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THE JOURNAL

OF

COMPARATIVE NEUROLOGY

EDITORIAL BOARD

Henry H. DonALDSON ApoLF MryYER

The Wistar Institute Johns Hopkins University
J. B. JOHNSTON OurveR 8S. Strona

University of Minnesota Columbia University

Cc. Jupson Herrick, University of Chicago
Managing Editor

VOLUME 31

OCTOBER, 1919—JUNE, 1920

|

THE WISTARINSTITUTE OF ANATOMY AND BIOLOGY
}

PHILADELPHIA, PA.

CONTENTS

No. i OCTOBER, 1919

A. C. Ivy. Experimental studies on the brain stem. II. Comparative study of the
relation of the cerebral cortex to vestibular nystagmus. Nine figures.............. 1

F. T. Rogers. Experimental studies on the brain stem. II. The effects on reflex
activities of wide variations in body temperature caused by lesions of the thalamus.

Meni GUTES: y= ee IN eto sone lvoe sere sin to oH Sears Sar nen eC raed 17
A. T. Rasmussen. The mitochondria in nerve cells during hibernation and inanition in
theswoodchucka(Vinm ota onax)) yaa pan ers A cei etaoe ieee eae cite 37

No. 2. DECEMBER, 1919

C. U. Arténs Kapprrs. The logetic character of growth. Two figures................. 51
SHIGEYUKI KominE. Metabolic activity of the nervous system. IV. The content of non-
protein nitrogen in the brain of the rats kept in a state of emotional and physical

Excitement: LOPysemetal OUTS Hae dds fe heucj Nei aes.< a enialtein Heron rays rele Me eee ee eee 69
Matuintve L. Kocw anp Oscar Rippue. Further studies on the chemical composition
of the brain ofmormnal and ataxie pigeons’... 2.0/4. -...)ncascscanea he cee nes ct use one 83

Teist Hosuino. A study of brains and spinal cords in a family of ataxic pigeons.

pie efi FUT eS)- RO 5. 5, 5k RASS once Se Se & oc yO Peano o albae e ereeeeeraye irae iil
No. 3. FEBRUARY, 1920
Frep W. Stewart. The development of the cranial sympathetic ganglia in the rat.
Bhirty Sux lian eo meee tect sss «eS wee ete SO A se Re Soe Bee eee ee 163

No. 4. APRIL, 1920

Henry C. Tracy. The membranous labyrinth and its relation to the precoelomic

diverticulum of the swimbladder in clupeoids. Twenty figures.................... 219
O. Larsen. The cerebellum of Amblystoma. Twenty-one figures....................- 259
SwaLE VINCENT AND A. T. Cameron. A note on an inhibitory respiratory reflex in

the frog and some other animals............. BOSON ED ': gE RIG oe 5 LUO ane a 283

No. 5. JUNE, 1920

H. W. Norris anp Satity P. Huenes. The cranial, occipital, and anterior spinal nerves

of the dogfish, Squalus acanthias. Fifty-three figures..................0--.-+...- 293
N. EB. McInvoo. The olfactory sense of Orthoptera. Ninety-two figures.............. 405
Epwarp Horne Craicrs. On the relative vascularity of various parts of the central

nervous system of the albino rat. Five figures and four charts.................... 429

J.M.D.O.umsrep. The nerve as a formative influence in the development of taste-buds. 465

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THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. ik,
OCTOBER, 1919.

Resumen por el autor, A. C. Ivy.
Universidad de Chicago.

Kstudios experimentales sobre el tallo cerebral.

Il. Un estudio comparativo de la relacién de la corteza cerebral
con el nistagmo vestibular.

El autor ha estudiado la relaci6n de la corteza cerebral con
el nistagmo vestibular en la rana, tortuga, paloma, conejo y
gatos y perros jOvenes y adultos. Llev6 a cabo varias ablaciones
del cerebro observando su efecto sobre el nistagmo vestibular,
usando como estimulo la rotacién. La extraccién del cerebro
en la rana, tortuga y paloma no perturba el nistagmo vestibular.
La extraccién completa del cerebro en el conejo con la destruccién
extensa del talamo no suprime el componete rapido del nistagmo,
siempre que la temperatura del cuerpo se conserve normal. Las
observaciones de F. 'T. Rogers sobre la reduccion de la tempera-
tura del cuerpo subsiguiente a las lesiones del talamo y su efecto
sobre los reflejos ha sido confirmada por le autor en el conejo.
Kn el gato y perro la ablacién de la corteza motriz en la region
del area ocular causa un aumento temporal, con alguna per-
manencia, de 5a 15 veces mayor, en la duracién de post-nistagmo,
cuando se hace girar al animal sobre el lado de la lesién. Hay
un aumento en la reaccién del nistagmo cuando la desviacién es
opuesta al lado de la lesién, con alguna disminuci6n, pero no
cesacion, cuando la desviacién tiene lugar hacia el lado de la
lesion. Los hechos apuntados dan validez a la conclusion de que
el componente rapido del nistagmo vestibular no se debe a la
integridad de un arco reflejo cerebral, sino que depende de
algtin centro situado debajo del talamo, sobre el cual ejerce el
cerebro una bien reconocida accién inhibidora.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR'S ABSTRACT OF THIS PAPHR IS8UND BY
THY PINWOGRAPHIC SHRVICH, SHPTHMBHR 20

EXPERIMENTAL STUDIES ON THE BRAIN STEM

Il. COMPARATIVE STUDY OF THE RELATION OF THE CEREBRAL
CORTEX TO VESTIBULAR NYSTAGMUS

A. Uiy 2

Hull Physiological Laboratory, The University of Chicago
NINE FIGURDS

During the course of a study involving a series.of cerebral
ablations, it was suggested by Dr. IF. T. Rogers that observa-
tions be made upon the nystagmus reaction. Wilson and Pike
C11, 18, 715) are of the opinion that the quick component of
nystagmus is dependent upon the integrity of a cerebral reflex
are. Pike (17) reports that removal of one cerebral hemisphere
abolishes the quick movement when the slow movement of the
eyes is directed to the side of the remaining cerebral hemisphere.
On the other hand, Bauer and Leidler (‘11) report that the quick
component of vestibular nystagmus is not dependent upon the
cerebral cortex and that ‘extirpation of the cerebrum, thalamus,
even extensive destruction of the midbrain and probably with the
inclusion of the oculomotor nucleus does not disturb vestibular
nystagmus.’ Hence there is quite a discrepancy between the
reports of the two groups of investigators which has stimulated
this study.

MBTHODS

I'rogs, turtles, pigeons, rabbits, kittens, cats, pups, and dogs
were studied. All operations upon mammals were done under
aseptic conditions. Observations were made before and at dif-
ferent periods following the operation. When the animals were
comatose, or markedly depressed, or showed symptoms of in-
creased intracranial pressure, a notation of such a condition
was made. Autopsy was done upon every animal and the brain
was preserved.

bo

ip (CG LE

Observations were made upon rotatory and postrotatory nys-
tagmus. The animals were placed upon a turntable and rotated,
the speed and number of rotations being controlled.

RESULTS

Frog. Some observers have reported the presence of compen-
satory movements of the eyes of the frog, others have not. This
discrepancy is probably due to the condition of the frog and the
acuteness of observation. Out of about one hundred frogs ex-
amined only a few were found that did not show on rotation a
true vestibular nystagmus with slow and quick .components.
The small green frog (Rana pipiens) and the jumbo bull-frog.
(Rana catesbiana) were used. The latter is much better than the
former for study, as the nystagmus reaction is more marked and
the eyes are larger. Several precautions are necessary in order
to observe the reaction. It is necessary to rotate the frog slowly ;
if rotated too rapidly, only deviation occurs. The quick com-
ponent is very slight in degree (2 to 3 inch, depending on the
size of the frog), for the deviation in the frog is not marked. It
is easier to observe, if the head is held between the fingers to
prevent head nystagmus. If the frog struggles much, it will be
absent. Pinning to the frog board often inhibits the reaction.
Postrotatory nystagmus is very infrequent. I have observed it,
however, consisting only of one or two movements. The tem-
perature of the frog is very important. The best reaction occurs —
at 18° to 20°C.

Decerebration in the frog never abolishes the quick compon-
ent of nystagmus nor interferes with the nystagmus reaction in
any way. If the frog is depressed as a result of the operation,
then deviation only is observed.

Turtle. Wilson and Pike (715) report that nystagmus is absent
in the turtle. My observations are to the contrary, provided the
turtle’s temperature is between 10° and 39°C. On either side
of these temperatures the quick component is abolished and
deviation only is present.

This effect of temperature upon nystagmus is only to be ex-
pected when it is recalled that reflexes in general are depressed
by temperature on either side of the normal or optimum.

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS 3

A true vestibular nystagmus is present in all species of turtles
and terrapins received at our laboratory (Chrysemys elegans,
Chrysemys concinia, Chelydra serpentina et al.). From two to
six quick movements of the eye occur while rotating the turtle
through ninety degrees at a rate of one turn in two seconds.
From three to twelve postrotatory quick movements occur when
rotated ten times at a rate of one turn in two seconds. There isa
latent period of from one to four seconds before postrotatory
nystagmus appears. Prince (’17) reports such a latent period
in very young animals, which I have confirmed. (This, I have
found, is also the case in new-born babies.)

TABLE 1

Showing the effect of temperature wpon the quick component of nystagmus in the
5 turtle

TURTLE QUICK COMPONENT DISAPPEARED AT OPTIMUM TEMPERATURE
2G SCe OE
A 10.0 38.0 12.0-36.0
B 9.0 37.0 13 .0-36.0
C 13.0 38.0 18 .0-36.0
D 9.5 38.0 16.0-35.0
E 9.5 37.5 10.0-35.0
FE 18.0 36.0 32.5-34.0

Deviation occurs at 2°C. Temperature was not reduced lower. Deviation
disappears at 39° to 40°C. Head nystagmus appears simultaneous with or
shortly after theeyenystagmus. Both head and eye movements occur synchron-
ously and simultaneously.

Hemi-decerebration and total decerebration without injury to
the optic lobes, midbrain, and underlying nerves have no effect
upon nystagmus in the turtle. If the turtle is depressed as a
result of the operation, the number of nystagmic movements is
diminished or entirely absent. A decided increase in the number
of nystagmic movements has been seen not infrequently. (This
increase and the effect of lesions of the optic lobe, reported at
the meetings of the American Physiological Society, spring, 1919,
will be discussed in a later paper.)

Pigeon. Ewald (10) reported the presence of true vestibular —
nystagmus in pigeons. According to Wilson and Pike (’15), it

4 AL Cay

is present in the pigeon only to a slight and less pronounced de-
gree than in mammals. According to my observations, the av-
erage number of rotatory nystagmic movements for thirty pigeons!
when rotated through an arc of ninety degrees at a speed of one
turn in two seconds was six, the minimum number being three,
the maximum ten. The average number of postrotatory move-
ments for the same group of pigeons when rotated ten times at a
speed of one turn in two seconds was eleven, the minimum being
four, the maximum twenty. The average duration of the af-
ter-nystagmus was five seconds.

Hemi-decerebration in the pigeon has no effect upon nystagmus.

Complete decerebration with even extensive injury to the
thalamus does not abolish the quick component of nystagmus
provided the temperature of the bird is kept normal. Rogers
(18) has shown that the temperature of the decerebrate bird with
thalamic lesion must be kept normal in order to get normal de-
cerebrate behavior. In two such pigeons, whose body tempera-
ture fluctuated with the temperature of the surrounding air, it
was found that the quick component of nystagmus disappeared
at 34°C. in one and 35°C. in the other, while deviation persisted.

Rabbits. True vestibular nystagmus is present in the rabbit.
The average number of rotatory movements for eight rabbits
when rotated though an are of ninety degrees at a speed of one
turn in two seconds was five, the minimum being four, the maxi-
mum seven. The average number of postrotatory movements
for the same group of rabbits when rotated at the same speed
was sixteen, the minimum being seven, the maximum twenty-
four. The average duration of the after-nystagmus was eight
seconds.

Some rabbits show a marked variation in the number of move-
ments and the duration of the after-nystagmus, although they
were rotated at the same rate of speed and other factors were con-
trolled. One of the rabbits varied from seven to twenty-two
movements, or from four to ten seconds, during the course of

! The pigeon’s head should be fixed so it cannot be moved. The pigeon has a
method of shaking and twisting its head which markedly inhibits the number
of the movements and duration of the after-nystagmus.

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS 5

one examination. Struggling has.a marked inhibitory effect
upon the duration and the number of movements of the after-
nystagmus. When the eye is turned in the direction of the quick
component, the nystagmus is increased, and vice versa, as is the
case in man. With these and other factors controlled, there
was a marked variation in two of the eight rabbits examined.
Hemi-decerebration in the rabbit does not abolish the quick
component of nystagmus. It is present when the animal is
rotated in both directions, but there is a difference in intensity

TABLE 2

Showing the effect of hemi-decerebration in the rabbit on vestibular nystagmus

NORMAL LEFT HALF CEREBRUM REMOVED
Rotatory Postrotatory Rotatory Postrotatory
AB B11 5 |e eee eens) ae

Rotated to Rotated to Rotated to Rotated to
Right Left Right Left Right Left Right Left
I 5? 5 18-22 18-22 Q-11 3-4 18-22 6-12
II 4-5 4-5 10 15 0-1! 5-6 10-20 5- 7
III 5 5 12-15 14-18 Q-1! 5 18-31 7-11
IV 5 5 14-16 15-18 0-2! 5-7 18-25 8-1l

1 When the table was stopped, having rotated only a quarter of a turn, two to
three postrotatory movements invariably occurred. This never occurs in the
normal rabbit nor in the hemi-decerebrate when rotated to the left.

* Figures represent the number of quick movements when the rabbit was ro-
tated through an arc of 90° at a speed of one turn in two seconds. The postrota-

tory movements were elicited by rotating ten times at a speed of one turn in two
seconds.

(table 1). The rotatory nystagmus is diminished, almost ab-
sent, when rotated opposite to the side of the lesion, but the post-
rotatory nystagmus is intensified. The rotatory nystagmus is
normal when rotated to the side of the lesion, the postrotatory
nystagmus being apparently somewhat diminished. Sometimes
a latent period of from two to five seconds occurs before the after-
nystagmus, which is liable to cause one to overlook the reaction
entirely. If the animal is depressed or manifests marked activ-
ity and restlessness, the quick component is irregular in its
occurrence or may be entirely absent.

6 MC. TVm

Complete decerebration in the rabbit does not abolish the
quick component of nystagmus. The entire thalamus can also
be destroyed (figs. 8 and 9) without abolishing the quick compo-
nent. In the decerebrate rabbit the quick component persists
until the animal becomes depressed because of degenerations in-
volving lower centers or because of inanition, it being very diffi-
cult to keep these animals in a good state of nutrition. In the
decerebrate rabbit with destruction of the thalamus the tempera-
ture becomes subnormal and the quick component disappears,
but will return again, if the animal is placed in an incubator and
its body temperature raised to normal. Deviation still persists
with subnormal temperature. In such a rabbit immediately
after the operation and for four to five hours later the quick com-
ponent is very manifest, but after this time it is irregular and sub-
ject to wide variations. Two such animals manifested no rota-
tory quick component when tied to a board, but when held in
the hands and rotated the quick component was present. With-
out taking into consideration these last two points, along with
body temperature, one might overlook the presence of the quick
component in rabbits without cerebrum and thalamus.

The rabbit is a convenient animal in which to demonstrate the
presence or absence of the quick component following various
brain lesions.

Cats. Six cats have been worked upon with the same results
as observed in the rabbit and the dog.

Kittens and pups. The same observations hold true in young
animals as observed in the adult, except for a general rule that
the depression from the operation is less marked and the effects
produced are more temporary. However, one pup, which was
operated at the age of four months and is now one year old
(August 1, 1919), in which the left motor cortex, occipital cortex
and basal portion of the temporal lobe was extirpated, now shows
three postrotatory movements when rotated to the left, and
eight when rotated to the right. The increase in the after-
nystagmus when rotated opposite to the side of the lesion seems
to be permanent in this pup.

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS a

Observations upon the time of occurrence of nystagmus in
new-born kitens confirm those of Prince (’17). Well-defined ves-
tibular nystagmus does not appear until the end of the second
week and the after-nystagmus is preceded by a latent period in
kittens and pups. (Observations which will be published later,
have been made upon new-born babies. )

Dogs. Rotatory vestibular nystagmus is present in the dog to
the same degree as it is in the rabbit. Postrotatory nystagmus,
however, is not so marked in the dog as in the rabbit. The av-
erage number of postrotatory movements for thirty dogs when
rotated ten times at a rate of one turn in two seconds was six,
the average time of duration being four seconds. One dog in
this series had to be rotated at a rate of one time per second in
order to elicit a postrotatory response of four movements. In
other words, individual variation occurs in dogs as in rabbits
and other animals studied, which necessitates the determination
of the normal of the dog before operating.

Ablation of the eye-motor area of the cerebral cortex, also with
inclusion of the lateral and basal portions of the temporal lobe,
does not abolish the quick component of nystagmus. On the
contrary, there is an increase in the rotatory nystagmus when
rotated to the side of the lesion and a marked increase in the post-
rotatory nystagmus when rotated opposite to the side of the lesion.
This increase is more or less temporary, but persists as long as
six and eight months (dog V, table 3) in two animals permitted
to live that long. This increase consists in a five- to fifteen-fold
increase in the number of movements and a two- to four-fold
increase in the time of duration of the after-nystagmus. This
marked increase only lasts from one to three weeks, after which
it reduces gradually to only a two- or three-fold increase. The
magnitude of the quick component is decreased, that is the arc
through which the eye is moved during the quick component is
decreased as compared with the normal.

There is also a tendency for the quick movements to occur with
the eye deviated, i.e., the quick movement does not bring the
eye back to the primary position, as normally occurs, but only
partially (from one- to two-thirds of the normal are). This tend-

8 Aer Oc TVX

ency for the quick movements to occur on deviation is generally
the case, but in some dogs the quick movement does bring the eye
back to the primary position.

Complete hemi-decerebration and extensive injury to the thal-
amus do not abolish the quick component of nystagmus. This
statement is based upon observations made on eight dogs that
lived from two weeks to eight months following the operation.
In some of these animals the lesion was produced in one opera-
tion, in others in two operations. Thirteen animals were oper-
ated in order to get this group of eight. Five of these animals
died in from one to five days showing various symptoms, as con-
tinued running movements, howling and crying, rapid respira-
tion, vomiting, subnormal temperature, deep depression and
coma. These five animals did not show the quick component
at any time following the operation. Three of them showed
deviation, the other two no eye movements (marked deviation
down and out was present) at all on rotation. In one animal the
left third nerve was torn from the brain stem. Four of the eight
animals kept alive had to be fed and watered daily by artificial
methods, as they would neither eat nor drink voluntarily.’ All
of these animals died of nutritional disturbance. The other
four dogs ate and drank voluntarily in four to ten days after the
operation. The lesions were verified by autopsy and brain rem-
nants preserved for later anatomical study.

In two animals with complete hemi-decerebration and lesion
to the lateral portion of the thalamus, the remaining motor cor-
tex including the eye-motor area and basal portion of the tem-
poral lobe was extirpated. Both of these animals showed an
increase in the postrotatory nystagmus when rotated to the side
opposite the fresh lesion. This latter operation was done six

* One was nourished via gastrostomy.

‘ Two of these animals during the last week of their lives, when their tempera-
ture was subnormal, passed in the stools particles of undigested food—particles
of meat whose substance was not even discolored and milk no further changed
than coagulated. These two animals and three others dying from extensive thal-
amus lesions passed liquid red-paint colored stools, which gave positive tests for
blood. Autopsy of the gastro-intestinal tract revealed petechial hemorrhages
and hyperemia of the gastric mucosa, the rest of the intestinal tract being normal,

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS 8)

to seven months following the complete hemi-decerebration. One
of the animals was kept alive four weeks, the other was killed
by a whelping bitch five days after the operation.

