
anterior limb of this suprasylvian arc (so we may call it) is 
very short. There is a short horizontal branch from the 
posterior part of the arc such as is often found in an analo- 
gous situation in the Carnivore’s brain. x 

There is a very small diagonal sulcus (compare the Cat’s 
brain) in front of and slightly below the suprasylvian arc. 

There is a sagittally-directed sulcus (y) analogous to that 
called “ lateral’? in the Carnivora ; it pursues a course 


216 PHYSIOLOGICAL SERIES. 


- 


parallel to the posterior two-thirds of the interhemi- 
spheral cleft. It also crosses on to the caudal surface of 
the hemisphere and approaches, though it usually does not 
join, the upper extremity of the vertical calcarine. This 
arrangement, which does not occur in the Carnivora, is of 
considerable interest in view of the relationship which exists 
between the calcarine and intraparietal (the probable 
representative of the lateral) sulcus and the newer inter- 
calated parieto-occipital sulcus in certain of the Primates 
(vide infra). 

The anterior extremity of the lateral sulcus (fig. 88, y) is 
overlapped on its lateral aspect by a short sagittal sulcus 
(7), which may possibly represent the coronal sulcus of — 
the Cat’s brain (vide infra). 

There is no crucial sulcus. 

The mesial surface (compare figs. 89 and 90) [which is 
not exposed in this specimen] resembles that of the Two- 
toed Sloth in allits essential features (vide specimen D. 275), _ 

The cerebellum appears to be relatively very small. The — 
floccular lobes are large cake-like masses flattened against — 
the lateral aspect of the organ. Hach of these lobes is com- 
posed of the usual three parts, flocculus and dorsal and — 
ventral paraflocculi. In marked contrast to the condition 
found in the Armadillos [vide Cabassous, fig. 83], the dorsal 
paraflocculus is much the largest part of the floccular lobe — 
in the Sloth. The rest of the cerebellum is small, narrow — 
and simple. Its lateral parts are not expanded to the same — 
extent as the corresponding parts in the Carnivores, the — 
Anteaters, or even the Armadillos, In this respect the cere-. 
bellum much more closely resembles that of such forms as — 
Dorcatherium (Ungulata) and Hydrocherus (Rodentia). 

O. C. 1328 Hb. 

Elliot Smith, Trans. Linn. Soe. vol. vii. 1899, p. 296. 


= 


D. 274. The brain of a Three-toed Sloth (Bradypus tridactylus) — 
( g ), enclosed in the vascular pia and arachnoid membranes. — 

In this specimen the independent intercalary sulcus can 
be seen on the mesial surface. The coronal and lateral 
sulci seem to be fused. O. C. 1323 Ha, 


NERVOUS SYSTEM.—VERTEBRATA. 217 


D. 275. The brain of a Two-toed Sloth (Cholapus didactylus). 
(Figs. 92 and 93 are not drawn from this specimen.) 
In most of its features this brain presents a most striking 
resemblance to that of the Three-toed Sloth. But this 


Fig. 91. (Nat. size.) 


OLF. BUL B. 


SULC. ORB 
\ 


SULC.COR-L.../ | 


SULC. SUPRAS :+4 


SULC.ENT.L”/ 


Fig. 92. (Nat. size.) 


OLF.BULB 


rioc.. 


ee 

o.r.tuper.  ***-*- PONS. trap, 
general similarity renders more remarkable the peculiar 
absence of the so-called ‘“‘ Sylvian fissure”’ in this larger of 


the two brains of the Family of Sloths. 


218 


PHYSIOLOGICAL SERIEs. 


The natiform eminence is much less prominent than it is _ 
in the Three-toed Sloth ; and the bending of the rhinal 
fissure is so slight that the whole fissure is approximately 
horizontal. These two facts are probably correlated with 
the peculiar absence of the so-called “ Sylvian fissure” of 
the Three-toed Sloth. Whilst it is surprising to find this 
feature absent in the larger of the two brains, in which we 
should expect it to be better developed, it seems to empha- — 
size the morphological instability of this so-called“ Sylvian 


e 
. 2 
4 


‘eal 


Fig. 93. (Nat. size.) 


HIP, VEST. 


a” 


CORP. CALL. 


OLF. BULB. 
\ 


FASC DENT. 


“HIP. INV. 


AREA PRECOM. 


OLF. TUBER. HIP. F. 


Fig. 94. (Nat. size.) 


sg P. 


CORP MAM 


COMM, MOLL. CORP. INTER. Ps 


fissure,” which a comprehensive survey of the Mammal Lo 
so clearly demonstrates. It also leads us to infer that what— 
we may call the “ feline type of Sylvian fissure” is a mere — 
kink produced by mechanical factors, of which the most 
important is the downward extension of the caudo-ventral - 
part of the neopallium. In Bradypus where such an — 
extension has taken place (witness the ventral curve of the — 
posterior rhinal fissure !), this so-called “ Sylvian fissure” 


NERVOUS SYSTEM.—VERTEBRATA, 219 


makes its appearance ; whereas in Cholepus, in which the 
neopallium has not extended downwards in its caudal region 
(witness the horizontal posterior rhinal fissure), there is no 
“ Sylvian fissure” even though the cerebral hemisphere is 
larger and therefore the greater a priori reason for a 
Sylvian fissure. 

The extensive and deep suprasylvian sulcus (fig. 92, 8) is 
also much less acutely flexed than is the corresponding 
feature in Bradypus. On its ventral side a short horizontal 
sulcus makes its appearance to compensate for the absence 
of the Sylvian element, thus affording further evidence of 
the mechanical mode of formation of the so-called “ Sylvian 
fissure ”’ of Bradypus. 

The presylvian or orbital sulcus (8) joins the rhinal fissure 
in both hemispheres ; otherwise it resembles that of Brady- 
pus. Onthe left side it joins or becomes confluent with the 
rostral sulcus, but on the right side it terminates near the 
mesial edge just behind the upper extremity of the rostral, 
which is a small independent sulcus. 

There is an extensive, sagittal, lateral sulcus, which bifur- 
cates posteriorly. In this specimen (fig. 91) the lateral 
sulcus is fused with the coronal, but in that from which 
figure 92 was drawn these two elements were independent 
(y and). There is also a well-defined entolateral sulcus 
—i. e. a compensatory sulcus developed on the mesial side 
of the lateral. 

The calearine sulcus is peculiar in the Sloths in that itis 
independent of the intercalary sulcus (with which it is fused 
in most mammals to form the so-called ‘ spleniai ” sulcus 
of Krueg). In this respect the Sloths agree with the true 
Anteaters, the Pangolins, and the Primates. This form of 
the calcarine sulcus is undoubtedly the primitive, ancestral 
type for all mammals. 

The calcarine sulcus is vertical and terminates near the 
upper margin of the hemisphere (fig. 93, a). 

The intercalary sulcus begins very far back between the 
splenium of the corpus callosum and the upper part of the 
ealcarine sulcus. On the left side it extends horizontally 
forward almost as far as the rostral sulcus. On the right 
side its anterior extremity bends upward and notches the 


220 PHYSIOLOGICAL SERIES. 


dorsal edge of the hemisphere in a manner curiously like 
the conjoint crucial and intercalary sulci of many Carni- 
vores, such as the Civet. [Figure 93 does not represent this 
specimen. ] 

The corpus callosum (¢.c.) and psalterium (P.s.) are 
relatively short and of a somewhat simple type (fig. 90), 
and the relations of the hippocampus to the commissures 
and to the supracallosal (v.H.) and precallosal (v.H//) 
vestiges of the hippocampal are are clearly shown. ; 

The posterior quadrigeminal bodies are more prominent 
than the anterior pair, and the mesial (posterior) geniculate 
body on each side is so large as to appear likea large caudal 
projection of the chief mass of the optic thalamus. It — 
touches the cerebellum posteriorly. These features are some 
of the physical expressions of a highly acute sense of hearing. __ 

The cerebellum resembles that of Bradypus but is con- 
siderably larger (figs. 92 and 94). 

The large paraflocculus is seen to great advantage. 

Elliot Smith, Trans. Linn. Soe. vol. vii. 1899, p. 309. 


D. 276. The brain of a Two-toed Sloth (Cholepus didactylus) 
(fig. 92). ) 

In this brain the chief sulcus in the region where the 

“lateral” sulcus should be found obviously corresponds to 
that which in the last specimen was called “ entolateral.” ” 
There is, however, a coronal sulcus like that of Bradypus 
(D. 273), occupying the situation of the anterior part of the _ 
“lateral” sulcus of the last specimen; and also a short 
caudal sulcus on the lateral side of the “ entolateral” which 
appears to join the calcarine. ‘a 
This shows to how great an extent this group of sulci 
lacks morphological stability. They accommodate them=- — 
selves to slight mechanical differences in the process of © : 
growth in such a way that no exact homology with appa- — 
rently identical sulci in other groups can be said to exist. 
0. C, 1823. — 


D, 277. A cast of the cranial cavity of a Two-toed Sloth q 
(Cholepus didactylus). 7 
This shows the exact shape and size of the cerebellum, — 


NERVOUS SYSTEM.—VERTEBRATA. 221 


the cerebellar hemispheres, and especially of the olfactory 
bulbs. 
Gervais, Nouv. Arch. Mus., t. v. 1869, p. 38. 


D. 278. The brain of a Hoffmann’s Sloth (Cholepus hof'manni). 

This brain closely resembles that of the ordinary Two- 
toed Sloth. 

In this specimen the anterior extremity of the supra- 
sylvian sulcus opens into the rhinal fissure, and a curious 
triangular depression is found behind the junction. This 
is more pronounced on the right hemisphere and presents 
a curious resemblance to the fossa Sylvii. There is, how- 
ever, no true Sylvian fissure, although on the left hemisphere 
the pit-like representatives of the compensatory supra- 
sylvian sulci open into the rhinal fissure so as to produce 
a spurious resemblance to it. 

It is instructive to note in this specimen how in the 
pyriform lobe the operation of factors such as produce the 
pseudosylvian sulcus in the neopallium of many mammals 
has converted the vallecula Sylvii into a sulcus like the 
neopallial pseudosylvian sulcus of other forms. 

On the left hemisphere there are two coextensive sagittal 
sulci, the mesial of which may represent either the 
“lateral”? or “ entolateral”’ sulcus, and the external may 
be either the caudally prolonged “‘coronal”’ or the “ lateral” 
(see account of specimen D. 276). 

On the right hemisphere the condition resembles that 
of specimen D.276. None of these cranial sulci join the 
calcarine. 

There are well-developed post-lateral and paracalcarine 
sulci. 

Turner, Journ. Anat. & Phys., vol. xxv. 1890, p. 122. 


Family MzGATHERIIDzA. 


D. 279. A cast of the cranial cavity of a Megatherium cuviert. 
This presents an extraordinarily close resemblance to the 
Bear’s brain, but is considerably larger. 
There is a deep oblique depression in the ‘“ Sylvian 
region,” and appearances suggest that there was a long 


222 PHYSIOLOGICAL SERIES, 


oblique pseudosylvian sulcus, like that of the Bears, with 
an extensive suprasylvian arc presenting such an acute 

flexure as is seen only in the Arctoid Carnivores (of existing _ 
mammals). Tocomplete the resemblance, the area between 
these two sulci is depressed, as it sometimes is in the Bears, _ 
and always in the Seals. There was an orbital suleusanda __ 
lateral sulcus of the typical Carnivore pattern. In front of 
the latter there was a great transverse sulcus, like the 
crucial sulcus ; this may, however, be the coronal sulcus. 

Gervais, Nouv. Arch. Mus., t. v. 1869, p. 39. 


D. 280. A cast of the cranial cavity of a Pampean Ground-Sloth 
(Grypotherium listat). 
‘‘Compared with the brains of Mylodon and Scelido- 
therium, . . . that of Grypotherium is observed to be more 
elongated, witht less divergent and prominent olfactory 
[bulbs], less constricted cerebral hemispheres, and a larger _ 
cerebellum. In the form and proportions of its cerebellum, _ 
it similarly differs from Megatherium. The cerebral hemi- 
spheres of the existing Cholepus didactylus and Bradypus _ 
tridactylus are more tapering forward, and their cerebellum _ 
is relatively smaller than in Grypotherium.” (Smith Wood- 
ward, Proc. Zool. Soc. 1900, p. 69.) 
The cast shows only in a very vague manner the arrange- 
ment of pre- and suprasylvian sulci, resembling those of 
Choloepus. This specimen is, moreover, interesting as 
an illustration of the caution needed in drawing inferences 
from the general shape of a cranial cast; for if the olfae- 
tory bulbs were broken, as so commonly happens, and the — 
sulci a little more blurred, one might easily mistake this — q 
for the cast of some Dugotigelike Sirenian. ay’ 


Family MyrmecopHacip”. 


D. 281. The brain of a Great Anteater (Myrmecophaga jubata), 
The right cerebral hemisphere has been separated from the — 
rest of the brain. [This drawing of the right hemisphere — 
has been reversed. ] 7 

The elongated form of the cerebral hemispheres presents 
a marked contrast to that of the Sloths. The olfactory 
bulbs are very large. 


NERVOUS SYSTEM.—VERTEBRATA. 223 


The anterior rhinal fissure is horizontal and forms an 
angle of about 120° with the posterior rhinal, which crosses 
on to the ventral surface at a point midway between the 
vallecula Sylvii and the caudo-ventral angle of the hemi- 
sphere. 

On the right hemisphere (fig. 95, reversed) there is a deep 
triangular depression communicating with the bend of the 
rhinal fissure. From the apex of this depression a very 
short sulcus (not more than 5 mm. long) extends upward 
and slightly backward ; this undoubtedly corresponds to 
the so-called “Sylvian fissure ” of Bradypus and Felis. 


Fig. 95. (x 3.) 


SULC.DIAG, —SULC. COR. LAT. 


SULC, SUPRAS. 
SULC.ORB." ies 


“™SYL.F. 


i : RHIN.F. 
OLF.TUBER. PYR.L. 


There is a short suprasylvian sulcus joined to a much 
longer postsylvian (or “ posterior suprasylvian” as it is 
more generally called). In front of the suprasylvian sulcus 
there is a small deep sulcus analogous to the diagonal of 
Bradypus and the Carnivores. 

There is a long, deep, presylvian or orbital sulcus ; it is 
separated by a short interval from the anterior rhinal fissure 
and is joined to the prorean sulcus (véde the Carnivora), 
near the interhemispheral cleft. 

There is a long, deep, lateral or conjoint corono-lateral 
sulcus in the posterior two-thirds of the hemisphere, and 
two short and relatively shallow post-lateral sulci behind it 
parallel to the postsylvian sulcus. 

There is a deep, vertical calearine sulcus on the medio- 
caudal aspect of the hemisphere. As in the Sloths it does 
not join the intercalary sulcus, which is represented in this 
hemisphere by two shallow sulci, 


224 PHYSIOLOGICAL SERIES. 


The chief interest of this brain is the wide separation of 
the so-called “ Sylvian fissure” and the suprasylvian suleus 
in the right hemisphere. The condition almost always 
found in Myrmecophaga is seen on the left hemisphere. 
There the so-called “ Sylvian fissure ” and the suprasylvian 
sulcus have become confluent so as to form a long, deep 
sulcus extending almost as far as the lateral sulcus. The 
postsylvian sulcus is not joined to the suprasylvian element. _ 

This confluence of these two elements to form a Sylvio- 
suprasylvian complex is of great interest, because there are 
many reasons for believing that a similar fusion takes place — 
in the Primates. If this be so, the “ Sylvio-suprasylvian ” 
complex of the Anteater is the nearest approach to the — 
condition of the true Sylvian fissure of the Primates. 

Now such a confluence of these two sulci may be regarded — 
as the normal condition in the Great Anteater. The interest _ 
of this fact is enhanced when it is recalled that the calearine 
sulcus is separated from the intercalary—another Primate _ 
feature. O. CO. 1323 kK. 

Presented by the Zoological Society. 

Elliot Smith, Trans. Linn. Soe. vol. vii. 1899, p. 293. 


D. 282. The brain of a Great Anteater (Myrmecophaga jubatu), in 
which the right hemisphere has been separated from the 
rest of the brain. (Figs. 96, 97, 98, 99.) 

The sulci in this brain are exceedingly interesting when 
compared with those of the above specimen (D. 281). | 
The Sylvio-suprasylvian complex approaches so near to — 
the upper extremity of the postsylvian, as to afford a 
striking resemblance to the suprasylvian are on the right 
hemisphere of specimen D, 281; thus it further confirms — 
the suprasylvian nature of the upper part of the “Sylvio- — 
suprasylvian ” sulcus, . 
There is no diagonal sulcus, such as is seen in the 
preceding specimen. There is a very short posterior ecto- 
sylvian sulcus on the right hemisphere and none on the left, 
On the left hemisphere the orbital or presylvian suleus — 
opens into the anterior rhinal fissure. On the right hemi- — 
sphere it does not do so; it is also quite independent — 
of the small prorean sulcus on this side. 


NERVOUS SYSTEM.—VERTEBRATA. 995: 


On the right hemisphere there is a typical corono-lateral 
sulcus ; buton the left side the coronary sulcus is prolonged 
obliquely backward and mesially beyond the junction. 
The same phenomenon occurs on the left hemisphere of 
specimen D. 281. 


Fig. 96. (x 2.) 


SULC.COR.LAT: 
SYL.SUPRAS.COM ” — suLC. P. LATE 
SuLc. ORB ie be 


SULC. PROR. 


OLF.BULB, 


Fig. 97. (x 3) 
_OLF. BULB. 


OLF. PED. 

Fete SULC PROR, 
_»SULC. ORB. 
‘ RHIN. Fs 


i -- SULC, COR.LAT. 


In the right hemisphere there is a single extensive inter- 
calary sulcus, which is prolonged forward in a “ genual 
manner ”’ to join the rostral, which is very short On the 
left hemisphere we find the same condition as in specimen 


D. 281. 
VoL, I. Q 


226 PHYSIOLOGICAL SERIES. 


In'this specimen the features of the typical hippocampus, — 
pyriform lobe, olfactory tubercle, and the large tubercle of ; 
the olfactory tract are exceedingly well shown (fig. 99). 
Note also the corpora quadrigemina and the large mesial 4 
geniculate body. -% 
The features of the cerebellum, which resembles that of a 
the Carnivores, are also very clearly shown. An » 5 
tionally clear demonstration of the floccular lobe is afforded. 


Fig. 98. (x 3.) 


SULC. INTERCAL.. 


: j q . 
OLF BULB. OLF, TUBER. FASC. DENT, HIP. F. 


Fig. 99. (x 2.) 
CAC. PERFOR: 
OPT TR. jj OLF. TUBER 


pe 
a 


The paraflocculus consists of two plump, horizontal, vermi- 
form bands, which become continuous in front but do no 
form any projecting petrosal lobule. The flocculus (sensu 
stricto) is a little mass wedged in between the ventral para- 
flocculus and the auditory nerve. 
D. 283. The brain of a Great Anteater (Myrmecophaga j | rat } 
(?), in which the right hemisphere is separated (fig. 10€ 

This brain is of great interest because the PS (a 
especially the anterior) of the Sylvian trigone are so poor 
developed that this depressed area is wholly exposed, 


NERVOUS SYSTEM.—VERTEBRATA. 227 


The suprasylvian element in the Sylvio-suprasylvian 
complex sulcus is very slightly developed on the left side, 
and there is a small diagonal sulcus (6' ). 

The Sylvian trigone shades away anteriorly on the right 
side, without any very definite terminal sulcus ; but on the 


Fig. 100. (x 3.) 


LOS.ANT, 


RHIN. F. ANT. : is ra 
DLF-TueER. PYRLL. RAIN. F-POST: 


left side there is a faintly-marked oblique terminal sulcus, 
which reaches almost as far as the lower extremity of the 

presylvian sulcus (8). 
The prorean sulcus (8’) is again separate only on the 
right side. QO. C. 1323 Ke. 
Presented by the Zoological Society. 


ony yi 


D. 284. The brain-stem, with part of the cerebral hemispheres, 
of a Great Anteater (Myrmecophaga jubata). — 

This specimen is intended to show the corpus striatum 
in the lateral ventricle ; the communication of the latter 
with the olfactory ventricle ; the optic tract spreading out 
on the optic thalami ; the tenia thalami and mesial geni- 
culate body ; the corpora quadrigemina, of which the 
posterior pair are the more prominent ; the insignificant 
tractus peduncularis transversus ; and the broad pons over- 
lapping to some extent the trapezoid bodies. 


m ———————————— 
‘ee aegis 


4 D. 285. The brain of a Tamandua (7% pnmatenk tetradactyla) 
(figs. 101, 102, 103, 104, 105 & 106). 

This is a smaller xn correspondingly simplified copy of 
_ the Great Anteater’s brain. All traces of the “ feline 
Q2 


eS * 
i, 


4 


228 


PHYSIOLOGICAL SERIES. 


Sylvian fissure” have vanished (fig. 102), but the more 
stable suprasylvian sulcus remains in this specimen (figs. 
101 & 102) to add further confirmation to the interpretation 
of the Sylvian complex of Myrmecophaga (D. 281). [Some- 
times, however, even the suprasylvian suleus disappears in 
Tamanduas (fig. 103) ; this is especially helpful in inter- 
preting the Rodent brain, for it shows that an undoubted 


Fig. 101. (Nat. size.) 


~ 
aN m 
1 i 
— ‘ Dp 
- os 
y * 
ae 
~ 


Fig. 102. (Nat. size.) 


SULC. SUPRAS. SULC. LAT. 
} my 


lateral (or corono-lateral) sulcus may exist without the — 
suprasylvian, which is usually the more precocious and 
stable feature. | 

The lateral sulcus is very shallow. In this specimen it — 
is unsymmetrical and consists of two irregular fragments 
on each side. 

The cerebellum (compare fig. 103) is a simplified and 
smaller copy of that of the Great Anteater. The floccular — 


NERVOUS SYSTEM.—VERTEBRATA. 229 


lobes, however, project.freely, whereas those of the Great 
Anteater are sessile. 

The mesial surface of the cerebral hemisphere of Ta- 
manduas (compare fig. 104) is instructive in showing the 


Fig. 103. (Nat. size.) 


...-OLF. BULB. 


SULC.ORB. 


SULC. LAT. 


MED OBL. ------ 


Fig..104.. (Nat. size.) 
PSAL. D. 


PSAL.V. 
% CORP, CALL. 


a” 


SULC. LIM. PALL. 


OLF. BULB. ------ 


’ 
’ 


OLF..PED.’ ! i * *PYR.L 
OLF. TUBER. / } \ — i 
AREA PRECOM. } TUB. OLR. TR. 
COMM.ANT. 


exceedingly rudimentary characier of the sulci, in spite of 
the fact that this brain. is. much larger than that of the 
Sloths and Armadillos, which have well-defined mesial 


q 


sulci. The cerebral commissures and hippocampus (figs. 
104 & 105) have now assumed characters like those of the 


Carnivores and Ungulates. 


230 PHYSIOLOGICAL SERIES. 


Fig. 105. (Nat. size.) 


Hi) _o.r. TR.TUBER. 


“%) ... iINFUN. 


=< 
aeons oer" ?" 


wn-ne-s-+efiml-- CRUS. CER, 


—_— ee. 


The typical features of the base of the brain are also 4 
well shown (fig. 106). ) 0. C. 13823 KO, — 
Elliot Smith, Trans. Linn. Soe. vol. vii. 1899, p. 293. 


D. 286. The brain of a Tamandua (7Zamanduas tetradactyla), (3). 
There is no suprasylvian suleus (compare fig. 103). The 

lateral sulcus is well marked and simple, as is also the pre- 
sylvian or orbital. There is a small shallow postlateral — 
sulcus. 0. C, 1323 Ka, 


NERVOUS SYSTEM.—VERTEBRATA. 231 


Family Manip, 


D, 287. The brain of a Pangolin (Manis tricuspis), in which the 
two cerebral hemispheres have been separated from the 
brain-stem (figs. 107, 108, and 109). 


Fig. 107. (Nat. size.) 
OLF. BULB. 


=~ Fig. 108. (Nat. size.) 


SULC. SUPRAS. 
SULC. LAT. 4 


{ 
ANT.RHIN.F SULC! POST. RHIN. 
F 


SYL.F. 


Fig. 109. (Nat. size.) 


SULC. INTER. 
“s 


SULC. CALC. 


This brain is exceedingly small in proportion to the size 
of the animal, and yet its small, short cerebral hemispheres 
present a series of deep sulci, which conform to the most 
typical mammalian pattern. In many points of detail this 
pattern resembles that of the Three-toed Sloth, while in 
other respects it resembles that of the Armadillos. 


232 


PHYSIOLOGICAL SERIES. 


There is a typical, short, vertical calcarine suleus close ia 
behind the upper half of the hippocampal fissure. Like 
that of the Sloths, it does not join the intercalary suleus. 
It, however, presents as an interesting peculiarity a short | 
retro-calearine branch, just as the homologous sulcus does a 
in the Lemurs. 
There is an elongated intercalary sulcus of about ! 
the length of the small corpus callosum. In front it joins 
a short, oblique, rostral sulcus. ne! 
It is a very suggestive fact that the intercalary suleus, — 
which is quite independent of the calcarine in the Anteaters — 
and Sloths and in no other mammals except the Primates, 
should also be separated from the calcarine sulcus in the 
Pangolin. 2 
The Sylvian region [which unfortunately is irretrievs 
damaged in this specimen] presents very interesti ng 
features. In another damaged specimen [in the Museum 
Store Room] the posterior rhinal fissure, which is ple 
high up on the lateral aspect, is prolonged forward ints : "a 
very deep orbital (presylvian) sulcus. Gervais and Weber 
have recorded further instances of a similar condition in 
Manis. This complex of posterior rhinal fissure and orbit u 
sulcus resembles the arrangement seen in the Armadillos 
and, more distantly, the condition found in Orycteropus, 
Tapirus, and Moschus (vide infra). In this particular 
specimen (D, 287), however, the left orbital suleus is 
certainly not joined to the rhinal fissure. 4 
The short anterior rhinal fissure does not reach so far 
back as the anterior extremity of the posterior rhinal. In 
this respect it resembles that of the Armadillos. A short, 
oblique “ Sylvian fissure” springs from the posterior n nal | 
fissure, just where the latter joins, or appears to join, 3 
orbital sulcus. ‘The appearance of the “Sylvian” ant 
orbital elements recalls that presented in Galeopi 
There is a typical semicircular suprasylvian sulcus pre 
ing an arcuate form. There is also a typical, cage 
directed lateral sulcus. P: 
The cerebellum and the other parts of the brain are not 
unlike those of the Sloths, or, rather, present ur 
intermediate between those of the Armadillos and Sloth 


NERVOUS SYSTEM.—VERTEBRATA. 233 


Considered as a whole, the brain of the Pangolin may be 
regarded as a smaller and correspondingly-simplified copy 
of that of the Three-toed Sloth. This fact, in view of the 
marked contrast in the modes of life of the two animals, 
must be allowed considerable. systematic importance*. 

O.C. 1323 M. 
Presented by the Zoological Society. 
Max Weber, Zool. Ergebnisse, Leyden, 1892, p. 87. 


Family OrycreroPopip~. 


D.288. The brain of an Aard-vark (Orycteropus afer), (2?) 
(figs. 110, 111, 112, 113, 114, & 115). 
The brain is of approximately the same size and shape as 
that of the Great Anteater, but its features present a most 
striking contrast to it. 


Fig. 110. (x 2.) 


RHIN.F. ANT. RHIN.F. POST. 


y § 


PYR.L. 


OLf. BULB. 


OLF.TUBER. 


PYR.L. 


In neither of the specimens [in this collection] does the 
posterior rhinal fissure join the anterior rhinal, but the two 
fissures overlap (fig. 110) as they do in the Tapir (vide infra). 
Sometimes, however, the two fragments unite to form a 


* When my memoir on the Edentate brain was written, I had not 
examined a good specimen of the brain of Manis and had to rely on Weber's 
account chiefly. I therefore saw no reason for associating Manis with the 
other Edentates, so far as the structure of its brain is concerned. Now 
that I know the brain itself, I quite agree with the conclusion drawn by 
Windle and Parsons from myological studies (P. Z. S. 1899), and believe 
that Manis shows undoubted affinities to all the other Edentates and 
especially to Bradypus. 


PHYSIOLOGICAL SERIES. 


great sai fissure (fig. 111), which divides the Latceul 
wall into two approximately equal parts—an upper one ie 
neopallium, and a lower composed of pyriform lobe, tuber- 
culum olfactorium, and olfactory bulb. 

There is no trace of a “Sylvian fissure.” There is *) P 
typical orbital (presylvian) sulcus (8) which links the — 
cephalic prolongation of the posterior rhinal fissure to th 7 
anterior extremity of the great sagittal lateral suleus” 
(figs. 110, 111, & 113, y), and from the junction the 
prorean sulcus extends forwards. 4 


’ 


Fig. 111. (x 4) 


* } e 
OLF.TR. i ae 
ovr. Tuer. *** 


Fig. 112. (x 3.) 


CER. 


PRIM.F. | — FLOC.F. 


CORP. PIN. } ae 
CORP :puUAD. Fis 
OPT.THAL. | (WH > MED. OBL. 


AREA TEGMEN. 


There is a short horizontal suleus (8) in the situation 
where we should look for the suprasylvian sulcus, 14 
peculiar insignificance of the suprasylvian as compare 
with the lateral sulcus, which is also seen in Tamanduas at 
many Rodents, presents a marked contrast to the Ungulat 
condition, where just the opposite condition obtains. ei 

On the mesial wall there is a large arcuate connra 
(fig. 114, a) of deep calearine, intercalary, and genual st 


NERVOUS SYSTEM.—VERTEBRATA. 235 


The latter joins the anterior extremity of the callosal 
sulcus. 

The corpus callosum is short. There is a very large 
vestigial hippocampus on its upper surface. 


Fig. 113. (x 2.) 


_/OLF. BULB. 


.-.-PED.QLF. 


t f------== MED . OBL- 


Fig. 114. (x 3.) 


HIP. VEST. 
*, CORP. CALL. 
\, \ 


 OLF. TUBER. 
OLF. PED. Comm. 


"D -n-0- onsen 


wn 
> 
r 


The other parts of the brain (vide fig. 112) are not unlike 
those of Myrmecophaga, although there is no evidence of 
any close affinity between the two forms. 


236 


PHYSIOLOGICAL SERIES. 


In general appearance and in the arrangement of the” 
horizontal rhinal fissure and its relation to the orbital sulcus, 
this brain presents some resemblance to that of an Ungulate. 
But the poor development of the suprasylvian sulcus is a — 
point in which it differs markedly from the Ungulata. The 
cerebellum also differs most markedly from the “— a 
transversely-foliate, Ungulate type. <a 

There is a peculiar feature in the lower extremity of th 
hippocampal formation—a hippocampal tubercle, which is 


Fig. 115. (xX 3.) 
OLF. BULB. 


.-OLF. PED. 


\ __- OLF. TUBER. 
aoseee OLF. TR . 


PYR. L. ANT~--— 
_»NALL. SYL 


LOC .PERF. .... /.2-™ ~A...-- OPT. TR. 


PYR.L.POST. ../_. 


not exposed in either of these specimens. Such a “ hippo- 
campal tubercle” of inverted hippocampus I have see i 
elsewhere only in one of three specimens of the Manat 
and in the Primates. 

I also insert here a drawing (made from a better s 
men) of the base of the brain, because it exhibits in Re 
striking manner the typical relations of the highly macro : 
matic brain (fig. 115). 0. C. 1328 4, 

Presented by the Zoological Societ f 

Elliot Smith, Trans. Linn. Soe. vol. vii. 1899, p. 286. 


NERVOUS SYSTEM.—VERTEBRATA. 237 


D. 289. The brain of an Aard-Vark (Orycteropus afer), ( ? ). 
This specimen resembles the preceding in most respects. 
The suprasylvian sulcus is very insignificant. The lateral 
sulcus is broken up into two fragments, the anterior 
(coronal?) of which does not join the orbital. 


O. C. 1323 La. 


Orprr CARNIVORA. 


Section AULUROIDEA. 
Family Feripz. 


D. 290. The brain of a Domestic Cat (Felis domestica), divided by 
a mesial sagittal section and the right hemisphere separated 
from its half of the brain-stem. 

The Cats exhibit in perhaps their most pronounced form 
the peculiarities distinctive of the true Carnivores, of which 
they form one of the most specialised types. 

In the Carnivora the brain attains to much larger 
dimensions in proportion to the size of the animal than is 
the case in the Rodentia, Edentata, and Insectivora, and 
this increase in size is to be attributed almost entirely to 
the larger growth of the neopallium. 

Among the secondary expressions of these larger dimen- 
sions of the neopallium the most noteworthy are:—A 
tendency of the dorso-caudal regions of the hemisphere to 
bulge over the cerebellum, so that the posterior margin of 
the hemisphere exhibits an increasing degree of obliquity : 
the hemisphere also grows forward so as to bulge over the 
olfactory bulb, and an olfactory sulcus developes on the 
ventral surface of this neopallium to lodge the bulb and 
its peduncle: and the arrangement of the sulci becomes 
more stable and, as it were, fixed. (Compare figs. 116-121, 
representing the Lion’s brain.) 

The brain is still macrosmatic; but the greater size of 
the neopallium renders the greatness of the parts of the 
brain chiefly concerned with olfactory functions less 
obtrusive. than is the case in mammals with a smaller 
neopallium, 


238 PHYSIOLOGICAL SERIES. 


Hence we find in the case of the Cat’s brain that the — 
rhinal fissure (which is the line of demarcation upon the — 
lateral aspect between the essentially olfactory pyriform — 
lobe and the neopallium) is placed very low down on the — 
lateral and partly on the basal surfaces of the hemisphere. 
[See the diagram of the Lion’s brain, fig. 116.] 

A short sulcus, generally known as the “ Sylvian fissure,” 
springs from the junction of the anterior and posterior — 
rhinal fissures. This “ fissure’ does not correspond to that 
called “Sylvian” in the Bears, and it has moreover a 
significance very different to the Human Sylvian fissure. 


Fig. 116. (x 3.)- 
SULC. SUPRAS. SULC . POSTS. 
, SULC. LAT, 
SULC. ANS. i SULC. LAT. P. 
SULC.CR. \ 


\ ced 
SULC.COR- \ , i 


SULC .PROR. 


RHIN.F, | 


OLF. BULB. | 
suc. DIAG. 


\ 


t SULC. ECTOS. P. ln x 


$ 


SULC. ECTOS. A. 


FLoc. 


Hence it will conduce to accuracy and clearness if we call — 
it the “Feline Sylvian fissure.’ It may be compared to — 
that already noticed in the brain of the Three-toed Sloth. 

In the left hemisphere the anterior lip of this fissure has ~ 
been cut away, but there is no distinct area of cortex sub- — 
merged in the fissure such as Holl describes (Arch, f. Anat, — 
u. Entwick. 1899, p. 229). At the same time it will be 
noticed that the lower part of the fissure cuts into the — 
hemisphere very obliquely, so that the anterior lip overlaps — 
the posterior lip. In the larger Felidae this becomes much — 
more accentuated, so that a relatively large area of the — 
posterior lip becomes overlapped by the anterior lip, In — 
such forms, and sometimes also in the Cat, a short suleus — 


NERVOUS SYSTEM.—VERTEBRATA. 239 


indents this submerged posterior lip and separates it from 
the general surface of the hemisphere, so that a much more 
definite submerged area is thus marked off. 

The long, deep orbital (or presylvian) sulcus is placed 
far forward: it opens into the rhinal fissure, and it resembles 
that of the Sloths. 

It is a characteristic of the Cats to have two vertical 
ectosylvian sulci—anterior and posterior—which do not 
unite above to form an are as they do in the Dogs: thus a 
broad cortical bridge, which Meynert has called the “ gyrus 
felinus,” joins the first and second arcuate gyri of Leuret. 

There is a deep suprasylvian sulcus which is almost 
horizontal; it becomes continuous with the vertical post- 
sylvian (or posterior suprasylvian) sulcus of Owen. 

The latter extends vertically downward to a point on the 
caudal margin of the hemisphere at the junction of its 
middle and lower thirds. 

The “lateral”? sulcus pursues a sagittal course midway 
between the suprasylvian sulcus and the mesial edge. In 
front it bends outward parallel to the suprasylvian and 
gives off an “ansate” branch. 

The “ post-lateral” sulcus begins anteriorly opposite the 
junction of the suprasylvian and postsylvian sulci, and 
pursues an arcuate course parallel to the medio-caudal 
“angle” of the hemisphere. On the right hemisphere it 
is joined to the lateral, bui is separate on the left side. 
There is a large transverse crucial sulcus placed very far 
forward on the anterior pole of the hemisphere, immediately 
behind the mesial extremity of the orbital sulcus. It 
crosses the mesial edge and proceeds horizontally back- 
ward on the mesial surface for a short distance above the 
genu of the corpus callosum. 

There is a short oblique coronal sulcus midway between 
the ends of the suprasylvian and crucial sulci. Its upper 
(posterior) end is opposite the angle between the lateral 
and ansate sulci, and its lower (anterior) end is close to the 
orbital. In front of the ventral extremity of the anterior 
ectosylvian sulcus there is a short oblique “ diagonal sulcus.” 
It is not uncommon to find the latter joined to the former 
sulcus. In other cases the diagonal suleus may be absent, 


240 PHYSIOLOGICAL SERIES. 


On the mesial surface of the right hemisphere, note the 
olfactory peduncle passing into continuity with the prem 
commissural area, the upper part of which fills up the gap ~ 
between the corpus callosum and the psalterium, and is 
commonly known as a folium of the septum lucidum. ; 

Underneath the splenium of the corpus callosum the 
subsplenial hippocampal flexure is visible, the pyriform: 
upper part being formed by the fascia dentata rapidly 
dwindling away as it surrounds the splenium: below th 
tapering fascia dentata there is a little tubercle of exposed 
hippocampus — the hippocampus nudus (the so-called 
“ Balkenwindung ”’). 7 

Behind the lower half of the typical hippocampal forma-_ 
tion the caudal part of the rhinal fissure is seen. It ends — 
in a bifid manner. ss 

The calcarine sulcus begins above the latter, ascends 
vertically, and is then prolonged forward and with a sli aI ie 
obliquity upward, so as to overlap, without joining, the 
crucial sulcus: in other words, the calcarine is continuou aa 
with the intercalary sulcus. It is a feature of contrast 
between the Auluroidea and the Cynoidea that in the former 
the crucial sulcus and the intercalary (so-called “ splenial ”) 
sulcus are usually separate, whereas they commonly join in 
the latter. There is a short marginal sulcus (Owen) — @ 
the intercalary in the region of the splenium. = 

On the mesial surface of the brain, note the cavity 0 
the third ventricle bridged by the large “ soft” or idle 
commissure: its anterior wall formed by the delic x 
lamina terminalis, which proceeds from the optic chi ma = 
to the anterior commissure and then from the latter to th 
ventral extremity of the psalterium; behind the latter, th , 
upper extremity of the lamina terminalis is seen as a little” 
gelatinous-like nodule, the crista, to which the epithelia 
roof of the ventricle is attached. (The epithelial roots 
been removed from the specimen.*) 


* 


* The general relations of all the structures enumerated in this and th 
following four paragraphs do not change to any great extent in the Eutheria 
Hence the reader may consult a text-book of Homan Anatomy for a fuller 
account of them, 


NERVOUS SYSTEM.-——VERTEBRATA. 241 


Note the pear-shaped ganglion habenule and the tzenia 
thalami ; the habenular commissure, the pineal body, and 
the posterior commissure forming the upper lip of the 
opening of the aqueduct of Sylvius. The latter is a large 
canal, which expands posteriorly into a trumpet-shape. 

The most noteworthy features upon the lateral aspect of 
the mid-brain are the huge size of the mesial (posterior) 
geniculate body and the prominence of the posterior quadri- 
geminal bodies. Both phenomena are probably related to 
the acuteness of hearing in Cats. 

There is an extremely well-defined tractus peduncularis 
transversus. | 

The pons, anterior pyramids, and trapezoid bodies are 
exceedingly clearly defined, and a slight olivary eminence 
now makes its appearance at the lateral border of the 
pyramid. All the cranial nerves are well-developed and 
present the typical relations. 

The cerebellum presents features closely resembling the 
corresponding organ in the larger Edentates and in some 
of the Rodents. 

There is a large floccular lobe closely applied to the 
lateral aspect of the middle (or pontine) peduncle of the 
cerebellum and the tuberculum acusticum. The latter is 
easily recognised by the insertion of the auditory nerve. 
The floccular lobe consists of three parts, viz. :—A flattened 
body, the flocculus (sensu stricto), closely applied to the 
surface of the acoustic tubercle; a horizontal multifoliate 
band, the ventral paraflocculus, immediately external to 
this; and the dorsal paraflocculus, also a horizontal vermi- 
form band continuous anteriorly with the ventral para- 
 flocculus and posteriorly prolonged into continuity with 
the pyramid (a part of the general mass of the cerebellum). 

The floccular lobes are separated from the general mass 
of the cerebellum by deep floccular fissures. [A similar 
floceular lobe may be seen to better advantage in Myrme- 
cophaga (specimen D, 282): the fundamental plan is ex- 
plained by a series of diagrams in the account of Cabassous 
(specimen D. 268). ] 

The interfloccular mass of the cerebellum may be sub- 
divided for descriptive purposes into three main parts or 
azygos lobes. 

VOL. II. R 


242 


PHYSIOLOGICAL SERIES. 


The whole of the anterior surface of this mass is separated 
from the rest of the cerebellum by means of the deepest 
fissure which crosses the middle line. This we may dis- 
tinguish as the anterior lobe, and its limiting fissure may 
be called “ primary,” as it is the first fissure to cross the 
middle line in the course of development. It corresponds to 
the preclival fissure of Human Anatomy. The anterior lobe 
represents the lobus centralis and lobus culminis of Human 
Anatomy. It is a large lozenge-shaped area, broad in the 


mesial plane and rapidly tapering towards the middle: 


peduncle and the front of the paraflocculus on each side. 

The most caudal or rather caudo-ventral part of the 
cerebellum consists of a small mesial mass, the grey matter 
of which is not continued laterally, as that of the rest of 
the mesial cerebellar areas is. This may be distinguished 
as the posterior lobe and its dorsal limiting fissure as 
“secondary.” The lobe represents the nodulus and uvula 
of Human Anatomy. Laterally it appears to be prolonged 
into a narrow medullary band, which is closely connected 
with the posterior medullary velum and leads to the 
flocculus. 

The great mass included between the primary and 
secondary fissures and limited laterally by the floccular 
fissures may be called the “central” or preferably (to avoid 
confusion with the “central lobe”? of Human Anatomy) 
the “ middle lobe.” 

The middle lobe is divisible into four parts, the behaviour 
of the lateral parts of each of which differs markedly from 
that of the others. 

The anterior lobule consists of a narrow band, which 
becomes slightly constricted on each side of the middle line 
and then expands again to a slight extent to form a long 
tapering fissured band, which forms the posterior lip of the 
primary fissure. In Man. this becomes greatly expanded 
to form the lobus clivi. 

The second lobule is narrow in the mesial plane, but 
expands enormously to form the great suprafloccular (i. e. 
above the paraflocculus) mass, the folia of which are 
arranged in a feather-like pattern in all the Carnivora. 
It presents a similar arrangement in the Anteaters, the 


NERVOUS SYSTEM.—VERTEBRATA. 243 


Aard-vark, and many Rodents, but in many Ungulates and 
Rodents there is no such lateral expansion in a feather-like 
pattern, but a simple transverse arrangement of the folia. 

In the Primates this region of the cerebellum becomes 
so enormously expanded that it forms the great mass of 
the organ. | 

The third lobule consists of an extremely narrow mesial 
bridge connecting two large vertical worm-like masses, 
which extend downward on the caudal surface and separate 
the posterior lobe from the paraflocculus. 

The fourth lobule consists of the pyramid, which is 
laterally joined to the dorsal paraflocculus by a narrow 
band, which has become so compressed by the downward 
growth of the third lobule as to be recognised with difficulty 
in the Cat’s brain. It is, however, clearly shown in such 
brains as that of Lepus and Cabassous. 

Burt G. Wilder, Proc. Amer. Phil. Soc. 1881, p. 524. 


D. 291. The brain of a Cat (Felis domestica), in which the corpus 
callosum has been cut through in a sagittal direction and 
the cerebral hemispheres widely divaricated. 

The caudate nuclei lying in the lateral ventricles have 
been thus exposed. The optic thalami have been drawn 
asunder and the soft commissure partially torn through, so 
that the slit-like third ventricle has been converted into a 
widely open space the limits of which are indicated by the 
teenize thalami, which together form a semicircle. The 
corpora quadrigemina are exposed, and external to the 
anterior quadrigeminal body the large mesial geniculate 
body may be seen immediately behind the optic thalamus. 
‘This mesiai geniculate body may also be well seen upon 
the left side of the base of the brain, the natiform portion 
of the pyriform lobe having been removed in order to 
expose it. QO. C. 1325 v. 


D. 292. The brain of a Cat (Helis domestica) presenting an 
anomalous arrangement of the cerebral sulci. 
On the right hemisphere the pseudosylvian sulcus is 
very short, and on the left is reduced to a mere notch in 
R 2 


244 PHYSIOLOGICAL SERIES. 
the upper lip of the rhinal fissure. This arrangement is 
similar to that presented by the brain of /erpestes, 

The ectosylvian sulci are very deep, as if to compensate 
for the diminutive size of the pseudosylvian. The anterior 
and posterior ectosylvian sulci appear to be joined intoan 
arc on both sides as in Cynoidea; but they are in reality 
separated by a feline gyrus which is partly submerged. 
There are a series of fragmentary sulci between the posterior 
ectosylvian and the postsylvian. The postlateral is a short 
branch of the latter sulcus, and is quite independent of the 
lateral sulcus. The latter is continuous on the left side 
with a long and tortuous coronal sulcus. There are well- 
marked but shallow representatives of an entolateral sulcus 
on each hemisphere. 

This specimen is of special interest as a further demon- 
stration of the fact, which has already been noted in the 
Sloths and the lowlier Mammalian Orders generally, that 
the “ Sylvian fissure” (so-called) is at first a very unstable 
feature and only becomes definitely “ fixed” in the higher — 
Mammalia, It further illustrates the reciprocally com- — 
pensatory development of the pseudosylvian and the ecto- 
sylvian sulci, of which we meet many instances elsewhere*. — 


% 


D. 293. The brain of a new born Lion (Felis leo). 
The only noteworthy features in this specimen are a series _ 

of peculiar notchings in the upper lip of the rhinal fissure — 

in front of the pseudosylvian sulcus, and the extreme — 
irregularity of the iatter and of the ectosylvian sulci. 


O. C. 1825 aa. 


D. 294. The brain of a Lioness (Felis leo), in which a dissection — 
has been made to show the hippocampus in the left hemi- — 
sphere. 4 

The brain of the Lion when compared with that of the a 
(at affords an admirable demonstration of the influence of 


* In the accentuation of the ecto- at the expense of the pseudosyl 
sulcus this anomalous brain resembles the Ungulate type, the so-called 
“ Sylvian fissure” of which is formed by the meeting of the lips of the two 4 
ectosylvian sulci, In this case also the feline pseudosylvian sulcus becomes — 
greatly reduced or even disappears, 


NERVOUS! SYSTEM.— VERTEBRATA. 245 


the size of the body upon the proportions and form of the 
brain. In animals of the same Order (and more especially 
of the same genus) the brain is much larger in the bigger 
species; but the increase in size is not proportionate to that 
of the bodily dimensions, the smaller animal having a brain 
relatively much larger than that of the bigger animal. 
This is due to the fact that in mammals of the same genus 
(2. é. in animals in which the other determining factors of 
the size of the brain may be neglected as being common to 
the two forms) the size of the pallium varies directly with 
that of the areas of the sensory surfaces, and these are 
relatively greater in a small than in a large animal. (See 
Dubois, Bull. d’Anthropol. de Paris, 1897, p. 337.) 

As a result of the larger size of the neopallium, the sulci 
become deeper and longer and secondary sulci make their 
appearance. 


Fig. 117. 


PYR.L.“ ee’ 


* The “Sylvian fissure” (so-called) is much deeper and 
cuts into the neopallium much more obliquely than is the 
case in the Cat’s brain. Thus a large anterior lip is de- 
veloped so as to overlap the depressed posterior lip, which is 
exposed by raising, or better by cutting away (fig. 117), 
the anterior lip. The submerged posterior lip is then seen 
to be indented by two sulci (fig. 117, A ands). In this 
specimen (D. 294) the condition thus described as typical 
of the Lion’s brain does not obtain, and a condition essen- 
tially identical with that of the Jaguar’s brain (vide infra 
D. 297) is present. 


* [The following remarks are based upon the careful examination of the 


brains of three Lions, which were removed from the skulls by the writer 
shortly after the death of the animals: thus a more accurate account is 
given than would be possible from the study of old Museum specimens. | 


246 


PHYSIOLOGICAL SERIES. 


In front of the “ Sylvian fissure” a short, deep, vertical — 
sulcus extends upward from the rhinal fissure (figs. 116 & 
117, x). @ 

The anterior ectosylvian sulcus (fig. 116) is very deep, — 
and its lips are puckered so as to produce short secondary — 
sulci in some cases. In all of the eight hemispheres I 
have examined it is confluent with a very deep, long, — 
horizontal “diagonal sulcus,” which also in most cases 
gives off short secondary branches. j 

In some cases (fig. 118) the anterior limb of the f 
arcuate gyrus of Leuret becomes submerged in the “ Sylvian a 
fissure,” so that the anterior ectosylvian suleus becomes 
hidden in the latter and the diagonal sulcus appears (at a 
casual glance) to emerge from the Sylvian fissure itself. 


Fig. 118. (x 4.) 


D sutc.ecros.p, 


Such a phenomenon is of great interest as an indication of 
the very general tendency (among the Mammalia generally) 
for the cortical areas in front of the “feline Sylvian” 
fissure to become engulfed in it. In the Bears, not only 
the anterior limb but the whole of the first arcuate gyrus 
becomes swallowed up in the “ Sylvian fissure.” 

It is unnecessary to describe in detail the effects of t 
deepening and development of secondary branches in = 
case of the posterior ectosylvian, suprasylvian, and corono- 
lateral group of sulci. These are obvious at a 
(fig. 116). ‘ 

It is of interest to note that the exceedingly iat orbit re 
(presylvian) sulcus is independent of the rhinal fissure ; 
a fact which is veiled in the Cat by the upper opereul im 
of the sulcus meeting the pyriform lobe. 


NERVOUS SYSTEM.—VERTEBRATA. 247 


It is a very interesting fact that an undoubted precrucial 
sulcus is found in the deep crucial sulcus. Sometimes this 
sulcus is exposed (fig. 119) ; in other cases it is hidden by 
the opercular posterior lip of the crucial sulcus and is visible 
only after raising or removing this (fig. 120). So that in 


Fig. 119. (x 2.) 


SULC.PRECRU. 


“SULC. CRU. 


Fig. 120. (x 2.) 


SULC. COR. 


. 
‘ 


Fig. 121. (x 2.) 


SULC. CRU. SULC.INTER. 
Fy ya 


SULC. PRECRU. SULC. MARG 


_-SULC.CALC. 


SULC. ROS. 


this Feline brain we find a very distinct “ Ursine lozenge” 
of Mivart. 

Another feature of great interest in the Lion’s brain is 
exposed on separating the lips of the deep “splenial ” 


( 


248 PHYSIOLOGICAL SERIES. 


complex, when it is seen that the calcarine sulcus is really 

distinct from the intercalary in this Carnivore, as it is in 

the Edentata and Primates (fig. 121). O. C. 1325 a. 
Krueg, Zeitsch. f. wiss. Zool., Bd. xxxiii. 1880, p. 617, 


D. 295. The brain of a Tiger (Felis tigris). 

In a comparison of the brain of the Tiger with that of 
the Cat, we observe a series of changes analogous to those 
which are found in the Lion’s brain when contrasted with 
the latter. The arrangement of the Sylvian region re- 
sembles that described as typical of the Lion (D. 292). 

O. C. 1824. Hunterian. 


D. 296. A cast of the cranial cavity ofa Tiger (Felis tigris). 
This shows the true proportions of the large flattened 
olfactory bulbs which are placed well in front of the 
hemispheres. 


D. 297. The brain of a Jaguar (felis onca). 

Note the continuity of the anterior ectosylvian and the 
long diagonal sulcus ; also the apparent connection of the 
former with the upper part of the pseudosylvian sulcus, as 
in the Lion’s brain (fig. 118): and the numerous secondary 
sulci springing from the convexity of the suprasylvian are, 


O. C. 1325 B. 


D. 298. The brain of a Leopard (Felis pardus). 

Note that the upturned cephalic extremity of the inter- 
ealary sulcus (the non-calcarine part of Krueg’s splenial 
sulcus) crosses the dorso-mesial edge of the hemisphere so 
as to simulate the crucial suleus. The true crucial sulcus 
is placed further forward and is completely separated from 
the intercalary sulcus, as is usual in the Felidae, 

Note the well-developed marginal sulcus of Owen (the 
conjoint supra- and post-splenial of many writers). 

The anterior ectosylvian sulcus is continuous with the 
diagonal, and on the left hemisphere joins the posterior 
ectosylvian to form a complete ectosylvian are as in the 
OCynoidea. QO. C. 1325 Ba, 

Krueg, Zeitsch. f. wiss. Zool., Bd, xxxiii. 1880, p. 617. 


; 
. 
|: 
4 
s 
. 
i 


NERVOUS SYSTEM.—VERTEBRATA. 249 


D. 299. The brain of an Ocelot (Felis pardalis). 
A typical simple Feline brain. O.C. 1325 Bd, 


D. 300. The brain of a Cheetah (Cynelurus jubatus). 

Note the exceptionally well-developed pseudo-crucial 
sulcus behind the ansate. Itis merely the upturned anterior 
extremity of the intercalary sulcus. The right suprasylvian 
sulcus is not joined to the postsylvian. 

As also in the Ocelot, the diagonal is an independent 
suleus. O. C. 1325 ©. 

Holl, His’s Archiv, 1899, p. 230. 


Family Viverrip. 


D.301. The brain of an African Civet (Viverra civetta), (2), 
(figs. 122, 123, and 124). 


Fig. 122. (Nat. size.) 


“. SULC. ORB. 
\ is 


L-+\-~ SULC. CRU. 


Fh. SULC. COR. LAT. 
. SULC. SUPRAS. 


ULC. ECTOS. 


The features of the brain in this family are especially 
interesting because the instability of the “ Sylvian fissure ” 
(so-called) and the crucial sulcus are so strikingly demon- 
strated. In regard to these peculiarities, the brain of the 


250 


PHYSIOLOGICAL SERIES. 


- 
-_ 


Civet and its near relations may be regarded as connecting 
links between the typical Carnivora and the lowlier mam- 
malian orders in which the crucial sulcus is absent and the 
“ Sylvian fissure ” imperfect or wanting. 

The orbital (presylvian), corono-lateral, and suprasylvian 
sulci are simple and quite typical (figs. 122 & 123). The 
suprasylvian sulcus is the deepest sulcus in the hemisphere. 


Fig. 128. (Nat. size.) 


SULC. COR. LAT: 
SULC. SUPRAS. fs 


. ORB. 
SULC. OR ty 


f 
x SYL.ECTOS. COMP. 


Fig. 124, (Nat. size.) 


SULC. INTER. SULC ..CALC, 


A very deep calcarine is prolonged forward into the 
intercalary sulcus which in turn joins the crucial suleus 
(fig. 124). The latter is so small (fig. 122), that it barely 
reaches the dorsal surface. % 

The genual sulcus is joined to the crucial sulcus on the 
left hemisphere by a shallow furrow (fig. 124). 

The “feline Sylvian fissure ” is so ill-defined that there 
is a conflict of opinion as to which sulcus really represents _ 
it. This further exemplifies the morphological instability 


NERVOUS SYSTEM.—VERTEBRATA. 251 


of this sulcus, which has already been noted in the Cats, 
Sloths, and other forms. 

According to Holl the representative of the Sylvian 
fissure is found in a small notch above the bend in the 
rhinal fissure. But there can be little doubt that this really 
represents what Holl himself would call the “ anterior ter- 
minal sulcus of the trigonum Sylvii.” It is continuous, 
under the pallial operculum, with the orbital (presylvian) 
sulcus. On the right hemisphere this notch is so insignifi- 
cant that it might easily pass unnoticed (fig. 123, x). 

The sulcus which ata casual glance would be unquestion- 
ably called “ Sylvian fissure ” in this hemisphere is fairly 
deep and extensive, and opens freely into the rhinal 
fissure behind the before-mentioned notch or “ Sylvian 
fissure ” (according to Holl). Holl regards this sulcus as 
the posterior ectosylvian : and there can be no doubt that 
it does represent the posterior ectosylvian ; but it is some- 
thing more—a confluence of the latter and the sulcus 
which Holl calls “ posterior terminal.” In the case of an 
anomalous Cat’s brain (vide specimen D. 292) it was seen 
that the ectosylvian sulcus and the “ feline Sylvian fissure ” 
might be compensatory factors in relieving the tension of 
pallial expansion in this region ; we know also that itis not 
uncommon for the posterior ectosylvian sulcus to open into 
the Sylvian fissure or to join Holl’s “ posterior terminal 
sulcus” ; it is also known to be unusual for the ectosylvian 
sulcus to join the rhinal fissure, whereas it is the usual 
arrangement of the Sylvian fissure : these facts and, finally, 
a comparison with other Viverridze and with Carnivores of 
other families (see especially Holl’s figures of the brain of 
a Cheetah [Taf. xi. fig. 2] and of a Fox’s brain [Taf. xi. 
fig. 12]) show that this posterior sulcus (fig. 123) in the 
Civet ought to be regarded as the representative not only 
of the posterior ectosylvian sulcus, but also of the “ feline 
Sylvian ”’ fissure *, 


* If we compare this brain with that of the Jaguar (D. 297), we can 
greatly simplify matters by calling the sulcus labelled “ syL. EcTos. 
comp.” (fig. 123) simply ‘‘ pseudosylvian,” and the sulcus x the repre- 
sentative of that similarly labelled in figs. 116 and 117. 


252 


PHYSIOLOGICAL !SERIES. 


The object of this lengthy digression is not so much to 
interpret the individual condition here present—a question 
of small moment—but to emphasise the variability and 
morphological instability of the “ feline Sylvian fissure ” 
and its compensatory ectosylvian sulci. It is only when 
the “feline Sylvian” becomes blended with the stable 
suprasylvian sulcus, as in Myrmecophaga and the Primates, 
that the real “Sylvian fissure” can be said to exist in a 
really stable condition. 

An irregular horizontal sulcus extends forward from the 
upper end of the ectosylvian in this specimen and, together 
with the several pit-like markings, represents the anterior 
ectosylvian sulcus. [Compare the condition in Felis onea, 
D. 297.] 

Otherwise this specimen affords an admirable demon- 
stration of the typical features of the Carnivore brain. Note 
the prominent tubercle of the olfactory tract in the vallecula 
Sylvii (the depression between the tuberculum olfactorium 
and the natiform, caudal part of the pyriform lobe) : the 
well-defined tractus peduncularis transversus of Gudden 
(Wilder’s cimbia) on the lateral aspect of the crus cerebri: 
the large auditory nerve inserted intoa very prominent and 
bulky acoustic tubercle, from which a large trapezium 
extends as far as the lateral edge of the exceptionally 
prominent pyramidal tract. 

The features of the cerebellum, which isa simplified form 
of that of the Cat, are shown exceeding clearly. 

O. C. 132514, 


Holl, Arch. f. Anat. u. Entwick. 1899, p. 243. 


D. 302. ‘The brain of an African Civet (Viverra civetta). 


This specimen even more decisively than the last supports 
the contention that the larger, deeper and more posterior of 
the two sulci opening into the bend of the rhinal fissure 
represents not only the posterior ectosylvian sulcus but also 
the “feline Sylvian fissure.” A comparison with the brain 
of the Mongoose (vide infra) shows this conclusively. It 
certainly cannot be regarded as the posterior ectosylvian 
only. Tho lower extremity of the latter can, in fact, be 


NERVOUS SYSTEM.—VERTEBRATA. 253 


seen indenting the posterior lip of the sulcus at about its 
mid-point. 
_ The posterior ectosylvian sulcus gives off no branches 
such as its representative in the other specimen exhibits. 
The suleus which Holl (op. cit.) would call the “ anterior 
terminal’ (7. e. the anterior limit of the area usually sub- 
merged in the “Sylvian fissure”) is much longer in this 
specimen, especially on the right side. O. C. 18251. 


D. 303. The brain of a Genet ( Genetta vulgaris). 

The brain of the Genet closely resembles that of the Civet 
as regards most of its features. There is notypical crucial 
sulcus. There is, however, a shallow depression on the 
dorsal surface, which is regarded by some writers as the 
representative of the crucial. 

On the right side the intercalary suleus extends obliquely 
forward and upward almost as far as the dorsal edge far 
forward in the hemisphere. 

On the left side the true intercalary sulcus is quite dis- 
tinct from an anterior sulcus which may possibly represent 
the crucial. 

No ectosylvian suleus can be recognised with any degree 
of certainty, but there is a pseudosylvian sulcus resembling 
that of the Cat. O. C. 13825 Hd. 


D, 304. The brain of a Genet (Genetia vulgaris). O.C. 1825 5. 


D. 305. The brain of an African Genet ((enetta tigrina), ( 2). 
_ This resembles that of the Common Genet. 
O. C. 1825 Ha. 
Presented by St. George Mivart, Esq. 


D. 306. The brain of a Cape Mongoose (Herpestes pulveru- 
lentus), (3). 

This brain is peculiar in many respects. 

There is a very extensive crucial sulcus placed far 
forward on the hemisphere and in free communication 
with the intercalary sulcus on the right side, but not on 
the left. This is all the more noteworthy when the slight 
development or absence of a crucial sulcus in other 
Viverridee is recalled. 


254 PHYSIOLOGICAL SERIES. 


. 


The orbital suleus is very small, and placed so far 
forward on the apex of the hemisphere that it is hidden by 
the olfactory bulb, and is believed by many writers (e. g., 
Ziehen, Arch. f. Psych. 1896) to be absent. 

The deepest sulcus on the hemisphere is the suprasylvian 
which extends backward above, but without joining the 
vertical postsylvian (compare fig. 125). 

Holl (op. czt. p. 238) considers that no Sylvian fissure is 
present, but we can have little hesitation in’ regarding the 
sulcus which springs from the junction of the deep anterior 
rhinal and the shallow post-rhinal fissures as the pseudo- 
sylvian sulcus. After a short obliqne course upward and 
slightly backward, it joins the posterior ectosylvian which 


Fig. 125. (Nat. size.) 


SULC.SUPRAS. _ SULC.ENT.LAT. 
SULC. CRU. SULC.LAT. 
t 


ss 
SULC. ECTOS.R 


pursues a short course upward and forward and is then 
joined to the anterior ectosylvian sulcus (compare Holl’s 
figure of Herpestes ichneumon). 

The lateral sulcus is apparently fused to an ansate 
element in front, but is not joined to the small oblique 
coronal sulcus. 

The shallow postlateral is prolonged forward as a 
fragmentary entolateral sulcus, O. C. 1825 Te. 

Holl, Arch. f. Anat. u., Entwick. 1899, p. 238. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 7. 

[Since this account was written I have examined the 
brains of two specimens of Herpestes ichnewmon, and the 
interesting variations in these four hemispheres decisively 
show that the real nature of the sulci in question accords 
with the suggestions in the accounts already given. - 


NERVOUS SYSTEM.—VERTEBRATA. 255 


On the left hemisphere of the first specimen (fig. 125), the 
“Sylvian fissure” is an extremely short notch in the upper 
lip of the rhinal fissure and the posterior ectosylvian suleus 
(which is independent of the anterior ectosylvian) ends 
in very close proximity to this small pseudosylvian. On the 
right hemisphere the pseudosylvian is larger and surrounded 
by a distinct ectosylvian are (fig. 126). In the left hemisphere 
of the second brain (fig. 127) there are two “Sylvian notches,” 
of which the longer overlaps the posterior ectosylvian so that 


Fig. 126, Fig 127. 
soa a j 
hen ra 
RHIN . ss 
RHIN 
Fig. 128. Fig. 129. 


ECTOSYL. ie _~ECTOSYL. 
Ww ™ 


at a casual glance they might easily be mistaken for one fissure. 
On the right hemisphere (fig. 128) a similar arrangement of the 
only “Sylvian element” is found. Figure 129 represents yet 
another variety. These specimens clearly show the real nature 
of the pseudosylvian sulcus, or “ Sylvian fissure ”’ so-called, in 
the Viverride. | 


D. 307. The brain of an Advisa (Crossarchus obscurus), (¢? ). 
This may be regarded as a simplified Herpestine brain. 
The “Sylvian fissure” seems to be absent in this 
specimen. O. C. 1825 10. 


D. 308. The brain of a Palm-Civet (Paradowurus typus), (2). 

There is a typical “ feline Sylvian fissure”’ ; orbital and 
posterior ectosylvian sulci as in the Felidee and Hyzenide ; 
a typical suprasylvian sulcus forming a regular are with 
the postsylvian ; conjoint coronal and lateral sulci without 
any ansate ; and no true crucial sulcus. There are, how- 
ever, some shallow pits, where the crucial sulcus occurs 
in other brains, and the coronal sulcus has an unusual 


256 PHYSIOLOGICAL SERIES. 


inclination forward and inward. The intercalary suleus 
(the cephalic extension of the calearine—the “ splenial” of 
Krueg) extends almost to the cephalic pole of the hemi- 
sphere. There is a short genual suleus. 0.0. 1325@¢e — 

Krueg, Zeitsch. f. wiss. Zool., Bd. xxxiii. 1880, p. 628. 


D. 309. The brain of a Palm-Civet (Paradoxurus typus). 
An ansate sulcus is present in this specimen, and in — 


front of it there is a definite furrow which may represent — 
the crucial sulcus. 0. C. 1325 4d. — 


D. 310. The brain of Hemigale hardwickii. 4 
This brain resembles that of Paradoxurus. Note, however, — 

the upturning of the anterior end-of the intercalary (or 
splenial) sulcus, which may represent the otherwise y 
missing crucial sulcus. (This, however, hardly accords — 
with the suggestion made concerning the representative of 


the crucial sulcus in Paradoxurus.) O. C. 1325 He. z 
% 


D. 311. The brain of a Binturong (Aretictis binturong). 

In most respects’ this brain resembles those of Para- — 
doxurus and Hemigale. 

