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MARINE BIOLOGICAL LABORATORY,

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THE JOURNAL

OF

Comparative Neurology.

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LATE OF 'THE UNIVERSITY OF CINCINNATI.

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The Journal of Comparative Neurology.
Contents of Vol. |. 1891.

March, 1891.
Pages 1—106, I—X VUI. Plates I—IX.

CONTRIBUTIONS TO THE COMPARATIVE MORPHOLOGY OF THE CEN.
TRAL NERVOUS SYSTEM. By C. L. Herrick.
J.-— Illustrations of the Architectonic of the Cerebellum.

WWithia Plates, bol Vistas nly arate dude ® Ge tas ot eee ee 5
Il.—Topography and Histology of the Brain of Certain Rep-
ies eu Neth Plates LX amg! So ae ieee ac hh ieee 14
BGM BOUATORY /VMCHNIQUEL Crt... 6c taion wile. ebig We eahel, oh SP Ser ee 38
MORPHOLOGY OF THE AVIAN BRAIN. By C. H. Turner.
Races taletbes Vin VT ie ea calede ee tet eS og ieee nine 39
EDITORIAL. Problems of comparative Neurology............ 93
Methyl Blue Nerve staining Intra-vitam ......-...6.-2.00%. 105
PPeIGE El NAM CHESS is SA gas 6S al nc NOs cw ah Wine iats os ES Re nwa. ea we ae 1
Histogenesis and combination of Nervous elements... I.
Nervous’system. of. the: Gorilla; soso 25s Seals seine EV:
Origin and central Course of the Eighth Nerve... .. VE
The Development of the Sympathic System. ..... VIF
ihe Bpiphysis. and Parital’ Wye. /cin ccs t.sg ethan « AAG Ri
SCENT CIRC gal ric 11a gs ae IX.
meme TM ICANISISY elves orto ae ein. sae ialte) oe ohve eae, lk MPa a IX.

June, 1891.
Pages 107—200, XIX—XXIV. Plates X—XVI.

MORPHOLOGY OF THE AVIAN BRAIN, continued. By C. H. Turner.
iM Late ORE te Mcgee Pct etree et ae Gis a gg 107
CER SECON UREN Steiner rete ee 2M LES PAP ON Oy ase: 133

Il

RECENT INVESTIGATIONS ON THE STRUCTURE AND RELATIONS OF

THE OPTIC THALAMI. By Henry Russell Pemberton .....

CONTRIBUTIONS TO THE COMPARATIVE MORPHOLOGY OF THE CEN-
TRAL NERVOUS SYSTEM, continued. By C. L. Herrick.

Ill.— Topography and Histology of the Brain of Certain

Ganoid Fishes. With Plates X, XI, XII and XIII .....

EDITORIAL. Neurology and Psychology .+..............

RECENT LITTORAL URE: 2}. 4 4 cee sree ie), .egnaeerie ee negra eee

October, 1891.
Pages 201—286, XXV—XLII. Plates XVU—XXI.

THE MORPHOLOGICAL IMPORTANCE OF THE MEMBRANOUS OR OTHER
THIN PORTIONS OF THE PARIETIES OF THE ENCEPHALIC CAVI-
pres. By BuriG. Walder <., carer acs che eh a ate

METAMERISM OF THE VERTEBRATE HEAD .............205

THE ARACHNOID OF THE BRAIN, with figures in the text. By J.
W. Trango Gent. Ae je ~ ME Pe ee SL) ae ee

CONTRIBUTIONS TO THE MORPHOLOGY OF THE BRAIN OF BONY
FISHES.

J.— SILURIDAE, with Plate XVI. By C. Judson Herrick
II.— STUDIES ON THE BRAINS OF SOME AMERICAN FRESH-
WATER FISHES. with Plates XIX, XX, XXI. By C. L.
TOPPA aos Da ela eee ba ow 94 Goes pelo ees at ee

THE DEVELOPMENT OF THE CRANIAL NERVES OF VERTEBRATES,
By C. von Kupffer. Translated by Oliver S. Strong ....

MORPHOLOGY OF THE AVIAN BRAIN. Continued. with Plate XVIII.
By 0. El Turnet os. 2 ohn es Scape sak. thea ae) =

107

149
183
xix

201
203

EXTORARY, NOTICES crap. OP. ae lee se os 0 Dee oe ee ee XXV.
The Trophic Function of Nerves........... XXV.
Degeneration and Atrophy as a result of Section of

ihe Granial (Nerves, << <o5 t.05 2-132: Us ese |e ee XXXVI.
The Developmont of Spinal Ganglia in Man .... XXVIII.

Electro-motor Disturbances in the Brain as Products

of. Psychical :Activaty “i:.:... sage. ve. com cep ects deepen XXIX.
The Relation of the Sympathic System to the

erectile Appendages of the head in the Gallinaceae. . XXIX.

The Sympathic Systems 70. is,. ve- ne oe ie eee XXX.

Contribution to the Study of the Brain of Tracheate
Arthropods):.4:5. %. cculecpient kee Ut neh 1a ee XXX.

The Nervous System of Copepods.......... X XXIII.

The Development of the Nervous System of Spiders XXXV

Nervous System of Serpula ............. XXXYV.
Development of the Brain of Horse-shoe Crab... XXXV.

te

Iil

Brain of the Horse-shoe: ‘Crab .o2:.-. 2. ws... XE Ve

Edinger’s Text-book of the Nervous System .... XXXVI.

LS VOT, TTR Ree eas On Si era a a ee a aL a at XXXVI.
ECON TD OLTPARATURE® a0 c-<stemei ame sides) cso cnn Soy bates XXX VIII.

December, 1891.
Pages 287—358. Plates XXIJ—XXV.
THE LUMBAR, THE SACRAL, AND THE COCCYGEAL NERVES IN THE

DOMESTIC CAT. With Plate XXIII. By J. B. Stowell .... 286
WEIGERTS’ METHOD STAINING THE MEDULLARY SHEATHS ...... 313

THE DEVELOPMENT OF THE CRANIAL NERVES OF VERTEBRATES,
With Plate XXII. By C. von Kupffer. Translated by Oliver
See OURO Goce aoe eer ote s eee ao A ee ee . ohh
CONTRIBUTIONS TO THE MORPHOLOGY OF THE BRAIN OF BONY
FISHES. IJ.— STUDIES ON THE BRAINS OF SOME AMERICAN
FRESH-WATER FISHES, Continued. With Plates XXITV—XXV.
Ls Naan FAROE Ca 9 Co) cee een ie nS an Metres oie ec hen, Jf bree a8 333
BOCKORS ANNOUNCEMENT gt oo Ae tees a8 See ROPER ees ee 358

CONTRIBUTIONS TO"SeHE “COMPARATIVE
MORPHOLOGY.:OF THE 'CENTRAL
NERVOUS SYSTEM.

I—ILLUSTRATIONS OF THE ARCHETECTONIC OF THE
CEREBELLUM.—Plates I-IV.

(Cy JG JelipmEwens.

Aside from the physiological questions offered by the
epencephalon, which are confessedly among the most difh-
cult of neurology, there are many more general problems re-
specting the principle and details of construction, relation to
other parts of the central organ, and histogenesis, which are
very far from a satisfactory solution. Even those points
which can be accepted as well settled require concrete
illustration to make them available for purposes of instruc-
tion. In the following notes it will not be necessary to |
sharply define that part which is regarded as a new con-
tribution to our knowledge from the points for which the
more general utility is hoped, since all the statements are
equally the result of direct observation and are quite inde-
pendent of the work of others.

It is hoped that the comparison of the several groups of
vertebrates and identification of the close ‘correspondence
between the respective adult conditions of the organ and the
transitory stages in the mammalian cerebellum during its
development may add force to the plea for more complete
application of this comparative method to the study of rieu-
rological problems. | ites

a

6 JouRNAL oF COMPARATIVE NEUROLOGY.

Like all other organs arising from the walls of the em-
bryonic vesicles, the cerebellum can be traced primarily to
a more or less distinctly circumscribed area of this wall; and
its subsequent modifications consist, in part, of irregularly
distributed increase in size accompanied by rapid multipli-
cation of cells, and, in part, of folds and contortions in the
resulting structure.

The several processes concerned in the development are
briefly outlined by Mihalkovics,(') rendering it unnecessary
to do more than briefly recapitulate the processes.

Fig. 2 of Plate II is a camera drawing of an exactly
median section through the brain of a guinea-pig before the
cerebellum has at all differentiated from the cephalic portion
of the dorsal wall of the nerve-tube. The transition cau-
dad into the velum medulare posterior (v. p.) is gradual, and
the latter shows very little tendency to fold upon itself, as it
will soon do in the formation of the metaplexus. Fig. 3 is
a similar section, though not strictly median, of a later stage
in the mouse embryo. Here the velum has sharply folded
and the plexus is very rapidly forming by a succession of
inward folds, as a result of which the original epithelium
of the roof of the fourth ventricle is converted into the
epithelium of the plexus. The cerebellum itself exhibits a
decided tendency to a forward (cephalad) fold, and the
whole organ may be readily compared with that of amphibia
or lower reptilia.

It will be specially observed that the dorsal surface is
devoid ot cells and contains a rudimentary superticial tract.
This condition is the permanent one in reptiles like the tur-
tles. Compare Plate III, Figs. 4, 5 and 6, with the above
mentioned. In the case of the turtle, Asp7donectes spintfer ,
as there figured, the basal portion of the cerebellum is per-
pendicular to the axis, the dorsal portion being twice flexed,
_ with a slight tendency to recurve at the tips. The specimen

1 MIKHALKoOvics, “ Entwicklungsgeschichte des Gehirns, nach Untersuchungen an
hdheren Wirhelthieren.”’

Herrick, Morphology of Nervous System. i

figured being very young, it cannot be supposed that these
folds have been completed. The pons flexture has been
considerable, bringing the extremity of the cerebellum cau-
dad into proximity to the obex and taenie fosse rhomboid-
ealis. The velum medullare posterior is therefore almost
wholly converted into the epithelium of the metaplexus.
The entire configuration of the cerebellum is hood-like( Plate
III, Figs. 9, 10 and 11).

In the black-snake the cerebellum is a leaf-like expan-
sion, having on the caudad surface (really the ventral or
ventricular aspect) the granular substance and the white
fibrous zone cephalad; but this leaf is folded ventro-caudad,
so that the white layer is dorsad and uppermost and the
gray matter faces toward tne ventricle in which lies the
large plexus.

In the case of the lizard we have apparently a com-
pletely dissimilar plan of structure. Here the gray matter
is dorsal and the white ventral (Plate IV, Figs. 4 and 5).
This reversal of the two layers is explained, upon a more
careful examination, as the product of a complete forward
and median fold of the caudad and lateral margins of the
cerebellum. (Compare Plate IV, Figs. 6-9). This is but
the completion of the process indicated by the incipient
retroflexion seen in the turtle. The result of this fold is the |
formation of an actual cavity surrounded caudad and laterad
by the white (morphologically dorsal) zone of the cerebel-
lum. Thus the fusion of the lateral margins, or, more
accurately, the union of the whole latero-caudad reflected
margins due to a general cephalo-median increase, produces
the hollow organ just described.

In the alligator the cerebellum is formed in the same
way, but the organ is larger and the internal secondary
cavity is much greater, the whole forming a cone with its
apex protruding caudad. In this case the folded portion has
undergone less flattening dorso-ventrally, and more clearly

8 JOURNAL OF COMPARATIVE NEUROLOGY.

illustrates the nature of the processes to which its formation
is due.

It seems at first sight quite out of the question to expect
to find any homologous processes in the brain of the higher
vertebrates. In the first place, the relation between the
Purkinje cells and the granular zone (molecular layer) is not
the same, and, in the second place, there seems to be no
evidence that such a wholesale revolution has taken place;
but, on the other hand, very sufficient evidence that the
increase in surface has been effected by a different plan, z.e.,
the corrugation of an organ, which increases in thickness
rather than length. It is true that in birds there is an
obvious partial revolution of the whole cerebellum through
a considerable arc, but this is more easily explained by ref-
erence to the flextures incident to the great compactness of
the avian brain and the freedom of rotation due to the
extensive development of the velum medullare anterior,
which leaves the cerebellum quite disassociated from the
corpus posterior and free to rotate upon the peduncles as a
lateral horizontal axis. —

Among mammalia, the cerebellum of the opossum indi-
cates a decided tendency to revolution from behind ceph-
alad. Of the several primary convolutions first formed,
the posterior continues growth longest and eventually cir-
cumscribes the anterior, and, with its secondary gyri, forms
the ectal surface, as may be readily seen in longitudinal
sections. One additional consideration may, nevertheless,
lead to a prosecution of a search for some plan of revolution
or evagination in the mammalian cerebellum as well as in
the reptilia. It is this: if the conclusions of His and others
regarding the typical histogenesis of nervous and connective
elements in the nerve-tube be correct, it is difficult to
understand the origin of the cells of the cerebellum by ref-
erence to the adult relations. We have the ventricular sur-
face lined with the usual epithelium, which is, during an
early period, proliferous, as may be easily demonstrated.

Herrick, JJorphology of Nervous System. 9

But the area of ventricular surface is progressively re-
stricted until it is reduced to insignificance, and can be
brought into no relation with the Deiters and Purkinje
cell-layers. His(') concludes that the nervous elements
have arisen by a subdivision of certain of the nuclei of the
epithelium near the ventricular wall and thence migrate to
their definitive foci. Such a direct migration is rendered
impossible in the present case by the early development of
the central tract of white matter.

Again, it is a fact of observation that at a period not long
before birth in rodents, for example, the surface of the cere-
bellum ectad to the Purkinje cells, which are already pres-
ent, is covered by a thin zone of rapidly dividing cells,
which, as they increase, are also passing entad, to a level
beneath the cells of Purkinje.

This remarkable assemblage of superficial cells with
dividing nuclei, caryokinetic figures and other evidences of
proliferation may be readily seen in the cerebellum of old
embryos of the guinea-pig (Plate II, Fig. 4, and Plate I, Fig.
g). The condition indicated in Fig. 9, where the corpuscles
are much more numerous superficially and are there more
frequently dividing than in the infraganglionic zone which
is their ultimate locus, and the fact that the superficial pro-
liferating zone almost entirely disappears in the adult suffi- |
ciently shows that these cells are not indigenous, and sug-
gests the necessity of tracing the history of the proliferating
zone. ‘That this zone does not arise 7z situ is rendered
somewhat probable by the fact that no such layer exists in
reptilia, but the ventricular surface is the proliferous locus,
even though in the higher reptiles it is reverted so as to
become spuriously ectal in position. On the other hand, it
would at first appear that we have a case quite comparable
to the present one in the cerebrum where the cells of the
cortex proliferate at the surface and migrate to their various

1 Wo. His, Archiv f. Anatomie u. Physiologie, Anatomische Abtheilung, 1890, p. 95
et seq.

10 JouRNAL oF COMPARATIVE NEUROLOGY.

positions, as may be gathered from sections of earlier
embryos than that figured on Plate II, Fig. 4. It may be
remarked in passing that, in our opinion, the latter analogy
is misleading, since, as we shall hope to show, the pro-
liferating centres from which the cortical cells are derived
are central or ental rather than superficial. The solution
of the problem of the histogenesis of the cerebellum is to be
sought in earliest stages of its development, which can be
shown to follow in a condensed manner the course just
indicated for reptiles.

Returning now to the embryo mammal (Fig. 2, Plate IIL)
and again noticing that the dorsal surface is devoid of cells
except at the caudad extremity, we observe that in an older
embryo (Fig. 3) a much larger portion of the dorsal surface
has been thus covered, and evidently from behind forward.
Fig. 1, which is a transverse section through one-half the
cerebellum near its base and part of the medulla in a mouse
embryo of a little older stage, shows that the entire surface
has now been covered by the proliferous zone, but that it is
curiously double, with a layer of white fibres separating
the two zones. It is also observed that the walls of the
nerve-tube at the recessus lateralis of the fourth ventricle
are very thin, and consist of very rapidly proliferating and
hence closely-packed cells which pass from the ental to the
ectal surface. This section suggests that possibly the lateral
(and caudad) portions of the ventricular surface of the cere-
bellum may be the sources of the proliferating superficial
layer of the dorson. Yet we have no clue to the double
character of this proliferous zone, and have no direct proof
that the suggestion is valid. Before we can secure such
proof it will be necessary to thoroughly understand the
nature of these lateral recesses of the fourth ventricle. The
description given by Mihalkovics, though incomplete, is very
suggestive:

Bemerkenswerth von der Seitentasche [Recessus lateralis] ist, dass
sie im ausgebildeten menschlichen Gehirn aus zwei einander berihr-

Herrick, Morphology of Nervous System. 11

enden Blattern besteht; das obere Blatt liegt dem Wurzeltheil des
Kleinhirns, dast untere-dem verlingerten Mark an. An giinstigen Ob-
jecten nach Alcohol-erhartung ist beim Abheben des Kleinhirns von
der Medulla gut zu sehen, dass die scheinbar aus einer Lamelle besteh-
ende Seitentasche sich 6ffnett und das Gange einer Blase gleich sieht.
Ich finde also Henle’s Bemerkung dass das velum medullare inferius,
wie er die Seitentasche nennt, manchmal den Eindruck einer collabir-
ten Blase macht, ganz zutreffend, obgleich er die zwei Blatter der Blase
nicht erwahnt.

Diese letzteren enstanden dadurch, dass die Seitentasche im embryo
blasenformige Gebilde resp. die vorgestiilpten Seitentheile der hinteren
Deckplatte waren, welche mit der starken Ausbildung der Kleinhirn-
hemispharen in den Winkel zwischen Kleinhirn und verlangertes Mark
eingeknickt und plattgedriickt wurden.

Das obere Blatt der plattgedriickten Blase, welches mit der lamina
basilaris (Aeby) des Kleinhirns in Berthrung steht, ist bedeutend
schwacher als das untere, und mit der Pia-hille in festem Zusammen-
hang —es tritt an dasselbe ein Zug von feinen Adergeflechtzotten vom
Plexus choroid. ventr. IV. zum gleich zu schildernden Blumen-Ko6rb-
chen. Mit dem starken unteren Blatt der Tasche sind die Wurzel-
fisen des N. glossopharyngeus und Vagus verwachsen. Die Taschen
sind also Mark-lamellen in welchen die nervésen Elemente nicht ganz
schwinden; sie sind rudimentare, nervGse Gebilde, wie die Nerven-
siume (taenie medullare) am Rande der Rautengrube. Gleiche wie
jene sind die Taschen mehr oder weniger ausgebildet, entsprechend
der schwiacheren oder stairkeren Involution der nerv6se Elemente. (*)

The passage quoted above gives a clear idea of the origin
of the recessus lateralis, but fails utterly to suggest any
cause or purpose for such a peculiar involution. Of course, ,
it might be regarded as a necessary mechanical concomitant
of the increase in growth of the cerebellum and the several
changes of position which that organ suffers during its de-
velopment as a result of the flextures of the brain axis and
corrugations and convolutions of its roof. It can, in fact, be
seen that the metaplexus and its lateral projections, known
as the cornucopiez (Blumenkorbchen), stand in intimate re-
lation to the lateral chambers, and that the development of
the eminentia acustica may also sustain a more or less di-
rect relation to these cavities, but the real ratson de etre
must be sought in the histogenetic necessities of the cere-

t Miracxkovics, Entwicklung des Gehirns, p. 5-8.

12 JouRNAL oF CoMPARATIVE NEUROLOGY.

bellum itself, while these, in turn, can be traced to the pro-
gressive metamorphosis of the primitive lamella, of which
the vertebrate cerebellum is the final product. <A reference
to Plate I, Figs. 3-8, will place all these relations in a clear
light. These sections through the cerebellum and medulla
of a guinea-pig exhibit the same process of lateral and re-
trorse growth and folding which are seen in reptilia, except
that, instead of the flexion of the entire organ, there is a
comparatively thin fold of epithelium containing a delicate
tract at the base, but consisting caudad solely of the
epithelium. These sections taken through the same cere-
bellum at different points may fairly claim to indicate the
several stages which would successively appear at any one
plane.

Fig. 3, taken through the base of the cerebellum, shows
the dorsal surface to be devoid of the gray matter. From
either side there extends a curious upward fold containing
a cavity. The source of the growth is evidently the walls
of the cavity, as witness the numerous cells clustered at that
point. Fig. 4 shows the circumscribed cavity to be a pouch
of the recessus lateralis of ventr. IV, extending cephalad,
and also shows that the newly-formed cells involved in the
fold are drived from the ventricular epithelium. It will be
noticed also that the entire dorsal portion of the organ is
affected by this overlapping growth from behind and the
sides, so that a groove is formed on either side meson, dor-
sally. It is likewise important to observe that the develop-
ment of the epithelium extends the recessus lateralis ven-
trally as well as dorsally, and that it there also fuses with
the entad body (here medulla) and gives rise to proliferous
clusters.

The above illustrations are derived from the guinea-pig,
but figures are also given derived from similar sections of
older stages of mouse embryos for demonstration of the last-
mentioned point. In these cases the dorso-lateral fold has
already fused with the walls of the cerebellum, and the

Herrick, Worphology of Nervous System. 13
cavity has nearly disappeared. Fig. 7 well exhibits the ex-
tent to which the gray matter of the dorso-lateral aspects
of the medulla is derived from the epithelium of the prim-
itive recessus lateralis. Fig. 8 illustrates the method of
plexus formation, the origin of the cornucopia, and condi-
tions prevailing at the tip of the cerebellum at this stage.

The origin of Purkinje’s cells cannot be fully made out
in this series, yet the great similarity to the cells of the den-
tate nidulus, at a stage shortly preceding birth, is such as to
suggest community of origin.

Additional evidence that the principle formulated above
is the prevailing one has been derived from a study of
embryos of the black-snake (see plate X). While in this
case the organ does not itself undergo retroflection, but re-
mains a leaf-like organ, longitudinal sections indicate that
proliferation is most rapid near the tip, and a dense cluster
of cells is pushed dorsad and then cephalad upon dorsal
surface. This does not exclude direct migration from the
ventricular aspect of the cerebellum. There is every reason
to conclude from these sections that the cells of Purkinje
likewise spring from near the ventricular border. At the
tip and lateral margins, the layer of these cells in the em-
bryo comes in contact with the epithelium, and the cells,
which are obviously multiplying rapidly, either spring from :
the epithelium by subdivision of its undifferentiated cells or
the multiplication of special germination cells. The neuro-
blasts at first become spindle-shaped and give rise to a pro-
cess which passes cephalad (Plate X, Fig. 11). Nearer the
base the layer of Purkinge cells is represented by a thick
nucleary zone from the epithelium. At the very base,
however, there is a superficial (dorsad) cell aggregate
which likewise seems to have its origin in the epithelium of
the ventricle.

It seems unnecessary to say more in illustration of the
complete homology between the method of cerebellum
formation in the several groups of vertebrates. That this

14 JOURNAL OF CoMPARATIVE NEUROLOGY.

development corresponds to the course of evolution as
deduced from the adult conditions of various reptiles
seems equally clear, and the whole argument forms a
beautiful illustration of the interdependence of all biologi-
cal sciences.(')

II_—TOPOGRAPHY AND HISTOLOGY OF THE BRAIN OF
CERTAIN REPTILES.

Materials.—The brief notes here following, like the first
paper of the series, published in the Yournal of the Cincin-
nati Society of Natural History for 1890, are to be regarded
as materials for elaboration in a more systematic way when
they shall have accumulated sufficiently to make such sys-
tematic treatment profitable. The present instalment deals
primarily with the prosencephalon, especially the distribu-
tion of its cells and commissures. The materials consist of
a number of brains of the small lizard Sceloporus undulatus,
locally abundant in Scioto county, adult and embryonic
brains of the black-snake, and a specimen of the turtle,
Aspidonectes spinifer.

Topography and external form of the lizard brain.—The
form of each hemisphere is, roughly speaking and exclusive
of the elongate olfactory lobe, a triangular pyramid. In
horizontal section the angle formed by the median and cau-
dad planes bounding the hemisphere is about 120°. The
third side is a gentle curve more rapidly arching to the
cephalad extremity. The diencephalon is included within
the reéntrant angle formed by the caudad planes of the two
hemispheres, for externally the latero-caudad angle of the
hemisphere is in contact with the cephalo-lateral projection

1 The close approach made by Obersteiner to the view here announced is indica-
ted by the following quotation from Meynert, Psychiatry, p. 116:

‘* According to Obersteiner, the cerebellar cortex in the child is covered by a layer of
formative cells, wnich are transformed into spindle-shaped fibrils, thus constituting an
imnermost stratum of the pia mater.”

Herrick, Worphology of Nervous System. 15

of the optic lobes, the horizontal section of which is triangu-
lar in the opposite sense to that of the hemispheres.

The base (ventral surface) of the hemispheres exhibits a
slight protuberance in the latero-caudad portion, which is
due to the protrusion of the occ¢f7to-basal lobe.(') The latter
is not a subdivision of the cortex, but a well-defined por-
tion of the axial lobe, in the sense elsewhere employed.
This lobe can probably be distinguished in all Sauropsida.
It is partially separated from the remainder of the axial lobe
by a fibre tract, and bears laterad and dorsad a film of cor-
tex which projects caudad as a free occtfital lobe of cortex
for a short distance and terminates in a velum cerebri. The
latter is morphologically a part of the wall of the lateral
ventricle, which has here lost its cellular elements and con-
tains at one point the tenia thalami.

The extent to which this lobe is developed varies greatly
even in reptiles. It is reduced to a minimum in birds. It
contains the undoubted homologue of the hippocampus, but
in the black-snake that portion homologous with the hippo-
campus is relatively highly differentiated. Even the por-
tions corresponding in cellular structure to the fornicate and
uncinate gyri may be distinguished, though there is, of
course, no external indication of this distinction. The
terminal, caudad portion (homologue of the uncinate gyrus) .
contains densely packed fusiform cells of relatively small
size, while, near the juncture of the free portion with the
axial lobe laterad, there is a larger area containing much
larger cells of the same type, which corresponds with the
fornicate gyrus of mammals (Plate X, Fig. 6). At some
levels a deep depression separates the hippocampus from the
remainder of the cortex.

Ventrally the occipito-basal lobe is set off from the axial
lobe proper by the pyramidal tracts, and is filled with small

t The use of the word “lobe” in this and subsequent cases is a pure convention,
from which no escape could be found. ‘‘ Region” might be a preferable term, if not too
vague.

16 JOURNAL OF CoMPARATIVE NEUROLOGY.

multipolar cells resembling those of the second olfactory
or rhinomorphic type, not exceeding .o10 mm. in greatest
diameter.

The occipito-basal lobe in the black-snake is much more
complicated, and, in order to understand it, a description of
the topography of the entire cerebrum may be necessary.
The hemispheres are strongly protuberant and abbreviated.
The cephalad portion is suddenly constricted and applied
laterad to the apparent crus of the olfactory, so that a con-
siderable portion of the cortex actually extends out upon
the olfactory lobe. The olfactory structures proper accumu-
late at the mesad surface, where they are strongly devel-
oped, while the laterad portions cephalad are reduced to a
thin film of fibres. The result of this peculiar limitation is
that the large olfactory ventricle curves laterad from the
base to near the tip, where it abruptly arches mesad, so
that the olfactory fibres take their origin from the mesal
surface, toward which the glomerulary layer presents a con-
cavity for their reception (Cf. Plate X, Fig. 6).

The concentration of the cortex caudad accounts, partly
at least, for much that here follows. The ventro-basal pro-
tuberance of the hemispheres, which seems analogous in
position to the pyriform lobe of Rodents, for example, con-
tains a concentric zone or hollow spheroid of gray matter
greatly (though spuriously) resembling the hippocampus.
This concentric mass of cells, which makes up the major
portion of the occipito-basal lobe, contains fusiform cells
which in some places are rapidly proliferating. Cephalad
to it lies a dense cell-mass representing the central division
of the axial lobe. Dorsally the concentric caudad_ portion
becomes quite distinct from the non-concentric cephalad
body. There is also a small latero-caudad cluster ectad
to the occipito-basal lobe, and it, like the ventral and
cephalad parts of the central lobe, contains pyramidal cells
predominatingly.

In the lizard a tract can be traced to the region of the

Herrick, Morphology of Nervous System. 17

occipito-basal lobe from the diencephalon, entering dorsad
to the peduncles: If correctly followed, these fibres have
their origin in dense cell-masses near the middle of the
thalamus at about the level of the dorsal part of the anterior
commissure.

A distinct bundle from the anterior commissure may be
traced to this lobe, though its exact destination is not
known. But, inasmuch as the tract can be followed to
the median part of the lobe and a well-defined nidulus(')
lies in their course produced caudad and laterad, it is
natural to conclude that the two are related.

This occtpito-basal nidulus is not a single cell cluster,
though it contains a central aggregate which is sharply
defined. A short distance dorsad to the ventro-basal pro-
tuberance of this lobe a few rather large fusiform cells with
large pale nuclei appear in clusters along the caudad border
of the lobe. These become more numerous in regions far-
ther dorsad and accumulate in small clusters, which fuse
at a level somewhat dorsad to the anterior commissure to
form the axial nidulus of the lobe above referred to. Such
nests or aggregates seem to be a constant feature in all rep-
tilia. We have observed them in the Chelonia, Ophidia,
and Sauria (see notes upon the brain of the alligator, Plate
VII, Figs. 7 and 8). Mr. Turner finds similar proliferating |
areas in the corresponding region in birds.

In the black-snake a distinct fibre-tract from the caudad
strands of the anterior commissure passes to the caudad
or ventricular surface of this lobe and passes to its laterad
portion. The cells of the lobe in this case are beautiful
illustrations of flask cells with apical processes chiefly
median.

In the frog the occipito-basal lobe is well developed, but
is very simply constructed, consisting of numerous more or
less concentrically arranged flask cells with fibres passing

1 A substitute for the word ‘‘nucleus”’ as applied to central cell clusters,

18 JourRNAL oF ComMPpARATIVE NEUROLOGY.

caudad and entering the thalamus from the caudo-lateral
aspect of the ventral part of the hemisphere. This tract
doubtless corresponds to the direct thalamus tract noticed in
the lizard.

In horizontal sections of the ventral part of the hem1-
sphere in the /izard a large central mass can be distin-
guished, which, although it may contain homologues of
part, at least, of the striatum, may here be called simply
central lobe. It receives the pyramidal tracts.

There is ectad to this a lenticular gray mass, with few or
inconspicuous cells, which is separated both from the lateral
cortex and the central lobe by fibre-tracts. There is a cer-
tain resemblance to the claustrum, though no such homology
is suggested for what may be termed the denticular nidulus.
Peripherad to this nidulus is the narrow farzeto-frontal lobe
of the cortex, with its densely-packed pyramidal cells.

Further cephalad and dorsad a small triangular cluster,
apparently connected with the lenticular nidulus, reaches
the surface, forming a frontal Jobe. Still further dorsad a
small oblique and very dense lamina of closely-packed cells
of the flask variety appears. This is the most conspicuous
of all the lobes in section, and may be termed the fronto-
median lobe. In transverse sections the fronto-median lobe
appears as a very densely cellular band of nearly uniform
width, occupying the middle of the width of the tectum
cerebri, and separated from the ventricle by the tracts pas-
sing cephalo-dorsad from the callosum via the intra-ven-
tricular lobe. There are very evident connective fibres
springing from the ventricular epithelium and_ passing
through the callosal tract toward the surface at the median
fissure. Upon these fibres are the usual ‘‘ glia” corpuscles,
with elongate outlines and granular texture. The cells of
the fronto-median lobe are fusiform elements of the sensory
type, except cephalad, where there is an admixture of the
deeply staining pyramidal variety. The contrast between
these cells and those of the frontal lobe is very striking.

Herrick, Morphology of Nervous System. 19

The ixtra-ventricular lobe, or that portion mesad of the
lateral ventricle, becomes quite distinct dorsad by the sepa-
ration from the thalamus and backward extension of the
ventricle. It is fille€d with irregularly dispersed flask cells,
and also contains the cephalo-dorsad prolongations of the
callosal tracts. The finer structure of the intraventricular
lobes may be gathered from the figures (Plate II, Fig. 16,
and Plate IV, Fig. 8). The portion drawn in Fig. 8 is from
that part of the lobe near the ventricle of the right hemi-
sphere. The epithelium of the ventricle is produced, as
usual, into long connective fibres, which do not appear in
the figure because the section is oblique to their axes. The
entire lobe is filled with bipolar or multipolar cells, with
the large reticular nuclei and generally fusiform contours of
esthesodic cells. The fibres do not preserve any definite
direction, but the long axis of most of the cells lies in the
horizontal plane and prevailingly in the cephalo-caudad di-
rection, while a smaller number extend perpendicularly or
obliquely. The drawing was made under a one-fifteenth
inch objective, with the aid of approximate micrometer
measurements.

The course of the fibres of the callosum may be traced in
transverse sections. At the point of crossing, the intra-ven-
tricular lobe fuses with the thalamus, but cephalad the
callosa] fibres pass through that lobe dorso-cephalad until
part of them pass dorsally to the ental aspect of the fronto-
median lobe (7.e., to the ventricular side) and thence to the
dorsal cortex.

Medianly and ventrally the intra-ventricular lobe passes
into that part of the axial Jobe cephalad to the chiasm.

In higher sections the fronto-median lobe extends caudad
and overlaps the intra-ventricular lobe on the median as-
pect. In the meantime the free caudad margin of the
cortex has extended medianly, receiving the tenia from
the habena and then fusing with the intra-ventricular lobe,
and ultimately uniting with the fronto-median, completing

20 JouRNAL oF CoMPARATIVE NEUROLOGY.

a ring or cap of cortex which entirely encloses the axial
lobe, which latter, by the encroachments of the ventricle,
has become separate from the walls. The cells of the oc-
cipital cortex resemble those of the fronto-median lobe (see
“Big.ss5 1B; Plate: Ii):

As already stated, the fronto-median and occipito-basal
lobes become continuous toward the dorson by circumscrib-
ing the intra-ventricular, which soon disappears. The re-
sult of the concrescence of the two areas and their subse-
quent increase in size is that nearly the caudo-median half
of the dorsal cortex is covered by the flask, or sensory type of
cells.

' The caudad portion of the lateral cortex is considerably
thickened, forming a distinct parietal lobe, of which the cells
seem to be pyramidal or multipolar and stain deeply.

The intra-ventricular lobe is also quite prominent in the
frog, forming a decided protuberance into the ventricle, and
consists of cells of the type having large clear nuclei and
fusiform outlines. Whether the function of these cells can
be safely predicated from their form may well be doubted,
but this much is certain, that these cells differ obviously
from those of the lateral aspects of the cerebrum.

The fusion of the olfactory lobes with the cephalad part
of the hemispheres somewhat disturbs the arrangement, but
one may perhaps identify the homologue of the fronto-
median lobe in an anterior projection into the ventricle,
which is distinct from that just described, though filled
with similar cells.

On the lateral aspect, the middle of the hemispheres
exhibit a series of concentrically arranged cells near the
ventricle and scarce and scattered pyramids in the ectal por-
tions of the mantle. Cephalad there is a distinct nidulus
ectad to the base of the olfactory protuberance. The cells
of this nidulus are rather flask-shaped than pyramidal.

At higher (more dorsal) levels the occipito-basal and
fronto-median lobes fuse through the mediation of the in-

Herrick, Morphology of Nervous System. 21

tra-ventricular lobe, forming a continuous band, as in the
lizard.

The whole lateral and latero-cephalad aspect of the hemi-
spheres, on the other hand, is filled, dorsad to the base of the
olfactory, with cells of a different type. They have the
smaller nuclei and often the pyramidal form and deeper
staining of the motor cells. It is true that these distinctions
are rather less marked in the frog than in higher verte-
brates, but they are perfectly obvious. These cells are also
arranged in concentric bands, especially entally

A very large nidulus of small cells occupies the median
portion of each hemisphere dorsad to the anterior commis-
sure. It corresponds to the nidulus found in reptiles ventrad
to the corpus callosum, but is very large.

It will not be attempted to homologize the axial lobe
and its derivatives with the striatum of mammals, as several
considerations seem to forbid a strict comparison. While
there can be no doubt that the several divisions of the axial
lobe contain the representatives of the striatum, yet there is
no such sharp localization of areas nor differentiation of
function as that seen in mammals. The cells of the central.
part of the cerebrum seem to be of the most generalized
type, and, as I suggested in an earlier paper(') there seems
to be good ground for assuming that there are distinct cen-
tres of proliferation in these regions. Observations recently
made on embryonic brains of rodents seem to indicate that
there are such distinct proliferating centres in the cerebrum
of mammals from which cortex cells are derived. A closer
connection between the so-called Deiter or nutritive cell and
neuroblasts than hitherto suspected may be suggested, as well
as the possibility that the so-called basal ganglia are chiefly
proliferating and trophic centres. Mr. Turner has arrived
at the same conclusion respecting the basal ganglia in birds,

1 ‘“‘ Notes on the Brain of the Alligator,’ Journal Cincinnati Soc. Nat. Hist., 1890

Ww
i)

JOURNAL oF COMPARATIVE NEUROLOGY.

as will be seen by reference to his paper elsewhere in this
fasciculus.

FIBRE-TRACTS OF THE CEREBRUM.

Sections near the ventral surface of the cerebrum of the
lizard exhibit the numerous fibres radiating rather uniformly
cephalad and laterad from the cephalad extremity of the
ventral peduncular tracts. A strong portion passes directly
laterad, separating the gray matter of the occipito-basal lobe
completely from the remainder of the section. This tract
passes to the surface and is distributed by a number of
branches in the cortical region, dorso-cephalad of its ap-
parent destination.

Dorsad to this corona radiata the whole base’ of the
cerebrum becomes filled with cells differentiating dorsad
into the niduli already described. A rather distinct tract
separates the intra-ventricular lobe from the frontal. This
can be traced backward to the corpus callosum, which con-
sists of few dark fibres passing frem one intra-ventricular
lobe to the other by a sharp caudo-ventral curvature.

As already stated, a very dense nidulus occupies the
terma caudo-ventral to the callosum. The cells composing
it are small, and, as only the nuclei stain, present the ap-
pearance of Deiter’s corpuscles. Beneath the anterior com-
missure in the lizard is a similar dense cluster, which forms
the only obvious demarkation between the prosencephalon
and diencephalon. The tracts in the frog are as in reptiles.
The tenia thalami can be traced with perfect ease from the
habena to the occipito-basal lobe, as also the fibres of the
anterior commissure. The origin of the descending fornix
fibres from the lateral] extremities of the anterior commissure
is likewise as in reptiles.

Pracommissura.—\n the lizard it is rather difficult to
trace the relation of the olfactory tracts and the precommis-
sura, because of the vertical height of the brain and the in-

ferior olfactory development. Nevertheless, a distinct ven-

Herrick, Worphology of Nervous System. 23

tral band of the anterior commissure can here be traced
ventrad and cephalad. In longitudinal sections an olfac-
tory tract lying medianly from the ventricle can be followed
caudad and laterad to nearly the point at which the above-
mentioned portion of the anterior commissure disappears.

In the black-snake, on the other hand, the anterior com-
missure is studied with great ease, and it exhibits greater
complication of structure than in other reptiles examined
(Plate X, Fig. 7). The commissure is readily separated into
three perfectly distinct portions or bundles. The ‘most
ventral or ventro-cephalad bundle is the olfactory commis-
sure, which is composed of large and deeply-stained fibres
arching ventrad very soon after crossing to the opposite side
and continuing almost directly ventrad to near the surface.
They then turn cephalad and enter the medi-basal part of
the crus olfactorius.

The second bundle (commissure of olfactory centres) lies
in contact with the olfactory commissure and follows its
course for some distance ventral, dividing into several dis-
tinct bundles of small size, which pass to the ventro-lateral
regions of the middle portion of the hemispheres. These:
various bundles seem to enter cellular masses lying near
the ventral and ventro-lateral surfaces of the cerebrum,
and can be traced no further. A strong ecto-lateral tract
from the olfactory lies superficially to these niduli, which
are composed of small, dark, angular cells similar to those
‘which in other animals are associated with the olfactory
regions of the cortex.

The relations so far described are in no way conjectural,
none of the fibres decussate, nor is there any connection
between the olfactory commissure and the commissure
of the olfactory centres. It might be supposed that the
-two tracts form a circuit broken by cellular matter in
‘the olfactory lobes and again by the cells of the olfactory
centres. .
“sts The third’ sét-of fibrés: lies dorsad to those’ just described ,

24 JouRNAL oF CoMPARATIVE NEUROLOGY.

and its fibres are not deeply stained, being perfectly distinct
from both the preceding. They pass caudo-laterad and
somewhat dorsad to the occipito-basal lobes, forming a
tract along the caudad margin of the latter and arching
over the peduncular tracts. It is from the lateral portion
of this tract that the tracts apparently homologous with the
descending pillars of the fornix arise. These fibres doubt-
less spring from the occipito-basal lobe and_ divaricate
from the commissure of those lobes and then pass entad to
the peduncles in their course to the homologue of the mam-
millare.

It will be seen that the fornix is a much more simple
body than in higher vertebrates. Instead of two distinct
portions with a cellular mass interposed near the median
line, we have a continuous tract on either side from the
occipital region to the mammillare. The nature of the
tract ascending from the ventro-basal region to beneath the
callosum in the alligator is left doubtful.

The complete differentiation of the commissural system
in serpents is no doubt due to the great comparative com-
plexity of the brain as a whole, and especially of the oc-
cipito-basal lobe and the greater extent of the free occipital
cortex.

It should be added that the above description of the
course pursued by the several branches of the anterior com-
missure leaves much to be desired as to the exact con-
nections in the olfactory. There is, as already stated, a
large mass of cortex upon the lateral and dorsal parts of the
olfactory crus. It is from this that the strong latero-ventral
tract originates, which then passes caudad, laterad, and
dorsad beneath the cortex to a point as far caudad as the
termination of the middle pracommissural tract. There
seems to be no direct connection with the last named or
the peduncular bundles. It also appears that the cephalad
branch of the anterior commissure enters the cortex of the
crus rather than the specific olfactory substance. The only

Herrick, Morphology of Nervous System. 25

tracts from the latter seem to be short superficial ventral
bundles, and, less certainly, a few median strands along the
longitudinal fissure. We have much evidence that a similar
condition prevails in mammals. The question also rises
whether the caudad precommissural tract be not homologous
with the fornix.

The connective elements of the cerebrum have been
variously interpreted, and chemical researches more refined
than now possible may be necessary to fully discriminate
the tissues. Our sections reveal two apparently distinct
systems. The framework consists of the epithelium of the
ventricles and their derivatives, the latter being in the form
of fibres extending to the periphery and bearing at intervals
fusiform inoblastic cells. The intervals left between these
fibres is filled with a material which after treatment with
acid and alcohol is reticular, and forms a mat or felt of great
uniformity supporting the cells. As to the normal condi-
tion of this stroma, two views are possible, either the
substance is composed of a reticulum and a soluble or
coagulable filling, or the reticular appearance is artificial and
the result of the partial solution and partial coagulation of
what was originally a gelatinous and homogeneous mass.
The latter view seems the more probable. Aside from the
nerve cells, nutritive bodies having the appearance of mi-
grant blood corpuscles are scattered in the stroma. These
have only the nucleus colored, while the body is either dis-
solved or entirely transparent.

There is no marked difference in structure between the
connective tissue of the cerebrum and that of the rest of the
brain.

The Diencephalon.—The habena in the lizard forms a
considerable cephalo-dorsal protuberance, consisting of two
closely-packed cell-masses on either side of the cylindrical
crus of the epiphysis. The two portions are connected by a
small but distinct commisural band, which may be termed
commissura habenaria. In the habena itself there are, in

26 JoURNAL oF COMPARATIVE NEUROLOGY.

addition to the prevailing fusiform cells with pale nuclei,
many small dark nuclei, probably representing cellular
elements like those of the granular layer of the cerebellum.
-The commissure does not seem like a decussation, and,
although it may sustain some relation to the conarium,
reveals none. Its convexity is caudad and dorsad, and its
tracts pass latero-ventrad until they approximate to the
optic tracts. It is impossible to determine at present
whether they fuse with the optic tract or cross into the
ventral part of the occipito-basal lobe. This tract comes
into close relation with the superior commissure tract, or
tenia thalami, but does not seem to fuse with it. We have
here the solution of the relations which puzzled Osborn and
myself in amphibia and the alligator. Instead of a division
of the superior commissure we have to recognize two origin-
ally distinct commissures. The commissura habenaria seems
to receive numerous fibres from the habena at a lower level.

The sapra-commissura lies entirely cephalad to the ha-
bena at a level considerably ventrad to commissure of the
habena (which lies caudad to it), and passes by a slight
ventral curvature into the median part of the medio-caudad
projection of the cortex, and thence across to the caudo-
lateral portion. The superior commissure is relatively
stronger than its neighbor, and it would appear that the two
are especially distinct in animals like the lizard, where the
epiphysis is highly developed.

If the superior projecting portion of the habena sur-
rounding the base of the stalk of the epiphysis be con-
sidered the habena. proper, the deeper and more ventro-
caudad portion may be distinguished as the nidulus : of
Meynert’s bundle or nidulus Meynerti. The fibres of Meyn-
ert can be traced to the portion mentioned (which in the
black snake forms a distinct nidulus). The cells are rather
larger than those of the habena, and less compactly clus-
tered about the walls of the fourth ventricle extending

‘some distrance ventrad.

Herrick, Worphology of Nervous System. 27

It seems probable that the projecting portion of the ha-
bena has been frequently mistaken for the epiphysis. The
plexus chorioideus which protrudes, and the fillet of epi-
thelial cells forming a part of the peduncle of the epiphys
constitute a body which may easily be regarded as an imper-
fectly developed pineal body. It would be possible to inter-
pret in this way the description given by Stieda of the epi-
physis of turtles. He says: ‘‘ Eine besondere Epiphysis-
cerebri existirt bei der Schildkrote nicht; das kleine keil-
formige Korperchen, welches den dritten Ventrikel und das
Zwischenhirn von oben deckend zwischen die hinteren Ab-
schnitte des Lobi hemispherici eingeschoben ist, zeigt sich
bei mikroskopischer Untersuchung nur als Plexus chorioideus
des Zwischenhirns oder des dritten Ventrikels. Nervése
Elemente sind nicht zu erkennen.” (Ueber den Bau des
Centralen Nervensystems der Schildkrote, p. 68.)

The epiphysis of the lizard has already been described.
Its general histology is well shown by Fig. 7, Plate III. In
longitudinal sections in the horizontal plane the structure
has an unmistakable resemblance to that of an undeveloped
retina, as seen in the eye of larve of amphibians. The pig-
ment clothes the inner wall facing the lumen. Then follows
a series of cylindrical cells, whose processes connect with
oval cells similar to those of the ganglionic layers of the
retina. While it is impossible to trace direct nervous con-
nection with the base, fibres can be followed from the gan-
glionic layer to the walls of the capsule. There is a lobe
of the plexus cephalad and a number of vessels caudad in
the sling of connective tissue supporting the organ.

Reference is here made to the valuable paper by Eh-
lers('). in which a critical review of previous literature of
the epiphysis may be found.

In spite of the great prolongation of the peduncle of
the epiphysis in sharks and the cephalad’ position of the

1 E. Ex_ers, Die Epiphysis der Plagiostomen, Zeitschrift f. Wissensch. Zoologie,
xxx, Suppl.

28 JoURNAL OF COMPARATIVE NEUROLOGY.

body itself with reference to the brain, the relations to the
habena and the surface seem similar to those in the lizard.

The epiphysis in Petromyzon is more complicated, but
obviously has a similar structure, so far as the epithelium is
concerned. (See A/born, Untersuchungen uber das Gehirn
der Petromyzonten, Zeitsch. f. Wis. Zoologie, xxxix. )

The relations in Amphibia are not essentially different,
though the organ in adults of Anura has suffered much
reduction. The evidence for the sensory, and even the optic
nature of the organ is conclusive aside from that of paleon-
tology. The embryonic condition of the epiphysis in the
serpents is illustrated by Fig. 5, Plate X.

The structure of the thalamus may be conveniently stud-
ied in transverse sections beginning cephalad. In the cere-
brum, in the region of the precommissura, the peduncular
fibres begin to aggregate near the ventral and median por-
tion, and sensory bundles arrange themselves laterad from
them. The latter are accompanied by fusiform cells. The
basal region—z. e., homologue of the pyriform lobe—con-
tains a dense mass of cellular elements, consisting largely
of small, dark, spidery cells of the olfactory type. On
entering the thalamus the peduncles acquire a circular sec-
tion, and the esthesodic fibres arch over the bundle median-
ly. The median nidulus of the thalamus which occupies
the sides of the third ventricle arches over them.

In sections somewhat farther caudad the habena is seen
perched, as it were, on the summit of the diencephalon,
and well circumscribed ventrally from Meynert’s nidulus.
The definite contours of the peduncles are soon lost as we
proceed caudad.

The optic tracts are everywhere separated from the thal-
amus by the ienticular gelatinous band forming the substantia
negra, entad to which is the nidulus, already described, con-
sisting of slender multipolar or pyramidal cells lying trans-
versely and sending processes toward the tract and cephalo-
medianly (Fig. 3b, Plate XII). The dorsal region of the

Herrick, Morphology of Nervous System. 20

thalamus is here filled with fusiform cells (Fig. 3, Plate XII:
Pig. 12, Plate IV, and: Fig. 1(a), Plate IV.

At the point where the nates begin to appear in the
section (Fig. 1, Plate IV), a strong decussation or commis-
sural system appears connecting the right and left peduncu-
lar regions. The decussation is a large one, and is separated
in its ventral course from the chiasm by dark fibres which
I have homologized in the alligator with the ansulate fibres.

The so-called commissure of von Gudden, above described,
extends as far caudad as to the front of the infundibulum,
which occupies a position beneath the mesencephalon, the
thalamus having been caudo-ventrally appressed upon the
corpora quadrigemina.

The ventral region of the thalamus may next be noticed.
The chiasm is very perfect in the snake. The optic fibres
being collected in small bundles, each bundle being crossed
by a corresponding bundle of the opposite side. Each of
the small bundles is enwrapped with a transverse meshwork
of connective fibres, thickly set with deeply staining trans-
verse inoblasts, giving to the optic nerve a different appear-
ance from that of any other cranial nerve. ’

The nidulus fornicis inferior consists of two sharply-
defined cell-clustres immediately cephalo-ventral of the in-
terpeduncular nidulus, occupying the caudad aspect of the
tuber cinereum. The cells are fusiform and transversely
placed. The two niduli are separated in the lizard by a
considerable interval. While these cell-clusters ought to
be unhesitatingly homologized with the mammillary, no
ascending tract to the thalamus was seen, and it may be
well to use a name not implying any homology.

In the caudal portion of the tuber at the level of the
chiasm, in both the black snake and lizard, are two niduli
of pyramidal or irregularly multipolar cells, rather larger
than those of the surrounding gray matter. They occupy
a position some distance laterad from the median line, and
are quite distinct from the interpeduncular nidulus, as well

30 JOURNAL OF COMPARATIVE NEUROLOGY.

as the nidulus of the fornix. The general direction of the
processes seems to be latero-caudad. An exactly similar
group of cells appears in the medulla with the ventral
longitudinal tracts and these two niduli are more or less
‘united and may be regarded as outlying accessory niduli of
that tract, a view which is confirmed by the motor facies of
the cells.

In sections at a little higher (dorsad) level than the
chiasm the cells are massed in great numbers in the ceph-
alad part of the tuber cinereum, constituting a more or less
definite. nidulus. The cells are of the fusiform bipolar
variety; and lie with their axes dorso-ventrad and _fibre-
tracts continuing their dorsal projections. This nidulu,
continues dorsad for some distance, while retaining its
relative position about the ventricle.

A conspicuous nidulus lies immediately entad of the
zone of opaque gelatinous substance forming the inner
boundary of the optic tract (substantia nigra?). The posi-
tion of this cell group is indicated in Plate II, Fig. 1 a, and
Plate I, Fig. 2 a. The general appearance of these cells is
illustrated on Plate Il, Fig. 12. They are of the so-called
motor type, being susceptible to stain and of pyramidal
form, while their apical processes extend entirely through
the substantia nigra. The cells are narrow and produced,
with the long axis in the ento-ectal direction. At right
angles to these cells are others of the fusiform type, with
clear large nuclei. It seems quite certain that the ental
fibres from the above described pyramidal cells pass ceph-
alad, while the peripheral fibre of each seems to fuse with
the optic tract. The substantia nigra is itself divided into
two portions, causing a similar division of the nidulus, due
perhaps to the entrance of large blood-vessels separating a
more dorso-caudad portion from that forming the lenticular
sheet just entad to the optic tracts.

Of the cranial nerves derived from the cephalad part
of the brain, only the following jottings on the olfactory

Herrick, J/orphology of Nervous System. 2)

are necessary. In the embryos of the black-snake, fre-
quently referred to above, the fibres from the greatly elong-
ated olfactory lobe collect in rather small bundles and pass
to the Schneiderian epithelium either of the nasal cavity or
of Jacobson’s organ. The fibres destined to the latter collect
from the mesal aspects of the lobes and form strong bundles
passing ventrad, though there is no sharp regional differen-
tiation. The epithelium of the two organs at this stage is
nearly identical, but the granular sub-epithelial layer of the
nasal passages is nearly homogeneous, while that of Jacob-
son’s organ has a follicular or lobose structure and receives

a larger proportion of nerves.
BRAIN OF THE FURTLE (ASPIDONECTES SPINIFER).

The brain of the small specimen of Aspidonectes figured
may serve as a rather generalized type for the Chelonide.
In many respects the external configuration reminds one of
that of the lizard. The abrupt flextures described by the
axis and the extremely small size of the hemispheres are
best seen from sections. The olfactory lobes are super-
ficially fused ventrally and are so closely appressed upon
the hemisphere that they may easily be regarded as a part of
the latter. The real shape of each of the hemispheres is
a very obliquely-placed ellipsoid, bearing a more or less ,
conical protuberance cephalad. The diencephalon presents
no noteworty peculiarity, except the great relative size and
independence of the medi-commissura. The optic lobes are
very high and large, their median length being much greater
than that of cerebrum. The ventricles of the mesencephalon
are large and extend far laterad, while the tectum is highly
developed. |

fiistology.—In the turtle the distinctions between the
areas of pyramidal and fusiform cortical cells are quite ob-
vious. The whole lateral surface is covered by a thin layer
of the pyramidal cells with deeply staining nuclei. In the
perpendicular section (Fig. 2, Plate III) through the lateral

22 JouRNAL OF COMPARATIVE NEUROLOGY.

portion of the hemisphere, the parieto-frontal lobe (a) is
made up of these kinesodic cells.

The same lobe in sections further mesad is greatly re-
duced (Figs. 2 and 3, a), having been encroached upon by
‘a dense mass of the spherical bodies constituting the central
granular part of the olfactory lobe. This close approxima-
tion of the olfactory lobe upon the hemispheres has the effect
of apparently driving the frontal lobe ventrad, for there is a
small cluster of pyramidal cells at the point represented at
Fig. 4,c. Almost the entire dorsal surface also bears cells of
the kinesodic type.

The cells of the occipital lobe, on the other hand,
have the spindle shape and large clear nuclei of the typical
zesthesodic cells.

The olfactory bulbs are very large and are soldered
obliquely upon the front of the cerebrum and ventrally are
fused with each other, producing an effect not unlike that
seen in Rana.

The histological structure is similar to that in the alliga-
tor. Externally, especially cephalad and ventrad, is the
area of convoluted olfactory fibres, each bundle being sepa-
rated from its neighbor by sheathing fibres richly filled with
dark elongate inoblastic nuclei and scattered oval Deiters’
corpuscles. Then follows the glomerary zone of gelatinous
aspect, in which almost the only cellular elements resemble
Deiters’ nuclei. An intervening zone nearly devoid of cells
separates this from the cortex olfactorii proper, in which,
besides Deiter cells, there are two distinct elements: first,
large, irregularly-angular or fusiform cells, with clear gran-
ulated nuclei of large size; second, small, densely staining
multipolar cells such as we have elsewhere recognized as
characteristic of the prosencephalic olfactory regions. This
variety of cells is abundant, for example, along the ventral
surface of the cerebrum in rodents. The nuclei of these cells
are irregular and stain deeply. Separating this zone from
the medullary portion is a second layer nearly devoid of

Herrick, Worphology of Nervous System. 22

cells. The medullary portion lying near the ventricle con-
tains cells of two sorts, the ordinary Deiter cells, with clear
granular nucleus and no obvious cell body, and deeply stain-
ing nuclei of smaller size, which perhaps belong to the con-
nective tissue system. There is a small branch of the olfac-
tory (Plate III, Fig. 4, ol. 2) which, after separating from
the main portion, passes along the ventral surface of the
bulb, without entering it, until it terminates in a detached
ventro-caudad portion of the glomerular layer.

The structure of the pyriform lobe is illustrated by Fig.
14, Plate X. The small, irregularly pyramidal or multipolar
cells scattered among the fusiform remind one at once of the
corresponding region in mammals. The chief difference
between these cells and those of the motor type lies in
their smaller size, greater irregularity and greater avidity
for stains.

The basi-occipital lobe is considerably developed, espe-
cially immediately dorsad to the basal part of the ventricle,
and projects as a distinct tuber into the posterior cornu (Plate
III, Fig. 3, ol.). Dorsad and cephalad to the basi-occipital
lobe is a tract forming a curved roof-like partition between
it and cephalad parts of the brain. This tract is densely
filled with spindle-cells with axes chiefly parallel to the
general direction of the tract, descending from the dorso- ,
cephalad angle of the posterior cornu obliquely cephalo-
ventrad to the basal part of the ventricle. Thence the
tracts and accompanying cells seem to pass caudo-laterad
toward the peduncles. A considerable axial portion of the
cerebrum lies beneath (ventral to) the anterior cornu, but
may be regarded as a part of the central lobe.

All of these axial portions, but especially the occipito-
basal, contain rosette-like clusters of fusiform cells. These
are obviously due to successive subdivision of cells; in fact,
all stages of such subdivision may be found, extending from
single cells with double nuclei to rosette-like clusters within
clear spaces in the neuroglia, It sometimes appears as

34 JOURNAL OF COMPARATIVE NEUROLOGY.

though certain cells suffer subdivision into nucleus-like
bodies or Deiters’ corpuscles, but of this there is insufficient
evidence.’ In the cephalad part of the axial lobe there is a
special mass of proliferating cells. The multiplication here
is the same as that in the occipito-basal lobe—longitudinal
fission rather than the endogenous multiplication described
beyond by Mr. Turner in the corresponding region of birds.

Miscellaneous Notes—TYhe two commissural systems of
the habena are well shown, as is the connection with the
epiphysis. The latter is constructed obviously upon the
same plan as that of the lizard, and, in the present case at
least, is of moderately large size. This fact makes it the
more surprising that Stieda should have overlooked the
existence of a true epiphysis in the turtle. It is true that
the body is obscured by the large plexus which envelops
it, but a glance at Fig. 7, Plate III, will show that the
nervous connection with the habena is complete, and the
neuro-epithelium of the tube is also very similar to that of
the lizard. The tubular organ is curved cephalad so as to
become somewhat sickle-shaped. The peduncle is hollow
throughout, and opens not into the third ventricle directly,
but into the canal connecting the optic ventricle with the
dorsal part of the third ventricle.

The optic ventricle is large and its cornua extend far
laterad. The tectum opticum is very thick and has the
usual structure, except that in the median portion immedi-
ately above the ventricle and lying in the inner zone of
concentric cells there is an unusual development of the bal-
loon cells mentioned in the alligator. It is impossible to
trace any connection with the trigeminal fibres, however.

In the thalamus the two large niduli, which in the alliga-
tor we ventured, for want of a better term, to call corpora
geniculata, are in this case very distinct, and lie some dis-
tance from the median line beneath the superior commissure
(Fig. 5, corp. g.).. The niduli themselves.consist of large
fusiform cells-in a. homologous stroma of neuroglia. ° Sur-

Herrick, JWorphology of Nervous System. 35

rounding these nearly spherical masses is a cortical band of
fibrous matter containing densely-packed fusiform cells.
This cortical portion of each side is produced mesad to
unite with its fellow, thus giving rise to the large medi-
commissura (m. c. Fig. 6). These bodies are probably what
Stieda refers to when he says: ‘‘ Ferner schliessen sich die
Nervenzellen in den beiden Thalami optici zu einen kugel-
runden Complex zusammen—den Nervenkern der Thalami.”

Nore.—Attention may be called to the fact, noticed by Stieda, that
there is a small ganglion on the root of the eighth (Plate III, Fig. 2),
through which the fibres pass mesad to the very large and protuberant
eminentia acustica (Plate III, Fig. 4, E, ac.), which projects cephalad,
dorsad and mesad into the ventricle below the cephalad part of the cere-
bellum. This projection it is, no doubt, which Carus(?) refers to as
‘Ganglion des Hornerven im vierten Ventrikel” which Stieda is una-
ble to identify.

PAA, Te

Figs. 1-4. Longitudinal horizontal sections ot the head of embryo
of the guinea-pig at different levels. |

Fig. 1. Illustrates the relations of the lateral and third ventricles, .
the formation of the plexus (P), and of the hippocampus (H), as portions
of the same fold of cortical substance, and also the existence of two re-
gions (a and 4), where the proliferating cells of the ventricular epithel-
ium come into relation with the cortex, suggesting the possibility of.
localized deep origin of the mother cells of the cortex in later stages.

Fig. 2. Section of the same brain at a more ventral level, the
investing structures being removed. The relations of the striatum to
the peduncles is well seen.

Fig. 3. Similar section from a still lower level, showing results
of the strong pons flexture. The medulla and cerebellum are cut
transversely, while the paired rudiments of the hypophysis are seen
between the Gasser’s ganglia. The recessus lateralis inferior of the
fourth ventricle is nearly closed, and the formation of the lateral niduli
of the medulla from the cells of its ventricles is just beginning. The
dorsad projection of proliferating cells begins to circumscribe the cere-
bellum.

Fig. 4. A section slightly ventrad to the above, showing especially
the dorsad prolongation of the recessus lateralis by which the germin-
ative area of the dorsal surface of the cerebellum is produced. It ulti-
mately becomes soldered upon the cerebellum, forming a double cellular
zone.

1 C. G. Carus, Darstellung des Nervensystems und Hirns, Leipzig, 1814, p. 172-181.
L. Strepa, Ueber den Bau des centralen Nervensystems der Schildkréte, 1875, p. 70.

36 JouRNAL oF CoMPARATIVE NEUROLOGY.

Figs. 5-}. Sections in the same plane from older embryos of the
mouse.

Fig. 5. Shows the relation of the olives to the roots of the trige-
minus, the recessus lateralis inferior being still open in part.

Fig. 8. Section near the tip of the cerebellum, showing the double
cellular layer of the dorsal surface and also the formation of the plexus
and cornucopia.

Fig. 9. Portion of the cortex of the cerebellum in an embryo of
guinea-pig near the end of embryonic life. The cells of E, the super-
ficial proliferating layer derived from the epithelium of the recessus
lateralis, are frequently provided with two or more nuclei. P, zone of
Purkinje “cells; N, zone of granules containing some large ganglion
cells; F, fibre zone with fusiform cells of the nerve sheaths.

Fig. 10. Portion of the ventricular region of the same section of
the cerebellum with cells of the dentate nidulus. Fig. 4 of Plate II. is a
drawing of the entire section.

PAVE Tie

Fig. 1. Portion of the cerebellum and medulla of the mouse embryo
figured upon Plate I. and lying dorsad to the section drawn in Fig. 8,
showing the two cellular layers, a and c, and the separating fibres, 4.

Fig. 2. Longitudinal median section of the optic lodes and cere-
bellum of guinea-pig embryo at an early stage. J”. /., velum medullare
posterior; cb., cerebellum.

Fig. 3. Longitudinal section of the cerebellum of the mouse.

Fig. 4. Nearly median longitudinal section of the brain of a
guinea-pig embryo near the end of embryonic life, showing the gray
proliferating zone on the surface of the cerebellum (an embryonic
character) and the proliferating cortex.

Fig. 5. Highly magnified cells of the deeper portions of the dorsal
cortex. The portion drawn lies nearly one-fifth the whole length of the
cerebrum from its caudad margin and nearly in the middle of the width
of the hemisphere. The divisions indicated in the scale have the ap-
proximate value of 1.25 micros.

PEA Une

Sections from the brain of a young turtle, Aspzdonectes spinifer.

Figs. 1-6. Wongitudinal sections passing from the lateral to the>
median plane. J’.2., Gasser’s ganglion; G. w777, ganglion of the eighth
nerve; P, pes pedunculi: «a, frontal lobe; 4, parietal lobe; c, fromto-
median lobe(?); 0.4./., occipito-basal lobe (part of so-called striatum
or axial lobe); c.f., corpus posterius; v.f., velum medullare posterior;
c.c., corpus callosum; a.c., preecommissura; m.c., medicommissura; ef.,
epiphysis; g7., glomerulary zone of the olfactory lobe: cf.g¢., corpus
geniculatum.

Fig. 7. Epiphysis and habena,

Herrick, Worphology of Nervous System. 27

Fig. 8. Portion of the olfactory cortex, with its three sorts of cells.

Figs. 9-11. Views of the brain in three positions.

(All the figures of this plate were drawn with the aid of the camera
lucida).

EASE VE

Figs. 1-11. A series of transverse sections through the mesen-
cephalon and metencephalon of the lizard, especially to illustrate the re-
lation of the cerebellum to adjacent parts.

Explanations of these figures will be given in the second part of the
paper.

Fig. 1. Section just cephalad to the optic lobes. a, nidtlus of the
substantia nigra; the reference line passes through the optic tracts and
substantia nigra.

Fig. 2. Section through the middle of the optic lobes. J/7.b., Mey-
nert’s bundle.

Fig. 4. Illustrates the relations at the base of the cerebellun: and
exit of the eighth nerve. The free tip of the cerebellum, having re-
curved to beyond the origin, appears as an independent organ.

Figs. 5-9. Indicate the method of retroflexion by which the cere-
bellum is formed.

Fig. 12. Cells from the nidulus of the substantia nigra. See Fig.
ae

Fig. 13. Cells from the root of the tenth nerve, drawn with a one-
fifth inch objective.

Fig. 15. Cells from the frontal lobe (see Fig. 6, x, Plate IX).

Fig. 16. Cells from the intra-ventricular lobe of the same section
at x.

PLATE ioe

A series of horizontal sections through the brain of the lizard.
The descriptions will be extended in Part II.

Fig. 1. Section near the ventral surface. «a, tuber cinerium.

Fig. 2. Section at a higher level. /, peduncles; a, nidulus of the
nigra; of.¢., optic tracts.

Fig. 3. M.b., Meynert’s fasciculus; w.7., posterior longitudinal
fasciculus.

Fig. 4. Section at the level of the corpus callosum.

Fig. 6. F.l., frontal lobe; /.1./., fronto-median lobe; O./., occipi-
tal lobe; M.L., intra-ventricular lobe; A.P., foramen of Munro; A.Z.,
central division of axial lobe; O.7., optic tracts; O.c., posterior or optic-
lobe commissure; J7.b., Meynert’s bundle; O.v., optic ventricle; /.,
habena; 7¢.f.¢r., tract to corpus posterius; »’ and w.,” see Figs. 15 and
16, Plate IV.

Figs. 8-9, C.p,, corpus posterius.

LABORATORY TECHNIQUE:

A new operating-bench.—F¥or operating upon the brain
of dogs or other animals, especially in cases where anes-
thetics cannot be employed throughout, the usual bench is
very inconvenient. The following substitute is suggested:

A low bench is provided with two davits, which may be
elevated or depressed at will. From these davits are sus-
pended two straps ending in a surcingle, to be strapped
about the body of the animal immediately in front of the
hind legs and just behind the fore legs respectively. To the
posterior surcingle a breech strap is attached, and to the
anterior one a breast strap. The two surcingles are con-
nected below with a longitudinal bar, which in use will pass
between the legs and extends forward to the head. Ante-
riorly it supports a halter passing over the neck and nose and
a perforated tin or leathern receptacle for the anesthetic, so
arranged as to fit over the nose of the animal. The longitu-
dinal bar may be firmly clamped to a sliding vertical bar at
any elevation. The animal is placed on the bench, the sur-
cingles and halter buckled in place, and the davits elevated
to the required height. The ventral bar is then firmly
clamped, and every motion of the limbs is unimpeded, while,
at the same time, the most violent struggles do not produce
change of position in the head or trunk. Adduction is abso-
lutely unrestricted, and it is possible at a moment's notice to
bring the feet in contact with the bench to observe practical

application of the contractions induced, etc.

MORPHOLOGY OF THE AVIAN BRAIN.

I.—TAXONOMIC VALUE OF THE AVIAN BRAIN AND
THE HISTOLOGY OF THE CEREBRUM.

C. H. TurRNeER.

Introduction.—This communication is the first of a series
of papers upon the avian brain. In these papers the author
does not think to exhaust the subject. If he succeeds in
directing attention to a much-neglected branch of neurology
he will consider that his labors have been well repaid.

Material——The remarks in this paper are based upon the
study of over one hundred and fifty birds, belonging to nine
orders, twenty families, more than forty genera, and above .
fifty species. In most cases I have had several specimens of
the same species; in a few cases, however (Aubo virginianus,
Botaurus mugitans, Butorides virescens, Ardea herodias), |
have had only one specimen. The major part of the bird
brains were collected by me during the summer and autumn
of 1890. The remainder were donated. For these donated
specimens I am indebted to the following gentlemen: to
Professor C. L. Herrick, for a specimen of Ardea herodias
and several other brains; to Professor W.G. Tight, for a
specimen of Botaurus mugitans; and to Mr. C. J. Herrick,
for a specimen of Lwébo virginianus.

I must confess that I have not read all that has been
written upon the avian brain; but, through the kindness of

1 Thesis offered for the degree of Bachelor of Science in Biology, Univ. of Cin-
cinnati,

40 JoURNAL OF COMPARATIVE NEUROLOGY.

Professor Herrick, I have been enabled to consult the greater
part of the recent and a number of the older works upon
this subject. In this connection, I thank Prof. Herrick, not
only for the use of his library, but also for many valuable
suggestions.

Techniqgue.—Almost all of the brains examined were
hardened in dilute chrom-acetic acid and alcohol. A solution
of chrom-acetic acid of from one-third to one-half of the
ordinary strength was found to be the most useful. The
fresh brain was placed in this fluid and allowed to remain
for twelve hours. It was then thoroughly washed with
distilled water and hardened in increasing strengths of
alcohol. After a specimen had been in go per cent. alcohol
for a short time, measurements were taken and its external
appearance was recorded.

Staining.—In preparing specimens for histological study,
several stains were tried. In a few cases, Kleinenberg’s
hematoxylin gave good results: in others, it was a failure.
Grenacher’s hematoxylin, applied to sections, sometimes
gave good results.

The best results, however, were obtained from aluminium
sulphate cochineal.(') In using this stain, the specimens
were transferred from go per cent. alcohol to 70 per cent.
After remaining for one day in this grade of alcohol they
were transferred to the stain and allowed to remain in it for
three or four days. They were then thoroughly washed in
70 per cent. alcohol, after which they were hardened and
sectioned in the usual way.

When the brains are prepared in this manner, the neu-
roglia does not stain at all, while the nerve cells are stained
and their nuclei and nucleoli well differentiated. The red
blood-corpscules also stain, but they stain much more densely
than the nerve cells. Fibres do not stain, but, in most cases,

can be readily traced.

1 This stain is prepared by substituting aluminium sulphate for the alum in Czokor’s
alum cochineal,

TurneER, Worphology of the Avian Brain. 41
EXTERNAL FORM.

Szze-—Compared with the brains of other Sauropsida,
the bird brain is quite large. It fills the entire cavity of the
skull. This cavity is relatively much larger in birds than it
is in other members of the same group.

Compactness.—The most remarkable characteristic of the
avian brain is its compactness. The large prosencephalon
entirely covers the diencephalon, and may or may not cover
the rhinencephalon and mesencephalon. Along about three-
fourths of their mesal border, the two lobes of the prosen-
cephalon are compressed against each other. Near their
narrow cephalic end, the two hemispheres are slightly
divaricated; near their broad caudal end, they are strongly
divaricated(') (Plate V, Figs. 5, 6, 8, 10.)

Into the caudal V thus formed, the cephalic portion of
the well-developed epencephalon is wedged so firmly that a
portion of it is crowded beneath the prosencephalon. The
metencephalon lies beneath the epencephalon, and is almost
completely covered by it (Plate V, Figs. 1, 4; Mt.).

Fvolution.—The compact excephalon, the well-developed
epencephalon, the ventral mesencephalon ,—all these character-
istics completely separate the avian from the reptilian type
of brain; yet it is easy to see how the first might have been
derived from the second. Allow me to refer to the form of
an alligator’s brain.(*) Viewing the dorsal surface of the
brain, we observe the following points. Between the small
prosencephalon and the poorly-developed epencephalon, lie
the two tangent sub-ellipsoidal lobes of the mesencephalon
In a brain of this type, suppose that the epencephalon de-

rt A. BuMM transcribes Tiedemann as follows: ‘‘ The avian brain resembles an ace of
hearts, whose apex is directed cephalad and whose base is directed caudad”’ (‘‘ Das
Grosshirn der Végel,’”’ von A. Bumm, Zeitschrift fiir Wissenschaftliche Zoologie, vol.
38, Pp. 431.

StrepA makes a similar figure, and then adds: “In die vertiefte Basis des kartenherz-
férmigen Grosshirn schiebt sich das Cerebellum.”

2 See “‘ Notes on the Brain of the Alligator,” by Prof. C. L. Herrick, Jour. of the
Cincinnati Nat. Hist. Soc, Vol. 12, Pl. VII, Figs. 1, 2, 3.

42 JournaLt or ComparativE NEUROLOGY.

velops rapidly. As this body grows cephalad and dorsad it
will separate the optic lobes. Now let the cerebral hemi-
spheres increase in length. Let the lateral and dorsal por-
tions of each hemisphere grow caudad much more rapidly
‘than the mesal and the ventral. This will cause the caudad
portion of each hemisphere to revolve toward the meson,
and, at the same time, to over-ride the optic lobe. A com-
parison of the different lobes found in the avian brain with
the corresponding lobes of the reptilian encephalon shows
that this mesal revolution has actually been performed.

RHINENCEPHALON.

Size. — Compared with that of other Sauropsida, the
avian rhinencephalon is quite small. In most birds, its
length is equal to about 10 per cent. of the length of the
brain; but in some types (Ardetde, Anatide), this ratio
rises to 18 or 20 per cent.; while in others ( Corvide), it
falls to about 6 per cent.(') (see Table 1).

Form.—With regard to position, the avian rhinencephala
fall into two classes. Into the first class fall those which
project beyond the cephalic end of the prosencephalon; into
the second class fall those which do not thus project.(*)

Each rhinencephalon of the first class consists of two
elongated sub-ellipsoidal bodies which arise side by side,
either at or immediately ventrad to the cephalic end of the
prosencephalon, and project cephalad. Each of these lobes
contains a ventricle, which, I think, is always continuous
with the lateral ventricle of the cerebral hemisphere.

Each rhinencephalon of the second class consists of one or
two short sub-ellipsoidal bodies which are partly imbedded

1 After carefully studying the cerebrum of European birds, A. Bumm remarks: “ In
swimming birds, the olfactory lobes are well developed; in wading birds (Sumpfvégel),
they are moderately developed; in all other cases, they are only slightly developed.” He
then adds the following table :

Ratio of the weight of the Rhinencephalon to the weight of the Prosencephalon,— \n
the goose as 1: 67.0; in the snipe as 1: 84.5; in the buzzard as 1: 543.0. Op. cit., p. 436.

2 In European birds, these two types of rhinencephalic structure have been recog-
nized by A. Bumm, Op. cit., p. 435-

Turner, Morphology of the Avian Brain. 43

in the prosencephalon. When there is only one lobe, it is
the result of the fusion of the primitive lobes. When two
lobes are present, each usually contains a ventricle; but when
there is only one lobe, it is usually solid.

The above types merge into each other. As we ascend
the scale, the olfactory lobes move caudad aud become
smaller. In the higher groups, the lobes are fused and

almost completely imbedded in the prosencephalon.

EXPLANATION OF TABLE I (SEE P. 78).

**Length ” is a contraction for ‘* Ratio of the length of the rhinenceph-
alon to the length of the brain.”

‘¢ Breadth” is a contraction for ‘‘ Ratio of the breadth of the rhinen-
cephalon to the length of the brain.”’

All ratios are expressed in hundredths of the length of the brain.

‘*Partly imbedded” is a contraction for ‘ Partly imbedded in the
prosencephalon.” E

A + affirms what is at the head of the column.

A — denies what is at the head of the column.

PROSENCEPHALON.

Szze.—In carinate birds, the prosencephalon is relatively
very large. In the birds examined, the dimensions vary in
different groups; thus, the ratio of the length of the prosen-
cephalon to the length of the brain varies from about 55 per
cent., in the Avdezde, to about 92 per cent., in the Corvide;
the ratio of the breadth of the prosencephalon to the length
of the brain varies from about 80 per cent., in the Ardezde,
to about 125 per cent.,in the Corvide, the ratio of the depth
of the prosencephalon to the length of the brain varies from
about 45 per cent., in the Ardezde, to about 68 per cent., in
the Corvide(') (see Table II).

In all types, the depth of the prosencephalon is less than
its length. In the Avatide, the length and breadth are about

1 After having carefully weighed the brains of various European. birds, A. Bumm
compiled the following table :

Ratio of the Weight of the prosencephalon to the weight of the remainder of the brain.
—In the oscinine birds, 2.79: 1; in the fringilline birds, 2.77: 1; in the parrots, 2.08: 1.
in the swimming birds, 1.94: 1; in the wading birds (Sumpfvégel), 1.75: 1; in the birds
of prey, 1.61: 1; in the fowls, 1.12: 1; in the doves, 0.95: 1. Op. cit., p. 433.

44 JouRNAL OF COMPARATIVE NEUROLOGY.

equal. In all other cases, the breadth exceeds the length(')
(see Table IT).

HEMISPHERES.

As usual, the prosencephalon is composed of two hemi-
spheres, which are compressed against each other at the
meson. Each hemisphere is a gibbous sub-conical body,
with its apex directed cephalad and its base directed caudad.
The ventral surface of each hemisphere is undulating; the
lateral surface may be either longitudinally undulating or
convex; the mesal surface is flattened; the cephalic, dorsal
and caudal surfaces are convex.

Connections.—At the meson, the hemispheres are sepa-
rated by a deep longitudinal fissure (Fissura longitudinalis).
The hemispheres are connected with each other by the
anterior commissure and the corpus callosum. The hemi-
spheres are connected with the diencephalon by the crura
cerebri.

Dorsal aspect (Plate V, Figs. 5, 6, 8, 10).— Viewed from
above, the outline of each hemisphere of the avian brain is
composed of the following elements:

1. A short convex curve, which passes caudo-mesad from
the cephalic extremity of the hemisphere to the meson.

2. A straight line, which continues this curve caudad
along almost the entire mesal border.

1 The following tables show that there is a great resemblance between the brains of
American and of European birds. All these tables are translated from A. Bumm’s work
on the avian prosencephalon Op. cit, p. 431-432.

Table of ratios of the transverse to the longitudinal diameter of the avian prosen-
cephalon (compiled by Leuret, after an examination of thirty-six species).—In the parrots,
I: 1.09; in the swimming birds, 1: 0.99; in the fringilline birds, 1: 0.91; in the oscinine
birds, 1: 0.81; in the wading birds, 1: 0.79; in the fowls, 1: 0.79; in the birds of prey,
1: 0.74; in the doves, 1: 0.74.

Table of ratios of the width to the length of the avian prosencephalon (compiled by
Serres, after the examination of thirty-one species).—In the parrots, 1: 1.00; in the
oscinine birds, 1: 0.85; in the wading birds, 1: 0.85; in the swimming birds, 1: 0,80; in
the running birds, 1 : 0.76; in the birds of prey, 1: 0.70; in the fowls, 1 : 0.66.

Table of ratios of the length to the depth of the avian prosencephalon (compiled by
Serres).—In the fowls, 1 : 0.75; in the running birds, 1 : 0.69; in the birds of prey, 1 : 0.69;
in the swimming birds, 1 : 0.60; in the wading birds, 1 : 0.60; in the parrots, 1: 0.59; in the
oscinine birds, 1 : 0.58.

Turner, Worphology of the Avian Brain. Ac
‘O- z 5

3. A convex curve, which extends caudo-laterad from the
caudad extremity of the second curve to the caudad extremity
of the hemisphere.

4. A convex curve, which extends cephalo-laterad from
the caudad extremity of the third curve to the widest part of
the prosencephalon, then cephalo-mesad to the cephalic ex-
tremity of the same. The widest part of the prosencephalon
is nearer its caudad than its cephalad extremity.

This is the usual appearance; but, in some types (Ar-
detde, Cuculide, Meleagridide, Domestic Fowl, Turdide),
the caudad and cephalad portions of the fourth curve are
convex, while the middle portion is concave (Plate V, Figs.
6,8). Each of the above curves grades so smoothly into its
successor that it is impossible to say where one curve ends
and another begins.

When the two hemispheres are in their natural position,
their combined outlines form a V at each extremity of the
prosencephalon. The smaller, cephalic V, is formed by the
intersection of curve number one of one hemisphere with
the corresponding curve of the other hemisphere. The
larger, caudal V, is formed by the intersection ef curve
number three of one hemisphere with the corresponding
curve of the other hemisphere.

In the Anatide (Plate V, Fig. 5) and Ardeide (Plate V,
Fig. 6) the caudal V is very shallow. As we ascend the
scale, this. V becomes deeper and deeper (Plate V, Figs.
8, 10). This I consider an affirmation of the above theory;
that, in its evolution, the lateral border of each hemisphere
extends caudad much more rapidly than the mesal. This
causes the caudal border of each hemisphere to revolve
towards the meson. The depth of the caudal V is a function
of this revolution, and varies directly as the amount of revo-
lution. According to this theory, the caudal V should be
shallow in the lower and deep in the higher types of avian
brains. Since this is the cases, I think we have an import-
ant confirmation of the truth of the theory.

40 JOURNAL OF CoMPARATIVE NEUROLOGY.

Lateral view (Plate V, Figs. 1, 4).—Viewed from the
side, the outline of the avian prosencephalon is composed of
the following curves:

1. A convex curve, which extends caudo-dorsad from the
cephalad to the dorsad extremity of the prosencephalon,
where it turns and passes caudo-ventrad to the caudad ex-
tremity of the prosencephalon. Here the curve turns again,
and, for a short distance, passes cephalo-ventrad.

2. A broken line, composed of two or three convex
curves, which extends cephalad from the end of the above
curve to the cephalad extremity of the prosencephalon.

In the lower types of avian brains, the cephalad portion
of curve number one slopes more gradually towards the base
of the brain than it does in the higher types.(')

Dorsal fissure.—This fissure is universally present, but is
not always in the same position (Plate V, Figs. 1, 4, 5, 6,
ifs rompiloy, |B) ae

In the Anatide (Plate V, Fig. 5, DF), this is a convex
curve, which lies upon the dorsal surface of the prosenceph-
alon. It arises from the meson at about one-third of the
length of the cerebrum from the cephalad extremity of the
brain. For more than half of its course, this curve passes
caudo-laterad; then it passes caudo-mesad to the caudad ex-
tremity of the cerebral hemisphere, where it merges into that
border of the hemisphere. The greatest width of this curve
is equal to about one-half of the greatest width of the cere-
bral hemisphere.

In the /cteride (Plate V, Fig. 7, DF), this curve is also
convex; but it has its origin upon the ventral surface of the
brain. Slightly caudad to the rhinencephalon, it arises from
the meson and extends cephalo-laterad fora short distance, then
it passes caudo-dorsad to the dorsal surface of the prosen-
cephalon.

1 According to A. Bumm, this is also true of the brains of European birds. Op. cit.,
P- 438-4309.

Turner, Worphology of the Avian Brain. 47

At first sight these two fissures appear to be distinct, but
I have considered them identical:

1. Because Bumm has done so.(')

2. Because both are never found in the same species.

3. Because I find all the intermediate stages.

In the Azatide (Plate V, Fig. 10, DF) this fissure lies
entirely upon the dorsal surface of the brain and is very long.

In the Picide (Plate V, Fig. 10, DF) it lies upon the dor-
sal surface of the prosencephalon, but it is near the cephalic
extremity of the same. It is also very short. In the Cucw-
lide, Ardeide, Meleagridide and Strigide this fissure arises
from the ventral surface of the brain, between the origin of
the rhinencephalon and the cephalad extremity of the prosen-
cephalon and terminates upon the dorsal surface of the cere-
bral hemisphere (Plate Vi, Figs, 0, 4,:6, 5; DP):

In the /cteride (Plate V, Fig. 7) it arises from the ven-
tral surface of the prosencephalon caudad to the rhinen-
cephalon and terminates upon the dorsal surface of the
cerebral hemisphere.

Dorsal tuber.—TVhe dorsal fissure either partly or entirely
surrounds a slight swelling. This swelling I have called the
‘¢ dorsal tuber.” Since the dorsal fissure surrounds the dorsal
tuber, whenever a portion of that fissure is on the ventral
surface of the brain,a portion of the dorsal tuber is also car-
ried ventrad.

On the ventral surface are several tubers. These may be
studied to the best advantage in the owl brain (4udo virgin-
tanus ), where they are enormously developed (Plate V, Fig.r).

Ventro-frontal tuber (Plate V, Figs. 1, 13).—This is a
small swelling which is situated upon the ventral surface of
the prosencephalon at the meson and near the cephalad
extremity of the hemispheres. When this tubei is present,

the rhinencephalon is situated immediately ventrad to it.

x Op. .cit.;s) Naf. 245 Figs: 1,5; Wr.

4s JouRNAL oF CoMPARATIVE NEUROLOGY.

This tuber is usually absent. In such cases the dorsal tuber
may be mistaken for it.

Ventro-median tuber (Plate V, Figs. 1, 7, 9, 13).— This
is a convex swelling, the sides of which slope gently in all
directions. It lies upon the mesal half of the prosencephalon
between the rhinencephalon and the optic chiasm. In some
species (Pate V, Figs. 1, 9, 13) this tuber is quite large, in
others (Plate V, Fig. 7) it is small, in still others it is
apparently absent.

Ventro-lateral tuber (Plate V, Figs. 1, 4, 7.9, 13).—This
tuber is almost universally present. It is usually the largest
tuber of the brain and seems to be the homologue of the
pyriform tuber of mammals. It isa relatively large swelling,
which is situated at the caudo-lateral angle of the ventral
surface of the cerebral hemisphere. Laterad, caudad, and
mesad, the surface of this tuber is strongly convex; cephalad,
the surface is slightly convex. This surface of the tuber
slopes gradually towards the surface of the prosencephalon.
Its length is usually a little more than one-third that of the
prosencephalon while its breadth is usually a little more than
half the breadth of the hemisphere.

Innominate tuber.—This is a small, slightly developed
tuber, which I have occasionally noticed. It is situated
somewhat mesad to the ventro-lateral tuber and is partly
covered by the optic lobe. Its small size and the irregularity
of its presence cast some doubt upon the propriety of recog-

nizing it as a distinct tuber.
EXPLANATION OF TABLE II (SEE P. 80).

‘* Length” is a contraction for “‘ Ratio of the length of the prosen-
cephalon to the length of the brain.”

“Breadth” is a contraction for ‘“‘ Ratio of the greatest breadth of
the prosencephalon to the length of the brain.”

“Depth” is a contraction for ‘‘ Ratio of the greatest depth of the
prosencephalou to the length of the brain.”

All ratios are expressed in hundredths of the length of
the brain.

The length of the brain is the distance from the cephalic extremity

TurRNER, Morphology of the Avian Brain. 49

of the prosencephalon to the center of the diamond-shaped depression
that lies immediately caudad to the twelfth nerve root.

Dorsal fissure median is a contraction for intersection of the dorsal
fissure with the meson visible from above.

Dorsal fissure frontal is a contraction for intersection of the dorsal
fissure with the meson not visible from above.

A + affirms the presence of the fissure or tuber mentioned at the
top of the column.

A — denies the presence of the fissure or tuber mentioned at the top
of the column.

MESENCEPHALON.

The avian mesencephalon consists of two subellipsoidal
bodies, which le partially or wholly beneath the prosence.
phalon. Each lies in a special cavity of the skull. These
lobes have no visible connection either with each other
or with the diencephalon. They are usually smooth, but
occasionally there is a faint indication of a_ transverse
fissure.

Szze.—In the same family the ratios of the dimensions of
the optic lobes to the length of the brain are approximately

constant. In different families these ratios vary. The ratio

of the axial length of the optic lobes to the length of the

brain varies from a little less than thirty per cent. in the
Tyrannide to a little more than forty per cent. in the
Corvide and Paride. The ratio of the greatest breadth of
the optic lobes to the length of the brain varies from about
twenty per cent. to a little more than thirty per cent. (see
‘able Wi):

7\ypes.—With regard to position, the avian mesence-
phala fall into two classes. Those in the first class are
entirely covered by the prosencephalon, while those in the
second are only partially covered.

When belonging to the second class the caudal portion of
each optic lobe lies immediately laterad to the epencephalon
and immediately caudad to the prosencephalon. Thence it
extends ventro-cephalo-mesad to beneath the prosence-

phalon.

‘

Lo) JOURNAL OF COMPARATIVE NEUROLOGY.

When belonging to the first class, each lobe lies immedi-
ately ventrad to the diencephalon and has its major axis
inclined towards the meson. As in the second class, its
caudal end is further from the meson than its cephalic end.(')

Excepting the Azatide and other birds of that type, as
we ascend the scale, the optic lobes become more and more
covered by the prosencephalon until in the highest groups
there is quite a margin between the caudad extremity of the
prosencephalon and the caudad extremity of the optic lobe.
(Plate V, Pigs, 956; 63135°7>)

This is a natural outcome of the process of cerebral revo-

lution, mentioned above.

EXPLANATION OF TABLE III (SEE P. 82).

‘“Length” is a contraction for ‘‘ Ratio of the axial length of the
optic lobes to the length of the brain.”

‘‘ Breadth ” is a contraction for ‘‘ Ratio of the greatest width of the
optic lobe to the length of the brain.”

The length of the brain is the distance from the cephalic extremity
of the prosencephalon to the center of the rhombic depression immedi-
ately caudad to the twelfth nerve root.

+- is a contraction for ‘‘Optic lobes entirely covered by the
prosencephalon.”

— is a contraction for “Optic lobes not entirely covered by the
prosencephaton.”’

DIENCEPHALON..

This portion of the brain is, relatively, small, and is
entirely covered by the prosencephalon. A ventral view
reveals it as a small sub-rectangular body lying between the
prosencephalon and metencephalon. It is intimately con-
nected to the mesencephalon and to the metencephalon, and

is also connected, by the crura cerebri, to the prosencephalon.
EPENCEPHALON.

Form.—As stated above, the epencephalon is well devel-
oped. Its form is that of a laterally compressed hepta-
te
1 Prof. Coues says, that the optic lobes are never covered; this is evidently an over-
sight. ‘* Coues’ Key to North American Birds, 2nd edition, (1884) p. 176.”

Turner, Morphology of the Avian Brain. 51

hedron, with two plane and five convex surfaces. ‘I'wo faces
are formed by the, practically plane, sub-parallel, sides. A
third face extends cephalo-dorsad from the caudad extremity
of the epencephalon to the dorsal extremity of the same.
A fourth face extends cephalo-ventrad from this place to the
pineal body. From this place, a fifth face extends, almost
perpendicularly, cephalo-ventrad to about where the meten-
cephalon joins the diencephalon. Thence a sixth face extends
ventro-caudad to the ventral extremity of the epencephalon.
The solid is closed by the seventh face, which extends caudo-
dorsad from this place to the caudal extremity of the epen-
cephalon. The last five faces are ectally convex and cre-
nated. In most cases, faces three to seven are of about the
same size (Plate VII, Fig. 3).

Convolutions.—The epencephalon is indented by several
transverse fissures, which extend entad from the periphery
almost to the ventricle. Near the surface, these fissures are
usually increased by the intercalation of one or more fissures
between each of the above. Corresponding to each of these
fissures, there is a transverse convolution. It is the presence
of these convolutions which gives the above-mentioned faces _
a crenated appearance (Plate VII, Fig. 3).

Flocculi.—These are two flaps, one of which projects
from each of the lateral surfaces of the epencephalon. They
are situated at a short distance caudad to the optic lobes and
immediately cephalad to the metencephalon. In the Anatide
and Ardeide (Plate V, Figs. 4, 5, 6, 9), these flaps are sub-
triangular; in the Passeres, Picarie, Strigide, etc. (Plate
Vo bies, 1; 7, 5, 10), these flaps ‘are sub-rectangular. Each
flocculus is almost completely imbedded in a special cavity
of the skull.

| entricie.—In the center of the epencephalon there is a.
small ventricle, which is connected to the fourth ventricle
by a narrow neck.

Proportions—In the Anatide (Plate V, Fig. 5), the

epencephalon is wider than long; in all the other families

Ww

JOURNAL OF COMPARATIVE NEUROLOGY.

a

that I have studied, it is longer than wide (Pate V, Fig. 6).
Connections. — The epencephalon is connected to the
metencephalon by the crura ceribellz.