Failure has attended all attempts to produce a complete de-
cerebrate dog. All these animals were markedly depressed and
comatose and did not live longer than four days. None of these
animals manifested the quick component of nystagmus. The
slow component, or rotatory deviation, was present in all but

TABLE 3

Effect of complete left hemi-decerebration and extensive lesion to the thalamus on the
quick component of nystagmus in the dog

NORMAL AFTER OPERATION!

Rotatory Postrotatory Rotatory Postrotatory

DOG

Rotated to Rotated to Rotated to Rotated to
Right Left Right Left Right Left Right Left

33 4 4 2 2 32 6 22 4
31 5 5 6 6 3? 7f AO 7
34 4 5 4 2? 7 42 9
27 4 4 5 if 0-3? 6 50 10
30 5 5) 7h 6 42 8 24 5
5? 6 5 9 8 6} 9 35 9
14 5 4 a if 4 ae — —_

1 Observations.are taken from records two days after the operation. For
interpretation of numbers see footnote to table 2.

2 One to four postrotatory movements occurred. See table 2.

3 Wight months after the first operation and five months after the second, the
after-nystagmus was six when rotated to the left, and sixteen when rotated to the
right.

4 Protocol only states that quick component was present when rotated in both
directions with a marked increase in the postrotatory nystagmus when rotated
opposite the side of the lesion.

three. In most instances the slow component disappeared from
three to twelve hours before respiration ceased.

The nearest approach to complete decerebration and destruc-
tion of the thalamus in the dog was made in dog 27 (table 3),
which was a complete left hemi-decerebrate with destruction of
the left lateral portion of the thalamus. This animal lived three
weeks. There days before it died its temperature became sub-

10 AsO TV

normal (32° to 35°C.) and it was very depressed, being comatose
forty-eight hours previous to death. The quick component was
absent during the last forty-eight hours. Autopsy revealed the
thalamus to have undergone complete malacia. At the time
observations were being made on this dog I was not aware of the
effect of body temperature upon the quick component of nystag-
mus, and hence did not study the effect of raising the body tem-
perature as was done in the case of the rabbits reported above.

A clean ablation of the occipital cortex in the dog does not alter
vestibular nystagmus as judged by the results from such a pro-
cedure in three dogs.

DISCUSSION

Tozer and Sherrington (’10) have demonstrated histologically
and physiologically the presence of sensory tendon nerves in the
extrinsic eye muscles which pass back to the midbrain via the
IlIrd, IVth, and VIth nerves. Wilson and Pike (’15) suggest
that afferent impulses from these tendon nerves ‘‘set up efferent
impulses in the oculomotor cells of the cerebrum, which result in
a quick, jerky contraction of the internal rectus on the side of the
slow deviation and of the external rectus of the opposite side, with
relaxation of the antagonistic muscles,” which effects a restora-
tion of the eyes to the primary position. In other words, these
latter investigators are of the opinion that the quick component
is dependent upon the presence of the neopallium or upon the
integrity of a cerebral reflex are. The presence of true vestib-
ular nystagmus in the frog, pigeon, and turtle questions this
idea from the viewpoint of comparative anatomy. The persist-
ence of true vestibular nystagmus following the removal of the
cerebral hemispheres in these forms) which is a very simple mat-
ter and causes no great physiological disturbance—questions this
idea physiologically. The observation that no disturbance of
nystagmus follows decerebration in these forms, while in the
higher forms (rabbit, cat, dog) there is a change in the number
and duration of the nystagmic movements, shows that some con-
stituent is absent in the cerebrum of the frog, turtle, and pigeon
which is present in the cerebrum of the rabbit, cat, and dog.

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS dig!

The presence of a motor cortex in rabbit, cat, and dog is well
recognized. Such an area has never been demonstrated in the
cerebrum of the frog and pigeon, while it has been alleged by
Johnston (716) for the turtle, which, however, is still a mooted
question. So, from the standpoint of comparative anatomy and
physiology, the idea that the quick component of nystagmus is
dependent upon the integrity of a cerebral reflex are is hardly
tenable.

The increase in nystagmus in animals with lesions to the eye
area of the motor cortex when the slow component is directed
opposite to the side of the lesion is explained by the withdrawal,
as a result of the ablation, of the well-recognized heterolateral
inhibitory influence which the cerebral cortex exerts over reflexes.
The absence of any disturbance of nystagmus by ablation of the
cerebral hemispheres in those forms that have not acquired this
cerebral inhibitory function is evidence, I take it, in favor of
this idea. An attempt at an explanation of the apparent diminu-
tion of the nystagmus in completely hemi-decerebrate animals
when the slow component is directed to the side of the lesion will
not be made in this report (tables 2 and 3).

Further, the observation that in the rabbit complete decerebra-
tion and destruction of the thalamus can be performed without
abolishing the quick component shows conclusively that the quick
component of vestibular nystagmus is dependent only upon the
integrity of the afferent-efferent nerves of the eye muscles and
their centers in the midbrain. The findings on the dog support
this view.

Why depressed and comatose animals show deviation of the
eye on rotation and no quick component is a question which
cannot be answered directly. If the body temperature is sub-
normal, the quick component can be restored by raising the tem-
perature to the normal. In other conditions of depression the
quick component disappears, while the slow deviation persists,
e.g., narcosis. It should also be pointed out that, although we
are dealing with an entirely proprioceptive phenomenon, vestib-
ular nystagmus apparently involves two kinds of propriocep-
tion, the quick component due to a segmental proprioceptive con-

i ADOT:

trol, the slow component, or deviation, due to stimulation of the
labyrinth, which exerts an intersegmental control (Sherrington,
06a). Then, since some reflexes are more easily interfered with
than others (Sherrington, ’06 b) it is reasonable to believe that
the quick component of nystagmus is a type of reflex of lower in-
tensity, more easily interfered with and suppressed than the
slow component, or deviation.

CONCLUSIONS

(Rotation was the stimulus used to produce vestibular nystag-
mus. )

True vestibular nystagmus is present in the frog, turtle, and
pigeon. If the body temperature of the frog and turtle is below
10°C., the quick component disappears while the slow component
persists.

Decerebration in the frog, turtle, and pigeon does not disturb
vestibular nystagmus.

The decerebrate pigeon with extensive lesion to the thalamus
manifests true vestibular nystagmus, provided its body tempera-
ture is kept normal. Otherwise, the quick component disap-
pears and only deviation persists.

Hemi-decerebration in the rabbit, cat, and dog causes an in-
crease in vestibular nystagmus when the slow component is di-
rected opposite to the side of the lesion. When the slow com-
ponent is directed to the side of the lesion it is not abolished,
although not infrequently it is diminished.

Complete decerebration with extensive destruction of the thal-
amus in the rabbit does not abolish the quick component of nys-
tagmus, provided the body temperature is kept normal. Rogers’
(718) observations of the reduction of body temperature following
lesions of the thalamus have been confirmed for the rabbit.

In the dog ablation of the motor cortex in the region of the eye
area with the inclusion of the lateral and basal portions of the
temporal lobe causes a five- to fifteen-fold increase in the number
of movements and a two- to four-fold increase in the duration of
the after-nystagmus when the animal is rotated opposite to the
side of the lesion. There is a slight increase in the rotatory nys-

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS 13

tagmus when the animal is rotated to the side of the lesion.
This marked increase is more or less temporary, but some increase
is permanent, as judged from animals kept eight months.

The general conclusion is warranted that the quick component
of vestibular nystagmus is not due to the integrity of a cerebral
reflex arc, but is dependent upon some center below the thala-
mus, over which the cerebrum exercises its well-recognized inhibi-
tory influence.

BIBLIOGRAPHY

Bartets, M. 1910 Uber Regulierung der Augenstellung durch den Ohrapparat
Arch. f. Ophthal., Bd. 77, S. 531.

Baupr, J., AND Lerpter 1911 Uber den Einfluss der Ausschaltung verschiede-
ner Hirnabschnitte auf die vestibuliren Augenereflexe. Monatsch. f.
Ohrenheilkunde und Laryngo-rhinologie, Bd. 45, 8. 937.

Jounston, J. B. 1916 Evidence of a motor pallium in the forebrain of reptiles.
Jour. Comp. Neur., vol. 26, p. 475.

Pixr, F. H. 1917 The effect of decerebration upon the quick component of
labyrinthine nystagmus. Proc. Soc. Exp. Biol. and Med., vol. 14,
p. 76.

Prince, A. L. 1917 The effect of rotation and of unilateral removal of the otic
labyrinth on the equilibrium and ocular reactions of kittens. Am.
Jour. Physiol., vol. 42, p. 308.

Rogers, F. T. 1918 Relations of lesions of the optic thalamus of the pigeon to
body temperature, nystagmus and spinal reflexes. Am. Jour. Physiol.,
vol. 45, p. 553.

SHERRINGTON, C.S. 1906 The integrative action of the nervous system. P. 348.
1906 b Ibid., pp. 231, 232.

Tozer, F. M., AND SHERRINGTON, C. 8. 1910 The receptors and afferents of the
third, fourth and sixth cranial nerves. Proe Roy. Soe., London, vol.
82, p. 450.

Witson, J. G., AND Prkr, F.H. 1911 The effects of stimulation and extirpation
of the ear and their relation to the motor system. Phil. Trans. Roy.
Soce., London, vol. 203, p. 158.

1913 The effects of stimulation of the ear in the living animal. Proc.
Soe. Exp. Biol. and Med., vol. 10, p. 81.

1915 The mechanism of labyrinthine nystagmus. Arch. Int. Med.,
Aol, 159. To, SIL

PLATE 1
EXPLANATION OF FIGURES

1 Dog. 18. Ablation of the posterior two-thirds of the left cerebral hemi--
sphere, including the basal portion of the temporal lobe and motor cortex. This
dog showed typical increase in nystagmus when slow component was directed
opposite to the side of the lesion. Quick component was present when rotated in
either direction.

2 Dog 3i. Complete left hemi-decerebration, including destruction of the
left half of the thalamus. See table 3. Seen from injured side.

3 Dog3l. Ventral view. Both third nerves and midbrain are intact. This
dog showed nystagmus when rotated in either direction with an increase as shown
in table 3. a, Third nerves.

4 Dog 32. Complete left hemi-decerebration, including destruction of left
lateral and middle portions of the thalamus and anterior left half of midbrain.
Nystagmus was absent in this dog which lived only three days. a, Right third
nerve intact; b, left third nerve absent with injury to midbrain.

5 Dogx. Hemi-decerebration. a, Thickened dura; b, section made through
fibrous tissue for examination of thalamus, which showed areas of degeneration.

6 Dog5. Complete left hemi-decerebration with injury to lateral portion of
thalamus done in two operations. Posterior two-thirds of right cerebral hemi-
sphere removed at a third operation. There was an increase in nystagmus when
the slow component was opposite to the side of the fresh lesion. The quick com-
ponent was present when rotated either direction. Dog was killed three days
after the third operation by another dog. See table 3. a, Temporal muscle drawn
inwards through defect in the skull; b, thickened dura; c, hemorrhagic remaining
portion of cerebrum (the only cortex present); d, fornix.

7 Rabbit III. Left hemi-decerebration with injury to lateral portion of
the thalamus. See table 3. a, anterior quadrigemina.

8 Rabbit VII. Complete decerebration and destruction of the thalamus.
a, Anterior quadrigemina; b, optic nerves and chiasma.

9 Rabbit VI. Complete decerebration and destruction of the lateral portions.
of the thalamus. a, anterior quadrigemina; b, optic nerves and chiasma.

14

CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS PLATE 1
ACEC LVN

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 1

Resumen por el autor, F. T. Rogers.
Universidad de Chicago.

Estudios experimentales sobre el tallo cerebral.

III. Los efectos de extensas variaciones de la temperatura del
cuerpo, causadas por las lesiones del talamo,
sobre las actividades reflejas.

La extraccién de los hemisferios cerebrales y el tilamo en la
palomo reduce al animal a una condicién poikiloterma perma-
nente. Unodeestos animales asi operado puede conservarse Vivo
durante un periodo de 1 a 3 meses, colocindole en una incuba-
dora a 30°C. El comportamiento ulterior y las actividades
reflejas varian con la temperatura del cuerpo. Los movimientos
indecisos tipicos de los animales desprovistos de cerebro aparecen
cuando el animal est’ hambriento, si la temperatura del cuerpo
es superior a 36°. Sise deja descender dicha temperatura hasta
los 80° aparecen perturbaciones en el equilibrio, que se mani-
fiestan primero por la presencia de una flexién tonica de la pata
y musculos del pié. A 24° 0 a menor temperatura el animal no
puede mantenerse en pié o volar. Los reflejos oculares, pupilares
y el nistagmo desaparecen a unos 30°. Todos ellos reaparecen
cuando la temperatura vuelve a ser la normal de 40°. El autor
consigna observaciones fisiologicas detalladas sobre un animal
después de la ablacion de todas las partes del cerebro anteriores
a la comisura posterior y al quiasma 6ptico, seguidas de un
estudio microscépico de cortes seriados de las restantes partes
del tallo cerebral.

Translation by José I’. Nonidez
Carnegie Institution of Washington

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED BY
THE BIBLIOGRAPHIC SERVICE, SEPTEMBER 29

EXPERIMENTAL STUDIES ON THE BRAIN STEM

Ill. THE EFFECTS ON REFLEX ACTIVITIES OF WIDE VARIATIONS IN
BODY TEMPERATURE CAUSED BY LESIONS OF THE THALAMUS

F. T. ROGERS
Hull Physiological Laboratory, University of Chicago

TEN FIGURES

In a previous study of decerebrate restlessness in the pigeon
attention was again called to the differences in behavior of decer-
ebrate birds according to whether or not the thalamus was
traumatized in the process of decerebration. It has been long
recognized by physiologists that the subsequent effects on the
animal are quite different in the two cases, but a clear-cut com-
parative study of the two sets of conditions, followed by a careful
study of the brain, is wanting. In part this has been due to
want of detailed knowledge of the structure of the basal gangha
in the bird and in part to failure to recognize the réle of second-
ary physiological conditions after the operation. Of the latter
factors, one important factor is that of maintaining a normal
body temperature, which the writer has considered in a previous
report. The writer is of the opinion that there are also others,
such as changes in the circulatory and digestive conditions, which
also modify the physiological picture. Experiments along these
lines are now under way and will be reported later.

HISTORICAL

Only a brief summary of the history of the question of the
role of the thalamus will be given here, as it is discussed in the
larger text-books of physiology, particularly those of Schaffer,
Luciani, and Hermann. The more important papers are cited
in the bibliography.

17

18 F. T. ROGERS

Vulpian in 1866 noticed that removal of the cerebral hemi-
spheres of the carp led to continuous excessive activity of the fish,
always however avoiding obstacles in its path.

Ferrier and Steiner found that removal of the hemispheres of
the shark gave the same picture as followed loss of the olfactory
lobes; that if the thalamus were removed, the animal lay quietly
on the floor of the aquartum without movement. Bethe denied
this, stating that loss of the thalamus did not abolish spontane-
ous movements.

Steimer, Bethe, and Loeb all agreed that damage to the mid-
brain leads to motor disturbances, in the form of forced move-
ments or circus movements, if the lesion is unilateral, in the
direction of the intact half of the midbrain.

Removal of the hemispheres and thalamus of the frog abolishes
spontaneous movements, according to Steiner; but not if the
thalamus is left intact (Schrader).

Rolando (’09) studied the effects of decerebration in the pigeon.
His observations were confined to birds which lived a few days
only after operation.

Flourens (’22) continued the work and kept the birds alive for
months after operation. He made no distinction between decer-
ebration with and without thalamic involvement.

Longet (47) was the first to attribute significance to sharp
localization of brain lesions and prepared decerebrate birds with
and without damage to the underlying parts.

Munk, in 1883, revived the controversy between Flourens, who
maintained that the hemispheres were necessary for the vari-
ous senses, and Cuvier, who thought that loss of the forebrain
led merely to the loss of memory images.

Schrader, in 1889, in an elaborate monograph reported results
on decerebrate pigeons in which the thalamus was carefully pre-
served. His primary interest was in the functions of the cere-
bral hemispheres and not much consideration was given to the
thalamus save to make sure that it was present.

Vulpian had previously considered the activities of decerebrate
animals as due automatically to stimuli ‘‘either internal or exter-
nal” which incited the movements of the animals.

EXPERIMENTAL STUDIES ON THE THALAMUS 19

Munk (’90) stated that the restlessness of the decerebrate
pigeon was dependent on hunger.

Exner and Onimus repeated the studies on chickens and ducks,
and Kalischer more recently has tried cerebral ablations on the
parrot.

Luciani has referred to the fact that the decerebrate rabbit
will make spontaneous movements if the thalamus is intact.

Goltz’s decerebrate dog showed continued restlessness, and in
the autopsy report of Holmes it is stated that the thalamus is
intact, but shrunken, due to secondary degenerations.

Bechterew and his students have attempted to get some defi-
nite experimental evidence on thalamic functions. He finds
thalamic injury leading to lowered reflex excitability, forced
movements which he suggests are cerebellar in origin, statis
of food in the gastric organs, and a characteristic flattening of
the feathers against the body instead of fluffed as in the sleeping
or decerebrate bird without thalamic lesion. Furthermore, he
considered that there were thalamic centers for the respiratory,
digestive, circulatory, and urogenital organs.

Sachs recently tested these hypotheses by stimulation methods,
and concluded that reflex effects on these organs can be obtained
by thalamic stimulation, but that there are no controlling cen-
ters of these organs in the thalamus.

METHODS

Decerebration in the pigeon is a relatively simple matter. Ex-
perience, however, showed two factors particularly which should
be closely watched. First, when the cranial vault is removed,
care must be taken that the underlying dura mater be left intact.
If this is rudely torn, mechanically the pathways for the circu-
lation of blood through the brain stem are so interfered with as
to lead to inefficient blood supply. It seems that this effect is
due to damage to both the sinuses and the arteries on the lower
surfaces of the brain. This may lead either to excess intracran-
ial hemorrhage with resulting pressure complications or to defi-
cient blood supply. Sometimes, however, it is found that the
animals recover in spite of torn meninges.

20 F, T. ROGERS

The writer has been accustomed to leave a bridge of bone over-
lying the longitudinal sinus and then cutting through the dura,
parallel to the median sulcus and to the occipital pole of the
hemisphere. Hemorrhage from the large superficial artery run-
ning over the anterior surface of the hemisphere may be con-
trolled with a cautery and the entire hemisphere removed with
a blunt probe whose tip has been curved to fit around the posterior
end of the hemisphere. This can be removed, the hemorrhage
controlled with cotton, and a clear view of the thalamus and the
third ventricle obtained. The writer has then destroyed the thala-
mus either by excision or by the use of a hot cautery. The lat-
ter is more satisfactory, in that it controls bleeding as well as
destroying the thalamus.

In the second place, it has never been found satisfactory to
leave cotton or any packing in the cranial cavity, but to allow
the cavity to fill itself with blood and sewing the skin over the
cavity. No attempt was made to approximate the cut edges
of the dura, because of its delicacy and the fact that traction on
the dura may increase the hemorrhage.

After the most careful operative work it is found that only one-
fourth to one-third of the animals will live for more than a few
days. These early fatalities seem to be due to circulatory dis-
turbances. The percentage of survivals can be increased mark-
edly if the thin medial and occipital cortex is not removed. These
parts are so closely related anatomically to the large blood-ves-
sels of the brain stem that their removal is particularly likely to
be associated with excessive bleeding.