There appear, however, to be two “ Sylvian-like ” sulci 
opening into the angle of the rhinal fissure. They may be — 
regarded as the two “ terminal sulci ” of Holl, the posterior ; 
of which is concurrent with the posterior ectosylvian sulcus, — 
In many Carnivores there is a small submerged area in the _ 
Sylvian fissure called the “trigonum Sylvii” by Holl. 
The bounding fissures of this trigone he calls the terminal — 
sulci: in this specimen they are exposed on the surface so 
that there is no true “ feline Sylvian fissure.” 

On the right hemisphere there is a faintty-maskall 
crucial sulcus quite independent of the forward prolongation _ 
of the so-called “splenial” sulcus. It is more indistinct — e.. 
on the left side. There is a broad gyrus between the 
corono-lateral sulcus and the mesial plane, indented by 
numerous short sulci on the right hemisphere and by pit- — 
like short sulci on the left side. The ansate is represented — 
by a peculiar arc-like sulcus quite independent of the — 
lateral. O. C. 1825 ra. q 

Mivart, Journ, Linn, Soc., vol. xix. 1886, p. 7. 


é 4 


NERVOUS SYSTEM.—VERTEBRATA. 257 


D. 312. The brain of the Suricate (Suricata tetradactyla), (3). 

In most. respects this brain closely resembles that of 
Hlerpestes. 

The “ Sylvian fissure ”’ is a mere notch in the upper lip 
of the rhinal fissure, surrounded by an arcuate ectosylvian 
sulcus: there is a large crucial sulcus and a small orbital 
(presylvian) sulcus, which, under normal conditions, would 
be completely hidden by the olfactory bulb. O.C. 1325 4. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 8. 

Presented by J. Lemage, Esq. 


D. 313. The brain of Nandinia binotata. 

This resembles the brain of the Genet in most of its 
features. The Sylvian region, however, resembles that of the 
Civet’s brain, more especially as seen in specimen D. 302. 

O. C. 1325 ea. 


Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 6. 


D. 314. The brain of Nandinia binotata. 
Note the absence of the crucial sulcus and the insig- 
nificant proportions of the mere notch which represents 
the “Sylvian fissure.” O. C. 1325 @ bd. 


Family Hyznipz. 


D. 315. The brain of a Hyxena (Hyena hyena), (3). 
The so-called “ Sylvian fissure” (fig. 130) presents a 
marked contrast to the similarly-named feature of the 


Fig. 130. (x32.) 


SULC.SUPRAS. 


SULC.COR. “Bie ae 


SULC.CRU.} 


_SULC.ECTOS.P. 


Cat’s brain ; in the latter it is short and relatively shallow, 
whereas it is very long and deep in the Hyena. Ata 
VOL. Il. s 


258 


PHYSIOLOGICAL SERIES. 


ante glance the anterior ectosylvian sulcus is absent, ar 
this at once reminds us of the spurious or appare) 
lengthening of the “ Sylvian fissure” in the me (via 
supra), where the anterior ectosylvian sulcus become: os 
engulfed in the “Sylvian” (fig. 118). If the Promina 
opercula-like lips of the “Sylvian fissure ” in the Hys 
be separated it will be found that the upper half of 
“fissure” is really a submerged ectosylvian ; in sc ne C 
cases (vide fig. 131), but not in this, the lower extremi 
of this ectosylvian element emerges from the “ Sylvian’ 
and deeply incises its anterior lip. But the condi i 1 
in the Hyzena’s brain is very different even from thea 
what we may call the anomalous Lion’s brain (fig. 116 
There is a very large triangular submerged area (wh ich 
fa 


Fig. 131. (Nat. size.) Fig. 132, (Nat. size.) 


SULC.ORB, YY 
/ 


4 


Holl would call “trigonum Sylvii”) overlapped no 
only by a large anterior operculum but also by a stil 
larger posterior operculum. This “ trigone” is li 
both in front and behind by well-defined limiting s 
The inferior extremity of the posterior limiting sule 
may emerge from the “Sylvian” cleft a short dis 
above the rhinal fissure (fig. 131, 0, also specimen D, 3 
In the middle of the trigone there is a deep sulla i 
the feline “ Sylvian fissure” (fig. 132, a). But a car 

study of the conditions existing here clearly shows 
neither the superficial pattern formed by the meeting 
the opercular lips nor this submerged suleus can — 
regarded as strictly homologous to the “ feline oy lv 
fissure.” The whole arrangement is a more or less di 
mechanical adaptation of the growing cortex in “7 
of kinking, and varies in different families of the Cs 


NERVOUS SYSTEM.—VERITEBRATA, 259 


just as it frequently does even in members of the same 
genus and species. 

There is a deep, simple, posterior ectosylvian sulcus, 
which is quite separate from the anterior sulcus, as in the 
Cats (fig. 130). 

There is a great suprasylvian arc formed usually of 
conjoint diagonal, suprasylvian and postsylvian sulci, but 


Fig. 1383. (x 32.) 


SULC.ORB. 


--- SULC. SUPRAS 


~~ SULC.ECTOS.P. 


“SULC.P. SYL. 


Fig. 184. (x3.) 


SULC.INTER. 
SULC .CRU. \ 


SULC.MARG. 
; 7 


SULC. CALC. 


HIP.F, 


sometimes the diagonal sulcus may be separate (figs. 130 
& 133), as in the right side of specimen D. 317. 

There are large typical coronal, lateral, and postlateral 
sulci and a very long deep orbital (presylvian) sulcus, with 
occasionally a small accessory orbital springing from the 
rhinal fissure still further forward. 

S 2 


260 PHYSIOLOGICAL SERIES. 


. 


There is a very deep, long, transverse, crucial sule one 
(fig. 183) ; and in some cases, if it be opened up, a small 
indubitable precrucial sulcus is present. The crucial sulc i r 
is joined by the intercalary to the deep calcarine suleus, — 
as is commonly the case in the Dogs (fig. 134). There 
are, in many Hyzenas, numerous irregular accessory post-_ 
calearine sulei—the irregular forerunners of the )- 
calcarine and collateral sulci of the human brain. The : 
is also a well-developed marginal (“ suprasplenial ”) st 
The genual sulcus in some cases proceeds upward to join 
the precrucial. O. C. 1325 we 1 


D. 316. The brain of a Hyzena (/Tyena hyena). O.C. 1825 if 


D. 317. The brain of a Hyzena (Hyawna hyena),(?).  ~ 
0. C. 1325 Bd. 


D. 318. The brain of a Hyzena (Hyena hyena), (2). | 
0.0. 1325 8 iD 


D. 319. A brain labelled “ Hyzena.” Although much larger ths 
the other specimens of the Hyzena’s brain, this spec om 
presents similar features. ‘ 
The “ Sylvian fissure,” however, is more open and ¢ 
sulcus which emerges and indents its posterior lip—perha 
the “posterior terminal sulcus” of Holl—is unusu Il 
well pronounced. 0. C, 13958 


D. 320. A cast of the cranial cavity of a Spotted Hyes 
erocuta). 

This shows the size and shape of the olfactory bt 

which are distorted in the specimens of the brains th a 

selves. Note that the open condition of the pene 

sulcus is natural, as it is seen in the cast. 


Gervais, Nouv. Arch. d. Mus., t. vi. 1870, p. 125. 


D. 321. The brain of a Proteles cristatus, (@). 
This closely resembles the brain of the Hyena. = 
It is of interest to note a retrocalcarine sulcus extendi 


NERVOUS SYSTEM.—VERTEBRATA. 261 


backward and upward from the “splenial”? complex of 
calearine and intercalary sulci after the manner of the 


/ 


Fig. 185. (x 2.) 
SULC.LAT.  SULC . SUPRAS. 


SULC. CRU. inane Pe 


/ ‘ 
SULC.ORB. \ 
SULC.ECTOS. 


Fig. 136. (x3.) 


SULC.CRU. SULC.INTER. 


SULC.GEN. 


Fig. 187. (x 3.) 


SULC.SUPRAS. 


posterior calearine sulcus in the Primates (figs. 185, 136, 


& 137). O.C. 1325 F. 
Flower, Proc. Zool. Soc. 1869, p. 478. 


262 PHYSIOLOGICAL SERIES. 


Section CyNOIDEA. 


Family Canipz. 


D. 322. The brain of an Otocyon (Otocyon niaglleetey 
The anterior and posterior ectosylvian sulci meet anil 
form a regular are around the short Sylvian fissure. This 
is one distinctive feature of the Cynoidea in contrast to the 
f®luroidea. On the left hemisphere there is a shor 
vertical offshoot from the ectosylvian are. Bi. 
The suprasylvian and postsylvian sulci are united into a 
regular arc and there is no separate diagonal sulcus. 
The lateral and short postlateral sulei are joined on 
both sides, and on the left side the lateral joins the coronal. — 
There is a well-developed orbital (presylvian) and a_ 
short transverse crucial sulcus. a 
Midway between the postsylvian and _postlateral sul 
there is a short vertical “ ectolateral” sulcus. Thisisa vy 
characteristic feature of the Cynoid brain. 0.0. 1325. 
Gervais, Nouv. Arch. Mus., t. vi. 1870, p. 109. 


a 


D. 323. The brain and the upper part of the spinal cord of a 
- Common Fox (Vulpes vulpes). r 
This specimen exhibits with diagrammatic clearness the 
typical Cynoid characters :—the three regular arcuate st ci 
(ectosylvian, suprasylvian, and corono-lateral respectively) 
surrounding the short oblique pseudosylvian. The cha- 
racteristic ectolateral sulcus, the orbital and the deeply- 
incised oblique crucial sulci complete the picture. re. 
is a small ansate sulcus joined to the coronal on the lef 
side, and an altogether insignificant separate ansate on ne 
right side. ‘ 
It will be noted that such other parts of the brain as ¢ 
be seen in this specimen resemble the rr Ca 
in the Cat’s brain. » On 
Krueg, Zeitsch. f. wiss. Zool., Bd. xxxiii. 1880, p. | 
D. 324. The brain of Canis microtis, in which the left cerebr 
hemisphere has been separated, ( ¢). “gi 
In this specimen we can see the continuity of the crucial 


NERVOUS SYSTEM.—VERTEBRATA. 263 


and the intercalary (“splenial’’) sulci (fig. 140)—another 
feature usually presented by the Dogs. 

In addition it also exhibits (figs. 188 & 139) the other 
two Cynoid characters—the complete ectosylvian are and 


Fig. 1388. (x2.) 


SULC. ANS, 
SULC.CRU. ; 
SULC. COR. * H 


SULC . LAT. 
i 


SULC. ECTOLAT. 


SULC. ORB. 
. he 


' 
Fy ' 


/ ee 
Ss / SULC.SUPRAS. 
SULC ECTOSYL. 


Fig. 139. (x3,) 


SULC.CRU. 


'SULC. ANS. 


SULC .LAT. 


SULC .SUPRAS. 


Fig. 140. (x#2.) 
SULG.INTERCAL.. MARE (POST CALC) 
a 


SULC.CRU... 
Fis 


the presence of the ectolateral sulcus—-in a typical 
form. O. C. 1325 Lf. 
Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 3. 


264 PHYSIOLOGICAL SERIES. 


D. 325. Thé brain of a Bush Dog (Speothos venaticus), (2). 
A complete ectosylvian arc is present only on the right 
side, and even there its anterior limb is short and appears — 
to be joined to the “Sylvian fissure.” On the left side de 
the small posterior ectosylvian sulcus joins the pseuc 
sylvian a short distance below the apex of the k ter. 
A comparison of this condition with that of the Vive 
is interesting. 


Fig. 141. (x3.) 


The postlateral sulcus is absent on the right side a 
represented merely by a shallow pit on the left s 
(fig. 141). 0. 0. 1825 ud. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 4. 

D. 326. The brain and upper part of the spinal cord of a Do 
(Canis familiaris). 

The cerebellum has been removed, the corpus callosu 
cut through, and the cerebral hemispheres widely diva 
cated. Upon the left side a portion of the pons Var 
has been cut away to demonstrate the continuity of 1 
pyramidal tract with part of the crus cerebri. 4 

The latera! ventricles have been opened so as to sl \ 
the corpora striata, each of which is separated from # 
optic thalamus by a deep oblique furrow. On the 1 righ 
side the optic thalamus is to a great extent hidden by t 
upper extremity of the hippocampus and the fornix’ ) 
ceeding forward from it. On the left side the thalam 
has been exposed by the removal of part of the fornix an 


NERVOUS SYSTEM.—VERTEBRATA. 265 


hippocampus. The corpora quadrigemina are fully ex- 
posed, and the narrow, elongated, fourth ventricle opened up. 
Upon the dorsal aspect of the spinal cord note the ex- 
ceedingly delicate columns of Goll alongside the mesial 
septum swelling out slightly at the calamus scriptorius to 
form the nuclei graciles. The columns of Burdach are 
much broader and swell out into the nuclei cuneati. 


QO. C. 1325 ka. 


D. 327. The brain of a Dog (Canis familiaris). 

In the left hemisphere the coronal is completely separate 
from the lateral sulcus. But the latter is connected with a 
deep and extensive ansate which passes into a minor ansate 
sulcus opening into the suprasylvian. The ectolateral 
sulcus also joins the minor ansate. 

- On the right side there is no communication of the 
minor ansate with either the lateral or ectolateral sulci. 

The crucial sulcus presents the unusual phenomenon for 
a Cynoid of being bifid. 

In this specimen all the cranial nerves except the 
trochlear (Iv) are well shown in the usual positions. 

O. C. 13825 K. 

Langley, Journ. of Physiology, vol. iv. p. 248. 


D. 328. The head of a Dog (Canis familiaris) cut in longitudinal 
section to show the relation of the brain to the skull. 

Note especially the large olfactory bulb separated from 

the nasal fossa by the thin cribriform plate. O.C. 1325 Kb. 


D. 329. Two casts of the cranial cavity of a Dog (Canis fami- 
liaris). These casts show the true shape of the olfactory 
bulbs and their relations to the hemispheres. 


D. 330. The brain of a South-American Fox-Wolf (Canis azare), 
(2 juv.). 

On the left hemisphere there appears to be a relatively 
extensive ectolateral sulcus, whereas on the right side this 
suleus is seen to be very short, and the separate lower 
suleus which represents the greater part of the apparent 
ectolateral of the other hemisphere is clearly the postlateral 
sulcus. O. C. 1325 Le. 


266 


PHYSIOLOGICAL SERIES, 


D. 331. The*brain of Canis rudis. 


D. 332. The brain of a Japanese Raccoon-Dog (NV yctereutes 


procyonoides), (¢). 
Note again how the ectolateral sulcus takes the place of 
the postlateral, which is absent. O. C. 1825 Le. 


D. 333. The brain of a Japanese Raccoon-Dog (Nyctereutes 


procyonoides), ( g ). O. C. 1325 Ld. 


D. 334. The brain ofa Cape Hunting Dog (Lycaon pictus), ( 3). 


O..C. 1825 1a: 


Section ARCTOIDEA. 


Family Procyonip»z, 


D. 335. The brain of a Raccoon (Procyon lotor). O. C. 1325 Ra*. 


Presented by St. George Mivart, Esq. 


D. 336. The brain of a Raccoon (Procyon lotor). O.C. 1325 R. 


D. 337. The brain of a Raccoon (Procyon lotor). 


It is distinctive of the Arctoid section of the Carnivora 
that the “ Sylvian fissure” is very long and deep, and that 
the first arcuate gyrus has become wholly engulfed in this 
great cleft so that the lips of the “fissure” are formed by 
the second arcuate gyrus, and not by the first gyrus as in 
the Cynoid section ; and a precrucial sulcus makes its ap- 
pearance, even in many of the smallest members, so as to 
mark off the area which Mivart has called the “ Ursine 
Lozenge.” (Compare fig. 155.) 

The crucial suleus is long, very deep, and placed ob- 
liquely, and is usually quite independent of the intercalary 
(the cephalic part of the splenial) sulcus. There are no 
precrucial sulci in one (D. 335) of these specimens, in 
another (D. 336) they are faintly, whilst in the third they 
are well-developed. 

A comparison of these three brains shows the great 
variations in the coronal, lateral, ansate, and postlateral sulci 


which may occur in one species. In one brain (D. 336) | 


NERVOUS SYSTEM.—VERTEBRATA. 267 


there is a definite postlateral sulcus and none in the other 
two. In one brain the coronal and ansate sulci are replaced 
by irregular triradiate and H-shaped sulci, whereas in the 
others we find the typical combination of ansate, coronal, 
and lateral sulci. O. C. 1325 Ra. 
Presented by St. George Mivart, Esq. 

St. George Mivart, Journ. Linn. Soc., vol. xix. 1886, 

p- 10. 


D. 338. The brain of a Crab-eating Raccoon (Procyon caneri- 
vorus), (¢)- 

This closely resembles the Raccoon’s brain. 

On the right hemisphere there is a short postlateral 
sulcus, which extends forward between the lateral and the 
postsylvian sulci so as to simulate the ectolateral sulcus. 

The latter, so characteristic of the Cynoidea, is absent in 
the Arctoidea, as it is also in the Adluroidea. O.C. 1325 Rb. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 11. 


D. 339. The brain of a Coati (Nasua nasua). 
This brain closely resembles that of the Raccoon. 
_ There is no trace of the precrucial sulcus. The coronal 
and lateral sulci, and a moderately extensive postlateral 
sulcus are joined to form a great arc. The ansate is repre- 
sented by several small postcrucial sulci. 
There is a shallow entolateral sulcus, joined to the lateral in 
a different manner on the two hemispheres. QO. C. 1325 Qb. 
St. G. Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 11. 


- D. 340. The brain of a Coati (Nasua nasua). 

A small precrucial sulcus can be seen near the mesial 
edge. 

The coronal, lateral, and postlateral sulci are each in- 
dependent of the others on the left side, but on the right 
side the lateral and postlateral are joined. O.C. 1325 Qc. 

Presented by St. George Mivart, Esq. 


D. 341. The brain of a Mexican Coati (Nasua narica), (3). 
This brain resembles that of the common Coati. There 
is a very small “ Ursine lozenge.” O. C. 1325 Qa. 


268 PHYSIOLOGICAL SERIES. 


D. 342. The brain of a Mexican Coati (Nasua narica). 
No precrucial sulci are present ; the postlateral sulci are 
less well-developed. O. C. 1325 Q. 


D. 343. The brain of a Raccoon Fox (Bassariscus astutus), in 
which the left hemisphere has been separated from the rest 
of the brain. 

This is a smaller and correspondingly simplified copy of 
the brain of the Raccoon. The mesial prolongation of the 
crucial sulcus is overlapped but not joined by the cephalic 
prolongation of the calcarine. There are regular supra- 
sylvian and corono-lateral arcs. There is a simple ansate 
and a triradiate compensatory ansate. There is a short 
vertical postlateral sulcus. In the left hemisphere the 
anterior lip of the pseudo-sylvian and the upper lip of the 
anterior rhinal fissures have been dissected away to show the 
submerged Sylvian trigone continued forward into the 
“ orbital gyrus.” There is no trace of an ectosylvian sulcus. 

Beddard, Proc. Zool. Soc. 1898, p. 129. 


D. 344. The brain of a Bassaricyon alleni. 
This closely resembles the brain of Bassariscus. The 
crucial sulcus is, however, longer and placed slightly further 
back in the hemisphere ; it also has a distinct notch-like 
precrucial sulcus, so that the “ Ursine lozenge” can be 
distinctly recognised. 
Beddard, Proc. Zool. Soc. 1900, p. 668, figs. 54 & B. 


D. 345. The brain of a Panda (Ailurus fulgens), (2). 
In most respects this brain (fig. 142) resembles those 

of Procyon and Nasua, 
Fig. 142. (x 3.) 


SULC. SUPRAS. ee. 


SULC, ANS, , 


SULC. CRU. ~ 


SuLC. ORB... [ 


There is a very faint indication of the precrucial sulcus. 
A sulcus which probably represents the posterior ecto- 


NERVOUS SYSTEM.—VERTEBRATA. 269 


sylvian emerges from the “ Sylvian fissure” at about its 


mid-point. 0, 0.1325 8. 
Flower, Proc. Zool. Soc. 1870, p. 763. 


D. 346. The brain of a Panda (Adlurus fulgens). 
The small precrucial sulci (and consequently Mivart’s 
“ Ursine lozenge ’’) are well marked in this specimen. 
So much of the posterior ectosylvian sulcus is exposed 
that it appears to join the apex of the “‘ Sylvian fissure.” 


O. C. 1325 sd. 
Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 12. 


D. 347. A cast of the cranial cavity ofa Panda (Azlurus fulgens). 

Note especially the deep broad depression corresponding 

to a part of the submerged first arcuate gyrus in the Sylvian 
region. 


D. 348. The brain of a Kinkajou (Potos caudivolvulus), (¢). 

The Sylvian region is very instructive in this brain. 
The “Sylvian trigone,” or depressed area, can be partly 
seen, and behind it alarge part of the posterior limb of the 
tirst arcuate gyrus makes its appearance. It is limited by 
the posterior ectosylvian sulcus, which appears to join the 
apex of the Sylvian fissure. The suprasylvian arc is 
complete, simple, and regular. 

The conjoined postlateral and lateral sulci form a great 
arc which passes directly into the ansate in front. The 
large simple coronal sulcus is quite independent. There is 
a large very obliquely-placed crucial sulcus passing directly 
into the intercalary prolongation of the calcarine (splenial), 
as in the Cynoidea. 

A faintly-marked notch in the tts lip of the right 
crucial is the only indication of a precrucial sulcus. 


O. C. 1825 sa. 
Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 13. 


Family MusTeripz. 


D. 349. The brains of a Weasel (Putorius vulgaris) and of a Stoat 
or Ermine (Putorius ermineus). 

It is very significant that in spite of the diminutive size 

of these brains—for they are much smaller than many 


270 PHYSIOLOGICAL SERIES. 


smooth brains of the Rodent, Insectivore, and Marsupial — 
Orders—they still present the typical Carnivore pattern of 
sulci. The pattern exhibited by these sulci essentially — 
conforms to the Arctoid type. 

The pseudosylvian sulcus corresponds to that of eee 
Procyonide and not to that of the Dogs and Cats ; the — 
suprasylvian arc is acutely flexed ; the lateral and coronal — 
form one simple sulcus ; there is Maiiher an ansate nor a 
postlateral sulcus ; there’ is a large transverse crucial ones J 
but no definite precrucial. There is a large orbita 
sulcus. O. C. 1825 Oo. “= 

Presented respectively by Dr. Rolleston and a 
_ RR. F. Tomes, Esq. © 
Mivart, Journ. Linn. Soe., vol. xix. 1886, p. 17. ~ 
Holl, Arch. f. Anat. u. Entwick. 1899, p. 239. | 


a 


D. 350. The brain of a Glutton or Wolverine (Gulo luscus). 
The typical Arctoid features are well shown in this — 
specimen: the long “ Sylvian fissure” encircled by the — 
acutely flexed suprasylvian are ; the long crucial suleus — 
which does not join the cephalic prolongation of the ; 
calcarine (splenial) suleus ; and the large precrucial sulcus _ 
and consequently a well-defined Ursine lozenge. q 
The extensive postlateral joins the lateral sulcus andi 
from the latter a large ansate extends forward. A large f 
sulcus on the lateral side of the ansate is obviously a com- a 
pensatory ansate sulcus; it opens into the great crucial — 
sulcus. The coronal is not joined to the lateral. 

On the left side the lips of the pseudosylvian sulcus have 
been removed to show the region of the “ Sylvian trigone a 
and the first arcuate gyrus. ; 

The cephalic prolongation of the calcarine is very short, — 
as in the Bears and Seals. There is a short vertical genual — 
sulcus. There is a long, deep, vertical postcalcarine. oq 

In front of the crucial sulcus there is a sagittal prorean” 
sulcus on the dorsal surface of the hemisphere. 

Note the peculiar square shape of the posterior part of 
the hemisphere. | 

Beddard, Proc, Zool. Soc. 1895, p. 139. 


’ 


NERVOUS SYSTEM.—VERTEBRATA. 271 


D. 351. The brain of the Tayra (Galera barbara). 
This brain resembles that of the Glutton. 
It presents a similar crucial sulcus with a very long, 
transverse, dorsal extent and a very short mesial part 
(figs. 143 & 144). On'the right side, however, it joins the 


Fig. 143. (Nat. size.) 


SULC. LAT. 


SULC. CRU. 


SULC . PRECRU. 
SULC. SUPRAS. 


ULC. P. LAT. 


i Hi 
SULC.COR. Ss 


Fig. 144. (Nat. size.) 


eee me, 


“* SULC. LAT. 


** SULC. ENTOLAT. 


intercalary prolongation of the calcarine, the true anterior 
extremity of which notches the dorsal edge behind the 
crucial. 

There is a well-developed precrucial sulcus. The post- 
lateral is separated from the lateral, There is also an 
entolateral. 


272 PHYSIOLOGICAL SERIES. 


The compensatory ansate sulcus does not join the crucial — ' 

sulcus. O. C, 1325 nb. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 16, figs. 4 
and 5. 


D. 352. The brain of the Grison (Galictis vittata), (3), (figs. g 
145 & 146). 


Fig. 145. (Nat. size.) 


SULC. SUPRAS. a 
>. 


SULC. LAT. 
. SULC. CRU. 


SULC. COR. Ss 


Fig. 146. (Nat. size.) 


SULC. LAT. 


The crucial sulcus joins the prolongation of the calcarine; — 
there is a very small precrucial suleus near the mesial — s 
plane ; the prorean sulcus already noted in Gulo is present 
also in this, as it is in Galera. O. C, 1325 Nay a 

Mivart, Journ. Linn, Soe., vol. xix. 1886, p. 16. 


D. 353. The brain of a Grison (Galictis vittata). O.C. 1825 we E 


D. 354. The brain of a Zorilla (Zetonyx zorilla). 3 
This brain resembles that of Putorius in almost all points. | 


It, however, presents a small ansate sulcus, which is lacking — a 
in Putorius. 


NERVOUS SYSTEM.—VERTEBRATA. 273 


This brain incidentally illustrates various points in the 
arrangement of sulci. The greater stability of the post- 
sylvian as compared with the postlateral is shown by the 
complete absence of the latter. The proximity of the 
suprasylvian to the “ Sylvian” is suggestive of its absorp- 
tion in the latter, as in the Seals and, in another sense, in 
the Primates. O.C. 1325 Ne. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 18. 


D. 355. The brain of Helictis subaurantiaca, (  ). 


Although this brain presents the common Arctoid cha- 
racters, it conforms more especially to the Musteline type 
(fig. 147). 

, Fig. 147. (Nat. size.) 


SULC. : 
SULC. CRU. SULC. LAT j SUPERS 


me, 
eo, 


Fig. 148. (Nat. size.) 


\  SULC.PRECRU. 
we 
\ _SULC.ORB. 


\ _.SULC“SPLEN” 


SULE. LAT. 


SULC. SUPRAS. 


It presents a most extraordinary feature for a Carnivore 
in that the intercalary prolongation of the calcarine sulcus 
(the so-called “splenial’’) extends on to the dorsal surface 
and is prolonged forward parallel to the interhemispheral 


cleft and ultimately joins the transverse crucial (fig. 148). 
VOL. II. Ay 


274 PHYSIOLOGICAL SERIES. 


Although this suleus occupies a dorsal position in the — 
Chevrotain, Musk-Deer, and others of the Ungulates, such 
behaviour is unknown elsewhere in the Carnivora. a 
The precrucial sulcus limiting the so-called “Ursine _ 
lozenge” is well developed (fig. 148). q 
As also in Ictonyz, the lateral sulcus does not extend far _ 
in the caudal direction. O. C. 1325 wd, 
Garrod, Proc. Zool. Soc. 1879, p. 307. 


D. 356. The brain of an Indian Ratel (Mellivora indie 


figs. 149 & 150 
(es. ) Fig. 149. (Nat. size.) 


Fig. 150. (Nat. size.) 
‘SULD, TRUS SULC. LAT. 


SULC. PRECRO. 


SULC. PROR, ‘Succ. suPras. 


SULC. ORB. g —_ 
This brain resembles that of the Glutton. The e: I ia 
sulcus is practically confined to the dorsal surface of th 
brain ; it has a large precrucial branch and also a com- 
pensatory ansate branch, as in Gulo. There is a shallow 
entolateral sulcus. 0.0. 1325 we 
Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 14, ‘ 


NERVOUS SYSTEM.—VERTEBRA''A, 275 


D 357. The brain of a Common Badger (Meles meles), in which 
the left hemisphere has been separated from the rest of the 
brain (figs. 151, 152, & 158). 


Fig. 151. (x3.) 


suic. cry, SULC. SUPRAS. 


SULC. LAT, 
SULE. PRECRU. ’ 


SULC. COR... 


SULC. ORB, --*-~(= 


+ 


Fig. 153. (x2.) 


‘§ SULC, CRU. 


SULC. INTERCAL. 
SULC GEN. t 


. 


SULC. ROS. 


“SULC. CALC. 


HIP. F. 


The exceedingly long transverse crucial sulcus is placed 

relatively far back in the hemisphere ; it appears to com- 

-municate freely with the intercalary prolongation of the 
T 2 


PHYSIOLOGICAL SERIES. 


calearine (splenial) sulcus, but, in reality, the two sulci are 
often entirely separate. There is a deep precrucial sulcus, 
which extends on to the mesial wall in some cases, as it 
does here. 

Just as in certain anomalous cases in the Felide and in 
all cases in the Hyzenidx, the anterior part of the first 
arcuate gyrus of Leuret becomes buried in the “ Sylvian 
fissure,”’ so in this brain the anterior of the second arcuate 
gyrus also tends to become buried in this great Sylvian 
cleft, which has already swallowed the whole of the first 
arcuate gyrus. Hence, in many cases, the upper part of the 
suprasylvian sulcus appears to join the “ Sylvian fissure,” 
while the postsylvian (posterior suprasylvian) remains 
exposed. 

The great elongation of the “ Sylvian fissure” in the 
Badger, as in the Arctoidea in general, is to be attributed 
to a factor such as that which elongates the corresponding 
fissure in the Hyena and sometimes in the Lion. The first 
arcuate gyrus is buried in the “Sylvian” and the small 
“feline Sylvian” is found in the triangular submerged 
area. 

The large orbital (presylvian) sulcus joins the prorean, 
and also frequently gives off a more lateral accessory 
prorean branch, 

In this brain the gap between the coronal and lateral 
sulci is complicated by a triradiate compensatory ansate 
sulcus ; but in other cases the conjoint corono-lateral gives 
off numerous short branches in this region. 

Flatau and Jacobsohn, Vergl. Anat. d. Centraln. 1899. 


D. 358. A cast of the cranial cavity of a Badger (Meles meles). 


Besides showing the true shape and proportions of the 
cerebellum, olfactory bulbs, and cerebral hemisphere, this 
specimen clearly exhibits the arrangement of the chief 
sulci. 


D. 359. A cast of the cranial cavity of the Common Otter (Lutra 


lutra). 


The most noteworthy feature of this cast is the demon- : 
stration of the small size of the olfactory bulbs and the 


NERVOUS SYSTEM.—VERTEBRATA. 277 


pyriform lobes—phenomena directly associated with the 
aquatic mode of life of the Otter. — 

The typical Arctoid plan of the sulci can be distinctly 
recognised. Note especially that the crucial sulci are 
placed very far forward and have well-marked precrucial 
branches. 

Mivart, Journ. Linn. Soc., vol. xix. 1886, p. 20. 


Family Ursipz. 


D. 360. The brain of a Polar Bear ( Ursus maritimus), ( 2), from 
which the left hemisphere has been separated. 

The ‘‘ Sylvian fissure” is distinguished by its great 
length and depth, and as a result the suprasylvian and 
corono-lateral arcs which are grouped around it become 
greatly elongated and acutely. flexed. 


Fig. 154. (Reversed, x3.) 


SULC. LAT. 


SULC. SU PRAS. 


SULC.- COR. 
*, SULC.?. CAUD. 


~ 
“s. 


SULC. ORB. 


a . S ; 1 \ 
RHIN.F. RYR.L. IST ARCU. GYR. § SULC. P. LAT, PARAFLOC, 
SULC. P. SYL 


Sir William Turner long ago pointed out that the whole 
of the first arcuate gyrus of Leuret is hidden in the depths 
of this deep “‘ Sylvian fissure.” On the right hemisphere 
(fig. 154) a considerable portion of the second arcuate 
gyrus (from which the lips of the fissure are formed) has 
been cut away so as to expose this buried gyrus. It will 
be seen to be acutely flexed around a long sulcus, which 


278 


PHYSIOLOGICAL SERIES, 


clearly corresponds to the “ feline Sylvian fissure.” This — 
arcuate gyrus is bounded by an extensive sulcus, which — 
may be regarded as the ectosylvian. 

The deep orbital sulcus presents the usual features snd 4 a 
is joined to the prorean sulcus. The enormously elongated *— 


Ws 


Fig. 155. ( x 3.) 


OLF. BULB. 


SULC. ORB 


SULC_PRECRU. 


~ 
- 
tee, 


suprasylvian are (conjoint suprasylvian and postsylviat 
sulci (is very deep and several deep kink-like radiating 
sulci proceed from its convexity. m 
The combined coronal, lateral, and post-lateral sulci 
form a great inverted- U-shaped arc, which is almost a 
acutely flexed as the suprasylvian (figs. 154 & 155). 


NERVOUS SYSTEM.—VERTEBRATA, 279 


One of the most distinctive features of the brain of the 
Bear is the nature of the crucial sulcus. This sulcus is of 
great length and depth and is almost wholly confined to 
the dorsal surface of the hemisphere (figs. 155 & 156), 
upon which it pursues an oblique course and is placed 
relatively far back on the hemisphere. After examining 
such a brain as this, we can readily appreciate the fact that 
this sulcus is the only one in the Carnivore which can, in 
uny sense, be regarded as the representative of the sulcus 
of Rolando of the Primate brain. [Compare the crucial and 
precrucial sulci of a Bear (say D. 365) with the central and 
superior precentral sulci of a Gorilla (say D. 661).] 


Fig. 156. (x3.) 


SULC VERT. SULC. (jitiagal 
SULC. CRU. 


SULC. BISECT., 
we SULC. P. CALC. 


SULC. GEN... : 
} ---- SULC. CALC. 


SULC.ROS., raf - | 
sS ({ J -——— A A ga} ~- SULC.PARACALC. 


“HIP. FD 


SULC. URS.(JOINING CALC.) 


On the right hemisphere there is a deep, long, precrucial 

_ sulcus proceeding forward from the crucial, and distinctly 

mapping out the right lateral boundary of Mivart’s ‘‘ Ursine 

lozenge” (fig. 155); but on the left side the sulcus is much 

smaller and is supplemented by a larger “ complementary 

precrucial,” which is quite independent of the crucial 
sulcus. 

Although precrucial sulci may make their appearance 
among the larger representatives of other families of the 
Carnivora, such, for instance, as the Lion and Hyzna, yet 
the presence of these sulci and the “ Ursine lozenge,” 
which they map out, is a valuable distinctive feature of the 


280 


PHYSIOLOGICAL SERIES. 


Arctoid families, in which it attains its greatest develop- — 
ment, and is found not only in the larger members but also — 
in many brains of small animals (vide supra). . 
The great complications produced in the area behind the a 
crucial sulcus by the development of “ ansate” and “com — 
pensatory ansate ” sulci are shown in the drawings (figs. 154 
& 155). h 
The broad gyrus which separates the lateral sulcus from_ 
the interhemispheral cleft is subdivided by a very dee Pp 
entolateral sulcus, from which numerous offshoots are gi en 
off both on the mesial and lateral aspects (fig. 155). 
The broad vertical gyrus between the postlateral sulcus — 
and the caudal margin of the hemisphere is complicated by | 
a series of three vertical sulci which are arranged in an — 
imbricate manner. For convenience of reference I shall — : 
call them “ paracaudal” (fig. 154). 7 
The calcarine sulcus (fig. 156) is exceedingly deep. It 
joins the intercalary suleus at an acute angle. The latter 
extends forward for a relatively short distance and ends in 
a shallow vertical suleus behind the crucial. Between the 
intercalary and crucial sulci there is a small but deep 
sulcus, which for convenience of reference may be called e 
“vertical.” This crosses on to the dorsal surface and 
there bifurcates (figs. 155 & 156). a 
From the angle of junction of the calcarine and intel ; 
calary sulci two short, deep, posterior branches are given — 
off (fig. 156). J 
On the extreme caudal edge of the mesial surface there — 
is a deep sulcus parallel to and coextensive with the cal-— 
earine. It may be called the “paracalcarine” suleus 
(fig. 156). | 4 
The lower extremity of the calcarine sulcus becom "4 
freely continuous (in this individual specimen) with 
suleus which begins (fig. 156) opposite the lower extre 
of the hippocampus, and proceeds as a deep cleft across t 
ventral surface of the hemisphere (fig. 157) just behind tk 
natiform eminence of the pyriform lobe and the cauds 1 
extremity of the posterior rhinal fissure. Although small. 
representatives of such a sulcus may occur among other 
Carnivores, this fully-developed form is so peculiar to the 


ay 
* 


_—_ 


NERVOUS SYSTEM.—VERTEBRATA. 281 


Bears that I shall distinguish it as “ ursine.” In the brains 
of all other Bears that I have examined it is independent 
of the calcarine sulcus, but in some cases it joins the rhinal 
fissure. 

There are typical genual and rostral sulci. The posterior 
extremity of the genual sulcus (in this specimen, fig. 156) 
is joined to a very constant vertical sulcus which bisects 


Fig. 157. (x 2.) 


.- OLF. BULB. 


SULC. ORB. 
_-SULC. COR, 


_-RHIN. F. 


- SULC.SUPRAS. 


. SULC. URS. 


j SULC. P. SYL. 
ri 


p) ... SULC. P. LAT. 


the “Ursine lozenge’ (fig. 155). As reference will be 
made to this in speaking of the Seals, it may be distinguished 
as the “ bisector sulcus.” 

There is a shallow sulcus midway between the calcarine- 
intercalary complex (splenial). It is the “sublimbic” of 
Guldberg. 

The typical characters of many other parts of the brain, 
such as the hippocampus, the cerebral commissures, the 
pyriform lobe, and especially the cerebellum, are exceed- 
ingly well-shown here. These features are remarkably 


282 PHYSIOLOGICAL SERIES. 


donstaht throughout the Carnivora (vide account of Cat's 
brain). O. C. 1325 TF 
Mivart, Journ. Linn. Soc., vol. xix. 1886, p.19. + 


D. 361. The brain of a Polar Bear (Ursus maritimus). 
On each hemisphere there is an ansate sulcus voall tou 
the corono-lateral sulcus, as well as complementary a ansate 
sulci. There is a simple entolateral sulcus. 
The posterior rhinal fissure appears to join the urs 
sulcus in both hemispheres. 
Note that the trapezoid bodies are partly overlapped 


the pons. 0. C. 1825 06, ‘3 
D. 362. A cast of the cranial cavity of a Polar Bear (Urs : 
maritimus). us 


The exact shape and size of the huge olfactory bulbs a 
pyriform lobes are clearly shown. - 
The great pseudosylvian cleft and all the sulci on Fe 
cranial aspect of the hemispheresareadmirably demonstra ” a 
The examination of a cast such as this enables us_ 
appreciate how closely the brain of the extinct Megathersam 
must have resembled that of Ursus not only in shape but a 
in the disposition of the pseudosylvian, suprasylvian, orbital 
lateral and possibly even the crucial sulci. 


D. 363. The brain of an American Black Bear (Ursus americanus). 
In this specimen the precrucial sulci are independent of © 
the crucial sulci, and the latter do not extend on to the | 
mesial surface. Hence the boundaries of the “ Ursine 
lozenge” are incomplete. This fact is of interest when it 
is recalled that certain writers (vide Soury) argue that the 
crucial sulcus of Carnivores cannot represent the suleus of 
Rolando, because the former is “essentially a feature of 
the mesial surface.” x 
The ursine sulcus is independent of both the calea 4 
sulcus and the rhinal fissure, and extends into the zap 
between these two furrows. 0. O. 1828 


D. 364. The brain of an American Black Bear (Ursus americanus). 
The region between the lateral suleus and the inte = | 
hemispheral cleft is broken up to an extraordinary deg 
by numerous irregular gyri. 0.C. 1325 ° rg qs 


NERVOUS SYSTEM.—VERTEBRATA. 283 


D. 365. A brain labelled Indian Bear—probably Ursus labiatus. 
This is a small and comparatively simple Bear’s brain; 

but it presents features of peculiar interest, which enable 

us to understand the arrangement of the sulci in the Seal’s 
brain. The anterior limb of the third arcuate gyrus has 
grown backward in an operculum-like formation so as to 
overlap a considerable portion of the second arcuate gyrus, 

so that the “ Sylvian fissure” and the suprasylvian sulcus 


Fig. 158. (x2.) 


SULC. SUPRAS. SUBMERGED 2yo GY’ 
— __7 SULC.COR. 


* SULC CRU. 
SULC.P, LAT. ...f : 


d. |) SULC. ORB. 
SULC.P. SYL--"" | 


_. SULC. COR. 
SULC. P. LAT. ----- 


SYL.F" : ™X 


(the anterior limb of the suprasylvian are) appear to 
become confluent. The operculum of the third gyrus has 
been removed on the right hemisphere (fig. 158). Fig. 
159 shows the appearance of the Sylvian region before the 
dissection was made. 

‘Similar phenomena occur in the Badger (Meles, vide 
supra) and in the Seals (vide infra). 

There is a sulcus analogous to that distinguished by the 
letter x in the Lion’s brain. O. C. 13825 Te. 


284 PHYSIOLOGICAL SERIES. 


D. 366. The brain of a “ Bornean Sun-Bear”’ (Ursus mala a alt 
O. C. 1825 vb. 


. 
r. 


0,0; 1325 7d. ii 


D. 368. The brain of a Syrian Bear (Ursus syriacus). | 
O. C. 1825 re . 
Presented by Dr. Bucklan 
D. 369. A cast of the cranial cavity of Ailuropus melanoleucus. 
The brain itself could not have afforded a better deme 
stration of the arrangement of the typically Arctoid ps eudo 0 
sylvian, suprasylvian, orbital, corono-lateral, ansate, cru cia 
and precrucial sulci, The lesser degree of macrosmati : 
resulting in the attenuation of the olfactory bulbs 
peduncles prepares us for the condition we find in the § 


Bear (Otaria). 


D. 367. The brain of a Grisly Bear (Ursus feroz). 


Suborder PINNIPEDIA. 


Family Ovarimpz. 


D. 370. The brain of a “ Sea-Bear” (Otaria gillespii) (3), i 
which the two cerebral hemispheres have been sep: 
from the rest of the brain. 

[The interpretation of the sulci of the Pinnipeds given 
in these accounts will be found to be utterly at variane 
with those of Turner and Kiikenthal and Ziehen (or Flatau 
and Jacobsohn, who follow the latter). This is no re 
discuss the grounds for the views presented, but if t 
reader carefully examines, in the order named, the brains 
of Ursus maritimus, Ursus labiatus (specimen D. 365) [¢ 
Meles meles|, Otaria, Odobenus, and Phoca, the 
feels assured that no further advocacy of his views wil 0 
necessary to convince the reader of their essential accurs 

“The brain of the Sea-Bear is Ao instructive, fe 
supplies what would otherwise be a ‘ missing-link’ of m 
importance between the brain of the Seals and that « 
ordinary land Carnivora. In the first place it is i 
mediate in general form. It is less rounded than in | 
Seals, but differs from that of ordinary Carnivora by k ial 


te 
ae 


NERVOUS SYSTEM.—VERTEBRATA. 285 


almost as broad in front as it is behind ”” (Mivart, op. cit.). 
These illuminating remarks of Mivart will be seen to have 
a much wider application than even their author intended, 
for the resemblance between the plan of the sulci in Otaria 
and Ursus is so very striking, even in the arrangement of 
small and apparently unimportant features, that there can 
be no question as to the identity of the two series of sulci. 
The olfactory bulb [lacking in this specimen] is large 
for a Pinniped Carnivore [compare the cast of the cranial 
cavity, D. 371]. It is borne on a long peduncle, which 
extends from the region of the tuberculum olfactorium 
forward on the base and then upward on the anterior surface 
almost to the antero-dorsal angle or apex of the hemisphere 
(fig. 160). It is lodged in a deep sagittal olfactory sulcus. 


Fig. 160. (x2) 


\ . SULC. ORB. 


p)....- SULC. COR. 


SULC.SUPRASA A SULC. SUPRAS. 
(Sas * SS 


Parallel to and coextensive with the latter there is an 

orbital (presylvian) sulcus, which does not join the rhinal 
fissure (fig. 160). A comparison of this with the human 
orbital (so-called triradiate) will make clear to the reader 
why the term “ orbital” has been employed in these notes 
throughout the whole mammalian series in place of the 
more customary “ presylvian.” 
_ The “Sylvian fissure” is distinctly Ursine. It begins 
on the ventral surface of the brain in a distinct vallecula 
Sylvii caused by the flexure of the small pyriform lobe 
(fig. 160): it ascends with a slight inclination backward. 

The clue to the complete understanding of the brain of 
the Seals is afforded by the study of the Bear’s brain. It 


PHYSIOLOGICAL SERIES. 


will be noticed in the latter that the first arcuate gyrus has 
been completely submerged in the “ Sylvian fissure,” an¢ 
there is a strongly-marked tendency for the anterior limb 
of the second arcuate gyrus to sink into the same great 
gulf. In some Bears and in the Badger this may ¢ ual ly 
oceur. And in Otaria and the Seals the tendency beec = | 
more distinctly pronounced ; in other words, the ante 
limb of the second arcuate gyrus becomes depron 
partially overlapped by the third arcuate gyrus. As 
result we find a great vertical depression on the latera 
aspect of the brain (fig. 161) in which the “ Ursine Sylvian 


Fig. 161. (x 4.) 
SULC SU 
SULC. LAT. 
SULC .ANS.MIN. \ 


SULCI] ANS. 


SULC. COR... 


es 
SULC. ORB. 


SULC.SUPRAS. Ss SULC.URS. 


SULC P.SYL. 
fissure’ and the suprasylvian sulcus are seen separated by 
a narrow strip of submerged second arcuate gyrus. The 
suprasylvian sulcus emerges from the apex of this great 
depression and, after giving off a minor ansate suleus, pro- 
ceeds obliquely upward and backward to end between the — 
two pieces of the forked upper end of the postsylviar 
(posterior suprasylvian) sulcus. This Sylvio-suprasyly ian 
complex may be regarded as analogous to the Syly 
fissure of Human Anatomy (vide infra). : 
The postsylvian sulcus is not joined to the suprasylvia 
(figs. 161 & 162); its lower extremity bends forward 
(fig. 161) almost as far as the Sylvian fissure. Severa 


NERVOUS SYSTEM.—VERTEBRATA. 287 


shallow oblique sulci extend across the broad gyrus which 
separates the postsylvian sulcus and the Sylvian fissure. 
The great corono-lateral sulcus is parallel to and co- 
extensive with the suprasylvian sulcus, from which it is 
separated by a broad gyrus. A large ansate sulcus and 
several smaller branches spring from the angle of junction 
of the coronal and lateral sulci. This region is further 
complicated by irregular compensatory ansate sulci. A 


SULC. PRECRU. 


_ SULT. BISEC. 
Pa SUEC . CRU. 


\ _-SULCI ANS. 
Nf” 


SULC.VERT. 
a 


an 


_-SULC . MARG, 


by aeeee SULC. LAT. 


wee SULC.SUPRAS. 


_SULC,P.SYL. 


«or™ 


D.- SULC. ENT. LAT. 


short oblique sulcus (fig. 162, A) is found on the gyrus 
separating the lateral from the postlateral sulcus. The 
latter is very well-developed (fig. 161). An exceedingly 
deep entolateral sulcus is found (fig. 162) near the posterior 
third of the mesial edge of the hemisphere. Posteriorly it 
is prolonged into a sulcus which is placed exactly on the 
caudo-lateral edge of the hemisphere [and is hence not 


288 


PHYSIOLOGICAL SERIES, 


visible in the figures]. This undoubtedly represents the 
paracalearine sulcus of the Bears (vide supra). This conjoint 
entolateral-paracalcarine sulcus is as much as 2 em, de se 
in parts of its course. This may be partly due to the fact 
that the paracaudal sulci of the Bear’s brain are not present — 
here. As in the Bear’s brain, the posterior rhinal fissure 
ends upon the ventral surface of the hemisphere, i. e. does 
not extend backward on to the mesial surface. Behind its” 
extremity we find in Otaria a well-developed representative 
of the peculiar sulcus distinguished by the name “ ursinu: 
in the Bear. In fact this sulcus is even larger than i is is 
in the Bear’s brain, and extends upward on the latera al 
surface between the Bip sihiias and postlateral sulci 
(fig. 161). E- 
Fig. 163. (xX #.) ! 


SULC.MARG. _ SULC. INTERCAL. 


SULC vale pe 


SULC. CRU., 


SULC.BISEC. Ripe: Ja Nil SULC. P. 
cece” SULC :, COLL 


“SuLC. URS. 


. 
a al 


RHIN, F. 


The calcarine sulcus is very deep and its forward con- 
tinuation (intercalary) is oblique and very short (fig. 163). 
There is a deep retrocalcarine branch (suLC. P. CALC.) of the 
calearine. There is a small collateral sulcus, analogot _ | 
to but not strictly homologous with the human collate 
(vide infra). 

There is a typically Ursine crucial sulcus (fig. 162) w 
large precrnois! branches, and consequently the ‘ Ursi 
lozenge ” of Mivart is very large and distinct. 

Those peculiar sulci which were distinguished by th 
names ‘ vertical”? and “ bisector ” in the Bear’s brain a ‘i 
present in the same forms in this brain (figs. 162 & 168). + 


NERVOUS SYSTEM.—VERTEBRATA. 289 


There is a great oblique marginal sulcus of Owen (“supra- 
splenial ” of other authors) parallel to the intercalary sulcus 
(fig. 163); it crosses on to the dorsal surface, where it 
pursues a considerable course (fig. 162). 

The cerebral hemispheres overlap the cerebellum to a 
much greater extent in this brain than is'the case in the 


Bear. 
In structure the cerebellum, like that of the Bears, pre- 
sents the usual Carnivore features. O. C. 13825 ve 


J. Murie, Trans. Zool. Soc., vol. viii. 1874, p. 517. 


D. 371. A cast of the cranial cavity of a Sea-Bear (Otaria jubata). 


D. 372. The brain of a Walrus (Odobenus [ Trichechus] rosmarus). 

The cerebral hemispheres are short and very broad, 

especially in the postsylvian region. They overlap the 

cerebellum to a much smaller extent than in Otaria ; and 

the great caudo-dorsal extension of the hemispheres, which 

is chiefly responsible for this in the ‘‘Sea-Bear,” is not 

developed to nearly the same degree in the Walrus. On 

the other hand, the lateral caudo-ventral region of the 

hemisphere is widely extended laterally, so as to partly 
overlap the cerebellum. 

The elongated olfactory peduncles are arranged as in 
Otaria and all the Seals ; but, as the cast of the cranial 
cavity shows, the olfactory bulbs are relatively very small. 
The broad anterior perforated spot, the flattened remains of 
the olfactory tubercle, and the pyriform lobe resemble the 
corresponding parts in Otaria. 

The sulci are described in the account of the next 
specimen. O. C. 1825 x. 

W. Turner, ‘Challenger’ Reports, vol. xxvi. 1887, p. 102. 


D. 373. The right cerebral hemisphere of a Walrus (Odobenus 
[Trichechus| rosmarus) (figs. 164, 165, 166, & 167). 

The sulci of this hemisphere, in spite of the difference of 
its shape and consequently of the mechanical factors during 
growth, conform essentially to the same plan as those of 

 Otaria. This leads us to an interpretation of the sulci 
which is utterly at variance with the views propounded by 

VOL, I. U 


290 


SULC PARACALC. 


PHYSIOLOGICAL SERIES. 


Ziehen and other writers on the brains of the Seals. It 
also differs in many respects from Sir William Turner’s— 
interpretation. The anomalous Bear’s brain (D. 365) and 
that of Otaria form the two links which connect the Bear’s — 


Fig. 164. (x 3.) 


SULC. P.LAT.. 
‘ 


t 
OLF. BULB. 


aoe he 
Ss SULC. SUPRAS 


Fig. 165. (x 3.) 
OLF. BULB. 


SULC. PRECRU_ 
SULC.BISEC.... f 


SULC. CRU. "~~ 


SULC. ENTOLAT.“4-~-2---" 


_. SULC.P.LAT. pan 


brain with those of the Walrus and Seals, and give the ¢ u ef 
which leads us to adopt the views here set forth. — 

The orbital sulcus, like that of Otaria, lies on the basal 
surface of the frontal region parallel to the olfactory 
peduncle (fig. 166). Its anterior extremity is hidden by 


‘ae 
% 


NERVOUS SYSTEM.—VERTEBRATA. 291 


“the olfactory peduncle ; but it is placed in front of the 


olfactory sulcus, which does not extend the whole length of 
the peduncle. 

There is a large crucial sulcus, as in Otaria, but it is 
placed on the anterior rather than the dorsal surface. It 


Fig. 166. (x 3.) 
SULC.CRU. 
/ 


ary 
“SULC.BISEC, 


Sic 
SULC.ORB. 


OPT. N, 


SULC.P.SYLz""{ | ae "OF. Tu, 


SULC.P. LAT.-" 


SULC. URS. 
Fig. 167. (x 3.) 
SULC.INTERCAL. 
SULC. CRU. “SULC, ENTOLAT. 
i 


SULG BISECT. 


OLF. BULB. --- SULC, P.CALC. 


SULC. GEN. * SULC. CALC. 


OPT. : 
HIP. F. 
joins the intercalary sulcus on the mesial surface (fig. 167). 
There is a large and very deep precrucial sulcus freely 
opening into the crucial. And the “ Ursine lozenge” is 
bisected as it is in Otaria and the Bears. 
U2 


292 PHYSIOLOGICAL SERIES. 


The features of the Sylvian region essentially agree with 
those of Otaria (figs. 164 & 166). We can, however, — 
recognise in the submerged area more definite traces of — 
the ectosylvian sulci than in Otaria. They are found ina 
position analogous to those of the Bear (D. 360). 

The anterior limb of the suprasylvian (“ ectosylvian” of 
Ziehen) sulcus is submerged, and can be exposed only by — 
drawing forward the anterior lip of the Sylvian fissure 
(fig. 164). It emerges at the apex of the Sylvian fissure, 
and, after giving off a short vertical branch, bends back 
ward for about an inch, and then passes freely into on 3 
tinuity with the vertical postsylvian ; the latter pursues a_ 
course exactly like that of Otaria (compare figs. 161 & 164), 

A large vertical branch proceeds from the junction of 
the suprasylvian and postsylvian sulci. 

As in Otaria, the region between the postsylvian and the 
pseudosylvian sulci is much broken up by a series of oblique 
sulci. 

The great vertical coronal sulcus passes freely into the | 
lateral sulcus. The latter is not joined to the large vertical - 
postlateral sulcus. There is a great oblique sulcus be- 
tween the crucial and the lateral sulci ; it corresponds to 
the dorsal prolongation of the marginal sulcus in Otaria, — 
but is to be regarded also as a compensatory ansate. The 
ansate sulcus is very small, and, as we have seen in the 
Bear’s brain, we should expect to find a large compensatory 
series of sulci in this situation. 

We find a deep entolateral (or paracalcarine) sulcus, . 
in Otaria and the Urside. Its lower part is represented 
by a separate sulcus, parallel to the postlateral on the 
cranial surface. t. 

There is a well-defined ‘ Ursine sulcus,” which is Pro- | 
longed laterally between ,the postsylvian and _postlater 
as in Otaria. e, 

There is a great, deep, vertical calcarine, which becomes 
forked at its ventral extremity ; in other words, the ec a 
pensatory calcarine (analogous to the Primate collate 
suleus opens into it. 

There is a postcalcarine branch, as in Otaria. 


NERVOUS SYSTEM.—VERTEBRATA. 293 


The calcarine is separated from the intercalary merely 
by a submerged gyrus. There is a shallow marginal 
sulcus, in addition to the compensatory ansate. 

There are rostral and genual sulci. The latter is sepa- 
rated from the sulcus which bisects the Ursine lozenge, 
merely by a submerged gyrus. 

Ziehen, Anat. Anzeiger, Bd. v. 1890, p. 692. 


D. 374. A cast of the cranial cavity of a Walrus (Odobenus 
[Trichechus] rosmarus). [In duplicate. ] 


Family Pazocip~z. 


D. 375. The brain of a footal Common Seal (Phoca vitulina). 

The shape of the hemispheres of the Common Seal differs 
most markedly from that of Otaria and Odobenus. 

[This account is based not on this specimen but ona 
damaged specimen in the Stores. | 

There is no great indentation of the lateral contour in 
the Sylvian region as in Otaria and Odobenus. The 
hemispheres present an elliptical appearance when viewed 
from above and an ovoid form in profile. The anterior 
pole is blunt and rounded, the posterior pole is prolonged 
baekward to cover the cerebellum and carries with it a 
diverticulum (posterior cornu) of the lateral ventricle. 

The upper extremity of the pseudosylvian sulcus appears 
to bifurcate. The anterior branch is formed by the anterior 
vertical portion of the suprasylvian sulcus emerging from 
the Sylvian fissure, in the anterior lip of which it is placed 
as in the Walrus. This overlaps without joining the 
horizontal part of the suprasylvian. 

The posterior limb of the bifurcation probably represents 
the upper part of the anterior ectosylvian sulcus or the 
“Ursine Sylvian fissure.” 

As a result of the backward growth of the hemisphere, 
the postsylvian sulcus is very oblique. It is joined to the 
horizontal are of the suprasylvian, and is also prolonged 
far beyond the junction to reach the apex of the occipital 
pole. 


294 PHYSIOLOGICAL SERIES. 


The orbital and coronal sulci are arranged as in Odobenus. 
There are some fragmentary paracoronal sulci between — 
them. The coronal joins a long, sagittal, lateral suleus 
which is placed close to the mesial plane and is very deep. — 
It extends on to the posterior pole. It is probably homo- — 
dynamous with the entolateral (paracalcarine) sulcus of q 
Otaria, Odobenus, and the Bears. 

The postlateral is represented by a horizontal sulev 
below the postsylvian, but the analogy is by no means 
exact. | 

There is a short, deep, crucial sulcus, the mesial branch ‘a 
which is short and not joined to the intercalary. There is 
also a deep and well-defined precrucial branch, but it i 8 
placed wholly on the mesial surface, so that the “ Car 
lozenge,” although exceedingly clearly defined, is no 
visible upon the dorsal, or rather anterior, surface of th 1e . 
hemisphere. _ 

A sulcus joined to the genual sulcus bisects this “‘ lorem” 
as in Otaria and some Bears. q 

The calcarine resembles that of Otaria. Its lower ex- 
tremity joins a long horizontal sulcus. The small oa 
sulcus is joined to the posterior rhinal fissure. The inte 
calary sulcus is independent both of the calcarine, gennal, 
and crucial sulci. 

‘The cerebellum in all the Seals conforms to the Cae 
nivore type already described in the case of the Cat. Its 
shape, however, is variously moulded in the different genera 
by the backward growth of the hemispheres, a 

The flocculus and both of the paraflocculi are very large 
and richly foliate, without, however, losing the general 
resemblance in form to that of the Cat. | 
A large part of the dorsal surface is formed by the richly — 
branched leaf-like lateral expansions of the second lobule 
of the middle lobe (see account of Cat’s cerebellum), The 
folia of the laterai parts of the third lobule are much m 
numerous, and as a result have lost the regular trans 
arrangement seen in the Cat. O. C. 1325 v 
Flatau & Jacobsohn, Vergl. Anat. d. Centralnervensy 
Saugethiere, 1899, p. 304. 


— ll 


NERVOUS SYSTEM.—VERTEBRATA. 295 


D. 376. The left half of the brain of a Common Seal (Phoca 


vitulina). 


D. 377. The right cerebral hemisphere of a Common Seal (Phoca 
vitulina), in which the whole of the lateral wall has been 
removed to open up the lateral ventricle. 

Behind the upper extremity of the hippocampus the 
small posterior horn of the ventricle is seen, and a bulging 
(calcar avis) is visible upon the mesial surface. A glass 
rod has been pushed through the calcarine (so-called 
“splenial”) sulcus to show that the calcar avis in this 
brain is really produced by the calcarine sulcus. This fact 
was first recorded by Serres (Anat. Comp. de Cerveau, 
Paris, 1826, t. ii. p. 470). 

Fish, who (in apparent ignorance of this) rediscovered 
the presence of the posterior cornu, singularly failed to 
appreciate its important bearing upon the question of the 
homology of the so-called “splenial fissure,” for he was 
doubtful whether the calcarine or the parieto-occipital 
sulcus should be regarded as its (splenial sulcus) Primate 
representative. 


P, A. Fish, Journ. Comp. Neurology, 1898, p. 79. 


_ D. 378. A cast of the cranial cavity of «a Common Seal (Phoca 
vitulina). 


D. 379. The brain of a Gray Seal (Halicherus grypus). 
This brain resembles that of the Common Seal. 


O.C. 1325 u a. 


D. 380. The brain of a Monk Seal (Monachus albiventer). 

i The general features of this brain closely resemble those 
of Phoca; but in many respects it is much more like the 
brains of Odobenus and Otaria than that of Phoca. It 
is therefure of considerable value to us in bridging over 
what would otherwise be the very considerable gap between 
the families of the Pinnipedia. 

The pseudosylvian, suprasylvian, and orbital sulci are 
like those of Phoca. ‘The coronal sulcus, however, is not 
joined to, the lateral sulcus. 


296 PHYSIOLOGICAL SERIES. 


In addition to the lateral sulcus there is an extremely 
well-developed entolateral sulcus, as in Odobenus ind a 
Otaria; its position and extent support the contention #! 
the lateral sulcus in Phoca really represents both the lat 
and the entolateral sulci of these other Pinnipeds. 

The dorsal part of the crucial sulcus is much 1 
extensive than it is in Phoca, and the small proces 
placed upon the dorsal surface. Hence the small “ Ursi 
lozenge” occupies a more usual position than it does in 
Phoca. [It is only right to mention that by Phoca I re 
more especially to the individual specimen upon which th 
above description is based.] 

The intercalary and calcarine sulci are joined. 

According to Fish, the posterior cornu of the | 
ventricle is smaller in Monachus than it isin Phoca, 

O. OC. 1825 vd. 

P. A. Fish, Journ. Comp. Neurology, 1898, p. 81. 


D. 381. A cast of the cranial cavity of a Sea-Leopard (& 
rhynchus leptonyz). 

D. 382. The brain of a young Hooded Seal (Cystophora cristata). 
This brain exhibits the features of the basal surface ina a 
very distinct manner. Note especially the acute flexure of ot 

the pyriform lobe, which produces a deep transverse val : 
cula Sylvii. =. 
Note also the large, expanded, and highly complex fle 


cular lobes. 
The olivary bodies may also be seen cropping out at t 


lateral edges of the pyramids. 0.0. 19859, , 


D. 383. The brain of a Hooded Seal (Cystophora cristata). 
This brain closely resembles that of the Monk & 

(D. 880), excepting that the calcarine sulcus does not join 

the intercalary but overlaps it obliquely, asin Phoca, 
As in all Pinnipedia, there is a well-developed “Ui 
lozenge” of Mivart. 0. 0, 1335 v1 


D. 384. The brain of a Hooded Seal (Cystophora cristata), (3: 3 
In this excellent specimen the features of the brai 
described in the other examples are shown with great 
clearness. 


el 


NERVOUS SYSTEM.—VERTEBRATA. 297 


The “ Ursine lozenge” is especially distinct and much 
larger than usual, the precrucial sulci being unusually 
great. The coronal sulcus is joined to the lateral. 

Almost the whole of the anterior vertical limb of the 
suprasylvian fissure can be seen in the anterior lip of the 
“ Sylvian fissure.” 

The cranial nerves are well demonstrated in this speci- 
men. They conform to the usual mammalian type. The 
large seventh and eighth pairs are especially prominent. 

O. C. 1825 va. 
D. 385. A cast of the cranial cavity of a Hooded Seal (Cystophora 
cristata). 


D. 386. A cast of the cranial cavity of an Elephant-Seal (Macro- 
rhinus leoninus). 
The extraordinary shape of the hemispheres produced by 
the pronounced lateral divergence of their caudal extremities 
is well shown. 3 
Turner, ‘ Challenger’ Reports, “ Seals,” p. 92. 


Orper UNGULATA. 
Suborder HyracorpEA. 


D. 387. The brain of a Hyrax (Procavia capensis), ( ¢ ), (figs. 168- 
170). 
Fig. 168. (Nat. size.) 


SULC.SPLEN. 


sutc.cor.-.f.[  ~ 


SULC. SUPRAS. ----f-f + 


SULC. LAT.” 


In the accounts of the brain of the Hyrax hitherto 
published a considerable amount of discrepancy exists, but 


298 


PHYSIOLOGICAL SERIES. 


examination shows (the writer has examined seven brains) 
that the features of the brain vary greatly in different 
specimens. 

The general appearance of the brain (fig. 168) is not 
unlike that of a Sloth. The pattern of the sulci on the 
hemisphere, however, is distinctly Ungulate—though much 
simplified. 

Thus the rhinal fissure is approximately horizontal (fig. 
169): the calcarine sulcus (fig. 170) is prolonged into an 


iD 


7 
‘ 7 


Fig. 169. (Nat. size.) 


SULC. LAT. 


suLc. SUPRAS, 
“> SULC. COR. 


SULC. SPLEN. 


intercalary sulcus which extends the whole length of 
hemisphere, and is placed wholly upon the dorsal surface 
such as is commonly the case among Ungulates and oceurs 
only in felictis among Carnivores; there is a well- 
developed suprasylvian suleus in the form of a flattened 
bow, such as we find in the smaller Cervidee and in the 
Tragulide ; there is either no postsylvian sulcus or ‘the 
slight notch below the suprasylvian sulcus represents a 
Herpestine form of this sulcus. ! 


NERVOUS SYSTEM.—VERTEBRATA. 299 


There is a small orbital (presylvian) sulcus, which does 
not join the rhinal fissure on the right side, but does so on 
the left hemisphere. 

On the right hemisphere there is a very slight notch in 
the upper lip of the rhinal fissure, such as represents the 
“Sylvian fissure”? in many Viverride. This is even more 
faint on the left hemisphere and is of doubtful significance. 
There is a short sagittal coronal and a similar lateral sulcus 
—both such as occur in the smaller Cervide and Tragu- 
lide. There is a small rostral sulcus. 