EXPLANATION OF TABLE IV (SEE P. 84).

“ Length” is a contraction for ‘‘ Ratio of the length of the efen-
cephalon to the length of the brain.

“Breadth ” is a contraction for ‘‘ Ratio of the greatest width of the
epencephalon to the length of the brain.”

“Depth” is a contraction for ‘“‘ Ratio of the depth of the efencep-
alon to the length of the brain.

“The length of the brain is the distance between the cephaiee por-
tion of the prosencephalon and the centre of the rhombic depression
that lies immediately caudad to the twelfth nerve root.

The length of epencephalon used is the distance between the apex
of the caudal V of the prosencephalon and the caudad extremity of the
epencephalon.

All ratios are expressed in hundredths of the length of the brain.

METENCEPHALON.

The metencephalon lies beneath the epencephalon and is
connected with it by the crura cerebelli. The metencephalon
is intimately connected with the diencephalon.

Foorm.—In form the metencephalon is a sub-rectangular
prism, all of the exposed faces of which are feebly convex.
Near the caudal extremity of the metencephalon, its lateral
and ventral faces slope, abruptly, ento-caudad, to the myelon.
On the ventral surface, at the union of the metencephalon
and myelon, there is a small diamond-shaped depression
(Piate Vi, Pigs..75) 13).

Surface.—The entire surface of the metencephalon is quite
smooth. There is no external indications of either pons or
pyramids. On the ventral surface, however, there is usually
a faint indication of a mesal fissure (Plate V, Figs. 7, 13).

Proportions.—The metencephalon is usually from one-half
to three-fourths as deep as wide, and about as wide as long
(see Table V ).

Fourth ventricle.—As usual, the metencephalon contains

Turner, Morphology of the Avian Brain. 53

the fourth ventricle, which is entirely covered by the epen-
cephalon.

EXPLANATION OF TABLE V (SEE P. 86).

“Length” is a contraction for “Ratio of the length of the metence-
phaton to the length of the brain.”

‘‘ Breath” is a contraction for ‘‘ Ratio of the greatest breadth of the
metencephalon to the length of the brain.”

“Depth” is a contraction for “ Ratio of the greatest depth of the
metencephaton to the length of the brain.”

All ratios are expressed in hundredths of the length of the brain.

The length of the brain is the distance between the cephalic extrem-
ity of the prosencephalon and the center of the rhombic depression
which lies immediately caudad to the twelfth nerve root.

Pineal body.—This is always present (Plate V, Figs. 5,
6,8, 10). It is a small sub-conical body, which lies in the
caudal V of the prosencephalon. The apex of this cone
points ventrad. From it the habenula passes ventrad, around
the cephalic portion of the epencephalon, to the habena.
The pineal gland is intimately connected with the dura and
is liable to be removed with it. |

Infundibulum (Plate V, Figs. 9, 13).—On the ventral
surface of the brain, between the diencephalon and _ the
metencephalon, lies the tuber cinerium, which is pierced by
the infundibulum.

Pituitary body.—Immediately ventrad to the infundibu-
lum, lies the pituitary body. It is encased in a special cavity
of the skull.

NERVES.

The external course of the nerves has been so well de-
scribed by Prof. Elliott Coues(’') that it is not necessary for

1 The cranial nerves are twelve pairs, as in mammals, the highest vertebrate number.

1. The olfactory, nerve of special sense (smell); origin from rhinencephalon; exit
from cranial cavity by olfactory foramen, high up in the orbital cavity; conducted along
a groove to find escape between the perpendicular and lateral plates of the ethmoid ito
the nasal chambers; distributed to the investing mucous membrane of the septal and
turbinal bones of the nose. The exit is through a sieve-like or cribzform plate only in
Afpteryx and Dinornis (Owen).

2. The offic, nerve of special sense (sight); origin from optic lobe and thalamus(?);
of great size and forming a chzasm (decussation) with its fellow; exit by optic foramen, a
large hole in the back of the orbital cavity between the centers of orbito-sphenoid and

54 JOURNAL OF COMPARATIVE NEUROLOGY.

me to do more than mention the position of the external
roots.

first, or olfactory nerve. — This nerve arises from the
cephalic extremity of the rhinencephalon.

Second, or optic nerve (Plate V, Figs. 4, 7, 9, 13).—The
optic-fibres arise from the cephalic end of the optic lobe and
pass, in a large bundle, to the chiasm. Here they decussate
with corresponding fibres of the opposite side, and, after

ali-sphenoid, close to, or in common with, its fellow. This nerve forms the retina of
the eye.,

3, 4,6. The oculi-motor, pathetic, abducent, collectively the motor nerves of the eye,
supplying the muscles moving the eyeball; 3, to all these muscles, excepting the superior
oblique and the external rectus; wrigin from crura cerebri, base of mesencephalon; 4, to
the superior oblique; origin behind the optic lobes, upper surface of metencephalon; 6, to
the external rectus (also to the muscle of the third eyelid in birds); 3, 4, 6, exit from the
cranial cavity into the orbital cavity by several small, not constant, foramina near the
optic foramen; or by this foramen sometimes all of the nerves which enter the orbit pass
out of the brain cavity through one greal hole.

5. Great ¢v¢facial or trigeminal, sensori-motor; feeling, skin of head, moving muscles
of jaws; origin (double) from mylencephalon, leaves brain from sides of metencepi alon;
sensory root has gasserian ganglion, motor root simple. This root has three divisions,
whence its name: 5 @, ophthalmic division, the most distinct; exit from cranial into the
orbital cavity above and to the outer side of the optic foramen; grooves orbital wall in
passing; c7l7ary ganglion; distribution mainly to Jachrymal and nasal parts; traceable to
end of upper mandible; 5 4, superior maxillary; exit by foramen ovale, in ali-sphenoid or
between that and the prootic centre; distribution to side of upper jaw; »ecklian ganglion;
5 ¢, inferior maxillary, derived chiefly from motor root; exit same as 5 J; distribution to
lower jaw (muscles, substance of bone, integument); no sfecéal sense (gustatory function);
no offic ganglion.

7. Facial or portio dura, motor. origin from mylencephalon; enters periotic bone,
escapes from ear behind quadrate bone, by what corresponds to stylo-mastoid foramen of
mammals; communicates with 5c by chordo tympanic nerve, with 9, 10, r2 and sympa-
thetic system; distribution to skin muscles and others of lower jaw and tongue, etc.

8. Auditory or portio mollis, nerve of special seuse (hearing); origin with 7; no exit
from skull; enters meatus auditorious internus of periotic bone; forms auditory apparatus
in labyrinth of ear. .

9. Glosso-pharyngeal, mixed nerve, sensori motor and gustatory (taste): origin mylen-
cephalon; exit by foramen in exoccipital bone. behind basi-temporal, near lower border
of tympanic recess; distribution to muscles and membranes of gullet, throat, tongue, etc.

10. Pueumogastric, sensori-motor; origin and exit next to 9; distribution to wind-pipe,
lungs, gullet, stomach, heart, etc;. has recurrent laryngeal to vocal organs,

11, The sfival accessory, sensori-motor; origin upper part of spinal cord; exit 9, 10;
distribution to these nerves and to muscles of the neck.

9, 10, I1 are intimately connected with one another, and with other nerves, espe-
pecially 10 with the sympathetic. The several foramina in a bird’s skull, which may be
seen in the place indicated at 8 (Figs. 60, 70), are for the divisions of this composite vagus
or ““wandering’’ nerve of respiration, circulation, digestion, etc.; they represent morpho-
logically a foramen lacerum postertus between exoccipitals and opisthotic centres.

12. Hyfoglossal, motor nerve of the tongue; origin from mylencephalon; exit by
anterior condyloid foramen in front of occipital condyle.

Thus the plan of the cranial nerves of birds is nearly coincident with that of mam-
mals,—ProFr. Etiiory Cougs, op. cit., pp. 176-7.

TurNnER, Morphology of the Avian Brain. 55
emerging, become the optic nerve. This is a very large
nerve.

Third, or oculo-motor (Plate V, Figs. 9, 13).—This is a
small nerve. It arises from the diencephalon near to and
laterad to the infundibulum and immediately cephalad to
the metencephalon.

Fourth, or pathetic (Plate V, Figs. 9, 13).—This is a
small nerve. At a short betes caudad of the cephalic
extremity of the metencephalon, the fourth nerve emerges
from between the mesencephalon and the metencephalon.

Fifth, or trigeminal (Plate V, Figs. 4, 7, 9, 13).—This
is a large nerve. It arises from the side of the metenceph-
alon, about half way between its dorsal and ventral surfaces
and a short distance caudad to the optic lobes.

Sixth, or abducens (Plate V, Figs. 7, 9, 13).—At a short
distance caudad to the trigeminal nerve and about half way
between the meson and the lateral border, the small sixth
nerve leaves the metencephalon.

Seventh and eighth, or facial and auditory (Plate V,
Figs. 9, 13).—A short distance caudad to the trigeminal
nerve and near the dorsal surface of the metencephalon,
there is a large nerve root. This is the common root of the
seventh and eighth nerves.

Ninth and tenth, or glossopharyngeal and pneumogastric
(Plate V, Figs. 1, 4, 9, 13).—Caudad and slightly ventrad
to the seventh and eighth nerve root, the medium-sized root
of the ninth and tenth nerves arises from the metencephalon.

Eleventh, or spinal accessory (Plate V, Fig. 4).— The
eleventh nerve arises, as a number of small strands, from the
lateral surface of the metencephalon. Cephalad, this nerve
unites with the common root of the ninth and tenth nerves;
caudad, it. passes beyond the root of the first cervical nerve.

Twelfth, or hypoglossal—This is a small nerve, which
arises from the metencephalon at about the same distance
from the meson as the sixth nerve and immediately cephalad

to the caudal extremity of the metencephalon,

56 JOURNAL OF COMPARATIVE NEUROLOGY.

II. RELATION OF BRAIN MEASUREMENTS TO
TAXONOMY.

Remembering that, owing to its position, the brain would
be very little influenced by external agencies, it is thought
that the comparative development of the brain should form
an important element in the classification of birds. With
this idea in mind, Table VI. has been compiled. This table
has been arranged, not to give a final classification for Amer-
ican birds, but to illustrate the taxonomic value of the avian

brain.

EXPLANATION OF TABLE VI (SEE P. 88).

The column headed ‘‘ Pros.” contains a classification based upon
the relative development of the different parts of the avian brain.

The column headed ‘“‘ HuxLEy ” contains Prof. Thomas Huxley’s
classification. His classification is based upon osteological character-
istics. (7)

The column headed ‘ PARKER” contains Prof. W. K. Parker’s
modification of Prof. Huxley’s classification. (?)

In all cases, excepting that of the Lar/de and Colymbide, the tabu-
lation is based upon original observation. My notes upon these two
groups are based upon a study of sketches by Briinnlich(3) and by
Gmelin.(+)

Taking it for granted that a well-developed prosenceph-
alon indicates a high degree of specialization, the majority
of the distinctions are based upon the development of that
portion of the brain. To say that the olfactory lobes are
covered is equivalent to saying that the prosencephalon is
flexed. To say that the optic lobes are covered is equivalent
to saying that the longftudinal axis of the prosencephalon is

quite long.

r ‘On the Classification of Birds; and on the Taxonomic Value of the Modifications
of Certain of the Cranial Bones.”” By Thomas Huxley, F.R.S., V.P.Z.S. Proc. of the
Zool. Soc., 1867, pp. 415-472.

» Encyclopaedia Britannica, ninth edition, Vol. ILI, p. 605.

3 United States Geological Survey, J. W. Powell, Director: third annual repart,
1881-82). p. 56, Fig. 8.
4 Ditto, p. 70, Fig. 20.

TurNER, Morphology of the Avian Brain. 57

After examining a large number of bird brains, it was
decided to divide the carinate birds into two major groups.
In the first group, which has been called ‘‘ A,” the greatest
width of the prosencepalon is more than go per cent. of the
length of the brain. In the second group, which has been
called ‘‘ B,” the greatest width of the prosencephalon is less
than 90 per cent. of the length of the brain. The waders
and fowls and their affines are placed in group ‘‘ A.” The
remainder of the carinate birds fall in group ‘‘ B.”

From the first appearance of the class Aves until now,
there has been a gradual retrograde evolution of the avian
rhinencephalon. In the lowest types, the rhinencephalon is
terminal and is composed of two distinct lobes; in the
highest types, the rhinencephalon is not only not terminal,
but it is covered by the prosencephalon and partly imbedded
in it. In these types, the two lobes of the primitive rhinen-
cephalon have fused to form a small single lobe.

In the light of these facts, group ‘‘ A” has been sub-
divided into two minor groups, ‘‘a” and ‘‘b.” In those
brains that fall into group ‘‘a,” the partly imbedded rhinen-
cephalon is entirely covered by the prosencephalon and is -
composed of a single lobe. In those brains that fall into
group ‘‘ b,” the partly imbedded rhinencephalon is covered,
but it is composed of two lobes.

Upon the same principle, group ‘‘B” has been sub-
divided into two minor groups, ‘‘c” and ‘‘d.” In those
brains that fall into group ‘‘c,” the rhinencephalon is com-
posed of two lobes and is sub-terminal. In those brains that
fall into group ‘‘ b,” the rhinencephalon is composed of two
lobes and is terminal.

These minor groups have been redivided into two groups.
In this case the position of the optic lobes has been the
criterion. Division ‘‘I” includes those birds in which the
optic lobes are entirely covered by the prosencephalon;
division ‘‘ II” contains those in which the optic lobes are

only partially covered.

a) JOURNAL OF COMPARATIVE NEUROLOGY.

wi

As in all natural schemes of classification, these minor
groups overlap each other. To determine the position of
doubtful cases, other characteristics have been tabulated.

To determine the position of a family within the smallest
subdivision, the relative size of the prosencephalon has been
considered a convenient criterion.

A series of either gravimetric, volumetric or linear measure-
ments would have furnished the desired data. Not being able
to use all three, it was necessary to decide which of these three
would best serve our purpose. Both volumetric and gravi-
metric measurements possess some advantages, but the errors
introduced by attempting to separate the various parts of a
small brain are so great that all the advantages of the meas- .
urements are negatived.(’)

There is also an objection to linear measurements. Dur-
ing the process of hardening some brains are slightly flat-
tened. In one brain this flattening will lengthen one
diameter, while in another brain it may shorten it. It is
evident then that ratios based upon any one diameter of the
prosencephalon would not serve our purpose. It is also cer-
tain that any pressure which causes an increase or decrease
in the length of one diameter will also cause a compensating
decrease or in increase in some other diameter. Hence,
if the ratios of the relative lengths of three diameters at
right angles to each can be conveniently combined, there will
result a ratio which will be practically free from errors
of manipulation. There are several means by which this
combination could be effected. I have used what I consider
the most convenient combination. I have multiplied the
respective ratios of the length, breadth and depth of the pro-
sencephalon to the length of the brain together and extracted
the cube root of the product. The resultant ratio represents

1 After attempting to tabulate the relative weights of the olfactory lobes of various
birds, A. Bumm remarks: ‘t Abgesehen davon, dass die Abtrennung der Riechhécker
uom iibrigen Grosshirn bei den kleinen Vogel nur schwierig and unsicher gelingt, war
auch die von mir benutze Wage fiir die hier in Betracht kommenden minimalen Gewichts-
differenzen nicht empfindlich genug.”’ Op. cit. p. 436,

TurRNER, Morphology of the Avian Brain. 59

approximately the ratio of the cube root of the volumn
of the prosencephalon to the length of the brain. This
ratio is tabulated in Table II, Column *\/(L x B x D).
In practice this ratio has proved very convenient. With one
exception (Ardeide) the members of the same family differ
from each other by less than three per cent.

Upon consulting Table VI, it will be seen that the group-
ing of the families examined agrees very well with the classi-
fication proposed by Prof. Huxley in 1867. Prof. Huxley’s
classification was based upon osteological characteristics.
The fact that this agreement exists is to my mind an excel-

lent testimonial of the taxonomic value of the avian brain.

EXPLANATION OF TABLE VII (SEE PAGE 90).

This table has been constructed to illustrate the value of the
3\/(L & B x D)as acriterion for determining the rank of a family within
a group. The passerine group has been chosen because it has been more
thoroughly studied than any other group.

In the column headed ‘‘ Coues”’ is tabulated the order found in
Coues’ Key to North American Birds.

In the column headed ‘ A. O. U.” is tabulated the order found in
the A. O. U. Check List of North American Birds.

In the column headed ‘‘ Shufeldt” is tabulated the order found in °
North American Passeres, by R. W. Shufeldt, M.P., C.M.Z.S.

In the column headed *\/(L >< B x D) is tabulated the order sug-
gested by the *\/(L x B x D).

It may not be out of place to say a word or two in defense
of the arrangement suggested by the \/(L >< BD).

The Corvide are placed at the top of the list. This
agrees with the arrangement proposed by R. W. Shufeldt.
In defending his position, Mr. Shufeldt remarks: ‘* Corvus
corax has a skeleton of the highest type of oscine organiza-
tion, a statement that applies with equal force to much else
in the economy; its brain is relatively larger in proportion to
the size of the bird than others of the same order; its young
substantially have the plumage of the parents at a time when,
as nestlings, they first take on their plumage; finally the

raven is a far more intelligent bird than any species of Sialia

60 JOURNAL OF COMPARATIVE NEUROLOGY.

that the author has ever made psychological study of, and,
indeed, than any other thrush. The power of song is by no
means an index ofa high order of intelligence, much less an
indication of a highly specialized organization.” (')
DAV Die position of the Paride and Sylvicolide agrees with
the arrangement in Coues’ Key and differs but little from the
arrangement in the A. O. U. Check List. After placing the
Paride below the Tanagride, Shufeldt remarks: ‘‘ Indeed,
were it not totally out of question to introduce a family in
among the first five I have placed in the list, the Paride
might hold a much mere exalted rank, for in my opinion ¢he
group of Tits and their immediate affines are birds of mark-
edly high organization. = ¢ = They possess un-
usually large brains for their size and there is just a possi-
bility that they are connected with the Corvide through such
species as Perisoreus; they show wonderful ingenuity in the
construction of their nests, and the plumage of the young is
almost identical with that of the parents, and finally, some
of their kin (as Chamza) have absolute scutellate podo-
thece.”(?) Since the Paride are birds of ‘ markedly high
organization’ and since ‘‘ there is just a possibility that they

5)

are connected with the Corvide,” why not place them next
to the Corvide? Judging by the type and relative size of
the prosencephalon, that is where the group belongs.

In giving the Fringillide and Icteride a high rank this
arrangement agrees with that of Shufeldt.

Placing the Hirundinide adjacent to the Tanagride
agrees with Coues’ Key and the A. O. U. Check List. Shu-
feldt places the swallows much lower in the scale, but

admits that their exact affinities are not known.(*)

t North American Passeres, by R. W. Shufeldt, M.P., C.M.Z.S., Journal of Mor-
phology, vol. iii, pp. 107, 108.

2 Op. cit .p. 108.

3 “‘ For a long time I was at a loss to know where to place the swallows (Hirundinidz)
and they have been crowded near the foot of the list, not that they have not a few points

in their economy indicative of a certain degree of rather high specialization; still,
although truly passerine birds, they are birds of comparatively small brains and th eir

TuRNER, Morphology of the Avian Brain. 61

It will be noticed that the Turdide have been placed
lower in the scale than either the Tanagride, the Fringillide,
or the Icteride. R. W. Shufeldt places the Turdide in about
the same position. In defending his position, Mr. Shufeldt
remarks, that the reduction of ten primaries to nine is an
index of great specialization; he then adds: ‘‘ The Tanagers
show this feature; and it is a good one to hold them in
the place which I have assigned them; moreover, it gives
them precedence over the more lowly organized Turdide,

which in realty should long ago have been recognized.”(')

RECAPITULATION.

1. The avian prosencephalon is large, but is not convoluted.

2. The avian epencephalon is well developed and trans-
versely convoluted.

3. From the introduction of the class Aves until now,
there has been a gradual retrograde evolution of the avian
rhinencephalon. In the lowest type of birds, the rhinenceph-
phalon is double and projects beyond the cephalic extremity
of the prosencephalon; in the highest type the rhinenceph-
alon -is single and does not project beyond the cephalic
extremity of the prosencephalon.

4. In the lower types of avian brains the optic lobes are
only partially covered by the prosencephalon; in the higher
types the optic lobes are entirely covered.

5. During both the evolution of the class Aves and the
differentiation of the families within it, the dorsal and lateral
portions of the avian prosencephalon have grown caudad
much more rapidly than the ventral and mesal portions.
This has caused the caudal portion of each cerebral hemis-

young differ in their plumage from the parents, and while we do not yet know the exact
affinities of the Hirundinide, all the speculations in that quarter have been in the direc-
tion of associating them with groups of recognized low type of organization.”’ Op.cit.,p.110.

Although the brain of the Hirundinide may be relatively small, yet it is as highly
developed as the brain of either the Tanagridz or Icteride. C. H. T.

r Op. cit., p. 10g.

62 JouRNAL oF COMPARATIVE NEUROLOGY.

phere to revolve towards the meson and at the same time to
gradually. cover the optic lobes.

6. The avian brain has a taxonomic value of great impor-
tance. So far, at least, as major groups are concerned, a
‘classification based upon it alone agrees in all essentials with
those that are based upon a careful study of all the structural

elements.

III—HISTOLOGY OF THE CEREBRUM.

Rhinencephalon (Plate VII, Figs. 6, 8, 10.) — Passing
entad we meet in succession the following zones:

1. A superficial fibre zone, from the cephalic portion
of which projects the olfactory nerve.

2. A gelatinous zone, in which the olfactory fibres appear
to become knotted. In about the middle of this zone there
is a narrow ring of small dense clusters of Deiter’s corpuscles.

3. A clear zone containing a few scattered Deiter’s cor-
puscles. Near the ental portion of this zone, there is a ring
of nerve cells. My sections do not enable me to describe
with certainty the structure of these cells. They appear to
be of two sorts, fusiform or flask-shaped and rhinomorphic.(')
The fusiform cells, although smaller, resemble the fusiform
cells of the prosencephalon. The rhinomorphic cells appear
to be small modified pyramidal cells. The fusiform or flask-
shaped cells are the prevailing type (Plate VII, Fig.9). In
most of my sections I have not seen any rhinomorphic cells.
When they were present, they appeared to be scattered
among the other cells.

4. A dense zone of Deiter’s corpuscles.

5. A row of epithelium cells lining the ventricle. Where
there is no olfactory ventricle this zone is necessarily absent.

Ventricle (Plate VII, Fig. 5.)—In all the bird brains

examined, a narrow projection of the lateral ventricle extends

1 A, Bum thinks that all of the nerve cells in the olfactory lobes are pyramidal.
Op. cit., p. 450.

Turner, Morphology of the Avian Brain. 63

towards the rhinencephalon. When there is only one olfac-
tory lobe this projection terminates in the olfactory crus.
When two olfactory lobes are present, an extension of this
projection enters each olfactory lobe and expanding, forms

the olfactory ventricle.
PROSENCEPHALON.

Ventricle (Plate V, Figs. 2,3,6,7; Plate VI, Figs. 3-5, 8, 10;
Plate VII, Figs. 1-5, 7).—For convenience the ventricle may
be divided into the following parts:

1. A narrow cavity, which is approximately parallel to
the meson.

2. A lateral expansion of this cavity. This expansion
curves over the dorsal portion of the axial lobe.

3. A common expansion of both of the above cavities.
This expansion curves around the caudad portion of the axial
lobe, and then turning, passes cephalad as far as the
crura cerebri.

Thus a large portion of the caudad part of the axial lobe
of each hemisphere is surrounded on all sides, excepting the
cephalic and lateral, by the ventricle; while a small portion
of the dorsal part of the axial lobe of each hemisphere is sur-
rounded on all sides, excepting the ventral, by the ventricle.

The first part of this ventricle is, approximately, a triangle,
with its base near the dorsal surface and its apex near the
ventral surface of the prosencephalon. This cavity lies near
the meson, but is not parallel to it. Near the dorsal surface
of the prosencephalon it is diverted laterad by a local thick-
ening of the cephalad portion of the mesal wall o¢
the ventricle. At the same level, but near the caudad
extremity of the prosencephalon, a local swelling of the
dorsal portion of the mesal wall of the ventricle causes
a laterad displacement of the ventricle. Slightly caudad
to this place a small convex portion of the axial lobe pro-
jects into the ventricle. The two above-mentioned swellings

of the mesal wall of the ventricle are connected by a narrow

64 JOURNAL OF COMPARATIVE NEUROLOGY.

neck. Ventrad to this neck another local swelling of the
wall of the ventricle diverts the ventricle from the meson.
Ventrad to this level the displaced ventricle does not return
to its former proximity to the meson.
. The second division of the ventricle is parallel to the
dorsal surface of that hemisphere in which it is found.
Divistons.—For convenience the prosencephalon has been
divided into three regions: the basal region, the mantle and
the axial region. The basal region is that portion of the
base of the prosencephalon which lies between the caudad
extremity of the ventro-lateral tuber and the olfactory crura.
It is histologically distinct from the remainder of the brain.
In it nerve cells are either entirely absent or else represented
by what Professor Herrick has termed rhinomorphic cells.
The outer portion of the remainder of each hemisphere is
called the mantle, while the inner portion is called the axial
region. Along the mesal, dorsal and caudal portions of the
hemisphere the mantle is separated from the axial region by
the lateral ventricle. Elsewhere these two regions of the
brain are distinguished by histological characteristics.

THE MANTLE.

In the mantle the nerve cells are not distributed promis-
cuously, but they are aggregated in distinct and constant
localities. The brains of several different groups of birds
have been examined, and in all cases the above statement
has proved correct. More than that; in the prosencephalon of
different birds, corresponding areas are supplied with similar
cells. In the reptilian brain, according to Prof. C. L. Her-
rick, this is also true. In his paper on the cerebrum of the
Lizard('), Prof. Herrick has called each of these cell clusters
a nidulus and that portion of the hemisphere in which the
cluster is found, a lobe. He has named each nidulus, and to
each lobe he has given the name of the contained nidulus.

t See ‘‘ Topography and Histology of the Brains of Certain Reptiles,” by Prof. C. L.
Herrick, Supra p. 14.

Turner, Morphology of the Avian Brain. 65

Omitting the lenticular nidulus and lobe, I have found in the
bird brain homologues of all the mantle niduli and lobes
described in Prof. Herrick’s paper.

Divisions.—For convenience the mantle has been divided
into two divisions, a mesal and a lateral division. The mesal
division is that portion of the mantle which lies mesad of
the lateral ventricle. The remainder of the mantle consti-
tutes the lateral division. Each division contains three lobes.
In describing these lobes, I shall begin at the cephalic extrem-
ity of the mesal division and pass caudad through the mesal
to the lateral division. Then I shall turn and pass cephalad
through the lateral division to the starting point.

Fronto-median Lobe.—This lobe constitutes the cephalad
portion of the mesal division of the mantle. It is the devel-
opment of this lobe that causes the cephalad portion of the
ventricle to be diverted from the meson. (Plate VI, Figs.
3,5; F.M.L.) The ental boundary of this lobe is formed
by the lateral ventricle; the mesal boundary is formed by the
fissura longitudinalis; the dorsal portion of the cephalad
boundary is formed by the frontal lobe, while the ventral
portion of the same boundary is at the cephalad extremity of
the prosencephalon. Near the dorsal surface of the hemis-
phere a projection of the frontal lobe is wedged in between
the fronto-median lobe and the meson.

Form and Size.—This lobe is about twice as long as its —
greatest width and both horizontal and transverse sections of
it are sub-triangular in outline. Dorsad and cephalad the
lobe is quite wide, but while passing entad it becomes very
narrow.

Near the dorsal surface of the brain the narrow caudad
portion of the fronto-median lobe fuses with the narrow
cephalad portion of the occipital lobe. Thus we have a nar-
row neck connecting two larger areas. (Plate VI, Fig. 3.)
Ventrad to this neck the fronto-median lobe is connected by
a narrow strip of brain substance to the intra-ventricular
lobe.

66 JoURNAL oF CoMPARATIVE NEUROLOGY.

Structure.—Passing laterad from the fissura longitudinalis
to the ventricle, the fronto-median lobe is composed of three
parts:

1. Bordering the meson, a narrow cell-less fibre layer.

2. A wider, inner portion containing nerve cells. This is
the fronto-median nidulus. This nidulus is composed of a
large number of irregularly arranged fusiform or flask cells,
among which are distributed numerous Deiter’s corpuscles.
These flask cells are about twenty-five micro-millimetres
wide. They stain faintly and have a clear, granular, sub-
spherical nucleus and a dense nucleolus. The nucleus is
quite large, being at least half as wide as the cell (Plate
WALT Niet) 2)e

3. Bordering the ventricle, a narrow gelatinous layer of
closely packed Deiter’s corpuscles.

Intra-ventricular Lobe (Plate V, Fig. 6; Plate VII,
Fig. 5).—This lobe occupies the middle portion of the
mesal division of the mantle. It constitutes that local swell-
ing of the mantle which lies ventrad to the fronto-median
and occipital lobes. Cephalad and dorsad this lobe is con-
nected by a narrow sheet of brain substance with the fronto-
median and occipital lobes. This connecting sheet does not
contain nerve cells, but it is moderately supplied with
Deiter’s corpuscles. The mesal boundary of this lobe is
formed by the fissura longitudinalis. The majority of the
ental boundary is formed by the lateral ventricle, the
remainder by the axial region of the hemisphere.

Transverse sections of this lobe are sub-triangular, while
horizontal sections may be either sub-triangular or diamond-
shaped. Cephalad and dorsad this lobe is quite narrow, but
while passing caudad and ventrad it gradually widens.

Structure.— Like the fronto-median, this lobe is com-
posed of three portions:

1. Bordering the meson, a dense layer of slender fusiform
cells. These cells are about three micro-millimetres wide

and from 13 to 16 micro-millimetres long. Although fusi-

Turner, Jlorphology of the Avian Brain. 67

form in shape, these cells stain densely and have a dense
nucleus. They lie in a fibre tract and have their major axes
parallel to the meson and to the base of the prosencephalon
(Plate VIII; Fig. 11):

2. A wider, inner portion, containing nerve cells. This
is the zztra-ventricular nidulus. It is composed of a large
number of irregularly arranged gibbous, fusiform or flask
cells, among which are distributed numerous Deiter’s cor-
puscles. These fusiform cells are about three micro-
millimetres wide and from g to 13 micro-millimetres long.
They stain faintly and have a large, clear, granular sub-
spherical nucleus and a dense nucleolus (Plate VIII, Fig. 11).

3. Extending along the ventricle, a narrow border of
slender densely stained fusiform cells. Histologically these
cells resemble the cells that extend along the meson. They
vary in length from 10 to 13 micro-millimetres. Like the
cells along the meson, their major axes are parallel to the
meson and to the base of the brain.

Occipital Lobe.—This lobe constitutes the caudad portion
of the mesal division of ‘the mantle: (Plate V1; Fig. 3;
Plate VII, Fig: 5; O. L). It is the development of this lobe
which causes the local swelling in the caudad portion of the
mesal wall of the ventricle. The mesal boundary of this
lobe is formed by the fissura longitudinalis, the lateral by the
ventricle, while the caudad is coincident with a portion of the
caudad surface of the hemisphere.

Horizontal sections of this lobe are crescent-shaped,
while transverse sections are sub-triangular. Dorsad this
lobe is quite wide, but while passing ventrad it gradually
becomes narrow.

Stracture.—This lobe also consists of three layers:

1. Along the mesal border there is a narrow cell-less
layer containing fibres.

2. An inner portion containing nerve cells. This is the
occipital nidulus. It consists of a large number of fusiform

or flask cells, among which are distributed numerous Deiter’s

68 JouRNAL oF COMPARATIVE NEUROLOGY.

corpuscles. These nerve cells are faintly stained and have a
large, clear, granular, sub-spherical nucleus and a dense
nucleolus. They are about seven micro-millimetres wide and
from 13 to 15 micro-millimetres long.

3. Extending along the ventricle, a narrow gelatinous
layer of Deiter’s corpuscles.

Parieto-occipital Lobe (Plate V1, Figs. 1, 5; P. O. L).—
This lobe constitutes the caudad portion of the lateral division
of the mantle. It forms the greater part of the caudad por-
tion of each hemisphere and extends from the occipital lobe
almost to the caudo-lateral border of the prosencephalon.
Entad this lobe is bounded by the basi-occipital lobe and the
corpus striatum, laterad it is bounded by the parieto-frontal
lobe, ectad it is superficial. In some types the lateral ven-
tricle penetrates this lobe. |

In the avian prosencephalon the parieto-occipital lobe is
much nearer the meson than is the corresponding lobe of the
reptilian brain.(') It is now almost universally admitted
that birds and reptiles have been evolved from the same
primitive group of vertebrates. If this be true, a mesal
revolution of the caudad portion of each hemisphere is the
only phenomenon that consistently accounts for the mesal
position of the parieto-occipital lobe in the avian brain.

Structure.—This lobe consists of the following parts:

1. A narrow outer cell-less layer of free cortex.

2. A wide, irregular, inner layer of nerve cells. This is
the parieto-occipital nidulus. It consists of a large number
of Deiter’s corpuscles and large pyramidal cells. These cells
vary in length from 22 to 26 micro-millimetres. Their sides
are either convex or straight. The apex of each cell is
extended into a long process, while the base is supplied with
several shorter processes. The apex process is often several
times as long as the cell. These cells stain densely and have

an elongated dense nucleus and denser nucleolus. Occasion-

1 See Prof. Herrick’s Paper on “ Topography and Histology of the Brains ef Cer-
tain Reptiles.’ Supra p. 14.

TuRNER, Morphology of the Avian Brain. 69

ally I have noticed cells with two well developed nuclei.
Sometimes the nucleus is sub-spherical (Plate VIII, Fig. r).

Masked convolution.—In the brain of Swainson’s thrush
(Hylocichla swainsont) I have noticed a masked convolution.
Near the mesal extremity of the parieto-occipital lobe and
about half way between the dorsal and ventral surface of the
prosencephalon a narrow projection of the parieto-occipital
lobe extends entad. Within the axial portion of the brain
this projection widens and form an ellipsoidal body. This
small ellipsoidal body is histologically distinct from the region
in which it is found, but it is histologically identical with the
parieto-occipital lobe. The region around it is composed of
fusiform nerve cells (Plate VIII, Fig. 12), while it is com-
posed of pyramidal cells (Plate VIII, Fig. 6).

Parteto-frontal Lobe (Plate VI, Fig. 1, P. F. L.).—This
lobe forms the middle portion of the lateral division of the
mantle and extends from the parieto-occipital lobe to the
fronto-median. It consists of two layers:

1. A narrow outer layer of free cortex.

2. A wider inner layer containing many Deiter’s corpuscles
and a few scattered nerve cells. This is the parieto-frontal |
nidulus. Near the cephalic portion of this lobe the cells are
more abundant than elsewhere. These cells are pyramidal
in outline and have either convex or straight sides. The
apex is extended into a long process, while the base is sup-
plied with several shorter processes. These cells stain
densely and have an elongated dense nucleus and denser
nucleolus.

Frontal Lobe.
the lateral division of the mantle. As has been mentioned

This lobe forms the cephalad portion of

above, a portion of it extends caudad between the cephalad
portion of the fronto-median lobe and the meson. Dorsad it
fuses with the parieto-frontal lobe and spreads over the
greater portion of the dorsal surface of the hemisphere.
Ventrad it is bounded by the fronto-median lobe (Plate VI,

Bags,, 1195.5).

70 JOURNAL OF COMPARATIVE NEUROLOGY.

Structure.—This lobe consists of the following parts:

1. A narrow outer layer of free cortex.

2. A broader inner collection of nerve cells, among
_which is scattered a large number of Deiter’s corpuscles.
This is the frontal nidulus. These cells are pyramidal in
outline and have convex or straight sides. They are from 12
to 16 micro-millimetres long and at the base are about six
micro-millimetres wide. The apex is extended into a long
process, while the base is supplied with several shorter
processes. These cells stain densely and have a dense
nucleus and a denser nucleolus. (Plate VIII, Fig. 4.)

AXIAL REGION.

The axial region is composed of two parts, the basi-
occipital lobe and the corpus striatum.

Basi-occipital Lobe-—As has been mentioned above, the
lateral division of each hemisphere is surrounded on the
ventral, mesal and dorsal sides by the lateral ventricle. In
the ventral part of this portion of the brain lies the
basi-occipital lobe: The caudad and part of the mesal boun-
dary of this lobe is formed by the parieto-occipital lobe.
The ental and dorsal boundaries are formed by the corpus
striatum.

Structure.—This lobe is composed of numerous Deiter’s
corpuscles, among which are distributed many fusiform
or flask cells. These cells are about six micro-millimetres
wide and from 12 to 16 micro-millimetres long. They stain
faintly and contain a large, clear, subspherical nucleus and a
dense nucleolus. In all probability these cells are undergo-
ing rapid transverse subdivision (Plate VIII, Fig. 12). In
the reptilian brain also, according to Prof. Herrick, the cells
of this lobe are undergoing rapid subdivision. In that case,

however, the subdivision is radial.(')

1 See ‘* Notes on the Brain of the Alligator,’’ by Prof. C. L. Herrick, Journal of
Cincinnati Society of Natural History, Vol. XII, Plate VII, Fig. 8.

TurNER, Morphology of the Avian Brain. 71

In the reptilian brain Professor Herrick has considered
this zone to be an area of great proliferation—an area in
which cortex cells are developed.(') In birds it may have
a similar function. .

Minor nidulus.— In the basi-occipital lobe, near the
meson, and about half way way between the dorsal and
ventral surfaces of the hemisphere, there is a small, dense,
ellipsoidal cluster of cells. I have called this cluster the
minor nidulus. From this nidulus, the major axis of which
is perpendicular to the major axis of the hemisphere, a tract
of fibres passes to the anterior commissure (Plate VI, Fig. 5).

Corpus striatum.—The remainder of the axial region of
the prosencephalon constitutes the corpus striatum. (*)

Histologically, the striatum is divided into two portions,
the striated portion and the caudate portion. In position,
these parts might be compared, respectively, to the lenticular
and caudate nucleus of the mammalian striatum. I am not
sure that these are true homologies, yet, as is stated below,
there are two fibre layers which might, perhaps, be consid-
ered homologues of the internal and external capsules.

Striated portion (Plate VI, Fig. 8).—This portion lies in
the ventral part of the prosencephalon and is adjacent to the
crura cerebri. Passing from the crura cerebri into the cere-
brum, we meet three divisions of the striated portion of the
striatum:

t. A narrow band of dense clusters of Deiter’s corpuscles.
This band is, approximately, perpendicular to the entering

1 ‘* The great bulk of the axial lobe—the portion which protrudes into the ventricle
—is filled with similar flask cells, but these are curiously clustered in groups of two or
multiples of two, The evidence that these cells are undergoing rapid increase by fission
in this young animal is very conclusive. All stages of the process may be observed. It
may be suggested that, if in the case of young animals this part of the brain is most
actively multiplying cells, it is possible that the growth of the mantle (in which there is
little material for rapid growth) may be in some way associated with this proliferation of
cells, resulting in the increase of the mantle from its margins, as though the material

were pushed up around the margin of the ventricle by a rapid growth within.” Op,
Cites eta s:
2 A. Bum regards the whole of the axial portion of the brain as the homologue. of

the corpus striatum. Op. cit., p. 455.

72 JouRNAL oF CoMPARATIVE NEUROLOGY.

peduncular tract, and extends caudo-laterad from a short
distance cephalo-mesad of the cephalo-lateral extremity of
the crura cerebri to about twice that distance caudo-laterad
of that place. In traversing this band, the peduncular fibres
pass between, not through, the dense clusters of Deiter’s
corpuscles (Plate VIII, Fig. 9).

2. A clear lenticular portion, which lies parallel to and
entad of number one. The nerve cells in this portion are
few and far between. They are of two sorts, flask-shape
and pyramidal (Plate VIII, Fig. 7). The cells of the first
type are large, gibbous, faintly stained, flask-shaped cells.
They have a large, clear, sub-spherical nucleus and a dense
nucleolus. The cells of the other type are elongated, densely
stained pyramidal cells. They have an elongated dense
nucleus and a denser nucleolus. In the meso-cephalad por-
tion of this nidulus the flask cells predominate, while in the
caudo-lateral portion the pyramidal predominate.

In traversing this portion, the peduncular fibres separate
into parallel bands of approximately the same size (Plate
WIL, Biggs),

3. A wide irregular portion, which consists chiefly of
Deiter’s corpuscles. Occasionally we find a fusiform cell,
and near the meso-cephalad extremity of part one there is
usually a cluster of small pyramidal cells.

After entering this part of the striatum, the peduncular
fibres radiate in all directions.

Caudate Portion.—This is the largest division of the
striatum.

Form.—Viewed from the side, the outline of this division
is composed of the following curves:

1. A convex curve, which forms the cephalad boundary.
This curve extends cephalo-ventrad from the dorsal extremity
of this division to the cephalo-ventral extremity of the same.

2. A convex curve, which extends ventro-caudad from
the ventral extremity of curve one to the caudo-ventral ex-
tremity of the lobe.

Turner, Morphology of the Avian Brain. 73
3. An undulating line, which passes, in general, dorso-
caudad from the dorsal extremity of curve two to the dorsal
extremity of this division.. The ventral half of this curve is
strongly concave, while the dorsal half is strongly convex.

Viewed from above, the outline of this division is com-
posed of the following curves:

rt. A convex curve, which extends cephalo-laterad from
the mesal extremity of this division to the cephalo-mesal
border of the same. This curve is formed by the ventricle.

2. An undulating line, which passes latero-cephalad from
the extremity of curve one to the latero-cephalad border of
this division. At its extremities this lobe is feebly convex,
in the middle it is feeble concave.

3. A convex curve, parallel to the lateral surface of the
hemisphere, which extends from the extremity of curve two
to the caudo-lateral margin of this division.

4. An undulating line, which extends, approximately,
mesad from this place to the beginning of curve one. The
lateral one-tenth of this curve is slightly concave, the suc-
ceeding four-tenths is moderately convex, the next four-
tenths is strongly concave, and the remaining one-tenth is
almost straight.

Cell structure.—Histologically, this division of the stria-
tum differs from all other parts of the brain. Some of the
cells are fusiform, while others are sub-pyramidal; but the
greater number are swollen and distorted and contain several
nuclei (Plate VIII, Fig. 10). The numerous small cells,
resembliug Deiter’s corpuscles, that are present in this part
of the striatum are of the same size as the nuclei of the large
cells. No other portion of the prosencephalon is so well
supplied with blood-vessels. This suggests that this is an
area of great activity. Evidently it has a special work to
perform. Professor Herrick suggests that it may be an area
where germinative corpuscles are produced.

The corpuscles of this region resemble Deiter’s corpuscles
in so many respects that one is tempted to believe that they

74 JOURNAL OF CoMPARATIVE NEUROLOGY.

are identical. Both the white and the red corpuscles of the
blood have special localities in which they are elaborated.
Why may not Deiter’s corpuscles have a special locality in
which they are developed and trom which they migrate in all
’ directions? The numerous Deiter’s corpuscles that are found
in the vicinity lead one to suppose that the caudate portion
of the striatum is such a locality.

Prof. His has shown that the original nerve cells develop
from small corpuscles, the neuroblasts.(') Why may not all
nerve cells be formed in the same way? Why may not these
so-called germinative corpuscles of the etriatum be the neuro-
blasts of future nerve cells?

Whatever the function of these corpuscles, the evidence
that they are produced in the caudate portion of the striatum
is most conclusive. Anywhere within this part of the brain
the one-fourth inch objective will reveal the whole process.
Within its field of view may be observed cells of all sizes
and ages. There is the normal cell with one nucleus and
one nucleolus. Of the same size as this cell, but a little
older, is the cell with one nucleus and two nucleoli. Then
come cells of two, three and more nuclei. The size of the
cells seems to endeavor to keep pace with the number of
nuclei. This is not fully accomplished, but cells that con-
tain eight or nine nuclei are two or three times the size of
the original cells. Such a cell may be regarded an aged one.
Its period of activity has passed. It becomes decrepit.
Little by little it fades away, until eight or nine clustered
nuclei are the only remains of its former greatness. These
nuclei are not inactive. Soon they migrate to other parts of
the brain, bearing within their walls the substance of the
mother cell (Plate VIII, Fig. 10).

Internal Capsule.—Between the striated and caudate por-
tions of the striatum there is a sheet of fibres that may be

considered as the homologue of the internal capsule.

rt Archiv fur Physiologie und Anatomie, 18go.

TurNER, Morphology of the Avian Brain. is

External Capsule. —Near the cephalic boudary of the
caudate portion of the striatum there is another sheet of
fibres. This may be regarded as the homologue of the
external capsule.

Anterior Commissure.—Immediately cephalad to the
diencephalon and near the base of the prosencephalon the
anterior commissure connects the two hemispheres of the
avian brain (Plate VII, Fig. 3; Plate VI).

After leaving the crura the majority of the fibres of this
commissure pass caudad and slightly dorsad into the basi-
occipital lobe. ‘These fibres keep near to the mesal surface
of the hemisphere. In addition to these a few fibres appear
to pass directly laterad. I have looked in vain for fibres
passing from this commissure to the olfactory lobes.

Corpus Callosum (Plate V1, Fig.2; Plate VII, Figs. 3, 7;
C. C.).—This commissure lies caudad and dorsad to the
anterior commissure. It is much smaller than the latter.
Between the ventricle and the meson the fibres of the
corpus callosum radiate towards the dorsal surface of the
brain.(')

Peduncular Tracts—These tracts enter the prosence-_
phalon by the crura cerebri. At the crura they are perpen-
dicular to the longitudinal axis of the hemisphere. <A few
of these fibres pass cephalo-dorsad to the caudate portion ot
the striatum. These fibres pass mesad of the striated portion
of the striatum, the remainder pass through it. As men-
tioned above, at this place the striatum is composed of
several layers. Passing entad we meet in succession: (1) A
layer containing dense clusters of Deiter’s corpuscles; (2) A
clear lenticular portion which contains two kinds of nerve
cells; (3) A large area which is composed chiefly of Deiter’s
corpuscles. In each of these portions the course of the
peduncular tracts is different. In the first the fibres pass

1 Most writers have said that birds do not have a corpus callosum, but A. Bumm,
the most recent European student of the avian prosencephalon, affirms its existence in
European birds. Op. cit., p. 462.

76 JouRNAL OF COMPARATIVE NEUROLOGY.

between the clusters of Deiter’s corpuscles; in the second
they separate into uniform parallel bundles; in the third
they radiate in all directions.

Tania Thalami.—Near the meson and dorsad to the
-peduncular tract, these fibres enter the prosencephalon. Im-
mediately they turn dorsad, and,if I have traced them cor-
rectly, after passing dorsad for a short distance they turn
laterad. After traversing about half the width of the hemis-
phere the tract again turns dorsad. Always keeping near the
caudad extremity of the hemisphere, it continues dorsad and
disappears near the dorsal surface of the brain.

Tractus Bummi (Plate VI, Figs. 7-9).—This tract orig-
inates in either the frontal or fronto-median lobe and passes
caudo-ventrad through the intra-ventricular lobe. After
passing beneath the anterior commissure it turns and passes
ventro-latero-caudad to the crura cerebri. Penetrating the
dorsal part of the crura it passes to the outer fibre layer
of the tectum opticum. This tract does not decussate. It
connects the mesal wall of the ventricle of one side of
the brain to the optic lobe of the same side. To the best of
my knowledge, A. Bumm(') is the only one who heretofore
has accurately described this tract. He called it, ‘‘ Mark-
biindle der strahligen Scheidewand.” This name being too
formidable for English readers, I have ventured to name this
tract, after its discoverer, 7ractus Bummt.

RECAPITULATION.

1. In addition to and distinct from the anterior commis-
sure, there is a corpus callosum.

2. There is a fibre tract connecting the mesal division of
the mantle with the optic lobe of the same side.

3. In different avian prosencephala corresponding areas
are supplied with similar cells.

4. In the mantle and axial region of the procephalon
there are two types of cells, fusiform and pyramidal.

1 Op, cit., p. 451.

Turner, Morphology of the Avian Brain. 74

Cells of the first type are fusiform, or flask-shaped. They
stain faintly, and contain a large, clear, granular, sub-spheri-
cal nucleus and a dense nucleolus.

The cells of the second type are pyramidal in form. They
have straight or concave outlines and a broad base. The
apex of the cell is extended into a long process, while the
base is supplied with several shorter processes. These cells
stain densely and have an elongated dense nucleus and a
denser nucleolus.

5. The mesal division of the mantle contains fusiform
cells only.

6. The lateral division of the mantle contains pyramidal
cells only.

7. The corpus striatum contains both fusiform and pyra-
midal cells.

8. There is a portion of the avian striatum in which
small cells, resembling Deiter’s corpuscles, are developed.

g. In the brain there may be an entad projection of grey

matter, without any external indication of a convolution.

NEUROLOGY.

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go JOURNAL OF COMPARATIVE NEUROLOGY.
TABLE VII.
COUuES. b oe s eee) 5 (LX aa D)
Turdide. Turdide. gee | Corvide (92)
Paride. Sylviide. Icteride. | Paride (84)

Sylvicolide.

Tanagride.

Hirundinide.

Vireonide.
Fringillide.
Icteride.

Corvide.

| Paride.

Vireonide.

| Hirundinide.

Tanagride.

| Fringillide.

| Icteride.

Corvide.

Fringillide.
Tanagride.
Paride.
Turdide.
Sylvitde.
Vireonide.

Hlirundinide.

| Sylvicolide (83)

Fringillide (78-82) |
Icteride (75-78)
Vireonide (79)
Tanagride (78)
Hirundinide (78)

Turdide (73-75)

Tyrannide. Tyrannide. Tyrannide. Tyrannide (65-68)
PLATE, V:
Fig. 1. Brain of Bubo virginianus. Lateral view. D.F., dorsal

fissure; /.AZ., ventro-frontal tuber.

WS em well el ee

Stalia stalis.

Fig. 4. Brain of Botaurus mugitans.

Transverse sections of the prosencephalon of

C.P., proliferating area of the corpus striatum; /.).L.,
intra-ventricular lobe; O.Z., occipital lobe; //., rhinencephalon.

numerals indicate the cranial nerve roots.

Fig. 5.
fissure.
Fig. 6.

Brain of domestic goose.

Brain of Butorides virescens.

sal fissure; /., flocculus; Of/., optic lobes.

Fig. 7.

Brain of Ageleus pheniceus.

Lateral view.

Dorsal view.

Dorsal view.

Ventral view.

The Roman
D.F., dorsal
D.F., dor-

D.F., dor-

sal fissure; 7., a diamond-shaped depression which marks the caudad
extremity of the brain.

Fig. 8.
sal fissure.
fig. 9.

Brain of Coccygus americanus.

Brain of Bofaurus mugitans.

numerals indicate the cranial nerve roots.

Fig. 10.

Brain of Colaptes auratus.

fissure; Py., prosencephalon.

Fig. 13.

Brain of Colaptes auratus.
numerals indicate the position of the cranial nerve roots.

Dorsal view.

Ventral view.

Dorsal view.

Ventral view.

D.F., dor-
The Roman

D.F., dorsal

The Roman
Fl., flocculus;

TurRNER, Morphology of the Avian Brain. gl

Mt., metencephalon; O.7'., optic tract; #/., rhinencephalon; V.F.7.,
ventro-frontal tuber; V’.7.7., ventro-lateral tuber; V’.4/./., ventro-
median fissure; ]’.47.7., ventro-median tuber.

All surface views are drawn to the same scale.

‘ AACE Vel:

Hts MAGN s GS, LO: borizontal longitudinal sections of the brain
of Hylocichla swatnsont, beginning near the dorsal surface. A.C.,
anterior commissure; C./., proliferating area of the corpus striatum;
F.L., frontal lobe; /.17.Z., fronto-median lobe; O.Z., occipital lobe;
P.F.L., parieto-frontal lobe; ?d., peduncular tracts; P.O.L., parieto-
occipital lobe; 7.B., tractus Bummi.

Fig. 2. Transverse section of a portion of the prosencephalon of
Stalia sialis, showing the corpus callosum and the anterior commissure,
A.C., anterior commissure; C.C., corpus callosum.

Fig. 6. Wongitudinal-perpendicular section of the brain of Szadia
sialis, Taken through the crura cerebri. C./., proliferating area of
the corpus striatum.

Figs. 7,9. WHorizontal longitudinal sections of a portion of the
prosencephalon of Harporhinchus rufus, for comparison with Figs. 5, 8.
10. ¢.#&., tractus Bummi.

[EAL WAN bles WANE

Figs. 1,2, 4. WUongitudinal perpendicular sections of the brain of
Sialia sialis. C.P., proliferating area of the corpus striatum; £7/.,
epencephalon; /.cf., internal capsule; J7.1’., ventricle of the optic lobe;
T. Th., tenia thalami.

Fig. 3. Mesal section of the brain of Meleagris gallipavo, A.C.,
anterior commissure; C.C., corpus callosum; O,ch., optic chiasm; Pzx.,
pineal body; //., rhinencephalon; .S.C., superior commissure.

Figs. 5,7. WHorizontal longitudinal sections of the brain of AZelea-
gris gallipavo to the same scale as Fig. 3. A.C., anterior commisure;
C.C., corpus callosum; O.Z., occipital lobe.

Fig. 6. Transverse section of the rhinencephalon of the goose; a.
outer layer of olfactory fibres; 4., gelatinous layer; c., dense clusters of
Deiter’s corpuscles in the gelatinous layer; d., clear granular layer; e.,
specific olfactory cells; 7., dense cluster of Deiter’s corpuscles; ¢., epi-
thelium of the ventricle.

Fig. 8. Transverse section through the middle of the rhinenceph-
alon of Passer domestica. a., outer layer of olfactory fibres; 6., gela-
tinous layer; d., clear granular layer; ¢., specific olfactory cells; /.,
dense cluster of Deiter’s corpuscles.

Fig. 9. Nerve cells from the rhinencephalon of //ylocichla swain-
SOnt.

Fig. 10. Transverse section through the rhinencephalon of //y/o-
cichla swainsoni. Nomenclature the same as in Fig. 8.

92 JOURNAL OF CoMPARATIVE NEUROLOGY.

PLATE VIII.

Fig. 1. Portion of the parieto-occipital lobe of Wylocichla swain-

SON. :
Fig. 2. Portion of the fronto-median lobe of Hy/ocichla swainson?,
Fig. 3. Portion of the occipital lobe of Hylocichla swainsont.
Fig. 4. Portion of the frontal lobe of /ylocichla swainsoni?.
Fig. 5. Portion of the striated portion of the corpus striatum of

Hylocichla swainsoni, showing parallel bands of peduncular fibres.

Fig. 6. Highly magnified pyramidal cells from the parieto-occipital
nidulus of Hylocichla swainsoni.

Fig. 7. Highly magnified cells from the corpus striatum of //ylo-
cichla swainsont.

Fig. 8. Highly magnified fusiform or flask cells from the fronto-
median lobe of Hylocichla swainsont.

Fig. 9. Portion of the striated portion of the corpus striatum of
Hylocichla swainsont showing peduncular fibres passing around a
cluster of Deiter’s corpuscles.

Fig. 10. A highly magnified section of the proliferating portion of
the corpus striatum. /, original cell, with one nucleus and one
nucleolus; 2, cell with one nucleus and two nucleoli; 3-8, cells with two
to eight nuclei; 9, cluster of nuclei that have lost the original common
cell wall.

Fig. 11. Portion of intra-ventricular lobe of Hylocichla swainsoni.

Fig. 12. Portion of basi-occipital lobe of Mylocichla swainsont.

Fig. 13. Magnified portion of the corpus callosum of Hylocichla
SWAINSONT.

Figs. 1-4 and 10-12 are drawn to the same scale.

Figs. 6-8 are drawn to a common scale.

The outlines of all drawings of sections were made with the camera.

EDITORIAL.
THE PROBLEMS OF COMPARATIVE NEUROLOGY.

It is natural for workers in every department of science
to feel that their own chosen field of investigation is that
which opens the most direct avenue to the Arcana of nature.
It is well, therefore, to reflect at times upon the necessary
limitations of each sphere, as well as the connections be-
tween allied departments. The brief review here following
is intended to illustrate a few recent tendencies rather than
to summarize the results in all directions. Such reviews
will be offered from time to time in the hope of affording a
perspective of the field represented by this periodical. The -
nervous system, in a sense, occupies a unique position among
the organs of the body, in that it is at once the medium of
communication between all organs and the ‘‘ governor”
which adjusts the function of each several organ to every
other function. Just what part the nervous system plays in
creating the organs cannot be decided at present, but the
phenomena of metamorphosis and of trophic action indicate
that the initiative in many cases proceeds from the nervous
system. The broad generalization of modern biology that
the function precedes, and, in a sense, creates its organ,
when applied to the problem of animal morphology leads to
the belief that in tracing the evolution of the nervous system
we are to a very considerable extent determining the pro-
gressive revelation of that which differentiates the animal
from the inanimate residuum.

O4 JoURNAL OF COMPARATIVE NEUROLOGY.

The problems of neurology resolve themselves into the
purely structural investigation, which appeals to microscope
and microtome, and physiological questions involving a
knowledge of the behavior of the living cell under the most
diverse conditions, as well as of the laws of composition of
function due to their interaction. Yet a higher class of
problems, which properly transcend the sphere of neurology,
as of all purely observational science, respecting the relation
of body and mind, can never be wholly ignored.

In the study of all these questions the methods and results
of morphology must always guide the investigator, though
it is not less true that the solution of many of the vexed
riddles of morphology depends upon the recognition and
employment of neurological laws and generalizations. That
part of the field which is being cultivated with the most
zeal and success is the structural province. Yet in this
most promising department the accumulation of details has .
too often proven unfruitful for the lack of a sufficiently com-
prehensive view of the entire field to enable the investigator
to appreciate the bearings of isolated facts.

The objection once urged against the employment of
comparative data in the determination of the functions of the
human organs, 7.e., that there can be no proof of homology
between the brain of man and that of lower animals has been
removed by the researches of Keen, Lloyd, Nancrede and
Horsley, which prove the substantial similarity in function
of the various cortical areas in man and the higher apes.

The brilliant success which even now attends operations
for the removal of localized cerebral disturbances based on
the data derived from experiments upon lower animals is
practical demonstration of the utility of the science, but in
the light of what has been done the future is palpitant with
suggestion.

During the last few years the more general homologies
have been established within the group of vertebrates, and

such papers as that of Alborn on Petromyzon have laid the

EpirortaL, Problems of Comparative Neurology. 95

foundation for the analytic study of the brain from the com-
parative standpoint.

It has so often happened that just the clue necessary for
the explanation of a complicated nervous structure has been
found in the simpler homologue in a lower type, that it
seems strange that the comparative method has been so fre-
quently neglected, and especially that embryology has been
so little employed in the investigation of the more compli-
cated organs. Nevertheless, since the publication of the
exhaustive work by Mihalkovics on the ‘‘ Development of
the Vertebrate Brain,” a great deal has been contributed to
our knowledge of the archetectonic of the nervous system by
embryology.

To a very large extent, effort has been concentrated of
late upon histological investigation, and, as usual, the pri-
mary impetus has been given by improvements in technique
which make accessible to any one structures which from
their delicacy and minuteness had hitherto been regarded as
beyond the reach of observation. These refinements in
technique have also had the effect of undermining several of
the most substantial generalizations of an earlier decade.

The methods which have excited most interest, and from
which much is expected, if not already obtained, are the
various forms of metallic impregnation introduced by Golgi,
elaborated by Cajal and adopted by Kolliker. While all of
these methods are more or less fickle and open to the objec-
tion that they emphasize one element in the structure with-
out affecting the others, and do not with certainty differen-
tiate nervous from non-nervous structures, yet in careful
hands the results can but prove very suggestive. The
following brief summary may serve at once to show what
has been done and to indicate the paths by which greater
attainment may be reached.

It is to-day an unquestioned dictum of biology that func-
tion and structure are intimately connected, and that differ-

ence in function implies difference in structure. Yet in the

96 JOURNAL OF COMPARATIVE NEUROLOGY.

case of the spinal cord it is impossible to assert that such a
relation has been demonstrated. For example, we know that
certain parts of the cord are the peculiar seat of sensory
activity, while others form centers for motor reactions, yet it
would be very difficult to point out exact anatomical distinc-
tions characteristic of these two areas. The following isa
condensed resumé of Golgi’s results:(')

1. All ganglion cells of the spinal cord (those of the dor-
sal cornu and Clarke’s column not excepted) are provided
with a special process connecting with a nerve and differing
in physico-chemical peculiarities from all other processes.
This process alone is a safe criterion for identifying a cell as
nervous. Upon this basis alone I identified numerous
ganglion cells in the substantia genlatinosa of Rolando. All
the cells of the spinal cord are, therefore, from the stand-
point of their specific function unipolar, the single process
referred to being the zervous process.

2. The so-called protoplasmic processes of the cells are
neither directly nor indirectly the source of nerve fibres, but
they are closely associated with connective tissue cells and
blood-vessels. They apparently constitute the avenues by
which nourishment reaches these cells from blood-vessels
and connective elements.

3. A comparison of the cells from various parts of the
grey matter of the spinal cord reveals certain differences in
the form, size, and ramifications of the protoplasmic process,
yet the only important distinctions are such as relate to the
nervous processes. .

4. Upon this basis two sorts of cells may be recognized
‘in the spinal cord, thus: (@) ganglion cells, in each of which
the nervous process divides into minute fibrils, so that it
loses its individuality in the formation of a diffuse nervous
reticulum; (4) ganglion cells which give rise to an axis

cylinder, though there may be small lateral processes.

1 GoLci, Ueber den feineren Bau des Riickenmarks; Anat. Anz., No. 15, 18go.

-

EpiroriaL, Predlems of Comparative Neurology. 97

The cells of the first class predominate in the dorsal
cornu, especially in the substantia gelatinosa of Rolando
and may be regarded as sensory, while the second class pre-
dominates in the ventral root zones.

5. In the gray substance there is a diffuse nervous reti-
culum, which is also continued into the medulla and higher
regions. This reticulum in the spinal cord consists of the
following elements: (a) fibres partly from the reticulum of
the gelatinous substance and partly from the dorsal cornu
proper; (6) nerve fibres from the dorsad roots, which sub-
divide in the same complicated manner as described for the
processes of the nerve cells; (c) fibrille from the processes
just named, which retain their identity; (d) fibrille which
arise from the axis cylinders of the various columns and pass
transversely into the gray matter and there subdivide as in
the other cases.

6. In order to establish the functions of cells or cell-
clusters from the evidence of anatomy, one must chiefly rely
upon the course and relations of the nervous processes.

7. In the gray substance of the spinal cord it is impossible
to give an accurate topographical description of the groups .
of ganglion cells, because their distribution varies exceed-
ingly in the smallest areas; neither would such a grouping be
serviceable, for it does not appear that cells of the same
group necessarily have the same function. It, in fact,
frequently happens that adjacent cells send their nervous
processes in opposite directions.

The following cells belong to the first class (those in
which the nervous process terminates in a reticulum): (a)
cells of the substantia gelatinosa of Rolando; (6) cells of
the dorsal cornu proper; (c) sporadic cells in the zone
between the dorsal and ventral and even within the latter.

To the second class (those with axis cylinder processes )
belong the following: (a) the larger part of the cells of the
ventral cornua; (4) a few cells pertaining to the dorsal;

98 JOURNAL OF COMPARATIVE NEUROLOGY.

(c) sporadic cells, especially in proximity to the lateral
columns.

The ganglion cells of the anterior cornua usually send
their processes directly or indirectly either to the ventral
roots or a medullary column; a considerable number, how-
ever, may be followed through the ventral commissure to the
columns of white matter of the opposite side. I have also
observed cases where the cells of the ventral cornu of one
side send processes through the ventral commissure to the

fibres of the ventral columns of the other side. The above
course is pursued by most of the fibres from a group of cells
laterad to the canalis centralis, though some of the fibres pass
to the lateral columns of the opposite side.

Those cells which occupy that part of the gray matter
adjacent to the lateral column send their process, for the
most part, to that column, but a part of the fibres pass
to the other side.

In seeking examples of undoubted motor cells, only such
as show an evident direct connection with a ventral root
could be safely chosen. In these cases a remarkable peculi-
arity consists in the fact that their fibres, generally before
entering the nerve root, give off a certain number of exceed-
ingly delicate fibrils, which curve toward the ventral part of
the gray substance and fuse with the complicated nervous
reticulum existing there. ‘‘The motor cells then stand
in immediate but not isolated connection with a nerve fibre.”

The dorsal nerve roots consist solely of fibres whose axis
cylinders enter the gray substance and there subdivide and
assist in forming a diffuse reticulum.

[It should be stated that Lenhossék has showed, July,
1890, that fibres arising from cells in the lateral part of the
ventral cornu pass through the dorsal roots and through the
spinal ganglion without entering into connection with cells of
this ganglion.(')—C. L. H.]|

1 Anatomischer Anzeiger, 1890, Nos. 13 and 14,

EpiroriaL, Problems of Comparative Neurology. 99

In summing up his results, Golgi emphasises the view
that the nerve fibres within the central organ are not isolated,
but give evidence of being related to a number of cells.
This conception excludes that of sharply limited and localized
areas governing a given function.

An important theoretical conclusion which apparently
does not grow out of the discussion, Golgi expresses as
follows: ‘‘ Inasmuch as I am convinced that what we con-
ventionally term soul is merely the interplay of the correlated
activities of the various parts of the central nervous system,
an activity which becomes more complicated (more genuinely
psychical) the more highly differentiated and complex the
component parts become, it not only seems to me that this
distinctinction (between psycho-motor and psycho-sensory
centres) is superfluous, but I incline to the assumption that
no essential difference exists between the individual activities
of the various cell-clusters in separate provinces.’’(')

In the sphere of experimental physiology interest still
centres largely in the localization of functions in sharply
limited areas of the cortex. Against the precise and positive
statements of Munk innumerable objections, mostly of a
negative character, have been raised. The portion of Munk’s
results which has been most severely handled is his claim
that it is possible to establish the existence of sharply defined
cortical areas in the occipital lobe of one side corresponding
to diagonally opposite areas of the retina of the opposite eye.
A very direct and complete apparent substantiation of this
view is afforded by the investigations of Obregia(*) who,
under the guidance of Munk, conducted a series of experi?
ments upon the motions of the eye in response to irritation of
various parts of the visual sphere. Obregia carried on all of

these experiments without the aid of anesthetics, under the

t For list of Golgi’s papers see end of his summary in Anatomischer Anzeiger,
No. 15, 1891. \

2 A, Oprecia, Ueber Augenbewegungen auf Sehsphzren-Reizung, Archiy. f. Anat.
und Phys., Jahrgang 1890; Phys. Abth,, p. 260,

100 JouRNAL OF COMPARATIVE NEUROLOGY.

belief that consciousness is a necessary condition to such re-
actions. Inasmuch as these motions are called out by irrita-
tions of various spots within the visual (sensory) area having
no direct relation to the eye-muscle centre ‘‘ F,” as deter-
mined by Fritsch and Hitzig, and since the resulting motions
are correlated just as they would be if the animal were con-
sciously fixing the gaze upon a special point, and, finally,
because these phenomena can only be prevented by division
of the fibres of the corona radiata, Obregia concludes that
such irritation actually produces optic sensations.

It is generally admitted that an irritation of a spot upon
the retina produces in consciousness the image of an external
luminous point in the diagonally opposite part of the field of
vision. The experiments show that irritation of the
posterior part of the visual area produces an upward
motion of the eye-ball, an irritation of the anterior part,
a motion in the downward direction, or, in other words, just
the same motion as would be called out by the irritation of
the lower or upper retinal areas respectively. The irritation
of the centre of most distinct vision produces simply the
appearance of attentive gazing with slight motion.

Without following these experiments in full, it may be
said that, if proven accurate, they seem to verify the most
detailed ascertions of Munk and prove a direct connection
between the sensory and motor areas.

There can be no doubt that the theoretical problem of
morphology, which has excited most interest of late and
which seems to have the strongest hold on the imagination of
investigators generally, is the question as to the origin of the
head and its various correlated structures. One reason for
this prolonged and persistent effort to solve a problem which
is essentially simply a theoretical one lies in the fact, that the
formation of the head is the culmination of the whole series
of progressive changes which constitutes organic evolution.
Whatever view may be taken of ‘‘cephalization” in its
technical form, all must agree that the tendency of eyolution

EpiToriaL, Problems of Comparative Neurology. tor

has been to subordinate more and more structures and func-
tions to the purposes of the head. Moreover, it has been
more or less distinctly seen that the solution of the anatomi-
cal and then the physiological problems connected with the
head is essential to the completion of any systematic theory
respecting the connection between body and mind. It has
been felt that if the head, with its structures so obviously
intended to serve as an avenue of expression for the mind,
can be explained as a compound of the somewhat modified
simple elements occurring in each segment of the body of a
lower animal, then the mind itself might prove but the sum
of all the functions represented by these several organs,
though rendered never so ‘‘ psychical,” by reason of their
complex interaction. Probably few biologists would care to
commit themselves to so extreme a view as this, yet the great
problem remains: what is the relation between the functions
of the nervous elements and the phenomena of mind as such,
or, in other words, just what has the nervous system, and
especially the brain, to do with thought. The analysis of
the head may of course be pursued from different stand-
points. When it was seen that many of the structures of the
head, such as the upper and lower jaws and the hyoid appa-
ratus were modified visceral arches, it was but natural that
the attempt should be made to apply the same analysis to the
skull itself. The failure of the now celebrated vertebral
theory of the skull by no means discouraged investigators
from the attempt to discover the law of combination in
accordance with which the region has differentiated.

The facts that much of the head lies beyond the end of the
chorda, and that the nerves of special sense seem to conform
to a different plan of structure and obey a peculiar law of
development, have led to the separation of a primitive
anterior part of the head and brain and a _ secondarily
acquired posterior portion. The original metamerism of the
head may fail to exhibit itself in the skull, partly because so

many extraneous elements have been from time to time amal-

102 JOURNAL OF COMPARATIVE NEUROLOGY.

gamated with the original cartilaginous cranium. The brain
may perhaps be depended on to reveal the true history of the
head. Balfour suggested that the fore-brain is the unseg-
mented primordial encephalon of the invertebrate progenitor
of higher animals. LKoelliker supposes that this unsegmented
portion is an outgrowth from the anterior part of the brain
proper, but the hypothesis which just now enjoys most
general acceptance is that of Kleinenberg and Dohrn, which
regards the fore-brain as the fused ganglia of a number of
primitive segments. The ingeneous theory of Gaskell will
be elsewhere alluded to.

The solution of this problem of the metamerism of the
head which is most simple is that of Rabl,(') who believes
that morphologically and physiogenetically there are but two
divisions in the head of vertebrates; an anterior, larger, and
unsegmented portion, and a smaller, segmented posterior
portion. The boundary between these portions is the audi- .
tory vesicle, which, nevertheless, belongs to the anterior
_ part. Although the mesoderm of the anterior portion may
be separated into several aggregates, they have no corre-
spondence, whether in the method of origin or relation to
the cranial nerves, with the true somatomeres.

The anterior division has the following nerve pairs, the
olfactory, optic, trigeminus, and acustico-facialis, the third,
fourth and sixth being derivatives of the trigeminal system.
The primary nerves of the posterior division are the glosso-
pharyngeal and vagus dorsad and the hypoglossus ventrad.
The accessory is considered a portion of the vagus. Rabl
is much influenced by the fact that the trigeminus and
facialis-acusticus do not spring from a continuous nervous
ridge like the glosso-pharyngeal and sensory nerves gener-
ally, but distinct from it and distinct from each other.

Anton Dohrn(*) calls attention to the fact, long before

1 C. Rasi, Morph. Jahrbuch. xv, 2 Heft,

2 Anatomischer Anzeiger, 1890, p. 56.

EpiroriAL, Problems of Comparative Neurology. 103

indicated by Spencer and Marshall, and His, that, in Selachii
at least, the dorsal nerve roots grow from the spinal ganglion
into the medullary tube, and that this process does not take
place till the peripheral growth of the nerve has been con-
siderably extended. In the cranial nerves motor fibres do
pass from the region of the lateral columns into the ganglion
ridge at a period earlier than that of the central growth of
the sensory fibres. These motor fibres find their way to the
muscles of the visceral arches. These fibres are always on
the inner side of the ganglion.

The ganglionic ridge originates from an outgrowth of the
dorsal part of the medullary tube where the closure is effected.
That portion of the ganglionic ridge which is not trans-
formed into actual ganglia is destroyed. Dohrn suggests
that the ridge is simply a primitive condition of the ganglia
and that they are only apparently nonsegmented at the begin-
ning, but wherever, as in the neck, they are not too much
crowded the ganglia are obviously distinct, though connected,
from the first.

In the attempt to separate the trigeminus and facialis
acusticus from the vagus and glossopharyngeal, Rabl dis-
tinctly terms the hypoglossus the ventral root of the neuro-
mere, of which the vagus is the dorsal root. Dohrn, how-
ever, quotes the observations of Balfour, Wijhe, Froriep and
Ostraumoff, as well as his own, in support of the view that
the hypoglossus contains all that remains of several spinal
nerves. The discovery of two or three ganglia in early
embryos of selachians attached to fibres of the hypoglossal
and the rapid disappearance of these ganglia without the
formation of sensory fibres may be regarded as strong evi-
dence of the development of the motor roots of XII from
the vagus neuromere. The trigeminus, facialis, glosso-
pharyngeal.and vagus all contribute to the formation of
organs of the lateral line, while no spinal nerves sustain any
such relation.

That no motor fibres enter any of the spinal ganglia, as

104 JOURNAL OF COMPARATIVE NEUROLOGY.

stated by Dohrn, seems to the writer doubtful. The other
statement, that the entrance of the sensory roots of the
vagus and glossopharyngeus into the medulla results in a de-
cided segmentation of the latter, seems to have much evi-
dence behind it, and though the acceptance of this evidence
will perhaps make it necessary to regard the vagus as poly-
merous, yet the same reasons enforce the homology between
the vagus, facial and trigeminal and the true spinal nerves.

The difficulties in the way of a satisfactory solution of
the nerves of the eye-muscles increase with research. The
fact that they primarily have root ganglia and the pres-
ence of a chiasm in the fourth prevent the acceptance
of Rabl’s theory of derivationfrom the trigeminus. The
organs of sense cannot be divorced from the nervous
system, and not the least important step in the solu-
tion of the problem of cephalic metamerism will be
the determination of the locus and nature of the organs of
special sense. An excellent general review of this field
is given by Professor C. A. Whitman.(') The comparison
of the segmental sensory organs of annelids with the organs
of special sense generally, is certainly suggestive. And
while it seems to the writer that there can be no doubt that
the pineal body has functioned as an eye in many cases,
it does not appear that its unpaired character need at all
militate against the theory that the vertebrate eye is an
excessively modified descendent of a non-specialized sensory
organ, like the segmental sensory organs of Vermes. That
the paired visual organs are older, phylogenetically speaking,
than those of either of the other special senses seems probable.
May it not prove that the paired eyes were developed before
the primitive nerve plate became a tube and that when the
invagination of the neural epithelium did occur the germina-

tive retinal cells were included in the involution, and that the

1 Biological Lectures delivered at the Marine Biological Laboratory of Woods’ Holl,
1890, p. 27.

EpiroriAL, Zechnigue and Memoranda. 105

pineal eye was developed to function during the period of
metamorphosis, during which the organ adapted itself to the
new conditions?

This theory may serve to explain the different course of
histogenesis pursued by the eye as compared with the other
organs of special sense.

TECHNIQUE AND MEMORANDA.

Metuyt BLuE NERVE STAINING INTRA-vITAM.— The
various methods of injecting staining reagents into the
circulation depending on _ incipient degeneration of
the tissues or the access of air to precipitate or differentiate
the colors, have thus far promised more than they have ful-
filled. The most promising of these, the methyl-blue stain,
has received a searching analysis at the hands of Dr. B.
Feist. (') The process as introduced by Ehrlich, consists
simply in injecting into the nervous system (cutaneous vein
or lymph hearts in the frog) a concentrated solution in nor-
mal salt fluid. The difficulties chiefly grow out of the ten-
dency of the color to fade rapidly after development, but
these may be avoided by fixation in Hoyer’s picrocarmine.
When used quite dilute and for not too long a time the blue
color is scarcely altered by its use while a longer action alters
the color to Burgundy red, or rusty red, while the nuclei of
adjacent cells are faintly tinted with rose. The exact reac-
tion which takes place in the nerve, after vital impregnation
with methyl blue and exposure to the air, is a matter of de-
bate. Aronson says, that during life nerves are so well supplied
with oxygen that the methyl blue absorbed by them cannot
be reduced. After the death of the animal nearly all the
colored portions, as well as the nerves, are rendered color-
less, because the affinity of the protoplasm for oxygen in-
creases to such an extent that the oxygen is abstracted and

rt Arch. f. Anat. u. Phys. 1890. Phys. Abth. p, 116.

106 JoURNAL OF COMPARATIVE NEUROLOGY.

the methyl compound is reduced to leucomethyl blue, which
is colorless. Nevertheless as soon as these tissues are ex-
posed to air in thin layers, the oxidation is repeated and the
color reappears.

Feist considers it improbable that oxidation alone is suffi-
cient to explain the change, and cites many careful experi-
ments to prove that the phenomena are connected with
decomposition.

For sections, fixation of the stained tissue with platinic
chloride proved useful, though the color became granular
after such treatment. For nerves, treatment with Hoyer’s
picrocarmine for fifteen minutes, and then with osmic acid
for a similar time, was sufficient to prepare them for imbed-
ding in gum arabic and glycerine. ‘Three or four days may
be necessary before the mass becomes of a suitable consis-
tency to cut when enclosed in pith. This method has many
difficulties growing out of the brief period during which the~
preparation is in condition to section. The color, if fixed by
osmic acid, is not permanent.

For the interesting results of the application of this
method, as well as a comprehensive review of the literature
of nerve histology, the original paper should be consulted.
The following papers will also be found useful;

O. Schultz. Die vitale Methylenblu reaction der Zell-
granula. Anatom. Anzeiger, 1887, No. 22.

P. Ehrlich. Ueber die Methylenblaureaction der le-
bender Nervensubstanz. Deutsch Med. Wochenschrift.
1886, No. 4.

C. Arnstein. Die Methylblaufaerbung als _histolog-
ische Methode, Anat. Anz. 1887, No. 17.

HT. Kuehn. Notiz u. vitale Reaction der Zellgranula
nuch subcutaner Methylblauinjection. Arch. f. Anat. u.
Phys. 1890.

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MORPHOLOGY- OF THE AVIAN: BRAIN.
( Continued. )
Ca Fi. furNEr:

Additional Remarks upon the Corpus Callosum.— Since
the publication of the first paper of this series, my attention
has been called to Professor Osborn’s paper upon ‘‘ The
Origin of the Corpus Callosum, a Contribution upon the
Cerebral Commissures of the Vertebrates.” (') In that paper
the author makes the following instructive remarks:

‘“‘If the brain of a duck (Azas boschas) be carefully
removed from the skull and the membranes uniting the
hemispheres cut, these bodies may be gently separated until
the anterior commissure comes into view; immediately above
and behind this is a fine white strand of fibres, quite as
figured by Meckel (1516), and so distinct that one cannot
understand how it was overlooked by Stieda. This little
bundle, which represents the rudimentary corpus callosum,
forms a portion of the lamina terminalis, and is about one-
sixth the diameter of the anterior commissure. It les some
distance below the foramen of Monro, and in vertical as
well as transverse sections its fibres are seen to pass directly
upwards in the thin inner wall of the lateral ventricle. So
far as could be ascertained, none of its fibres pass back into
the hippocampal region, as the commissure of the cornu
ammonis.”

t Morphologischer Jahrbiicher, Bd. xii, pp. 223-251, 530-543.

a

108 JOURNAL OF COMPARATIVE NEUROLOGY.

It affords me pleasure to state that my observations upon
this commissure substantiate and extend those of Meckel
and Professor Osborn. My sections show a corpus callosum,
_ not only in the brains of the lower type of birds, but also in
the encephala of the highly-specialized Passerine group.
Therefore, I think we may safely emphasize the statement
that all birds have a corpus callosum.(')

Errata.—Before proceeding, I would like to correct a
couple of misprints that crept, unobserved, into the first
paper of this series. The first occurs on page 57, seventh to
ninth lines. Those lines should read: ‘‘ The waders and
fowls and their affines are placed in group ‘B. The re-
mainder of the carinate birds fall in group ‘A.’” The
second error occurs on page 91. The last statement in the
explanation of Figure 3 of Plate VII should read: “5. C.,
posterior commissure.”

Technigue.—Additional remarks upon the methods em-
ployed may seem superfluous. It must be remembered,
however, that different tissues require different treatment.
In the prosencephalon, where tracts are few and quite dis-
tinct, a stain that differentiates cells well, even though it
does not dye the fibres, is all-sufficient. In the diencephalon
and mesencephalon, however, where fibre tracts are numer-
ous and somewhat intermingled, it becomes imperative to
use a stain that differentiates fibres. While looking about for
a good fibre stain, Kolliker’s article, ‘‘Zur feineren Anatomie
des central Nervensystem,”(*) was referred to. The plates
illustrating that article are excellent. In them the finest
nerve fibres are depicted. The sections from which these
remarkable plates were drawn had been prepared by
Golgi’s shorter method,(*) and I determined to test the
application of the method to avian brains. The brain of a

pigeon (Columba livia) was selected for the experiment.

1 JouRNAL OF ComMPpARATIVE NeEuROLOGY, Vol. I, p. 76.
2 Zeit. f. wiss. Zool., Bd. LI, taf. i-vi.
3 Op. cit., Bd. UL, po.

TurnER, Morphology of the Avian Brain. 109

The encephalon was removed and the lateral half of one
optic lobe and all of the prosencephalon and epencephalon
dissected away. What remained was immersed for one
hour in a 2 per cent. aqueous solution of potassium bichro-
mate. It was then placed in a 3 per cent. solution of the
same substance. After remaining in this fluid for twenty-
three hours, the specimen was transferred to a mixture of
three parts of a 3 per cent. aqueous solution of potassium
bichromate and one part of a 1 per cent. aqueous solution of
osmic acid. After remaining in this medium for twenty-five
hours, the specimen was washed in a.75 per cent. aqueous
solution of silver nitrate, and then immersed in a 1 per cent.
solution of the same salt. There, protected from the light,
it remained eight days. The brain was then transferred to
50 per cent. alcohol, after which it was hardened and sec-
tioned in the usual manner. Although every precaution was
taken to insure success, yet the desired result was not pro-
duced; it was impossible for me to decide what had been
impregnated, for evidently much was stained that was not
nervous, and it was equally evident that not all nerve tracts
had been acted upon by the reagent. While still seeking a
good fibre stain, I tried overstaining with Professor Her-
rick’s modification of Grenacher’s hematoxylon.(') The
result was quite satisfactory. The fibers were well differ-
entiated, and the nerve cells, although stained quite densely,
were not destroyed.

IV.—HISTOLOGY OF THE DIENCEPHALON AND
MESENCEPHALON.

Third ventricle (Plate VII, Figs. 3, 7; Plate XIV, Figs.
ints, Plate XV, Figs, 45 15, 6,7, 9).— In" birds, the dien-
cephalon is small but compact. The third ventricle is the
only cavity within it, and is very narrow. This ventricle

t This consists of Grenacher’s hematoxylin to which has been added a trace of
corrosive sublimate. This stain cannot be used for staining zz fofo.

I1O JOURNAL OF COMPARATIVE NEUROLOGY.

consists of a narrow triangular slit extending along the
meson. ‘The apex of this triangle terminates, upon the base
of the brain, in the infundibulum. Caudad, this ventricle is
connected with the aqueduct of Sylvius, while cephalad it
is connected, through the foramen of Monro, with the lateral
ventricles. It may be noted that the narrowness of the third
ventricle in the avian diencephalon corresponds to the
appearance of that cavity in the human brain, where, accord-
ing to Ranney,(') the third ventricle is ‘‘a narrow chink
between the optic thalami.” j

NIDULI OF THE DIENCEPHALON.

Corpus geniculatum externum (Plate XV, Figs. 5, 7,9,
10, 11).—Upon passing from the avian prosencephalon into
the diencephalon, one of the first niduli encountered is the
corpus:geniculatum externum. This is a large sub-ellipsoidal
cell cluster, which is situated in the cephalo-laterad portion
of the dorsal region of the diencephalon. Although located
at some distance from the meson, yet this nidulus does not
lie adjacent to the lateral surface of the thalamus; indeed,
between it and the surface there is a large fibre tract. I have
already stated that this nidulus is sub-ellipsoidal. The major
axis of this sub-ellipsoid is oblique to the longitudinal axis
of the brain. The size of the corpus geniculatum externum
varies in different bird brains. In the brain of Swainson’s
thrush (//ylocichla swainsonz) the major axis is about 1,250
micro-millimetres and the horizontal about 938 micro-milli-
metres long.

ffistology.—The structure of this nidulus is unique. For
the most part, the cells are arranged in irregular concentric
lamine. It looks very much as though, originally, the cells
had been arranged in concentric spheres, and that, by rapid
growth, these spheres had become contorted.

The cells of this nidulus are fusiform (Plate XVI, Fig. 5).

1 ‘‘ The Applied Anatomy of the Nervous System,” by Ambrose L. Ranney. Second
edition, p. 312.

TurRNER, Worphology of the Avian Brain. III

In hematoxylin and in aluminium-sulphate cochineal prepa-
rations, each cell has a faintly stained spherical nucleus and
a densely stained nucleolus. In different avian brains the
dimensions of these cells vary. In the thrushes ( //y/ocichla
swainsont, Turdus migratorius, Sialia sialis) these are
from twenty-one to twenty-four micro-millimetres long and
from seven to nine micro-millimetres broad. In addition to
these large cells, the nidulus is well supplied with Deiter’s
corpuscles.

Bellonci has called this body the corpus geniculatum.(')
Since in the human brain we find two geniculate bodies,
it is but just that some reason should be given for consider-
ing this nidulus the homologue of the corpus geniculatum
externum. Ranney(*) describes the geniculate bodies of the
human brain as follows:

‘In the external geniculate body the gray matter is
arranged in lamine, which present, in cross sections made
through its substance, a zigzag outline, as if the laminz had
been crushed or folded together. The cells of this nidulus
are large, granular and pigmented.

‘The zxternal geniculate body is less intimately con-
nected with the optic lobes and the fibres of the optic tract,
as proved by the latest researches of Flechsig, Gudden and
Ganzer. J/ts gray matter ts not arranged in the manner
peculiar to its companion, although it is apparently traversed
by the optic tract connected with both the nates and testes
eerebri.,’

Therefore, since the above described contorted stratifica-
tion is peculiar to the corpus geniculatum externum, and since
the nidulus under consideration possesses that structure, the
evidence that that nidulus is the homologue of the mamma-
lian corpus geniculatum externum seems conclusive.

A large number of nerve fibres pass around the corpus

t ‘* Ueber die centrale Endigung des nervus Opticus bei den Vertebraten.’”’ Von
Professor Josef Bellonciin Bologna. Zeit. f. wiss. Zool., Bd. XLVII, s. 16, Fig. iii, cgt.
2 Op. Cit., pe 214.

112 JoURNAL OF COMPARATIVE NEUROLOGY.

geniculatum externus; a few arise from it, and others termi-
nate in its substance. These fasciculi will be described in
connection with the tracts of the optic nerve.

Nidulus posterius (Plate XV, Fig. 8).—A short distance
caudo-laterad of the corpus geniculatum externum, there is a
small spherical cell cluster. This nidulus has been called by
Bellonci(') ‘‘ nucleus posterius.” For the sake of uniformity,
I have called it ‘‘nidulus posterius.” Compared with the
corpus geniculatum externum, this nidulus is quite small.

Histologically, it might be considered a sphere within a
sphere, the two spheres fitting so perfectly that no space is
left between the inner core and the outer shell. The shell
is granular, and does not contain nerve cells. The core,
however, is composed of densely packed, distorted, fusiform
nerve cells.

Crescent-shaped nidulus (Plate XV, Figs. 7-9).—In the
same region, adjoining the corpus geniculatum externum and
the nidulus posterius, there is a third nidulus. In horizontal
longitudinal sections this nidulus is a crescent, the horns of
which are directed cephalo-mesad. It lies caudad to the
corpus geniculatum externum, and extends from the nidulus
posterius caudo-mesad half way to the meson. Although
larger than the last-mentioned nidulus, it is not so large as
the corpus geniculatum.

Flistology.—The cells of this nidulus are of two sorts,
fusiform and pyramidal (Plate XVI, Fig. 3). In alumi-
nium-sulphate cochineal and in hematoxylin preparations,
each cell has a densely stained nucleus and a more densely
stained nucleolus. The cells are closely packed, and have
their major axes parallel to the longest axis of the nidulus.
In different bird brains the size of these cells varies. In
Swainson’s thrush (//y/ocichla swainsoni) they are from
sixteen to twenty-two micro-millimetres long and from six

to eight micro-millimetres wide. ‘This cell cluster appears

x Op. cit., p. 16, Fig. iii; Plate V, Fig. ii, np.

a

TuRNER, JZorphology of the Avian Brain. 113

to contain less than the average number of Deiter’s cor-
puscles.

As far as I know, this nidulus has not been described
before. I have ventured to christen it the crescent-shaped
nidulus.

Central nidulus of the diencephalon (Plate XIV, Fig. 5).
—In the ventral region of the brain, near the laterad portion
of the diencephalon, there is a large, conspicuous nidulus.
It lies upon the the border of the mesencephalon and the
diencephalon, and is situated about half way between the
chiasm and the caudad surface of the thalamus. This is a
large nidulus. It is almost as large as the corpus genicu-
latum externum. It is composed of fusiform nerve cells, and
is traversed by medullated nerve fibres.

NIDULI OF THE MESENCEPHALON.

Nidulus of the third nerve. —In man, according to
Ranney,(') ‘‘the w*otor-oculi and trochlear nerves have
their deep origin apparently from a gray nucleus (which,
according to some authors, is common to both nerves)
within the gray matter surrounding the aqueduct of Sylvius.

The nucleus of the fourth nerve seems to be com-
posed of larger cells than that of the third nerve, however,
and to occupy the level defined by the line of separation
between the anterior and posterior corpora quadrigemina.”

From the above quotation it appears that, even in mam-
mals, evidence is forthcoming to indicate that the niduli of
the third and fourth nerves are probably distinct. In the
avian brain this separation becomes more complete. These
niduli are not only distinct, but they are separated by a
broad longitudinal tract of nerve fibres (Plate XIV, Fig. 12).
These two niduli lie near the meson in the caudo-dorsad
portion of the mesencephalon, the third lying a short distance

cephalo-ventrad of the fourth. The motor-oculi nidulus is a

1 Op. cit., p. 336.

114 JouRNAL OF COMPARATIVE NEUROLOGY.

large, dense cell cluster, and is composed of irregular pyra-
midal cells (Plate XVI, Fig. 14). In all my preparations
these cells are obscurely stained, and have dense, indistinct
nuclei.

Peduncular nidulus (Plate XVI, Fig. 3; Plate XV,
Fig. 7).—Laterad to the tract of the third nerve and about
half way between the nidulus of that nerve and the base of
the diencephalon, there is a large, conspicuous nidulus. This
cell cluster has been named by Stieda the ‘‘ peduncular
nidulus.”” In the blue bird (Sza/za szalis) this nidulus is
about 577 micro-millimetres long and about 388 micro-milli-
metres wide. The most important elements of this nidulus
are large, gibbous, pyramidal cells (Plate XVI, Fig.g). In
different birds the dimensions of these cells vary. In
Swainson’s thrush (/7/ylocichla swainsont) they are about
twenty-five micro-millimetres long and about twelve micro-
millimetres wide. In the blue bird (Szalia stalis) these
cells are about sixteen micro-millimetres long and ten micro-
millimetres wide. When stained with hematoxylin or
aluminium-sulphate cochineal, each of these cells pre-
sents a densely stained nucleus and more densely colored
nucleolus.

The most conspicuous cells of this cluster are of the above
type. But, in addition to these, there are a few cells of a
smaller type. In Swainson’s thrush (//ylocichla swainsont)
these cells are about fifteen micro-millimetres long and six
broad, or only about half as large as the typical cells of this
cluster (Plate XVI, Fig. 9), When stained with hema-
toxylin or aluminium-sulphate cochineal, these cells present
small, densely stained nuclei and denser nucleoli. Although
these cells appear to be pyramidal, yet they are so much
smaller than the typical cells of this nidulus that one is in-
clined to believe that they are physiologically distinct. But
the fact that these cells are not universally present in this
nidulus, and that diminutive cells are often found in other

niduli, gives weight to the idea that these are immature

TurNER, Morphology of the Avian Brain. Ts

growths of the same type as the predominant cells. In addi-
tion to these undoubted nerve cells, the nidulus contains a
large number of Deiter’s corpuscles. A commissure connects
this nidulus with its fellow.

Nidulus of the fourth nerve (Plate XIV, Fig. 12; Plate
XV. Fig. 5).—As has been ‘mentioned above, this cell cluster
lies near the meson in the caudo-dorsad portion of the mesen-
cephalon. Unlike the nidulus of the third nerve, it is located
near the surface. Histologically, it resembles the nidulus of
the motor-oculi nerve.