EXPERIMENTAL RESULTS

Complete removal of all forebrain substance anterior to the
thalamus gives a preparation which, if the animal lives over the
initial shock, conforms to the classic description. Certain fea-
tures are characteristic of such an animal:

1. The bird stands quietly on one or both feet most of the
time.

2. The feathers are fluffed as in the sleeping condition.

EXPERIMENTAL STUDIES ON THE THALAMUS 21

3. Digestion processes are normal if the animal is fed and
watered by hand.

4. Body temperature, maintenance and regulation is nearly
normal.

5. There are no disturbances of equilibrium, so that the bird
can walk and fly in a normal manner.

6. The bird moves only when some stimulus, either external,
as irritation of the skin, or internal, such as hunger, thirst, or
defecation, disturbs it.

7. When deprived of food and water, a characteristic periodic
restless walking to and fro, which ceases on feeding.

8. The loss of all typical instinctive types of actions, such as
feeding, bathing, courting and mating, nesting, etc.

After three or four months there is added to this picture a rest-
less type of walking whose causation is obscure. The bird may
be restless in the day time and ‘sleep’ quietly at night. Fur-
thermore, this alternation of walking in the day time and quiet
at night is not merely a matter of illumination, for the blind
decerebrate bird will exhibit the same type of behavior. In
part it is related to hunger, but not wholly, for at this stage it
may be independent of feeding or starvation. The writer has
seen this type of behavior in those birds only which have survived
the operation for months. This is not to be confused with a
type of violent, forced, continuous walking or flying movements
that sometimes appear when there has been some damage done to
the thalamus or midbrain, also of unknown causation.

As pointed out by Bechterew, if the thalamus also be removed
at the time of operation, the animal differs from the preceding
picture.

1. The animal stands quietly without spontaneous movements.

2. The feathers lie flat against the body and not fluffed. This
is so striking as to become diagnostic.

3. Digestion disturbances appear. Some of these are difficulty
in swallowing, vomiting, and an apparent diarrhea or excess
urination.

4. There may be indefinite or marked disturbances in main-
taining body equilibrium. These may assume the most bizarre

22, F. T. ROGERS

types, such as to suggest damage to the cerebellum or to the
labyrinthine mechanisms.

5. Body temperature may become subnormal. (The normal
in the pigeon is from 39° to 42°C.).

6. Immediately after operation forced continuous walking or
flying independently of the conditions of the digestive tract.
These I have seen only during the first day or two after operation.

As recognized by Vulpian and Munk:

7. No characteristic periodic restlessness associated with
hunger.

8. Loss of all instincts, as in the bird deprived of hemispheres
only.

As a matter of fact, if the thalamus be removed, such animals
usually die unless, 1) particular care has been taken that the
operation is properly done, and, 2) great care is taken after oper-
ating to keep the animal warm and furnish some food and water
by forced feeding if necessary. Furthermore, the picture of such
animals after operation is quite variable, including all kinds of
mixtures of the points just outlined as characteristic of thalamic
injury. Examples of such behavior are as follows:

Pigeon 104

November 10. Decerebration and thalamus cauterized.

November 11. Bird walking about.

November 12. Temperature subnormal; feathers flat; bird sluggish;
bird stands with difficulty with outspread feet.

November 18. Feathers slightly fluffed; bird stands quietly; pupils
dilated; temperature subnormal.

November 15. Bird rejects food put in mouth; pupils constricted ;
reflexes sluggish.

November 16. Bird quiet; no movement. Given feed and water.

November 22. Bird stands on its feet unsteadily; pupils normal;
temperature normal; reflexes sluggish.

November 23, Bird dead with crop and gizzard filled with food.

Pigeon 105

November 8. Decerebration and thalamus cauterized.
November 9. ‘Temperature subnormal; pupils dilated; swallows water
easily; bird sits on floor of cage.

EXPERIMENTAL STUDIES ON THE THALAMUS 23

November 11. Reflexes sluggish (to irritants); no spontaneous move-
ments; pupils dilated.

November 13. Temperature subnormall; stands unsteadily on its
feet; pupils dilated.

November 16. Bird seems weak; swallows water readily; unable to
stand steadily; uses its tail to support itself; pupils constricted and no
eye nystagmus on rotation of bird.

November 18. Bird died.

Examples of this sort could be multiplied indefinitely. Decer-
ebration with combined thalamic lesions of one kind or another
have been done on sixty birds. The details have varied consider-
ably from bird to bird. In an attempt to analyze this variable
complex, two factors stood out as at least essential. First, in
each different experimental animal it is probable that there were
some detailed differences in the amount of brain-stem tissue
injured; and, secondly, attention was gradually drawn to the pos-
sible influence of the body temperature variations. This latter
problem was then approached and a specific study made of body
temperature regulation after thalamic injury. This has been
reported elsewhere in detail.

With reference to the first factor, it seemed evident that it
could only be controlled by a careful series of histologic prepara-
tions of the remaining brain tissue after a detailed study had
been made of the behavior of the animal during life. In accord-
ance with these principles, a bird was prepared by the usual
method of decerebration with what was thought to be a thor-
oughly complete destruction of the thalamus. A careful record
of the behavior of this animal was kept with due regard to the
control of the body temperature, and after death serial sections
were cut of the parts of the brain that were still intact. The
writer can therefore state definitely the changes in behavior and
reflex activity of this bird with wide changes in body tempera-
ture with a definite statement of how much of the brain was his-
tologically intact at time of death.

rr F. T. ROGERS

Pigeon 126

June 21. Bird decerebrated and thalamus cauterized with a hot

probe.
- June 22. 9.00 am. Temp., 36°C. Bird sluggish; stands with
difficulty; toes are slightly arched upward so that the bird tends to
stand on the claws only. (This condition is referred to as ‘claw foot’
in the laboratory record.) Bird put in a warm incubator kept at 32°C.

10.00 p.m. Bird is walking around; temperature of bird is 43°C.

June 23. Incubator in which bird is kept adjusted to 30°C., and
bird stays in incubator until July 1.

June 26. Bird is preening itself. Is fed and watered by hand. No
difficulty in feeding. Temperature of bird, 41°C.

June 28. Temperature of bird 38°C. Rotatory and post-rotatory
nystagmus of eyes when bird is rotated. Equilibrium normal; feathers
fluffed. Difficulties in feeding, as bird rejects much of the food put in
the mouth. By use of much water, however, some is swallowed.

June 30. Bird quiet; no restlessness when starved.

July 1. Bird removed to room temperature (24°C.). Temperature
of bird falls to 37°. Pupillary reactions to light present but sluggish.

Size of pupil, bright light, 3 mm. diam.

Size of pupil, dim light, 4.5 mm. diam.

Change in size of pupil with every winking movement of the eyelids.

Vomiting. Respiration, 22. Equilibrium normal. Bird perches on
my finger.

July 2. 10.00 a.m. Bird has been in cool place over night. Body
temperature, 33.5°. Respiration, 17. Slight tendency to claw foot.
Slight disturbances in maintaining balance on a perch. Bird preens
itself. Bird put in incubator at 34°.

11.00 a.m. Bird squatting on floor. Temperature of bird 36°:
Preening.

Bird has been starved for forty-eight hours, but no restless walking
movements occurred.

4.00 p.m. Temperature of bird has risen to 40°. Typical decerebrate
restlessness; bird walking about the cage. This does not cease when
bird is given excess water. Bird is picked up by hand and put down
again. Walking movements stop momentarily and then resumed. J

July 4. 6.00 p.m. Very hot day. Temperature of room 34.
Bird has body temperature of 44°. Bird walking around its cage all
day. Given water and it becomes quiet. Feathers fluffed in normal
way. Pupils widely dilated.

10.00 p.m. Temperature of bird 39.5°. Temperature of room 30°,
Bird standing quietly asleep on one foot. Feathers slightly fluffed.

Turn on light in cage suddenly. Bird begins walking around. ‘Turn
off the light and bird becomes quiet. Again the light was turned on.
The bird appears to wake up. Turns its head, moves a few steps, hesi-
tates, and then begins walking arpund the cage. Light removed.
The bird continues walking in semi-darkness and walks against the walls
of the cage. Repeats this several times.

EXPERIMENTAL STUDIES ON THE THALAMUS 25

July 5. 8.00 a.m. Bird fed. Room temperature, 28°. Tempera-
ture of bird, 37°. No restlessness during the day; stands sleeping.

3.00 p.m. Sudden change in the weather. Rain and wind. At-
mospheric temperature falls to 22°.

10.00 p.m. Temperature of bird has fallen to 33°. The bird stands

-on its feet with difficulty supported by its tail: or bird lies on floor of
cage. Unable to perch on my finger.

Nystagmus of eyes, rotatory and post-rotatory barely detectible when
bird is rotated. Nystagmus sometimes uncertain or it may appear
after a long latent period. Nystagmus can be seen if the rate of rota-
tion is very slow; reactions of the eyes are very slow. Slight claw foot.
Head nystagmus (or compensatory movements) very distinct, although
the nystagmus of the eye is very sluggish. Respiration slow and deep;
12 per minute. |

The toes irritated with a needle. The head is lowered and bird
preens the leg or runs its beak over the toes. This was repeated
fifty times in succession. Twelve times the bird brought its beak
to the exact point of irritation. Movements are rather slow and slug-
gish, not quick and vigorous. I use a stronger stimulus to the toes.
The foot was raised.

Increase strength of stimulus. Foot jerked sharply backwards.

Still stronger irritation (painful). Bird steps backward and turns
around.

This kind of stimulation applied to both feet. Seventy-five times
to right foot and then the lowering of the head to the right foot ceased,
although the stimulus continued.

Then repeated the stimulus on the left foot; head promptly brought
to the left toes twenty-two times in succession, but not to the right when
right was again stimulated.

July 6. 11.00 a. Temperature of bird, 31.5°. Respiration, 12,
~shallow. Marked claw foot. Bird supports itself by tail; unable to
stand without this support; unable to perch on finger. Feathers flat.
Renewed irritation of toes with a needle.

Repeated stimulation a number of times. Only once as the head
lowered to the toes, and then very slowly.

Strong stimulus to toes and foot slowly lifted.

Movement sluggish.

Nystagmus: rapid rotation; no quick component; slow rotation;
quick component present; both rotatory and post-rotatory.

By choosing the proper rate of rotation, it is possible to show devia-
tion without the quick component; another rate will show both devia-
tion and quick component.

Bird put in incubator at 30°.

July 6. 9.00 p.m. Temperature of bird 38°. Equilibrium normal;
swallows water easily; removed from incubator.

July 7. 8.00 p.m. Temperature bird, 32°. No feed to-day.

9.00 p.m. Temperature bird, 32°.

Slight tendency to claw foot; bird tries to walk in a clumsy fashion;

-tries to coo in a low difficult gurgle.
‘

26 F. T. ROGERS

Bird preens itself; preening ceases on striking a sudden blow to the
cage.

Bird makes slow circus walking movements to the right. No inhibi-
tion of this slow labored swaying type of locomotion by giving water.
Walks with outstretched head and neck in a rather comical fashion. .
Tendency to claw foot most marked just after the bird has been handled.

Given more water; walking continues.

Pupils widely dilated. Respiration, fourteen per minute and shallow.

Nystagmus of eye: Deviation present alone if rotated rapidly.

Slow rotation; once in twenty seconds. Quick component present.

Quick rotation; once in five seconds. Quick component absent; devi-
ation present.

Bird unable to perch on finger.

Bird put in incubator at 30° over night.

July 8. Given feed and water. Temperature of bird, 38°.

July 9. Crop still contains feed from yesterday. No restlessness.
Preening at times.

July 10. Bird taken from incubator.

July 11. 8.00 am. Temperature of bird is 28.5°.

Bird can barely support itself on its feet. Wings outspread. Marked
claw foot.

Nystagmus of eyes absent on rotating rapidly or slowly.

Compensatory movements of head to rotation very active.

11.00. a.m. Put bird in incubator at 31°.

6.00 p.m. Temperature of bird, 38°.

Bird is standing in a normal fashion. Eye and head nystagmus pres-
ent, normal. Given feed and water.

9.00 p.m. Typical decerebrate restless walking movements; crop
nearly empty.

July 12. Bird in incubator. Temperature of bird, 41°. Normal
restless walking movements. Given water and walking movements.
cease for a short time and then again begin.

July 14. Bird died about 3.00 P.M.

In emaciated condition.

Young female bird.

AUTOPSY

The skin was sunken in over the medial bridge of bone so as
to leave large cavities on either side of the head. The stump
of the brain stem was covered by a small blood clot.

All of the cerebral hemispheres was gone except possibly a
small bit of the cortical parts bordering the longitudinal sinus.
Histologically, this showed no nerve fibers or nerve cells nor in
the serial sections that were made could any continuity be traced
with the brain stem.

,

EXPERIMENTAL STUDIES ON THE THALAMUS Bi

-The brain stem was imbedded in celloidin and serial sections
cut of the entire preparation. These were stained with iron-
hematoxylin.

The medulla oblongata and cerebellum showed no alteration,
judged by this method of staining.

The midbrain and optic lobes showed no alteration except for
a small pocket of unstained vacuolated tissue on the left side at
the anterior end. The posterior commissure and oculomotor
nerves are intact and stained in a normal way.

All of the optic thalamus is gone except the hypothalamus and
the posterior end of the right side of the thalamus. The anterior
commissure is gone. The line of excision runs from the poste-
rior commissure above to the anterior surface of the optic chiasma
in a slightly oblique frontal plane so as to slightly damage the
left optic lobe and leave part of the posterior end of the right
thalamus.

DISCUSSION

The points of major interest in the preceding protocol may be
summarized as follows:

1. A nearly complete removal of the thalamus destroys the
temperature regulating mechanism of the pigeon so that its body
temperature is determined by that of the environment.

2. As the body temperature fluctuates, the behavior and reflex
activities also vary.

3. If the body temperature is kept normal, the behavior of the
bird resembles that of a decerebrate bird without thalamic
injury in the following respects:

a. Periodic spontaneous walking movements occur, particu-
larly during periods of food deprivation.

b. The maintenance of body equilibrium remains normal.

c. The feathers may assume a fluffed condition that resembles
that of the decerebrate bird, but is never as marked as in the
latter.

d. Complicated spinal reflexes involving the coordinated move-
ment of the beak to the toes are carried on efficiently.

28 F. T. ROGERS

4. Birds with thalamic lesion and body temperature kept nor-
mal, so far as the analysis at present stands, differ from decerebrate
birds with thalamus intact in the following respects:

a. A shorter period of life after operation.

b. A tendency to stasis of food in the gastric cavities, asso-
ciated very frequently with vomiting.

5. If the body temperature is allowed to fall, a gradual de-
pression of reflex activities ensues.

a. In the preceding protocol it is seen that decerebrate rest-
lessness (walking movements) occurred with the temperature of
the bird at 43°, 40°, 39°, 38°, 41°. That it did not occur during
starvation at body temperatures of 36° and 37°, with one excep-
tion and that one was at 32°. The writer is inclined to think
that two types of restless walking movements are to be recog-
nized. One associated with hunger or other visceral disturb-
ances, and a second which is independent of reflex stimuli and is
automatic in the sense that it results from changes within the
brain tissue only. The nature of this automatic activity cannot
be stated now, but this type of restlessness is independent of
either hunger or feeding and shows itself as forced continuous
movements. This type of behavior is well shown in the protocol
of July 7.

6. Equilibrium apparently remains normal, so far as observa-
tion’ goes, until the body temperature falls to 36° or less. At 33°
a characteristic tonic flexion of the toes is evident which has
suggested the term ‘claw foot.’ At this temperature the animal
is unable to carry on the fine balancing reactions involved in
perching. At —20° the bird is unable to stand and lies on the
floorin an uncoordinated fashion with flexed toes and outspread
wings (fig. 2).

c. With a decline in body temperature the nystagmus reactions
of the eye become more and more sluggish, disappearing alto-
gether at about 30°. As the body temperature falls, the rate of
rotation used to elicit the nystagmus must be made slower, other-
wise it may be overlooked and the deviation alone observed.
Very curiously, the compensatory movements of the head to rota-
tion may persist at temperatures below those at which the eye

EXPERIMENTAL STUDIES ON THE THALAMUS 29

nystagmus has disappeared. (This, however, may be more
apparent than real, because of the smaller amplitude of the
movements of the eye as compared with those of the head.)

d. Intersegmental reflexes persisted until the body tempera-
ture fell to 33° and disappeared at 31°.

e. The typical spread of reflexes was obtained with a body tem-
perature of 33°.

f. Inhibition of the preening reflex by mechanical vibrations
of the wall of the cage was elicited at a body temperature of 32°.

In order to illustrate these changes a series of four photographs
are inserted to show the influence of these temperature changes
on the equilibratory mechanism. These photographs were made
at two-hour intervals, from the same bird at body temperatures
Ob oo, 20.222 nana.

6. Sections of the brain stem are figured in this bird which had
lost the power of maintaining its body temperature. Destruc-
tion of the cerebral hemispheres and major part of the thalamus
abolishes the ability to maintain and regulate a normal body
temperature.

30 F. T. ROGERS

BIBLIOGRAPHY
BEcHTEREW, W. v. 1909 Funktionen der Nervencentra. Jena, Bd. 21, S. 1137
to 1178.
Brucke 1875 Ein enthirnten Hugh. Vorlesungen iiber Physiologie, Wien, Bd.
2, 8. 53.

EpINnGER, L., AND WALLENBERG, A. 1899 Untersuchungen iiber das Gehirn der
Tauben. Anat. Anz., Bd. 15, 8S. 245.

Exner, 8. 1890 Hermann’s Handbuch der Physiologie. Bd. II, Theil II, S.
198. Berlin.

Ferrier, D. 1886 Functions of the brain. New York, 2nd ed.

Fiourens, P. 1842 Recherches expérimentales sur lesystéme nerveux. Paris.

Goutz, Fr. 1892 Der Hund ohne Grosshirn. Pfliiger’s Arch., Bd. 51, 8S. 570.

KALIscHER 1905 Grosshirn der Papageien. K6nig. Preuss. Akad. der Wiss.,
Berlin.

Loncet, F. A. 1842 Anatomie et physiologie du systeme nerveux du homme.
Ranis®

Luctani, L. 1905-1911 Physiologie des Menschens. Jena.

Munk, Hr. 1890 Uber die Funktionen der grosshirnrinde. Berlin, 2nd ed.,
Delos:

Onimuvs. 1871 Recherches experimentales sur phenomenes consecutifs a la
ablation du cerveau. Jour. de Anat. et Physiol.

Rocers, F. T. 1916 Hunger mechanism of the pigeon and its relation to the
central nervous system. Amer. Jour. Physiol., vol. 41, p. 555.
1919 Studies on the brain stem. I. Regulation of body temperature
in the pigeon and its relation to certain cerebral lesions. Amer. Jour.
Physiol., vol. 49, p. 271.

Sacus, E. 1909 On the structure and functional relationships of the optic thala-
mus. Brain, vol. 32, p. 95.
1911 On the relation of optic thalamus to respiration, circulation,
temperature and the spleen. Jour. Exp. Med., vol. 14, p. 408.

ScHAEFFER, E. A. 1898-1900 Textbook of physiology. Edinburgh.

ScurapEeR, Max. E. G. 1887 Zur physiologie des Froschgehirns. Pfliigers
Arch. ges, Physiol., Bd. 41.
1889 Zur Physiologie des Vogelhirns. Pfliigers Arch. ges. Physiol.,
Bd. 44, S. 175.

Sreiner, J. 1885-1888 Funktionen des central Nervensystems und ihre Phylo-
genese. I and II, Braunschweig.

Vuurian, A. 1866 Legons sur la physiologie générale et comparee du Systéme
Nerveux. Paris.