The small cerebellum is rounded and compact, and its 
folia present the simple transverse arrangement found in 
the Capybara and other Rodents and most Ungulates. 

O. C. 1830 «a. 

Krueg, Zeitsch. f. wiss. Zool., Bd. xxxiii. 1880, p. 648. 

Turner, Journ. Anat. and Phys., vol. xxv. 1890, p. 122. 


D. 388. The two cerebral hemispheres of a Hyrax (Procavia sp.) 


(fig. 171). 
In these hemispheres there is a long and fairly definite 
sulcus (fig. 171, s), such as would by most writers be 


Fig. 171. (Nat. size.) 


SULC. SUPRAS. 


SULC.COR. 
“ 


SULC. P.SYL. 


3 


unhesitatingly branded “Sylvian” in a Carnivore. This 
suleus was found in only one of seven brains examined, 
although in a second specimen such a groove was produced 
by the middle cerebral artery. On the other hand, the 
presence of a more definite vertical postsylvian sulcus 
parallel to this pseudosylvian sulcus shows that the latter is 


sufficiently definite to influence the adjoining cortical areas. 


300 PHYSIOLOGICAL SERIES. 


“The suprasylvian sulcus is here bent at right angles and : 
opens into the anterior rhinal fissure. There can be no 
doubt concerning the small postsylvian sulcus in this brain, 
The orbital sulcus appears to be missing. The coronal 
sulcus is prolonged in a peculiar manner. 

A comparison of this specimen with the preceding at once 
explains the apparent discrepancy between the accounts of 
Turner (op. cit.) and Krueg (op. cit.) respectively. 


D. 389. A cast of the cranial cavity of a Hyrax (Procavia capensis). 
[In duplicate. ] 

The olfactory bulbs project well in front of the hemi- 
spheres. In addition to the constant sulci, there is a well- 
developed vertical postsylvian and also a faint indication of 
an orbital sulcus. 


oe 


Extinct Suborder AmBLYOPODA. 


D. 390. A cast of the cranial cavity of Dinoceras mirabile. 

This cast proves conclusively that the brain of this — 
Eocene mammal, which nearly equalled the Elephant in 
size, was proportionately smaller than that in any other 
known mammal, recent or fossil, and even less than in — 
some reptiles. 

Its general appearance is not unlike that of many reptiles, 
and the colossal size of the olfactory bulbs leads us to infer 
that the diminutive cerebral hemispheres must have been 
almost wholly composed of pyriform lobe, tuberculum — 
olfactorium, and hippocampus (together with the corpus — 
striatum). q 

The neopallium could not have been much greater than — 
it is in Reptiles, in which it is so insignificant that it has — 
hitherto never been definitely described as such. It is 
unlikely that any rhinal fissure had yet developed, and — 
probably the hippocampus constituted the whole of the — 
mesial surface of the hemisphere, as it does in Reptiles. 

The simple leaf-like cerebellum must have closely re- 
sembled that of the Marsupial Mole (Notoryctes), " 

Marsh, American Journ. of Sci. and Art, vol. xi. 1876, — 

p. 165, 


NERVOUS SYSTEM.—VERTEBRATA., 301 


Suborder ProposcipEa. 
Family EzePHANTIDz. 


D. 391. The brain of an Asiatic Elephant (Hlephas indicus) : 
a female about 25 years old. 
[The arrangement of the sulci in this brain is funda- 
- mentally different to that represented by Krueg (Mayer) 
and Flatau and Jacobsohn. | 
An Elephant weighing approximately 46 times as much 
as a Man is provided with a brain almost four times the 
size of the human brain. In comparison with the brain- 
weights of other large Ungulates it must be regarded as a 
large and well-developed brain. According to the most 
recent studies on the question of the size of the brain, the 
dimensions of the cerebral hemispheres, which are chiefly 
responsible for the great variations in the size of the mam- 
malian brain, are in any given Order determined largely, 
or even wholly, by the extent of the sensory surfaces. 
Thus an animal like the Elephant possessing an enormous 
surface-area would have a correspondingly large extent of 
cerebral cortex. But the degree of this cortical repre- 
sentation of sensory surfaces, or “ cephalisation,” as it is 
called, varies in different orders, so that, for instance, a 
given area of bodily surface in a Primate is represented by 
a much larger cortical area than the same extent of surface 
would be in an Ungulate. This degree of “ cephalisation” 
has also rapidly increased, even in the same Order, within 
recent (geologically speaking) times. Thus the Titano- 
therium, a Miocene Perissodactyle as large as the Elephant, 
was provided with a brain considerably smaller than that 
of the Horse. On the other hand, this brain was very con- 
siderably greater than that of the Hocene Dinoceras. It is 
not improbable that the enormous extent of the neopallium 
in the Hlephant—proportionately much greater than in 
other Ungulates—becomes necessary to such an immense 
animal which lives in the open, because such a creature is 
naturally exposed to greater risks of pursuit &c. than a 
smaller animal, and needs to display greater cunning to 


302 


PHYSIOLOGICAL SERIES. 


avoid extermination. Hence the “ organ of associative 
memory,” the neopallium, becomes of vital importance, and — 
becomes, for an Ungulate, disproportionately great. 

The posterior parts of the large cerebral hemispheres x 
have expanded laterally rather than longitudinally, and — 
hence the enormous cerebellum remains almost wholly — 
uncovered—a fact to which an altogether undue importance — 


oe 


is usually attached as an index of cerebral greatness. The 


Fig. 172. (x 3.) 


OLF. vs 


7 LC.ORB. ACCES. 


eet ewnes 


"Oliv, BODY 
““PLOC. 


anterior part of the hemispheres, however, remains narro’ 
and pointed, as in most Mammals. Pe 

The cerebellum increases pari passu with the cerebre an 
and, in spite of the fact that the organ is built up e 
tially on the Ungulate plan, it comes to assume a striking 
general resemblance to the human cerebellum, The fle 
cular lobes, of course, do not share in this greatness. he 
pons Varolii also assumes an appearance closely resembling 


NERVOUS SYSTEM.—VERTEBRATA. 303 


the Human pons, although it is not yet quite large enough 
to completely hide the trapezoid bodies. The development 
of large olivary bodies still further increases the resem- 
blance of the bulbar region to that of the brain of Man, 
but they differ in being placed some distance to the caudal 
side of the pons. 


Fig. 173. 


-- OLF, BULB. 


Fig. 174. (x 3.) 
D 


.\ . SULC. PARAORB. 


SULC.ORB. 


‘ 
‘ 
' 
' 
Uy 


SULC. P. LAT: SULC.P. SYL. 


There is a large, flattened, olfactory bulb (the exact size 
and shape of which is seen to better advantage in the cranial 
cast, fig. 173). A broad olfactory peduncle leads backward 
to a huge flattened olfactory tubercle (fig. 172) ; but the 
pyriform lobe, which must be of considerable extent, is so 


304 


PHYSIOLOGICAL SERIES. 


buried in the deep cleft of the “Sylvian fissure” that it 
cannot be satisfactorily seen. These regions of the brain 
show a considerable resemblance to the corresponding parts 
of the Tapir’s brain. 

The extension downward (ventrally) and forward of that 
part of the hemisphere which lies behind the tuberculum 
olfactorium gives rise to a great ventral boss distantly 


resembling the temporal lobe of the human brain (figs. 173 


& 174). This is separated from the anterior parts of the 
hemisphere by a great gulf, which may for convenience be 
termed the “ Sylvian fissure.” This is extraordinarily deep, 
and consists of a deep vallecula extending upward and 
backward for a considerable distance *. The suleus which 


Fig. 175. 


probably represents the “Sylvian fissure ” of other Ungu- 
lates is placed in this deep vallecula. [In this specimen 
the surface of the brain is in an excellent state of preser- 
vation, but the areas buried in the pseudosylvian sulcus 
are soft and utterly destroyed. It is thus impossible to 
accurately interpret this region. And the only existing 
accounts do not help us in this matter.] 

The orbital (presylvian) sulcus is placed chiefly upon the 
ventral surface, and appears, at least on the left side, to 
open into the clearly-defined rhinal fissure. 

Bearing in mind the exceedingly irregular manner in 
which such stable sulci as the suprasylvian, postsylvian, 


* In this respect it differs most markedly from the condition represented 
by Krueg and Flatau and Jacobsohn. 


~_/- 


' > 
“ER | ———————— 


a 
hy 
| 
i 
a 
Ss) 
3 


NERVOUS SYSTEM.—VERTEBRATA. 305 


lateral, and coronal, become broken up and supplemented 
by irregular and unstable sulci in other large Ungulates, 
it becomes a matter of the greatest difficulty to even recog- 
nise these chief sulci in the Elephant’s brain. There can 


be little doubt as to the identity of the postsylvian sulcus, 


which is so obliquely placed as to be almost horizontal 
(fig. 174). This is in marked contrast to the observations 


Fig. 176. 


SULC. PARAORB. 


of Krueg on the Asiatic Elephant, and Flatau and Jacob- 
sohn on the African Elephant, in both of which this sulcus 
is represented as vertical. 

The sulcus below and parallel to it is probably the post- 
lateral suleus (fig. 174). 

The suprasylvian sulcus proper is broken up and rendered 
complex by numerous branches, some of which seem (but 
probably do not actually do so) to join the “ Sylvian 
fissure.’ The coronal sulcus is probably the deep, almost 
VOL, IL. x 


5306 PHYSIOLOGICAL SERIES. 


vertical, suleus in front of the suprasylvian. The “ lateral” 
series of sulci is represented by a group of short, irregular, 
and richly branched sulci between the suprasylvian sulcus 
and the mesial edge of the hemisphere *. 


Concerning the mesial aspect of the hemisphere nothing 
can be said with certainty. O. C, 18381 4. 
Krueg, Zeitsch. f. wiss. Zool., Bd. xxxiii, 1880, p. 652. 
Flatau & Jacobsohn, Centralnervensyst. d. Siiugethiere, 

1899, pp. 423 & 435. 


* In the absence of any developmental data, it is quite impossible to 
satisfactorily solve the problem of interpreting the involved tangle of short, 
branching, and intertwining sulci in the Elephant’s brain. The homologies 
suggested above are merely those which seem most likely. I have therefore _ 
inserted three illustrations of this brain, which have been drawn from t 
photographs so as to be quite accurate; and, as such a huge mass of soft — 
tissue is specially liable to distortion, a drawing of a cast of the cranial — 
cavity has been placed alongside each to show the true shape of the brain, __ 

If we compare the brain of the Elephant with those of such Ungulates as — 
the Tapir (figs. 179 & 180), and especially the Hippopotamus (figs. 185 & 
186), we shall gain a much more accurate conception of the meaning of the 
Proboscidean pattern of sulci than a study of the Elephant’s brain alone 
could afford. 

In the brain of the Hippopotamus (fig. 185) the suprasylvian suleus (which 
presents a close resemblance to the complex of the sulci a and B of the — 


NERVOUS SYSTEM.—VERTEBRATA, 307 


D. 392. A cast of the cranial cavity of an Indian Elephant 
(Elephas indicus). 

This shows that the enormous brain of the Elephant has 
very much the same form as that of the Yak (Poéphagus 
grunniens), but the caudal broadening and the frontal 
narrowing of the hemispheres is much exaggerated. 


Extinct Suborder TypoTHERIA. 


D. 393. A cast of the cranial cavity of Typotherium cristatum. 

In this cast the horizontal rhinal fissure of the Ungulates 
can be recognised. There is a deep impression in the 
“Sylvian region,” produced apparently by a suprasylvian 
sulcus, analogous to that of Myrmecophaga, and the hemi- 
spheres are considerably expanded behind it. As a whole, 
the brain is not unlike that of a Chevrotain. 

It has a small rounded cerebellum such as Procavia and 
Fydrocherus present. 

Gervais, Journ. de Zool., t. i. 1872, p. 430. 


Elephant’s brain (fig. 174]) is separated from the irregularly Y-shaped post- 
sylvian sulcus by an oblique sulcus (fig. 185, £), in a manner similar to the 
separation of the sulcus B in the Elephant from the long, oblique, Y-shaped 
postsylvian by the sulci © and F (fig. 174). The lateral and entolateral sulci 
become exceedingly irregular in many Ungulates (compare the Tapir’s brain, 
fig. 180) by the development of accessory branches, and in the Elephant 
the continuity of the main sulcus becomes broken, so that instead of a long, 
well-defined, lateral and entolateral sulcus, we find a very complicated pattern 
formed by short, deep, irregular sulci. In the Tapir the coronal sulcus 
(fig. 180) has become so much shifted from the sagittal direction, which it 
usually has in the Ungulata, that it is more nearly transverse. In the 
Hippopotamus the main coronal sulcus is still sagittal (fig. 186), but it is 
provided with numerous transverse rami. In addition there is in this brain 
& transverse sulcus (figs. 185 & 186, c) parallel to and compensatory to the 
suprasylvian sulcus. In the Elephant’s brain we find in the region where 
we should seek for the coronal sulcus no trace of any sagittally directed 
furrows, but there are two deep transverse sulci (figs. 174 & 176, c & H), 
which must be regarded as representatives of the coronal sulcus of the Tapir 
and the sulcus c of the Hippopotamus respectively. Between the sulcus c 
and the orbital sulcus there is a deep, long, paraorbital sulcus, such as we 
find in almost all Ungulates. 
x2 


308 


PHYSIOLOGICAL SERIES. 


Suborder PERISSODACTYLA. 


Family TpripZ. 


D. 394. The brain of an American Tapir ( Tapirus terrestris), (2). 


In this large and highly macrosmatic brain the typical 
features of those parts of the cerebral hemispheres which 
are most intimately concerned with olfactory functions are 
shown in an exceedingly clear manner. On the mesial 
surface (fig. 178) the large supracallosal vestiges of the 
hippocampus may be distinctly seen in front of the genu 
of the corpus callosum passing into continuity with the 


Fig. 178. (x 3) 


SULCI. SUBCING. 
“4 


SULC. INTERCAL 


~ 
Oe. os 


: Sess. FIM. 
‘ 
OLF . PED. 


precommissural area and the olfactory peduncle. Pos- 

teriorly they are prolonged into an enormous subsplenial— 
hippocampal flexure, the limits and subdivisions of which - 
are demonstated in an unusually clear manner. The large 

plump anterior portion (fascia dentata) is distinctly marke 
off from the posterior portion (hippocampus nudus) by a 
definite sulcus ; and the latter is separated from the neo- 
pallium by an equally distinct groove or “ sulcus limitans.’ 

The structure which I have called “ hippocampus nudus 
is merely an exposed part of the hippocampus, and— 
variously known as “ Balkenwindung ” (Zuackerkandl) an 
“ gyrus Andre Retzii ” (Gustav Retzius). 


NERVOUS SYSTEM.—VERTEBRATA. 309 


The features of the olfactory bulb, tuberculum olfac- 
torium, and pyriform lobe are also shown very clearly. 
The arrangement of the rhinal fissure, which separates the 
latter from the neopallium, is peculiar. The anterior and 
posterior rhinal fissures do not join (fig. 179), and appear 
_to pursue a very considerable course parallel to one another 
in such a manner that the forward extension of the pos- 
terior rhinal fissure lies in the neopallium (and may be 
joined to the orbital sulcus), and the caudal extension of 
the anterior rhinal fissure lies in the pyriform lobe. This 
arrangement may be compared to that found in the Aard- 
vark. : 

The furrow usually called “Sylvian fissure” in the 
Ungulata cannot be strictly regarded as the exact repre- 


Fig. 179. (x 2.) 
(-SULC. LAT. 


,SULC. SUPRAS, 
a 


_~- SULE.ORB. 


sentative of any of the various forms of “ Sylvian fissure ” 
(so-called) of the Carnivora nor of the true (Primate) Sylvian 
fissure. It may be caused by factors analogous to those 
which produce the similarly-named “fissure” in the 
Carnivora, and hence it is convenient to retain the name ; 
but only with the distinct reservation that no strict 
homology is thereby implied. Holl has shown that the 
sulcus usually called “Sylvian ” in the Ungulata more nearly 
represents a complex of two sulci, representing the ecto- 
sylvian of Carnivores, the so-called “ Sylvian fissure ” of the 
Carnivore being represented by a very insignificant furrow. 
But I have here retained the conventional nomenclature. 


310 


1 


PHYSIOLOGICAL SERIES. 


“In the brain of the Tapir the “Sylvian fissure” is 
represented by a short deep sulcus (fig. 179) ascending 
vertically from the cephalic prolongation of the posterior 
rhinal fissure for less than half an inch. The posterior lip 
of this ‘‘ fissure ”’ is a large operculum covering a depressed 
area which is continuous with a narrow, uncovered, de- 
pressed area above the posterior part of the orbital sulcus. 
The latter area is limited above by an operculum, the hori- 


* 


zontal limiting suleus of which (fig. 179, A) appears to ‘ 


join the “ Sylvian fissure.” There is no feline pseudo- 
sylvian sulcus. | 

There is an inverted-U-shaped suprasylvian are (conjoint 
supra- and postsylvian sulci), which appears to join the 
above-mentioned horizontal limb (A) of the Sylvian com- 
plex. In reality a submerged gyrus separates the two 
sulci. 

The posterior part of the suprasylvian are is formed of a 
vertical limb (postsylvian sulcus), as in most Carnivores. 


It will be seen, however, to give off a short horizontal q 


posterior ramus, which is a very characteristic Ungulate 
feature, 

The Ungulate lateral sulcus is generally oblique (as it is 
in this case), so that its anterior extremity is nearer the 
mesial plane than the posterior, and it is not joined to 
the coronal sulcus. There is an entolateral sulcus of com- 
plicated shape (fig. 180). The coronal sulcus is also placed 
very obliquely, as it is in many early Tertiary Ungulates, 
such as Titanotherium. 


The orbital sulcus is like that of the Carnivora. There — 
are also compensatory orbital sulci (fig. 179). Most of the — 
sulci of the hemisphere have numerous offshoots, so that — 


the appearance of its surface is very complicated. 


In the left hemisphere (fig. 178) the conjoint calcarine — 
and intercalary (splenial) sulci are united with the genaal — 


to form a complete cingular are. On the right side the 


genual does not join the intercalary sulcus. Midway — 
between the cingular complex there is a series of shallow 


sulci which may be called the “ subeingular sulci.” 


In spite of its large size, the cerebellum exhibits exceed-— 
ingly simple features. The floceular lobe is very large, — 


NERVOUS SYSTEM.—VERTEBRATA, 311 


and instead of being formed chiefly by two regular hori- 
zontal parafloccular bands as in the Carnivora, it consists 
of a great cake-like mass of very large irregular folia 
arranged like those of the Sloths. The lateral parts of the 


~ 

: interfloccular regions of the cerebellum are not markedly 
, expanded as they are in the Carnivora, but are made up of 
: a simple arrangement of transverse folia. O. C. 1830 c. 
E Krueg, Zeitsch. f. wiss. Zool., Bd. xxxi. 1878, p. 326. 
a Holl, Archiv f. Anat. u. Phys., (Anat. Abth.) 1900, p.329. 
_-*D.395. The cast of the cranial cavity of an American Tapir 
2. (Tapirus americanus) . 

i This shows the enormous flattened olfactory bulbs, like 


those of the Elephant. 


D. 396. The brain of a Baird’s eee ( Tapirus baird?), (g juv.). 
O. C. 13380 D. 
Presented by the Zoological Society. 


312 PHYSIOLOGICAL SERIES. 


D.397. The brain of an Asiatic Tapir (Zapirus indicus). 

In this brain the lips of the main sulci have been sepa- 
rated. The opercular nature of the perisylvian cortex is 
well shown. 

The posterior horizontal limb of the suprasylvian sulcus 
is well developed and more like that of other Ungulates. 

—O. C. 1830 Ba, 


D. 398. The brain of a Tapir (Zapirus sp.) in which the arach- a 
noid and pia mater have been left im situ on the right side. 


O. C. 1380ae 


Family Rarwoceroripé. 


D. 399. The brain of an Indian Rhinoceros (Rhinoceros unicornis). 
This brain resembles that of the Horse in size and strue- 
ture. The cerebral hemispheres, however, are narrower in — 
front and broader behind than those of the Horse. a 

The pyriform lobe presents the peculiar features seen in 
the Equidze, and to a less extent in the Tapiride. 
The Sylvian region is like that of the Horse. 
The coronal, lateral, suprasylvian, and orbital sulci are 
like those of the Tapir, but enormously more complicated 
by lateral branches and compensatory sulci. O. C. 13308. — 
Krueg, Zeitsch. f. wiss. Zool., Bd. xxxi. 1878, p. 327. 
Holl, Archiv. f. Anat. 1900, p. 328. 


D. 400. The brain of a Sumatran Rhinoceros (Dicerorhinus suma- — 

trensis), ( 2 ). ; 

Although the Sumatran Rhinoceros is smaller than the — 

Indian species, the brain is even more richly supplied with 

secondary sulci, so that the surface of the hemisphere — 

presents an exceedingly complicated pattern of enteriform 
gyri. The fundamental plan, however, is the same as that— 

of the Tapir. O. C. 1830 Fr, 

Presented by the Zoological Society. 

Garrod, ‘T'rans. Zool. Soc., vol. x. 1877, p. 411. : 


D. 401. The cast of the cranial’cavity of a Sumatran Rhinoceros — 
(Dicerorhinus sumatrensis). 


NERVOUS SYSTEM.—VERTEBRATA. 313 


Family EHquipz. 


D. 402. The brain of a Horse (Hquus caballus). 

The Horse is about six times as big as a Man; but in 
spite of this fact its brain weighs less than one-half as 
much as the human brain. 

In structure the brain may be regarded as a larger and 
correspondingly more complicated Tapir’s brain. The 
cerebral hemispheres are relatively less macrosmatic than 
the latter, and consequently only a very small area of the 
great kidney-shaped lateral aspect of the hemisphere of the 
Horse is formed of pyriform lobe. 

The “ Sylvian fissure ”’ is essentially of the same nature 
as that of the Tapir, but there are usually two or more 
compensatory sulci parallel to the chief “ fissure,” which is 
also relatively very short. The irregular H-shaped sulcus 
found in the Tapir’s brain (fig. 179) between the “‘ Sylvian 
fissure’ and the postsylvian sulcus is here simplified and 
prolonged to form part of an irregular arcuate sulcus like 
the ectosylvian of the Cynoidea. It is not, however, homo- 
logous to the latter, for, as Holl has shown, the “ Sylvian 
fissure” of the Horse is really formed by the ectosylvian 
sulci. 

Then again the “ anterior horizontal limb of the Sylvian 
complex ” is prolonged to form an enormous sulcus parallel 
to and much longer than the orbital sulcus. 

The posterior horizontal ramus of the suprasylvian arc is 
greatly elongated and gives off numerous branches. The 
postsylvian sulcus is also large, and the great quadrilateral 
area between it and the latter sulcus is rendered exceed- 
ingly complicated by numerous irregular sulci. 

In addition to the typical lateral sulcus there are large 
ecto- and entolateral sulci. On the mesial surface there is 
a complete cingular arc (conjoint calcarine, intercalary, and 
genual sulci), as in the Tapir. There is also a complete 
subcingular arc (the so-called ‘“ sublimbic ” sulcus of Guld- 
berg). 

Numerous secondary sulci, not present in the Tapir’s 
brain, have now made their appearance. On the whole, 


314 PHYSIOLOGICAL SERIES. 


they. are analogous to those found in the Camel’s brain | 
(vide infra). 
There isa peculiar, large, elongated, olfactory bulb, which 
projects upwards and forwards free from the hemisphere. 
The cerebellum is relatively simple. It presents a large, 
cake-like, floccular lobe, which Flatau and Jacobsohn loosely 
term the “ tonsil.” 0. C. 138045. 
Presented by H. Power, Esq. _ 
Flatau and Jacobsohn, Vergl. Anat. d. Centralnerven- 
syst. 1899, p. 405. ’ 
Bradley, Journ. Anat. & Phys., vol. xxxiii. 1899, p. 215. 


D. 403. Entire brain of a Horse (Zquus caballus). O. C. 1329. 
Hunterian. 


D.404. A cast of the cranial cavity of a Horse (Equus caballus) 


D. 405. The brain of an Ass (Equus asinus). O. C. 13304 ¢. 
Presented by H. Power, Esq. 


Krueg, Zeitschr. wiss. Zool., Bd. xxxi. p, 328. 


D.406. Brain of an Ass (Equus asinus) having the lateral - 
portion of the left hemisphere and of the cerebellum 
removed. O. C. 1330. 

Hunterian. 


D. 407. The brain of an Onager (Hquus onager), (2). 
0. C. 1830 aa. 
Suborder ARTIODACTYLA. 


Family Sui. 


D. 408. The brain of a Diminutive Pig (Sus salvanius), ( 2 ). 5 
The brain in this Family, which includes the Pigs and 


the Wart-Hogs, is distinguishable from that of any other 4 


Artiodactyle animal by one or two well-marked characters, — 
the most striking of which is the blending of the coronal 
with the intercalary (splenial) sulcus. Behind the coronal 
sulcus there is generally an equally characteristic second 
sulcus parallel to it joining the intercalary to an offshoot of 


NERVOUS SYSTEM.—VERTEBRATA. 315 


the suprasylvian sulcus. ‘This sulcus is seen to best 
advantage in the Common Pig and is not complete in this 
Diminutive Pig. 

In the Pigs also the anterior and posterior opercula of 
the “Sylvian fissure” are so well developed that the latter 
appears to spring from the rhinal fissure (fig. 181) as in the 
Carnivora. It presents, however, essentially the same 
arrangement as other Ungulates. 

The suprasylvian and ectosylvian sulci may be compared 
to those of the Tapir (vide supra). According to Holl, 
however, the homologue of the ectosylvian sulcus of the 


Fig. 181. (x 3.) 


SULC. SUPRAS. 


SULC. COR. 


SULC. ORB. 


SULC.OBL. s 


Carnivora is not to be sought in that which topcgraphically 
resembles it here, but in the sulci, the opercular lips of 
which form the pseudosylvian sulcus. 
The orbital (presylvian) sulcus is placed very far forward 
and springs from the rhinal fissure. 
As is usual among Ungulates, the rhinal fissure is 
horizontal. O. C. 1328 N. 
Garson, Proc. Zool. Soc. 1883, p. 416. 
For general remarks on the Pig’s brain, see Garrod, 
fe Trans. Zool. Soe. vol. xi. 1879, p. 13, and also Holl, Archiv 
‘ f. Anat. 1900, p. 298. 


D.409. The brain of a Corean Pig (Sus scrofa). O. C. 13280. 


D. 410. The brain of a Pig (Sus serofa). 
The features distinctive of the Pig Family mentioned in 
the description of specimen D. 408 are seen in a much more 
pronounced and typical form here. Observe the junction 


316 


PHYSIOLOGICAL SERIES. 


of thecoronal and so-called “splenial” sulci; the connecting- 
link from the latter to the suprasylvian ; the definite post- 
sylvian sulcus, usually absent or very small in the Cotylo- 
phora ; and the apparent origin of the “ Sylvian fissure” 
from the rhinal, whereas in the Cotylophora this so-called 
* fissure” usually ends below in two sulci which pursue a 
course parallel to the rhinal fissure. O. C. 1828 1. 
Flatau and Jacobsohn, op. cit. 1899, p. 384. 


D. 411. A cast of the cranial cavity of Sus scrofa. [In dupli- be 


D. 412. The brain of a Pallas’s Wart-Hog (Phacochwrus wthio- 


cate. | 


picus) (figs. 182, 183, 184). 
In most respects the brain of the Wart-Hog resembles 
that of the Pigs, but it exhibits some peculiar features. 


Fig. 182. (x 3.) 


As in the Pig’s brain, the orbital sulcus is placed very — 
far forward ; it does not really join the rhinal fissure, but 
is separated from it by a narrow strip of submerged cortex. 
The apparent posterior prolongation of the orbital sulcus _ 
inclines obliquely upward away from the rhinal fissure 
(fig. 184), and finally ends in the position where we should 


NERVOUS SYSTEM.—VERTEBRATA. 317 


expect to find the “Sylvian fissure.” The operculum 
which forms its anterior (upper) lip meets a slighter 
posterior operculum, so as to form a pseudosylvian sulcus of 
the Ungulate type (fig. 184, s). On the left hemisphere there 
is no other feature which could be called “‘ Sylvian fissure ” ; 


Fig. 183. (x 3.) 


SULC.CALC. SULC.INTERCAL. 


Fig. 184. (x 2.) 


SULC. SUPRAS. 


ea 


Ss’ SULC. ORB. 


but on the right sidé (fig. 184) there is a very short deep 
notch (s!') above the rhinal fissure, the exact analogue of 
which is perhaps seen in the brain of the Ox (vide infra), 
or in the pseudosylvian sulcus of Carnivores. 


O. C, 1328 K. 
D. 413. The brain of an Adlian’s Wart-Hog (Phacocherus afri- 


canus) . 

The Sylvian region of this brain exhibits interesting 
variations of the condition found in the last specimen. On 
the left hemisphere the sulcus which emerges from the 
rhinal fissure forms a complex more like the ectosylvian 
than the pseudosylvian of Carnivores; and the pit-like 
depression above the rhinal fissure, noted on the right 


318 PHYSIOLOGICAL SERIES. 


hemisphere of the last specimen, has formed a definite 
“ pseudosylvian fissure.”’ 

This confirms the view of Holl that the Unguilate 
pseudosylvian suleus is formed by the homologues of the 
ectosylvian sulci of Carnivores. 

This is but one more example of the morphological 
instability of the so-called “ Sylvian fissure,” of which the 
Carnivora and especially the Ungulata afford so many 
examples. O. C. 1828 ka, 


Family Dicoryiip«. 


D. 414. The brain of a Collared Peccary ( Tayassu tajagu), ( 2 ). 

According to Garrod (Trans. Zool. Soc. vol. xi. 1879, 
p- 13) the brain of Tayassu does not resemble that of the 
true Swine so closely as Krueg suggests. The arrangement 
of the orbital sulcus is like that seen in the Wart-Hog ; and 
the so-called “Sylvian fissure,” which is. here very 
insignificant, finds its closest analogue in Phacocherus. 
The postsylvian suleus is quite wanting. 

There is a complete cingular are of fused calcarine, 
intercalary, and genual sulci, as in the Tapir. This is 
joined (on the right side only) to the coronal sulcus, but 
is not prolonged into the latter, as is the case in the Swine 
family. There is a cephalic prolongation of the lateral 
sulcus midway between the coronal and suprasylvian sulci. 
There is also a well-defined entolateral sulcus. 

O. C, 1828 m. 

Krueg, Zeitsch. f. wiss. Zool., Bd. xxxi. 1878, p. 323. 


a a 


e ' ro 


ie 


3 


‘ 
‘ 


D. 415. The brain of a Collared Peceary ( Tayassu tajagu), (¢). 
In this smaller specimen the “ Sylvian fissure” is more 


pronounced. 
The sulcus between the coronal and suprasylvian sulci is 
much shorter. O. CO. 1328 Ma, 


D, 416. The brain of a Collared Peceary ( Tayassu tajagu). 
No “Sylvian fissure” can be seen, but the upper lip of 
the rhinal fissure is much puckered by numerous small 
sulci, especially on the right hemisphere. O. C. 1828 m0. 


NERVOUS SYSTEM.——VERTEBRATA. 319 


Family H7rpropoTamipZ. 


D. 417. The brain of a new born Hippopotamus (Hippopotamus 


amphibius). , O. C. 1328 1. 


D. 418. The brain of a Hippopotamus (Hippopotamus amphibius), 
(3), (figs. 185 & 186). 

In comparison with the dimensions of its body the 
Hippopotamus has a remarkably small brain. Thus the 
brain is smaller than that of the Horse, in spite of the fact 
that the Horse is about one-fifth the weight of the Hippo- 
potamus: an Elephant of approximately the same size as a 
Hippopotamus has a brain more than five times as large. 


Fig. 185. (x3) 


SULC.LAT. 
\ 4 


SULC.P. SYL. SULC.SUPRAS. 


SULC. PARAORB. 


OLF.TUBER. OLF. BULB. 


PYR.L. 


This points to the conclusion, which is supported by the 
general evidence of Comparative Anatomy, that the Hippo- 
potamus is an instance of the persistence of a primitive 
small-brained mammal in virtue of the fact that it has 
maintained itself in the fierce struggle for existence simply 
by pursuing an eminently safe and retired mode of life. 
The cunning and alertness of the mammal living in the 
open thus cease to have that vital importance which implies 
one or other of the only alternatives—a large brain or 
extinction (Max Weber, Kon. Ak. v. Wetens. t. Amsterd. 
1896). 


320 PHYSIOLOGICAL SERIES. © 


“The hemispheres exhibit a comparative paucity of sulci, 
which are certainly no more abundant than in the brain of 
the Ox and are much fewer and simpler than in that of the 
Giraffe. 

The Sylvian region is modelled upon the same general 
plan as that of the Horse and Camel. The horizontal — 


Fig. 186. (x3.) r 


limiting suleus of the Sylvian depression is prolonged — 
forward into a short paraorbital suleus which appears to be — 
joined to the orbital suleus (fig. 185). 

On the right hemisphere the lateral and coronal sulei 
are fused to form one great sagittal complex extending the 
whole length of the hemisphere. According to Garrod, 
“no other Ungulate has these sulci joined, but they are — 


NERVOUS SYSTEM.—VERTEBRATA. 321 


almost so in the Camels, Giraffe, Dicotyles, and Pig,” as 
they are also on the left hemisphere of this specimen. The 
common occurrence of this phenomenon in other Orders 
indicates the probability of its being a primitive character. 

The suprasylvian sulcus is represented by a relatively 
short transverse are which is separated from the postsylvian 
sulcus by an oblique sulcus (fig. 185, £). There is a well- 
defined entolateral sulcus. There is also a complete cingular 
are, as in the Horse and the Tapir. 

“‘ Looked at generally, the brain of the Hippopotamus is 
evidently very different from that of the genus Sus and 
its nearest allies. Inthe great breadth and complicatedness 
of the [third arcuate gyrus of Leuret] it most resembles 
the Camels and the Giraffe, from the form of which it 
strikingly differs in the much less ‘ pronation’ [inward 
rotation] of the hemisphere. On the whole, it stands very 
much by itself ” (Garrod). O. C. 1328 La. 

Garrod, Trans. Zool. Soc., vol. xi. 1879, p. 16. 

0.419. A cast of the cranial cavity of a Hippopotamus ( Hippo- 
potamus amphibius). 


Family Camecipz. 


D. 420. The brain of an Arabian Camel (Camelus dromedarius). 
In general appearance and size the brain of the Camel 
resembles that of the Horse ; and this resemblance is also 
found to obtain toa very considerable extent.in the arrange- 
ment of the sulci of the cerebral hemisphere. The anterior 
rhinal fissure has disappeared except in its most posterior 
part, but nevertheless the line of demarcation between 
pyriform lobe and neopallium is quite obvious. The 
posterior rhinal fissure is also exceedingly shallow and is 

not joined to the anterior rhinal. 

The posterior end of the anterior rhinal fissure is very 
deep and is prolonged upward and backward for a short 
distance in the neopallium as the posterior limiting sulcus 
of the Sylvian depression: this depression is partially 
overlapped above by an operculum, the horizontal limiting 


sulcus of which is parallel to the rhinal fissure. This 
VOL. Il. : Y 


operealam is deeply incised by several salci, of which the 
most posterior corresponds to that which in many Ungalates — 
is called the “Syivian fssare.” The horizontal Limiting — 
salees is joined in front to a great oblique parsorbital saleas, 
as im the Horse’s brain. q 

The orbital saleus is im front of and parallel to the Litter: _ 
it is deep and long and does not join the rhinal fissure, or, 
atin daticka | TM 
the rhinal fissure should be found. 


There is an exeeedingiy deep sagittal seprasyivian = 
placed very high up on the dorsal surface ; it gives off 
numerous offshoots. There is a very deep, short, ir - 
saleas between it and the parsorbital saleus, which may 
represent either the dizgonal saleus or a part of the 
sylvian saleus itself, There is a long vertical postsyivian 
saleus of irregular shape, which is separated from the 

In the broad cortical area between the Syivmn 
and the suprasyivian suleus there is an Irregular ec 
are, which is of the same nature as, bat far more ¢ 
than, that of the Horse *- 

The dap, mith), commal milan is apes Gage 

The exceedingly deep complex of calcarime and inter 
ealary salei (so-called “splenial”) is prolonged g 
upward and forward om to the dorsal surface, wit 
jeiming the genual saleus as im the Horse's beam. 
mamy eases there is a small posterior cornz of the 
ventricle into which the eolerige cubved pulan'n 
balging or calear avis. 

There is am interesting grouping of saki around the 
ealearime strongly suggestive of the arrangement which 
becomes fixed im the Human braim as the aleurime 
(poslarior calcarins), perteio-aihipitel, und calilaniial 

O. C_ 13236. 
Kreg, Zoinch wim esl, BL xo 197% pe 


© Hel (Arch f Amst. u Phys, Amt Abth 2000) colle this mie 
< obiiquas,” and rerards the eetosyiviam as the constituumts of the : 
syiviaa sulcus. 


a 


; 


NERVOUS SYSTEM.—VERTEBRATA. 323 


D. 421. The brain of a Bactrian Camel (Camelus bactrianus), 


(2). 
This brain closely resembles that of the Arabian Camel. 


O. C. 1828 aa. 


D. 422. The cast of the cranial cavity of a Bactrian Camel 
(Camelus bactrianus). 


D. 423. The brain of a Llama (Lama glama). 
A smaller, much simplified, Camel’s brain. O. ©, 1328 a. 


Family TracvLip~”. 


D. 424, The brain of a Chevrotain (7ragulus sp.). 

“The brain of Tragulus as far as its surface-marking is 
concerned is a simplified miniature of the Cervidee’’ (Flower). 

There is an elongated, deep, suprasylvian sulcus. But 
there does not appear to be any definite representative of a 
pseudosylvian sulcus, although the shallow vertical furrow 
[on the left side there are two furrows] below the supra-~ 
sylvian sulcus may represent the “ Sylvian fissure,” so-called. 

No coronal sulcus, such as Krueg describes (from Owen’s 
figures), is present in this specimen. Nor is there any 
lateral sulcus, as Krueg represents; but the suprasylvian 
sulcus gives off a horizontal branch which may in a sense 
serve the same purpose as the lateral sulcus. 

There is a short orbital sulcus placed very far forward in 
the hemisphere. 

Perhaps the most peculiar feature of this brain is the 
position of the sulcus which a comparison with the brains 
of other Ungulates compels us to regard as the “ splenial ” 
complex of calcarine and intercalary sulci. It is placed 
almost wholly upon the dorsal surface and only reaches the 
mesial surface at its extreme anterior end. 0. C. 1328 Fr, 

Krueg, Zeitsch. f. wiss. Zool., Bd. xxxi. 1878, p. 315. 


D. 425. The brain of a Javanese Chevrotain ( Tragulus javanicus). 
This extremely simple and highly-macrosmatic brain is 
of interest as exemplifying the primitive types which may 
occur exhibiting distinctly-Ungulate characters. 
Y2 


324 PHYSIOLOGICAL SERIES. 


There appears to be a definite coronal suleus quite 
distinct from the suprasylvian. 
The posterior horizontal branch of the suprasylvian 
sulcus is seen to better advantage in this than in the last 
specimen. 
In this brain, and more especially on the right side, 
there seems to be a definite representative of the Ungulate __ 
»: sesh en fissure.” O. C. 1328 Fa. 
Presented by J. Abrahams, me * 


D. 426. A cast of the cranial cavity of a Stanley’s Chevrotain — 
(Tragulus stanleyanus). 
This shows the true size and shape of the olfactory bulbs, — 
It also shows that as regards the suprasylvian suleus and — 
its horizontal branch this Chevrotain closely agrees with 

the Javan representative. 
Gervais, Journal de Zoologie, t. i. 1872, p. 460. 


D. 427. The brain of an African Water-Chevrotain (Doreatherium ! 

aquaticum), ( $ ). 

This brain presents a very close resemblance to that of 

the Chevrotain both as regards its general features and 

shape and also in respect of the suprasylvian and “splenial” — 
sulci. The orbital sulcus, however, is more pronounced — 

and approaches very close to the suprasylvian sulcus. | 

There is a definite short “Sylvian fissure” ascending — 

from the rhinal fissure toward the suprasylvian sulcus. | 


0. C. 1398 rb. 


D. 428. ‘I'he brain of an African Water-Chevrotain, divided by 
mesial sagittal section, and with the right cerebral hemiepa re 
separated from the brain-stem. 

This is an excellent example of the simplest type 0 
Ungulate brain. It clearly exhibits the characteri 
relationship of the Ungulate pseudosylvian sulcus to | 8 
rhinal fissure and to the orbital sulcus. It can now be clear. 
seen that the pseudosylvian sulcus does not really join the 
rhinal fissure and is therefore not identical with the Carni- 
vore pseudosylvian sulcus. There is no latéral sulcus, anc 
the intercalary and suprasylvian sulci occupy their distine- 
tively Ungulate positions on the dorsal surface of the 
hemisphere. 


NERVOUS SYSTEM.—VERTEBRATA. 325 


Family Czervip~. 


D. 429. The brain of a Musk-Deer (Moschus moschiferus), (2). 
This brain is like a larger and slightly more complicated 
edition of the Chevrotain’s brain. 
There is the same type of suprasylvian sulcus passing 
directly by a transverse connecting-link at its anterior end 
into a sulcus, which Krueg reyards as the coronal (figs. 187 


Fig. 187. (x 3.) 
SULC. COR. 
oa 
SULC. SUPRAS 
SULC. LAT 
).. SULC.'SPLEN” 
e 
Fig. 188. (x 3.) 
SULG. SUPRAS. SULE. LAT, 
5 ra 
site tie. : ve LC. OBL. 
2% SULC.ORB. RHIN.F. 


There is a very long orbital (presylvian) sulcus pursuing 
a course parallel to the anterior rhinal fissure ; it, however, 
never joins the latter. The posterior half of the sulcus 
Krueg regards as the “ processus anterior of the Sylvian 
fissure,” but it would be less confusing to follow Holl and 


326 .PHYSIOLOGICAL SERIES, 


call it “anterior ectosylvian.” It is continued into a short 
vertical suleus—the pseudosylvian. From the latter a wv 
suleus, which Krueg calls the “ processus posterior of the 
Sylvian fissure,” leads backward toward the posterior rhinal 
fissure. Itis the posterior ectosylvian sulcus of Holl. 

There is a depressed area between the rhinal fissure and 
these three parts of the so-called “ Sylvian fissure.” Thisis 
the trigonum Sylvii (Holl) and it is continuous anteriorly | 
with the so-called “ gyrus orbitalis,” 7. e., the narrow strip 
of pallium between the orbital (presylvian) suleus and the 
rhinal fissure (fig. 188). 

Although the calcarine (splenial) sulcus can be partly 
seen on the dorsal surface, it is placed chiefly upon the . 
mesial surface, as in most mammals (fig. 189). The position | 


Fig. 189. (x3.) 


SULC.INTERC. 
i 


SULC.GEN. 
% 


SULC. ROST. 


. 
‘ 
a = 
‘, é t/a 
\ 
Y 
% ° A 
. pia Ne Pa 


of this sulcus in the Ungulata seems to be determined 
largely by the size of the hemispheres. In the small 
Chevrotain it is chiefly dorsal, in the larger Musk-Deer it 
is on the dorso-mesial border, and in the larger Deer it is 
mesial. | 

There is a well-developed lateral sulcus pursuing acourse 
parallel to the posterior half of the suprasylvian sulcus, and 
there are several short sulci behind and in front of it. 

There is a small genual sulcus above the anterior 
extremity of. the corpus callosum and a rostral sulcus in 
front of it. 

The anterior extremity of the prolongation of the 
calearine (splenial) sulcus is upturned and may correspond 
to the crucial sulcus. A small ansate sulcus given off from 
the junction of the coronary and suprasylvian sulci presents 


NERVOUS SYSTEM.—VERTEBRATA. 327 


the same relation to the upturned splenial as to the crucial 
in the Canidee. 

There is no sulcus posticus, as Krueg describes; but 
between the posterior rhinal fissure and the suprasylvian 
sulcus there are several vertical fragmentary sulci. On the 
left side the suprasylvian sulcus itself extends downward 
in this situation. There it shows that what Krueg regards 
as the posterior part of this latter sulcus is merely a branch 

or extension backward. O. C. 1828 Ee. 

Krueg, Zeitsch. f. wiss. Zool., Bd. xxxi. 1878, p. 317. 


D. 430. The brain of a Musk-Deer (Moschus moschiferus), ( 2 ). 
This brain differs only in minor details, such as the 
poorer development of the ansate and lateral sulci, from 
the other specimen. 
The sulcus posticus, which Krueg mentions in this brain, 
is present only in the right hemisphere as a small horizontal 


depression between the suprasylvian sulcus and the posterior 
rhinal fissure. O.C. 13828 £2. 


D. 431. A cast of the cranial cavity of Moschus moschiferus. 


D. 432. The brain of a Muntjac (Cervulus muntjac). 

In spite of its much larger proportions this brain presents 
many resemblances to that of the Musk-Deer. 

The splenial sulcus is dorsally situated during a con- 
siderable part of its course. Its anterior extremity bends 
outward like a crucial sulcus. 

The pseudosylvian, suprasylvian, lateral, coronal, and 
orbital sulci conform to the same type. 

There is a small diagonal sulcus and a shallow sulcus 
posticus of Krueg (sulcus obliquus of Holl). 

O. C. 13828 Er, 
Presented by the Zoological Society. 


D. 433. The brain of a Michie’s Deer (Elaphodus michianus), 
(¢). 

The brain is fairly rich in sulci considering its size. It 

is somewhat larger than that of the Pudu; but it closely 

resembles it in the arrangement of its sulci as well as in the 


328 PHYSIOLOGICAL SERIES. 


considerable size, and especially the breadth, of the anterior 
part of the hemispheres. As in the Musk-Deer and the 
Pudu, the cephalic prolongation of the calcarine sulcus 
appears on the dorsal surface of the hemisphere. The 
brain is not unlike that of the Muntjac, but the sulci are 
better developed in Michie’s Deer, and the anterior parts 
of the hemispheres are broader in the latter (Garrod). 
O.C.1328 Es. 


Presented by the Zoological Society. — 
Garrod, Proc. Zool. Soc. 1876, p. 763. ; 


D. 434. The brain of a Sambur (Cervus aristotelis). | 

This is a typical Deer’s brain; it is larger and corre- 

spondingly more complicated than the brain of Michie’s 

Deer. « 
There is a long vertical “ pseudosylvian sulcus.” Keto- 

lateral and entolateral sulci are present. O.C. 1328 Ha. 


Presented by the Zoological Society. 4 


D. 435. The brain of a Moluccan Deer (Cervus moluccensis), (2). 

This resembles the last specimen in most of its essential 
features. 0.C.1328nt. 
Presented by the Zoological Society. — 


D.436. The brain of a Swamp-Deer (Cervus duvaucelli). 3 
This resembles the brain of theSambur. O.C.1828n0. _ 


Presented by the Zoological Society. ; 


D, 437. The brain of a new-born Axis (Cervus avis). 

The extraordinary richness of sulci in this brain is very 

remarkable, when its small size is taken into account. a | 
This is especially noteworthy in the region of the lateral — 

sulcus, where also well-developed ecto- and entolateral sulei — 

are found. O. C.1828 nl. — 

Presented by the Zoological Society. 

D. 438. The brain of a Red Deer (Cervus elaphus), ( 2 ). 

The magnitude of the vertical “ pseudosylvian sulcus” — 

of the Deer and the characteristic fusion of the coronal and — 

suprasylvian sulci are well shown. O. C. 1328 Bf. 

Presented by Sir Victor Brooke, Bart. — 


NERVOUS SYSTEM.~—VERTEBRATA, 329 


D. 439. The brain of a Kashmir Stag (Cervus cashmeerianus), 
(8). 
An excellent example of the typical Deer’s brain. 
O. C. 1328 Em. 
Presented by the Zoological Society. 


D. 440. The brain of a Common Fallow-Deer (Cervus dama), 
figs. 190, 191). 
CF) (ig Fig. 190. (x3.) | 


SULC.LAT. SULC.OBL. 
‘, j SULC.SUPRAS. 


Z 
: 
’ 
2 


SULC.PARAORB. 


s 
Fig. 191. (x2.) 


oem 
- 
Po 


SULC.SUPRAS. 


SULC.EGTOLAT. - 


SULC. LAT. ------- 


SULC. ENTOLAT. ..---\ 


_ This may be taken as the type of the brain in the great 
_ Family of Deer. 


330 PHYSIOLOGICAL SERIES. 


The great vertical pseudosylvian sulcus (s) is formed by 
the meeting of the vertical parts of the two ectosylvian sulci, 
which diverge below to form a horizontal sulcus parallel 
to the rhinal fissure. ‘he anterior ectosylvian sulcus is 
prolonged forward as a paraorbital sulcus, which overlaps the 
true orbital sulcus. 

The suprasylvian are surmounts the pseudosylvian 
sulcus, and is then prolonged back to the posterior margin 
of the hemisphere. The anterior part of the suprasylvian ; 
are is joined to the coronal sulcus. ea 

There is no proper postsylvian sulcus, but the great — 
quadrilateral area between the suprasylvian sulcus and the 
posterior rhinal fissure is broken up by an irregular series _ 
of sulci. 4 

There is a characteristic arrangement of lateral, ecto- — 
lateral, and entolateral sulci (fig. 191). 

O. C.1328 k d. 
Presented by Sir Victor Brooke, Bart. 


D. 441. A cast of the cranial cavity of an extinct Irish Deer — 
(Cervus giganteus). 


D. 442. The brain of a Reindeer (Rangifer tarandus), three — 
weeks old. 

This small specimen of the Reindeer’s brain resembles 
such brains as that of Odocoileus, especially in the pre- 
sylvian region, more closely than the succeeding specimens. 

The diagonal sulcus is quite independent of the supra- 
sylvian sulcus. — QO, 0. 13828 8h. 5 


D. 443. The brain of a Reindeer (Rangifer tarandus), ( ¢ ). 
This is a highly complicated Deer’s brain. If we imagine — 

the progressive series of changes which are to be noted in — 

a successive comparison of the brains of Hydropotes, Pudu,— 
Capreolus, and Odocoileus to be carried a step further, an — 
accurate conception of the Reindeer’s brain will be gained. — 

O. C. 1328 Bg. 

Holl, Archiv f. Anat. 1900, p. 818. . 


D. 444. The brain of a Reindeer (Rangifer tarandus). 
This resembles D, 442, but is considerably larger. 
O. C. 1328 B. 


NERVOUS SYSTEM.—VERTEBRATA. 331 


D. 445. The brain of an Elk (Alces machlis), (3). 
This is a typical Deer’s brain. O. C. 1328 Bg. 
Presented by the Zoological Society. 


D. 446. The brain of a Roe Deer (Capreolus caprea), (2 ). 

In spite of its much greater size, this brain is only very 
slightly more complicated than that of the Chinese Water- 
Deer, which it resembles. 

The posterior descending limb of the suprasylvian sulcus 
has completely aborted and a_ horizontal sulcus has 
developed below the posterior horizontal ramus of the 
suprasylvian, which may be regarded as a compensatory 
sulcus. 

The orbital suleus is still placed very far forward and a 
paraorbital sulcus is formed by the cephalic extension 
of the anterior ectosylvian sulcus, which is prolonged 
obliquely upward and forward as a deep incision in the 
upper opercular lip of the anterior rhinal fissure. 

The splenial complex is placed much higher than in 
Hydropotes, so that it comes to lie on the dorsal rather 
than the mesial surface. This is just the reverse of what 
we should expect after a study of the brain of other Deer, 
for, as a rule, the larger the brain the more mesial and the 
nearer the corpus callosum the position of the conjoint 
calcarine and intercalary sulci is. 

There is a most pronounced crucial-like lateral bending 
of the anterior extremity of this sulcus. O. C. 1328 Ee. 

Presented by Sir Victor Brooke, Bart. 


D. 447. The brain of a Chinese Water-Deer (Hydropotes inermis). 

| “In its cerebral organization Hydropotes approaches 

the genus Capreolus more nearly than any other Cervine 
form known to me”’ (Forbes). 

In the greatly simplified arrangement of sulci in this 

brain, the type common to all the Deer is well exemplified. 

There is a simple vertical “ Sylvian fissure” (fig. 192, 

S.), ascending from the rhinal fissure ; a long, simple, 

orbital (presylvian) sulcus, also springing from the latter 

far forward on the anterior pole; a simple semicircular 

suprasylvian sulcus with a short posterior descending limb 

and a longer posterior horizontal ramus, its anterior 


332 PHYSIOLOGICAL SERIES. . | 


extremity joins the diagonal sulcus ; and the extensi ve » 3 
coronal sulcus joins the convexity of the suprasylvian are 
opposite the apex of the “ Sylvian fissure.” : ee 
There is a short, vertical, posterior, “ oblique” sulcus. — 
The characteristically oblique lateral sulcus of the Deer is 
also present, and is quite independent of the coronal suleus 
(fig. 193). x 
Fig. 192. (x 3.) 


SULC. SUPRAS. 
SULC. COR. 


SULC. LAT. 
- SULC. DIAG. 


SULC. ORB. 


v 
RHIN. F. 


Fig. 198. (x 3.) 


SULC. COR. 
S. Sat 


_- SULD.“SFL" 


The calcarine and intercalary sulci are joined to form a_ 
typical “ splenial ” sulcus, the anterior extremity of which 
bends upward and indents the dorsal surface (spt.), like’ 
the crucial in the Cynoidea, opposite the junction of the 
coronal and suprasylvian and in front of a small ansate 
branch of the latter. a 
Small independent genual and rostral sulci are present. 
The cerebellum conforms to the simple transversely 
foliated Ungulate type. O. C. 1328 Bu. 
Forbes, Proc. Zool. Soc. 1882, p. 638. q 


NERVOUS SYSTEM.—VERTEBRATA. 833 


D. 448. The brain of a Chinese Water-Deer (/ydropotes 
inermis), (3). 

This specimen shows better than the last how closely the 
brain conforms to the same type as that of the Musk-Deer. 
The pseudosylvian sulcus is longer and more complete, for 
the depressed area is now almost completely hidden by the 
downgrowth of opercular folds, especially in front of the 
sulcus. As a result the orbital sulcus now appears to 
spring far forward from the rhinal fissure. 

The anterior part of the suprasylvian sulcus is prolonged 
beyond the junction with the coronal sulcus, and a vertical 
secondary sulcus (the diagonal of Krueg) has made its 
appearance between the coronal and suprasylvian sulci. 
The diagonal is not joined to the suprasylvian sulcus as it 
is in the last specimen. 

There is a longer lateral sulcus than there is in the 
Musk-Deer. The splenial sulcus is now wholly mesial, 
probably because the brain is larger. It does not, how- 

a ever, extend so far forward. The genual sulcus is 
2 longer and so also is the rostral, which appears to cross 
the dorso-mesial margin of the hemisphere and join the 

coronal sulcus. O. C. 1328 Ek. 

7 Presented by the Zoological Society. 


D. 449. ‘The brain of a Mexican Deer ( Odocoileus mexicanus). 
This brain is a larger and correspondingly more com- 
- plicated copy of that of Capreolus. 
The true nature of the paraorbital sulcus is clearly seen. 
There is no posterior descending ramus of the supra- 
sylvian sulcus, but the posterior horizontal branch is very 
deep and extensive and its ventral compensatory sulcus is 
also extremely well developed. 
Well-defined ecto- and entolateral sulci have made their 
appearance. QO. C. 1328 Ea. 


D. 450. The brain of a Virginian Deer ( Odocoileus virginianus). 
This brain agrees with the description of O. meaicanus. 

O. C. 1328 Ep. 

Presented by the Zoological Society. 


334 PHYSIOLOGICAL SERIES. 


D.451.°The brain of a Chilian Deer (Pudu pudu), (2). 
This brain shows features of great interest in com- 
parison with those of Odocoileus and Capreolus. The 
suprarhinal operculum is poorly developed and the anterior — 
ectosylvian sulcus forms a short, vertical, paraorbital suleus % 
which is joined by the true orbital. -s 
The splenial complex lies upon the dorsal surface in a § 
great part of its course. a 
This brain in other respects may be réduiiied as a 
smaller and correspondingly much simplified copy of that 
of Capreolus. 0. C. 13828 gb, 


Family Gmrarripe. 


D. 452. The brain of a Giraffe (Giraffa camelopardalis). 
In this brain the Sylvian and presylvian regions conform _ 
essentially to the same plan as we find in the larger Deer, 
There is a vertical pseudosylvian sulcus, from the lower — 
end of which the anterior ectosylvian sulcus proceeds — 
forwards parallel to, and a considerable distance on the — 
dorsal side of, the anterior rhinal fissure. This ectosylvian 
sulcus joins the orbital sulcus anteriorly, and at the junction 
a large, vertical, paraorbital sulcus is formed, as in the larger — 
Deer. The region between the anterior ectosylvian sulcus — 
and the anterior rhinal fissure is a large depressed area 
marked by vertical sulci and partly hidden by a great — 
dorsal overhanging operculum. o 3 
There is also a large operculum extending towards the 
rhinal fissure and overhanging the posterior ectosylvian — 
sulcus. This is deeply incised by two radial sulci, which _ 
may be regarded as compensatory to the pseudosylvian. 
There is a very deep and complete arcuate suleus, with — 

a large, vertical, apical process between the pseudosylyian 
and suprasylvian sulci. = 
Unlike the condition found in the Deer, the suprasylvian _ 
sulcus has a very large, vertical, posterior, descending ramus, — 
in addition to the posterior horizontal ramus. And the — 
compensatory sulcus is vertical in relation to the former, — 
and not to the latter as in the Deer. The suprasylvian 


NERVOUS SYSTEM.—VERTEBRATA. 835 


sulcus is not joined to the coronal, and its connection with 
the large, irregular, triradiate, diagonal sulcus is very 
doubtful. 

The splenial complex is wholly mesial in position and is 
not connected with any crucial-like sulcus. 

The cerebellum is of the usual transversely foliate 


Ungulate type. O. C. 1828 Da. 
Krueg, op. cit. Bd, xxxi. p. 318. 


D. 453. The brain of a Giraffe (Giraffa camelopardalis), (3). 
O CU. 1328 p. 


Family AN7ILOCAPRIDA. 


D. 454. A cast of the cranium of a Prongbuck (Antilocapra 
americana). 


Family Bovip~z. 


D. 455. The brain of a Gnu (Connochetes gnu). O.C.1327¢1. 
D. 456. A cast of the cranial cavity of a Gnu (Connochetes gnu). 


D. 457. The brain of a Tora Antelope (Bubalis tora), (¢ ). 
This brain closely resembles that of Odocoileus. 


O. C. 1327 o4. 


D.458. A cast of the cranial cavity of a Hartebeest (Bubalis 
caama). 


D.459. The brain of a Duikerbok (Cephalophus monticola). 

This brain is remarkable by reason of its exceeding 

abundance of sulci, in spite of the fact that it is of small 

size. Although the brain is smaller than that of Hydropotes, 

it exhibits a wealth of sulci as rich as that of the much 

larger Odocoileus. 

In proportion to the size of the animal this brain is large. 
The plan of its cerebral sulci and the features of the 

cerebellum resemble those of the Deer Family. 


O. C. 1327 od. 


336 PHYSIOLOGICAL SERIES. 


D. 460. ‘The brain of a Duikerbok (Cephalophus dorsalis), (2). 
This larger brain conforms to the same type as the — 
pygmy species. The suprarhinal operculum is notably — 
better developed. 0. C. 1327 oe. ae 


D.461. The brain of a Duikerbok (Cephalophus maawelli), (2). 
See the account of the pygmy species. 0.0. 13270f. © 


D. 462. The brain of a Cephalophus grimmi. 


D. 463. A cast of the cranial cavity of a Duikerbok (Cey 
lophus natalensis). 


D, 464. The brain of a Four-horned Antelope ( Tetraceros quadri- 


cornis). 


D. 465. A cast of the cranial cavity of the Royal Antelope 
(Ourebia montana). ~¢ 


D. 466. A cast of the cranial cavity of a Reitbok (Coricapra 


arundinum). 


D. 467. The brain of a Black-Buck (Antilope cervicapra), ( 2 ia 
This brain conforms to the same pattern as those of he 

Deer. 3 

Of the three oblique furrows of the “ lateral series” thie | 

mesial is the deepest and the most pronounced — Instead of © 

this being the lateral, as might be imagined, it represents — 

an entolateral suleus, which has attained to a greater 

importance at the expense of the true lateral—the inter-_ 

mediate of the three sulci. 

There is a small, ectosylvian, arcuate sulcus, the postal : 

limb of which joins the Sylvian fissure, as in some of ae ; 

Carnivora. 0. C, 1327 ca. — 

D.468. The brain of an Antelope (Antilope sp.). e 

Note the junction of the ecrucial-like prolongation of t 

intercalary with the coronal suleus on the right side. a | 


O. U. 1327 0. 


D. 469. A cast of the cranial cavity of a Palla (Alpyceros. . 
melampus ). a 


NERVOUS SYSTEM.—VERTEBRATA. 337 
D. 470. A cast of the cranial cavity of a Saiga (Saiga tatarica). 


D. 471. The brain of a Gazelle (Gazella dorcas). 
The “lateral series’’ of sulci resembles that of the 
Black-Buck. 
There is, however, no ectosylvian arc, such as we find in 
the latter. O. 0. 1327 ob. 


D. 472. The brain of a Gazelle (Gazella subgutturosa), (2 ). 

In this specimen it is clear that the intermediate. of the 
“lateral series”’ of three sulci is the true lateral, and that 
the large sulcus in the last Gazelle and the Black-Buck 
must be an unusually pronounced entolateral. 

The crucial-like prolongation of the splenial complex 


(calearine and intercalary) joins the coronal sulcus. 
O. C. 1327 ce. 


D. 473. A cast of the cranial cavity of a Gazelle (Gazella sem- 
merring?). 


0.474. A cast of the cranial cavity of a Sable Antelope (Hippo- 


tragus equinus). 


D. 475. The brain of a Beisa (Oryza beisa). 
This brain may be regarded as an extremely complicated 
form-of the type found in the Gazelle and Antelope. 
The complications are introduced by means of numerous 
additional secondary sulci. O. C. 1327 ok. 


D. 476. The brain of an Arabian Beatrix Antelope ( Oryx beatriz). 
Note the marked twisting of the mesial part of the 
cerebellum, which presents such a strong contrast to the 
symmetrical arrangement of the corresponding part in 

the Deer. Indications of a similar phenomenon are found 
even in the brain of a Cephalophus dorsalis. ©,.C. 13270 p. 


D. 477. A cast of the cranial cavity of the Nilghai (Boselaphus 
tragocamelus) . 


D. 478. The brain of a Guib (Tragelaphus scriptus). 
The suprasylvian sulcus is placed unusually high up on 
the dorsal surface and pursues a sagittal course. It has 
VOL. II. Z 


838 PHYSIOLOGICAL SERIES. 


an_extensive posterior horizontal and a very small posterior 
vertical ramus. There is a well-developed ectosylvian are. 
O. C. 1327 oo. 


D. 479. A cast of the cranial cavity of the Harnessed Antelope 
(Limnotragus spekit). 


D. 480. The brain of a Kudu (Strepsiceros kudu). 

This may be regarded as an exceedingly compan ; 
Guib’s brain. The dorsally-placed suprasylvian sulcus is — 
exceedingly well developed, and on the left side has a very ‘ 
large posterior vertical ramus. It joins the coronal and, on 
the right side, the crucial-like prolongations of the inten 
calary. There is a well-developed ectosylvian arc, with — 
several radiating branches. 0.C. 1327 on. 


D. 481. The brain of an Eland ( Taurotragus ory), ( ¢ ). 

In most respects this brain resembles that of the Kudu, 
but is larger and more complicated. The branches of the — 
ectosylvian are prolonged to form a great horizontal suleus — 
parallel to the suprasylvian. 

Behind the “Sylvian fissure” there is a deep sulcus 
cutting obliquely into the posterior operculum from the — 
rhinal fissure. It is probably a representative of the feline — 
pseudosylvian sulcus. O. C. 1827 cg. 


D. 482. Cast of the cranial cavity of a Takin (Budorcas). 


D. 483, The right cerebral hemisphere of a Goat (Capra hircus), 
partially dissected. 
There is a large vertical “Sylvian fissure’’ extending 
upward from a long horizontal suleus—the conjoint anterior 
and posterior terminal sulei—which runs parallel to and 
some distance to the dorsal side of the rhinal fissure. The 
orbital (presylvian) sulcus is quite independent of 
anterior terminal sulcus. These terminal sulci are analogous 
to the ectosylvian sulci of the Carnivora. 
There is a typically Ungulate suprasylvian suleus, with 
long horizontal and short vertical rami. It is not join 
to the well-developed diagonal sulcus, but is connected with 


ae 


m- 


NERVOUS SYSTEM.—VERTEBRATA. 339 


the coronal. The lateral sulcus is broken up into tri- 
radiate fragments anteriorly. O. C. 1327 B. 
Holl, Arch. f. Anat. 1900, p. 313. 


D. 484. A cast of the cranial cavity of a Goat (Capra hircus). 


D, 485. The brain of a Goat (Capra), dissected to show the hip- 
pocampus in the left cerebral hemisphere. O. C. 1327 Ba. 


D, 486. The brain of a Sheep (Ovis aries) (figs. 194, 195, 196). 
This brain clearly exhibits the typically Ungulate ar- 
rangement of the pseudosylvian, orbital, and suprasylvian 
sulci, as described in the Goat. The coronal, however, is 
not joined to the suprasylvian sulcus in this specimen. 
The three accompanying diagrams explain the general 
disposition of the cerebral sulci. The small insignificant 
notch (8) above the rhinal fissure probably represents the 


Fig. 194. (x 3.) 


SULC. LAT. 
‘ 
SULC. SUPRAS. i 


SULC. COR. 