In birds, as in reptiles and lower vertebrates, each optic
lobe contains a ventricle. In the aves, this ventricle is a
narrow expansion, which passes from the third ventricle into
the body of the optic lobe (Plate XIV, Figs. 1-6; Plate XV,
Figs. 2-5, 7-11). This cavity is convex, the convexity being
directed cephalad. From the body of each optic lobe a dome-
shaped expansion of the mesencephalon projects cephalad
into the ventricle. This expansion has been called the
‘‘colliculus” (Plate XV, Figs. 2,4). In some bird brains
this feature is more pronounced than in others.

The histology of the mesencephalon is very pretty. Each
optic lobe may be said to consist of an interior core or body,
which is surrounded on all sides except the mesad by a
stratified shell. This shell, the tectum opticum, consists
chiefly of alternate layers of neuroglia and Deiter’s cor-
puscles; while the core consists, in the main, of nerve
niduli and their concomitant fibre tracts. With one ex-
ception, all the niduli of the body of each optic lobe are
situated caudad to the mesencephalic ventricle (Plate XV,
Figs. 5, 7-9).

Tectum opticum.—The tectum, as here considered, con-
sists of all that portion of the optic lobe which lies ectad to
the fasciculus internus.(') Passing from the periphery entad
through the tectum opticum of Swainson’s thrush (/7ylo-

t For a description of this tract see p. 129.

116 JOURNAL OF COMPARATIVE NEUROLOGY.

cichla swainsoni), we meet in succession the following
parts (Plate XVI, Figs. 2, 12):

1. The narrow pia mater.

2. A wide layer of fibres, the external optic tracts.

3. A narrow layer of densely packed Deiter’s corpuscles.

4. A wide granular layer, which contains no nerve cells
and only a few scattered Deiter’s corpuscles.

5. A wide layer of densely packed Deiter’s corpuscles.

6. A wide granular layer which contains no nerve cells
and only a few scattered Deiter’s corpuscles.

7. A very narrow layer of closely packed Deiter’s cor-
puscles.

S. A narrow granular layer which contains no nerve cells
and only a few scattered Deiter’s corpuscles.

9g. A wide layer of densely packed Deiter’s corpuscles.

to. A narrow granular layer which contains no cells and
only a few scattered Deiter’s corpuscles.

11. A wide layer of densely packed Deiter’s corpuscles.

12. A narrow granular layer which contains no nerve
cells, but numerous scattered Deiter’s corpuscles.

13. An elongated nidulus, probably the sfecific optic
nidulus. This nidulus consists of several longitudinal layers
of elongated, slender, pyramidal cells(') (Plate XVI, Fig. 6).
The major axes of these cells are arranged approximately
parallel to the axis of the nidulus. These cells are exceed-
ingly slender, being often six to eight times as long as broad.
In Swainson’s thrush (//ylocichla swainsont) they are from
twenty-five to thirty micro-millimetres long and from three
to five micro-millimetres wide. In aluminium-sulphate cochi-
neal and in hematoxylin preparations, these cells are densely
stained and possess dense nuclei. In addition to the cells just
just described, this nidulus is well supplied with Deiter’s
corpuscles.

1 StTrepa~ thinks the cells of this nidulus are fusiform. ‘Studien iiber das centrale
Nervensystem der Végel und Saugethiere.”” Von Dr. Ludwig Stieda, Leipzig, 1868,
Pe 4}-

TuRNER, Morphology of the Avian Brain. 114

This description gives the appearance of the tectum in
the caudad portion of either optic lobe. In the cephalad
portion of each lobe, stratum twelve is much wider, and the
cells of thirteen have become intermingled with the fibres
that lie entad to the nidulus (Plate XVI, Fig. 2). Further,
in the caudad portion of each optic lobe the fibre tract that
forms the entad boundary of this nidulus hes immediately
ectad to two large niduli, while in the cephalad portion of
the same lobe that tract lies immediately ectad to the epithe-
lium of the mesencephalic ventricle. It may be of interest
to note that, in the specimens examined, this epithelium is
represented by two or more rows of densely packed nuclei.(')

‘To recapitulate, in general, the avian tectum opticum
consists of three parts:

1. Four dense concentric shells of Deiter’s corpuscles.

2. These are isolated from each other and from the re-
mainder of the tectum by five cell-less neuroglia layers.

3. A nidulus of elongated cells. The general trend of
this nidulus is parallel to the concentric shells.

I have been agreeably surprised to find that this arrange-
ment appears to be constant. Two apparent exceptions have
been noticed. In one case there were only three concentric .
shells, and in another there was none. However, in each of
these cases it is probable that the specimens were in a patho-
logical condition, for in one case the brain had been used in
an extirpation experiment, while in the other the head con-
taining the brain spent a mid-winter’s night upon the floor
of a butcher’s shop. If the number of these concentric shells
of the avian tectum opticum be constant, they must have a
special function to perform. It seems very suggestive that
Deiter’s corpuscles are factors of much greater importance
than is usually admitted.

Above I stated that entad to the tectum and caudad to

1 This peculiarity has been-noticed by Stiepa. After describing the nerve tract
mentioned above, he remarks: ‘‘An diese reiht sich das Pflaster-epithel des Ventrikels,
dessen Kerne allein sichtbar sind.’’ Op. cit., p. 44.

118 JOURNAL OF COMPARATIVE NEUROLOGY.

the mesencephalic ventricle, there are two prominent niduli.
One of these I have called nidulus lenticularis, and the other
nidulus sub-pyriformis.

Nidulus lenticularis (Plate XV, Figs. 5, 7-10).—This is
a large lenticular nidulus, which is situated in the central
part of the optic lobe. It lies caudad to the mesencephalic
ventricle, and immediately entad to the fasciculus internus.
The laterad extremity of this nidulus is about on a level with
the laterad extremity of the mesencephalic ventricle. The
major axis of this nidulus is oblique to the ventricle, the
cephalo-laterad extremity of that axis being much nearer the
ventricle than the caudo-mesad extremity. In different bird
brains the size of this nidulus varies. In Swainson’s thrush
(flylocichla swainsonz) the major axis of this nidulus is from
Soo to 1,000 micro-millimetres long, while the minor axes are
respectively about 300 micro-millimetres and 125 micro-
millimetres long. In the blue bird (Szadéa s¢a/is) the major’
axis is about 916 micro-millimetres long, while the shortest
axis is about 190 micro-millimetres long.

flistology.—The principal cells of this cluster are large
and gibbous, and have their longitudinal axes parallel to the
longest axis of the nidulus (Plate XVI, Fig. 7). These cells
rank among the largest in the brain. In Swainson’s thrush
(/lylocichla swainsont) these cells are from twenty-two to
twenty’six micro-millimetres long and from eight to sixteen
micro-millimetres broad. In the blue bird (Sza/éa szalis)
the same cells are from sixteen to nineteen micro-millimetres
long and from six to ten micro-millimetres wide. In shape
these cells are pyramids. A prominent fibre projects from
the apical process of each cell, while smaller fibres project
from each of the several basal processes. When stained with
hematoxylin or with aluminium-sulphate cochineal, the cells
are densely colored, and each possesses an elongaged or sub-
spherical dense nucleus and a denser nucleolus.

In some of my sections the cells of this nidulus appear to
be flask-shaped (Plate NVI, Fig. 11). These cells, however,

Turner, Morphology of the Avian Brain. 119

were of very nearly the same size as those just described.
Moreover, in one case the lenticular nidulus of the optic lobe
of one side was apparently supplied with pyramidal cells,
while the corresponding nidulus of the lobe of the other side
was apparently supplied with flask-shaped cells. In this
case the plane of the sections was known to be laterally
oblique to the base of the brain. These facts led to the
supposition that the difference in the appearance of the cells
was a function of the obliquity of the plane of the sections.
» Since it is easy to see how pyramidal cells might thus be
made to appear fusiform, and since it is impossible to see
how fusiform cells could ever be made to appear pyramidal
it is evident that the predominant cells of this nidulus are
pyramidal.

These large pyramidal nerve cells are, apparently, not
the only nerve cells in this nidulus. Many of my sections
exhibit numerous smaller cells (Plate XVI, Fig. 7). These
cells appear to be pyramidal. They are very slender. A\l-
though about as long as the typical cells of this nidulus, yet
they are often less than half as wide. Furthermore, they
have no obvious basal processes. Personally, I have grave
suspicions that these may be lateral sections of the larger
cells. But since I have not been able to demonstrate this,
and since in other niduli there are undoubted cases of cells
smaller than the typical ones, I have ventured to describe
these cells. Perhaps they are immature growths of the same
type as the the predominant cells. This nidulus is well
supplied with Deiter’s corpuscles.

In addition to the large bundle that hes ectad to this
nidulus, two sets of nerve fibres are associated with it. The
first set consists of several loose fibre bundles, which pass
from the fasciculus internus meso-cephalad through the
nidulus; the other is a narrow band of fibres, which lies
entad to this cell cluster and separates it from the following
nidulus.

Nidulus sub-pyriformis (Plate XV, Figs. 5, 7-10).—This

120 JOURNAL OF CoMPARATIVE NEUROLOGY.

nidulus lies cephalo-mesad to the lenticular nidulus, and is
separated from it by a narrow band of nerve fibres. This is
the largest nidulus in either the mesencephalon or the dien-
cephalon. It extends from the lenticular nidulus almost to
the union of the mesencephalon and diencephalon. Being
widest at its contact with the nidulus lenticularis, it tapers
gradually from that nidulus to its extremity. In shape this
cell cluster is not a perfect pear, the symmetry being de-
stroyed by the lenticular nidulus, which rests upon the
obliquely truncated caudo-laterad extremity of this nidulus.
fTistology.—The cells of this nidulus are numerous, and
are arranged parallel to its longitudinal axis. This arrange-
ment makes the cells of the lenticular nidulus perpendicular
to the cells of the pyriform nidulus. These cells bear no
resemblance whatever to those of the lenticular nidulus.
They are much smaller and of an entirely different type. In
the blue bird (S¢a/éa stalis) these cells are about ten micro- —
millimetres long and five micro-millimetres broad. They are
fusiform in outline, thus contrasting strongly with the pyra-
midal cells of the neighboring nidulus. In hematoxylin and
in aluminium-sulphate cochineal preparations, each cell is
faintly stained, and presents a clear sub-spherical nucleus
and a dense nucleolus (Plate XVI, Fig.1). This cell cluster
is amply supplied with Deiter’s corpuscles, and is surrounded
by fibre tracts.

Corpus posterius (Plate XV, Figs. 5, 8).—In the caudo-
laterad portion of the diencephalon, at the junction of that
portion of the brain and the mesencephalon, there is a small
but well-defined nidulus. This cell cluster has received
several names. In 1889 Dr. Perlia(') named it the ‘‘ nidulus
of the median optic fasciculus” (Kern des median optic
Bundle). In the previous year Bellonci(*) christened it

‘¢corpus posterius.” This nidulus varies in shape from a

1 ‘Ueber ein neues Opticus centrum beim Huhne.’ Von Dr. PeRLiA. Albrecht
von Graefe’s Archiv f. Ophthalmologie, Bd. XX XV, taf. 11, Fig. 5.
2 Op. cit., p, 16, Fig, ili, Kep.

TurRNER, WWorphologsy of the Avian Brain. L2n
’ Ov s

sub-spheroidal to a flattened sub-ellipsoidal body. When
of the latter shape, its major axis is parallel to the meson.
In haematoxylin and in aluminium-sulphate cochineal prepa-
rations, this nidulus consists of a dense, deeply stained outer
shell, within which is a solid core of lighter material.
Exactly what the cell structure is, I] have been unable to
determine. This nidulus is surrounded by fibre tracts, and
one originates in it. In all probability this body is the
homologue of the testis of the mammalian corpora quadri-
gemina.

Nidulus inferius (Plate XV, Fig. 6).—Near the ventral
surface of the mesencephalon, mesad to the external optic
tracts and adjoining the tuber cinerium, there is an elongated
lenticular nidulus. This nidulus extends from the junction
of the mesencephalon with the metencephalon cephalo-mesad
about half way to the optic chiasm. It is a dense nidulus,
containing scattered bipolar and multipolar nerve cells.
These cells are large and irregular. In hematoxylin and in
aluminium-sulphate cochineal preparations, these cells are
densely stained, and each presents an elongated dense
nucleus. This nidulus is associated with both the pedun-
cular fibres and with the fibres passing to the decussatio-
inferior. Bellonci(') has called this body the ‘‘ peduncular
nidulus.” But, since this name has previously been applied
by Stieda to the nidulus which hes immediately laterad to
the tract of the third nerve, and since two niduli of the same
name in the same brain can but breed confusion, the appella-

tion ‘‘ nidulus inferius”’

is proposed.

flabena.—cephalad to the epencephalon, there is a slight
dome-shaped protuberance from the dorsal surface of the
diencephalon. This is the habena. In the brains examined
this protuberance contains an ill-defined nidulus, the nidulus
of the habena.

Mesencephalic nidulus of the fifth nerve (Plate XV,

1 Op. cit., taf. V. Figs, 1-4, x.

122 JOURNAL oF CoMPARATIVE NEUROLOGY.

Fig. 3).—In the roof of the aqueduct of Sylvius are found a
number of large flask cells.(!) These cells rank among the
largest in the avian brain. Although I have not been able
to trace any connection between these cells and any nerve
root, yet their position, their form and their size all combine
in indicating that these cells constitute the mesencephalic

nidulus of the fifth nerve.
TRACTS OF THE DIENCEPHALON AND MESENCEPHALON.

In describing the tracts of these regions of the brain, it is
thought best to consider the combined diencephalon and
mesencephalon as a unit. This method has one decided
advantage, it facilitates an intelligent description of the
tracts. In discussing these tracts I have pursued the follow-
ing order. First, I have described all the obvious com-

missures and decussations and all the tracts that appear to

be associated with them; secondly, I have described the »

various nerve roots and associated fibres; finally, I have
described the remaining tracts of this region.

Excluding the anterior commissure, which has been de-
scribed in a previous paper,(*) this region of the brain con-
tains six well-defined commissures and decussations. Near
the dorsal surface the superior, posterior and Sylvian com-
missures are found; further ventrad lies the medi-commissure;
while near the base of the thalamus we find the inferior com-
missure and the ‘‘ decussatio inferior.”

Superior commissure (Plate XIV, Figs. 8, 9).— This
commissure les in the caudad extremity of the habena. In
the bird brain it is very small, and might be easily over-
looked. In the amphibian brain, according to Professor
Osborn,(’) ‘‘the superior commissure divides into two distinct

bundles, one of which descends into the inner mantle of the

These cells have been observed by STIEDA. Op. cit., p. 44.

JouRNAL OF CoMPARATIVE NEuROLOGY, Vol. I, p. 75.

*“ A Contribution to the Internal Structure of the Amphibian Brain,” by Professor
Henry FatrrieLp Osgorn, Princeton College. Journal of Morphology, Vol. II, p. 80,

ww N

TuRNER, Morphology of the Avian Brain. 123

hemispheres and finally disappears after bending around into
the outer portion of the mantle. The second bundle descends
directly along the outer wall of the thalami. These bundles
are clearly seen when the commissure is well developed.
One fact militates against our considering the
commissure as a purely decussational system; that is, the
bundle entering the hemispheres is much larger than that
entering the thalami.’ In the avian brain it has not been
possible to find more than one tract leading from the superior
commissure. The tenia thalami, the tract leading to the
prosencephalon, is present, but the other is, apparently,
absent. I say apparently, for it must be kept in mind that
the avian tenia thalami is a very small tract; hence if in the
avian brain the ratio of the tract going to the prosencephalon
to the tract leading to the diencephalon is the same as it is in
the amphibian brain, the tract passing to the thalamus would
be so minute that its discovery would be next to impossible.
Tenia thalami.—This tract passes from the vicinity of
the superior commissure cephalo-ventrad to the crura cerebri.
As has been stated,(') near the meson and dorsad to the
peduncular tracts these fibres enter the prosencephalon.
Immediately they turn dorsad, and, if I have traced them
correctly, after passing dorsad for a short distance, they turn
laterad. After traversing about half the width of the hemi-
sphere, the tract again turns dorsad. Always keeping near
the caudad extremity of the hemisphere, it continues dorsad
and disappears near the dorsal surface of the brain.
Posterior commissure (Plate XIV, Figs. 8, 9).— This
commissure lies in the dorsal portion of the diencephalon at
a short distance caudad to the superior commissure. Com-
pared with the latter commissure, this fasciculus is more than
ten times as large. In longitudinal-perpendicular sections
the posterior commissure resembles an inverted horse-shoe.
In the amphibia, according to Professor Osborn,(’) ‘‘ the

1 JOURNAL OF ComPpaARATIVE NEuROLOGY, Vol. I, p. 76.
2 Op. cit. p. 79-80.

124 JOURNAL OF COMPARATIVE NEUROLOGY.

relation of this commissure is three-fold: First, to the oculo-
motor nucleus, and probably to the main sensory tract;
second, to the pale ganglion behind this nucleus; third, to
the tectum opticum. As it descends the fibres divide into
two bundles, of which the anterior surrounds the superior
processes of the ganglion cells of the oculo-motor nucleus;
the connection is so close that some of these fibres seem to
be actually continuous with the cells. The posterior bundle
has a similar connection with the cell processes of the pale
ganglion, which may, in fact, also belong to the oculo-motor
nerve. None of the fibres of this commissure can be traced
directly into the main (sensory) tracts adjoining these nuclei,
as observed by Pawlowsky, although such a connection
seems highly probable. Dorsally, the fibres in this com-
missure in Rana can be clearly followed into the peripheral
white substance of the tectum opticum, as shown in hori-
zontal sections.”

In the bird brain there is a tract which might be con-
sidered the homologue of the first two tracts described above.
However, it is not connected with the nidulus of the third
nerve. This tract is a bundle of fibres which passes caudo-
ventrad from the posterior commissure and looses itself in
the substance of the diencephalon.(') Apparently this is a
true commissure of the thalamus.

In the bird brain I cannot detect any fibres passing from
the posterior commissure to the tectum opticum. This fact
apparently militates against our considering the avian and
amphibian posterior commissures as homologous. However,
since Professor Osborn does not mention a commissura
Sylvii, it seems quite probable that what he has described as
the posterior commissure consists of the posterior commissure

proper and of the commissura Sylvii. If this surmise be

1 In the mammalian brain, according to Professor Stricker, this tract presents the
same appearance. ‘‘A Manual of Histolology,” by Prof.S. Stricker. . . . American
trans., edited by AtperT H. Buck. New York: Wm. Wood & Company, 1872, p. 693,
Fig. 270, Ch.

TuRNER, Worphology of the Avian Brain. 12

al

true, then the homology between the avian and amphibian
posterior commissure is sufficiently close, for the commissura
Sylvii is essentially a commissure of the tectum opticum.

In the avian diencephalon two other tracts appear to be
associated with the posterior commissure. One of these
tracts comes from the epencephalon, the other from the
metencephalon.

Tract from the epencephaton (Plate XVI, Fig. 4).—This
tract arises in the cephalad portion of the epencephalon, and
passes cephalad through the valve of Vieussens into the
mesencephalon. There it loses itself in the vicinity of the
posterior commissnre. Apparently this tract decussates in
that commissnre. This tract is not the anterior peduncle of
the epencephalon.

Fasciculus cuneatus (Plate XVI, Fig. 4).—The tract that
comes from the metencephalon is probably a continuation of
the fasciculus cuneatus. It passes from the medulla cephalad
into the optic lobes. In company with the fibres from the
cerebellum, it loses itself near the posterior commissure. (')

Commissura Sylvit.— From the posterior commissure
almost to the origin of the fourth nerve, the aqueduct of
Sylvius is occupied by a long band of commissural fibres.
As long ago as 1868 Stieda recognized this band as distinct
from the posterior commissure. He christened it the ‘‘ com-
missura Sylvii.” He included under that name not only the
commissural fibres, but also the large flask cells which
laterad lie ventrad to them.(*) In this paper the name is

1 Inthe ‘‘ Applied Anatomy of the Nervous System,” p. 230, RANNEY, in describing
the tracts of the valve of Vieussens, writes: ‘‘ Certain longitudinal fibres may be demon-
strated which can be traced into the superior vermiform process of the cerebellum, The
course of these fibres is peculiar. They decussate before leaving the superior vermiform
process; they then traverse the valve of Vieussens almost to the lower portion of the
corpus quadrigeminum; at this point they double upon themselves, describing curves
whose convexity looks upward; finally, they join the inferior lamina of the lemniscus at
its posterior bundle, and pass onward with the latter, in the posterior division of the pons
Varolii to the spinal cord ”’ This quotation seems to indicate that the two tracts described
above are one, and, further, that that one is the homologue of this tract described by
Ranney. In defense, | aver that my sections do not warrant such a conclusion.

2 Op. cit., p. 44.

126 JOURNAL OF COMPARATIVE NEUROLOGY.

restricted to the commissural fibres. The cells have been
described elsewhere as the mesencephalic nidulus of the fifth
nerve. This commissure is identical with what some authors
have named the ‘‘ commissure of the optic lobes.” It appears
to be a true commissure of the mesencephalon. The fibres
composing it arise from both the entad and the ectad sides of
the mesencephalic ventricle. At the meson they converge
and form a conspicuous commissure.

Inferior commissure (Plate XV, Fig. 1o).—In the ventral
part of the thalamus, between the optic chiasm and the tuber
cinereum, there is a well-defined commissure. This has been
named by Bellonci the ‘‘ inferior commissure.” In well-
stained sections the fibres of this commissure can be traced
into the interior of the optic lobe, where they apparently
intermingle with the fibres of the fasciculus internus. The

majority of its fibres pass mesad to the central nidulus of the

diencephalon; a few, however, pass undisturbed through -

that nidulus.

Fibre ansulate.—A few fibres arise in the ventral part
of the diencephalon, decussate in the region of the chiasm,
and then pass cephalo-dorso-laterad, through the optic
chiasm, into the prosencephalon. JBellonci thinks these
fibres are homologous with the fibre ansulate of higher
brains.

Optic chiasm (Plate XIV, Figs. 11; 123, Platepeaye
Figs. 6, 10).—JIn all the specimens examined the avian
chiasm differs in some essential features from that of the
human subject. In the human brain some of the optic fibres
decussate in the chiasm and others do not.(') In the avian
brain all of the optic fibres decussate in the chiasm. There
is also another difference. In the avian brain there do not
appear to be any homologues of the two commissures found
in the human chiasm.

Optic tracts.—After decussation the majority of the fibres

1 “Applied Anatomy of the Nervous System,” by AmprosE L. Ranney, A.M.,
M.D. Second edition. D. Appleton & Co. Page 351, Fig. 81.

TurNER, Morphology of the Avian Brain. 124

in going to the optic tracts pass caudo-laterad and spread
out over the ventral and lateral surfaces of each optic lobe.
Although this is a continuous sheet of fibres, yet Bellonci(')
has divided it into two portions, a cephalo-dorsal (vorderes-
oberes) and a caudo-ventral (unteres hinteres) portion.
Thus he obtains two tracts, which are homologous to corre-
sponding tracts found in the brains of fishes ( 7v/eos¢e’) and
amphibians. The cephalo-dorsal root passes ectad of the
corpus geniculatum externus (Plate XV, Fig. 7).

All of the fibres of the chiasm do not pass into this exter-
nal optic tract. A few meagre bundles lose themselves in
the vicinity of the third ventricle.

Intimately associated with the external optic tracts are
three fasciculi which demand our attention. Two of these
tracts come from the mesencephalon and one from the pro-
sencephalon. These tracts are: the median optic fasciculus,
an unnamed tract, and tractus Bummi.

Tractus Bummi (Plate XV, Fig. 7).— Permit me to
repeat(°>) that ‘‘ this tract originates in either the frontal or
fronto-median lobe of the prosencephalon and passes caudo-
ventrad through the intra-ventricular lobe. After passing
beneath the anterior commissure, the tract turns and passes
ventro-latero-caudad to the crura cerebri. Penetrating the
crura, it passes to the outer fibre layer of the tectum.” Be-
yond its union with the external fibre layer of the tectum the
course of this tract becomes obscure.

A short distance caudad to the fusion of tractus Bummi
with the external optic fibres, a tract from the interior of the
optic lobe unites with the external optic fibres (Plate XIV,
Fig. 11). This seems to indicate that Bumm’s tract passes
into the interior of the mesencephalon. One serious objec-
tion militates against such a conclusion, viz., the tract pass-
ing to the interior of the optic lobe has a much smaller
diameter than tractus Bummi.

r Op. cit., p. 17.
2 JOURNAL OF CoMPARATIVE NEUROLOGY, Pp. 76.

125 JOURNAL OF COMPARATIVE NEUROLOGY.

Median optic fasiculus (Plate XIV, Fig. 7).—This is a
well-defined bundle which arises from the corpus posterius
and passes to the cephalad portion of the optic lobe. There
it turns laterad and fuses with the external optic tract.
Throughout its entire course this tract hes ectad to the
mesencephalic ventricle. In passing from its nidulus to the
external optic tract this fasciculus describes an ectally convex
curve.

In 1889 Dr. Perlia(') destroyed the retina of one eye of a
young chick and then allowed the specimen to live for
several months. The brain was then removed and prepared
for microscopical examination. Asa result of the extirpa-
tion it was found that, in the optic lobe connected with the
injured eye, several tracts had atrophied. One of these
atrophied tracts was the one just described. This experiment
seems to demonstrate that this tract 1s connected with the
optic nerve. Dr. Perlia has christened this tract the ‘* median
optic fasciculus.”

Third nerve (Plate XIV, Fig. 12).—In the avian brain
the root of the oculo-motor nerve is quite prominent.
Arising from its nidulus in the caudo-dorsad portion of the
diencephalon and passes ventro-laterad to its external root.

Mesencephalic root of the third nerve (Plate XIV, Fig. 3).
—In addition to the main root of the third nerve, there is
another tract which appears to be connected with that nerve.
This tract arises in the optic lobe, entad to the mesencephalic
ventricle. Describing a curve the convexity of which is
directed dorsad, this tract passes mesad to the peduncular
nidulus. The majority of these fibres pass throngh this
nidulus and decussate at the meson. There are fibres which
connect the two niduli, but I have not been able to trace any
of these fibres into the third nerve root:(*)

,

x “ Ueber ein neues Opticus Centrum beim Huhne,” Von Dr. PErRLia, Augenarzt
in Frankfurt a, M. Aus dem Senkenberg’schen Institute (Prof. Weigert), Albrecht von
Graefe’s Archiv f. Ophthalmologie, Bd. XX XV, s. 20-24, taf. 11.

2 A tract homologous with the one just described is found in reptiles, See ‘‘ Notes

Turner, J/orphology of the Avian Brain. 129

Fourth nerve (Plate XIN, Figs..3,°9;° Plate XV , Wigs.
5,8, 9).—In the human brain, according to Ranney,(') ‘‘ the
deep fibres of this nerve may be traced to four different
localities, as follows: First, some to the substance of the
peduncles; second, other fibres to the valve of Vieussens,
where they are lost, with the exception of a few which can
be traced to the frenulum; third, a few fibres to the tubercula
quadrigemina; fourth, a large bundle which passes inward
towards the median line and then decussate with its fellow
of the opposite side.”

In the avian brain I have not been able to trace, with
certainty, any fibres from the fourth nerve to the peduncles
of the cerebellum. Neither have I been able to demonstrate
that any of the fibres of the fourth nerve originate in the
valve of Vieussens. However, homologues of the two re-
maining tracts are constant in the avian brain.

As in the human brain, that portion of the fourth nerve
which decussates constitutes the largest root of that nerve.
The fibres of the fourth nerve arise from their nidulus in the
caudo-dorsal part of the diencephalon, and, after decussating
in the valve, pass ventro-laterad, around the cephalad ex-
tremity of the pedunculi cerebelli, to the surface.

Mesencephalic tract of the fourth nerve (Plate XV,
Fig. 5).—This tract arises from the fasciculus internus, at the
junction of that bundle with the caudo-laterad corner of the
mesesencephalic ventricle. It then passes, in an undulating
line, dorso-mesad to the valve of Vieussens. In all proba-
bility this tract participates in reflex actions.

From the vicinity of the niduli of the third and fourth
nerves a tract passes cephalo-laterad to the prosencephalon
(Plate XV, Fig. 10).

Fasciculus internus (Plate XV, Fig. 5).—Entad to the
cell layers of the tectum opticum there is a large bundle of

upon the Brain of the Alligator,” by C. L. Herrick. Journal of the Cincinnati Society
of Natural History, Vol. XII, Plate XIII, Fig. 6, R. III.
1 Op, cit., pp. 395-396.

130 JOURNAL oF COMPARATIVE NEUROLOGY.

fibres, from which several tracts arise. For this bundle the
name ‘‘ fasciculus internus”’ is proposed.

Central tract of the diencephalon (Plate XV, Fig. 10).—
One of the most conspicuous tracts of the diencephalon is
one passing from the caudad extremity of the fasciculus in-
ternus to the central nidulus of the diencephalon. Bellonci
has christened this fasciculus the ‘‘ central tract of the dien-
cephalon.” At one place, near the ventral surface of the
mesencephalon, this tract becomes tangent to the external
optic tract. At another place it is tangent to the tract pass-
ing to the inferior commissure.

Connecting the central nidulus of the diencephalon and
the corpus geniculatum externus, there is a definite tract.
This tract is quite short, and lies near the ventral surface of
the brain. Histologically, this tract consists partly of fibres
and partly of cells.

Prosencephatic tract of the corpus geniculatum externum.
—From the cephalad (Plate XV, Fig. 11) and mesad (Plate
XIV, Fig. 13) surfaces of the external geniculate body arise
a number of fibres. These unite into a definite tract, which
passes caudo-laterad into the prosencephalon. After enter-
ing the crura cerebri these fibres fuse with the peduncular
tracts. This renders it difhult to say which portion of the
cortex is supplied by this tract.

Tract from the mesencephalon to the metencephaton (Pilate
XIV, Fig. 10; Plate XV, Fig. 10).—From the caudad portion
of the fasciculus internus a well-differentiated tract passes
from the mesencephalon to an ellipsoidal nidulus in the
metencephalon. This cell cluster lies near one of the niduli
of the fifth nerve.

Tract to the prosencephalon (Plate XIV, Fig. 10).—
Another small tract arises within the mesencephalon, and,
curving around the mesad portion of the corpus geniculatum
externum, passes cephalo-laterad into the prosencephalon.

Anterior peduncle of the epencephalon (Plate XIV, Fig. 7).
—This tract passes cephalo-ventrad from the epencephalon

TurNER, Jlorphology of the Avian Brain. 131

to the vicinity of the chiasm. It then turns cephalo-mesad
and decussates in the cephalo-ventral part of the dien-
cephalon.

Dorso-median fasciculus (Plate XIV, Fig. 12).— This
bundle passes between the roots of the fourth and third
nerves. It will be more ‘fully described in a subsequent

paper.

Pyramidal tracts—In the first paper of this series all
tracts, excepting the tractus Bummi, passing from the dien-
cephalon to the prosencephalon were included under this
name. Here this name is restricted to the crossed and the
direct pyramidal tracts of the cord.. In the lateral portion
of the diencephalon these tracts pass along the ventral sur-
face of the brain, slightly dorsad to the chiasm. Cephalad
to the crura cerebri they curve laterad into the prosen-

cephalon.
[EI DyeN INS, IDV

Figs. 1-6. ‘Transverse sections of the diencephalon and mesen-
cephalon of Sadia stalis. F. /., fasciculus internus; A., mesencephalic
tract of the third nerve; C. P., corpus posterius; WV. Z., nidulus lenticu-
laris; WV. P., nidulus pyriformis; O. C., commissura Sylvii; P. C., pos-
terior commissure; /. JV., peduncular nidulus; S. C., superior com-
missure; ///, root of third nerve; /V, root of fourth nerve.

Figs. 7-9. Worizontal longitudinal sections of the caudad portion of
the brain of a chicken. A. P., anterior peduncle of epencephalon;
D. M. F., dorso-median fasciculus; JZ. O. 7., median optic bundle;
O. C., commissura Sylvii; P. C., posterior commissure; P. JV., pedun-
cular nidulus; S. C., superior commissure; ///, root of third nerve;
ZT/ x, nidulus of third nerve; 7V, root of fourth nerve; /V 7, nidulus
of fourth nerve.

Fig. 10. Uorizontal longitudinal section of a portion of the brain
of Hylocichla swainsont. A, tract passing from the mesencephalon to
a nidulus in the medulla; /J’, root of fourth nerve.

Fig. 11. Horizontal longitudinal section of the diencephalon of
Columba livia, taken near the ventral surface. J. /., decussatio infe-
rior, /. A., fibre ansulate; O. C., optic chiasm.

Fig. 12. Wongitudinal-perpendicular section of Sva/éa szal7s, taken
through the root of the third nerve. J. M7. #.,dorso-median fasciculus;
///, root ot third nerve; 7V x, nidulus of third nerve.

fig. 13. Horizontal longitudinal section through a portion of the

132 JOURNAL OF COMPARATIVE NEUROLOGY.

diencephalon of Columba livia, taken through the corpus geniculatum
externum. A, tract passing from mesencephalon to prosencephalon;
C.G.,corpus geniculatum externum,; C.G. 7., tract from corpus genicu-
latum externum to prosencephalon; QO. C., commissura Sylvii.

PLATE, XV.

Figs. 1-6. Horizontal longitudinal sections of the diencephalon
and mesencephalon of Columba livia. a, crescent-shaped nidulus;
C. G., corpus geniculatum externum; C. P., corpus posterius; d, tract
from within the mesencephalon to the external optic tract; /. /., fasci-
culus internus; 2, tract from mesencephal to prosencephalon; 7, mesen-
cephalic tract of fourth nerve; P. 7., peduncular tracts; iV. 7., nucleus
inferius; O. C., commissura Sylvii; O. 7., external optic tract; 7. B.,
tractus Bummi.

Figs. 7-10. Worizontal longitudinal sections through the dien-
cephalon and mesencephalon of /ylocichla swainsont. a, crescent-
shaped nidulus; 4, tract from mesencephalon to the prosencephalon;
C. G., corpus geniculatum externum; C. WV. 7., central nidulus of the
thalamus; /. C., inferior commissure; /V. P., nidulus posterius; P. JV.,
peduncular nidulus; ///, third nerve root; /// 7, nidulus of third nerve;
1V, root of fourth nerve; 7V x, nidulus of fourth nerve.

Fig. 11. Wongitudinal perpendicular section of the diencephalon
of a chicken. a, tract from corpus geniculatum externum to prosen-
cephalon; C. G., corpus geniculatum externum.

Fig. 12. Longitudinal perpendicular sections of the caudad portion
of the brain of Svaléa sialis. I//7,root of third nerve; 7V, root of fourth
nerve.

PACA Se Vall:

Fig. 1. Cells from the nidulus pyriformis of /Zylocichla swatnsont,

Fig. 2. Magnified portion of the tectum of the cephalad portion
of the optic lobe of H/ylocichla swainsont.

Fig. 3. Cells from the crescent-shaped nidulus of /ylocichla
SWALNSONL.

Fig. 4. Wongitudinal perpendicular section of a portion of the
caudad part of the brain of a chicken.

Fig. 5. Cells from the corpus geniculatum externum of H/ylocichla
SWAINSONL.

Fig. 6. Cells from the optic nidulus of ylocichla swainsont,

Fig. 7. Cells from the nidulus lenticularis of 7ylocichla swatusont,

Fig. 8. Cells from the nidulus inferius of Meleagris gallipavo.

Fig. 9. Cells from the peduncular nidulus of /7ylocichla swainsont.

Fig. 10. Horizontal longitudinal section of part of the brain of
Columba livia, to show the tract passing from the vicinity of the third
and fourth niduli to the prosencephalon. :

Fig. 11. Cells from the nidulus lenticularis of Hy/locichla swain-.

TuRNER, Morphology of the Avian Brain. 132

sont, to show the appearance of the cells when the nidulus is cut
obliquely.

Fig. 12. Section of tectum of the caudad portion of the optic lobe
of Hylocichla swainsont.

Fig. 13. Cells of the nidulus of the fourth nerve, from Svadia
stalis.

Fig. 14. Cells of the nidulus of the third nerve, from Svadia sialis.

NOTES” UPON "TECHNIQUE.

The following suggestions may prove useful to others as

they have to us.

1. FELT-TIPPED PLIERS.—Every one has experienced the
difficulty of using pliers or forceps of the ordinary pattern in
handling delicate and slippery tissues. If the corrugations
are sufficiently sharp to be of service there is much danger of
lacerating or perforating the membrane. This is true in the
dissection of amphibia with mucous glands in the skin as
well as in the mucous and serous membranes of other verte-
brates and the meninges of the brain. This difficulty may
be almost entirely obviated by gluing to the points accurately
fitted pieces of close-textured felt or chamois skin, which
facilitate steady and firm tension without danger of lacera-

tion.

2. KuirscuirzkKy’s HEMATOXYLIN PRocEss.—A method
which possesses many of the advantages of Weigert’s, be-
sides being shorter and more simple, is described as follows:
The material is fixed in Erlicki’s fluid one to two months
and is then washed in flowing water one to two days. The
precipitation of chromium salts, which is one of the great

134 JOURNAL OF COMPARATIVE NEUROLOGY.

drawbacks to Weigert’s method, is thus avoided. The hard-
ening takes place in alcohol as usual. After imbedding in
celloidin and sectioning in the usual way, the sections are
stained in hematoxylin dissolved in 2 per cent. acetic acid
solution (100 gr. 2 per cent. acetic acid, 1 gr. hematoxylin in
absolute alcohol). The staining may occupy one to three
hours. The sections are then transferred to a mixture of one
hundred parts of saturated lithium carbonate and ten parts of
I per cent. ferrocyanide (red) of potassium. A larger
amount of the ferrocyanide hastens the washing of the stain
from the gray matter. The operation requires two to three
hours. After washing in water the sections are imbedded in
balsam as usual. The resulting preparation has the axis
cylinder fibres stained dark blue or violet and the gray matter
yellowish. A solution of carmine in acetic acid may be
used in the same way with similar results.

3. ALUMINIUM SULPHATE CocHINEAL.—An accident led
to the discovery that 'the substitution of aluminium sulphate
for the alum called for in the formula of Czokor’s alum
cochineal isa vast improvement. The stain not only becomes
more selective, acting almost solely upon the nuclei, but it
is more prompt and reliable and the color resulting is more
pronounced and agreeable. A similar substitution in other

stains using alum is suggested.

RECENT INVESTIGATIONS ON THE STRUC-
TURE AND RELATIONS OF THE
OPTIC THALAMT

Henry RussELL PEMBERTON, M.A., B.S.,

University Fellow in Biology, Princeton College.

There has been much written of late concerning the optic
thalami and their connection with neighboring structures
in the brain. To present all the various views held with re-
gard to these important basal ganglia would be tedious,
while to discuss them fully within the compass of these
pages would be impossible. Consequently, let us confine
ourselves to the matter that has been published during and
since the year 1885, filling up with discoveries made before
that date such gaps as may arise, because during the last six
years all structures herein brought to notice have not
received equal share of attention.

A precise description of the two structures in the brains
of mammals called the optic thalami, would at this stage of
neurological research be unnecessary. The structure and
relations of the epiphysis are not here discussed. So much
has been written recently concerning this subject, that a
further setting forth of it is not necessary. The reader is re-
ferred to Cattie’s excellent article (Archives de Biologie,
Tome III, 1882).

The fishes are characterized by a small development
of the thalamencephalon, and in them we can recognize
structures corresponding only to parts of the thalamus in the

higher vertebrates, e. o., that part of the thalami in the mam-

Ex

136 JouRNAL OF COMPARATIVE NEUROLOGY.

mals which is called trigonum habenule is found in the
fishes. The thalamencephalon in the fishes seems indeed to
be of small importance; it appears in many of the species
as if it were a mere band of nerve-tissue, connecting the
prosencephalon with the mesencephalon. In the amphibians
and also in the reptiles the development of this part of
the brain is carried further; not that the relative size is
so much greater, but that the fibre connections are more
complex. The general arrangement of the parts is more sug-
gestive of that of the lower mammals. In the birds the
thalamencephalon is perhaps as well developed as in the rep-
tiles, but relatively to the other structures is not deemed of
such importance, partly because the corpora striata are
so much larger than in the preceding type, and also because
of the enormous size of the optic lobes.

Relations to Cerebral Tracts.—We shall now consider the

relation of the thalami to the basal prosencephalic tract, and -

at the same time, their relations to the bundles of fibres con-
necting them with the cerebellum, the medulla oblongata,
and the optic lobes.

With regard to the teleosts, Mayser |’ p. 322, et seq. | says
that the connection of the valvula cerebelli with the inferior
lobes is very distinct. After the tract reaches the inferior
lobes, it becomes dorsal to, and spreads over the part con-
necting the inferior lobe and the pars peduncularis. Some
of the fibres divide off, and go to the cerebellar tract. This
is somewhat the same view as that of Bellonci, for he con-
siders |* p. 24] that the inferior lobes are really parts of what
he, in his researches, calls the inner and the outer commis-
sures. Goronowitsch also states [" p. 545, et seq.] with
regard to the teleosts, that the tract running through the
base of the mesencephalon and ending in the region of
the thalamencephalon is perhaps homologous to the tract in
the subthalamic region of the higher vertebrates.

In the amphibian brain [Osborn,” p. 78] the bundle
of tibres composing the dorsal portion of the cerebral

PEMBERTON, Structure of the Optic Thalamt. 47)

peduncles, as shown in the transverse section of the thalami,
is made up of the prosencephalic sensory tracts formed
by the mesencephalon and the diencephalon. The _ basal
prosencephalic tract passes from the medulla into the basal
portion of the prosencephalon. Some fibres terminate im-
mediately below the anterior commissure, others enter the
corpus striatum. He also says that the bundles of fibres
coming from the lateral regions of the medulla and spreading
over the mesencephalon, in the same manner spread over the
diencephalon. The connection is a well-known one. As far
back as 1875, Stieda |* p. 396] showed that in the case of the
turtle, the fibre-bundle coming from the mesencephalon is
joined by the bundle from the thalamus and continues into
the prosencephalon. Stieda [* p. 395] also says that in the
reptiles the nerve-fibres of the thalamencephalon are for the
most part the continuations of the peduncle, both of the
lateral and of the central tracts. Some fibres come from the
mesencephalon, and other fibres joining these, pass to the
prosencephalon; and some from the mesencephalon cannot be
traced further, and probably terminate in the thalamus. This
is, of course, the basal prosencephalic tract to which Stieda
referred, and is exactly like the course of the fibres in the
amphibian brain.

In birds, the tract in which all the fibres join, descend
cephalad to the anterior commissure, to the base of the cere-
brum; it passes this at the front edge of the optic tract (of
the same side), goes around the crus, bending laterad, and
terminates between the posterior dorsal edge of the thalamus
and the optic lobe.

Edinger shows |*' see Fig. 64, p. 79,] us that in the
human brain the fibres passing from the anterior peduncle of
the cerebellum, and running just under the corpora quadrige-
mina, enter the ‘‘ red nucleus,” after decussating, and thence
send fibres to the thalamus, to the internal capsule, and to the
tegmentum. The fibres passing just above the pons,

go into the thalamus, and from there run dorsad in radiating

135 JouRNAL OF COMPARATIVE NEUROLOGY.

lines; some, after passing through the ‘‘ red nucleus,” unite
with this bundle, and then go in the same direction.

Relations to the Optic Tracts.—Let us first consider these
~ in the human brain. The optic nerves [Edinger”', p. 77]
after crossing at the chiasma (he does not mean complete de-
cussation) become the optic tracts; these turn around the
cerebral peduncles, and passing up behind the thalami,
spread out, partly entering them, but with other branches
going to the cerebellum and to the nidulus of the oculor-
motor nerve. He thinks that some fibres that enter the
thalamus, go no further, but that others do, by ‘way of
the tract towards the cortical optic centres (the occipital
convolutions of the hemispheres). In the neighborhood
[Stilling*, p. 474] of the optic lobes the tract divides into
three branches. The first runs through and partly around the
external geniculate body, and in a band thus covering the
gray substance of this body, passes to the surface of the
thalamus and runs on further (that is, to the cortical optic
centres; see Edinger’s opinion just above). The second,
passing through the two geniculate bodies, and then giving
off a small shoot, which loses itself in the tenia, reaches the
corpora quadrigemina, where it divides into two branches, of
which the one penetrates the nates, and the other, passing by
on the surface and again dividing, partly forms a commissure
with its fellow and partly goes to the frenulum. The third
goes to the internal geniculate body, some of its fibres stop-
ping there, but most of them, passing on, go to the nates or
to the anterior cerebellar peduncles which can only partly be
regarded as a branch of the opticus; its connection with the
testes is certain.

Associated with the optic fibres in the teleosts | Bellonci",
p. 7| are (1) the inferior commissure, which largely corres-
ponds with Gudden’s commissure and is in connection with
the inferior lobes; (2) the fibre ansulate, which cross mostly
above, but also partly within the inferior commissure, as in

the reptiles and amphibians; (3) a small number of thick

PEMBERTON, Structure of the Optic Thalamt. 139

peduncular fibres that descend from the thalamus and pass
partly through the base of the optic tract, also connecting
with the inferior lobes; (4) the stratum zanole, which does
not come from the optic nerve, but from the outer layer
of the anterior part of the tectum. Some fibres of the
stratum zonale assist in the formation of the inferior commis-
sure, and intertwine themselves in a complex manner with
the optic and with the thalamus fibres that originate partly
in the inferior commissure.

In the amphibians the optic tracts are principally confined
to the median portions of the tectum opticum. According
to Osborn |*’ p. 81, 82] they can be traced as far as the pos-
terior portion of the lobes. A second tract arises from a
mass of cells imbedded in the thalamus; a third enters the
hemisphere directly. These are the main sources of origin.
The course of the optic tract in reptiles, as described by
Rabl-Ruckard is quite similar to the course of the same tract
in amphibians.

Gadow says |", p. 378] that in the birds, the coverings of
the optic lobes join on either side to form the optic tract,
some of the fibres passing by the thalamencephalon and
others entering it. After examining some of my own
sections of the pigeon’s brain, it seems to me that whatever
fibres terminate in the thalamus are those coming from the
chiasma; I discovered none from the corpora bigemina that
terminated there. In birds, according to Bellonci |", p. 17],
the optic tract divides into two portions, an upper anterior
one, and a lower posterior one. The division is not an entire
separation, a layer of nerve-fibres lying between them. Of
course they correspond to the optic nerve-roots of the fishes,
amphibians and reptiles. The anterior one covers a swelling
that no doubt corresponds to the geniculate body of the
mammals. The grey substance of the thalamus is traversed
by optic fibres as follows: 1. The lower ones, which, having
separated from the chiasma, and being joined in small

bundles, penetrate the lower grey substance of the third

140 JouRNAL OF CoMPARATIVE NEUROLOGY.

ventricle; these afterwards join the main tract, mostly
uniting with its dorsal anterior portion. 2. The upper ones,
which pass through the geniculate body, and also join the
- dorsal anterior portion of the optic tract. 3. The upper
fibres. These do not terminate in the thalamus, but may
possibly, as in the lower vertebrates, have some connection
with this grey substance through which they pass. In close
proximity to the tract are peduncular fibres, other fibres that
form the inferior commissure, and fibres of the subthalamic
posterior decussation, corresponding, perhaps to the fibre
ansulate of the lower vertebrates. The correspondence is a
true one, no doubt, for, according to Bellonci’s description,
and also according to the figures of the various types, the
position of this decussation, as well as the terminal arrange-
ment of the fibres composing it, are similar to those of the
fibre ansulate. There are also thick medullary fibres which,
forming a network, cross inside of the inferior commissure
and the decussation; and in addition to all these there is a
thick bundle of medullary fibres which comes from the
interior of the optic lobes and goes to the central nidulus of
the thalamus.

It is Bellonci’s opinion |", p. 19| that some of the optic
fibres in the mammalian brain never crosses either in the
chiasma or in the subthalamic substance, and this, he says, is
more easily seen in the rodents than in any other of the
mammalian types. Some fibres that do not cross at the
chiasma, do so in the tuber cinereum, and then join the optic
tract. In the region of the chiasma the following kinds of
fibres are associated with the optic ones: the inferior com-
missure, the inferior fibre ansulate, of which he mentions
three groups: the first goes caudad and dorsad inside of the
thalamus; the second goes towards the optic tract, some of
the fibres running just outside of the tract finally enter the
occipital lobe; the third goes vertically dorsad and loses
itself in the corona radiata, the medial thalamus fibres that

pass from various portions of the thalamus to the dorsal part

PEMBERTON, Structure of the Optic Thalami. 141

of the chiasma, the lateral thalamus fibres that belong to the
peduncular tract and come from the region of the inter-
peduncular nucleus. The optic tract, accompanied by fibres
of the inferior commissure, takes a direction toward the
geniculate bodies; a few leave it, but not until it has reached
a position just under the internal geniculate, do the fibres of
the commissure separate from the tract and enter the internal
geniculate body. Most of the optic fibres remain on the
surface; a few enter, but only to pass through to the surface
of the thalamus. Fibres from the hemispheres, fibres from
the ‘‘ red nucleus,” also fibres coming from the corona radiata
and passing transversely through the dorsal portion of the
thalamus—all these enter the internal geniculate body and by
their presence render the identification of the optic tract —
fibres more difficult. The lower caudal root of the tract
passes laterally from the geniculate body to the corpora
quadrigemina. Especially worthy of notice is the connection
of the thalami with the corpora quadrigemina. This corres-
ponds to the outer anterior portion of the tectum opticum of
the lower vertebrates. Near the posterior commissure this
tract commences to give off branches, all of which sink into
the grey substance of the nates and probably terminate there.

Posterior Commissure.—One probable function of this is
to connect the two thalami; in fact, Mayser says [‘, p. 357]
that this is the only true commissure in the brain, connect-
ing, as it does, the two sidewalls of the third ventricle.
There is no such structure as the pons in the teleosts, and
Rohon thinks that this posterior commissure takes its place
and performs the same function as the pons of the higher
vertebrates. Osborn tells us [*', p. 79] that the posterior
commissure in the amphibians has a three-fold relationship:
1. To the oculo- motor nidulus, and perhaps to the main
sensory tract. 2. To the pale ganglion cells behind this
nucleus. 3. To the tectum opticum. As the fibres of the
posterior commissure descend, they divide into two bundles;

the anterior surrounds the superior processes of the ganglion

142 JoURNAL OF COMPARATIVE NEUROLOGY.

cells of the oculo-motor nidulus, the posterior connects with
the cell-processes of the pale ganglion. None of the fibres
of the commissure can be traced directly into the main
“sensory tract; in /eavza they can be followed into the peri-
pheral white substance of the tectum opticum. According
to the investigations of Goronowitsch [", p. 551] on the
brain of Actpenser, the posterior commissure consists of
three parts. The distal portion is formed of medullated
fibres which, in sagittal sections, can be traced to the base of
the mesencephalon. The proximal portion is made up of
fine medullated fibres which appear to come from a group of
small nerve-cells, dorsal to the bundle of Meynert; the
further course of this portion he was unable to trace. The
third portion is divisible into three parts: the first consists of
a granular fibrous structure, in whose periphery well-defined
fibres of the optic tract may be seén; the second of two or
three rows of cells, the processes of which are sent out in the
direction of the peripheral layer; the third is made by the
inner surface of the tectum. In the proximal portion of the
tectum the granular layer becomes thinner. Median to this,
large, rather thick?y scattered ganglion-cells are to be found.
The small processes of these cells run upwards to the surface
of the tectum, and appear to enter into connection with the
optic fibres. Auerbach [", p. 373 et seq.| has made a series
of investigations on the structure of the posterior commissure
in the teleosts and in the higher vertebrates; but the con-
clusions embodied in his paper need not be mentioned in
addition to the above.

Pawlosky says: ‘‘ The so-called posterior commissure
(in mammals) consists of crossed nerve-fibres descending
from the brain to the tegmentum of the crus.” They origi-
nate: 1. In the habenular ganglia. 2. In the frontal lobes of
the brain, through the anterior peduncle of the thalami. 3.
In the temporal lobes, through the lower peduncle. 4. Per-
haps in the thalami themselves.

This commissure, throughout all the vertebrate types, is

PEMBERTON, Structure of the Optic Thalami. 143

one of the first bundles to become medullated. In the human
brain [Edinger *! p. 73, 74] the fibres take their origin inside
of the thalamencephalon near the median ganglion, and
running caudad, decussate just cephalad to the corpora
quadrigemina, and soon pass lower down and run along the
base of the tegmentum. Running parallel to this, and being
reinforced by fibres from it, they finally reach the meten-
cephalon. The investigations of Spitzka and of Darkschew-
itsch confirm this statement of Edinger. The fibres that lie
nearest to the median line probably terminate in the nidulus
of the oculo-motor nerve.

The Supra-commissura.—Osborn, |‘‘ Preliminary Obser-
1884, p.
268], says: ‘‘In the forward portion of the roof of the
diaceelia (in amphibians), just above the optic chiasma, is

5

vations upon the Brain of Menopoma and Rana,’

the supra-commissura. It is closely connected with, and is
just in front of the ganglia habenule. It passes across the
posterior ends of the thalami. The distribution is similar to
that of the fibres of the tenia of the thalami. It divides
into two bundles, one going down to the inner mantle of the
hemispheres, the other descending directly along the outer
wall ot the thalami. Thus is occupies the same relative
position as the commissure of the pineal stalk of the mam-
malian brain. Osborn [* p. 8o| does not consider this
commissure a purely decussational system, as the bundle
entering the hemisphere is much larger than that entering
the thalami; consequently, it forms either partly a com-
missural system between the posterior portions of the hemi-
spheres and between the thalami, or partly a decussational
system between the hemispheres and the thalami. Bellonci
_ lays especial stress upon ‘the presence, in this commissure as
in the other cerebral commissures, of decussational fibres in
addition to the commissural ones. Herrick says [* p. 26]:
‘¢The supra-commissure (of reptiles) lies entirely cephalad
to the habena ata level considerably ventrad to the com-
missure of the habena, which lies caudad to it, and passes by

144 JOURNAL OF COMPARATIVE NEUROLOGY.
’

a slight ventral curvature into the median part of medio-
caudad projection of the cortex, and thence across to the
caudo-lateral portion. The superior commissure is relatively
stronger than its neighbor, and it would appear that the two
are especially distinct in animals like the lizard, where the
epiphysis is highly developed.” A comparison of the re-
searches in the mammalian brain with those in the brains of
the lower vertebrates, would lead us to conclude that the
median commissure [see *' p. 63| in the one and the supra-
commissure in the other, though not entirely homologous, are
still in their structure and in their connections, capable of
similar functions. It is Herrick’s opinion |[™ p. 26] that
instead of considering that the supra-commissura is divided
into two parts in the amphibians and reptiles, we would do
better to reccognize two originally distinct commissures.
Meynert’s Bundle.—Mayser [' p. 357| has told us that in
the fishes this bundle consists of non-medullary fibres. It is
of a single nature, running from the habenular ganglion
ventrad and caudad. Breaking through the commissure of
the fibre ansulate, it divides into many fascicles. It enlarges
at the point where an addition of fibres is made from the
wall of the aqueduct. Most investigators have traced the
bundle only as far as the inter-peduncular ganglion, but in
the amphibians Osborn has found fibres of it running past
this point, and Ahlborn |" p. 285] claims that in the brain of
Petromyzon he has traced them even into the metencephalon.
Wright’s investigations with Amdcurus lead him to conclu-
sions similar to those of Mayser just stated above. Gorono-
witsch |" p. 551] traced these fibres caudad only as far as
the proximal boundary of the inter-pedunclar ganglion. In
the mammalian brain the course of Meynert’s bundle is not
such a simple one. The course [| Honegger,** p. 407] in some
of the mammals is quite different in detail from that in others.
The main cause of the difference is the large development of
the‘‘ red nucleus ” in some of these brains. In man the bun-
dle is very strongly deflected from its course as it passes the

PEMBERTON, Structure of the Optic Thalamt. 145

‘‘ red nucleus.” In other mammals there is a slight bend, but
in the mouse the course is nearly a straight line at this point.
Honegger distinguishes [* p. 405] two kinds of fibres in
Meynert’s bundle. The carmine stain affects one kind of
fibres, making them more or less red, while the other kind
remains unstained. For ventral connections of this bundle
see ‘‘ Interpeduncular Ganglion.”

LInfundibular Tract.— Goronowitsch’s investigations on
the brain of Aczfenser show us |" p. 549] that the fibres in
the peripheral part of the infundibular lobes run parallel to
the surface. In the central portion the fibres are more defi-
nitely marked, and consist of two systems. One has its
fibres parallel to the surface, as in the peripheral layer; the
other crosses the first at right angles, thus having its fibres’
perpendicular to the surface. By means of their fibre-con-
nections, the lobes are put into direct association with the
prosencephalon. A distinct tract [" p.550| of non-medullary
fibres from the infundibular lobes passes to a ganglionic body
in the wall of the mesencephalic ventricle. Osborn traces
[*’ p. 79] the tract cephalad, in the amphibians, beneath the
basal prosencephalic tract towards the hemispheres. In
Rana it has the appearance of entering the thalami, but
‘“‘not in the Urodela, where it appears to pass directly
forwards and not upwards.”

Mammillary Body, Corpus Candicans.—The position of
this structure just below the thalami, and its connection with
the tegmental bundle, and the bundle of Vicq d’ Azyr, both
of which pass through or by the thalamus, bring it into
notice in this article. It is particularly well developed
|“ p. 341] in the cat, the dog, the monkey, the rabbit, and
in man. Fritsch thinks that it is homologous with the infe-
rior lobes of the teleosts. Its main connection, as far as we
are here concerned, is with the two bundles just mentioned
above, but the pillar of the fornix also enters it, having,
however, no functional connection with the bundle of Vicq
d’Azyr, according to the careful and systematic pathological

146 JOURNAL OF COMPARATIVE NEUROLOGY.

experiments of von Gudden |[° p. 429|. We must refer to
Honegger’s work |” p. 348 e¢ seg.| for the discussion of this
point. Vicq d’Azyr’s bundle arises |*' p.65] from that one of
the two median niduli that is caudad; it passes up through
the thalamus and loses itself in the anterior tubercle. By its
side, following Edinger’s description |*' p. 65], the tegmental
bundle of the mammillary body passes dorsad, but soon sepa-
rating from its companion, bends caudad, and passing through
the tegmentum, can be traced to ganglia lying under the
aqueduct.

Ganglia Habenule |Goronowitsch, ” pp. 442,551 ].—The
habenular ganglia of Acipenser are not symmetrically devel-
oped; the right one is noticeably larger than the left. In
cross-section the dorsal corner of the thalamus (into which
the optic fibres run) contains the habenular ganglion. Some
fibres, running into this, can be traced from the vertical
rons of small cells lying between the ventrical epithelial and
the granular substance. It is almost certain that these
ganglia are homologues of those in the higher vertebrates,
for in both types the connections with Meynert’s bundle are
very similar. In Amiurus |Wright, ” p. 32] the ganglia
have the same position and connections. Mayser thinks that
in the Ze/eosts the bundle that passes along the upper edge
of the wall of the third ventricle is homologous to the tenia
of the higher vertebrates. These ganglia in the amphibians
lie just behind the supra-commissura, and send out fibres
forming a conspicuous tract (Meynert’s) in all of these
animals. Each of the ganglia habenule in the mammals
gives off fibres which go to form Meynert’s bundle. This
connection is an intimate one | von Gudden, ° p. 423].

Interpeduncular Ganglion | von Gudden, ’ p. 424 et seq. ].
—In the rabbit this.consists of ground substance, which is
an aggregation of more or less sharply defined nests of fine-
fibred, band-shaped bundles, somewhat like the glomeruli of
the olfactory bulb. Besides this, there are small rounded or
spindle-shaped ganglionic cells. The bundle of Meynert

PEMBERTON, Structure of the Optic Thalamt. 147

divides here and crosses its fellow inside of the ganglion, and
it and the ganglion degenerate after removal of the ganglia
habenule. Not much is known of its physiological import-
ance, but it is probably rather a stimulating than a stimulated
centre of the habenular ganglia. The interpeduncular gan-
glion appears in all the vertebrates, being situated between
the mesencephalon and the metencephalon. In the fishes it is
of simple construction, and so also in the amphibians, being

composed of very small triangular cells. As mentioned

?

under ‘‘ Meynert’s Bundle,” there are two kinds of fibres

distinguishable in this fibre-connection. Of these | Honegger,
* pb, 408], the darkly stained ones enter into connection with
the cells present in this ganglion; the more lightly stained
ones go further caudad.

LITERATURE.

1. 1870. STIEDA: Studien tber das centrale Nervensystem der
Wirbelthiere. Zettschrift f. wissenschaftliche Zoologie, Band XX,
Pp. 273-

2. 1875. STIEDA: Ueber den Bau des centralen Nervensystems
der Schildkrote. Zezt. f. wiss. Zool., Bd. XXV, p. 361.

3. 1880. StTitLinG: Ueber die centralen Endigungen des Nervus
opticus. Schultze’s Archiv f. mtk. Anat., Bd. X VIII, p. 468.

4. 1881. BrLLoncri: Ueber den Ursprung des Nervus opticus
und den feineren Bau des Tectum opticum der Knochenfische. Ze??.
VCDESS< 0 Z/001.), SOO Sp. 23.

5. 1881. von GUDDEN: Mittheilung tuber das Ganglion interpedun-
culare. Archiv f. Psychiatrie, Bd. XI, p. 424.

6. 1881. VON GUDDEN: Beitrag zur Kenntniss des Corpus mam-
millare, und der sogenannten Schenkel des Fornix. Archiv /. Psycht-
atrie, Bd. XI, p. 428.

7. 1882. MaAyser: Vergleichend anatomische Studien tiber das
Gehirn der Knochenfische. Zezt. f. wiss. Zool., Bd. XXXVI, p. 259.

8. 1882. Rasri-RtcKARD: Zur Deutung und Entwickelung des
Gehirns der Knochenfische. Archiv f. Anat., fahrgang, 1882, p. 111.

g- 1883. AHLBORN: Untersuchungen tiber das Gehirn der Petro-
myzonten. Zezt. f. wiss. Zool., Bd. XXXIX, p. tot.

10. 1883. Bumm: Das Grosshirn der Vogel. Zert. f. wiss. Zool.,
Bd. XX XVIII, p. 430.

11. RABL-RUCHARD: Das Grosshirn der Knochenfische und seine
Anhangsgebilde. Archiv f. Anat., fahrgang, 1883, p. 280.

12. 1884. AnLBORN: Ueber den Ursprung und Austritt der Hirn-
nerven von Petromyzon, Ze/tt. f. wiss. Zool,. Bd. XL, p. 286.

148 JoURNAL oF COMPARATIVE NEUROLOGY.

13. 1884 (circ.). WriGcHr: The Nervous System and Sense
Organs of Amiurus.

14. 1887. EptnGer: On the Importance of the Corpus Striatum
_and the Basal Fore-brain Bundle. Sournal of Nervous and Mental
Diseases, Vol. XIV, p. t.

15. 1887. Gapow: Dr. H. G. Bronn’s Classen und Ordnungen des
Thier-Reiches. VI Bd., 1V Abtheilung, 16 und 17 Lieferung.

16. 1888. AuvERBACH: Die Lobi optici der Teleostier und die
Vierhigel der hoher organizirten Gehirne. Morph. Fahrb., Bd. XIV,
P- 373:

17. 1888. BrLLoNcI: Ueber die centrale Endigung der Nervus
opticus bei den Vertebraten. Zeit. f. wiss. Zool., Bd. XLVII, p. 1.

18. 1888. Gapow: Dr. H. G. Bronn’s Klassen und Ordnungen des
Thier-Reiches. VI Bd., 1V Abtheilung, 18, rg und 20 Lieferung.

1g. 1888. GoroNowitscH: Das Gehirn und die Cranialnerven
von Acipenser ruthenus. Morph. Fahrb., Bd. 13. pp- 527, 514.

20. 1888. Ossporn: A Contribution to the Internal Structure of
the Amphibian Brain.

21. 1889. Eprncrer: Zwélf Vorlesungen itber den Bau der Ner-
vosen Centralorgane.

22. 1889. JELGERSMA: Ueber den Bau des Saugethiergehirns.
Schultze’s Morphologishes Fahrbuch., Bd. XV, p. 61.

23. 1890. HOoNEGGER: Vergleichend-anatomische Untersuchungen
uber den Fornix. ;

24. 1891. HERRICK: Contributions to the Comparative Morphol-
ogy of the Central Nervous System. JOURNAL OF COMPARATIVE
NeEvuROLOGY, Vol. I, March, 1881, p. 5.

25. 1891. TURNER: Morphology of the Avian Brain. JOURNAL
OF COMPARATIVE NEUROLOGY, Vol. I, March, 1891, p. 39.

CatTie: Récherches sur la Gland pinéale. Archiv de Biologie
Tome III, 1882.

CONTRIBUTIONS TO THE COMPARATIVE
MORPHOLOGY OF THE} CENTRAL
NERVOUS SYSTEM.

( Continued. )

III.—_ TOPOGRAPHY AND HISTOLOGY OF THE BRAIN OF
CERTAIN GANOID FISHES.—Piates XI and XIII.

It seems desirable for several reasons to introduce at this
point in the series a few data relating to the Ganoid brain.
The Ganoids form a natural point of departure for any
minute study of the brains of the lower fishes, and if the
peculiarities of structure which at first seem so irreconcilable
can be shown to present no morphological difficulties, one
may hope to be able to apply the homologies made out in
such a typical brain as that of a lizard to any vertebrate. As
a matter of fact, no better illustration of the value of morpho-
logical generalizations in the solution of special problems
need be sought than that afforded by the complete and satis-
factory solution of the puzzle so long unread in the case of
the brain of fishes. Thus the Ganoids are found to possess a
brain curiously modified, it is true, but one in which every
important organ of the reptilian brain may be satisfactorily
identified. The laws of development, read backward, enable
us to trace the connection very satisfactorily in most cases,
while the aberrant features are found to be modifications of
familiar organs rather than new structures.

A brief outline is offered at this time relating to the
topography and a few points only in the histology of the
cephalic parts of the brain. Two types are used, and one or

Rea

150 JOURNAL OF COMPARATIVE NEUROLOGY.

both are referred to as seems most convenient. No attempt
is made to give reference to the extensive literature of this
subject, though a partial list of papers is appended.

The brain of the Gar-pike (Zefidosteus) may serve as
a convenient standard of reference for fish brains. If it could
have been satisfactorily studied before that of the aberrant
Teleosts, science would have been saved a long period of
grouping and a vast deal of confusing synonomy.

The olfactory lobes are generally unmistakable, but
where, as in the cods, separated by a wide interval from the
hemispheres they have been overlooked, leading to an identi-
fication of the cephalad part of the hemispheres with the
olfactories. The microscopic structure of the olfactory lobes
is so unmistakable that there is no excuse for the confusion.
The second paired or apparently fused bodies have been very
differently interpreted. Haller supposed them organs of
smell, together with the hypoaria. Kuhl, Gottsche, Mayer
and others homologized them unhesitatingly with the olfac-
tory lobes. Philipeaux and Vulpian thought they represent
the caruncula mammillaris of the olfactory. Tiedemann
thought he discovered in them the homologues of the striata
and hemispheres. Though most of the later writers have
accepted some phase of this interpretation, the apparent
absence of the lateral ventricles or the attempt to homologize
the olfactory ventricle with them has led to great diversity
in minor points. The third pair of dorsal tuberosities is often
apparently single, and, though it has often been identified
with the optic lobes, yet, because of a failure to recognize
the thalamus (which scarcely reaches the dorsal surface in
many fishes), it has been given every possible name. Very
generally, among the earlier writers, it has been called the
cerebrum, and the Sylvian commissure poses as corpus
callosum. Two projections into the ventricles of the optic
lobes have been identified as the fornix (Gottsche). Carus
and Tiedemann, the one from comparative, the other from

embryological considerations, identified these bodies with

Herrick, Morphology of Nervous System. I51

the optic lobes. The histological structure, position of the
optic tracts and mesencephalic nidulus of the fifth nerve, etc.,
make the identification certain.

The diencephalon is not usually conspicuous, though
quite obvious dorsad in the gars. As though to compensate
for this limitation, the ventral portion is highly developed,
and from the lateral aspects of the infundibulum two pouches
are formed, apparently without direct homologues in higher
brains, though possibly having some relation to the mam-
millare. Hypophysis and epiphysis have the usual form and
position, and in histological structure vary but little from the
reptilian type.

The cerebellum is enormously developed, standing in
relation with the relatively large size of the axial lobes of the
cerebrum. The extended work of Miklucho-Maclay has done
much to prevent a true understanding of the relations, espe-
cially when accepted by Gegenbaur. Overlooking the *thala-
mus entirely, he identifies the optic lobes as the diencephalon
and designates a part of the cerebellum as optic lobes, the
rest as cerebellum, and the posterior part of the medulla as
‘¢ nachhirn.”

As will be gathered from what follows, the minute struc-
ture as well as the position of the commissures, etc., settle
the homologies in most respects quite decisively.

Our present purpose requires specific reference to only the
following papers, which have chiefly influenced the synon-
omy employed. (See end of this article for bibliography.)

WiLperR, B.G. On the Brains of Fishes. Proc. of the Academy
of Natural Sciences of Philadelphia, 1876, pp. 51-53.

WILDER, B.G. Proc. Am. Assoc. Adv. of Sciences for 1875.

SANDERS, A. Contributions to the Anatomy of the Central Ner-
vous System in Vertebrate Animals. Part I, Section 1, Sub-section 1—
Teleostei. Philos. Transactions, 1878. (This paper gives summary of
literature prior to 1879.)

AvLBporn, F. Untersuchungen tiber das Gehirn der Petromyzonten.
Zeitsch. f. wiss. Zoologie, XX XIX, pp. 192-294, 1883.

N. GoronowitscH. Das Gehirn und die Cranialnerven von Aci-
penser ruthenus. Morph. Fahrbuch., Bd. XIII, 1888, pp. 427-574.

152 JouRNAL OF CoMPARATIVE NEUROLOGY.

Horr, E. W. L. Observations upon the Development of the Tele-
ostean Brain, with Especial Reference to that of Clupea harengus.
Zool. Fahrbuch., Morph. Abth., Bd. IV.

The first paper, that of Prof. Wilder, relates to the
present group. We quote as follows: ‘‘ The front pair of
lobes [of the the fish brain] have usually, not always, been
called olfactory lobes. In Myzonts or Marsipobranchs (lam-
prey eels, etc.), in Ganoids and some Teleosts, as in higher
vertebrates they are sessile; but in many Teleosts and most,
if not all, Selachians (sharks and skates) they are connected
by elongate crwra with the second lobes. These latter are
almost universally called hemispheres. Yet the essential
feautures of hemispheres, namely, lateral ventricles and
foramina of Monro, have never been found in the second pair
of lobes of any fish-like form excepting those of the Dipnoans
(Lepidosiren, Protopterus, and Ceratodus), which seem in
most respects more like those of Batrachians than of fishes.
The second pair of lobes are either solid lateral laminz joined
below, but with the upper borders more or less everted, as
in Teleosts and Ganoids, or joined above also so as to inclose
a cavity, as in Salachians. In either case the median space
must be regarded as a forward continuation of the median or
third ventricle, and the lateral walls as enlargements of the
thalami. These enlargements Prof. Wilder proposes to call
prothalamti, in Salachians and Ganoids they are connected
by more or less elongated and depressed craura thalami with
the optic lobes behind. From the anterior part of the space
between the prothalami and, in Ganoids and Teleosts, appar-
ently in the base of the olfactory lobes, are two openings
leading into the cavity of the olfactory lobes. These open-
ings are regarded as foramina of Monro, leading into dis-
tinct, though small, lateral ventricles.” ‘‘ The true hemi-
spheres of Ganoids may be represented by a raised lip of the
foramen of Monro.”

We think the failure to recognize the well-defined hemi-

spheres in this case was due to the peculiar membranous

a

Herrick, Morphology of Nervous System. mee

dorsal and mesal walls (pallium of Rabl Ruckhard), which
were not fully distinguished from the brain membranes.
The proplexus, which is quite large, is sufficient to call
attention to this condition. The openings lying beneath the
median walls would, according to the useful system since
proposed by Prof. Wilder, constitute the porte, and the
opening identified above as the porta becomes the opening of
the olfactory. With these changes, and remembering that
one of the most remarkable incidents of brain development
has been the backward revolution of the mantle portion of
the cerebrum, all the difficulties disappear, and we seek the
commissures of the mantle far cephalad in front of the thin
membranous portion, which seems to be homologous, in part
at least, with the velum cerebri supporting the proplexus.

Rabl-Ruckhard has the credit of first demonstrating the
fact that the prosencephalon of fishes consists of two thick
ventral ganglia, which before had been regarded as the
hemispheres themselves, while the whole dorsal surface is
membranous.

The most thorough investigation of the ganoid brain is
the paper quoted above by Goronowitsch. Since this may
not be universally accessible, a somewhat condensed transla-
tion is added of such parts as apply to the present instalment
of this paper:

‘¢ Cerebrum.—The roof of the prosencephalon is mem-
branous, and consists of a variously folded epithelial lamina.
The roof of the olfactory lobes, however, consists of thick
medullary walls. Between the roof of the prosencephalon
and the epiphysis there is a broad membranous sac, the cavity
of which is distally in wide connection with the cavity of the
prosencephalon. ‘The blind end of the sac is directed proxi-
mally (cephalad!). The sac, therefore, must be considered
as a broad diverticle of the roof of the prosencephalon,
springing from a point cephalad to the origin of the epiphy-
sis. This may he called, for the sake of brevity, simply the
dorsal sac.

154 JOURNAL OF COMPARATIVE NEUROLOGY.

‘* At the anterior margin of the left ganglion habenula
(the left is much the smaller) a lateral induplication of the
membranous roof of the prosencephalon enters the ventricle.
This fold is somewhat complicated. The epithelial layer of
which it consists forms numerous folds and sacs, into which
projections of the membranes and blood-vessels enter. The
structure is, in other words, that of a plexus choroideus.

‘¢ Careful study of continuous series of sections indicates
that there is nowhere a discontinuity in the epithelial layer.
The cavity of the prosencephalon is therefore completely
closed. The dorsal lamina of the fold forms the ventral wall
of the dorsal sac, and the ventral lamina forms the mem-
branous wall of the prosencephalon. It thus appears that
the opening of the dorsal sac is asymmetrical. Cephalad
from this point the two chambers are separate. The ventral
portion of the neural tube at this region consists of thick
paired masses, the basal ganglia. The membranous roof’
bears a system of folds which becomes more complicated.
The middle portion -projects into the ventricle and forms a
sort of falx cerebri. The dorsal wall also circumscribes the
dorsal sac laterad and encloses it in a plexiform structure
derived from the roof of the prosencephalon.

‘¢ Somewhat cephalad to the base of the olfactory lobes
a groove appears upon the dorso-median aspect of the basal
ganglia which passes mesad and can be traced directly into
the cavity of the olfactory lobe. The median falx of the roof
dips deeply into the ventricle of the prosencephalon. The
falx extends to the epithelial lamina which connects the two
olfactory lobes. Cephalad to this point the membranous roof
of the prosencephalon is continued to form paired sacs dorsad
to the olfactory lobes.

‘¢In this structure of the prosencephalon of A. ruthenus
I detect the paired nature of the prosencephalon, which con-
sists in the strongly developed falx as well as the mem-
branous sacs of its cephalad portion.

‘At the cephalad level of the chiasm two prominences

. ao

Herrick, Morphology of Nervous System. 155

appear upon the dorsal portion of the encephalon wall,
which have the structure of the basal ganglia. This struc-
ture extends soon to embrace the entire lateral walls of the
prosencephalon. These ganglia consist of a very compact,
finely-granular stroma, with peculiarly arranged ganglion
cells, and of a system of ‘exceedingly fine, non-medullated
fibres. Beneath the epithelium, in the dorsal region of the
ganglia, is a layer of small cells whose fibres extend ventrad
and radially. Such cells are not found in the ventral por-
tions, but instead irregularly scattered small cells. In the
midst of the ganglion are large cells with large round nuclei
and pale body. The processes are here also radially disposed
to the ventricular surface, producing in cross-sections a very
characteristic habitus. The transition in structure in passing
into the olfactory lobes is gradual.

‘¢In transections corresponding to about the middle of
the prosencephalon the basal ganglia are connected by a
thick commissure—the commissura interlobularis. I preserve
the older name for reasons suggested by Osborn. The mass
of the commissure is composed of finely-granular substance,
with scattered small nuclei. It is only in its dorsal portion

that fibres may be seen crossing. It proved impossible to

determine their further course. Besides these, there are a

few thicker bundles of non-medullated fibres from the olfac-
tory lobes which cross with those of the opposite side, and,
passing caudad, apparently combine with the systems leading
to the lobus infundibuli. The latter observation is neverthe-
less somewhat doubtful.

‘¢ Ventro-mesad to the optic tracts there is a well-devel-
oped system containing apparently fibres from the anterior
(interlobular) commissure. The greater part is derived from
the central substance of the basal ganglia. Associated with
these are a number of fibres from a cluster of small nerve
cells lying cephalad to the chiasm. Sagittal sections show
that the lateral portions of the above-mentioned systems of
fibres pass to the caudal part of the lobi inferiores. The

156 JOURNAL OF COMPARATIVE NEUROLOGY.

median and ventral portion of the system passes ventrad to
the cephalic part of the lobus infundibuli. Between these
are a few bundles of non-medullated fibres of the same char-
acter as those which come from the olfactory lobe and cross
in the commissure. It may be suggested that the bundle in
question is the direct continuation of the tract from the olfac-
tory lobe. In the path of both these tracts there are fusiform
nerve cells whose processes extend in the direction of the
fibres. It is very probable that such cells interrupt some of
the fibres. The above system is the chief connection between
the prosencephalon and caudal parts of the brain.”

The course of the tenia thalami is the same as usual,
though it cannot be traced into the prosencephalon, probably
because of its reduced dorsal walls.

Goronowitsch sums up his views upon the prosencephalon
as follows:

‘¢The cephalic ventrally arched end of the embryonic
nerve tube, which, according to Gotte, forms the primitive
prosencephalon, is to be regarded as the most primitive phy-
letic condition of the prosencephalon which ontogony sug-
gests. The primitive prosencephalon is homodynomous with
a segment of the spinal cord. By the growth of the dorsal
surface of the primitive prosencephalon arose the discrete
central organ of smell, while the lobus infundibuli is the
result of a protrusion from its base. The formation of the
olfactory centre led to the development of the prechordal
portion of the skull. The architecture of the cranium of the
most primitive of the Gnathostomata, the Notidaide, corre-
sponds to that of the brain. The gradual development of the
organ of smell gave rise to the rhinencephalon of recent
Selachii. This still indifferent organ exhibits no special
homologies with the diencephalon and prosencephalon of
higher vertebrates. It is closely connected with the lobus
infundibuli, which is reduced in higher vertebrates.

‘*On one hand, the reduced form of rhinencephalon of

Ganoids and Teleosts is derived from the rhinencephalon of

Herrick, Morphology of Nervous System. ay

Selachii, which, on the other hand, gives rise to the structure
of the prosencephalon in Dipnoii, Amphibia, and Reptilia.
It is among these forms that the first indications of the origin
of the prosencephalon of higher vertebrates may be sought.
The first step toward the higher organization consists in the
reduction of the lobus inftndibuli and a transformation of
the tracts connecting with the caudal parts of the nervous
system. The development of the thalami and the reduction
of the lobus infundibuli alters the development process of the
neural tube in higher vertebrates from the earliest stages on.
There appears a diencephalic and a secondary fore-brain, the
former having an entirely different significance from the
posterior part of the prosencephalon of fishes, for it is the
result of accelerated development of a certain dorsal portion
of the neural tube which remains undeveloped in fishes.
With the gradual development of the thalami and alteration
of the rhinencephalon of Selachii, there gradually arise the
tegmentum cruris and the pes pedunculi of higher verte-
brates.

“©The Thalamus.—The lateral walls of the lobus infun-
dibuli form two round, lateral projections, the lobi inferiores,
containing a considerable cavity. The posterior part of the
lobe extends into a membranous sac, the so-called saccus
vasculosus. Ventrad, the lobe connects with the bilobed
hypophysis.

‘¢The walls of the lobus infundibuli consist of finely-
granular stroma, staining pink with carmine, resembling
that of the peripheral portion of the cerebellum. In the
peripheral portion this stroma is compact, and it requires
high powers to make out a fine fibrous structure parallel to
the surface. Two fibre systems are more obvious entad.
The fibres of the first run parallel to the surface, those of the
second radial to the surface. The latter spring from a layer
of tissue clothing the inner surface. This layer is composed
of a few series of round cells, much resembling those of the
granular layer of the cerebellum. They are, however, some-

158 JouRNAL OF COMPARATIVE NEUROLOGY.

what larger than the latter, and the dark protoplasm mass
surrounding the round nucleus of these cells is more highly
developed. It is possible to trace the processes of these cells
into the fibres of the radial system. In the fibrous zone
round cells are scattered, as well as rod-like cells of the
neuroglia.

‘¢In the ventral portion of the cleft-like canal connecting
the lobus infundibuli with the mesencephalic ventricle a
ganglionic body composed of large cells occupies either side.
Out of these ganglia springs a tract of non-medullated fibres
which, passing caudad, subdivides, part of the fibres passing
to the caudal part of the lobus infundibuli, and part to the
dorsal portion of the sacculus vasculosus. Associated with
this system is a rather large bundle of non-medullated fibres
derived from a small cluster of nerve cells lying dorsad to
the above-mentioned ganglion and ventrad to Meynert’s
bundle, immediately beneath the epithelium. The ventral
portion of the caudal wall of the lobus passes into the thin
epithelial wall of the saccus vasculosus, a part of the fibrous
layer entering it. The saccus itself is a broad, very vascular,
. folded sac, clothed within by a peculiarly modified epithe-
lum.

‘“The discoidal hypfophysis consists of two completely
distinct parts. The caudal portion is composed of three or
four lobes, into each of which passes a thick bundle of non-
medullated fibres, which pass to the ventral portion and sub-
divide in the several sacculi. The sacculi of the cephalic
portion are covered, like the former, with multilamellate epi-
thelium with fusiform cells, but no nerve fibres are present.
The interstitial substance is connective tissue only. A thin
layer of epithelium connects the two portions.

‘“* The ganglion habenule.—Cephalad to the ganglion inter-
pedunculare and ventrad to the transverse fibres of the com-
missura ansulate, there are two longitudinal bundles, which
could be followed caudad only to the interpeduncular ganglia.

These are Meynert’s bundles, the right being much stronger

Herrick, Morphology of Nervous System. 159

than the left. The bundles pass cephalad and mesad to the
fibres of the oculo-motor, and gradually pass dorsad, and :at
the point of communication of the ventricle of the lobus
infundibuli with the mesencephalic ventricle they lie adja-
cent to the epithelium. These bundles terminate cephalad
to the anterior commissure in the ganglion habenule.

‘*The ganglion habenule is but slightly different from
that of the teleosts, except for the pronounced asymmetry,
which is responsible for the unequal development of Mey-
nert’s bundles. Each ganglion consists of a central collection
of granular substance, which in cross-sections appears fibrous
at the periphery. The fibres converge to the median surface
of the ganglion and form a commissure uniting the ganglia.
The central substance is surrounded by several layers of
granular cells, which greatly resemble those of the lobus
infundibuli. The plasmatic body surrounding the large
round nucleus is more highly developed, and its produced
poles are radial to the surface. These cells send their pro-
cesses into the central substance, even to the middle of the
ganglion. The dorsal surface of the ganglion has a thinner
layer of granular tissue than the ventral, which is separated
from the central substance by a layer of longitudinal fibres.
The chief portion of these fibres belongs to Meynert’s bundle;
the smaller portion collects from the ventral portions of the
brain walls. The radial fibre systems which spring from the
granular cells of the ventral layer are divided into small
bundles by the fibres just described. In the feebly developed
left ganglion the ventral granular cells lie directly upon the
central substance. The fibres of Meynert’s bundle, as well
as the fibres of the ventral part of the brain walls, are dis-
persed in the central tissue of the left ganglion.”

Lateral ventricles.—The lateral ventricles are not absent,
as Wilder supposed, nor are they merged in the olfactory
ventricles, as stated by others.(') Fig.1, Plate XI, taken at a

1 SANDERS, op. cit., p. 768: ‘‘The cerebral lobes homologize the corpora striata,

160 JouRNAL oF CoMPARATIVE NEUROLOGY.

point in front of the foramen of Monro in the sturgeon brain,
shows that a cavity clothed by tela choridea (or pallium)
extends cephalad along the dorso-mesal surface of each olfac-
tory lobe. This cavity is of great morphological importance;
part of its walls are modified to form a plexus, and it comes
into direct communication with the aula. The surface of the
lobe bordering is, like other ventricular surfaces, covered
with epithelium. The cellular structure is also unlike that
of the remainder of the lobe. It seems unqestionable that
this space is homologous with the cavity of the lateral ven-
tricle, which is not roofed over with nervous matter, but has
merely the tela or pallium. These two ventricles become con-
fluent cephalad to the openings of the olfactory lobes, but a
partial division, by a depending loop corresponding to the
dorso-mesal walls of the mantle, may be traced back of that
point. From the ventral extension of these median walls
two arms, forming with them an irregular inverted Y, pass
laterad nearly to the ectal thickened walls of the hemisphere,
shutting off a median aula from the lateral ventricles, with
which the former is connected by large porte. It is from
the ventricles thus bounded, and not from the median cham-
ber, that the olfactory aqueduct springs.

The development of nervous matter in the cerebrum
is greater relatively in the gars, therefore the membranous
portion of the mantle is greater in Scaphirhynchus. In Lepi-
dosteus the ventricle gives off two spurs in the median por-
tion delimiting a body somewhat resembling the corpus len-
ticulare of the striatum. The posterior cornu sweeps back
of the crura and then circumscribes the ventral and ectal
portions of the cerebrum, finally meeting the dorsal exten-
sion of the ventricle, enclosing a large occipito-basal lobe
much as in reptilia. The extent of the ventricle may be most

combined with the hemispheres of the brain; and although I have not discovered in the
species examined by me the ventricles in those bodies described by Wilder, yet I do not
doubt that in other species they may exist.”

Herrick, Aorphology of Nervous System. 161

easily recognized by the epithelial covering of the axial lobe
where it is present.

The conversion of the free portion of the mantle to a
functionless membrane is carried to its extreme in fishes, but
birds furnish many resemblances.

The cerebrum is more highly developed in Lepidosteus.
Cephalad, it projects beyond the olfactory, and appears in
transection as two independent bodies dorsad to the olfactory
lobes. Plate XIII, Fig. 1, illustrates a section through the
olfactory and extreme cephalic part of the lateral ventricle,
which is bounded only by the pallium. The relations are
essentially the same in all ganoids. Fig. 2, which passes
through the corpus callosum, shows the relation between the
olfactory aqueducts and lateral ventricle. The real homo-
logues of the foramina of Monro are considerable slits. In
the sturgeon, as may be gathered from Plate XI, Fig. 2, the
relations are similar, but the partial eversion of the hemi-
spheres laterally brings the opening of the aqueduct of the
olfactory lobes farther laterad.

In the figure, because of some distortion in the section,
the median walls of the ventricles have been rendered
asymmetrical, and the openings of the foramina of Monro
appear too large.

In Fig. 3, of the same plate, the median walls are
occupied by the plexus, which is shaded dark.

The middle portion of the hemispheres are somewhat
quadrangular in transection (Plate XIII, Fig. 3). Cephalad,
the dorsal portion projects laterally considerably, while
further caudad the lateral aspects are nearly perpendicular.
The two hemispheres become separate at the chiasm, the
connection being formed by a portion of the velum, united
with the cephalo-lateral aspects of the habenz.

Respecting the dorsal sac, Lepidosteus affords much clearer
information than the sturgeon, and renders necessary a con-
siderable change in the interpretation of this structure,
offered by Goronowitsch. Morphologically it is a dorsal

162 JOURNAL OF COMPARATIVE NEUROLOGY.

pouch of the diatella, such as may be detected in all reptiles
in which the epiphysis is strongly developed. The asym-
metry upon which Goronowitsch lays so much stress is slight,
and more apparent than real. The fact that it extends so far
cephalad between the hemispheres, is an incident to the
cephalad projection of the epiphysis. It may be useful to
first study the structure of the latter.

The epiphysis springs from the most caudal portion of the
recessus pinealis, which is clothed, as usual, with very large
and dense epithelium, very different from that of the adjacent
parts of the third ventricle. There seems to be a perforation
passing obliquely dorso-caudad, forming the communication
between the cavity of the epiphysis and the recessus. The
epiphysis itself is tubular, and arches rapidly caudad to a
point over the tectum, then curving more rapidly cephalad,
between the hemispheres, is slung, as it were, in the
membrane connecting them. The structure is like that of
reptiles, varying much in different localities by the greater
or less development of certain elements. In characteristic
portions, there is, first, the wall of connective tissue; seated
upon this are slender cells, fibrous in character, which
support small granular nuclei in several series, and centrally
a larger nucleus beyond which the cell extends as a long
narrow flagellum projecting into the cavity. The appearance
is as though the single stalk supports nuclei of both sorts,
though this may be an illusion. Nerve fibres may be followed
in the spaces between the cell bases, extending in the direc-
tion of the axis of the organ, and passing into the larger
nuclei. There can be no doubt of the nervous character of
the organ.

A blood sinus closely invests the epiphysis, outside of
which is a second investment from the dorsal sac which
projects caudad to ensheath it. The walls of the dorsal sac
consist of a single-layered epithelium with long cilia or
flagella projecting into the lumen. Numerous plexiform
diverticles also project into the cavity. The fibres from the

~~

Herrick, Morphology of Nervous System. 163

epiphysis were traced, with apparent certainty to the supra-
commissura.

Cephalad to the habenulz, as well as immediately above
them, the dorsal sac communicates with the third ventricle,
the lateral ventricles being entirely distinct. Slightly further
cephalad the dorsal sac, is shut off from a median portion
which must be considered as homologous with the aula.
Into this median portion the cavities of the lateral ventricles
open, as usual, the only difference being that the aula is
more elongated than usual, and the porte are correspondingly
enlarged. It has sufficiently appeared from the above that
the dorsal sac is not a portion of the cavity of the pros-
encephalon, but of the diencephalon. It is not a new struc-
ture, but one found in reptilia as well, and pertains to the
epiphysis.

In Scaphirhynchus the relations are essentially the same,
though the plexiform development along the median wall is
much greater, and the epiphysis is scarcely as large. The
caudal portion of the dorsal sac is smaller, and an irregu-
larity is introduced by the greater size of the right habena.

The less retro-development of the hemisphere may ex-
plain why the epiphysis is not arched so far caudad as in
Lepidosteus.

Serious exception must be taken to the use of the term
‘¢falx”? for the median projection of the pallium or dorsal
roof of the cerebrum. ‘There can be no reason for rejecting
the homology between the membranous roof of the cerebrum
in fishes and the mantle part of the cerebrum. ‘The extent to
which cellular elements develop in the walls of the embryonic
nerve tube varies within the broadest limits. The birds have
a great reduction in the cellular mantle structures. The
median portion of the pallium must be homologous with the
median or interventricular portion of the mantle in other
vertebrates. The portion of the investing membranes, which
is associated with this fold, must represent the falx.

Histology of the Brain of Lepidosteus and Scaphirhyn-

164 JoURNAL OF COMPARATIVE NEUROLOGY.

chus.—In Scaphirhynchus the o/factory lobes are ovoid tuber-
osities upon the cephalo-lateral aspects of the hemispheres,
with their longer diameter in the axes of the strongly divari-
_cated olfactory nerves (Plate XI, Fig. 15). Cephalad, they
are completely closed, and a considerable ventricle occupies
the centre (Fig. 1, Plate XI). Caudad, where they pass into
the cerebrum, they stand in communication with the hemi-
spheres, and are roofed over only by the thin pallium or
dorsal lamina of the cerebrum.

The histological structure is similar to that in reptiles,
save that the specific cells are relatively more elongate and
more sparingly distributed, nowhere forming a connected
layer. The glomerulary layer is highly developed, and there
is a noticeable absence of the Deiter corpuscles, so usual an
accompaniment of the glomerules.. The neuroglia layer,
between the glomerules and the inner granular zone, is wide,
and contains few very irregular elongated cells with large,
pale, round nuclei.

These cells are of the most various forms, often having a
long, apical process, and two or more basal processes, but
the relations may be reversed. Frequently these cells are
seen between the massed glomerules, occupying the irregular
interspaces. There are also cells of irregular shapes and
more deeply stained, which are scattered among the above.
These are, perhaps, to be compared with the rhinomorphic
cells elsewhere referred to. The granular zone is well
developed. The epithelium is many-layed.

In sections of Scaphirhynchus caudad to the point where
the olfactory opens into the lateral ventricle (Plate XI, Fig.
3), there is a rapid eversion of the hemisphere, causing the
olfactory portion to be carried ventrad and laterad. <A small
groove separates a projection which is adjacent to the
olfactory from the basal portion of the hemisphere (see right
side of the figure quoted). This may be called the ala, and it
contains concentrically arranged cells. The segment of the

cerebrum remains distinct in structure from the basal portion.