PLATES

ol

PLATE 1
EXPLANATION OF FIGURES

. Figs. 1, 2, 3, 4 Photographs of a bird with cerebrum and thalamus removed '
at different body temperatures. Photographs made at two-hour intervals. Body
temperature lowered and raised by putting the bird in a cooled.or.warmincubator.
Body temperature 33°.

Body temperature 26°.
Body temperature 22°.
Body temperature 39°.

mm Whe

EXPERIMENTAL STUDIES ON THE THALAMUS PLATE 1
F. T. ROGERS

33

PLATE 2
EXPLANATION OF FIGURES

5 to 10 Sagittal sections taken in order passing from the right to the left
sides of the brain stem of pigeon 126. Because of lack of detailed knowledge of
the thalamic and mesencephalic nuclei and fiber tracts in the bird, these parts
are not labeled. Camera-lucida drawings. X 6.

Ce., cerebellum O.ch., optic chiasma

Hy., hypothalamus O.L., optic lobe cortex

IIT., oculomotor nerve O.N., optic nerve

M., midbrain P.C., posterior commissure
M.O., medulla oblongata V., ventricle of the optic lobe

N., region of broken, unstained, ap-
parently softened or necrotic tissue

34

EXPERIMENTAL STUDIES ON THE THALAMUS PLATE 2
F, T. ROGERS

30

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 1
el

Resumen por el autor, A. T. Rasmussen.

Las mitocondrias en las células nerviosas durante la hibernaci6n
e inanicién de la marmota (Marmota monax).

' Los marcados cambios funcionales que tienen lugar durante el
comienzo y la terminacién del suefio invernal en los mamiferos
ofrecen una exclente oportunidad para el estudio de la relaci6n
entre los varios elementos estructurales y la actividad celular.
Basandose en esta suposicién el autor ha llevado a cabo una
determinacién cuantitativa del nimero de mitocondrias (con-
driosomas) en las principales células nerviosas de la marmota
durante tres diferentes periodos: 1) Inmediatamente antes del
comienzo de la hibernaci6n; 2) durante la fase final de la hiber-
nacion, y 3) después de despertar el animal y comenzar una vida
activa, en la primavera. Durante el suefio invernal o después, el
animal no tomé ni alimentos ni agua. Los resultados obtenidos
no indican diferencia notable en el nimero, tamafo, forma o
reaccion colorante de las mitocondrias durante los tres periodos
seleccionados. El ntimero de mitocondrias, expresado en mil-
lones por milimetro ctibico de citoplasma, en los ocho tipos de
células examinadas varia entre 186 y 354. La constancia del
numero de mitocondrias en las células de un nticleo determinado
corrobora los hallazgos de Thurlos, esto es, que hay una relacién
constante entre las mitocondrias y el citoplasma para cada tipo
de célula nerviosa. Varias semanas de absoluta inanicion a raiz
de la hibernacién no afectaron de un modo apreciable a las
mitocondrias de las células nerviosas.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR'S ABSTRACT OF THIS PAPER ISSUED BY
THE BIBLIOGRAPHIC SERVI°E, SEPTEMBER 29

THE MITOCHONDRIA IN NERVE CELLS DURING
HIBERNATION AND INANITION IN THE
WOODCHUCK (MARMOTA MONAX)

A. T. RASMUSSEN

Institute of Anatomy, Medical School, University of Minnesota

CONTENTS
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RS UUM ET EER TRY. tock, ROR eo gh Se nh oh Oh op Ps. Gig dh dhd Mle a!S incre Bape 6 hm he Ame
INTRODUCTION

The discovery of mitochondria (chondriosomes) in practically
all living cells—except possibly in the simple blue-green algae,
Cyanophyceae, and in most bacteria—and the striking similarity
between those in plants and those in animals, add much interest
to the question of the rdle played by these cytoplasmic granules,
as 1s evident from the increasing number of papers appearing on
the various phases of the subject. Since excellent general dis-
cussions are found in many publications, none will be attempted
in this brief report. Four of the more recent papers, by E. V.
Cowdry (’16 a, ’18), N. H. Cowdry (’17), and by Duesberg (’19),
taken together cover the subject most admirably. E. V. Cow-
dry’s 1918 article is unusually comprehensive. It is fully evi-
dent from the literature that the function of mitochondria is a
much disputed question. The widespread distribution and great
similarity wherever found naturally suggest some close connec-
tion with fundamental cell processes.

Alterations in the number, size, shape, and staining reaction
as a result of degrees of cell activity has been described to some
extent especially in glands. But the literature on the corre-
spondence between mitochondria and functional states in nerv-

37

38 A. T. RASMUSSEN

ous tissue is extremely limited. Strongman (’17), who inves-
tigated the results of muscular fatigue in white mice, found no
constant variation due to such activity, except possibly a tendency
toward a clumping together of the mitochondria in the fatigued
animals. This effect was especially apparent at the base of the
large dendrite of Purkinje cells in the cerebellum. Luna (’13)
found that shortly after cutting a large peripheral nerve trunk
in the toad the mitochondria of corresponding ganglion cells lost
their regular distribution, increased in size, and showed an
increased affinity for the iron-haematoxylin stain. In more
advanced stages of degeneration the mitochondria disappeared
entirely. Busacca (’15) found that stimulation of the eye of the
toad with light caused a decrease in the number of mitochondria
in the pigment cells of the retina.

Earlier observations on the behavior of neurosomes—the
smaller of which have been shown by E. V. Cowdry (12) to be
mitochondria—made by Levi (’96), Motta-Coco and Lombardo
(03), and by Scott (’05) indicate an increase in the number of
these fuchsinophil granules during activity in nerve cells. Scott
suggests, however, that such changes may be only apparent, since
the entire cell is not examined, but merely the cell body, while
the most important point of activity is at the nerve endings.

On the whole, it appears that mitochondria of nerve cells are
comparatively resistant to conditions associated with normal
processes.

'In many pathological tissues (for literature see McCann, ’18,
and E. V. Cowdry, ’18) mitochondria often show marked altera-
tions even in early stages, and yet, according to McCann (’18),
in experimental poliomyelitis the mitochondria persist in normal
number in proportion to the cytoplasm in cells not only where the
Nissl substance has disappeared, but also in the latest stages of
neurophagocytosis. |

Having seen nothing on record concerning mitochondria in
nerve cells during hibernation, it seemed desirable to investigate
the influence of profound dormancy in mammals, such as is char-
acteristic of hibernating marmots, notwithstanding the fact that
changes during lethargy in the Nissl granules, which are consid-

MITOCHONDRIA IN NERVE CELLS 39

ered very labile, are doubtful (Rasmussen and Myers, 716). It
was hoped that the enormous reduction in nearly all, if not all,
vital processes of such animals during winter-sleep would add
one more link to the chain of evidence for or against some of the
theories concerning the connection between mitochondria and
functional activity. Since alterations in the nervous system are
important factors in all the more thoroughgoing hypotheses con-
cerning the cause of hibernation (Rasmussen, 716 a), the facts
discovered would be of interest also in connection with the mech-
anism involved in the production of dormancy.

MATERIALS AND METHODS

In this investigation there are involved fifteen adult wood-
chucks of the lot used in connection with a determination of
blood volume as already reported (Rasmussen and Rasmussen,
17). The conditions under which the animals hibernated is
there described. Five animals (two females and three males)
were sacrificed between December Ist and December 3rd, just
before the onset of hibernation, while still active and under full
feed. Five others (two females and three males) were killed
while dormant during the last few weeks of hibernation (between
February 26th and March 18th). The remaining five (two fe-
males and three males) were bled between April 3rd and April
18th while active and after having been awake from four days to
three weeks, but without having available any food or water
either during or after winter-sleep.

After the blood was washed out by gradual perfusion with
oxygenated Locke’s fluid, warmed or cooled to the body tempera-
ture, according to the technique employed by Dreyer and Ray
(11), the vessels were flushed out with physiological salt solution
and then Regaud’s fixer (one part of commercial formalin neu-
tralized with magnesium carbonate and four parts of a 3 per
cent aq. sol. potassium bichromate) was allowed to perfuse the
entire animal for an hour. In order to see if the length of the
perfusion with Locke’s solution had any noticeable effect on the
mitochondria, the last animal of each of the three groups was per-
fused only long enough to cause a return of a colorless fluid from

40 A. T. RASMUSSEN

the veins before the fixer was injected, as is done regularly by
Cowdry. ‘These three control animals are at the bottom of each
group in the accompanying table of results. Further treatment
was done according to the outline given by E. V. Cowdry (16 b).
Sections were cut 2u thick except in the case of the spinal cord
where the sections were cut 3u. Such thin sections were neces-
sary to facilitate and make more accurate the counting of
mitochondria.

At least four consecutive sections from a given block were
mounted on each of ten or more slides and stained with a 20 per
cent solution of acid fuchsin in aniline water and differentiated
with a 1 per cent aq. sol. of methylgreen after various degrees
of dechromation. Several slides were made under what appeared
to be the optimum conditions so as to insure plenty of well-
differentiated sections. By having four or more consecutive
sections mounted on each slide it is possible to rule out any varia-
tion in thickness which might escape general inspection by count-
ing the mitochondria in an equal number of cells from each of the
four (or a larger even number) consecutive sections and using the
average. As a matter of fact, only in a few cases was there any
trouble in getting uniform cutting, despite the extreme hardness
resulting from long fixation and the high melting point (60° to
62°C.) of the paraffin. A difference in thickness in sections cut
as thin as 2u is readily noticed by the much greater tendency of
the thinner ones to wrinkle, so that only such regions of the rib-
bon as showed uniformity in cutting were used.

In selecting the levels for study important nuclei and ganglia
in which the cells have a more or less well-known function were
selected, as is seen in the accompanying table of results and re-
lated data. In the case of the spinal cord the sixth cervical seg-
ment was used for somatic motor cells of the ventral cornu and
the seventh thoracic segment for visceral motor cells of the lateral
cornu. The seventh thoracic and sixth cervical spinal ganglia
were used for dorsal root ganglion cells. In the cerebellum the
cortex from the inferior portion of the vermis was utilized. No
comment is necessary on the other regions selected. It is be-
lieved that sufficiently varied types of cells have been chosen to

MITOCHONDRIA IN NERVE CELLS 41

be a fair index to the mitochondrial behavior in the nervous sys-
tem under the conditions of hibernation and to rule out the ob-
jections frequently made to conclusions drawn from alterations
detected in only a single type of cells (usually the Purkinje cells
of the cerebellum) which often are apparently only remotely
related to the physiological process under investigation.

In determining the number of mitochondria a Whipple eye-
piece micrometer disc (Bausch & Lomb), on which squares of
various sizes are ruled, was used. In general the medium-sized
square (jy) of the entire ruled field) was used as the unit. This
area with the oil-immersion objective, ocular, tube length, etc.,
used and which were, of course, kept constant throughout the
determinations, gave a field of wen sq. mm. In the case of
sections 2u thick the cubic volume represented by each square
is St cu.mm. In order to reduce all figures to the number
of mitochondria in million per cu. mm. of cytoplasm the num-
ber of mitochondria found in the above small volume was mul-
tiplied by the factor 6.8. The corresponding factor for sections
3u thick is 4.537. All figures given, therefore, indicate millions
per cu. mm. of cytoplasm. For each type of cell in each animal
the average of at least twenty fields from twenty different cells
is given. Since there are five animals in each stage, the figure
for each stage as a whole is the average of 100 cells.

As a preliminary study, the total number of mitochondria in
such sections of cells as contained the nucleolus were counted.
On account of the irregularity in shape and the great personal
factor necessarily involved in deciding on what shall be consid-
ered the limits of the cell body, these figures are not given. They
showed, however, exactly the same results as obtained by the
quantitative determinations. Obviously, the results stated in
terms of the number in a known volume of cytoplasm are the
only facts capable of comparison with the work of other investi-
gators. Due to the difficulty experienced, under the best optical
conditions available, in determining the number of mitochondria
when too closely packed, as they are occasionally in small clumps,
the figures are necessarily only approximate; but they are be-
lieved to be sufficiently accurate for comparative purposes.

42 A. T. RASMUSSEN

RESULTS

A description of the mitochondria of the nerve cells in this par-
ticular animal is unnecessary since they are essentially as de-
scribed in other vertebrates by E. V. Cowdry (’12, 714), Busacca
(13), Nicholson (716), and others. Suffice it to say that in the
central nervous system they are usually granular near the
nucleus and tend to become short rods more peripherally and long
filamentous in the base of the processes and out in the dendrites
and axon proper. In the spinal ganglion they are glandular or
very short rods rather uniformly distributed throughout the cell
body except in places where there is an accumulation of lipoid.
In such regions the mitochondria tend to be excluded. ‘This
reciprocal relation between lipoid and mitochondria in spinal gan-
glion cells has been noted especially by Cowdry (14) in a number
of species of vertebrates. In no case, however, was there much
lipoid, and in spinal ganglia, where most often encountered,
only two or three cells in a section through an entire ganglion
would contain any obvious lipoid by the method employed.
But since there are innumerable gradations between granules
and filaments, it was not practicable to determine any variation
in the different types of mitochondria upon any quantitative
basis. General examination, however, indicated no variation in
shape or size characteristic of either particular individuals or of
any of the three stages.

Many of what appeared to be rods are undoubtedly merely
rows of two or more granules so closely packed that it is not
possible to distinguish the separate components with the avail-
able apparatus. In imperfectly fixed tissue mitochondria are fre-
quently clumped into larger masses which are clearly not repre-
sentative of the normal condition. To what extent this occurs —
in the case of the best fixation is difficult to say. The long fila-
ments in the axon and dendrites and in the cell body at the base
of these processes are undoubtedly continuous filaments, since
they are never seen as rows of granules and are always elongated
continuous bodies even in the most superficial fibers in a block and
next to large vessels where the fixation has been instantaneous
while the tissue was still warm. ‘Too much reliance cannot be

MITOCHONDRIA IN NERVE CELLS 43

placed on the form of mitocnondria, at least within certain wide
limits and especially in regard to length, for in living cells, as
was observed by the Lewises (15), elongated ones broke up into
granules and granules fused into rods and they seemed to readily
bend and assume various shapes as they moved about in the
eytoplasm. E.V.Cowdry (18) has pointed out that the form of
mitochondria is not correlated with protoplasmic activity or
quiescence.

The long perfusion with oxygenated Locke’s solution (the
maximum total length being one hour) at body temperature pro-
duced no obvious effect on the morphology or distribution of
the mitochondria in nerve cells. Autolytic changes after death
being comparatively slow in nervous tissue, no change should be
expected. In fact, E. V. Cowdry (18, p. 188) makes the state-
ment that it is not even necessary to fix nervous tissue while
still warm; “six or eight hours after death is often soon enough.”
It was, however, necessary to rule out this variable.

In regard to the number of mitochondria, the accompanying
table gives the results in a compact form. It is clearly evident
that the number of mitochondria, as already noted by Thur-
low (17), in a unit of cytoplasm in the cells of a given nucleus
is comparatively uniform. The individual variations between
neighboring cells of the same type was, of course, much greater
than the averages tabulated. This is due, to a large extent, to
the necessity of using such a small surface area—one that will
fit in between the nucleus and the periphery of the cell. If the
Nissl granules are large the mitochondria are less uniformly dis-
tributed in such a small square because in general the mitochon-
‘dria lie between the masses of tigroid substance. The results
to be of value must be based upon a sufficiently large number of
fields to eliminate this irregularity of distribution. To do this
in connection with the motor cells of the ventral horn it was
necessary to count the mitochondria in at least twice as many
unit areas as was used in general.

The only other attempt at quantitative determination of mito-
‘chondria is that by Thurlow (’17). This was done on the nuclei
of the cranial nerves of the white mouse by utilizing sections 4u

44 A. T. RASMUSSEN
DATE Selec | 2 Oe fe) | 23 22
$3] we |es |g JS) LOM Roars, peste call Sel
Number | Sex ae a8 BEE Reel Ses 2°9 oe S83 ao
Bal go | S22) Se8|saz|s8s| 28 | Ses] 3
Pare Meza hes a oO a or 3 a
Before hibernation. Active and fed
46h
December 1... 1-SIV | o | 35 | 300 | 185 | 252 | 253 | 360 | 229 | 326 | 261
December 2...| 2-SIV | 2 | 36 | 305 | 174 | 260 | 266 | 349 | 335 | 300 | 260
December 2...| 3-SIV | co | 36 | 293 | 181 | 258 | 254 | 362 | 246 | 307 | 246
December 3...| 4-SIV | @ | 36 | 309 | 195 | 255 | 261 | 354 | 244 | 295 | 259
December 3... 5-SIV | o | 35 | 287 | 178 | 259 | 242 | 351 | 236 | 297 | 262
Average ...........:00.044-.-+.-) 802 | 183) | 257 |255 | 355") 238 1 805/258
During hibernation. Dormant. Not fed since early in December
February 26...) 51-SIII | 9 | 7 | 298 | 180 | 256 | 254 | 251 | 240 | 300 | 265:
Marchi 3... 2 6-SIV | 2 | 15 | 295 | 198 | 250 | 240 | 344 | 249 | 296 | 255
March 4...... 7-SIV | &@ | 16 | 310 | 189 | 258 | 258 | 359 | 232 | 305 | 262
March 17... 2: 8-SIV | oc | 14 | 286 | 187 | 246 | 255 | 341 | 236 | 303 | 259
Mareh‘l8.2. 9-SIV | o&@ | 12 | 298 | 194 | 266 | 249 | 355 | 248 | 302 | 265
AVEFAZE 2. iin. pete end ime ode -| 296,| 190 | 255 | 251.) (350 | 240) ees 2a
After hibernation. Awake. Active. Not fed since early in December
April 3.......| 56-SIIL| @ | 34 | 291 | 187 | 245 | 243 | 358 | 244 | 292 | 249
April 14.......| 10-SIV | o& | 34 | 312 | 177 | 267 | 260 | 348 | 220 | 290 | 266
April 14.......| 11-SIV | ? | 34 | 300 | 188 | 249 | 248 | 363 | 237 | 310 | 255
April 15.......| 13-SIV | 9 | 36 | 312 | 186 | 260 | 258 | 355 | 240 | 299 | 258
April 18.......| 15-SIV | S| 37 | 283 | 194 | 251 | 239 | 359 | 238 | 287 | 253
Average ..............s00.0---.-| B00 | 186 | 254 | 250 | 357 | 236 | 296 | 256
Average of all animals ..........| 299 | 186 | 255 | 252 | 354 | 238 | 301 | 258

thick. Her results showed a variation in the number of mitochon-
dria per cu. mm. of cytoplasm from 178 million (in the dorsal
motor nucleus of the vagus) to 284 million (in the mesencephalic
nucleus of the trigeminus). The final averages of the fifteen
woodchucks will be seen to vary between somewhat higher limits
or 186 million (in the motor cells of the ventral horn of the spinal

MITOCHONDRIA IN NERVE CELLS 45

cord) and 354 million (in the Purkinje cells of the cerebellum).
The levels selected for this investigation and the small pieces of
tissue taken from these levels did not include the nuclei exam-
ined by Thurlow, so that specific comparisons can not rigidly be
made. The magnitudes are seen, however, to be of the same
order, except that the upper limit is considerably higher. The
number of mitochondria in the large motor cells in the nucleus of
the hypoglossus of the white rat was among the lowest determi-
nations (187 million) and agrees strikingly with the number here
reported in the large motor cells of the spinal cord in the wood-
chuck, which is also the lowest determination (186 million).
As was found by Thurlow, sensory cells are not distinguishable
as a class from motor cells upon the basis of the number of
mitochondria.