“, 


= 
ca 


OLF BULB* 


‘ E “a 
SULC. ORB. RHIN.F 


_ pseudosylvian fissure of the Carnivora, whereas the much 
longer (8’) furrow, generally called “ Sylvian fissure,” is 
formed by the meeting of the opercular upper lips of the 
anterior (fig. 194,") and posterior (F) ectosylvian sulci. 
It will be seen from the account of the brain in the 
Lemuroidea that neither the Carnivore nor the Ungulate 
type of pseudosylvian fissure represents the true (Primate) 
Sylvian fissure, which is a complex of several elements. 
The chief of these, and therefore the nearest homologue of 

Z2 


340 


PHYSIOLOGICAL SERIES. 


dg 


the true Sylvian fissure, is the suprasylvian fissure. The 
latter forms an are around the apex of the Ungulate 
pseudosylvian fissure (S’) and gives off a characteristically 
Ungulate posterior branch (s.s.P.). Below the latter are the 
representatives (B) of a constant sulcus called “ obliquus” — 

by Holl. The sulcus a is distinguished as “ perpendicularis.” _ 

The diagonal (p) and its very constant accessory sulcus (CG) 


are also seen (fig. 194). 4 4 


Fig. 195. (x 4.) 


_ es 


Fig. 196. (x 4.) 
SULC. INTERCAL SULC. CRU. 


. SULC. GEN. 


SULC. P. CALC. 


The lateral, ento- and ectolateral sulci (fig. 195, suLC. LAT.) 
are better developed than they are in the specimen of | 
the Goat’s brain. — 

The splenial complex of intercalary and calearine sulei 
is seen to bend upward anteriorly in a crucial-like manner. 

O.C. 1327 am. 

Holl, Arch, f, Anat. 1900, p. 308, a 


NERVOUS SYSTEM.—VERTEBRATA. 341 


D. 487. A cast of the cranial cavity of a Sheep (Ovis aries). 


D. 488. The left half of the brain of a Sheep (Ovis aries), sepa- 
rated by a mesial sagittal section. 
The Sylvian depressed area is very well shown. 


O. C. 1327 ab. 


D. 489. The right half of the brain of a Sheep (Ovis aries). 

The typical arrangement of sulci is well demonstrated. 

The paraorbitai sulcus, which is merely the upturned 
anterior extremity of the anterior ectosylvian sulcus, is 
joined to the true orbital sulcus. 

The posterior ectosylvian sulcus is joined to the rhinal 
fissure by an accessory sulcus, which completes the caudal 
boundary of the Sylvian trigone and probably represents the 
pseudosylvian fissure of the Carnivora. O. O. 1327 ac. 


D. 490. The brain of a Sheep (Ovis aries), in which the lateral 
ventricles have been opened and the corpora striata and 
hippocampi exposed. O.C. 1327 aa. 


D.491. The brain of a Sheep (Ovis aries), in which a great part 
of the cerebral hemispheres has been removed so as to 
expose the corpora striata, optic thalami, pineal body, 
corpora quadrigemina, and cerebellum. 

The great extent of the anterior quadrigeminal bodies is 
shown. 

The characteristic features of the typically Ungulate 
cerebellum—the narrowness and the simple transverse 
arrangement of the folia on the lateral parts of the organ— 
are clearly seen. The floccular lobes are exceedingly 

_ large and complicated ; they form cake-like masses applied 
to the lateral aspect of the truncated lateral regions of the 
‘“‘ middle lobe ” of the cerebellum. 

The flocculus (sensu stricto) is a little feather-like structure 
placed on the middle peduncle below the great irregular 
paraflocculus. O. C. 1327 a. 


D. 492. The right half of the brain of a Sheep (Ovis aries). 
The orbital (presylvian) sulcus is quite independent of 
the anterior ectosylvian sulcus. QO, C. 1327 ae. 


342 PHYSIOLOGICAL SERIES. 


D. 493. The left half of the brain of a Sheep (Ovis aries). 
The appearance of the mesial sagittal section of the 
cerebellum, the pattern of which is remarkably constant 
throughout the Meta- and Eutheria, is clearly shown. | 

0. C. 1327 Ag. a 

W. Kiiithan, Die Entwickl. des Kleinhirn. Miinchen, 1895. 


D. 494. The right cerebral hemisphere of a Sheep, dissected to i 
expose the hippocampus. 0. C. 1327 Ah 


D. 495. Part of the left half of the brain-stem of a Sheep (Ovis — 
aries). - 
The large size of the anterior quadrigeminal bodies in 
comparison with the posterior pair is shown. The tractus 
peduncularis transversus can be very clearly seen as a 
prominent strand crossing the inferior brachium from the 
groove between the optic thalamus and the anterior quadri- _ 
geminal bodies to reach the surface of the pes pedunculi. — 
The mesial geniculate body lies in front of the tract; itis — 
flattened and unobtrusive. 0.C. 13827 ai. 


D, 496. The brain of an Anoa (Anoa depressicornis), ( ¢ ). 
The simplest and most generalised Ox-brain. 5 
O.C.138270m, — 
D. 497. The head of a fotal Ox (Bos taurus) with the dorsal 
surface of the brain exposed in situ. 4 

The simple corono-suprasylvian and lateral are the only — 

sulci present on the dorsal surface, and the splenial complex — 

can also be seen on the dorso-mesial edge. 

The corpora quadrigemina are not yet covered by the — 
hemispheres. O. C. 1328 ab, 
Krueg, Zeitsch. wiss. Zool., Bd. xxxi. 1878, p. 319. ‘ 


? 


D. 498, The brain of an Ox (Bos taurus), from which the ts 
branes have been only partially removed. 4 

The brain of the Ox resembles that of the Sheep, but is 

more richly supplied with sulci as a result of its greater 
size. | 

A very peculiar arrangement of the “ Sylvian region * is 
found in this specimen. 


NERVOUS SYSTEM.—VERTEBRATA. 343 


There is a large vertical Ungulate pseudosylvian sulcus 
placed high up on the lateral wall of the hemisphere 
(fig. 197, 8) ; its lower extremity joins a short posterior 
ectosylvian sulcus and a long horizontal: anterior ecto- 
sylvian sulcus continuous with the orbital. These ecto- 


Fig. 197. (x3.) 


SULC.SUPRAS. 


--- SULC. OBL. 


SULC. ORB. s' < = Fe 
sylvian sulci are far removed from the rhinal fissure, 
from which a Y-shaped feline pseudosylvian sulcus 8’ 
ascends through the Sylvian depressed area, and is sur- 
rounded by a small arc formed by the two ectosylvian 


sulci. O. OC. 13828. 
Hunterian. 

D. 499. A dissection of a brain of a Calf (Bos taurus), to show 
the relations of the optic tract. O. C. 1828 a. 

_ D. 500. The brain of a Calf (Bos taurus). O. C. 1328 Bb. 


D. 501. A cast of the cranial cavity of an Ox (Bos taurus). 
D. 502. The brain of an Indian Ox (Bos indicus). O.C. 1828 Ba. 


D. 503. The right half of the brain of an Indian Ox (Bos indicus). 


O. C. 1328 B. 
D, 504. The brain of a Bison (Bison ewropeus). 


This closely resembles the brain of the Qx. 
O. C. 1328 c. 


344 PHYSIOLOGICAL SERIES. 


D. 505.. Two casts of the cranial cavity of a Yak (Poéphagus 
grunniens). | 
The shape of this brain is very much like that of the — 
Elephant. q 


Orpvmr SIRENIA, 


D. 506. The brain of a Manatee ( Trichechus manatus), which had 
been sliced in various planes by Mr. Garrod and partially 
built up again. G 

Amongst the whole series of placental mammals there is _ 
no other animal in which the brain presents features so _ 
extraordinary and so bizarre as in the Sirenia. The oa 4 
parallel which can be found for the peculiar cases pre- — 
sented by the Manatee and the Dugong is that occasionally — 


Fig. 198. (x4) 


PSEUDO SYL.F. 
eA 


. : \. 
SULCI.ecTosy,, OPT. CHIASMA, 


presented in the brains of idiots, in which the process a 
elaboration has ceased in the earlier months of intra-u : 
life, and the organ has simply grown in size without — 
becoming perfected i in structure. a 

In the two species of Manatee the shape of the cerebra 
hemispheres varies considerably, as Beddard has sho = 
(Proc. Zool. Soc. 1897). “a 

The cerebral hemisphere is a large thick-walled bladder 
(figs. 198 & 200) with a very spacious ventricular cavity, 
such as is found in foetal brains, but not usually in those of 
adult animals. 


NERVOUS SYSTEM.—VERTEBRATA. 345 


_The lateral wall is deeply invaginated into the cavity 
of this ventricle (fig. 200), so as to produce a great ver- 
tical furrow on the surface (fig. 198). This “complete ” 
sulcus is of a very different nature to the Sylvian fissure 
of any mammal of other Orders. In some brains this 
sulcus appears to bifurcate both above and below (fig. 198), 
but in other cases the posterior limb at the upper extremity 
may be a separate sulcus (? suprasylvian); and sometimes 
also: the postero-inferior limb is wanting. 

Neither of these lower limbs represents the rhinal fissure, 
as Beddard believes, because the situation of the rhinal 
fissure can be readily determined at a lower level, although 


Fig. 199. . ( x.) 


SULC.“SPLEN” 


COMM. ANT, OPT.CHIASMA. 


the fissure itself is almost wholly aborted. The inferior 
bifurcation ought rather to be compared to the limiting 
furrows of the Sylvian depressed area, which are such 
constant appendages of the ventral extremity of the 
“Sylvian fissure” of the Ungulata. Their nearest 
analogues are therefore the two sulci called “ ectosylvian ” 
in the Ungulata. 

The small olfactory bulb, the flattened ribbon-like olfac- 
tory peduncle, and the ill-defined tuberculum olfactorium 
and pyriform lobe present no unusual features beyond 
their smallness (as a result of the aquatic habits of the 
Manatee) and the abortion of their boundary, the rhinal 
fissure. The hippocampus also presents the characteristic 


PHYSIOLOGICAL SERIES. 


fedtures. In one specimen of Manatee (specimen D, 507), — 
however, I have seen a peculiar large tubercle of inverted 
hippocampus such as I have found elsewhere only in the __ 
primitive brain of Orycteropus and in the Primates, 
Strange to relate, this condition was present in only one of — 
three Manatees’ brains examined. a 

The corpus callosum is peculiarly short and small, but it 
has an extraordinarily complete genu (fig. 199). F 

Sometimes there is a deep “splenial” (conjoint ol 
carine and intercalary) sulcus, in other cases only one or — 
two shallow furrows take its place. 


Fig. 200. (x #.) 


The left half of a Manatee’s brain, in which the roof of the we 
ventricle has been removed by horizontal section, 


The base of the brain is quite typical, which one voll 
hardly gather from Murie’s representation of it. There 
are small optic tracts, prominent exposed crura cerebri, a a 
large interpeduncular body, very prominent pons, tra 
pezium, and pyramids, and very large fifth, seventh, and 
eighth nerves. Contrary to the statements of Murie, these — 
nerves are found in the positions usual in other Mammals. — 


NERVOUS SYSTEM.—VERTEBRATA. 347 


Although the cerebellum conforms to the usual mammalian 
(and especially Ungulate) plan it presents some very 
peculiar features. The floccular lobes (figs. 198 & 200) 
can only be properly described as enormous; they consist 
of large, cake-like, compact masses of very complicated 
character forming the whole of the lateral aspects of the 
organ. The flocculus (sensu stricto) is a small foliate plump 
mass, quite distinct from the great parafloccular masses 
which form the bulk of the floccular lobe. The inter- 
floccular mass is relatively small; its lateral portion is 
marked by a simple transverse pattern, as in most 
Ungulates; and its mesial part is reduced to extra- 
ordinarily small dimensions. 

The references to somewhat unsatisfactory accounts of 
this brain which Murie, Chapman, and Garrod have given 
will be found in the recent note by Beddard, Proc. Zool. 
Soc. 1897, p. 52. O. C. 13318. 

Presented by the Zoological Society. 


D. 507. The lateral wall (separated by a sagittal section) of the left 

cerebral hemisphere of a Manatee ( Trichechus latirostris). 

The lower half of the hippocampus is exposed in the 
descending cornu of the lateral ventricle. The peculiar 
hippocampal tubercle described in the account of the last 
specimen is exposed at the lower end of the fascia dentata. 
The fimbria appears to spread out on its anterior border. 

On the lateral aspect the peculiar Ungulate type of 
pseudosylvian sulcus is exhibited. 


D. 508. A cast of the cranial cavity of a Manatee (Trichechus 
senegalensis). 


D.509. A cast of the cranial cavity of a Dugong (Halicore dugong). 
The brain of the Dugong, as Miklucho-Maclay’s account 
shows, closely agrees in structure with that of the Manatee. 
Miklucho-Maclay, Proc. Linn. Soc. New South Wales, 


vol. x. 


D. 510. A cast of the cranial cavity of a Rhytina. 
In spite of its lowly organisation, this brain (according 
to Brandt) shares with the Elephant and the great Baleen 


348 


D. 511. The brain of a Porpoise (Phocena phocena). 


PHYSIOLOGICAL SERIES. . 


Whales the distinction of exceeding the dimensions of the - 
Human brain (Dubois, Bull. Soc. d’Anthropol. de Paris, — 
t. viii. 1897, p. 338). a 
The cerebral hemisphere in each of the three Sirenians — 
consists of a great elliptical bladder, the lateral wall of 
which is deeply indented at its mid-point. The hemisphere — 
of the Dugong is relatively much narrower and more like 
those of the extinct Hotherium and Halitherium than that 
of the Manatee. In this respect Rhytina occupies a positic 
intermediate between the two living genera. The olfae : 
bulbs of /alicore are long, conical, projecting strobe fi ay > 
those of Trichechus are broad flattened cakes closely applied — 
to the anterior surface of the hemispheres ; and here ¢ 
Rhytina occupies the intermediate position. In all extinols 
and living Sirenians the cerebellum has the same peculiar 
shape. | 
Brandt, Mélanges Biolog. , Bull. de l’Acad. Imp. des Sci. 
de St. Pétersbourg, t. vi. 1867, p. 364. 


4 


Orver CETACEA. 
Suborder OpoNnTocRTI, 


Family Dexeuinips. 


“The size of the brain differs much in the different genera o' 
the Whale-tribe, and likewise in the different proportion it bea 3. 
to the bulk of the animal. In the Porpoise, I believe, it st 
largest, and perhaps in that respect comes nearest to the Human, 

“The size of the cerebellum in proportion to that of the — 
cerebrum is smaller in the Human subject than in any ¢ 
with which I am acquainted, In many quadrupeds, as the H 
Cow, &c., the disproportion in size between cecobeliaa 
cerebrum is not great, and in this tribe it is still less, yet not: 80 
small as in the bird, &c. 7 

“The whole brain in this tribe is compact, the anterior part of 
the cerebrum not projecting so far forwards as in either the 


ee 


NERVOUS SYSTEM.—VERTEBRATA. 849 


Quadruped or in the Human subject; neither is the medulla 
oblongata so prominent, but flat, lying in a hollow made by the 
two lobes of the cerebellum. 

“ The brain is composed of cortical and medullary substances, 
very distinctly marked; the cortical being, in colour, like the 
tubular substance of a kidney ; the medullary very white. These 
substances are nearly in the same proportion as in the Human 
brain. The two lateral ventricles are large, and in those that 
have olfactory nerves are not continued into them as in many 
Quadrupeds; nor do they wind so much outwards as in the 
Human subject, but pass close round the posterior ends of the 
thalami nervorum opticorum. The thalami themselves are large; 
the corpora striata small ; the crura of the fornix are continued 
around the windings of the ventricles, much as in the Human 
subject. The plexus choroides is attached to a strong membrane, 
which covers the thalami nervorum opticorum, and passes through 
the whole course of the ventricle, much as in the Human subject. 

“The substance of the brain is more visibly fibrous [specimens 
D. 527 and D. 528 were prepared by Hunter to demonstrate this] 
than I ever saw it in any other animal, the fibres passing from the 
ventricle, as from a centre, to the circumference, which fibrous 
texture is also continued through the cortical substance. The 
whole brain in the Piked Whale [Balenoptera acuto-rostrata] 
weighed four pounds ten ounces. 

The nerves going out from the brain, I believe, are similar 
to those of the Quadruped, except in the want of olfactory nerves 
in the genus of the Porpoise.”—John Hunter, on Whales, Phil. 
Trans. 1787, p. 423. 0. GC. 1333. 


Hunterian. 


D. 512. The brain of a Porpoise (Phocena phocena), (3). 
O. C. 1833 a. 


D. 518. A cast of the cranial cavity of a Porpoise (Phocena 
phocena). 

The large brain of the Porpoise is one of the smallest in 
the Cetacean Order, in which the organ attains to a much 
greater absolute size than in any other animals. In a 
record by Flataz and Jacobsohn the brain of a Porpoise 
weighed 468 grammes, being sth the total body-weight. 
Haswell has recorded a lesser brain-weight in this Order, 
that of Kogia grayi, which was 454 grammes, 


350 


PHYSIOLOGICAL SERIES. 


The brain of the Odontoceti is peculiar in that the — 
olfactory apparatus, which develops in the early embryo 
just as it does in other mammals, becomes entirely aborted 
before the time of birth. As a result the olfactory bulb 
and its peduncle completely disappear; the cortex of the 
tuberculum olfactorium atrophies so that a broad expanse 
of corpus striatum comes to the surface immediately in front 
of the optic chiasma on the basal surface of each hemisphere; _ 4 
the pyriform lobe becomes greatly reduced insize and altered — 
in structure ; the hippocampus, including the fascia dentata, — 
and fornix become reduced to very diminutive proportions; — , 
and the anterior commissure becomes greatly ee 
or may even disappear entirely. This abortion of the 
apparatus of smell is undoubtedly to be attributed to the — 
purely aquatic habits of the Cetacea; and it is of interest 4 
because in other purely aquatic animals, such as Fish, 
Amphibia, and Reptiles, such a complete disappearance of 
the mechanism of smell cannot occur because there is no 
neopallium, which as a “sensorium commune” can make — 
good the absence of the sense of smell. , 

The peculiar spherical shape of the cerebral hemisphere 
is to be attributed chiefly to this waning importance of the — 
rhinencephalon. a 

The primitive cerebrum of all mammals consists essen- _ 
tially of two parts: a basal olfactory part and a dorsal — 
neopallium. The relatively greater expansion of the latter, 
which the dwindling of the former must entail, naturally 
produces the marked ventral bending of the anterior and 
“temporal” poles of the hemisphere, so that when the — 
enormous growth of the neopallium, which distinguishes — 
this Order, occurs the hemispheres become moulded by this 
early bias and assume a shape which appears roughly "4 
spherical from above and kidney-shaped in profile. oe 
“hilus” of the kidney-shape forms the “ Sylvian fissure ” 
(using this term with the reservation already adopted a - 
the Carnivora and Ungulata). * 

The hemispheres in all the Cetacea become complicated — 
in a most intricate and highly elaborate manner by the — 
development of innumerable sulci. But the essential plan — 
of the chief sulci of the hemisphere is a modification of the 3 


NERVOUS SYSTEM.—VERTEBRATA. 351 


well-known plan of suprasylvian, corono-lateral, and cal- 
carine-intercalary arcuate sulci, which divide the hemisphere 
into broad strips which become broken up by an extra- 
ordinarily rich supply of sulci. 

The plan of these sulci is very constant in Odontoceti, 
so that the description of the brain of Delphinus tursio (vide 
infra) may be considered sufficient for the Suborder. It 
must, however, be remembered that, rich as the supply of 
sulci is in Phocena, the surface of the hemisphere becomes 
even more broken up in the larger members of the Order. 

Pari passu with the growth of the cerebral hemispheres 
the cerebellum also attains to very great proportions, in 
order, no doubt, that it may co-ordinate the activities of 
the enormous body, the large sensory surface of which has 
called into being the extensive neopallium. 

The structure of the cerebellum is essentially identical 
with that of other large mammals. 

The other parts of the brain call for little mention. It 
is, however, worthy of note that the olivary bodies are 
placed some distance to the caudal side of the large pons 
Varolii. 

Flatau and Jacobsohn, Vergl. Anat. d. Centralnerven- 

systems, 1899, p. 449. 


D, 514. The left half of the brain of a Dolphin (Delphinus tursio) 
(3), which has been split in the mesial sagittal plane. 

O. C. 13833 8. 

Presented by the Westminster Aquarium. 


D. 515. The right half of the same brain. 

This brain is larger and correspondingly richer in sulci 
than that of the Porpoise; but the structure of the two 
organs is essentially the same. 

The so-called “ Sylvian fissure” begins upon the base 
of the brain ina deep cleft-like vallecula Sylvii. It ascends 
for only a short distance upward and slightly backward 
(fig. 201) upon the lateral aspect. In this respect it differs 
most markedly from the larger Carnivora, in the brains of 
which (compare the Bears and Seals) the “ Sylvian fissure ” 
becomes greatly elongated. There is a much more striking 


352 


PHYSIOLOGICAL SERIES, 


resemblance to the arrangement found in the larger Ungu- © 
lata (compare the Horse’s and Camel’s brain). For in the 
latter the “ Sylvian fissure ” becomes relatively shorter the — 
larger the brain becomes, and it also gives off several 
radiating branches, just as the larger Cetacean brain gives 
off a group of deep radiating branches (fig. 201,8.R.), some 
of which actually open into the “Sylvian fissure,” while 
others merely seem to do so. | i 

Extending across the lateral convexity of the hemisphere 
there is a series of large concentric arcuate sulci, the — 


Fig. 201. (x$.) 


lowermost of which surrounds the radial branches of the 
“ Sylvian fissure.” ‘ 
It is customary to regard these great arcs as the homo- _ 
logues of (i) the ectosylvian, (ii) the suprasylvian, and (iii) 
the corono-lateral arcuate sulci respectively from below up- 
ward (fig. 201, 7, 2, and 3). If such be the case (which 
is hardly probable), the reservation must be made that it is a 
unusual in the Carnivora and Ungulata to find the ecto- — 
sylvian suleus so exceptionally well developed as it is in — 
this Cetacean, in which it so closely simulates the supra- 
sylvian sulcus of other mammalian Orders. 


~~ 
t 
vi 
iy 


NERVOUS SYSTEM.—VERTEBRATA. 853 


On the mesial surface, which is of unusually great area, 
there is a sulcus (fig. 202, 5) of extraordinary depth, which 
pursues most of its course on the mesial surface near the 
rounded dorsal margin ; both of its extremities cross on to 
the cranial aspect. If this sulcus does not represent the 
lateral it must be an unusually accentuated entolateral 
sulcus, such as occurs in the Seals. } 

The calcarine sulcus is very deep and is placed very 
close to the splenium of the corpus callosum. It is joined 


CORP. CALL 


SULC.INTERCAL.. hss 


SULC.GEN. --~"f<" 9 


i % : 
LAM. TERM. OPT. CHIAS. 


to the intercalary and genual sulci to form a complete 
cingular are (fig. 202). The wide gap between the latter 
and sulcus 5 contains innumerable sulci, three of which 
are very pronounced posteriorly (fig. 202, 6). 

The orbital sulcus is represented by two or three rela- 
tively insignificant furrows on the basal surface. It is 
possible that the dwindling of the olfactory regions accounts 
for the insignificance of the orbital sulcus. O. C. 13331. 


Presented by the Westminster Aquartum. 
D. 516. The brain of a Dolphin (Delphinus tursio). O. C. 1383 5. 


D, 517. The brain of a Dolphin (Delphinus sp.). O, C. 1883 ¢. 
VOL. I. 2A 


354 _ PHYSIOLOGICAL SERIES. 


D. 518. The brain of a Dolphin (Delphinus sp.). i 
; 0. ©. 1833p. 
D. 519. The brain of a Dolphin (Delphinus delphis), (2 ). 


"0.0. 1883 aa 
Presented by Matthias Dunn, Tags , | 


D. 520. A cast of the cranial cavity of a Beluga or White Whal e a 
Sis cone he leucas). 


D. 521. The brain of a Beluga or White Whale , (Delphina 
leucas) : from a female 9 ft.long. The fresh brain weighs € 


1797 grammes. 
The brains of the Beluga and all the Dolphins closely 
resemble that of the Porpoise. 0. C. 1333 9. 


Presented by M. Morris, Esq. 
Kiikenthal and Ziehen, Denksch. d. med.-nat. Gesell. — 
Jena, Bd. iii. 1893, p. 108. 


Family Paysererip~. 


D. 522. A cast of the cranial cavity of a Sperm Whale (Physe 
macrocephalus). 


Suborder Mysracocgrt. 
Family Barznip2. 


D. 523. ‘Che brain of a Rorqual (Balenoptera, probably musculus), 
from which the right hemisphere has been removed. ty 


D. 524. The right hemisphere of the same brain. % 
[In the absence of any definite information concerning 

the species of the Whale of which this is the brain, I hay e 
called it “ musculus,” because its dimensions agree to within 
a millimetre with those given by Guldberg for this species, 
whereas they differ considerably from the measurements 0 
the other species of Rorqual as given by the same writer:] 
This is the largest brain of any living animal, and yet, 


NERVOUS SYSTEM.—VERTEBRATA, 355 


relatively to the size of its enormous body, it is the smallest 
mammalian brain. Thus, according to one record, the 
brain of a Common Rorqual weighed 4700 grammes and 
the body of the animal, approximately, 25,000 times as 
much. 

From recent investigations as to the factors which deter- 
mine the size of the brain in mammals, there can be little 
doubt that in any given Order of mammals of the same 
geological epoch the size of the cerebral cortex varies directly 
with the extent of the sensory surfaces of the body. It 
must, however, be borne in mind that the impressionable 
surfaces of the organs of the special senses have a relatively 
greater representation in the cortex than the general sensory 
areas, because the psychical importance of the olfactory, 
visual, and auditory impressions is greater than that of 
mere tactile sensibility. In the Whale the olfactory areas 
become reduced to insignificant proportions. The diameter 
of the retina of Sibbald’s Whale is only 23 times as great 
as that of the Porpoise (Dubois, op. cit. p. 356). So that, 
presumably, the visual area of cortex, although much ee 
in the Whale than in the Porpoise, is relatively much 
smaller in the former than in the latter. Then, again, the 
disproportion between the general surface areas of the 
Porpoise and Whale is much greater than that of the body- 
weight. Hence the brain of a small animal (the Porpoise) 
is much greater than that of a large animal (the Whale) 
per unit of body-weight. 

For a given unit of sensory surface the extent of the 
cerebral cortex varies in different Orders, or, as Dubois puts 
it, ‘the index of cephalisation increases as the organisation 
of the animal becomes higher.” Thus, in a series of esti- 
mations of this index, Dubois gives 2°8186 and 2°6778 as 
the human male and female figures respectively ; for the 
Apes indices ranging from 0°3636 (Macacus) to 0°7607 
(Hylobates) ; for the Carnivores from 0°2166 (Putorius) to 
0:4413 (Lycaon—very old specimen); for the Ungulates 
from 0°2026 (Tapir) to 0°4573 (Equus), sinking in ex- 
ceptional cases as low as 0°1819 (Aippopotamus) and rising 
as high as 1:2484 (Hlephas): and finally for the Rodents 
from 0:0767 Sa to 0°2369 (Hydrocherus). Hstimating 

Z2A2 


356 


PHYSIOLOGICAL SERIES. 


this index in the same way for Balenoptera sibbaldi, he — 
calculates it at between 0°2263 and 0°2680, i.e. as being — 
slightly below the average Carnivore and Ungulate status — 
and considerably higher than the average Rodent index. 

The apparently extraordinary dimensions of the Whale’s 
brain cannot therefore be considered an unusual pheno- — 
menon, because this enormous extent of cerebral cortex to r 
receive and “store” the impressions of such vast sensory 
surfaces becomes a condition of survival of the animal. __ 

The marvellous complexity of the surface of the cerebrum — 
is the direct result of its great size. In order, apparent iy a a 
that the cerebral cortex may be efficiently nourished and 
at the same time be spared to as great a degree as poesia 7 : | 
the risk of vascular disturbancés [such as would be pre 
duced by large vessels passing into it], its thickness does r 
appreciably increase in large animals, Thus Dubois quotes — 
the following figures to show this :—In a Whale (Hype | 
roodon) cortex 2-8 mm. (Kiikenthal and Ziehen), in Bos 
2 mm., in Lepus 2 mm., and Homo 2-3 mm. Such being 
the dint it naturally results that the increased bulk of 
cortex in a large animal can only be packed by becoming 
thrown into an increasing number of folds, separated by a 
correspondingly large number of sulci. In Balenop a4 
this process is carried to a much greater extent than a 
any other animal. 

(E. Dubois, Bull. Soc. d’Anthropologie de Paris, t. 
1897, p. 337.) : 
The presence of a diminutive olfactory bulb and peduncle 
is a noteworthy feature which distinguishes the Baleen 
Whales from the Toothed Whales, in which all the olfacte 
structures are wanting. [In this specimen, unfortunat re 
the olfactory regions are damaged.] According to Gu Id- - 
berg the cerebral hemispheres ‘and the two halves of tl 
cerebellum are asymmetrical both in shape and size in 
Balenoptera musculus, but not in the other Baleen Wha ‘. >) 
From the measurements of this specimen there cannot be 
much doubt that it belongs to the species “ musculus,” r 
yet the asymmetry, if present, is so slight that it migl 
easily have occurred during the preservation of such a hug 
mass of soft tissue. 

The so-called “ fissure of Sylvius” is peculiar in that it 


NERVOUS SYSTEM.—VERTEBRATA. 357 


pursues a course obliquely upward and forward for a con- 
siderable distance (fig. 203,8). It thus presents a marked 


(X 3) 


Fig. 203. 


contrast to the “ Sylvian fissure” of the Odontoceti. The 
difference is further increased by the different arrangement 


358 


PHYSIOLOGICAL SERIES. 


of the branches of the “ fissure,” which do notissume the 
peculiar radiating grouping found in the Porpee’s brain, 

The chief sulci form a series of concentric res around 
the “Sylvian fissure,” the lowermost of whic are much 
more acutely flexed than is the case in th Porpoise. 
There is little exact information to guide us in etermining 
the exact homologies of these five great are but it is 
customary to call them from below upwards: () the ecto- 
sylvian, (ii.) the suprasylvian, (iii.) the ectolaterl, (iv.) the 
lateral, and (v.) the entolateral sulci, respective! (figs. 203 
and 204). In the depths of the “ Sylvan fissur” there is 
a very large submerged area, which is usually armed the 
“insula,” although it cannot be regarded asthe strict 
homologue of the human “ island of Reil.” 

On the mesial surface the most peculiar feaire is the 
enormous rostrum of the corpus callosum (fig. 25). 


Fig. 205. (x 4.) 
SULC. INTERCAL. SPLEN. 


SULC. GEN: \y 


ost OANA GALL. 


There is a very deep cingular arc formed by te united 
calcarine, intercalary, and what we may call the pragenual 
sulci (fig. 205). 

Beyond this arc the irregular tangle of sulci ‘oes not 
permit any satisfactory analysis. 

Guldberg, Forhand. Vidensk, Selsk. Christiam, 1889, 

p. 19. 


D. 525. A cast of the cranial cavity of a young Rorqui (Bale- 


noptera musculus). 


-- SULC, CALC. 


Ry: _ NERVOUS SYSTEM.—VERTEBRATA, 359 


. cast of the cranial cavity of a Common Rorqual 
jalanoptera musculus). 
A x : * of the brain of a Piked Whale (Balenoptera 
to-ros ete), “ showing a fibrous texture.” O. ©. 1335.. 
Hunterian. 
ee O. C. 1336. Hunterian. 
1 hese two specimens were prepared to demonstrate some 
; rk of Hunter’s (vide notes, specimen D, 511). 
i O. C. 1837. 
A cast of the cranial cavity of an Arctic Right Whale 
a mysticetus). 


ro the right half of the cranial cavity of a Megaptera, 


Oxper PRIMATES. 
Suborder * Prosi. 
Family Cxmomyrx. 
1 Th brain of an Aye-aye (Daubentonia _[Chiromys] 


6 TT ee ee ee i we 


360 _ PHYSIOLOGICAL SERIES, 


‘ 


7 Fig. 207. (Nat. size.) 
=  SULC. SUPRAS. cx LAT. 


rust é rowuLe rose, RIN. ANT, ova 

D. 532, The brain of an Aye-aye (Daubentonia [Chiromys] 

madagascariensis), split in the mesial plane and the left _ 

cerebral hemisphere separated from its half of the brain- 
stem (figs. 208 and 209). 

Fig 208, (Nat size.) =a 

SULC. LAT. a 


SULC. SUPRAS. 


“SULC. PSEUDO. SYL. 


Fig. 209. (Nat. size.) 
SULC. INTERCAL, 


CORP, CALL. 
a 


HIP. TUB. 


OLF. BULB. 
The characters of these two brains indicate the wide sepa- a 
ration of the Aye-aye and the true Lemurs; and yet, highly 


™ 
—— 
i | 
i) 


4 


1) 


NERVOUS SYSTEM.—VERTEBRATA, 361 


specialised as the brain is in both families, that of the Aye- 
aye clearly exhibits features indicative of the affinity of its 
possessor to the Lemurs. At the same time several of the 
peculiarities of the brain of Daubentonia are unquestionably 
features intermediate between those of the great body of 
mammals and the Primates (more especially the Lemurs), 
and as such afford the clue to the interpretation of an exact 
comparison between the Primates and other mammals, 
which would otherwise be far less definite and sure than it 
is now possible to make it *. 

The accounts of the Aye-aye’s brain which have hitherto 
been published by Owen, Oudemans, and Chudzinsky, and 
Gervais’s remarks concerning a cast of the cranial cavity, 
are so conflicting that one would hardly imagine that 
they all apply to the same species of mammal. Moreover 
they all seem to me to disregard the most instructive and 
significant features of this remarkable brain. It must, 
however, be admitted that the brain is subject to extreme 
variation in this species—a fact which emphasises the 
importance of those features which are constant; and 
fortunately the two specimens in this Collection are not 
unlike the only two examples of which we possess anything 
like an intelligible account. Specimen D. 531 might be 
compared with that described by Oudemans, and D. 532 
with that described by Owen f. 

The cerebral hemispheres completely overlap the broad, 
flattened olfactory bulbs, but in the caudal direction they 
are so short as to leave almost the whole of the cerebellum 
uncovered. In the latter respect they approximate to the 
condition found in the Carnivora and Ungulata more de- 
cidedly than do the Lemur’s cerebral hemispheres. 


* The fact that many of these peculiarities are undoubtedly due to retro- 
gressive changes does not, in this particular instance, lessen their importance. 

+ I was at first inclined to believe that this old specimen, which 1 found 
only after searching through the Store-room of this Museum, had probably 
been stowed away there since the late Sir Richard Owen was Conservator, 
and might be the identical specimen described by him in the ‘ Transactions’ 
of the Zoological Society. But he described and figured a dissection of his 
specimen, whereas this was undissected when I happened to find it. There 
was no note, either with the specimen or in the old manuscript catalogue, 
to indicate the source of this interesting brain. 


362 


~ s i fr ee ee ; 


PHYSIOLOGICAL SERIES, 


The anterior poles of the hemispheres are remarkably 
blunt and flattened. In this respect they present a resem- 
blance to those of the extinct Lemuroid Megaladapis. 

The broad flattened olfactory bulbs must be considered 
large, even for a Prosimian brain; and the proportions of 
the typical olfactory tubercles and pyriform lobes are in 
accord with this fact. The rhinal fissure is clearly defined 
in its anterior part; but it becomes obliterated behind the 
vallecula Sylvii, so that there is no clearly defined line of 
demarcation between the caudal part of the pyriform lobe _ 
and the neopallium (fig. 207). 

There is a relatively large corpus callosum with a plump 
splenium and a well-formed genu, which is linked to the 
anterior commissure by a delicate rostrum. 

The lower extremity of the hippocampal formation exhibits 
that peculiar swelling of inverted hippocampus (fig. 209, 
HIP.TUB.) which occurs in all the Primates, and is found 
so well developed elsewhere, so far as I know, only in 
Orycteropus (vide “The Brain in the Edentata,” Trans. 
Linn. Soc. 1899), and sometimes in the Manatee. There is 
also a peculiar notch-like offshoot from the hippocampal 
fissure just above this “hippocampal tubercle,” such as is 
commonly found in the brains of Lemurs (compare figs. 209 
and 212, x). 

The oondiien of the “ daater ” group of sulci is par- 
ticularly interesting. At a casual glance the calcarine, 
intercalary, and genual sulci on the separate left hemisphere 
(fig. 209) seem to be joined to form one long “ cingular” 
suleus as, for instance, in the Tapir’s brain. But a close 
examination reveals the fact that the calcarine sulcus is 


separated from the intercalary-genual complex (or calloso- 


marginal sulcus, as we may now call it), as in all other 
Primates. But in this instance the separation is effected 


only by a very narrow, partially submerged gyrus. The — . 


condition of the calcarine suleus thus exhibited (which — 3 
essentially resembles not only that found in Lemurs, but 
also that of the Edentate Manis) affords yet anotherdemon- — 


stration of the identity of the calcarine sulcus of the Primates 


and the vertical posterior part of the sulcus generally called 
“ splenial” in other mammals. 


a 


NERVOUS SYSTEM.—VERTEBRATA. 863 


By far the most significant feature of these brains of the 
Aye-aye is the existence of a separate suprasylvian are. 
In the Carnivora and many other mammals (e. g. Bradypus) 
the suprasylvian sulcus is joined to the postsylvian 
(generally known as “ posterior suprasylvian”’) to form 
a “supra-sylvian arc.” Such an arc is generally found in 
the brain of Daubentonia, but in that of no other Primate. 
In all the Lemurs and Apes the suprasylvian sulcus is 
separated from the postsylvian (which is then called 


_ “parallel” or “superior temporal”) sulcus; and the 


former then appears to be joined to the angle of the rhinal 


fissure by means of a shallow depression, the nearest parallel 


for which is to be sought in the sulcus erroneously called 
“Sylvian fissure”’ in most mammals. The latter is not the 
true Sylvian fissure, but a sulcus of no morphological 
stability, which is probably produced as a kink in the 
neopallium at the site of its bending. The true Sylvian 
fissure is a peculiar complex of many elements, which is 
seen in its perfect form only in the human brain. Its 
fundamental constituent is the. suprasylvian sulcus, and in 
some Lemurs the “Sylvian fissure” is the suprasylvian 
sulcus, pure and simple. Butin most Primates the dorsal lip 
of the suprasylvian sulcus would seem to become opercular 
and tends to overlap a depressed area which is also partly 
covered by the forwardly extending posterior opercular 
lip of the pseudosylvian sulcus. According to this hypo- 
thesis, the suprasylvian sulcus of non-Primate mammals is 
represented in the Primates by the superior limiting sulcus 
of the “island of Reil,”’ which is the fundamental 
constituent of the complex known as the Sylvian fissure. 
The great importance attaching to the brain of Dauben- 
tonia lies in the fact that the suprasylvian sulcus (which a 
comparison at once shows to be identical with the Lemurine 
“ Sylvian fissure ””) is not linked to the rhinal fissure, but is 
joined in most cases to the postsylvian sulcus, as it is in the 
‘Carnivora and many other mammals. An interesting parallel 
phenomenon is found in the brain of the Great Anteater 
(Myrmecophaga jubata). In most cases the suprasylvian 
sulcus of this creature is completely separated from the 
postsylvian and joined by that suprarhinal kink, which may 


364 


PHYSIOLOGICAL SERIES. 


be called the “ pseudo-sylvian fissure,” to the rhinal fissure. 
It is therefore the rule in Myrmecophaga (vide specimens 
D. 282 and D. 283) to find the suprasylvian sulcus 
converted into a Lemuroid Sylvian fissure. But it may 
happen (vide specimen D. 281) that the suprasylvian sulcus 
becomes separated from the “ pseudosylvian fissure” and 
joined to the postsylvian. This anomalous Anteater’s brain, 
therefore, presents exactly the same relationship to the 
normal Anteater’s brain as the brain of the Aye-Aye does 
to the Lemur’s. 


None of the various sulci which Owen, Oudemans, and ~ x 


Chudzinsky have labelled “Sylvian” is the true Primate 
“ Sylvian fissure.” The morphological instability of the 
pseudosylvian furrow (which has also been abundantly 
demonstrated in the Carnivora, especially in the Viverride) 
is clearly exhibited by these two specimens. In one brain 
(D. 582) there is a deep, well-defined sulcus extending 
obliquely upward from the neighbourhood of the rhinal bend, 
like the pseudo-sylvian fissure of a Carnivore (fig. 208). 
In the other brain there is no such sulcus, its place being 
taken by a vertical sulcus (fig. 207,«) and several shallow 
depressions (8 and y). A further variation in the dispo- 
sition of these regions is shown by Oudeman’s specimen. 

There is a simple linear “lateral” (or ‘ intraparietal,” 
as it is called in the Primates). sulcus (fig. 206). 

The interpretation of the sulci in front of the supra- 
sylvian sulcus presents great difficulty. If we attempt to 
compare them with those of the Lemur’s brain, we find 
a most marked contrast between the two brains, such 
as we should hardly expect to find after noting the close 


similarity of the mesial surfaces of the cerebral hemi- = 


spheres. If, however, we compare the brain of Daubentonia 
with that of other Mammals (such as the Cat’s), there 
would be little hesitation in labelling the great transverse _ 
sulcus (fig. 208, £) in front of the lateral sulcus of one 


brain (D. 532) “coronal.” In the other specimen (D. 531) a 


the representative of this suleus is broken up into two 
fragments, the upper of which (£) is joined to the lateral 


NERVOUS SYSTEM.—VERTEBRATA, 865 


sulcus on the right hemisphere (figs. 206 and 207), whereas 
the lower remains entirely independent (fig. 207, e). 

Such an interpretation, however, is not wholly correct 
because the resemblance to the Carnivore condition is 
largely spurious: it is not the persistence in a Primate of 
the common mammalian plan of sulci, but a special com- 
bination produced by profound retrogressive changes oc- 
curring in a distinctly and characteristically-Primate brain. 
In most of the Lemuroidea the coronal sulcus of the 
Ungulates and of the more generalised members of other 
Orders (the conjoint proreo-coronal sulcus of the Rodentia, 
or the union of the separated coronal and prorean elements 
of the Carnivora, Edentata, and Marsupialia) persists in a 
practically unchanged form. In the series of retrogressive _ 
modifications which the primitive Prosimian brain must 
have undergone to produce the condition found in the 
Aye-aye, the region surrounding the coronal sulcus has 
suffered most change, and, as these four hemispheres 
abundantly show, exhibits the greatest amount of varia- 
bility. ‘The correct interpretation is a matter of extreme 
difficulty ; but a thorough study of the Prosimian brain 
leads me to the opinion that the coronal sulcus becomes 
broken up into two irregular fragments in Daubentonia : 
the anterior of these (7) usually joins the orbital sulcus, 
The posterior (¢) exhibits great irregularity in shape and 
in behaviour. It may join a furrow (%) which probably 
represents the crucial sulcus of other mammals, and the 
result is the furrow e+ ¢ which I believe to be identical 
with the sulcus centralis of the Primates. The furrows e 
and may remain separate and € may be linked to the 
lateral sulcus (fig. 207). [These views are put forward 
chiefly as the result of a study of the brain in the Indri- 
sine, which are the nearest relations of the Aye-aye. | 

Most of the other parts of the brain conform to the type 
presented by the great majority of mammals. But, in 
accordance with the relatively large dimensions of the 
cerebral hemispheres, the crura cerebri and pyramidal 
tracts are large and prominent, as in all the Primates. 
Moreover a definite olivary body is present. 


366 


- PHYSIOLOGICAL SERIES. 


The tuberculum acusticum and the trapezoid body are 


very large. 
The cerebellum conforms to the simple, common mam- 


malian type such as is presented by Tamanduas, for example. — Bs 
The details of this common fundamental plan have been 


demonstrated by a series of six diagrams in the case of 
Cabassous (figs. 79, 80, 82, 83, 84, and 85). The floccular ~ 
lobes are built-up on the:same plan in Daubentonia, but the — 
dorsal part of the paraflocculus (comp. fig. 83, PARAFLOC.D.) 


is much the largest part of the lobe. From the anterior _ 


part of the paraflocculus a prominent “ petrosal lobule” 
projects into a fossa in the petrous temporal. a 


In comparison with the simple cerebellum of Cabassous — 4 


there is a noteworthy expansion (fig. 206) of the region 
labelled “area B” in this Armadillo’s brain (figs. 82 and _ 
85). Such a development also occurs in the Anteaters, — 
Carnivores, and many other mammals. 


Considered as a whole, the brain of the Aye-aye exhibits — a 
a curious blending of many of the features of the Lemur’s 
brain and those of most non-Primate mammals, and more 


especially those of the Sloths, Anteaters, and Pangolins. 
Oudemans, Nat. Verh. Akad. Amsterdam, 1890, p. 26. 
Chudzinsky, Bull. Soc. d’Anthrop., t. vii. 1896, p. 12. 


Family Leuvrip2. 


D. 533. The brain of a Ruffed Lemur (Lemur varius), ( 2.) 


(figs. 210, 211, 212 & 213). 

The brain of the Lemurs is of great interest in that it 
exhibits features which undoubtedly indicate its genetic 
affinity to the brain of the Apes, and at the same time 
shows characters which allow an accurate comparison to be 
instituted with the organ of Daubentonia and of the lowlier 
mammalian Orders*. As in Daubentonia, the cerebellum 
is almost wholly uncovered in the adult. 


* By this I do not mean to imply that the Lemurs, or even Daubentonia, 
are primitive types (because there is much to suggest that they are to some 
extent reversionary); but they certainly permit accurate comparisons to be 
instituted with the lowlier mammals more readily than do the Anthropoidea, 


NERVOUS SYSTEM.—VERTEBRATA, 367 


The mesial surface of the brain exhibits features—corpus 
callosum, hippocampus, hippocampal fissure, the bifureated 
calcarine sulcus, and the separate intercalary suleus—the 
almost exact parallel of which is exhibited by the brain of 
the Aye-aye (compare figs. 212 and 209). 


Fig. 210. (Nat. size.) 


_OLF. BULB. 


SYL.F. 
; 


~ SULC. LAT. 


“™ SULC. PAR, 
aay: 


o/-~ SULC. P. LAT. 


Fig. 211. (Nat. size.) 


is: SULC. LAT (INT. PAR) 


FLOC. SULC. PAR. (P.SYiL) 


Upon the external aspect of the hemisphere there is an 
interesting modification of the primitive type represented 


by Daubentonia (in common with most mammals, such as 


the Carnivora, Ungulata, and the Sloths). In the latter the 
suprasylvian and postsylvian sulci are joined to form one 
arc, whereas in the Primates there is a complete separation 
of the postsylvian sulcus from the suprasylvian, and the 


oe ae 


368 PHYSIOLOGICAL SERIES, 


conversion of the latter into the Primate or true Sylvian 
fissure.. The separate postsylvian sulcus (see the left 
hemisphere of D. 531) is clearly the representative of the 
“parallel suleus” of Human Anatomy. And the supra- 
sylvian suleus, which has absorbed, or become merged in, 
certain inconstant kinks above the bend of the rhinal fissure 
which in the Carnivora and Ungulata would be called 
“Sylvian fissure,” now becomes the true “ Sylvian fissure.” 


Fig. 212. (Nat. size.) 


SULC. ee 


SULC CALC.-~ 


SULC.INF.OCC.” 


i sy 
HIP. TUBER. OLF. TUBER. 


Fig. 218. (Slightly enlarged.) — 


OLF. BULB. 


This process of blending of suprasylvian suleus and what — 
may be called the “‘ feline Sylvian fissure,” will be the better 
appreciated if the reader studies the varied analogous phe- 
nomena exhibited by Myrmecophaga (vide supra), Dolichotis _ 
(vide supra), and (in a different manner) the Seals (vide 
supra). In the case of the Lemurs the ventral parts of 
this Sylvian fissure may be absent so that it does not 
join the rhinal fissure and is practically the homologue of 
the suprasylvian sulcus, pure and simple (fig. 218). In other 


NERVOUS SYSTEM.—VERTEBRATA, 869 


cases the lower part of the Sylvian fissure is shallow, and at 

the point where the shallow part (“feline Sylvian ”) joins 
the deep part (suprasylvian) the lower extremity of the 
suprasylvian sulcus may be seen emerging so as to cut 
into the anterior lip of the fissure. [It is only right to 
inform the reader that these views are here put forward 
for the first time, and are in direct conflict with the usual 
teaching. | 

The lateral (intraparietal) sulcus forms an are around 
the Sylvian fissure, as it does in Daubentonia. Behind it 
there is a small postlateral or, as we now should probably 
call it, “transverse occipital ” sulcus. 

The crucial sulcus of the Carnivora is apparently repre- 
sented by a small pit on the dorsal surface (figs. 210 and 
211, y¥), which may perhaps be regarded as the first rudi- 
ment of the sulcus centralis (Rolandi) of the Primates *. 

The intrepretation of a well-marked sagittal sulcus on 
the dorso-lateral aspect of the front part of the hemisphere 
raises a question of great difficulty. For reasons which 
cannot be stated in full here (but which will be apparent 
if the reader refers to the brains of Procavia and Viverra), 
this furrow (SULC. RECT.) is almost certainly the coronal. 

On the other hand, it is regarded as the representative of 
the sulcus rectus of the Apes, which in turn is considered 
by Eberstaller and many others as the homologue of the 
sulcus frontalis medius, and by Cunningham as the sulcus 
frontalis inferior. If the tendencies which are to be noted 
in the evolution of the lowlier Primate brain continue to 
exercise their influence in the Anthropoidea (and in this 
matter they unquestionably do), there can be little doubt 
as to the accuracy of Cunningham’s interpretation T. 


* It is difficult to be otherwise than sceptical concerning the suggestion 
of this being sulcus centralis, although it occupies the position where we 
find the earliest rudiment of the central sulcus in the Cebide. The only 
other sulcus it can possibly be is the ramus postcentralis superior of the 
intraparietal sulcus. A careful study of the whole series of Primate brains, 
however, seems to point to the conclusion that the sulcus ¥ represents the 
upper part of the sulcus of Rolando. oe : 

+ The sulcus in question probably represents the conjoint sulci rectus 
(inferior frontal) and arcuatus (inferior precentral) of the Apes. 


VOL, Il. 2B 


870 


PHYSIOLOGICAL SERIES. 


In this particular brain the orbital sulcus appears to be 
almost, if not completely, aborted. 

The right cerebral hemisphere has been dissected so as 
to expose the hippocampus (major) as a vertical column. 
Behind and above its upper end is the obverse of the 
calcarine sulcus, ¢. e. the calear avis (so-called “ hippo- 
campus minor”). Nothing points the contrast between 
Lemurs and Apes so forcibly as a comparison of these struc- 
tures with those exposed in the brain of Hapale (D. 553). 
Figures 210 and 211 represent the condition of this speci- 
men before the dissection was made. 

There is no posterior horn of the ventricle in the Lemur, 
and the dissection shown in fig. 213 was effected only by 
separating from the surface of the eminence labelled 
“calcar ” a mass of adherent medullary matter. 

The features of most of the other parts of the brain 
resemble, like those of Daubentonia, the type which prevails 
in such forms as the Edentata, Rodentia, Insectivora, and 
Chiroptera. O. C. 1887 a. 

T. Ziehen, Arch. f. Psych., Bd. xxviii. 1896, p. 913. 


D. 534. The brain of a Black-faced Lemur (Lemur nigrifrons). 


In this brain the lateral and postlateral sulci are united 
to form the complete intraparietal suleus, The anterior 
extremity of this sulcus is almost (and in the left hemi- 
sphere quite) confluent with the sulcus rectus. 

The anterior rhinal fissure is faintly indicated, and ex- 
ternal to it there is a small representative of the orbital 
(presylvian) sulcus. A small sulcus makes its appearance 
between the orbital suleus and the Sylvian fissure in the 
brain of some Lemurs. It probably represents the fronto- 
orbital suleus of the Apes and the diagonal sulcus of other 
mammals, 

A comparison of the brains of a number of Lemurs shows 
a series of short sulci in the interval between the dorsal 
ends of the Sylvian (suprasylvian) and parallel (postsylvian) 


sulci. They may be joined to either of these sulci, and add 


further testimony to their original connection as a single 
suprasylvian arc, as in Daubentonia and most non-Primate 


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NERVOUS SYSTEM.—VERTEBRATA, 871 


mammals. [The specimens of Myrmecophaga are especially 
instructive in regard to this point.] 

The torm which the calcarine sulcus has assumed in this 
brain may raise some doubt whether the anterior limb of 
the calcarine sulcus should not be regarded as the strict 
homologue of the parieto-occipital suleus of the Anthro- 
poidea. It must be admitted that the length of the upper 
limb of the Y, its wide separation from the other post- 
calearine limb, and its relation (on the dorsal surface) to 
the intraparietal sulcus (especially on the right hemi- 
sphere), closely simulate the corresponding relations of 
the parieto-occipital sulcus in the Apes. Its wide separa- 
tion from the intercalary (calloso-marginal) sulcus serves 
to accentuate the likeness. 

When the cerebral hemisphere begins to extend into a 
caudal or occipital process, as it does in the Lemurs, and 
to a much more pronounced degree in the Anthropoidea, 
the calcarine sulcus assumes an increasingly oblique position 
and blends with certain postcalcarine elements (which occur 
in most mammalian Orders). These postcalcarine elements 
are morphologically very unstable and inconstant in their 
arrangement (compare the larger Carnivores and Ungulates, 
and also the Apes), and tend to adapt themselves solely to 
the mechanical conditions which prevail. Thus in the 
Carnivora they are generally parallel to the calcarine, 
because the tendency to caudal extension is restrained : in 
the Primates this is not so, and the sulcus runs in the long 
axis of the occipital diverticulum (compare Midas or 
Hapale). But in many forms (compare Manis and Dauben- 
tonia) a second element, simulating the parieto-occipital 
of higher forms, develops to relieve the tension of the 
growing cortex in that region, which is accommodated in 
most mammals by the fusion of the calcarine and inter- 
calary sulci. The condition found in Daubentonia makes it 
abundantly clear that this is so ; and we can have no hesi- 
tation in regarding the state of affairs in the Lemurs as 
essentially identical with that of the Aye-aye, however 
closely the former may simulate the condition sometimes 


found in the human brain. But just as we know that the 
2B2 


372 PHYSIOLOGICAL SERIES. 


occasional blending of parieto-occipital and calcarine sulci 
in the human brain is quite a secondary development, so also 
the series of Anthropoidean brains in this collection clearly — 
shows that the parieto-occipital sulcus makes its first ap- 
pearance in the Cebidee as a sulcus obviously compensatory 
to an already Y-shaped calcarine complex. Moreover there 
is no parallel anywhere in the Anthropoidea fora Y-shaped 
complex of calcarine and parieto-occipital sulci except 
occasionally in the human brain. If, however, it be urgeag 
that the Lemurs are reversionary forms, which are not — 
strictly comparable with the lowlier Apes, it remains to be 4 
explained how Daubentonia and Manis (the calcarine sulci — 
of which are essentially identical with those of the Lemurs) — 
came to assume the form they present *. 0. C. 133740, — 

W. H. Flower, Phil. Trans. vol. clii. 1862, p. 195. 


D. 535. The brain of a Black-faced Lemur (Lemur nigrifrons), — 
from which almost the whole of the right cerebral — 
hemisphere and a considerable part of the left have been 
removed. In the left hemisphere the whole of the ventri- — 
cular surface of the hippocampus [major] has been exposed, — 
and a purely artificial posterior cornu of the lateral ventricle 
has been made. ‘The latter and the calear avis lying in it 
are seen to be relatively smaller than the corresponding 
parts in many of the Cebide. ef 

The small oblique optic thalami and the typical corpora — 
quadrigemina are exposed. On the right side, the whole — 
extent of the large optic tract and prominent external 
(anterior) geniculate body are clearly demonstrated. . 

There is a large projecting mesial (posterior) geniculate — 
body and a very prominent tractus peduncolaris trans- — 
versus. “7 

The features of the typically simple cerebellum, which — 
resembles that of the Viverride and Sloths and many — 
other lowly mammals, stand out very distinctly. fj 

O. C. 1337 Ate 

Flower, Phil. Trans. vol. clii. 1862, p. 195. a 

* Further investigations (made since this was written) have convinced 
me that the apparent anterior limb of the Y-shaped calcarine group of sulei — 

represents the more ventral of the two elements of which the true cs 7 

parieto-occipital sulcus (vide infra) is composed. 


NERVOUS SYSTEM.—VERTEBRATA. 373, 


D. 536. The brain of a Ring-tailed Lemur (Lemur catta), in 
which the left hemisphere has been separated from the rest 
of the brain. 

The deficiency of the lower end of the Sylvian fissure is 
clearly shown. 

The composite character of the Sylvian fissure is well- 
demonstrated in the left hemisphere of this specimen. The 
lower extremity of the suprasylvian sulcus emerges from 
the Sylvian complex. 

The peculiar hook-like appendage of the upper extremity 
of the Sylvian fissure is also another reminder of the rela- 
tionship of the suprasylvian (Sylvian) sulcus to the post- 
sylvian (parallel), such as we have also seen elsewhere 
in Myrmecophaga (Edentata). O. C. 1837 a d. 


D. 537. The brain of a young Ring-tailed Lemur (Lemur catia). 
The left cerebral hemisphere has been separated. 

In this specimen there is no trace of a separate supra- 
sylvian element-in the Sylvian fissure such as the last 
specimen exhibited. The Sylvian is a straight, unbroken 
fissure passing below into a deep cleft-like vallecula Sylvii 
such as is found in the Apes. The upper extremity of the 
Sylvian fissure is not hook-like, but the short sulcus (which 
in the last specimen gave rise to the hook) is seen here in 
the interval between the upper ends of the parallel and 


Sylvian elements. QO. C. 1337 aa. 
Presented by J. Wiblin, Esq. 


D. 538. The brain of a Mongoose-Lemur (Lemur mongoz). 
Bristles have been inserted in the several cranial nerves. 
In this brain a small sulcus, such as that tentatively called 


“ fronto-orbital,”’ is present. 0. C. 9. 
Hunterian. 


D. 539. The brain of a White-faced Lemur (Lemur albifrons), 


with its left cerebral hemisphere separate. . va 

The parallel sulcus of the left hemisphere of this brain is 
interesting in comparison with those of the Ring-tailed 
Lemur, for its upper extremity is hooked forward, « e. 


374 PHYSIOLOGICAL SERIES. 


the intermediate sulcus, which is joined to the Sylvian in _ 
D. 536, is here joined to the parallel sulcus. 
O. C. 1337 A g. 


D. 540. Two casts of the cranial ae of a Lemur (Lemur 
macaco). 

This shows in an admirable mannér the exact shape and 
relations of the cerebral hemispheres, olfactory bulbs,and the 
cerebellum. We can also distinctly see deep grooves — 
produced by the Sylvian and posterior rhinal fissures, the — 
intraparietal, parallel, and coronal (“ rectus a sulci, and 
also the small sulcus tentatively called “central.” . 


D. 541. The brain of a Great Galago (Galago orassioaudate), of 
which the left hemisphere is separate. 
The rhinal and Sylvian fissures present the chara claciailt 
features. 4 
There is a typical intraparietal sulcus, but its postlateral — * 
(transverse occipital) elements are fragmentary and separate, 
The parallel sulcus is represented merely by a ‘short 4 
shallow furrow. J 
There is a typical orbital sulcus and a sulcus rectus vd , 
approaches near to the intraparietal, There is no signofa 
separate “central” sulcus, except a shallow depression — 
above the sulcus rectus. 0. C. 1337 Ba. 
F. E. Beddard, Proc. Zool. Soc. 1895, p. 146. ‘ 


542. The brain of a Garnett’s Galago (Galago garnetti) 
tet 214 and 215). Though only slightly smaller than the 


Fig. 214, (Nat. size.) : 
SULC. INTRAPAR. a 


other brain of a Galago, this specimen exhibits in comparison — i 
with the latter a pronounced paucity of sulci. It also 
serves to demonstrate how great a change has taken place 
in the occipital regions of the brain. When compared — . 


NERVOUS SYSTEM.—VERTEBRATA. 875 


with that of Daubentonia, which presents a blunt occipital 
pole, like that of a Dog’s brain, the contrast exhibited 
by Galago, in which the occipital pole approaches the 
condition found in the Marmosets, is very striking. 

There are typically complete rhinal and Sylvian fissures, 
a short rectilinear intraparietal sulcus, and a short orbital 
sulcus alongside the anterior rhinal fissure (fig. 214). In 
the place of the sulcus rectus and the parallel sulcus very 
faint depressions are found. 


Fig, 215. .(Nat. size.) 


SULC. INTERCAL. 


SULC. ROS. 


SULC. CALC. 


On the mesial surface the typical Lemurine calcarine 
and intercalary (calloso-marginal) sulci are found (fig. 215). 

There is a considerable depressed area in the lower part 
of the Sylvian fissure. It is chiefly covered by a temporal 
operculum, O. C. 13378 b. 

Th. Ziehen, Arch. f. Psych., Bd. xxviii. 1896, p. 910. 


D. 543. The brain of a Smith’s Dwarf-Lemur (Jcrocebus 
smithit), (2). 

In this diminutive brain the sulci are few in number. 
On the external surface, in addition to the Sylvian fissure, 
there is a small sulcus rectus on the right side and a shallow 
depression which may be the posterior rhinal fissure (in- 
cisura temporalis of Human Anatomy). 

There is a typical calcarine suleus with the usual 
Lemurine dorsal bifurcation. There is neither an inter- 
calary nor a genual sulcus. 

It is interesting to compare this brain with that of the 
peculiar little aberrant Prosimian Tarsius*, which possesses 


* There is no brain of Tarsius in this Collection. For the opportunity of 
examining several excellently-preserved specimens I am indebted to 
Dr. Charles Hose of Borneo. 


376 PHYSIOLOGICAL SERIES. 


only the Sylvian fissure and the calcarine group of furrows. 


This fact indicates the increased morphological stability of 


the Sylvian and calcarine sulci in the Family Lemuride. 


0. 0. 1387af. 
D. 544, A cast of the cranial cavity of an extinct sub-fossil 4 


Lemuroid ( Globilemur flacourti). 


The brain of this extinct Lemurid is much larger and its j ; 


hemispheres very much richer in sulci than that of any 
Lemur. 


Fig. 216." (x 3.) 


Fig. 217. (x3.) 


SULC. LL SULC CENT. ? 


Its “form approaches most to that of the smallest — 
members of the Family (Lemuride), viz. Microcebus, both — 7 
being broad in their posterior moiety and suddenly at- — 


tenuated anteriorly... . In the arrangement of its con- 


volutions the fossil departs from the Lemurid and approaches a 


the Cebidee and the Cercopithecide.” 


D 


NERVOUS SYSTEM.—VERTEBRATA. 377 


It is extremely difficult to accurately determine the 
pattern formed by the numerous sulci which indent the 
neopallium. But we can certainly say that, however we 
interpret such sulci as can be mapped out (figs. 216 and 
217), their arrangement differs considerably from that of 
the Lemurs and Apes. Jn the accompanying drawings, 
a tentative interpretation of the sulci is attempted. 


Dr. Forsyth Major, Proc. Roy. Soc. vol. lxii. 1898, p. 46. 


D. 545. A cast of the cranial cavity of an extinct Lemuroid 
(Megaladapis madagascariensis). 
The general appearance of this brain is not unlike that 


Fig. 218. (x 3.) 
Y) 


_~SULC. RECT. 


» _.SULC. INT. 
_eSYL Fi 
s~ SULC. CENT, 


“~“SULC. PAR. 


Fig. 219. (x3.) 


SULC, CENT. SULC. INT. 


SULC. RECT. 


SULC.PAR. SYL.F. 


of Daubentonia, but the olfactory bulbs appear to be borne 
‘ on long stalks, a part only of which is represented in this 
cast as a prominent rostrum. 


378 


PHYSIOLOGICAL SERIES, 


As Dr. Forsyth Major has clearly and decisively demon- 
strated; the optic nerves enter the cranium in a situation 
extraordinarily far forward. The pattern formed by the 
cerebral sulci, however, closely follows that of the other 
Lemuridee. 

These peculiar modifications are the result of retrogres- 
sive changes which occur partly in the ontogeny of every 
individual, as a result of which the brain becomes actually 
smaller in the adult than it is in the young animal. 

Forsyth Major, Proc. Roy. Soe. vol. lxii. 1898, p. 47. 


D. 546. The brain of a Slender Loris (Loris gracilis). 


This brain resembles that of the Lemur. 

The rhinal fissure is distinct in front, but rapidly becomes 
indistinct on the caudal side of the vallecula Sylvii. 

The usual Lemurine forms of the Sylvian fissure, the 
intraparietal and the parallel sulci are present. The in- 
teresting relationship between the upper extremities of the 
Sylvian fissure and the parallel sulcus, noted in the Lemurs 
proper, is also found here. 

The mesial surface shows the typical Lemurine features. 

Ziehen, Arch. f. Psych., Bd. xxviii. 1896, p. 908. 

O.C, 1337 4h. 


D. 547. The brain of a Potto (Perodicticus potto) (fig. 220). 


[Although this brain is presumably that described by 
Ziehen (op. cit. 1896, p. 901), the fig. 3 of his memoir can 


Fig. 220, (Nat. size.) 


SULC. 1% 


hardly be regarded as an accurate representation of this 
specimen. ] 

The excellent preservation of the olfactory bulb and its 
cerebral appendages enables us to appreciate the large [for 
a Primate] size of these olfactory regions of the brain, and 


NERVOUS SYSTEM.—VERTEBRATA. 379 


how closely they resemble the corresponding regions in 
other mammalian Orders. 

The rhinal fissure is very distinct and can be seen cross- 
ing the vallecula Sylvii to become the posterior rhinal. 
The latter soon ends near the parallel sulcus, with the 
lower end of which it appears to become continuous. The 
Sylvian fissure and the intraparietal sulcus are like those 
of the Lemur. The upper extremity of the parallel sulcus 
curves forward so as almost to join the upper end of the 
Sylvian fissure, as sometimes occurs in the Lemur. 

There is a short arcuate sulcus rectus and, between it 
and the Sylvian fissure, a sulcus (x) closely resembling the 
central sulcus of the Anthropoidea. There is no conclusive 
evidence to enable us to determine the homology of this 


- sulcus, which often makes its appearance in the Lemurs, in 


Propithecus (occasionally), and in Daubentonia*. There is 
a well-marked orbital sulcus. The lower extremity of the 
fascia dentata is distinctly seen on the base of the brain 


on each side of the tuber cinereum; and the projections 


of the posterior part of the pyriform lobe which Gustav 
Retzius calls gyrus lunaris and gyrus ambiens are very 
prominent. The structure which Retzius calls “gyrus 
lunaris”? is not a cortical formation, but is merely the 
surface of the nucleus amygdale and ought to be so called. 

| O. C. 1837 B. 