Herrick, Morphology of Nervous System. 165

The olfactory structure comes soon to he entirely ventrad to
the ala and then disappears.

In Lefpidosteus the relations of the olfactory to the cerebrum
are quite different (compare Plate XIII). Here the olfactory
lobes extend in the same vertical plane as the cerebrum, but
are obliquely applied to the ventral aspect of the hemi-
speres, extending well toward the chiasm. The glomerulary
structure extends far back, especially mesad, but is overarched
laterad by a densely cellular descending portion from the
dorsal region of the cerebrum. From this ectal layer fibres
appear to converge to the callosum (Fig. 2, Plate XIII).

At about the level of the callosum the lateral aspects of
the olfactory lobes, beneath the cortical invasion above
mentioned, there accumulates a large cluster of olfactory
cells which may be traced caudad some distance beyond the
olfactory ventricle.

It will be convenient to begin the study of the cerebrum
by reference to the structure of a section cephalad to the
chiasm and caudad to the olfactory.

The transection at this point is somewhat quadrangular,
being broadest dorsad. The hemispheres may each be
divided, for convenience, into a basal and a lateral portion.
The two hemispheres are connected by a small intermediate
portion which must be regarded as morphologically equiva-
lent to the lamina terminalis, and consequently the cephalic
portion of the thalamus.

The portion of the ventricle adjacent to this thalamus
segment differs in the appearance of its epithelial lining
from the lateral ventricle. The median walls of the pallium
descend to near this level

The cellular structure of this segment is also unlike that
of the cerebrum, consisting of small, clear nuclei with
granular contents and pale body, which can rarely be made
out in these preparations.

The basal portion of each hemisphere contains a circular

nidulus consisting of the cells which form the caudad con-

166 JOURNAL OF COMPARATIVE NEUROLOGY.

tinuation of the cell cluster which envelops the olfactory.
The centre of the nidulus is filled with non-medullated fibres
and afew small cells. The cortical portion is composed of
densely clustered fusiform cells with round, clear nuclei.
These cells are less than half the size of those which occupy
the centre of the lateral portions. The lateral and ventral
part of the basal portion is occupied by a broad band of
neuroglia, with numerous non-medulated fibres passing
apparently toward the anterior commissure.

The lateral portion of the hemispheres’consists of a more
or less quadrangular segment, bordered dorsad and mesad by
the ventricle; laterad it forms the wall of the brain, and
ventrad it is in direct contact with the basal portion just
described. From this portion it is separated laterad by a fibre
tract which, in transverse section arches ventrad from the
lateral surface to the nidulus of the basal portion. Ventrad
to it and apparently associated with it is the system of con-
centric fibres, already described upon the periphery of the
basal portion. Dorsad, this tract may be traced along the
entire lateral periphery of the lateral lobe. Immediately
dorsad and mesad from the tract there are a number of small,
dark pyramidal cells, with their long axes toward the peri-
phery. Similar cells are crowded at the dorso-lateral angles.
The entire dorsal and mesal portion of this part of the
cerebrum is filled with from six to ten irregularly concentric
series of fusiform cells. These are of moderate size, and are
characterized by the circular, clear and granular nuclei, and
by the pale protoplasm of the body, which varies greatly.
Often the form is flask-shaped, with one strong process
peripherad, and several from the blunt end extending toward
the ventricle. Along the median portion of the ventricle the
number of rows is reduced, and the character of the cells
changes. Here the cells are much larger and more multipolar
in form, still preserving the same general character otherwise.

It is obvious that it is this region which proliferates the
large wzsthesodic cells of the central portion of this region

ot) Ge! eel

Herrick, Aorphology of Nervous System. 167

of the cerebrum. These latter are the largest and most
characteristic cells of the cerebrum, being fusiform or multi-
polar in outline. Without attempting any special hom-
ologies of the regions indicated with the lobes already
described in the cerebrum of reptiles, it becomes at once
obvious that there is a great similarity in the disposition of
cellular elements. The cephalo-lateral aspects contain pyram-
idal cells, the ventro-median fusiform, while the interior of
the axial lobe contains a paraxial esthesodic variety. It
would appear, then, that regions corresponding to the
parietal lobes of Sauropsida exist in fish brains. That these
regions of pyramidal cells are motor, is farther indicated by
the strong tract arising in this neighborhood.

Caudad to the section just described the thalamus expands,
and a pouch of the third ventricle is formed above the chiasm
with its opening caudad. At the chiasm the ventral walls of
this supra-chiasmic fossa are driven laterad and become filled,
next the ventricle, with densely-packed cells. In passing
caudad the basal portion of the cerebrum gradually becomes
more distinct, until it attains a measure of independence and
is finally overarched by a diverticle from the lateral ventricle.

By reason of its connection with the olfactory, and its
position, this lobe may be compared in a general way with
the hippocampus.

The caudal portion of the lateral lobe is circumscribed
by a diverticle of the ventricle, and becomes completely
homologous with the occipito-basal lobe of reptiles.

Commissures of the Cerebrum.—The exact equivalence of
the commissures of the cerebrum is a matter of much diff-
culty in these fishes where the whole dorsal and median por-
tion of the tectum cerebri or mantle portion is apparently
represented by the pallium cerebri. Considering, however,
that the direction in which the cerebrum has. been differ-
entiated in higher animals is caudad, and that, in the lower
brains, bodies which lie caudad or dorsad in higher verte-

brates must be sought dorsad or cephalad, it is not difficult to

168 JOURNAL OF COMPARATIVE NEUROLOGY.

homologize the pallium with the plexus-bearing projection
from the posterior and mesal margin of the mantle. Since
the plexus in this case occupies the vertex, instead of pro-
jecting from the caudal region, all structures morphologically
‘cephalad to the plexus must be sought still further cephalad
or ventrad. Using this clue, and observing that the cerebral
cortex folds ventrad over the olfactory structure, we think
we find a homologue of the calloso-hippocampal commissure
connecting the two halves of the cerebrum cephalad to the
openings of the olfactory crura into the common ventricle,
and lying just entad to the membranous lamina terminalis
(Fig. 2, Plate XIII). The bundle is very small and seems
to contain a few fibres from the olfactory regions, as well as
others from the cephalic portions of the cerebrum. No in
dication of the callosum was seen in Scaphirhynchus.(')

Regarding the azterior commissure there can scarcely be
a mistake, as it is a very strong though disperse band of
fibres lying in the ventral fused portion of the cerebrum
cephalad to the chiasm and cephalo-dorsad to the supra-
chiasmic fossa of the third ventricle, and thus well in front
of the crura cerebri. This commissure has been generally
recognized by later writers, while the callosum seems to
have been overlooked. See above for description of the an-
terior commissure (C. interlobularis) by Goronowitsch.

Tracts from the Prosencephalon.—We are unable to agree
with Goronowitsch in his remarks upon the thalamus and the
tracts connecting it with the cerebrum. So far from the
pedunculi being absent in ganoids, the gars at least have the
tracts as highly developed as could be expected where
the gray matter is in so relatively small amount.

The motor tracts which accumulate along the lateral
aspects of the prosencephalon collect, as already described,
to form curved tracts dorsad to the basal lobe (homologous

1 Hott, |. c., mentions what he calls an olfactory commissure in the herring, which
may prove to be the same structure as that above described. He does not appear
to have thought it possible to homologize it with the callosum,

Herrick, Morphology of Nervous System. 169

with the postrhinal lobe of mammals), thence crossing in the
anterior commissure precisely as in the opossum. The tracts
then lie on either side the ventricle. The supra-chiasmic
fossa of the third ventricle fuses with the main portion of
the ventricle a short distance caudad to the pracommissura.
At that point and for some distance caudad these motor
bundles lie in the central regions of the thalamus near the
ventricles.

A large number of sensory fibres accumulate in the
lateral aspects of the basal lobes and with the olfactory fibres
pass into intimate relations with a dense granular nidulus.
Apparently receiving numerous fibres from the hippocampus
portion of the occipito-basal lobe, which also has a strong
tract connecting with the cephalic part of the hemisphere,
this compound sensory tract passes, without crossing, into the
lateral regions of the thalamus and, passing in the opposite
direction from, but nearly parallel to the optic tract, reaches
a ventral portion of the thalamus in the cephalic part of the
infundibular region. A part of the sensory fibres turn laterad
beneath the corpus geniculatum and enter the hypoarium.
The motor tracts continue in the central portion of the.
thalamus.

A special tract comparable with the fornix was not
observed, though some of the fibres passing to the hypoaria
might be compared with it. The tract of dark fibres passing
from the median part of the infundibular lobe and the dorso-
median portion of the hyporaria to niduli beneath Meynert’s
bundle might be likened to the bundle of Vicq d’Azyr.

The Gray Matter of the Thalamus.—The thalamus ex-
tends somewhat cephalad to the anterior commissure and
beneath the latter in the walls of the supra-chiasmic fossa.
The cells here are in several series near the ventricle and are
of the usual fusiform sort. The peduncles with both sensory
and motor tracts pass into the thalamus at its latero-dorsal
aspects. Immediately caudad to the point where the pedun-
cular connection ceases, a small nidulus of rather large, pale

170 JOURNAL OF COMPARATIVE NEUROLOGY.

cells makes its appearance, apparently connected with the
sensory bundle. It is bounded laterad by the optic tracts
and dorsad by the tenia thalami.

Immediately caudad to the chiasm the large corpus gent-
culatum appears upon the ventro-lateral aspects of the thala-
mus and occupies a position ventrad to the optic tracts for
their whole length. The cells are irregularly scattered and
of the fusiform variety.

Somewhat further caudad there appears a peculiar cluster
of deeply staining cells ventrad to the geniculatum. The
cells of this nidulus are extremely irregular and quite large,
with long branching processes, and they are arranged in no
definite direction, yet the apical processes are chiefly turned
from the periphery. A part of the cells lying.massed near
the surface have a rather fusiform character and seem to con-
stitute a distinct portion. This nidulus may be designated
as the nidulus precinereus, although its homology with the
anterior nidulus of the cinereum of mammals remains to be
proven. A very similar cluster of cells occurs in reptiles
near the crura, as also in the opossum.

The habena is imperfectly divided into two parts, a
ventro-median portion, with smaller cells, giving rise to
Meynert’s bundle, and a cephalo-dorsal and ectal portion, of
larger cells, giving rise to the tenia. The right habena is
somewhat larger and is apparently chiefly associated with
the fibres of the epiphysis.

The hyfoaria, or lateral lobes of the cinereum, are less
highly developed in Lepidosteus than in the sturgeon. They
arise caudad to the chiasm as‘tuberosities of the lateral wall
of the infundibulum dorsad to the ventral nidulus of large
cells above mentioned. A diverticle of the infundibulum
enters them, and this cavity expands to a spheroidal cavity.
The cell structure is similar to that of the tuber. In Lepidos-
teus they extend much farther caudad, so as to reach the
exit of the third nerve. A rather strong tract enters the
caudo-mesad portion where it is becoming separated from the

Herrick, Morphology of Nervous System. 171

thalamus and passes toward the tract of the third nerve,
passing Meynert’s bundle, and apparently unites with fibres
passing toward the cerebrum. If these fibres be compared
with the fornix tract, they might seem to warrant the
suggested homology of the hypoaria with the mammillaria.
This seems the more reasonable inasmuch as there seems
to be a homologue of the corpus geniculatum dorsad
to them.

The third ventricle varies somewhat from the form found
in Acipenser. In the region of the infundibulum it is a long
slit, opening above into the dorsal sac and connecting by
a narrow triangular opening dorsad with the cephalic section
of the ventricle. Ventrad, there is a short cephalad
diverticle, so that transections in front of the habenz present
the appearance of having the two halves connected by a soft
commissure. After passing for a short distance cephalad, the
ventricle again passes to the ventral surface and extends for-
ward into the supra-chiasmic fossa. It would appear that
all that would be necessary to produce a real soft commissure
would be the opening of a communication between the ven-
tral portion of the two segments of the third ventricle.
Caudad, the ventricle gives rise to the ventro-median ventricle
of the saccus vasculosus and two lateral ventricles of the
hy poaria.

The third and fourth nerves have the usual relations,
though somewhat complicated by the inward growth of the
cerebellum. In the sturgeon (Plate XI, Fig. 7) the third
nerve can be traced, from its nidulus near the floor of the
aqueduct not far from the median line, ventrad to its exit,
from which point it passes laterad. In Lepidosteus it pursues
a more curved course and emerges in the space between the
hypoaria and dorsad to the overlapping part of the cinereum,
thence arching caudo-laterad about the neck of the hypoaria,
and turning cephalad, it occupies a small groove in the lateral
aspect of the thalamus dorsad to the hypoarium.

The fourth nerve crosses in the valve and escapes in the

172 JourRNAL or CoMPARATIVE NEUROLOGY.

groove behind the optic lobes, following the usual course
thereafter.

The offic tracts may be traced caudo-dorsad along the
thalamus to the mesencephalon, where they divide into a
median and a lateral portion. These are doubtless continu-
ous superficially, but are separated in the plane of the section
by the corpus opticum, as in birds.

The posterior commissure occupies the usual position. It
is over-arched by the cephalad projection of the optic lobes
(see Plate XIII, Fig. 5) in which the Sylvian commissure
occupies the usual position. The relations are somewhal ob-
scured in Scaphirhynchus.

The Jodi oftici are very large and resemble those of rep-
tiles in nearly every respect. Very large ventricles occupy
their centres, and where these are confluent (Fig. 9) there is
a curious pendant body on either side of the median line due
to a lateral diversion of the median walls of the tecta, below
their union with each other. This body, originally called
fornix by Carus, may perhaps retain the name suggested by
Fritsch, torus longitudinalis, since it is free from the false
homology involved in the other. The structure of this body
is very simple, consisting of dense clusters of small cells like
Deiter’s corpuscles.

The surface of the tectum (1) is clothed with a very
thick neuroglia layer, beneath which (2) is a rather narrow
uniform band of the superficial optic fibres. Within this (3)
is a broad band, containing peripherally a few radially
arranged elongate pyramidal cells. Quite near the ventricle
(4) is a multiple or single series of small pale fusiform cells,
with circular nuclei and interspersed Deiter’s cells. The
ventricle is lined with the usual epithelium, (5) the fibres
from which radiate to the surface of the tectum, bearing, as
in reptiles, distinct inoblastic nuclei. The above are the
primary divisions of the tectum, but are susceptible of
farther subdivision on the basis of the course pursued by the

nerve fibres in each. Just ectad to the zone of small cells

Herrick, JJorphology of Nervous System. ype

(4) is a tract of nerve fibres passing to the ‘‘ crura of the
optic lobes” or ental optic tract. The outer part of (3)
might be divided in the same way. For a description of the
minute structure of the tectum in teleosts, see Sanders.(')
Bloodvessels are very numerous, indicating a high degree of
activity in this region. The necessary regenerative or nutri-
tive cells seem to be collected in the tori.

From the base of each optic ventricle there is a projec-
tion which has been called torus semicircularis. Sanders
says:(°) ‘* The tori semicirculares may be considered as the
anterior termination of the medulla oblongata; they are
tuberosities of a more or less semicircular shape, which pro-
ject into the floor of the ventricle of the optic lobe; they are
principally composed of grey matter, through which the
bundles of the crura lobi optici pass on their way to the in-
ternal surface of the tectum.” To this it is to be said
that these lobes must be regarded as an inherent part of the
mesencephalon, being provided with a slightly modified ven-
tral accumulation of the cell-layer constituting the fourth of
the above-mentioned layers of the tectum. The structures .
are those already familiar in reptiles, and called (rather un-
fortunately) by Rab] Ruckhard the cod/icudz.(*)

The roof of the aqueduct is thickened and thrust far for-
ward under the optic lobes, or better, the optic lobes are
thrust so far caudad that they over-arch the valve of Vieus-
sens or valvula cerebelli. The presence in this body of the
decussation of the fourth nerve is sufficient proof of the cor-
rectness of the homology.

In the sturgeon the relations are greatly disguised by the
forward protrusion of the great medio-cephalic lobe of the
cerebellum within the common ventricle of the optic lobes.

Tee Crp a7 cs

Beles Gese De 754s

3 SANDERS, op, cit., p, 768, ‘‘the torus semicircularis I would, with some doubt, refer
to the corpus geniculatum externum.” Fritsch regarded the deeper part of this body as
the corpus quadrigeminum and the superficial part as the thalamus.

174 JouRNAL oF CoMPARATIVE NEUROLOGY.

The valve thus becomes restricted and the cephalic lobe of
the cerebellum is rolled upon itself (Plate XI, Figs. 7, §).
One result of this modification is the great distension of the
- optic ventricle and commensurate thinning of the tectum pos-
teriorly. The colliculi are also reduced in size thereby.

In Lepidosteus the adhesion of the valve dorsally upon a
forward tongue of cerebellum ventrad is considerable, but in
Accipenser the ventral (cerebellar) portion is pushed for-
ward and rolls cephalo-dorsad, fairly filling the cavity. The
structure of this body, which may be called volvula cerebelli
or volvula, is identical with that of the cerebellum proper.

The Cerebcllum.—In the development of the cerebellum
we have the most characteristic feature in the brain of the
ganoid fishes and, at the same time, the peculiar modifi-
cations of the theme express the generic variations most dis-
tinctly. In the gars, where the whole brain is quite reptilian,
the cerebellum is highly developed superficially, while in the
sturgeon only a relatively small part is exposed, the
remainder being packed in the cavity of the mesencephalon
and the laterally enlarged fourth ventricle. In Lepidosteus
the cerebellum may be divided into the following parts:
first, a cephalad invasion of the mesencephalic cavity, more
or less closely associated with the valve, constituting the vod-
vula as above described; second, the median lobe or vermz-
form lobe, third, two dateral lobes; fourth, a posterior pouch
or bursa.

As a whole, and excepting the volvula, the cerebellum
resembles that of the alligator. The vermiform process is
moderately convoluted, so that in longitudinal section there
is anteriorly a caudad invagination, then a cephalad projec-
tion carrying a part of the ventricle forward as an anterior
recess lying dorsad to the pocket formed from without, due
to the invagination or concrescence above-mentioned. The
main cavity of the vermiform lobe is pentagonal in transec-
tion, giving off diverticles into the cayities of the lateral
lobes.

Herrick, Morphology of Nervous System. 175

The lateral lobes in a median transection of the cere-
bellum form two large projections laterad, somewhat more
than half as large as the vermiform process dorsad, and about
half as large as the medulla ventrad to it. At this point the
recessus lateralis of either side (not to be confounded with
the ventricle of the lateral lobes) makes its appearance, be-
ing closed with the usual velum or protrusion of the endyma.
This membranous sac is small as compared to the develop-
ment in the sturgeon (Plate XI, Fig. ro).

In Scaphirhynchus the volvula is enormously developed
and thrust far forward, completely obscuring the valve. Ap-
pearing first as a pentagonal projection from the inner
(dorsal) surface of the (inverted) valve, it goes on increas-
ing cephalad, till, rolling ventrad, it folds upon itself, turns
caudad, carrying its median protuberance upon its (now
ventral) surface, and passing somewhat dorsad to connect
with the vermiform lobe. The central portion consists of
white matter filled with enormous and beautiful branching
Purkinje’s cells, the lateral portions containing the Deiter’s
corpuscles. There is no bursa nor distinct cephalad
diverticle, as in Lepidosteus, but the vermiform lobe remains
a solid mass with its white matter mesad and dorsad and its
granular layer laterad and ventrad to the end (Fig. 11,
Plate X1).

The lateral lobes are enormous and contain small ven-
tricles. Caudad, the dorsal portion is separated by the forma-
tion of the large recessus lateralis (Fig. 10, Plate XI) and
becomes a wing-like expasion of the vermiforme. The ven-
tral portion adheres to the latero-dorsal margin of the fourth
ventricle, retaining its characteristic structure far caudad.
Cephalad, the lateral lobes are perforated by several nerve
roots as beyond (Fig. 9, Plate XI).

I am glad to acknowledge the kind assistance of Pror. H. F. Osborn in securing
necessary literature for this article.—C. L. H.

176 JOURNAL OF COMPARATIVE NEUROLOGY.

PARTIAL LIST OF WORKS RELATING TO THE CENTRAL
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TIEDEMANN,F. Deutsches Archiv f. die Physiologie, Bd. II, 1816.

Kuni, H. Beitrage zur Zoologie und vergleichenden Anatomie,
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Somme, C. S. Recherches sur l’Anatomie comp. du Cerveau, 1824.

SERRES, E.R. A. Anatomie comparée du Cerveau, 1824.

RATHKE, H. Bemerkungen u. d. inneren Bau der Pricke. Dan-
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RATHKE, H. Bemerkungen u. d. inneren Bau des Querders.
Schriften der naturforschenden Gesellschaft zu Danzig, I.

Born, G. Ueber den inneren Bau der Lamprete (Petromyzon
marinus). Heusinger’s Zeitschrift, 1, 1827.

WesBER, E.H. Meckel’s Archiv, 1827.

CuVIER ET VALENCIENNES. Histoire naturelle des Poissons, 1828.

TREVIRANUS, G. R. Ueber die hinteren Hemispharen des Gehirns
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Gittay, C. M. Descriptio Neurologica Esocis lucii. Azvnales
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ZAGORSKY. De System. Nerv. Piscium. 1833.

Barr, K. E. v. Untersuchungen tuber d. Entwickelungsgeschichte
der Fische. 1835.

BucHNER, G. Mém.sur la Systéme nerveux du Barbeau (Cyprinus
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GoTrscHE, M. C. Vergleichende Anatomie des Gehirns der
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ArSAKI, A. Commentatio de Piscium cerebro et Medulla Spinali.
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MULLER, J. Vergleichende Anatomie der Myxinoiden. 1840,

Voet, C. Embryologie des Salmones (in Hist. Naturelle des Pois-
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STANNIus, H. Peripherisches Nervensystem des Dorsch (Gadus
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STANNIUS, H. Ueber den Bau des Gehirns des Stérs. MWJudller’s
Archiv, 1843.

GIRGENSOHN, O.G. L. Anat. u. Phys. des Fischnervensystems.
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STannius,H. Das Peripherische Nervensystem der Fische. 1849.

KrLAAtTscH, H. M. A. De Cerebris Piscium, Halle. 1850.

OwsJANNIKOW, P. Disquisitiones Microscopic de Medullz spin-
alis textura in Piscibus factitate. 1854.

Herrick, Alorphology of Nervous System. 177

Ecker, A. Anatom. Beschreibung des Gehirns von Karphen-
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Mayer, F. J.C. Ueber den Bau des Gehirns der Fische. Ver-
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MAvuTHNER, L. Untersuch. u. d. Bau d. Ruckenmarks der Fische.
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MARCUSEN, JOHANN. ‘Die Familie Mormyren. Mém. del’ Acad.
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Dum_ERIL, A. Hist. Naturelle des Poissons. 1864.

SWANN, J. Illustrations of the Comparative Anatomy of the
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BAUDELOoT. Functions of the Encephalon of Fishes. Axwales des
Sciences Naturelles, 1864.

VuLpPIAN, A. Lecons sur la Physiologie générale et comparée du
Systéme nerveux. 1866.

OEFFINGER, H. Neue Untersuchungen u.d. Bau des Gehirns vom
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STieEDA, L. Studien u. das Central Nervensystems der Knochen-
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KupFFER. Beob.u. d. Entwickelung der Knochenfische. Archiv
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CLARKE, L. Researches into the Intimate Structure of the Brain.
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BAubDELoT. Etude sur l’Anatomie Comparée de l’Encephale des
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gehirns. Zeits. f. wiss. Zoologie, XXIII, 1873.

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178 JOURNAL OF COMPARATIVE NEUROLOGY.

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Herrick, JJorphology of Nervous System. 179

STEINER, J. Ueber das Centralnervensystem des Haifisches und
des Amphioxus. Jat. u. nat. wiss. Mitth. Akad., Berlin, 1886.

AUERBACH. Die Lobi Optici der Teleostei und die Vierhigel der
hoher organiz. Gehirne. Morph. Fahrbucher, XIV, 1888.

GoronowiTscH. Das Gehirn und die Cranialnerven von Aci-
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Hort, E. Observations upon the Development of the Teleostean
Brain, with Especial Reference to that of Clupea Harengi. Zoologische
Fahrbucher, 1V, 3, 1890.

VAN WiIjHE. Ueber die Mesodermsegmente und die Entwickelung
der Nerven des Selachierkopfes; und tuber das Visceralskelet und die
Nerven des Kopfes der Ganoiden und von Ceratodus. Miederlandisches
Archiv f. Zoologie, Bd. V.

NOTE TO PLATES X AND) XII.

In the previous instalment of the article entitled ‘‘ Contributions to
the Comparative Morphology of the Central Nervous System,” refer-
ence was made in several instances to plates which it was impossible to
distribute with that number. In making up the present number it
became necessary to rearrange the figures upon the plates, causing the
following changes:

Honeablate XxX. ic. (5.7 read = blate Xhihis 10.

Bor ->Plate X, Fig: 14,” read “ Plate X, Pig.o.”

Elsewhere substitute ‘‘ Plate XII” for ‘‘ Plate X.”

For<*Plate XI, Fig. 3,” read “ Plate XD Figs8.”

On pasel27, for “Tig. 7, Plate IT,” read): Plate X, Pig..6,”

IPC YAC IIS) | he

HISTOLOGY OF THE BRAIN OF THE LIZARD, SNAKE, AND
TURTLE.

Fig. 1. Purkinje’s cells from the cerebellum of the lizard.

Fig. 2. Cells from near the caudal margin of the pyriform lobe of
the black-snake.

Fig. 3. Portion of the intra-ventricular lobe of the lizard, drawn
with the aid of a one-fifteenth inch objective and camera.

Fig. 4. Cells from the caudo-lateral part of the tuber cinereum of
the black-snake, with one-fifteenth inch objective.

Fig. 5. Cells from Gasser’s ganglion.

Fig. 6. Transection of epiphysis of the lizard.

Fig. 7. Portion of the caudal part of the cerebral mantle near the
ventricle, to illustrate the nature of the neuroglia.

Fig. 8. Motor and sensory cells from frontal cortex of lizard.

Fig. 9. Structure of the pyriform lobe of lizard brain, with rhino-
morphic and proliferating sensory cells.

Fig. 10. Portion of a longitudinal section of the optic lobes of the
turtle, showing cells of fifth nidulus.

1850 JOURNAL OF COMPARATIVE NEUROLOGY.

PLATE XI.

Figs. 1-12. Transections of the brain of Scaphirhynchus.

Fig. 1. Section of the olfactory lobe. Dorsally the cephalad ex-
tension of the lateral ventricle occupies the median aspect. Laterally
the olfactory nerve fibres are emerging.

Fig. 2. Portion of transection of the anterior part of the cerebrum.
The median walls cf the ventricle are not naturally represented, partly
because of obliquity and distortion of the section. The opening of the
olfactory ventricle is into the lateral ventricle, which is connected with
a median aula by the foramina of Monro.

fig. 38. Section near the posterior margin of the olfactories, some-
what oblique, so that the right side passes through the olfactory while
the left cuts the ala alone. The ala on the right side lies dorsad to the
olfactory, and is separated from the basal portion of the cerebrum by a
fissure.

Fig. 4. Section through the superior commissure; the loop of the
membrane to the left is to be ignored. The hypoaria occupy the whole
ventro-lateral aspects.

Fig. 5. Section through the posterior commissure. AZ. b., Mey- ~
nert’s bundle.

Fig. 6. Section through the optic lobes. The ventricles of the
hypoaria are confluent.

Fig. 7. Section at the exit of the third nerves. The volvula occu-
pies the cavity of the optic lobes.

Fig. 8. Section near the anterior margin of the medulla.

Figs. 9-12. Sections farther caudad.

Fig. 13. Cells from the apparent origin of the third nerve.

Fig. 14. Cells from the cerebellum.

Fig. 15. Ventral surface of the entire brain.

AAW Ey excl:

Figs. 1-3. Portion of horizontal sections of the black-snake brain,
to show the relations of the prazcommissura, callosum, fornix, etc.
Fig. 1 lies farthest ventrad. /., fornix; 6.0.t7., occipital portion of the
precommissura; /./., parietal portion; ac’, frontal, or ‘‘ olfactory ”’
portion. Compare with Figs. 7 and 8.

Fig 4. Cells from the Gasser’s ganglion of the turtle.
Fig. 5. \ongitudinal perpendicular section through the middle of
the hemispheres of the brain of an embryo of the black-snake.

Fig. 6. Wongitudinal horizontal section of the brain of a black-
snake.

Fig. 7. Diagram to illustrate the principal tracts and niduli of the
brain of the black-snake, formed by the composition of several sections.
o.c., olfactory cortex; 7.e., that portion of the cortex lying upon the crus
olfactorii; 0, tract connecting the above with the frontal region; c.c.,

Herrick. Morphology of Nervous System. ISt

corpus callosum; ac’, ac’

, ac’, frontal, parietal and occipital portions
of precommissura; /., fornix; ¢./., tract from the tania thalami into the
thalamus.

fig. 8. Section somewhat cephalad to Fig. 9. //., habena; J/,,
nidulus Meynerti; .V., substantia nigra; B., nidulus of the substantia
nigra; P., peduncles.

Fig. 9. ‘Transection through optic lobes and infundibulum of the
lizard. c.S., commissura Sylvii; P.c., postcommissura; /., pedunculi;
op.tr., optic tracts.

Fig. 10. Median longitudinal section of an embryonic black-snake
brain, (see Fig. 5), to show the relation of the epiphysis to the habena,
membranes, and skull.

Fig. 11. Section through the cerebellum of one of the same set of
embryos near the caudal extremity, to illustrate the proliferation of
Purkinje’s cells. (Compare Fig. 14.)

Fig. 12. Section through the same brain at the base of the cere-
bellum at the exit of the trigeminal nerve.

Fig. 13. Similar section at the exit of the eighth, which, by reason
of its slight obliquity, also displays the course of the seventh nerve.

Fig. 14. A portion of a section adjacent to that of Fig. 11, at the
angle of the ventricle, illustrating, as is supposed, the proliferation of
Purkinje’s cells from cells associated with the ventricular epithelium.

Fig. 15. Pyramidal cells from the motor region of the brain of a
lizard.

IL VNIMS, DUI

Figs. 1-8. Transections through the brain of the Gar-pike, Lep/-
dosteus.

Fig. 1. Olfactory lobe. wv./., cephalad projection of the lateral
ventricle, roofed over by the velum.

Fig, 2. Transection at the callosum, c.c. v./., lateral ventricle;
m., membranous roof of the ventricle corresponding to the mantle; a./.,
axial lobe of the cerebrum; /.//., foramen of Monro; .o7., remnant of
the glomerular layer of the olfactory; x 7, olfactory nidulus beneath the
aqueduct of the olfactory.

Fig. 3. Transection back of the chiasm. A mesad protuberance
of the axial lobe corresponding to a part of the striatum is separated by
projections of the ventricle. The aula is partly confluent with the ven-
tricles. wv./., spur of the posterior cornu passing cephalad. In the con-
necting portion uniting the thalamus and hemispheres some evidence of
the tenia thalami was detected.

Fig. 4. Transection at the level of the habenz. The lateral ven-
tricles have completely circumscribed the axial lobe. c.g.e., corpus
geniculatum externum; ~, lateral nidulus of the thalamus; //y., hypo-
physis; 2.4/., nidulus Meynerti; /.4/., foramen of Monro.

fig. 5. Transection through the posterior commissure. A portion

182 JOURNAL OF COMPARATIVE NEUROLOGY.

of the epiphysis is seen above, cf. S.c., commissura Sylvii; P c., post-
commissura; J/.b., Meynert’s bundle; //a., Hypoarium.

Fig. 6. Transection at the middle of the optic lobes. ///, third
nerve in a groove between the hypoaria and lateral lobe of the thalamus.
The tori project medianly into the ventricle.

Fig. 7. Transection through the posterior part of the optic lobes.
ZV, fourth nerve; vo/., volvulus, or portion of the cerebellum thrust
into the optic ventricle.

Fig. 8. Transection through the medulla and cerebellum at the
opening of the recessus lateralis.

Figs. 9-10. Dorsal and ventral views of the entire brain of the gar.
The bi-lobed mass lying behind the cerebellum is not of a nervous
character.

EDITORIAL.

NEUROLOGY AND PSYCHOLOGY,

It is but natural that a marked transformation in externals
should awaken expectation of corresponding improvement
within. A pretentious gateway immediately creates visions
of a roomy chateau. But in our day, improvement is fre-
quently long delayed at the surface, and the elegant garments
and equipage of Mrs. Newrich afford an erroneous indication
of her mental equipment. Nor do we gain much consolation
from the knowledge that her daughters have acquired at
least the affectations of culture.

The case is somewhat so with regard to psychology. The
study of brain and nerve is recognized as the gateway of
psychology, and the enormous though heterogeneous body of
the science of neurology, which has grown up in the last
twenty years, may legitimately lead us to expect a commen-
surate advance in the inner domain. But psychology, after
long hesitating to avail itself of the help thus offered, has
apparently been able to do little more than clothe itself
in the garb and acquire the language of neurophysiology.
It may be useful to cast a glance backward and observe some
of the steps toward the recognition of physiology by psych-
ology and the consequent reinterpretation of metaphysics.(')

The first modern attempt at such a reconciliation is linked
with the name of René Descartes, who, at a time when the

1 For part of ihe material here employed I am indebted to the paper of Professor
Wilhelm Wundt, entitled ‘‘ Gehirn und Seele,”’ forming a part of his well-known volume

of popular essays. .
("I

154 JOURNAL OF COMPARATIVE NEUROLOGY.

awakened intellect surged everywhere over the weakened
ecclesiastical barriers, was content to view the struggle across
the moat of his chateau at Fraueker and to contribute to the
conflict indirectly so far as personal safety permitted.

- Ina time when the Copernican astronomy deprived man
of his commanding position at the heart of the universe, but
opened a vaster though humbler arena to his intellect, when
Gallileo was formulating the laws of motion, and when Har-
vey had awakened the hope of affording for the activities of
the body a similar mechanical explanation, it was quite
natural that the attempt should be made to discover a
mechanical explanation for the phenomena of mind.

Influenced by Baconian teaching, Descartes insists upon a
basis for speculation in observation, though his philosophical
system seems to show so little evidence of it and stands forth
in systematic completeness and logical unassailability strik-
ingly contrasted with his famous fundamental doubt.

It is evident that in his study of the relation of soul and
body, which he regarded as one of his most important
achievements, and whose effects have long outlived his philo-
sophical system, he was very largely influenced by anatom-
ical investigations. Even vivisection was employed by him,
since his conception of lower animals as soulless automata
opposed no scruples to such studies, however repugnant
to popular feeling or condemned by his church. He was
wont to point to the animals he had dissected, saying, ‘‘ here
are my books.” Science he compared to a tree; metaphysics
being the root, physics the trunk, and the most important
branches mechanics, medicine, and morals; nor is it difficult
to trace the effects of this conception in his treatment of the
body.

Proceeding upon Harvey’s discovery of the mechanics of
circulation, he taught that the friction involved in circulation
sufficed to vaporize and excite various elements in the blood.
Some of these elements pass to the reproductive organs and

behave as the forerunners of Darwin’s gemmules might be

EpiroriaL, Weurology and Psychology. 185

expected to, while others, destined to the brain, there evolve
the gaseous ‘‘animal spirits” on which nervous action de-
pends. So far as was necessary for his purposes, all ambi-
guities were cleared away and the relations between the un-
extended individual soul and the interblending currents
of animal spirits as they entered or issued from the brain
were dogmatically settled in a way refreshing to ears accus-
tomed to the guarded statements of modern observers. It
should be remembered, however, that his statements rested
upon no inconsiderable amount of medical and philosophical
authority.

That the notion that the soul, being unextended and
a unit in our consciousness, must sustain a definite relation
with the body at a single point, can be ascribed to Descartes,
as implied by Wundt, is unwarranted, yet he did extend its
currency so that even to-day, in a more or less obscure way,
it burdens all psychological speculation.

Mechanical as were the doctrines of Descartes, he never
went to the lengths of modern materialism in identifying
physical and psychical. He did not identify the ‘‘ vital
spirits” or their interplay with the soul life.

All nerves are tubes containing these spirits, and in sen-
sory nerves the agitation passes toward the brain, where in
the ventricles it is communicated to the central mass of vital
fluid therein. The currents thus produced may, under suit-
able conditions, pass out through motor nerves to the appro-
priate muscles, producing what have since been termed
reflexes.

The soul itself is lodged in the pineal body, which must
be its specific seat; because, first, it is centrally located; sec-
ond, it is the only unpaired organ of the brain; third, it is in
direct communication with the ventricles.

The soul is usually affected by the currents setting from
the body and fabricates its presentations from the impressions
thus derived, but it also impresses its own acts upon the

‘« vital fluids” giving rise to motor currents. Aimless eddys

156 JOURNAL OF COMPARATIVE NEUROLOGY.

in this fluid may issue in phantasy while there is a separate
spiritual activity to correspond to each form of motion of the
vital spirits. Emotions, for example, are the result of cur-
rents from the heart.

Ina sense the soul is, as Wundt says, superfluous in this
theory, and Descartes evidently is lead to postulate its exis-
tence to account for the unity of consciousness. He accounts
it an unnecessary luxury for lower animals which accordingly
are automata, with only the illusiory appearance of conscious-
ness. It was a step easily taken by the French metaphysi-
cians, a few years later, to apply the same principle to man
and eliminate the psychical element entirely.

Under the influence of the German metaphysicians of the
school of Wolff, for whom classification and analysis passed
for explanation, there followed a revival of a tendency which
had been frequently exhibited before to assign to various
organs the mental processes separated by their analysis.

That the brain is associated with thought was recognized
very early, and this view prevailed among the Greek physi-
cians in spite of the fact that Aristotle described the brain as
the most bloodless and inert organ of the body, designed
to regulate the temperature of the latter, much as the
condensing vapors of the sky mitigate summer heat and
drought. Pythagoras, Hippocrates, and Plato clearly recog-
nized the head as the seat of the intellect and will.

In the days of Ptolemy Soter, some attempt was made to
localize functions; Erasistratus believed that the sensory
nerves spring from the meninges, while the motor are de-
rived from the substance of the brain itself, and Herophilus
is said to have anticipated Descartes in teaching that the
vital forces reside in the ventricles. The followers of Galen
subscribed to the same view.

The Arabian physicians extended the doctrine of localiza-
tion. Albertus Magnus assigned judgment to the frontal,
imagination to the parietal, and memory to the occipital por-
tions of the brain. The notion of animal spirits within the

EpiroriaAL, Neurology and Psychology. 187

ventricles survived to some extent until the eighteenth cen-
tury. Malpighi was the first to ascribe the higher functions
to the gray matter.

Now, to return to the period following Descartes, we find
the rudiments of the theory of localization rapidly develop-
ing. Willis located memory and the will in the convolutions.
Imagination was situated in the corpus callosum, sense per-
ception in the striatum, sight in the thalamus, and involuntary
acts in the cerebellum. Lancasi placed sense perception in
the callosum, while others located memory there. Meyer
considered the cerebellum as the organ of abstraction and
located memory at the roots of the cranial nerves.

Thus the way was prepared for Gall and Spurzheim.
Though phrenology is primarily a system of psychology
rather than of physiology, its hold upon the mind of the
people is largely due to the purely empirical form in which
it was clothed. Those who were incompetent to discuss the
propriety of dividing all mental manifestations into twenty-
six or forty-three faculties fancied it a matter of mere obser-
vation to determine whether special development of various
regions of the head coincided with great preponderance of
such faculties.

Gall’s theory was based on the fallacious belief that the
skull depends for its form on the growing brain, and therefore,
its surface is a reflex of the development of the brain, and
that the size and configuration alone determine mental
power. :

What really gave phrenology its popular power was the
fact that it served to give a scientific character to certain the-
ories which survived astrology under the name physiognomy
or chiromantia. When deprived of other methods of antici-
pating the future, the people eagerly grasped at what prom-
ised to be an indirect method of accomplishing the same
thing. Many of the principles utilized by these sciences are
to-day recognized, as the effect of the environment upon the
body, the effect of habit on the mind, the effect of the mind

1858 JOURNAL OF CoMPARATIVE NEUROLOGY.

upon the body, the laws of heredity, and the effect of
acquired characters and environs of the parent upon the off-
spring. It is doubtless to the more or less skillful (often un-
conscious) utilization of the elements of truth contained
in these principles that the apparent success of phrenology
is to be ascribed.

So important did the practice of physiognomy become,
that in the time of George II. Parliament passed an act
condemning all persons pretending to skill in physiog-
nomy as rogues and vagabonds and rendering them liable
to public whipping and detention in the house of cor-
rection. Yet phrenology, with less of fact and no less of
danger, claimed the adherence of no less a thinker than
Comte, and Gall was given a nitch in the temple of Fame in
close proximity to the critical philosopher.

While the appeal to nature has produced good results,
and Gall’s efforts have led to such works as Bell’s Anatomy
of Expression and have prepared the public for better things,
it may be that they have long hindered scientific investi-
gation in this fascinating field and account for the fact, that
aside from Charles Darwin almost no capable observer has
ventured to discuss the physiology of expression.

While Florens must be honered as the pathfinder in the
experimental aspect of neurology, it must be remembered
that although he recognized the cerebrum as the seat of the
will and perception, he did not admit any direct relation to
voluntary motions and sensations, but supposed the cerebrum
to act as a whole, every part participating in every function
with which the organ was endowed.(')

Lorry, in 1760, had also suggested the non-participation
of the cerebrum in functions of sensation and motion. This
view, which was readily accepted as agreeing with psycho-
logical preconceptions, closed this field to investigation for
upwards of fifty years.

1 FLrorens. ‘‘ Recherches expérim. sur les propriétés et les fontions du systeme ner-
veux.” 1824-1842.

EpiroriaL, Veurology and Psychology. 189

The attempts which the more inquisitive or venturesome
students made to awaken activities of the cerebrum by elec-
tric stimulation proving ineffectual, the whole territory of
the cerebrum was abandoned until a fortunate accident dur-
ing the Franco-Prussian war gave the impetus to observation
and research. While operating upon a wounded brain,
Fritsch had occasion to apply the galvanic current and was
astonished to observe twitching of certain groups of muscles.
The close of the war afforded Fritsch and Hitzig opportunity
to apply the suggestion and experimentally verify the conclu-
sions reached.

It was soon seen that the opening or closing of the cur-
rent constituted the necessary stimulus, and that an intermit-
tent current might be employed in the irritation of various
parts of the cortex, with the result of invariably producing
localized muscular contractions in some regions and awaken-
ing no reaction in others. These investigators openly avowed
their belief that all psychical functions which owe their
origin to excitement of the nerves or produce such excitation
have localized areas upon the cerebral cortex.

The next step naturally was the verification of these sug-
gestions by the removal of those areas to which the various
functions were attributed. But extirpation did not at once
perform what was expected of it. Its results were often am-
biguous. Hitzig observed as a result of extirpation, loss of
muscular sense or recollection of previous motions.

Carville and Duret(') applied the term ‘‘ paralysie de la
motricité volontaire corticale” to this disturbance of function
which by some observers was considered as loss of sensation.
So Nothnagel(*) and Schiff.

Nothnagel called attention to the fact that the loss
was sooner or later made good, and a gradual restoration of
function followed. He believed that this fact militated
against the belief in exact cerebral localization.

1 Arch. de Physiologie norm. et pathol. 1875.
2 Virchow’s Archiv, Bd. 57, 1873.

190 JouRNAL OF COMPARATIVE NEUROLOGY.

Various suggestions were offered; some supposing that
the corresponding area of the opposite hemisphere might ac-
quire the function of the lost portion, others that any other
_part of the same hemisphere might substitute for it.

In 1876 appeared Ferrier’s Functions of the Brain which,
however applicable the criticism of Munk may be (‘‘roh
war operirt, roh beobachtet, roh geschlossen”’) served to
awaken interest and collected a large body of facts for subse-
quent analysis. From twenty-four experiments or so he was
able to lay off the entire cerebrum into areas whose functions
were defined in no ambiguous or doubtful manner—in strong
contrast to the methods of German investigators.

Hitzig entered this field about the same time, but was un-
able to escape from the contradictions presented by his
experiments.

Goltz brought to his aid a new method of investigation,
which was expected to control the hemorrhage which inter-
fered with extensive extirpation. The brain substance was
removed by jets of water. His observations(') led him to
believe that injury to any part of the cortex produced dis-
turbance of all the sensory and motor functions, which dis-
turbances were roughly proportional to amount of injury. In
most cases the disturbances were temporary and were con-
sidered due to inhibitory action of the injured part. He
recognized that in some cases there was actual and permanent
loss.

Prominent among those who have contributed permanent
materials to the doctrine of cerebral localization is Hermann
Munk, whose papers appeared in various periodicals from
1877 to the present time and bear evidence of unlimited
patience and critical acumen. The first of these papers(*)
contains a resumé of results obtained by extirpating circular
cortical areas fifteen mm. in diameter and two mm. thick
over the exposed portions of the brain. He concluded that a

1 GoLTz, Pfliger’s Archiv, Bd. 13-14.
2 Verhandlungen der Physiologischen Gesellschaft zu Berlin, 1876-77, No. 16.

EpiroriaL, WVeurology and Psychology. 19!

line drawn perpendicularly to the longitudinal fissure from
the sylvian fissure over the dorsal cortex limits a cephalic
motor from a caudal sensory region, and marked out the now
famous areas constituting the recollection centres of sight
and hearing, laying much stress upon the fact that there is a
gradual restoration of function in the case of vision. The
restitution, instead of being due to a vicarious substitution of
the corresponding organ of the opposite side, he ascribed to
an acquisition of new vestiges by uninjured adjacent areas of
the same hemisphere. The discrimination of disturbances of
hearing made necessary simultaneous extirpation on both
sides, an operation too severe to permit long subsequent ob-
servation for the determination of the period of restoration,
if such exists.

The second paper(') covers experiments upon atrophy or
failure to develop in the cortical areas previously located in
the case of puppies deprived of organs of vision and hearing.
The experiments were carried on in duplicate with animals of
the same litter and with ample control, giving results seem-
ing to show that early loss of the eye produces slight but no-
ticeable limitation in the development of the occipital
region, etc. These results stand in opposition to those of
Gudden, and the author admits that the macroscopic
changes are on the whole insignificant, though sufficient
in some cases to produce thickening or other modifications in
the skull.

The third communication extends the investigation to in-
clude the monkeys, the results agreeing with those derived
from the dog, except that in the monkey total extirpation of
the visual region produces hemiopia, in other words, the vis-
ual fields of the two eyes overlap and optic fibres are distrib-
uted accordingly. Moreover, he was able to locate with
more or less certainty the centres of general sensation within
the motor areas. So complete a coincidence between the

t Berliner klin. Wochenschrift, No. 35.

192 JOURNAL OF COMPARATIVE NEUROLOGY.

sensory and motor areas for special groups of muscles
seemed, to say the least, remarkable, and in the view of the
rather limited and cursory details given by Munk, it is not
-surprising that other investigators were somewhat incredu-
lous.(')

In closing the article, Munk offers a suggestion or two
upon our topic, not without interest. Sensations of innerva-
tion which accompany motion are of greatest importance in
assisting in the formation of concepts of motions of the

body. From such innervation sensations the primary con-

cepts of motor acts are derived in the young, and in case of
loss of such concepts of motor acts in the adult by injury to
the specific centres, they may be recreated from the reflex
motions.

While it may be very convenient to predicate volition
and voluntary motion as functions of the cortex, there is no
observational basis for such a localization. We simply know
that the cortex is the seat of perception and conception, and
we are only justified in assuming with Meynert that concepts
of motion are the causes of so-called voluntary motions; that
when such concepts arise from association, the motion fol-
lows eco ipso, unless in some way inhibited; and that the mo-
tion is the more extensive the greater the concept of motion
producing it. The perception of the intensity of will in
voluntary motion is an attribute of a concept of motion.

Those familiar with the recent literature of physiological
psychology will observe that these statements are somewhat
at variance with those of Wundt, etc.

In the fourth contribution(*) new evidence is added to the
same effect. The whole available surface of the cerebrum
was found to contain sensory centres, even the frontal region,
usually relegated to higher faculties, not excepted. Instead
of psycho-motor and psycho-sensory centres there are only
sensory areas. The cortex has only to do with perceptions

1 See supra p. 99.
2 Verhand. der Physiolog. Gesellsch. zu Berlin, 1878-79, Nr. 4, 5.

a ere

EpiroriaL, Meurology and Psychology. 193

and concepts which may issue in motions. In response to
the question: ‘‘ Where then, is the seat of the intellect?”
Munk replies, ‘‘ The intellect has its seat over the entire cor-
tex, for it is but the sum and result of all the concepts aris-
ing from sense-perceptions. Every lesion of the cortex im-
pairs the intelligence, the injury increasing with the extent
of the lesion.”

The fifth contribution is chiefly of interest because of the
attempt to determine areas of the occipital cortex correspond-
ing to all parts of the retina, and the discussion of causes of
partial decussation of optic fibres in animals whose visual
fields are not mutually exclusive.

In the seventh of these papers we need only notice the
single case recorded of a bilateral disease of the hippo-
campus which resulted, in all appearance, in complete loss of
the sense of smell, an observation which derives some value
from the fact that the hippocampus is about the only region
which has not been experimentally investigated, and smell
and taste and smell are the only specific sensory functions
not localized. _

At a time when Munk’s views seemed to enjoy an easy
triumph, there appeared an article by Loeb(') which con-
tained results, which, if reliable, would have undermined all
the work of Munk and his Italian colaborators, Luciani and
Tamburini, not to mention Ferrier.

He concludes, ‘‘ I have never observed a motor disturb-
ance after lesions of the occipital lobe without injury to
vision or disturbance of vision, after lesions of the parietal
lobe without motor disturbance. On the other hand, visual
disturbance was frequently encountered alone on injury to
the occipital lobe.” Injury to any part of the cortex might
produce visual disturbance. In short, we cannot tell whether
the cortex contains a specific apparatus for visual perception
or not.

1 Loes, ‘‘ Die Sehst6rungen nach Verletzung der Grosshirnrinde,” Pfliiger’s Archiv,
XXXIV. 1884.

194 JOURNAL OF COMPARATIVE NEUROLOGY.

In 1885 there appeared a work bearing the names of Lu-
ciani and Seppilli, already familiar to specialists by reason of
numerous smaller works, which may long serve as a vade
mecum for experimenter in this domain. Although almost
immediately translated into German(') this work is almost
unknown in this country.

The unwarrantable assumptions of Goltz, which demand
positive inhibitory reactions from the injured areas in explan-
ation of the restitution of function, and the great diversity
in the use of terms led these authors to an analysis of the
available methods for determining cortical functions from
extirpation, which it may not be useless to repeat. These
methods are as follows:

1. Negative results of extirpation. We may safely and
confidently assume that functions not disturbed by the lesion |
have nothing to do with the area removed.

2. Comparison of positive effects of extirpation of homo-
logous parts. This method suffers from the impossibility of
distinguishing the effects of removal of a given area from
the accessory disturbance due to the irritation and circulatory
disturbances, especially the septic after-effects. The com-
parison is also rendered difficult by the variability of the
cortical topography even in the same species or sides of the
same brain.

3. Comparison of effects of extirpation of different areas
of the cortex. This method is of especial value in determin-
ing the extent of the collateral effects, and indicates as a rule
that the collateral disturbances usually include functions
closely allied to those directly involved in the injury.

4. Comparison of effects of successive extirpation in the
same animal. This method is especially available in the in-
vestigation of compensating areas.

5. Determination of the minimum extirpation producing

1 LucIANNI UND Seppitt, “f Die Functions- Localization auf der Grosshirnrinde an
Thierexperimenten und klinischen Fallen naschgewiesen,” German by Fraenkel).
Leipzig, 1886.

EpiroriaL, Neurology and Psychology. 195

a given physiological effect. This method serves to define
the limits of special centres.

A useful criticism of methods of determining the nature
and extent of functional (sensory) disturbance follows.

Of the conclusions growing out of the extended and de-
tailed researches of these authors, the following resumé must
suffice.

Both schools of experimenters are partly right and partly
wrong. Localization is not possible in the arbitrary way at-
tempted by Munk, neither can it be denied so abruptly as by
Goltz. There are areas corresponding to the several classes
of sensations, but these cortical areas overlap to a very
great extent, so that injury to any part of the cortex may in-
duce disturbances of a large number of functions. There is
an inner nucleus or sphere for each sense, however, and
these are located much as indicated by Munk.

Extensive cortical lesions produce changes in disposition
because of the loss of the normal association of percepts
and images in the soul. Of the two views, Ist, that the
cortex contains centres for all mental manifestations, even
to the crudest sensations and motor impulses; and 2d, that
the cortex is solely concerned with concepts derived from the
several senses and voluntary impulses as well as memory and
attention, the authors seem to lean to the latter. The corpus
striatum is regarded as an integral part of the cortex as
much as the hippocampus.

The attempt of Munk to substantiate a topographical
projection of the retinal areas upon the cortex is considered
contrary to the facts brought out and summarily dismissed.
On the other hand, it is concluded that the cortex contains
only centres of sense-perception with their correlated mem-
ory-images, while simple sensation and motor impulses are
located in the lower centres.

One apparent contradiction involved in the localization
theory grows out of the phenomena associated with complete

removal of the hemispheres. Goltz succeeded in extirpat-

196 JouURNAL OF COMPARATIVE NEUROLOGY.

ing both hemispheres of the dog and preserving the animal
alive for fifty-one days after the operation. (')There was a
complete loss of special sensation, though dermal sensation
was persistent and there was no muscular paralysis. A
touch was sufficient to awaken it fiom its lethargy, and loco-
motor coordination was not destroyed. Goltz claims that
this operation does not necessarily completely destroy vision.
When food was introduced far enough back in the mouth, it
was properly masticated and swallowed. Goltz concludes
that the disturbances following extirpation are largely due to
inhibition arising from degenerative changes in the tracts
injured.

This view Wundt has used in an opposite way. After
repeating the experiments of Goltz, with his usual careful
analysis of technique, he concludes that many of the functions
ascribed by Goltz to inferior centres, are due to irritative de-
generation along the stumps of the severed nervous tracts.
His own experiments, he thinks, prove conclusively that
when such irritations are excluded, not only are the psychical
functions entirely obliterated, but the illusory appearance of
spontaneity and sensation disappear. Goltz’s methods are
regarded as crude and unreliable.

It would be unfair to neglect the older results of Chris-
tiani and Schrader. The former(*) removed both hemis-
pheres of the rabbit and concluded that under those circum-
stances the animal retained the functions of vision and hear-
ing as well as dermal sensation, though in a vague and feeble
form.

A pigeon when deprived of the hemispheres seems to re-
tain many of the functions usually ascribed to the cerebrum,
and in lower animals it is still more difficult to determine any
definite localization of functions.

The bearing of the progressive differentiation of cerebral
localization upon psychical evolution will be discussed in the

1 Pfliiger’s Archiv. Bad. 42. 1888
2 CHRISTIANA, Fiir Physiologie des Gehirns, 1885.

EpiroriaL, Veurology and Psychology. 197

second part of this article. The writer has endeavored
to show that consciousness in the limited sense is of compar-
atively late origin, and that a rigid application of the doc-
trine of natural selection would exclude it from all participa-
tion in nervous activities until such time as the struggle for
survival had become ameliorated to an extent, making con-
scious selection possible without involving direct loss or
destruction. After such a field for spotaneity had been
opened, consciousness would become a valuable and then
a necessary adjunct, and the effect of the reaction of con-
scious beings upon each other would be to widen the arena
for its display and increase the complexity of its activities. (')

Passing over the valuable evidence derived from human
pathology and so ably analyzed by Nothnagel and Naunyn(’)
and the digest of recent efforts in this direction given in
Brain during 1889 by C. K. Mills, we may examine, for
a moment the bearing of the most recent histological work.
A paper by Koelliker,(*) which appeared in December, 1890,
is occupied chiefly with the application of Golgi’s method to
the study of the spinal cord. The positive anatomical
results may be summarized as follows:

1. Sensory fibres on entering the cord divide into an
ascending and descending limb, which pass through the
dorsal column and lie on the surface of the substantia
gelatinosa.

2. No connection of the dorsal root fibres with nerve cells
has so far been observed.

3. The fibres of the longitudinal dorsal tracts give rise to
lateral branches (collaterals), which enter the gray sub-
stance, terminating in free stumps which are especially
abundant in the marginal zones of the substantia gelatinosa
and Clarke’s columns.

t This subject was discussed in a lecture before the University of Cincinnati, April,
1891, a synopsis of which will be incorporated beyond.

2 Verhand. des VI Congresses f. innere Medicin zu Wiesbaden, 1887.

3 “Zur feineren Anatomie des centralen Nervensystems” Zeitschrift f. wiss.
Zoologie, Bd. LI, p. r.

198 JoURNAL OF COMPARATIVE NEUROLOGY.

4. Motor root fibres arise from large and small nerve cells
in all parts of the ventral cornua, each by a single nervous
process.

_ 5. The ventral and lateral columns consist in part of
fibres from all regions of the cord.

6. The greater number of longitudinal fibres of the ven-
tral and lateral columns give rise to lateral branches (col-
laterals), which enter the gray matter, especially of the
ventral cornua and ventral part of the dorsal cornua.

7. All collaterals of lateral columns and nervous branches
of cellular processes, as well as the inflexed termini of sen-
sory nerves, give rise to a larger or smaller number of
branches, each finally form fine brushes of fibres, which col-
lect about nerve cells without coming into actual connection
with them or anastamosing with each other.

. 8. Nerve cells of the cord are, (a) motor cells, (4) cells
of the columns, (c) cells of the dorsal cornua whose nervous
processes do not extend beyond the gray matter, but sub-
divide uniformly.

Respecting:the relation of cell and fibre, Koelliker con-

cludes that interaction may follow two methods: tst, direct
stimulation of a fibre by a cell (motor); 2nd, operation of
nerve fibres upon cells with which they are simply in contact
but are not directly connected (sensory cells).
_ Voluntary motion is thus construed. Impulses conveyed
through pyramidal fibres pass into collaterals whose fine
branches are in close contact with cells of the ventral cornua
from which motor nerves arise. The excitement is thus im-
parted to these cells, and is transmitted through the nerve
fibres to the muscle. Koelliker considers that the motor
cells are collected in niduli which correspond to the
metameres of the body.

Sensations, on the other hand, are conveyed by the dorsal
columns, but there is no evidence that they continue to the
cerebrum. Data derived from ascending degeneration seem
to indicate that these fibres end in the niduli of the medulla.

EpiroriaL, Veurology and Psychology. 199

In this connection we may call attention to data derived
from our study of the opossum, which have an indirect bear-
ing on the above. In the ventro-caudal part of the cortex,
z. e., cortex beneath the rhinalis fissure, we were able to
demonstrate the termination of the numerous elongate cells
in a peripheral branch, which divides in the neurolgia layer
to form just such a neuro-pilem as has been described by
Golgi and Koelliker in the cord. Peripherad to this is a
tract derived in part from the olfactory. It seems probable
that there is over the entire sensory region at least such
a continuous meshwork or felting of fibres which might be
regarded as an anatomical basis for assuming a single organ
of consciousness. A similar neuro-pilem is found asa result
of the subdivision of the central (basi-lateral) processes
of these cells, so that the cells do not pass into direct connec-
tion with axis cylinders in either direction. In motor cells
we have traced axis cylinders to the fibrous meshwork con-
nected with the lateral processes of the deeper pyramids, but
suspect that the apical processes are connected with a neuro-
pilem or nervous felting of a similar sort, but observation is
here made enormously difficult by the mingling of sensory
and motor cells which are sharply distinguished.

These questions will be discussed hereafter, as this review
is already longer than was intended, so that the bearing
of the neurological suggestions upon the question with
which we set out must be deferred to a later article. It may
be added, that if psychology really needed a material senso-
motorium commune, or a common arena for consciousness,
the suggestions which we now have of a neuro-pilem cover-
ing the entire cortex and containing the finely divided fibres
of centripetal and centrifugal nerves which are merely
closely associated without anastamosis, might seem to afford
it without the necessity of setting aside the results of locali-
zation already given. If, on the other hand, we are justified
in accepting the assurances of Wundt and Lotze that the
concept of extension is out of place as applied to the soul,

200 JOURNAL OF COMPARATIVE NEUROLOGY.

we still require from the standpoint of physiology some com-
mon ground for interaction, such as would be furnished by the
nerve-felt of the cortex. See in this connection the discussion
of the cortex in the article upon the ‘‘ Anatomy of the Brain
of the Opossum,” supra.(')

1 Since the above was written we have received the “ Report of Six Lectures on
Cerebral Localization,” by Dr. HENry H, Donatpson, American Journal of Psychology,
IV; 5 sp) 253

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THE. MORPHOLOGICAL IMPORTANCE: OF >THE
MEMBRANOUS OR OTHER THIN PORTIONS
OF GLHE,, (PARTIE ELES) :OR (Wie
ENCEPHALIC CAVITIES.(*)

Burt G. Wiper, M.D. ‘

Professor in Cornell University.

In the JouRNAL OF COMPARATIVE NEUROLOGY for June,
1891, p. 152, the editor, Prof. Herrick, in reviewing previous
publications upon the brains of the ganoids and other fishes,
ascribes my failure, in 1875, to recognize a certain homology
to my not taking into account the existence of certain thin
portions which are commonly removed in preparing the
brain.

Upon the present occasion I offer no opinion upon the
particular homologies in question; these and many others in
the diversified brains of the fish-like vertebrates, I hope to
~ reconsider hereafter. My object now is to acknowledge the
justice of Prof. Herrick’s criticism, and to add that for
several years it has been my intention to publish a far more
vigorous denunciation of the errors as to method and in-
terpretation of which I was guilty fifteen years ago.

This would have been in accordance with the sentiment,
long entertained but hitherto unexpressed, that, since every
one makes mistakes, the interests of all concerned would be

best subserved by the adoption of the custom of each correct-

t Read at the meeting of the Association of American Anatomists, September, 24

1891. ey

202 JOURNAL OF COMPARATIVE NEUROLOGY.

ing his own, either as soon as discovered or periodically; a
sort of scientific confession of sins.

The natural corollary to this would be that each well-
disposed discoverer of another’s fault would inform him
privately so that he might make prompt correction. This
plan I have followed in several cases, and have reason to
believe it has served to avoid personal irritation and the
needless repetition of criticism.

As to the particular matter to which Prof. Herrick has
called attention, my procrastination has been due to several
causes; one, the lack of time to review the whole subject,
and another, the consciousness that, whenever it was done,
there would have to be condemned not only my figures and
descriptions but those of our morphological leaders, Agassiz,
Gegenbaur, Huxley, Owen and Jeffries Wyman; for neither
they nor any others, so far as I know, up to the publication
of Rabl-Ruckhard’s papers in 1883 and 1884, seem to have
perceived adequately the necessity of admitting the com-
plete circumscription of the encephalic cavities with ‘‘fishes,”
and thus of recognizing the morphological significance of the
thin, or even wholly membranous portions of the brain. This
criticism, ungracious as it is, can be no longer deferred; to
speak pathologically, the predisposition which has long been
dormant in my mind has found in Prof. Herrick’s kindly
commentary an ‘‘ exciting cause.”

I may be permitted to add, in partial reparation for my
own share in this grave morphological dereliction, that the
need of considering the membranous portions of the mam-
malian brain was recognized as early as November, 1876;(')
that in several subsequent publications(*) the morphological

1 My colleague, then fourth-year student, Prof. S. H. Gage, has preserved the notes
of dissections of cats’ brains, dated November 25, 1879, and January 1, 1877, made for the
purpose of demonstrating the complete exclusion of the thalamus from the paraceele
(lateral ventricle) by the membranes and plexus connecting the contiguous margins of the
tenia and fimbria, and the point 1s made in the printed synopsis of a lecture to the class
in Physiology in the former month.

2 ‘* The Brain of the Cat,”’ Philos. Soc. Proc., 1881; ‘“‘ Anatomical Technology,” 1882,
1886 ; ‘‘ The Cartwright Lectures,” 1884, N. Y. Medical Journal, XXXIX, pp. 142, 147,

WiLvER, Wembranous Walls of the Brain. 203

significance of apparently atelic portions of the brain is
insisted upon; that, in 1887 (American Assoc. Proceedings,
251, and American Naturalist, XXI, 913-917), I based a
primary classification of animals upon the presence of a cir-
cumscribed cavity (neurocele) in the central nervous system
(neuraxis); that, since 1880, all vertebrate brains in the
Museum of Cornell University have been prepared with
special heed to these parts, and the method of alinjection or
injection of alcohol has been generally employed; finally,
that, in addition to the special students in the anatomical
laboratories, there is no member of even my general classes
in Physiology and Vertebrate Zoology who has not learned
the meaning of the phrases exdymal continuity and celian

circumscription.

METAMERISM OF THE VERTEBRATE HEAD.

If anything were necessary to convince one of the strong
place the problem of the segmentation of the head has made
for itself in all branches of morphology, it would be afforded
by the large number of papers more or less directly concerned
with it read at the last meeting of the Anatomical Society
held in Munich during the present year.(').

The paper by Zimmermann quoted is devoted to a dis-
cussion of the segmentation of the brain, and the conclusions
may be summarized as follows:

In an early stage there appear in Salamander on either
side of the medullary tube and in front of the first pro-
vertebra-rudiment eight similar dilations. In higher verte-

179, 654, etc.; ‘* The Relation of the Thalamus to the Paraceele,”’ Journal of Nervous and
Mental Diseases, July, 1889; and the articles in the ‘‘ Reference Handbook of the Medi-
cal Sciences,” Vol. III, 1889

t C. von Kuprrer, ‘‘ Die Entwickelung der Kopfnerven der Vertebraten.”’

Froriep, ‘‘ Zur Entwickelungsgeschichte der Kopfnerven.”

KILviAL, ‘* Zur Metamerie des Selachierkopfes.”’

ZIMMERMANN, “‘ Ueber die Metamerie der Wirbelthierkopfes.”’

Gaupp, “ Zur Kenntniss des Primordial-Craniums der Amphibien und Reptilien.”’

204 JOURNAL OF COMPARATIVE NEUROLOGY.

brates the three cephalad encephalomeres are much larger.
These subsequently divide, the primitive prosencephalic
vesicle into two, the mesencephalic and the third each into
three. The author thinks the three first are originally com-
pound, and that for some reason the subdivision is retarded in
this region. The thirteen encephalomeres are therefore
homologous. These are especially prominent in J/ustelus
and Acanthus (Selachii).

The first encephalomere forms the secondary prosenceph-
alon, with only a dorsal nerve root represented by the olfac-
tory. The second forms the thalamus, and is devoid of nerve
roots. The third, or first mesencephalic encephalomere, is
also devoid of nerves. The fourth bears the ciliaris as a
dorsal aud the oculo-motor asa ventral root. The seventh
is doubtfully credited with the trochlearis. The eighth has
the sensory root of the trigeminus as its dorsal and the motor
trigeminus as its lateral root. Ihe ninth has no nerves. The
tenth with the profacialis (sensory part + acoustic) as a
dorsal root and a lateral root. The eleventh bears the
acoustic ganglion as dorsal root, a lateral branch entering
the genu of the facialis, and the abducens, The twelfth
bears the sensory glosso-pharyngeal, a lateral branch, and a
ventral branch which passes dorsad behind the glosso-pharyn-
geal. ‘lhe thirteenth also has three roots, the sensory fibres
of the tenth, a lateral branch chiefly in the accessory, and a
ventral branch passing dorsad behind the vagus.

The four following neuromeres enter the skull in mammals
and have dorsal roots in the vagus, lateral ones in the acces-
sory, and ventral ones in the hypoglossus.

The vagus of mammals includes five dorsal roots. Prof.
Froriep remarks that he has detected two neuromeres in the
diencephalon. This latter statement the present writer is
able to substantiate from his own observations on Cavia and
Canis embryos, though very doubtful as to the homology of
these segments with the neuromeres of the spinal regions.

—| Ep. |

PH SAR ACTNOMD: OF THE, BRAIN. (*)

Ps W. Lanepon, M.D.,

Professor of Surgical Anatomy in Miami Medical College, Cincinnati.

1. Its General Homology with the Serous Membranes of the
Other Great Cavities.

Modern works on human anatomy do not give, as a rule,
an account of the cerebro-spinal arachnoid, which is, in the
opinion of the writer, in harmony with its structure, topog-
raphy, and relations as shown by dissection.

Some of the different views which have existed respecting
the subject, as well as the present consensus of opinion of
our commonly accepted authorities, are exhibited in the
following historical notes:

According to Bichat,(*) ‘‘in the middle of the seven-
teenth century it began to be suspected that . . . the
arachnoid and pia . . . might possess a separate exist-
ence.” ‘‘The Anatomical Society of Amsterdam assured
themselves of the fact in 1665; Van Horne soon after demon-
strated the arachnoides separately to his pupils.”

Bichat himself (*) describes the arachnoid as a serous shut
sac, conforming in all essential particulars with the serous
membranes of the other cavities. This was apparently the

1 Read before the Association of American Anatomists at the annual meeting, Boston,
December 29, 1890, and reprinted from the N. Y. Medical Record, August rs, 1891.

2 XAvIER Bicuat, etc., ‘* A Treatise on the Membranes in General, and on Different
Membranes in Particular,’’ Paris, 1802. Translated by John G. Coffin, M.D. Boston,
1813, p. 163.

3 Op. cit.

al

206 JoURNAL OF COMPARATIVE NEUROLOGY.

generally accepted view up to the time of Kolliker, who
wrote:(*) ‘It is generally stated that the inner surface of the
dura mater is covered by an outer layer of the arachnoid; but
nothing is fonnd here excepting an epithelium composed of
polygonal cells, and there is not a trace of a special mem-
brane.”

The same writer (page 238), speaking of the spinal
membranes, says: ‘‘ The inner surface of the dura mater is
covered with a multiple layer of pavement epithelium cells,
but has no other investment which could be regarded asa
parietal lamina of the arachnoid.” Again, Frey(*) says:
‘¢ The arachnoid, which has also been numbered among these
(the serous membranes), has no parietal layer.” And, ‘‘ The
second membrane, the arachnoidea, was tormerly described
as forming a shut serous sac, but erroneously so; the parietal
leaf being usually represented as fused together with the
outer layer of the dura mater, since it could not be demon-
strated separately.” (")

Without multiplying references unnecessarily, it is suffi-
cient to state further that in the various editions of Gray’s
‘¢ Anatomy,” previous to 1870, the arachnoid is described as
a shut sac. Darling and Ranney, 1882, also teach this view;
while Gray (after 1570), Holden, fifth edition, 1885; Leidy,
1889; Weisse, 1856, and other leading works in common use
as text-books, speak of it as consisting of one layer only—the
“¢ visceral” layer.

It has occurred to the writer that this question of one or
two layers was one which it was desirable to have settled,
and if possible by macroscopic rather than microscopic evi-
dence. With this object in view a series of dissections were
made as follows:

First dissection: Foetus at term, still-born.—The scalp
being removed, a section of skull was made in the parietal

4 ‘* Manual of Human Microscopic Anatomy,”’ p. 237-238. London, 1860.
5 ‘* Histology and Histo-chemistry of Man,” p. 227. Appleton, 1875.
6 Op. cit., p. 599.

Lancpon, The Arachnoid of the Brain. 207

region, removing the bone only. The following features
were then easily demonstrated in successive order: 1. Peri-
osteal layer of dura, traceable to its continuity with the
sutural ‘‘ ligament.” 2. The dura proper (subserous connec-
tive tissue), forming the walls of sinuses and carrying the
nutrient vessels for, 3, The parietal layer of arachnoid, a thin
pellicle separable with the handle of the scalpel. 4. Space
between parietal and visceral layers of arachnoid, or the
arachnoid cavity proper. 5. Visceral layer of arachnoid
passing over sulci, etc. 6. Subarachnoid space. 7. The
pia mater. 8. The convolutions.

Second dissection: Fotus at term.—This was practically
a repetition of the first, except as to region, the frontal bone
being removed instead of the parietal.

Third dissection: Adult, negro, aged about thirty-five,
brain and membranes normal.—The dura covering vertex
and forming falx cerebri and tentorium was found to be
inseparably united with the parietal arachnoid; at the base
of the skull, however, and especially in the region of the
sella turcica and orbital plates, the two membranes are quite
freely separable with an ordinary scalpel, and the arachnoid
could be stripped off in places. This separation also was
more marked at the points of exit of the larger cranial nerves
—e.g., the optic. The following diagram (A) will show at
at a glance these points in the parietal region of the new-
born infant—the only change in adult life being fusion of the
vertical parietal arachnoid with the subserous dura, a condi-
tion in every way similar to the conditions which exist in the
pericardium. At the base of the skull, however, the separa-
tion is readily appreciable in the adult, as already stated.

Considering the nature of the sinuses—as simply dilated
veins—and the fact that the inner dura is the necessary
medium for vascular supply of the parietal arachnoid, it
would seem in every point of view proper to consider the
inner dura as homologous with the subserous connective
tissues elsewhere.

208 JouRNAL OF COMPARATIVE NEUROLOGY.

The writer regrets that material and time have not per-
mitted these observations to be carried to their logical con-
clusion, by actual sections of cranial nerve exits, to show the
arachnoid reflections.

NO AAW

1a

DiaGRAM A. Vertical Transverse Section of Parietal Region to
Show the Various Membranes and their Layers.— 1, Sutural “liga-
ment,” continuous with external periosteum and periosteal layer of dura;
2, parietal bone; 3, periosteal layer of dura; 4, inner layer of dura, form-
ing sinuses; 5, subserous connective tissue, between dura and parietal
arachnoid; 6, parietal arachnoid; 7, arachnoid cavity; 8, visceral arach-
noid; g, subarachnoid space; 10, pia mater; S, superior longitudinal
sinus; s, inferior longitudinal sinus; F, falx; C, convolutions.

2. The Communications between the Arachnoid Cavity and
the Subarachnoid Space by Way of the ‘* Lunulate
Foramina.”

During the progress of the last dissection it was evident
that there were two points at the base of the cranium where
the arachnoid was deficient over a considerable area on either
side of the medulla oblongata. These deficiencies present
the form of bilateral foramina—one on each side—and are
situated in the ‘‘ bridge” of visceral arachnoid which stretches
across from the cerebellar lobes to the under surface of the
medulla. These foramina measure about half an inch in
longitudinal diameter by one-fourth inch transversely, and
are crossed by three or four fibrous bands, the attachment of

LANGpoN, Zhe Arachnoid of the Brain. 209

which to the edges of the openings produces a multiple
crescentic appearance of their margins, which suggests the
name adopted above. (See Diagram B.)

As the body had been subjected to but little handling
before the autopsy, and the brain was removed with special
care, it does not seem likely that these openings were pro-
duced accidentally; the finished appearance of their edges
and close correspondence with each other in all “respects
would also negative this supposition. |

DraGrRaAam B.—Lower or ventral surface of pons (P), medulla (M),
and cerebellum (C), supposed to be covered by the visceral arachnoid,
in which are seen the lunulate foramina (F. L.) in outline. Nore.—The
artist has failed to represent the membrane, but the outlines of the
foramina are correctly placed.

It is evident that, if constant, they form a large and direct
communication between the arachnoid cavity and the sub-
arachnoid space and ventricles, just opposite the ‘‘ foramen
of Magendie”—by which the subarachnoid space is stated
by most anatomists to communicate with the internal
cavities.

Hence, it would seem reasonable to suppose that the
cerebro-spinal fluid may have its origin, in large part at
least, in the walls of the arachnoid cavity proper, reaching
its final destination through the lunulate foramina to the sub-

210 JOURNAL oF COMPARATIVE NEUROLOGY.

arachnoid space, thence vza the ‘‘ foramen of Magendie” to
the ventricles.

Further observations on these points are therefore de-
sirable.

For assistance and courtesies extended in connection with
these dissections and observations, acknowledgments are due
Dr. F. Kebler, pathologist, and Dr. George B. Twitchell,
house-physician to the Cincinnati Hospital; also to Messrs.
S. Newlin and J. G. Williams, students at Miami College.

To summarize these observations I would conclude:

1. The arachnoid membrane is a true shut sac, similar in
structure and function to the serous membranes of the other
great cavities. Its parietal layer is easily separable from the
dura at the vertex in the fetus and young infant, but practi-
cally inseparable in this region in the adult. At the base of
the skull it is demonstrable as a separate membrane even in
the adult. To assert that the parietal layer of arachnoid is
absent, because its subepithelial connective tissue has fused
at the vertex with the dura (connective tissue), is as incor-
rect as to describe the great omentum as one layer of perito-
neum, because its original four layers have become matted
and adherent.

2. The arachnoid cavity communicates freely with the
subarachnoid space, by means of two foramina situated in
the visceral arachnoid, one on either side of the medulla.
For these I Would propose the name ‘‘ lunulate foramina,”
from their crescentic or lunulated edges, produced by the
attachments of fibrous bands which cross the openings trans-
versely. Subsequent observations, in two instances, confirm
the presence of the ‘‘ lunulate foramina.” In one of these,
the basilar process of the occipital and the sphenoid body
were cut away from the base and the dura removed, so as to
show the foramina zz sz/w,; thus excluding the possibility of
of their artificial production during the extraction of the
brain.

CINCINNATI, December 16, 1890.

CONTRIBUTIONS TO THE MORPHOLOGY OF
THE BRAIN OF BONY FISHES.

C. L. anp C. Jupson HERRICK.

I. — SILURIDA., — With Plate XVII.
C. Jupson HERRICK.

The family Siluride, comprising the cat fishes and bull-
pouts, forms a very convenient starting point for a discussion
of the brain of the teleosts. It is a very close family, at
least as far as our inland fresh-water forms are concerned,
and at the same time it is distributed in great abundance
over the entire North American Continent with considerable
diversity of habitat.

Of all the Teleostei the Siluride, according to Prof.
Cope,(') are more closely related in internal structure to the
gars and other ganoids. The brain, however, is as distinctly
teleostean as that of any other fish examined and shows very
little evidence of any close relationship with the ganoid
fishes. On the other hand, the elongation of the olfactory
crura, the structure of the cerebrum, the extrusion of the
cerebellum and the form of the medulla all suggest affinities
with the more highly specialized teleosts, while the brain of
some of the other bony fishes, particularly the mud-eating
fishes, Hyodon, Dorosoma, etc., has a very pronounced
reptilian aspect. Judging from brain characters alone, the

x Fide Jordan and Gilbert, ‘‘ Manual,” p. gs.

fet}

212 JOURNAL OF COMPARATIVE NEUROLOGY.

Siluride should be placed among the most highly specialized
bony fishes, though this, of course, does not necessarily
involve a position high in the scale, phylogenetically con-
sidered.

The present contribution is based upon the study of
dissections and histological preparations of such species of
Siluride as are most accessible in the Ohio Valley., viz.,
Amiurus catus gill, Ptlodictis olivaris Gill and Jordan,
Ictalurus punctatus Jordan, and J/ctalurus lacustris Gill and
Jordon. The adult brains of these species are so nearly alike
that it would be difficult to distinguish them externally, and
in the following descriptions the statements apply to all of
them unless otherwise expressly indicated. In the case of
some of our large river cats especially, and probably of the
other species also, the brain practically ceases to grow when
the fish attains a moderate size, even though the weight of
the body may afterward increase many fold. A specimen of
the mud cat, Plodictis olivaris, for instance, weighing
twenty-one pounds, had a brain which, when hardened,
could scarcely be distinguished by careful measurements
from that of another specimen weighing less than five pounds.
The cranial cavity, however, enlarges more nearly in pro-
portion to the size of the head. In large specimens it is more
than twice the size of the brain, which lies in the ventral and
caudal portion. In the remaining space an oily arachnoid
tissue is closely packed around the emerging nerves. In
smaller specimens the brain is much larger in proportion to
the head until in individuals one inch long it fills the entire
cranial cavity and, in fact, almost the entire head.

Measurements.——The following measurement are taken
from an alcoholic brain of Pzlodictis olivaris. Other measure-
ments in the text refer to the same specimen. This fish was 40
cm. long, and would weigh about four pounds. The measure-
ments, however, would be almost equally exact for the brain
of a specimen weighing twenty pounds: Length of brain from
end of cerebrum to exit of dorsal root of vagus, 17 mm.;

Herrick, IJorphology of Brain of Bony Fishes. 213

length of cerebrum, 6 mm.; width of cerebrum, 7.5 mm.;
width of optic lobes, 10 mm.; width of cerebellum, 11.25
mm.; length of cerebellum in the median median line, 8.5
mm.

Cranial Nerves.—Compared with the size of the brain, the
cranial nerves are enormous, much larger than in any other
fish which has come to our notice. This is a function, doubt-
less, of the enormous size of the head in the cat fishes. The
olfactory nerves are very short, passing directly from the
olfactory lobes into the nasal cavities in numerous separate
bundles. The optic nerves are long, passing out; in large
fish , for several centimetres parallel to the olfactory crura, then
diverging at at acute angle to the orbits. They arise from the
ventral surface of the thalamus, immediately cephalad of the
hypoaria, are quite distinct from each other at the origin and
remain so throughout, crossing, however, below the cere-
brum. They are not, at first, cylindrical, but very strongly
flattened dorso-ventrally. The other cranial nerves may be
conveniently divided, after Gegenbaur, into two groups, the
trigeminus group and the vagus group. In both of these
groups the relations are greatly complicated, not only by the
large size of some of the nerve roots, but by the presence of
plexi. Only the more important of these are noted, and in
the peripheral distribution many of the smaller branches are
omitted.

In the trigeminus group the fifth is of supreme import-
ance, and absorbs many of the others. The third arises as
a single strand under the caudo-lateral angle of the hypoaria,
passes into the fifth and loses its identity completely (Plate
XVII, Fig. 4, 111). The fourth is minute. It arises from the
caudal end of the optic lobe and also passes out with the
fifth. The fifth is larger than all of the other cranial nerves
combined, and passes out of the cranial cavity by no less than
four distinct foramina. These are indicated in approximately
their relative positions in Plate XVII, Fig. 5. For convenience
of description the various branches of the fifth will be

214 JOURNAL OF COMPARATIVE NEUROLOGY.

numbered as in the figure last referred to and treated
successively. The branch V, is discrete from the others and
passes farther dorsad to a separate foramen, F,, having pre-
viously divided, giving off a large branch ventrad which passes
through the foramen F,. Before this division it receives
a small ramus from V,, another from V,, and gives one to the
combined trunk of V, and VII. The dorsal branch of V,
gives off a small twig before entering its foramen which
passes dorsad, then cephalad between the frontal bones.
After passing through the foramen it takes its course not far
from the median line superficially, giving off various fibres to
the frontal region, to terminate in the premaxillary. The
more ventral division of V,, after passing through the lower
foramen, F#, is wrapped up with the fibres of V, without,
however, losing its separate identity, receives at least two
separate small strands from V,, and passes through the lower
part of the orbit, giving off several branches to the infra- _
orbital region and the region behind and above the angle of
the mouth. The branch V, is also nearly discrete to its
origin. After passing through the foramen F,, it gives off
the two branches above referred to, several small twigs to
the frontal region, two large branches to the posterior nasal
barbel, and terminates in several branches in the premaxillary
not far from the terminus of the dorsal part of V,. It also
gives off a considerable branch which supplies the supra-
orbital region and passes on to the anterior nasal region.
The branch V, is nearly distinct from the two preceding, but
more closely united with V, until after they leave their
foramen. It gives off a considerable ramus soon after leaving
the foramen, which sinks down to the roof of the mouth and
terminates in the dental cavity of the premaxillary. The
major part of this branch passes farther laterad through the
orbit, giving two large rami to the barble at the angle of the
mouth and others to the regions adjacent. Another branch
which passes through the foramen F, is V,, which connects
by means of a small ramus with V,. After leaving the fora-

Herrick, Morphology of Brain of Bony Fishes. 215

men it divides into two. A smaller branch turning caudo-
laterad passes to the masseter. The remainder passes through
the orbit to the angle of the mouth and _ infra-maxillary
region. The remaining fibres, which pass through the
foramen F,, are those of V, and VII, which are inseparably
united for several centimetres. This trunk receives, in
addition to the fibres from V, and V,, referred to above, a
small fascicle from V,. After leaving the foramen a con-
siderable branch is given off from the cephalic division
which dips down and passes caudo-laterad to the depressor
operculi. The branches V, and VII subsequently partially
reunite before their final separation. This plexus may serve
the function of a chorda tympani. The more cephalic branch,
V., 1s considered to be the homologue of the inferior maxillary
nerve. It gives off a few small fibres to the ental surface of
the masseter and then divides. The more superficial division
passes cephalad to the infra-maxillary region. The deeper
division passes through a foramen ‘in the articulare inferius
suspensorii maxille (of Meckel) and again divides into a
dentary branch penetrating the end of the inferior maxillary
into its dental cavity and a mylo-hyoid branch which passes
by the end of the inferior maxillary, then cephalad on the
ventro-mesal surface of the latter to the inferior barbels, two
branches being given to each barbel. Ramus VII, which is
considered to be the homologue of the facial nerve, after
separating from V., passes laterad, giving off a twig to the
levator operculi. Passing then to the ventral surface, it
supplies the muscles of that region, apparently those con-
cerned chiefly with deglution. The carotid plexus, if present,
is probably all intra-foraminal. With reference to the first
four divisions of the fifth, homologies cannot be pushed very
far; and yet it seems legitimate to consider that the more
dorsal division of V, andV, are, roughly speaking, homolog-
ous with the orbito-nasal (of Parker), the rest of V,, V;,
and V, with the superior maxillary. Two important divisions
of the fifth remain to be considered. The small branch V,

216 JOURNAL OF COMPARATIVE NEUROLOGY.

springs from the base of V, very near its origin and passes
cephalo-dorsad through a separate foramen, F.,, thence laterad
to the opercle, superficially. Before entering its foramen it
sends a very small twig cephalad to ramify in the frontal
bone near the median line. V, is one of the largest
separate branches of the fifth nerve. Its apparent origin is
not from the medulla, but from the roots of the other
divisions. It passes dorso-caudad through a foramen, F,,
situated over the caudal end of the medulla, thence caudad
superticially near the median line the entire length of the
body. It appears to partake of the function of the nerve of
the lateral line. Gasser’s ganglion is obviously developed on
this branch alone. The microscope, however, shows elon-
gated bands of ganglion cells between the strands of the
other branches also. The sixth nerve could not be separately
distinguished. The auditory nerve springs from the medulla
immediately caudad of the trigeminal by several roots which
are united into a broad, flat band. The cephalic and caudal
portions supply the semi-circular canals, the middle portion
the otolithic sac.

In the vagus group the ninth and tenth nerves are quite
distinct. The ninth arises immediately caudad of the eighth
and closely associated with it. After sending a branch to
communicate with the ventral root of the vagus it divides,
one branch going to the opercle, the other to the first gill.
One or two small branches arise near the medulla and pass
caudad. ‘Their connections were not discovered. The tenth
arises by two large roots, dorsal and ventral, which combine
into a ganglion outside the foramen. Cephalad, there branch
off from this ganglion nerves to the several gills, one branch
to the first and second, another to the second and third, and
another to the third and fourth. Each gill thus receives two
distinct nerves. Passing caudad, there is a large branch
which divides, one portion supplying the levator of the
pectoral fin, the other the depressor of the pectoral fin.
From the latter arises a small cutaneous branch to the post-

Herrick, Morphology of Brain of Bony Fishes. 217

opercular region. Arising from the ganglion of the vagus
immediately dorsad of the last 1s a very small fibre passing
to the lower pharyngeal region. Farther dorsad is the visceral
branch of the vagus. This gives a small branch to the
middle of the fourth gill and a larger one to the organs of the
- thorax. The main trunk passes caudad and spreads out over
the stomach, mesentary, etc. The largest division of the
vagus nerve is the nerve of the lateral line. It communicates
by a delicate plexus with the nerves of the muscles of the
pectoral fin and the cutaneous nerve connected with them,
then passes caudad superficially along the lateral line for the
whole length of the body. The spinal accessory nerve cannot
be separately distinguished. ‘The first spinal nerve, which
might, perhaps, with equal propriety be called the twelfth
cranial nerve, arises behind the medulla by two roots, dorsal
and ventral. The latter is considerably farther cephalad
than the former. The two roots remain distinct until after
they pass through their foramen (Plate XVII, Fig. 5, . s.p).

Rhinencephalon.—The olfactory lobes in the adult are in
immediate proximity to the nasal cavities, and therefore far
distant from the rest of the brain. In large specimens the
olfactory crura would thus be more than fifteen centimetres
long, while the olfactory nerves would be only a few mill-
metres. In very young specimens one inch long the brain is
so large that it fills the whole front part of the head, and the
olfactory lobes are in their usual position, closely appressed
to the cerebrum. Compare Plate XVII, Fig. 2, with Fig. 3.
Each lobe is sub-spherical, three millimetres in diameter,
attached to the crus on the caudal aspect, with the fibres of
the olfactory nerve springing from the opposite side. The
internal structure is very much as in reptilia. Ectad there
is a glomerulary zone which is well developed, though not
so much as in Hyodon. Within this are specific olfactory
cells irregularly and sparsely distributed in a single series.
They are fusiform to flask-shaped, with the apices usually
directed peripherally. The centre of the lobe contains small

218 JOURNAL OF COMPARATIVE NEUROLOGY.

dense cells resembling Deiter’s cells. There is an olfactory
ventricle which extends from the cerebral ventricle the
whole length of the crus and well out into the lobe, though
not to its centre. It lies in the dorsal part of the lobe and
retreats farther dorsad as the lobe passes into the crus. In
the crus itself all of the fibres lie ventrad of the ventricle
which is bounded laterally, as well as dorsally, merely by a
membrane. The entire cavity is lined with epithelium. This
membrane is continuous caudad with the pallium of the
cerebrum and, with the epithelium of the ventricle, is the
apparent homologue, using Prof. Wilder’s terminology,’ of
the pes, while the fibrous portion of the crus and the body of
the lobe constitute the pero of the olfactory. In the olfactory
crus the fibres are gathered into numerous bundles which are
separated by layers of small spherical cells. The crus, upon
entering the cerebrum, divides into a well-defined radix
mesalis and radix lateralis.

Prosencephalon.—Vhe mantle portion of the cerebrum is
represented, as usual among fishes, only by a delicate trans-
parent membrane, the pallium, lined with epithelium. This
pallium is entirely free from the basal portion of the cerebrum
on the dorsal and lateral aspects, and below it is free as far
mesad as the lateral edge of the radix lateralis of the
olfactory, z.e., the sinus rhinalis. The median fissure is not
prominent, being represented dorsally by a slight fold of the
pallium in the median line. Caudad the pallium is plicated
in this region to form a considerable choroid plexus. Ceph-
alad the median fissure is deepened until at the exit of the
olfactory crura a similar fold is thrust up from below and the
two crura are entirely separated. The pallium, however,
continues to envelop the crura, maintaining about the same
relations as in the cerebrum, i.e., attached only ventrally,
free at the sides and above. Thus the lateral ventricles are
continued cephalad into the rhinencephalon, as described
above. For a discussion of the cerebral ventricles see
beyond,

Herrick, Morphology of Brain of Bony Fishes. 219

The basal portion of the cerebrum consists of two lobes
which are considered to be the homologues of the axial lobes
of the Sauropsida. They are connected below by a mem-
brane which may be considered as a continuation of the
pallium, and are otherwise quite distinct from each other
except in the region of the anterior commissure. Each lobe
is oblong, about as high as it is wide, and about one-fourth
longer than it is wide and is attached to the diencephalon by
by its caudo-ventral angle. The dorsal (ventricular) surface
of these lobes is marked with an intricate system of
fissures and convolutions, which, however, seem not to be
very constant, even in the same species. There are four
fissures which are almost always obvious externally, though
somewhat variable in size and position. They are found in
other fishes quite generallv and are here named in accordance
with the nomenclature of Prof. C. L. Herrick as given else-
where in this number. The most strongly-marked and con-
stant fissure is the rhinalic fissure, or sinus rhinalis, on the
ventral surface. This marks the line of union between the
pallium and the basal lobe. This line passes from the lateral
edge of the olfactory crus at its point of exit caudo-laterad to
about the centre of the hemisphere; it then turns at an obtuse
angle, passing caudo-mesad to the lateral edge of the optic
nerve at its exit. The two rhinalic fissures thus define a
broad pentagonal depression in which lies the decussation of
the optic nerves, and dorsad of which, in the substance of the
basal lobes, lie the olfactory crura, and farther caudad, the
fibres of the crura cerebri. It is present in other teleostean
brains, though not usually as strongly marked as in the
Siluride, and may be called the rhinalic aspect. On the
dorsal surface the most prominent fissure is the frontal fissure,
which arises on the fronto-median aspect of the cerebrum
from about the middle of the olfactory crus at its exit and
passes caudo-laterad in an irregular line almost to the
diagonally opposite angle of the basal lobe. Here it meets
the occipital fissure, which arises on the latero-caudal aspect

220 JouRNAL OF CoMPARATIVE NEUROLOGY.

and passes caudo-mesad. By these two fissures there are
defined a large mesaxial lobe mesad of the frontal fissure and
a narrow occipital lobe caudad of the occipital fissure. The
fourth important fissure is the Sylvian, which is not so
strongly developed as the preceding. It arises on the ventral
surface in the centre of the lateral aspect and passes dorsad.
This fissure, with the occipital, defines a triangular lobe, with
the apex directed ventrad, the cuneate lobe. Behind the
cuneate and ventrad of the occipital lobe, from which it is
separated by a small fissure, is a large lobe which may be
called the temporal lobe, though in the cat fish it occupies
the caudo-ventral end of the cerebrum. The term hippo-
campal lobe is applied to the lip, or. ventral extrusion, just
laterad of the sinus rhinalis. Cephalad there is another
small fissure which may be considered as a part of the
rhinalis. It arises from the lateral edge of the radix lateralis,
passes dorsad and, with the frontal fissure, circumscribes a
frontal lobe. This lobe lies immediately dorsad of the olfac-
tory crus and is very small. There is still another noteworthy
fissure in the median sinus between the two basal lobes. It
runs in each lobe longitudinally in both directions from the
anterior commissure, It is best observed in transection.
There are are other small fissures on the dorsal surface, but
they seem not to be constant and are considered unimportant.
It is to be remembered that all of these fissures, except the
rhinalis and possibly the Sylvian, are spurious fissures and are
not to be homologized with the cerebral fissures of higher
animals. That is, they are fissures of the axial lobe, not of
the cortex, for this dorsal surface is a ventricular surface and
is clothed with epithelium, like the pallium. The epi-
thelium here, however, tends to be more columnar than that
of the pallium.