As has been observed before, particularly by E. V. Cowdry,
now and then an individual cell will contain many more or, less
frequently, distinctly fewer mitochondria than the neighboring
cells of the same type, which, being found in the same region of
the same section, must have been through exactly the same tech-
nique. This possibly indicates that individual cells may be in
quite a different condition from the vast majority. Such a situ-
ation has been assumed to explain the classical Golgi technique
when, as frequently happens, only here and there a cell is picked
out and hundreds of surrounding cells are left unstained. In
the spinal ganglion the few cells which contained an unusually
large number of mitochondria were usually of the smallest type.

This more or less specific mitochondria-cytoplasmic ratio is
another argument against the view maintained by Portier (see
discussion in Compt. Rend. Soc. Biol., 1919, T. 82, pp. 244, 309,
337) to the effect that mitochondria are organisms living in
symbiosis in larger cells.

The relationship of the mitochondria to the Nissl bodies as it
appears in this investigation does not support the idea that the
tigroid substance is normally more or less diffused throughout
the cytoplasm and that the appearance of rather definite masses
is an artifact produced by the reagents. Were this contention
correct one would expect more of the mitochondria to be embedded
in these precipitation products.

46 A. T. RASMUSSEN

It further appears certain that there is no appreciable modifi-
cation in the number of mitochondria as a result of the altera-
tions attending hibernation, awakening, and subsequent inani-
tion, thus testifying to the stability of these bodies under greatly
modified functional conditions.

In the first place, during winter-sleep there is a great reduction
in the metabolic processes. From the excellent summary of the
literature on respiratory exchange during hibernation by Krogh
(16), it would appear that in mammals with a normal body tem-
perature of about 36°C. when awake and whose body tempera-
ture approaches 10°C. or less during hibernation, the oxygen
consumption falls to one-twentieth or less of the amount used
before dormancy occurred. ‘The CO, eliminated decreases rela-
tively much more. This great reduction in oxidation processes
in the body does not apparently affect the mitochondrial content
of nerve cells, although in all probability the nervous system
shares at least to some extent in the reduced oxygen consump-
tion. There is, then, from this source no evidence in favor of
the theory that mitochondria are associated with oxidation proc-
esses. The possibility exists, however, that they may be in-
volved in such processes without showing any morphological or
numerical changes with degrees of activity. N. H. Cowdry
(18) found in myxomycetes that the mitochondria were found
in all stages of the organism, even in fully formed spores with
a thick horny capsule and supposedly in a state where the physi-
ological processes are nearly at a standstill.

What other tissues in the woodchuck will show remains to be
determined. The glands‘are now under investigation.

During hibernation the absorbing power of the blood for CO,
decreases and there is a distinct increase in the amount of CO,
actually found in the blood (Rasmussen, 716 b). These changes
as found in the venous blood reflect an increase in the H-ion con-
centration of the tissues. This tendency toward acidosis does
not seem to have any effect on the mitochondria in nerve cells,
although there must be readjustments in the nervous system to
this altered condition of its blood supply.

MITOCHONDRIA IN NERVE CELLS 47

Next we may mention the relation of mitochondria in nerve
cells to the transition of a mammal from the warm-blooded
(homoiothermal) type with a body temperature of about 36°C. to
what is in many respects the cold-blooded (poikilothermal) type
with a temperature only slightly higher than that of the surround-
ings, and which reached as low as 7°C. in one animal here
involved. ‘This striking alteration seems to have had no effect.

Finally, attention is drawn to the fact that durmg dormancy
and for as long as three weeks after waking up, i.e., until the
last animal was killed, no food or water was available. This ina-
nition during hibernation as well as after becoming active did
not apparently affect the mitochondria of nerve cells, although
during the three months of winter-sleep the body weight decreases
about one-fourth while the animals allowed to live several weeks
after waking up lost fully one-third.

SUMMARY

1. Profound dormancy such.as is seen in a fully hibernating
marmot with a rectal temperature as low as 7°C. does not affect
noticeably in any way the mitochondria of the central nervous
system or of the spinal ganglion.

2. Complete inanition for three months during winter-sleep
and for three weeks after waking up does not modify the mor-
phology, number, or distribution of mitochondria in nerve cells.

3. Perfusion with oxygenated Locke’s solution at body tem-
perature for a period as long as one hour does not modify the
mitochondrial content of nerve cells beyond what is produced by
a more rapid flushing out of the vessels for a duration of only
fifteen minutes.

AS A. T. RASMUSSEN

BIBLIOGRAPHY

Busacca, A. 1913 L’apparato mitocondriale nelle cellule nervose adulte.
Arch. f. Zellforsch., Bd. 11, 8. 327-339.

1915 Sulle modificazioni dei plastosomi nelle cellule dell’epitelio pig-
mentato della retina sotto l’azione della luce e dell’ oscurita. Ricerche
Lab. Anat. Univ. Roma, vol. 18, pp. 217-237.

Cowpry, E. V. 1912 The relation of mitochondria and other cytoplasmic con-
stituents in spinal ganglion cells of the pigeon. Intern. Monatsschr.
f. Anat. u. Physiol., Bd. 29, S. 473-504.

1914 The comparative distribution of mitochondria in spinal ganglion
cells of vertebrates. Am. Jour. Anat., vol. 17, pp. 1-29.

1916 a The general functional significance of mitochondria. Am.
Jour. Anat., vol. 19, pp. 423-446.

1916 b The structure of chromophile cells of the nervous system.
Contributions to Embryology, vol. 4 (Publication no. 224, Carnegie
Institution, Washington), no. 11, pp. 27-43.

1918 The mitochondrial constituents of protoplasm. Contributions
to Embryology, vol. 8 (Publication no. 271, Carnegie Institution of
Washington), no. 25, pp. 39-148. j

Cowpry, N. H. 1917 A comparison of mitochondria in plant and animal cells.
Biol. Bull., vol. 33, pp. 196-228.

1918 The cytology of the myxomycetes with special reference to mito-
chondria. Biol. Bull., vol. 35. pp. 71-94.

Dreyer, G., AND Ray, W. 1911 The blood volume of mammals as determined
by experiments upon rabbits, guinea-pigs and mice; and its relation-
ship to the body weight and to the surface area expressed in a formula.
Phil. Trans., London, Series B, vol. 201, pp. 1383-160.

Duessera, J. 1919 On the present status of the chondriosome-problem. Biol.
Bull., vol. 36. pp. 71-81.

Kroeu, Aucust 1916 The respiratory exchange of animals and man. Long-
man Green & Co., pp. 124-130.

Levi, G. 1896 Contributo alla fisiologia della cellula nervosa. Riv. di Patol.
Nerv. e Ment., vol. 1, pp. 168-180.

Lewis, M. R., anp Lewis, W. H. 1915 Mitochondria in tissue cultures. Am.
Jour. Anat., vol. 17, pp. 339-401.

Luna, E. 1913 Sulle modificazioni dei plastosomi delle cellule nervose nel tra-
pianto ed in seguito al taglio deinervi. Anat. Anz., Bd. 44, 8.413415.

M Cann, Gerrrupe F. 1918 A study of mitochondria in experimental polio-
myelitis. Jour. Exper. Med., vol. 27, pp. 31-36.

Morra-Coco, A., e Lomaarpo, G. 1903 Contributo allo studio della cellula dei
gangli spinali. Anat. Anz., Bd. 23, 8. 635-640.

Nicuotson, N. ©. 1916 Morphological and microchemical variations in mito-
chondria in nerve cells of the central nervous system. Am. Jour.
Anat., vol. 20, pp. 329-349.

aAsMUSSEN, A. T. 1916a Theories of hibernation. Am. Naturalist, vo . 50,
pp. 609-625.

MITOCHONDRIA IN NERVE CELLS 49

Rasmussen, A. T. 1916 b A further study of the blood gasses during hiberna-
tion in the woodchuck (Marmota monax)—The respiratory capacity of
the blood. Am. Jour. Physiol., vol. 41, pp. 162-172.

Rasmussen, A. T., anp Myers, J. A. 1916 Absence of chromatolytic change
in the central nervous system of the woodchuck (Marmota monax)
during hibernation. Jour. Comp. Neur., vol. 26, pp. 391-401.

Rasmussen, A. T., AND Rasmussen, G. B. 1917 The volume of the blood dur-
ing hibernation and other periods of the year in the woodchuck (Mar-
mota monax). Am. Jour. Physiol., vol. 44, pp. 1382-148.

Scorr, F. H. 1905 On the metabolism and action of nerve cells. Brain, vol.
28, pp. 506-526.

Srroneman, B. T. 1917 A preliminary experimental study on the relation be-
tween mitochondria and discharge of nervous activity. Anat. Rec.,
vol. 12, pp. 167-171.

‘THurtow, M. DeG. 1917 Quantitative studies on mitochondria in nerve cells.
Contribution to Embryology, vol. 6 (Publication no. 226, Carnegie
Institution of Washington), no. 16, pp. 35-4.

ay

| . oi 4 f i
Tah i

ERRATUM

Tue JouRNAL or Comparative NrevuroLoacy, volume 31, number 1, October,
1919, page 28, line 28, “At — 20° the bird is unable to stand’’ etc., should read,
- At 20° the bird is unable to stand. This slip should be pasted on page 29 when
the volume is bound.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOI.. 31, NO. 2
DECEMBER, 1919

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOI. 31, No. 2
DECEMBER, 1919

Resumen por el autor, C. U. Ariéns Kappers,
Amsterdam.

El caracter logético del crecimiento.

Los diferentes factores que toman parte en nuestra experi-
encia consciente o en la construccién de nuestras concepciones
mentales, tales como la asociacién, memoria, atencién y la ley de
Weber, son reconocimientos conscientes de las propiedades gen-
erales del a vida, los cuales pueden demostrarse ugualmente en el
desarrollo inconsciente del cuerpo. En el acto de pensar se
experimenta directamente su influencia 0 se reconoce por intro-
speccién (en las percepciones, por los resultedos de algunos estf-
mulos); en el crecimiento del cuerpo aparecen sin embargo, “de
facto.’’ La vida mental y el desarrollo corpéreo también estan
relacionados entre si bajo este aspecto: en que la unidad de
nuestro ser en ambos precede a las influencias externas, cuyas
influencias en ambos casos acttian expotencializando la “multi-
plicidad del yo’! (ego) primaria. En la vida mental las aso-
ciaciones de esta multiplicidad primaria producen una multi-
plicidad secundaria durante la vida personal, la cual es mucho
menos coherente que la primaria. Por consiguiente la consciencia
del factor de la atencién solamente puede abarcar unidades,
bien sea en un sentido espacial, tal como sucede con los objetos
concretos, o bien sean unidades abstractas, unidades en un sen-
tido espiritual, tal como sucede con las leyes. La multiplicidad
del ego en su ambiente est4, sin embargo, fuera del propésito
de la consideraci6n cientifica atenta; su presencia se reconoce y
experimenta. La atencién toma una parte en ella pero no la
revisa.

166 . ”
many-in-oneness.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, AUGUST II

THE LOGETIC CHARACTER OF GROWTH!

C. U. ARIENS KAPPERS

Amsterdam

TWO FIGURES

That growth is wonderfully logical in its results, as a rule,
has often struck biological students. This has led me to raise
the questions: Is there perhaps a connection between what we
call logical reasoning and the logic of growth? May the rules
of logical reasoning be analogous to those in the logic of growth?

This question has been raised before? in the following form:
May introspection be considered not only as a psychological
method (nobody will doubt that), but also as a biological one?
In other words: Have peculiarities which we experience in our
psychic life a general biological significance, and if so, to what
extent?

The answer to this question will not always be the same, and
in general it may be said that great circumspection is necessary
here, and that, though there may be common points of agree-
ment, the characteristic nature of the rational functions, of the
instinctive actions, and of the somatic development should not be
lost sight of.

Hence, when, in 1870, Hering delivered his lecture in Vienna,
“On Memory as a General Function of Organized Matter,” he
rightly began with the following very true words:

When the naturalist leaves the workshop of his limited special re-
searches, and ventures on an excursion into the domain of philosophi-
cal speculations, where he hopes to find the solution of those great prob-
lems for the sake of which he devotes his days to solving the small

1 Read before the Sixteenth Dutch Congress for Natural and Medical
Sciences. The Hague.

2 See, for instance, C. J. Herrick, Introspection as a biological method, Jour.
Philosophy, Psychology and Scientific Methods, vol. 12, 1915.

51

GD C. U. ARIENS KAPPERS

ones, he is accompanied by the secret fears of those whom he leaves
behind at the work-table of special research, and he is received with
justifiable distrust by those whom he salutes as the denizens of the
empire of speculation. . . . . Thus he is in danger of losing
with the former and of not. gaining with the latter.

These words are very true, but still this danger did not make
him refrain from expressing his thoughts on a subject that we all
as biologists both love and fear—natural philosophy in the
widest sense of the term.

That this same danger threatens me, who not only consider
memory, but also association and attention (concentration) as
general functions of organized matter, is clear. It was therefore,
not without some hesitation, that I sent this paper to the editor
of The Journal of Comparative Neurology. Its title sounds a
little bold in the ears of most biologists.

I also thought it better at first to change ‘logetic’ in its title
into ‘logical.’ Since, however, we are accustomed to consider
logic, reason, as something that is peculiar to conscious thinking,
and there will be question here of a general principle of life,
which, with other faculties but according to similar laws, also
operates outside conscious thinking, I have preferred to use the
word ‘logetic’ to indicate a broader idea of ‘logos’, formerly used
to give expression to something that is more than that small part
of reason of which we become conscious in our ‘logical’ thinking.

I do not want to be misunderstood. I do not mean to say that
logical ‘thinking’ accompanies the somatic development, nor that
a tissue differentiation of the same form that obtains in the soma
accompanies the building up of our spiritual life. No spirituali-
zation of the somatic, therefore, nor a materialization of the spir-
itual. I only want to point out that one and the same principle
of life, which Aristotle called ‘psyche,’* with other faculties, but
ruling with similar conformities, is peculiar to both, and leads in
both to results which are different in effect, but which agree in

* So this is a psyche in a much wider sense than it has been used in the word
‘psychology.’ Cf. Hammond, Aristotle’s Psychology. A Treatise on the Prin-
ciple of Life. De Anima, book 1, chapter 5, Alinea 31: ‘‘parts of the soul are all
found in every one of these bodily divisions and they are of like with each other
and with the entire soul.’’

LOGETIC CHARACTER OF GROWTH 4

being adapted to the influences of the environment in a rational
manner.

ASSOCIATION (CORRELATION) IN SOMATIC AND MENTAL
DEVELOPMENT

One of the striking factors in the construction of mental con-
ceptions is the preponderant réle which the simultaneity or direct
successivity of stimuli playsin them. This was realized by Aristotle
and has always been confirmed. It has also been found that in
all forms of association it is the simultaneity of stimuli or residua
of stimuli that act the chief part.

Similarly comparative anatomy of the brain shows that the
neurons in the central nervous system‘ always effect connections
between two areas, which (even before the neuron joins them)
stand to each other in a stimulative correlation, that is to say,
which are often simultaneously or successively in a condition of
irritation.

This stimulative correlation—in keeping with the chief law of
neurobiotaxis—precedes the anatomic relation (the formation of
the neuron which will join them) and this neuronic junction is
the result of it. In other words, simultaneous irritations, which
repeatedly penetrate into the nervous system‘in different places,
cause in this nervous system a neuronic association’ or associative
integration between the centers where they arrive.

This law is for the material development of the nervous system
the same as what we have known for centuries as the law of as-
sociation in our conscious conceptions (though it was discovered
independently of it, without any psychological afterthought).

Now, if we consider what we observe in the development of a
germ-cell into an organism, we find there, too, simultaneously
two poles which are conspicuous in the division of the germ cell,

4That this also obtains for the peripheral nervous system has been lately
proved by Bok in a very ingenious article. Vide Psychiatrische en Neurolo-
gische Bladen, 1917, no. 4, ‘‘The reflex circle.”’

6 What the physicochemical processes are that attend the formation”of this
neuronic linking, I cannot discuss here; I beg to refer the reader to The Journal
of Comparative Neurology, vol. 27, 1916.

54 Cc. U. ARIENS KAPPERS

and which are mostly indicated by the two centrosomes. So
here, too, there are two (sometimes more) simultaneous centers
of influence, which play an essential part in the accomplishment
of the process.

Whereas, however, the simultaneous action of influences causes
a ‘linking,’ an association in the construction of mental life and
also of the nervous system, there appears a differentiation in the
other case (in somatic development), a differentiation which, how-
ever, remains a unit, an individual; in other words, the ‘linking’
of the parts which is a consequence of the process in mental life,
is present at the starting-point in somatic development and
persists.

Speaking properly, however, it may be Maa that here, too, the
‘linking’ of the results of those influences does not arise till the
differentiation has been accomplished, because, when the germ-
cell was still one cell, the influences, which bring about the differ-
entiation, had not yet acted, and so (apart from engrammatic
factors) the results of those simultaneous influences, too, could
not as yet have been linked.

So in both processes there are simultaneous influences, from which
originates a formative process, in both a linking of those influences;
in the cerebral linking, however, an integrated association of them
and in the development of the germ-cell a differentiated association.
In both cases, however, there arises a construction, which is a
product of correlated influences of the surroundings.

Let us consider in this light the influence of the medium on
the differentiation of the cells. In order to explain how the divi-
sion and multiplication of the cells is at the same time attended
with a qualitative differentiation of the daughter-cells, it is sup-
posed on good experimental grounds that the two sides of the
mother cell, owing to their different situation—owing to the fact
that they are exposed to different influences—do not undergo the
same differentiation. That from the same blastomeres entirely

6 Wilson (also Driesch and Hertwig): ‘‘The relative position of the blastomere
in the whole determines in general what develops from it; if its position be
changed, it gives rise to something different; its prospective value is a function
of its position.’’ (The cell in development and inheritance.)

LOGETIC CHARACTER OF GROWTH B15)

different differentiations may result by only changing their posi-
tion with regard to their environment has been shown by Mor-
gan by his experiments on the development of frogs’ eggs.

It seems probable to me that these different influences operate
upon the centrosomes and by means of the centrosomes on the
rest of the cell and the nucleus. It seems probable also that in
this way each centrosome introduces different somatic properties
into the plasm of the daughter cells, so that by means of the
centrosomes not only an increase of the cells is effected, but also
an adequate organoplastic differentiation.

In this connection it seems to me of great importance to inquire
whether in malignant new growths where the adequate organoplastic
formation of cells is absent the centrosome has undergone a change.
The fact that the centrosome, or the substance from which it is derived,
is very sensitive to external influences makes it easy to believe that the
centrosome can become ill under the influence of inadequate processes
and this illness of the centrosome might include the failure of organo-
plastic development.

My opinion about the centrosome as an intermediary of extra-
cellular influences seems to be confirmed by the relation of the
centrosomes in sense-cells, where they are always found in that
part of the cell that is turned to the external side which receives
the influence.

In the larval retina they are found (First) as real centrosomes
in the receptive part of the neuro-epithelium. In the adult rods
and cones they are found in the ‘Aussenglied’ (Kolmer), while in
the olfactory cells, auditory cells (Held), and cells of the saccus
vasculosus (Dammerman) they are attached (eventually as
diplosomes) to the hairs which project into the surroundings
(fig.1). This clearly demonstrates that the centrosomes have to
do with external influences.

The same is seen in nerve-cells. In the embryonic nerve-cell,
the neuroblast, the centrosome generally lies near the pole where
the first offshoot of the nerve-cell, the axis cylinder arises (Held).
The position of the fibrillogenetic zone, so says Held, always coin-
cides with the position of the centrosome.

56 Cc. U. ARIENS KAPPERS

Since we have to accept that the fibrillogenetic zone is the part
that is first subject to formative (stimulative) influences, it fol-
lows that in the embryonic cells the centrosome coincides with
the primitive stimulative center. When later the dendrites have
arisen, they form the chief receptive apparatus for stimuli, and
it is not strange to see the centrosome of the adult cell near the
dendrites.