D. 548. The brain of a Javan Slow-Loris (Nycticebus tardigradus) 


fio, 221). 
(fig ) Fig. 221. (Nat. size.) 


SULC. INT. 
a. i SULC. TR. OCC. 


SULC. RECT. 


~SULC. PAR. 


SULC.ORB. 


The brain of Nycticebus is, for a Lemur, unusually rich 
in sulci, the arrangement of which is peculiar in several 
respects, and is not symmetrical on the two sides. 


* Since the above was written I have become conyinced that the furrow x 
can be no other than the true sulcus centralis, 


380 


PHYSIOLOGICAL SERIES, 


There is a clearly defined rhinal fissure from the bend of 
which the Sylvian fissure ascends obliquely. The Sylvian 
fissure is concurrent with the intraparietal, as in the brain 
of Chrysothriz. This “ suprasylvio-lateral” fusion is of 
interest as a further extension of that process which results 
in the formation of the Sylvian fissure of the Primates by 
a blending of the suprasylvian and the inconstant supra- 
rhinal kinks (pseudosylvian fissure). 

There is an extensive parallel suleus behind the Sylvio- 


intraparietal complex, and fragments representinganinferior __ 


temporal sulcus behind and below the parallel. 

In front of the Sylvian fissure we find the following 
sulci in order from below upward :—the almost sagittally 
directed orbital close to the olfactory peduncle, a triradiate 
sulcus rectus, and then another sagittal suleus (of very 
doubtful homology) nearer the mesial plane (fig. 221, a). It 
often happens, however, in the Apes that when the Sylvian 
and intraparietal elements fuse, an accessory intra-parietal 
sulcus makes its appearance in a position analogous to that 
occupied by this sulcus. 

On the left hemisphere the posterior part of the intra- 
parietal sulcus is separated from the rest. ‘The parallel 
sulcus is not bifurcated as it is on the right side. 

On the mesial surface the two limbs of the calcarine 
are so large as to simulate the parieto-occipital and post- 
calcarine (posterior calearine) sulci of the Anthropoidea, 
There is a short intercalary sulcus and also a small and 
faintly marked rostral sulcus. 

There is a deep notch on the ventro-caudal margin of the 
hemisphere (not only in this brain but in most Lemurid 
brains), for the true interpretation of which we must 
examine a series of Ape-brains, It will then be found to 
represent a compensatory sulcus, the place of which is 
taken in a higher phase of development by the collateral 
and inferior occipital sulci, to which in the highest Apes 
we may add the occipito-temporal. It cannot, however, 
be strictly said to represent any one of these three sulci 
exclusively. O. C. 1387 Be. 

Th. Ziehen, Arch. f. Psych., Bd. xxviii. 1896, p. 905. 


he 


NERVOUS SYSTEM.—VERTEBRATA. 881 


Suborder AnrHROPoIDEA. 


Family Haparip«. 


D. 549. The brain of a Pinche Monkey or Tamarin (Midas 
edipus), (3), (fig. 222). 

With this specimen we enter on the account of the brain 
in that higher division of the Primates known as the Sub- 
order Anthropoidea*, Although the brain may be smaller 
than that of many Lemurs, its proportions are different, 
masmuch as the occipital parts of the cerebral hemispheres 
overlap the cerebellum to a distinctly greater extent than 
is the case in the brains of the Lemuroidea. This character 
reaches its greatest degree in a member of the Family 
Cebidee, viz., in Chrysothrix, in which it is developed to an 
extent unsurpassed even in Man. 


Fig. 222, (Nat. size.) 


CALCAR. 


_ This small brain is characterized by a remarkable poverty 
of sulci, even when allowance is made for the absolutely 
small dimensions of the cerebral hemisphere, as will be 
better understood when this brain is compared with those 
of Nyzticebus tardigradus and Loris gracilis, which it 
resembles in size. The Sylvian fissure commences below 
in a Sylvian vallecula which is so fissure-like that the dis- 
tinction between vallecula and fissure would be unjustifiable, 
but for the fact that the limits of the two are marked by 
the postsylvian part of the rhinal fissure. The latter is 


* The separation of the Lemuroidea from the other Primates as a separate 
suborder is certainly not justified by the evidence of cerebral anatomy, as 
there is a very close affinity between the brain-type of the Lemurs and the 


Cebidee. 


382 


PHYSIOLOGICAL SERIES. 


visible crossing the lower part of the temporal lobe very 
much fs it does in Lemuroidea. (The posterior rhinal — 
fissure, however, is placed relatively much nearer the mesial 
surface than it is in the Lemurs.) 

The Sylvian fissure runs up and backwards across the 


hemisphere, pursuing a much more oblique course than in 


the Lemuroidea. In this brain there appears to be abso- 
lutely no sulcus in the position of the intraparietal of the 
Lemuroidea (note, however, the difference from Hapale 
penicillata in this respect) ; but a very faintly-marked 


depression is seen about the spot at which the intraparietal — 3 


sulcus might be expected to give off its terminal offshoot 
posteriorly. The only other sulci on this surface are a 
short but distinct parallel suleus and an indistinct orbital. 

The hippocampal fissure presents those features which 
are common to all placental mammals. The calcarine 
sulcus is prolonged far back into the elongated occipital 
pole as a simple linear furrow without any trace of bifur- 
cation. 

The olfactory parts of the brain exhibit a most pronounced 
diminution in size when compared with the corresponding 
regions in the Lemurs and other mammals. 

There is a noteworthy reduction in the size of the floccular 
lobes, and the cerebellum itself, although still simple, exhibits 
a greater lateral expansion. O. C. 1387 ¢. 

For a general survey of the literature relating to the 
brain in the Anthropoidea, see Kiikenthal and Ziehen 
(Jenaische Zeitsch. f. Naturwiss., Bd. xxix. 1895, p. 1). 


D. 550. The brainof a Black-eared Marmoset (//apale penicillata). 


The description of the preceding specimen applies in 
almost every detail to this. A short intraparietal sulcus, 
however, is visible in the right hemisphere ; the Sylvian 
fissure turns slightly backwards at its upper end; on the 
orbital surface there is merely a depression and no orbital 
sulcus, and on the mesial aspect there is a short calloso- 
marginal (intercalary) sulcus. The olfactory bulbs and 
peduncles are preserved in this specimen. The anterior 
part of the pyriform lobe is slender, and the anterior rhinal 


\" 


NERVOUS SYSTEM.—VERTEBRATA. 383 


fissure by which it is bounded becomes much fainter as the 
Sylvian vallecula is approached. O. C. 1337 ca. 
Presented by C. E. Flower, Esq. 


D. 551. The brainof a Black-eared Marmoset ( Hapale penicillata). 
The left hemisphere has been separated. 

This is a more carefully-preserved specimen than any of 
the others, and not only are all parts of the brain preserved 
intact, but they all retain their natural shapes. 

Thus the true proportions of the small ellipsoidal olfactory 
bulb and its exceedingly delicate ribbon-like peduncle can 
be appreciated. The (external) olfactory tract is very 
distinct (as, in fact, is the case in all Anthropoidea), pursuing 
its backward course in the olfactory peduncle, then skirting 

_ the lateral edge of the tuberculum olfactorium (which is 
still recognisable as such, in spite of its diminutive pro- 
portions), and finally disappearing in the vallecula Sylvii to 
reach the posterior part of the pyriform lobe. The rhinal 
fissure indicates the lateral boundary of the latter. 

It is a peculiarity of all the Anthropoidea that these 
olfactory areas of the brain are greatly reduced in com- 
parison with those of other Mammals. For in Man and 
Monkeys the sense of smell loses the predominant réle which 
it exercises in most other (non-aquatic) Mammals. The 
Sylvian fissure, the simple orbital, parallel, calcarine, and 
the faint trace of the calloso-marginal sulci need only be 
mentioned. There is, however, an oblique sulcus on the 
ventral surface, which probably represents the collateral 
sulcus. 

The features of the corpus callosum, the diminutive 
psalterium, the anterior commissure, the lamina terminalis, 
the optic chiasma, and the cerebellum are beautifully 
demonstrated in this specimen. 


D. 552. The brain of a Common Marmoset (Hapale jacchus). 
The intraparietal sulcus is absent (or possibly represented 
by an. almost imperceptible depression in the left hemi- 
sphere) ; the parallel sulcus is very faint ; and on the mesial 
aspect there is a sulcus in a corresponding position to that 


384 PHYSIOLOGICAL SERIES. 


tentatively called inferior occipital or collateral in the 
Lemurs. There is also a depression in a position that 
might be occupied by the extreme hinder end of the 
calloso-marginal sulcus. O. C. 1337 6 b. 


D. 553. The brain of a Marmoset (Hapale jacchus) (fig. 223). 
A dissection has been made in the left cerebral hemi- 
sphere to open up the descending and posterior cornua of 
the lateral ventricle. 


Fig. 228. 


In the descending cornu the diminutive hippocampus is 
exposed. The posterior cornu is very extensive and is 
occupied by a relatively enormous swelling—calcar avis— 
‘of the mesial wall, which is produced by its indentation by 
the calcarine sulcus. Even if it were not inappropriate 
and confusing for other reasons, the term “ hippocampus 
minor ” would be singularly inapt if it were applied to the 
enormous broad expanse of the indented ventricular wall, 
which is much better called “ calear.” 

Although a posterior cornu of the lateral ventricle is 
occasionally found in other Orders, such as the Cetacea, 
Ungulata (e. g. in the Camel), and Carnivora (e. g. in certain 
Seals), it is only in the Primates, and more especially in 
the Suborder Anthropoidea, that it assumes the extensive 
proportions exhibited in this specimen. 

W. H. Flower, Phil. ‘Trans. vol. clii. 1862, p. 185. 


NERVOUS SYSTEM.—VERTEBRATA. 885 


Family Czeimz. 


D. 554. The brain of a Squirrel-Monkey (Chrysothrix sciurea), 
(3); in which the left hemisphere has been separated 
(figs. 224, 225, 226). 


Fig. 224. (Nat. size.) 
,SULC. RECT, 


_ SULC. CENT. ? 


Fig. 225. (Nat, size.) 
— . SULC. INT, SYL F. 


’ 
a 


SULG. RECT. 


SULC. PAR. 


Fig. 226. (Nat. size.) 


SULC.INTRAPAR. yx SULC.INTERCAL. 
. f i 


SULC.PAR.OCC. | 


SULC.R CAL 


SULC.CAL. SULC. COLL. 

In this brain perhaps the most striking feature is the 

very pronounced manner in which the caudal extension 
VOL. Il. 20 


a 


386 


PHYSIOLOGICAL SERIES, 


of the cerebral hemisphere has taken place so as to com- 
pletely cover the flattened cerebellum. The extent of this 
backward growth is most strikingly shown upon the mesial 
surface (fig. 226): almost half of the hemisphere lies behind 
the situation of the splenium of the corpus callosum (figs. 
224 & 225). 

Upon the cranial surface the Sylvian fissure will be 
seen to have fused with the intraparietal sulcus, as in 
Nycticebus ; and the sulcus has even become prolonged 
on to the mesial surface (fig. 226) where it runs parallel 
and in close proximity to anew suleus—the parieto-occipital 
of Human Anatomy. So close are these two sulci that they 
appear to become concurrent, but if the lips of the common 
cleft be separated the condition represented in fig. 226 is 
found *. An elongated parallel sulcus is present. In front 
of the Sylvio-intraparietal complex there is a short trans- 
verse sulcus on the dorsal surface (fig. 224), which may be 
the earliest Primate form of the central (Rolando’s) ‘sulcus. 
On the other hand, it may represent part of the intraparietal 
sulcus which has not joined the Sylvian fissure. 

As a result of the pronounced caudal elongation of the 
hemisphere the calcarine sulcus becomes almost horizontal: 
it ends posteriorly by joining a great vertically transverse 
sulcus t+, which must be regarded as analogous to the retro- 
calearine sulcus of other mammalian Orders. As a result 
of the altered mechanical conditions, a series of new com- 
pensatory-calcarine sulci make their appearance. By 
reason of its altered direction, the calcarine sulcus is not 
extended downward to the neighbourhood of the rhinal 
fissure, as in most mammals, and a ventral compensatory 
suleus—the “collateral” of Human Anatomy—develops 
to make good this defect. It appears in this case to join 
the calcarine, but is in reality separated from it by a sub- 


merged gyrus (fig. 226). A vertical compensatory sulcus — 


makes its appearance on the dorsal side of the calcarine and 


* In reality the parieto-occipital sulcus represents the fusion of two 
separate sulci. In this case the dorsal of these two fundamental elements is 
concurrent with the intraparietal sulci. 

+ Perhaps it would be more correct to say that it joins the stem of a 
T-shaped postcalcarine sulcus. 


NERVOUS SYSTEM.—VERTEBRATA., 387 


becomes the “ parieto-occipital” sulcus. It is quite inde- 
pendent of the calcarine, but parallel to its forked caudal 
branches. In this brain the parieto-occipital appears to 
join the intraparietal sulcus, but in reality the two sulci are 
separated by a submerged gyrus (fig. 226). 

The interealary sulcus is here independent of all other 
sulci, and it is significant that its posterior extremity is 
turned upward. This tendency becomes much more pro- 
nounced in the higher Anthropoidea. 

In the situation corresponding to that in which the cal- 
carine-intercalary union takes place in the Carnivora and 
Ungulata there is a small triradiate sulcus (x), which in 
Human Anatomy is still often called by Broca’s name 
“postlimbic,” in spite of the fact that the hypothesis of a 
limbie lobe, which is implied in this name, is not now 
seriously entertained. We might more aptly call it the 
“compensatory ” sulcus, in reference to its obvious rdéle. 
It will be seen to be a very constant element throughout 
the Anthropoidea. 

There is a small transverse occipital sulcus on the left 
hemisphere. And far forward on the apex ofthe hemisphere 
there is a short sagittally-directed sulcus, which may repre- 
sent an early phase of the sulcus rectus. 

The posterior rhinal fissure occupies a position on the 
ventral and not on the strictly lateral aspect of the hemi- 
sphere, whereas in the Lemurs the rhinal fissure occupies 
the lateral aspect of the cerebral hemisphere. (C/. also 
with regard to this point, the cerebral hemisphere in Wycti- 
pithecus trivirgatus or Aotus felinus.) 

If the lips of the Sylvian fissure be separated, a small 
insula is exposed, chiefly under the larger fronto-parietal 
operculum. Its surface is smooth. 0. C. 1337 Da. 


D. 555. A cast of the cranial cavity of the Common Squirrel- 
Monkey (Chrysothrix sciurea). 


D.556. The brain of a Black-fronted Squirrel-Monkey (Callithriz 
nigrifrons), (¢)- The left hemisphere has been separated 


fios. 227 & 228). 
(fig 28) ie 


388 - PHYSIOLOGICAL SERIES. 


The sulci of this brain are much simpler than those of 
Chrysothrix, and the cerebral hemispheres as a whole present 
a striking resemblance to those of the Lemurs in all points 
except the difference in shape resulting from the occipital 
prolongation *. 

The Sylvian and intraparietal elements are here separate. 
The upper end of the parallel sulcus approaches the Sylvian 
fissure, as in many Lemurs. 

There are typical sulci rectus and orbitalis. 


Fig. 227, (Nat. size,) 
SUL[.. INTRAPAR. “ae PAR. 


Fig. 228. (Nat. size.) 


SULC. CALL. MARG. 
SULC. PAR.OCC. § 


SULC. CAL. 


On the mesial surface the calcarine sulcus is concurrent, 
as in most Primates, with the retrocalcarine sulcus and the 
latter is markedly bifid at its posterior extremity. There is 
no parieto-occipital sulcus on the left hemisphere ; but on 
the right there is a shallow groove in the position where 


this sulcus may make its appearance, There is a well- a 


* This likeness becomes all the more significant when it is recalled that 
in some of the Prosimiw the restriction of the caudal pole is a secondary 
modification which occurs during ontogeny, Thus, among a number of. 
skulls kindly lent me by Dr. Forsyth Major was one of a Propithecus 
coronatus 15 days old, from which it was evident that the cerebral hemi- 
spheres must have almost wholly covered the cerebellum, 


NERVOUS SYSTEM.—VERTEBRATA. 889 


marked oblique sulcus crossing the inferior margin of the 
hemisphere in the situation where a great inferior operculum 
is found in many Cercopithecide. Kiikenthal and Ziehen 
call it “inferior occipital.’ But the presence of such a 
sulcus in this brain clearly does away with the necessity for 
a collateral sulcus. QO. C. 1387 De. 


D. 557. The brain of a Masked Titi (Callithriz brunnea), (3). 
This specimen closely resembles the last described. If 

the lips of the Sylvian fissure be divaricated in either of 
these brains a small, smooth, submerged area or insula will 
be found. The anterior (fronto-parietal) is much more 
extensive than the posterior (temporal) operculum. 

d There is a short but definite central sulcus on the right 

hemisphere. 

The manner in which the upper end of the parallel suleus 
approaches the Sylvian fissure (especially in the right hemi- 
. sphere) is very instructive, when we recall that in most 
; 


non-Primate brains the representatives of these two sulci 
4 are united to form a suprasylvian arc. 
: The calcarine complex is unbranched, as in Hapale. 
3 O. C. 1337 pb. 
D. 558. The brain of an Orabassu Titi (Callithria moloch). 
This closely resembles the last speciinen. There is, how- 

ever, no central sulcus. The simple calcarine sulcus is 

clearly shown. 


D. 559. The brain of a Three-banded Dourocoli (Vyctipithecus 
trivirgatus), (2). 

The right cerebral hemisphere has been separated from 
the remainder of the encephalon. The left cerebral hemi- 
sphere has been dissected so as to exhibit the principal 
structures in the lateral ventricle ; the descending and the 
posterior cornua of the ventricle have been laid open, ex- 
posing, in the former, the hippocampus major and the 
fimbria and, in the latter which is prolonged into the 
overhanging occipital lobe, a large calcar avis. 

The arrangement of the sulci resembles that in Chrysothria 
sciurea, and, less closely, that in Lemur. The pyriform 
lobe is rather broader than in Chrysothriz, and the posterior 
rhinal fissure is placed very low down on the lateral 


390 ' PHYSIOLOGICAL SERIES. 


conyexity of the hemisphere. The principal sulcus on the _ 
iateral convexity is a combination of the Sylvian fissure 
with the intraparietal sulcus. (To this compound sulcus — 
greater apparent length is given by the appearance of the _ 
Sylvian vallecula, which is a deep groove and thus differs 
decidedly from the shallow form of vallecula met with in 
Lemur-brains. Unlike the long furrow of the brain of 
Chrysothriz, it does not attain the mesial aspect.) , 

Anteriorly to this compound fissure the following sulci 
are found on the frontal part of the hemisphere, viz.: a 
small depression in a situation similar to that occupied in— 
other Primate brains by the central sulcus, of which the 
depression is probably a rudiment: near the frontal extremity ; 
of the hemisphere is a sagitally-running shallow groove — 
which probably represents the sulcus rectus (inferior — 
frontal) of higher forms ; it is, however, interesting to note 
that it is a little more mesially placed than is usually the — 
case with the s. rectus*: on the orbital surface of the 
frontal lobe is a single, sagittally-directed, distinct orbital — 
sulcus ; and on the same surface, under the posterior eg 
of the olfactory peduncle, is a shallow sulcus olfactorius. — 
Behind the combined Sylvian and intraparietal fissures is a | 
distinct parallel sulcus ; above and behind this are one or 
two indistinct depressions, but none can justifiably be | 
described as genuine sulci (compare fig. 229). 4 

The calcarine sulcus is ¥-shaped rather than T-shaped, — 
the two posterior limbs meeting at an angle of about 60°, 7 
instead of being in the same straight line. The stem 
of this Y-shaped sulcus almost reaches the hippocampal 
fissure. Below the calcarine is a curved collateral sulcus. — 
There is another sulcus behind this; it is placed almost 
coronally, though it does not run into the calcarine. 
This somewhat unusual sulcus occurs in both hemispheres 
of this specimen of JV, trivirgatus, but in neither of i a 
hemispheres of the other specimen of LV, trivirgatus (D. 560) 
and in none of the six hemispheres of Aotus felinus which ; 
were available for examination. a 


* In other words, the sulcus rectus occupies a progressively — 
in the hemisphere in the evolution of the Ape-brain ; so that it seems to be 4 
placed exceptionally high up in those forms where it first appears. A 


NERVOUS SYSTEM.—VERTEBRATA. 391 


Above the calcarine there is in this specimen no trace of 
a parieto-occipital sulcus ; further downwards, however, 
there is a short and obliquely-placed illaee-tabeginns 
sulcus. ; O. C. 1337 z. 


D. 560. The brain of a Three-banded Dourocoli (Nyctipithecus tri- 
virgatus). The left cerebral hemisphere has been separated. 

In spite of its damaged condition this specimen has been 
retained because it exhibits in an especially clear manner a 
rhinencephalon with the typical features such as we find in 
mammals other than Primates and which are not usually 
so clearly demonstrable in the Anthropoidea. 

Note the absence of central sulci. The sulcus rectus is 
also very poorly developed. 

The dorsal limb of bifurcation of the calcarine is so 
diminutive that at a casual glance the sulcus resembles the 
unbranched condition found in the Marmosets. 


D. 561. The brain of a Lemurine Dourocoii (Aotus Jelinus). 
The left hemisphere has been detached. 
This brain resembles the preceding specimen. Note, how- 
ever, that the calcarine complex presents the usual Y-shape. 
O. C. 1337 Ea. 
D. 562. The brain of a Lemurine Dourocoli (Aotus felinus). 
The left hemisphere has been separated. 
This brain resembles the two previous specimens. There 
- is, however, a small central sulcus and a very faint rudiment 
% of a parieto-occipital sulcus. 0. C. 1337 Bd. 


-. 563. The brain of a Lemurine Dourocoli ( Aotus felinus), (¢). 
The left hemisphere has been detached (fig. 229). 


Fig. 229. (Nat. size.) 


a 


a 


SULC. INTRAPAR. 


=" SuLt. FAR 


This specimen resembles the preceding. QO. C. 1337 Ee. 


392 _ PHYSIOLOGICAL SERIES. | 


D. 564. The brain of a Hairy Saki (Pithecia monachus), (¢) 
(figs. 280 & 231). 

The right hemisphere has been detached and dissected so 
as to show the general relations of the descending horn of 
the lateral ventricle. The posterior cornu is clearly visible. 

Although the general plan is the same, there is a much 
richer supply of sulci than in any of the Primate brains 
hitherto described in this Catalogue. The sulcus rectus is 
deeper and has become bent. There is a deep, well-defined 
central sulcus. The intraparietal sulcus ends posteriorly i in 


‘ 


Fig. 230. (xX 3). 
SULC. CENT. 


SULC. REC! SULC. INTRAPAR. 


"- SULC. TR. OCC. 
“ 
SULC. INF. OCC. 


OLF BULB. 
SULC. PAR. 


Fig. 231. (x 3) 


SULC, CALL. MARG. 
SULC. PAR. OCC. f 
‘ 


SULC.COMP, 


SULC.COLL. 


a bifid extremity—the transverse occipital sulcus. There is 
a short but deep parieto-occipital sulcus, and a welldetined, 
calloso-marginal sulcus. The Sylvian fissure is quite 
independent of the intraparietal sulcus, There is on the — 
tentorial surface a deep sulcus, which must be regarded as 
the collateral. 

In the right hemisphere the hippocampus lying in eed 4 
descending cornu and the calcar in the large roomy posi q 
cornu are exposed. The disproportion between the sizes of — 
these two bodies is not so marked as it is in Hapale, 


NERVOUS SYSTEM.—VERTEBRATA. 393 


; The cerebellum is very instructive. Its floccular lobe 

still retains the form exhibited by most mammals. It 

: possesses a large projecting petrosal lobule of the parafloc- 

culus. But these lobes appear to be very small because 

‘ the rest of the cerebellum has attained such great 

i dimensions. O. C. 1337 F. 
Flower, Proc. Zool. Soc. 1862, p. 328. 


: D. 565. The brain of a Hairy Saki (Pithecia monachus). The left 
: hemisphere has been detached. 
The parieto-occipital sulcus extends further on to the 


dorsal aspect and produces a corresponding bend in the 
ramus occipitalis of the intraparietal sulcus. There is an 
extensive sulcus behind and parallel to the transverse occi- 
pital. It may represent the earliest phase of the Simian 
sulcus—the “ Affenspalte ” of German writers. 

Below this there is a small sulcus parallel to the tentorial 
margin, which may represent the inferior occipital sulcus 


of euie Apes. O. C. 1337 Fd. 


4 D. 566. The brain of a Black Saki (Pithecia satanas). The left 
} hemisphere has been detached. 

| This brain is much richer in sulci. The Sylvian fissure 
is crossed obliquely at its upper end by the terminal portion 


F . of the elongated parallel sulcus, with which (on the left 
: _ side) it is superficially continuous, though deeply it is found 
2 that the two are separated bya submerged gyrus. The 
intraparietal sulcus is acutely bent around the apex of the 
parallel sulcus ; and from the angle of the former a deep 
furrow extends on to the mesial surface. The upper end of 
the parieto-occipital sulcus becomes swept, as it were, into 
this intraparietal cleft, so that at a superficial glance the 
two sulci appear to be concurrent. ‘This furrow, which is 
constituted by two separate elements, represents the parieto- 
occipital sulcus of the highest Anthropoids. It consists of 
a ventral element, which is clearly compensatory to the 
calcariné, and a dorsal element (the “ intraparietal cleft” 
of this paragraph). 

There is an extensive Simian sulcus. Itruns rather more 
than halfway across the hemisphere, and gives off a short 


394 


PHYSIOLOGICAL SERIES. 


branch which is directed forwards. The antero-superior 
extremity of a definite inferior occipital sulcus approaches 
very close to the lower end of the Simian sulcus. This 
leaves a comparatively large occipital area free from any- 
thing more than faint depressions, and in the possession of 
this character, these brains of Pithecia and those of Brachy- 
urus form a strong contrast to that of Lagothria. 
Anteriorly to the Sylvian and intraparietal fissures there 
is a well-developed central suleus and immediately in 
front of this another sulcus, shorter than, but having the 


same general direction as, the central sulcus itself. The 


sulcus rectus is tri-radiate (on the left hemisphere). On 
the orbital surface is an H-shaped orbital sulcus. 

The calloso-marginal suleus (prolonged forwards into a 
genual) , the internal parieto-occipital, the T-shaped calcarine 
(with a single long collateral suleus running superficially 
into it), and the hippocampal fissures occupy their usual 
positions (for which see, inter alia, especially accounts of 
Alonatta.and Lagothriz). O. C. 1337 Fa. 


D. 567. The brain of a White-nosed Saki (Pithecia albinasia). 


The right hemisphere has been detached. 

Its general appearance is remarkably similar to D. 566, 
but the Sylvian fissure does not quite reach the parallel 
suleus even superficially. In the left hemisphere of this 
specimen, D. 567, as in the left hemisphere of D. 566, 
the connection between the two sulci is closer than that 
obtaining in the corresponding right hemispheres. Near 
the temporal pole there is a short, well-marked inferior 
temporal sulcus. 

The sulcus seen in front of the central fissure in D.566, 
and named pre-central, is here represented by two short 
sulci, an upper and a lower on the left side. Further forward 
there is a short oblique sulcus above the sulcus rectus, 

Note the peculiar shape and direction of the orbital sulci. 

O. O. 1337 Fe. 


D. 568. The brain of a Red Uakari (Brachyurus rubicundus), (2). 


The left hemisphere has been detached. O. C. 1337 Fe. 


NERVOUS SYSTEM.—VERTEBRATA. 395 


D. 569. The brain of a Red Uakari (Brachyurus rubicundus). 

Both cerebral hemispheres have been detached. 

This brain clearly resembles that of Pithecia satanas 
(D. 566). 

The Sylvian fissure (superficially) joins the parallel sulcus 
on both sides. 

The peculiar relation of intraparietal and parieto-occipital 
sulci found in Pithecia also occurs here. 

The Simian sulcus is more rudimentary, whereas the 
inferior occipital is deeper and its upper lip tends to become 


opercular. 
The sulcus rectus is plain. The orbital sulcus is H- 
shaped. O. C. 1337 Fb. 


D. 570. Cast of the cranial cavity of Brachyurus calvus. 


D. 571. The right cerebral hemisphere of a Red Howler (Alo- 
| natta senicula), (3) (figs. 232 & 233). 


Fig. 282, (x 3.) 


SULC. CENT. ? 


SULC. INTRAPAR. SULC, RECT. 


SULC. PAR. 


Fig. 288. (x 3). 


SULS. CALL.MARG. 
‘ SULC. PAR.OCC. 
“0 


“ SULC. CALC. 


we “suuc. COLL. 
RHIN.F.“ 


This presents some resemblance to the brain of Nycti- 


-pithecus. 


396 


PHYSIOLOGICAL SERIES. 


The Sylvian fissure and the intraparietal sulcus are con- 
current, There is a simple parallel sulcus, which does not 
approach the Sylvian fissure. Between the short central 
sulcus and the intraparietal element of the complex there is 
a short compensatory intraparietal sulcus. There is no 
Simian sulcus, but there are two small sulci representing 
the inferior occipital sulcus. There is a very deep sulcus 
rectus and an H-shaped orbital sulcus. There is a deep, 
straight, unbranched calcarine sulcus. The essentially 
calcarine-compensatory nature of the parieto-occipital suleus 
is shown by the fact that as the result of the peculiarity of 
the calcarine sulcus, the parieto-occipital is represented 
chiefly by a sulcus parallel'to the almost horizontal calearine, 
which is merely analogous to, and cannot be homologous 
with, it. A slight notch in the upper margin of the hemi- 
sphere shows the usual situation of the parieto-occipital 
sulcus and represents the more dorsal of the two elements 
which go to form the parieto-occipital sulcus in Man (vide 
infra). There is a short, plain, collateral sulcus and a calloso- 
marginal which has no genual element. O. C. 1887 Ga. 


D.572. The brain of a Red Howler (Alonatta senicula), ( ¢) 


(fig. 234). ; 
Fig. 234. (x 3) 
OLF. BULB. 


SULC. ORB. ° 
~ 


“es, 


‘This well-preserved specimen is perfect in all parts except 
the olfactory bulbs, which are missing. 

External to the orbital sulcus (which is triradiate on the 
right and simply linear on the left hemisphere) there is a 


NERVOUS SYSTEM.—VERTEBRATA. 397 


small sulcus (triradiate on the right side, and on the left 
linear and prolonged forward into what is obviously a com- 
pensatory orbital sulcus). This small sulcus is one of the 
earliest. forms of the fronto-orbital suleus of the Simiide, 
which becomes in Man the anterior limiting sulcus of the 
island of Reil. 

The Sylvian fissure becomes confluent with the simple 
linear intraparietal sulcus, which ends just behind the 
parieto-occipital sulcus. 

There is a very short central sulcus, and. between it and 
the intraparietal a small punctate ramus postcentralis 
superior of the intraparietal. 

The simple parallel sulcus nowhere approaches the Sylvian 
fissure. 

There is a simple arcuate sulcus rectus running parallel 
to the fronto-orbital margin. On the right side it gives off 
a small branch. In front of the mid-point of the central 
sulcus there is a small depression, which may possibly 
represent the incipient arcuate sulcus. 

Behind the upper end of the parallel sulcus there is a 
short transverse occipital sulcus, and behind this a second 
small furrow (? inferior occipital sulcus). Beginning near 
the end of the posterior rhinal sulcus there is a deep and 
well-defined occipito-temporal sulcus on the tentorial 
surface. 

The cerebellum is of great interest, because it is still 
sufficiently simple to permit us to recognize the principal 
features exhibited by the non-Primate organ, and yet the 
exuberant growth of its lateral parts clearly points to the 
human homologies of the various regions. 

The most instructive parts of the organ in this specimen, 
however, are the floccular lobes. For this example clearly 
shows that this part of the cerebellum is composed in the 
Apes, as in other mammals, of two distinct parts or lobules 
—a small mesial part (surrounding the auditory nerve) 
being the flocculus proper, i. e. the part we call by that 
name in the human brain ; and a large lateral part or para- 
flocculus, which dwindles to a mere vestige (floceuli 
secundarii of Henle) in the brain of Man. In this brain 
the flocculus is a narrow sagittal band of about seven 


398 


PHYSIOLOGICAL SERIES. 


rounded “ folia,” whereas the paraflocculus is a great pro- 
jectinig mass of folia arranged in a feather-like pattern. 
Unlike the condition found in most mammals with projecting 
lobules (compare Yamanduas), almost the whole of the 
paraflocculus contributes to form the so-called ‘ petrosal 
lobule” in this case. O. C. 1337 «. 


D. 573. The brain of a young Red Howler (Alonatta senicula). 


The left cerebral hemisphere has been separated. 

The sinuous intraparietal element of the Sylvio-intra- 
parietal complex ends in a bifid manner so as to form a 
small transverse occipital. sulcus. There is, however, a 
well-developed compensatory-intraparietal suleus behind 
the central and parallel to the main intraparietal element. 

There is a long deep sulcus parallel to the caudal part of 
the “ parallel ” sulcus, which can only be the Simian sulcus. 

There are small and faintly-marked. inferior occipital, 
inferior temporal, and collateral sulci ; and at the point 
toward which these three sulci converge there is a peculiar 
deep irregular pucker. The meaning of this is not quite 
clear, but it is significant that the inferior occipital may, in 
different brains, be confluent with either of the other two 
sulci. Here all three sulci are poorly developed, and this 
peculiar depression makes its appearance—apparently as a 
compensatory factor. 

There is a simple linear orbital sulcus and an equally 
plain external compensatory-orbital, which we can now have 
no hesitation in calling fronto-orbital. This is the lowliest 
Ape in which this suleus (which in the Man-like Apes 
marks the anterior boundary of the insula) has been 
observed. 

The sulci upon the mesial aspect of these hemispheres 
are particularly interesting. Although the calcarine sulcus 
(unlike that of D. 572) has a bifid extremity, its caudal limbs 
are so small that they produce no mechanical disturbance. 
The parieto-occipital sulcus is broken up to an even greater 
extent than in specimen D. 571. ‘The notch in the superior 
border is present only on the left hemisphere. ‘The calloso- 
marginal sulcus joins the “compensatory ” sulcus, and the 
latter is quite separate from the small detached parieto- 


NERVOUS SYSTEM.—VERTEBRATA. 399 


occipital element which is found above the calcarine sulcus, 
Further, on the right hemisphere (in which the notch in 
the superior margin is absent) the latter element is more 
strongly marked. 
: | This apparently hopeless confusion becomes quite intelli- 
4 gible if the student remembers (1) that the parieto-occipital 
: _ sulcus arises merely as a furrow compensatory to the 
calearine complex ; (2) that in the interval between the 
calloso-marginal and calcarine sulci another sulcus (which 
I have called ‘: compensatory ”) generally makes its appear- 
ance for reasons similar to those that call the parieto- 
occipital into being ; and (3) that the relations of the 
“compensatory” sulcus to the calloso-marginal and calcarine 
sulci are determined mainly by the nature of the other 
compensatory sulcus, which is the parieto-occipital. 
O. C. 1337 a b. 


D. 574. Two casts of the cranial cavity of a Red Howler (Alo- 
natta senicula). 


‘ 


~—  D.575. The brain of a White-cheeked Capuchin (Cebus lunatus) : 
the left cerebral hemisphere has beeen separated (figs. 235, 
236, 237, 238). 

Fig. 295. (x 2.) 


SULC. RECT. 
< 


“sue. sim. 


Occupying as it does a central position among the 
Primates, Cebus lends itself very favourably to a wide 
comparison. For while its brain has attained to a suffi- 
ciently high stage of development to permit accurate 


400 


PHYSIOLOGICAL SERIES. — 


comparison with that of the large Old World Apes and 
Man, it is at the same time sufficiently simple to be 
compared with all the New World Apes, and even with 
the Lemurs. 

The olfactory bulb and its long attenuated peduncle are 
well shown in this specimen. The diminutive proportions 
of these bodies, and also of the pyriform lobe, are common 
to all the Anthropoidea. 


Fig. 236. 


= PAR. OCC. 


: ; 
/ AG _— SULC. INF, OCC, 
i 
: 
sul. INTRAPAR vee a 
Fig. 237. (x 3.) 


SULC. CENT. SULC. INTRAPAR, 


SULC. ARC. _ SULC, SIM. 


SOLC. RECT. 


OLF. BULB. 


The deep long oblique Sylvian fissure begins on the base 
of the hemisphere in a deep vallecula Sylvii. It appears 
to end above by joining the parallel sulcus:(fig. 237), but 
they are in reality separated by a submerged gyrus, beyond 
which the latter is prolonged for some distance (fig. 236) 
into the angle of the intraparietal sulcus. 


The neopulliam becomes folded in a most complicated a | 
manner in the neighbourhood of the caudal part of the . 


intraparietal sulcus (fig. 236). 

The intraparietal suleus has the form of an inyerted 
V, the anterior limb of which is about twice as long asthe 
posterior. The sulcus is exceedingly!deep in the greater 


NERVOUS SYSTEM.—VERTEBRATA. 401 


part of its extent, and from its apex a deep cleft extends 
on to the mesial surface of the hemisphere. The depth of 
this cleft (which we may call the ramus parieto-occipitalis 
sulci intraparietalis) is expressed by its length on the 
mesial surface (fig. 238, x). 

The parieto-occipital sulcus is swept, as it were, into 

the mesial part of this great cleft*. It emerges near the 
“ventral extremity of the latter, and fuses with one of the 
two “compensatory” sulci. Thus a V-shaped sulcus is 
produced which is parallel to the calcarine sulcus and the 
upper part of the retrocalcarine. 

At a superficial glance the Simian sulcus seems to join 
the posterior limb of the V-shaped intraparietal sulcus. 
But on separating the lips of the sulci it will be seen that 
the shallow Affenspalte lies entirely behind the deep intra- 
parietal. In fact the réle (which is assumed by the 
Affenspalte in many Cercopithecide) of relieving the 
tension of the expanding occipital regions is fulfilled by 
the operculation of the posterior lip of the ramus parieto- 
occipitalis sulci intraparietalis, rather than by that of the 
Simian sulcus. 

The Affenspalte becomes much deeper, and its posterior 
lip slightly opercular in its lateral part. On the left 
hemisphere it (superficially) joins the inferior occipital 
sulcus, the upper lip of which is also operculated. On the 
right hemisphere the Simian sulcus is much more poorly 

_ developed, but its posterior lip is operculated in its whole 
extent. It is separated from the inferior occipital sulcus 
by a wide interval, and not merely by a narrow submerged 
gyrus, as on the left side. 

There is a T-shaped calcarine complex. The long col- 
lateral sulcus is superficially joined to the retrocalcarine 
sulcus (fig. 238, sULC. P. CALC.). 

The superior limiting sulcus of the insula (the supra- 
sylvian sulcus of other mammals) emerges anteriorly from 


* The parieto-occipital suleus of Human Anatomy really consists of two 
separate sulci (corresponding to those just referred to as ramus parieto- 
occipitalis of the intraparietal and the parieto-occipital sulcus) submerged 
in the one cleft as in this case, but the dorsal sulcus does not join the intra- 
varietal as it does in this brain. 

VOL, Il. 2D 


402 PHYSIOLOGICAL SERIES. = 


the Sylvian fissure. On the left hemisphere it is linked by 
a shallow furrow to the orbital sulcus. 

The sulcus called “ rectus” in the lowlier Cebide is now 
broken up into two separate sulci:—the “ rectus” (sensu 
stricto) and the “arcuatus;” corresponding respectively to 


Fig. 288. (x 3.) 


INTERCAL. ELEMENTS, SULC. CALL.MARG. (INTERCAL) 


SULC. PAR.OCC. .__ 


SULC, P. CALC. i 
SULC. CALC. 
the inferior frontal and the inferior precentral sulci of 
Human Anatomy. y 
Immediately external to the typical posterior rhinal fissure __ 
there is a small inferior temporal sulcus. 0.0. 1337 Ke 


D. 576. The brain of a White-cheeked Capuchin (Cebus Jwnatus). 
This specimen closely resembles the last. Upon the 

right hemisphere the anterior end of the superior limiting 
sulcus of Reil can just be seen emerging from tho Sylvian _ 
fissure on to the orbital surface. 0. C. 13837 Efe 


D. 577. The brain of a White-fronted Capuchin (Cebus albifrons). 
In this brain the Affenspalte is a simple sulcus lying — 

some distance behind the transverse occipital ramus of the 
intraparietal sulcus. There is a feeble depression repre-— 
senting the ramus postcentralis superior of the intraparietal 
sulcus in the left hemisphere, 0. ©. 1837 Ke. 


D. 578. Tho brain of a White-fronted Capuchin (Cebus albifrons) a 
The region around the intraparietal sulcus is disposed — 

like that in the two specimens of C. lunatus. The Simian 
sulcus, however, is very small on the left hemisphere, so — 
that the whole of the intraparietal sulcus can be seen, 


No part of the superior limiting sulcus is exposed. a 
0.0. 1887Ka. 


a 


NERVOUS SYSTEM.—VERTEBRATA. 403 


D. 579. The brain of a Brown Capuchin (Cebus fatuellus). 

The small simple Simian sulcus is separated from the 
transverse occipital ramus of the intraparietal by a broad 
exposed gyrus. 

The ramus postcentralis superior of the intraparietal 
sulcus is wanting. O. C. 1337 x d. 


D. 580. The brain of a Brown Capuchin { Cebus fatuellus). 
This specimen, on the other hand, closely resembles the 
two brains of C. lunatus, especially in regard to the 
Affenspalte. O. C. 1837 Kg. 


D. 581. The brain of a Brown Capuchin (Cebus fatuellus). 
O. C. 1337 gh. 


_ D.582. The brain of a White-throated Capuchin (Cebus hypo- 


leucus). 
This brain resembles that of Cebus albifrons so far as the 
Affenspalte is concerned. O. C. 13837 Kk. 


D. 583. The brain of a White-throated Capuchin (Cebus hypo- 


leucus), (3). 
This resembles the preceding specimen. O.C. 1837 K b. 


D. 584. The brain of a Smooth-headed Capuchin (Cebus 
monachus). The left hemisphere has been separated. 

In this large series of Cebus-brains the features are 
so constant that the only variation specially noted above 
has been the somewhat trivial point— whether or not 
the posterior lip of the Simian sulcus extends forward 
sufficiently far to give the appearance of a fusion of the 
intraparietal and Simian sulci. On the right hemisphere 
of this specimen, the opercular lip of the Simian sulcus 
almost (but not quite) reaches the anterior lip of the ramus 
occipitalis transversus, whereas they are more widely 
separated on the left hemisphere. This brain therefore 
exhibits two interesting stages intermediate between the 
condition of the Affenspalte-region in the extreme types 
exhibited by Cebus lunatus (D.575) and C. hypoleucus 
(D. 582) (D. J. Cunningham, Mem. -Roy. Irish Acad. 
1892, p. 222). 

Note on the right hemisphere two faint depressions 


representing a superior frontal sulcus. O. C. 1837 Ki. 
2D2 


404 PHYSIOLOGICAL SERIES. 


D.585. The brain of a Cebus (sp.). 

The'left cerebral hemisphere has been separated and the 
dorsal operculum of the Sylvian fissure removed to show 
the extent of the insula. The mesial lip of the intraparietal 
suleus (in the region of its bend) has been removed to 
show that the parieto-occipital sulcus does not become 
confluent with the ramus parieto-occipitalis sulci intra- 
parietalis, but merely cuts into its posterior wall. 

On the right hemisphere the inferior lip of the Sylvian _ 
fissure has been cut away to show how the superior limiting 
sulcus of Reil ends anteriorly. 

This is a small and correspondingly simple brain for a 
Cebus. The sulci rectus and arcuatus have fused to form a 
simple bow. The Simian sulcus is. especially diminutive 
and is quite independent of the ramus transversus occipitalis 
of the intraparietal sulcus. O. C. 1337 K. 


D. 586. The brain of a Humboldt’s Woolly Monkey (Lagothrix 
humboldti), (3), (figs. 239, 240). 


Fig. 239. (x 3.) 
SULC. ARC. se CENT. 
%. t 


SULC. RECT. 


““SULC. INF. OCC, 
SULC. INF. TEMP. SULC. PAR. 

This brain still further demonstrates the extreme in- — 
stability of the region of the parieto-occipital suleus. The 
tension of the expanding cortex in this region of the 
Primate hemisphere may be relieved by the development — 
of a deep sulcus which may be derived from the intra- 
parietal system (as in Cebus, where we have seen the ramus 
parieto-occipitalis), or from the Simian sulcus (asin many 
Cercopithecids), or, as in this case, by a great extension — 
and deepening of the parieto-occipital sulcus, The latter 


pm PE, eA one 


NERVOUS SYSTEM.—VERTEBRATA. 405 


sulcus has extended far on to the dorsal surface, and has 
become exceedingly deep. Not only so, but its walls are 
rendered very irregular by numerous sulci, one of which 
emerges from the sulcus on the mesial surface of the left 
hemisphere. With the presence of this deep sulcus there 
is no need for a “ compensatory ”’ (Broca’s “ postlimbic ””) 
sulcus: and all the less so because the calloso-marginal 
sulcus approaches very near to the parieto-occipital sulcus. 
The unusually great dorsal extent of the parieto-occipital 
sulcus greatly disturbs the intraparietal sulcus. The latter 
consists of a triradiate arrangement far removed from the 
mesial plane. One limb of the sulcus extends between the 
upper ends of the Sylvian fissure and the parallel sulcus 
(both of which are very short). A second limb appears to 


Fig. 240. (x 3.) 


SULC. PAR. occ. SULC. CALL. MARG. 


SULC. L.oce. . 
SULC. CALC. . SULC. ROST. 
SULG. COLL. RHIN.F. 
join the mid-point of the Affenspalte, but in reality it runs 
parallel to the upper half of the latter, separated from it by 
a very deeply-submerged gyrus. The anterior limb of the 
triradiate sulcus extends above the Sylvian fissure toward 
the mid-point of the central gyrus. On the left hemisphere 
it joins the ramus postcentralis superior, which is a separate 
sulcus on the right side. 

The Simian suleus (Affenspalte) is short but very deep, 
and its posterior lip is slightly opercular. Behind its upper 
end there is a short compensatory sulcus, such as is some- 
times seen in Cebus. The inferior occipital sulcus approaches 
very close to the caudal end of the collateral sulcus. An 
obliquely directed lateral occipital suleus (not hitherto met 
with) crosses the hemisphere from the occipital pole toward 
the mid-point of the Simian sulcus (SULC. L. OCC.). 


406 


PHYSIOLOGICAL SERIES, 


The collateral sulcus is represented by two deep sulci. 

Thé-sulci rectus et arcuatus are concurrent. 

There is a small superior precentral sulcus. 

External to the orbital sulcus there is now a definite 
fronto-orbital (anterior limiting) sulcus. The floccular 
lobes of the cerebellum, which closely resemble those of 
Alonatta (D. 572), are particularly well-demonstrated. The 
vermiform flocculus alongside the auditory nerve is very 
distinct, and the peculiar club-shaped “ petrosal lobule ” of 
the paraflocculus presents very well-marked features. 


OQ. C, 18371. 


D. 587. The brain of a Humboldt’s Woolly Monkey (Lagothria 


humboldti). The left hemisphere is detached. 

The peculiar features of the parieto-occipital and intra- 
parietal sulci are found here also. The posterior ramus of 
the triradiate intraparietal sulcus is separated from the 
Affenspalte by a wide gyrus, especially on the right side. 

The posterior sulcus compensatory to the Simian sulcus 
is much larger than in the last specimen. Nevertheless the 
lateral occipital sulcus is well-developed. The result of 
this, however, is that the inferior occipital sulcus is poorly 
developed, but there is a compensatory deepening of the 
anterior segment of the collateral sulcus. 

On the right hemisphere the dual nature of the conjoint 
sulci rectus et arcuatus is indicated by a submerged gyrus. 
On the left hemisphere, however, the conjoint sulci form an 
irregular crucial pattern. 

The inferior temporal sulcus is unusually well-developed. 


O. C. 133714. 


D. 588. The brain of a Black-faced Spider-Monkey (Ateles ater), 


The condition of the parieto-occipital and intraparietal 
sulci is essentially identical with that just described in 
Lagothriz. But the inferior limb of the triradiate intra- 
parietal seems, at a casual glance, to actually join the Sylvian 
fissure. But in reality it ends behind the upper extremity 
of the Sylvian fissure, as in Lagothriz, and is separated 
from the latter only by a deeply submerged gyrus. On 
the right side the ramus postcentralis superior is united to 


NERVOUS SYSTEM.—VERTEBRATA, 407 


the intraparietal, but on the left side it consists of three 
fragments, of which only the inferior is united to the main 
sulcus. 

The ramus occipitalis of the intraparietal is bifid and 
quite independent of the Simian sulcus. The latter is 
extensive and irregular on the right side, but is more frag- 

. mentary on the left. It is a simple sulcus, i. e. its posterior 

lip is not operculated. The lateral occipital sulcus is dis- 

_ located to such a ventral position that the inferior occipital 
sulcus seems to be entirely aborted. 

There is a simple sulcus rectus, not joined to the sulcus 
arcuatus. The latter gives off a peculiar, extraordinarily 
long, posterior horizontal branch. Fragmentary repre- 
sentatives of the superior precentral and superior frontal 
sulci are present. 

Few Apes possess such a complicated occipital region, 
with such a complete absence of operculation and, for its 
size, such a well-furrowed frontal area as Ateles. In these 
respects the comparison of Ateles and Homo is very 
instructive. O. C. 1837 He. 

Huxley, Proc. Zool. Soc. 1861, p. 247. 


D. 589. The brain of a Black-faced Spider-Monkey (Ateles ater). 
Note again the apparent continuity of Sylvian fissure 
and intraparietal sulcus, such as occasionally occurs in 
Lemurs and Apes, with the difference that here there is a 
submerged gyrus to indicate the line of separation of the 
overlapping elements. All the superior precentral elements 

are separate here. 

The Simian sulcus is much larger and deeper here than 
in the last specimen. This is particularly marked on the 
right hemisphere, where the posterior lip of the sulcus is 
obviously operculated. 

The caudal ramus of the arcuate suleus is much shorter 

and the central sulcus correspondingly larger than in the 
last specimen. 

The anterior end of the superior limiting sulcus of Reil 
is clearly exposed on the right hemisphere (compare with 
the Anthropoid Apes). 0. C. 1837 nf, 


408 PHYSIOLOGICAL SERIES. 


D. 590. The brain of a Geoffroy’s Spider-Monkey (Ateles geof- 
Sroyé). 

This is a smaller and simpler beats than the last two. 

The frontal region resembles that of specimen D. 588. 

In addition to the chief parieto-occipital sulcus (which 
has only a short dorsal course in front of the intraparietal 
sulcus, where it ends in a bifid manner) there is a second, 
shallower, vertical accessory parieto-occipital sulcus behind 
the occipital part of the intraparietal sulcus. The latter is 
not joined by its superior post-central ramus (the chief 
element of which has an unusually sagittal direction). 
Anteriorly it appears to join the Sylvian fissure: posteriorly 
it dips into the Simian sulcus and its termination is thus 
hidden from view. , O. C. 18387 ud. 


D. 591. The brain of ‘* Ateles,” species unknown : the left hemi- 
sphere has been detached. The ramus postcentralis superior 
of the intraparietal sulcus is triradiate and not joined to the 
rest. 

There is a well-developed ramus occipitalis (transversus) 
of the intraparietal sulcus which lies in front of and parallel 
to the Affenspalte and behind the extensive parieto-occipital 
sulcus. So that the typical relations of these three sulci 
are demonstrated (especially on the left side) with dia- 
grammatic clearness. 

The calcarine has but very short limbs of bifurcation and 
seems to be joined by the parieto-occipital sulcus, as some- 
times happens in the human brain but exceedingly rarely in 
the Apes. And the collateral sulcus is composed of inner and 
outer parts, of which the inner approaches, but does not quite 
reach, the stem of the calcarine sulcus. QO. C. 1387 He. 


D. 592. The brain of a Long-haired Spider-Monkey (Ateles vel- 
lerosus). The left hemisphere has been detached. The 
membranes have not been removéd. The backwardly- 
directed branch of the arcuate sulcus is detached on the 
right side, but on the left is continuous with the rest of 
the sulcus. 

The superior limiting sulci of Reil (Marchand’s opercular 
sulci) are again partially exposed. 0. C. 1837 Ha. 


NERVOUS SYSTEM.—VERTEBRATA, 409 


D. 593. The brain of a Long-haired Spider-Monkey (Ateles vel- 
lerosus) : young male. 

The right hemisphere has been dissected from above to 
display the structures in the descending and posterior cornua 
of the lateral ventricle. The hippocampus major and the 
fimbriated extremity of the fornix accompanying it are well 
shown ; the optic thalamus and corpus striatum are also 
visible ; the great length of the posterior cornu of the 
lateral ventricle and the prominence in its wall corresponding 
to the calcarine sulcus, are very noteworthy features of the 
dissection. 0. C. 1337 u. 


Family CercoPiTHEciIDA. 


'D. 594. The brain of a Bonnet Macaque (Macacus sinicus) : the 
left hemisphere has been detached. 


Fig. 241, (x 4.) 


Y + B SULC INTERCAL. 
a : : 


SULC. ROST. 
/ 


\’ 


ne OLF. BULB. 


"“OLP.PED. 
/ Suincac. = ”~ OLF. TUBER. 
suce. cout. Fs 


jt 
vt “GYRUS LUNARIS™ 
BENDERELiA ~ / 


/ RUIN.E, " SULC. COLL, 


HIP.F, * PYR.L, 


The “ gyrus lunaris” of Retzius is the nucleus amygdalee 
SULC. P. CALC. refers to the retrocalcarine sulcus. 


With the present specimen we enter upon the consider- 
ation of the brain among the Catarrhine Apes (Old World 
Monkeys). 

There is a close resemblance between the brain in the 
larger Cebidee and that of the Cercopithecide. The general 
form of the brain is the same in the two Families. 

In spite of this identity of structure with the Cebide, it 


410 


PHYSIOLOGICAL SERIES. 


is useful to enter into a somewhat minute examination of a 
Macaque’s brain, not only that we may emphasize those 
common mammalian features which become obscured in the 
Simiidz and especially in Man, but also because the brain 
of Macacus has been so often explored by physiological 
methods that the homologies of its various parts thus acquire 
an added interest. 


The olfactory bulb (which has been destroyed in this 


specimen) is a small ellipsoidal mass of grey matter. Asia 


result of the great forward extension of the cerebral 
hemispheres in the Anthropoidea, the place of attachment 
of the olfactory peduncle to the hemisphere becomes removed _ 


Fig. 242, (Xx 3.) ; 


SULC. CENT, 


SULC. ARC. x RAMUS. POSTC. SUP. 


SULC. RECT. o< > L_ SULC.INTRAPAR. 
~*~, , 


progressively further away from the cribriform plate of the 
ethmoid bone, where the olfactory bulb is, as it were, 
moored by the olfactory nerves. The olfactory peduncle 
therefore becomes greatly elongated, and as a result the 
proportion of grey matter to white fibres (olfactory tract) 
becomes greatly reduced, so that the peduncle becomes a 
long, attenuated, white ribbon. In most Cercopithecid 
brains no olfactory sulcus is developed to accommodate this 
flattened peduncle. 


The relations of the olfactory peduncle to the tubereulum 
olfactorium and pyriform lobe are identical with those so 


clearly demonstrable, say, in the brain of a Dog or of a Sheep. 
The tuberculum olfactorium is still very distinct, because it 
has not become flattened out to the same extent as it has in 
the human brain. A very pronounced flexure has occurred 


SST ee ee eee 


- eds eg eo — ee see er 


ea ae a) or 


Serna 


it 


NERVOUS SYSTEM.—VERTEBRATA. 411 


in the pyriform lobe producing the vallecula Sylvii. The 
part of the pyriform lobe in front of this vallecula has 
become greatly reduced and would not be recognizable as 
such if it were not for the presence of the distinct olfactory 
tract extending from the olfactory peduncle to the posterior 
part of the lobe. The anterior rhinal fissure has vanished. 
The posterior rhinal fissure, however, forms a very distinct 
incisura temporalis, which constitutes the lateral boundary 
of the pyriform lobe. 

The Sylvian fissure appears to begin upon the base of the 
brain as a lateral extension of this vallecula Sylvii of the 
pyriform lobe. It then extends obliquely upward and 
backward as a deep cleft upon the lateral aspect ; its dorsal 
extremity almost reaches the parallel sulcus, from which it. 


_ is separated by a very narrow gyrus, which is often sub- 


merged so that the Sylvian fissure appears to join the 


parallel sulcus in a superficial view. 


If the lips of the Sylvian fissure be separated or cut 
away (as has been done in the right hemisphere) a large 
triangular depressed area—the insula *—will be found, over- 
lapped chiefly by the dorsal (or fronto-parietal) operculum. 


_ The dorsal limiting sulcus of the insula probably represents 


the suprasylvian sulcus of other mammals (which in the 


Primates forms the chief and most stable factor in the 


complex called “ Sylvian fissure’). When this fissure is 


opened up ina Macaque, the anterior extremity of this dorsal 
limiting sulcus will be found to extend forward into the deep 


surface of the operculum just external to the junction of Syl- 
vian vallecula and fissure.. In the Gibbons and higher Apes 


_ this limiting sulcus extends still further forward and becomes 


visible. The anterior part of the fronto-parietal operculum 
which borders on this upturned extremity of the limiting 
sulcus, meets in the human brain another lip which arises 
in front of the insula and forms the anterior limb (or limbs) 


- of the Sylvian fissure. In the brains of the Macaques 


there is no trace of this anterior operculum (or opercula) : 
but in this brain there is a well-defined, simple, linear 


* It must, however, be remembered that in the Apes the anterior part of 
the insula is not submerged but extends forward to the fronto-orbital sulcus. 


412 


PHYSIOLOGICAL SERIES. 


fronto-orbital sulcus between the Sylvian fissure and the 
triradiate orbital sulcus. When the anterior lip of this 
sulcus becomes opercular it forms the orbital operculum. 
In other words, the fronto-orbital is the anterior limiting 
sulcus of the island of Reil. 

Upon the orbital surface we always find an orbital sulcus, 
which (as I have frequently insisted elsewhere in these 
notes) probably represents the ‘ presylvian” sulcus of 
other mammals, An exceedingly variable series of com-— 
pensatory-orbital sulci develope alongside the true orbital 
sulcus, sometimes on its mesial side, sometimes on its lateral 
side, and often on both sides. Frequently in this way an 
H-shaped or triradiate arrangement of sulci is formed. 
The external compensatory-orbital sulcus often becomes 
deep and well-defined (as in this case) to form the fronto- 
orbital sulcus. 

The parallel sulcus extends beyond the Sylvian fissure at 
both extremities. 

The intraparietal (lateral) sulcus arches around the apex 
of the parallel. Its bifurcated caudal extremity—the 
transverse occipital suleus—is hidden under that peculiar 
occipital operculum, the outgrowth of which produces 
that great cleft known as the “ Affenspalte” or “ Simian 
sulcus.” [On the left hemisphere the operculum has been 
cut away so as to show the transverse occipital sulcus. ] 

Occupying the same relation to the intraparietal sulcus 
as the ansate does to the lateral sulcus in the Carnivora, 
we often find in the Cercopithecide: a small ramus post- 
centralis superior of the intraparietal sulcus. This is 
very poorly developed, especially on the right side, in this 
specimen. 

There is a typical central sulcus. 

There is a plain sagittal sulcus rectus (the inferior frontal 
sulcus) and a typical sulcus arcuatus (inferior precentral). . 

Above the sulcus arcuatus there are two small depressions 
representing the superior frontal sulcus. Below the central 
sulcus there is a small plain sulcus, which Eberstaller calls 
“ inferior transverse.” 

The inferior occipital sulcus is an elongated furrow the 
upper lip of which is markedly opercular. It skirts the 


Oe a a 


a ee a 


oe 


NERVOUS SYSTEM.—VERTEBRATA. 413 


ventro-lateral margin and then bends upward in front so as 
either to superficially join the Affenspalte or, as in this case, 
to end between the lower end of the latter and the parallel 
sulcus. 

Two fragmentary sulci, generally regarded as inferior 
temporal, are found in the triangle formed by the parallel, 

‘inferior occipital, and collateral sulci. There is also a 
shallow horizontal sulcus on the cranial aspect of the occipital 
pole, corresponding to that called “ lateral occipital” in the 
Cebide. 

On the mesial surface we find the deep calcarine suleus 
placed almost horizontally and passing without any line of 
demarcation into the stem of the T-shaped retro-calearine 
sulcus. The collateral sulcus begins in the inferior angle 
of the T and, after an extensive course along the inferior 
margin, ends in close proximity to the rhinal fissure 
(fig. 241). 

The parieto-occipital, being essentially a compensatory 
sulcus, exhibits extreme variation. We may find a simple 
deep incision (a) in the dorso-mesial angle of the hemisphere 
opposite the apex of the occipital arc of the intraparietal, 
which it joins. This fundamental sulcus may be surrounded 
by a U-shaped arc (8 +7) on the mesial surface, the posterior 
limb (y) of which is essentially “ parieto-occipital,” whereas 
the anterior limb (8) really belongs to the intercalary series— 
being the “compensatory” or so-called *‘ post-limbic”’ sulcus 
of Broca. The fundamental sulcus («) in this case is exactly 
analogous to that which was named ramus parieto-occipitalis 
sulci intraparietalis in Cebus (vide supra). The anterior limb 
(8) of the U-shaped compensatory sulcus is often separated 
as a distinct “compensatory”? element. While all this 
variety bears out the fundamentally compensatory nature 
of the sulcus, it renders a concise definition of the parieto- 
occipital sulcus impossible *. 

A glance at the illustration (fig. 241) or at the mesial 
surface of the brain of any Ape, will at once show how 
the majority of the (posterior) mesial sulci are essentially 


* The human parieto-occipital sulcus consists of the representatives of 
the sulci a and y, the intervening area being submerged so that the two 
sulci appear to form one cleft. 


414 


PHYSIOLOGICAL SERIES. 


compensatory to the calearine sulcus, around which they are 
grouped in such a peculiar manner. 

There is always a well-developed intercalary (calloso- 
marginal) sulcus with an upturned caudal extremity. And 
generally there is a small separate rostral sulcus. 

In proportion to the size of the cerebral hemispheres, the 
other regions of the brain seem very diminutive in the Apes. 
This is very striking in the case of the quadrigeminal and 
geniculate bodies, and even more so as regards the corpora 


mammillaria and interpeduncular body. Even the cere- a 


bellum appears to be very small in the Apes, although its 
actual size—in comparison with that of the body—is great. 
The pons Varolii is relatively broad, but not sufficiently so 
to hide the trapezoid body, which is in the Cercopithecide 
quite as distinct as it is in the Carnivora. The pyramidal 
tracts are relatively very large and prominent. And the 
olivary body is very distinct. 

The cerebellum in the Apes is very different in shape 
from that of other mammals because it becomes moulded 
to the configuration of the cerebral hemispheres which 
overlap it. Structurally it does not differ much from the 
organ in other mammals. But the relative size of the 
floccular lobe has become greatly reduced, although not 
nearly to such a marked extent as it is in Homo, Anthropo- 
pithecus, and Simia. It is noteworthy that the lateral 
lobule of the floccular lobe, i. e. the paraflocculus, is still 
larger than the mesial lobe (flocculus) and is provided with 
a projecting pedunculated appendage—the petrosal lobule— 
as is the case in many lowlier mammals. 0. C. 1838 Cg. 


D. 595. The brain of a new-born Bengal Macaque (Macacus 


rhesus). The left hemisphere has been detached. 

The intraparietal sulcus gives off (in each hemisphere) a 
short branch towards the upper margin of the hemisphere. 
Such a short branch is probably a representative of part, 
and not of the whole of the ramus postcentralis superior of 
the intraparietal sulcus, for its direction is not that taken 
by the isolated subdivision of the latter. Otherwise the 
specimen presents characters wholly in agreement with 
those of D. 594. O. C. 1838 0b, 


NERVOUS SYSTEM.—VERTEBRATA. 415 


D. 596. The brain of a Bengal Macaque (Macacus rhesus). 

This is a much better specimen than D. 594, which it 
closely resembles. 

The gyrus separating the sulcus y (see fig. 241) from that 
labelled @ is very narrow and deeply submerged, so that 
the former appears to be concurrent with the latter, i.e. to 
be a branch of the intraparietal. O. C. 1338 ce. 


D. 597. Two casts of the cranial cavity of a Rhesus Monkey 
(Macacus rhesus). 
Unlike most casts of the cranial cavity, this shows no trace 
of the cerebral sulci but a good impression of the meningeal 
vessels and of the sutures separating the cranial bones. 


D. 598. The brain and part of the skull of a footal Crab-eating 
Macaque (Macacus cynomolgus). 

There has been an injection into the membranes. 

A horizontal section opens the lateral ventricles (most of 
the corpus callosum has been removed, but a slight bridge still 
remains) and exposes the corpora striata, optic thalami, and 
the hippocampi in the descending cornua. Q. C. 1338 ce. 


D. 599. The brain of a Crab-eating Macaque ( Macacus cynomolgus), 
(2). O. C. 1338 o d. 


D. 600. The brain of a Crab-eating Macaque (Macacus cynomolgus), 
The left hemisphere has been detached from the remainder 
of the encephalon. 

The collateral is represented by two sulci in the left 
hemisphere, but by one only in the right hemisphere. 
The fronto-orbital sulcus is especially well-developed. 


O. C. 1338 of. 


D. 601. Two casts of the cranial cavity of a Crab-eating Macaque 
_ (Macacus cynomolgus). 


D. 602. The brain of a Lion-tailed Macaque (Macacus silenus) in 
which the left hemisphere has been detached. 

The opercular fold at the lower margin of the occipital 
lobe is particularly well developed and the hinder end of the 
collateral sulcus runs under it. Otherwise the conformation 
of this brain agrees with that of D, 594. O. C. 1838 h. 


416 PHYSIOLOGICAL SERIES. 


D. 603. The brain of a Lion-tailed Macaque (Macacus silenus). 
k | O. C. 1338 ca. 


D. 604. The brain of a Barbary Macaque or Magot (Macacus 
inuus),(¢). The left hemisphere has been detached. 

On both sides the Sylvian fissure is separated from the 
parallel sulcus by an exposed gyrus. Just above the pos- 
terior end of the Sylvian is a small lincar accessory furrow 
in the left hemisphere. O. C. 1838 ci. 