To understand the full significance of these lobes it will
be necessary to examine the cellular histology of the cerebrum
in some detail. A transection cephalad to the anterior
commissure reveals three areas sharply differentiated histo-

Herrick, AWorphology of Brain of Bony Fishes. 221

logically. The mesaxial lobe is characterized by small flask-
cells, with large granular nuclei and dense nucleoli. They
are very closely packed, with a strong tendency toward
a zonary arrangement. The lateral lobe is characterized by
similar elements more ‘sparingly distributed, but still show-
ing an evident zonary arrangement. This latter is particu-
larly true ventrally. Dorsally the cells are less numerous,
and those of the type found in the central lobe predominate.
The central lobe hes between the two last mentioned and
typically does not appear on the dorsal surface, being tri-
angular with the apex directed dorsad. The cat fishes, how-
ever, present a marked exception to the latter point. The
histological elements are large cells lying in a clear stroma.
They are spindle-shaped or multiangular, all with very large
processes, large circulr nuclei and dense nucleoli. The
central lobe is nowhere sharply separated from the lateral
lobe. On the other hand, the frontal fissure separates it very
clearly from the mesaxial lobe, especially peripherally. The
structure of the occipital lobe closely resembles that of the
central, while the temporal lobe has the small cells of the
mesaxial, somewhat less abundant, but with the same zonary
arrangement.

The prosencephalon, as a whole, is considerably larger
than the optic lobes, but very much smaller than the cere-
bellum. It attains to about the average size as compared
with other Teleostei thus far examined.

Diencephalon.—The thalamus in the adult cat fish is
entirely hidden from the dorsal aspect by the optic lobes and
the cerebellum. Even the attachment of the epiphysis is
obscured by the forward extension of the cerebellum. The
epiphysis is very much as in some Lacertilia. It arises as a
small membranous tube lined with epithelium immediately
cephalad of the superior commissure, passes dorsad en-
wrapped by the plexus which fills this region, then turns
abruptly cephalad passing under the cerebellum and over the
cerebrum. It lies in the shallow median fissure in intimate

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JOURNAL oF COMPARATIVE NEUROLOGY.

contact with the pallium as far cephalad as the exit of the
olfactory crura, then turns dorsad to the roof of the cranial
cavity. The diameter of the tube is about .1 mm. at the
base, but increases slightly as it passes out. About the base
of the epiphysis the membranous roof of the third ventricle
is inflated dorsad to form a small closed sac which is nearly
spherical and about 1 mm. in diameter. This represents the
dorsal sac, which is so conspicuous a feature in many fish
brains. In this case it is entirely obscured from view in the
brain before dissection by the over-arching cerebellum. The
walls of this sac are intricately plicated, the folds embracing
the base of the epiphysis and forming what has been pre-
viously mentioned as the homologue of the choroid plexus.
The epiphysis is related to the roof of the cerebral ventricles
cephalad in essentially the same way; 7.e., it is imbedded in
the pallium and surrounded by it. Thus morphologically the
dorsal sac is produced forward nearly to the end of the
cerebrum, though its cavity has been all but obliterated.

On the ventral aspect the hypoaria and hypophysis cover
nearly the entire cephalic portion of the brain. Each hypo-
arium is a pear-shaped body, flattened dorso-ventrally, with
the smaller end directed cephalad and the more concave
surface mesad. At the cephalic end of each hypoarium is a
small tubercle lying immediately ventrad to the lateral
portion of the optic nerve at its exit from the brain. In the
adult the hypoaria are divaricated cephalad by the cinereum.
This body is cordate with the apex directed caudad, and is
somewhat over half as long as the hypoaria. Attached to its
apex and lying in the narrow cleft between the caudal ends
of the hypoaria is the saccus vasculosus, which, in large
brains, sometimes attains a diameter of 3 mm. This is a
membranous sac, the base of which, lying between the
hypoaria, is filled with a vascular plexus, resembling in
structure the vascular portion of the epiphysis of higher
animals. The more expanded portion, overlying the larger
ends of the hypoaria, is discoid or sub-spherical, more delicate

Herrick, Morphology of Brain of Bony Fishes. 222
in texture and dilated with fluid. Immediately caudad of the
saccus vasculosus a large blood-vessel enters the brain in the
median line. This is always present and seems to represent
the area perforata posterior of higher brains. The broader
end of the cinereum is directed cephalad and is indented in
the median line by a deep sinus extending to its centre. This
point is the most ventral projection of the cinereum, and
from it the infundibulum passes out into the hypophysis.
This appendage is slightly ovoid, with the larger end
directed cephalad, 4.5 mm. long by 3.5 mm. wide and high.
The stipe is filiform, slightly thicker at the base and attached
to the body of the hypophysis at a point about one-fourth of
the distance from the caudal end of the latter. The hypo-
physis is solid, and of a uniform texture.

Mesencephalon.—The portion of each optic lobe which is
exposed is ovoid, with the larger end directed cephalad and
the long axis passing obliquely dorso-caudad. The two
lobes are widely divaricated by the cerebellum. The roof of
the mesencephalon is depressed, thin, and devoid of cellular
elements, except internally in the tori longitudinales
* of authors) adjacent to the ventricle. The
mesencephalon does not reach the ventral surface of the
brain at any point. In this region, cephalad, that surface is
entirely occupied by the hypoaria, while the portion caudad
of the hypoaria is to be considered a forward extension of the
medulla, as in higher animals.

Etpencephalon.—In this group of fishes the cerebellum is
the most characteristic feature. It consists of two major
divisions, one external and one internal. Both are well
developed, the former to an unusual degree. The whole mass

Ces fornix’

of the first division is folded upon itself at an angle of 90°,
thrust cephalad, and closely appressed to the subjacent optic
lobes and hemispheres. The entire extent of the fourth
ventricle is thus exposed, in striking contrast to the brains of
most other fishes. As viewed from above, the cerebellum is
nearly rectangular, with a lateral expansion caudad, and it

224 JOURNAL OF COMPARATIVE NEUROLOGY.

extends forward far enough to cover a quarter of the cere-
brum. This portion is oval in transection with the longer
axis horizontal. Caudad, at the point of union with the
medulla, it expands to a width greater than that of the brain
at any other point. The two lateral lobes thus produced
contain white matter, chiefly in the form of fibres, passing
caudad into the medulla, and are to be considered as portions
of that body, homologous in part with the restiform bodies.
They lie farther caudad than the cerebellum proper, one on
each side of the fourth ventricle over about the middle of the
medulla. A small transverse fissure is present on the dorsal
surface of the cerebellum, a few millimetres cephalad of the
fourth ventricle. Between this fissure and the fourth ventricle
are transverse fibres passing apparently from one lateral lobe
to that on the opposite side. Cephalad of this fissure the grey
and white matter are arranged in the usual manner, the grey
filling the centre and enveloped by the white. White fibres
enter the cerebellum from below in the centre of the grey
matter and thus form a sort of arbor vite, as in higher
animals. In the median line, about 1 mm. cephalad of the
to the caudal end of the cerebellum, a very narrow ventricle
arises from the aqueduct of Sylvius and passes dorsad into the
cerebellum for about two-thirds of the way to its dorsal
surface. With this exception the cerebellum is solid.

The internal division, or volvula, lies in the aqueduct of
Sylvius immediately cephalad of the small ventricle of the
cerebellum. It presents the appearance of having been
formed by folding back upon itself through an angle of 90°,
not the entire cerebellum, as before, but merely the half
which lies cephalad to the cerebellar ventricle. It is as if
that half had projected much farther ventrad than the other
half, as a free lip, and had then been bent cephalad into a
horizontal position. Thus the grey matter which normally
lies next the cerebellar ventricle becomes ventral adjacent to
the aqueduct of Sylvius, and the white matter becomes dorsal
adjacent to the roof of the optic lobes. This volvula is about

Herrick, Morphology of Brain of Bony Fishes. 225

half as long as the exposed part of the cerebellum, and is
thrust cephalad into the third ventricle nearly to the superior
commissure.

Metencephaton.—\he medulla is remarkable for its great
depth, as well as its great width. The width is due, in
large measure, to the presence of the wide, lateral lobes
connected with the descending tracts of the cerebellum.
The depth is, in part, due to the great development of the
two pairs of dorsal tuberosities. Of these the cephalic or
trigeminal tubers are much the larger. They rise in the floor
of the fourth ventricle to a height nearly as great as that of
the cerebellum. They are strictly intra-ventricular, and are
covered by the membranous roof of the ventricle. The
interior is occupied by fibres and cells pertaining chiefly to
the trigeminal nerves. The other pair of prominences, the
vagal tubers, are, for the most part, extra-ventricular. The
fourth ventricle lies between them, and its membranous roof
extends from the mesal surface of the one to that of the other.
Most of the fibres of the dorsal root of the vagus take their
origin from this pair of tuberosities. Behind the vagal
tuberosities the fourth ventricle closes. Its caudal
limit is marked by an elevated ridge, or crest, of
transverse fibres. Farther caudad, at the exit of the so called
first spinal nerve, the medulla is thickened on both dorsal and
ventral surfaces, behind which it passes at once into the
spinal cord. On the ventral surface there is another con-
siderable thickening at the exit of the trigeminus. The
ventral surface otherwise presents very few features of note.
The ventral fissure, too, is not so deep as the dorsal. The
cranial nerves are discussed elsewhere in this article.

Ventricles.—In discussing the encephalic ventricles we
shall pass from the spinal cord cephalad. The canalis spinalis
is very small. It gradually enlarges in the medulla up to the
exit of the dorsal root of the vagus, where it is suddenly
extended dorsad to the surface, thus forming the fourth
ventricle. From this point the ventricle is very deep, but

226 JOURNAL OF COMPARATIVE NEUROLOGY.

quite narrow until the vagal tubers are passed, after which it
rapidly expands until at the exit of the ventral root of the
vagus it occupies the whole dorsal surface, not excepting the
lateral, lobes or cerebellar peduncles. Farther forward the
ventricle contracts into the aqueduct of Sylvius and passes
under the cerebellum, into which it sends a very narrow arm.
This cerebellar ventricle passes directly dorsad and does not
turn cephalad with the cerebellum. Immediately cephalad
of the volvula the aqueduct expands into the third ventricle,
which, at the same time, communicates laterally, by wide
openings, with the ventricles of the optic lobes near their
cephalic ends. The latter bodies are hollow throughout their
entire length, though the ventricle is much larger cephalad.
In this region the triangular ventral part of the third ventricle
is bridged over by the superior commissure, and from this
point forward severs its connection with the dorsal part.
The torus longitudinalis (fornix ) very soon comes into contact
with the superior commissure, and thus separates the ven-
tricles of the two optic lobes again near their cephalic ends.
Beneath the superior commissure the third ventricle dips
suddenly ventrad in the form of a narrow cleft, reaching to
the surface. In its descent it sends two branches laterad into
the hypoaria, expands in the cinereum, and then sends an
arm caudad into the saccus vasculosus and another cephalad
into the infundibulum. The ventricle of the cinereum lies
in about the centre of that body. It is about one-third as
wide as the cinereum, but very thin dorso-ventrally. Ventrad
of this expansion the third ventricle gives off a very small
branch on each side (.5 mm. in diameter) which is lined with
very strong epithelium and extends caudad near the median
line between the hypoaria for some distance into the base of
the saccus vasculosus. The ventricles of the hypoaria are
crescent-shaped, diminishing caudad to sub-triangular and
oval. Just cephalad of the superior commissure the epiphysis
arises from the dorsal surface, as above described. Cephalad
of the dorsal sac the third ventricle passes into the cerebral

Herrick, Morphology of Brain of Bony Fishes. 2247

ventricles by a wide foramen of Monro. Aula and porte can
scarcely be separately distinguished. The median fissure is
so poorly developed that the lateral ventricles of the two
hemispheres are practically continuous for the whole length
of the cerebrum. The limits of the cerebral ventricles are
implied in the description of the pallium given above. They
pass from the median fissure laterad to the sinus rhinalis of
each side and envelop the entire cephalic aspect of the basal
lobes. The basal lobes are entirely separated, except in the
region of the anterior commissure, by the cerebral ventricle,
down, even to the extreme ventral limit of the cerebrum,
where the ventricle is bounded by a membranous floor. The
relations of the cerebral ventricles to the ventricles of the
olfactory lobes are discussed in the section devoted to the
rhinencephalon.

DESCRIPTION OF PLATE XVII.

Fig. 1. Dorsal view of the brain of the adult mud cat fish, or
yellow cat, Prlodictis olivaris Gill and Jordon. The olfactory lobes,
with most of the crura, have been removed. The trigeminal, vagus and
first spinal nerve-roots are shown. 2.

Fig. 2. Dorsal view of the brain of a young bull-pout, Amurus
catus Gill, three inches long. The olfactory lobes have been removed.
xX 4-

Fig. 3. Dorsal view of the brain of a much younger bull-pout, one
inch long. The olfactory crura are reduced until the olfactory lobes are
closely appressed to the hemispheres. to.

Fig. 4. Ventral view of the brain of the adult mud cat, Prlodictis
olivarts. The olfactory lobes, hypophysis and saccus vasculosus have
been removed. The Roman numerals refer to cranial nerves. 2.

Fig. 5. Lateral view of the brain of Pvlodictis olivaris, designed
to illustrate the distribution of the cranial nerves. The various nerve-
roots are retained, as nearly as may be, in their natural positions. The
olfactory lobes have been removed; o/., olfactory crus; x. of., optic
nerve; V,, V2, V3, V4, V5, Vg, Vz, the seven principal branches of the
trigeminus nerve; F,, F,, F;, F,, the four principal foramina of the
trigeminus verve; V//, the facial nerve; ~. dep. of., nerve of the
depressor operculi; ~. /ev. of., nerve of the levator operculi; V///,
acoustic nerve; /X’, glosso-pharyngeal nerve; gX, ganglion of the
vagus nerve; z.//., nerve of the lateral line; X vsc., visceral branch of
the vagus; .Y ¢h., thoracic branch of the vagus; x. d. f., nerve of thc
depressor of the pectoral fin; x. 2. /., nerve of the levator of the pectoral

228 JOURNAL OF COMPARATIVE NEUROLOGY.

fin; 7, 77, 7/7, 7V., nerves to the four gills, respectively; 7. sp., the
first spinal nerves.

For full discussion of these nerves see text under cranial nerves.

Fig.6. Transection of cerebrum of /ctalurus cephalad of the
anterior commissure.

Fig. 7. Transection of the same brain at the level of the pre-
commissura, Prec. The tracts from the olfactory radices are seen in
section dorsad of the precommissura on either side the median line.
O. tr., optic tracts; Ped., peduncular fibres.

Fig. 8. Transection of the same brain at the level of the habena,
H.; Cer., cerebellum.

II. STUDIES ON THE BRAINS OF SOME AMERICAN
FRESH-WATER FISHES.

Cala HERRICK:

A.—TopoGRAPHy.

The olfactory lobes have an essentially similar structure
throughout the various families of Teleosts, but there is
a great variation in position, which is a function of the
position of the nasal capsules and the form of the cranial
cavity.

Every gradation between an olfactory lobe closely sol-
dered to the cerebrum and one separated by many times the
length of the whole brain from the hemispheres may be en-
encountered in our fresh-water fishes. The gizzard-shad
(Dorosoma), which has a decidedly reptilian brain, is an
illustration of the first type (Figs. 6-7, Plate XIX). Sec-
tions of the olfactories of this species in front of the cerebrum
are semi-oval, with the larger extremity of the oval dorsad.
A shallow groove occupies the middle of the dorsal surface.
In section, the membranes may tend to separate from the
lobe, but there is no true ventricle. At this level the lobe is
composed of the usual glomerulary structure with Deiter’s
nuclei, and the whole is richly supplied with small vessels.

Herrick, Morphology of Brain of Bony Fishes. 229

The glomerules are chiefly massed ectad. The nervous ele-
ment are small and inconspicuous.

The cerebrum overlaps the olfactory dorsally, and the
lateral ventricle descends to the level of the olfactory
mesally, but is separated from the crus by a small spur of
the cerebrum. Gradually the olfactory lobe narrows into the
crus, and is embraced by the cerebrum laterad as well as
mesad. The cerebrum is completely enveloped by the pal-
lum and ventricle except near the attachment of the crus
and thence some distance laterad to beyond the rhinalis
fissure or sinus of the ventral surface. There is a dense col-
lection of fusiform cells mesad of the crus on either side of
the ventricle. The latter represents a forward protrusion
of the third ventricle rather than the aula. The centre of the
crus is occupied by a tract, while others gather about the
rhinalis sinus. The first mentioned tract can be easily traced
as far caudad as to the anterior (or interlobular) commissure,
where it turns mesad, decussates with its fellow and con-
tinues in nearly the same relative position toward the thala-
mus upon the opposite side. Other fibres derived from the
crus follow the rhinalis sinus and constitute a distinct radix
lateralis which can be traced to a point opposite to the com-
missure, where they seem to enter the hippocampal lobe, to
be described beyond, although part may pass directly mesad
to the commissure.

In //yodon (the moon-eye) the olfactory lobes are un-
usually large and lie some distance from the cerebrum, while
the lateral ventricles extend well out upon the dorsal surface
of the crura cephalad of the cerebrum. The crura are accord-
ingly flattened, and enter the meso-cephalic angle of the
cerebral lobes in two partially distinct radices. The radix
lateralis is smaller, and spreads out about the sinus rhinalis
in the form of a series of small bundles. The radix mesalis
is a large bundle, which retains its position in the ventro-
mesal angle of the cerebrum as far caudad as the anterior
commissure.

230 JOURNAL oF COMPARATIVE NEUROLOGY.

The buffalo fish ( Carfzodes) furnishes an illustration of
long-stalked olfactories. The crura are enormously elongate
and the ventricles extend a long distance upon the dorsal
surface of the crura proper, being covered by a thin pallium
similar to that of the hemispheres.

The arrangement is well seen in Fig. 1, Plate XIX, where
the dorsal pallium has been removed from the cerebrum but
remains on the crura. The sections (Figs. 4-5, Plate XXI)
illustrate substantially the same arrangement as seen in the
black-horse ( Cycleptus). The radix lateralis is wider than
its fellow and very thin vertically, while the radix mesalis is
rather compact and enters the ventro-mesal angle of the
cerebral hemispheres.

The radix lateralis first becomes attached to the cerebrum
by its lateral border. Then the mesal radix becomes attached
to the mesaxial lobe, which is here quite distinct, thus cut-
ting off a spur of the ventricle, which remains distinct some
distance caudad. The connection with the common ventricle
or aula is upon the cephalic aspect, affording evidence that
the porte in this case may almost be said to lie entirely
cephalad of the hemispheres. The forward extension of the
ventricles beyond the cerebrum is, we believe, a fact of
primary importance in understanding the morphological
significance of fish brains. The subsequent course of the two
radices are distinct, and corresponds to that described in the
black-horse ( Cycleptus), which furnishes one of the best
illustrations of the tubular olfactory crus. Transverse sec-
tions show that the arrangement of ventricles, etc., is the
same as that described by my brother in the cat-fish. The
transection of the crus cephalad of the cerebrum shows it to
be composed of a tubular sheath of membrane, with the fibres
collected in two somewhat distinct bundles along the ventral
surface, entering the radix lateralis and mesalis respectively.
There is, however, a narrow band of fibres between the
sheath and the epithelium lining the ventricle. The ven-
tricle passes into that of the cerebrum at a point where the

Herrick, Morphology of Brain of Bony Fishes. 221
? ped 1 g; f

latter entirely surrounds the frontal projection of the hemi-
spheres. The pallium thus embraces both the olfactory and
cerebrum before the olfactory enters the hemisphere (see
Plate XX, Figs. 1-4).

In Siluroid fiishes the olfactory lobes are stalked in the
adult. The two radices are scarcely distinct before entrance
into the cerebrum, but at once separate thereafter. Accord-
ing to C. Judson Herrick, the ventricles enwrap the crura
nearly completely throughout their course (see above for
details. }

In the eel the olfactory lobes are relatively large and
sessile (Plate XIX, Figs. 9-11), and are overlapped by the
hemispheres, which are lunulate in section. The mesaxial
lobe is distinct but large, and receives the radix mesalis on
the ventro-mesal angle. The two radices appear before the
crus enters the hemisphere.

In the eel, more easily than in any other fish examined,
the course of the radix mesalis can be clearly traced. The
tract preserves its identity fully, and crosses as an entirely
distinct bundle of the hippocampal element of the anterior
commissure. After decussating it reappears in the corre-
sponding position on the opposite side, and can be traced to
the medi-dorsal part of the thalamus. The radix lateralis
follows cephalad to the region of the anterior commissure,
where it turns suddenly mesad and crosses through the
peduncular bundles and unites with the tract of the radix
mesalis and decussates with the latter. The fibres of both of
these radices are light-colored, while the bulk of the anterior
commissure fibres are very dark. Horizontal sections
especially leave no doubt as to the course pursued by these
fibres, though, of course, the possibility is not excluded that
other connections exist, especially with the cell masses corre-
sponding to the hippocampus.

In the buffalo fish (Carpiodes) longitudinal sections seem
to show that part, at least, of the fibres of the radix lateralis
pass to the hippocampel lobe,

232 JOURNAL OF COMPARATIVE NEUROLOGY.

SUMMARY OF OLFACTORY LOBES.

1. The olfactory lobes are exceedingly variable in size
and position, but exhibit no decided differences in structure.

2. The primary condition is similar to the permanent
condition in Sauropsida, z.c., the lobes are sessile or attached
by short crura to the base of the cerebrum; but their con-
nection with the cerebrum is more accidential than essential.

3. Whether they become stalked or not depends on
whether the growth of the head removes the peripheral
organs of smell from the brain at an early period, and
whether, in case it is so removed, the olfactory nerve or crus
is elongated. The probable determinant for the latter is the
relative rate of development of the various regions of the
head. The olfactories are always sessile in an early stage.

4. The crura contain two distinct tracts, forming a radix
mesalis and lateralis.

5. The lateral ventricle is frequently extended into the
the crura, but the form it assumes varies. In the extreme
case the crus is a hollow cylinder, with the fibres chiefly
collected in the ventral portion. In other cases the ventricle
simply extends a short distance along the dorsal surface of the
crus.

6. In some cases there is a rudimentary olfactory ven-
tricle in the substance of the lobe.

7. The radix mesalis enters a special mesaxial lobe of
the cerebrum and its fibres decussate in the commissura
interloborum, forming with the next a hippocampal com-
missure and fornix.

8. The radix lateralis follows a gentle groove (sinus
rhinalis) on the ventral surface of the hemispheres to a point
opposite the decussation of the radix mesalis when it turns
abruptly mesad and crosses to the opposite side; but probably
also gives off fibres to the hippocampus. According to
Owen the olfactory lobes are sessile in Perca, Scomber,
Esox, Pleuronectes, Blennius, Anguilla, Gasterosteus, Eper-

Herrick, Morphology of Brain of Bony Fishes. 233

lanus, Cottus, Trigla, Amblyopsis, Echeneis, the Ganoidei
and Lepidosiren; and long-stalked in Salmo, Cyprinus,
Brama, Tinca, Gadus, Lota, Hippoglossus, Clupea, Belone,
Leucioperca, Cobitis, Plectognathi and Plagiostomi.

The Cerebrum.—The topography of the cerebrum cannot
be satisfactorily discussed until much extended and careful
observations have been accumulated. In the groups examined
it is relatively constant, and such differences as appear are
often less important than they at first seem. The form varies
chiefly as a result of the varying size and position of adjacent
_portions of the brain. The dorsal view usually presents a
sub-quadrangular outline, tending to oval. From the side
one may observe a rudimentary fissure and curvature corre-
sponding to the fissure of Sylvius of higher brains. The
transverse section is nearly always sub-triangular, with the
curved base of the triangle dorsad. The cerebrum presents
three well-marked aspects: a mesal surface, facing the median
fissure (in cases where the pallium of the two hemispheres
fuses completely this aspect is absent or represented solely by
the corresponding aspect of the axial lobe); a dorso lateral
aspect, generally one continuous curved surface; and, third, a
ventral or rhinalic aspect. The last mentioned surface differs
from the others in being chiefly a non-cortical or axial
surface, as is the case in the corresponding area of higher
brains. It is bounded laterally by a more or less distinct
fissure or sinus, the rhinalis sinus, which is more distinct,
cephalad. This fissure is the undoubted homologue of the
rhinalis fissure of highér vertebrates in so much as the radix
lateralis of the olfactory crus occupies the adjacent region.
The pallium separates at this point. It must be constantly
kept in mind that the. fissures upon the dorsal surface of the
cerebrum of fishes cannot have the same significance as the
cortical fissures of mammals. The Sylvian fissure, however,
seems to be obscurely indicated by a depression near the
middle of the lateral surface, which results from an incipient
flexture. There are upon the dorsal surface a number of de-

234 J OURNAL OF COMPARATIVE NEUROLOGY.

pressions, which are impressed upon the axial lobe, and may
or may not be obvious before the removal of the pallium.
Three of these are especially constant. First, the frontal
jissure, separating the mesaxial lobe superficially from the
remainder of the cerebrum. This fissure begins upon the
cephalic or ventral surface and extends parallel to the longi-
tudinal fissure a longer or shorter distance upon the dorsal
surface. The occipital fissure occupies an analogous position
upon the occipital region, and in extreme cases unites with
the frontal to form an occipito-frontal groove. The third
fissure is the dorsal portion of the Sy/vian fissure, and extends
a variable distance toward the occipito-frontal.

By the aid of these external landmarks and the variations
in internal structure, a few pretty well-marked regions of the
axial lobe may be conveniently designated. The mesaxial
lobe is that region bordering the longitudinal fissure and
limited laterally by the frontal fissure. The cextral lobe is
an ill-defined region, with few large spindle cells lying in the
central and ventral portions of the cerebrum. In some cases
there is a well-defined line of demarkation between this and
adjoining areas. It is in the ventral portion of this lobe that
the peduncles enter the cerebrum, and it may be looked upon
as forming in a special sense the homologue of the striatum.
The /ateral or parietal lobe embraces the lateral portions of
the cerebrum, and, though frequently imperfectly defined
externally, differs in cellular structure sufficiently to make its
recognition possible. A small lobule lying between the
Sylvian and occipital fissures may be called the cazeus with-
out implying any homologies with higher brains (see Fig. 1,
Plate XIX). An occifita! lobe may be recognized in the
caudad projection lying adjacent to the haben, and a ¢em-
poral lobe upon the caudo-lateral aspects behind the Sylvian
fissure. There is a caudo-ventral projection which is invaria-
bly present, and, from its being the starting-point of the
posterior part of the pallium, may be compared to a hippo-
campus, and will be referred to as the hippocampal lobule.

Herrick, Morphology of Brain of Bony Fishes. 235

The Thalamus.—In general, it may be admitted that Baer
correctly characterized this region in the statement, ‘‘ Es
sieht so aus, als ob das Mittelhirn das Zwischenhirn unter-
driickt habe.” The strong optic nerves and tracts serve to
constrict the organ greatly and obscure the original form.
In some cases the origin of the epiphysis and habena are
visible from above, while in others, like the black-horse, the
mesencephalon is thrust forward by the great development
of the volvula, so as to cover much of the cerebrum itself.
Apparently, as a result of the constriction of the middle of
the thalamus, it is forced caudad, and, to supply the requisite
nervous material, develops the hypoaria or inferior lobes,
which, instead of representing the mammillary bodies, seem
to contain the homologues of the displaced walls of the
median part of the thalamus. The saccus vasculosus marks
the caudad extension of the thalamus. It seems necessary
to recognize three parts of the thalamus, as follows. Zhe
prethalamus: This includes the ventral median region
caudad of the anterior commissure and ventrad of the hippo-
campal lobules. It is quite distinct from the adjacent parts
of the cerebrum, and contains the various tracts passing
from it toward the lower parts of the brain. The mzd-thala-
mus is that part which corresponds to the principal part of
the organ in reptiles and bears the habena. Its caudal limit
may be recognized in the inferior commissure. Caudad of
the this, and extending as far as the saccus vasculosus, is a
portion which is covered dorsad by the optic lobes, and
bears laterally the hypoaria. This may be termed the Jost-
thalamus .

There is no difficulty in recognizing these divisions in
any of the Teleosts examined.

Mesencephalon.—The topography of the optic lobes differs
from that of reptiles only by reason of the greater or less
invasion of the optic ventricle by the volvula. Transections
of the mesencephalon of the eel cephalad resemble corre-
sponding sections of the turtle closely. There is a slight pro-

236 JOURNAL OF COMPARATIVE NEUROLOGY.

jection into the ventricle from the base, forming the colliculus
or torus, with the concentric arrangement of cells character-
istic of the colliculi, and the rather thick tectum exhibits the
the same pronounced stratification of elements. Along the
median dorsal line the dependent ridges known as the tori
longitudinalis are evident, though relatively small, and seem
to make up for the slight development of the granular zone
of the tectum.

In the drum the extensive development of the volvula,
and its compact plication within the ventricle serve to greatly
modify the tectum and other bodies. The whole organ is tilted
forward so that the apparent cephalic aspect really represents
a large part of the dorsal. The tori are therefore cut longitu-
dinally in transections cephalad, so that their apparent size
is increased. On the dorsal surface, however, the tectum is
forced apart, and the tori form the starting points for the
membranous expansion which bridges over the interval sepa-
rating the two halves. The colliculi are likewise thrust
apart and modified as to form by the same means.

The black-horse affords an illustration of an extreme
modification resulting from the exceptional development of
the volvula. The mesencephalon in this case extends far
cephalad over the hemispheres, while its entire dorsal surface
-is reduced to a membrane. The tori are thus extended in
the same plane as the tectum, and serve as supports for
the membranous roofs (Plate XIX, Fig. 4). The position
and structure of the corpus posterior will be discussed
in the histological part of this paper, as will the cranial
nerves.

The Cerebellum.—The present notes may be regarded as
supplementary to the earlier paper on the archetectonic of
the cerebellum. In it we attempted to show that the varia-
tions in structure exhibited in different groups could all be
reduced to a common type and their differences explained by
tracing the invaginations and evaginations of the walls of the

fourth ventricle. No better illustration of this principle

Herrick, Morphology of Brain of Bony Fishes. 237

could be selected than that furnished by the Teleosts. The
cerebellum is the most variable, and, at the same time, the
most characteristic segment of the brain. It varies greatly
even in the same group, yet the plan of structure is constant
and is even suited to characterize families and genera. The
structural peculiarity which is characteristic of all fishes is
the volvula (valvula of authors). This organ may be briefly
defined as a modification of that part of the roof of the aque-
duct of Sylvius which lies between the valve and the tectum.
Its structure is essentially that of the cerebellum, and it is
directly connected with the tectum cephalad. The extent to
which it develops seems to depend upon a variety of circum-
stances. When for any reason the cerebellum fails to acquire
the normal size the volvula may compensate therefor. The
size of the cerebellum as a whole (including volvula) is un-
doubtedly a function of the activity of the fish. Thus, for
example, the black-horse and buffalo-fish are allied systemat-
ically and live in the same streams, but the former is a very
active carp, while the latter is sluggish and massive. The
main portion of the cerebellum is of relatively the same size
in the two fishes, but a glance at Plate XIX, Figs. 1 and 4,
will convince one that the development of the volvula in the
black-horse corresponds to its active habits. In the typical
cases the volvula is but a forward fold into the optic ventricle,
but numerous secondary modifications obscure this primitive
simplicity. It may be well to refer to several illustrations at
this point, remembering that the cerebellum is mechanically
the least stable of the structures of the brain. The axial
portion of the organ is a thickening of the roof of the fourth
ventricle. The caudal and lateral aspects of the roof are
reduced toa membranous velum or infolded to form a plexus,
while the cephalic boundary is altered to form the velum
anterior or volvula. Thus the only rigid attachment of the
cerebellum is that formed from the relatively small pedun-
culi. Rotations in all directions except cephalad meet with
no opposition, and the absence of closed cranial walls permits

238 JOURNAL OF COMPARATIVE NEUROLOGY.

the resulting organ to occupy almost any portion with refer-
ence to the axis of the brain.

The moon-eye, //yodon, is perhaps the most reptilian
brain of the osseous fishes here noticed, and has the simplest
cerebellum. It is probably one of the best types in which to
study the archetectonic of the cerebellum and optic lobes in
comparison with those of reptiles. The optic lobes are large
and almost absolutely unmodified by the cerebellum, except
in so far as the corpora posteriores are thrust ventrad and
laterad. The volvula is well developed, and its dorsal lamina
passes directly into the tectum. The valve is small. Im-
mediately caudad of the valve the cerebellum swells into a
large, thick sac which soon becomes free from the walls of
the medulla. The cavity of the cerebellar ventricle is not
suppressed, and there is very little to suggest the complicated
projections of the calamus and vagus regions of the medulla
found in most fishes, especially the carps. The cerebellum
thus forms a simple lobe, projecting over the partly exposed
opening of the fourth ventricle. It is relatively small, as may
be gathered by a comparison with corresponding views of the
Gizzard-shad (Plate XIX, Fig. 7).

As in Lepidosteus, the cephalic part of the mesencephalic
ventricle is not entered by the volvula. Transections in front
of the oculomotor roots resemble similar sections of reptilian
brains, except for the presence of the small hypoaria. The
tori longitudinalis, or appendages of the median line of the
tectum, are large.

The volvula extends cephalad to just in front of the third
nerve-roots where it appears two-lobed, having the appar-
ently ectal (ventricular) surface composed of gray matter, a
median zone of Purkinje’s cells, and a central mass of white
matter. Farther caudad the cavity due to the invagination
is encountered, surrounded by the white zone, which is,
therefore, morphologically ectal. The dorsal wall of the sac
thins out and passes into the membranous caudal wall of the
optic lobes, which are obviously paired at this level.

Herrick, Morphology of Brain of Bony Fishes. 239

The fourth nerves pass caudad to the optic lobes, around
which they arch, and enter the narrow, slit-like opening of
the volvula and then continue cephalad nearly to the level
of the caudal margin of the hypoaria, where they meet and
dip suddenly ventrad into the substance of the valve, then,
after decussating, they continue cephalad to the ventro-
lateral margin of the valve, and, arching about the aqueduct,
enter the nidulus near the median line and adjacent to the
aqueduct and bounded ventrad by the dorso-median fasciculus.

Caudad of the valve the roof of the fourth ventricle
expands and thickens into the median lobe or vermiforme of
the cerebellum, being for sometime connected with the lateral
walls of the ventricle by thick lateral lobes which have not
the structure of the cerebellum, but contain an intimate
mixture of granules, nerve-cells and fibres. The cerebellum
proper is, as above said, simply a caudad pouch
from the roof of the fourth ventricle, which, however,
remains for some distance in contact with a mass similar in
composition to the lateral lobes which forms the transition
into the velum posterior, and is homologous with the ‘‘bursa”
of the sturgeons.

In the gizzard-shad, although the brain is so similar to the
moon-eye, externally, the cerebellum is remarkably modified
in details of structure. What at first gives great trouble, is
the fact that in the axial part of the cerebellum or vermiform
lobe the gray matter is apparently ectad instead of internal.

To a point about one-third the length of the optic lobes
from their caudal boundary the relations are as above. The
volvula is small, and its cavity nearly closed. The cerebellum
proper is driven forward between the optic lobes, and
especially dorsad, so that, as though by actual lateral
pressure, the organ is thrust together upon itself and its
dorsal and cephalic surfaces are folded in along the median
line and the lateral white matter is reduced to a mere
membrane, only recognized by careful examination. The
appearance of lateral compression in the fungiform contours

240 JOURNAL OF COMPARATIVE NEUROLOGY.

is remarkably verified in transverse section. A caudad
diverticle of the cul-de-sac from the exterior extends to the
level of the valve where the fourth nerve enters without the
curvature described in the moon-eye, but which is here un-
necessary by reason of the divarication of the optic lobes.
At this level the cerebellum is obviously folded upon a
longitudinal fissure for almost its whole height, though the
fissure has been practically obliterated by the union of the
walls. <A little caudad a rudiment of the caudal diverticle of
the fourth ventricle can be detected, and the arrangement of
the gray and white matter shows that the duplication has
been affected in the usual manner, yet the cavity is absent,
and the whole organ is so closely adherent to the combined
lateral lobes that only a comparison with simpler types
explains the seeming anomalies.

This case is very instructive as showing how far the
distortion and secondary union of parts may obscure perfectly
simple homologies.

In the eel the cerebellum may be characterized as a simple
depressed variety with small volvula. In striking contrast to
the gizzard shad, the modifications are such as could most
easily be referred to the effects of pressure from above. The
volvula is exceptionally small. The fourth nerve enters
directly behind the optic lobes, decussating in a very obvious
and uncomplicated valve. The dorsal lamina of ‘the volvula
passes into the tectum opticum with but a short velum
cerebelli anterior. Caudad of the trochlearis there is a slight
pocket and corresponding revolution cephalad. Then for
some distance the cerebellum is a simple thickened dorsal
wall of the fourth ventricle which, nevertheless, has the
appearance of having been thrust ventrally into that cavity,
with the result of thrusting the ventricular gray layer of the
cerebellum laterad and dorsad, so that it is thicker on the
lateral than the ventral aspects and projects on either side as
a slight protuberance on the lateral margin of the dorsal
surface. The caudad portion of the cerebellum is a sac-like

Herrick, Morphology of Brain of Bony Fishes. 241

diverticle, the lumen of which has been extinguished by the
same ventrad pressure, so that the dorsal and ventral granular
layers adhere and fuse in the centre. Some evidence of the
cavity still remains, however, in spurious lateral recesses,
consisting only of membrane connecting the partially everted
lateral portions of this ventricular layer. The posterior por-
tion of the cerebellum is thus reduced to a double leaf-like
valve over the calamus region.

In Cyprinoid fishes the cerebellum is greatly developed,
but strictly the same principle is followed as indicated above.
The volvula is highly developed and complicated. The con-
nection between the dorsal lamina of the volvula and the
caudo-lateral edges of the optic tectum is affected well ceph-
alad near the median line between the tori longitudinalis.
Behind the valve there is a sudden dorsal expansion contain-
ing a moderate cephalad protrusion of the cerebellar ven-
tricle, which latter is connected by a dorsally elongated strait
with the fourth ventricle. The posterior part of the cere-
bellum is free and directed obliquely dorso-caudad, and is
flattened somewhat. The caudad protrusion of the ventricle
thus becomes a mere line or is indicated only by the fused
granular zones of the dorsal end ventral lamina. The lateral
lobes of the cerebellum are very large.

In the buffalo-fish, Carpfzodes, the cerebellum has a strong
but not exaggerated development. The optic lobes, in con-
sequence, are thrust cephalad and moderately dilated. The
volvula is enormously developed and thrust forward. Its
most remarkable peculiarity is that cephalad it becomes
bifurcate. The dorsal lamina is fused with the ventral for
much of its length, and the granular portion of the dorsal
lamina is present only near the tip. The lamina becomes free
caudad and unites with the velum near the median line, as in
the carp, though the union does not take place so far within
the optic lobes and the tori extend far out on the velum.

In the region of the valve the lower lamina is greatly
thickened. Except that the cephalad diverticle of the cere-

242 JOURNAL OF COMPARATIVE NEUROLOGY.

bellar ventricle is somewhat larger; the remainder of the
cerebellum is precisely as in the carp.

In the older individuals the great lateral expansion of the
volvula is remarkable.

The extreme in this type of cerebellar differentiation is
reached in the black horse, Cycleptus elongatus. In this case”
the optic lobes are thrust far cephalad over the cerebrum and
expanded laterally like a hood. The tectum is wedged apart
and the two tori are connected by a wide stretch of thin
membrane only. The volvula is enormous, and consists of a
central and two lateral lobes, in which the simple fold, which
is the real source of the structure, is effectually obscured.
The lateral lobes are pushed cephalad as divergen tuber-
osities. The appearance is as though these bodies had been
formed by excessive lateral growth, which, among other
things, had removed the granular layer entirely from the
dorsal lamina and then crumpled the whole organ by lateral
pressure. The middle lobe is morphologically the ventral
lamina, which is thrust between the the two moities of the
dorsal lamina.

This explanation solves the apparently unreconcilable
conditions. The lateral lobes or severed portions of the
dorsal lamina of the volvula extend far caudad of the point
where the ventral lamina emerges as the roof of the fourth
ventricle or vermiform portion of the cerebellum.

The presence of these two latero-caudal excrescences on
either side of the median portion of the cerebellum is the
obvious external cause of a median infolding of its dorsal
roof, which is indicated even in the external view by the
groove seen in Fig. 4, Plate XIX. In transverse sections the
fold is seen to be an exceedingly deep one, though the edges
coalesce completely.

The remainder of the cerebellum is as in the carp, except
that the mode of connection with the medulla is modified by
the lateral pockets containing the divaricated caudal protru-
sions of the volvula.

Herrick, Morphology of Brain of Bony Fishes. 243

The cat-fish group presents more remarkable variations,
which have been explained in detail by C. Judson Herrick.

In the drum the most remarkable peculiarity of the mid-
region of the brain is its relative shortness; the cerebellum is
crowded far dorsad and lies perched, as it were, between the
trigeminal lobes and the vertically elongate optic lobes. The
great dorsal elevation and corresponding shortening of the
optic lobes could not fail to exert a greatly modifying influ-
ence on the volvula, which in these fishes is very large. The
result is seen in a curious multiple folding of the dorsal
lamina in the frontal plane; so that successive lobes appear
in transverse section. The remainder of the cerebellum
shows no other effect of the compression than that exhibited
in its position and a slight cephalo-dorsal protuberance.

The examples cited are sufficient to show that the most
divergent types may easily be reduced to a single funda-
mental form.

The cranial nerves have not been carefully studied in this
connection, because of an exegency of publication, nor has
there been opportunity to compare the papers of Prof.
Wright on the cranial nerves of the cat fish. In the cat
fish the exaggerated development of the trigeminal system is
well illustrated in the earlier installment of this series, by C.
Judson Herrick.

In the drum (//aploidonotus) the following relations
prevail: The vagus consists of two nearly equal branches, one
of which springs from the caudal portion of the vagal tuber-
osity, while the other is derived from the extreme cephalic
portion, and both are apparently derived from nearly the
same dorso-ventral level. The two branches remain distinct
for some distance, so that the cephalad root has an in-
dependent course, nearly twice as long as that of its fellow.
At their union a more or less distinct ganglion is developed. »
From the latter the small nerve of the lateral line arises. A
visceral branch and a branch probably supplying the pectoral
fin-muscles follow, and then five branches to the gills, the

244 JOURNAL OF COMPARATIVE NEUROLOGY.

caudal one dividing peripherally. The ninth nerve is much
smaller than either branch of the vagus, and arises from the
caudo-ventral aspect of the very tumid trigeminal lobe, a
short distance caudad of the eighth. It soon receives a small
anastamosing branch from the cephalic root 6f the vagus,
which returns to the latter a little farther peripherad, but
proximad of the ganglion. The distribution of the ninth is
as described in the cat fish.

The eighth has two distinct roots, but the cephalic branch
is closely associated with the seventh, which is distinct
from the fifth beyond Gasser’s ganglion, and is distributed to
the opercular and gular regions.

At its roots the fifth nerve is composed of three chief divi-
sions, but beyond the ganglion there are five, the most dorsal
of which is the trigeminal accessory nerve of the lateral line.

The sixth is small, and no separate root was found. The
third and fourth are small, but normal, and the remaining
nerves offer no peculiarities.

AGT Ee Ole

Fig. 1. Dorsal view of the brain of the buffalo-fish, Carpiodes
tumidus, B. and G. L.v g., vagal lobes; VIII, eighth nerve; da. Z.,
mesaxial lobe of the cerebrum; Cuz. /., cuneate lobe; Z. /., lateral lobe;
Op., optic nerve.

Fig. 2, Lateral view of the same brain. Hy., hypophysis;
F. oc., occipital fissure; /’. Sy/., Sylvian fissure; V 7 d., dorsal root of
cephalic division of trigeminus; I’ 7. v., ventral division of the same;
V 2., caudal trigeminus.

Figs. 3-5. Three views of the brain of the black-horse, Cycleptus
elongatus. Hyp., hypophysis; 7. czz., tuber cinereum; vg. /., vagal
lobe; //pa., hypoaria.

Figs. 6-7. Wateral and dorsal views of the brain of the gizzard-
shad, Dorosoma crepidianum.

Fig. 8. Dorsal view of the brain of the moon-eye, //yodou tergt-
sus. The hemispheres are divaricated and deprived of the pallium.

Figs. 9-11. Three views of the brain of the common eel,

PLATE XX.

A series of transections of the brain of the black-horse, Cycleptus
elongatus. A description of histological details will be given in a sub-
sequent paper.

Herrick, Morphology of Brain of Bony Fishes. 245

Fig. 1. Section at the union of the olfactoria with the rhinalic
aspect of the hemispheres. Of. x., optic nerve.

Fig. 2. Section somewhat caudad of the above. Caf. /., lateral
lobe; AZesa. /., mesaxial lobe; /. rhrn., rhinalis fissure.

Fig. 3. Section cephalad of the decussation of the optic nerves.
The cerebrum is here overarched by the mesencephalon and the volvula.
Hip. l., hippocampal lobe; dvo/v., volvula cerebelli.

Fig. 4. Section at the decussation of the optic nerves. Torus
long., torus longitudinalis; A/embr. tect., the tela tecti or membranous
portion of the tectum opticum.

Fig. 5. Section through the priethalamus, pre. 7h.

Fie. 6. Section through the mid-thalamus. //., habena.

Fig. 7. Section cephalad to hypoaria. J/. 6., Meynert’s bundle.

Fig. 8. Section through post-thalmus.

Fig. 9. Section at the caudal level of the hypoaria. Region of
mesencephalic decussations. Ag. S., aqueduct of Sylvius.

Fig. 10. Section at the beginning of the cerebellum.

Figs. 11-13. Successive sections through the medulla and cere-
bellum. Description will be deferred to subsequent installment.

PA xexc:

Figs. 1-3. Sections through the medulla of the black-horse, con-
tinuing the series of Plate XX. Ld. ¢rigem., trigeminal lobe; L. vag?,
vagal lobes or tubers. Details will be given in later installment.

Figs. 4-5. Transections through the olfactory crura and cerebrum.
Fig. 4 is some distance cephalad of Fig. 5, and on the opposite (left)

side.
Figs. 7-10. Transections of the brain of Dorosoma.

Fig. 7. Section at the anterior commissure.

Fig. 8. Section at the superior commissure.

Fig. 9. Section at the exit of the third nerve.

Fig. 10. Section at the caudal level of the optic lobes to illustrate
the great induplication of the cerebellum along the median (line at a).
The suppressed lateral ventricle, or recessus lateralis, with its mem-
branous lateral walls is indicated at ventr. lat. cerebel,

THE DEVELOPMENT OF THE CRANIAL NERVES
OF VERTEBRATES.(')

PROFESSOR C. VON KUPFFER.

Gentlemen:

There is scarcely need of the assurance that I do not stand
before you with the pretense of presenting the comprehensive
subject of my report with perfect symmetry on all sides. That
would only be possible if the development of the vertebrate
head as a whole could receive thorough treatment at the same
time. The works which relate to the cranial nerves are still
issuing, and it is difficult to predict, up to the present, how
the course of these works will influence the solution of the
problem of the vertebrate head.

In consideration of the time here allotted to such a report,
I limit my remarks to a condensed summary of the present
trend and results of research in relation solely to the morpho-
geny of the cranial nerves, apart from their histogeny and
from the remaining phases of the problem of the head.

So much may be said in advance: that in the formation of
the vertebrate head very remarkable reductions and fusions
of endodermal and mesodermal parts, and, in connection
therewith, of the peripheral nervous system, extending in
direction from before backwards, have occurred. And,

further, I venture to assert that, besides a branchial system

1 Report read at the meeting of the Anatomical Society at its fifth annual session, at
Munich, May 18, 18901. Translated for this journal, from advance sheets, by OLIvER S.
STRONG, Fellow in Biology in Columbia University.

lea

v. Kuprrer, Cranial Nerves of Vertebrates. 244

of cranial nerves, sharply distinguishable genetically from
the spinal system and belonging to the gill apparatus, a
spinal system of dorsal nerves has likewise more or less com-
pletely maintained itself.

The old theory of the spinal nature of the cranial nerves,
dating its beginnings from Proschaska and Sommering, re-
ceived weighty support through the Goethe-Oken vertebrate
theory of the skull; it outlasted the latter doctrine, and ap-
peared until recently consistent with Bell’s law. But the
embryological works of the last decade have so severely
shaken the foundations of this doctrine that so decided a de-
fender of it as C. Gegenbaur(') found himself obliged to
admit that the homodynamy of the cranial and spinal nerves
appeared to him no longer tenable. The first shock this the-
ory received was through the observation of Balfour,(*) on
elasmobranch embryos, that the mixed cranial nerves are de-
cidedly of dorsal origin, and they are also to be distinguished
essentially from the dorsal roots of spinal nerves owing to
the motor elements in them.

While Balfour did not succeed in finding in the region
of the cranial nerves any roots whatever which might be
compared with the ventral roots of the spinal nerves, he,
on the other hand, did not doubt the complete validity
of Bell’s law, and accordingly advanced the hypothesis
that there had existed originally a common fundamental
form of the nerves in the whole body which are only
represented by the dorsal roots of a mixed nature. At this
stage the differentiation of head and trunk took place, so
that the type of the spinal nerves corresponding to Bell’s law
would be regarded as secondarily acquired, while the cranial
nerves have preserved the original condition. This hypothe-

sis appeared to Balfour so much the more probable in that he

1 ‘©The Metamerism of the Head and the Vertebrate Theory of the Cranial Skele-
ton,’ Morph. Jahrb., XIII, p. 64 and 1o4.

2 “The Development of the Elasmobranch Fishes,’”’ Journal Anat. and Phys., Vol.
XI, 1877, and Handbook of Comp Anat, trans. by Vetter, Jena, 188r, Bd. II, p. 4rr.

248 JOURNAL oF COMPARATIVE NEUROLOGY.

decided,(') in opposition to the observations of Stieda(*) and
Schneider,(*) that in Amphioxus ventral motor roots were
lacking.

This hypothesis appeared untenable, since, on the one
hand, ventral spinal nerves of a motor nature are found in
Amphioxus, and, on the other hand, the development ot
ventral nerves was observed in the region of the head, as, for
example, the origin of the abducens from the ventral aspect
of the medulla in the chick, as well as in Scyllium, by
Marshall.

But, aside from the hypothesis, the fact remains that the
undoubtedly dorsal cranial nerves do not conform to Bell’s
law, but are of a mixed nature.

Van Wihje’s(*) treatise, appearing soon after the works
of Balfour above mentioned, brougnt to light the new dis-
closures, known to you, concerning the ontogeny of the
cranial nerves in Selachians as proof, on one side, that at
least two pairs of muscle nerves in the head, the oculomotor
and abducens, appear after the manner of the ventral spinal
nerve roots, and, like these, innervate only muscles arising,
as alleged, from somites, to which the eye-muscles should
belong; while the motor elements of the cranial nerves
arising dorsally are confined to the innervation of the muscles
of the visceral arches, which proceed from the lateral plates.
Relying upon this observation, Van Wihje impeached the
validity of Bell’s law, and showed the possibility that the
relations discovered for the head have further application in
the trunk, as in the enunciation of Bell’s law the vegetative
muscles in the t-unk proceeding from the lateral plates were
left out of consideration.

While Van Wihje sought in this way to establish the

t ‘*On the Spinal Nerves of Amphioxus,”’ Quart, Jour. Mic. Soc., Jan., 1880, p. go.

2 “Studies on Amphioxus Lanceolatus,’’ Mem. d. l’Academ, d. Sc. de St. Peters-
bourg, 1873, 1. 46.

3 ‘‘ Contrib. to the Comp. Anat. and Devel. of Vert.,”’ Berlin, 1878, p. 15.

4 “ On the Mesodermsegments and the Development of the Nerves of the Selachian
Head,’ Amsterdam, 1882.

v. Kuprrer, Cranial Nerves of Vertebrates. 24¢
9

agreement between cranial and spinal nerves, he himself dis-
covered at the same time facts which cause the distinction
between both groups to appear more marked than was
hitherto supposed. On one side, he shows that the dorsal
cranial nerves in respect to their course bear relations
_to the somites entirely different from the spinal nerves,
and it furthermore emerges, from his _ investigations
that the epidermis participates in the development of
the peripheral twigs of the cranial nerves, as Gotte(')
and Semper(*) had already affirmed for the N. lateralis
vagl.

Concerning the relation to the mesoderm, the dorsal
cranial nerves first take their course over the mesoderm
and on between the somites and the epidermis, but the
dorsal roots of spinal nerves pass within and below
the somites. This distinction is so important that it was
especially by this that C. Gegenbaur was driven to abandon
the homodynamy of cranial and spinal nerves, which he had
previously defended.

According to Van Wihje’s discovery, the facial, glosso-
pharyngeus and vagus enter into close connection with the
epidermis in a double row of points. On the one hand,
fusion of their ventral branches occurs at the upper hinder
side of the gill cleft which lies cephalad; on the other hand,
the rudiments (Anlage) of their dorsal branches fuse with
thickened portions of the epidermis. From the dorsal places
of connection are developed portions of the lateral-line sys-
tem with its nerves, in such a way that Van Wihje thought
the participation of elements of the epidermis in the forma-
tion of the nerves might be regarded as certain. From the
places of fusion of the ventral branches with the epithelium
of the gill clefts the terminal twigs of those branches are
developed.

1 ‘‘ Embryology of the Toad.”’
2 **Uro-genital System of Plagiostomes,’’ Arbeiten aus d. Zool.-Zoot. Institute zu
Wurzburg, Bd. II, p. 398.

250 JOURNAL OF COMPARATIVE NEUROLOGY.

A. Froriep(') has pointed out the part played by the epi-
dermis in the development of the cranial nerves in mam-
malian embryos, where, in comparison with the condition
discovered by Van Wihje in Elasmobranchs, the share of the
epidermis in this process seems scarcely less important. In
cow embryos such processes take place in the region of the
facial, glosso-pharyngeal and vagus, whose course is briefly
as follows: In embrys 8-9 mm. long with three gill furrows
apparent outside and four pharyngeal pouches, the spindle-
shaped ganglion of the facial unites with a pit-like, sunken
and at the same time greatly thickened place in the epi-
dermis, which corresponds to the dorsal extremity of the first
external gill furrow. The same thing occurs with the glosso-
pharyngeus; here also the distal end of the ganglion in the
rudiment of this nerve unites with a greatly thickened and
depressed portion of the epidermis dorsad to the second
pharyngeal cleft. The vagus rudiment behaves similarly.
Its large ganglion locates itself adjacent to a thickened epi-
dermal surface, of the shape of a figure 8, which is situated
dorsad to the third gill furrow and the vicinity of the fourth.

In cow embryos 15 mm. long the connections of the facial
and glosso-pharyngeus are lost, but not of the vagus, and
here the thickened mass of epidermis reaches deep into the
ganglion, so that the two components cannot be definitely
separated from each other.

Froriep compares these ‘‘ organs of the gill clefts,” though
with reserve, to the connections, described by Van Wihje,
of the ventral branches of the same nerves with the epi-
dermis, dorsally to the gill clefts, and explains them as rudi-
ments of sense organs which do not attain further develop-
ment, and probably belong in the category of organs of the
lateral line but with which they cannot be fully homologous,
since the lateral organs of fishes are formed on the dorsal
branches of the cranial nerves. As those ganglia which enter

1 “Rudiments af Sense-organs in the Facial, Glosso-pharyngeal and Vagus,” Arch.
f. Anat, u. Physiol., Anat. Abth., 1885.

v. KuprFrer, Cranial Nerves of Vertebrates. 20%

into the connections under discussion and accordingly origi-
nate through a union of central with epidermoid elements,
Froriep indicates the gang. geniculi, gang. petrosum and
gang. nodosum; they exhibit the phylogenetic remnants of
former sense organs; they cannot consequently be considered
homologous with the spinal ganglia, and thereby fails a chief
support of the spinal hypothesis. The nerves of the visceral
arches as segmental nerves can no longer be identified with
spinal nerves.

In a long series of works J. Beard(') has handled the
problem of the cranial nerves and their sensory end organs.
Torpedo ocellata furnished the principal object of Beard’s
investigations, although sharks, teleosts, Amphibia and Am-
niota (Lacerta, chick) came under consideration. In the
main, Beard follows, in facts as well as in the interpretation
of the conditions, the observations and conceptions of the
previously mentioned investigators, but also contributes the
fact that the participation of the epidermis in the formation
of ganglia and nerves occurs also in the region of the
trigeminus.

The complete representation of the development of a
dorsal cranial nerve would, according to him, be as follows:
The rudiments of the ganglia in the head, agreeing through-
out with those of the spinal nerves, arise as differentiations
of the inner layer of the ectoderm, just outside the limits of
the neural plate. They separate from the ectoderm, become
displaced upwards in the closing of the neural tube, and
come to lie between its lips, but are always distinguishable
from it. After the closure of the neural tube, the portion of

t “On the Segmental Sense Organs of the Lateral Line and on the Morphology of
the Vertebrate Auditory Organ,” Zool. Anz., 1884, p. 123; ‘The System of Branchial
Sense Organs and their Associated Ganglia in Ichthyopsida,’’ Quart. Jour. Mic:ose Sc.,
1886, Vol. XX VI, new series, p. 95; ‘‘ The Ciliary or Motor-Oculi Gangl. and the Gangl.
of the Ophthal. Profund. in Sharks,’ Anat. Anz., 1887, p. 585; ‘‘ The Old Mouth and the
New,” Anat, Anz., 1888, p. 15; ‘‘ A Contribution to the Morphology and Development of
the Nervous Syst. of Verteb.,”” Anat. Anz., 1888, pp. 874, 899; ‘“‘ The Development of the
Peripheral Nerv. Syst. of Vertebr ,”’ Quart. Jour. Micros. Sc., Vol. XXIX, new series,
1889, p' 153; ‘* Prof. Rabl on the Mode of Development of the Vertebrate Peripheral
Nervous System,”’ Anat. Anz., 1890, p. 125.

252 JouRNAL OF COMPARATIVE NEUROLOGY.

these rudiments corresponding to each cranial nerve grows
ventrad, unites with the central organ by means of root
fibres, probably growing out centripetally, and comes to lie
on the outer side of the mesoderm, between this and the epi-
dermis; while the rudiments of the spinal ganglia (of the
trunk) proceed ventrally on the inner side of the mesoderm,
thus between this and the central organ. These cranial
ganglia rudiments, designated by Beard ‘‘xeuralganglia,”
fuse at the level of the chorda with a thickened place in the
epidermis dorsad of the neighboring gill cleft, which thick-
ening represents externally the rudiment of a ‘‘ branchial sense

?

organ,” internally that of a ganglion belonging to the latter,
the ‘‘dateral ganglion.” Here the elements of the neural and
lateral ganglia blend indistinguishably with each other; there
thus arises the definitive and apparently single ganglion of the
cranial nerve in question. This separates from the epidermis
—that is, from the rudiment of the branchial sense organ—
but remains connected with the latter by a nerve strand, the
‘suprabranchial nerve (dorsal branch of Van Wihje). From
the ganglion are developed distally three nerves, namely, the
N. prebranchialis, N. postbranchialis, and \. pharyngeus.
As to the N. suprabranchialis, it is, according to Beard, clear
that it arises from the epidermis; for the N. prebranchialis he
accepts the same mode of formation. With regard to the two
other nerves, he remains undecided whether the epidermis
takes part in their formation.(') Beard regards it as cer-
tain in the case of the postbranchial twigs of the vagus(’*)
and in the case of the trigeminus (mandibularis).(*)

For the trigeminus the same law of formation is said to
obtain, inasmuch as the mouth represents a pair of gill clefts.
But where gill clefts, with the musculature belonging, have
entirely disappeared, yet sense organs persist, there, accord
ing to this author, the structure is simplified; the N. post- and

rt Quart. Jour. Mic. Sc., Vol. XX VI, 1886, p. 102.
2 Ibidem, p. 110.
3 Ibidem, p. 113

v. Kuprrer, Cranial Nerves of Vertebrates. 253
prebranchialis disappear, and the sole ones remaining are the
N. suprabranchiales.

As such may be regarded: (1) The N. olfactorius (I seg-
ment), more clearly so after it was shown, through the olfac-
tory buds discovered by Blaue, that the organ of smell
belongs to the system of the lateral line, z.e., the branchial
sense organs. 2. The ophthalmicus profundus (II segment),
whose meso-cephalic ganglion (Gn. ciliare, Van Wihje, His)
fuses with the epidermis close above and behind the eyes;
later this root unites with that of the trigeminus, and the Gn.
meso-cephalicum with the Gn. Gasseri.(') 3. The acusticus
(VI segment), which is regarded as a remnant of a segmental
nerve. The development of the nerve, of its ganglion, and
of the ear, corresponds essentially to that of the homodyna-
mous parts of complete segments. The auditory vesicle is
the persistent, functionally modified branchial sense organ;
the pertaining segment remains in the hyoid arch. Whether
the aborted gill cleft is to be found, as Van Wihje thinks,
behind the facial, or,as Dohrn takes it, is to be sought before
the hyoid cleft, remains undecided.

Regarding the relation of cranial to spinal nerves, Beard
at first declared himself in complete agreement with Froriep
in so far as the dorsal roots and ganglia of the one could not
be homologized with those of the other. Possibly Balfour
was right, that the cranial nerves showed a more primitive
condition than the spinal nerves, but it may be doubtful
whether the spinal nerves ever had the same primitive char-
acter:(*) Later he changes this opinion, and, in regard to the
supposed similar method of formation of the first ganglion
rudiment in head and trunk, declares that there is a partial
homology between the neural ganglia of the head and the
spinal ganglia, but the first might possibly be only homolo-
gous with the sympathetic portions of the latter(*)

t Anat. Anz., 1887, p. 565.
2 Quart. Jour. Mic. Sc., Vol. XX VI, 1886, p. 142-143.
3 Quart. Jour. Mic, Se., Vol. X XEX, 1889, p. £53.

254 JOURNAL OF COMPARATIVE NEUROLOGY.

Judging from this, the entirely different position of the
neural cranial ganglia on the one hand, of the spinal ganglia
on the other, relative to the dorsal mesoderm, was not taken
into account by Beard in the comparison.

In a recently published article(') on the development of
Petromyzon Planeri, I have likewise treated of the method
of formation of the peripheral nervous system, in the course
of which the previous works of Scott and Shipley on the
same object received thorough consideration.

On the one hand, my observations not only yielded a con-
firmation of the participation, discovered in Gnathostomata,
of the peripheral regions of the epidermis in the develop-
ment of the cranial nerves, but caused this participation to
appear still more considerable than could be admitted from
what was previously known. But, on the other hand,
facts emerged which do not accord with the results of the
above mentioned authors, and display the complicated nature
of the cranial nerves in a new light.

I was then led to essentially the following conception of
the composition of the dorsal cranial nerves: Each one is
composed of two parts, a spfzza/ and a lateral, which latter,
comprising all its components, can also be designated as
branchial. The first behaves, with respect to its origin, its
course and its relation to the dorsal mesoderm, entirely like
a dorsal spinal nerve of the trunk. The dorsal cranial nerves
thus originally contain parts homodynamous with the spinal
nerves, but thereto is added the second variously formed
component, which, arising with the spinal, proceeds over the
dorsal border of the mesoderm and is situated on the outer
side, between mesoderm and epidermis. It is these lateral
components of the cranial nerves into whose composition
growths of the epidermis enter, and that occurs in two series
lying the one above the other. I distinguished them as
lateral and epibranchial ganglia. The first lie in the hori-

x ‘* The Development of Petromyzon Planeri,” Arch. f. Mik. Anat., Bd, 35, 1890.

v. Kuprrer, Cranial Nerves of Vertebrates. 255

zontal plane of the auditory vesicle, and arise at three sepa-
rate places, z.e.,in the region of the trigeminus, acustico-
facialis and vagus. The epibranchial ganglia likewise emerge
descretely, and there is always one close above each gill
pouch. The part of the corresponding cranial nerve proceed-
ing over and outside the mesoderm secondarily unites with
these structures, and, indeed, the union with the lateral
ganglia is of such a nature that the rudiment of the nerve
itself swells into a new ganglion, the wzedza/ (neural ganglion,
Beard). From this union of the medial and lateral ganglia
proceeds the definitive ganglion (Hauptganglion) of the
cranial nerve concerned. The epibranchial ganglia take part
in the development of the terminal twigs of the cranial
nerves. In the separation of the lateral, as well as the epi-
branchial ganglia from the epidermis, there is nowhere
shown the rudiment of a sense organ. With the sole excep-
tion of the auditory vesicle, which is formed in the closest
proximity to the lateral ganglion of the acustico-facialis
region and is homodynamous with this lateral ganglion, all
these ganglia of both series are entirely independent struc-
tures, standing in no connection with principal sense organs.

These were the results which I had reached. I had to
break off these investigations, on account of lack of material,
at a stage in which the formation of the peripheral nervous
system is far from concluded. It was the moment of the
escape of the larve (from the egg). I have since, with new
and more complete material, carried the work on further,
and extended it to the stage of larve 4 mm. in length. At
the same time I discovered that my older material, upon
which the work cited had been based, contained gaps which
prevented me from arriving at a complete understanding of
the earliest beginnings of the cranial nerves. After interpo-
lation of the then lacking stages of development, it is neces-
sary to complete in many respects and partially correct my
earlier representation.

The first rudiment I have sufficiently described and

256 JOURNAL OF COMPARATIVE NEUROLOGY.

drawn. ‘Towards the conclusion of the folding process
taking place in the ectoderm, by means of which the massive
central organ is formed, but before its separation from the
ectoderm, one sees in the fore half of the embryo (head
region) three cords, the median neural and the paired lateral
cords, which latter, on either side, correspond entirely to the
intermediate fascicles (Zwischenstrang ) of His (Fig. 1 z).(’)
But I have not ascertained the succeeding phase since, as I
now see, | have lacked the connecting links. I assumed that
in the separation from the ectoderm the paired—.e., the
intermediate—fascicles came at the same time to lie on both
sides of the median neural cord, that is to say, of the massive
brain. That is not the case; the paired rudiments move
farther mesad together, so that they unite dorsad of the brain
cord, into a plate lying between this and the epidermis
(Fig. 2 d P), and which is distinguished from the regularly
biserially arranged elongated epithelium-like cells of the
brain by reason of the irregular and, subsequently, loose dis-
position of their elements. This plate exhibits the same
structure which His had already sketched, in 1879, in a
Scyllium embryo and Beard more recently has drawn in
various elasmobranchs and of the chick.

Not to anticipate the difficult question as to which parts
of the peripheral nervous system are derived from this plate,
in our terminology I will refer to it neither as ganglion- nor
nerve-plate, but call it the dorsal brain-flate, since, although
divided into three segments, it extends over the whole length
of the brain. Furthermore, in the spinal cord I find the plate
not so distinct and represented by a double row of cells,
which my pupil, Dr. Victor Rohon, has first described,(*)
albeit from later stages, in the trout.

Next the cells of the dorsal brain-plate advance laterad

x1 Compare my drawings in the Arch. f. Mikr. Anat., 1890, Bd, 35, Taf. XX VIII, Fig.
25, and His’ figure in the Arch. f. Anat. u. Phys., 1879, Anat. Abt., p. 465.

2 “On the Histiog. of the Spinal Cord of the Trout,” Sitzgsber. d. math. physik.
Kl. d. K. Bayer. Acad. d. W., Munchen, 1884, Heft I, p. 39.

Vv. KupFFER, Cranial Nerves of Vertebrates. 257
between brain and epidermis, forming the well-known
ganglion- or nerve-‘‘ border” (Leiste) of writers, and now it
becomes necessary in considering the development of the
cranial nerves to keep distinctly in mind the different
regions.

I distinguish accordingly: (1) The region of the fore head
to the eye, inclusive; (2) the fore gill region, comprising the
mouth and the three fore gill pouches; (3) the hind gill
region to the eighth gill pouch, inclusive; (4) the trunk
region.

In the region of the fore head (Fig. 3) begins the forma-
tion of the borders (Leiste), which I designate as root-
borders (Wurzelleiste), from the dorsal brain-plate, before
the formation of the eye has begun; and the cells soon
extend along the whole lateral surface of the fore-brain,
whereby the connection with the brain here becomes severed.
These cells are at first rounded, then become spindle-shaped
and touch each other, so that they appear in connected
layers. They are ranged mostly in two rows, but so that in
one place a larger collection always shows itself. In my
treatise I gave a figure(') of this, indicated this accumulation
as a ganglion, and regarded it as the first rudiment of the
first trigeminus ganglion. That it behaves like the rudiment
of a ganglion I still hold, but I have come to doubt whether
it goes into the first trigeminus ganglion or forms the first
spinal ganglion, to be mentioned later. The determination
is difficult, and requires more extended and especially more
comparative investigations. But the whole mass of cells
does not in every case collect itself into a compact ganglion,
but it arranges itself in lines, which, after the appearance of
the sense organs, extend both towards the nose and eye and
also towards the hypophysial pouch. Later they unite, in
the main, with the first trigeminus ganglion, whose branches
they appear.

x Arch. f. Mikrosk. Anat., Bd. 35, 1890. Taf. X XIX, Fig. 39 g).

i)
mn
oe

JoURNAL OF CoMPARATIVE NEUROLOGY.

In the fore gill region, which extends from the eye to the
third primitive gill pouch, the process takes place otherwise.
Here the mesoderm occurs in addition, which, until the time
of the appearance of the dorsal root-borders at the brain, still
shows an entirely epithelial arrangement. There are nowhere
present detached cells which enter into the formation of con-
nective tissue.

The root-border grows on rapidly to the dorsal border of
mesoderm, and spreads out so that it lies cap-like upon the
border cells of the mesoderm (Fig. 4). Then two tracts
(Zige) of cells separate, of which the inner proceeds be-
tween mesoderm and brain, while the other grows on laterad
from the mesoderm between it and the epidermis. This latter
course is characteristic of the fore gill region. It is wanting
in the hind gill region and in the trunk.

As these tracts (Zuge) display separate rudiments, I
choose for them exact designations. I call the inner tract,
which remains in connection with the dorsal border of meso-
derm and proceeds ventrad between brain and mesoderm, the
dorsal spinal nerve, since this rudiment extends in the same
way in all parts of the body, the outer tract I designate the
branchial nerve (Figs. 5 and 6, 26).

The border (Leiste), and what proceeds from it, is not
continuous in the fore gill region, but at the beginning is
divided into three successive segments, which correspond to
the regions of the trigeminus, acustico-facialis and vagus, and
consists exclusively of elongated, serially arranged cells.

While the separation of the border into the tracts
mentioned, the spinal and the branchial rudiments, takes
place over the dorsal border of mesoderm—it takes place
about the time of the appearance of the eye-rudiment —
growths of the epidermis begin in three places; they are the
trigeminus, the acustico-facialis and the vagus swellings.
They lie laterad of the dorsal mesoderm, and arise, not sim-
ultaneously but successively, from before backwards. The
method of formation of these swellings I have minutely

v. KuPFFER, Cranial Nerves of Vertebrates. 259

described and drawn in my article. But I must here, on the
the basis of later investigations, make some additions and
corrections.

The trigeminus swelling, appearing close behind the eye-
rudiment, forms a projection (Fig. 4, 27 ) directed entad and
dorsad, and consisting of closely crowded cells, upon which,
although still continuous, may be noticed two prominences
lying the one behind and under the other. The root of the
branchial nerve grows toward this swelling, unites with it
by means of a tract of cells, and passes along, with another
tract close by, growing in a ventral direction. The growth
of these nerve-rudiments results partly from division of these
cells, partly through the invasion of new elements from the
dorsal brain-plate. At the point of junction of the root of
the branchial nerve with the swelling of epidermis, there
results a multiplication of the cells belonging to the nerve
whereby two heaps of cells, corresponding to the two promi-
nences on the swelling, arise, the elements of which are
inserted between the epidermis cells of the swelling, so that
later on they could not be distinguished according to their
origin.

From this complex two ganglia are isolated successively
with simultaneous separation from the epidermis, each of
which consists of two parts, one epidermal and one arising
from the dorsal brain-plate, of which the first part has been
designated by me the /a/era/, the other as the medzal ganglion
(Figs. 5 and 7, 2/, em). But the two parts are gradually
merged into each other, so that finally no clear boundary
between them can be pointed out. It is thus necessary to
designate the whole body as one, and | propose the term
‘* principal” ganglion (Hauptganglion) for it. There belong
to the trigeminus ¢wo principal ganglia, formed in the
same way, the frst and the second. The two are homo-
dynamous. 1 correct herewith my earlier view that the first
trigeminus ganglion is exclusively of central origin, and has
the same value as the medial part of the second trigeminus

260 JOURNAL OF COMPARATIVE NEUROLOGY.

ganglion.(') A more complete series of stages has sub-
sequently convinced me of the incorrectness of this view.

The first trigeminus ganglion lies before and over the
second, can always be distinguished from this and is con-
nected with the nerve-rudiments of the fore head.

The epidermal swelling next behind gives rise to the
labyrinth vesicle and the lateral part of the factalis ganglion,
as likewise homodynamous parts, a portion of its cells
also entering into the rudiment of the glossopharyngeus.
Vesicle and ganglion arise in close connection, so that in the
beginning of the invagination of the pit of the labyrinth, the
ganglion is situated within, like a large knob, on the wall of
the pit. It becomes further enlarged through proliferation of
the cells of the wall. The root of the pertaining branchial
nerve itself enters by way of addition, as well with the gan.
glion as with labyrinth vesicle, and stretches to one other part
in this structure, lengthening in a ventral part. The ganglion
acquires a median portion from the latter.

The third epidermal swelling, which belongs to the vagus,
is more stmple than the two preceding. There proceeds from
it a rounded, simple lateral ganglion, which, however, by
means of the root of the pertaining branchial nerve connect-
ing with it, acquires a considerable medial part and thereby
becomes a principal ganglion.

During the formation of this principal ganglion, and
before it has yet completely separated from the epidermis,
there appear new growths of the epidermis. They lead, in
like manner, to the formation of ganglia, without the
connection with them of rudiments of sense organs, at
least directly. These are the efzbranchial ganglia (Figs.
4, 6, 7 ge). They arise singly, close above the three
primitive gill pouches, and lie thus in a second series
removed ventrally from that of the principal ganglia. The
epibranchial ganglion appearing first is not the formost, but

t Arch. f. Mikr. Anat., Bd. 35, 1890, S. 538.

v. Kuprrer, Cranial Nerves of Vertebrates. 261

the one over the second gill pouch. At the end of the
embryonic period, and after the release of the larvae, this
process advances cephalad into the region of the trigeminus,
and also caudad in proportion as the hind gill pouches
successively arise. These ganglia thus exhibit regular
branchiomerism, and those arising in the region of the
trigeminus point to aborted anterior gill pouches.

How the branchial nerves, passing along by the principal
ganglia and proceeding to the visceral arches, connect with
the epibranchial ganglia, I shall show later.

In the hzzd gill zegion, from the fourth primary gill
pouch to the eighth, the development of the peripheral
nervous system shows a less complicated course. The border
(leiste) growing out from the dorsal brain-plate appears first
as a continuous one, connects with the dorsal border cells
of the mesoderm segments and sends a ventral extension
between brain and mesoderm; there thus arises from it only
the dorsal spinal nerve, the rudiment of branchial nerves
remains apart from the border. There nevertheless arise, as
already mentioned, in regular order from the epidermis, the
epibranchial ganglia corresponding to the gill pouches of this
region.

So long as the rudiments of the nerves consist of con-
tinuous chains of cells, it is not difficult to follow their
course and establish the connections. But there comes a
stage where, connected with the cells, fibrille appear and
separate the cells, and with this difficulty ensues for the
investigation, so long as the fibrille are not united into
thicker cords. The latter has occurred after the release of
the embryo, so the investigation is prosecuted on a firmer
basis. One can then enumerate the roots in the different
regions, and follow the ramifications of the distal nerves.
The stage intervening between the first rudiment, consisting
of continuous rows, and the later first evident compact nerve
cords renders uncommonly difficult the determination of the
question whether the rudiments and ganglia proceeding

262 JOURNAL OF COMPARATIVE NEUROLOGY.

from the dorsal brain-plate and border respectively at any
time give up their connection with the dorsal region of the
brain. I assume this separation oz/y for the region of the fore-
brain, where the rudiments also possess secondarily no
connection with this region of the brain, but are united
with the trigeminus and the mid-brain respectively. Be-
hind this it does not occur, at least not up to the point of
time when the formations of ganglia from epidermis begin
and come forth in connection with the roots of the branchial
nerves. With this question is bound up the other question of
the final fate of the dorsal brain-plate. Do its cells advance
in a body laterad and ventrad, or a middle portion of the cells
of the plate remain in loco, while these cells intercalate
themselves in the epithelial covering of the neural tube?
According to my observations the latter takes place. A great
part of the plate is applied to the formation of the peripheral
nerves, but the remainder appears wedged in between the
cells of the roof of the brain without the interruption of the
connection with the peripheral parts.

I do not propose to discuss the histogeny of the nerves in
this place, since the details are still not clearly enough
established to admit of generalizations; but I may devote
space for the view to which the embryo and the youngest
larval stages of Petromyzon have led me. None of my
observations contradicts the view, but rather everything
indicates that the fibrillz arise as processes of cells, but not
merely from cells of the ganglia and central organ but also
from those cells which, ranged in chains, form the first rudi-
ments of peripheral nerves. This being accepted, it appears
to me, further, most probable that the growth of the fibrillz
in the dorsal nerves extends in both directions, centripetal as
well as centrifugal. Thus, when the rudiments have attained
the stage of formation at which they display fibrille along
with the cells, the cells appear moved apart from each other,
and at both ends, the central as well as the peripheral, pro-

ceeding forth in fine filaments.

v. Kuprrer, Cranial Nerves of Vertebrates. 263

All other questions bearing further upon the peculiarities
in this process appear to me at the present not ripe for dis.
cussion. Yet I believe I may say one thing definitely, that
the rudiments of the dorsal nerves, as well in the earliest
phase of the cell chains as also later, when fibrille have
already appeared, always show the connection with the
central organ.

According to what has been hitherto communicated, there
enter into the composition of the cranial nerves two systems,
the sfina/ and the branchial. The first is common to the
head and trunk; the latter appears exclusively in the head,
is most developed in the fore gill region, and one part is pro-
duced into the hind gill region.

Concerning the spinal system of the head, I thus confine
myself here to the dorsal rudiments, reserving the ventral
spinal nerves for later mention. The complete interruption
of the roots between the regions of the trigeminus, acustico-
facialis and vagus self-evidently also affects the spinal system.
It also divides, therefore. into three regions, of which the
hindermost adjoins the spinal system of the trunk. Proceed-.
ing from the root-border, the rudiment of a spinal nerve
divides into two tracts. The lateral tract (zug) remains in
connection with the dorsal border of mesoderm—lI denote it
as the dorsal branch of the dorsal spinal nerve—the median
tract, or ventral branch of the dorsal spinal nerve, passes
between mesoderm and brain towards the chorda, passes
around this and arrives at the outer side of the aorta. At
first consisting of serially arranged cells, this tract includes
in itself the rudiments of the sAzva/ ganglia and of the sym-
pathetic ganglia (Fig. 6).

So far as I have been yet able to discover, the spinal
spinal system of the head does not keep pace in further
development with the branchial system, but instead under-
goes remarkable reductions.

The nerves of the éranchial system are, in respect to their

mode of origin, more composite. The rudiments proceeding

264 JOURNAL OF COMPARATIVE NEUROLOGY.

from the root-border grow, with a participation in the prin-
cipal ganglion then originating, over into the ventral region
(Fig. 5, 24). It there connects secondarily with a portion
proceeding from the distal end of the associated principal
ganglion, of which I cannot definitely say whether it is of
central or of epidermal derivation—that is to say, whether
it is derived from the medial or lateral part of the ganglion,
or from: both. Then, later, when the epibranchial ganglia
arise, further complications ensue. In conjunction with the
formation of these ganglia, there appears a peculiar sub-
epidermal layer of cells, which gradually spreads from the
eye to the hindermost gill pouch, dat remains confined to the
ventral side.

If it were not preoccupied, 1 would suggest the name
‘‘hypodermis” for this layer, but, as it is, propose the term
‘‘neurodermis”’ (Figs. 6,7, 10, 26). The point of origin of
this structure is the vicinity of earliest epibranchial ganglion,
dorsad and cephalad of the second gill pouch. At the lateral
line, z.c., the outer boundary between the dorsal and ventral
region, the neurodermis is not strongly developed; here it
consists of several layers of cells which form an inwardly
projecting ridge, but in general it remains one-layered and
consists of closely arranged but disconnected epithelium-like
cells, with a prevailingly cylindrical form.

Nore.—The figures which are referred to in this paper will be
collected in plates at the end of the article.

[TO BE CONTINUED.]

MORPHOLOGY OF VE -AVTAN) BRAUN. (7)
( Continued. )
Cae iain:

Additional Remark upon the E-xternal Morphology of the
E-pencephalon.—As has been remarked above, the most re-
markable characteristic of the avian brain is a tendency
towards great compactness. This tendency has left its stamp
upon the epencephalon. In addition to being wedged into
the caudal V of the hemispheres,(*) and to being trans-
versely convoluted,(*) the epencephalon suffers a most note-
worthy modification. Its cephalo-ventral extremity projects
mesad into the cavity of the fourth ventricle, thus producing
the almost unique phenomenon of a portion of the epen-
cephalon being embraced by the metencephalon (Plate VII,
rena ilate XIV Biss no; Plate XV Piss]; Plate XV IIT,
igs.9) 10, 2.1).

V.—HISTOLOGY OF THE EPENCEPHALON.

Although in its external form the avian epencephalon

resembles one of the embryonic stages of the higher verte-

1 A Correction.—Dr. R. W. Shufeldt has called my attention to an error that
occurs on page 56, lines 16 to18. Those lines should read: “‘ My notes upon these two
birds are based upon a study of sketches given in the United States Geological Survey,
J. W. Powell, Director; third annual report (1881-82), p. 56, Fig. 8, and p. 70, Fig 20.”

2 Supra, p. 41. :

3 Supra, p. 51.

Pad

266 JoURNAL OF COMPARATIVE NEUROLOGY.

brates, yet in its internal structure it differs but little from
the adult mammalian cerebellum. As in the mammalia, so
here, the epencephalon consists of three major histological
regions; the epithelium, the cerebellar cortex, and the body.
Around the periphery, lining the convolutions, we find
the narrow epithelial layer; entad to this we find the
cortex, while further entad, forming the core, we find the
body.

Cerebellar Cortex (Plate X VIII, Fig. 6).—The transversely
and unequally convoluted cerebellar cortex is composed of
three lamine. The most ectal lamina is the widest of all. It
is composed of neuroglia through which are scattered a few
of Deiter’s corpuscles. The second lamina is very narrow. It
consists of a single layer of the well-known Purkinje’s cells.
These are large and gibbous flask cells. In hematoxylin
and aluminium-sulphate cochineal preparations, these cells
are densely stained and present large, clear, spherical nuclei
and large, dense nucleoli. In different brains the size of
these cells varies greatly, but in all cases they rank with the
largest cells in the brain. The width of the next layer isa
variable quantity. This dimension varies not only in differ-
ent brains, but also in different parts of the same epenceph-
alon. But, in every epencephalon, the major local thicken-
ings of this lamina take place in a definite and constant
manner. In all cases this layer is narrowest at the proximal
extremity of each canvolution. Thence the width in-
creases gradually, although irregularly, until the distal ex-
tremity of the convolution is reached. There the layer is
widest. Although at the proximal extremity of each convo-
lution this layer is often but little wider than the layer of
Purkinje’s cells, yet at the distal extremity of each convolu-
tion it will be almost as wide as the external neuroglia layer
(Plate VII, Fig. 4; Plate XIV, Fig. 8). This fact seems to
warrant the following suppositions:

1. This layer of the avian epencephalon was deposited
before that body became convoluted.

TurRNER, Morphology of the Avian Brain. 267

2. Originally this was a uniform layer parallel to the
surface of the epencephalon.

3. Its present shape is due to a tendency to remain parallel
to the surface which has now become greatly increased by
convolutions.

Although the cerebellar cortex is here described as being
composed of three distinct layers, it must be borne in mind
that neither membranes nor ventricles separate these lamine.
Nor is there either membrane or ventricle between the cortex
and the remainder of the epencephalon.

White Substance of the Epencephalon.—The body or core
of the epencephalon is an irregular solid polyhedron, from
the periphery of which projections extend into all the irregu-
larities of the ental surface of the cerebellar cortex, and com-
pletely fill them. The centre of this core is occupied by a
small ventricle, which is connected with the fourth ventricle
by a narrow median isthmus. Histologically, this region is
composed almost exclusively of fibres. It contains, however,
two niduli, one of which is near the ventricle, while the other
is in the peduncle.

Dentate Nidulus.—The nidulus near the ventricle is large
and conspicuous, and is known as the dentate nidulus. It
lies, for the most part, cephalad of the ventricle, and is very
irregular in outline. In many cases the nerve cells consti-
tuting this nidulus are large pyramidal cells, in other cases
they are multipolar, while in still others both pyramidal and
multipolar cells are found in the same nidulus. In some brains
these cells are densely compacted, while in others they are
only loosely aggregated. In all cases they lie in a bed
of nerve fibres. In my preparations these cells are so
densely stained that their nuclei and their nucleoli are
invisible. This nidulus is abundantly supplied with Deiter’s
corpuscles.

268 JouRNAL OF COMPARATIVE NEUROLOGY.

VI.—HISTOLOGY OF THE METENCEPHALON.

Niduli of the Fifth Nerve-—The mesencephalic nidulus
‘of the trigeminal nerve has been described in connection with
the niduli of the mesencephalon.(') One tract of the fifth
nerve arises in the epencephalon, but the niduli of that
region also have been described above. There remains then
to describe in this connection those niduli only of the tri-
geminal nerve which are located in the metencephalon.

Lateral Motor Nidulus of the Fifth Nerve (Plate XVIII,
Figs. 8, 15).—This is a well-defined nidulus which is situated
near the lateral surface of the medulla, adjacent to the ceph-
alad root of the trigeminal nerve. Although situated quite
near to the lateral surface of the metencephalon, yet it lies
entad to that tract of the fifth nerve which passes to the
myelon. It also lies cephalad to the tract which passes to
the deep motor nidulus of the trigeminus. In different birds
the shape of this nidulus undergoes considerable variation.
As far as my observations go, the two extremes are repre-
sented by the young dove ( Colwmba livia) and by the adult
Swainson’s thrush (//ylocitchla Swainsoni). In the first case
it is a compact spherical nidulus; in the other it is an elon-
gated, straggling nidulus, which lies parallel to the deep
motor root of the fifth nerve.

This nidulus is well supplied with large pyramidal nerve
cells. The apex of each cell is prolonged into a long pro-
cess, which process is often curved. In hematoxylin and in
aluminium-sulphate cochineal preparations, these cells are
densely stained, and each one presents a densely stained
nucleus and nucleolus. This nidulus is well supphed with
Deiters’ corpuscles, and nerve fibres traverse it in several
directions.

Ventrad to the above nidulus there exists, in some of my
sections, an ill-defined cell cluster, which probably deserves

1 Supra, p. 121; Plate XV, Fig. 3.

Turner, Wortholoey of the Avian Brain. 26
) a we 9

to be considered a distinct nidulus. In the medulla of the
young dove (Columba livia) and in a few other cases this
cell cluster appears to be undoubtedly distinct from the
lateral motor nidulus of the trigeminus, while in other cases
(some of the 7urdide) it is evidently amalgamated with
that nidulus. Histologically, it could hardly be considered a
distinct nidulus. For, although the cells are not typical
pyramidal cells, and although they appear to differ from the
typical cells of the lateral motor nidulus of the trigeminal
nerve, neither are they typical fusiform or flask cells. Al-
though tending towards the flask cells in outline, yet they
agree with the pyramidal cells in the structure of their nuclei.
In hematoxylin and in aluminium-sulphate cochineal prepa-
rations, these nuclei are densely stained. After due consid-
eration it has been thought best to consider this cell cluster
as a slightly modified portion of the lateral motor nidulus
of the trigeminus, which portion occasionally becomes
distinct.

Lateral Sensory Nidulus of the Fifth Nerve (Plate XVIII,
Fig. 8).—This nidulus lies near the lateral surface of the
metencephalon, and on the same level as the lateral motor
nidulus of the trigeminus. It lies about as near to the lateral
surface of the medulla as does the latter nidulus, but it lies
upon the opposite side of the deep motor fasciculus of the
trigeminal nerve. The form of this nidulus is not constant
throughout the class Aves. In some cases (//ylocichla
Swainsont) the outline of this nidulus is sub-spherical, while
in others (Columba livia) it is somewhat irregular. This
nidulus is smaller than the lateral motor nidulus of the same
nerve.

The cells of this nidulus are flask shaped. In hematoxy-
lin and in aluminium-sulphate cochineal preparations, these
cells are densely stained, and each one presents a faintly
stained nucleus and a densely stained nucleolus. The niduli
of these cells are relatively smaller than the niduli of sensory
cells usually are. These cells are loosely and irregularly

270 JOURNAL OF COMPARATIVE NEUROLOGY.

aggregated, and among them is dirtributed a large number of
Deiter’s corpuscles,

Deep Motor Nidulus of the Fifth Nerve (Plate XVIII,
‘Fig. 16).—Near the meson, on a level with the niduli of the
glosso-pharyngeal and pneumogastric nerves and extending
as far cephalad as the roots of the trigeminal nerve, there
exists an elongated sub-ellipsoidal nidulus. This small cell
cluster lies immediately cephalad of the mesal extremity
of the deep motor root of the fifth nerve, and has its major
axis approximately parallel to the longitudinal axis of the
metencephalon.

The nidulus is composed of a loose aggregate of large
pyramidal cells, among which numerous Deiter’s corpuscles
are distributed. The apex of each cell is prolonged into a
long process, while the base is supplied with several shorter
processes. The apical process is often curved. In hema-
toxylon and in aluminium-sulphate cochineal preparations,
these cells are densely stained, and each one presents a
densely stained nucleus and a densely stained nucleolus.
Several small fasciculi of nerve fibres pass from this nidulus
to the raphe.

In the avian brain there does not appear to be any homo-
logue of what in the human medulla(’) is known as the
inferior sensory root of the trigeminus.

Gasserian Ganglion (Plate XVIII, Figs. 8,15, 19).—This
is a large ganglion which is situated upon the root of the
trigeminal nerve. This ganglion consists of large typical
bipolar cells, which are arranged with their longitudinal axes
perpendicular to the metencephalon. In addition to the
ordinary cell wall, each of these cells is surrounded by an
additional sheath. In this sheath several nuclei are visible.
In hematoxylin and in aluminium-sulphate cochineal prepa-
rations, these cells are densely stained, and each one presents
a faintly stained spherical nucleus, within which is a

1 AmpBrosE L. RANNEY, ‘The Applied Anatomy of the Nervous System,” second
edition, p. 254, Figs. 55, 5.

TuRNER, Morphology of the Avian Brain. 271

densely stained nucleolus. From the proximal extremity of
each cell a nerve fibre passes into the metencephalon, while
from the distal extremity of the same cell a nerve fibre passes
into the nerve.

Nidulus of the Abducens Nerve (Plate XVIII, Fig. ro, 13).
—This is an ill-defined nidulus which lies hear the meson
and which extends as far cephalad as the external root of the
sixth nerve. In the alligator brain(') and in the human
brain(*) this cell cluster is situated on the floor of the fourth
ventricle. In the avian brain, however, this nidulus is not
adjacent to the ventricle, but is separated from it by a large
faciculus of nerve fibres.