In the ganglion-cells of the retina O. v.d. Stricht found the
centrosome in the dendritic part of the cells and so did N. v.d.
Stricht in young spinal ganglion cells still in the bipolar stage.
(In adult monopolar ganglion cells they seem to lie often near

Fig. 1 Sense cell of the saccus vasculosus of Pleuronectes limanda. After
Dammerman.

the monopolar offshoot). Hatai also found them in the cells of
the spinal cord and in the Purkinje cells nearly always in that part
of the pericaryon which is directed toward the dendrites (the same
seems to prevail in the drawings published by del Rio Hortenga
and others).

This position of the centrosome near the place which receives
the influences from the surroundings reminds us of the structure
of the spermatozoid where it is attached to the flagellum, and the
same applies to ciliated epithelium.

LOGETIC CHARACTER OF GROWTH aye

All these facts lead us to believe that the centrosome may re-
. ceive influences from the cell environment and support the sup-
position that the centrosome also during division may be the
center by which influences from the environs of the cell are
received and activated.

In metazoa where the cells are heaped together this cannot be
proved histologically, but the relations found in several Protozoa
seem to support this opinion. The centrosome in a ‘dividing’
protozoon can have a material relation with the outer world
and can readily suffer an influence from the outer world during
the partition.

QHODS

Fig. 2. Mitosis in Stypocaulon. The polar radiation is connected with
extracellular offshoots which are subject to external influer ces. After Swingle.

This is demonstrated by the Lophomonadidae’ and proved
also by cases like Stypocaulon (fig. 2), where the centrosomes of
a dividing cell are attached to protoplasmic fibers which project
into the environment. ;

As to the manner in which a cell of the body responds to the
influence transmitted by the centrosome, nothing can be said as
yet. It would seem, however, that this response is a striving of
the body after equilibrium.

Probably the somatic response will be such that the equilibrium
disturbed by the irritation from without is restored; that is, it is

7 Cf. Hartmann’s Protistenstudien, Fischer, Jena, and Doflein’s Protozoen-
Kunde.

58 Cc. U. ARIENS KAPPERS

a reciprocal action, based on a striving after equilibrium, a con-
trary differentiation or manifestation of energy which can react
toward a defect with a proliferation, toward pressure with in-
creased hardness, toward light with pigment, toward toxin with
antitoxin.®

Moreover, the organism whose reciprocating energy has thus
been evoked remains throughout a unit materially and func-
tionally, viz., it shows in all its parts an associated correlation,
and the developed organism manifests itself as one correlated
system whose harmony is astonishingly reasonable in a logetic
sense.

One need only think of the relation between lens, retina, and
pigment in the eye, the mutual development of which far exceeds
in logical, or rather logetic, relation the mental possibilities of
our conscious logical intellect.

Thus, there is in our somatic development a logetically
correlated relation which has its origin in the same cause as the
mental associations, viz., in different but simultaneously oper-
ating, 1.e., correlated, influences.

In this development of form the ‘function’ is inherent of which
the ‘logetical’ relation with the surrounding world and with the
rest of the body is not less evident, and operates with the exact-
ness of mathematical reasoning; witness the different ways in
which accommodation of vision is effected in the animal series.

It appears, therefore, that the associative differentiation of the
body is in its result a different thing from the associative linking
in the nervous system, but that both of them find their origin in cor-
related stimult.

Both the neuronic linking and the building up of our conscious
mental life, on the one hand, and bodily differentiation, on the
other, are reasonable correlations,originating in correlated irrita-
tions, two different forms of logetic realization.

Besides these, there are in both processes other common fac-
tors, which again manifest themselves in each in a different way,

8 The manner in which nature forms its somatic images differs from that in
which its mental images are conceived in that the latter are not contrary to the
influence in the sense just described.

LOGETIC CHARACTER OF GROWTH 59

but which may perhaps be shown to be identical, viz., memory,
Weber’s law, and attention.

MEMORY AND THE ‘EGO’ IN SOMATIC AND MENTAL DEVELOPMENT

On memory I shall not dwelllong. Better qualified men (Her-
ing, Laycock, Butler, Semon) have pointed out the part which
engrammata may play in all organized matter and the impor-
tance of their reproducticn, their ‘ekphorie,’ as Semon calls it.

That authors have occasionally gone too far in the ‘engram
theory’ and in what respects, I will not discuss for the present.
Here I will only point out a special part which the engrams play
in our conscious or subconscious mental life and what analogy
they have with our bodily life.

In this connection I must point, in the first place, to an appar-
ently very great contrast between the construction of our mental
life and the differentiation of our body. For, whereas the physi-
cal development begins as a real unit—the germ cell—which
contains all potentialities, and this unit is sustained in the devel-
oped individual, the conscious integration of the observations
and conceptions is, on the contrary, very incoherent in the be-
ginning, and besides confined to very few data, as we know from
our own spiritual development.

The phylogenetic development of the brain, too, would seem to show
that the integration of impressions advances but gradually. In fishes
the forebrain, midbrain, oblongata, and spinal cord function to a
large extent autonomously. Only in the higher animals, and espe-
cially in man, is there a greater linking or integration by the associa-
tion of everything, or at least of a great deal, in the cortex cerebri.

In the mental integration (as well in the phylogenetic integra-
tion of brain functions) the coherent unit seems to come only
as a final result, indeed, is only very incompletely reached in
this final result as the many ‘gaps’ in our knowledge prove.

Concerning ourselves, the contents of our spiritual life, how-
ever, are not built up merely by secondary linking of observa-
tions, for as we know by experience, every separate observation
and stimulation falls into the primitive but in a certain way com-

60 Cc. U. ARIENS KAPPERS

plete ego, which seems to be present in the nerve-cell as a deriva-
tive of the germ-cell; and from this it follows, not that ‘the light
is to be seen,’ but that ‘I’ (i.e., the primitive many-in-oneness of
potentialities) ‘see this light’ (cf. also Hughlings Jackson, Pick,
and others).

All perceptions? and correlations always lie in this ego, which
may represent the primitive many-in-oneness of mental life. In
these perceptions, however, the ego stands in the background of
one’s consciousness. Indeed, it is not seldom in the first instance
made active by a perception, which it precedes, however, in
potentiality.

It seems now probable to me that here, too, this ‘ego,’ 1.e., the
direct experience of myself, the primitive unit, is bound to all
nerve-cells, and that owing to this the consciousness of self (not
the secondarily formed conception of myself) can remain, not-
withstanding large destructions by illness, which it would not
be possible to explain in an exclusively secondary linking of the
different neurons in a very imperfect secondary ‘ego.’

The secondarily integrated conscious image is very incomplete
of its kind, and human ingenuity would require much more than
a lifetime of observations and experiences to build up, in second-
ary integrations, all that which works as spiritually active factors
in the individual ego.

The ‘egoity’ awaked by influences from without includes, how-
ever, undoubtedly much more than lifetime experience and be-
gins with a completion (be it un- or subconscious) which bears a
perhaps infinite series of engrams and peculiarities, which in our
subconsciousness are joined ‘intuitively’ (in an ‘entelechic’!° way).

° These perceptions preserve a certain separation because the interval also
represents a situation of the ego.

10 The word ‘entelechia,’ first used by Aristotle, comes probably from ‘en-
teles’ (fulfilment, completion) and ‘echein,’ to have. It is in a way opposite
to teleology. In teleologic functions the ‘logos’ of the ‘telos,’ the knowledge
of the end (the aim) is present. In entelechic processes the character of the
result develops through intrinsic forces and the result is only known when
reached (unforeseen). An example of the latter is the development of man
from ape-like ancestors, who could not have the man-like chirp coe meHits as an
aim, since these did not yet occur at that time.

LOGETIC CHARACTER OF GROWTH 61

This intuitive entelechic junction of engrammata is of a very
high order, especially where it concerns our life as individuals and
part of the human race.

Consciousness can, on account of the factor of attention (con-
centration) which plays an important part in it, never see more
than one point at a time with sufficient intensity. It cannot
survey the reality as an active ‘many-in-oneness,’ but at the
best the natural ‘laws’ which dominate it, which, however, are
also only single threads, and just because they are different and
separately illuminated parts of the reality offer a resting-point
for the attention.

A law which unites all laws in itself is impossible in our atten-
tive spiritual life. The many-in-oneness of our ego in its envi-
ronment in completely intuitive or entelechic relation is experi-
enced, therefore, but is not beheld in the attentive consciousness.
In the often. excellent intuitive judgments much more extensive,
especially also more heterogeneous, complexes are sometimes
elaborated rather without attention (subconsciously) and mostly
these do not become conscious till the final conclusion.

Correlations may also be effected by one single irritation, and
manifest themselves in a successive series of imageless instinctive loget-
ical actions, just as after the action of fertilization or parthenogenetic
irritation of a germ-cell an engrammatic differentiation takes place.

This instinct, not accompanied by conscious images, but manifest-
ing itself in a series of actions, is in some sense an intermediate form
between intuition and growth.

The relation of instinct to physical growth may even be very great,
as is shown by the fact that in insects special instinctive series of
actions coincide according to special seasons and circumstances with
phenomena of growth in those seasons.

Indeed, we see logetical adaptations in nature, of which it is difficult
to say whether they are actions of instinct or growth-phenomena,
e.g., in the protrusion of pseudopodia in lower animals.

On the other hand, we see a vicarious action of growth and of in-
stinct. An example of this vicarious action is the way in which stato-
liths are obtained.

Some animals (the lobster) take them from their environment and
lay them in the statocyst, in other animals they grow in it.

Instinct and growth act together and complete each other in such
cases, if an animal eats special stuffs instinctively and these change
after a series of phenomena of growth into an armor, as in the shell-

62 Cc. U. ARIENS KAPPERS

formation of bird’s eggs. Then instinct and growth, logetical action
and logetical formation, become one, both of them based on the
logetic entelechy of life.

Since we see this relationship between spiritual life and growth,
and we find in both of them associated correlations, memory
and entelechy, the question arises, whether in our physical devel-
opment we can indicate still other factors, which we know play
a part in our mental or perceptual life.

I shall discuss still two points here, attention and Weber’s
law for perceptions.

ATTENTION (CONCENTRATION) IN GROWTH

It appears indeed that in bodily development there occurs
something that may be regarded as the spatial transposition of
the attention concentrated on one point, viz., the fact that a
tissue can only be fully one thing at a time, and the living sub-
stance in its specific tissue strives after losing a defective fitness
for everything in favor of a concentrated adaptation with regard
to one function. Thisis, however, nothing but the developmental
transposition of that which operates as attention in our conscious-
ness. Attention taken in this sense is, just like memory, a gen-
eral function of organized matter—a functional principle peculiar
to the cell in general.

Just as it is I that am attentive and not the attention that is
there, so the specificity of a tissue is a specificity which only
has significance in the ‘many-in-oneness’ of the body.

Perhaps we can also explain now by a somatic transposition
why the scientific, that is the attentive (discursive, analytic) in-
tellect can have no image of the ‘many-in-oneness’ of the micro-
cosm or the macrocosm. For conscious eonception includes at-
tention, 1.e., concentric visioning, and just as a specific tissue
which is to-day only a muscle, to-morrow a connective tissue,
and the day after tomorrow another thing again, would not
form an organ even if it preserves the properties which all the
tissues have in common, so the attentive conceptions of our con-
sciousness cannot give us an idea of the world or of life, though
we can recognize laws in it as many single threads.

LOGETIC CHARACTER OF GROWTH 63

WEBER’S LAW IN PERCEPTIVE AND SOMATIC PROCESSES

It is impossible for me to enter into a discussion at length of
the experiments which have been made on Weber’s law in con-
nection with phenomena of growth. I will only say that the
rather general importance of this law, to which also van Wayen-
burg has called attention in his thesis, has been confirmed more
and more of late.

That the stimulation, which can bring about a modification in
situation, forms a constant percentage of the already active in-
fluexces, has been shown by Pfeffer for chemotactic, by Massart
for heliotropic movements of seed.

Regarding growth it is, of course, very difficult to show that
the general growth of a body, either of a plant or animal, experi-
ences arithmetical consequences of geometrically increasing in-
fluences, but the chemotropic researches of Miyoshi and the pho-
totropic researches of Miss Wisse, who examined molds, prove
that Weber’s law holds for specially directed, tropistic phenomena
of growth, so that it seems that this law so important in percep-
tions is to be traced back in growth.

SUMMARY

In summing up the results of my considerations, I come to the
following conclusion:

Different factors, which play a part in our conscious experience
or in the construction of our mental conceptions, as association,
memory, attention, and Weber’s law, are conscious realizations
of general properties of life, which can be demonstrated equally
in the unconscious development of the body.

In our thinking their influence is experienced directly or real-
ized by introspection (in perceptions by the results of certain
reflexes); in the growth of the body they appear however ‘in
eoncreto.’

Mental life and bodily development are also related in this
respect that the unity of our being in both precedes external
influences, which influences in both cases activate a primary
‘many-in-oneness’ (ego).

64 Cc. U. ARIENS KAPPERS

In mental life the associations in the primary many-in-oneness
bring about a secondary many-in-oneness during personal life,
which is much less coherent than the primary. Consciousness
in consequence of the factor of attention, which always plays a
part in it, can never envisage any but units, whether in a spatial
sense, such as concrete objects, or abstract units, units in a spirit-
ual sense, such as laws. The many-in-oneness of the ego in its
environment, however, is beyond the scope of attentive, scientific
consideration, its presence is realized, experienced. Attention
operates in it, analyzes it, but does not survey it.

It seems hardly necessary to say that the ideas expressed here
are in the main very much in harmony with Aristotle’s doctrine
concerning the ‘psyche’ as a general principle of life, which under-
lies both the rational functions and instinctive actions and phe-
nomena of growth, a conception also defended by Driesch. That
also between these three functions there are considerable differ-
ences needs no further explanation.

These differences are even so considerable and so evident that
they have prevented the greater part of students from seeing the
underlying common principles, which, however, by poets are
often emphasized (Maeterlinck, for instance, in his ‘Intelligence
des fleurs’) and also by philosophers like Schelling.

I will not end without a ‘plaidoyer” in favor of psychological
studies for biological students. It has often appeared to me that
this is of great value. Immediate knowledge and the results of
introspection must complete our study of the phenomena. fev-
eral properties of life—among which the most important—can
only be known immediately, not or mainly a posteriori from the
study of phenomena.

LOGETIC CHARACTER OF GROWTH 65

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Resumen por el autor, Shigeyuki Komine.
Actividad metabdlica del sistema nervioso.

IV. La cantidad de nitrégeno no proteinico en el cerebro de las
ratas mantenidas en un estado de excitacién
emocional y fisica durante varias horas.

Las ratas estimuladas eléctricamente durante un periodo de
10 a 24 horas presentan en su cerebro una cantidad de nitrégeno
no protefnico relativamente mayor que el de las ratas normales
escogidas como término de comparacién. Una estimulacién
semejante durante 6 horas no aumenta el contenido normal en la
rata que “no lucha,’ pero las que luchan presentan un incre-
mento de productos metabdlicos en el cerebro. Las ratas que
lucharon violentamente produjeron una cantidad considerable
de nitrégeno no proteinico, aun después de una a cuatro horas
de estimulacién. Las que lucharon durante una hora presentan
la cantidad normal de nitrégeno no proteinico en el cerebro
después de 42 horas de descanso. El aumento de este nitré-
geno en el cerebro como resultado de una lucha violenta, se
interpreta como debido en parte a productos metabdlicos, que
resultan del aumento de la actividad fisiolégica general del
cuerpo, los cuales llegan al cerebro con la sangre, y, parcialmente
también, como el resultado del aumento de la actividad
metabélica del mismo cerebro.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR'S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 7

METABOLIC ACTIVITY OF THE NERVOUS SYSTEM

IV. THE CONTENT OF NON-PROTEIN NITROGEN IN THE BRAIN OF
THE RATS KEPT IN A STATE OF EMOTIONAL AND PHYSICAL
EXCITEMENT FOR SEVERAL HOURS

SHIGEYUKI KOMINE
The Wistar Institute of Anatomy and Biology

Following great emotional disturbances in man, such as fear,
horror, or rage, various bodily changes are familiar; for
example, cold sweat, the stoppage of saliva, rapid heart beats,
trembling, etc. The researches of Pavlov (’10) show beau-
tifully various physiological changes due to the normal activity
of the alimentary tract following even insignificant emotional
disturbances, and the recent investigation of Cannon and his
colleagues (715) adds to the list of bodily changes, some occurring
in connection with the suprarenal glands.

I desired to determine whether there could be revealed any
alterations, ehemical, physical, or histological, in the brain under
such emotional disturbances as are capable of producing the
various other bodily changes. So far as I am aware, there are
no studies of chemical changes in the brain under a great emo-
tional disturbance. . For this reason I undertook to determine as
a first step whether or not the content of non-protein nitrogen
would change under an altered state of mental activity, or, more

precisely, in the state of fear or rage induced when one rat fights
with another.

MATERIAL

Albino rats alone were used. The rats were brought into the
laboratory from the rat house two or three days before they
were tested, and were kept there during this interval in order to
accustom them to their new surroundings and with the hope of

69

70 SHIGEYUKI KOMINE

eliminating as much as possible the factor of fear from the con-
trol rats. The rats were usually fed with a mixture of ‘Uneeda
biscuit? and condensed milk, at about 9 a.m. In making the
tests two male rats were put into a box which was constructed
in the following manner: A wooden box about 11 inches long, 10
inches wide and 8 inches high was made, in the bottom of which
numerous nails were placed with their tips just exposed on the
inner surface of the bottom. These nails were connected by
means of a copper wire and the ends of these wires were in turn
connected with a battery, so that an electric current could pass
through them. ‘The rats standing in this box were stimulated for
a period of three seconds in every two minutes by the passage
of a current. The rats began to fight immediately or shortly
after the electrical shock was given, as if one rat held the
other responsibile for the shock received. Sometimes the rats
refuse to fight, and in such eases a light pricking of the tail with
a sharp needle always provokes fight almost at once. When once
started, the rats continued fighting under the stimulus of the
electrical shock alone. Usually the two test rats were taken from
different litters, because the rats which belong to the same litter
and are accustomed to living in the same cage do not normally
fight with each other.

When the rats were brought from the rat house, I put those
of the same litter in two separate boxes, one control rat and
one test rat in one box, another control and test rat in the other
box. Rats of more than 120 days of age were chosen, because
Hatai (’17) found that the amount of non-protein nitrogen shows
very slight age alteration after the rats pass this age, while on
the other hand the rats which are younger do not fight vigor-
ously. Males only were used. |

The rats may continue fighting vigorously for several hours.
In this operation both rats stand on their hind feet and push
each other with their front paws, holding their bodies erect and
straight and their mouths almost touching each other. Every
time a shock passes both squeak and each pushes the other
strongly and they may even bite one another. In some cases
the rats continue this performance for more than six hours, while

NON-PROTEIN NITROGEN, BRAIN OF FIGHTING RATS 71

in other cases they assume a fighting attitude only when a shock
passes.

The amount of non-protein nitrogen in the brains of these
fighting rats was determined and experiments were also made to
determine the amount of non-protein nitrogen in the brains of
the rats which had rested for twenty-four hours or more, follow-
ing a severe fight for a period of one hour. For this latter pur-
pose the stimulated rats were returned to their original cages
separately, because such excited rats continue to fight when two
of them are placed in the same cage.