D. 605. The brain of a Himalayan Macaque (Macacus erythreus). 
This is an exceedingly well-preserved specimen. The 
left hemisphere has been divided into several portions by a 
series of horizontal sections. An opercular growth has 
taken place in the upper lip of the inferior occipital sulcus. 
Such an operculum is suggested feebly by most specimens 
of Macacus, but here it has carried a fold of cortex down- 
wards and has folded it almost over on to the mesial aspect. 
This operculum, combined with the normally-developed one 
at the “* Affenspalte,”’ confers a striking appearance on this 
specimen. 


D. 606. The brain of a Sooty Mangabey ( Cercocebus fuliginosus) : 
the left hemisphere has been detached. 

This specimen closely resembles the brain of a Macacus. 

It is noteworthy that in the right hemisphere the arcuate 

sulcus sends off a posterior branch which reaches the central 

sulcus. Cunningham has pointed out that in the Mangabeys 

the transverse occipital ramus of the intraparietal sulcus 

may become concurrent with the “ Affenspalte ”’ (Memoirs 

Roy. Irish Acad. 1892, p. 229). O. C. 1338 v. 


D. 607. The brain of a Sooty Mangabey (Cercocebus fuliginosus), 
(2). The left hemisphere has been detached. 
There is a well-developed lateral occipital sulcus. 
O. C. 1338 pa. 


D. 608. The brain of a Sooty Mangabey ( Cercocebus fuliginosus), 
(2), from which the left hemisphere has been detached. 
This specimen closely resembles the Macacus-brain, 
QO. C, 1338 p b. 


NERVOUS SYSTEM.—VERTEBRATA. 417 


D. 609. The brain of a White-collared Mangabey (Cercocebus 
collaris), (2): the left hemisphere has been detached. 

There is no important difference from the foregoing or 

from the Macacus-brains. The opercular fold in the lower 

margin of the occipital lobe of the right side is very 

extensive, stretching forward into the temporal region ; it 

is also deep, so much so that the collateral sulcus is repre- 

sented by two short sinuous sulci only, there being 

presumably no call for the greater amount of surface they 

would provide if better developed. 

There is a slight tendency among these Cercocebus-hemi- 

_ spheres to irregularity (more so than in Macacus) in the 

- arrangement of the collateral sulcus. O. C. 1338 pe. 


D. 610. The brain of a Diana Guenon (Cercopithecus diana), (2): 
_ the left hemisphere has been detached. 

The differences from Macacus (and also from Cercocebus) 
are insignificant, being attributable to the smaller size of 
the brains in the present genus. The arcuate sulcus gives 
no posterior branch in the right hemisphere and only a very 
short one in the left. On the mesial aspect the collateral 
sulcus is seen to be represented by three isolated sulci the 
posterior of which appears to spring from the calcarine. 


O. C. 1338 zB. 


D. 611. The brain of a Diana Guenon (Cercopithecus diana) : the 
- left hemisphere has been detached. The floccular lobes are 
well preserved. There are three sulci in the collateral 
group of the left hemisphere, two in the right hemisphere. 

O. C. 1338 Em. 


D. 612. The brain of a Lesser White-nosed Guenon (Cercopithecus 
petaurista), (¥): the left hemisphere has been detached. 

There is a slight irregularity in the collateral sulcus, 
which in each hemisphere is represented by two sulci. 


O. C. 1338 Ba. 


D. 613. The brain of a Lesser White-nosed Guenon ( Cercopithecus 


petaurista), (3): the left hemisphere has been detached. 
. O. C. 1338 E aa. 


VOL. IL. 2E 


418 PHYSIOLOGICAL SERIES, 


D. 614. The brain of a Lesser White-nosed Guenon (Cercopithecus 
petaurista) : the left hemisphere has been detached. 
O. C. 1338 Bab. 


D. 615. The brain of a Cercopithecus (sp.): the left hemisphere 
has been detached. O. C. 1338 kb. 


D. 616. The brain of a Grivet Monkey (Cercopithecus sabeus), (2): 
the left hemisphere has been separated from the rest of the 
brain. O. C. 1338 Ef. 

Presented by C. FE, Flower, Esq. 


D. 617. The brain of a Grivet Monkey (Cercopithecus sabeus), 
(2). O. C. 1338 Eg. 


D. 618. The brain of a Vervet Guenon (Cercopithecus lalandit) : 
the left hemisphere has been detached from the remainder 
of the encephalon. 

The Sylvian fissure does not join the parallel in the left 
hemisphere, and only does so very superficially in the right 
hemisphere. O. C. 1338 Bh. 


D. 619. The brain of a Patas Guenon (Cercopithecus ruber), (2): 
the left hemisphere has been detached. 

The orbital surface of the left hemisphere bears three 

sagittally-directed sulci, the outermost being represented by 

a depression only, in the right hemisphere, O. C. 1338 E2. 


D. 620. Brain of the Hocheur Guenon (Cercopithecus nictitans). 
The left hemisphere has been detached. O. C. 1338 Ex. 


D. 621. The brain of a Campbell’s Guenon (Cercopithecus 
campbelli), (3). 

Notice a deep sagittally-directed sulcus on. the occipital 

lobe. O. C. 1338 & k- 


D. 622. The brain of a Green Guenon (Cercopithecus calli- 
‘ trichus), (2). 

The left hemisphere has been detached from the re- 

mainder of the encephalon. O. C. 1338 Bl. 


D.623. The brain of a Malbrouck Guenon (Cercopithecus cynosurus) : 
the left hemisphere has been detached. O. C. 1338 Bo. 


NERVOUS SYSTEM.—VERTEBRATA. 419 


D. 624. The brain of a Malbrouck Guenon (Cercopithecus cyno-~ 
surus): the left hemisphere has been detached. 

Both brains conform precisely to the typical arrange- 

ment. O. C. 1338 & p. 


D. 625. The brain of a Yellow Baboon (Papio babuin),( ¢): 
the left hemisphere has been separated. 

__ This is a very much larger brain than that of any of the 
Primates yet considered. The cerebral hemispheres are 
also proportionately longer than in the other genera. 

In accordance with its greater extent, the surface of the 
hemispheres is more richly furrowed than in the smaller 
Cercopithecidze, but its pattern is essentially the same. 

The Sylvian fissure is separated from the parallel sulcus 
throughout by a wide exposed gyrus. The parallel sulcus _ 
is prolonged far beyond the Sylvian, and its apex is 
encircled by the ramus horizontalis of the intraparietal 
sulcus. The latter splits and forms a transverse occipital 
sulcus, but, unlike the condition found in the Apes hitherto 
considered, the mesial limb of the transverse occipital cuts 
deeply into the mesial wall of the hemisphere, so that it 
represents (functionally) the sulcus « of Macacus (vide 
supra). Such being the case, it is not surprising to find 
that the parieto-occipital sulcus (which in a superficial view 
of the left hemisphere seems to join the intraparietal 
element) cuts into the anterior wall (and not the posterior, 
as in the higher Cebide and in the Macaques) of the 
intraparietal ramus. On the right side the parieto-occipital 

sulcus lies wholly in front of the ramus intraparietalis. On 
both sides the former sulcus appears to join the calcarine, 
but a submerged gyrus separates them *. 

There is a well-developed occipital operculum, which has 
been partially removed on the right side in order to expose 
the transverse occipital sulcus. No proper operculum is 
formed by the upper lip of the horizontal inferior occipital 
sulcus. 

Three horizontal sulci, representing the transverse 


* By parieto-occipital sulcus is meant that labelled y in Macacus, which, 
as explained above, does not strictly represent the parieto-occipital sulcus of 


Human Anatomy. 9 
28% 


420 


PHYSIOLOGICAL SERIES. 


occipital sulcus, are found in the triangle partially formed 
by the Simian sulcus and the inferior occipital sulcus. 

There is a very rudimentary superior postcentral sulcus. 
In addition to the typical sulcus rectus and sulcus arcuatus 
there is a small ‘inferior transverse” sulcus of Eberstaller 
(between the lower ends of the latter and the central 
sulcus) and a small “diagonal” suleus (in front of the 
lower end of the arcuate sulcus) *. 

An irregular series of small furrows represents the 
superior precentral and superior frontal sulci. Simple 
orbital and fronto-orbital sulci are present. 

The floccular lobes of the cerebellum are still very large 
and retain those features common to most mammals. The 
flocculus consists of a narrow band of small folia encircling 
the eighth nerve. The paraflocculus consists of a much 
larger and broader band surrounding the flocculus. Its 
mesial lobule lies in front of (and without minute exam- 
ination is indistinguishable from) the flocculus. From the 
antero-lateral part of the paraflocculus projects a small, 
though widely salient, “ petrosal lobule.” But in contrast 
to the condition found in the Cebidee and many Cerco- 
pithecide, the “ petrosal lobule” constitutes a very small 
part of the paraflocculus. 

As this is a larger brain than that of any Ape yet 
considered, it affords an excellent demonstration of the 
great increase in size and prominence of the olivary bodies 
and pyramidal tracts. Although the pons has become very 
broad, the large trapezoid bodies are still uncovered, as in 
lowlier mammals. O. C. 1888 a a, 


D. 626. The brain of a Yellow Baboon (Papio babuin), (3). 


The left hemisphere is separate. 

In the presence of a deep long collateral sulcus (such as 
we shall see in specimen D, 627) the occipito-temporal 
almost completely disappears as a separate sulcus, and the 
inferior occipital sulcus becomes smaller. 

In the right hemisphere both the lateral and mesial 
olfactory tracts are unusually clearly shown. O.C. 1338 af. 


* This sulcus, called “ diagonalis”’ by Eberstaller, is not the furrow called 
by this name in other Mammals by Krueg, The latter, in all probability, 
becomes the fronto-orbital in Primates. 


NERVOUS SYSTEM.—VERTEBRATA. 421 


D. 627. The brain of a Chacma Baboon (Papio porcarius), (2). 
The left hemisphere has been detached. [The right 
hemisphere has been damaged by a horizontal saw- 
cut. | 

There is an exceptionally well-developed anterior limiting 
sulcus of Reil or, as it is more generally known, fronto- 
orbital sulcus. External to this there is a short deep sulcus 
[best seen on the right hemisphere] just in front of the 
exposed end of the superior limiting sulcus of Reil, that 
emerges from the Sylvian fissure. This is of great interest 
because it indicates that extension of the surface in this 
region which in a slightly higher phase of development 
leads to the formation of an operculum. An examination 
of the series of brains of Anthropoid Apes shows that this 
operculum is often formed by the upper lip of a small 
sulcus in this position, which is not part of either the 
superior (Marchand’s “opercular’’) or the anterior 
(fronto-orbital) limiting sulcus. 

The collateral sulcus is unusually extensive, its caudal 
end almost joining the calcarine sulcus, and its anterior 
end overlapping the rhinal fissure. There is, therefore, no 
separate occipito-temporal sulcus such as we find in the 
brain of some Baboons. 

On the left hemisphere there are small superior pre- 
central and superior frontal sulci of diagrammatic sim- 
plicity. O. C. 1338 a. 

[For fuller information concerning this brain, see 
D. J. Cunningham, Mem. Roy. Irish Acad. vol. iii. 1892, 
p- 282.] 


D. 628. The brain of a Chacma Baboon (Papio porcarius). The 
left cerebral hemisphere has been separated. 

The peculiarly extensive collateral sulcus of the pre- 
ceding specimen is exactly reproduced here also. 

On the left hemisphere, the opercular lip of the Simian 
sulcus has been pulled backward sufficiently far to show 
that the relations of the intraparietal sulcus and that which 
we may now call “ parieto-occipital ” are essentially the 


same as those described in specimen D, 630 (vide infra). . 
O. C. 1338 az. 


422 PHYSIOLOGICAL SERIES. 


D. 629. The cerebellum, medulla oblongata, &., of an Arabian 
Baboon (Papio hamadryas), (3). 
The floccular lobe of the left side is well preserved. 
O. C. 1338 ab, 


_D. 630. The left cerebral hemisphere of the same brain. 
This is a smaller hemisphere, and the sulci are slightly 
less complex than in the preceding examples (D. 626). 
The anterior part of the collateral is separated from the 
posterior part, and is prolonged backward as an occipito- 
parietal sulcus to join the inferior ovcipital. O. C. 1338 Ac. 


D. 631. The brain of a Guinea Baboon (Papio sphinx). The 
two cerebral hemispheres have been detached. 

This specimen affords two more interesting variations in 

the ever-changing area around the parieto-occipital sulcus. 


In a superficial view of the mesial aspect of the right E 


hemisphere there appears to be a Y-shaped combination of 
parieto-occipital and calcarine elements. If, however, the 
lips of the sulci be drawn asunder, the parieto-occipital is 
found to be separated from the calcarine sulcus by a narrow, 
deeply-submerged gyrus; and the apparent parieto-occipital 
sulcus consists of two distinct sulci, which are seen as such 
on the left hemisphere widely separated by a broad gyrus. 
On the right side, however, the two sulci are separated by 
a submerged gyrus, and, after comparison with the last 
specimen, there can be no doubt that the anterior sulcus 
(that which appears to join the calcarine) corresponds to 
the element hitherto called “ parieto-occipital,” whereas 
the deeper and more extensive posterior sulcus (compare 
the left hemisphere) is unquestionably identical with that 
distinguished as the “ ramus parieto-occipitalis sulci intra- 
parietalis.” But the importance of this specimen depends 


upon the fact that upon the right hemisphere the latter — } 
sulcus is separated from the intraparietal sulcus by a small, 


exposed, arcuate gyrus, which can be no other than that 
called arcus occipitalis in Human Anatomy. Essentially 
the same condition is found on the left hemisphere, but 
the arcus occipitalis is submerged. 


a nen 


NERVOUS SYSTEM.—VERTEBRATA. 423 


There can be no doubt that the parieto-occipital sulcus 
of Man is represented not merely by the sulcus so named 
in the last specimen and other Apes, but also by the second 
element distinguished as “ramus parieto-occipitalis sulci 
intraparietalis,”” 

The caudal extremity of the intraparietal sulcus ends 
without bifurcating under cover of the occipital operculum, 
but does not reach the bottom of the Simian sulcus. 
| In the right hemisphere the collateral series is repre- 
: sented by two long deep sulci. Below the calcarine there 
f is the true collateral sulcus, the posterior end of which is 
J separated from the calcarine by a submerged gyrus. 
| Occupying a more lateral position there is a second longer 
‘ and deeper sulcus of the same series, which must now be 
called the inferior (or third) temporal or the occipito- 
temporal sulcus. Posteriorly this appears to join the very 
long inferior occipital sulcus at about its mid-point, but 
there is a narrow submerged gyrus between them. ‘The 
anterior end of the inferior occipital is separated from the 
Simian suleus by a partially submerged gyrus, and its 
caudal end is prolonged far back on to the mesial surface 
almost as far as the calcarine sulcus. 

On the left hemisphere the inferior occipital is a very 
short sulcus, the mid-point of which is joined by a vertical 
furrow to the mid-point of the occipito-temporal sulcus. 
The posterior half of the latter therefore takes the place of 
the posterior (mesial) prolongation of the inferior occipital 
sulcus on the right side. O. C. 1338 Ae. 


a ee Se eee 


a a i 


- 

7 D.632. The brain of a Gelada Baboon (Papio gelada), ( ¢ ). 
; This brain is much smaller than those of most Baboons, 
. and hence the surface is less complicated. 
There is a collateral sulcus like that of the last specimen, 
but the inferior occipital sulcus is placed lower, and is 
greatly prolonged to form a sulcus parallel to and almost 


coextensive with the collateral. QO. C. 1338 ag. 


D. 688, The brain of a Drill (Papio leweophews)» 
This is a relatively small and simple brain, which ares 
the characteristic features of the Baboon’s brain particularly 


424 PHYSIOLOGICAL SERIES. 


clearly... This is especially so in the region of the hind 
brain;.where an admirable demonstration is afforded of the 
relations of the pyramidal tracts, olivary bodies, trapezoid 
bodies, eighth nerves, and the three parts of the floccular 
lobes—the mesial paraflocculus in front, the flocculus behind 
it, and the large lateral paraflocculus, which is placed 
behind the rest. Although the floccular lobes do not seem 
to be damaged, there is no projecting ‘ petrosal lobule.” 
O. C. 1338 ah, 


D. 634. Two casts of the cranial cavity of a Drill (Papio 
leucopheus). 


D. 635. The brain of a young female hybrid between a male 
Macaque (Macacus cynomolgus) and a female Baboon 
(Papio mormon). From the Zoological Gardens, 1880. 

This brain is indistinguishable from that of a Macaque. 
In that region of the brain—around the parieto-occipital 
suleus—where alone noteworthy distinctive features are 
found in the two genera, this brain exhibits the typical 
features of the Macaque. 

The influence of the male parent has therefore been 
clearly predominant in determining the features of the 
brain in this instance. O, C. 1338 Bd, 


D. 636. The brain of a Hanuman Langur or Entellus Monkey 
(Semnopithecus entellus), (3g). The left hemisphere has 
been separated. 

The seven brains representative of the genus Semno- 
pithecus in this Collection are of varying sizes, some larger 
and some smaller than those of the genus Macacus, but on 
the average they are rather larger than the latter. On the 
other hand, they are much smaller than those of the genus 
Papio, and accordingly the pattern formed by the sulci 
of the cerebral hemisphere is somewhat simpler than that 
found in the Baboons. 

The parieto-occipital sulcus and the representative of that 
called “ramus parieto-occipitalis” of the intraparietal in 
the Macaques have now become confluent (although slight 
irregularities exist in the depths of the sulcus to indicate 


NERVOUS SYSTEM.—VERTEBRATA. 425 


its dual nature in the Baboons ‘and lowlier Apes). The 
resulting single sulcus is obviously the parieto-occipital 
sulcus of Man. It is a simple linear sulcus, the lower end 
of which is separated from the calcarine by a submerged 
gyrus (as in the human brain) ; its upper extremity is 
surrounded by a broad arcus occipitalis which separates it 
completely from the intraparietal sulcus. As occasionally 
happens in the genus Papio, the occipital operculum is not 
extensive enough to hide the arcus occipitalis or the 
parieto-occipital sulcus. 

The inferior occipital operculum (i.e. the dorsal lip of 
the inferior occipital sulcus) is much less developed than 
it is in Macacus. In other respects the brain closely 
resembles that of Macacus, with the exception that the — 
calcarine sulcus is not bifid. O. C. 1338 F. 


D. 637. The brain of an Hntellus Monkey (Semnopithecus 
entellus), (@). The left hemisphere has been separated. 
This closely resembles the preceding specimen. The 
sulcus arcuatus is, however, triradiate in this case. 
The collateral series of sulci vary in the two brains in the 
same way as we have already noted in Papio. 
O. C. 1338 Fa. 
Presented by P. L. Sclater, Esq. 


D. 638. The brain of an Entellus Monkey (Semnopithecus 
entellus) . 
This old specimen exhibits the same arrangement of 
sulci as the preceding. | 
In spite of its damaged condition it shows the relations 
of the flocculus, paraflocculus, and the projecting “ petrosal 
lobule” better than the more recent specimens. 


O. C. 1338 Fb. 


D.639. The brain of an Entellus Monkey (Semnopithecus 
entellus). The left hemisphere has been separated. 

In these hemispheres the arcus occipitalis has become 
submerged under the occipital operculum, 80 that, ata 
superficial glance, the Simian and the parieto-occipital 
sulci seem to be confluent. 


426 PHYSIOLOGICAL SERIES. 


The lips of the Sylvian fissure have been separated on 
the right hemisphere so as to expose the anterior end of 
the superior limiting sulcus of Reil. 

The petrosal lobule of the floccular lobe is more distinctly 
demonstrable. O. C. 1338 Fe. 


D. 640. The brain of an Entellus Monkey (Semnopithecus 
entellus). The left hemisphere has been separated. 

Unlike the condition found in all the other Entellus 
Monkeys, the calcarine sulcus presents the bifurcated form 
more usual in the Cercopithecide. The cerebellum and 
floccular lobes are better preserved in this specimen. 

QO. C. 1338 Fd. 


D. 641. Two casts of the cranial cavity of an Entellus Monkey 
(Semnopithecus entellus). 


D. 642. The brain of a Purple-faced Langur (Semnopithecus 
leucoprymnus). The left hemisphere has been detached. 

This is a much smaller brain than those of many other 
Langurs. 

The lower opercular lip of the Sylvian fissure has been 
removed in the left hemisphere, so as to expose the insula 
and its superior limiting sulcus. 

The inferior occipital sulcus has dwindled to most 
insignificant proportions, and unless the student examines 
a large series of brains he will hardly recognize in the 
little arc around the lower end of the Simian sulcus the 
representative of the deep operculated infra-occipital suleus 
of the Macaques. O. C. 1338 Fe. 


D. 643. The brain of a Purple-faced Langur (Semnopithecus 
leucoprymnus), The left hemisphere has been separated. 

This is a well-preserved typical Langur’s brain. The 
features of the floccular lobe are very clearly shown here. 

If the Simian suleus be opened up in a series of brains 

of this genus, the transverse occipital sulcus will be found 


in many cases to be confluent with it, as it is here. 
O. C. 1338 Ff. 


NERVOUS SYSTEM.—VERTEBRATA. 427 


Family Srxuirpx, 


D. 644. The brain of a Hoolock Gibbon (LHylobates hoolock), 


(?). The left cerebral hemisphere has be 
(figs. 243, 244). P en separated 


Fig. 243. (x 3.) 


_-’ SULC, RECT, 


SULC, PAR.OCC. 


Fig. 244. (x 2.) 


SULC. CENT. 


SULC. SUP. FRONT. 
‘ SULC. LAT. OCC, 


SULC. SUP Lim. 


SULC. RECT... 


SULC.FR.ORB? Se 


SULC.ORB. INS. SULC. PAR. SULC. INF. OCC. 


The brain is of special interest in the Gibbons, because it 
presents many features which may be regarded as inter- 
mediate between those of the Anthropoid and other Apes. 

The series of modifications which would be necessary to 

convert the brain of a Macacus into that of a Semnopithecus 
are carried a stage further in the case of //ylobates. 


428 


PHYSIOLOGICAL SERIES, 


The parieto-occipital sulcus is now a simple sulcus with 
external (dorsal) extent almost as great as its internal . 
portion. It is separated from the intraparietal and Simian 
sulci by a wide gyrus on the left hemisphere. On the 
right hemisphere, the Simian sulcus curves forward so as 
almost to reach the parieto-occipital sulcus. 

The calearine sulcus presents upon the left hemisphere 
the usual bifid form common to most Apes, whereas upon 
the left side it is plain and undivided, as in most Semno- 
pithect. The occipital operculum is smaller even than it is 
in the Langur-family, and the inferior occipital sulcus is 
reduced to a mere vestige, which is triradiate on the left 
hemisphere. | 

The lateral occipital sulcus, which is well developed in 
Semnopithecus in comparison with other Apes, is even 
better developed in this brain. It is a deeply-incised 
Y-shaped sulcus, the two limbs of the Y embracing the 
caudal end of the calcarine sulcus. 

The sulci rectus and arcuatus are concurrent, as they are 
in many of the lower Apes. 

But the most characteristic feature of the brain in the 
Gibbons is the condition of the insular region, which 
distinguishes this brain from that of all mammals except the 
Anthropoid Apes. The fronto-orbital sulcus is especially 
well-developed (see the left hemisphere), and now con- 
stitutes the anterior limit of the exposed part of the insula, 
the dorsal boundary of which has been mapped out by the 
superior limiting (Marchand’s “‘ opercular”’) sulcus, which 
has emerged from the Sylvian fissure to a much greater 
extent than in any of the lowlier Apes. 0, C. 1338 Ga. 


D.645. The brain of a Gibbon (Hylobates lar). The left 


hemisphere has been separated. 

This is a smaller and somewhat simpler brain than the 
above. 

The calearine sulcus is unbranched on both hemispheres. 
The ramus postcentralis superior of the intraparietal (which 
is very well developed and united to the main sulcus in the 
last specimen) is a mere disconnected depression. The 
two-limbed sulcus formed by the union of the superior 


NERVOUS SYSTEM.—VERTEBRATA. 429 


precentral and superior frontal sulcus explains the sig- 
nificance of the obliquely-placed sulcus in the preceding 
specimen. The orbital sulcus is simply linear, instead of 
being irregularly triradiate, as in the last specimen. 

The other sulci do not essentially differ. [In both 
brains the collateral is represented by two sulci, the 
anterior of which overlaps the posterior laterally, and 
thus relieves the tension of the growing cortex, which 
in other hemispheres is relieved by a special suleus—the 
occipito-temporal. O. C. 1338 a, 


D. 646. The brain of a White-cheeked Gibbon (Hylobates 
leucogenys),( 3). The left cerebral hemisphere has been 
separated. 

The cerebral hemispheres of this brain are much larger 
and richer in sulci than those of the other two Gibbons’ 
brains. 

A peculiar appearance is produced in the occipital 
region by the parieto-occipital sulcus (after crossing on to 
the dorsal surface) being prolonged (superficially) back- 
ward for some distance so as to form a V-shaped pattern 
with an analogous backward extension of the Simian sulcus. 
The two sulci, however, do not join. This peculiar appear- 
ance seems to be the result of a very pronounced broadening 
of the anterior limb of the gyrus called arcus occipitalis, 
which has pushed back, so to speak, the occipital operculum 
and the mesial end of the Simian sulcus, and driven the 
diminutive posterior limb of the arcus under cover of 
the mesial lip of the peculiar sagittally-directed part of the 
parieto-occipital sulcus. As a further result, the bifid 
extremity of the intraparietal sulcus, which forms the 
transverse occipital sulcus, not only lies far in front of the 
Simian sulcus and operculum, but also in front of the bent 
parieto-occipital sulcus. 

The complexity of the intraparietal series of sulci is still 
further increased not only by the ramus postcentralis but 

_ by several other additional rami. 

The inferior occipital sulcus is present as a short deep 
furrow, and is joined on the right hemisphere to the 
posterior element of the middle temporal sulcus. The 


PHYSIOLOGICAL SERIES. 


occipito-temporal sulcus is very long and deep, its extension 
having taken place at the expense of the collateral sulcus. 
On the left hemisphere the little inferior occipital sulcus — 
is linked to the occipito-temporal sulcus, just as occurs — 
in the corresponding hemisphere of the Guinea Baboon _ 
(D. 631). 

The calecarine sulcus bas two long diverging caudal 
limbs, as well as several accessory sulci surrounding it. 

The superior frontal suleus is exceptionally well- 
developed. 

But by far the most interesting and important feature of 
this brain is the condition of the anterior insular region. 
On the right side, this region does not markedly differ 
from that already described in the case of the Hoolock — 
Gibbon (D. 644). But in the left hemisphere the fronto- — 
orbital sulcus is very deep (as it also is on the right a . 
and the superior limiting sulcus is prolonged forward soas 


f eB? 
DORS. P FLOC. FLOC. 


almost to reach the fronto-orbital (in fact, on casual exam- 
ination it appears to do so): moreover, the dorsal lip of the 
superior limiting sulcus has become opercular, so that the 
anterior insular region is not only almost completely 
surrounded by sulci, but is also depressed below the level 
of the surrounding areas. Thus a condition is produced “i 
which finds a close parallel in the developing human brain. 
(Compare Cunningham’ s observations on the analogous 
phenomena in the Chimpanzee’s brain, Journ. Anat. & 
Phys. vol. xxxii. 1898, pp. 11 et seq.) ‘4 

The trapezium, although covered by the pons toa much — 
greater extent than in Papio, is still distinct laterally. 

The floccular lobe resembles that of the Cercopithecide, 
and is relatively much larger than it is in the Anthropoid 


eo ale Siti 


ee ee ee ee 
> : 


NERVOUS SYSTEM.—VERTEBRATA. 481 


Apes. It consists of a small mesially-placed flocculus, 
consisting of a series of simple folia grouped around the 
auditory nerve, and a very large external paraflocculus. The 
latter consists of the usual two parts, viz., a dorsal (lateral) 


_ paraflocculus composed of broad flattened folia, and a 


ventral (mesial) paraflocculus composed of narrower folia. 
From the angle of junction of dorsal and ventral lobules a 
large strongly-projecting feather-like group of parafloceular 
folia projects to form the pedunculated petrosal lobule 
(fig. 245). O. C. 1338 ad. 


_ D. 647. Two casts of the cranial cavity of a Siamang (/Hylobates 


syndactylus), (3). 


D. 648. The left cerebral hemisphere and the rest of the brain 


of a young Mias or Orang-Outang (Simia satyrus). 

In comparison with those of other Apes the brains 
of the Anthropoids are characterized by their greater 
absolute dimensions. The cerebral hemispheres are fuller 
and more rounded than those of Hylobates, and especially 
so in the frontal region. There is, however, a very pro- 
nounced rostration of the orbital region resulting in the 
formation of a most prominent keel. The floccular lobes 
of the cerebellum (and more especially the paraflocculus) 
undergo a noteworthy reduction in size. The trapezoid 
bodies become covered by the pons to a much greater 
extent than is the case in other Apes; and also, partly, as a 
result of the increasing breadth of the pons, the large 
olivary bodies now extend as far as the latter body. 

But by far the most important changes are found in the 
cerebral hemispheres, the surfaces of which are much more 
extensive, and consequently much more richly supplied 
with sulci than is the case in lower Apes. 

The anterior insular region presents features such as have 
been already described in the Gibbons. The fronto-orbital 
(anterior limiting) sulcus is deep and very long, extending 
across the orbital margin so as almost to meet the inferior 
precentral (arcuate) sulcus. The exposed portion of the 
superior limiting (opercular) sulcus is also deep and long, 
but is still separated from the fronto-orbital by a broad 


432 


PHYSIOLOGICAL SERIES. 


gyrus. The upper lip of this sulcus is the more prominent, 
an indication of its conversion into an operculum in a 
higher phase of development. 

The Sylvian fissure has a T-shaped caudal extremity. 
The long central (Rolando’s) suleus has a slight genu: 
it does not attain to the mesial surface. 

The inferior precentral (arcuate sulcus) is a deep irre- 
gularly-triradriate sulcus, the inferior limb of which is 
superficially joined to the Sylvian sulcus by the inferior 
transverse sulcus. The gyrus which separates these sulci is 
wholly submerged on the left, and only partially so on the 
right hemisphere. In calling this sulcus “ arcuate ” it must 
be borne in mind that in the earliest phase of its history 
(curiously reproduced again in the Gibbons) the arcuate 
and straight (rectus) sulci are one, and later this single 
sulcus becomes broken up into the two distinct elements, 
which acquire a very questionable individuality, so that 
one must not imagine that the sulci called respectively 
arcuatus and rectus in a higher Ape correspond exactly to 
those similarly named in the Macaques and Capuchin 
Monkeys, even if it be admitted that the complex of the 
two sulci in the Anthropoid represents the two elements of 
the lower Apes. At the same time it often happens in 


the case of the Anthropoid Apes, and even in Man, that 


the exact forms of arcuate (inferior precentral) and straight 
(inferior frontal) sulci which occur in Macacus and Cebus 
may be developed. 

In the case under consideration, I am inclined to believe 
that the sulcus arcuatus has become deeper and longer at 
the expense of the sulcus rectus, which is a diminutive 
element (triradiate on the left, arcuate on the right side) 
in the position where the sulcus fronto-marginalis of 
Wernicke is found in the human brain. 

On the right hemisphere it is joined to the irregularly 
linear orbital sulcus, the posterior part of which is also 
linked to the fronto-orbital by a transverse sulcus. 

This somewhat lengthy digression has been introduced in 
order to render intelligible the status of a suleus which 
makes its appearance external to the anterior extremity of 
the sulcus rectus, to which it is obviously compensatory. 


 ? 


NERVOUS SYSTEM.—VERTEBRATA, 433 


It is the sulcus frontalis medius, and is seen in its primitive 
and typical form on the left hemisphere of Hylobates 
leucogenys (D. 646), and also on the left hemisphere of 
this Orang just above the triradriate sulcus, which, with a 
reservation, has been called “rectus.” Yet on the right 
hemisphere the function of this sulcus frontalis medius has 
obviously been taken partly by the sulcus frontalis inferior 
(rectus) and partly by the anterior end of the superior 
frontal. The extensive, deep, superior precentral and 
superior frontal sulci are united to form a triradiate pattern, 
and are arranged with quite diagrammatic simplicity. 

Between the superior frontal sulcus and the mesial edge 
there are two small shallow sulci, which can only represent 
a “sulcus frontalis mesialis,” which, so Cunningham 
believes, “ never occurs in the cerebral hemisphere of the 
Apes” (Mem. Roy. Irish Acad. 1892, p. 296). 

The parieto-occipital sulcus is very deeply and irregu- 
larly incised, and if its lips be separated (or even without 
doing so in the right hemisphere) the dual composition of 
the suleus (which was explained in the case of Papio) 
is rendered evident. The suleus has a much greater 
dersal extent (see especially the left hemisphere) than in 
any of the Cercopithecidee. The elongated arcus occipitalis 
is wholly exposed on the left hemisphere, so that it has the 
appearance of having pushed back the occipital operculum. 
On the right side, however, the posterior limb of the arcus 
is hidden under the operculum. 

In the right hemisphere there is an ideally complete 
intraparietal sulcus, with a very long ramus postcentralis 
superior and ramus occipitalis transversus, which is con- 
current with the Simian sulcus. There are in addition 
compensatory sulci parallel to and on both sides of the 
ramus horizontalis and in front of the ramus postcentralis 
inferior. 

On the left hemisphere, the intraparietal sulcus presents 
a condition such as often occurs in Man, but never (so far 
as I am aware) in lower Apes. The ramus postcentralis 
superior, and not the inferior, is joined to the ramus 
horizontalis. 


The upper end of the parallel sulcus forms a hook-like 


VOL. Il. a 


434 


PHYSIOLOGICAL SERIES. 


arch around the bifid Sylvian, such as sometimes happens 
in the Baboons. 

There is a very long and complete linear collateral 
sulcus. The calcarine sulcus is parallel to the parieto- 
occipital, and the two are separated throughout by an 
exposed gyrus. 

The inferior occipital suleus is very small, but the 
posterior element of the occipito-temporal sulcus is deepened 
and lengthened in compensation, and ends posteriorly in a 
horizontal sulcus below and parallel to the typical Y-shaped 
lateral occipital sulcus. On the left hemisphere there is a 
shallow compensatory sulcus both above and below the 
latter. 

The anterior separate portion of the occipito-temporal 
sulcus is parallel to the anterior half of the collateral, and 
is deepened at the expense of the inferior (middle) temporal 
sulcus, the anterior portion of which consequently dis- 
appears on the left side. The posterior part of the inferior 
(middle) temporal suleus is prolonged on to the tentorial 
surface between the anterior part of the occipito-temporal 
and inferior occipital sulci. On the mesial surface there 
are typical calloso-marginal and rostral sulci. 

The whole of the ventral surface of the brain-stem 
closely resembles that of a very small human brain. The 
optic and auditory nerves are, however, proportionately 
much larger than in Man. A very small area of the 
trapezium seems to be exposed just to the outer side of the 
sixth nerve. 

The floccular lobe presents a very marked contrast to 
that of the Gibbon and all the Cercopithecidee and Cebide. 
It is relatively very much smaller, and the shrinkage 
affects almost wholly the paraflocculus, which becomes 
reduced to very small proportions, so that none of its folia 
project to form a “ petrosal lobule.” In this specimen the 
paraflocculus is even so reduced as to be completely hidden 
under the flocculus, like the flocculi secundarii of Henle in 
the human brain. 

The enormous lateral expansion of the main mass of the 
cerebellum has resulted in the formation of an organ 
exactly like a small human cerebellum. 


O. C. 1338 Ha*® & Ha, 


NERVOUS SYSTEM.—VERTEBRATA. 435 


D. 649. The brain of a nearly adult female Orang-Outang (Simia 
satyrus) 

This excellent specimen admirably demonstrates the high 
vaulting and rotundity of the hemispheres and the great 
extent of the prominent orbital keel and consequent ex- 
cavation of the orbital surface. 

The floccular lobe of the cerebellum is distinctly larger 

than that of the last specimen; the difference in size 
appears to chiefly affect the paraflocculus, which is much 
the larger of the two lobules, and is also exposed, as in the 
lower Apes. 
_ On the right cerebral hemisphere there is a peculiar 
arrangement of the superior limiting sulcus of Reil, which 
seems to end in a T-piece so as to simulate the Y-shaped 
disposition of the anterior rami of the human Sylvian 
fissure. A short branch of the fronto-orbital sulcus affords 
a further indication of the closing-in of the anterior insular 
area, 

By its irregular mode of union with the oblique sulcus 
the arcuate contributes to the formation of a very irregular 
and asymmetrical pattern. The inferior frontal (“ rectus”) 
sulcus is simple and well-developed on each hemisphere. 

The upper frontal region is occupied by such an irregular 
group of scattered, disjointed sulci that it is impossible to 
say which are superior or middle frontal elements. 

There is a typical (Primate) intraparietal sulcus. The 
ramus postcentralis superior is separate on both sides: it 
is particularly well developed on the right side, but broken 
up into four irregular fragments on the left. 

The Sylvian fissure has a bifid extremity on both sides. 
But the hooked extremity of the parallel sulcus is not 
nearly so complete as in the last specimen. 

The broad plump arcus occipitalis is wholly exposed on 


both sides. 
The occipital operculum is now quite small. 


O. C, 1338 #. 
D. 650. The brain of an Orang-Outang (Simia satyrus). The 

left hemisphere has been detached. 
This specimen is especially interesting because all the 


sulci are gaping as a result of the treatment of the brain 
2¥F2 


436 


PHYSIOLOGICAL SERIES. 


during preservation. This enables us to see at a glance the 
real “eondition of the various sulci, and not merely the 
surface-pattern. 

The floccular lobes are very small, as in D. 648, and 
practically reduced to flocculus (sensu stricto), as in the 
human brain. On the mesial aspect of the right hemi- 
sphere the septum lucidum and fornix of the left side are 
displayed, and in that portion of the section just above the 
mammillary bodies is seen a white ascending streak, which 
is the mammillo-thalamic tract (Vieq d’Azyr’s). In the 
section of the crus the substantia nigra is clearly seen. On 
the mesial aspect of the left hemisphere, the head of the 
nucleus caudatus is seen bulging into the anterior cornu of 
the lateral ventricle. The gaping sulci afford an exceptional 
opportunity of studying the true relations of these im- 
portant features of the brain. : 

The submerged posterior part of the insula is visible, 
and its relation to the uncovered anterior part (which is 
partly mapped out by the fronto-orbital and superior 
limiting sulci) is clearly demonstrated. The relation of the 
inferior transverse suleus of Hberstaller to the Sylvian 
fissure is admirably shown. ; 

There is a simple and saitlg whadetatost grouping of the 
inferior precentral (arcuate), inferior frontal (‘ rectus”), 
superior precentral (vide right hemisphere), and superior 
and middle frontal sulci. 

There is a typical intraparietal sulcus. The occipital 
region is disposed as in the last specimen. The small 
inferior occipital sulcus is fused to the lower end of the 
Simian sulcus. But it is functionally represented by a 
deep occipito-temporal sulcus, the anterior end of which is 
joined to the posterior element of the inferior (middle) 
temporal series. 

The collateral sulcus is represented by two parallel 
furrows. 


D.651. The brain of an Orang-Outang (Siméa satyrus). The 


left hemisphere has been separated. 
The irregular pattern formed by the sulci in the left 
frontal area is essentially identical with that of specimen 


NERVOUS SYSTEM.—VERTEBRATA. 487 


_ D.649. That of the right side, however, probably gives the 
clue to the interpretation of all the other brains. A very 
well-developed inferior transverse sulcus appears to unite 
(superficially) the Sylvian fissure to a very extensive 
arcuate sulcus, which has now altogether dissociated itself 
from the suleus rectus, and has become so far extended 
mesially as to usurp the place of the anterior part of the 
superior frontal sulcus. The suleus rectus also is now 
represented by two irregularly branched sulci, the posterior 
of which is in other brains joined to the arcuate. 

The lower end of the fronto-orbital suleus bends back- 
ward into the Sylvian fissure in a peculiar manner on both 
hemispheres, and particularly so on the left side. 

The occipital operculum is much better developed in this 
than in most Orang’s brains, so as to almost completely 
cover the submerged arcus occipitalis (which has been 
exposed on the left hemisphere by drawing apart the lips 
of the Simian sulcus). 

The calcarine sulcus is unbranched. In the right hemi- 
sphere there is an extensive accessory calloso-marginal 
sulcus parallel to the main sulcus, below which it is placed. 

A small paraflocculus may be seen emerging at the outer 
side of the flocculus. ~ 


D. 652. The brain of an Orang-Outang (Sima satyrus). 

In spite of the large number of Orang’s brains in this 
Collection, this small and damaged specimen has been 
added because it exhibits some unusual features. 

The exposed part of the superior limiting (Marchand’s 
“opercular”’) sulcus is so diminutive that the anterior 
insular region is hardly more distinctly delimited than in 
the larger Cercopithecide. 

The left fronto-orbital sulcus is small, whereas the right 
is long and Y-shaped. 

There is an unusually complete superior frontal sulcus in 
both hemispheres. 

It is peculiar how frequent is the union of the inferior 
transverse ( diagonal,” according to Cunningham) and 
arcuate sulci on the right, and not on the left hemisphere. 
On the left hemisphere the sulci arcuatus and rectus are 


438 PHYSIOLOGICAL SERIES, 


quite independent of the great vertical sulcus (so peculiar 
to the.Orang), which I am inclined to regard as a separate 
posterior element of the “ rectus,” in spite of the fact that 
in most brains of Simia it is joined not to the straight but 
to the arcuate sulcus. 
The arcus occipitalis is wholly submerged on both sides. 
After studying a series of intermediate forms, I am 
persuaded to regard that sulcus, which we would unhesi- 
tatingly call “inferior occipital” if we compared this 
specimen directly with a Macaque’s brain, as the occipito- 
temporal, which has become so deepened at the expense of 
the inferior occipital, that the latter has become reduced to 
an altogether insignificant furrow. 
The shape of the corpus callosum and septum lucidum 
are most admirably demonstrated. 
Presented by Professor John Marshall, 


D. 653. The brain of a small Orang-Outang (Simia morio), 
The left hemisphere has been detached. 

In this alone of all the Orang-brains the posterior end of 
the Sylvian fissure is not bifurcated. Here again the 
arcuate suleus and posterior element of the “rectus” 
present that peculiar relationship, which seems to be so 
characteristic of the Orangs (compare D. 651 and D. 649). 
And in the right hemisphere again the arcuate sulcus is pro- 
longed into the position of the superior frontal, and is also 
superficially linked to the Sylvian fissure by the inferior 
transverse sulcus (Cunningham calls it “ diagonal ” in the 
case of the Orang ; Mem. Roy. Irish Acad. 1890, p. 294), 
as in the corresponding hemisphere of D. 651. 

The union of orbital and inferior frontal (rectus) sulci is 
again found here in both hemispheres. 

The calcarine sulcus is unbranched, as in Alonatia and 
Ateles, but some of the postcalcarine elements exist as 
independent sulci, 

The arcus occipitalis is wholly uncovered on the left, and 
almost completely hidden by the occipital operculum on the 
right hemisphere. 

Although the general appearance of the anterior insular 


NERVOUS SYSTEM.—VERTEBRATA. 439 


region presents very striking contrasts in this series of 


Orang-brains, close examination shows that its fundamental 
plan is identical in all. 


D. 654. Two casts of the cranial cavity of an Orang-Outang 
(Simia satyrus). 
Note the prominent orbital keel. 


D. 655. Two casts of the cranial cavity of a smaller Orang- 
Outang (Simia satyrus). 


_ D. 656. The left cerebral hemisphere of a Gorilla (Anthropo- 
pithecus gorilla) (figs. 246, 247, 250). O. C. 1338 rf. 


D. 657. The remainder of the left half of the same brain. 
O. C. 1338 rf. 
D. 658. The right half of the same brain (figs. 248, 249). 

This excellently preserved brain (obtained from a young 
male Gorilla some 38 lbs. in weight and 34 inches high) is 
probably by far the best specimen of its kind to be found 
anywhere. And, so far as the writer is aware, it has never 
been adequately described, although Kiikenthal and Ziehen 

. (who seem to imagine that “ T’roglodytes savagii”’ [the old 

legend on this specimen] is a Chimpanzee) and Beddard 
(Proc. Zool. Soc. 1899) have published brief notes con- 
cerning it. ) | 

The brain of the Gorilla is the largest found in any Ape, 
and (so far as this large collection of Anthropoid brains is 

- concerned) presents a much stronger resemblance to the 
human brain than does that of any other Ape. According 
to Keith, there is a very marked difference in the cranial 
capacity of the two sexes (Proc. Zool. Soc. 1899, p. 299). 

In general shape the brains of the three great Anthropoid 
Apes exhibit a strong resemblance. This is best shown by 
the casts of the cranial cavity. The hemispheres of the 
Orang present a more exaggerated oval outline, when 
viewed from above, than do those of either of the two 

_Anthropopitheci ; and of the latter the frontal regions of 


440 PHYSIOLOGICAL SERIES. 


the Gorilla are fuller and less Cercopithecoid than those 
of the Chimpanzee. On the whole the shape of the Gorilla’s 
brain approximates nearest to that of Man, whereas that 
of the Orang most resembles the lower .Ape-form. 

Each of the three types is provided with a prominent 
orbital keel, which is probably slightly more pronounced in 
the Orang’s brain than in that of the other genus *. 


‘Fig. 246. (x 3.) 


SULC. Sur FR.PAR, SULC. INTRAPAK. 


SULC. INF. ‘ ar 4 > y : J a a Ng o “ » 
eee AY a he “SA _L-suic ut oce 


SULC. INF, TRANS. _{/ 


SULC. FR. mace 


ae 


SULC. INF. OCC. 


sy, 
SULC. PAR, 


SULC. ORB.” 4 
4 


OLF.BULB. — SULC. SUB_LIM. 


As in the Orang and Chimpanzee, there is a very wide 
range of variation in the arrangement of the different parts 
of the brain, especially in those regions in which the human 
brain differs from the Simian f. 

Upon the base of the brain the posterior rhinal fissure is 
retained in its entirety with a diagrammatic clearness, 
which is rarely seen in Man (although I have often seen 


* In the literature of this subject many erroneous statements will be 
found in regard to this point. 

+ In order that the student should not draw erroneous conclusions as to 
the nature of the brain in the Anthropoid Apes from the examination of © 
solitary specimens, the Museum Committee has generously acceded to 
my request thut a valuable set of Anthropoid brains be purchased from 
the Zoological Gardens. Thus a series of specimens, which is probably 
unique in its completeness, is available for comparison. For it is the 
apparently fortuitous variations in the Anthropoid Apes which point the way 
or the possibility of human evolution, 


NERVOUS SYSTEM.—VERTEBRATA. 441 


it in the Soudanese races). In this way the demarcation 
between the neopallium and the pyriform lobe is as distinet 
as it is in the Cercopithecide and in the macrosmatic 
Mammalia. To the student of Human Anatomy, who 
is taught to unite this part of the pyriform lobe with 


Fig. 247. (x 3.) 


SULC. COMP. SULC. CALL. MARS. 


’ 
*¢ 
. 


SULC .COLL, 


PYR. L” i 
RHIN.F. 


Fig. 248. (x 2.) 


VENT. VERG., 


SEPT. LUCID. 


ANT. COMM. 


LAM. TERM. ---” i i - 
GANG.HAB, POST.COMM. 


i 
SOFT COMM. 


a strip of neopallium (and sometimes, also, with the uncus 
which is partly hippocampal) and call the heterogeneous 
collection “ uncinate gyrus,” or, even by the more confused 
designation, “hippocampal gyrus,” this specimen is par- 
ticularly instructive, because it resembles the human brain 


442 PHYSIOLOGICAL SERIES, 


so closely that he can see at a glance how far the rhinal 

fissure and the pyriform lobe extend (figs. 249 and 250). 

_ There is a deep vallecula Sylvii, which leads into the 
..» stem of the Sylvian fissure. The latter is clearly formed in 

this interesting specimen by the meeting of two definite 

opercula, temporai and orbital respectively, as in the human 

brain. As these opercula extend laterally they diverge 


Fig. 249. (x 2.) 


SULC. SUP. LIM. 
~, 


“= 


from one another so as to expose a small triangular de- 
pressed area of insula (fig. 250). In this specimen one can 
see at a glance that the fronto-orbital sulcus (the anterior lip 
of which is so markedly opercular) is really the anterior 
limiting sulcus of the insula. And the dorsal operculum 
is also so complete that the forward prolongation of the 
superior limiting (Marchand’s “ opercular ’’) sulcus appears 
to join the anterior limiting sulcus*. That this close 
resemblance to the human condition is not the rule in the 


* It is interesting to note that the superior limiting sulcus does not 
actually join the fronto-orbital even in this extreme case, the two sulci being 


separated by a submerged gyrus. Thus we cannot speak of anterior limbs 
of the Sylvian fissure in the Anthropoids, 


NERVOUS SYSTEM.—VERTEBRATA. 443 


Gorilla is shown by the other six hemispheres, in all of 
which the superior limiting sulcus is separated by an 
eaposed gyrus from the anterior limiting suleus; and 
neither sulcus possesses a markedly opercular lip. In six 
out of the eight hemispheres the mesial end of the fronto- 
orbital sulcus appears to join the stem of the Sylvian 
fissure ; in the other brain the orbital region is damaged, 
but probably its fronto-orbital sulci were always separated 
from the Sylvian. | ne 


Fig. 250. (x 2.) 


Gr SUEC. ORB, 


a SULC. FR.ORB. 
SUED, DEF: : 


Esute, occ. Teme. 


SUE. COLL, 


In contrast to the conditions found in the human brain, 
it is noteworthy that the fronto-orbital sulcus is very long. 

The orbital sulcus is seen on the right hemisphere in its 
primitive state as a long, deep, simple linear sulcus. It 
pursues a course parallel to the fronto-orbital sulcus. To 
its mesial side there is an unimportant secondary orbital 
sulcus, which is joined to the main sulcus on the left hemi- 
sphere, to form a triradiate sulcus such as is often found in 
the human brain. If a large. series of human brains be 
examined (because this sulcus is exceedingly variable), it 


444 


PHYSIOLOGICAL SERIES. 


will be found that the fundamental plan of the orbital 
suleus (which is that often called “ presylvian” in other 
mammals) is that exhibited on the right hemisphere of 
this Gorilla’s brain. In the other three Gorilla-brains, 
different variants of this plan of orbital are exhibited. 

_ The peculiar bifurcation of the termination of the Sylvian 
fissure, which is such a constant feature of the Orang’s 
brain, is very poorly developed on the right hemisphere of 
this, and even less distinctly in the two hemispheres of 
specimen D. 659. The central sulcus exhibits a very 
distinct genu. 

On the right hemisphere there is a typical primitive 
sulcus arcuatus (inferior precentral) such as the Apes 
exhibit. There is a long bow-shaped sulcus rectus, which 
joins the mesial accessory-orbital sulcus in front. A short 
branch of the “ straight” suleus passes between the dorsal 
ends of the orbital and fronto-orbital sulci. On the left 
hemisphere, the oblique upper limb of the arcuate seems 
considerably curtailed and its lower end passes (super- 
ficially) into the central sulcus. Moreover, the upper part 
of the sulcus is linked by a short deep branch to the sulcus 
rectus. If the reader compares this specimen with those 
of the Orang and notes the relations of the sulci to the 
fronto-orbital sulcus, he cannot fail to understand why the 
anterior limb of that peculiar H-shaped frontal system of 
furrows, which is so characteristic of the Orang, was called 
(in these notes) the posterior part of the “ sulcus rectus ” 
(the inferior frontal of Human Anatomy). On the left 
hemisphere a small cephalic element of the “ rectus ”’ series 
has become separated to form a fronto-marginal sulcus of 
Wernicke. In both hemispheres, the superior precentral 
and superior frontal sulci are arranged with a simplicity 
and regularity which is quite diagrammatic. 

On the left hemisphere there is a short “sulcus frontalis 
medius,” placed very far forward between the anterior 
ends of the superior and inferior frontal sulci. On the 
right hemisphere there is a short, almost coronal suleus in 
the same region. 

When we recall how constant in the Orang’s brain is the 
presence of an inferior transverse sulcus (superficially) 


NERVOUS SYSTEM.—VERTEBRATA. 445 


joined to the Sylvian sulcus, it is worthy of note that it is 
absent, at any rate as a separate element, in all the eight 
hemispheres of the Gorilla. There is a small diagonal 
sulcus of Eberstaller on both hemispheres, and the lower 
end of the central (Rolando’s) sulcus is curved forward 
into such a position that it would relieve the tension of the 
expanding cortex which expends itself in the Orang in the 
formation of the inferior transverse sulcus. 

The parallel sulcus is prolonged into a very extensive 
hook around the end of the Sylvian fissure on the left 
hemisphere. On the right hemisphere the recurved portion 
of the “hook” is a separate triradiate sulcus. The deep, 
richly-branched intraparietal sulcus extends around these 
sulci. Its lower extemity is linked (superficially) to the 
Sylvian fissure by a deep, oblique sulcus, the free end of 
which extends towards and seems to accentuate. the bend in 


the central sulcus. The very irregular and unsymmetrical 


ramus postcentralis superior is not joined to the intra- 
parietal ; but the latter gives off deep branches (two on the 
right and one on the left side) alongside the chief element 
of the ramus. Posteriorly the intraparietal suleus dips 
into the Simian sulcus (Affenspalte) and is hidden under 
the occipital operculum. The apparent bifid mesial ex- 
tremity of the Affenspalte may represent the transverse 
occipital sulcus. 

The arcus occipitalis is very large and wholly exposed, 
the mesial end of the occipital operculum having been 
pushed completely outward and backward. 

There is a typical, obliquely placed, Y-shaped lateral 
occipital sulcus in all eight hemispheres. 

The occipital operculum is bounded by an almost hemi- 
spherical Affenspalte, both the superior (mesial) and 
inferior (lateral) extremities of which are about 1 cm. 
distant from the dorso-mesial and tentorial borders 
respectively. 

The calcarine sulcus (of the left hemishere, in which 
alone it is wholly exposed) is an unbranched furrow of 
which the anterior half (calcarine sensu stricto) is much 
deeper than the posterior half (retrocalcarine). The caudal 
extremity of the latter bends almost at right angles and 


PHYSIOLOGICAL SERIES. 


ends near the inferior limb of the Y-shaped lateral occipital _ 
suleus.- 

At the bend of the retrocalearine a second postealcarine 
sulcus appears to emerge from the former and then run 
parallel to and on the dorsal side of it. It is separated 
from the ventral postcalearine by a gyrus which is sub- 
merged at its anterior end. The dorsal postcalcarine sulcus 
is much shallower and more widely separated from the 
ealearine complex on the right side. 

The parieto-occipital sulens is a deep and well-defined -— 
sulcus on the right hemisphere, and there are also several 
small accessory sulci. On the left hemisphere the sulcus is 
represented by three sulci of varying depths. The meaning 
of these separate sulei will be best appreciated if the 
reader refers to the account of the Baboon’s brain. There 
is, first, a deep irregular notch in the upper margin of the 
hemisphere, which represents the sulcus distinguished as 
the ramus parieto-occipitalis (sulci intraparietalis) in the 
larger Cercopithecide. There is a very deep sulcus on 
the mesial surface, which begins above in front of the | 
last-described element and ends near and parallel to the __ 
ealcarine sulcus, to which it is joined by a shallow connecting __ 
furrow. Then there is a third shallower furrow making (on 
the surface) a Y-shaped pattern with the last. The two 
limbs of the Y¥ are separated from the first (“ramus _par.- 
occ. s. intrap.”) element by a plump arcuate gyrus. If the 
other Gorilla-brains be examined, further variations of 
the calcarine and parieto-occipital systems will be found. 
Thus in specimen D. 659 the calcarine complex is T-shaped 
in both hemispheres ; in specimen D. 660 the calcarine 
and retrocalcarine unite at an obtuse angle and small 
compensatory sulci surround the latter. All this shows 
that the true calcarine (Cunningham’s “anterior calcarine ’’) 
is the only stable element in the calearine series and the 
retrocalearine (Cunningham’s “ posterior calcarine ”’) series 
is extremely variable, although the chief suleus is always 
concurrent with the calcarine. 

The parieto-occipital series, being essentially of the 
nature of compensatory sulci, is even more variable. In 
specimen D. 659 the state of affairs is essentially identical 


NERVOUS SYSTEM.—VERTEBRATA. 447 


with the left hemisphere of this individual (D. 656), but the 
sulcus around which the partially submerged arcus occipitalis 
is arranged seems to join the posterior limb of the Y-shaped 
arrangement of the other two elements; and a branch of 
the intraparietal cuts into and thereby complicates the 
arcus occipitalis. In D. 660 there seems to be a long, simple, 
vertical, parieto-occipital sulcus cutting deeply and trans- 
versely into the hemisphere: its dorsal limb is surrounded 
by a broad extensive simple arcus occipitalis. A peculiar 
sulcus, however, emerges from the dorsal part of the 
parieto-occipital sulcus and pursues a sagittal course 
backward. 

There is on the left hemisphere of this individual (D. 656) 
a simple collateral sulcus, beginning below the bend in the 
postcalearine, from which it is separated by a partially 
submerged gyrus, and ending immediately below the 
anterior end of the calcarine. It is linked to the posterior 
element of the occipito-temporal sulcus, which is very 
deep. It crosses on to the external surface and fulfils the 
function of the inferior occipital sulcus of other Apes. Its 
anterior segment is separate and deepened at the expense 
of the inferior occipital. There is a very complete calloso- 
marginal sulcus. But it is peculiar that in all these 
hemispheres of the Gorilla the sulcus is prolonged much 
further back than the neighbourhood of the upper end of 
the central sulcus (where it usually ends in the human 
brain). The sulcus, however, which represents its caudal 
part in the human subject, has all the appearance in the left 
hemisphere (also in the right hemisphere of specimen D. 660 
and in both sides in D. 659) of being merely a vertical 
branch of the sulcus and in the right hemisphere is quite 
separate from it. 

In the left hemisphere of specimen D. 660 the manner in 
which these variations are brought into line with the 
human condition is shown. The form of the “compen- 
satory” (Broca’s “ postlimbic”) varies with the form of 
the calloso-marginal. It is best developed as a large 
triradiate figure in the right hemisphere of this specimen. 

This brain affords an admirable demonstration of the 
mesial structures—corpus callosum, fornix, septum lucidum, 


448 


' PHYSIOLOGICAL SERIES. 


anterior commissure, lamina terminalis, and the large optic 
chiasma. The anterior commissure is slightly larger than 
in the human brain and the optic tracts are considerably 
greater. 

It is of interest to note the presence of a large ventricle 
of Verga under the posterior part of the corpus callosum— 
an anomaly occasionally found in the human brain. 

The other structures exposed in the mesial section closely 
resemble the corresponding features of the human brain. 
They are here shown exceptionally clearly. Note especially 


- the foramen of Monro, the soft commissure, the ganglion 


habenule, the posterior commissure, the smooth lateral 
wall of the third ventricle, the optic recess, the remains of 
the embryonic optic diverticulum just above the optic 
chiasma, the aqueduct of Sylvius and the fourth veniricie, 
[The description of all these structures found in text-books 
of Human Anatomy applies equally here. | 

The cerebellum has now assumed a close likeness to tlie 
human organ. The floccular lobe, however, is still larger 
than it is in most human brains, although it is subject to 
extreme variation in Man as in the Anthropoid Apes. The 
floccular lobe, which is best seen on the left side, is com- 
posed of two distinct lobules each attached by its own 
stalk. Of these, the mesial is much the larger and plumper 
of the two and is composed of three separate groups of 
folia (three or four in each group), the separate stalks 
of which unite into a common peduncle. The lateral 
lobule is much smaller and is almost hidden by the mesial 


lobule.. Two or three of its folia may, however, be seen 


emerging in the great horizontal fissure external to the 


- mesial lobule. 


There can be no doubt that the lateral lobule represents 
the floceuli secundarii of Man, and these may correspond 
to the paraflocculus (although much fuller developmental 

evidence than Stroud [Journ, Comp, Neur. 1895] adduces 
is necessary to prove the identity). 

In appearance the other parts of the brain exposed 
in these specimens closely resemble the corresponding 
regions in the human brain. The olivary body is now in 
contact with the lower border. of the pons. To the naked 


NERVOUS SYSTEM.—VERTEBRATA. 449 


eye no trapezoid body is apparent, although it seems to be 
partially exposed in specimen D. 661 (left side), 

The mesial geniculate body seems to be much more 
prominent than it is in Man—a prominence possibly 
associated with the larger size of the auditory nerve. 

Beddard (Proc.: Zool. Soc. 1899, p. 65), in a memoir 
based upon these four specimens and one other, gives a 
list of the literature of the Gorilla-brain. His figures 1, 2 
and 4 represent this specimen. 

[In drawing up a comparison between the brains of the 
Chimpanzee and Gorilla, Kiikenthal and Ziehen place this 
specimen (formerly labelled “ Troglodytes savagii”) among 
the Chimpanzees, and state that they have had no oppor- 
tunity of studying the brain of a Gorilla! Jenaische 
Zeitschr. f. Naturwiss., Bd. xxix. 1894.] 0. C. 1338 re. 


D. 659. The brain of a Gorilla (Anthropopithecus gorilla), sub- 
divided by a mesial sagittal section. 

In this brain we find the usual Anthropoid arrangement 
of the anterior insular region, instead of the more human 
disposition presented by the preceding specimen. The 
superior limiting (Marchand’s “opercular’’) sulcus emerges 
from the Sylvian fissure and approaches without even 
appearing to join the long fronto-orbital (anterior limiting) 
sulcus. Nor are the lips of these sulci opercular as in that 
specimen. In other words, the condition found in this 
specimen is that which is usual in the three great Anthro- 
poids. Unlike the arrangement in the last specimen, the 
sulci arcuatus and rectus are here blended to form a single 
sulcus, as in the Gibbons. ‘The superior frontal and 
superior precentral sulci resemble those of the previous 
specimen, except that they are less regular. There are also 
a few small furrows which can only represent the sulcus 
frontalis mesialis, which Cunningham regards as dis- 
tinctively human. : 

The parallel sulcus resembles that of the last specimen, 
as also does the intraparietal excepting the fusion with its 
ramus postcentralis superior on the left side. 

The mesial portion of the Simian sulcus seems to have 
been pushed backward into a peculiar ag 2 by the 

G 


VOL. I. 


450 PHYSIOLOGICAL SERIES. 


expanding arcus occipitalis, which is still partially sub- 
merged. 
In this brain there seems to be a definite inferior 
occipital suleus which is joined to the parallel sulcus, 
There is no ventricle of Verga in this specimen. 
Beddard, Proc. Zool. Soc. 1899, p. 71, fig. 5. 


D. 660. The brain of a Gorilla, cut in mesial sagittal section. 

The condition of the insular region in this is essentially 
the same as in the preceding specimen. But more of the 
insula and much more of the superior limiting sulcus are 
exposed. Nor does the mesial extremity of the fronto- 
orbital (anterior limiting) suleus become hidden by the 
temporal pole, so that the insula can be seen passing into 
continuity with the locus perforatus. The superior limiting 
sulcus gives off a deep, short branch cutting into the 
insula on each hemisphere. 

The two great T-shaped complexes of inferior precentral 
and inferior frontal sulci and superior precentral and 
superior frontal sulci respectively are disposed with dia- 
grammatic simplicity, especially on the right hemisphere. 

The other sulci of this brain agree in arrangement with 
those of the last specimen. The intraparietal sulcus, how- 
ever, is joined to its ramus postcentralis superior on both 
sides ; and a series of compensatory intraparietal sulci are 
found which are not exactly comparable to those of the 
other brains. 

Beddard, op. cit. p. 73, fig. 7. 


D. 661. The brain of a Gorilla ( Anthropopithecus gorilla). 

The insular region resembles that of specimen D. 659. 

The inferior precentral and inferior frontal sulci are 
fused. The superior frontal sulcus is subdivided into two 
parts of which the posterior is joined to the superior pre- 
central and also (on the right side) to the inferior frontal. 

The intraparietal sulcus resembles that of the last 
specimen. 

In the foregoing accounts it was suggested that there 
was some reason to regard the lateral sulcus of Carnivores 
as the intraparietal, the ansate as its ramus postcentralis 


NERVOUS SYSTEM.—VERTEBRATA, 451 


superior, and the crucial as the repr i 
central (Rolando’s) sulcus. Such ‘eriaaptoaaat it ‘i me 
altogether surprising to find in two mammals which 
possess brains of approximately the same size althou h 
they have diverged so widely as the Bear and the Gorilla, 
that this central region of the hemispheres has retained 
some resemblance, even though the frontal and occipital 
poles have become so vastly altered. Even if it be vari 
fortuitous, there can be no question of the essential identity 
of the chief features of these regions say in eae 
D. 365 (Bear) and this Gorilla’s brain. Even the peculiar 
curves of the crucial (central) sulcus and its relations to 
the precrucial (precentral), to the ansate (ramus post~ 
centralis) and lateral (intraparietal) are curiously reproduced 
in each hemisphere. | 

The paraflocculi are equal to the flocculi in size and are 
freely exposed. 

Beddard, op. cit. p. 72, fig. 6. 


D. 662. Two casts of the cranial cavity of a young Gorilla 
(Anthropopithecus gorilla). 


D. 663. Two casts of the cranial cavity of an adult Gorilla 
(Anthropopithecus gorilla). 

These are of interest as showing the exact shape and 

especially the degree of rostration of the cerebral hemi- 


spheres. 


D. 664. The brain of a Chimpanzee (Anthropopithecus troglo- 
dytes), (3). 

Apart from the difference in size there is little to dis- 
tinguish the brain of the Chimpanzee from that of the 
Gorilla. If, however, the four specimens of Gorilla-brains 
in this Collection be compared with the ten specimens of 
Chimpanzee-brains, it will be noticed that the Simian cleft 
or Affenspalte is much more complete and Cercopithecoid 
in the Chimpanzee than it is in the Gorilla. At the same 
time, one must not hastily conclude that the Gorilla’s brain 
is therefore more like the human than is that of the Chim- 


_ panzee, for, as specimens D. 666 & D. 667 show, the brain 
242 


452 


PHYSIOLOGICAL SERIES. 


of the latter may resemble that of Man quite as closely 
as any Gorilla-brain. Those most competent to express an 
opinion, regard the Chimpanzee as the nearest relative of 
Man. Still the fact remains that the series of Gorilla- 
brains in this Collection is certainly nearer the human type 
than is the series of Chimpanzee-brains. 