This nidulus is composed chiefly of rather small, irregular,
pyramidal cells, which resemble those of the niduli of the
oculo-motor and pathetic nerves. True, these cells are more
irregular than those figured in Plate XVI, Figs. 13, 14; but
the cells of the niduli of the third and fourth nerves also are
usually more irregular than the cells there delineated. In
hematoxylin and in alumininium-sulphate cochineal prepa-
rations, these cells are usually densely stained, and each cell
presents a small densely stained nucleus, within which is a
densely stained nucleolus. This nidulus is well supplied
with Deiter’s corpuscles.

Niduli of the Facial and of the Auditory Nerves (Plate
XVIII, Figs. 3, 4, 11, 13, 18).—Since in the avian brain the
seventh and eighth nerves have a common root, it has been
thought wise to describe the niduli pertaining to that root as
though they were the niduli of a single mixed nerve. In the
avian metencephalon at least three distinct niduli are related
to the fibres of facial and auditory nerves. For convenience
these are here designated as ‘‘nidulus L,” ‘‘nidulus B,”
‘¢nidulus Y.”

Nidulus £ (Plate XVIII, Fig. 18).—Far laterad, near the
the root of the auditory nerve, there is a small sub-spherical

rt Pror. C, L. HERRICK, op. cit., p. 153.
2 Pror. AmpBrose L. RANNEY, op, cit., p. 330.

272 JOURNAL OF COMPARATIVE NEUROLOGY.

nidulus. The cells of this nidulus are very irregular in out-
line. They are neither typical pyramidal cells nor typical
flask cells. Probably they resemble the former more than
than they do the latter. In hematoxylin and in aluminium-
sulphate cochineal preparations, these cells are densely and
obscurely stained, and each one presents a densely stained
nucleus, within which is a densely stained nucleolus.

The eminentia acustica is a slight projection into the
cavity of the fourth ventricle. This projection is situated
upon the floor of the fourth ventricle, about half way be-
tween the external root of the eighth nerve and the meson
(Plate XVIII, Fig. 11). This is a sub-elliptical body, and is
divided by a band of fibres into two unequal portions. That
division which lies nearest the ventricle is much larger than
the other portion. This eminentia contains nidulus B.

Nidulus B (Plate XVIII, Fig. 18).—As has been men-
tioned above, this cell cluster constitutes the nervous portion
of the eminentia acustica. The band of fibres which divides
the eminentia into two unequal portions divides this nidulus
in a similar manner. In that section of this nidulus which is
nearest the fourth ventricle the nerve cells are crowded into
the mesal half, while the remainder of that portion of the
nidulus is filled with Deiter’s corpuscles. In that section of
the nidulus which is on the other side of the band of fibres
the nerve cells are uniformly distributed. The cells of this
nidulus are small, gibbous, flask cells, which, in hematoxylin
and in aluminium-sulphate cochineal preparations, are faintly
and obscurely stained, and each of which presents a faintly
stained nucleus, within which is a densely stained nucleolus.
This nidulus is surrounded on all sides by nerve fibres.

It is quite probable that the two divisions of this nidulus
correspond to the two small and distinct but adjacent niduli
which occupy a similar position in the alligator brain.(’)

Nidulus Y (Plate XVIII, Figs. 4, 11).—Mesad to the

xt Pror. C. L. Herrick, ‘‘ Notes on the Brain of the Alligator,” 1. cit., p. 153.

TurRNER, Morphology of the Avian Brain. 273

above nidulus and between the surface and that tract of the
auditory nerve which passes to the raphe, there is an incon-
spicuous nidulus. This nidulus contains a few scattered
fusiform cells and numerous Deiter’s corpuscles. In hema-
toxylin and in aluminium-sulphate cochineale preparations,
these cells are obscurely stained, and each one presents a
faintly stained nucleus, within which is a densely stained
nucleolus.

foot Ganglion of the Auditory Nerve (Plate XVIII, Figs.
1, 4).—Within the skull cavity the avian eighth nerve bears
a small root ganglion. This ganglion is closely appressed
upon the metencephalon. Indeed, in some cases it is so inti-
mately connected with the brain that it resembles a super-
ficial nidulus. This ganglion contains large spindle-shaped
cells, which apparently are of the same type as those in the
Gasserion genglion. In hematoxylin and in aluminium-sul-
phate cochineal preparations, these cells are densely stained,
and each cell presents a faintly stained spherical nucleus,
within which is a densely stained nucleolus. Unfortunately,
in all my sections that show this ganglion these cells are cut
approximately at right angles, thus rendering it impossible
to demonstrate whether or not each extremity of the cell is
prolonged into a nerve fibre. However, each cell is sur-
rounded by a nuclei-bearing sheath, which resembles the
sheaths described and figured for the cells of Gasser’s gan-
glion (Plate XVIII, Fig. r).

Nidulus of the Glosso-pharyngeal Nerve (Plate XVIII,
Fig. 16).—At the surface it is almost impossible to distin-
guish beteen the roots of the glosso-pharyngeal and pneumo-
gastric nerve, but when we pass entad a knowledge of the
physiological functions of each nerve renders the separation
of the glosso-pharyngeal and pneumogastric niduli an easy
matter. Both niduli lie at the meson and in the floor of the
fourth ventricle. But the nidulus of the glosso-pharyngeal
nerve lies further cephalad and extends forther dorsad than
the nidulus of the pneumogastric nerve.

274 JOURNAL OF COMPARATIVE NEUROLOGY.

The glosso-pharyngeal nidulus is composed of a close
aggregate of small pyramidal cells, among which a few fusi-
form cells are scattered. The fusiform cells are mostly con-
fined to the caudal portion. The pyramidal cells are quite
irregular in outline. In hematoxylin and in aluminium-sul-
phate cochineal preparations, these cells are densely stained,
and each one presents a densely stained nucleus, within
which is a densely stained nucleolus. This nidulus is abund-
antly supplied with Deiter’s corpuscles.

Nidulus of the Pneumogastric Nerve (Plate XVIII, Fig.
16).—Anatomically, the nidulus of the tenth nerve is some-
times distinct from the nidulus of the ninth nerve and some-
times not. Histologically, it is always distinct. It lies
caudad to the nidulus of the glosso-pharyngeal nerve, and,
usually, does not extend so far dorsad as that nidulus does.
Like the above nidulus, the pneumogastric nidulus is elon-
gated, with its major axis parallel to the longitudinal axis of
the metencephalon. This nidulus is not quite so wide as the
nidulus of the ninth nerve.

The pneumogastric nidulus is composed of large, typical,
irregular gibbous cells, which present a strong contrast to
the small pyramidal cells of the glosso-pharyngeal nidulus.
In hematoxylin and in aluminium-sulphate cochineal prepa-
rations, these cells are densely stained, and each one presents
a large, clearly stained nucleus, within which is a densely
stained nucleolus. This nidulus is well supplied with
Deiter’s corpuscles.

Nidulus of the Spinal Accessory Nerve (Plate XVIII,
Fig. 16).—Immediately ventrad of the nidulus of the pneu-
mogastric nerve, and extending from the nidulus of the
glosso-pharyngeal nerve caudad into the myelon, there is a
narrow, elongated cluster of cells. This cell cluster is sup-
posed to be the nidulus of the spinal accessory nerve. ‘This
nidulus is composed of large, irregularly arranged, pyramidal
cells, which are larger than those of the glosso-pharyngeal
nidulus. In hematoxylin and in aluminium-sulphate cocht-

TurRNER, Morphology of the Avian Brain. 275

neal preparations, these cells are densely stained, and each
one presents a densely stained nucleus, within which is a
densely stained nucleolus. This nidulus is well supplied
with Deiter’s corpuscles.

Nidulus of the Hypoglossal Nerve (Plate XVIII, Fig. 17).
—Further ventrad, and separated from the nidulus of the
spinal accessory by a cell-less region, lies the large nidulus
of the hypoglossal nerve. This nidulus is sub-pyramidal in
shape. Its base is about at the junction of the myelon with
the metencephalon, while its apex is as far cephalad as the
caudad extremity of the nidulus of the glosso-pharyngeal
nerve.

This nidulus is composed of large pyramidal cells, which
resemble those of the nidulus of the spinal accessory nerve.
In hematoxylin and in aluminium-sulphate cochineal prepa-
rations, these cells are densely stained, and each one presents
a densely stained nucleus, within which is a densely stained
nucleolus. This nidulus is well supplied with Deiter’s
corpuscles.

Olives.—Near the ventral surface of the metencephalon,
and immediately laterad of the root of the hypoglossal nerve,
there is a small, ill-defined cluster of cells. This nidulus is
probably the homologue of the olivary body. However, this
nidulus does not exhibit the slightest trace of the complex
structure of the human olivary body.(') The cells of this
nidulus are small. In hematoxylin and in aluminium-sulphate
cochineal preparations, the nuclei of these cells are much
more densely stained than is usually the case in flask cells.

Accessory Olives (Plate XVIII, Fig. 13).—Near the ven-
tral surface of the metencephalon of a young dove ( Columba
livia) a small, ill-defined cell cluster has been observed. It
is composed of fusiform cells, and is probably a homologue
of the accessory olives. In hematoxylin preparations these
cells are faintly stained, and each one presents a large, clear

tr See RANNEY, op. cit., p. 268 and p. 262, Fig. 59.

276 JOURNAL OF COMPARATIVE NEUROLOGY.

nucleus, within which is a large, densely stained granular
nucleolus.

TRACTS OF THE METENCEPHALON.

Root of the Trigeminal Nerve.—In the amphiban brain,
according to Professor Osborn,(') the fifth nerve root is com-
posed of the following tracts: 1. Ascending tract of the
cervical region, reinforced by 2, fibres from the deep motor
nidulus, representing two tracts. 3. Fibres from the sensory
nidulus. 4. Descending tract from the mesencephalic nidulus.
4. Direct encephalic tract.

In the avian brain the composition of the root of the tri-
geminal nerve tallies even more closely with the composition
of the corresponding nerve of the human metencephalon.(*)
As in the human brain, so here this nerve is composed of two
distinct roots, each of which is composed of several distinct
fasciculi. In the lower types of birds ( Columba livia, etc.)
this appearance is quite distinct, but in the higher types
(Hylocichla swainsoni, etc.) it is often somewhat obscured.
One of these roots lies caudad to the other. The cephalad
root is composed of two fasciculi, the lateral motor fasciculus
and the ascending cervical fasciculus. The caudad root is
also composed of two tracts, the lateral sensory fasciculus
and the deep motor fasciculus.

Lateral Motor Fasciculus of the Trigeminal Nerve (Plate
XVIII, Fig. 8). This is a short bundle of loosely aggregated
fibres which passes from the lateral motor nidulus of the tri-
geminal nerve laterad into that nerve. This tract is feebly
convex, the convexity projecting caudad.

Ascending Cervical Fasciculus of the Trigeminal Nerve
(Plate XVIII, Fig. 16).—This is a narrow fasciculus, which,
after passing entad for a short distance, turns abruptly and
passes caudad into the myelon.

Lateral Sensory Fasciculus of the Trigeminal Nerve

x “ Amphibian Brain Studies,” Jour. of Morphology, Vol. II, p. 69.
2 See RANNEY’s ‘“‘ Applied Anatomy of the Nervous System,” p. 338.

TurNER, JVorphology of the Avian Brain. 2447

(Plate XVIII, Fig. 8).—This is a small tract which passes
from the lateral sensory nidulus of the trigeminal nerve
laterad into the root of that nerve.

Deep Motor Fasciculus of the Trigeminal Nerve (Plate
XVIII, Figs. 8, 15).—This is a broad bundle of fibres which
passes from the root of the trigeminal nerve directly mesad
to the raphe. It intersects the raphe immediately dorsad of
the deep motor nidulus of the fifth nerve. This faciculus is
composed of several narrow, isolated bundles.

In addition to the these tracts, there is a tract which de-
scends from the epencephalon and enters one of the roots of
the fifth nerve. There appears to be no trace of what Pro-
fessor Osborn has called the direct encephalic tract, but there
appears to be a tract passing into the mesencephalon. Prob-
ably that tract communicates with the mesencephalic nidulus
of the fifth.

Tract of the Abducens Nerve (Plate XV, Fig. 12; Plate
XVIII, Figs. 10, 13).—As in the amphibian(') and in the
reptilian(*) and in the mammalian(*) brain, so here, the
internal course of the abducens nerve consists of a single
narrow fasciculus. This bundle passes from the nidulus of
the abducens nerve ventro-laterad to the external root of that
nerve. Although small, this tract is relatively larger than
the corresponding tract of the mammalian brain.

Fasciculi of the Facial and Auditory Nerves (Plate XVIII,
Fig. 18).—In birds the root-fibres of the facial and auditory
nerves are so intimately associated that it is not now possible
to say which fibres belong to the eighth and which to the
seventh nerve. In this connection we find four fasciculi,(*)

one of which passes to the epencephalon. For convenience,

rt H, F. Ossorn, ‘‘ Amphibian Brain Studies,” p. 70.

2 C. L. Herrick, ‘‘ Notes on the Alligator Brain,” p. 153.

3 AmBrosE L RANNEY, op. Cit., p. 339.

4 Among my notes I have one, dated several months ago, in which is described for
the avian brain a tract resembling the genu of the seventh nerve as it appears in the
mammalian brain. Since that time the series that furnished the note has faded so much
that verification has been impossible. Other series have been carefully studied, but no
such tract has been since encountered.—C. H. T,

278 JOURNAL OF COMPARATIVE NEUROLOGY.

the three tracts that are confined to the medulla are desig-
nated ‘* tractus L,” “‘ tractus B,”’** tractus D.”

Tractus £.—This is a short fasciculus which passes from
nidulus L directly laterad to the common root of the auditory
and facial nerves.

Tractus &.—This fasciculus passes direct from the root
of the auditory nerve meso-dorsad to the eminentia acustica.
There it envelops nidulus B, after which it passes meso-
caudad to the raphe. This latter portion of the tract is
convex, with the convexity projecting caudad. <A similar
tract is found in almost all vertebrate brains.

Tractus D (Plate XVIII, Fig. 18).—This is a narrow
bundle which passes from the common origin of the auditory
and facial nerves mesad to the raphe. There it probably de-
cussates. This fasciculus appears to be the homologue of a
similar tract discovered by Professor C. L. Herrick in the
alligator brain,(') a tract which he considers to be a fascicu-
lus of the facial nerve.

There does not appear to be any very great resemblance
between the tracts of the auditory nerve of the birds and the
tracts of the corresponding nerve of the amphibia. Accord-
ing to Professor Osborn,(*) the eighth nerve of the amphibia
is composed of the following tracts: 1. A tract from the pos-
terior longitudinal fasciculus, connecting with the myelon.
2. A tract from a large nucleus situated directly above the
exit of the ninth nerve and above the motor nidulus of the
trigeminal nerve. (This cell cluster is probably Deiter’s
nidulus.) 3. A tract from a small group of cells in the lower
angle of the metencephalon. 4. A tract from the fasciculus
communis. 5. A tract from the epencephalon. Certainly
the resemblance is not very striking. Better preparations,
however, than those, at my disposal might strengthen the
homologies between these two groups, for occasionally I
have observed a faint indication of what might be a connec-

x Ops cits, p: 153.
2 ‘“‘ Amphibian Brain Studies,” p. 66.

TurnER, Morphology of the Avian Brain. 279

tion between the root of the auditory nerve and the longitu-
dinal fasciculus.

Fasciculi of the Glosso-pharyngeal and Pneumogastric
Nerves.—The fibres of these nerves pass directly entad to
their respective niduli. .

Fasciculi of the Spinal Accessory Nerve.—The internal
root of this nerve consists of a longitudinal series of fasciculi
which pass entad from the root to the nidulus of the spinal
accessory nerve.

Fasciculus of the Hypoglossal Nerve.—This fasciculus
passes from its nidulus directly ventro-laterad to its external
root.

Raphe.—The only commissure in this region is the com-
missure which connects the two halves of the metencephalon.
This commissure extends along almost the entire length of
the metencephalon, and is familiarly known as the raphe.

Crossed Pyramidal Tract.—TVhe course of this bundle is
the same in the avian brain as it is in the human.

Direct Pyramidal Tract.—The course of this tract in the
avian brain is similar to the corresponding tract of the human.
But it is composed of a small fraction only of the median
longitudinal fibres that are found near the ventral surface of
the medulla. The remainder go to form the dorso-median
fasciculus. :

Direct Cerebellar Tract.—The homologue of this tract is
present and has a course similar to its course in the human
brain.

Posterior Longitudinal Fasciculus (dorso-median fascicu-
lus). — Among anatomists the cephalad terminus of this
bundle has long been a open problem. During the past two
years two distinguished anatomists, Edinger(') and Honeg-
ger,(*) have each offered a solution of this problem. Each

1 Dr. Lupwic EpinGer, ‘‘ Twelve Lectures on the Structure of the Central Nervous
System.”’ Trans. by Willis Hall Vittum, M.D., p. 120,

2 Jacop Honeccer, ‘‘ Vergleichende Anatomische Untersuchung iiber den Fornix
und die zu ihm Beziehung Gebrachten Gebilde in Gehirns des Menschen und der
Saiigethiere.”’

280 JOURNAL OF COMPARATIVE NEUROLOGY.

is describing it as it appears in the human subject. Edinger,
after remarking that certain of the fibres of the posterior
commissure curve caudad, continues: ‘‘ These fibres, together
with others which arise in the depth of the inter-brain, are
met with as a fine fasciculus ventrad of the anterior oculo-
motor nidulus. As we pass back this fasciculus progressively
increases. There are added to it numerous fibres from the
nucleus of the oculo-motor. We shall, from ow on, meet
with the triangular cross-section of this bundle, which is
composed of fibres from such various regions on every trans-
verse section of the brain, from the corpora quadrigemina
down to the beginning of the spinal dord. This bundle has
been called the fasciculus longitudinalis posterior. Inasmuch
as fibres are given off along the whole course of this bundle
to the nerve-nuclei, as can be plainly seen in embryos of the
sixth to seventh month, when few other fibres are medullated,
and, as this bundle projects further back than the nucleus of
the abducens, it is probable that the fasciculus longitudinalis
posterior not only contains the fibres of communication be-
tween the nuclei of the ocular muscles, but that it also con-
tains fibres to other cranial nerves. Flechsig is also of this
opinion,” etc.

Honegger’s solution, written contemporaneously, cer-
tainly is not in accord with the above. This author con-
siders that this tract does not give off fibres to the posterior
commissure. He has also demonstrated that a portion of the
fibres of the posterior longitudinal fasciculus pass to the
mammillary body, and that other fibres of this bundle decus-
sate in the ventral portion of the diencephalon.

In the avian brain that portion of this fasciculus which
lies cephalad of the oculo-motor nidulus consists of a few
scattered fibres. Cephalad, these fibres terminate abruptly,
near the posterior commissure. Passing caudad, between the
oculo-motor and the trochlear niduli, these few fibres become
a large bundle. From this point to the myelon there is a
progressive increase in the size of this bundle. A short dis-

TurRNER, Morphology of the Avian Brain. 281

tance cephalad of the trochlear nidulus the major portion of
this fasciculus turns and passes obliquely to the ventral sur-
face of the medulla, thence into the myelon. A few fibres,
however, continue caudad and remain near the dorsal surface
of the metencephalon. Throughout its course this tract con-
tinues near the meson. Although it has not been possible to
trace fibres from this fasciculus into any of the niduli of the
avian medulla, yet it is evident that fibres are given off all
along the line. Although the evidence at hand is not quite
conclusive, yet I am inclined to believe the relationship of
the avian posterior longitudinal fasciculus is the same as that
described above by Edinger for the human posterior longitu-
dinal fasciculus.

Fibre Arcuate (Plate XVIII, Fig. 14).—On a level with
the auditory nidulus a convex tract, with its convexity pro-
jecting laterad, passes from a nidulus in the peduncle of
the epencephalon to a nidulus in the ventral portion of the

metencephalon.
CONCLUDING REMARKS.

1. Economy of space is evidenced in all parts of the avian

9

brain, and the phrase ‘‘ higher type of birds” carries with it
the significance ‘‘ greater compactness of the brain.” Indeed,
progressive compactness has played so important a part in
the evolution of birds that there is a vast difference between
the lowest avian brains, with their large projecting olfactory
lobes and exposed optic lobes, and the highest avian brains,
with their small, inconspicuous olfactory lobes and covered
optic lobes. The difference between these two extremes is
almost as great as that between the brain of the lizard and
the brain of the lower types of birds. Yet there is no im-
passable gulf between the brains of the lowest and the brains
of the highest types of birds, for all the intervening stages
are supplied by the brains of the various avian groups. In
reviewing this remarkable sequence, we are almost forced to
believe that this tendency towards compactness of the brain

282 JoURNAL OF COMPARATIVE NEUROLOGY.

existed long before the first bird was evolved. If this be
true, then this tendency towards a progressive compactness
of the brain, combined with a tendency to develop all parts
pertaining to vision and to atrophy all parts pertaining to
smell, will account for all the major differences between the
avian and reptilian brain.

Furthermore, within this class of animals, this progressive

compactness of the brain is a factor of taxonomic importance.
So far, at least, as the major groups are concerned, a classifi-
cation based upon this alone is in harmony with those classi-
fications that are based upon a study of the structural ele-
wents of birds.
_ 2. Neurologically considered, birds are preéminently see-
ing animals, and all parts that appertain to vision are devel-
oped to a great degree. The optic nerve is the largest of all
the cranial nerves, and the optic lobes are complexly differ-
entiated bodies. Even the third, fourth and sixth nerves,
although quite small, are relatively larger than the corre-
sponding nerves of the mammalian brain.

An extraordinary development of one set of organs is
never accomplished but at the expense of some other set. In
this case the organs of smell have been the martyrs. Al-
though in the lower avian types the olfactory lobes are paired
and conspicuous, yet in the highest type of birds the rhinen-
cephalon is a small unpaired body, which is partly embedded
in the base of the cerebrum.

3. Histologically, the avian brain is composed of nerve
fibres, nerve cells and neuroglia. In this connection we are
concerned with nerve cells only. Although these cells pre-
sent a great diversity of forms, yet they may all be grouped
in the following classes: ganglionic cells, Deiter’s corpuscles,
fusiform or flask cells, pyramidal cells, and multipolar cells.
The ganglionic cells are large bipolar cells, which are never
found outside of the root ganglia. Each extremity of each
of these cells is prolonged into a nerve fibre. In addition to
the ordinary cell wall, each cell is surrounded by a special,

TuRNER, Morphology of the Avian Brain. 283

“

nuclei-bearing sheath. Deiter’s corpuscles are small cells,
which contain so small an amount of protoplasm that ordi-
nary preparations reveal only their nuclei. These minute
cells are universally distributed. The remaining three types
are encountered throughout the brain; but in any one nidulus
some one type always predominates, often to the exclusion of
the other two. The flask cells resemble a flask in shape, and
when stained each cell presents a faintly stained nucleus,
within which is a densely stained nucleolus. Such cells are
supposed to be sensory in function. The pyramidal cells are
sub-pyramidal in outline. These cells stain densely, when
each one presents a densely stained nucleus, within which is
a densely stained nucleolus. Such cells are probably motor
in function. The multipolar cells resemble distorted, many-
branched pyramidal cells. Such cells probably act as switch
stations for nervous energy.

EXPLANATION OF PLATE XVIII.

Fig. 1. Transverse section of the brain of Hylocichla Swainsona,
taken through the root ganglion of the auditory nerve; a., tractus B of -
the seventh and eighth nerves; 4, nidulus B of the seventh and nerves;
d, nidulus d of the seventh and eighth nerves; Se, root ganglion of the
auditory nerve.

Figs. 2,3, 4,5. Transverse section of the metencephalon of Szalia
sialis; V, root of fifth nerve; V///, root of seventh and eighth nerve.

Fig. 6. Section through the cortex of the epencephalon.

Fig. 8. WHorizontal-longitudinal section through the fifth nerve
root of Hylocichla Swainsoni; 7V, root of trochlear nerve; V3, lateral
sensory root of the trigeminal nerve; 51, lateral motor nidulus of the
trigeminal nerve; 5°, lateral sensory nidulus of the trigeminal nerve.

_ Fig. 9. Horizontal longitudinal section through the metencephalon
of the domestic turkey brain, taken through the tenth nerve root; _Y,
tenth nerve root; 9; nidulus of the ninth nerve; 70, nidulus of tenth
nerve.

Figs. 10-12. Successive transverse sections of the metencephalon
of Hylocichla Swatnsonz; a. tractus B of the auditory nerve; 4, nidulus
B of the seventh and eighth nerves; d, nidulus Y of the seventh and
eighth nerves; V’, root of the trigeminal nerve; V’/, root of the abducens
nerve; 7/, nidulus B of the seventh and eighth nerves; 9, nidulus of the
ninth nerve.

Figs, 13-14. ‘Transverse section through the metencephalon of

JOURNAL OF COMPARATIVE NEUROLOGY.

Ww
Jes

Columba livia (nestling); A. O., accesory olives; /. a., Fibre arcuate,
17, root of abducens nerve; I’///, root of seventh and eighth nerves.

Fig: 15-17. Horizontal longitudinal sections of the metencephalon
of Columba livia: Va, lateral motor fasciculus of the trigeminal nerve;
Ib, deep motor fasciculus of do; Ic, cervical fasciculus of do; /-X, root
of ninth nerve; -V, root of tenth nerve; 5, deep motor nidulus of the
trigeminal nerve; //, nidulus of the eleventh nerve.

Fig. 18. Transverse section through the metencephalon of
Ageleus pheniceus, taken through the root of the auditory nerve; )’//?,
tractus d of the seventh and eighth nerves.

Fig. 19. Cells from the Gasserian ganglion of H/ylocichla Swain-
SONL,

Fig. 20. Diagram illustrating the course of a few of the tracts of
metencephalon. No attempt has been made to represent the relative
thickness of the tracts; 4. C., anterior commissure; 4. /., anterior
peduncle of the cerebellum; C. C., corpus callosum, C. S., commissura
sylvii; D. C., direct cerebellar tract; 1. /., posterior longitudinal
fasciculus; P. C., posterior commissure. P. /., pons fibres (these are
very few and scattered); P. \V., peduncular nidulus; P. 7’, pyramidal
tracts; 7. &., tract from the epencephalon (see v. 125); 7. 7., tenia
thalami. Roman numerals indicate the corresponding nerve niduli.

Fig. 21. Diagram illustrating the course of a few tracts of the
metencephalon. No attempt is made to represent the relative size of the
tracts; C. @., corpus geniculatum externum; c. z#.,. crescent-shape
nidulus; c. /., crossed pyramidal tracts; Y. P., direct pyramidal tracts;
7. C., inferior commissure; 17. V., mesencephalic ventricle; VV. /..
nucleus posterious; 7. g., prosencephalic tract from the corpus genicu-
latum; P. V., nidulus pyriformis and nidulus lenticularis; P. V.,
prosencephalic ventricle; 7. &., Tractus Bummi. Roman numerals
indicate the corresponding nerve tracts. Arabic numerals indicate the
corresponding nerve niduli.

Fig. 22. Transverse section of the brain of Svadéa sialts,

Fig. 23. Cells from lateral sensory nidulus of the trigeminal nerve
of Columba livia (nestling).

Fig. 24. Cells from lateral metor nidulus of the trigeminal nerve of
Columba livia (nestling).

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286 JouRNAL OF COMPARATIVE NEUROLOGY.

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SPU MBAK, DHE SACRAL, AND THE COCCY-
GEAL NERVES IN THE DOMESTIC CAT.

With Plate XXIII.

DSB STOwELE, A.M.) Pa Ds;

Principal of the State Normal and Training School at Potsdam, N. Y.

The present contribution to comparative neurology is
offered in the hope that it may serve as a factor to strengthen
the argument in favor of the substitution of comparative
anatomy for anthropotomy in the first year’s work of our
medical courses, and also to justify the practice of calli-
section or painless physiological experimentation. The con-
stancy of character, z.e., the slight variation in nerve ramuli
and their distribution, seems to favor making neurology the
basis of comparative anatomy, rather than osteology or my-
ology. Believing such to be the case, it is hoped that this
study may prove helpful in establishing doubtful homologies.
If the educational or cultural in contradistinction to the
utilitarian view of the subject be considered, there seems
abundant demand for the work undertaken by the paper as a
guide to laboratory students with whom the end is general
and not specific. For it is quite generally conceded that
comparative anatomy furnishes one of the most available
means for training the perceptive activities as well as those
of comparison and induction. Furthermore, physiology is
almost wholly a comparative science; while some of the facts
known to physiology have followed direct experiment, the
great majority are the results of partial experimentation upon

other mammals. It needs no proof beyond mention to show

aie

288 JourNAL oF ComparaTIVE NEUROLOGY.

that the present plan of study in the medical college is not
as extensive as it should be to furnish the technical skill and
exact knowledge which the profession demands. That human
physiology is largely comparative will be readily admitted,
but unless the student knows that the structures in the animal
experimented upon are strictly homologous with the struc-
tures in man the physiological experiment becomes merely
an illustrative exercise, interesting and instructive, but not a
demonstration of function in man.

When it is shown that the nerve-supply is identical with
the nerve-supply in man, then these experiments in which
the nervous system is a controlling factor are conclusive
evidence in human physiology also; e.g., at this moment my
mind selects the elaborate experiments of Dr. H. P. Bow-
ditch upon the vaso-motor nerves, the results of which were
presented before Section F, A. A. A. 8., Buffalo meeting,
1886.

Among reasons for the selection of a small mammal may
be named the cost and convenience of suitable preparation,
preservation and manipulation. In regard to cost, it should
be remembered that for exact work each individual should
dissect an entire body—the reserve half serving for corrobo-
ration, verification, correction of errors from accident or over-
sight, study of variations in the same individual, etc. The
writer found it a matter of no small expense and labor to
prepare and to preserve in alcohol the adult cadavers which
formed the basis of his studies in anthropotomy; the conve-
nience of manipulation will be appreciated by those who
have had the experience of transferring a large adult cadaver
from tank to table.

The adaptation of the domestic cat to the ends sought
(comparative neurology) may be briefly stated as follows:

1. The readiness with which structures may be homolo-
gized with corresponding structures in man (certain nerves
in the dog are quite unlike those in man, ¢.g., vagi). That

there are marked differences between the human brain and

STOWELL, JVerves in the Domestic Cat. 289

other mammalian brains is generally known, and _ possibly
some other animal is preferable to the cat as a type for this
portion of the neur-axis.

2. The abundance of material for study.

3. The inexpensiveness of (a) the body; (6) of suitable
preparation of the same, injection, etc.; (c) of preservation
of the same.

4. The ease of manipulation; the tissues are much firmer
than they are in a small human subject, foetus or infant.

To these more apparent considerations may be added the
fact that already elaborate works on felitomy are accessible,
é.g., Straus-Durckheim’s monogram on the ‘‘ Skeleton Liga-
ments and Muscles of the Cat” (‘‘ Anatomie du Chat,” two
vols.), or the less expensive reduced copies with ‘‘ Explana-
tions” by Prof. H. S. Williams; St. George Mivart’s ‘‘ The
Cat,” although this work does not seem to be a reliable guide
to the study of American cats; the more scientific and exact
work of Wilder and Gage, entitled ‘‘ Anatomical Technol-
ogy,’
authors, a partial list of which is found in the work cited;

and the numerous papers and addresses of the same

and the papers embodying some of the writer’s studies in

comparative neurology.(')
PREPARATION.

The cats were killed with chloroform and both arteries
and veins were injected with the starch injection mass.
When not in use the body was wrapped ina napkin saturated
with alcohol and then placed ina tight vessel; the tissues are

by this means preserved in excellent condition.
GENERAL DESCRIPTION.

The myel may be regarded anatomically as an elongated

mass of alba and cinerea, and functionally as an aggregation

t “The Vagus Nerves in the Domestic Cat:’’ The Trigeminus, The Facial, The
Glosso-pharyngeal, The Accessory, The Hypoglossal, The Soft Palate. The literature of
the subject was cited in a paper read before the American Philosophical Society, May
21, 1886.

290 JOURNAL oF COMPARATIVE NEUROLOGY.

of sensory and motor centres especially characterized by
reflex action. Corresponding to its relations with the ver-
tebrz, it is usually divided into the five regions, cervical,
thoracic, lumbar, sacral,and coccygeal; and the myelic nerves
are named from the vertebre cephalad of which they have
their respective ectal origins. ‘The lumbar and the sacral
nerves form open plexuses (PI. lumbalis and PI. sacralis),
from which nerves are distributed to the integument and the
subjacent muscles.

POSTURE.

Ventri-cumbent, head toward dissector’s left, or lateri-
cumbent, with the venter toward the dissector.

EXPOSURE.

It is not imperative that the dissection begin at any par-
ticular point, but most of the nerves send branches caudad
rather than cephalad (v. diagram), hence it is recommended
to begin at the thirteenth thoracic nerve and dissect caudad,
removing the neural arch and exposing the myel as the dis-
section progresses. Make a long incision through the integ-
ument about 2 cm. sinistrad of the dorsi-meson, from the
tenth thoracic vertebra to the base of the tail. From the
cephalic end of this incision make a second incision ventrad
4-6 cm., and reflect the flap of integument over the twelfth
and thirteenth ribs. With the arthrotome remove the dorsal
muscle from the sinistral side of the meson to the level of the
vertebral laminez of the twelfth and the thirteenth thoracic
vertebrae. With the tracer find the thirteenth thoracic and
the first lumbar nerves just peripherad of the vertebre, trace
them centrad to the foramina intervertebrales, separate the
connecting tissues from the foramina, then with the side-
cutting nippers remove the neural arch of the thirteenth
thoracic vertebra, taking the precaution to make the first
incision near the neurapophysis, to insure protection to the

myel. The dextral lamina can be removed without injury to

STOWELL, Werves in the Domestic Cat. 291

the dorsal muscles or integument, making it possible to use
the dextral side to corroborate and to correct results obtained
by dissecting the sinistral. The exposure of the myel in the
arch of the caudal thoracic vertebra (thirteenth) exposes the
ectal origin of the first lumbar nerve. The arch can be re-
moved in a similar manner caudad and dextrad as the dissec-
tion requires, using the precaution to trace the dorsal division
of each nerve before removal of the dorsal muscle. The

nerves should be traced from the ectal origin peripherad.
LUMBAR NERVES. NERVI LUMBALES.

Common Characters.—The lumbar nerves are seven pairs,
and have characters in common. ‘They are related with the
sympathic system by anastomotic filaments to the adjacent
ganglia (Fig. Pl. S. and S.), which filaments leave the ental
surface of the nerve as it traverses the groove from the neural
arch to the inter-vertebral foramen (foramen of exit); these
anastomotic filaments are apposed to an arteriole—the dorsal
branch of the A. lumbalis. At the ectal border of the fora-
men of exit, each nerve divides into a dorsal and ventral
portion; the dorsal nerve divides into two or more branches,
which innerve the muscles of the back (MM. quadratus lum-
borum, erector spine, intervertebrales) (Fig. M. dor,), which
are especially large in the cat. A branch from each dorsal
nerve can be traced to the integument (Fig. Int.), where it
joins in an open plexus with the adjacent nerves.

The nerve trunk or ventral division dips ventrad close to
the border of the centrum and mesad of the diapophysis; the
origin is thus concealed by fascia, aponeuroses and super-
posed muscles. At the ventral border of the centrum the
nerve usually passes laterad (except the branch to form the
lumbar plexus) apposed to the abdominal branch of the lum-
bar artery. From the ental surface of the trunk adjacent to
the centrum a branch is given off which separates into three
to five ramuli to the proximal or aponeurotic portions of the
M. psoas (Fig. Pso.), and two anastomotic rami to the sym-

292 JOURNAL OF COMPARATIVE NEUROLOGY.

pathic ganglia (Fig.S.) cephalad and caudad; in the cephalic
three lumbar nerves, these rami join the great solar plexus
(Hie PLS.)

The lumbar nerves are conveniently grouped into two
groups, those which do not enter into the lumbar plexus,
viz., the cephalic four pairs, comparable with the first lumbar
(anthropotomy), and those which are so related, viz., the
caudal three pairs, comparable with the lower four lumbar
nerves (anthropotomy ).

Special Characters.— The first and second lumbar nerves
give the first branch to the diaphragm (Fig. Dia.) instead of
the M. psoas; they join the solar plexus (PI. S.), they follow
the abdominal lumbar artery through the aponeurotic origin
fibres of the diaphragm, and lie upon its cephalic surface 25
mm. peripherad of the foramen of exit. Five mm. still
peripherad, in the aponeurotic interdigitations of the ectal
oblique muscle (M. abdominis obliquus ectalis), the trunk
separates into cephalic (Fig. ce.) and caudal (Fig. ca.) divi-
sions. Zhe cephalic division follows the abdominal artery,
penetrates the overlying (ectal) muscle, innerves the ental,
the transverse and the rectus muscles of the abdomen, anasto-
moses with the cephalic divisions of the adjacent nerves (Fig.
anas.), and sends terminal filaments to the adjacent integu-
ment (umbilical and hypogastric). The caudal division has
its course caudad and slightly ventrad; it lies upon the ectal
surface of the ental muscle, to which it gives filaments in the
umbilical and the hypogastric regions. This division lies
entad of the cephalic division of the lumbar nerve next
caudad.

The third and fourth lumbar nerves (first lumbar of
anthropotomy). These nerves have the ectal origins and
proximal rami similar to the first and second. The third
nerve joins the solar plexus cephalad, but the sympathic
ganglion caudad. The fourth does not anastomose with the
plexus. Zhe cephalic divisions are distributed farther caudad,
reaching the gluteal (Fig. Th.) and inguinal regions (Fig.

STOWELL, /Verves in the Domestic Cat. 293

Pub.), and giving numerous filaments in plexiform relations
over the hypogastric integument. Zhe caudal division of
the third lies entad of the cephalic division of the fourth,
and ectad of the cephalic ramus of the ilio-lumbar artery; 20
mim. from its origin it crosses a ramulus of the caudal ramus
of the same artery as the arteriole perforates the lateral
border of the M. abdominis rectus. The nerve gives filaments
to the transverse (Fig. trans.) and to the ental oblique (Fig.
M. ent.) muscles. Zhe caudal division of the fourth lies
apposed to the caudal ramus of the ilio-lumbar artery for 15-
20 mm.; it passes between the cephalic and the caudal divi-
sions of the genito-crural nerve. It innerves the transverse
and ental muscles 10-15 mm. dorsad of the region supplied
by the caudal division of the third, and terminates in the
rectus abdominis muscle.

The fifth, sixth and seventh lumbar nerves are distin-
guished from the other lumbar nerves by the plexus (PI. lum-
balis) formed by the dorsal or caudal divisions of the ventral
nerve trunks. These nerves rapidly increase in size, the
seventh being considerably the largest. The union of the
divisions or branches just ventrad of the vertebral diapophy-
ses forms not only an important part of the lumbar plexus,
but constitutes the lumbo-sacral cord of anthropotomy, from
which nerves take their ectal origins, v. below.

N. GENITO-CRURALIS, N. LUMBO-INGUINALIS; N. PUDENDUS
EXTERNUS.

The genito-crural nerve (second lumbar of anthropotomy)
has its ectal origin by two roots; the cephalic root seems to
be the lateral continuation of the fifth lumbar nerve, the
caudal root is a large branch of the sixth lumbar nerve, given
off at the foramen of exit centrad of the plexus. The root
nerves are inter-related by anastomotic filaments. The trunk
formed by the union of the roots penetrates the aponeurosis
of the M. psoas, lies upon its ectal surface about 2 mm.
laterad of the mesal border of the muscle, and separates into

204 JOURNAL OF COMPARATIVE NEUROLOGY.

two divisions, cephalic and caudal. The cephalic division,
the crural branch (crur.), bends around the lateral border of
the M. psoas, and 20 mm. peripherad of its origin it accom-
panies the ilio-lumbar artery into the transverse muscle. Its
course is caudad in the transverse and ectal muscles, and
leaves the pelvis by the ectal abdominal ring entad of Pou-
part’s ligament; its course outside the pelvis is along the
ectal fascia over the caudal thigh to the knee, and terminates
in the integument of the proximal crus, where it joins fila-
ments of the external cutaneous nerve. Zhe caudal or dorsal
division, the genital branch (gen.) lies upon the meso-ental
surface or border of the M. psoas, entad of the ilio-lumbar
artery, at which point it gives a large anastomotic branch to
the open plexus of nerves and vessels of that region, and
thence continues caudad in the ental muscle, to which it
gives several filaments. At the Poupart’s ligament (Fig. P.)
it is reflected ventro-cephalad, and terminates in the integu-
ment of the hypogastric region; filaments from the point of
reflection extend to the integument over the pubes. (I have

not traced this nerve in the male.)
N. CUTANEUS ECTALIS.

The external cutaneous nerve (Ext. Cut.) has its ectal
origin by two roots; the cephalic root is a branch of the loop
(Fig. Loop) between the fifth and the sixth lumbar nerves;
the caudal root is a branch of the sixth nerve in common
with the caudal root of the genito-crural. The origin and
the distribution of the genito-crural and the external cutane-
ous nerves indicate an intimate inter-relation.

The course of the nerve lies ectad of the anastomotic
branch from the G. sympathicus to the sixth lumbar nerve;
it runs obliquely through the origin fibres of the M. psoas
and comes to superficial view at the mesal border of that
muscle at the point where the iliac artery lies apposed to the
aponeurosis of the M. psoas, about 20-30 mm. cephalad
of the ramus of the pubis. Exposure is readily made by

STOWELL, /Verves in the Domestic Cat. 295

tracing the mesal border of the M. psoas caudad from this
point. |

The nerve lies ectad (ventrad ) of the external iliac artery
and vein, and entad of the common iliac vein which is ven-
trad of and apposed to the artery; it bends around the artery
and lies upon its ental surface, ectad (ventrad) of the hypo-
gastric artery just cephalad of the ramus pubis.

It leaves the pelvis through the abdominal ring, 20 mm.
peripherad of which it separates into two divisions, one of
which (Fig. ce.) is distributed to the integument of the hip
(Fig. H.) and the proximal half of the caudal thigh (Fig.
Th); the other division (Fig. ca.) is distributed to the in-
tegument over the biceps muscle as far as the knee. The
nerve was wanting on the sinistral side of one specimen
(female).

N. CRURUS ANTERIOR.

The anterior crural (Ant. Crur.), the seventh lumbar
nerve, is the largest of the spinal nerves whose origin is not
referable to the union of two or more nerve trunks. It sup-
plies mzscular branches to the psoas, the iliacus, the sar-
torius, the pectineus muscles and the muscles of the cephalic
(inner) thigh except the tensor vagine femoris, which is
innerved by a slender ramus of the superior gluteal nerve
(q. v'); and cutaneous branches to the integument of the
thigh, the leg, the cephalic part of the foot and the plantar
surface of the toes.

The seventh lumbar nerve at the foramen of exit sends
anastomotic branches to the adjacent sympathic ganglia; its
dorsal division innerves the muscles of the back (Fig. M.
dor.) and the adjacent integument (Fig. Int.); the large
ventral division (2 mm. in section) lies close to the lateral
surface of the centrum and at its ventral border receives the
large trunk (Fig. L. S.C.) of the sixth lumbar nerve, and
sends an equally large trunk caudad (Fig. L. S. C., lumbo-
sacral cord of anthropotomy) to the first sacral nerve.

296 JouRNAL OF COMPARATIVE NEUROLOGY.

Origin.—The anterior crural nerve is the ventral division
of the seventh lumbar, of which it is strictly the continuation
with a large accession from the sixth—or its origin may be
referred to the lumbar plexus.

Principal Rami.—The ectal origin of the nerve lies entad
of the M. psoas, to which several filaments are given (Fig.
Pso.) 2 mm. peripherad of its origin; 5 mm. peripherad a
large branch is given caudad to the M. iliacus (Fig. M. il.).
The general course of the nerve trunk is embraced by the
M. psoas, the nerve reaching the ectal surface or lateral
border of the muscle in the region of the iliac notch, or 20
mm. ventro-caudad of its origin. Entad of Poupart’s liga.
ment (Fig. P.) it gives from its lateral border a large ramus
which innerves the sartorius muscle (Fig. Sar.), which ramus
lies entad of a ramus of the profund artery 10 mm. from its
origin. As the nerve crosses the artery a slender branch
passes ectad of the artery to the mesal border of the sartorius
muscle. The larger portion of this branch lies upon the
ental surface of the muscle, and can be traced to its distal
extremity or insertion, thus innerving its distal three-fourths;
the smaller portion of the nerve is reflected proximad at the
profund artery, and innerves the proximal (origin) one-fourth
of the sartorius muscle, lying upon its ental surface.

Entad of Poupart’s ligament and 2 mm. peripherad of the
sartorial branch, from the mesal border of the nerve is the
ectal origin of the long saphenous nerve (N. cutaneus in
ternus longus, Fig. Saph. 1.).

THE LONG SAPHENOUS NERVE.

This nerve lies ectad of the femoral artery and apposed to
it and the long saphenous vein, the vein being mesad, the
artery in the middle, and the nerve laterad upon the surface
of the thigh.

Principal Rami.—tThe first branch is given to the artery
(Fig. A. fem.). At the knee (Fig. K.) two ramuli are given
off; the dateral ramulus (Fig. 1. r.) is cutaneous; it accom-

STowELL, WVerves in the Domestic Cat. 29

Ti

panies an arteriole and is distributed to the integument over
the cephalic surface of the proximal third of the crus; the
mesal ramulus (Fig. m. r.) lies ectad of the artery and vein
and is distributed to the integument mesad of the vein, its
terminal filaments anastomosing with other filaments of the
nerve trunk. Below the knee (Fig. K.) (upon the crus) the
nerve continues as two divisions corresponding with the two
arteries, with whose courses they are nearly parallel; the
lateral division is distributed to the integument over the
cephalic surface of the distal half of the crus and the pes;
the mesal division lies in the fascia ectad of the tibia; its
course is just mesad of (behind) the cephalic malleolus, ectad
of the tendon of the M. tibialis anticus; it forms a dense
plexus upon the cephalic metatarsale (2) and joins the
plantar plexus (Fig. Pl. Plan.), its terminal filaments being
traceable to the distal extremities of the toes and to the
plantar pads.

The muscular division (deep layer of anthropotomy) of
the anterior crural nerve, near its origin at Poupart’s liga-
ment, follows the profund artery, dips entad in Scarpa’s
triangle, and gives a branch to the M. sartorius (Fig. Sar.),
which branch, 5 mm. peripherad (at the border of the M.
rectus femoris), lies entad of the artery and separates into a
peripheral and a central portion; the peripheral branch may
be traced in pinniform arrangement throughout the distal
three-fourths of the muscle to the knee; the central branch is
reflected at the artery and is distributed to the proximal
fourth of the muscle.

At the origin of the last branch the nerve penetrates the
M. rectus femoris (Fig. M. r. fem.), to which three rami are
given. The proximal ramus innerves the proximal third of
the muscle, the second lies upon the ental surface of the
muscle and innerves its distal two-thirds, to the insertion at
the patella; the third ramus enters the caudal border of the
muscle near its middle. These three rami are motor. Five

mm. peripherad of the branch to the M. sartorius a ramus is

298 JoURNAL OF COMPARATIVE NEUROLOGY.

given to the M. vastus internus (V. int.) and to the M. crureus.
At the caudal border of the M. vastus internus filaments are
given to the muscle; the nerve lies entad of the M. rectus
femoris and the adjacent M. vastus externus, whose ental
surface it penetrates, accompanied by an artery, and distri-
butes filaments from three ramuli to the M. vastus externus.
The nerve can be traced around the lateral border of the
femur with the internal circumflex (?) artery into the M.

pectineus.
N. OBTURATOR.

Origin.—The obturator nerve (N. Obt.) has its ectal
origin from the lumbo-sacral cord between the seventh
lumbar and first sacral nerves, 16 mm. caudad of the anterior
crural nerve; in one specimen the origin was by the union of
a lumbar (seventh) and a sacral (first) root at the ventral
border of the ilium. Its course is caudad, ectad of the ental
iliac artery and ventro-mesad of the ventral border of the
ilium; it pierces the obturator muscle 30 mm. caudad of the
origin of the nerve; it leaves the pelvis through the Fm.
obturator, peripherad of which it divides into several rami.

Principal Rami.—The first ramus (N. obturator acces-
sorius (?)) is directed ectad to the superposed M. pectineus
(Fig. M. Pec.). A long ramus bends over the cephalic
surface of the origin of the adductor muscle, lies upon the
ental surface of the M. gracilis apposed to an arteriole, and
innerves the gracilis (Fig. M. grac.), in which muscle it may
be traced to its aponeurotic insertion at the knee, centrad of
which anastomotic filaments relate it with the long saphenous
nerve.

Four rami lie upon the ectal surface of the proximal end
of the adductor muscles (MM. magnus and brevis), just peri-
pherad of the foramen, in which muscles they terminate.

Entad of the M. adductor longus, between it and the M.
adductor brevis, two ramuli cross the M. adductor brevis and
are distributed to the M. adductor magnus, attended by rami

STOWELL, WVerves in the Domestic Cat. 299

of the internal iliac artery. Terminal ramuli like a leash
supply the M. adductor longus and the M. obturator externus.

SACRAL NERVES.

General Description.—The sacral vertebre are three, and
the nerves are corresponding three pairs. These nerves are
characterized by the length of the ectal roots and by the dis-
tance through which they are traced in the neural arch and
in the groove from the arch to the intervertebral foramina..
At their respective foramina of exit they separate into two
unequal divisions, the dorsal and the ventral; the dorsal
division passes directly dorsad and divides into cephalic and
caudal rami, each of which anastomoses with the terminal
filaments of the adjacent nerves, and each sends a considerable
branch to the open plexus of cutaneous nerves; the ventral
division passes directly ventrad and laterad to join in the
formation of the sacral plexus, from which nerves are distri-
buted to the caudal extremity. Each ventral nerve receives
an anastomotic nerve from the adjacent sympathic ganglia

(Fig. S.).
THE FIRST SACRAL NERVE.

Special Description.—The first sacral nerve is the largest
of the spinal nerves, and has its ectal origin in the neural
arch of the sixth lumbar vertebra, at the caudal border of
which may be found its dorsal root ganglion; it traverses the
long groove (10 mm.) in the seventh lumbar vertebra, and
finds its exit through the foramen mesad of the crista ilii and
ventro-mesad of the broad diapophysis of the first sacral
vertebra. Immediately peripherad of the foramen of exit it
is joined by the lumbo-sacral cord (Fig. L.-S. C.)—which in
a medium-sized cat is 2 mm. in section—and has its course
mesad and ventrad of the diapophysis and the crista ilii, by
which it is concealed, and which renders its exposure some-
what difficult. The nerve trunk at this point (its central

10 mm.) is about 4 mm. in section.

300 JOURNAL OF COMPARATIVE NEUROLOGY.

Principal Rami.—The first nerve from the sacral plexus,
AV. Gemellus (Fig. Gem.), is given from the ectal surface of
the first sacral nerve where it is joined by the lumbo-sacral
cord (Fig. L.-S. C.) at the caudal border of the first sacral
vertebra, and is directed dorsad; it lies close to the vertebra
for its central 5 mm.,and then passes laterad into the gemellus
muscle, and is distributed by three branches. This muscle
has its origin along the sacral vertebra, but its relation with
the M. gluteus maximus and its insertion with the M. obtu-
rator internus, as well as the innervation, lead to its identifi-
cation as the M. gemellus superior.

From the cephalic border of the first sacral nerve a branch
is sent laterad and around the ramus of the ilium cephalad of
the acetabulum to the M. pyriformis (Fig. Pyr.). The nerve
trunk lies ectad of the sacral artery and vein, and leaves the
pelvis through the great sciatic foramen upon the ectal sur-
face of the M. quadratus femoris, the M. obturator and the
M. pyriformis, and entad of the MM. glutei.

About 10 mm. caudad of the foramen of exit a branch
from the ental surface is given to the M. gluteus maximus
(Fig. M. gl. max.), and 5 mm. still peripherad a branch
caudad and entad of the M. obturator internus (M. obt. in.),
which branch divides into two rami, the shorter being dis-
tributed to the overlying obturator and the longer terminat-
ing in the quadratus muscles. The nerve to the M. gluteus

is sometimes a branch from the second sacral nerve (see

Fig. F).
THE SECOND SACRAL NERVE.

The ventral division of this nerve is much smaller than
the first sacral nerve; it takes a ventro-laterad course, and
joins the first sacral just mesad of the trochanter. The union
of these two trunks constitutes the great sciatic nerve Bq. v.2.

Principal Rami.— The dorsal division is already described
in common with the other sacral nerves, v. ‘‘ General De-

scription.” Its caudal branch joins the plexus which innerves

STOWELL, /Verves in the Domestic Cat. 301

the dorsal muscles and the integument of the tail. A large
anastomotic /oop joins the ventral division of the third sacral
nerve just peripherad of the foramen of exit. A slender
branch is sometimes given as a distinct nerve to the overlying
M. gluteus maximus (Fig. M. gl. max.).

THE THIRD SACRAL NERVE.

The ventral division is the smallest of the sacral nerves;
it divides into ental and ectal branches. The ental or deep
branch lies upon the ectal surface of the long levator ani
muscle (Fig. L. A.), to which it is distributed. Zhe ectal
branch joins the second sacral nerve in a large anastomotic
branch or /oof, and peripherad of this a smaller loop joins
the first coccygeal nerve (Fig. N. Coc.) and at the same
point gives off the second root of the N. coccygeus (Fig. N.
Coc.).

Principal Rami—The nerve trunk divides into three
branches, which lie entad of the rami to the M. gluteus maxi-
mus and the M. obturator internus, already described. The
cephalic branch joins the N. ischiadicus at the origin of the
sciatic root of the pudic nerve; fhe middle branch is the
sacral root of the pudic nerve; the caudal branch separates
into two rami, one of which is the sacral root of the N. glu-
teus (N. glut.), and the other forms, with a branch from the
first coccygeal nerve (q. v.) and a branch from the pudic, a
slender nerve to a ribband muscle (Fig. M?) described below
v. N. Coccygeus.

N. GLUTEUS SUPERIOR.

At the union of the lumbo-sacral cord with the first
sacral nerve to form the main trunk of the great sciatic, a
large branch, the superior gluteal nerve (N. gl. S.), is sent
laterad and bends over the dorsal border of the ilium just
cephalad of the acetabulum and entad of the MM. glutei. It
leaves the pelvis by the great sciatic foramen, and to mm.

peripherad of its origin divides into three branches; fhe

302 JOURNAL OF COMPARATIVE NEUROLOGY.

cephalic branch is distributed to the M. gluteus medius (M.
gl. med.), which lies ectad of the nerve and whose ental
surface it penetrates; the caudal branch is distributed to the
M: gluteus minimus (M. gl. min.), which lies entad and
caudad—these two rami are the homologue of the superior
branch of anthropotomy; the middle branch — inferior of
anthropotomy—the largest branch, perforates the M. gluteus
minimus and innerves the M. tensor vaginew femoris (T.V.F.),
in which it can be traced to the distal fourth. A few fila-
ments are given to the M. gluteus minimis.

N. ISCHIADICUS.

The great sciatic nerve (Fig. Ischiad.) is the largest of
the spinal nerves; its ectal origin is the sacral plexus, or the
union of the first and second sacral nerves. Within the
pelvis, its course is caudad to the sciatic foramen; peripherad
of the pelvis it lies upon the ectal border of the M. obturator
internus and the MM. gemelli, mesad of the great trochanter,
laterad of the ischiac tuberosity, and entad of the MM. pyri-
formis, biceps and glutei. Its exposure is effected in the
meros by the removal of the M. gluteus maximus and the M.
biceps. The great sciatic nerve is cutaneous and muscular in
its distribution; it supplies the integument of nearly all the
caudal limb, and the muscles of the meros, the crus, and the
pes as given below.

Principal Rami.—The first branch is given off at the
union of the second sacral nerve, and innerves the M. quad-
ratus femoris (Fig. Quad.). Zhe second branch is the sciatic
root of the pudic nerve (q. v.), in common with the root of a
gluteal nerve (b. v.). Zhe third branch is a considerable
nerve entad of the M. pyriformis, and which is divided into
three smaller rami: (a) the first of which enters the ental:
surface of the M. biceps, 5-S mm. peripherad of its origin
(Fig. M. bi.); (4) the second is covered by the M. biceps,
to which it gives it ramulus at its mesal (lower) border, and

continues entad of the M. semi-tendinosus and a plexus of

STOWELL, Werves in the Domestic Cat. 303

vessels (ramuli of the profund artery and veins (?)); it lies
upon the ental surface of the muscle 20-30 mm., then pene-
trates its substance as two terminal ramuli (Fig. M. semi-
ten.); (c) the third ramus crosses the ectal surface of the
vessels named, peripherad of which, or 20 mm. from its
origin, it enters the M. semi-membranosus as two terminal
ramuli (Fig. M.semi-mem.). Zhe fourth branch is a slender
filament, about the middle of the thigh, which is given to the
distal half of a ribband muscle (Fig. M?) 2 mm. in width,
which lies in the fascia upon the ental surface of the M.
biceps, which muscle it crosses obliquely—this muscle has
its origin just cephalad of the M. pyriformis upon the dia-
pophysis of the first caudal vertebra, lies entad of the M.
pyriformis and the M. biceps, and is inserted in the aponeu-
rotic fascia of the mesal border of the biceps about midway
between knee and ankle; it is readily separable from the
biceps; the total length in a cat of medium size is about go
mm.; the proximal end of the muscle is innerved by a ramu-
lus whose roots are traceable to the third sacral, the first
coccygeal and the pudic nerves. Zhe fifth branch innerves
the distal third of the M. biceps (M. bi.); it is given off 4o
mm. peripherad of the trochanter, just centrad of the short
saphenous nerve.

N. CUTANEUS INTERNUS.

The short saphenous nerve (Saph. br.) has its ectal origin
just centrad of the division of the sciatic trunk into the pop-
liteal and the peroneal nerves. It crosses the popliteal space
embedded in the adipose which occupies this region, is ectad
of the artery and entad of the M. biceps; it lies apposed to
the artery upon the dorsal surface of the biceps and entad of
the ectal fascia. Its filaments terminate in the integument
over the caudal side of the foot and the fifth toe.

The great sciatic trunk divides into two unequal nerves,
the caudal and smaller, N. peroneus, and the cephalic, larger
nerve, N. popliteus.

304 JOURNAL OF COMPARATIVE NEUROLOGY.

N. PERONEUS.

This nerve lies entad of the insertion third of the M.
biceps and ectad of the M. gastrocnemius, which muscle it
crossesa bout 10 mm. peripherad of the caudal condyle. As
the nerve dips between the M. peroneus longus and the
M. peroneus tertius, the

N. MUSCULO-CUTANEUS

(Fig. mus.-cut.) takes its origin and has its course entad of
the M. peroneus, apposed to the anterior tibial artery; it
becomes ectal (superficial) with the artery about midway
between the knee and the ankle, or near the tendinous part
of the M. peroneus longus; following the artery its ramuli
may be traced to the integument upon the dorsum of the foot
and the second, third and fourth toes. Its caudal filaments
anastomose with the short saphenous nerve. Ten mm. peri-
pherad of its origin it gives a branch to the M. peroneus
tertius, and 10 mm. still peripherad a large ramus passes
entad and lies upon the ectal surface of the M. peroneus
brevis, apposed to an arteriole (a branch of the anterior tibial
arte:y), which muscle it innerves. The trunk crosses the
ectal surface of the muscle (peroneus brevis) obliquely and
bends around the caudal border of the large tendon as it
passes through the sheath caudad of the malleolus; it then
lies entad of the tendon and upon the ectal surface of the
short extensors of the toes, which muscles it penetrates,
lying between the fourth and the fifth metatarsalia, and entad
of the tendon to the fifth toe, bnt ectad of the one to the
fourth toe at the distal end of the metatarsale, at which point
it joins a ramus of the (?) nerve, thence it is distributed to
the integument of the fourth toe.

The nerve trunk at the origin of the musculo-cutaneous
branch gives a ramus to the overlying M. peroneus longus,
which nerve accompanies an arteriole from the anterior tibial
artery. Entad of the M. peroneus longus with the last

STOWELL, Werves in the Domestic Cat. 305

described nerve, an equally large branch lies just entad and
dips between the M. extensor digitorum longus and the M.
peroneus tertius. Ten mm. peripherad of its origin the nerve
bifurcates, the anterior tibial artery (Fig. A.) occupying the
angle between the branches. Zhe cephalic branch (Fig. ce.)
innerves the M. extensor longus digitorum; the caudal branch
(Fig. ca.) lies entad of the anterior tibial artery and accom-
panies the artery to the dorsum of the foot. Entad of the
groove a ramus is given to the tarsal ligament and the origin
fibres of the M. extensor brevis. The terminal filaments join
in the plexus to the integument of the dorsum of the foot
and toes.

N. TIBIALIS ANTICUS.

This branch (Fig. Tib. a., and m.) of the peroneal is
given off between the origin of the musculo-cutaneous
nerve and the bifurcation of the peroneal; it can be traced
30-40 mm. in the substance of the M. tibialis anticus,
and sends a ramus peripherad to the M. extensor longus
digitorum.

N. POPLITEUS.

The cephalic division of the great sciatic nerve crosses
the popliteal space and continues peripherad between the
heads of the M. gastrocnemius. At the proximal end of the
crus it gives its 77vs¢ branch to the ectal surface of the caudal
head of the M. gastrocnemius (Fig. M. gas.), and immedi-
ately peripherad a large ramus penetrates the same muscle
and is distributed to the muscle from its ental surface; a con-
siderable portion of this ramus perforates the gastrocnemius
and innerves the M. Soleus (Sol.), which is entad; from this
penetrating ramus ramuli are given to both heads of the
muscle. Twenty mm. peripherad a second large branch to
the body of the same muscle (Fig. M. gas.), peripherad of
which the nerve trunk bifurcates, forming ental (Fig. dv.

ent.) and ectal (Fig. dv. ect.) divisions.

3206 JOURNAL OF COMPARATIVE NEUROLOGY.

N. POST-TIBIALIS.

The extal division of the popliteal nerve is muscular in
distribution. Ten mm. peripherad of its origin a large ramus
innerves the M. popliteus (Fig. Pop.), which lies just entad.
The trunk crosses the ectal surface of the post-tibial artery,
and 10 mm. peripherad it innerves the M. flexor longus digi-
torum (M. fl. long. dig.) by several pinniform ramuli. As
the nerve penetrates the flexor muscle a ramus is given to
the M. tibialis posticus, and still peripherad three or four
filaments are given to the M. flexor longus pollicis? —a
muscle whose tendon unites in the plantar surface with
the broad tendon of the long flexors (pollex is wanting in
the cat).

The ectal division lies apposed to the post-tibial artery
and gives no rami centrad of the groove of the long flexor
muscle, in which groove are the tendon, the nerve and the
post-tibial artery. Peripherad of the groove the nerve bifur-
cates and lies upon the ental surface of the M. flexor brevis
digitorum. The cephalic ramus,

N. INTER-PLANTARIS,

innerves the short flexor muscles, lies along its cephalic
border, and terminates in cutaneous ramuli to the pads of
the second and third toes; a few filaments are directed
entad to the underlying muscle, the M. flexor accessorius

(flac):
N. PLANTARIS,

The caudal ramus of the ectal division, lies upon the broad
tendon of the long flexor muscle and the second layer of
muscles. A slender ramus is given caudad to a small muscle
upon the distal end of the calcaneum—the fibres of this
muscle run transverse and the aponeurosis joins the broad
tendon of the long flexor. Near the proximal end of the

meta tarsalia a branch is given entad,

STOWELL, (WVerves in the Domestic Cat. 20

“i

THE ENTAL PLANTAR NERVE,

which hes ectad of the proximal end of the interosseus
muscles and within their substance, and crosses the foot
obliquely from the head of the metatarsale of the fifth toe
toward the distal end of the metatarsale of the second. The
nerve trunk lies entad of the caudal border of the short flexor
and at the distal end of the second metatarsale (pollex want-
ing); it divides into a leash of four nerves, each of which
dichotomoses and innerves the interosseous muscles (M. int.) ;
slender filaments are given to the third layer of muscles.
The ental branch innerves the third and fourth lumbricales,
the three plantar interossei muscles, and the four muscles
which occupy the plantar arch of the metatarsalia—these
muscles have their origins at the proximal end of the meta-
tarsalia and insertion in the aponeurosis of the common ex-
tensor tendon and by a short tendon into the proximal end
of the proximal phalange. <A portion of the muscle seems
to be equivalent to the dorsal interossei (anthropotomy ), and
a portion is not satisfactorily homologized. The deep plantar
also innerves a muscle, which has its origin from the os
cuboides and crosses the plantar metatarsus obliquely and
inserts by a tendon upon the caudal surface of the proximal
phalange of the second toe, probably an adductor muscle.

THE ECTAL PLANTAR NERVE

bends around the tendon of the muscle, and, crossing its
ectal surface, lies entad of the tendon of the long flexor of
the second toe. At the distal end of the proximal segment
of the fifth toe it bifurcates, and can be traced to the pad of
the fourth and fifth toes. A slender filament is given to the
M. abductor minimus (Fig. M. ab. min.).

N. PUDICUS (N. PUDENDUS).

The pudic nerve (Pud.) has its ectal origin by two roots.
The sacral root is the largest of the terminal branches of the

308 JoURNAL OF CoMPARATIVE NEUROLOGY.

third sacral nerve, and lies entad of the pudic artery; the
sciatic root is given off from the sciatic nerve abont 15 mm.
peripherad of the union of the first and second sacral nerves,
in common with the sciatic root of the N. gluteus to the
M. glutei (Fig. N. glu.). It leaves the pelvis through the
sacro-sciatic foramen, and is apposed to the pudic artery; its
general course is meso-caudad, entad of the pudic artery and
vein, upon the ectal surface of the internal obturator muscle.
Twenty mm. peripherad of the union of the two root nerves,
the pudic separates into dorsal and ventral divisions, which

are muscular and cutaneous respectively in distribution.
N. PERINEUS DORSALIS,

The dorsal division (Fig. dor.), lies upon the ectal surface of
the rectal muscle; its branches innerve the broad M. levator
ani (Fig. L. A.), the M. sphincter ani (Fig. sph. A.), and
20 mm. of the longitudinal rectal muscles (Fig. rec.), which
muscles are supplied by the hemorrhoidal artery and vein.
The last nerve is the

N. HAMORRHOIDES.

A branch is given to the anal gland (Fig. gl.)—a large
olive-colored gland just laterad of the anus, whose duct opens
ectad of the sphincter muscles, or sometimes just entad.

Another ramus,
N. PERINEUS DORSALIS,

Innerves the sphincter vagine and the ectal labium(?).
N. PERINEUS VENTRALIS,

The ventra! division (Fig. ven.), is distributed to the vagina,
the ectal iabium, the perineum, the urethra, the M. accelera-
tor urine, and the transverse muscle just entad of the peri-
neal integument. A considerable ramus is given to its plate-
trope (Plat.) in the meson, and the nerve terminates as a

large nerve in the glans clitoris (N. dorsalis penis seu clitoris,

STOWELL, Werves in the. Domestic Cat. 309

Fig. Cl.), the peripheral 5 mm. being parallel with its plate-
trope.

NN. COCCYGEI.

The coccygeal nerves are seven or more pairs, and with
the exception of the first (cephalic) one, innerve the caudal
muscles and integument. They decrease in size caudad, until
it may be questioned whether the extreme filaments are
properly designated nerves. The ectal root fibres are
attenuated and the dorsal ganglion is hardly distinguishable
caudad of the seventh; hence I have mentioned the number
as seven. Like the other spinal nerves, they divide into
dorsal andventral divisions; ¢he dorsal innerve the dorsal
muscles and integument and form the roots of a single nerve
trunk,

N. DORSALIS

(Fig. dor.?), caudad of the seventh caudal vertebra, whose
filaments innerve the adjacent structures. Zhe ventral divi-

sions join their fellows to form a ventral nerve trunk,
N. VENTRALIS

(Fig. vent.?). The rami of the ventral trunk have a two-fold
distribution; the first ramulus innerves the ental or the
inter-vertebral muscle (Fig. M. ent.), and midway between
the several pairs a ramulus innerves the ectal muscle of
the tail (Fig. M. ect.). The plan of formation of the
dorsal and the ventral caudal nerves is seen in the diagram
(Fig. B).

N. COCCYGEUS CEPHALICUS.

The first coccygeal nerve has a distinctive distribution,
and requires a separate description. The ventral division
separates into a ventral and a dorsal or caudal branch. The
ventral branch becomes the anastomotic loop to the third
sacral nerve, the coccygeal or principal root of the

310 JOURNAL OF COMPARATIVE NEUROLOGY.

N. COCCYGEUS

(Fig. N. coc.) to the muscle by the same name, one root of a
nerve to the urocyst (Fig. Uro.),and one root of the nerve to
the ribband muscle ? (Fig. M.?).

RECAPITULATION.

The cat is a good type for the study of comparative
anatomy. The nervous system offers special advantages, as
a basis of comparison, for establishing homologies, for iden-
tification, etc.

Zootomy should precede anthropotomy in the collegiate
and the medical curricula.

Preparation.—Injection of arteries and veins with starch
injection mass.

Posture.—Ventri-cumbent, head sinistrad.

Exposure.— By reflection of integument over caudal
thorax, sinistral side, beginning with removal of neural arch

of caudal thoracic vertebra; dissection caudad.
LUMBAR NERVES.

Characters in common: Paired; dorsal and ventral divi-
sions at ectal origin; related with sympathic system; muscu-
lar and cutaneous in distribution; two groups, cephalic four
not involved in lumbar plexus, cawdal three so involved; the
cephalic group innerve muscles and integument of back,
MM. psoas, phrenicus, abdominis entalis, ectalis, transver-
salis and rectus, and the abdominal integument.

N. Genito-cruralis.— Origin: Fifth and sixth lumbar
nerves, ¢wo roots. Distribution: Crural division, integu-
ment of caudal meros, and proximal crus; anastomoses with
N. N. cutaneus ectalis; gexztal division, plexus at ilio lumbar
artery, hypogastric and ventro-perineal integument.

N. Cutaneus Ectalis—Origin: Loop and sixth lumbar
nerve, ‘wo roots. Distribution: Integument of hip and thigh,

joins last described nerve.

STowELL, /Verves in the Domestic Cat. 2TI
, 3

N. Crureus Anterior.— Origin: Seventh lumbar. Dis-
tribution: MM. psoas, iliacus, sartorius, vastus externus,
V. internus, rectus femoris, crurzeus, pectineus, and gives
origin to

N. Cutaneus Internus Longus.— Mistribution: To in-
tegument of cephalic crus, dorsum of foot and plantar
plexus.

NV. Obturator.— Origin: Loop between seventh lumbar
and first sacral nerves, /wmbo-sacral cord (anthropotomy).
Distribution: MM. pectineus, obturator, adductor magnus

and longus, gracilis.
SACRAL NERVES.

Characters in common: Paired, three pairs; dorsal and
ventral divisions; related with sympathic system; muscular
and cutaneous; unequal size; formation of sacral plexus,
which is the origin of several nerves.

Special Characters: First sacral nerve, largest of spinal
nerves; joined with the lumbar cord in the lumbo-sacral cord.

NV. Gemellus.— Origin: Ramus of first sacral at foramen -
of exit. Distribution: M. gemellus superior.

Second Sacral Nerve.—Much smaller than the first nerve;
union with first nerve forms N. ischiadicus; joins the third
nerve in the anastomotic loop.

Third Sacral Nerve.—Smallest sacral nerve; joins sacral
and coccygeal plexuses; innerves the M. levator ani; the
urocyst; by its rami becomes the sacral root of NN. coccy-
geus, gluteus, pudicus, and a nerve not homologized.

N. Gluteus Superior.— Origin: Sacral plexus at first
sacral nerve. Dzstribution: Cephalic branch to M. gluteus
medius, cazda/ branch to M. gluteus minimus, szddle branch
to M. tensor vagine femoris.

NV. [schiadicus.— Origin: Union of first and second sacral
nerves. Distribution. MM. quadratus femoris, glutei, pyri-
formis, biceps, semi-tendinosus, semi-membranosus, obtura-
tor internus, ribband muscle?.

212 JoURNAL OF COMPARATIVE NEUROLOGY.

Rami Known as Nerve Trunks.—NN. pudicus, cutaneus
internus brevis, popliteus, peroneus, gluteus, q. v.

NV. Peroneus.— Origin: Division of N. ischiadicus cen-
‘trad of knee. Dustribution: Rami: \. musculo-cutaneus, in-
tegument of dorsum of foot, and second, third and fourth
toes, M. peroneus brevis, M. peroneus tertius; JV. ¢zbzalzs
anticus, MM. tibialis anticus, extensor longus digitorum,
extensor brevis digitorum; ligamentum tarsale; plexus dor-
salis pedis.

NV. Popliteus.— Origin: Division of N. ischiadicus, cen-
trad of knee. Distribution: MM. gastrocnemius, soleus,
popliteus, flexor longus digitorum, tibialis posticus, flexor
longus pollicis(?), flexor brevis digitorum, transversus, ab-
ductor minim1, interossei; integument of foot and pads.

N. Pudicus. —Origin: wo roots, sciatic and sacral.
Distribution: Dorsat division, to MM. levator ani, sphincter
ani; rectum, vagina, anal gland; ventral division, to M.
accelerator urine, perineum, vagina, ectal labium, urethra,
glans clitoris, platetrope.

COCCYGEAL NERVES.

Characters in common: Paired, seven or more pairs;
great length of ectal roots; rapid decrease in size, caudad;
dorsal and ventral divisions; dorsal divisions unite to form a
dorsal trunk, N. dorsalis, and the ventral divisions form
ventral trunk, N. ventralis.

Distribution: Muscles and integument of tail.

LV. Coccygeus cephalicus.— Origin: First coccygeal nerve.
Distribution: MM. levator ani, sphincter ani; gives anasto-
motic loop to third sacral nerve in the sacral plexus; by its
rami forms the coccygeal roots of several nerves—N. coccy-
geus, nerve to the urocyst, nerve to ribband muscle.

DESCRIPTION OF DIAGRAM.

A. fem., arteria femoralis; Acc., musculus accelerator urine; anas.,
N. anastomoticus; Ca., divisio caudalis: Ce., divisio cephalica; C/.,
glans clitoris; crwr., crural division of the genito-crural nerve; dac.,

STOWELL, Verves in the Domestic Cat. 212

dactylus; Dza., diaphragm, M. phrenicus; ev. dor., divisio dorsalis;
Dz. ven., divisio ventralis; /m., foramen exitus; oex., genital division
of the genito-crural nerve; G/., glandula ani; /7., hip, integument over
the gluteal region; zv/., integument, cutaneous nerve; ¢sch., ischium;
k., knee; Lab., labium ectale; /oof, anastomotic nerve joining nerve
trunks in plexiform relation; 7.-.S. C., lumbo-sacral cord; /.7., ramus
lateralis; 47.7, muscle not idéntified, v. text; AZ. ad. long., M. adductor
longus; M.ad. mag.,M. adductor magnus; JZ. b7., M. biceps; W/Z. CFUr. |
M.crureus; JZ. dor., musculi dorsales, quadratus lumborum, erector
spine, inter-vertebrales, etc.; JZ. ect., M. obliquus abdominis ectalis;
M. ent., M. obl. abd. entalis; MZ. flex. long. dig., M. flexor longus digi-
torum; J. flex. br. dig., M. flexor brevis; AZ. flex. Jong. pol., M. flexor
longus pollicis; M7. gas.. M. gastrocnemius; J/. 9/7. max., M. gluteus
maximus; WW. o/. med., M. medius; AZ. of. min,, M. minimus; J7.e7.S.,
M. superior; /. grac., M. gracilis; 7. zlz., M. iliacus; M.7/. A., M.
levator ani; 7/. obt., M. obturator; MW. obt. ¢nt., M. internus; JZ. pec.,
M. pectineus; MW. pso., M. psoas; M. pyr., M. pyriformis; MZ. guad.,
M. quadratus femoris; m.r.., ramus mesalis; JZ. rect.. M. abdominis
rectus; JZ. fem., M. rectus femoris; W. sar., M. sartorius; MZ. semi-
mem , M. semi-membranosus; AZ. semi-ten., M. semi-tendinosus; J/.
sph.a., M. sphincter ani; MW. ¢7b. £., M. tibialis posticus; J/. trans. M.
abdominis transversalis; M7. 7. V. &., M. tensor vaginz femoris: JZ. v.
ext., M. vastus externus; JV. v. ivt., M. vastus internus; JV. coc., N.
coccygeus; WV. crur.. N. ramus crureus; WV. gem., N. gemellus; V. gen.,
N. ramus genitalis; WV. gdut., N. gluteus; VV. 97. s., N. gluteus superior;
N. mus,-cut., N. musculo-cutaneus; WV. obt.. N. obturator; MV. fer., N.
peroneus; iV. fof., N. popliteus; VV. saph. br., N. cutaneus internus
brevis, short saphenous; .V. sap. /., N. cutaneus internus longus, long
saphenous; /. Poupart’s ligament; fer7., perineum; f/at., platetrope;
Pl. plan. Plexus plantaris; P/. S., plexus solaris; pub., pubes; S,, gan-
glium sympathicum;, 7%., integument over the meros, thigh; wre.,
urethra; wro., urocystis; vag., vagina.

oa

WEIGERT’S METHOD OF STAINING THE
MEDULLARY SHEATH OF NERVES.(’)

In the paper quoted, Dr. Weigert gives a full account of
the famous method bearing his name, together with a his-
torical review of the stages in its differentiation.

The method, as now revised, consists of four stages, as
follows: (1) Hardening in chromic salts; (2) introduction

1 WEIGERT, ‘‘ Zur Markscheidenfarbung ’’ Deutsche medicinische Wochenschrift.
Festnummer zur Ehren Rudolf Virchows, October 13, r8or.

314 JOURNAL OF COMPARATIVE NEUROLOGY.

of copper in the chromium compound within the sheaths;
(3) staining with hematoxylin; (4) differentiation by means
of borax-ferricyanid of potassium. The precipitate which
tends to appear during the staining is prevented by the addi-
tion of the carbonate of lthium.

The modified method, as here published for the first time,
is as follows: Fragments suitable for microscopic sections are
thoroughly hardened in bichromate of potassium, and, after
treatment with alcohol, are imbedded in celloidin. After
coagulation in 80 per cent. alcohol they were, according to
the old method, brought into a solution of neutral cupric
acetate in an equal volume of water and kept in the brood-
‘oven twenty-four hours. The modification consists in the
substitution of equal volumes of neutral cupric acetate and
tartrate of soda (C'H*O°KNa+4H’O). Large fragments
may remain for forty-eight hours without injury, provided
the temperature is not permitted to rise too high. The frag-
ment then is passed into an aqueous solution of cupric ace-
tate and remains twenty-four hours longer in the warm
chamber. After rinsing, the specimens go into 8o per cent. ©
alcohol, where they become available for sectioning any time
after an hour or so.

For staining, two stock solutions are required: (4) 7 c.cm.
saturated aqueous solution of carbonate of lithium + 93 c.cm.
distilled water; (4) 1 gm. hemotoxylin + 10 c.cm. alcohol.
These are to be combined just before using in the proportion
of 9 volumes of A to 1 volume of 4. Sections stain in three
or four hours, though the staining is not injured by leaving
them twenty-four hours in the fluid. This process is, unfor-
tunately, only available for free sections, which then require
no development, but, after rinsing, are brought into 90 per
cent. alcohol and are cleared in a mixture of 2 volumes of
analin oil + 1 volume of xylol, followed by pure xylol and

balsam.

THE DEVELOPMENT OF THE CRANIAL NERVES
OF VERTEBRATES .(*)

Pror. C. von KUPFFER.

Tracing their origin, these cells are seen to proceed from
the epidermis. The latter thickens by elongation of its ele-
ments, which then divide transversely, after which the ental
layer of daughter cells do not reassume their epithelial
arrangement, but constitute the special sub-epidermal layer
or neurodermis. The latter has in any case a close relation
with the development of the peripheral part of the branchial
nervous system, evidence of which is furnished by the fact-
that the thickening of the epidermis, which precedes the
development of this structure, is derived from the rudiment
of the epibranchial ganglion.

It is cells of this layer which furnish the first commissures
connecting the epibranchial ganglia with each other, as well
as with the preformed branchial nerves and with the defini-
tive (principal) ganglia. It may, therefore, be said that the
epidermis contributes to the development of the peripheral
branches of the branchial system, but whether these cells
play a rdle in the formation of the fibrille, or simply have a

secondary significance, cannot be determined at present.
CRANIAL NERVES OF YOUNG AMMOCETES.
After this exposition of the main features in the develop-

Translated for this journal, from advance sheets, by OtiveER S. SrronG, Fellow in
Biology in Columbia College.
eee

316 JoURNAL OF COMPARATIVE NEUROLOGY.

ment of the cranial nerves, I pass on to their description in
young Ammoceetes, which, when fixed (sublimate, alcohol),
measure 34-3? mm. While living they might have been
fully 4mm. The stage of development of these specimens,
upon which I base my description, is as follows: There are
seven pairs of gill pouches present; the hindermost (eighth)
pair is in formation. In the foremost, obliquely placed and
temporary pair of pouches, the withdrawal of the endoderm
from the epidermis has already taken place and the meso-
derm interposed. The diaphragms in the pouches are not
yet formed; outer spiracles are still wanting throughout.
The septum between the oral cavity and the branchial gut is
not yet perforated, but is thinned, and the formation of the
stomodeum from pouches, described by Dohrn,(') whereby
the free surface of the velum is enlarged, has set in. There
is as yet no pigment in the eye, the lens is constricted off,
and the recessus labyrinthi extends dorsad to the exit of the
roots of the facial. There exist three pronephric canals with
funnels formed, and on each side a large glomerulus. The
pronephric duct reaches the hind gut.

BRANCHIAL SYSTEM.

I begin with the description of the branchial system of
the cranial nerves of this larva, referring to Fig. 8, which is
drawn from three sagittal series of sections, and shows the
roots, ganglia and peripheral nerves of the system projected
on the median plane. One sees in the figure two rows of
ganglia, 7.c., dorsally the row of large or principal (Haupt-
ganglion) ganglia (I-V), and ventrally, over the gill septa
(gill arches), the epibranchial ganglia (1-12) bound by com-
missures into one cord. A third row of ganglia is shown in
the drawing between the gill pouches.

1. Region of the Trigeminus.—The two principal ganglia
of this region are plainly set off from each other. The first

t Dourn, XII, “ Stndies,” 1888, p. 238-239.

v. KuprrerR, Cranial Nerves of Vericbrates. aay

is somewhat smaller than the second, and has an approxi-
mately triangular shape, the base directed dorsad. It hes
over the eye. From the fore corner there go out two stout
nerve trunks, which proceed in an arch cephalad and ven-
trad. In the ganglion two portions may be distinguished.
The dorsal, broader part is traversed by fibrillea which pro-
ceed, in direction, from the roots to the branches; in the
ventral, tapering part no fibrille can be perceived among the
nerve cells.

The second principal ganglion, more voluminous than the
first, has also a stouter root (perhaps already two). It lies
over the stomodeum and likewise displays two divisions,
which have the same relations as those of the first principal
ganglion; fibrille traverse the fore dorsal part, the hinder
part appear free of fibrille. From the fore part there go
close together the two branchial nerves, the N. maxillaris
and N. mandibularis. Both consist of a compact cord of
fibres, which contains nuclei within, and at the surface
shows an envelope of cells.

The epibranchial ganglia of this region show a continuous.
chain which impinges cephalad upon the lens, so that it
appears as the foremost part of the chain. One can distin-
guish between the lens (it not being reckoned in) and the
N. mandibularis, three parts of the chain, marked off by
constrictions, which may be designated the first, second and
third epibranchial ganglia. The first is inserted slightly
under the lens, the second projects somewhat dorsally and is
directly connected with the first principal ganglion. The
third epibranchial ganglion lies at the lateral side of the
origin of the NN. maxillaris and mandibularis, and stands in
broad connection with the cell mass of the second principal
ganglion.

2. Region of the Acustico-Facialis—TVhe facial ganglion
and the auditory vesicle of the principal ganglia belong to
the series. The principal ganglion of the facial projects far

forward over the auditory vesicle, and its fore end les under

318 JOURNAL OF COMPARATIVE NEUROLOGY.

the hinder surface of the second principal ganglion of the
trigeminus. It reaches around the auditory vesicle on the
median and ventral sides as far as its middle, and here ends
‘ina point. The contact with the wall of the auditory vesicle
is very close.

I assign to the same region two ganglia of the epibranchial
chain, namely, those lying in front of the first and second
gill pouches, and which, numbered from before, would be
four and five. The fifth epibranchial ganglion is immediately
connected with the principal ganglion of the facial, and par-
ticipates in the composition of the N. branchialis, a massive
cord proceeding chiefly from the principal ganglion into the
hyoid arch. The diminished fore end of the principal gan-
glion extends into the commissure which connects the fifth
with the fourth epibranchial ganglion. At this stage a short
nerve ‘‘ anlage” proceeds from the latter, which is produced
into the substance of the mandibular arch, superficially, in a
ventral direction. But this fourth epibranchial ganglion
occupies an intermediate position, and is connected both
with the principal ganglion of the facial and the second
principal ganglion of the trigeminus. While I assign it pro-
visionally to the facial region, this view needs to be proved
by further investigations as to its later fate.

I have, from earlier stages, represented as acusticus the
hinder portion of the one continuous branchial root of this
region,(') which is connected with the wall of the auditory
vesicle at the base of the recessus labyrinthi, and has, at that
time, developed no ganglion. It has not essentially changed
from there on to the stage now under consideration. The
acusticus, too, only shows here this one place of connection
with the auditory vesicle. Although cells may be seen be-
tween its fibrille and in connection with them, they cannot
yet be called a ganglion.

3. Legion of the Vagus Group—As belonging to this

1 Arch. f. Mikr. Anat., 1890, Bd. 35, p. 543.

v. Kuprrer, Cranial Nerves of Vertebrates. 319

region I have described, from the stage of development
reached in the days immediately preceding the exit of the
embryo:(') (1) A large isolated lateral ganglion arising from
the epidermis, and located over the second and third gill
pouches; (2) a medial ganglion proceeding from the root-
border (Wurzel Leiste) and uniting with the latter; thus
there are, according to my present terminology, the compo-
nents of a principal ganglion of the vagus; (3) epibranchial
ganglia over the second and the following gill pouches. A
lateral ganglion assigned to the glosso-pharyngeus is devel-
oped between the auditory vesicle and the vagus, and not
isolated from the epidermis. I supposed, therefore, that the
glosso-pharyngeal ganglion described:by Scott and Shipley
is an epibranchial ganglion.(*) At the same time I pointed
out that there is no sharp division between the facial group
and that of the vagus at this stage. The epibranchial gan-
glion lying over the second gill pouch received a very notice-
able addition from the root-border, consisting of cells and
fibrille, but at the same time a nerve originating from the
facial root sinks into this ganglion, which I called the ramus —
recurrens of the facial.

In Ammoceetes of 4 mm. the relations are much clearer,
the individual parts are more separated, and at the same time
there has taken place a displacement laterad which renders
easier the comparison with the relations in older Ammoceetes.
The epibranchial ganglia experience a transference caudad, so
that they are no longer located over the gill pouches, but are
over the corresponding gill septa (visceral arches), 7.c., the
ganglion formed over the second gill pouch now lies directly
over the septum between the second and third gill pouches.
The auditory vesicle in larve of 4 mm. is situated over the
second gill pouch, projecting somewhat beyond it both
caudad and cephalad. As the principal ganglion of the
facial lies close to the wall in the fore half of the auditory

1 Ibidem, p. 544.
2 Ibidem, p. 552.

320 JOURNAL OF CoMPARATIVE NEUROLOGY.

vesicle, so is the ganglion of the glosso-pharyngeus in close
contact with its caudo-ventral wall, and has fused with the
portion of its cells which I have mentioned and drawn as
the sickle-shaped investment of this part of the wall of the
vesicle.(') This cell-girdle, up to the time of the exit of
the embryo is continuous with the mass of the principal
ganglion of the facial, and I have accordingly assigned it to
the latter. But it changes later. In larve of 4 mm. the
separation is completed, and the cell group under considera-
tion has by this time connected itself with the glosso-
pharyngeus. It thus comes to pass that the continuous cell
mass, which originates from the epidermis in closest contact
with the labyrinth pit and is further augmented by the cells
of the wall of the latter, embraces the lateral portions of two
ganglia, the larger fore part going over to the principal gan-
glion of the facial and the smaller hind part to the ganglion
of the glosso-pharyngeus. Along with this the glosso-
pharyngeus moves out of the particular place which I believe —
must be assigned to it originally, before the separation of the
ganglion mass adjoining the labyrinth vesicle into two parts
has been completed.

As the glosso-pharyngeus is now, it consists of a stout
fibrillar root, which is evidently separated from the acusticus
but unites with the vagus root lying caudad. The root enters
an elongated ganglion whose medial part, likewise present
from the first, has united secondarily with the lateral part
which was joined to the labyrinth vesicle. This principal
ganglion, extending further, now fuses with the epibranchial
cord, so that it completely takes in the sixth epibranchial
ganglion. At the same time, however, it connects itself, by
a tract (Zug) directed cephalad, with the fifth epibranchial
ganglion. The latter is thereby closely related both to the
facialis and to the glosso-pharyngeus.

The relations of the vagus, in the strict sense, when

x Arch. f, Mikr. Anat., 1890, p. 524, Figs. 54, 74.

v. Kuperrer, Cranial Nerves of Vertebrates. 321

compared with the earlier stages, have changed the
least.

Its large principal ganglion, arising typically, lies above
the septum between the third and fourth gill pouches and
over the fourth pouch itself. The short, stout, single root is
mostly fibrillar, but also contains cells, both in the interior
and as an envelope outside. It sinks into the cephalo-dorsal
angle of the ganglion. The hind point of the approximately
triangular ganglion extends into the N. lateralis, entirely
lacking ganglia, which ends in the caudal half of the trunk in
a swelling of the epidermis. The cephalo-ventral angle of the
principal ganglion sends out the stout N. branchio-gastricus,
rich in cells, which connects itself with the seventh epi-
branchial ganglion (numbering from before). Five more
ganglia lie behind this in the epibranchial cord. There are
thus found in the whole chain, which extends from the eye to
behind the eight gill pouches, altogether ¢welve epibranchial
ganglia.

THE BRANCHIAL NERVES.

I begin with those lying caudad, where the relations are
simplest. The zxdmost five branchial nerves have the same
relations. Each one arises as a cord from the appropriate
epibranchial ganglion, and is connected by means of a second
more slender cord with a sympathic ganglion of the spinal
system. It proceeds then ventrally into the gill arch and
divides into a cutaneous and a muscular branch. The cuta-
neous branch is the foremost, and connects itself with a
rounded protuberance of the epidermis projecting entad.
The muscular branch accompanies the arch of the aorta ven-
trad and ramifies further (Fig.9). The external spiracula
(gill openings), which are formed behind the pertaining gill
pouch, have arisen. Thus the cutaneous branches are shown
to be the rami pretrematici, and the epidermal prominences
small separated ganglia, which I will denote as ganglia pre-
trematici.

322 JouRNAL OF COMPARATIVE NEUROLOGY.

The sixth branchial nerve, numbered from behind, arises
from that epibranchial ganglion which the N. branchio-
_gastricus of the vagus enters. Here, as well as with the
branchial nerves lying cephalad, it can be established that
their most important part is derived from the principal gan-
glion, and that the portions derived from the epibranchial
and sympathic ganglia are the smaller.

The branchial nerve of the glosso-pharyngeus, the seventh
from behind, and that of the facialis behave like the foremost
one of the vagus. All these nerves divide within the gill
arch into the cutaneous and muscular branches, the first of
which fuses with an epidermal prominence, the subsequent
ganglion pretrematicum.

In the region of the four anterior epibranchial ganglia this
arrangement is destroyed, owing to the stomodzum, and the
interpretation of the peripheral nerves present here is diffi-
cult. Three nerves come into consideration, namely: (1) A
short nerve springing from the fourth epibranchial ganglion
(numbered from before), which proceeds behind the N. man-
dibularis to the epidermis and ends in a small ganglion
(probably the r. mand. ext., Furbringer); (2) the N. man-
dibularis, which, as a stout fibrillar cord, leaves the second
principal ganglion of the trigeminus and derives the greater
part of the fibrille directly from the branchial root; a more
slender cord from the third epibranchial ganglion joins this;
(3) the N. maxillaris; this arises from the principal ganglion -
and the second epibranchial ganglion. I must let it remain
undetermined whether the first epibranchial likewise has a
share in this nerve. The N. maxillaris divides into branches
for muscles in the upper lip, for the side wall of the stomo-
deum and for the skin of the lip. A twig proceeding along
the skin ends in a ganglion lying close under the epidermis,
which behaves entirely like the pretrematic ganglia of the
gill region.

There are thus always present in the region of the tri-
geminus small ganglia of a third series, which I might annex

v. KuprFrer, Cranial Nerves of Vertebrates. 323

to the pretrematics of the gill region, and it is worth noticing
that such a one lies in front of the stomodeum.

Since at least one epibranchial ganglion participates in
the formation of the N. mandibularis, as well as of the N.
maxillaris, I regard both nerves as homodynamous to at least
one branchial nerve, but reserve a final judgment as to their
value.

I cannot clearly demonstrate a participation of the first
epibranchial ganglion, impinging upon the lens, in the
formation of peripheral nerves.