TECHNIQUE

The rats were etherized and the blood removed by severing the
carotid artery, followed by evisceration. ‘The brain was removed
quickly and the left half used for the determination of the non-
protein nitrogen, while the right half was taken for a water esti-
mation. From the dried residue the total nitrogen was deter-
mined by the usual Kjeldahl method. For the determination
of non-protein nitrogen I have employed the method adopted
for my former studies on the metabolic activity of the brain (719);
that is, the brain material was finely ground with 2.5 per cent
aqueous solution of trichloracetic acid and then transferred to
an Erlenmeyer flask (50 cc.) with a small amount of distilled
water. The amount of trichloracetic solution taken was always
twenty times the weight of the sample in grams, while the
amount of water used was five times the brain weight similarly
expressed, in volume. The mixture of tissue and reagents in the
flask is shaken repeatedly during the first hour and then left
for twenty-four hours at room temperature. ‘The clear filtrate ob-
tained from this extraction was analyzed by Folin and Farmer’s
micro-method (’12) as modified by Benedict and Bock (715).
In all cases the nitrogen was estimated by means of the Duboseq
colorimeter. The water content of the brain was determined by
drying the tissue at 98°C. for one week and the total nitrogen by
the usual Kjeldahl method. In this investigation, as in my pre-
vious studies, the designation on each flask was replaced by a

Bs SHIGEYUKI KOMINE

conventional mark made by some other member of the laboratory
and thus the non-protein nitrcgen determinations were conducted
in entire ignorance as to which flask belonged to the control or
which to the test series, thus avoiding any personal bias in the
determinations.

EXPERIMENT SERIES 1

These experiments have been made to see whether cr not the
amount of non-protein nitrcgen in the brain is changed as the
result of stimulation (fghting). Altcgether six control and six
test animals were used. ‘The pericd of stimulation extended
from ten to twenty-four hours. ‘The rats did not fight at all
in two cases and only slightly in one. In no instance was the -
method of pricking with a needle applied to induce f ghting.
During the experimental pericd both the control and test ani-
mals were not fed except with water. ‘The results are shown in
table 1.

As will be seen from table 1, the relative amount of non-protein
nitrogen (per 100 grams) in the brain of the test rat is signifi-
cantly greater than those given by the control rat. ‘The amount
of difference is greatest in the rats which had been stimulated
for the longest period, but this may be mere coincidence, since
the other two cases do not follow in this relation. ‘The present
results bring out at least two points. ince these rats were not
fed during the pericd of stimulation, it is conceivable that the
electrical shocks, although they did not induce actual fighting,
might nevertheless through pericdic irritation accelerate meta-
bolic activity as compared with the rats which were not stimu-
lated, and thus produce a form of mild inanition. It has been
already found in my previous studies (719) that during inanition
(represented by the later part of the twenty-four-hour period)
the non-protein nitrogen content of the brain shows some in-
crease. It will be seen, however, from the later experiments that
this increase in the non-protein nitrcgen may be mainly due to
stimulation, though inanition may also contribute to it.

We might also assume that this increase of non-protein nitro-
gen in the test brain is due to the increased metabolic activity of

73

NON-PROTEIN NITROGEN, BRAIN OF FIGHTING RATS

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74 SHIGEYUKI KOMINE

the nerve cells as the result of electrical stimulation, since we
know from the work of previous investigators that the nerve _
cells show a definite alteration as the result of direct stimulation
of peripheral nerves (Hodge, Dolley, and others).

We shall, however, reserve this discussion until further experi-
mental data are presented.

Whatever might be the real cause or causes, we see from this
preliminary test that as the result of stimulation the amount of
non-protein nitrogen in the brain increases. On account of some
defects in our kymograph, it became impossible in the subse-
quent experiments to run the machine for long periods continu-
ously, and in the later tests we were thus obliged to reduce the
maximum stimulation period to six hours.

EXPERIMENT SERIES 2

In the present experiments the test. rats were stimulated for
six hours with a current from four batteries... Some of these
rats did not fight at all, while others made a good fight. When
the data are arranged according to the amount of fighting, we
obtain interesting results.

As will be seen from table 2, after six hours of stimulation those
rats which fought give a significantly greater amount of non-pro-
tein nitrogen as compared with the controls, while those rats
which did not fight give an amount of non-protein nitrogen al-
most identical with that for the control brains. It appears from
these results that the electrical stimulation alone for a period of
six hours is not sufficient to produce a greater accumulation of
non-protein nitrogen in the brain, but an emotional disturbance
does cause an excessive accumulation of the non-protein nitrogen.

The present experiment seems to indicate that an increased
amount of non-protein nitrogen found in the brain of the rats
which were stimulated for more than ten hours, and which did
not fight at all (experiment 1) might be mainly due to a some-
what increased rate of metabolic activity of the test rats, thus
producing a mild inanition. It seems from these data reasonable

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75

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76 SHIGEYUKI KOMINE

to conclude that as a result of great emotional disturbance the
circulation of the blocd is accelerated, and as a consequence the
cell metabolism of the brain is also accelerated, thus producing a
greater amount of metabolites in the brain.

EXPERIMENT SERIES 3

Thus far the test rats did not fght vigorously, owing to their
lack of response to the electrical stimulus. We found later that
when their tails are lightly pricked with a sharp needle they at
once begin fighting. By such a simple procedure, accompanied
by the electrical stimulus, the rats are made to fight severely,
at the same time squealing and biting each other. When once
such a violent fight starts the periodic shock is irritating enough
to make the fight continue until one rat becomes exhausted and
tries to avoid its opponent’s attacks. The amount of non-pro-
tein nitregen was determined for those rats which had such a
very severe fight for from one to four hours. The results are
given in table 3. -

The results obtained from the eight independent experiments,
using sixteen test rats, show clearly that the amount of non-pro-
tein nitrogen in the brain increases as the result of severe fight-
ing when compared with that obtained from the control brain.
The amount of non-protein found is, however, irregular and there
is no precise indication of a proportional increase with prolonga-
tion of the fighting period. In fact, in one instance (the third in
table 3) a large amount of decrease is shown as the result of
severe fighting for three hours. This decrease in the amount of
non-protein nitrogen might have been the result of a complete
exhaustion. These irregularities in the amount of non-protein
nitrogen found in the brains of test animals may be due to the
fact that there are considerable individual differences as to the
behavior during experimentation. Some rats are very aggres-
sive and may continue violent fighting without cessation, while
there are instances in which the rats fight severely for a few sec-
onds, then stop fighting for some time, only to resume again.
Still more important in accounting for the irregularities is the

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78 SHIGEYUKI KOMINE

fact that some rats show physical exhaustion much quicker than
others. It seems to be clear also from the present data that this
increase in the amount of non-protein nitrogen in the test brain
cannot be the result of inanition, since the period of stimulation
is only from one to four hours—mostly one hour—and indeed the
increase is often more marked with rats which were stimulated
for one hour only. |

We may conclude, then, that as the result of violent fighting
the amount of non-protein nitrogen accumulates far in excess of
that in the control brain, although the exact cause for such an
increase is still to be carefully considered.

EXPERIMENT SERIES 4

The experiments so far show clearly that the amount of non-
protein nitrogen in the brain increases as the result of stimula-
tion, and it was now thought desirable to determine the effect of
rest on the content of the metabolites. For this purpose the rats
were induced to fight violently for one hour by methods already
described. After the lapse of this period, the test rats were placed |
separately in the usual laboratory cages and kept there with
abundant food and water for from twenty-four to forty-two hours.
The results of recuperation for these periods are shown in
table 4.

From table 4 it is clear that the amount of non-protein nitrogen
in the brain of rats which have rested for twenty-four hours is
still significantly higher than those in the control brain. How-
ever, in the rats which have rested for forty-two hours the rela-
tive amount of non-protein nitrogen is almost the same in both
the control and test animals, though the test brains still give a
slightly higher value. We might conclude from these data,
therefore, that for full recovery to the normal state the rats which
have fought violently for one hour require more than forty-two
hours’ rest. I regret that I cannot extend the observations on
resting rats, owing to the limitations of my stay in this country.

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80 SHIGEYUKI KOMINE

DISCUSSION

From the data presented it seems clear that as the result of
severe fighting the amount of non-protein nitrogen increases con-
siderably in the brain. The interpretation of this phenomenon
is difficult. In association with violent fighting there is more or
less physical exercise, which necessarily accompanies fighting,
and we should anticipate an effect of fatigue and whatever
changes such fatigue may produce on the brain. Because great
emotional disturbance is necessarily associated in this case with
marked bodily activity, the greater amount of non-protein nitro-
gen found in the brain in the present experiment might be con-
sidered a result of abnormal physiological activity cf various
organs and tissues, besides that of the nervous system itself.

-The sources of non-protein nitrogen in the central nervous sys-
tem are two; one is that of the metabolites transported to the
brain by means of the blood, and the second is the production
of metabolites by the nervous tissue itself. It is, however, im-
possible to determine from the present experiments alone which
of these sources should be held more largely responsible for the
greater accumulation of the metabolites in the brain. It is, how-
ever, true that the greater activity of the muscles and organs
during severe fighting must increase the amount of metabolites
in general, and at the same time we are also justified in conclud-
ing that the brain tissue itself must increase in its activity. This
latter conclusion follows from the investigations of Hodge (’92),
which showed that conspicuous structural alterations of the
spinal ganglion cells follow the direct electrical stimulation of
peripheral nerves. Hodge further demonstrated that the cells of
spinal ganglia of English sparrows, of the cerebrum of pigeons,
and cerebellum of swallows and antennal lobes of bees obtained
at the end of the day, that is, after a period of activity, show
structural changes as compared with those obtained at the be-
ginning of the day, or after a night of rest.

Similar observations were made subsequently by several ob-
servers, and we may mention here the work of Mann (’95) on
the motor cells of the spinal cord and cells of the retina as one
illustration.

NON-PROTEIN NITROGEN, BRAIN OF FIGHTING RATS 81

A series of researches which have been carried on by Dolley
(09, ’09 a, 710, 711) show clearly that not only as the result of
extreme physical exercises, but even during normal activity, or as
the result of surgical shock, the Purkinje cells of the cerebellum
show pronounced alterations, not only in structure of the cell
body, but in the nucleus-plasma relation. The investigation of .
Mann (’95) shows clearly the effect of anesthetics on the Nissl
granules of nerve cells in producing the so-called chromatolysis,
which takes many hours for complete recovery. All these in-
vestigations demonstrate that the nerve cells are readily influenced
by shock, fatigue, chemical reagents, etc. These cytological
alterations of the nerve cells under varied conditions indicate a
considerable metabolic activity of the nervous organ, and the
increase of non-protein nitrogen in the brain during the great
emotional disturbance, which is noted in the present investiga-
tion, may thus be regarded as partly the result of activity of the
nervous tissue itself. It is the hope of the present writer to
further investigate this problem and at least to analyze the non-
protein nitrogen bodies here determined into their components
(urea, ammonia, amino acids, ete.) in order to throw further light
on the source of these metabolites.

CONCLUSIONS

1. The rats which were stimulated electrically for the period
of ten to twenty-four hours show a relatively greater amount of
non-protein nitrogen in the brain than do the control rats.

2. Similar stimulation for six hours does not increase the nor-
mal content in the ‘non-fighting’ rat, but those rats which do
fight show an increase of the metabolites in the brain.

3. The rats which fought violently produced a considerably
increased amount of non-protein nitrogen, even after one to four
hours of stimulation.

4. The rats which fought severely for one hour show return to
the normal content of the non-protein nitrogen in the brain
after forty-two hours of rest.

5. The increase of non-protein nitrogen in the brain, as the
result of severe fighting, is interpreted as partly due to metab-

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 2

82 SHIGEYUKI KOMINE

olites, resulting from the heightened physiological activity
throughout the body in general, and brought into the brain with
the blood, and partly as a result of the increased metabolic
activity of the brain itself.

LITERATURE CITED

Bock, J. C., anp Benepict, S. R. 1915 An estimation of the Folin-Farmer
method for the colorimetric estimation of nitrogen. J. Biol. Chem.,
vol. 20.

Cannon, W. B. 1915 Bodily changes in pain, hunger, fear and rage. D.
Appleton & Co., New York.

Do.tury, Davin H. 1909 The morphological changes in nerve cells resulting
from overwork in relation with experimental anemia and shock. J.
of Medical Research, vol. 21, (n. s. vol. 16), pp. 95-113.

1909 a The pathological cytology of surgicalshock. I. Prel'minary
communication. The alterations occurring in the Purkinje cells of
the dog’s cerebellum. J. of Medical Research, vol. 20 (n.s. vol. 15), pp.
275-295.

1910 The pathological cytology of surgicalshock. II. Thenumerical
statement of the upset of the nucleus-plasma relation in the Purkinje
cells. J. of Medical Research, vol. 22 (n. s. vol. 17), pp. 831-378.

1911 Studies on the recuperation of nerve cells after functional activ-
ity from youth to senility. J. of Medical Research, vol. 24 (n. s. vol.
19), pp. 309-348.

Foun, O., AND Denis, W. 1912 Protein metabolism from the standpoint of
blood and tissue analysis. J. Biol. Chem., vol. 11.

Harar, S. 1917 Metabolic activity of the nervous sysem. I. The amount of

non-protein nitrogen nthe central nervous system of the normal albino
rat. Jour. Comp. Neur., vol. 28.
1918 Metabolic activity of the nervous system. II. The partition of
non-protein nitrogen in the brain of the gray snapper (Neomaenis
griseus) and also the brain weight in relation to the body length of
this fish. Jour. Comp. Neur., vol. 29.

Hover, C. F. 1892 A microscopical study of changes due to functional activity
in nerve cells. Jour. Morph., vol. 7.

Komine, S. 1919 Metabolic activity of the nervous system. III. On the
amount of non-protein nitrogen in the brain of albino rats during
twenty-four hours after feeding. Jour. Comp. Neur., vol. 30.

Mann, Gustav 1895 Histological changes induced in sympathetic, motor, and
sensory nerve cells by functional activity (preliminary note). J. of
Anat. and Physiol., vol. 299, pp. 100-108.

Pavuov, I. P. 1910 The work of the digestive glands. 2nd Ed. Griffin,

London.

Resumen por los autores, Mathilde L. Koch y Oscar Riddle.

Nuevos estudios sobre la composicién quimica de los cerebros de
palomas normales y atdxicas.

Una segunda series de andlisis de cerebros de palomas afecta-
das de una falta hereditaria de regulacién en los movimientos
voluntarios, demuestra que estos cerebros se distinguen del cere-
bro normal por el tamafio y composicién quimica. Los cerebros
de las palomas atdxicas son mas pequefios. Los autores han
hecho ocho andlisis de la parte anterior (cerebro) y posterior
(cerebro-médula) del encéfalo. Cuatro de estos andlisis se llev-
aron a cabo en palomas atdxicas y los otros cuatro en aves
normales de una edad comparable. Las cambios quimicos en-
contrados estan mds pronunciados en los cerebros de las palomas
fuertemente atdxicas que en los de las menos afectadas. Tam-
bién han hecho andlisis adicionales de los encéfalos completos
de aves muy jOvenes y muy viejas. Los datos sobre los cam-
bios quimicos del cerebro que acompafian a la edad han sido
obtenidos para una serie de individuos de diversas edades en la
paloma. Estos cambios son paralelos a los observados previa-
mente en el hombre y la rata. El exdmen de esta “serie de
edad” mas extensa de cerebros de palomas les ha permitido
evaluar mucho mejor que en su trabajo precedente la relacién
entre las diversas fracciones quimicas y la edad. Las diversas
fracciones de fésforo y azufre lipoide parecen variar en con-
sistencia con la edad hasta los 600 dias. Una revisién de la
significacién de los resultados obtenidos en la presente serie de
anidlisis y en la precedente, conduce a la conclusién de que las
diferencias observadas indican una escasa diferenciaciOn quimica
o relativa falte de madurez de los cerebros atdxicos. La dif-
erenciaciOn quimica, que probablemente incluye en parte la
mielinizacién, no procede aparentemente tan deprisa en el
encéfalo y, mds particularmente, en el cerebelo-médula de los
individuos atdxicos como en el encéfalo de los individuos
normales.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR’S ABSTRACT OF THIS PAPER ISSUEC
BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 17

FURTHER STUDIES ON THE CHEMICAL COMPOSI-
TION OF THE BRAIN OF NORMAL AND
ATAXIC PIGEONS

MATHILDE L. KOCH anp OSCAR RIDDLE

The Psychiatric Institute of the New York State Hospitals, and the Station for
Experimental Evolution, Carnegie Institution of Washington

In an earlier paper (’18) we published the results of five analy-
ses made on the brains of normal and ataxic’ pigeons. Two of
these analyses were of younger and older normal brains; three
were of brains affected to three different degrees with an heredi-
tary (Riddle, ’18) lack of control of the voluntary movements.
Previous observation of the functional derangement led to the
conclusion that the seat of the disturbance was probably in the
brain.

The five analyses just mentioned supplied some evidence that
the functional disorder is associated with deviations from the
normal composition of the brain. These deviations or differences
we interpreted as indicating a tendency toward infantilism or
chemical under-differentiation of the brain of the affected indi-
viduals. In other words, the brains of affected individuals of a
given age seem chemically more like the brains of normal indi-
viduals of a younger age. In that study the number of analyses
was not large and the brain (five brains in each analysis) was
analyzed entire—without a separation of its parts.

In the present study ten additional analyses were made of
brain tissue obtained from birds of still other ages than those
previously used. Eight of these analyses were upon samples rep-
resenting separate portions of the brain—the cerebrum having

‘In earlier papers the disorder was provisionally ca'led ‘ataxia (?).’ In view
of the work of Hoshino (’19), mentioned at the conclusion of this paper, and our
own present results, it is now perhaps unnecessary to qualify this description of
the disease.

83

84 MATHILDE L. KOCH AND OSCAR RIDDLE

been analyzed apart from the rest of the brain (cerebellum and
medulla). ‘These ten samples were selected with the purpose of
supplementing our previous results in the following respects:
a) To obtain information concerning the localization (cerebrum
or cerebellum-medulla) or non-localization of the previously ob-
served chemical changes in the brain of the affected birds; b) a
further comparison of the chemical constituents of the ataxic
and the normal brain; c) the persistence or non-persistence of
such differences in older birds; d) the extension of our knowledge
of the relation of age? to the chemical composition of the brain.

MATERIALS AND METHODS

The brains used in the preparation of samples I, II, III, IV,
and VI are from birds similar to those used in our previous study
except for age differences. ‘The two groups of ataxic birds showed
the disorder to different degrees. ‘The older group (sample III)
being clearly the more affected.? The birds which supplied the
material for sample VI were considerably younger than the
birds used in the earlier study, while the other four samples were
obtained from somewhat older birds (IJ and IV), and from much
older (I and III) birds. The birds used in the preparation of
sample VI were mostly too young to classify as normal or ataxic.

All of the above-mentioned birds, like those used for the pre-
vious study, were birds descended from the first obtained ataxic
or affected individual. ‘These birds, ataxics and normals, were
therefore considerably inbred. The normals or ‘controls’ of
these groups were of the same strain and parentage as the ataxics;
they were, in the main, brothers and sisters of the ataxics. Sam-
ple V contained the brains of the oldest common pigeons (mostly
homers) of the same general kind, but without ataxic blood, which
we could obtain from our collection.

In the present study the cerebrum was analyzed separately
from the cerebellum-medulla in four cases; i.e., four groups of

2 Precise information of this sort has been obtained hitherto, so far as we are
aware, only in man andintherat. The data for man are very incomplete.

* The reader should consult our earlier papers for adequate descriptions of the
various manifestations or degrees of manifestation of the ataxia.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 85

brains yielded materials for eight analyses. ‘The two additional
analyses, samples V and VI, were of entire brains, although here
also the cerebrum was weighed separately from the rest of the
brain.