I have so far referred only to the region of the “ Affen- 
spalte,” because in all other parts there seems to be a close 
agreement in the brains of the two species. 

The insular region is just as variable as it is in the other 
Anthropoids. In the left hemisphere of this specimen, we 
find the simple short exposed superior limiting sulcus, 
approaching the fronto-orbital just as it does in the Gibbon. 
On the left hemisphere, however, the exposed part of the 
superior limiting suleus is much longer (so that at a casual 
glance it seems to join the fronto-orbital suleus) and its 
upper lip is markedly opercular. 

The right inferior precentral sulcus is very long and 
approaches very close to the caudal end of the superior 
frontal, and, to a great extent, usurps the place of the 
superior precentral which is represented merely by the 
short bifid caudal process of the superior frontal sulcus. 
The long typical inferior frontal sulcus is joined to the 
inferior precentral. 

On the left side, the inferior precentral is joined to the 
ventral extremity of the central (Rolando’s) sulcus. The 
inferior frontal is not so long as on the right side, the 
cephalic extremity being separated as a fronto-marginal 
sulcus of Wernicke. Thus we have a curious reproduction 
of what we may call the “Orang condition,” such as we 
have also seen in the left hemisphere of a Gorilla-brain 
(D. 656). The middle frontal gyrus is broken up by 
irregularly-placed sulci, but none of these can be strictly 
called the middle frontal sulcus. 

- Behind the sinuous central sulcus there is a typical 
intraparietal complex, all the four constituent parts of 
which are united. It passes posteriorly under cover of a 
much more complete occipital operculum than any of the 
eight Gorilla-hemispheres presents, and then joins the 


NERVOUS SYSTEM.—VERTEBRATA, 453 


_ transverse occipital sulcus which (as the right side, in 
which the operculum has been cut away, shows) does not 
exactly coincide with the bottom of the Simian cleft 
(“ Affenspalte ”’), 

A comparison of the dissected and the undissected halves 
of this specimen shows how extensive an operculum is 
present, and how complete the Simian sulcus is in this 
Chimpanzee. In marked contrast to the condition found 
in the Gorilla, the dorsal part of the parieto-occipital suleus 


is altogether covered by the operculum (see the right 
side). 


Fig. 251. <x 3.) 


cut £o6e 
(OPERC) 


SULC , TRANS.OCC. 


i, 
SULC. PAR. OCS 


The parallel sulcus is partially hooked around the bifid 
extremity of the Sylvian fissure on the right side, but not 
so completely on the left hemisphere. 

The posterior element of the inferior temporal sulcus is 
prolonged backward into a very deep sulcus skirting the 
ventral border of the occipital region. A similar disposition 
is found in the Gorilla. 

The area lying behind the ‘ Affenspalte”’ seems to be 
much poorer in sulci than is that of the Gorilla. The 
lateral occipital sulcus has lost the typical Y-shape, and is 
an irregularly arcuate shallow sulcus. 


454 PHYSIOLOGICAL SERIES. 


The lateral lobule of the floceular lobe (7. e. the para- 
flocculu8) is quite as large as the flocculus and is wholly 
exposed. O. C. 1338 re. 


Benham, Quart. Journ. Mier, Sci., vol. xxxvii. p. 47. 


D. 665. The left cerebral hemisphere and the rest of the brain 
of a Chimpanzee (Anthropopithecus troglodytes), ( 2). 

The anterior insular region conforms to the usual An- 
thropoid type. 

There is a well-marked inferior transverse suleus such 
as always occurs in the Orang, but rarely in the Gorilla. 

There is a typically united, triradiate complex of sulci 
rectus and arcuatus; but it is difficult to say whether the 
upper part of the precentral limb (which is separate and 
H-shaped on the right side, but linear and concurrent on 
the left) ought to be regarded as part of the superior or 
inferior precentral. 

Again, there is an extensive occipital operculum hiding 
the arcus occipitalis and the parieto-occipital sulcus. The 
Affenspalte extends as far as the mesial edge. Unlike the 
condition found in the last specimen, there is a typical 
deep, Y-shaped lateral occipital sulcus. 

There is a very deep and long inferior occipital sulcus, 
but it is questionable whether it can be homologised with 
the suleus so-called in the Cercopithecide or with the 
occipito-temporal sulcus. There is an unusually well- 
developed inferior (middle) temporal sulcus. 

The calearine complex presents the typical T-shaped 
“tail-piece.” If the lips of the sulcus be separated, a 
submerged gyrus will be found at about its mid-point 
imperfectly separating the calcarine and retrocalcarine 
elements, as in the human brain. 

In the left hemisphere the parieto-occipital sulcus is 
represented by the two distinct sulci (hidden in one great 
furrow) such as we have seen in the Baboons. But in the 
right hemisphere, the functions of a parieto-occipital sulcus 
are only partially fulfilled by the wholly mesial sulcal 
complex of that name; for a deep cleft, formed by an 
irregular apical branch of the intraparietal sulcus, buried 
deeply in the unusually extensive mesial prolongation of 


—_— 


a ee Ne ee eee me ae 


D. 6 


NERVOUS SYSTEM.—VERTEBRATA. 455 


the Simian sulcus is chiefly instrumental in accommodating 
the expanding cortex in this region. This Cercopithecoid 
arrangement affords a striking contrast to the condition - 
found in the Gorilla and in Man. There is a typical 
calloso-marginal sulcus. 

The floceular lobe seems to conform to the usual human 
pattern. It is composed of a plump oval mass of folia 
which completely hides the flattened diminutive para- 
flocculus. O. C. 18388 1a; 1338 1a*. 


66. The brain of a Chimpanzee (Anthropopithecus troglo- 
dytes), which has been subdivided by a mesial sagittal 
section. The arteries have been injected. 

In this specimen the anterior insular area is depressed 
and the limiting sulci almost meet. It is of interest to 
note that the relations of branches of the middle cerebral 
artery to this insula and its diminutive opercula are iden- 
tical with those in the human brain. 

A short sulcus proceeding backward from the fronto- 
orbital toward the superior limiting sulcus is of interest 
as an indication of the expansion of the cortex in this 
region, which leads to such marked results in the human 
brain. 

There is a remarkably close agreement between the 
features of these cerebral hemispheres and those of D. 664. 

The structures cut in the mesial sagittal section are 
exceedingly clearly shown. They closely resemble the 
corresponding human structures. 

The inferior transverse sulcus is present in a different 
form in the two hemispheres. In the left hemisphere 
there is a complete precentral sulcus. Further evidence 
of the variability of the calcarine and parieto-occipital 
sulci is afforded by this specimen, but the variations are 
not new, parallel instances having been described in the 


Gorilla and Orang (vide supra). 


D. 667. The brain of a Chimpanzee (Anthropopithecus troglo- 


dytes). 
This somewhat imperfectly-preserved specimen 18 Fe- 
tained in the Museum because it exhibits a very interesting 


456 PHYSIOLOGICAL SERIES. 


and rare condition of the insular region. The sup 
limiting sulcus (on both sides) passes forward and actu 
joins the fronto-orbital sulcus so as to completely map 
the anterior insular region. . It is the normal state in M 
In the left hemisphere the superior and inferior p 
central sulci are confluent. O. C. 138 
Presented by W. E. 


D. 668, The brain of a young female Chimpanzee (A: 
pithecus troglodytes). 
The left cerebral hemisphere has been separated. a 
This is a small and in some respects simple brain. — 
the right hemisphere the insular region eon 
simplest and most primitive Anthropoid type, 7. ¢. the li 


of the superior limiting and the fronto-orbital sulci are z% 


opercular and the sulci are widely separated. On the lef 
hemisphere, the sulci approach so close that they a 
meet (at a casual glance they appear to join) ; and there is 
a faintly marked tendency to operculation. 

The extent of the occipital operculum and the ereedonitl 
of the exposed surface of the occipital area from any other — 
sulci except the plain linear inferior occipital, are quite 
Cercopithecoid characteristics. On the left hemisphere — 


= the oe Ye 


the occipital operculum has been cut away, and the wide 
separation of the transverse occipital sulcus from the — 
bottom of the “ Affenspalte” is thus demonstrated in a — 
much more decisive fashion than is the case in D. 664, — 
In this brain the parieto-occipital series is represented 
by the parieto-occipital sulcus proper, a shallow suleus — 
behind it, and especially by the deep mesial limb of the — 


transversal occipital sulcus. 


In front of the tortuous central sulcus there are typical 4 


superior and inferior precentral sulci. The latter is fused — 
to the inferior frontal sulcus, which (in the right hemi- 
sphere) gives off a peculiar mesial transverse branch. A 
sulcus frontalis medius is (superficially) joined both to this 
sulcus and also to the inferior precentral. O. C. 1338 1d, 


D. 669. The brain of a Chimpanzee (Anthropopithecus troglo- 
dytes). 
This specimen is of interest as a demonstration of the 


— oe ae eh hcehlUreelhlCUmclhlC(i<CiStC<‘<‘ 


a 


“fi 


a 
:. 
oo te : 
i 
~ ae 


a 
“<= 
jt oa 


to conform essentially to the most primitive Aattivssnysh tops 


NERVOUS SYSTEM —-VEWPERRATA, Wye 


manner in which the three great Anthropoid typenst baw 


_ merge indefinitely one into the other, 


If the insular region be carefully studied, it wi be hound 
already defined. But the unusual direction ff the eupetior 


| limiting sulcus gives the insula the ill-dehned appeonanas 


which is sometimes seen in the Orang’s brain, 
Then again, although the occipital operceulans ie beter 


developed than it is in most Gorillas and Orange, @ dows 
signs of retrogression in comparison with the other ntew- 


panzee’s brains ; and as this involves the mesial ond of Ge 


g operculum a condition not unlike the meuch mone gro- 


nounced dwindling in the Gorilla’s brain ie grodwoxt. 
Still the institution of this comparison tende rather t 
emphasize the primitive Cercopithecoid festarcs & Ge 
occipital operculum as being a most decisive Chacactetintac 
of the Chimpanzee among the Anthropoide, or 2 least iw 
the two species of Anthropopitheci. 

Note the large size of the lobule, which appears to be 
the paraflocculus. 


D670. The brain of a Chimpanzee ( Anthropopitherns 


. 


‘ 
a4 


This small and simply convolated brain is retained chicthy 
because it exhibits another interesting arrangement of the 
TP : 


of the fronte-crtiial eheus ie 
oblique, and the branch pgs 
st and the ior Vinmiting suleme 
between ee 2 dean dems irn 


458 


PHYSIQLOGICAL SERIES. 


divided into flocculus and paraflocculus in such a manner 
that the former completely overlaps the latter, although in 
this case the two lobules are of approximately the same 
size. O. C. 1338 18. 


D. 671. The brain of a Chimpanzee (Anthropopithecus troglo- 


dutes). 

In spite of the fact that this excellently preserved spe- 
cimen has been badly injured by saw-cuts in the occipital 
region, it has been mounted because of the interest attach- 
ing to its insular and occipital regions. 

The remarks made concerning the insule of the last 
specimen apply to the corresponding regions of the two 
respective hemispheres of this specimen. But the chief 
interest here is the instructive demonstration of opercular 
formation. The dorsal operculum of the anterior insular 
area is being formed in spite of the fact that the superior 
limiting sulcus is incomplete. This is especially well 
shown on the left side. 

The marked dwindling of the mesial extremity of the 
occipital operculum forms a most pronounced contrast to 
the condition met with in all the other Chimpanzee’s 
brains in this Collection. It shows that we cannot rely in 
every case upon this character to distinguish a Chimpanzee 
from a Gorilla or even an Orang (¢/r. specimen D. 649). 

The floceular lobe is very interesting. The paraflocculus 
and floceulus being clearly distinguished not only by 
position but also by shape in a manner quite unusual in 
the Anthropoid Apes. Presented by Prof. J. Marshall. 


D. 672. The brain of a Chimpanzee (Anthropopithecus troglo- 


dytes). 

A considerable part of the right cerebral hemisphere has 
been removed by dissection in order to expose the whole 
insula ; and the left hemisphere has been cut horizontally 
in order to show the relationship of the insula to the 
claustrum and the lenticular nucleus. This section has 
been made in order that it may be compared with specimen 
D. 728, which is a corresponding section of the human 
brain. 


4 

Ps 
~ 
a 
ae 


NERVOUS SYSTEM.—VERTEBRATA. 459 


A similar section was made by Prof. D. J. Cunningham 
to show that the anterior exposed part of the insula in the 


Figs. 252. (x 3.) 


1 (HIDDEN PART) 


“ 
INS. (EXPOSED PART)  SULC. ORB. 


Anthropoid Apes presents the same relation to the claus- 
trum and lenticular nucleus as the human insula does. 
D. J. Cunningham, Journ. of Anat. & Phys., vol. xxxii, 
1898, p. 11. : 


D. 673. T'wo casts of the cranial cavity of a Chimpanzee (Anthyo- 
popithecus troglodytes). 


D. 674. Two casts of the cranial cavity of a smaller Chimpanzee 
(Anthropopithecus troglodytes). 


Family Hominip.2z. 


D. 675. The brain of an early human foetus (about 2 months ?) in 
situ in the head, showing the post-mortem wrinkling of the 
thin neopallium, which is generally regarded (probably 
erroneously) as a system of “transitory fissures.” 

The roof of the right hemisphere has been removed 
so that the corpus striatum can be seen in the lateral 
ventricle. 

The corpora quadrigemina are exposed. 


460 : PHYSIOLOGICAL SERIES. 


The cerebellum exhibits an interesting phase, for. it 
consists of two primitive laterally placed rudiments united 
across the middle line by a narrow bridge. 

[Wax models of this and the following five specimens 
are in Guy’s Hospital Museum. | O. C. 1341 A. 

Presented by John Hilton, Esq. 

Hochstetter, Bibliotheca Medica A: Heft 2, 1898. 


D. 676. The whole central nervous system of a human totus; 
somewhat older than the last specimen. 

The brain is partially divided by a mesial sagittal 
section. 

The pyriform lobe is recognisable as an acutely-bent 
band fringing the locus perforatus anticus, ending pos- 
teriorly in a swollen extremity on the temporal pole. 

External to it we see a slight depression on the lateral _ 
wall of the hemisphere, representing the fossa Sylvii, the 
dorsal limit of which is marked by a faint furrow—the 
superior limiting sulcus (suprasylvian sulcus of other 
mammals). 

On the mesial surface of each hemisphere there is a deep 
irregular furrow resulting from post-mortem softening of 
the thin-walled hemisphere, and its consequent collapse. 
This was until recently supposed to be a real suleus— 
sulcus arcuatus (“ Bogenfurche” of German writers), 
but Hochstetter has recently shown it to be a post-mortem 
change. 

Note that the cerebellar bridge is broader than in the last 
specimen, but that the lateral masses are still much plumper 
than the mesial bridge. O. C. 1341 B. 

Presented by John Hilton, Esq. 

Gustav Retzius, “ Das Menschenhirn,” 1896. 


. 
| 
| 
. 


a een 


D. 677. The body of a human foetus (older than last specimen) , 
dissected to show the whole central nervous system in situ. 
The fossa Sylvii is now much deeper and its superior and © 
inferior limiting sulci quite definite. 
On the mesial wall of the hemisphere the calearine 
sulcus has now made its appearance. 


NERVOUS SYSTEM.—VERTEBRATA, 461 


The cerebellar bridge is now complete and two fissures 
| 3 (in addition to the limiting fissure of the floccular lobe) 
have now developed. They are the primary fissure (usually 
called “ preclival”) and the secondary fissure (usually 
called “ prepyramidal ”’). 

In the spinal cord the cervical and lumbar enlargements 
: are now apparent. O. C. 1341 ¢. 
2 Presented by John Hilton, Esq. 


So ARETE MS onta 


D. 678. A human fotal brain (of about the same age as the last 
. specimen) lying in situ in the head. A great part of the 
: lateral wall of the left hemisphere has been removed so as 
to show the corpus striatum, hippocampus and choroid 
plexus in the lateral ventricle. It also shows the relation 
of the fossa Sylvii to the corpus striatum. 

Most of the ridges on the mesial wall are the obverse of 
those post-mortem puckerings called “ transitory fissures.” 
The most caudal of them, however, is not of this nature 
but is the calear avis produced by the calcarine sulcus. 
Roe] O. C. 1341 p. 
Presented by John Hilton, Esq. 


a i | “s 


D. 679. The central nervous system of a slightly older human 
embryo, dissected to show the lateral ventricles. 
On the right side the whole of the hippocampus is 
exposed, whereas on the left side it is hidden by the 
i choroid plexus. 
The calcarine sulcus is well shown on the left side. 
On the base of the hemisphere note the acutely flexed 
pyriform lobe. 
The cerebellum is now rich in fissures in the mesial 
region, but only a few of them have yet extended laterally. 
O. C. 1341 £. 
Presented by John Hilton, Esq. 


D. 680. The brain of a later human fotus. The left hemisphere 


has been separated. 
The posterior part of the Sylvian fissure 1s now taking 
form. The superior limiting sulcus of Reil can be dis- 


-_tinctly seen. 


462 PHYSIOLOGICAL SERIES. 


The form of calcarine sulcus is somewhat unusual, for it 
appears to be prolonged into an extraordinarily precocious 
parieto-occipital sulcus. 

The cerebellum is now well-fissured. 0. C. 1341 2. Se 

Presented by John Hilton, Esq. 


D. 681. The right hemisphere of the brain of a seven months’ 
female foetus, hardened in chromic acid. 

On the mesial surface of this hemisphere the vestiges of the 
supra-callosal hippocampus (vide account of Marsupial 
brain) are very clearly seen in the callosal sulcus, especially 
near the splenium of the corpus callosum. The calcarine  __ 
and parieto-occipital sulci appear to be united to form a | 


Fig. 258. (x 2.) 


SULC. CENT, 


SULC, INTRAPAR, 


Y-shaped figure ; but, as we have seen in the Apes, so also 
in the developing human brain the parieto-occipital sulcus 
is usually quite independent of and altogether subsidiary to 
the calcarine sulcus. The retrocalearine suleus—the cross 
of the T—is widely separated from the calcarine. The 
collateral sulcus is represented by very faintly-marked 
depressions, but the occipito-temporal suleus is present as 
two deep sulci. The calloso-marginal and rostral sulci are — 
~ well developed. 

The orbital sulcus is fully formed. 

The Sylvian fissure is in an interesting stage of develop- 
ment. The fronto-parietal, temporal and orbital opercula 
surround a triangular Sylvian fossa. [Unfortunately the 
anterior part of the specimen is damaged so that the frontal 


NERVOUS SYSTEM.—VERTEBRATA. 468 


operculum cannot be seen.] The suleus rectus (inferior 
frontal) is already developed. The central is a simple 
(and single) straight linear sulcus. 

The intraparietal system is represented by short shallow 
sulci representing the ramus postcentralis inferior and 
ramus horizontalis, and very faintly-marked depressions 
representing the ramus postcentralis superior and ramus 
occipitalis. 

The parallel is a very short sulcus. O. C, 1341 4. 

Presented by S. G. Shattock, Esq. 

D. J. Cunningham, Royal Irish Acad. Memoirs, Nos. 6 

& 7 (1892). 


D.682. The left hemisphere of a human fotus shortly before 
birth. 


D.683. The brain of a Microcephalic male Idiot, twenty-two 
years of age. He was 4 feet 84 inches in height. 

When first removed from the body, the brain weighed 
124 ounces (355 grms.). (In adult human males of a stature 
of 65 inches and under, the weight of the brain averages 
46°95 ounces [1315 grms.].) The extreme length of the 
median curve of the hemispheres was 120 mm. ‘The cere- 
bellum projected.20 mm. beyond the occipital lobe. 

After preservation in spirit the median curve of the frontal 
lobe from its anterior pole to the fissure of Rolando measures 
76 mm., the parietal lobe 37 mm., and the occipital lobe 
from the parieto-occipital fissure to its posterior pole 7 mm.; 
there is therefore a marked deficiency of the occipital lobes, 
which do not nearly cover the cerebellum. The anterior 
inferior portion of the central lobe or island of Reil is ex- 
posed on the surface of the hemisphere, and is only slightly 
below the level of the frontal cortex. The exposure of this 
part of the island of Reil is due to the deficiency of the 
frontal and orbital opercula which cover the central lobe in 
the healthy adult human brain. The fronto-orbital sulcus 
bounds the exposed part of the insula anteriorly ; above, it 
is limited by the superior limiting sulcus or lower free 
border of the third frontal convolution. On the right side 


464 


PHYSIOLOGICAL SERIES. 


of the brain the temporal and the parieto-frontal opercula 
have been removed so as to expose the whole of the external 
surface of the island of Reil. If the central lobe of this 
brain is compared with that of a healthy adult human 
cerebrum, or that of the Chimpanzee (see specimen 
D. 673), it will be seen how small and ill-developed the 
island of Reil is in this microcephalic cerebrum. The 
marked deficiency in the weight of this human cerebrum, 
its defective orbital and fronto-parietal opercula, together 
with the anatomical characteristics of the island of Reil, — 
place it among brains of the Simian type. } 

With the exception of the remarkable imperfections in 
this brain above referred to, its various external fissures — 
and convolutions, although simple in character, do not differ 
essentially from those of the average adult humancerebrum, 

The individual to whom this brain belonged is reported _ 


to have been a well-behaved lad when left alone, though 4 
mischievous ; but under provocation was passionate and 


uncontrolled. Ile was called, from his appearance (2. e., 
large coarse features and long arms), “ The Monkey boy,” 
and knew those who treated him well, following them about 
like a dog, with a peculiar gait. He was incapable of 
articulate speech, but expressed his wants by noises and 
signs. Music had a great attraction for him and he could 
imitate the actions of playing the violin or trumpet. He 
liked to be taken notice of by visitors, and, when asked, 
would show off certain tricks he had learnt, as, for instance, 
imitating the action of playing cricket. His habits were 
dirty at times. 


D. 684. A cast of the brain of a Microcephalic Idiot. 


D. 685. The brain of C. Babbage, Esq., F.R.S., a distinguished 


mathematician and inventor. The brain (with the pia 
mater) weighed 494 ozs. (1406 grms.) immediately after 
removal, O. C, 13839 aa. 


A fall description of the human brain does not come within the 
scope of this Catalogue. This the student will find in text-books of 


Human Anatomy. 


ee 
7 


NERVOUS SYSTEM.—VERTEBRATA. 465 


Ir would perhaps be more in keeping with the intentions of the 
founder of this Museum, who brought together such specimens as 
would throw any light upon the structure of Man, to briefly summarise 
such facts revealed in studying this collection of Vertebrate brains as 
help to explain the complicated anatomy of the human brain. 

The human brain is by no means the largest known to us. The 
Elephant and the Great Whales possess much larger organs, and even 
the extinct Sirenian Ihytina was provided with a brain of larger 
absolute dimensions than that of Man. In the case of these huge 
animals the enormous mass of the brain is probably to be explained 
by the fact that the increase in size of the surface of the body 
necessitates a corresponding growth of the neopallium (to which the 
great proportions are chiefly due), which is the ultimate receptive- 
organ for sensory impressions. 

In the case of the human brain, however, the Anthropoid Apes 
(which approach near to Man in bodily dimensions) afford us a criterion 
as to the amount of neopallium which may be regarded as “ necessary ” 
(in the Family Simiide) for the reception of impressions coming from 
such an extent of sensory surface as Man possesses. When it is 
remembered that the largest Ape’s brain is approximately half the size 
of the smallest normal human brain, and the average Gorilla’s brain 
only about one third (approximately) the weight of the average 
European’s brain, it will then be understood how great an area of 
neopallium (to which the disproportionate size of the human and 
Anthropoid brains is chiefly due) Man possesses over and above the 
needs of the average member of the Simiide, to serve as the physical 
basis (so to speak) of an associative memory of immeasurably greater 
potentialities (for storing and comparing sensory impressions) than 
that of any other animal. The feature, therefore, which distinguishes 
the human from all other brains is the relatively enormous size of the 
neopallium in comparison with the minimum which the forces of 
natural selection have made a condition of survival in a member of 
the Simiide *. 

The neopallium assumes important functions and becomes a condition 
of survival for the first time in the Mammalia, and in each successive 
epoch it has become incumbent upon every mammal either, on the 
one hand, to adopt some eminently safe mode of life or some special 
protective apparatus to avoid extinction, or, on the other hand, to 
“cultivate” a larger neopallium, which, as the organ of associative 


* I use the term “ neopallium” (Journ. Anat. and Phys. vol. xxxv. 1901, 
p. 431) because the other parts of the pallium, i. e. the hippocampus and 
pyriform lobe, do not share in this increase. 


VOL. Il. 24 


466 PHYSIOLOGICAL SERIES. 


memory, would enable it to acquire the cunning and skill to evade 
danger and_yet adequately attend to its needs. In many of the 
Eocene Mammalia (cf. the cranial cast of Dinoceras) the neopallium 
is reduced to such diminutive proportions that the brain resembles 
the reptilian type; and in each successive generation the neopallium 
becomes larger or the creature, in self-defence, is compelled to adopt 
some safe form of life. The Hippopotamus and the Sirenia are 
-examples of mammals which have not kept pace in the fierce race 
for neopallial supremacy but survive by adopting habits of life which 
are eminently safe. The condition of the human brain represents the 
other extreme. Here the neopallium has attained its maximum 
development, and its possessor has not had to seek refuge either in 
a retired mode of life or by any protective specialisations of structure 
either for offence or defence, but has attained the dominant position in 
the animal kingdom, whilst retaining much of the generalised structural 
features of a primitive mammal. 

This expansion of the neopallium is general and not restricted to 
any localised areas. Thus we cannot say that the greatness of the 
human neopallium is to be wholly attributed to a growth of the frontal 
or of the parietal or of the occipital areas, as various writers have 
maintained; because all parts exhibit distinct evidences of extension. 
But some regions exhibit the effects of this general expansion more 
decisively than others, and many writers have assumed (quite 
erroneously, | believe) that such effects are to be attributed to localised 
growth *, ‘Thus there are very noteworthy evidences of growth in the 
region around the insula in the human brain, but this is probably for 
the most part an expression of the general extension in a region 
which lends itself to a clear demonstration of any. increase. 

In the early mammals the olfactory areas form’ by far the greater 
part of the cerebral hemisphere, which is not surprising when it is 
recalled that the forebrain is in the primitive brain essentially an 
appendage, so to speak, of the smell-apparatus. When the cerebral 
hemisphere comes to occupy such a dominant position in the brain it 
is perhaps not unnatural to find that the sense of smell is the most 
influential and the chief source of information to the animal; or 
perhaps it would be more accurate to say that the olfactory sense, 
which conveys general information to the animal such as no other 
sense can bring concerning its prey (whether near or far, hidden or 


* There is no doubt that localised hypertrophies do occur, but the funda- 
mental distinction of the human brain is the general expansion of the whole 


neopallium, 


NERVOUS SYSTEM.—VERTEBRATA 467 


name esl 
, wialars ife and therefore becomes 
predominant ; and its particular domain—the forebrain—be 

ruling portion of the nervous system. geo 

This early predominance of the sense of smell persists in most 
mammals (unless an aquatic mode of life interferes and deposes it: 
compare the Cetacea, Sirenia, and Pinnipedia for example) even thou h 
a large neopallium develops to receive visual, auditory, tactile a 
other impressions pouring into the forebrain. In the Auithropdldin alias 
of non-aquatic mammals the olfactory regions undergo an absolute (and 
not only relative, as in the Carnivora and Ungulata) dwindling, which 
is equally shared by the human brain, in common with those of the 
other Simiide, the Cercopithecide, and the Cebide. But all the parts 

of the rhinencephalon, which are so distinct in macrosmatic mammals 
can also be recognised in the human brain. The small aflipaotiial 
olfactory bulb is moored, so to speak, on the cribriform plate of the 
ethmoid bone by the olfactory nerves so that, as the place of attachment 
of the olfactory peduncle to the expanding cerebral hemisphere becomes 
removed (as a result of the forward extension of the hemisphere) 

| progressively farther and farther backward, the peduncle becomes 

greatly stretched and elongated. And as this stretching involves the 
grey matter without lessening the number of nerve-fibres in the 
olfactory tract, the peduncle becomes practically what it is usually 
called, 7. ¢. the olfactory “ tract.” The tuberculum olfactorium becomes 
greatly reduced and at the same time flattened, so that it is not easy to 
‘draw a line of demarcation between it and the anterior perforated 
space. The anterior rhinal fissure, which is present in the early 
human foetus vanishes (almost, if not altogether) in the adult. Part 
of the posterior rhinal fissure is always present as the “ incisura 
temporalis,” and sometimes (D.710), especially in some of the non- 
European races, the whole of the posterior rhinal fissure is retained in 
that typical form which we find in the Anthropoid Apes. When this 
occurs we can easily recognise the caudal limits of the pyriform lobe, 
which otherwise becomes confused with the neopallium. 

Tho hippocampal fissure is of a peculiarly consistent nature, and is 
found in all mammalian brains from Ornithorhynchus to Homo, The 
rhinal fissure is equally sui generis and almost as constant as the hippo- 
campal. A few small mammals, such as Notoryctes, Chlamydophorus, 

 Chrysochloris, and some small Chiroptera, have no rhinal fissure. 

Of the sulci perhaps the most constant is the calcarine, which is 
found in the Marsupials (both Poly- and Diprotodont), in the larger 
Chiroptera, Galeopithecus, (but not in any true Insectivore, nor, strange 

2H 2 


468 PHYSIOLOGICAL SERIES. 


to relate, Rodent, so far as I am aware), and in all the Edentates, 
Carnivores,.Ungulates, Cetaceans, and Primates. This wide distri- 
bution of the calearine sulcus is not generally admitted, for most 
writers regard the calcar avis and the calcarine sulcus as the 
special prerogative of the Primates or even Anthropoidea, and in 
the celebrated controversy of 1864 the late Professor Owen strove 
to prove that it was confined to the human brain. It is, however, 
the most primitive (it may, however, first appear at the same time 
as the orbital and suprasylvian sulci) and widely prevalent neopallial 
sulcus in the Mammalia. It makes its appearance in most mammals 
(soon after the hippocampal and rhinal fissures have developed) as 
a short oblique sulcus behind the splenium of the corpus callosum 
(or in the corresponding situation in Marsupials), and hence it is 
commonly called “ splenial ” (Krueg) in non-Primate Orders, in which 
its true nature has not been properly recognised hitherto *. 

Its subsequent history varies greatly in different Orders. In the 
Carnivora, Ungulata, Chiroptera, and many other mammals the sulcus 
becomes concurrent with another element of vastly less morphological 
importance, which I have called the ‘*intercalary” sulcus. The 
calcarine-intercalary complex forms the “ splenial sulcus” of these 
brains. 

In most mammals, with the exception of the Primates, the tension 
of the growing cortex in the infracalearine region is relieved by the 
downward extension of the calcarine sulcus to the neighbourhood of 
the rhinal fissure. 

In the Anteaters, Sloths, Pangolins, Lemurs, and Apes the calearine 
sulcus always remains separate from the intercalary sulcus, and the 
latter joins with the genual sulcus in the Primates to form the calloso- 
marginal sulcus. 

In many Carnivores and Ungulates (and in large mammals generally) 
one or more deep sulci make their appearance behind the calcarine 
sulcus, and in most cases one of these, which we may call the “ retro- 
calcarine” sulcus, is deeper and more constant than the others and 
often joins the calcarine sulcus. This is seen to advantage in the 
brain of the Lion, Tiger, or Seal among Carnivores, or in the Horse, 
Camel, or Ox among Ungulates. This retrocalcarine sulcus is 
obviously of very minor morphological importance in comparison with 


—— 


* Meynert and Ziehen have called the splenial sulcus “calcarine” in 
some Carnivores, without indicating any valid reasons for their views. 
They have attempted to extend its supposed homologies to the Anthropoid 
pattern so far as to utterly discredit any value that may attach to their 
recognition of its calcarine nature. 


yee 


~~) Gee 5 4— 


2 re ew 


NERVOUS SYSTEM.—VERTEBRATA. 469 


the true calcarine sulcus, and this is shown by its adaptability to the 
varying mechanical conditions prevalent in different Orders *. In the 
Primates both the retrocalcarine (Cunningham’s “ posterior calearine ”) 
and the true calearine (Cunningham’s “ anterior calcarine ”) sulci 
tend, as a result of the occipital extension of the hemisphere, to 
become horizontal and in most cases become concurrent. In the 
more rapidly expanding human brain it often happens that the two 
sulci do not exactly meet, as they generally do in the Apes. Cun- 
ningham is thus led to the belief that the human brain differs from 
the Simian brain in possessing a retrocalcarine sulcus; but there can 
be little doubt that the so-called “calcarine” sulcus of the Apes 
is really a fusion of the retrocalcarine and true calcarine sulci, and 
therefore does not materially differ from the human calcarine complex. 
If the caudal extremity of this “ calearine complex ” be studied in the 
Apes it will be found to be exceedingly variable and unstable, so that 
one cannot regard it as part of the true calcarine, which is an 
exceedingly stable sulcus. 

By true “ calearine sulcus” I mean that depression which corre- 
sponds to or produces the calcar avis. As Flower long ago pointed 


out (Phil. Trans. 1862, p. 198, footnote), the presence of a posterior 


cornu of the lateral ventricle is not necessary for the existence of a 
calear avis. Thus we find a free calcar in many hemispheres (those 
of Orycteropus, Thylacinus, Pteropvs, for example) in which there is 
no posterior cornu. But in most mammals the calcar becomes hidden 
by a great mass of fibres (compare most Carnivores and Ungulates), 
and cannot therefore be said to exist as a projection in the ventricle ; 
and yet in many large Carnivores (Phoca for instance) and Ungulates 
(Camelus) a small posterior cornu of the lateral ventricle makes its 
appearance, and with it a typical calcar again becomes exposed as in 
the Primates. 

It would be strange indeed if the most constant and stable suleus 


‘of the mesial surface of the hemisphere of most mammals should 


entirely disappear in the Primates, to be replaced by another sulcus 
presenting identical relations to the lateral ventricle and a similar 
developmental history, but without being homologous. There is an 
overwhelming mass of evidence to show that the vertical part of the 
sulcus generally called “splenial” is the direct homologue of the 
calcarine sulcus of the Primates. 

ry At the same time the fact that it develops in the midst of the region 
in which Vicq d’Azyyr’s stripe occurs in the Primates, and which represents 
the visual “centre,” Jends a special interest to this sulcus, which obviously 
accommodates the expanding visual cortex. 


470 PHYSIOLOGICAL SERIES. 


In many mammals (such as the Lion) the tension of the growing 
infracalcarine neopallium is relieved chiefly by the downward exten- 
sion of the calcarine sulcus toward the posterior rhinal fissure, but 
also partly by certain irregular and inconstant compensatory sulci 
behind and parallel to this extension. In the Primates, however, the 
calearine sulcus becomes very obliquely placed, not only because the 
. occipital region of the hemisphere becomes caudally extended above 
the cerebellum, but also because the elongating corpus callosum pushes 
back, as it were, the pericalcarine neopallium ; and as a result of this 
obliquity the sulcus cannot be prolonged towards the rhinal fissure, 
as happens in the Carnivora and Ungulata, so that the compensatory 
sulcus, which is known as the “ collateral” sulcus, attains a greatly 
enhanced importance, and fulfils the réle of the ventral extension of 
the calcarine sulcus. 

A study of the variable collateral sulcus in the brain of Man and 
the Apes clearly shows its compensatory-calearine nature. 

Another result of the occipital prolongation of the hemisphere is 
that the calcarine sulcus becomes widely separated from the intercalary 
(calloso-marginal) sulcus, to which it is joined in most mammals, 
The stages in this separation are well shown by comparing, say, the 
brain of a typical Carnivore with those of Daubentonia and the Lemurs. 
As the result of this separation a new set of mechanical conditions 
prevail in the area between the calcarine and the calloso-marginal 
sulci; and, to further complicate matters, the arcuate sulcus formed 
on the dorso-lateral aspect of the hemisphere by the lateral and post- 
lateral sulci (i.¢. the intraparietal and its ramus occipitalis trans- 
versus respectively) becomes more and more acutely flexed as the 
occipital prolongation occurs, so that in the Cebide the sharp-pointed 
apex of the V-shaped sulcus so-formed extends toward this region of 
the mesial wall, which is, for the reasons just mentioned, already in a 
state of “unstable equilibrium,” so to speak, As the result two sulci 
(which may, however, be concurrent) are formed :—(a) a ventral 
compensatory-calcarine parallel to the calcarine and the dorsal limb 
of the postcalcarine sulcus, and (+) a vertical sulcus cutting into the 
dorsal edge of the hemisphere. The latter appears to relieve the 
tension of the extending surface in a region which is obviously in- 
fluenced by the proximity of the “apex” of the intraparietal sulcus. 
In some cases (e.g. Chrysothriv, D, 554) this sulcus b may be joined 
to the intraparietal, but in most Apes it is independent of it. The two 
sulci a and } usually overlap, and in most cases the intervening gyrus 
becomes submerged so that the two elements appear to form one 
furrow, which is the “ parieto-occipital sulcus.” The latter, therefore, 


a el 


ge 


NERVOUS SYSTEM.—VERTEBRATA. 471 


is a complex of two (and often three) new elements; it makes its 
appearance for the first time in the Anthropoidea in the region 
between the phylogenetically old calcarine and intraparietal sulci, 
which are the common heritage of the Meta- and Eutheria, This 
account will explain the extreme variability of the parieto-occipital 
sulci in the human brain. 

There is yet another remnant in the Primate-brain of the calcarine- 
intercalary junction (which occurs in so many mammals) in the form 
of a short sulcus above and behind the splenium, which I have called 
“compensatory ” (instead of Broca’s misleading title ‘ postlimbic ”). 

The Sylvian fissure in its complete form is found only in the 
human brain, and even in Man it is often imperfect. It is really a 
great cleft upon the ventro-lateral aspect of the hemisphere formed 
by the meeting of the peripheral opercular lips of three sulei, 
which are quite distinct in origin and in their phylogenetic history. 
The most stable of these three sulci, and therefore that which takes 
the chief share in the development of the Sylvian fissure, is that called 
“suprasylvian” in most mammals. The second is an unstable suleus 
analogous to the pseudosylvian sulcus (that which is commonly called 
the ‘Sylvian fissure”) of the Carnivora and many other mammals, 
And the third sulcus is the fronto-orbital. 

The suprasylvian sulcus is one of the most primitive and constant 
in the Mammalian series. It is the earliest neopallial suleus to make 
its appearance on the external surface of the hemisphere in the course 
of the development of the Carnivore, Ungulate, and (according to the 
old observations of Pouchet) Edentate brain, synchronising in this 
respect with the calcarine sulcus on the mesial surface. Even if its 
identification is not altogether sure in the Marsupialia (see the 
accounts of Thylacinus, Macropus, and Phascolomys), we know that it 
is a most stable sulcus in the Edentata, Rodentia, Carnivora, and 
Ungulata. In many Mammals it is joined to the less stable post- 
sylvian (“posterior suprasylvian” of most writers) sulcus, which 
we call “parallel” in the Anthropoidea. In the Great Anteater, 
however, it usually becomes separated from the latter and joined 
to a pseudosylvian sulcus to form a Sylvian fissure, not unlike 
that found in the Lemuroidea. It is significant that in the 
only case in six hemispheres of Myrmecophaga where this junction 
does not take place, it should also happen that the supra- 
sylvian sulcus is joined to the postsylvian, as in the Carnivora. In 
Daubentonia the suprasylvian sulcus is always separate from the 
pseudosylvian, and is generally joined to the postsylvian sulcus. In 
the Family Lemuride the suprasylvian sulcus is always (or practically 


472 PHYSIOLOGICAL SERIES. 


always) separated from the parallel (postsylvian) sulcus, but numerous 
fragmentary sulci, and a backwardly-directed hook at the upper end 
of the suprasylvian (Sylvian) sulcus, or a forwardly-directed hook to 
the postsylvian (parallel) sulcus, serve to remind us of the old link 
between these two sulci, which has been broken. 

The lower end of the suprasylvian sulcus in the Lemurs overlaps 
the upper part of a pseudosylvian sulcus (of the feline type), the gyrus 
between the two sulci becomes submerged, and the resulting suleus 
we now call the “Sylvian fissure.” The lower end of the supra- 
sylvian sulcus can be seen in many Prosimian hemispheres emerging 
from the front of the ‘‘ Sylvian complex ” « short distance above the 
rhinal fissure. 

In the Apes the submerged area increases in extent and is called 
the “insula.” It is hidden by two opercula; and a comparison of a 
large series of Ape-brains seems to clearly demonstrate that the dorsal 
limiting sulcus of the insula is no other than the suprasylvian 
sulcus. 

In no brain does this sulcus extend so far (in the ventral direction) 
as the rhinal fissure. In many of the larger Apes it emerges slightly 
and cuts into the anterior lip of the Sylvian fissure. In Hylobates, 
Simia, and the Anthropopithect it extends forward upon the surface 
so as almost to reach the fronto-orbital sulcus. 

The early history of the latter sulcus is not satisfactorily known. 
It is present in an exceedingly well-developed condition in all the 
Simiide, and in a less obtrusive form in many of the larger Apes: 
but, on the other hand, it is absent in many of the Cebide and Cer- 
copithecide. Such being the case, it is very surprising to sometimes 
find in the Lemurs a small sulcus, which can be no other than the 
fronto-orbital. It is impossible to say with any degree of probability 
whether this sulcus is represented beyond the limits of the Primates. 
The diagonal sulcus of the Carnivora, Ungulata, Edentata (Bradypus, 
Myrmecophaga) occupies a position analogous to that of the fronto- 
orbital in the Primates. 

In the Anthropoid Apes there is a pronounced tendency for the 
anterior lip of this (fronto-orbital) sulcus to become opercular and 
to extend backward over the insula, the anterior limit of which is 
marked out by the sulcus itself. 

This process of operculation may be carried very far even in /Hylo- 
bates, Simia, and Anthropopithecus troglodytes ; and in one specimen of 
Anthropopithecus gorilla (D. 656) a very close though spurious imita- 
tion of the human condition of this region is attained. 

In the human brain this process of operculation generally leads to 


—_"~ ee i i a ak it 


hs 


a 


NERVOUS SYSTEM.—VERTEBRATA. 473 


the complete covering of the insula. The anterior lip of the fronto- 
orbital (or, as we may now call it, anterior limiting sulcus of Reil) grows 
backward to meet the temporal operculum, and thus gives rise to the 
‘‘stem” of the Sylvian fissure. The dorsal lip of the forward exten- 
sion of the superior limiting sulcus grows down to meet the temporal 
operculum (thus forming the anterior part of the posterior limb of the 
Sylvian fissure) and also the orbital operculum (which is the anterior 
operculated lip of the fronto-orbital sulcus). The latter meeting gives 
rise to the anterior limb of the Sylvian fissure. It often happens, 
however, that the expanding cortex in the neighbourhood of the 
meeting place of the anterior and superior limiting sulci becomes ac- 
commodated by the formation of an additional operculum—the frontal. 
As the result two anterior limbs of the Sylvian fissure (instead of one) 
are produced. 

It follows from this account that a complete Sylvian fissure exists 
only in the human brain, and that the so-called Sylvian fissure of 
even the Anthropoid Apes lacks properly-constituted anterior limbs, a 
small part of the posterior limb, and generally also the “ stem” of the 
complete sulcus. 

The full development of the opercula leads to the abortion of the 
upper part of the fronto-orbital sulcus in the human brain. 

The lateral, post-lateral, and ansate sulci of the Carnivora and 
other Mammalian Orders become in the Primates the intraparietal, 
transverse occipital, and ramus postcentralis superior respectively. 
It is a moot point whether the coronal sulcus, which is so constant 
and precocious, in the Carnivora, Ungulata, and Edentata, forms 
the ramus postcentralis inferior of the intraparietal system. The 
evidence seems to point to the sulcus rectus and the lower part of the 


-central sulcus as being the real derivatives of this furrow. 


In most Apes the region lying behind the transverse occipital sulcus 
undergoes a peculiar modification leading to the formation of a great 
operculum from the posterior lip of a new sulcus, called Simian or, as 


' the Germans say, “ Affenspalte.” This does not usually occur in the 


human brain, probably because the cortical areas around the transverse 
occipital sulcus undergo a greater expansion than is the case in the 
Apes. 

I have seen, however, in the brain of an Egyptian fellah a small 
indubitable Simian sulcus like that of the Gorilla. It was separated 
by a considerable interval from the mesial plane. 

It thus happens that this region of the human brain more closely 
resembles the condition found in many of the larger Cebide (in which 
the opercular formation has either not begun or is only just com- 


474 PHYSIOLOGICAL SERIES. 


mencing) than that of the Anthropoid Apes. Of the latter the brain 
of the Gorilla approaches the human condition much more nearly than 
does that either of the Chimpanzee or Orang. It must be remembered, 
however, that the “ occipital” and “insular” regions exhibit an 
extraordinary amount of variation in each of the Simiide; the 
average condition of these two changing areas is much nearer the 
human type in the Gorilla than in either of the other great Apes. 

Of the other sulci of the human brain (besides those already dis- 
cussed) the only ones which can be called “ old” in the phylogenetic 
sense are the orbital and possibly the inferior frontal sulci. 

The orbital sulcus is probably one of the most primitive furrows in 
the neopallium, if not the earliest. It is the only sulcus found in 
the most generalised mammals, Hrinaceus and Perameles. It is a very 
constant and precocious sulcus in all the Carnivora, Ungulata, Edentata, 
Cetacea, and many Rodents and G‘aleopithecus. Most writers call it 
** presylvian ” in all these non-Primate orders, but there can be little 
doubt as to its homology with the orbital sulcus, although, so far as I 
am aware, such an interpretation has never hitherto been suggested. 
But it would be strange if this (the most widespread and constant) 
sulcus of the neopallium should not be represented, in the Primates, and 
there is no other furrow of sufficient constancy in the pararhinal region 
to represent the presylvian sulcus of other mammals. If moreover we 
compare such brains as those of Dolichotis (Rodent), Galeopithecus 
(Insectivore), Bradypus (Edentate), and Phascolomys (Marsupial) with 
' the Lemur’s, it is clear that the “ presylvian ” sulcus of the former can 
be represented in the Prosimiz only by the orbital or the fronto-orbital 
sulcus. Of these the former is not only by far the more constant of 
the two sulci, but it is also that which occupies the same position and 
relationship to the rhinal fissure as the “ presylvian.” A comparison 
of Galago and Dolichotis shows this. 

If again we compare the behaviour of the orbital sulcus in the 
larger Ungulates (e¢. g., the Camel, Horse, and Ox) and Carnivores 
(¢. g., the Seals), we shall find that as the hemisphere increases in 
magnitude (and more especially if at the same time it becomes more 
microsmatic) the “ presylvian ” sulcus becomes relegated to a position 
alongside the anterior rhinal fissure exactly analogous to that occupied 
by the orbital sulcus in the Gorilla’s brain. In Man the simple linear 
orbital sulcus becomes complicated by numerous side branches so as to 
form triradiate, H-shaped or other patterns; but if a large number of 
human brains be examined, the orbital suleus will be found to consist 
in a very considerable proportion of these cases of a single deep linear 
sulcus, the apparent branches of which are mere shallow furrows of 


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aa 


ND ie 
ae 


—  . 


NERVOUS SYSTEM.—VERTEBRATA, 475 


little importance. Not unfrequently this sulcus joins a small anterior 
rhinal fissure—thus completing the resemblance to the junction of the 
“‘ presylvian ” sulcus with the rhinal in the Carnivora and others. 

The coronal sulcus of the non-Primate mammals may be represented 
in the inferior frontal and the inferior precentral sulci of Man. One 
of the earliest sulci to make its appearance in the developing Carnivore 
and Ungulate brain is the coronal. In the Carnivores it often joins 
the lateral sulcus, in many Ungulates it is linked to the suprasylvian, 
in the Pig-family it is united with the intercalary suleus. In the 
Primates the so-called sulcus rectus exhibits a similar precocity, and 
occupies a position not unlike that of the coronal in the Ungulates 
and the primitive Viverrine Carnivores. It becomes split up in the 
Cebide and Cercopithecide into two parts, the sulcus rectus (sensu 
stricto) and the sulcus arcuatus. The former develops into the 
inferior frontal and the latter into the inferior precentral sulcus. 

The problem of the exact interpretation of the central (Rolando’s) 
sulcus presents many difficulties. There can be no doubt whatever as 
to the homology of the mammalian lateral with the intraparietal sulcus 
of the Primates, and the interpretation of the ansate as the ramus 
postcentralis superior is almost as sure. We find in the Carnivora and 
the Primates respectively a deep and important sulcus bearing the 
same relations to the ansate and lateral sulci. Inthe former we call it 
“crucial” and in the latter “central”; the solution thus naturally 
auggested is that the central sulcus of the Primates represents the 
crucial sulcus of the Carnivora. Such a view has often been pro- 
pounded before, and has in several instances been discarded for no 
yalid reason. Thus it has been urged (with a singular disregard for 
the facts of the case) that the crucial sulcus “belongs to the mesial 
wall,” in spite of the patent evidence afforded by the Arctoid Carnivora 
that when the crucial sulcus becomes dissociated from the intercalary 
sulcus it often lies wholly on the dorsal surface of the hemisphere 
(see the brain of the Bears, the Glutton, and in fact most“of the 
Arctoidea). 

If we study the forms assumed by the crucial sulcus in the large 
Carnivores (such as the Bears and Seals) and by the central sulous 
in the large Apes (Simiide), we cavnot fail to be struck with a 
striking parallelism, which could only be produced by the operation 
of similar factors in the two cases. Moreover, the earliest phases of 
the development of the central sulcus in the Lemurs are similar to the 


first rudiments of the crucial sulcus in the Viverride. 


Physiological evidence (which, however, in such matters is notoriously 
misleading) does not altogether support such an homology. In the 


476 PHYSIOLOGICAL SERIES. 


Anthropoidea the central sulcus sharply marks the cxact caudal limit 
of the area of excitable cortex, whereas in the Carnivora (so the 
physiologists tell us) the crucial sulcus lies in the midst of the excitable 
area. 

If we admit the homology of the central and crucial sulci we shall 
(by comparison with the behaviour of the latter) find an explanation 
of many features of the former. According to such an hypothesis a 
glance at a Bear’s brain will at once make intelligible the meaning of 
the superior genu, the caudal bend in the mesial extremity, and the 
tendency of the central sulcus in the Anthropoid Apes and Man to 
extend on to the mesial surface in front of the upturned end of the 
calloso-marginal sulcus. : 

In the features of its central sulcus (the relative positions of the 
genua and the behaviour of the mesial extremity of the sulcus) the 
Anthropopithect approach much nearer to Man than does the Orang or 
any other Ape *. 

The human brain is distinguished from those of the Apes by the 
abundance of sulci between these stable and constant elements. 

The superior frontal and especially the middle frontal sulci are much 
better developed than in the Apes, and innumerable sulci develop in 
connection with these. The inferior transverse sulcus (so constant 
in the Simiide and larger Cercopithecide) is longer and deeper; and 
the diagonal sulcus, rarely or never seen in a well-developed form 
in the Apes, is now almost constantly present as a deep, extensive 
sulcus, lying between the anterior ascending limb of the Sylvian and 
the inferior precentral sulcus. 

The parietal area is notably much more variable and much richer 
in secondary sulci than it is inthe Apes. __ 

In the temporo-occipital region the ‘* Affenspalte” of the Apes has 
disappeared, and the depth and extent of the dorsal end of the parallel, 
the transverse occipital and lateral occipital sulci are correspondingly 
increased. The inferior occipital, inferior temporal, occipito-temporal, 
and collateral sulci are usually all present in a well-developed form, 
In the Apes the deepening and lengthening of any one of these sulci 
involved a dwindling of its neighbour—a highly developed occipito- 
temporal sulcus often led to the abortion of the inferior temporal, the 
disappearance of the anterior end of the collateral, or the curtailment 


* As the result of further investigations since the above was written, I 
have come to the conclusion that the crucial sulcus represents the dorsal part 
of the central sulcus and that the ventral part of the latter is formed either 
from or at the expense of (mechanically) the caudal extremity of the coronal 
sulcus. 


it 


NERVOUS SYSTEM.—VERTEBRATA. A477 


of the inferior occipital or vice versa ; but in the human brain there is 
room for all these unstable and mutually compensatory sulci to exist 
in a well-developed form side by side. 

The expansion of the neopallium has far-reaching effects upon other 
regions of the nervous system: the fibre systems connected with it 
become more bulky, the cerebellum becomes larger, its middle 
peduncle—the pons—becomes so broad that it completely covers the 
trapezoid bodies and extends down to the inferior olives, In 
innumerable ways the whole nervous system is profoundly influenced 
and modified in structure as the result, directly or indirectly, of the 
attainment of the neopallium to the height of its perfection. 


D. 686. A human brain, presumably British, O OC, 13390, 
D. 687. A human brain, presumably British. O. C. 1339 a, 


D. 688. The right half of a brain, presumably British. 
OQ. C. 1339 p. 


D. 689. The left half of the same brain. O. C. 1339 p’. 


D. 690. The left cerebral hemisphere of a man, hardened in 
dilute nitric acid and then dried. 
Prepared and presented by S. G. Shattock, Esq. 


D. 691. Fragment of a human left cerebral hemisphere from a 
Prehistoric burial place at El] Amrah, Upper Egypt. 
Presented by Prof. G. Elliot Smith. 


D. 692. A cast of the interior of the Neanderthal skull. 
Presented by Professor Huzley. 
Huxley, “ Man’s Place in Nature,” p. 168. 


D. 693. A cast of the frontal region of the cranial cavity of the 
“ Gibraltar” skull—a paleolithic cranium, remarkable for 
the low retreating forehead, found in the breeciated talus 
of a quarry behind “ Forbes’ Battery ” under the north 
front of the Rock of Gibraltar. (See Osteol. Series, 371.) 

Presented by N. C. Macnamara, Esq. 


D. 694. Two casts of the cranial cavity of a “ Huropean.” 


478 PHYSIOLOGICAL SERIES. 


D. 695. A cast of the cavity of Dean Swift’s skull. 
D. 696. Two casts of the cranial cavity of a Chinaman. 


D. 697. Two casts of the cranial cavity of a Tartar (male), 
This is so extraordinarily broad that the outline is almost 
circular. 


D. 698. Two casts of the cranial cavity of a Turk. 
This also is very broad. 


D. 699. A human brain labelled “ New Zealand.” O. CO. 1339 B. 


D. 700. Two casts of the cranial cavity of a Maori (male). 
D. 701. Two casts of the cranial cavity of an Australian (male), 
D. 702. Two casts of the cranial cavity of an Australian (male). 


D. 703. Two casts of the cranial cavity of an Australian (male). 

The first two of these casts (D. 701, D. 702) are remark. — 

able by reason of their extreme narrowness, especially in 

the frontal region. The third (D. 703), however, is quite 
broad. 


D. 704. A cast of the interior of a narrow skull. 

This cast was made, at the instance of the late Professor 
Huxley, from a skull (probably of an Australian) to 
contrast with that of a Tartar (specimen D. 697) so as to 
demonstrate the extreme variations in the form of the 
cranial cavity, and consequently of the brain, in different 
races of mankind. Presented by Professor Hualey. 

Huxley, Journ. of Anat. & Phys. vol. i. 1867, p. 60. 


D. 705. A cast of the cranial cavity of a Papuan. 


D. 706. The brain of a young female “ Bushman,” from which 
the left cerebral hemisphere has been removed. 

This specimen has been described in detail by Professor 

John Marshall (Phil. Trans. 1864, pp. 501-525). He 


NERVOUS SYSTEM.—VERTEBRATA. 479 


pointed out the relative simplicity of the sulci and the 
proportionate scarcity of secondary sulci when compared 
with the European brain, and came to the conclusion that 
these phenomena could not be wholly attributed to the sex 
of the individual but constituted definite evidence of the 
racial inferiority of the Bushmen. 

At the same time one is bound to add to Marshall’s 
remarks, that those parts of the brain which we know to 
have been markedly modified during the short recent 
phases of human evolution (such, for example, as the 
insular region and the areas around the parieto-occipital 
and calcarine sulci) show little if any sign of inferiority in 


comparison with the European brain. O. C. 1339 Ba, 
D. 707. The left cerebral hemisphere belonging to the previous 
specimen. O. C. 1339 Bb. 
D, 708. The brain of a Bushman. O. C. 1339 B db. 


Presented by Professor John Marshall. 
D. 709. Two casts of the cranial cavity of a Bushman. 


D. 710. The brain of a Zulu (¢ wt. 22 yrs.). O. C. 1339 Be. 
Presented by Dr. W. H, Allehin. 


D. 711. Two casts of the cranial cavity of an “ African.” 
D. 712. Two pairs of casts of the cranial cavities of Negroes. 


D. 713. Casts of two preparations made by Prof. D. J. Cun- 
ningham to demonstrate the cranio-cerebral topographical 
relations. 

Cunningham, Memoirs Royal Irish Acad. vol. vii. 


D. 714. Coloured cast of the human calvarium, showing the 
relations of the cerebral sulci to the bony sutures. 
Prepared by Professor P. Broca of Paris. 


D. 715. A coronal section of the human head passing through 
the genu corporis callosi. 0. C. 1339 c. 


D. 716. A similar section passing through the rostrum corporis 
callosi and opening up the anterior cornua of the lateral 
ventricles. O. C. 1389 ca. 


480 PHYSIOLOGICAL SERIES. 


D. 717. A similar section passing through the splenium corporis 
callosi._ 
lt exposes the upper part of the descending cornu of the 
lateral ventricle and also the floor of the fourth ventricle. 
QO. C. 1339 cb. 


D. 718. A similar section cutting the cerebellum at its maximum 
breadth. O. C. 1339 ce. 


D. 719. A similar section passing through the occipital poles of 
the hemispheres. O. C. 1339 ed. 


D. 720. The pons Varolii, medulla oblongata, and cerebellum of 
a human brain. 
The medulla oblongata has been dissected by Mr. Swan 
in order to show the pyramidal decussation. 
O. C. 1339 £16, 


D. 721. A sagittal section through the lateral mass of the human 
cerebellum. 
This shows the dentate nucleus lying in the medulla. 
O. ©. 1339 £18. 


D. 722. A dissection to show the nerve-fibres collecting from all 
parts of the cerebral hemisphere to form the pes pedunculi. 
O. C. 1339 £10. 


D. 723. A similar specimen. O. C. 1339 #11, 


D, 724. A dissection of the human medulla oblongata to show 
the pyramidal decussation. O. C. 1339 p 36, 


D. 725. A preparation of the human optic thalami, mid-brain, 
pons, and medulla oblongata in which a bristle has been 
passed from the 3rd to the 4th ventricle through the 
aqueduct of Sylvius. 


D. 726. A dissection to show the behaviour of the fibres of the 


corpus callosum, in the cerebral hemispheres: mesial view. 
O. C. 1889 D7. 


D. 727. A specimen showing the relations of the corpus callosum 
to the cerebral hemispheres from above. 0. C. 1839 D8. 


NERVOUS SYSTEM.—VERTEBRATA. 481 


D. 728. A horizontal section of the human brain mounted by 
Mr. Greenwood, of Leeds, in glycerine jelly (Miall’s 
_ process). 

If this specimen be compared with the section made in 
a corresponding plane through the left cerebral hemisphere 
of a Chimpanzee (D. 672), a striking demonstration is 
afforded of the contrast between the human insula (which 
is wholly covered) and the Anthropoid island of Reil (which 

is partially exposed on the surface). 
Presented by C. G. Wheelhouse, Esq. 
D. J. Cunningham, Journ. Anat. & Phys., vol. XXxii., 

1898, p. 11. 


Membranes of the Brain. 


The brain is enveloped by at least two distinct sheaths of 
connective tissue, which serve for its protection and support 
and give passage to its blood-vessels and lymphatics. The 
innermost sheath (pia mater, or in lower Vertebrates where 
two sheaths only are present, the combined rudiment of the 
pia and arachnoid) is closely applied to its surface, and follows 
accurately all the brain contours and conveys into its substance 
blood-vessels and lymphatics. The outermost sheath (dura 
mater) is a modification of the periosteum, and in some cases 
(e.g. Mammalia) forms a single sheet with it, but is more 
generally separated into periosteal and dural layers by a zone of 
looser tissue. In Teleosts this interdural space is frequently 
very extensive, and is occupied by a very delicate trabecular 
connective tissue containing a gelatinous substance or fat. The 
dura mater is separated from the underlying layer or layers by 
a subdural lymph-space. This in the higher groups is a relatively 


narrow and almost continuous cavity, but in Elasmobranchs and 


Reptiles is large and is occupied by a delicate trabecular tissue. 
In Birds and Mammals there is interposed between the pia and 
dura mater a third layer (arachnoid) which is nothing but the 
outer parts of the pia separated off by the increase and confluence 
of lymph-spaces. The subarachnoid space _thus formed is 
traversed by numerous trabecule and is filled with cerebro-spinal 
fluid. In the Mammalia processes of the arachnoid (glandule 


Pacchioni) protrude between the fibres of the dura into the 


VOL. I. 21 


482 PHYSIOLOGICAL SERIES. 


cavities of the venous sinuses, and, apparently, by allowing the 
cerebro-spinal fluid to escape into the veins, ensure an adjustment 
of the pressure in and around the cerebro-spinal axis, when 
the flow of blood to those organs is increased. 

The surfaces of all three sheaths are covered by a pavement 
epithelium. 


D.729. The head of a Sea Bream (Pagellus centronotus) in 
sagittal section. The brain occupies only the ventral parts 


of the spaceous cranial cavity ; it is enveloped above by a — ; 


deep layer of fat lodged in the subdural space. 
Preserved in 5 per cent. formol. 


D. 730. A portion of the vascular covering, or pia mater, of the 
brain of a Goose (Anser ferus). The internal surface is 
smooth like the external, corresponding to the smooth 
unconvoluted surface of the brain which it invests. The 
vessels are injected showing their ramifications upon the 
membrane, O.C. 1342. Hunterian. 


D. 731. The cranial roof of a Dog (Canis familiaris var. borealis) 
showing two sheet-like processes of the dura mater or outer 
covering of the brain. One—the falx—projects down- 
wards in the sagittal plane, and in its natural position lies 
between the dorsal parts of the two hemispheres. The 
other—the tentorium—is attached transversely to the hinder 
margin of the falx; it stretches across the posterior part of 
the cranial cavity and is inserted between the cerebrum and 
cerebellum. 

In the Carnivora extensive ossification occurs within the 
tentorial membrane. In this specimen part of the mem- 
brane has been reflected to show the bony tentorium 


beneath. O. C. 1346 a. 


D. 732. A portion of the dura mater of an Elephant (Zlephas 
indicus) showing the union of the falx and tentorium. The 
dura is of considerable thickness, and can be separated into 
three Jayers, of which the outer and inner are firm and 
compact, the intermediate zone being of looser texture, 
and containing venous sinuses. 


Sta pe a 


ee ee ee oe 
/ 
, 


ee oe 


—_ = 


\ 


NERVOUS SYSTEM.—VERTEBRATA, 483 


D. 733. The choroid plexus of a Porpoise (Phocena phocena). 


The choroid plexuses are pleated invaginations of the 
anterior and posterior tela choroidea into the lateral and 
fourth ventricles of the brain, They consist of highly 
vascular pia mater covered on its inner surface by the 
columnar epithelium that lines the brain cavities, They 
are mainly concerned in the production of the cerebro- 
spinal fluid. O.C. 1834. Hunterian. 


D. 734. The choroid plexus of a Piked Whale (Balenoptera 


acuto-rostrata) . O.C. 1337. Hunterian. 


D. 735. The head of a small American Monkey (Callithria sp.) 


from which the calvarium has been removed, leaving the 
external surface of the dura mater exposed to view. The 
outer parts of the dura are closely applied to the cranial 
bones and form their periosteum. The arteries have been 
injected. O. C. 1345 a. 


D. 736. A vertical section of the head of a young child, showing 


the processes of the dura mater that project into the cranial 
cavity and support the several regions of the brain. These 
are: the falx cerebri—an extensive sagittal partition 
between the upper parts of the hemispheres ; the tentorium, 
crossing the hinder part of the cranial cavity in a trans- 
verse and obliquely horizontal direction and situated 
between the jcerebrum and cerebellum; and the falx cere- 
belli, a small sagittal partition lying between the hemi- 
spheres of the cerebellum. ‘The transit of the cranial 
nerves through the dura mater at the base of the cranium 
is also shown. The proximal ends of the straight and 
superior longitudinal sinuses have been exposed by the 
section, and a black bristle has been inserted into the 
superior longitudinal sinus. Black bristles have been in- 


serted into the optic foramen and into the cavity of the 
O. C, 1344. 


nose. 


D. 737. The dura mater removed from the dorsal parts of a 


human brain, showing the falx cerebri and the parts of the 
3 212 


484 


PHYSIOLOGICAL SERIES. 


tentorium in connection with it. The straight sinus and 
proximal parts of the lateral sinuses have been opened from 
below, the walls of the former being kept apart by a black 
bristle. Other bristles have been inserted between the layers 
of the falx cerebri and into a cavity beside the superior 
longitudinal sinus, the cut end of which is situated just 
posterior to the right lateral sinus. A similar opening 
can also be seen upon the left side. In this specimen the 
arteries are injected. O.C. 1344. Hunterian. 


D. 738. A portion of the dura mater from the dorsal parts of a 


Kuman cranium. Its fibrous nature isclearly shown. The 
superior longitudinal sinus has been laid open to show a 
number of “ glandulee Pacchioni ’—irregular outgrowths 
of the arachnoid membrane, through which the cerebro- 
spinal fluid contained in the sub-arachnoid space can exude 

into the blood. 7 
The two layers of the dura mater have been separated 
and a portion of the external layer removed from one side. 
QO. C. 1345. Hunterian. 


D. 739. The brain of a Human Female covered by the pia mater 


and arachnoid membranes. O. ©. 1389. Hunterian. 


D. 740. A portion of the pia mater with the arachnoid membrane 


adhering to it, from one of the cerebral hemispheres of a 
Human brain. The pia mater is thrown into a series of 
folds, that pass between the convolutions of the brain, and 
support the blood-vessels in their progress to the deeper 
parts. The villous character of the inner surface of this 
membrane is produced by the minute vessels which, adher- 
ing to the pia mater, have been torn from the cerebral 
substance. The arachnoid membrane is extended smoothly 
over the external surface of the pia mater, attached to it 
by numerous delicate lamin and trabecule, but is not 
reflected with it into the sulci of the hemisphere. The 
arteries in this specimen have been minutely injected. 
The external surface of the arachnoid membrane is smooth 
and i is rin ate by a slight cavity from the dura mater. 
O.C. 1843. Hunterian. 


ee eee Lee PN On gE ary 


i 


NERVOUS SYSTEM.—VERTEBRATA. 485 


Blood-vessels of the Brain. 