SPINAL SYSTEM OF CRANIAL NERVES.

The determination of the parts of this system encounters
great difficulties. The somites, which re present only a
short time between the ear and eye, already dwindle away
a perceptible time before the exit of the embryo, and with
them the dorsal branches of the dorsal spinal nerves. The
principal ganglia of the branchial system, the eye and the
lateral muscles of the head growing cephalad take up so
much space that the spinal nerves have to be sought in
narrow interspaces. In every case they are less developed
than those of the branchial system. One does not meet com-
pact cords in the developmental stage under consideration,
but only loose strands of fibrilla connected with cells. One
applies himself with more advantage to the ganglia than to
the roots for the determination of their number and arrange-
ment.

One encounters the foremost ventral spinal nerve, the
root and the little ganglion of a dorsal spinal nerve, which I
regard the foremost almost in a single transection (Fig. ro,
vs, ds). This spinal ganglion lies between the secondary
optic vesicle and the brain. Ina cross section close behind
this there lies a second ganglion, ventrad from the first, on
the outer wall of a blind extension of the aorta. It is con-
nected with the first, and I can regard it only as the foremost
sympathic ganglion.

324 JoURNAL OF COMPARATIVE NEUROLOGY.

The foremost ventral spinal nerve is a short fibrillar cord,
with cells disposed in and on it, which springs from the
ventral aspect of the mid-brain close outwards from its
basal plate. It proceeds between the fore end of the
chorda and the aorta, and approaches a hollow epithelial
cord which serves to connect with each other, under the end
of the chorda, a pair of bodies rich in yolk and lying later- |
ally. There can be not doubt but that these two bodies are
the head cavities which Dohrn(') describes and from which
he derives the eye-muscles. If, however, Dohrn made his
observation upon these, the median piece connecting them
would not be a ventral but a dorsal structure, because the
carotis lies beneath it; so I must call attention to the fact that
this connecting part has its location over the carotis, indeed,
but under the blind foremost terminal piece of the aorta.
Recently Dohrn, departing from his earlier view, states that
the middle connecting part originates, in fact, from the
median fusion of two entirely distinct myotomes;(*) with
which I cannot agree. I consider the two head cavities
under discussion, together with the cord uniting them, the
foremost part of the anterior endodermal pouch which in
this stage of development has even separated from the hind
part of the pouch.

Peculiar as is the behavior of the nerve now in approach-
ing this connecting piece destined to atrophy, I nevertheless
believe it may be considered as the oculomotorius, since the
paired prechordal head cavities, made single by the connect-
ing piece, always participate in the formation of the eye-
muscles.

I must for the present leave undetermined whether a cord
which springs dorsally from the mid-brain, between the roots
of the first and second principal ganglia of the trigeminus,
and behind the eye approaches the second epibranchial gan-

1 XII Studie. Mitteil. aus d. Zool. Station zu Neapel, Bd. VIII, 1887, pp. 325,

328, 330.
2 XV Studie. Mitteil. aus. d. Zool. Station zu Neapel, Bd. IX, p. 332, Anmerk.

v. Kuprrer, Crantal Nerves of Vertebrates. 325

glion, persists as an eye-muscle nerve (comp. Fig. 8).
Should this conjecture be established, this nerve would not
belong to the spinal but to the branchial system.

If one can say that the foremost pair of dorsal and ventral
spinal nerves are situated within the vicinity of the first prin-
cipal ganglion of the trigeminus, in the same way one meets
a second pair of dorsal spinal ganglia, connected with its
sympathic ganglia, mesad from the second principal gan-
glion of the same region and in the same transverse plane
with the exit of the N. mandibularis from the principal gan-
glion just mentioned. I can state nothing definite concerning
the terminal twigs belonging to this pair.

The same difficulty in following out the spinal nerves
exists in the region of the facialis. The large principal gan-
glion and the labyrinth vesicle take up the space between the
epidermis and brain almost entirely, and push the remaining
elements apart. I have not been able to demonstrate a dorsal
spinal nerve in the whole course, in a 4 mm. larve, but have,
indeed, a spinal ganglion, wedged in between the principal
ganglion of the facialis and the chorda, and also a long sym-
pathic ganglion, lying close to the aorta, which gives off
fibres to the branchial nerve of the facialis. This spinal
ganglion probably fuses later with the principal ganglion.

The pointed fore end of the first myomere of the body
pushes up close to the hind end of the principal ganglion of
the facialis, and even inserts itself slightly under the gan-
glion. The lateral muscles of the head do not first proceed
from this, but from the second myomere, close behind the
first branchial nerve of the vagus. Here, over the fore end
of the second myomere, for the time being, the regular series
of the spinal ganglia and spinal nerves of the trunk also
begins.

This first myomere of the 4 mm. Ammocetes lies thus in
the region of the glosso-pharyngeus, with its fore end over
the second gill pouch. I have not found a ventral spinal
nerve connected with the myomere, but have found a dorsal

326 JOURNAL OF COMPARATIVE NEUROLOGY.

spinal nerve with a slight ganglion, and observed its dorsal
branch approach the dorsal border of the myomere and its
ventral branch proceed on to uniformly small sympathic
‘ganglion. I do not know whether this myomere persists.
But in any case the pertaining spinal nerve would not be
reckoned among the cranial nerves.

I have only succeeded in demonstrating three pairs of
dorsal and one pair of ventral spinal nerves of the head, and
that over an extent to which belong five pairs of epibranchial
ganglia.

The spinal system is therefore in Ammoceetes, at least in
the stages of development known to me, of little value for
the determination of the segmentation of the head. The
epibranchial ganglia furnish the surest basis for this.

I have enlarged so particularly on the cranial nerves of
Ammoceetes because, on the basis of what has been com-
municated, I am of the opinion that here very primitive rela-
tions exist, which furnish important hints for the criticism of
the cranial nerves of Gnathostomata. Three-fold phenomena
determine me to this view: First, the far-extending formation
of the epibranchial ganglia in the trigeminus region; then
the close proximity of the /exs to this chain of ganglia,
whereby a new light falls upon the phylogeny of the eye;
and, finally, the very important—probably preponderating—
part which the epidermis plays in the formation of the prin-
cipal ganglia. As the auditory organ is referred to the series
of principal ganglia, the eye appears to belong to the epi-

branchial series.

The works, already cursorily mentioned, of Van Wihje,
Froriep and Beard furnish guaranty that the develop-
mental processes, which I have described in Ammocetes,
also essentially recur in Gnathostomata. These named have
not seen the separation of the first cranial nerve rudiment
(Anlage) into spinal and branchial nerves, cephalad of the

v. Kuprrer, Cranial Nerves of Vertebrates. 324

vagus, but the formation of epibranchial ganglia from elas-
mobranchs on to mammalia is clearly established through
their works. There remains on this side the evidence that
the epidermis also participates in the principal ganglia.

There cannot be the least doubt but that the fusions, de-
scribed by Van Wihje, of the ventral twigs of the facialis,
glosso-pharyngeus and vagus with thickened places in the
epidermis on the upper hinder wall of the pertaining gill
clefts correspond to the places of formation of the epi-
branchial ganglia. Besides the local relations to the gill
clefts cr pouches, the circumstance that these places are de-
scribed as starting points for the branchial terminal twigs:
the rami post- and pretrematici also argue for this. In
sagittal sections these terminal twigs appear, in fact, as out-
growths of these ganglia, while cross sections teach that the
epibranchial ganglia have, indeed, an essential] but not exclu-
sive share in the formation of the NN. branchiales.

For a time I was of the opinion that the more dorsally
situated places of fusion of the dorsal branches of the cranial
nerves with the epidermis, which Van Wihje mentioned, '
could be brought into connection with the formation of the
principal ganglia. But on closer examination of the rela-
tions, this conjecture proves untenable. These dorsal branches
in Selachians are purely cutaneous sensory nerves; the thick-
ened patches of epidermis furnish the lateral organs, remain-
ing in connection with the epidermis, and their peripheral
nerve apparatus. On the other hand, the lateral portions of
the principal ganglia have nothing to do, directly, with the
sense organs; they separate cleanly from the epidermis,
which shows thereupon a marked thinning, and move deeper
within.

Beard has occupied himself more particularly than Van
Wihje with these epidermal formations; only it is difficult
to get a clear idea of the particulars from his publications,
since this active investigator is so filled with his hypothesis
of the branchial sense organs that his exposition of the de-

328 JoURNAL OF COMPARATIVE NEUROLOGY.

velopment of the cranial nerves aims before all to bring its
processes into harmony with this hypothesis.

From no place in his numerous writings does it clearly
emerge that he has, in general, seen or noticed the formation
of the lateral portion of the principal ganglia from the epi-
dermis. In one place(') in his last large publication but one
he says, much more explicitly, that the nerves growing out
from the border (Leiste) connected themselves at the level
of the chorda with the epidermis, which statement points to
the epibranchial and not to the principal ganglia. Then, it
is said further on, the dorsal branches or supra-branchial
nerves arose at the same time with the prebranchtial nerves,
along with the separation from the epidermis of the ganglia
that arose in the region pointed out—that is, after the origin
of the epibranchial ganglia. This expression, also, does not
permit us to suppose the formation of the dorsal branches
connected with the principal ganglia, since the latter arise
noticeably earlier than the epibranchial ganglia.

Also in the last treatis of Beard’s, furnished with numer-
ous figures, it is said, in accordance with the above-men-
tioned expression, that the cranial ganglia corresponding to
the spinal ganglia received additional form-elements from
the lateral epiblast over the gill clefts and at the height of the
chorda. To draw aconclusion from this, Beard might not
have seen the formation of the lateral portions of the prin-
cipal ganglia, and the lateral ganglia in his and in my sense
would not be identical, but Beard’s lateral ganglia would
correspond to my epibranchial ganglia. Nevertheless, some
of his figures show that in the elasmobranchs also the epi-
dermis forms ganglia in two well-distinguished series lying
apart one over the other, lateral and epibranchial. I refer
thereupon to the Quart. Four. Mic. Se., Vol. XXVI, 1886,
Plate IX, Figs. 20 and 22, on the facialis of Torpedo. Prob-
ably the principal and epibranchial ganglia mingle very early

1 Quart. Jour. Mic. Sc., Vol. X XVI, 1886, p. ror.

v. KuprFEeR, Cranial Nerves of Vertebrates. 329

in Torpedo, whereby the perception of their separate origin
is rendered difficult. This being the case, Beard’s lateral
ganglia would correspond to the lateral and epibranchial
ganglia together in my sense. A renewed investigation of
the development of the cranial nerves of elasmobranchs is
necessary to obtain clearness here.

Froriep’s communications are much more intelligible. In
the youngest cow embryos on wiich he began his investiga-
tions, the principal ganglia were already formed and re-
moved from the epidermis, so only the formation of the epi-
branchial ganglia could be treated of, the rudiments ( Anlage)
of which exist in Froriep’s ‘‘ gill cleft organs.” The thick-
ened patches of epidermis behind the eye in young cow
embryos, mentioned by him, I might pronounce without
hesitation to be the rudiments of the foremost epibranchial
ganglia.

So that I could express from personal inspection an
opinion upon the mode of formation of the cranial nerves in
Amniota, I have commenced a piece of work in the Institute
of this place upon bird embryos, which, begun not long
ago, already has led to the result that there exists essentially
a complete agreement with the processes in Cyclostomes. The
duck appears to furnish an especially suitable object. It has
become apparent that the rudiments of the cranial nerves
proceeding from the root-border (Wurzelleiste) divide into
the spinal and branchial nerves, and that these branchial
nerve rudiments, while they are yet mainly composed of
cells, grow distally between epidermis and protovertebre,
and on the one hand fuse with the epidermis for the forma-
tion of the principal ganglia, on the other hand, after the
separation of the principal ganglia from the epidermis, enter
into a second connection with it over the gill pouches.

This work has not progressed far enough to enable me to
go into particulars, but this much may be said, that in the
trigeminus region also the typical mode of development is
preserved, since in the formation of the first principal gan-

330 JOURNAL OF COMPARATIVE NEUROLOGY.

glion of the trigeminus in the duck there can be demonstrated
a very considerable participation of the epidermis. In the
chick with nine to ten protovertebrz, we see the root-borders
reach the dorsal border of the mesoderm. Duck embryos
with eleven to twelve protovertebre show the ganglion of
the trigeminus in connection with a lateral swelling of the
epidermis. Somewhat later the connection with the epi-
branchial ganglion appears. In the daw with twelve proto-
vertebre I saw a branchial nerve connected with the epi-
dermis in both places at the same time.

You will grant that it would be altogether premature for
me to express an opinion now, more or less probable, upon
the changes which the scheme of the nerves of the head of
vertebrates here presented experiences up to the completion
of development. The reductions, fusions, solutions of con-
tinuity and secondary connections appear to vary according
to the class in very many ways.

A comparison of the representation of the branchial nerv-
ous system in the Ammoceetes (Fig. 8) of 4 mm. with a
diagram of the cranial nerves of the adult (Fig. 11) shows
you how important these changes may be. I have constructed
this diagram after Ahlborn’s and Julin’s drawings, taking
into consideration also the statements of Max Furbringer and
Wiedersheim. To present a better general view, the oculo-
motor nerves and hypoglossus are omitted.

The whole anterior portion of the epibranchial cord,
cephalad of the vagus, appears to have appeared, but is still
represented by the ramus recurrens and ramus anterior of the
facialis. The latter, behind and under the eye, possesses the
spindle-shaped ganglion discovered by M. Furbringer. I
conjecture this ganglion to be the remant of the foremost
epibranchial ganglion or a complex of such ganglia. One
might express it in this way: That in the course of develop-
ment the facialis annexes all those portions of the epi-
branchial cord lying cephalad of the vagus. Whether the

v. Kuprrer, Cranial Nerves of Vertebrates. 331

commissure, described by Ahlborn, between the first tri-
geminus ganglion (Gn. ophthalmicum) and the facialis gan-
glion (v. Fig. 11) has also been derived from the epibranchial
cord, and the latter has consequently divided as it proceeds
cephalad, cannot be finally answered now, with probability,
either way. But I must call attention to the fact that I did
not see direct commissures between the principal ganglia, so
that there is a certain warrant, pending further disclosures,
in deriving all commissures in general between the vagus and
trigeminus regions from the epibranchial cord.

DESCRIPTION OF PLATE XXII.

Fig. 1. h, neural cord: z, ’twixt cord (Zwischenstrang). 6°.
Fig. 2. h, neural cord; d P, dorsal brain-plate. 19°,
Fig. 3. h, fore brain; a, rudiment of eye; d P, dorsal brain-plate;

mz, rudiment of nerve; 2, ganglion. 79°,

Fig. 4. h, mid brain; /, root-border; m, mesoderm; ch, chorda,
d, gut; g7, lateral ganglion. ge, epibranchial ganglion. 29°,

Fig. 5. h, mid brain; ch, chorda; d, gut; m, mesoderm; J, root-
border; zs, dorsal spinal nerve; 7, branchial nerve; 7, lateral ganglion;
gm, medial ganglion,

Fig. 6. h, hind ,brain; 7, root border; xs, dorsal spinal nerve; 73, -
branchial nerve, 27, lateral ganglion of vagus; ge, epibranchial ganglion;
gs, sympathic ganglion; 7d,neurodermis. 29°.

Fig.6. h, hind brain; ch, chorda; d, gut; m, mesoderm; zs, dorsal
spinal nerve; #0, branchial spinal nerve; g/, hind end of lateral ganglion
of vagus; ge, epibranchial ganglion; zd, neurodermis.

Fig. 7. h, fore brain; », medial ganglion; .2/, lateral ganglion,
both belonging to the I principal ganglion of the trigeminus; ve, epi-
branchial ganglion; ws, dorsal spinal nerve; zd, neurodermis. 79°.

Fig. 8. Branchial nervous system of an Ammoccetes 4 mm. long,
projected on the median plane, about 12° A, eye; WV, nose; O, ear;
/, first, 77, second principal ganglion of the trigeminus; ///, principal
ganglion of facial; 7)’, principal ganglion of glosso-pharyngeus, fusing
ventrally with the sixth epibranchial ganglion; V, principal ganglion of
vagus, first, seventh and twelfth epibranchial ganglia; A1-A‘®, gill
pouches; ch, chorda; /, nervus lateralis. Going out from the epi-
branchial ganglia and proceeding ventrally between the gill pouches are
the terminal branches of the branchial nerves, forking into the ramus
posttrematicus and pretrematicus. The rr. pretrematici end in the
structure with a knob, the ganglion pratrematicum, about half way up
the gill pouch. The foremost of these ganglia is before the stomodeum,
on a twig of the maxillaris. The small circles behind the second to the

332 JOURNAL oF COMPARATIVE NEUROLOGY.

eighth gill pouches, between the rr. post- and prztrematici, show the
locations of the later appearing spiracula externa.

fig. 9. h, hind brain; a, aorta; m, muscle; V, principal ganglion
_ of vagus; 7, seventh epibranchial ganglion; @, rudiment of a gang. pre-
trematicum, with which the r. pretrematicus is connected. Inwards
from it twigs of the r. posttrematicus. s,a sympathic ganglion; zd,
neurodermis. 299°,

Fig. 10. h,mid brain; A, eye; ch, chorda; A, prechordal head
cavity, connected by means of the hollow connecting cord with that of
the other side; », stomrodeum; vs, foremost ventral spinal nerve; ds,
foremost dorsal spinal nerve; xd, neurodermis. 29°,

fig. 11. Dorsal cranial nerves of adult Ammoceetes, 7.e., Petro-
myzon, semi-diagrammatic. The ganglia, especially those caudad, are
somewhat separated, so as not to overlap in the figure. A, eye; JV, nose;
O, cartilaginous auditory capsule; A’, foremost gill cleft; 7, first, 77,
second principal ganglion of trigeminus; ///, principal ganglion of
facialis; /V, principal ganglion of glosso-pharyngeus; JV, principal
ganglion of vagus; 1, first, 7, seventh epibranchial ganglion (comp.
Fig. 8); va, ramus anterior; rf, ramus posterior; 77, ramus recurrens
of the facialis.

Norer,.—The fractions representing the amplification of the figures are those accom-
panying the original. All the figures have been somewhat reduced during reproduction.
—Ep.

CONTRIBUTIONS TO-THE MORPHOLOGY ‘OF
THE BRAIN OF BONY FISHES.

II—STUDIES ON THE BRAINS OF SOME AMERICAN
FRESH-WATER FISHES. — Continued,
With Plates XXIV and XXV.

CC. Ee Herrick.

B.— HIstToLtoGy OF THE RHINENCEPHALON AND PROSEN-
CEPHALON.

The following observations are restricted primarily to the
brain of the drum, Haploidonotus prunniens, although also’
based on a study of a large series of native fishes.

In view of the novelty of many of the views presented, it
should be said that great pains has been taken to verify each
point, while our sections are so perfect as to make determina-
tion unusually easy. Nevertheless, in tracing unmedullated
fibres like those of the callosum and hippocampal commis-
sures, considerable uncertainty may exist respecting definite
connections. Such success as we have had in a satisfactory .
settlement of a number of the vexed questions of the fish
cerebrum may be ascribed to improved technique and con-
stant reference to comparative data.

The cerebrum and its related structures in fishes have so
long baffled investigation largely because of the failure to
recognize the morphological equivalent of the cortex and a
consequent misinterpretation of the celia. The only hope of
correcting this error lay in the strict and philosophical appli-

ed

334 JOURNAL OF CoMPARATIVE NEUROLOGY.

cation of the comparative method as insisted upon and en-
forced by the teaching and example of Prof. Wilder, of
Cornell University, and numerous European investigators.
| Although Rabl-Ruckhard was the first to specifically
apply this method to fish brains in the satisfactory solution
of the homologies of the pallium, the same identifications
would have been made by any observer moderately familiar
with modern comparative data. The writer independently
recognized the same relations some time since, as doubtless
every student of fish brains has done, whether or not his eye
has met the works of Ruckhard.

With the discovery that the membranous pallium is the
specific homologue of the cerebral cortex of the higher verte-
brates, a large field of enquiry was opened, which has thus
far yielded comparatively meager results. The questions as
to the fate of the commissure and tracts of the cerebrum,
as well as of the cellular elements proper to the cortex, yield
to none in neurology in far-reaching significance.

Before entering upon these details, I shall be but fulfilling
a promise long since made in giving in detail the methods
employed. In making the description as detailed and precise
as possible it is by no means implied that all of these methods
are the best or most convenient, or that there is any special
significance in the exact proportions employed. But some
experience in laboratory practice has conclusively shown
that for a beginner no minutiz are unimportant, and no
latitude can be safely afforded to inexperience. The formule
and directions given in histological hand-books very generally
omit what seem to their compilers self-evident precautions,
on which, in many cases, the success of the preparation
depends just as truly as upon the fundamental reactions
involved.

It would seem to be an axiom that a method will be most
generally available which combines the necessary differentia-
tion of tissues with the nearest approximation to the perfect
prervation of the essential details of each. Especially is this

Herrick, Morphology of Brain of Bony Fishes. 335

true of the methods of neurological technique. It may be
replied that a necessary condition of the sharp differentiation
of one set of structures is the failure to develop or the diverse
modification of other tissues adjacent; it may even be con-
tended that this divergent modification is the essence of
differential staining, etc. Notwithstanding this objection,
we contend that for general purposes that treatment is best
which brings out cells and fibres, neuroglia and nutrient
tissues most nearly in their normal relations. This conclu-
sion does not weigh against the use of special fibre stains or
metallic impregnation where a specific investigation of the
fibres is intended, but it suggests that such studies should be
controlled by recourse to a method which shows fibres in
their normal relations to cells, etc. It is also obvious that
for the general purpose a stain which brings out all the
cells of a given type ina uniform manner is better than a
brilliantly selective stain which is also elective of one cell
and not of its neighbor of the same sort. The same consid-
eration renders a stain applied in section more reliable than
one used zz ¢ofo with the inevitable danger of affecting super-
ficial structures more than deeper ones.

In the present case we fortunately have in a modification
of methods long since familiar all that is needed for a reason-
ably good cotemporaneous differentiation of the important
elements of the brain.

METHODS.

The removal of the brain is attended with considerable
difficulty in many cases. It will be remembered that the
brain of fishes is usually included in a cavity much larger
than itself, and is enveloped in a large and more or less
closely adherent sheath of loose adipose tissue, which sepa-
rates it from the cranial walls except ventrad. It freqently
is most difficult to remove the fatty mass without distorting
or injuring the pallium, the dorsal sac, and the epiphysis.
The great plexus of blood-vessels which is connected with

336 JouRNAL OF CoMPARATIVE NEUROLOGY.

the cerebellum often offers great difficulties to orientation.
If the brain be approached from above, by a cautious paring
down of the head in the horizontal plane until the cavity of
the skull is reached, the opening may be gradually enlarged
by strong shears and the forceps, snipping away carefully
with sharp scissors the membranous adhesions. The olfac-
tories, if included, give comparatively little trouble, but, if
excluded, not a little skill is required to isolate the crura and
dislodge the bulbus. The principal objection to this method
is the difficulty of satisfactorily dissecting out the stumps of
the cranial nerves. In many cases we have found it safest to
remove the whole mass of fat containing the brain and pass
it through the solutions unaltered. In this case the solution
of the fats in the alcohol leaves cavities which become filled
with vapor and are permeated with extreme slowness by the
imbedding media. When they are imperfectly filled there is
little hope of securing a consecutive series of sections.

It is advisable to remove some of the brains from below,
in which case the jaw is carefully cut (not torn) away,
taking pains not to bring to bear any tension on the nerves in
the process. The opercular apparatus is then removed and
the region of the eighth nerve is easily located by the appear-
ance of the otolith sac. The opening is extended with the
shears, with the precaution of cutting each nerve fibre within
the cranial cavity before the corresponding area is removed.
The saccus vasculosus and hypophysis are then isolated, and
all the fibrous connections of one side are removed. The
whole lower part of the head is cut away piece-meal until
the nerve roots of the other side are reached. The cord is
then severed, and, as the nerves are cut the brain is gently
pushed laterad and allowed to drop into the fixing bath,
without first removing the fatty envelopes.

Fixing.—While it is desirable that a fish brain shall be
perfectly fresh, the importance of having it absolutely alive
has been exaggerated. The supposed necessity of plunging
it at once into absolute alcohol will account for many of the

Herrick, Morphology of Brain of Bony Fishes. 337

infelicities of earlier technique. Several hours in cool
weather will not materially injure a fish brain zz sztw. The
medium which best fixes the brain elements in this case 1s a
modification of Fol’s chrom-acetic solution. It is prepared
in a stock solution consisting of chromic acid of 1 per cent.,
25 volumes; acetic acid of 2 per cent., 50 volumes; distilled
water, 25 volumes. This is the generally available fluid for
mammalian brains. For fishes it is reduced by the addition of
an equal volume of water. Large quantities of the fluid are
employed (20-30 volumes), and the brain left in it twenty to
twenty-four hours. Before setting the preparation aside the
utmost pains must be used to secure a natural and symmetrical
position of parts, in order to orientate sections properly. For
this purpose it is often of advantage to form a sling of tissue
paper suspended in the fluid to lift the specimen from the
bottom of the vessel and prevent flattening due to gravitation.

Washing —The brain, after fixing, is suspended in large
quantities of distilled water, which may be changed fre-
quently until the yellow color disappears (about one hour .
usually suffices ).

Hlardening.— The brain is passed successively through
50, 60, 70, 80 and go per cent. alcohol, remaining twenty to
twenty-four hours in each. It is of advantage in warm
weather to leave in 50 per cent. spirit ten hours and then
change to 55 per cent. for six to eight more before entering
60 per cent. The effect of sudden and great changes in con-
centration is to shrink and alter the cells.

If the brains are to be cut at once they may be passed
from go per cent. alcohol to absolute after thirty-six to forty-
eight hours, but if they are to be preserved for some weeks
$5 to 90 per cent. alcohol may be used. After remaining in
absolute alcohol for one day or more the brain is ready for
imbedding. After a bath in turpentine lasting one to three
hours the tissue is placed in a mixture of turpentine and
paraffin, which is fluid at blood heat or a little higher tem-
perature, for an hour or two.

er
338 JOURNAL OF COMPARATIVE NEUROLOGY.

For the actual imbedding, a mixture of hard and soft
paraffin is chosen, which, at the temperature of the room,
will cut without too great a tendency to roll. If too hard,
the paraffin rolls into a close scroll, which not only is difficult
to smooth upon the slide, but tends to fracture and distort
the tissue. It is well to experiment on a block of the paraffin
in which the tissue is to be imbedded beforehand.

For summer, a fusing point of about 30° C. is desirable.
In lieu of a thermo-regulator, when the latter is unavailable,
a copper plate supported on a tripod will serve to conduct
the heat from the gas flame at one end toa narrow metal
tray at such a distance as may be necessary to keep the
paraffin just fused. The brain is suspended in the tray in
any convenient way to avoid contact with the metal. Even
the tinned spoons frequently used may conduct too much heat
heat to the object. A beaker over a water bath is a simpler
but less reliable method.

Care must be exercised in removing the brain from alco-
hol to turpentine, and in all subsequent removals, to avoid
contact with (especially moist) air. The alcohol must be
absolute, and should be used in sufficient quantity.

The imbedding is performed in the usual way. An
oblong box is made by folding writing-paper, and a layer of
the paraffin is allowed to cool on the bottom, say one-eighth
of an inch think. When this has solidified a small portion
of paraffin is heated nearly to boiling in a spoon and poured
into the tray, so as to partly fuse the surface of the solidified
layer. This precaution prevents the flaking off of the first-
formed layer. The box is then filled with paraffin from the
tray containing the specimen, which is orientated carefully
on the paraffin bottom, and pinned out if necessay. Gener-
ally the viscid layer will serve to hold the specimen in any
desired position. When cooled, if the work has been care-
fully done, the whole mass solidifies about the specimen.

In cutting longitudinal horizontal sections the brain
should be orientated to begin cutting from the dorson, in

Herrick, Morphology of Brain of Bory Fishes. 339

order to avoid loss in orientating in the microtome. It should
be remembered that the slightest overheating or contact with
water may vitiate the entire process at any stage in it.

Previous to cutting the sections a dozen or so of oblong
glass trays, similar to developing trays for photography, and
also a narrow glass vessel about two and three-quarters
inches high and two inches or less wide, are provided for the
reagents. The block is fastened in the microtome and orien-
tated, the superfluous parafin cut away, and the block is
notched at one end to enable one to determine the position
of each section at a glance. A diagram of slide and intended
position of section and cover is made on paper and guide
pins are arranged to facilitate placing the slide. The slide
is brushed over with the albumen fixative, which consists of
one part of filtered egg albumen and two to three parts of
of glycerine. The fluid may be indefinitely preserved by
placing in the hood of the bottle a sponge moistened with
a few droys of carbolic acid. It is of first importance to
remove as much of the albumen as possible, as it is discolored —
by the stain. One may wipe gently with a soft cloth, leav-
ing an almost imperceptible uniformly distributed film,
which will nevertheless adhere to the section.

After the slide is furnished with its quota of sections,
which are carefully pressed upon the slide to avoid air-
bubbles, it is heated to the melting point of paraffin and
cooled before passing into a tray containing turpentine.
When the paraffin is completely removed the slides are
drained and washed with absolute alcohol from a dropper
and passed into go per cent. alcohol and thence into distilled
water. They are then covered with the stain, which is used
as dilute as possible, and allowed to stain until of a deep
blue color. After washing in water, the sections are passed
into alcohol, and ultimately are placed in the narrow vessel
above described filled with absolute alcohol. In order not to
vitiate the absolute alcohol too rapidly, the sections are flowed
with it before entering the vessel. They are then cleared

340 JOURNAL oF COMPARATIVE NEUROLOGY.

in turpentine and mounted in balsam dissolved in benzole.
The stain employed consists of Grenacher’s hematoxylin
with the addition of a small proportion of corrosive subli-
‘mate and ammonium chloride. Seven and _ seven-tenths
grains sublimate and seven and three-tenths grains ammo-
nium chloride (z.e., one of Wyeth’s compressed antiseptic
tablets supplies a quart of the fluid.(')

The addition of the mercuric chloride not only acts as a
preservative, but improves the stain, especially in its effect
on the fibres. It remains unaltered for any length of time in
any climate, but before use it should be exposed to the air
in an open vessel for a number of days. Even when evapo-
rated to dryness it may be redissolved and filtered without
impairing its value. The resulting stain is a clear, trans-
parent, purplish blue when the fluid has properly aged. The
neuroglia scarcely stains, but the fibres are well brought out,
and cells (unshrunken and not enclosed in vacuoles) pre-
sent their characteristic structures most distinctly. The
presence of acid changes the color to a purplish red, between
which and the bluish tint are all gradations, depending on
the exposure to air. When thus prepared, the fish brain
yields to none in beauty and distinctness, and, because of the
very large size of the fibres and their sheaths, forms the best

subject for the study of tracts known to me.
RHINENCEPHALON.

In a previous paper the external topography has been
sufficiently discussed.(*) In the drum, where the olfactory
lobe is closely soldered to the base of the cerebrum, the
former is very obviously divided into a pes and pero portion,
as was, in fact, recognized by Sanders, whose description of
the ichthic olfactory lobe is most detailed of any with which
I am acquainted. I have elsewhere indicated the belief that

1 Grenacher’s hematoxylin is made by mixing 4 cc. saturated alcoholic solution of
hematoxylin with 150 cc. strong ammonia alum solution in water, which, after a week or
two, is filtered and mixed with 25 cc. glycerine and 25 cc. methyl alcohol.

2 This journal, Vol. 1, p. 217-218, p. 228-233.

Herrick, Morphology of Brain of Bory Fishes. 341

these two portions are essentially different and have unlike
connections, and the structure of the olfactory of fishes but
strengthens an opinion primarily based on a study of Saurop-
sida and mammals.(') In serpents it was shown that that
so-called olfactory tract which crosses in the anterior com-
missure is derived from the pes or cerebral part of the bulbus,
while the radix lateralis is derived from the true olfactory or
glomerulary structure, and it terminates in the homologue of
the hippocampus or adjacent structures. This appears to be
equally true of the fish, and the destination of the several
tracts is much more distinctly made out than in any other
group.

The pero consists of a dense investment of fibres which
lie in greatly confused strands about the glomerular layer,
not unlike that of all higher animals. Within the glomerular
zone is an irregular layer of specific olfactory cells, which are
unusually large and irregular (Plate XXV, Fig. 1). These
cells are multipolar, with several long processes beside the
one which enters the nerve fibre. The nuclei are small and
spherical and unstained. The proximal fibres derived from
this layer collect at the lateral aspect as a large and very dis-
tinct radix lateralis.

The core of the olfactory, or pes proper, is filled with a
small type of fusiform cells, not unlike those of the hippo-
campal lobe. From this there obscurely arises the large
circular bundle of the radix mesalis. The subjoined account
from Sanders may be taken as applying pretty well to the
case in hand:(*)

‘¢ The lobi olfactorii consist essentially of three layers. Of
these the external is thicker in front, and is formed by the
fibres of the olfactory nerve, which in entering diverge in all
directions and form a sort of envelope for the anterior part of

the lobe. More internal comes a layer of finely granular
1 C. L. Herrick, “Topography and Histology of the Brain of Certain Reptiles,”
JourNAL oF CompaRATIVE NEUROLOGY, p. 24, 1891.

2 Saxprrs “Contr. to the Anatomy of the Central Nervous System in Vertebrate
Animals,” Subsection 1, Teleostei. Philos. Trans., p. 748.

342 JOURNAL OF CoMPARATIVE NEUROLOGY.

neuroglia, which surrounds on the upper, anterior and lower
sides a mass of small cells, which occupy the central and
posterior part of the lobe. s 3 *

‘‘The cells of the central group are small in size, re-
sembling to a certain extent those of the cerebrum. Many
are oval or circular in outline, but generally they are more or
less pear-shaped. Each cell has a nucleus of comparatively
large size, which is invariably situated at the broader end of
the cell; the protoplasm or cell-contents occupy the narrower
side, which terminates in a more or less blunt point, from
which a single free fibril emerges. The nucleus contains a
single spot-like nucleolus, situated near the centre, which
occasionally shows symptoms of breaking up into its con-
stituent granules. The total average length of these cells is
0.007 millim. or 0.008 millim., their diameter 0.004—0.005
millim.; the nuclei are generally round, or nearly so, and
their diameter averages 0.004 millim.

‘‘Many of these cells occupy spaces in the neuroglia
which probably correspond to the spaces surrounding the cells
of the cerebrum described by Obersteiner and Bevan Lewis.
Occasionally nearly the whole of the cell projects into this
chamber, but more generally only the broad end, so that the
nucleus alone would be bathed in lymph in the latter case.
The granules, which to a great extent compose the neuroglia
of the olfactory lobes, become aggregated together and form
a smooth surface on the walls of these spaces; they do not
actually form an epithelial layer, but seem to be a rudi-
mentary form of that structure.

‘© A layer of neuroglia surrounds this group of cells, as
before mentioned, on all sides except posteriorly, in which
with high powers only very fine granules are to be observed.
The above described cells occur very sparingly here.

‘¢ The external portion of the lobule is formed principally
by the fibres of the olfactory nerve. These fibres enter at
the anterior end, and occupy about half the length of the
lobe; they do not go straight, but the bundle, dividing at the

Herrick, Morphology of Brain of Bony Fishes. 343

apex, forms an interlacing layer, which encloses the fore part
of the lobe as in a sheath, and envelops small rounded masses
of coarse granular neuroglia, which may be looked upon as
representing the glomeruli in the bulbus olfactorius of mam-
malia, described by Meynert.

‘‘ Larger cells are seen to occupy the inner edge of this
layer of nerve fibres, where it begins to pass over into the
stratum of finely granular neuroglia above described; at this
part the neuroglia is coarser, and the cells in question occupy
spaces therein in the same way that the small cells do in the
central group, These cells are mostly tripolar, with some-
times one and sometimes two broad protoplasmic processes,
the others being fine and probably axis-cylinder prolonga-
tions. They measure .o13 millim. long by .oro broad, the
nucleus measuring .007 by .oo6 millim.; some have a dis-
tinct spot-like nucleolus, which, however, in many speci-
mens, cannot be so easily distinguished. Besides these,
other unipolar cells occur in which the protoplasm greatly
preponderates, and where the nucleus is not much larger
than that of the small cells of the central group.

‘In addition to the larger cells, which, as before men-
tioned, occupy the border of the layer of fibres, some of these
fibres themselves show cell-like swellings in their course,
which somewhat resemble the cells described by Meynert in
the glomeruli olfactorii of the human subject. These cell-
like swellings in the course of the fibres are like some kinds
of bipolar cells: they have large oval nucleoli and conspicu-
ous nucleoli.”

We dissent completely from the author’s views respecting
the cavities within the lobe and regarding them as products
of shrinkage. Especially the curious suggestion as to the
origin of epithelium seems uncalled for.

The only data at hand on the development of the olfac-
tory in fishes are meager. I quote from Holt as follows:

In the herring at one day (Holt, p. 480, Plate XXIX,
Fig. 2, and 5 od.) ‘‘ the nasal sacs are closely apposed to this

344 JouRNAL OF CoMPARATIVE NEUROLOGY.

region of the cerebrum, and from the ventral patch of white
matter the short and stout olfactory nerves pass to the bases
of the first named.

In ax early post-larval stage, the anterior commissure is
situated farther forward, and is broader than in the earlier
stage. The third ventricle passes for a considerable distance
in front of the commissure, and the cerebrum appears in
transverse section as a vesicular mass with dorso-lateral
patches of white matter; from the latter the olfactory nerves
pass forwards and outwards to the nasal sacs, now removed
some little distance from the cerebrum and disposed partly
in front of it.

In the stage one-half-inch long, the crebrum has under-
gone a further upward rotation, and the olfactory lobes are
now seen as bulbous masses projecting from the front end.
From the anterior ventral edge of each lobe the olfactory
nerve passes toward the nasal mucous membrane. Each
olfactory lobe consists, histologically, of fibrous matter, with
a few scattered deeply staining cells, and a narrow peri-
pheral margin. It is constricted at its point of origin from
the cerebrum, as in later stages, but its height is as yet
insignificant.

In the stage three-fourths inch long, the olfactory lobes
are more elongated than in the last stage, and the constriction
at their point of origin is better marked. A transverse com-
missure unites their bases. The olfactory nerves turn outwards.

|The commissure above mentioned can hardly be other
than that we have identified with the corpus callosum. |

Upon the general question of the nature of the olfactory
lobe and fibres, the following remarks are quoted from
Kolliker:(')

‘In my studies upon the development of the organs of
smell in human embryos(*) I discovered that the olfactory,

1 KécirKER, A., ‘‘ Ueber die erste Entwicklung der Nervi olfactorius,’”’ Sitzungs-
berichten der Wiirzburger phys. med. Gesellschaft, 1890, XIV Sitzung von 12. Juli.
2 K6.LiikeER, A., Festschrift fiir Ziirich, 1883.

Herrick, Morphology of Brain of Bony Fishes. 345

unlike all other nerves, in the earliest stages consists through-
out their entire extent of nucleated bundles of the finest
parallel fibrils, which bundles I compared with the axis-
cylinders of other nerves. From this circumstance I con-
cluded that these nuclei correspond to the nuclei of nerve
cells, and that a nucleated sheath of Schwann accordingly is
not present, although it has been assumed by all authors since
Max Schultze. If this were correct, then the olfactory fibres
consist of bipolar nerve cells, which either each sends a pro-
cess peripherad, or, as seemed to me probable, are united in
moniliform series, as must be assumed in the sympathic; in
this case the nerve grows by successive subdivision of the
nucleated portions without complete separation of the result-
ing segments.

‘In any case the development of such a nerve from the
central nervous system is difficult to explain from any exist-
ing analogy, and it afforded a very desirable solution of the
matter when His, a short time since, announced that the
olfactory does not develop from the olfactory lobe, but rather
takes its origin from the epithelium of the olfactory pits, and ~
grows in the centripetal direction, like the cells of the spinal
ganglion. This investigation of His I have recently verified
with the following results:

‘‘In the earliest stages the olfactory pits have no nerves,
and are not connected with the olfactory lobe. In an embryo
chick of four days there is a slight proliferation of the epi-
thelium of the olfactory at the end nearest the brain only,
forming a bundle .030-.054 millim. thick, which can _ be
followed to the outer margin of the hemisphere without
entering into any connection therewith. The bundle is
finely fibrous and nucleated, and exhibits on its surface fusi-
form cells.”

Prof. Kolliker records similar observations upon mammals
and concludes:

‘*T consider the assumption made by His as very prob-

able, and may add that when the olfactory nerve has once

3,46 JOURNAL OF COMPARATIVE NEUROLOGY.

entered the bulbus the latter acquires, even in the embryo, a
very peculiar appearance.

_ ** As regards the anatomical significance of the elements
of the olfactory nerve, His regards them in the embryonic
state as bipolar nerve cells, and the nerves themselves as the
olfactory ganglion. Furthermore, he states that the greater
number of these cells can be re-identified later in the olfac-
tory lobe itself. These cells, inasmuch as they were origi-
nally epithelium of the nasal pit, have undergone a consider-
able migration, so that the question naturally arises whether
all the nerve cells of the olfactory ganglion have not gradu-
ally entered the bulbus. The solution of the question de-
pends upon the interpretation of the histological structure of
the olfactory nerve of the adult. If the nuclei of the olfac-
tory belong to the nerve fibres, then the peripheral portion
of the olfactory is to be regarded as the ganglion; if, on the
other hand, these nuclei belong to the sheath, it may
be assumed that all the ganglion cells have entered the
bulbus.

‘In this discussion His has overlooked my statement,
made in 1883 and based on the investigation of a human
embryo of the second month, ‘ that the nucleated fibrillated
bundles of the olfactory nerve of embryos are the direct fore-
runners of the nucleated pale olfactory fibres of the adult,
and therefore are to be compared with the axis-cylinders of
other nerves and the nuclei with the nuclei of nerve cells.’
Nevertheless, these elements differ from those of a typical
ganglion in that each olfactory fibre possesses a number of
nuclei, and therefore corresponds to a considerable complex
of nerve cells. The mitotic figures found in olfactory fibres
of the rabbit show that the bipolar cells of the olfactory
nerve do not grow into the bulbus, but extend in length in
such a way that with the increased length of the fibre the
nuclei multiply, so that finally there results a peculiar long,
multi-nucleate nerve cell, which can only be compared with
the sympathic.

Herrick, Morphology of Brain of Bony Fishes. 347

‘¢Tf we assume that the sensory peripheral fibres termi-
nate in free branches in clusters of gray matter, and that
from the cells of such niduli new nerve fibres arise and con-
duct the excitement centrad, the conditions for determining
central tracts and centres are satisfied.”

In 1854 Kolliker described the olfactory fibres of the ox
and sheep as tubes with nucleated contents.

The above view, which is theorectically so probable,
receives considerable confirmation from the facts to be pre-
sented, as well as a partial new interpretation.

A glance at Fig. 1, Plate XXIV, will show that the radix
lateralis passes directly and without interruption to a special
caudo-ventrad projection of the cerebrum, already identified
upon topographical grounds as the homologue of the hippo-
campus (see previous paper of this series). There the fibres
end near a special zone of cells. Entad of this specific homo-
logue of the hippocampal cells a tract of non-medullated
fibres seems to arise, which passes cephalo-ventrad and
crosses to the opposite side immediately caudad of the callo-
sum. This fibre tract can be nothing else than a rudimentary
hippocampal commissure, together with the fornix. That
the latter structure is included is shown by the fact that a
small branch passes to a bifid cellular mass projecting into
the ventricle from the caudo-ventrad aspect of the callosum;
in other words, an unmistakable homologue of the body of
the fornix. To complete the identification, we think we
find a small tract extending from the latter to the thalamus.
The unmeduilated nature of the fibres makes the study
difficult.

The radix mesalis pursues an altogether different course.
After entering the post-rhinalic region of the cerebrum, this
cylindrical bundle passes caudo-mesad, and, after dividing
into a number of smaller tracts, forms a part of the pracom-
missural system. Nevertheless, this band is distinct from
both the true precommissura and the axial commissure or
decussation beneath it.

348 JouRNAL oF CoMPARATIVE NEUROLOGY.

In assuming an entirely distinct function for the two
radices and the structures supplied by them, we meet an
apparent difficulty in the fact that in those fishes whose
olfactory bulb is exserted the radices are both produced from
the cerebrum in the elongate crura. It must be remembered,
however, that we have already shown that in these cases the
ventricle continues out with the radices, so that, morpho-
logically at least, the bulb contains even in this case a part of
the cerebrum, 7.e., a distinct pes.

PROSENCEPHALON.

The study of the cerebrum of fishes is likely to furnish the
best and most convenient basis for determining their position
among the classes of vertebrates. The skeleton is less trust-
worthy than usual, by reason of its specialized nature. The
development of a vast number of membrane bones, with the
marvelous changes in the whole bodily configuration and
structure dependent thereon, can, at most, only be regarded
as superficial characters as compared with those entirely
independent changes in the brain within a spacious cavity
shielded from all direct external influences.

Accepting the fundamental homologies laid down by em-
bryology, our morphological study proceeds from a condition
when the prosencephalon consists of a single dilation of the
neural tube, the primitive prosencephalic vesicle. Any
attempt to construe vertebrate brains which fails to recog-
nize this primary wzdivided and closed character of the
cephalic cavity must fail. It is possible for the requisite
increase in cerebral substance to be produced in at least three
different ways. First, there may be developed from the sides
of the tube thick excrescences in which cells may proliferate.
Second, the vesicle may increase in size as a whole, retaining
its undivided character. Third, the vesicle may enlarge in
certain portions, while elsewhere it may retain its simple
original form. In Teleosts the first and the second methods
chiefly prevail in contrast to the higher vertebrates, where

Herrick, Morphology of Brain of Bony Fishes. 349

the first and third methods maintain. In regions of the
neural tube farther caudad there are two sets of commissures,
one lying in the dorsal and the other in the ventral wall
of the tube. These remain in their primitive form in the
cord.

The question now arises, to what extent the same rela-
tions persist in the cerebrum. In fishes, since the cortex is
anatomically absent and simply morphologically represented
by the pallium, it is obvious that the cells and commissures
are either absent entirely or represented functionally by
structures in other parts of the primary prosencephalic
vesicle. Theoretical considerations, as well as such evidence
as we have from embryology, show that the tendency of de-
velopment in the cerebrum proper is dorso-caudad, 7.e., the
outgrowths of the primitive vesicle are reflexed and tend to
overlap the axial portions caudad. This is also the case to a
certain extent even in the growth of the pallial sac in fishes,
but since the latter does not contain nervous elements, such
revolution cannot change the position of the commissures,
etc., belonging properly to the roof. Following this clue as ©
given in a previous article,(') it has been possible to deter-
mine the relations of all the important tracts, commissures,
and niduli of the cerebrum, including esthesodic and kine-
sodic niduli, corpus callosum, fornix, hippocampal commis-
sure, fornix body, and hippocampus, in an unexpectedly
simple way. When we remember that the cortex of higher
vertebrates contains those centres whose functions associate
them most closely with conscious acts, and that it is regarded
as the true organ of consciousness, including all the higher
faculties, it becomes of great interest to discover whether the
axial lobe of fishes contains cell clusters which can be looked
upon as the physiological equivalent of the cortical areas of
higher animals.

The writer, in a series of publications covering most of

t C. L. Herrick, ‘ Topography and Histology of Certain Ganoid Fishes,’’ JouRNAL
oF ComPARATIVE NEurROLOGY, Vol, I, p. 167, June, 1891.

350 JOURNAL OF COMPARATIVE NEUROLOGY.

the major divisions of vertebrates, has striven to show that
there is a constant difference in form between the kinesodic
and zthesodic cells. On this basis areas are marked off more
or less distinctively associated with one or the other function.
It was noted that the two kinds of cells are more distinctly
segregated in lower vertebrates, while in higher types there
is a greater tendency to inter-blend and form complex clus-
ters. In other words, there is a very obvious anatomical
basis for the assumption of more complex inter-action be-
tween afferent and efferent excitements in the cortex of
higher vertebrates.

If the fish is not purely reflex and automatic in its re-
actions, some substitute for the undeveloped cortex must be
found, and would be sought for in the only remaining part
of the cerebrum, z.c., the axial lobe. As we have seen, the
axial lobe of Sauropsida is certainly much more than the
homologue of the striatum of mammals. The writer en-
deavored to show that in alligator and other reptiles there
are definite proliferating areas, which may be regarded as
centres of origin for the cortical niduli.(’) Mr. Turner has
observed the same appearance in birds,(*) and his studies
make it probable that in that group, where the cortex is
greatly reduced, its loss is substituted for by involuted cell
niduli of cortical origin, but buried within the axial lobe.
This forms an important clue in the search for the homo-
logues of sensory and motor areas in the fish.

In general, then, we believe that the fish cerebrum is
derived from a primitive type in which the primary prosen-
cephalic vesicle had scarcely, if at all, developed lateral (or
definitely cerebral) structures; that most teleosts have arisen
from types which possessed a slightly developed cortex, but
that an increase in the size of the head without the commen-

r ‘Notes on the Brain of the Alligator,’’ Journ. Cin. Soc, Nat. Hist., Vol. XII, p.
455; ‘‘ Topography and Histology of the Brain of Certain Reptiles,” JouRNAL oF Com-
PARATIVE NEuROLOGY, Vol. I, p. 21.

2 C. H. Turner, ‘ Morphology of the Avian Brain,’ JouRNAL OF COMPARATIVE
Nevurovoey, Vol. I, p, 71.

Herrick, Morphology of Brain of Bony Fishes. I
) Oy ee 35

surate development of cranial walls forming a direct support
for the cortex has resulted in the gradual limitation of the
nervous matter within the axial lobe leaving only the pal-
lium to represent its former position; that the cell structures
proper to the cortex are contained in the axial lobe, which
is, accordingly, more complex than that of any other group
of vertebrates; that the two types of zsthesodic and kinesodic
cells are as distinct in fishes as in reptiles; that these cells are
grouped in distinct areas and may be classified into minor
divisions, based on size, etc.; and that the commissures and
tracts sustain much the same relations to these clusters that
they would if the latter lay in a cortex cerebri instead of the
axial lobe. Of the above conclusions, the suggestion as to
the cause of the suppression of the cortex is a mere guess,
incapable of serious attempt at demonstration; the others
seem to me well supported by the facts at hand. It is ob-
vious that one result of this peculiar limitation of the cortex
is to largely interfere with a free and generous development
ot the organs of consciousness and spontaneity. A fish
would be handicapped in any competition with animals
whose cortex would permit of easy increase by centrifugal
growth or by infolding and plications.

In a preceding article it was shown that the axial lobe of
fishes is marked by deep and more or less constant fissures
separating topographically several lobes or areas. It remains
to show that each of these lobes has its own peculiar cell
structure and fibre connections, warranting the assertion
above made, that the axial lobe of a fish is more complex
than that of other animals, not even excepting the bird.
Before passing to the special description, reference is made
to the useful paper by Edinger, in which a great deal of
useful comparative matter is collected and discussed in the
light of recent literature.(') The statement on page 106,
that ‘‘the amphibian brain is the simplest brain which is

1 Epincer, Dr. L, ‘‘ Untersuchungen iiber die Wergleichende Anatomie des
Gehirns,” I.; “‘ Das Vorderhirn,” Abhandl. Senkenbergischen naturf, Gesellschaft, 1888.

352 JouRNAL OF COMPARATIVE NEUROLOGY.

found in the vertebrate series,” should be understood in some
other than the phylogenetic sense probably, for even a more
highly differentiated brain in which the primitive simplicity
of the prosencephalic vesicle is preserved may be believed to
indicate a more primitive origin.(')

In order to get an idea of the histological differentiation
of the axial lobe, we may first examine a horizontal section
somewhat dorsad of the anterior commissure (Plate XXIV,
Fig. 2). The anterior commissure fibres are situated near
the median margin and are spreading out dorso-laterad in the
mesaxial lobe. The actual crossing of the fibres takes place
in the prethalamus or a projection from its dorsal aspect.
The fibres of the anterior commissure proper pass laterad
into the central lobe, beyond which they were not followed.
The central lobe is occupied with the numerous bundles of
the peduncles around which are grouped niduli of large
pyramidal cells such as are commonly found in motor areas
of higher animals. The processes are long and subdivide.
The apical process is usually peripherad. The nuclei are
small and densely stained. The entire cell stains more
deeply than other adjacent elements. A spur of such cells
follows the callosal fibres toward the meson (Fig. 2, Plate
XXV). The whole cephalo-lateral aspect is occupied by
the Jateral, or parietal lobe, the cells of which are of the
esthesodic variety. From the frontal part of the mesaxial
lobe it is separated by a distinct frontal fissure, as it is from
the cuneus by the Sylvian fissure. From the central lobe it
is separated by a thin tract passing obliquely dorso-cephalad
and laterad, z.e., radiating toward the periphery. From this
tract, which extends from the frontal fissure cephalad to the

1 It is interestimg to see that Owen has arrived at a conclusion similar to the above
on the basis of external form and gross dissection, as may be gathered from page 286 of
the first volume of his ‘‘ Comparative Anatomy,” especially the following paragraphs:
“Tt is interesting to perceive on the superficies of the solid prosencephalon in many fishes
the foreshadowing of the convolutions, which are not fully established until an advanced
mammalian grade is attained. The prosencephalon of the fish is far from being a minia-
ture model, but it may be regarded as the potential representative of the complex cerebral
hemispheres of man.”

Herrick, Morphology of Brain of Bony Fishes. 353

Sylvian caudo-laterad, isolated fibres and small tracts pass
toward the periphery nearly in the plane of the section. The
peripheral or ventricular border of this lobe is clothed with a
single-layered epithelium, from the apices of the cells. of
which fibres extend long distances entad, as in the brains
of Sauropsida. The cells of the lateral lobe (Plate XXV,
Fig. 6) are fusiform, with clear spherical nuclei of large
size. The protoplasm is faintly stained and the processes
are short. The cells are similar to those found in zsthesodic
areas of the cortex in reptiles.

The cuneus consists of concentric layers of smaller fusi-
form cells. Near the surface, however, is a small zone of
cells like those of the lateral lobe, or nearly twice the size
of those composing the bulk of the lobe. Dorsad this lobe
borders upon the occipital, and caudad it is separated from
the temporal and hippocampal.

The occipital lobe merges insensibly into the temporal ventro-
laterad, but extends cephalad a long distance upon the dorsal
aspect. In the present region it is difficult to say which is cut.

The mesaxial lobe occupies the whole mesal aspect, and is
divided into a cephalic and caudal portion by a fissure in the
mesal surface. This may be the homologue of a fissure men-
tion by C. Judson Herrick in the cat-fish.

The cellular elements are small and vary considerably.
Cephalad of the above fissure, which may be called splenial
for convenience, and caudad of the callosal tracts, is an area
where numerous small fusiform cells are closely massed.
Caudad of the splenial is a region where there is a mixture
of the above described and narrow deeply stained pyramidal
cells resembling the so-called rhinomorphic cells. A similar
sort of cells occupies the tract caudad of the peduncles in the
central lobe (Fig. 4, Plate XXV). Cephalo-mesad of the
pyramids at this level is a dense clustre of small fusiform
cells, with a slight admixtute of pyramidal elements. A
section at the dorsal level of the callosum is figured in Plate
XXIV, Fig. 2, and requires no special description.

354 JOURNAL OF COMPARATIVE NEUROLOGY.

Some distance dorsad of the section first mentioned, a
strong projection of the central lobe passes toward the caudal
surface and is interposed between the temporal below and
the occipital above. The cells are small pyramids, staining
very deeply. There are similar projections along the frontal
fissure. Thus, while the pyramidal cells are central, they
are connected with the surface of the axial lobe at several
points. The occipital Jobe dorsally contains flask cells simply,
and forms a cap over the one just described.

In longitudinal sections the caudad projection of the pyra-
midal cells of the central lobe is seen to be accompanied by
a strong tract. Although the details of these arrangements
would be interesting, it is intended to reserve them for a
wider range of comparison.

The temporal lobe merges ventro-mesad into the hippo-
campal, both of which contain small flask cells, with clear
spherical nuclei and inconspicuous processes.

The specific representation of the hippocampal niduli is a
mass of somewhat smaller and more deeply staining cells,
forming a layer near the caudal margin of the lobe, into
which the fibres of the radix lateralis may be traced. These
cells are grouped in clusters, and are essentially bipolar or
flask-shaped.

The ventral projection of the mesaxial lobe terminates
cephalad in the bifid body, which is here recognized as a
probable homologue of the corpus fornicis, and caudad of the
latter in a gradually diminishing area cephalo-ventrad of the
anterior commissure, perhaps homologous with what I have
termed the prerhinalic lobe in mammals. Both these areas
abound in small, dark-colored and spherical nuclei, like those
of the blood corpuscles, and clearly homologous with the
so-called Deiter’s corpuscles. There are less numerous flask
cells of the smallest size.

The tracts and commissures of the cerebrum complete in
a very satisfactory way the chain of evidence begun above.
The callosum of fishes was first correctly identified, I believe,

Herrick, Morphology of Brain of Bony Fishes. 355

by the writer as indicated above.(') Previous writers have
either regarded it as absent or fused with the precommissura.
In the latter view, proposed and defended by Osborn, the
present author coincided for a time, in spite of the grave
morphological objection that the callosum and hippocampal
commissure on the one hand and the precommissural system
on the other belong to distinct systems. The former are
cortical, the latter basal. It would be necessary, in a case
like that of fishes where the cortex is suppressed, to consider
that the axis of the cerebrum had been greadly modified and
shortened in order to bring the two systems into juxtaposi-
tion. No such supposition is necessary, for the callosum
and fornix systems are present and in just the position which
the nature of brain development would lead one to predict,
z.e., well forward near the union of pallium and axial lobe,
in close relations to the lamina terminalis and on the oppo-
site side the axial part of the ventricle from the callosum.
Fig. 8, Plate XXV, illustrates the relation. A glance at
Fig. 2, Plate XXIV, will indicate how distinct the two
systems are. It will also be noticed that the callosum is
intimately associated with the pyramidal cells of the central
lobe, which we insist upon as representing suppressed motor
cortical areas. Immediately caudad of the callosum are two
cellular projections into the ventricle, which in all respects
represent the corpus fornicis. A tract homologous with the
combined fornix and hippocampal commissure springs from
the hippocampal cells entad of the radix lateralis and passes
to the median line, part entering the fornix body and part
form a commissure caudad of but adjacent to the callosum.
There is a cellular interval between the two commissural
systems. There is a small tract arising in the fornix body of
either side destined for the thalamus.

In the second part of Professor Osborn’s valuable paper
on the corpus callosum(*) these words occur: ‘‘ In regard to

1 JOURNAL OF COMPARATIVE NEUROLOGY, pp. 164-168.
2 Morphologische.Jahrbuch., Band XII.

356 JOURNAL OF COMPARATIVE NEUROLOGY.

other groups of fishes [than Dipnoi], I still adhere to the
hypothesis that the commissura interlobularis is a primitive
- form of the whole transverse commissural system of the
hemispheres, thus representing both the anterior commissure
and the callosum.”

The facts above presented, while they seem to disprove
this position, serve to establish only the more firmly the
philosophical theory founded by Osborn, by which the struc-
tures above referred to are homologized throughout the
vertebrata.

The so-called anterior commissure consists of three parts,
viz.,a true commissural band connecting the two sides of the
base of the cerebrum; second, the decussation or commissura
of the radix mesalis olfactorii; third, the axial commissura,
first described by Edinger as the commissure of the basal
cerebral fasciculus. He says:(') ‘‘ Diese commissur kommt
in allen Tierklassen vor, is aber bis jetzt nur einmal, von
Osborn gesehen worden, bei Reptilien. Mit der Commis-
sura anterior (com. interlobularis, autt.) darf sie nicht ver-
wechselt werden, sie liegt weiter hintern und gehort bereits
der Zwischenhirn an. Es ist mir fraglieh ob sie eine Com-
missur oder eine Kreuzung einzelner Bundel darstellt.” The
commissure is of considerable size, and is closely associated
with the commissure of the radix mesalis.

The peduncles consist of three portions or bundles.

The basal cerebral fasciculus, the decussation of which is
above noticed, was seen in ganoids and described as forming
a part of the anterior commissure.(*) In the drum it is en-
tirely distinct from the lateral motor and sensory tracts (only
the latter was included in the description just referred to).
This decussation lies between the precommissura and the
decussation of the radix mesalis, and, after crossing, the fibres
may be traced some distance into the thalamus, passing on

1 EpINGER, Dr. L., ‘‘ Untersuchung. u. d. vergl. Anat. des Gehirns,” I; ‘‘ Das
Vorderhirn,”’ 1888.
2 Herrick, C. L., JouRNAL oF ComPpARATIVE NeEuROLOGY, Vol. I, p. 169.

Herrick, Morphology of Brain of Bony Fishes. 357

its way the dense nidulus of multipolar cells which is so con-
spicuous a feature of the ventricular aspect of the thalamus.

The ventro-mesal portion of the peduncles proper seems
to have a different course, both in the cerebrum and the
thalamus, from the dorso-lateral portion. The former pass
cephalad and mesad and give rise to the thin disperse tract
which separates the lateral from the central lobe. Many of
its fibres cross in the callosum. The latter forms the con-
spicuous peduncular tract occupying the posterior part of the
central lobe. Its fibres appear to supply the dorsal and
caudal parts of the axial lobe.

PIA OX XV.

Horizontal longitudinal sections through the entire brain of the
drum, Haflotdonotus. Those parts especially referred to in this instal-
ment are, for the most part, named on the plate. The left side is ata
slightly more ventral level than the right.

Fig. 1. Section through the olfactory lobes and corpus fornicis.
The radix lateralis is easily followed throughout its entire length from
the lateral aspect of the pero to the hippocampal lobe. The radix
mesalis arises in the pes, and, curving ventrad and then dorsad, appears
cepalo-ventrad of the axial commissure as a circular bundle.

Fig. 2. Section at the level of the axial commissure (see text) and
callosum.

Fig. 3. Section above the level of the preecommissura, whose tracts
are nevertheless seen in the section. The index letters indicate regions
from which the detailed drawings of histology were taken as given on
Plate XXV.

Fig. 4. Section near the dorsal surface of the cerebrum. The
figure illustrates the structure of the volvula and cerebellum. Compare
BiG 7 slate: XO

PLATE XXV.

Fig. 1. Highly magnified portion of the pero entad of the glom-
erules. There happen to be no instances of direct connection of cells
with glomerules in the field.

Fig. 2. Pyramidal kinesodic cells from central lobe (see Fig. 3,
Plate XXIV).

Fig. 3. Superficial part of lateral lobe to show epithelium. The
esthesodic cells of that region are cut transversely.

Fig. 4. Peculiar cells in tract e, Plate XXIV.

Fig. 5. Portion of cuneus to show both sorts of flask cells. The
outermost properly are associated with the cells of the lateral lobe.

358 JouRNAL OF COMPARATIVE NEUROLOGY.

Fig. 6. Normal esthesodic cells of the parietal lobe.

Fig. 7. Wongitudinal perpendicular section through the entire
brain.

Fig. 8. Section just dorsad of the olfactory crus to show the course
of the fornix tracts and the callosum.

Fig. 9, Wongitudinal section of cerebrum somewhat dorsad of that
of Fig. 3, Plate XXIV.

EDITOR’S ANNOUNCEMENT.

The editor hoped to be able to announce in this number
the result of preparations now making for greatly improving
and extending the scope of this journal. Inasmuch as he is
about to be absent in Europe for some months, the place of
publication ad interim cannot be definitely announced, but
all correspondence should be directed to Granville, Ohio.
An extra number will be issued in January, 1892, and the -
regular March issue will perhaps be somewhat delayed. On
the other hand, our readers are assured that the volume will
be made more comprehensive and valuable than the present
one.

Among the articles for the ensuing year will be a de-
scriptive sketch of the neurological students and laboratories
of Europe, and the ‘‘ Development and Histology of the
Thalamus.”

The cooperation of the ablest specialists in Europe and
America is expected. The department of Comparative
Psychology will receive special attention.

After October, 1892, the JouRNAL will be issued regu-
larly from the University of Chicago.

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THE NEURASTHENIC -FACTOR IN THE DEVELOP-
MENT OF MENTAL DISEASE.

A. B. RicHarpson, M. D., Superintendent of the Columbus
Asylum for Insane.

To have an intelligent conception of the relation of nerve
exhaustion to the development of mental disorders it is neces-
sary to learn something of the manner in which the brain cells
receive their nutritive supply and how the products of their
physiological activity are removed. We will assume that the
cells of the cerebral cortex are the chief organs concerned in
the evolution of mental phenomena, and that a study of the
physical basis of mind is a study of these microscopic bodies,
their connections, supports, sources and methods of renewal and
the manner of their riddance of waste and deleterious products.
After these have been as fully investigated as the facts at hand
will permit, we will then be in position to investigate in what
manner they are disordered in the various stages of the develop-
ment of mental disease, and I have chosen the name which
heads this paper because I believe it wise to impress the fact
that these incipient changes are in every instance such as cause
errors in the nutrition of the cell elements and derange the nor-
mal balance between their supply of assimilative material, on
the one hand, and the demands made upon their stores of en-
ergy, on the other.

The histology of the cells of the cerebral cortex has been
carefully studied of recent years. Many useful facts have been
established, but much remains more or less uncertain. We
shall not attempt a review of this further than to describe their
relations to the other constituents of the cortex.

The brain cells of the cortex lie imbedded in a soft matrix
of delicate branching cells, composed of numerous branching
fibrils from a small central focus, which entwine in all directions
and form a most delicate cushion for the support of the more
highly developed brain cells. Their uses seem to be those of
support of these cells and possibly a share in their nutrition.

178 JOURNAL OF COMPARATIVE NEUROLOGY.

The brain cells, proper, are connected with the exterior and with
each other, by both direct and indirect methods. They have
two or more branching fibres or poles, through which their con-
nections are effected. Some of the cells have a basal process
which does not diminish in size and _ has in some instances been
connected directly with an axis cylinder of an efferent nerve
filament. The other processes diminish gradually in size by
subdivision until it is very difficult to trace them to their termin-
ation. They seem finally to form a delicate matrix of fibrils,
and many of the cells have no distinctive processes other than
those which form this matrix. From the aggregation of the
fibrils of this matrix on its ventral side larger fibres arise which
have been traced into the axis cylinder of other nerve fibres.
Whether or not this differenc2 in the connection of the brain
cells with the axis cylinders of the nerve fibres indicates a differ-
ent function in the two classes, is not well determined, but anal-
ogy would indicate that it does so, and it has been assumed that
the direct connection is with efferent nerve fibres and the indi-
rect with afferent fibres.

The blood vessels to the central cortex are exceedingly del-
icate in structure and are susceptible of great variation in
diameter. In the capillaries the various coats disappear, leaving
the endothelial lining alone, and this is quite delicate in struc-
ture.

The blood vessels lie in a lymph space, which is much larger
than the diameter of the vessel and is probably lined with a del-
icate membrane which closely invests the brain tissue. About
the brain cells there is a similar lymph space and these peri-vas-
cular and peri-cellular lymph spaces have been seen to be con-
nected by lymph tracts or clefts in the brain substance, which
thus afford a direct drainage of the cell surfaces into the great
lymph reservoirs between the membranes of the brain. Along
the course of the vessels and in the neighborhood of the cells,
most delicate and almost indiscoverable (in the normal state)
cells are found which are sometimes connected to the vessel and
reach out toward the cell elements. In pathological states these
become much more visible, increase {in size, are more readily
stained, and become filled with the products of cell degenera-
tion,

RICHARDSON, /Vewrasthenic Factor in Mental Disease. 179

These anatomical data will enable us better to understand
the pathological changes which are found in incipient mental
disorders and to note the connection which they have with the
problem of nutrition. Still beyond our vision lies the field in
which the connection is made between mind activities and the
brain elements, and the seeming impossibility of the solution of
this problem has necessitated the introduction of theory in the
treatment of the subject of mind disorder; but theory is often
admissable as a basis for guidance in therapeusis or prophylaxis
and for such purposes we shall not hesitate to use it when full
investigation partly fails.

The primary steps in the development of mind disorders
would seem to be dependent upon the following anatomical,
physiological and pathological data: (1). The capacity of the
cell elements of the cerebral cortex to assimilate nutritive mate-
rial varies in different types of cells as found in different organ-
isms, and in some is defective. (2). That susceptibility of these
cells to impressions, which gives them their functional power, is
possessed by different types in varying degree and in some is
excessive and out of proportion to the assimilative capacity of
the same cells, in others is deficient. (3). That delicate poise
of functional power in the brain cell, which, on the one’ hand,
enables it to react to impressions, and on the other gives it the
power to restrain, inhibit and direct the results of these impres-
sions, is possessed by different types of cells in varying degree.
When deficient in delicacy it results in defective capacity and
the nutritional errors which are due to inactivity. When the
normal power of reaction is present but the power to inhibit and
direct is deficient, excessive reaction, and particularly such as is
disproportionate to the supply of nutritive material assimilated
by the cells, leads to serious cell degeneration.

It is only by some such terms as these that we can intelli-
gently explain in physiological language the transmitted, congeni-
tal or acquired tendency toward mental derangement. The want
of balance in the brain cell between its capacity and opportunt-
ty to assimilate nutritive supplies, on the one hand, and its sus-
ceptibility to impressions and its power to exercise inhibitory
control of its energy, on the other, is handed down from defect-

180 JoURNAL OF COMPARATIVE NEUROLOGY.

ive parentage, is the accompaniment of arrested development,
or is the penalty left by previous disease.

As the result of the first of these causes, to-wit, the capacity
of the cell to assimilate nourishment, some types of cells have a
very limited functional capacity, within the limits of safety, and
slight power of resistance. They are easily overworked and
their possessors constitute oftentimes the mental invalids which
abound to enliven the tedium of the busy practitioner. Still
other types of cells are essentially short-lived, coming early to
maturity, possessing their maximum of functional power for a
comparatively short period, and soon falling into decay and the
degeneracy of premature old age Hysteria is an excellent ex-
ample of a form of mental disorder due to the third class of cell
defects, and has its origin in defective inhibitory control of cell
energy. That recovery from mental disease is so seldom satis-
factory, and the tendency toward recurrence after one attack is
so great, is due to the changed nutrition of the brain cells and
their diminished capacity to assimilate nourishment. It is to be
borne in mind also that the large lymph spaces around the
blood vessels of the brain and about the brain cells, and the con-
nection seen between these in some cases, at least, indicate the
importance which we must attach to the rapid elimination of
waste products from contact with the cellular elements. The
products of cell metabolism are extremely inimical to the normal
activity of the cells, and their toxic effects upon the system have
been fully established.

To understand more clearly cell nutrition and cell energy
and their delicate adjustment and interdependence, we must re-
member that there is an extreme susceptibility in these carrying
blood vessels, to stimulation from the activity of the cells them-
selves, and that their calibre and the supply of material which
they convey, vary with the slightest variation of cell activity, or
their stimulation from the exterior. With this varying calibre
and the consequent changes in the blood pressure come the
modifications in the relation which the nutritive supply bears to
the activity of the cell. There is a genuine hyperaemia of the
brain cortex during its period of activity, which seems essential
to the rapid evolution of energy, and during which both the
amount of nourishment consumed and of waste products pro-

RiIcHARDSON, JVeurasthenie Factor tn Mental Disease. 181

duced are increased. During the periods of quiescence in cell
activity, the blood pressure is diminished, the amount of nour-
ishment sent to cells is lessened and the waste products dimin-
ished, yet it 1s then that the ‘cells store up energy because their
activity is almost nil and the balance is far on the credit side of
the account.

Reasoning from these data, then, we see that the incipient
variations in cell nutrition and consequent mental derangement,
come from two sources, the first those that diminish the amount
of material assimilated by the cell, the second, those that in-
crease the demands made upon it. ‘The first of these may be
induced indirectly by a diminution in the amount of the blood
or a deterioration in its quality. In such states there is an
anaemia of the brain cell, in some cases, and, in others, a passive
hyperaemia, the result of a want of proper tonic in the vessels.
Much oftener, however, the diminution in the nutritive supply
depends upon a genuine hyperaemia of the cortex. The in-
creased pressure of this, which is either excessive in degree or
continued beyond the normal limit, prevents the healthy transfer
of nutritive material through the vessel walls. The cause of
this abnormal hyperaemia is usually the over stimulation of the
cells themselves. This of itself endangers the safety of the cells
by increasing their requirements for nourishment. It is impos-
sible to separate the effects of these two causes. Overstimula-
tion of the cells accompanies the thousands of exciting causes
of mental disorder. None, however, is more effective in its pro-
duction than worry. Whatever may be its origin this induces a
rapid destruction of tissue in the cerebral cortex. There is a
prolongation of the normal hyperaemia, and an inability of the
vessels to contract upon their contents with the normal diminu-
tion in their stimulation, due to exhaustion and paresis of their
nervous control. It is not difficult for any one to test this in
himself. Apply yourself to intellectual work which is felt to be
a strain on you and continue this to an hour beyond that usual
for your retirement. You will notice how difficult you will find
it to settle your brain for repose, and how long before re-
freshing slumber comes to your relief. Worry acts in a similar
manner and we have all felt its disquieting influence, lying
awake hour after hour in a vain attempt to calm the restless ac-

182 JOURNAL OF COMPARATIVE NEUROLOGY.

tivity of our thoughts. There is an irritability of the nervous
tissue which is the product of exhaustion and an evidence of
its defective nutrition, or what is equivalent, of its overstimula-
tion. ‘This irritability simply means weakened inhibition, which
is as surely a sign of exhaustion as is the want of the power to react
to animpression. Repetition of this prolonged hyperaemia leads
to its easier production. The nutrition of the cells soon becomes
permanently modified. They energize differently. The vessel
walls become permanently distended. They are not equally
strong at all points and aneurismal dilations or pouches form
along their course. Obstruction results to the blood current.
Nutrition is more greatly impaired. The contents of the vessels
transude through their walls under the increased pressure and
block up the peri-vascular lymph spaces. The changes in the
vessel walls also favor this. The flow of the waste products is
obstructed and the cells become bathed in the products of
their own metabolism. The toxic effect of these still fur-
ther deranges their functional activity. Permanent degen-
eration of the cells soon ensues. They change in form,
their prolongations become rounded off, their interior becomes
granular, or is filled with fat globules. The delicate plexus
from which springs the afferent nerve fibrils is permanently
damaged. The scavenger cells become enlarged, more visible
and filled with the products of cell degeneration. Finally the
entire cell is removed or so disorganized that its distinctive fea-
tures entirely disappears. These changes are seen in exag-
gerated degree in such forms of mental disorders as paretic
dementia, in which the nutritive changes and consequent loss of
power are rapid and marked.

Bear in mind that in all these cases the incipient change,
the first step in the degenerative process, 1s a simple error in cell
nutritive,an interference with the opportunity to secure sufficient
nourishment and a demand for more energy than the supply
given will produce. When the problem is in its simplest form
its solution should be comparatively easy, let it become complex
through the lapse of time and its solution is no longer possible.
when the vessel walls become changed in character or even
dilated permanently, the recuperation is slow and does not
always advance with the improvement in the general condition

RICHARDSON, LVewrasthenic Factor in Mental Disease. 183

of the patient. The nutritive error in the cell elements of the
brain often continues long after the general condition has im-
proved. I know of no other form of disease in which such
patient perseverance in well doing is necessary.

The treatment of such nutritional errors is a complex sub-
ject. It will require every resource of the physician and tax
his ingenuity to the utmost. Itis by no means restricted to the use
of medicinal agents. The first requisite is a sufficient supply ofas-
similative material of good quality as represented in healthy blood.
The second is to secure the opportunity of the brain cells to receive
this by a correction of the hyperaemia, obstruction or degener-
ation which has prevented it reaching them. ‘The third is to
diminish the demands upon the cells so that their work shall
NOLMDe yin) excess: ‘on ther) Tecuperative’ power, | “Ihe
fourth is to secure the prompt removal oft their waste
products by clearing the channel of the lymph spaces of the
debris which has come from the obstruction of the blood cur- -
rent. The fifth is to divert the functional activity of the cells
from the directions in which it is defective, and to develop new
functional tendencies, new habits of action, if such they may be
called, to the end that the healthy balance may be re-estab-
lished. We are required to repair their diminished inhibitory
control and to stimulate them to activity where disuse has led
to disorder,

We have not space to go further into details, but it may be
said, in general terms, that medicinal agents are not so potent as
the regulation of functional activity in the cell elements.

NERVE HYGIENE!

By Dr. AuGcustus FOREL.

Professor of Psychiatry in Zurich.

‘¢'Too many nerves and too little nerve,” complains Pro-
fessor von Krafft Ebing of our generation. What do they mean,
fo mMenVies:: ‘‘nervous prostration,”’ seurasthenia,
and similar terms ?

We must first clear away a common mistake, as if all this
had reference to the nerves of the skin or of various parts of
the body. It is no more these that are ‘‘ nervous” than the
fingers of an amputated arm which cause the pain that the
former possessor of the arm imagines he feels there. Arm and
fingers dissappeared long ago, were buried after amputation and
are now decayed, and yet there is a sensation of pain as if they
were still present, the seat of the disease.

It is nothing but the brain that is ‘‘nervous.” We make
the mistake of attributing its excitement to the so-called sensory
nerves of the body, because usually they convey to the brain
the impressions of the external world, such as light, warmth,
sensation of touch, sound and odors. It is the brain alone that
occasions the sprawl, the convulsive twichings of the nervous
woman, the deceptive senses of the victim of delirium tremens,
the evil conduct of a drunken man, the great deeds of the ge-
nius, the indolence of the man who hangs around the saloon,
the folly and the pain of insanity, the misdeeds of the criminal
and the industry of the sober laborer.

In health, in the sound working capacity of the brain, les
the chief condition for happiness. Professor Hiltz is certainly
right who believes that the happiness of an individual depends

rp)

‘* nervous,

I. No apology is necessary for reproducing, in connection with the thoughtful
article by Dr. Richardson, whose eminence as an alienist will command attention
for what he writes, the above selection from the pen of one of the greatest psychi-
atrists of Europe. The subject, which is awakening remarkable interest on the con-
tinent, has hardly yet attracted merited attention here. Our obligations are to Mary
G, Stuckenberg, whose translation (with slight modification) we borrow.

Fore., Verve Hygiene. 185

upon his fulfilling the purpose of his life by labor. But since
man’s labor is not accomplished like that of the plant and the
lowest worm, for he applies a higher understanding and feeling
to it, the fundamental possibility of happiness for him lies in a
sound brain.

How are you going to convert a sound brain into a happy
spirit, disposition and will, and keep them up? By continually
patching at an impaired organ with medicines and cures in nerve
or lunatic asylums? Such patchwork is good, or perhaps a ne-
cessity, if injury has already taken place, or has become great.
But always the best prescription is prevention, in general, that
one which any reasonable person can apply without either phy-
sician or apothecary.

Would you, by means of poisonous stimulants, urge the in-
capable modern brain to some unusual activity, which neces-
sarily must exhaust and incapacitate still more ? That would be
putting out a fire with petroleum. Yet it is just what we are
doing when we use alcoholic drinks, morphine and similar so-
called nerve tonics. We injure the organ we desire to strength-
en and wear it out prematurely. We see the fruits of alcohol-
drinking in the saloon and in large part in the nervousness of
our age. We see them in the prisons, the lunatic asylums, the
idiots, the vagabonds, the idlers—consequences that are only
partly the result of the drinking customs of these people them-
selves, those of their forefathers bear part of the blame.

Of course the use of alcohol is not the only occasion of the
‘- nervousness’ of our age. There are others, such as poverty,
over-population of the cities, insufficient nourishment, but espe-
cially the unsuitable, the thoughtless marriages of stupid, eccen-
tric or evil people, whose defective brain peculiarities perpetu-
ate themselves in their posterity and contaminate society with
incapable, lazy, untruthful, immorally inclined, in brief, with
individuals that are a menace to the general good.

How ought and can we oppose these evils, successfully
Overcome our nervousness, and grow happier? That riches
cannot make us either healthy or happy, that poverty occasions
unhappiness and disease, has been so clearly shown that we
need lose no words upon this subject. It stands approved by
experience that nerves and muscles which remain inactive lose

186 JOURNAL OF COMPARATIVE NEUROLOGY.

strength and shrink; and just so the brain needs exercise, and
in fact, earnest, hard labor, but not too one-sided, in order to
become and remain strong and healthy. Over-weariness and
aver-exertion, however, injure the brain as they injure muscles
and nerves. ‘To furnish power and working capacity, the mus-
cles and nerves require a sufficient amount of such nourishment
as will produce matter and force ; but over-feeding is an injury.
It is just so with the brain.

Sleep is the indispensable rest of the brain during which it
recovers the substance lost by the wear of the day and gathers
up strength. Good sleep is the fundamental requirement for
brain health. Every nerve stimulant, and on the other hand all
substances that produce artificial sleep, are nerve poisons and
are to be condemned by a healthy nerve hygiene. The worst-
foes of the human brain are alcohol, morphia, ether, cocaine,
and the like. Their use is never justified except very temporar-
ily as medicine, or in order to allay the pain and the agony of
death in a fatal illness.

Every one who desires to secure and to strengthen a healthy
and useful brain, must really labor, and that daily, and not too
little. Four hours of work a day fora healthy being is alto-
gether too little. Let any one spend his time in enjoyment and
idleness, and enjoyment soon ceases to be enjoyment. He will
accumulate artificial wants in ever increasing numbers until
they burden his life. He will become more and more depend
ent and morose. His mental horizon will grow narrower con
tinually and more rigid. The plastic brain of youth, that is, its
docility and adaptability, will become less and less active and
capable of comprehending and elaborating new thoughts.

On the other hand, mental labor preserves the plasticity of
the brain to a much more advanced age. Idlers, theretore, in
spite of the best brain capacity, become prematurely old men-
tally, narrow-hearted, limited in horizon, and not seldom abso-
lutely stupid. We often observe moderately gifted students be.
coming, by means of work, men of power, and highly gifted
young men, as a result of idleness, gradually grow useless,
peevish, and now and then narrow-minded Philistines.

Secondly, one must not overwork. The work day must

Fore., Verve Hygiene. 187

not be prolonged into the night. One ought not to continue to
labor with an exhausted, harrassed mind.

Thirdly, it is necessary to take sufficient nourishment, but
must partake of farinaceous food, the
fats and albumen in proper proportions

Fourthly, eight hours of sleep are a necessity, and above all
one must not retire too late. There must Le no excesses of any
kind.

Fifthly, all alcoholic drinks as well as all artificial producers
of sleep and nerve stimulants must be absolutely avoided, as a
matter of principle. Resolutely and bravely turn the back upon
all places of tippling and seek the society of total abstainers,
for to them belongs the future. Those people who wholly ab-
stain from alcohol and the other things mentioned are more ca-
pable of work, healthier, happier and live longer. They do not
endanger their posterity, run no risk of picking up some vener-
. eal disease in a state of intoxication. * * * Poverty and
social enslavement are also the daughters of alcohol and the
mothers of nervousness and of brain stupefaction.

But nervous people and those who have weak nerves ought
especially to regulate their lives according to these principles.
Often they are cured by this means alone, without a physician,
without drugs. Of course, however, since in their case the
brain is already enfeebled, they are in need of a different pre-
scription; they will be obliged to engage very moderately in
mental labor, in fact, not at all until there is improvement,
meanwhile exercising the muscles in order indirectly to provide
the brain with power substance. The best means of all is ordi-
nary labor on a farm, on generous, nourishing diet, and water.
This method of cure I have prescribed for distinguished pa-
tients, ladies as well as gentlemen, which met with the very best
success.

But thus far we have as yet done nothing to invigorate and
improve the brain of our posterity. To take thought for that is
certainly beautiful and important, although most people are too
crass, egotistic or thoughtless to take practical interest. But in
many cases only ignorance is the cause of criminal neglect of
the subject. It is to the latter we address ourselves.

It. is criminal towards posterity to bring forth children

one must not overeat

188 JOURNAL OF COMPARATIVE NEUROLOGY.

thoughtlessly or without taking counsel with conscience. The
tendency to crime is transmitted, stupidity is transmitted, men-
tal aberration is transmitted, malice is transmitted, indolence is
transmitted, selfishness is transmitted; but, on the other hand
goodness is hereditary, industry is hereditary, mental and physical
health are hereditary, conscience and disposition are hereditary,
intelligence is hereditary. Training and the experiences of life
may more or less develop or arrest the hereditary disposition, but
they can never produce or destroy them. Alcohol destroys the
gifts of nature in the embryo of the brain, injures all of them
and never can improve one iota.

When the love of a man and a woman for each other
awakes a desire to become united for life, they ought never to
forget that they are undertaking a very grave responsibility, the
responsibility for their future children. They ought to re-
nounce marriage rather than to produce physical, or what is
much worse, mental cripples. Unfortunately, however, we see
noble people with highly gifted natures who carry their pru-
dence to so anxious an extreme as not to marry, or at least not
to bring forth offspring, while the most frivolous, brutal and
stupid, under the protection of lax laws that had their origin in
a mistaken humanity, multiply like rabbits and carelessly aban-
don their progeny to the state or to public philanthropy—pro-
geny made more hable to danger by reason of previous alco-
holic excesses.

And with such false political economy, such mistaken
breeding, is it any wonder this increase in the number of men-
tally diseased, of lunatic asylums, of a weak-eyed proletariat, of
morally defective vagabonds and criminals? There is talk of
overwork as the occasion of these evils, overlooking the fact
that this proletariat mentally never has overworked, but rather
has been indolent and useless always. ‘‘ Nervousness,”’ really
brought about by means of mental overwork, forms only a
small and comparatively safe fraction, while the great, innumer-
able company of mental wrecks nearly always owe their catas-
trophe to diseased or defective brain conditions, to excesses, and
in enormous percentage, to alcohol.

It is therefore a duty to consider hereditary conditions.
Every respectable woman ought to look for solidity, soberness,

ForEL, Verve Hygiene. 189

good sense and a good disposition, as she chooses a bridegroom.
The capable young man ought to have a care not to marry a
money-bag, or a hysterical siren, or a body without a soul, but a
sensible, modest, industrious, respectable and intelligent young
woman.

Meanwhile, let the able-bodied and sound of brain not be
affected by any silly, pessimistic philosophy, but seek each other
in love and in marriage, bring forth children without careful re-
gard of money, for, with the right choice in marriage, good for-
tune will not fail them.

But what shall we do with the others, with the eccentric,
stupid, wicked, defective? This is a question as difficult as it
is critical. They should be prevented from multiplying them-
selves, for they will only bring forth mental cripples, unhappi-
ness for themselves and for their children. They bring forth
unfortunates who will afterwards execrate their parents. One
simple and safe counsel that ought, however, to reach the good
as well as the evil, the highest genius as well as the dullard,
would prevent much evil. Renounce forever all those system-
atically stupefying, brutalizing and demoralizing factors of hu-
man misery—the alcoholic drinks, and also the so-called ‘‘ en-
joyment” of narcotics. Flee the perilous counsel of the pessi-
mists, who cry: ‘‘ After us the deluge.” That flood of men-
tal disaster which these very people, so heartless and selfish,
inflict upon their descendants may overtake themselve before
death reaches them; for selfishness brings forth misery ; love,
happiness.

LOCALIZATION Iv THE CAT

By Cl HERRICK

An operation, performed in connection with Mr. E. G.
Stanley, which it is hoped to describe in full in a subsequent
issue, perhaps deserves notice on account of its suggestiveness
upon points raised in Munk’s last paper in the Proceedings of
the Berlin Academy. 1!

Munk states that in the dog and monkey the region for the
extremities is concerned with the formation of tactile and press-
ure sensations and perceptions of the limbs of the opposite side.
The tactile reflex is also located in this region and 1s completely
lost when it is extirpated. In addition to this, this region is at
least chiefly responsible for the pain sensations of the members;
pain is dependent for its perception up to a certain degree of in-
tensity on this region, and complete extirpation of the region
nearly destroys the sense of pain which may gradually be gained
by substitution of other regions. Again, there is a connection
between the cortical centre and the reflex centre for the limbs,
and that which inhibits the reflexes.

After removal of these areas the animal moves awkwardly,
lifting the feet too high or too little, placing them irregularly so
that the feet double under. ‘There is a tendency for the feet to
slip laterally from the body permitting the body to fall toward
the side opposite the operation. ‘These irregularities disappear,
so far as superficial observation goes, completely.

The feet corresponding to the operation lose their respon-
siveness to slight tactile irritation. When a strong pressure is
brought to bear there is reflex response, z. e. movement of the
limb, but no evidence of sensation, as is proven by the fact that
the head is not turned toward the irritated member as it is to-
ward any other.

1. Ueber die Fuehlspheren der Grosshirnrinde. Mittheilungen aus den Sitz-
ungsb. d. Koenigl. Preus. Akad. der Wissenschaften zu Berlin. July, 1892.

HERRICK, Localization in the Cat. IgI

Bechterew’s mistake,‘according to Munk, is in not remov-
ing the entire region, enough of the cortex remaining to explain
the evidence of sensation.brought forward by the former.

Munk “distinguishes between tactile reflex and general re-
flex. The former is completely lost, the latter reduced, but sub-
sequently regained. He seeks to explain a part of the phenom-
ena supposed by Goltz to be due to the repressive effect of irri-
tative processes as the result of isolation.

Our subject was a half-grown kitten, and portions were re-
moved from the left hemisphere in three successive operations,
so that a long, narrow area extending from the crucial?sulcus to the
limits of the middle external gyrus caudad, and including nearly
the whole of that gyrus, was extirpated. The entire thickness of
the cortex and most of the white matter was removed. ‘The first
operation was apparently near the front of Munk’s visual sphere
and the kitten showed jsome disturbance of vision in the op-
posite eye, but, though the incision was subsequently carried
further caudad, these symptoms did not reappear. After the
last operation, which invaded the fore-leg area of Munk, there
was decided disturbance of the motor and sensory functions for
both limbs. The skin sensation and reaction against pain was
reduced immediately after the operation, but these disturbances
soon disappeared. The voluntary motion was but little dis-
turbed but the fore foot tended constantly to double under and
trip up and slipped helplessly away from the line of support.
The hind leg was similarly affected, sliding laterad and failing to
support the body. In walking and running no imperfection was
noticeable, except when obstacles or changes in the direction of
motion called out what has been described. Most noticeable of
all was the change in tie position of the limb when permitted to
hang free. If the body were supported upon the ventral aspect
the left legs were drawn up and quickly responded to any tend-
ency to fall in that direction, while the right legs hung pendant
and failed to react against a push threatening a fall to the right.
The kitten was watched four or five weeks, during which time
nearly all symptoms disappeared except those last mentioned,
which remained to a certain extent to the last. Another curious
effect of the operation was a strong tendency, for some time
after the extirpation, to shake the feet of the right side (rarely

192 JOURNAL OF COMPARATIVE NEUROLOGY.

the left hind foot in sympathy), as if they were wet or otherwise
irritated. The shaking was apparently a reflex and was at times
almost convulsively violent. It is to be compared with the
scratching reflex described by Goltz.

In contradistinction to Munk, therefore, we find loss of
muscular sense a more important and permanent feature than
tactile or pressure disturbance, though the extirpated area ex-
tended further caudad than in his experiments. It must be ob-
served that the area we removed lies farther from the median
line than that operated on by Munk and affected directly only
his fore limb area, though the depth of the excised portion sug-
gests the possibility of an injury of other tracts.

We are confident, moreover, that many of the contradictory
results of experiment are due to proliferating regenerations
which supply the lost material in the case of young animals.

A SIMPLE ALCOHOL FORMULA.

Students frequently experience difficulty in recalling the
proportions in which water should be added to alcohol of vari-
ous grades to prepare the stock solutions for hardening grada-
tim. The formula given in our guides are singularly and ab-
surdly complicated. The following may be suggested: Take
as many parts of the alcohol given as the percentage required ;
add as many parts of water as the difference between the given
and the required percentages.

Example. Given 70 per cent. alcohol to make 4o per cent.
Take 40 parts alcohol of 70 per cent. and (7o—40) 30 parts water.

LITERARY NOTICES.

HISTOGENESIS AND COMBINATION OF NERVOUS ELEMENTSs.(?)

At the time of its separation, the medullary plate consists of a single-
layered epithelium. The cells scon begin to vary, some enlarging at the
peripheral portion and others entad. The nuclei in each case move to-
ward the larger end of the cell and thus form two or more rows, though
remaining nearer the middle than the ends of the cells.

The body of the cells soon differentiates into a transparent fluid or
gelatinous substance and a more dense granular or striated portion.
Usually the first step in this differentiation is the formation of vacuoles
which, as they increase in size, tend to coalesce.

The denser reticular portion accumulates in the peripheral portion of
the cells. Thus, briefly stated, the original epithelium cells form a
frame-work, which His calls the myelo- or neuro-spongium, the indi-
vidual cells being spongioblasts. The nucleated bodies of the spongio-
blasts form a broad median zone, while the outer and inner margins are
devoid of cells. The inner or co/umnar zone consists of longitudinally
striate columns, which expand at the inner surface to form a continuous
marginal layer. ‘The outer marginal or mantle zone (randschleier) con-
sists of a reticulum of fibres which is penetrated by radiating pillars
expanding at the periphery.

The nervous elements appear at an early stage in spaces between the
ventricular part of the epithelium cells in the form of germinal cells of
uncertain origin. ‘The number varies with the stage of development,
being especially abundant at the time of the appearance of the first
nerve roots. The period of maximum development also varies with the
locality, being earlier in the cervical than the cerebral or lumbar regions.
The number diminishes gradually and this reduction takes place earlier
in the ventral than the dorsal half of the medullary plate.

These germinal cells at a definite time begin to change their form,
becoming acute peripherally, until they give rise to a more or less
thread-like process, which becomes the nerve fibre, connected at its base

1 Wo. His, Histogenese und Zusammenhang der Nerven-elemente. Referat in
der anatomischen Section des internationalen medicinischen Congresses zu Berlin.- Sitz-
ung von 7 August, 1890. Archiv. f. Anat. u. Phys., 1890. Supplement-Band. p, 95.

il JouRNAL oF CoMPARATIVE NEUROLOGY.

by a conical cap of protoplasm with the nucleus of the cell or neuro-
blast.

During the period of transition when the germinal cells are being
transformed into neuroblasts, they are motile. In the first place, they
move ectad between the cells of the columnar zone, but find a hinder-
ance to their farther migration in the mantle zone. Along this contact
line the neuroblasts assemble, forming a mantle layer, of which the
dorsal and ventral portions react dissimilarly. The cells of the dorsal
half, because of the oblique position of the epithelial frame-work, strike
the mantle zone at an angle and turn parallel to the surface. Their
fibres describe long curves ventrad and, in part, reach the median line.

The cells of the ventral region on the other hand impinge more or
less perpendicularly upon the mantle layer and, though the cells do not
penetrate it but collect in clusters, the fibres make their way through
this zone and pass out as motor nerve fibres.

The migration of neuroblasts is especially extensive in the medulla.
The thick lateral walls of the tube here are divided by a groove into
a dorsal plate or ala and a ventral half or basal plate. In the latter the
groups of neuroblasts form the motor niduli of the hypoglossus,
accessory, vagus, and glossopharyngeal. On the lateral margin between
the ala and basal plates lies the tractus solitar‘us containing the
sensory fibres from the vagus and glossopharyngeus. The margins of
the alz fold outward and the two lips of the fold grew together. From
this evaginated portion there arise multitudes of neuroblasts which pass
medianly entad from the ¢ractus solitarius to near the median line.
Out of the clusters thus derived arise the olives and accessory olives,
the fibres from which cross the median line within the raphe. Blood
vessels enter the walls of the medullary tube at an early period but it is
not until a much later period that ameboid cells transude into the neu-
roglia and lodge in its meshes. These connective or wandering cells
constitute the third element of the complex.

The neuroblasts of the medullary plate produce intramedullary
fibres as well as motor nerve roots. The sensory roots spring from the
spinal ganglia, the cells of which assume a bipolar form and extend
into two fibres, one passing centrad, the other peripherad. The central
processes collect at first upon the exterior of the medullary tube
in special longitudinal fasciculi which, in the cord, form the primary
posterior fasciculus, and in the brain constitute the ascending roots (as
the ascending root of the trigeminus and the tractus solitarius, or com-
mon ascending root of the glossopharyngeal and vagus).

The origin of the spinal ganglia, though long controverted, is doubt-
less from that portion of the ectoderm connecting the medullary plate
with the definitive ectoderm where a groove-like depression with num-
erous germinative cells forms as the medullary tube separates. These
cells are originally motile and multiply by division until they reach their
ultimate site.

—e

LITERARY NOTICES. il

The sympathetic ganglia arise much later than the spinal (at the be-
ginning of the second month in man). The thick stem of a spinal
nerve divides where it comes in contact with the dorsal margin of the
celom, giving off a visceral branch, some fibres of which reach the
aorta, while others turn longitudinally, there being no sympathetic cord
or ganglia at this stage. Onody(') considers that the sympathetic
ganglion originates as an outgrowth from the ventral portion of the
spinal ganglia. He believes that undifferentiated motile elements
wander out of the spinal ganglia and transform themselves into sympa-
thelic ganglion cells. The lateral sympathetic ganglia are, in their
turn, points of origin for the visceral ganglia.(?)

His has shown in earlier papers that the olfactory grows from
an external ganglion into the brain as do other sensory nerves.
The olfactory ganglion adheres secondarily to the olfactory bulb.
In all probability, its cells are derived trom the epithelium of the
olfactory region of the nasal cavity.

The origin of the eighth fibres is to be sought in the bipolar
ganglion cells of the ganglia vestibuli and cochlex, and of gustatory
fibres in the ganglion cells of the glossopharyngeus.

In the case of the optic nerve the relations are more complicated.
From the investigations of Ramon y Cajal it appears that its stalk con-
tains fibres springing from the central as well as the peripheral region.

The neuroblasts of the retina spring from germinative cells which
develop near the ventricular surface. The granular layer corresponds
to the mantle zone of the medullary plate.

It appears, therefore, that in the development of the nervous system
and sensory organs two forms of cells are differentiated at a very early
period—the germinative and epithelial cells. One furnishes the specific
elements, the other the frame-work.

In general, every nerve fibre springs from a single cell. Until the
recent observations of Golgi it was supposed that the nervous process of
a cell was always unbranched, but Golgi has shown that not only is the
axis cylinder provided with processes, but in cells of the second type the
axis cylinder divides into a complete mesh-work. Thus the distinction
between axis cylinder and other processes of the cell disappears. Yet
embryology shows that the former is very distinct from all others in be-
ing the first, and for a long time, the only process. The nerve cells de-
velop much later in the brain than in the cord.

The nervous processes continue to grow perhaps for months, and
when the blunt end reaches its ultimate terminus it usually divides
dichotomously into a cluster of fibrils. In Pacini’s and Krause’s cor-
puscles we have instances where, instead of dividing, the terminus forms
an endothelial capsule with soft contents. In another form of end organ,

rt Cf. A. M. Parerson. On the Development of the Sympathetic System. Philos.
Trans., 1890, A. p. 159, as reviewed elsewhere in this number.
2 Arch, f. Anat. u. Entwickl,, 1885.

.

i
lV JOURNAL OF COMPARATIVE NEUROLOGY.

Graudry’s body, the nerve forms a flat disc-like plate. Those fibres
which extend to the epidermis pass to the epithelium and subdivide,
forming fine fibres lying free in intercellular spaces. In muscles the
nerve fibres penetrate the substance and end in the branching muscle
plate. In unstriped fibres the nerve fibres are said to extend to their
nuclei, while the connection between sensory nerve and specific cell
seems to be a sort of splicing by intimate contact not involving actual
continuity.

In respect to the fibres entering the central organ, the first clue was
given by the discovery of Cajal that the optic nerve fibres arising in the
retina terminate freely in the quadrigemina in the form of much
branched tufts. The sensory fibres entering the cord divide into an
ascending and descending branch, each of which sends collateral
off-shoots into the gray matter of the two cornua, where they generally
embrace a nerve cell in a mesh-work without uniting with its processes.

Cajal and Koelliker have shown that the protoplasmic processes of
medullated nerve fibres do not anastamose, but end in free stumps. In-
stead of the earlier notion of a nerve reticulum that of a neuropilem is
suggested. The gray substance contains in the meshes of its reticulum
innumerable termini of nerve fibres and protoplasmic processes, which
are imbedded in a diffuse stroma which must constitute the means
of communication. The reaction will necessarily pursue the path of
least resistance.

THE NERVOUS SYSTEM OF THE GORILLA.(?)

This beautiful quarto volume of 78 pages, with heliotype plates
of the nervous and vascular systems, is an important addition to the
rather meager anatomical data upon anthropoids. The following sum-
mary may serve to indicate the differences between the peripheral
nervous system of the gorilla and of man, as well as to afford a basis
for other comparisons.

1. The facralis of the gorilla is more complicated than that of
the chimpanzee, but less so than that of the orang or of man.

2. The glossopharyngeus of the left side forms a plexiform reticulum
and gives off anastamosing fibres to thé vagus and sympathetic, form-
ing nearly all the rami pharyngei. On the right side it anastamoses
with the hypoglossus and conveys to it fibres of the vagus and sympa-
thetic.

3. The vagus sends a depressor branch to the cardiac plexus from
either side. The internal branch of the right superior laryngeal is
divided, the upper part passing through the membrana thyrohyoidea,
the lower, in connection with the external branch, through a foramen
in the cartilage. The cardiac branch of the right side passes

1. ErsLer, Paut. Das Geffiss und periphere Nervensystem des Gorilla. Nine plates.
Halle a, S. Tausche und Grosse, 1890.

LirERARY NOTICES. Vv

through a trachealis plexus, but the left cardiac passes directly to the
heart.

4. The descending rami of the /yfoglossus contribute to the inner-
vation of the sterno-cleidomastoides muscle, while the ansa hypoglossi
are supplied solely from the first two cervicals.

5. The auricularis magnys and subcutaneus colli medius arise only
from C. II, theswpraclaviculares from C. II-IV.

6. The phrenic nerve of both sides contains indubitable sympa-
thetic fibres, and on the right it is directly connected with D. I and the
ganglion stellatum.

7. C. Vil on the right side for the most part and on the left ee
passes to the middle medianus root of the brachial plexus.

8. The suprascapularis arises from C.1V and V, instead of C. V
and VI, as in man.

9g. The dorsalis scapule is present only partially on the left side,
being replaced by C. III and IV (and for the M. rhomboides by D. III
and VI).

10. The axillaris springs from all the plexal nerves and contains
also the branch to the teres major.

11. There is no distinct swbclavius.

12. Cutaneus brachii internus is chiefly formed from a lateral branch
of D. I and the inter-costo-humeralis.

13. The musculocutaneus receives no fibres from C. VII and gives
off a branch to the coracobrachialis muscle.

14. The w/naris and medianus give a fine fibre to the brachialis:
artery. The ramus volaris profundus of the unar springs from a strong
anastamosis with the medianus, passing under the lig. carp. volare into
the hand.

15- The cutaneus brachii post. sup. of the radialis is wanting, its
place being taken by a descending branch of the axillaris.

16. The clunium superior and a subcostalis passes from D. XII
under the thirteenth rib.

17. The ¢leohypogastricus receives a branch from D. XII.

18. The genttocruralis bears fibres for the rami communicantes of
the sympathetic and the obturatorius.

19. The crurad’s receives most of its fibres from L. IV.

20. The feroneus springs from the posterior surface of the ischiatic
plexus, as also the clunium inferior, glutei, and pyriform nerves, while
the tibialis, cutaneus fem. post. and the nerves to the obturator internus
quadratus gemelli and flexors cruras spring from the anterior surface.

21. No fibres caudad to the second sacral enter the ischiatic plexus.

22. The pudendalis plexus is formed by the second and third sacrals,
while coccygeus plexus springs from S. IV and V.

23. The ¢/bialis and peroneus each give off to the knee an articular
branch with numerous Pacini’s bodies.

vl JOURNAL OF COMPARATIVE NEUROLOGY.

24. The feroneus profundus supplies the adjacent sides of the second
and third toes.

25. The plantares lateralis and medialis anastamose within the
adductor obliquus halucis, which both supply.

26. The flexor digitorum brevis is innervated from the plantaris
lateralis.

27. Three isolated cervical sympathetic ganglia besides the stellatum
are present.

28. The ganglion meseraicum medium, which is wanting in man,
lies between the cceliac plexus and the aorticus. Especial emphasis is
laid upon the great distinctness of parts in the lumbosacral plexus. The
analysis of this plexus has proven impossible in man, but in the present
case the several nerves may each be followed to the plexus, excluding
any doubt as to their origin. In this, as in the brachial plexus, a ventral
and dorsal portion may be distinguished. Thus a distinct advance is
made in settling the homologies of the limbs. In general only related
nerves can substitute for each other in the innervation of a given group
of muscles. Ventral muscles can only be supplied by ventral branches
of spinal nerves and vice versa.

THE ORIGIN AND CENTRAL COURSE OF THE EIGHTH NERVE.(*)

These observations are based on the study of sections stained by
Weigert’s method after destruction of the auditory organs from the cer-
vical aspect. In cases where the cochlea alone was injured there was
atrophy of the posterior root of the eighth, the anterior nidulus of the
acusticus and the tuberculum laterale. There was also a reduction in
the number of fibres in the corpus trapezoides and the upper olives.
Farther cephalad there was evidence of degeneration in the ventral
fillet of the opposite side, which could be traced as far as the arm of the
testes. The striz medullares were somewhat atrophied, enabling
Baginsky to trace their course as follows: Passing from the tuberculum
laterale of the medulla and in part from the anterior acusticus nidulus
they pass ectad to the restiforme, crossing dorsally to the median side
and there divide into two bundles, both of which pass to the upper olives,
though a few fibres enter the arcuate bundles. The decussation is com-
plete in the corpus trapezoides, as stated by Fleschsig. Serious opera-
tive difficulties stand in the way of the destruction of the anterior
branch of the eighth and in the experiments cited only partial success
was secured. The fibres from the anterior root lie upon the median sur-
face of the restiforme. Farther cephalad there appears another bundle
lying ventrad which arches ventrad, to be lost in the formatio reticularis.
Still a third tract from the same root radiates from the ventral aspect of

1 Ueber den Ursprung und den centralen Verlauf des Nervus acusticus des
Kaninchens und der Katze. B. BaGinsky. Math. u, naturwiss. Mitth., Berlin, Akad,

1889, VI., pp. 441-445-

LirERARY NOTICES. vil

the restiforme toward the walls of the fourth ventricle. The cells of
this region were in part atrophied.

A certain amount of atrophy appeared in the inner part of the crus
of the cerebellum, which did not however extend above one-third the
length of the anterior root of the eighth. Deiter’s nidulus sustains no
relationship to the acusticus.

THE DEVELOPMENT OF THE SYMPATHETIC SYSTEM.(?)

The cells of the ganglia of the sympathetic chain are shown by
Gaskell to be trophic simply. The gray rami communicantes spring
from the ganglia and are distributed as trophic fibres to the roots
of each spinal nerve and their meninges and the bodies of the vertebre.
The white ram? communicantes are only between the tenth and twenty-
fifth spinal nerves and in the rami of the second and third sacral nerves
(in the dog).

In the anterior region the white rami pass from the spinal nerves to
the ganglia and there separate into two groups; one set forms vaso-
motor fibres which are distributed peripherally as gray fibres, the other set
does not join the ganglia, but forms vicero-inhibitory fibres in the abdo-
men. The white rami of the posterior region pass to the hypogastric
plexus without joining the ganglia and form wervi erigentes (vaso-
inhibitory) and perhaps viscero-inhibitory fibres.

Patterson believes with Gaskell that the sympathetic is primarily
unsegmented. Two views prevail as to its origin. Onodi and Birdsell
consider it a distinct proliferation from the spinal ganglion, and Balfour.
from the spinal nerve (in either case ectodermal).

In mouse and rat embryos of about eight days the first indication of
the formation of the sympathetic cord has been found. The general
condition of development then corresponds to that of the chick at the
end of the third day. The spinal nerve has extended almost as far as
the somato-sphlanchnic angle, and to the cardinal vein in places where
the latter is present; and in some sections the superior primary division
is visible. A change is now apparent among the cells of the meso-
blast surrounding the aorta. In the interval between the latter and the
cardinal vein an irregular group of cells is seen on the ventral side
of the intercostal arteries. This mass is composed of cells which stain
more deeply; the nuclei are larger and they are more often multi-
nucleate than adjacent cells.

The mass is comparatively large cephalad, and tapers off and be-
comes indistinct caudad. There is no connection, fibrous or cellular,
with the spinal nerves or ganglia. Longitudinal sections show that
this mass is a long rod or column on either side the median line, con-
sisting of fusiform cells with ovoid nuclei and thread-like processes.

t A. M. Patrerson. Development of the Sympathetic System in Mammals,
Philosoph. Trans. Roy. Soc., Lond., 1890, pp. 159-186, g plates.

vill JOURNAL OF COMPARATIVE NEUROLOGY.

The column can be traced as far as the level of the mouth and caudad
as far as the Wolffian bodies, where it becomes connected with a mass
of mesoderm cells which form one portion of the supra-renal bodies.
_This rod is mesodermal in origin; it is formed 77 stu, and it is unseg-
mented and unc: nnected with the spinal nerves.

In rat embryos at about ten days cellular outgrowths from the cellu-
lar sympathetic cord can be traced ventrally round the aorta, especially
in the region of the kidney, and in front of it to form the collateral
ganglia, and to join the supra-renal bodies.

The superior (dorsal) primary division of the spinal nerve is not yet
differentiated into separate roots. The somatic part of the inferior,
(ventral) primary division has divided into its dorsal and ventral
branches. The sphlanchnic part is directed inwards above the card-
inal vein and reaches nearly to the sympathetic cord.

In mouse sections at eleven days the union between the sphlanchnic
branch and the sympathetic is complete.

In front of the fore limbs and behind the kidney no such connection
of the sphlanchnic branch with the sympathetic can be made out.

Up to the time of the formation of the vertebral centra there is no
gangliation or constriction of the main sympathetic cord.

The formation of ganglia is determined first, by the entrance of the
sphlanchnic nerves; second, by the position of the cord with reference to
the vertebral column.

The sphlanchnic branches correspond to the white ram communt-
cantes and are derived from both the dorsal and ventral roots of
the spinal cord.

‘The gray rami communicantes arise from the sympathetic cord as
cellular outgrowths, which find their way along the sphlanchnic branches
to their central connections.

THE EPIPHYSIS AND THE PARIETAL EyE.(*)

This discussion of the relation of the epiphysis to the so-called
parietal eye is timely and fills an important gap in our knowledge.
While anything like a complete construction of the facts presented
must await embryological investigation of these types, yet the observa-
tions are suggestive.

Mr. Ritter describes the parietal vesicle in Phyrosoma as lying
within the parietal foramen, though extending somewhat above the
parietal bone and firmly imbedded in connective tissue. The various
tissues above the parietal vesicle are all modified and the skin is unpig-
mented. A cord of connective tissue passes from the .end of the
epiphysis to the sheath of the vesicle, but no evidence could be secured
of their actual passage through the walls. The wall of the vesicle

« W. E. Rirtrer. The Parietal Eye in some Lizards from the Western United
States, Bulletin of the Museum of Comparative Zoology, Jan., 1891.

LITERARY NOTICES. 1x

is distinctly differentiated into lense and retinal portions, the line of
demarkation between them being distinct.

The epiphysis consists of a curved cylinder of a composite char-
acter, the greater portion consisting of plexiform epithelium. Distally
connected with the plexus is a vesicle which is composed of columnar
and, in some species, pigmented epithelium. The cavity of the vesicle
is stated not to be connected with infundibuliform proximal portion of
the epiphysis. Connective fibres pass from the vesicle to the parietal
organ. An immense blood sinus covers the epiphysis on the caudo-
dorsad aspect.

Ritter concludes that the parietal organ is a degenerate eye, though
having no nervous connection with the brain. He thinks, however, that
the epiphysis may have secondarily acquired some function in connec-
tion with the lymph system.

A very complete bibliography adds value to the paper.

BRAINS OF DINOSAURS.(?)

Two points in the paper quoted are of interest to neurologists;
first, the new evidence as to the former functional condition of the
pineal eye, and second, the primitive condition of the brain.

At the union of the squamosal and parietal bones there is a
median foramen which Marsh calls the ‘‘pineal foramen.” It is the
same as the opening termed parietal foramen by other writers. ‘‘In old
individuals it is nearly or quite closed. When open it leads into a large
sinus, extending above the brain case into the cavities of the horn-cores.
This foramen has not before been observed in Dinosaurs.”

“The brain of 7'réceratops appears to have been smaller in propor-
tion to the entire skull than in any known vertebrate. The position of
the brain in the skull does not correspond to the axis of the latter, the
front being elevated at an angle of about thirty degrees. The brain-
case is well ossified in front, and in old animals there is a strong septum
separating the olfactory lobes.”

Even when compared with stegosaurus the brain seems of a low
type. The hemispheres are practically absent. An enormous fossa for
the reception of the hypophysis and a great development of the optic,
trigeminal and other cranial nerves are characteristics shown by
the casts.

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xix

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LITERARY NOTICES.

THE Tropuic FUNCTION OF NERVES.

It is to be feared that teachers and investigators are prone to greatly
underestimate or ignore those functions of centrifugal nerves which fail
to express themselves in actual muscular contraction. Such acts as
perspiration, weeping and congestion are obviously under the control of
the nerves, and as long ago as 1854 Virchow claimed that fever is an
expression of nervous activity. In addition to such temporary effects of
the nervous system on the vegetative, more permanent changes may be
noted, embracing atrophy, hypertrophy and hyperplasy, consisting in
the diminution or increase in organs through nervous influence. Para-
plasy, or the production of new structures from old ones, also occurs in
various forms as the result of neuropathies.

The amount of influence exerted upon organs remote from nerve
centres and indirectly connected with them, both as regards function
and growth in abnormal conditions of the nervous mechanism, is sug-
gestive of the great influence of the nervous system upon the develop-
ment, correlation, and growth of the same organs under normal condi-
tions. From a most suggestive article by Professor Arndt on this
subject most of the following notes are compiled. (?)

It has long been recognized that the section of the trigeminal and
vagus nerves produce pathological changes in the mucous membrane of
the eye, nasal passages, mouth, and in the lungs. The fact that the
sensory nerves supplying these organs are of necessity simultaneously
cut has led to the suggestion that the irritation is due to external
sources which would have been perceived and removed but for the loss
of sensation.

That this assumption is incorrect is shown by a comparison of cases
where gouty or rheumatic patients are prevented from the use of the
limbs because of joint affection, the motor nerves themselves being
relatively uninjured, with cases of paralysis due to central nervous dis-
turbance. In the former case there is no special tendency to decubitis
(a degeneration of the tissue in the extremities often accompanied by

1 ARNDT, Ruporr, ‘‘ Ueber trophische Nerven,” Archiv f. Anat. und Phys. Physiol.
Abth., 1801, p. 54.
[zee

XXV1 JOURNAL OF COMPARATIVE NEUROLOGY.

great pain), while in the latter an acute form of this affection may
rapidly set in. ;

In cases where the ischiatic nerve has been cut, as in the guinea-pig
for the purpose of inducing epilepsy, the limb is paralyzed and becomes
inflamed, swollen and discolored. In a short time spontaneous sores
appear, and the toes are lost, leaving a deformed stump, which, never-
theless, ultimately heals and remains well, evidently because of a restor-
ation of nervous connections.

A case where all the soft parts of an arm had been accidentally cut
and prevented from healing by first intention illustrates the same point.
Only the A. interossea were uninjured, and decubitus resulted in a few
days, followed by swelling of the fingers. The hypertrophy of the joints
seems to have been persistent. This the author ascribes to the section
of the nerves.

In the case of the guinea-pig before referred to, there develops on
the neck on the same side as the injured leg a so-called epileptogene
zone or area. In this region the skin becomes gradually more sensitive,
until finally the hair falls out, and pinching the skin in this area gives
rise to epileptiform symptoms. The disturbances in the skin bear an
unmistakable resemblance to the accompanying changes in the leg.

These trophic disturbances certainly are not due to loss of sensation,
but to reflex modification in the innervation.

In this connection the- many cases may be noted where a great
mental excitement (fear, anger, etc.) produced functional derangement
of the visceral organs. A case referred to by the author exhibited not
only liver-disturbance, but albuminuria and other kidney affection. The
author suggests that the nervous excitement was so great as to actually
destroy the epithelial cells of the kidney, which, accordingly, had an
unusual shrivelled appearance.

Gouty people often afford illustrations of trophic disturbance result-
ing from nervous excitement. Gout itself is regarded as a neuropathy
by the author. The following diseases may also result from neurotic
causes: erythema, erysipelas, urticaria, herpes, prurigo, eczema, pem-
phigus, pityriasis, psoriasis, acne, furunculi and lupus.

The fact that weak and nervous people lose the hair or become gray
upon bilaterally symmetrical areas of head and face points to a nervous
origin of baldness, etc. The symmetrical degeneration of the body is
but the converse of the law of symmetrical bilateral growth, and both
are to be referred to the bilateral nervous control. Such control can
only be explained by the assumption of nerves charged with the nutri-
tive function, 7.e., trophic nerves. How, then, does it happen that
trophic nerves have never been demonstrated anatomically? The author
answers that it is because we have not been clear as to what was sought,
that the real trophic nerves have long been known.

The nervous system, in this view, is rather an interdependent retlex
complex in which every part exerts its influence than an automatic

LITERARY NOTICES. : XXV11

centre with distributing tracts. Asa result of each molecular disturb-
ance, the end cells suffer a change in the processes of metabolism, which
change will vary with the nature of the cells (tendon, muscle, etc ). The
nutritive processes are there influenced through the more elementary
metabolic processes. Every nerve, and especially every centrifugal
nerve, is therefore a trophic nerve. The various processes governed by
these nerves (secretion, contraction, etc.) are simply the results of the
trophic influence.

For example, the young muscle cell contains an_ irregularly
arranged mass of granules, which gradually arrange themselves into
the transverse bars so characteristic of voluntary muscle. This struc-
ture is the result of the oft-repeated contraction. It has been observed
that, in contraction, the elementary granules enlarge, and their combined
increase causes the increase in diameter of the Bowman’s discs or dark
stripes. The author regards the only satisfactory explanation to be an
increased absorption of fluid from the light portion of the fibre, which
absorption is the result of altered molecular conditions or a form of
metabolism brought about in the granules by the nerve stimulus. Ina
similar way the centripetal nerve gives rise to sensation simply because
its stimulus alters the vital activity of its central terminal cell.

Thus there are no special trophic nerves because every nerve is
trophic. The distinction between sensory and motor nerves, while
useful for c: nvenience sake, is more accurately expressed by centripetal
and centrifugal.

DEGENERATION AND ATROPHY AS A RESULT OF SECTION OF THE
CRANIAL NERVES.(?)

This exceedingly interesting paper affords a brief historical review
of the development of the v. Gudden-Waller method of experiment.
Mayser, Ganser, von Gudden and the author had been associated for a
number of years in this difficult department, with results which certainly
substantiate the author’s claim for it. Two classes of experiments are
chiefly relied upon:

1. A cell group is extirpated in a young animal. When adult the
associated fibres are atrophied, enabling one to trace the course of the
tract in question in detail. In this way, after injury to the Gasser’s
ganglion, the author demonstrated the loss of the fibre branches in the
substantia gelatinosa of the tuberculum Rolandi, and Monakow found
similar result in the corpus geniculatum externum after enucleation of
the eye, while Gudden determined that the pyramid fibres pass directly
into the cord by extirpation of motor areas,

2. A nerve root or fibre system is sectioned in a young animal, and,

1 Foret, AuG., ‘‘ Ueber das Verhiltniss der experimentallen Atrophie und Degen-
erations:methode zur Anatomie und Histologie des Centralnervensystem,” Festschrift
zur Feier des fiinfzig-jahrigen Doctor-Jubilaums der Herren Prof. Dr. Karl Wilhelm von
Nageli und Prof. Dr. Albert von Kélliker, Zurich, 18or.

XXVIil JOURNAL OF COMPARATIVE NEUROLOGY.

when mature, the corresponding niduli are found to be degenerated. In
this way Gudden has identified the niduli of the nerves of the eye-
muscles, Ganser discovered a degeneration of retinal elements after
section of the optic tracts, Monakow demonstrated degeneration of the
cortical pyramidal cells after section of the pyramidal fasciculi, and
Mendel corrected Meynert’s account of the acoustic.

The experiments described in the present paper were all by the
second method, and related to the ninth, tenth and twelfth nerves. The
section of one of the roots of the latter in the young causes entire
loss of the nidulus, though without affecting the small-celled hypo-
glossus nidulus of Roller, and proves that there are no crossed fibres.

There is no connection with the olives, and the various parts of the
true nidulus (Stilling’s nidulus) are not connected with each other or
the opposite side.

The author denies (somewhat inconsequently, we think) any con-
nection with the nidulus of the lateral fasciculus, nidulus of the vagus,
or dorsal longitudinal fasciculus.

Extreme difficulty attends experimentation upon the ninth and tenth
and it is usually impossible to avoid injury to the eleventh. Mayser,
however, succeeded in extirpating the ninth and tenth, and our author
figures and describes the sections of one of these brains.

' The definite results are the following:

1. The sensory fibres of the lateral mixed system (IX—XI) spring
from the fascicularis solitaris or respiratory bundle and end between the
cells of the surrounding gelatinosa.

2. The motor fibres of the vagus and glosso-pharyngeal spring from
the nidulus cephalad and dorsad of the hypoglossus nidulus.

3. There is no decussation in either case.

THE DEVELOPMENT OF THE SPINAL GANGLIA IN MAN.

Lenhdéssek(!) has availed himself of the section of a haman embryo
2.5 mm. long and possessing twenty myomeres to discuss anew the
origin of the spinal ganglia. The results may be thus summarized. At
an early period the material of the future ganglia separates in the form
of an unsegmented band on either side of the medullary plate. It is
distinguished by its spherical cells—ganglioblasts. The closing of the
plate to form a tube brings the two bands toward each other, and results
in a temporary union. Soon, however, a rapid proliferation of the cells
results in a return to their lateral position and an indication of segmen-
tation. The method described is similar, except in unimportant details,
with that described in other groups by His and Beard. The author,
however, believes that the medullary nerve plate includes the germs of
the sympathetic system, as well as of the central and peripheral.

1 LenudssEk, M. v., ‘‘ Die Entwickelung der Ganglienanlagen bei dem menschlichen
Embryo,” Archiy f. Anat. und Phys., 1891, I.

LITERARY NOTICES. : XX1X

PERIPHERAL CONTROL OF THE CIRCULATION IN THE BRAIN.

An editorial in the Aléenist and Neurologist for July, 1891, calls
attention to a fact of much significance in physiology, aside from its
value in neurotherapy.

M. Onimus(?) shows that the application of the continuous galvanic
current to the sciatic nerve produces sleep. This is in accord with the
well-known fact that stimulation of the sciatic produces changes in the
cerebral circulation. The observations were made upon patients suffer-
ing with atrophy of the legs or sciatica, mostly combined with insomnia.
He thinks that the sciatic nerve is, of all the peripheral nerves, capable
of exerting most influence on the nervous centres, and makes a practical
induction against the exposure of the limbs, especially in children.

The use of warm foot-baths for relief of congestion in the brain thus
finds a more direct explanation than the usual one.

ELEcTRO-Moror DISTURBANCES IN THE BRAIN AS PRODUCTS OF
PsycHIcCAL ACTIVITY.

During 1890 a number of papers bearing on the interesting question
as to how far cerebral activity may be estimated by measurement of the
electro-motor activity induced in the organ have appeared in the Cez-
tralblatt f. Phystologie. These independent researches by Professors
Beck, Marxow, Gotch and Horsley have induced Prof. B. Danilewsky,
of Charkow, to describe experiments undertaken in 1876 for the same
purpose, which have nevertheless more than an historic interest.(?)
The animals were operated on under morphium narcosis by means of
unpolarizable glass electrodes, separated by from 10-12 mm., and a very
sensitive Du Bois Raymond “ multiplicator”’ served as a galvanometer.
In spite of a wide range of ‘variation, the author satisfied himself that
“every slightest irritation of the sensory organs, as well as of the inner
sensory nerves (vagus), produced an obvious change in the electro-
motor state of a definite area of the cortex of the hemispheres (generally
the effect is crossed). While it proved impossible to sharply localize
these effects, it appeared that stimulation of the sensory nerves of the
skin produced a variation in the current in the frontal lobes, while a
loud sound affected the occipital region. A pistol shot, for example
produced negative variation of 40°.

THE RELATION OF THE SYMPATHETIC SYSTEM TO THE ERECTILE
APPENDAGES OF THE HEAD OF THE GALLINACE#.(*)

In this paper, which gives an illustrated description of the sympa-
thetic system of birds, Prof. Jegorow shows that the vaso-constrictor

rt Soc. de Med. de Paris, 1870.

2 Centralblatt f. Physiologie, V. I, p. 1-4.

3 J. JeEGorow, ‘‘ Ueber das Verhiltniss des Sympathicus zur Kopfversierung einiger
Vogel,” Du Bois-Raymond’s Archiv, 1890, Suppl., p. 33-

ook JouRNAL oF CoMPARATIVE NEUROLOGY.

fibres governing the erectile vessels in the comb and other analogous
appendages arise from the sympathetic system. The fibres supplying
the cervical appendages accompany branches of the anterior roots of
‘ spinal nerves, while those passing to the head lie in the first and second
trigeminal branches. The lids and muscles of the feather papillz are
also supplied by the sympathetic.

THe SYMPATHETIC SYSTEM.

In the same line are the observations of Arloing.(1) After section
of the cervical sympathetic in the case of the ox the corresponding part
of the snout became dry and soon began to desquamate. In the case of
the dog the effect was not obvious for two months, but then followed
the same course.

Recent researches of Doyon(*) showed that, while some vaso-dilator
fibres of the retinal vessels arise from the sympathetic, others lie in the
trigeminus. The author concludes from analogy that the vaso-con-
strictors are also in the trigeminus. The experiments consisted chiefly
in stimulation of ‘the Gasser’s ganglion after section of the sympathetic,
but without isolation of the ganglion.

By a different method Langley and Dickinson, and later, Langen-
dorff, have endeavored to experimentally determine the function of the
cervical sympathetic.(*)

CONTRIBUTION TO THE STUDY OF THE BRAIN OF TRACHEATE
ARTHROPODS.(*)

1. Technique.—Of several methods of preparation tried, the follow-
ing was found to yield the best results. After dissecting away the major
portion of the insect, the nervous system was hardened in osmic acid,
followed by alcohol. The brain was then stained 77 ¢ofo with alum or
borax carmine.

2. Histological Elements.—The arthropod brain is composed of
three principal nervous elements: ganglionic cells, nerve fibres and

r S. ARLOING, “Des rapports fonctionnels du cordon sympathetique cervical avec
l’épiderme et les glands,’ Arch. de Phys. normale et pathol., 1890, III, 1, p. 160.

2 M. Doyon, ‘t Recherches sur les nerfs vasomoteurs de la rétine et en particulier sur
le nerf trijumeau,’’ Arch. de Phys., 1890, ITI, 1, p. 13.

3 LanGiey and Dickinson, *‘ On the Local Paralysis of Peripheral Ganglia, and the
Connection of Different Classes of Nerve Fibres with Them,” Proc, Roy. Soc., XLVI,
p. 423; ‘‘ The Connections of Peripheral Nerve Cells with the Nerve Fibres which Run
to the Sub-Lingual and Sub-Maxillary Glands,” Journal of Physiology, XI, p. 123; ‘On
the Progressive Paralysis of the Nerve Cells of the Superior Cervical Ganglion,”’ Proc.
Roy. Soc., XLVII, p. 370; “ Pituri and Nicotin,” Journal of Physiology, XI, p. 265;
“ Action of Various Poisons upon Nerve Fibres and Peripheral Nerve Cells,” Journal of
Physiology, XI, Suppl., p. 509. O. LancEenporrF. “ Die Beziehungen der Nervenfasern
des Halssympathicus zu den Ganglienzellen des oberen Halsknotens,” Centralblatt fiir
Physiologie, V, 5, June, 1891, p. 129-131.

4G. Saint-Remy, “Contribution a L’Etude du Cerveau chez les Arthropodes
Trachéates,”’ Poitiers, 1890, 276 pp., 12 pl, 159 figs.

Literary NOorTrices. XXX1

neuroglia. The ganglionic cells lack a true cell wall, but are surrounded
by a sheath of connective-tissue fibres. These cells present various
shapes, two of which deserve special mention. One of these types has
been called by the author ‘‘chromatic cells,” the other ‘‘ ganglionic
nuclei.” ‘The chromatic cells are small and unipolar, and are confined
to the sensory regions of the ‘brain. The bodies of these cells are so
poorly supplied with protoplasm that a casual glance reveals nothing
but the densely stained nuclei, The higher the type of brain the more
numerous these cells become. Among the A/yrdofoda, these cells are
very abundant in the complicated brain of Fwdus and Scutigera, while
they are absent from the rudimentary brain of Geophilus. Among the
Arachnida, they are abundant in the highly developed optic lobes of the
Lycoside and Phalangide ; in the less differentiated optic lobes of the
the Agalenide they are represented by faintly stained cells; while in
the rudimentary lobes of Pholcides they are replaced by cells of the
ordinary type. The ganglionic nuclei are small, granular; densely
stained nuclei are found in the brain of Scutigera. The nerves are
hollow tubes containing a liquid. The tubes passing entad penetrate
the brain and expand to form the sheaths of the ganglionic cells. The
neuroglia has a more delicate structure in sensory and psychical areas
than elsewhere.

3. Myriopoda.—The myriopod brain is constructed upon the same

plan as the insect brain; it consists of three ganglia homologous to those
that are found in the insect brain. Consequently there exists in the
myriopods three pre-oral somites homologous to the corresponding ©
somites of insects and crustaceans.
' The frotocerebron (the ganglion of the first cephalic somite) is com-
posed of two portions, corresponding to similar divisions of the insect
brain. The lateral portions of the protocerebron constitute the optic
lobes, and are in direct communication with the eyes. The remaining
portion is psychical in function, and gives off a pair of nerves to the
organ of Témosvary.

The deutocerebron (the ganglion of the second cephalic somite) is
composed of two antennary lobes, which are united by the antennary
commissure, and of an undifferentiated portion, corresponding respec-
tively to the olfactory and dorsal lobes of insects and crustaceans.
Except in $udus, where it is divided into an olfactory and probably a
motor fasciculus, the antennary nerve is a mixed nerve, as it is in the
insects and crustacea. As in the insects and crustacea, so here the
dorsal lobe gives origin to a small peripheral nerve (nerf tegumentaire),
and, as among the insects, it also gives origin to a pair of visceral nerves.
Consequently it is homologous to the first paired ganglia of the insects.

The ¢ritocerebron (the ganglion of the third cephalic somite) corre-
sponds both to the tritocerebron and to the first visceral gangiion of
insects and crustacea. According to Viallanes, the tritocerebron of the
crustacea is composed of the following parts: Two antennary lobes, two

XXX1i JOURNAL OF COMPARATIVE NEUROLOGY.

cesophageal lobes, and an infra-cesophageal commissure, which traverses
the pharyngeal collar. From the antennary lobes a pair of nerves pass
to the second pair of antenne; from the cesophageal lobes nerves pass to
“the root of the first unpaired visceral ganglion (g. stomato-gastrique)
and to the labium. Among insects the third somite and its ganglion
suffer great reduction. The somite does not bear appendages, and the
antennary nerves, with their lobes, have disappeared. However, the
representative of the infra-cesophageal commissure remains. It is united
to the brain, and gives off a nerve to each root of the first visceral gan-
glion and to the labium. From the first visceral ganglion arises an
important nerve, which during its course suffers several l~cal ganglionic
swellings. In the crustacea this is called the visceral nerve, while in
the insects it is called the recurrent. In the myrzopods the tritocerebron
consists of the same elements as the corresponding portion of the insect
brain. In the Chilognathes and Scutigera the commissure traverses the
pharyngeal collar, while in the otter Chz/opfodes it is situated in the
brain itself. In most families the ganglia consist either of two small
bodies situated one at each extremity of the transverse commissure
(Fulides, Glomerides) or of a ganglionic mass situated upon the ventral
surface of the commissure (Scutigeres, Lithobiides). Between these
two masses, and isolated from the remainder of the brain, there is a
median longitudinal nervous mass, from which arises the visceral nerve.
This suppression of the first visceral ganglion and the substitution of a
portion of the brain for it is a noteworthy fact. If we admit that the
myriopoda are inferior to the crustacea, then this fact warrants the sup-
position that an isolated visceral ganglion is a secondary feature, and
that originally the visceral nerve had its origin in the brain itself. A
study of the visceral nerve strengthens this belief. Usually the visceral
nerve consists of fine fibres, resembling those of the neuroglia, at whose
origin several ganglionic cells are located. In the Scutzgera, however,
this nerve is composed of the neuroglia itself, and contains several nerve
cells. It is no longer a nerve, but an elongated ganglion, the homo-
logue of the visceral nervous system of the crustacea and the insects.

4. Arachnida.—Among the Arachnida the brain consists of three
ganglia, corresponding to three somites; but only two of these are pre-
oral the third (the mandibular ganglion) is post-oral. The two pre-oral
ganglia and their concomitant somites correspond to the first and third
ganglia and concomitant somites of the insecta, myriopoda, and crus-
tacea. No trace of a homologue of what constitutes the deutocerebron
of these latter arthropods is found in the Arachnida, This implies the
absence of the second cephalic somite, the somite which bears the first
pair of antenne of the Crustacea, and the antenne of the /zsecta and
Myriopoda.

The optic ganglion is divided into three parts; the optic niduli, the
posterior stratified body, and the cerebral niduli. In the Aranefde the
structure of the cerebral nidulus is quite simple, but in the Scorfionide

LirERARY NOTICEs. XXX111

and the Phalangide@ it is. quite complex. The optic lobe gives origin to
a pair of nerves corresponding to one kind of eyes; the nidulus, how-
ever, contains two nervous centres, corresponding to two kinds of eyes.

The structure of the rostro-mandibular ganglion is more simple and
more uniform. It consists of a nervous mass penetrated by the alimen-
tary canal. The supra-cesophageal portion is composed of three niduli;
one small rostral nidulus and two large mandibular niduli. The rostral
nidulus lies cephalad to the csophagus. From it an unpaired median
nerve passes to the rostrum. ‘This nerve is the homologue of the nerve
that passes to the upper labia of insects, myriopods and crustaceans,
The mandibular niduli are laterally situated. They serve to enervate
the mandibles. In the Phalangide there is a single pair of mandibular
nerves; in the Araneide, also, there is only a single pair of nerves, but
each nerve is bifurcate; while in the Scorpionide we find two pairs of
nerves.

5. In Peripatus the brain is not obviously segmented, but in the
remaining tracheate arthropods it is composed of a cephalic and a
caudal region. The cephalic portion is pre-oral, and is evidently
homologous to both the protocerebron and the deutocerebron of insects,
myriopods and crustaceans. ‘The caudal region is shown by both em-
bryology and anatomy to be composed of the ganglion of the first post-
oral somite. It is probably homologous to the tritocerebron of insects,
myriopods and crustaceans.

6. The roots of the unpaired visceral nerves of myriopods and the
paired sympathetic nerves of the Araneid@ and Paripatus appear to |
have the same morphological value and to correspond to the unpaired
visceral nerves of insects and crustaceans.

7. Among all the tracheate arthropods that possess eyes the first
cerebral ganglion contains a more or less differentiated organ (the optic
lobes), which is interposed between the deeper regions and the retina.
Its function appears to be the elaboration of visual impressions. The
structure of this organ is not necessarily constant for the same kind of
eye, and variations in its structure apparently greatly modify the phe-
nomena of vision. Indeed, modifications of this body appear to be of
more importance than variations of the eye itself. The remainder of the
cerebral ganglion is not entirely concerned with vision; it is psychical
in function. The structure of these regions is greatly influenced by
their physiological role. [eo enerairet

THe NERVOUS SYSTEM OF COPEPODS.(!)

The brain of Diaptomus, according to this author, is an irregular
body, consisting of a central mass of ‘‘ dotted substance” surrounded by
a layer of cells, varying in thickness at various points. The primary
brain consists chiefly of ‘“‘ dotted substance,” the secondary of nerve

rt M, J. RicHarp, Bull. Soc. Zool. France XV, 1891,

XXxiv JOURNAL OF COMPARATIVE NEUROLOGY.

cells. Nerves arise from the brain for the frontal organ, eyes, first pair
of antenne and the labrum. This supra-cesophageal ganglion is united
by strong connectives with the sub-cesophageal, and the connective is
supplied with scattered cells laterad. Nerves are given off from it to
the second antenne and labrum. A number of ganglia are united in the
band-like sub-cesophageal mass. Three tuberosities correspond to
mandibles, maxillz and maxillipedes. There are regular blood sinuses
or lacune extending through the system. All the nerve cells are of the
multipolar type.

THE DEVELOPMENT OF THE NERVOUS SYSTEM OF SPIDERS.(?)

This Japanese author has investigated especially the development of
the eyes, using the genera 4ga/ena and Lycosa principally, and verifying
statements by comparison with TVheridion, Epetra, Dolomedes and
Pholcus. Wis statements conflict with those of Locy, Schimkewitch
and Patten in several particulars. Segmenting stages of the eggs were
plunged directly into hot water, while older eggs were gradually heated
in water to 70 or 80° C. The process was continued until the eggs were
opaque and white. After cooling they were placed in 7o per cent.
alcohol and carried up to absolute gradatim. The precaution was taken
of examining the eggs one by one under a dissecting microscope and all
those in which the membrane was not burst were perforated by a
needle to facilitate permeation. They were stained in alcoholic
cochineal, picrocarmine, alcoholic carmine and hematoxylin. Paraffin
was the imbedding agent.

The following statements from the author’s summary are germain
to our work:

The brain and the ventral nerve cords are formed as a continuous
ectodermal thickening. The brain is composed of the semicircular
grooves and the lateral vesicles cut off from the ectoderm. Later it is
divided into three segments. The development of the posterior median
eyes is connected with that of the brain. Their development is quite
different from that of the other eyes; but all the eyes are dermal
in origin, not neural, and the nerves of the eyes always enter from the
inner ends of the ectoderm cells.

The spider’s brain consists of three segments, as Patten claims.
From his description, Patten seems to mean that in scorpions and
spiders the three segments of the brain are formed from three separate
invaginations; but I am unable to corroborate this statement. Moreover,
he says that the anterior median eyes (my posterior median) belong
to the second segment, while the three remaining pairs belong to
the third segment. Supposing that his second segment is anterior
to the third segment, I cannot corroborate this statement either,

t Kamaxicut KIsHINouyeE, ‘f On the Development of Araneina,” the Journal of the
College of Science, Imperial University of Japan, Vol. 1V, Part I, pp. 55-88, Plates XI-
XVI.

LirErARY NOTICEs. XXXV

as, according to my observations, all the eyes belong to the third
segment.

The concentration of the nervous system toward the cephalothorax
continues until the lateral ganglionic chains are united into one and
form the sub-cesophageal ganglion. The inner portion of the ganglion
becomes finely fibrous. The abdominal ganglia gradually atrophy and
attach themselves to the posterior end of the sub-cesophageal ganglion.

The plates are well executed, though lacking in detail.

NERVOUS SYSTEM OF SERPULA(?).

“The nervous system is quite highly developed, the cerebral
ganglion attaining a diameter of .5 mm. in specimens whose whole body
diameter was 1.4. This ganglion gives off, in front, two large branchial
nerves, which supply the branchie and two smaller nerves to the
cesophagus. A single nerve from its posterior, ventral, median edge
runs to the posterior part of the cesophagus.

The cerebral ganglion gives off, on either side, a large commissure,
which passes down around the cesophagus and into the large ventral
ganglion of the corresponding side.’ The ventral chain continues
through the entire body with a ganglion for each segment. The sub-
cesophageal ganglion has three transverse commissures, and the others
which decrease backward have but one. About two-thirds of the mass
of the cerebral ganglion is made up of cells, while the inner portion is
composed of fibres. The other ganglia contain but few cells, arranged
on the outer surface.

‘‘At its posterior end, the dorsal portion of the cerebral ganglion is
prolonged into a most remarkable process; from the dorsal, posterior
corner on either side a large lobe passes outward and backward, and
then, bending suddenly downward, passes into the first ventral ganglion.
It will be seen that we have here, in reality, two pairs of cesophageal
commissures.”

DEVELOPMENT OF THE BRAIN OF THE HORSE-SHOE CRAB.(?)

“The nervous system arises from a paired, longitudinal thickening
of the ectoderm. The anterior ends of these thickenings are much
broader than the posterior parts, and there are two pairs of ectodermic
invaginations. These parts form the brain. About twenty-four days
after fertilization nine pairs of ganglia may be seen (there is a pair in the
metastoma). They are separated from the general ectoderm from the
anterior end gradually. From the third pair of ganglia, backwards,
there is a lateral commissure in each segment. The brain has one
transverse commissure.

1 TREADWELL, A. S., ‘‘ Preliminary Note on the Anatomy and Histology of Serpula
Dianthus,” Zool. Anz., XIV, 370, p. 276.

2 KIsHINOUYE, K., “‘ Preliminary Note on the Development of Limulus Longispinis,”
Zool. Anzeiger, XIV, 369, pp. 264-266.

Xxxvi JOURNAL OF COMPARATIVE NEUROLOGY.

The separation of the brain from the general ectoderm is later than
that of ganglia. There is a peculiar grouping of the nuclei, as that found
in the retinal portion of the eye, in the nervous system before it is
- separated from the general ectoderm.”

BRAIN OF THE HORSE-SHOE CRAB.(1)

The brain of the adult is made up of three pairs of lobes, enveloped
in thick masses of chromatic cells. The uppermost are the pair of
lateral eye lobes, widely separated from each other on the top of the
brain and give off well-developed nerves.

The nerve cells appear to arise from the chromatic cells. ‘t The lobe
just below the middle is seen to be imbedded in the dense ring or ruffle-
like masses of deeply-stained chromatic cells, which we have called the
‘nucleogenous bodies.’’’ The brain of Limulus differs from that of
Arachnida in sending no nerves to the first appendages, and is homo-
logous with the forebrain of spiders, according to Patten. “The nerves
which give rise to the first pair of appendages do not arise from the
base of the brain, but the ganglion cells giving rise to them are situated
entirely outside of and behind the brain proper.” The lobes of the
median-eye nerves are small and slender and not much swollen, and lie
far below [ventrad of ?] the plane of the lateral-eye lobes. Their form
and size indicate that they have atrophied.

There is, below the median-eye lobes, a pair of minute lobes, each
sending off a bundle of fibrillee backwark [caudad?] toward the cerebral
commissure, which may possibly give rise to a pair of tegumental or
hemal nerves. No traces were discovered of Patten’s nerves of the
median eye of the first segment.”

The third pair of (major) lobes are the cerebral lobes. These are
very irregular in outline, slender and apparently shrunken, and very
different from the full well-developed sub-sperical shape of those of
arachnids.

Prof. Packard differs from Viallanes in believing that there are
‘but three preoral segments of the head” of insects. He considers that
the differences are of sufficient importance to forbid the union of the
Podostomata with the arachnids.

EDINGER’S TEXT-BOoOK ON THE NERVOUS SYSTEM.(?)

It is a pleasure to note the publication in this country of a con-
densed manual of the anatomy of the human brain by so eminent an
investigator as Dr. Edinger. It is equally pleasant to note that the

1 Packarp, AvLpueEus S., ‘‘ Farther Studies on the Brain of Limulus Polyphemus,”
Zool. Anzeiger, XIV, 361, pp. 129-133.

2 Epincer, Lupwic, ‘‘ Twelve Lectures on the Structure of the Central Nervous
System, for Physicians and Students’”’ Second revised edition, with 133 illustrations.
Translated by WiLLis Hatt Virtum; edited by C. EuGENE Riccs Philadelphia: F. A.
Davis, 1890.

LiteErARY NOTICES. XXXVI1

translator and editor are connected with the newly equipped medical
department of the University of Minnesota. That thestudent of anatomy
at this institution may now avail himself of the ripest fruit of German
scholarship is a matter of congratulation to alumni of that institution,
who, like the writer, recall a very different state of things.

The book itself is familiar to students of neurology in the earlier
edition. The improvements introduced in the second edition are im-
portant, and in most, though not all, respects it represents fairly the
present state of our knowledge. The translator and editor are to be
congratulated on their share in the work. The originally clear style is
rendered into perspicuous English with little of the awkwardness often
attending a translation. It is a wholesome symptom that in descriptions
involving direction the reformed terminology is employed, and we may
soon hope to escape from the ambiguous “ back,” ‘‘ above” and “inward”
of anthropotomy.

The figures, which are numerous and excellently adapted to the
purpose, suffer somewhat in reproduction, but there is, perhaps, a
decided gain in the fact that the original German terms are printed 77
sifu, preventing ambiguity and affording an opportunity for becoming
familiar with the indispensable nomenclature in its mother tongue. A
few, like Fig. 83, are useless by reason of careless neglect of reference
lines. Many who consult the work will regret its brevity, but these will
not be those for whom it has obviously been written—medical students.
The book is a text-book, and we must admire the self-control exercised
by the author in omitting doubtful points, even where he himself is per- .
sonally interested in a militant theory. One thing we greatly miss; a
detailed description of a few of the modern technical methods would
greatly extend the value of the work for Americans who have no hand-
book of neurological technique. We hope the next edition may be pro-
vided with an appendix containing sufficiently minute technical recipes
and directions.

It would be easy to point out omissions and cases where the author’s
statements conflict with the results of recent investigation, but in a
science which is advancing as rapidly as the present one this is inev-
itable, and something must be granted to private judgment. If the
treatment of the cephalic cranial nerves is less satisfactory than other
portions, the cause is not far to seek in the nature of the subject. On
the whole, there is no other work which occupies this important field so
satisfactorily.

MyocLonus.

While strictly beyond our limits, the recent pathological work of
Unverricht(1) may be mentioned as a model of thoroughness and dis-
crimination in an exceedingly different realm. The disease known as

x UNnverrRICcHT, H., ‘‘ Die Myoclonie,”’ Leipzig and Vienna, Franz Deutiche, r8gr.

XXXVlli JOURNAL OF COMPARATIVE NEUROLOGY.

paramyoclonus multiplex was described by Friedreich in 1881, with
symptoms such as clonic contractions in a number of symmetrical
muscles of the extremities, without affecting the normal co6érdination
‘and reaction of tae muscles otherwise. Reflexes were abnormally sen-
sitive. A fright or other psychical cause is claimed for the disease,
which may be spontaneously self-limited. The author cites a number
of very instructive cases showing that it may assume the congenital
phase, and apparently succeeds in effecting a differential diagnosis. The
prognosis is as unpromising as the therapathy unsatisfactory.

RECENT LITERATURE.

ASsSAKy. Despre topographia cranio-cerebrala. J/ustit. de Chir.,
Bucresci, 1891, pp. 123-159.

BECHTEREW, W. Ueber die Erscheinungen welche die Durch-
schneidung der Hinterstrange des Ruckenmarks bei Thieren hervorruft,
und iiber die Beziehungen dieser Strange zur Gleichgewichtsfunction.
DuBois-Reymond’s Archiv., 1890, 5-6, p. 489.

BEDDARD, F. Es On the Pouch and Brain of the Male Thylacine.
Proc. Zool. Society, London, 1891, pp. 138-145.

BERTELLI, DANTE. II solco intermediario anteriore del midollo
spinale umana. Afti della Societa toscana di scienze, X1, 1891, pp. 213-
225.

BERTELLI, D. Rapporti della pia-madre con i solchi del midollo
spinaleumano. A?¢i Societa toscana di scienza naturali, Piza, XII, 20 p.

BELMONDO, E., and Oppr, R. Intorna all’ influenza delle radici
spinali posteriori sull’ excitabilita della anteriori. Revista Sperimentale
di Freniatria, X V1, 3.

BELMONDO, E. Sulle modificazioni dell’ excitabilita corticale
indotte dalla cocaina e sulla natura dei centri psicomotori. La Speri-
mentale, August, 1890.

BIEDERMANN, W. Ueber den Ursprung und die Endigungsweise
der Nerven in den Ganglien wirbelloser Thiere. Fenaische Zeitschrift
f. Naturwissenschaft, XXV.

Binet, A. Sur la chaine nerveuse sousintestinale du Hanneton
(Melolontha) Compt. rendus hebdomad. de la Soc. de Biologie [1X],
III, 22, 1891, p. 489.

BouCHERON. Nerfs ciliaires superficiels chez l? homme. MJém. de
la Société de Biologie, Series IX, II], 14, pp. 51-64.

BowonitcH, H. P. Ueber den Nachweis der Unermidlichkeit der
Saugethiernerven. DuBois Reymond’s Archiv., 18g0, p. 505.

BRosseET, J. Contribution a |’ etude deo connexions du cervelet,
Lyons, 1890, 113 pp. 4to.

BurRKHARDT, R. Untersuchungen am Hirn und Geruchsorgan

RECENT LITERATURE. XXX1xX

von Triton und Ichthyophis. Zeztsch. 7. Wiss. Zool., LUI, 3, August,
1Sgl.

CajyAL, S. RAYMON y. Sur la structure de 1’ écorce cérébrale de
quelques mammiferes. a Cellule, VII, 1, pp. 123-176.

CHARNAY DeEsIRE. Cervelles humaines conservées. Bull de la
soc. @’ anthropologie de Paris, 1. 4, 1891.

CuHIARUGI, G. Osservazioni intorno alle prime fasi de sviloppo
dei encefalici nei mammiferi e in particolare sulla formazione del
nervo olfattivo. Monzitore Zoolog. Italiano, II, 3, Florence, March,
18g1.

CHIARUGI. Sur les myotomes et sur les nerts de la téte posterieure
et de la région proximale du tronec dans les embryons des amphibiens
anoures. Archives ttaliennes de biologie, T, XV, 2, 1891, pp. 229-239.

Craccio, G. V. Sur les plaques nerveuses finales dans les tendons
des vertébrés. Arch. Ital. de Biologie, X1V, p. 31.

DANILEWSKY, B. Zur Frage ueber die electro-motorischen Vor-
gange im Gehirn als Ausdruck seines Thatigkeitszustandes. Central-
blatt fur Physiologie, V, 1, April, 1891, p. 1-4.

DARKSCHEWITCH, L. and PriByTKow, G. Ueber die Faser-
systeme am Boden des dritten Hirnventricles. Mewrologisches Central-
blatt, X, 14, 1891, pp. 417-420. 2

DEBIERRE, CH. La togographie cranio-vérébrale. Compte rendu
de la 19 sesston dela Assoc. franc. pour l’ advancement des sciences,
1891, Paris, p. 672-677.

DEBIERRE, CH. Sur les anomalies des circonvolution du cerveau
de l’ homme. Comptes rendus hebd. de la société de biologie, 111, 18,
1891, pp. 369-372.

DEBOoECK, J., and VERHOOGEN, J. Contr. a 1’ étude de la circu-
lation cérébrale. Travail fait al’ Institut Solvay, Brussels, 1890.

Doyon, M. Recherches sur les nerfs vasomoteurs de la rétine et
en particulier sur le nerf trijumeau. Arch. de Physiologie, III, 1.

ErsLter, P. Der Plexus lumbosacralis des Menschen. Avzat.
Anzeiger, V1, g-10, 1891.

Fusari, R.. and PaANAScI, A. Les terminaisons des nerfs dans la
muqueuse et dans les glandes sereuses de la langue des mammiféres.
Arch. Ital..de Biologie XIV, 9.

GOLDBERG, MAx. Ueber die Entwickelung der Ganglien beim
Hinchen. Archiv. f. mtk. Anatomie, XXXVI, 4, 1891, pp. 587-602.

GouGi, CAmILLo. La rete nervosa diffusa degli organi centrali del
sistema nervosa. Suo significato fisiologico. Reale [nustituto lombardo
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HAL ter, B. Ueber das Centralnervensystem, insbesondere tber
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Herrick, C. L. Contributions to the Comparative Morphology
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xl] JOURNAL OF COMPARATIVE NEUROLOGY.

the Brain of Certain Genoid Fishes. our. of Comp. Neurology, Vol.
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Herrick, C. L. Neurology and Psychology. ‘our. of Comp.
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Hocne, A. Beitrage zur Kenntniss des anatomischen Verhaltens
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HocuHeE, A. Ueber die Ganglienzellen der vorderen Wurzeln
im menschlichen Ruickenmark. Munchener med. Wochenschrift, 2
P- 423.

Houssay, F. Sur la question du développement du systéme
ganglionaire chez le poulet. Arch. de Zool, experimentale et générale,
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Howe LL, W. H., and Huser, G. C. Physiology of the Com-
municating Branch between the Superior and Inferior Laryngeal
Nerves. SFourn. of Physiology, X11. 1.

JOHANSSON and GAULE. Die Ringbander der Nervenfaser. Cen-
tralblatt f. Physiologie, V, I, 1891, pp. 299-30!.

JourDAIN, Er. L’ innervation de la trompe de Glyceres. Comft.
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JurgeEN, ALexis. Loi de la position des centres nerveux, 1891,
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KAZZANDER, GIULIO.. Sulla radice dorsale del nervo ipoglosso
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KRONTHAL, P. Lymph-capillaren im Gehirn. Vewrologisch.
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Lacui, PILADE. Contributo alla istogenesi della neuroglia sul
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LATASTE, F . Pourquoi dans un meme type de vertébrés la masse
relative de |’ encéphale varie en sens inverse de la masse du corps.
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MINGAZZINI, G. Recherches complémentaires sur le traget du

RECENT LITERATURE. xli

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LITERARY INOTIGES.

DEGENERATION OF PERIPHERAL NERVES.1

In 1795 Cruikshank divided the vagus-sympathetic nerve trunk in
the neck of a dog and found that, when the section was performed on
both sides, death followed very promptly, while a unilateral section was
not fatal. He then divided the nerve on one side and, after an interval
of three or more weeks, cut the other. The animal survived, thus show-
ing that the severed trunk had meanwhile united. This experiment
seems to have been the starting point for a long series of research upon
the nature of the dependence of nerve fibres upon nerve centres, which
have culminated in the masterly monograph before us.

Flourens (as it is claimed) succeeded in suturing the cut ends of the
median and ulnar nerve, each to the stump of the other. Functional
union was effected and stimulation of the dorsal nerve caused motion of
the ventral peripheral muscles and z7ce versa. Since Flourens’ time the
fact that a severed nerve may again become functional has been repeat-
edly demonstrated, but it has not been so easy to determine whether the
union was preceeded by a degeneration and regeneration of the entire
peripheral portion. The histological problems involved, e. g. whether
the axis cylinder repenetrated the sheath from the stump, have remained
unsolved.

When the nerve is cut and the stumps not reunited or sutured, every
one admits that a process of degeneration follows. Beyond this there is
little unanimity. All admit that the myelin disappears, but Neumann,
Eichhorst, Mayer, etc., suppose that the myelin simply suffers transfor-
mation and forms the material of the new sheath in case of regeneration.
While some describe the process of degeneration as beginning at the

proximal end, the majority recognize the process as coetaneous through-

4. Howett, W. H. and Huser, G.C. A Physiological, Histological and Clinical
Study of the Degeneration and Regeneration in Peripheral Nerve Fibres atter sever-
ance of their connections with the nerve centres. Journal of Physiology, XIII, 5,

1892.

CXXXV1 JouURNAL OF CoMPARATIVE NEUROLOGY.

out the peripheral portion. Earlier writers suppose that the axis cylin-
der remains intact. Neumann and Eichhorst believe that it suffers trans-
formation without actually disappearing, but most writers describe its
disappearance with the sheath structures. The belief that a nerve fibre
is an outgrowth of a cell in the central system (often several feet long!)
has contributed to produce a predisposition to a belief in the degenera-
tion as a result of trophic disturbance. Great difference of opinion
exists as to the possibility of a union by first intention. Some cases in
which, after suturing a nerve, there was almost immediate restoration of
function seem to sustain such a view.

The paper above noticed contains abundant historical matter and a
full list of titles. The work of the authors themselves has been largely
experimental, but in all cases the results have been elaborately checked
and enlarged by histological investigation, thus giving to the results ob-
tained a degree of precision which cannot be too highly commended.
Dogs were used in the experiments and the ulnar, or ulnar and median
nerves were selected. Operations were carried on with antiseptic pre-
cautions and the nerve fibres were sutured with carbolized catgut or cat-
gut in juniper oil. Two sutures were used, one on each side, the needle
being passed through the epineurium. Continuity of the nerve was de-
stroyed by section with sharp scissors, crushing by a ligature, or coagula-
tion by means of a current of water at 80 degrees C. passing through a
curved glass tube. Morphia and éther were employed as anesthetics.
The testing stimulus was a unipolar electric current, the indifferent elec-
trode being applied over the skin of the sternum. In some cases a small
block of hard rubber was passed under the nerve and a direct impact
employed as stimulant.

1. In none of the cases was there union by first intention, the per-

ipheral end degenerating throughout its whole extent.

2. The time necessary before loss of irritability and conducting ap- :

pears, varies greatly (between 2 and 4 days.)

3. The return of function readily but gradually takes place if the
ends are primarily sutured.

4. The irritability returns first in the vicinity of the wound. It
only returns when regeneration has proceeded so far that some medul-
lated fibres are present.

5. The return of function takes place more quickly in sensory than

in motor fibres. This is explained by the authors as due to the greater

sae

LrrERARY NOTICES. CXXXVI11

difficulty of affecting connections (in the end-plates of muscles, for ex-

ample.)

6. Light mechanical stimuli were often more effective in exciting
the fibres in an early stage of regeneration than electrical induction
Shocks. [May this not be due to the greater autonomy of the segments
and the functional activity of the ijocal elements during this stage ?.—ED.]

7- Conductivity is restored before irritability; but these embryonic
fibres respond to mechanical impulse when not to electric shock. [See

remark above. ]

8. The possibility of the functional union of two spinal nerves was
proven. The central end of the median was united to the peripheral end
of the ulnar nerve and the peripheral stump of the median and the cen-
tral stump of the ulnar were dissected away. Functional union occurred
and the animal was examined after 75 days. The physiological results of

the union were unfortunately poorly differentiated.

In the histological study the best results were obtained by the method
ofteasing. The fresh nerve was pinned out, hardened and stained in osmic
caid 24 hours, then washed in water 24 hours or six to seven days. Nextit
was partially teased, stained in Boehmer’s hematoxylin and examined by
teasing on the slide in glycerine or Farrant’s solution. Other nerves .
were hardened in Mueller’s fluid, then, after partial teasing, were stained
by Freud’s potash-gold method and treated with hematoxylin for nuclei.
This method brings out the axis cylinder. A third method is recom-
mended, which consists in pinning out in picric acid, saturated solution,
48 hours. They were then washed out in water 5 or 6 hours and _ subse-
quently in 33 and 50 per cent. alcohol and preserved in 95 per cent.
They were then partially teased and stained 10-15 minutes in Bcehmer’s
hamatoxylin. The process seems to expose the axis cylinder by re-

moval of the myelin.

«« After the interruption of the connection between a nerve fibre and
its centre, whether the interruption be by actual section, by crushing, or,
by coagulation, the peripheral end of the fibre undergoes degeneration,
the changes affecting first the myeline and the axis, and subsequently the
sheath and its nuclei.’”’? The degeneration begins, in the dog, after about
4 days. The fragmentation of the myelin sheath (at the lines of Lanter-
mann) is regarded as independent of and prior to the increase of proto-

plasm about the nuclei. The axis cylinder breaks up with the myelin

CXXxVlll_ JOURNAL OF COMPARATIVE NEUROLOGY.

and remains enclosed within the latter. These changes take place sub-
stantially cotemporaneously throughout the peripheral end. A secondary
fragmentation occurs first in the vicinity of the nuclei. By the seventh
day there is active proliferation of the nuclei. After subdivision the nu-
clei migrate and set up new centres of absorption.

Regeneration begins with the formation of new protopiasm about the
nuclei, which then assume the form of bipolar cells; at a later period the
whole sheath is filled with a continuous belt of protoplasm in which the
nuclei are imbedded. Sucha fibre is called an embryonic fibre by reason
of its resemblance to the early condition. In some cases it appears that
two new fibres may be formed in one old sheath.

In case the cut ends are not united, regeneration never gets beyond
the embryonic stage. If united the myelin is formed discontinuously,
generally near the nucleus, subsequently uniting to form a continuous
sheath. Respecting the nuclei, the authors are not clear. They suppose
that they disappear by absorption.

‘With reference to the nodes and internodes of Ranvier, it is evi-
dent that no simple hypothesis, such as the development of each inter-
node from a single cell, will fit the facts as they appear in regenerating
fibres.”’ They admit that the internodal nucleus must, throughout life,
play an important part in the nutrition of the protoplasm in connection
with it and of the myelin sheath. ‘‘In an indefinite way we may sup-
pose that this nutritive influence on the myeline can only extend over a
limited area—the distance of an internode, —but to connect this with the
formation of these internodes takes us into the field of speculation,

though it seems to us that the true explanation lies along this line of

thought. The origin of the segments of Lantermann may doubtless be

traced directly to the primitive, disconnected deposits of myeline which
we have described.’? The authors seem to believe that the axis cylinder
proceeds from the stump into the newly formed myelin, a position ren-
dered very improbable by their figures.

‘«TIn the central end, especially when connection with the periphery
is not made, several new fibres may form within the sheath of an old one
to take the place of the portion degenerated. Each of these may de-
velop myeline and receive a branch from the axis cylinder above.”’

The paper is a credit to American science and it is a great pity that
it should not have found an American medium of publication. The

plates are exceedingly instructive.

LIrERARY NOTICES. CXXX1X

We cannot forbear adding that the obvious influence of a strongly
supported histogenetic hypothesis has been a serious detriment to the
theoretical portion of the work. Even our elementary text books teach
that the peripheral nerves are formed as the outgrowths of a single cen-
tral cell. Such outgrowths being, accordingly, in some cases, several
feet long (Martin’s Human Body.) So far as can be gathered, this is
pure assumption and is inherently very improbable. Study of the growth
of nerves in embryos of serpents, amphibians and mammals, has —-con-
vinced the writer that, in some cases at least, the growth is by monili-
form adhesions.of neurons. The process is essentially the same as that
occurring in the tracts of the cord where the longer reaches of tracts are
in like-manner thus formed. When definite functional paths are formed
the nuclei are relieved of part of their function and a variety of subsidi-
ary processes resembling fatty degeneration occur, and in this way sheaths
are formed. The case of the olfactory is therefore simply a striking illus-
tration of the normal process which is less clearly seen elsewhere. If
this be accepted, it may be admitted that the effect of a proliferating
nerve upon the developing adjacent tissues may for a time be less de-
pendent on the central than the peripheral neurons.

It is not a little strange that a second work covering the same
ground, with similar methods should appear at nearly the same time.1!

This paper was awarded the medical prize of the Faculty of Wiirz-
burg University for 1891.

The author’s summary is substantially as follows: After an injury
to a peripheral nerve destroying its substance at any point, the entire
peripheral portion, as well as a short part of the central stump, degener-
ates. Healing by first intention does not occur. The degeneration of the
immediate vicinity of the wound is followed, 48 hours after, by a par-
alytic degeneration of the peripheral part, which is due to various causes.
The axis cylinder gives up fluid and grows smaller, Its shrinking pro-
duces fragmentation of the sheath. The contraction of these fragments
produces a corresponding rupture of the axis. At about the fourth day
the nuclei of Schwann’s sheath begin to proliferate and the proto-

plasm increases, which process perhaps assists in the degeneration. The

1. Novruarrr, A. F.N. Neue Untersuchungen ueber den Verlauf der Degener-
ations- und Regenerationsprocesse am yerletzten peripheren Nerven. Zeitsch. f. wis,
Zool., LV, 1. Nov., 1892.

cx) JOURNAL OF COMPARATIVE NEUROLOGY.

degenerating medullary sheath leaves a fluid in the sheath which is grad-.

ually absorbed. There is not a fatty degeneration of the medullary
sheath, though infiltration of fat in adjacent structures cannot be denied.
Neither is there a chemical transformation in the sense of Neumann and
Eichhorst. Leucocytes have nothing to do with the degeneration, and
Ranvier went too far in ascribing it solely to the proliferation of the nu-
clei. The axis cylinder decomposes before the medulla and sheath. The
degeneration passes with marvelous speed from the site of injury periph-
erad. .

The proliferating nuclei of Schwann’s sheath seem to facilitate the
degeneration and regeneration, but neither they nor the increased proto-
plasm have anything to do with the formation of the axis cylinder.
Biinger’s protoplasm bands are probably simply folds in Schwann’s
sheath. There is no reason to doubt the statements of Koelliker as to
the consistency of the axis cylinder and the connective nature of the
sheath. The axis cylinder grows from the central stump continuously.
The new fibres appear in 8 or Ito days. In some cases the medullary
sheath is not at once formed. Nerves caused to degenerate by crushing
do not form more than a single fibre in a sheath. The new Schwann’s

sheath is apparently formed by the nuclei of the old sheath.

To judge from the drawings there is much reason to suspect that a
better interpretation would show an intimate connection between the nu-
clei of Schwann and the axis cylinder, which latter is jointed ina way

suggestive of moniliform concresence.

THE CEREBRUM OF REpTILEs.!

This extensive paper by a young physician recently Americanized
contains promise of good work, but fails of adding materially to our
knowledge by reason of ignoring previous writers and the crude methods
employed. The terminology is that of Edinger. Brains hardened in
Mueller’s fluid and stained with analine cannot be expected to yield his-
tology. The differentiation of cells seems to have beeu imperfect, but
the difference between the pyramidal and fusiform cells of the various
areas were made out. Although special attention is given to the snake
brain we find no mention ef the remarkable peculiarities of the tuber

with its lateral pero and olfactory fossa and no recognition of the relation

1. Meyer, A. Ueber das Vorderhirn einiger Reptilien. Zeitsch. f. wiss. Zool. 1

LITERARY NOTICES. cxli

between pero and pes. Although strongly criticising the misuse of an-
thropotomic terms he employs septum and nucleus sphericus contrary to
the law of priority.

It is hoped that the author may continue his studies and extend the

present publication, which will be critically discussed in another place.

Is THE RETENTION OF Uric AcID PATHOGENETIC OF NERVOUS DIs-

EASE ?1

This paper contains much of great value to the physiologist and
pathologist. The methods of determining uric acid and urea, physio-
logical variations in the excretions, quantitative relations of urea and
uric acid in health, influence of drugs, etc., are treated critically as pre-
liminary to the question of the excretion of uric acid in disease.

The authors devote considerable space to the criticism of Haig’s the-
ories that certain kinds of food render the blood less alkaline and thus
occasion a storing up of the uric acid (which is more soluble in an alka-
line solution) in the tissues. When the blood becomes more alkaline an
excess is thrown into the blood, producing migraine headache, epileptic
paroxysm or mental depression. A general criticism of this view rests
‘on the scantiness of evidence adduced. The theory of storage of uric
acid is regarded as inherently improbable. The authors observe increase
of uric acid excretion in chorea, proportional to the severity of the attack.
With respect to epilepsy the authors say, ‘‘ We may, however, say that
we have as yet obtained no grounds for the view that the grand mal par-
oxysm of idiopathic epilepsy is regularly or even usually preceeded by
diminished uric acid excretion.”

The increase follows the paroxysm, being often greatest on the sec-
ond day, which fact may be supposed to suggest that the uric acid in-
crease is due to conditions associated with, or perhaps occasioning the
attack. Pett mal cases exhibit a large and persistent excess.

Paroxysmal vomiting in children is often followed by a very remark-
able increase: and migraine shows a considerable increase. It is con-
cluded that the increased execretion is an effect of numerous different

derangements of nitrogeneous metabolism.
A second paper by the same authors? discusses these questions fur-

1. Heerer ann Suiru. Observations on the Excretion of Urie Acid in Health
and Disease N.Y. Med Journ , June 4. 1892.

2. Researches upon the Aetiology of Idiopathic Epilepsy. N. Y. Med, Journ,,
Aug.-Sept., 1892.

cxll JOURNAL OF COMPARATIVE NEUROLOGY.

ther and seems‘to indicate some connection between intestinal putrefac- -_

tion and epilepsy. The evidence on this head is interesting but far from
convincing.
EXCISION OF CORTEX AS A CURE FOR INSANITY.1

Six cases of chronic mania, dementia, etc., were operated by removal
of 2 cm. or more of the cortex, the areas corresponding to the seat of the
sense chiefly affected by hallucination. In five cases, amelioration, in
one, death resulted. The effect seems to consist in the transformation of
impulsive mania into passive dementia, frequently with removal of the

hallucinations.

JAMES BRIEFER COURSE IN PsyCHOLOGyY.?2

Professor James is a teacher, and his much used work is conceived as
only a teacher could. It contrives to supply very much of the vivacity
and piquancy of personal instruction within the compass of a text book.
Add to this the fact that he is especially alive to the prevailing tenden-
cies in psychological thought and we have a partial explanation of the
sudden success of a work which is neither logical in arrangement nor
faultless in psychical analysis. The briefer course seems to us a vastly
more usable book. The author describes it as three-fifths ‘scissors and

b]

paste.’’ These three-fifths have greatly gained, from the stndent’s stand-
point, through both these modifying agents. The scissors have relieved
him of tapestries which would, in all prohability have hung in shreds
about his hurrying feet, and the paste has been ‘‘mixed with brains.”
The two-fifths not accounted for supply important physiological details
as to the sensory organs which American classical courses seem never to
adequately supply in the term or two of physiology.

Many teachers will object to building up the fabric of an elementary

’

text-book upon such a ‘working hypothesis’ as this: ‘ Mental action
may be uniformly and absolutely a function of brain-action, varying as
the latter varies, and being to the brain as effect to cause.’? Conscious
processes are divided into sensation, cerebration, and tendency to action.

The paragraphs on sensation fail to distinguish adequately sensation

and perception. Especially unsatisfactory is the discussion of externali-

1. Burkcvarnpt, G. Allg. Zeitsch f. Psychiatrie, XLVII.

2. James, WitutaAm. Psychology, American Science Series. Briefer Course.

Henry Holt & Co,, New York, 1892.

)

[= |

LITERARY NOTICES. exliil

zation and excentric projection. The author claims that ‘‘the very first
sensation which an infant gets zs for him the outer universe.’? ‘* The
object which the numerous impouring currents of the baby bring to his
consciousness is one big, blooming, buzzing confusion. That confusion
is the baby’s universe.’”’ Many such expressions make us wish that the
author could have escaped from some of the consequences of the contact
with American tendencies which nevertheless impart the breeziness of
style which compel almost unwilling admiration. The chapter on the
structure of the brain, supplemented by that on its functions, gives a
synoptical sketch of the neurology, and it is the teacher who says, with
a sigh perhaps, ‘*‘ When is all is said and done, -the fact remains that, for
the beginner, the understanding of the brain’s structure is not an easy
thing. It must be gone over and forgotten and learned again many times
before it is definitely assimilated by the mind.”

The chapter on habit is full of useful maxims. Many will gratefully
agree that ‘‘the traditional psychology talks like one who should say a
river consists of nothing but pailsful, spoonsful, quart pots full, barrels

full and other moulded forms of water;”’

and accept with such grace as
he may the conclusion that ‘‘each of us dichotomises the Kosmos in a
different place.”’

The chapter on attention is especially good. James adopts (with
regret) the terms recept (or construct) and isolate of comparative psychol-
ogy. He goes the full length of Professor Bain in assuming that all con-
sciousness is motor according to a law of diffusion. ‘* A process set up
anywhere in the centres reverberates everywhere, and in some way or
other affects the organism throughout, making its activities either
greater or less.”” James follows Lange in asserting that ‘‘ bodily changes
follow directly the perception of the exciting fact and that our feeling of
the same changes as they occur zs ¢he emotion.” While not wishing to
belittle the physical concomitants in emotion, we protest that it is a pity
to strip these important sections of our psychical life of their cognitive
elements. It seems to us that James has fallen into an error analogous to
those against which he has warned us. In classing emotions as a variety
of impulses, as in the earlier work, he prepared the way for this error.
A more natural order is here followed, viz: (1) Expression of emotion, (2)
Instinctive or impulsive performances. (3) voluntary deeds. We object
to identifying emotion with either its expression or physiological ele-

ment. No doubt many emotions are due to reflexes producing total sen-

exliv JOURNAL OF COMPARATIVE NEUROLOGY.

sations, but such sensations have this as a characteristic that they impli-
cate the empirical ego, and that act of cognition which forms the
nexus between the physical shock and the subject of consciousness can
no more be left out than the data of effort can be left out of perception.

The chapter on will is quite a full reproduction of that in the larger
work and is so suggestive that no attempt can be made to discuss it here.
The work has that prime requisite of a text book, it is suggestive and fresh
and does not leave the student with the deadly delusion that he has fin-

ished the subject.

RECENT LITERATURE.

ANDERSON,-O, A, Zur Kenntnis des sympathischen Nervensystems

der urodelen Amphibien. Zool. Jurbiicher, Abth. f, Ontog. u. Anat. V. 2.

ANON. Metamerism of the Vertebrate Head. Journ. Comp. Neurol.

II, Dec., 1892.

Transformation of Nervous Matter in the Insane. /owrw. Amer,
Med. Assoc., XX, 21.

BERANECK, E. Sur le nerf parietal et la morpho!ogie du troisieme
oeil des Vertebres. Anat. Anzeiger, VII, 21-22.

Biror and LAMAcQ. Syringomyelie. Bu/. Soc. ad’ Anat. de Bor-
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CAPOBIANCO, F. Sulle fine alterazioni dei centri nervosi e delle ra-
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CHILARDUCCI. Contribution au diagnostic differentiel entre Vhys-
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CousIN. Paralysis agitante sans tremblement. Bu/. Soc. ad’ Anat. de
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DANILEWSKI, B. Zur Physiologie des Centralnervensystems von
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EpirortaL. The recent Therapeusis of Diseases of the Nervous
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FusaklI, R. Contribuzione allo studio dello sviluppo delle capsule
surrenali e del simpatico nel pollo e nei mammiferi. Archivio per le se.

med. Turin, 1892, p. 244.

ae

RECENT LITERATURE. cxlv

FusarI, R. Sul modo di distribuirsi delle fibre nervose nel paren-

chima della milza. MMonztore Zoolgico, I11, 78

GuITEL, F. Recherches sur les boutons nerveux bucco-pharyngiens

de la Baudroie (Lophius.) Archiv. Zool. Exp. IX, 4.

HERGENHAHN, E. Ueber die Bedeutung des Offenstehens der Fossa
Sylvii und des Freiliegens der Insel. J/aréurg, 1892.

Herrick, C. L. Embryological notes on the brain of the snake.
Journ. Comp. Neurol., 11, Dec., 1890.

Herrick, C. L. Scope and Methods of Comparative Psychology.
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HerrRIcK, C. L. Histogenesis and Physiology of the Nervous Ele-
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Kawtiius, E. Ueber die Medulla spinalis und die Medulla obiongata
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KoEPpPEN, M. Ein Fall von sogenannter Heterotopie der grauen

substanz des Riickenmarks, Charite Annalen, XVII.

LAMARQUE. Fracture du crane par coup de pied de cheval; abces
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LINDEMANN, L. Zur kasuistik des Mikrocephalengehirnes. Mu-
nich, 1891.

MATIGNON. Tumeur ducerveau. Bul. Soc. d’ Anat. de Bordeaux,
SIU,

Moussous. Idiotie; acces epileptiformes; pachymeningite et me-
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PELSENEER, M. P. Les organes des sens chez les mollusques. Aa-
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PELSENEER, M. P. Sur lceil de quelques mollusques gasteropodes.

Annales de la Soc. Belge de Micros., XV1.

Pevuizzi, G. B. Sur les modificationes, qui survienment dans la

moelle epiniere des amputes. Arch. ttaliennes de biologie, XVIII, 1.

PEPIN and SABRAGES. Cerebro-spinale meningite suppuree chez un
enfant de vingt cinq jours; pneumocoques dans le pus. Axl. Soc.
@ Anat. de Bordeaux, X11.

PEPIN and FRoMAZET. Atrophie du cerveau; absence de la capsule
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exlvi JOURNAL OF COMPARATIVE NEUROLOGY.

ProrrowskI, G. Plethysmographische Untersuchungen am Kan-
inchenohre.

SALA, L. Sulla fina anatomia dei gangli del simpatico. Monttore
Zoologico ttaltano, II, 7-8.

SABRAZES, Meningite cerebrospinale a pneuma-coques. Az. Soc.
@’ Anat de Bordeaux, X11.

SCLAVANOS, G. L. Beitrige zur feineren Anatomie des Riicken-
markes der Amphibien. Leipzig, 1892.

SEPPILLI, G. Sui rapporti della cecita bilaterale colle affezioni dei
lobi occipitali. Rezvesta sperimentale di Fren., XVI, 2.

SIEMERLING, E. Ein Fall von schwerer neuropsychose ausgezeich-
net durch Kongenitale Anomalien des Centralnervensystems. Charite
Annalen, XVII, 1892.

SAVORY, Sir WM. Bruises of the Brain. From the Zancet. West-
ern Medical Reporter, Oct.

STADERINA, R. Sur une particularite de structure de quelques ra-
cines nervenses encephaliques. Arch, ttal. de biologie, XVIII, 1.

STANLEY, E.G. An illustration of the taxonomic application of
brain measurement. Fulica. Journ. Comp. Neurol., 11, Dec., 1892.

TREPINSKI. Beitrag zur kenntniss der entwicklung der Markscheid-
en in den Hinterstringen des Riickenmarkes. <Ad/gem. Zeits. f. Psychiat-
rie und psych.—gericht. Med., XIX, 1-2.

VERGELY. Pachymeningite hemorragique; epilepsie jacksonienne.
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WHASSAK, R. Die Centralorgane der statischen Functionen des

Acusticus. Centralblatt f. Phys., V1, 16.

PHYSIOLOGICALS PSYCHOLOGY:

ANON. The Psychological Laboratory at Yale. Scéence, XX, 514,
Dec. 9, 1892.

AMERY, €. F. Instinct. Sczence, XX, 512.

BALDWIN, J. Mark. Origin of Volition in Childhood. Sczence,
XX, 511, Nov. 18, 1892.

PHYSIOLOGICAL PSYCHOLOGY. exlvul

Boas, F. The Growth of Children. Sczezce, XX, 216.

BuTLer, A. G. Songs of birds reared from thenest. Zoo/og7st, Vol.

16, January.
CAMPBELL, J. T. Sense of Direction. Sczence, XX, 513.

Cork, E. D. Parallel color-patterns in. Lizards. Amer. Nat., Vol.
]

26, June.
Cummines, W. F. Is there a sense of direction? Screwce, XX, 515.
Dennis, W. Watching a snake for an hour. Sczence, XX, 515.

Evans, W. Notes on the Periods occupied by birds in the incuba-

tion of theireggs. Zhe /bis, Vol. 4, Jan.

FEILDEN, H. W. Heron catching arat. Zoologist, Vol. 15, March.

Gibps, Morris. Birds that sing in the night. Sczence, XX, 513.

GopbFREY, Ros. Ground-building Birds removing Egg-shells. Zoolo-
gist, Vol. 16, January.

L. H. H. Jealousy of a Dog. Sagence, XX, 512.

James, W. Thought before language. /Phzlosoph. Review, I, 6.
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Mackay, G. H. Habits of the black-belted Plover in Massachusetts.
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MARSHALL, H. R. Pleasure, pain, and sensation. Phzlos. Review,
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RIDGEWAY, R. Nocturnal songsters and other bird-notes. Sczence,
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SANBORN, J. W. How are young spiders fed? Sczence, XX, 515.

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exlvil JOURNAL OF COMPARATIVE NEUROLOGY.

VANDEMAN, H. E. Sense of Direction in Animals. Sczence, XX,
_ 511, Nov. 18, 1892.
Vorcur, A. Anleitung zum Studium der Vogelstimmen. Leipzig,
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WILLIAMS, J. B. Water rattlesnakes in captivity. Scéence, XX, 515.

MISCELLANEOUS.

Der GARMO, CHARLES. A Popular View of Apperception, Diagram.
Public School Journal, November.

Swirt, JAMEs EoGar. Disturbance of the Attention During Simple
Mental Processes. Am-rican Journal of Psychology, October.

S\ILEY, E. H, S. Taste and Smell. Review of ten works. Ameri-
can Journal of Psychology, October.

Space, Time. Review of seven works. American Journal of Psy-
chology, October.

Touch, Pain, Internal Sénsations, etc. Review of sixteen works.
American Journal of Psychology, October.

Imagination in Dreams. Leligto- Philosophical Journal, Nov. 12.

WerrHERWAX, M. Workings of Instinct. Common to human _be-
ings and the brute animal. Zvoy Times, Nov. 5.

KROHN, WILLIAM H. Pseudo-Chromesthesia, or the Association of
Colors with Words, Letters, and Sounds. American Journal of Psychol-
ogy, Oct.

CHAMBERLAIN, A. F. Some Points in Linguistic Psychology. A
series of experiments. American Journal of Psychology, October.

Hypnotism in Crime. Should the hypnotic agency be employed in
criminal cases? Tests that have excited profound scientific interest.
Portraits. MV. Y. World, Nov. 13.

Noyes, WILLIAM. Psychiatry. Review of sixteen works on insan-
ity, general paralysis, melanchology, ete. American Journal of Psychol-
ogy, October.

Insane Illusions. Paranoia; cranks and criminals; inherited ten-
dencies. Pawtucket Times, Nov. 11.

EpirorIALt. Do Snakes Think? 7Zyvoy Press, Nov. 8.

MISCELLANEOUS. cxlix

The Evolution of Mind I. Review of Dr. Hardwicke’s ‘* Evolu-

tion and Creation” in Secular Thought, Aug. 27.

o
g.
Cures by Hypnotism. (Mind influence, and its practical value; re-
port of sessions of experimental-psychology congress.) From Pall Jfal/
Gazette. Memphis Commercial, Aug. 21.
’

EpirortaL. Psychical Research. WV O. Picayune, Aug. 21.

The Problem of the Hearing of Colors. Alfred Binet in ‘* Revue

des Deux Mondes.”’ Pudlic Opinion, Nov. 25.

Some Optical Illusions, From ‘* Nature.’’ Diagrams. Seéentéfic
American Supplement, Nov. 26,

BoorH, HENry M. Thoughts Without Words. (On the possibility
of having thoughts without words and communicating them freely.) V.
Y. Evangelist, Nov. 24

Science of Human Nature. Institute of phrenology; scope of study,
etes wn). 97072, INOW 0:

STRODE, E L. Cerebral and Pelvic Abscess. Jledical World, Oct

PLEDRA-SANTA, Dr. A Strange Disease—NKitsune-Tsuki, or Posses-
sion by Foxes—in the ‘‘ Journal d’Hygiene.”” National Drugyist, Oct. 1.

NicHou“s, HERBERT. The Origin of Pleasure and Pain, II. (Bio-
logical origin of mind, ete.) Phzlosophical Review. September.

HoLprook, L. Good and Bad Powers of Observation. [New set
of observers needed for studying spiritualism.] Ae/¢gvo- Philosophical
Journal, Sept. 17.

AGNosco. The Evolution of Mind. Secular Thought, Oct. 8.

STANLEY, HiRAM M. Some Remarks Upon Prof. James’ Discussion

of Attention. JZonzst, October.

.

SANGREE, Ernest B. Maternal Impressions on the Fcetus. Cases.
Phila. Times and Register, August.

ROBERTSON, G. M. Psycho-Therapeutics. From the ‘* London
Lancet.’? American Practitioner and News, Oct. 8.

AGnosco. The Evolution of Mind. III. Seeewlar Thought, Sep-
tember Io.

Keeping the Head Down to Restore the Exhausted Brain. An Eng-
lish doctor’s theory. Phila. Times, Sept. 4.

The Evoltion of Mind II. Review of Hardwick’s ‘* Evolution

and Creation.”’ Secelar Thought, Sept. 3.

cl JOURNAL OF COMPARATIVE NEUROLOGY.

The Present Status of Psychology. Editorial in Journal of Educa-

‘tion, Aug. 25.

BALDWIN, MARK J. Experimental Psychology. Proceedings of the
International Congress; outlines of the leading papers; suzzestions. WV.

Viv Post, septs 10:

BALDWIN, MARK J. The Hypnotic Cure. Dr. Bernheim’s Theory

as exemplified in hospital at Nancy. WV. Y. Post, Aug. 20.

VAN GIEsON, IRA. A Study of the Artifacts of the Nervous System.
VI. Analysis of the erroneous cases of spinal cord malformations pro-
duced by manipulation, or disease, or both combined. VII. The diag-
nosis of spinal-cord bruises; general remarks. Illustrated, WV. VY. MWed-
tcal Journal, Oct. 15

NORBURY, FRANK PaksONS. Surgical Interference in Cerebral Dis-
eases of Children. JAfLedical and Surgical Reporter, Sept. 3.

A. L. ‘©The Man Who Thinks.”’ (Not merely the brain; intellect-

5)

ual work in sickness, etc.; illustrated.) I. ‘* From National Reformer.’
Twentieth Cenfury, Oct. 27.

Mackay, F. F. Passions and Emotions (and forms of Expressing
Them) With discussion. Werner's Voice Magazine, September.

LUETKEN, GEORGE—in the Copenhagen ‘‘Illustreret Familie-Jour-

nal’? Animal Language. Chicago Graphic, Oct. 29.

STRUTHERS, WILLIAM. The Seat of Language and Lingual Dis-
eases. Medtco- Legal Journal, June.

HERTER, C. A. and SmiTH, E. E. Researches upon the tiology
of Idiopathic Epilepsy. A preliminary communication. (Concluded.)
N. Y. Medical Journal, Sept. 3.

HucGuHes, C. H. Hysterical Concomitants of Organic Neuroses.
Medical Standard, October.

The Study of Dreams. F. Greenwood in the ‘* New Review.’ | Pud-
lic Opinion, Nov. 26.

SEGUIN, E.C | Eye-Strain and its Relations to ** Cerebral Hyper-
emia.” - V. Y. Afedical Journal, Dec. 3.

BROWN, GEORGES. Gunshot Injury of the Great Sciatic Nerve.

Medical News, Oct. 22.

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