D. 741. ‘he head of a Dog-fish (Acanthias vulgaris) showing, 
from the ventral surface, the arteries of the brain and their 
connection with the carotids. Two carotid arteries arise on 
either side from the efferent vessel of the first demibranch 
—an anterior carotid or hyoidean artery and a posterior 
carotid. The posterior carotid divides at the hinder border 
of the orbit into an external and an internal trunk ; the 
latter enters the cranial cavity and passes across it in the 
perichondrium below the hypophysis, to form a connection 
with the internal branch of the opposite hyoidean artery. 
The hyoidean artery gives off in the orbit an external 
(ophthalmic) and an internal branch. The latter divides 
into (i.) the above-mentioned connection with the posterior 
carotid artery, and (ii.) a trunk that breaks up into anterior 
and posterior cerebral arteries, the first of which supplies 
the cerebrum and olfactory bulbs, and the second, the rest 
of the brain by branches to its dorsal and ventral surface. 
The latter unite upon the ventral surface of the medulla 
oblongata, to form a median (myelonic) artery continued 
backward along the spinal cord. 

Parker, Phil. Trans. vol. clxxvii. 1886, p. 690. 


D. 742. The brain of a Turtle (Chelone mydas) with the arterial 
blood-vessels injected. The cut ends of the internal 
carotids can be seen on either side of the infundibulum. 
Each divides on the base of the brain into two branches, 
one of which runs forwards and branches out over the 
cerebrum and olfactory bulbs. The other passes backwards 
and shortly unites with its fellow at the base of the 
medulla to form the basilar artery; but gives off before this 
union two large branches to the optic lobes and cerebellum. 


O. C. 1313 c. 


D. 743. The brain of a Goose (Anser ferus) with the arteries 
injected. Bristles have been inserted into the ruptured _ 
of the left olfactory bulb and into the roots r4 4 a 


cranial nerves. ; 
Flunterian. 


486 PHYSIOLOGICAL SERIES. 


D. 744. The brain and the upper part of the spinal cord of a Lion 
(Felis leo) with the arteries injected. 

In this beautiful preparation, the origin of the chief 
arteries of the brain and a great part of their distribution 
are clearly shown. The essential points of the arterial 
arrangement are comparable to the condition found in Man. 
Anterior, middle, and posterior cerebral arteries can be dis- 
tinguished arising in much the usual places from the circle — 
of Willis. Upon the right side the posterior cerebral 
artery consists of two separate trunks. 

The superior cerebellar artery arises by two roots on the 
left side, one from the basilar artery, the other from the 
posterior arm of the circle of Willis. 

The anterior (ventral) and inferior (posterior) cerebellar 
arteries form branches of a common trunk. 

The lateral parts of the circle of Willis are very strongly 
developed. 7 O. C. 1826. 

Hunterian. 


D. 745. The brain of a Sheep (Ovis aries) with the arteries in- 
jected. In this specimen the origin of the anterior and 
middle cerebral arteries from the circle of Willis is more 
plainly visible than in the preceding specimen. The posterior 
cerebral and superior cerebellar artéries ire represented by 
a number of small vessels that arise from the hinder part 
of the circle of Willis and from the anterior end of the 
basilar artery. The lateral parts of the circle of Willis are 
remarkably stout, as in the Lion (D. 744). Bristles have 
been inserted into the various cranial nerves. O.C. 1327. 


tye Hunterian. 
D. 746. The brain and the upper part of the spinal cord of a 
Porpoise (Phocena phocena), injected. O. C. 13832. 
Hunterian. 
D. 747. The basilar artery of a Rorqual (Balenoptera sp.). e 
0. C. 939.8 4. ie 


D. 748. The main arteries of the human brain, injected, isolated, 
and spread out on a flat surface. The anterior communi- 
cating artery is abnormally long and slender, 


a REPRE em, 2 Rien emma 


NERVOUS SYSTEM.—VERTEBRATA. 487 


SPINAL CORD. 


The spinal cord is a direct backward continuation of the 
medulla oblongata. It extends for a variable distance towards 
the tail, being in lower forms coextensive with the vertebral 
column, but in the higher showing a more or less marked 
shortening in relation to it. In the latter case, a degenerate 
vestige of the hinder end of the cord is still present in the pos- 
terior parts of the neural canal, surrounded by a bundle of spinal 
nerve-roots (cauda equina). Extreme shortening of the cord 
occurs in isolated cases in widely separated groups (Diodon, 
Erinaceus) . 

In transverse section, the cord is usually oval or circular, 
rarely flattened and ribbon-like (Cyclostom) or quadrangular 
(Rays). The central canal is lined by an ependyma and 
surrounded by a layer of grey matter. 

In many fishes there is no definite boundary between the grey 
and white matter, but in most cases it is clearly defined and has 
in transverse section the form of a St. Andrew’s cross. 

In the lower groups, where the sense-organs of the skin are 
mainly innervated by certain cranial nerves, the dorsal (sensory) 
horns of grey matter are relatively very weak. Ganglion-cells 
occur chiefly in the ventral (motor) horns, evenly distributed 
throughout their length. The presence of limbs, if of sufficient 
size and activity to require nerves markedly larger than those 
of the trunk, is accompanied by a swelling of the cord due to an 
increase in the number of nerve-elements at the point of origin of 
the limb-nerves. In a similar way, any other increased nerve- 
supply occasions a corresponding local thickening of the cord : 
(e. g.. Gurnard, tactile pectoral fin-rays. Gymnotus, electric 
organ). Conversely, diminished nerve-supply, as in the thoracic 
region in the Chelonia, is accompanied by diminution in the size 
of the cord. 

The cord is more or less extensively united by tracts to the 
different regions of the brain. In lowly forms this connection 
is comparatively slight, being restricted mainly to the ventral 
tracts (fasciculi longitudinales posteriores) and fillet. Hence 
in these the cord is far more independent of the brain in its 


488 PHYSIOLOGICAL SERIES. 


actions than in higher vertebrates in which tracts from the 
cortex, cerebellum, and other parts of the brain form the greater 
part of its white matter. 

In most bony fishes, Ganoids, Dipnoi, and larval Amphibians, 
the ventral (motor) tracts contain a pair of giant nerve-fibres 
(Mauthner’s fibres) which arise from a pair of giant cells in the 
neighbourhood of the acoustic nucleus. They cross in the floor 
of the medulla and at the hinder end of the cord break up and 
enter the motor nerves of the tail-fin. A number of somewhat 
similar fibres (Miiller’s fibres) occur in the ventral tracts of the 


Fig. 254. 


: * MAUTH. FIB, 
PERIPH.V. COMM. 


cord in Cyclostomi. In many Fishes a number of remarkable 
giant ganglion-cells are found in the dorsal fissure, usually at 
the anterior end of the cord ; their axis cylinders apparently run 
in some cases forwards, in others backwards, and form connec- 
tions either with the dorsal roots of the spinal nerves or with 
the sensory branches of the trigeminal. The development of 
these elements has been noticed to be particularly strong in 
fish with special epidermal sensory processes (Lophius, Batra- 
chus tau). Whether these cells are homologous wherever they 
occur, and whot their exact relations may be to similar cells 
that form a transient nervous system in Elasmobranch embryos, 
is still a matter of doubt. 


NERVOUS SYSTEM.—VERTEBRATA. 489 


PISCES. 
CYCLOSTOMI. 


D. 749. T'wo pieces of the trunk of a Sea-~Lamprey ( Petromyzon 
marinus) with the cord exposed from above in one, and in 
transverse section in the other, to show its dorso-ventrally 
flattened, ribbon-like form. The grey matter of the cord 
surrounds the central canal and has the same outline in 
cross-section as the cord itself. In the white matter are a 
number of large fibres (Miiller’s fibres). The cord occupies 
only a small part of the neural canal, and is surrounded by 
two fibrous sheaths—an outer dura mater attached here and 
there by trabeculee to the fibrous walls of the canal, and a 
delicate pia mater close to the cord. Between the two 
there is a large subdural space occupied by loose trabecular 
tissue. In the upper specimen, the cord is seen in 
transverse section situated near the floor of the neural canal 
and surrounded by a mass of subdural tissue. In the lower 
specimen the two sheaths have been slit along the dorsal 
mid-line, and black paper has been inserted beneath them. 
A red rod has been placed beneath the posterior part of 
the cord. 


ELASMOBRANOHILI. 


D. 750. A section of the head and vertebral column of a Skate 
(Raia batis), in which the cerebro-spinal axis has been 
laid bare by the removal of the posterior walls of the 
cranial and spinal cavities. The spinal cord is continued 
to the caudal end of the vertebral column, regularly and 
very gradually decreasing in size. The dorsal roots of 
the spinal nerves can be seen arising from the dorso-lateral 
borders of the cord at regular intervals and passing diagon- 
ally backwards to their point of exit from the neural canal, 
their direction becoming more and more oblique towards 
the hinder end of the body. In the anterior region 
the dorsal roots occur at more frequent intervals than 
further back, and here perforate the continuous cartilaginous 
walls of the neural canal. When separate vertebral arches 
are differentiated (about 80 mm. behind the skull) a dorsal 


490 PHYSIOLOGICAL SERIES. 


root perforates each of the interdorsalia. A number of the 
anterior spinal nerves converge as they pass outwards to 
form the cervical and brachial plexuses. The parts have 
been finely injected. O. C. 1347. Hunterian. 


D. 751. A similar specimen of the anterior part of the spinal 
cord of a Skate (Raia batis). The cord is surrounded by a 
large subdural space. 0. C. 1347 . 


D. 752. A portion of the spinal cord of a Skate (J?aia batis) ex- 
posed within the neural canal from above. Upon the left 
side, the passage of the dorsal roots of the spinal nerves 
through the interdorsalia is shown upon the section surface, 
and in a similar way upon the right side that of the motor 
(ventral) roots at a lower level through the dorsalia, The 
dorsal and ventral roots emerge from the cord in the same 
transverse plane, but pass through the neural arches at 
different levels, the ventral root perforating a dorsalium 
and the dorsal root the succeeding interdorsalium. The 
increasing obliquity of the nerve-roots, towards the lower 
end of the specimen, in their passage to the walls of the 
neural canal is very clearly shown. O. C. 1347 b. 


TELEOSTEA. 


D. 753. The posterior end of the vertebral column of a Cod 
(Gadus morrhua), showing from above the hinder portion 
of the spinal cord. Before reaching the extremity of the 
vertebral column it swells to form a large pear-shaped 
terminal ganglion, from the hinder end of which a delicate 
terminal filament is given off. A similar enlargement is 
found in many bony fish. O. C. 1347 F. 


D. 754. The cranium and vertebral column of a Fishing Frog 
(Lophius piscatorius), from which the dorsal parts have 
been removed to expose the brain and spinal cord in situ. 

The anterior end of the cord, where it passes into the 
medulla, is much enlarged and shows upon the dorsal 
surface a pair of pyriform prominences, abruptly swollen 
in front and gradually decreasing to the normal level of the 


NERVOUS SYSTEM.—VERTEBRATA. 491 


cord behind. The nerves that arise from this region of the 
cord are stouter than the rest of the spinal nerves. In 
minute structure, these eminences agree with the metameric 
enlargements at the anterior end of the cord in the Gur- 
nards. In both cases they are due to an increase in the 
dorsal horns of the grey matter of the cord corresponding 
to an increase in the development of the sensory roots of 
the anterior spinal nerves. The cleft between the two 
prominences is occupied by a mass of giant ganglion-cells, 
whose axis cylinders have been traced to the roots of the 
trigeminal. They are probably connected with the innerva- 
tion of the epidermal processes upon the head of the fish. 
The cord rapidly diminishes in size posteriorly, until upon 
a level with the ard or 4th vertebra it is represented by a 
delicate thread lying in the centre of a “ cauda equina” 
formed by the roots of the posterior spinal nerves. The 
actual posterior limit of this terminal filament is not very 
clear in the specimen, but it apparently stops at some 
distance from the extremity of the tail. The filament is 
indicated by bristles and black paper placed beneath it. 
Another example of the spinal cord of this fish is shown 
in D. 100. O. CU, 1347 &. 
Fritsch, Arch. f. Mikr. Anat., Bd. xxvii. 1886, p. 13. 


D. 755. A Gurnard (Zrigla hirundo) with the brain and spinal 
cord exposed from above. The cord is remarkable for a 
series of five pairs of rounded eminences upon its dorsal 
surface close behind the medulla. The first two pairs are 
relatively insignificant, but the last three are large and of 
about equal size. The eminences consist of grey matter 
with a superficial layer of small ganglion-cells. Like the 
sensory cranial nerve-nuclei, which they much resemble in 
structure, they are formed by a great development of the 
grey matter of the anterior horns, arising in response to a 
demand for increased nerve-supply. They give origin to 
the dorsal roots of the three anterior pairs of spinal nerves. 
These (especially the roots of the 3rd pair) are of great 
size and supply the free digitiform rays of the pectoral 


fins. ise 
Ussow, Arch. Biol. t. iii. 1882, p. 605. 


492 PHYSIOLOGICAL SERIES. 


AMPHIBIA. 


D. 756. A Menobranchus lateralis with the brain and spinal cord 
exposed from above. The cord, like that of a fish, extends 
to the tip of the tail gradually decreasing in size. It 
shows no appreciable thickening at the points of orig of 
the limb-nerves. 


D. 757. A Common Toad (Bufo vulgaris) with the brain and 
spinal cord exposed from above. The cord is much shortened 
relative to the vertebral column It rapidly tapers to form, 
on a level with the fifth vertebra, a filum terminale that ex- 
tends into the urostyle and is surrounded at its proximal end 
by a cauda equina formed by the posterior nerve-roots. 
Brachial and crural swellings are distinguishable, separated 
by a short narrower segment of the cord. 


REPTILIA. 


D. 758. A Monitor Lizard (Varanus indicus) with the brain 
and spinal cord exposed from the dorsal aspect. The cord 
is cylindrical and except for the brachial and crural 
enlargements, is of about equal calibre from its anterior 
extremity to the root of the tail. From this point to its 
termination at the tip of the tail it rapidly diminishes in 
size. The brachial and crural enlargements are of quite 
moderate dimensions. As in all other cases where they 
occur, they are mainly due to an enlargement of the ventral 
horns of grey matter, occasioned by the increased motor 
nerve-supply necessary for the limbs. The cord completely 
fills the neural canal. O. C. 1849 a. 


D.759. The spinal cord of some large Reptile, apparently a — 
Snake, showing the gradual diminution of the cord to its 
caudal extremity. There are no indications of brachial or 
crural enlargements. O.C. 13851. Hunterian, 


D. 760. The tail of a Python (Python sp.) showing the spinal 
cord in situ from above. As in Varanus, the cord extends 
to the tip of the tail gradually diminishing in size. It fills 
the cavity of the neural canal. O. C, 1349 B. 


NERVOUS SYSTEM.—VERTEBRATA. 493 


D.761. Parts of the cranium and neck of a young Crocodile with 
the brain and cervical part of the spinal cord exposed from 
above. ‘The cord is surrounded by two protective mem- 
branes—the dura mater which has been divided along the 
dorsal mid-line and turned to either side, and a delicate pia 
mater closely investing the cord and carrying the blood- 
vessels. Between the two sheaths is a subdural lymph- 
space. The arteries of the pia mater have been injected. 
The entrance of the dorsal roots of the spinal nerves into the 
cord by several spreading rootlets is clearly seen through 
the transparent pia mater. The brain has been preserved 
to show its comparatively small size in relation to the 
spinal cord. The right tympanic membrane and columella 
auris are also shown. QO. C. 1348. Hunterian, — 


D. 762. The hinder part of the spinal cord of a young Crocodile, 
isolated. This is apparently the rest of the cord shown 
in the preceding specimen. It has been cut off at the 
anterior end of the brachial enlargement (the posterior 
limit of the previous specimen) and its arteries have been 
injected. The brachial and crural enlargements are of 
moderate development. Behind the latter, the cord rapidly 
diminishes to form the caudal segment. The extreme caudal 
end has been removed. The cord is enveloped by the pia 
mater, and in places also by the dura. O. C. 1349. 

Hunterian, 


D. 763. The brain and spinal cord of a Tortoise (Testudo greca). 
This specimen is a striking example of the correlation that 
occurs between the size of the different regions of the central 
nervous system and the activity of the parts innervated by 
them. In the Tortoises movements are mainly restricted to 
the head, neck, tail, and limbs, the trunk region being 
rendered immotile by the development of the carapace. 
In consequence of the absence of the greater part of the 
usual muscles and integumentary sense-organs from this 
immotile region, the cord and spinal nerves are here re- 
markably slender. In its other parts (cervical and caudal 
regions and limb swellings) the cord shows a considerable 


state of development. 


494 PHYSIOLOGICAL SERIES. 


D. 764. Part of the spinal cord of a Turtle (Chelone mydas) 
invested in its protective membranes. Parts of the dura 
mater have been removed, exposing the underlying pia 
mater and the subdural space. The slenderness of the cord 
relative to the distance between the origins of the spinal 
nerve-roots is well shown. O.C. 1850. Hunterian, 


AVES. 


D. 765. A part of the spinal cord from the neck of an Ostrich 
(Struthio camelus). The protecting membranes have been 
reflected from the dorsal surface of the cord, showing the 
longitudinal dorsal fissure extending down to the dorsal 
grey commissure. In one part the two halves of the cord 
have been thrust apart, rupturing this commissure and 
exposing the central canal. Upon the ventral surface of 
the cord the dura mater has in part been preserved. It is 
folded back to expose the origins of the dorsal and ventral 
roots of a pair of spinal nerves. The dorsal root is the 
larger of the two and enters the cord by several well-defined 
rootlets. O.C. 1352. Hunterian. 


D. 766. A smaller portion of the cervical region of the spinal cord 
of an Ostrich (Struthio camelus). The dura mater has been 
removed. In the posterior part of the specimen the right 
dorsal column of the cord has been cut away to show the 
depth of the dorsal longitudinal fissure. A black bristle 
has been inserted into the central canal. The roots of a 
pair of spinal nerves are shown in detail. The dorsal root 
breaks up before entering the cord into nine or ten 
rootlets, whose several points of entrance-into the cord lie ~ 
in a straight line, some 15 mm. in length, upon its lateral 
border. The ventral root rises from the cord near the mid- 
ventral line by three main rootlets. The dorsal and ventral 
roots run for some distance (20 mm.) before uniting. At 
the point of union lies the large ganglion of the dorsal root. 

O. C. 1353. Hunterian. 


D. 767. A portion of the thoracic segment of the spinal cord of 


an Ostrich (Struthio camelus) with the dura mater partly 
removed, O.C. 1354. Hunterian. 


I a ae 


NERVOUS SYSTEM.—VERTEBRATA. 495 


D. 768. The sacral and caudal parts of the spinal cord of an 
Ostrich, showing the enlargement which takes place at the 
point of origin of the nerves for the hind limbs, and the 
lateral separation of the posterior columns of the cord at 
this part, leaving an interspace—the “sinus rhomboidalis,” 
The cavity of this space in Birds is filled by a cellular mass 
derived apparently from the ependyma of the central canal. 
The following is the original description of this prepa- 
ration :—“ The part of the medulla which lies in the loins 

and tail of an Ostrich. That part which lies in the loins 
is considerably larger than those which belonged to the 
neck and back ; and then it becomes pretty fast smaller to 
the tail. This swelling in the loins is owing, perhaps, to 
this. bird having such large thighs and legs; and when we 
consider that this bird, having such small wings, must have 
the whole progressive motion performed by the legs, and 
the legs are therefore longer in proportion to the size of the 
bird than in birds in common, we must see why the medulla 
ought to be large at this part in this bird.” 0. C, 1855. 
. Hunterian. 


D. 769. The hinder part of the crural swelling and the caudal 
part of the spinal cord of an Ostrich, with the membranes 
partially reflected showing, upon the ventral surface, the 
origins of some of the motor roots of the nerves to the 
legs. The dorsal longitudinal fissure is shown in the caudal 
part. There is never in Birds a cauda equina due to the 
shortening of the spinal cord in relation to the vertebral 
column. QO. C. 1856. Hunterian. 


D. 770. The attenuated caudal prolongation of the spinal cord 
of an Ostrich. O.C. 1357. Hunterian. 


D.771. The brain and spinal cord of a Partridge (Perdix rufa) 
exposed in situ from above. This specimen shows clearly 
the relative proportions of the different regions of the cord: 
the long cylindrical cervical segment ; the fusiform swelling 
at the origin of the brachial plexus; the relatively short 
thoracic portion; the crural swelling, with its open rhomboid 
fossa; and the rapid diminution of the cord behind the 


sacrum. ‘The cord almost completely fills the cavity of the 


neural canal. O.C. 1358. Hunterian, 


496 


PHYSIOLOGICAL SERIES. 


lo MAMMATIA, 


MONOTREMATA. 


D.772. The brain and spinal cord of a Duck-billed Platypus 


(Ornithorhynchus paradozus) exposed from above. The 
cord extends into the tail, gradually diminishing in size as 


it passes backwards. The brachial and crural enlargements 


are but slightly marked. O. C. 1358 a. 


- 


D. 773. A similar specimen of the brain and spinal cord of a 


Spiny Ant-eater (Tachyglossus [Echidna] aculeatus). The 
cord is remarkably stout and terminates in the thoracic 
region, at a point about a third of the distance from the 
brachial plexus to the sacrum. From the medulla to 
within two centimetres of its termination it is of great 
size and of about equal calibre, but then rapidly comes 
to a point and ends in a filum terminale amidst the bundle 
of backwardly directed nerve-roots that constitutes the 
cauda equina. The branching rootlets of the sensory roots 
of the spinal nerves are well shown, particularly in the 
brachial region. There is no marked swelling of the cord 
at this point. O. C. 1358 . 


INSECTIVORA. 


D.774. A Hedgehog (Frinaceus europeus) with the brain and 


spinal cord exposed from above. The spinal cord, as in 
Tachyglossus, is remarkably short. It extends, of about the 
same calibre, from the medulla to the level of the third rib, 
and from this point rapidly diminishes in size, until on a 
level with the fifth rib it is replaced by a delicate terminal 
filament, which forms the central strand of the cauda 

equina. 
In this specimen the brachial plexuses have been dissected. 
O. C. 1372 B. 


it 


NERVOUS SYSTEM.—VERTEBRATA. 497 


EDENTATA, 


D.775. The brain and spinal cord of an Armadillo (Dasypus sp.), 
isolated. The cervical part of the cord is of considerable 
thickness and scarcely swells at all at the point of origin 
of the brachial nerves. Between the brachial and luambo- 
sacral plexuses, the cord is somewhat reduced in size and 
is slightly flattened from above downwards. The crural 
swelling is of great length and not sharply defined. The 
cord is replaced posteriorly by a terminal filament and a 
cauda equina. O. C. 1358 k. 


D.776. A similar specimen of the brain and spinal cord of a 
Two-toed Sloth (Cholapus didactylus). In its general 
proportions this cord differs considerably from that of 
Dasypus, owing partly to the greater length of the thoracie 
region of the vertebral column and the consequent backward 
shifting of the lumbo-sacral plexus and crural enlargement, 
and partly to the greater development of the limbs accom- 
panied by a corresponding prominence of the limb-swellings. 
The thoracic part of the cord is relatively very slender. 
The crural swelling tapers abruptly behind to form the 
terminal filament. 

In this specimen the nerve-roots, particularly in the 
cervical and brachial regions, are very distinct. On either 
side, a bristle has been passed along the cord between the 
dorsal and ventral roots to demonstrate their division, 
towards the cord, into numerous delicate rootlets. The 
ganglia on the dorsal roots are in many cases very clear. 


O. C. 1358 b. 


CARNIVORA, 


_ D.777. The hinder part of the spinal cord of a Lion (Felis leo), 
injected. The dura mater has been divided along the dorsal 
mid-line and reflected to either side, exposing the sub- 
dural lymph-space and the delicate inner sheath of the cord 
composed of arachnoid and vascular pia mater. Behind 
the crural swelling, the cord rapidly diminishes and gives 

VOL. Il. 25 


498 


PHYSIOLOGICAL SERIES. 


place to a cauda equina. The main nerve-roots that form 
the cauda lie in the specimen somewhat apart, and thus 
display very clearly the terminal part of the cord dwindling 
rapidly to a filament and giving off on either side delicate 
nerve-roots of diminishing size. At the anterior extremity 
of the specimen the subdural lymph-space is relatively small, 
but it gradually increases as the cord tapers and forms a 
capacious cavity in which the proximal parts of the cauda 
equina lie free. O.C. 1373. Hunterian. 


D. 778. The hinder part of the spinal cord of a young Lion (Felis 


leo), injected. The dura mater has been removed from the 
dorsal surface, showing very clearly the division of the 
dorsal roots of the spinal nerves into radiating rootlets 
before their entrance into the cord. It should be noticed 
that the shortening of the cord in relation to the vertebral 
column (indicated by the backward passage of the nerve- 
roots towards the intervertebral foramina) is not apparent 
until about the middle of the crural swelling. The relations 
of the dura mater and subdural space to the cord and 
proximal parts of the cauda equina are very clear. 

O.C. 1374. Hunterian. 


D.779. The brain and spinal cord of a Coati-mundi (Nasua 


narica). The dura mater has been removed from the 
dorsal surface. The cervical part of the cord, as in Dasypus, 
is little, if at all, smaller than the brachial swelling. The 
crural swelling is very long and tapers gradually towards 
the tail, forming a cauda equina in which the components 
are closely compacted together. O. C, 18748. 


D. 780. The isolated brain and spinal cord of a Badger (Meles 


meles). The cord is enveloped in its membranes, Pos- 
teriorly it terminates in a cauda equina. O.C. 13744, 


UNGULATA, 


D. 781. “The lower part of the medulla spinalis of a Fawn 


(Cervus dama) with the dura mater turned off from one 
side, to show the origins of the nerves arising from the 


% 
aE, 


NERVOUS SYSTEM.—VERTEBRATA. 499 


medulla, and that the cauda equina is formed by the nerves 
after they have passed through the dura mater, as in the 
Porpesse; but here it may be observed that after they have 
perforated the dura mater they do not run so obliquely 
downwards [backwards], and therefore the cauda is not so 
perfect.” 

The crural swelling merges very gradually into the rest of 
the cord in front. In the interspaces between the nerves 
the arachnoid forms a series of lateral connections with the 
dura mater—the external attachments of a longitudinal 
ligament (1. denticulatum) by which the cord is suspended 
in the centre of the neural canal. 

QO. C. 1365. Hunterian. 


D. 782. The spinal cord of a Giraffe (Giraffa camelopardalis) 
The dura mater has been removed except around the nerve- 
roots. In the cervical region the nerves are widely sepa- 
rated, but their tributary rootlets arise from so large an 
area of the cord that the last rootlet of one nerve-root 
arises almost on the same level as the first of the succeeding 
root. The rootlets of the second cervical nerve are indicated 
on the right side by the insertion of a black rod between 
the sensory and motor series. The brachial and crural 
swellings are slightly developed. O. C. 1365 a. 


D. 783. The spinal cord of a Calf (Bos taurus). The dura 
mater has been longitudinally divided above and below and 
reflected to either side. By this means the subdural space 
and nerve-roots are well shown, as well as a series of pro- 
cesses of the pia mater and arachnoid (ligamentum den- 
ticulatum), by which these membranes are laterally united 
to the dura in the intervals between each pair of spinal 
nerves. 

The arachnoid also accompanies the rootlets of the spinal 
nerve-roots, and is at these points clearly distinguishable 
from the underlying pia mater. 

In front of the crural swelling the cord has been folded 
upon itself, and in this part the dura mater has not been cut. 


The brachial and crural swellings merge very gradually 
2K 2 


500 PHYSIOLOGICAL SERIES. 


into the rest of the cord, and are thus not very definite 
although in fact well developed. O. C. 1364 B. 
Presented by J. Holm, Esq. 


D. 784. Part of the spinal cord of a Calf (Bos taurus). The 
dura mater, except around the nerve-roots, and the arachnoid 
and pia mater of the left side have been removed. The 
arteries of the pia mater have been injected. The ventral 
longitudinal furrow, occupied by a lamina of pia mater, 
and the lateral dorsal furrows at the entrance of the rootlets 
of the dorsal roots of the spinal nerves are also clearly 


shown. O. C. 1365 s. 


D. 785. A portion of the spinal cord of an Ox (Bos taurus) 
stripped of its membranes. Parts of the dorsal and ventral 
columns have been partially torn away and teased at their 
free ends to show their ready cleavage in a longitudinal 
direction, in uccordance with the course of their component 


fibres. O. C. 1365 F. 


D. 786. The terminal portion of the spinal cord of a Calf (Bos 
taurus) stripped of its membranes, and showing the ventral 
longitudinal fissure and the passage of the cord into the 
filum terminale. O. C. 1365 a. 


D. 787. The posterior cervical and anterior thoracic regions of 
the spinal cord of an Elephant (Elephas indicus). 

The dura mater and arachnoid have been reflected from 
the dorsal surface, showing the loose subarachnoid tissue 
and, at the cut margin of the membranes, the slit-like 
subdural space. The rootlets of the dorsal roots of the 
spinal nerves are very strongly developed at the brachial 
swelling, and form an almost continuous series on either 


side. O. C. 13868. Hunterian. 


D. 788. Part of the thoracic region of the spinal cord of an 
Elephant (Zlephas indicus). The dorsal and ventral roots 
of the spinal nerves are very dissimilar in their mode of 
connection with the cord. The dorsal roots enter the cord 


See ee 


NERVOUS SYSTEM.—VERTEBRATA. 501 


abruptly by a few large and distinct rootlets; the ventral 
rootlets take their origin from a more extended area, and 
are numerous and small, converging and uniting to form 
several fasciculi before they finally pass through the dura 
mater. The arachnoid membrane can be seen at the cut 
edge of the dura, separated from it by a narrow subdural - 
space. The much larger space between the arachnoid and 
pia mater is occupied by laminar and trabecular subarachnoid 
tissue.’ On either side a stout ligament (I. denticulatum) 
runs longitudinally within this tissue between the dorsal 
and ventral nerve-roots. In each interspace between the 
nerves it bends outwards towards the arachnoid and unites 
with it, and with the dura mater. 


O. C. 1369. Hunterian. 


D. 789. The posterior end of the spinal cord of the same 
Elephant, showing the crural enlargement and the origin 
of the caudaequina. The dura has been removed from the 
ventral surface. Where the cord gives place to the cauda 
equina the dura lies at some distance from it, and encloses 
within its general cavity a considerable length of the nerve- 
roots that form the cauda. The median spinal artery is 
shown within the pia mater in the ventral mid-line. 


O.C. 1370. Hunterian. 


D. 790. Part of the spinal cord of an Elephant from the lumbo- 
sacral region. ‘The dura mater is removed from both 
dorsal and ventral surfaces, showing the origins of the 
nerves. The specimen is suspended by the ligamentum 
denticulatum. A small portion of the pia mater is reflected 
from the dorsal surface of the cord, showing the lamina that 
projects from its inner surface into the dorsal longitudinal 
fissure. The corresponding lamina in the ventral fissure is 
seen upon the upper sectional surface. A portion of the 
dorsal columns of the cord has been removed at the lower 
end of the specimen, showing the fibrils of the dorsal roots 
passing a little way into the substance of the cord. A 
bristle has been placed beneath them on the left side. 

0.0. 1371. Hunterian. 


502 PHYSIOLOGICAL SERIES. 


7 CETAOBRA. 


- 


“The medulla spinalis is much smaller in proportion to the size of 
the body than in the human species, but still bears some proportion to 
the quantity of brain; for in the Porpoise, where the brain is largest, 
the medulla spinalis is largest; yet this did not hold good in the 
Spermaceti Whale, the size of the medulla spinalis appearing to be 
proportionately larger than the brain, which was small when compared 
to the size of the animal ...._ The dura mater .... where it covers 
the medulla spinalis, differs from all the quadrupeds I am acquainted 
with, inclosing the medulla closely, and the nerves immediately passing 
out through it at the lower part, as they do at the upper, so that the 
cauda equina, as it forms, is on the outside of the dura mater.”— 
Hunter, “ Observations on the Structure and @conomy of Whales,” 
Phil. Trans. vol. |xxvii. 1787, p. 424. 


D. 791. The hinder part of the brain and the spinal cord of a 
Porpoise (Phocena phocena). 

“The dura mater is removed from about one half of the 
breadth of the posterior surface [on the left side] through 
its whole length to expose the medulla. It is not so loose 
as in the Human subject, but incloses the medulla very 
tightly. It goes no further than to the lower end of the 
medullary substance ; so that it does not inclose the cauda 
equina beyond that termination, as in the Human subject 
or Monkey. The nerves go out of this sheath immediately, 
through the whole length of the medulla; so there is no 
cauda equina on the inside of the dura mater either above 
or below the termination of the medullary substance. The 
cauda equina is therefore on the outside of the sheath of 
the dura mater.” 

Although in a sense the strands of the cauda equina and 
the distal parts of the other nerve-roots may be said to lie 
outside the dura, if by that we mean the common dural 
investment of the cord, yet each root from its emergence 
from this common investment to its exit from the neural 
canal is covered by a reflexion of the dura, and thus in fact 
lies within it. The cervical region of the cord is remarkably 
short. The nerves in this part are consequently aggregated 
together, the hindermost arising from a fairly pronounced 


SD ee ee - 


NERVOUS SYSTEM.—VERTEBRATA. 503 


brachial swelling. The shortening of the cord in relation 
to the vertebral column is indicated by the gradually 
increasing obliquity of the nerve-roots towards the hinder 
end. Although there are no functional hind limbs, the 
posterior part of the cord shows a well marked swelling, due 
to the great nerve-supply necessary for the tail. There is 
a strongly developed cauda equina, the component strands 
of which are more or less tortuous. This condition has 
been thought to be “ due to the great freedom of movement 
and flexibility possessed by the caudal portion of the 


animal ” (Cunningham, p. 212). O. C. 1359. 
D. J. Cunningham, Jour. Anat. & Phys., vol. xi. 1877, 
p. 209. 


D. 792. The spinal cord of a Porpoise (Phocena phocena), in- 
jected. The dura mater has been removed from the dorsal 
surface. O. C. 1360. Hunterian. 


D. 793. The cervical portion of the spinal cord of a Dolphin 
(Delphinus tursto), showing the origins of the eight cervical 
and first thoracic pairs of nerves. The dura mater has 
been removed from the ventral surface, and has been 
longitudinally divided upon the dorsal surface and reflected 
to either side to show the underlying membranes. The 
arachnoid is distinguished by a white bristle inserted 
between it and the pia. The roots of the first four cervical 
nerves are very oblique, O.C. 1361. Hunterian. 


D. 794. A transverse section through the thoracic region of the 
spinal cord of the same Dolphin, showing on the section 
surface the central canal and the infolding of the pia mater 
into the ventral longitudinal fissure. The membranes of 


the cord have been treated as in the preceding specimen. 
O. C. 1362. Hunterian. 


D. 795. Part of the spinal cord of a Piked Whale (Balenoptera 


acuto-rostrata) showing the rootlets of the spinal nerve- 


roots. O. CG. 1363. Hunterian. 


504 PHYSIOLOGICAL SERIES. 


D. 796. The posterior part of the spinal cord of the same Whale, 
from the dorsal surface of which the left half of the thick 
dura mater has been removed, showing that it forms a 
comparatively close investment to the cord, as in the 
Porpoise (D. 791), and that the long separate roots of 
the posterior nerves, that compose the cauda equina, 
are external to the common dura mater investment of the 
cord, although each is covered by an independent sheath 
derived from that investment. O. 0. 1364. Hunterian. 


PRIMATES. 


D. 797. “ Part of the brain, and the whole medulla spinalis of a 
common Monkey. ‘The dura mater is in part removed 
from the front [ventral] part, and exposes the cauda equina, 
which is inclosed in that membrane. ‘There is little or no 
difference between these parts in this animal and the human 
subject, only that the dura mater is not so large in propor- 
tion to the size of the medulla.” The brachial and crural 
swellings are well shown. O.C. 1375. Hunterian. 


D. 798. The cerebellum, medulla oblongata, and spinal cord of 
a young Orang-Outang (Simia satyrus) exposed from the 
dorsal aspect. The proximal parts of the first pair of ribs 
have been left to mark the limit of the cervical region of 
the cord. The brachial swelling is strongly pronounced. 
The large size of the nerves arising from it is well shown, 
and the abrupt termination of their dorsal roots in the 
lateral dorsal furrow of the cord. Behind the cervical 
region the nerve-roots take a very oblique backward course 
and on a level with the second lumbar vertebra form the 
cauda equina. The lumbo-sacral swelling is very slight. 

The ganglia upon the dorsal nerve-roots can be clearly 
seen; in the cervical region they lie upon the roots in the 
intervertebral canals, but further. back are situated within 
the neural canal before the nerve passes between the 
vertebree. O.C. 1375 B. 

Presented by Sir Victor Horsley. 
Vigueiredo-Rodriques, Arch. Mikr. Anat., Bd. lix. 1901, 
p- 417. 


NERVOUS SYSTEM.—VERTEBRATA. 505 


D. 799. The spinal cord of a young Gorilla (Anthropopithecus 
gorilla) with the dura mater removed, and the constituent 
nerve-roots of the cauda equina separated to either side to 
show the filum terminale. 

In its general features the cord resembles that of Man. 
O.C. 1375 a. 
Waldeyer, Abhandl. Akad. Wiss. Berlin, 1888, p. 61. 


D. 800. The vertebral column and spinal cord of an infant, in- 
cluding the thoracic and lumbo-sacral regions. The vertebral 
column and dura mater have been divided by a sagittal 
section and spread apart, exposing the cord. In places. 
the ligamentum denticulatum can be seen, binding the 
arachnoid membrane to the dura in the interspaces between 
the nerves. Upon the right side the arachnoid has been 
stretched away from the pia mater, and shows very clearly. 
A great part of the cauda equina lies within the common 
dura mater sheath. Several of the arteries have been 
injected. O. C. 1378 A. 

Mus. Heaviside. 


D. 80). The medulla oblongata and spinal cord of Man. The 
dura mater and arachnoid membrane have been sagit- 
tally divided and spread to either side, thus extending 
the nerve-roots and showing clearly the subarachnoid 
tissue and the ligamentum denticulatum. The brachial 
and crural swellings, the cauda equina and terminal 
filament are well shown. The gradually increasing obliquity 
of the course of the spinal nerve-roots towards the 
hinder end of the cord is very striking, and affords an 
indication of the shortening of the cord relative to the 
vertebral column. O.C. 1376 B. 

Presented by J. Holm, Esq. 


D. 802. “ Nearly the whole length of the medulla spinalis, with 
the cauda equina, of the Human subject. The dura mater 
is in part removed to show the medulla and the going out 
of the nerves through that membrane.” The arachnoid 


membrane is well shown upon the ventral surface. 
O. C. 1376. Hunterian. 


506 PHYSIOLOGICAL SERIES. — 


D. 803. * The termination of the medulla spinalis with the nerves 
cut off;~which formed the cauda equina, excepting the last 
nerve, which arises from the very termination of the 
medulla. It shows that the medulla is lengthened out in 
the form of a nerve, and, as it were, continued into the last 
nerve.” 

The “last nerve ”’ of the above description is the degene- 
rate remains of the hinder part of the cord (filum terminale), 
and consists mainly of connective tissue and a few medullated 
nerve-fibres. At its anterior end there are vestiges of the 
central canal and grey matter. QO. C. 1377. 

Hunterian, 


D. 804. A portion of the spinal cord of Man, showing the roots 
of the spinal nerves and the relations of the protective 
membranes to the cord. A strip of dura mater has been 
left attached to the nerve-roots on the right side. Close 
beneath it upon the ventral surface, but separated from it by 
a narrow subdural space, is the delicate arachnoid membrane. 
The pia mater adheres closely to the cord; it has been 
removed from the left half of the specimen; its cut edge 
can be seen between the termination of the nerve-roots and 
the ventral fissure. Within the fissure lies a lamina of 
pia mater. The dorsal and ventral nerve-roots, as in the 
Elephant and other mammals, arise from the cord in a cha- 
racteristic manner—the dorsal roots enter the cord abruptly 
in the dorso-lateral fissure by a few stout rootlets; the 
ventral leave it by more numerous branching rootlets that 
emerge at slightly different distances from the ventral mid- 
line. QO. C. 1878 F, 


D. 805. A similar specimen showing the origin of two pairs of 
spinal nerve-roots. The dura mater has been removed and 
the spinal ganglia dissected on the right side. 

O. C. 1378 ¢. 


NERVOUS SYSTEM.——-VERTEBRATA. 507 


Membranes of the Spinal Cord. 


D. 806. A section of the vertebral column, with the spinal cord 
and its membranes, of a Basking Shark (Selache maxima). 
The neural canal is lined by a thin fibrous membrane—the 
outer, perichondrial layer of the dura mater. The space 
between this layer and the cord is occupied by loose tra- 
becular tissue forming the deeper parts of the dura, and 
giving support to a network of blood-vessels. The cord is 
surrounded by a close-fitting pia mater. 


D. 807. Part of the spinal cord of a Calf (Bos taurus). The 
dura mater has been removed except at the sides of the 
upper part of the specimen. Upon the ventral surface of 
the cord the arachnoid membrane has been longitudinally 
divided and reflected, exposing the pia mater closely ad- 
herent to the cord. The cut edge of the pia can be seen 
on either side of the ventral longitudinal fissure at the upper 
end of the specimen. } O. C. 1865 c. 


D. 808. A portion of the spinal cord of Man. The dura mater 
has been removed from the dorsal and ventral surfaces, 


exposing the subdural space and arachnoid membrane. 
UO. C. 1378 B. 


[ 508 ] 


ABBREVIATIONS USED IN FiGuRES OF VERTEBRATE CENTRAL 
Nervous System. 


he ar 


AcoU. TUB., acoustic tubercle. 

ALY., alveus of the hippocampus. 

ANT. COMM., anterior commissure (Fishes). 

ANT. QUAD. CoRP., anterior corpora quadrigemina. 

ANT. WING, anterior wing of valvula cerebelli (Mormyrus). 
AQUA, 8¥L., Aqueduct of Sylvius. 

AREA PRECOM., precommissural area. 

AREA TEGMEN., tegmental area. 

AREA A, B, C., see page 211. 

BL. core., blood corpuscles. 

BL. V., blood-vessel. 

CALCAR., calcar avis (calcarine sulcus in fig. 222). 

CAP. EXT., external capsule. 

cap. INT., internal capsule. 

CER. 0” CEREBEL., cerebellum. 

CER. HEM., cerebral hemispheres. 

COMM. ANT. Or COMM. A., anterior commissure (Mammals), 
coms. D., dorsal or hippocampal commissure. 

COMM. MOL, 07° SOFT COMM., commissura mollis, 

COMM. SUP., Superior commissure. 

comM.v., ventral or true anterior commissure. 

CORP. CALL., corpus callosum. 

CORP. GEN. ANT., Corpus geniculatum anterior. 

CORP. GEN. POST. or CORP. GEN., corpus geniculatum posterior. 
CORP, INTERPED., INTER., INTERP., 07 GANGL, INTER., Corpus interpeduncu- 
CORP. MAM., corpus mammillare, {lare. 
CORP. PARATERM., paraterminal body. 

CORP. PIN., pineal body. 

CORP. PIT., pituitary body. 

CORP. QUAD., corpora quadrigemina, 

CORP. 8T., CORP. STR., CORP. STRI., 07° C. STR., Corpus striatum. 
CRUS CER., crus cerebri. 

pors. P. FLOC., dorsal paraflocculus, 

pors. sac., dorsal sac. 

EOTOSYL., ectosylvian arc. 


ABBREVIATIONS. 509 


EPEND., ependyma. 

EPIPH., epiphysis. 

EPISTRI., epistriatum. 

FASC. ABERR., fasciculus aberrans. 

FASC, DENT., fascia dentata. 

Fasc. LONG., fasciculus longitudinalis posterior. 

FI. or FIM., fimbria. 

Ist arcu. GyR., first arcuate gyrus of Leuret. 

F1o0c., floceular lobe of cerebellum. 

FLOC., (in figs. 77, 83, 84, 85, 92, 106, 112, 116, 245, 249), flocculus 
Foc. F., floccular fissure. (sensu stricto). 
FoRC. MAJ., forceps major. 

FOR. LAB. INF., passage from the infundibulum into the lobus inferior. 
FoR. MoNR., Foramen of Monro, 

47x vENT., fourth ventricle. 

F. PRIM., primary fissure of cerebellum. 

F, SECUND., secondary fissure of cerebellum. 

GANG. HAB., ganglia habenule. 

GANG. INTER., 07 CORP. INTER., corpus interpedunculare. 
GEN. or GENU, genu of corpus callosum. 

HEM., cerebral hemisphere. 

HIP., hippocampus. 

HIP. F., hippocampal fissure. 

HIP. 1NV., inverted hippocampus. 

HIP. NUDUS, hippocampus nudus. 

HIP. TUB., 07 TUBER., hippocampal tubercle. 

HIP. VEST., vestiges of the hippocampal arc. 

INF., Or INFUN., infundibulum. 

INS., insula. 

IsTH., isthmus. 

LAM. TERM., lamina terminalis. 

LAT. VENT., lateral ventricle. 

LoB. ANT., anterior lobe of cerebellum. 

LOB. CENT., middle lobe of cerebellum. 

LoB. FAC., lobus facialis. 

LOB. IMPAR, lobus impar. 

Los. INF., lobus inferior. 

LOB. LIN. LAT., lobus linex lateralis. 

LOB. OPT., optic lobes. 

LoB. Post., lobus posterior of cerebellum. 

LOB. vaG., lobus vagi. 

LOC. PERFOR. or PERF., locus perforatus. | 
LONG. ZoNE, longitudinal zones of cerebellum in lower vertebrates. 
MARG. (POST. CALL.), marginal sulcus, 


510 ABBREVIATIONS. 


MAUTH. F1B., Mauthner’s fibres. 
meD., medulla oblongata. 

MED. AUR., medullary auricles. 

MED. OB. or OBL., medulla oblongata. 
MESEN., mesencephalon, 


MID. winG., middle or lateral wing of valvular cerebelli of Mormyrus. 


MONRO FoR., Foramen of Monro. 

N. AMYGD., nucleus amygdale. 

NEOPAL., neopallium, 

NEUROP., neuropile. 

NON-HIP. PAL,, non-hippocampal pallium. 

Nuc. v,, nucleus quinti. 

Nuc, x., nucleus vagi. 

OLY. BULB., olfactory bulb. 

OL¥. PED., olfactory peduncle. 

OLF. N., olfactory nerve. 

oLF. TR., (lower vertebrates) olfactory sedeunie? 

OLF. TR., (mammals) olfactory tract, “ external olfactory root.” 
OLF. TR. TUBER., tubercle of the olfactory tract. 

OLF, TUBER. 07 TUB., tuberculum olfactorium. 

OLF. VENT., ventricle of olfactory bulb. 

OLIV. or OLIV. BoDy, Olivary body. 

OPERC., occipital operculum. 

OPT. CHIASMA., OPT. CHIAS., 07 OPT, CHI., optic chiasma. 
opt. LoB., lobus opticus. 

OPT. N., optic nerve. 

OPT. THAL., optic thalamus. 

OPT. TR., optic tract. 

PALL., pallium. 

PARAFLOC., paraflocculus. 

PARAPLOC. D., & v., paraflocculus dorsalis and ventralis. 
PARALLEL 8., parallel sulcus, 

PARAPHY., paraphysis. 

PARATERM., paraterminal body. 

PAR. 8TALK., parietal stalk. 

PED. OL¥., olfactory peduncle. 

PERIPH, V. coMM., peripheral ventral commissure of spinal cord, 
prt. Los., petrosal lobule of the paraflocculus. 
PINEAL, pineal body. 

PIT. BODY, pituitary body. 

PONS. or PONS. VAROL., pons Varolii. 

Post, CoMM., posterior commissure. 


POST, QUAD. CORP:, posterior corpora quadrigemina. 
post. WING, posterior wing of valyula cerebelli of Mormyrus. 


ABBREVIATIONS. 511 


PRECOM. AREA., precommissural area. 

PRIM. F., primary (preclival) fissure of cerebellum. 

PSAL. 07 PSALT., psalterium (hippocampal commissure). 

PSAL, V., PSAL. D., psalterium ventrale and dorsale. 

PSEUDO SYL. F., pseudosylvian fissure (Sirenia). 

PYR., pyramids, 

PYRAMID, pyramid of cerebellum. 

PYR.L., pyriform lobe. 

PYR. L. ANT., PYR. L. Post., anterior and posterior parts of pyriform lobe. 

RAMUS POST, SUP., ramus postcentralis superior of intraparietal sulcus. 

RHIN. F., rhinal fissure. 

RHIN. F. ANT., anterior rhinal fissure. 

RHIN. F. PostT., posterior rhinal fissure. 

ROOT VALY. CER., root of the valvula cerebelli. 

ROST, CORP. CALL., rostrum of corpus callosum. 

SAC. INF., saccus infundibuli. 

SAC. VASC., saccus vasculosus. 

SECUN. F., secondary fissure of the cerebellum. 

2np @yR., second arcuate gyrus of Leuret. 

SEPT. Or SEPT. LUCID., septum lucidum, 

SOFT. COMM. 07° COMM. MOL., soft commissure, 

SPLEN. or SPL., splenium of corpus callosum. 

s.8.P., posterior branch of the supra-sylvian sulcus. 

SUP. GENU, superior genu of the central sulcus. 

s., 8, or SYL.F., the various modifications of the Sylvian and pseudo- 

sylvian fissures. 

SYL, EcTOs. coMP., sylvio-ectosylvian complex. 

SYL. SUPRAS. CoM., sylvio-suprasylvian complex (true Sylvian fissure). 

SULC. ANS., ansate sulcus. 

SULC. ANS. MIN., minor ansate sulcus. 

sULC. ARC., sulcus arcuatus. 

SULC. BISECT. 07° SULC. BISEC., bisector sulcus. 

SULC. CALC, or CAL., calcarine sulcus. 

SULC. CALL. MARG., calloso-marginal sulcus. 

SULC. CENT., central (Rolando’s) sulcus. 

suc. coLL., collateral sulcus. 

SULC. COMP., compensatory sulcus. 

SULC. COR., coronary sulcus. 

SULC. COR. LAT., 07 COR. L., corono-lateral sulcus. 

SULC. OR. 07 CRU., crucial sulcus. 

SULC. DIAG., diagonal sulcus. 

SULC. ECTOLAT., ectolateral sulcus. 

SULC. ECTOSYL., posterior ectosylvian sulcus (fig. 135), and ectosylvian 
_ are. 


512 ABBREVIATIONS, 


SULC, ECTOS, A., SULC. ECTOS, P., anterior and posterior ectosylvian sulci. 
SULC. ENTOLAT., ENT. LAT., or ENT. L., entolateral sulcus. 
SULC. EPISTRI., epistriatic invagination (Reptiles). 

SULC. FR. oRB., fronto-orbital sulcus. 

SULC. GEN., genual sulcus. 

SULC, INF. FRONT., inferior frontal sulcus. 

SULC. INF. occ., inferior occipital sulcus. 

SULC, INF. PRECENT., sulcus arcuatus (inferior precentral). 
SULC, INF. TEMP., inferior temporal sulcus. 

SULC, INF. TRANS., inferior transverse sulcus. 

SULC. INT., intraparietal sulcus. 

SULC, INTER, OF INTERCAL., intercalary sulcus, 

SULC. INTRA. OF INTRAPAR., intraparietal sulcus. 

SULC. LAT, 07 SULC. LAT. (INT. PAR.), lateral (intraparietal) sulcus. 
SULC. LAT. P., post-lateral sulcus. 

SULC. L, occ, or LAT. occ., lateral occipital sulcus. 

SULC. LIM. PALL., sulcus limitans pallii. 

SULC. MARG., marginal sulcus. 

SULC. OBL., oblique sulcus. 

SULC. OCC, TEMP., occipito-temporal sulcus. 

sULC, OLF., sulcus olfactorius. 

SULC, ORB., orbital (presylvian) sulcus, 

SULC. ORB. ACCES., accessory orbital sulcus. 

SULC. PAR. ov PAR. (P. SYL.), parallel sulcus, 

SULC. PARACALC., paracalcarine sulcus. 

SULC. PARACAUD. 07 SULC. P. CAUD., paracaudal sulci. 

SULC. PARAM., paramedial sulcus. 

SULC. PARAORB., paraorbital sulcus. 

SULC. PAR. 0cc., parieto-occipital sulcus. 

SULC. P. CALC., post- or retro-calcarine sulcus. 

SULC, P. LAT., post-lateral sulcus, 

SULC. POST. RHIN., posterior rhinal fissure. 

SULC. Posts., post-sylvian sulcus. 

SULC, PRECRU., precrucial sulcus, 

SULC. PROR., prorean sulcus. 

SULC. P. SYL., post-sylvian sulcus. 

SULC, PSEUDO SYL., pseudosylvian sulcus. 

8ULO. RECT., sulcus rectus. 

8ULC, ROS., or RosT., rostral sulcus. 

suLc. siM., Simian sulcus. 

SULC. SPLEN., splenial sulcus (intercalary prolongation of calcarine). 
SULCI suBCING., subcingular sulci. 

SULO. SUP. FRONT., superior frontal sulcus. 

SULO, SUP. LIM., superior limiting (Marchand’s opercular) sulcus. 


ABBREVIATIONS. 513 


SULC, SUP. PREC., superior precentral sulcus. 

SULC. SUPRAS., suprasylvian sulcus. 

SULC. TR. occ., transverse occipital sulcus. 

suLc. urs., Ursine sulcus. 

SULC. VERT., vertical sulcus. 

THN. THAL., tenia thalami. 

TECT. oPt., tectum opticum. 

TELA or TEL. CHOR., tela choroidea. 

THAL., thalamencephalon. 

THAL. STRI.JUNC., Junction of striatum and thalamus. 

THIRD VENT. 07 3RD VENT., third ventricle. 

TORUS LoNGI., torus longitudinalis. 

TOR. SEMICIRC., torus semicircularis. 

TRAP., trapezium. 

TUB. Acoust., acoustic tubercle. 

TUB. CIN., tuber cinereum. 

TUBER. V., tuberculum quinti. 

TUB. OLF.TR., tubercle of the olfactory tract. 

uRS. Loz., Ursine lozenge. 

VALL. SYL., Vallecula Sylvii. 

V. CEREB. MAG., vena cerebralis magna. 

VALY.CER., valvula cerebelli. 

VENT. CER., cerebral ventricle. 

VEL. MED., velum medullare. 

VENT. P. FLOC., ventral paraflocculus. 

VENT. 111., third ventricle. 

VENT. vERG., Ventricle of Verga. 

II. II. V. VI. VII. VIII. IX. X. XI. x11., roots of the cranial nerves. 

v.M., motor root of v. 

For letters asc etc., aBy etc., see text, except the following, in 
figs. 78, 90, 105:—r.p., fascia dentata; ri., fimbria; ¢., genu 
of corpus callosum; u.¥., hippocampal fissure; 1F.1H., inverted 
hippocampus; L. 1., lamina terminalis; ps, v., Ps. D., dorsal and 
ventral psalterium. 


VOL. I. | 21 


[514 ] 


INDEX TO COMPARATIVE ANATOMY 
OF MAMMALIAN BRAIN. 


[The figures in italics refer to statements in the general summary. | 


Alveus, 151, 175. 
Aqueduct of Sylvius, 166. 
Arcus occipitalis, 422, 429. 
Auditory nerve, 434. 


Balkenwindung. See Hippocampus nudus. 


Calear avis, 167, 295, 322, 370, 384, 461, 469. 

Cerebellum, 156, 164, 179, 203, 211, 216, 241, 242, 243, 294, 299, 
310, 341, 347, 366, 393, 397, 414, 434, 448, 460. 

Cerebral hemispheres, 142, 145, 146, 147, 190, 237, 245, 300, 301, 
319, 344, 348, 350, 361, 381, 385, 431, 439, 465, 466. 

Cingular arc = Calcarine + intercalary + genual sulci, 234, 310, 318, 
353, 362. 

Commissura anterior. See Commissura ventralis. 

Commissura dorsalis, 150, 151, 159, 160, 173, 187, 209. 

Commissure, hippocampal. See C. dorsalis. 

Commissura ventralis, 149, 173, 174. 

Corpora quadrigemina, 155, 170, 194, 197, 220, 241. 

Corpus callosum, 150, 160, 161, 191, 207, 346, 358. 

Cortex. See Cerebral hemispheres. 

Crista, 240. 


Ectosylvian are, See Ectosylvian sulcus. 
Endorhinal fissure, 140. 


Fascia dentata, 144, 151, 160, 176, 190. 
Fasciculus aberrans, 174. 
Fimbria. See Fornix. 


Floccular lobe, } 241, 242, 243. See also Cerebellum. 
Floceulus, 


INDEX. 515 


Flocculi secundarii, 397. 
Fornix, 152, 159, 175, 196. 
Fornix, anterior pillar of, 152, 159. 


Geniculate body, lateral, 156. 

Geniculate body, mesial, 146, 156, 220, 241, 449. 
Gyrus ambiens, 379. 

Gyrus Andrex Retzii. See Hippocampus nudus. 

' Gyri, arcuate, of Leuret, 246, 266, 277, 283, 286. 
Gyrus felinus, 239. 

Gyrus, hippocampal, 441. 

Gyrus intermedius. See Olfactory tract, tubercle of. 
Gyrus lunaris, 379. 

Gyrus, uncinate, 441. 


Hippocampal fissure, 151, 162, 467. 

_ Hippocampal tubercle, 236, 346, 362. 

Hippocampus, 142, 144, 149, 160, 161, 173, 174, 175, 191, 210, 230, 
235, 308, 462. 

Hippocampus, inverted. See Hippocampal tubercle. 

Hippocampus minor. See Calcar avis. 

Hippocampus nudus, 240, 308. 


Incisura temporalis. See Rhinal fissure. 
Insula, 358, 363, 387, 389, 411, 428, 430, 487, 442, 450, 455, 457, 
458, 462, 463, 464, 472, 


Lamina terminalis, 240. 

Lobus centralis, 

Lobus xii 242. See also Cerebellum. 
Lobus clivi, 


Middle lobe of cerebellum, 242. 


Neopallium. See Cerebral hemispheres. 
Nodulus, 242. | 
Nucleus amygdala, 379. 


Occipital operculum. See Simian sulcus. 

Olfactory bulb, 1389, 180, 191, 207, 212, 227, 285, 356. See also 
Rhinencephalon. 

Olfactory nerve, 139. 

Olfactory peduncle, 170, 377, 467. 

Olfactory tract=external olfactory root, 158, 383. 

Olfactory tract, tubercle of, 158. 


516 INDEX. 


Olfactory tubercle, 140. See also Rhinencephalon. 
Olivary bodies, 241, 303, 351, 365, 420, 448. 
Opercula, 421, 472, 473. 

Optic nerves, 141, 434. 

Optic tracts, 448. 


Pallium, 142. 

Paraflocculus, 216, 241, 242, 243. See also Cerebellum. 

Pes pedunculi, 143. 

Petrosal lobule, 398. See also Cerebellum. 

Pons Varolii, 141, 156, 164, 282, 302, 414, 477. 

Posterior cornu (lateral ventricle), 293, 322, 370, 384, 409, 469. 
Posterior lobe of cerebellum, 242. 

Precommissural area, 161, 240. 

Precommissural fibres, 152. 

Primary (Preclival) fissure, 242. See also Cerebellum. 
Psalterium. See Commissura dorsalis. 

Pyramid of cerebellum, 243. 

Pyramidal decussation, 143, 149, 164. 

Pyramidal tract, 143, 148, 414. 

Pyriform lobe, 139, 140, 142, 148. See also Rhinencephalon. 


Rhinal fissure, 140, 152, 159, 172, 176, 194, 195, 202, 207, 208, 215, 
232, 233, 238, 307, 309, 321, 362, 382, 387, 411, 440, 467. 
Rhinencephalon, 140, 158, 190, 300, 350, 356, 378, 382, 400, 466, 

467. 


Secondary fissure, 242. 
Septum lucidum, 161, 240. 
Strie of Lancisius, 161. 
Suleus ambiguus, 200. 
» »,ansate, 239, 254, 256, 265, 267, 272, 280, 287, 292, 826, 473. 
» , anterior limiting. See fronto-orbital. 
»  areuatus, 397, 402, 404, 432, 437, 475. See also 8. rectus. 
» bisector, 281, 288. 
» ,ealearine, 154, 161, 162, 167, 193, 203, 211, 219, 232, 240, 
248, 292, 298, 362, 371, 372, 386, 388, 408, 446, 467, 468, 
469. | 
,, , calloso-marginal (=Intercalary, Primates), 362, 399, 447. 
,, , central (Rolando), 279, 365, 369, 379, 386, 451, 475, 476. 
, collateral, 260, 288, 322, 380, 383, 386, 398, 470. 
»» », compensatory, 387, 398, 413, 477. 
, coronal, 169, 179, 186, 203, 204, 216, 222, 225, 239, 278, 
299,305, 314, 320,332, 352, 364, 365, 475. See also 8. rectus, 


INDEX. 517 


Sulcus, corono-lateral. See coronal. ‘ 


99 


3? 


, crucial, 222, 289, 248, 253, 260, 265, 279, 291, 326, 365, 369. 
See further 8. central. 
, diagonal, 215, 223, 239, 246, 322, 333, 370, 472. 


' , ectolateral, 262, 267, 313, 333, 336, 358. 


, ectosylvian, 202, 239, 251, 254, 255, 258, 259, 262, 278, 292, 
309, 322, 326, 330, 334, 343, 345, 352. : 
, entolateral, 219, 244, 280, 287, 292, 294, 296, 307, 310, 336,353. 
frontalis medius, 433. 
frontalis mesialis, 433, 449. 
, fronto-marginal of Wernicke, 444, 452. 
, fronto-orbital, 370, 397, 398, 406, 412, 428, 471, 472; 478. 
, genual, 176, 179, 203, 260, 326. See Cingular are. 
, horizontal, 163. 
, inferior frontal. See S. rectus. 
, inferior occipital, 380, 389, 393, 395, 396, 398, 416, 488, 454. 
, inferior precentral. See S. arcuatus. 
, inferior temporal, 380, 398, 423, 438. 
, inferior transverse, 412, 437, 444. 
, intercalary, 163, 203, 219, 228, 232, 248, 268, 294, 367, 387. 
, intraparietal, 216, 369, 370, 380, 386, 393, 396, 400, 483, 470. 
See also lateral. 
, lateral, 182, 186, 200, 215, 223, 228, 239, 262, 278, 299, 306, 
307, 310, 336, 353, 364, 473. See also intraparietal. 
, lateral occipital, 405, 413. 
limitans pallii, 308. 
, marginal, 240, 248, 260, 289. 
, oblique, 332, 340. 
, occipito-temporal. See inferior temporal. 
olfactorius, 237, 285, 390, 410. 
, opercular (Marchand). See superior limiting. 
, orbital, 154, 163, 168, 177, 181, 184, 190, 194, 202, 208, 223, 
234, 239, 246, 254, 285, 290,310, 316, 325, 353, 412, 443, 474. 
, paracalcarine, 221, 280, 288, 294. 
, paracaudal, 280. 
, paracoronal, 294. 
, paragenual, 358. 
, parallel, 363, 368, 373, 378, 389, 393, 433. See also post- 
sylvian sulcus and suprasylvian arc. 
, paramedian, 178, 182, 183, 186, 187, 198, 206. 
, paraorbital, 307, 320, 330, 341. 
, parieto-occipital, 216, 322, 371, 372, 386, 393, 396, 398, 401, 
404, 413, 419, 422, 424, 429, 446, 454, 470. 
perpendicularis, 340. 
, postealcarine, 261, 292, 322. See also retrocalearine. 
VOL. II. 2M 


518 _ INDEX. 


Sulcus posticus, 327. 
»» » postlateral, 181, 186, 189, 223, 239, 267, 278, 305, 478, 
»» »postlimbic. See compensatory. ; 
» , postsylvian, 186, 215, 239,286, 298,305,310, 316, 330, 368,477. 
» » precentral, 394. ; 
» 5 precrucial, 247, 260, 266, 279, 282, 288, aol; 294, 297. 
»» »presylvian. See orbital. 
»» 3prorean, 169, 178, 200, 223, 272. 
rectus, 369, 374, 387, 390, 402, 404, 432, 488, 444, 473, 476. 
» ,Yretrocalcarine, 232, 260, 288, 386, 388, 445, 468. , 
» ,rostral, 176, 179, 194, 203, 215, 281, 299, 332, 414. 
ss f 393, 398, 401, 403; 407, 412, 451, 4738. 
Vapléniad, 161, 163, 207, 211, 240, 273, 323, 326, 331, 332, 346, 
468. See also intercalary and calcarine. 
» ,S8ubcingular, 281, 310, 313. 
», ,S8ublimbic (Guldberg). See subcingular. 
» , Superior frontal, 412, 476. 
» , superior limiting, 363, 401, 411, 428, 430, 442, 456, 460. 
» ,Suprasplenial. See marginal. 
, suprasylvian, 154, 169, 181, 194, 199, 234, 286, 293, 305, 306, 
322, 334, 352, 368, 471, 472. 
,, terminalis, 256. } 
, transverse occipital, 369, 387, 398, 412. See also postlateral. 
» , ursine, 280, 288, 292, 294. 
» , vertical, 280, 288. 
Suprasylvian arc, 215, 222, 228, 239, 259, 310, 363, 370, 373. 
Sylvian fissure, 152, 153, 168, 177, 194, 205, 217, 218, 224, 238, 244, 
246, 249, 251, 252, 255, 257, 258, 266, 276, 285, 286, 304, 309, 
310, 317, 339, 345, 351, 352, 363, 364, 368, 380, 386, 407, 442, 
471, 472. 
Sylvian trigone, 256, 326. 


Tractus peduncularis transversus, 194, 241. 

Transitory fissures, 459. 

Trapezoid body, 149, 164, 420, 430, 431, 434, 449. 

Trigeminal nerve, 141, 142, 148. 

Tuberculum quinti (Rolando), 141. ¢ 


Ursine lozenge, 247, 266, 279, 288, 291, 294, 296. 
Uvula, 242. 


Vallecula Sylvii, 215, 285, 296, 304, 351, 390. 
Ventricle of Verga, 448. 


PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 


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