The birds were all killed by decapitation and the brain removed
immediately, using the following technique: After removing the
feathers and skin, the skull was opened at the posterior end.
The dorsal surface of the medulla and cerebellum was exposed
up to the point of the anterior border of the cerebellum by re-
moval of the skull and meninges. The cerebellum was then
turned back until the posterior border of the optic lobes was
exposed. The separation of cerebellum and anterior region of
the brain was affected by cutting just posterior to the cerebral
peduncles and the posterior border of the optic lobes. The me-
dulla and cord were severed at the foramen magnum and the
posterior brain weighed (between watch-glasses) immediately.

The remainder of the dorsal and anterior skull was next re-
moved. The olfactory nerves were cut and the cerebrum turned
back so as to expose the optic chiasma. ‘The optic nerves were
severed about 1 mm. anterior to the chiasma. The cerebrum
was removed by tilting it backward and cutting the cranial nerves
close to the brain. It was then immediately weighed (between
watch-glasses) and placed in a sufficient quantity of redistilled
alcohol to make the final concentration of alcohol about 85 per
cent. Analysis was begun two months after the collection of the
material.

The method used in the analysis of this material is that of
Waldemar Koch (’09) and the same‘ as was used in the previous
study.

PRESENTATION OF DATA

Our earlier work with the brain of the pigeon made it evident
that it is necessary to obtain data on the age, sex, body weight,
and normality or abnormality of each bird whose brain was col-
lected for chemical analysis. These data for the birds used in

4'The method has been recently republished with slight modification by M.
L. Koch and C. Voegtlin (716).

86 MATHILDE L. KOCH AND OSCAR RIDDLE

the present study are given in tables 1 to 3. The weights of the
two parts of the brain, the weight of the entire brain, the
weight of body, the sex, and the age of the birds of the group
are included in the same tables. In these tables the birds are

TABLE 1
Details on the materials used in the preparation of the normal (control) pigeons’
brains
BRAIN WEIGHT
NUMBER BODY TL TELA ee PE, a
OF SEX Cere- AGE
ny) ‘leer pete Cerebrum eee
medulla

days

B530 | @ | 307 0.445 | 1.485 | 1.880 887

B523 | oc | 352 0.457 | 1.563 | 2.020 820

B548 | | 344 0.465 | 1.500 | 1.965 783

B665 | o | 376 0.466 | 1.413 | 1.879 722

Older normals (sam- } B489 | o@ | 372 0.460 | 1.423 | 1.883 674

ples I and Ia) K288 | «| 315 0.450 | 1.518 | 1.968 564

FIT: 315 0.395 | 1.385 | 1.780 432

K178 | «#7 | 340 0.505 | 1.471 -| 1.976 414

K217 | 9 305 0.462 | 1.364 | 1.826 392

E232 | @ | 304 0.447 | 1.406 | 1.853 298
AVETAGC..... 5005 c0e cee cess seeeees| 004.0 | '0:4552") 14478 | 190304" 598.6

K251 | Q@ | 225 0.418 | 1.360 | 1.778 294

K239 | 9 316 Q:403 12418, | 13827 290

K284 | o | 291 0.482 | 1.573 | 2.055 281

y , anal K235 | 9 | 288 0.465 | 1.874 | 1.839 262

ae fs 7 aoe J| 265] 9 | 293 | 0.435 | 1.383 | 1.768 | 255

tla) K250 | @ | 313 | 0.492 | 1.486 | 1.978 | 219

‘ M364 | o | 291 0.503 | 1.400 | 1.903 169

M366 | | 352 0.520 | 1.507 | 2.027 129

M471 | #1 | 322 0.487 | 1.443 | 1.930 80

M430 | 9 | 274 0.420 | 1.358 | 1.778 76
AVeTAGCs <b ie seis Sen eee tee sar eeeal- 200.02) 0.4625 | 1.4262.) 1 88774 evan

all arranged according to decreasing age. These tables are
given in order that all of the necessary data may be presented,
including the size and composition of each sample as prepared
for analysis. These tables are not used directly in the compari-
sons made below.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 87

Relations of sex, body weight, and age to brain weight (table 4)

When the data concerning the six bird and brain groups of the
above tables are subdivided on the basis of sex and arranged in

258 0.473
202 0.400
173 0.442

: TABLE 2
Details on the materials used in the preparation of the ataxic (affected) pigeons’
brains
BRAIN WEIGHT
“ee BEX) |poneee Cere- AGE
BIRD, eat pete Cerebrum wh ole
medulla
days
A436 | @ | 249 0.395 | 1.541 | 1.936 943
B565 Q | 284 0.404 | 1.481 | 1.835 820
B661 Q | 318 0.391 | 1.328 | 1.719 731
Older ataxica (cant B615! |-Q | 335 0.3886 | 1.224 | 1.610 701
piles Aliand Lie) B492 9 366 0.393 | 1.280 | 1.673 673
Mlors ataxic) K105 | «| 330 0.424 | 1.520 | 1.944 537
K139 Q 332 0.414 | 1.393 | 1.807 511
K198 | | 263 0.4380 | 1.315 | 1.745 398
K169! | 9 342 0.453. | 1.303 | 1.758 392
K292? | o& | 268 0.462 | 1.503 | 1.965 298
PSV EUS... se s,eaiee Mee ara st ee ae aie 308.7 | 0.4152 | 1.3838 | 1.7992 | 600.4
K274 Q@ | 282 0.410 | 1.470 | 1.880 285
K269 Q | 254 0.373 | 1.390 | 1.770 283
K255 (267 0.417 | 1.382 | 1.799 275
K241 Q | 261 0.403 | 1.325 | 1.728 258
Younger ataxics K248 Q 252 0.426 | 1.365 { 1.791 258
(samples IV and || K293 | @ | 293 0.444 | 1.585 | 2.029 220
IVa) (Less ataxic) |} M369 | # | 295 0.495 | 1.478 | 1.973 187
of 1.5:
rot 1
roe ile

PACT RRC 3555.5 sal ch tal ohnbar eer at 253.7 | 0.4283 | 1.4233 | 1.8516 | 206.0

1 Very scraggly feathers.
2 This bird ataxic when younger; practically normal when killed.
3 Somewhat emaciated.

order of age, a number of interesting facts are made clear. It
may first be noted that in every case the males of a group show a
larger average brain weight than that of the females of the group.

88 MATHILDE L. KOCH AND OSCAR RIDDLE

Indeed, in the four really comparable’ groups the lowest average
brain weight for males is higher than the highest average for fe-
males. The same is true for the two separate parts of the brain—
the male cerebellum-medulla is larger and the male cerebrum is
larger.

That this larger size of the brain, and of both parts of the
brain, of the male is not wholly dependent upon the larger body
size of the male is indicated by the fact that two only of the male

TABLE 3
Details on the materials used in the preparation of groups V and VI

BRAIN WEIGHT

NUMBER LE, 1 OF Ge PS Sa ee =
OE ibe || ees Cere- AGE

ue ar eS belua Cerebrum Whole
medulla

iin bse 50 gece op aa eee
H-A oa | 435 OFAS8r 4) 125201965 3266
Older pigeons of|| H-B o | 394 O:511 | 1.535 | 2.046 3264
other strains (sam- 4 | 169 ce) 334 0.510 | 1.528 | 2.0388 1287
ple V) A21 Q 335 ORAZ 1523) 9995 1238
A313 fe) 258 OF45 | 1505) 12962 1048
ASVETAICe Win. 22 2.. Orn hater her Ae nice 351 0.4776 | 1.5236 | 2.0012 | 2021
M475 Q 316 (249) |) ise |) 7 59
M452 Q 163 Orson e225 eleolG 59
Younger pigeons of || M478 | @| 255 0.454 | 1.384 | 1.888 52
the ataxic strain | M4791 | «| 319 OMA eal leeZaun | ledoo 50
(sample VI) M441 fe) 264 0.367 | 0.941 | 1.308 37
M408 Q 129 0.3385 | 0.940 | 1.275 35
M415 g 75 0.198 | 0.542 | 0.740 22
AVeraA Pe na (Ks) Sei idee Meee Te 217.3 | 0.3737 | 1.1007 | 1.4744 45

1 Known to be ataxic.

groups are larger and two are smaller than the associated females.
For the mature birds the brain weight shows considerable inde-
pendence of body weight.

The relation of age to the size of the brain and to each of the
two parts into which we have divided it can be partly under-

5’ Group VI is clearly immature; group V is not of the same strain. In the
latter group, moreover, the disparity of age is extreme; the males being very old
(nine years) and the females in their prime (three years).

89

COMPOSITION OF BRAIN OF ATAXIC PIGEONS

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90 MATHILDE L. KOCH AND OSCAR RIDDLE

stood from a study of the data of table 4 and partly from the data
previously obtained by us (’18, table 3; in part reproduced here,
table 8). It is clear that neither females of 42 days nor males of
51 days (averages on table 4) have fully developed brains. Two
females of 69 and 127 days (18, table 3), however, each hada
brain nearly as large (1.811 grams and 1.813 grams) as that of
the largest female brain of groups I and II (K235 = 1.839 grams,
age 262 days, table 1) and larger than the average brain (1.803
grams and 1.797 grams, table 4) of the females of these much
older normal groups. Similarly, a male of 124 days (18, table 3)
had a brain larger (1.943 grams) than the average (1.928 grams)
of eight normal males of 645 days (average, table 4).

It is reasonably clear that in this particular strain of birds the
maximum brain weight is usually attained not much later than
100 days after the beginning of development (eighteen days for
incubation). In all of our present and previous analyses of
pigeon brains (table 8), therefore, only the brains of group VI
of the present series were undersized because of age. Groups II
* and IV, which are compared with each other, have each two birds
aged less than 100 days.

Relation of ataxia to brain size

The relation of brain size to normality and ataxia may now be
confidently studied, since the influence of sex, body weight, and
age have already been considered. Four quite comparable groups
(I to IV, table 4) are available; two of these are brains from nor-
mal birds and two from ataxics, and there are both males and
females in each of the four groups for comparison. The following
is found:

The whole brain of each of the ataxic groups is smaller® than
that of either of the two normal groups (tables 1 and 2). The

® There is a high percentage of males in one normal group and a high percent-
age of females in one ataxic group which considerably affects the brain size of
these two. But the comparison between the normal and ataxic males of these
two groups, and between the normal and ataxic females of these two groups, is
just as val.d as are the similar comparisons between the other two groups in which
no disparity of sex exists. The mean weights of the various groups permit a
quite fair comparison from one group to another.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 9]

males of both ataxic groups have smaller brains (table 4) than
have the males of either normal group. The females of both
ataxic groups have smaller brains than the females of either
normal group.

The cerebrum of all of the above-mentioned groups and subdi-
visions of groups of ataxics is smaller than the corresponding
groups of normals in a precisely similar way except that the fe-
males of the less ataxic group have a larger cerebrum than do the
females of the other three groups. The females of the strongly
ataxic group have the smallest cerebrum found for the four
groups.

The cerebellum-medulla of all the ataxic groups and subdivisions
is smaller in every case.

Further study of these data (four comparable age and strain
groups of table 4) shows, moreover, that the posterior portion
of the brain (cerebellum-medulla) of the ataxic groups is dispro-
portionately small in comparison with the cerebrum. That is
to say, the cerebrum of ataxics is somewhat reduced (1.5 per cent
in males and 0.0 per cent in females) below that of the normals,
while the cerebellum-medulla is much below (7.2 per cent in
males and 5.4 per cent in females) the normal size. The mean
weight of the cerebrum of the older ataxics is 1.3 per cent below
that of the older normals. That of the younger ataxics 1.7 per
cent below that of the younger normals. For the cerebellum-
medulla these figures are 5.3 and 5.5 per cent, respectively. The
disproportionate decrease of the ataxic cerebellum-medulla is
also shown by the figures for the ‘ratio of parts’ of the brain.
These figures are given in the next to the last column of table 4.
All of the (four) subdivisions of ataxics are there shown to have
abnormally small posterior brains. These same ratios also dem-
onstrate that in all of the four comparable groups—normals and
ataxics—the cerebellum-medulla is a smaller fraction of the total
brain in females than in males.

It follows, therefore, that ataxia carries the male brain in the
direction of the normal female brain, both in regard to size and
relative proportion of its parts. We have hitherto noted that
ataxia also reduces the body size of the male; this is again in the

92 MATHILDE L. KOCH AND OSCAR RIDDLE

direction of the normal female. It will be pointed out later that
ataxia is found more often in females than in males. Since the
observed effects of ataxia on the male all take the direction of
the female, it may be asked, does this fact have any bearing upon
the predominant appearance of the derangement in female
offspring?

Before concluding the above considerations (in which the mate-
rials entering into the composition of the samples are being con-
sidered as fully as a paper presenting chemical data permits),
emphasis may be placed upon the fact that samples I-Ia and
III-II]Ja (older normals and older ataxics), though quite com-
parable as to age, are not so in regard to sex. Also, that this sex
difference at least partially accounts for the size differences of
the brains of these two groups. And, further, that differences of
brain size may be of significance in the results of the chemical
analysis. Donaldson (’16) obtained from the rat evidence “that
both the relative and absolute weight of the brain * * *,ata
given age, are factors tending to modify the percentage of water
present, in the sense that the heavier brain or cord shows the
smaller percentage of water.’’ Donaldson’ also indicates that in
a given species the larger (heavier) brains at a given age tend to
have a higher percentage of white substance. On this basis the
larger brains of both the older and younger normals (samples
I-Ia, II-Ila) might be expected to show lower water values
(and other chemical evidences of greater age) than the ataxic
groups of somewhat smaller brain size with which they are com-
pared. Possibly such size relations do slightly influence the
amount of the various chemical fractions obtained by us. We
would note, however, that the cerebrum of the younger normals
(Ila) and the younger ataxics (IVa) were of equivalent (total)
size (14.252 grams and 14.233 grams, tables 1 and 2), and in
each sample the sexes were equally represented; nevertheless,
when the figures obtained for these two groups are compared,
on the basis of the nine constituents found to be characteristic
of age in this series (p. 98), it is found that six of these nine con-
stituents here indicate the relative immaturity of the ataxic

7 Personal communication,

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 93

group. Further, until exact information as to the nature of the
changes in the (smaller) ataxic brains are made known by neuro-
logical study (Hoshino), it does not seem practicable or profitable
for us to attempt to evaluate the influence of the brain-size dif-
ferences, which are present in some of the samples, upon the
chemical data obtained by us.

Chemical criteria of under-differentiation or immaturity in pigeon
brain

In the presentation of our earlier results (18) we endeavored
to make a comparison of the observed chemical differences of
ataxics and normals in terms of known or expected changes due
to age. It seems advisable to follow the same plan in the present
paper. At the time of our earlier publication we had only the
five different ages (only two of which were brains of normal birds)
represented in our own analyses to guide us as to the actual
nature and direction of chemical changes due to age in the pigeon
brain. The brains utilized by us ranged between the relatively
narrow limits of 106 days and 183 days. As a check and as a
more complete guide to the direction followed by chemical change
in brain tissue with increasing age, we utilized (and freely quoted)
two available series of results on other animals. Human brains
(Koch and Mann, ’07) aged six weeks, two years, and nineteen
years, and rat brains (W. Koch and M. L. Koch, 713) aged one to
120 days—all of which were analyzed by methods essentially the
same as those used by us—were our only additional guides.

Realizing the need for specific and positive knowledge of the
course of chemical differentiation in the pigeon brain in still
younger and in much older ages in our present study, we have
examined the brains of normal birds aged (averages) 45, 205, 598,
and 2,021 days. Asaresult of these additional analyses, we can
now see that several of the most pronounced chemical changes,
which elsewhere are known to accompany increased age in brain
tissues, were largely completed in the youngest of the brains
utilized in our former study. And further, it has now become
plain that some chemical fractions (extractives, sulphatids, and

94 MATHILDE L. KOCH AND OSCAR RIDDLE

phosphatids) which are really indicative of age in very young
brains have very limited or quite uncertain values when applied
to brains of some of the older ages. ‘This particularly applies to
several ages actually studied by us. It is, therefore, necessary to
restate here the chemical criteria for differentiating younger and
older stages, as this applies to the pigeon brain for those particu-
lar ages which we are now to compare.

The data given in table 8 require the following conclusions:

Water is decreased relative to solids throughout the entire age
series. It is true that the moisture figures obtained for the sev-
eral groups of normals do not correctly indicate the age of the
group in all cases. For example, the normal brain of 106 days
is shown to have a slightly lower percentage of water than the
normal brains of 205 days, and an ataxic of 133 days slightly less
water than an ataxic of 206 days. Ataxia itself probably further
complicates the smoothness of the figures for the series as a
whole. Nevertheless, a general tendency to a decrease of water
with increasing age is unquestionable.®

Protein plainly decreases with increased age. Only the figure
for the normals of 106 days breaks the complete smoothness of
the curve for the entire series of normals.

Lipoids increase with increased age, although the figures actu-
ally obtained are not wholly consistent, neither for the normals
considered alone nor for the ataxic series. In fact, between 106
days and 598 days very little change is indicated in the amount
of lipoids. This doubtless indicates that myelination is prac-
tically completed in these pigeons at 106 days.

Extractives are present in the solids in greater amount in the
forty-five day brain than at any other time. In normals of 106
days, however, no more extractives are present than in normals
of 2,021 days, and less is found than in normals of 205 and 598

8 It should be borne in mind that there is opportunity for error in the moisture
estimation of any organ such as the brain. First, through unequal evaporation
from the brain surface during the preparation of the sample, and, second, through
the presence of unequal quantities of blood within the organ when weighed.
Whether ataxia itself offers any special complication is at present unknown to us.
Again, any loss or gain to the solids of either the aleohol-ether soluble or alcohol-
ether insoluble fraction would serve to modify the recorded amount of moisture.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 95

days. The smallest percentage of extractives was found in nor-
mals of 183 days. It is therefore clear that in brains older than
106 days the variations in amount of extractives noted by us
have a wholly doubtful significance with respect to age.

Cholesterol steadily increases with age. The relative age of all
except one of the normal groups is correctly expressed by the
amount of cholesterol found.

Phosphatids increase with age (total phosphorus, in per cent of
solids, steadily decreases with age) until about 205 days. The
amount then decreases slightly. It is probable that low phos-
phatids, as in birds of 600 days, is indicative of relative imma-
turity, since it is only in very immature brains that low phospha-
tids are normally found. The highest figure obtained was for a
group of 183 days.'!° In general, therefore, phosphatids cannot
be considered distinctive of age in brains older than 183 days.

Sulphatids certainly increase with increased age (total sulphur,
in per cent of solids, fluctuates with age) to 205 days or more;
but the figures obtained, like those for phosphatids, are not en-
tirely consistent. The highest figure for sulphatids was obtained
in brains of 205 days. It seems probable that the percentage of
sulphatids is actually higher in the cerebrum of birds of about
205 days than in those of about 600 days (table 5). Although
the series as a whole indicates that lower sulphatids signifies
younger age, we do not seem warranted in applying this rule to
brains of 200 to 600 days old. (This is in no way contradictory
to W. Koch’s conclusion that phosphatids and sulphatids in-
crease in the brain of the growing animal.)

Phosphatids and sulphatids, however, require a further remark.
When the amounts of phosphatids (lipoid-phosphorus) and sul-
phatids (lipoid-sulphur) are calculated respectively in terms of
percentage of total phosphorus and total sulphur (table 7), the

° The cerebellum-medulla of 598 and of 600 days constitute a further exception.
These have less lipoid-phosphorus than their corresponding (normal and ataxic)
groups of 205 and 206 days (table 5). Possibly in the pigeon the cerebellum-
medulla is chemically a more fully differentiated ‘brain tissue,’ and attains its
chemical differentiation earlier than the cerebrum.

10 A similar situation has been found for the brain phosphatids of the rat
(Koch and Koch, ’18).

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 2

96 MATHILDE L. KOCH AND OSCAR RIDDLE

above-stated abnormal relation of phosphatids and sulphatids
to age (at 200 to 600 days) disappears. The difference of result
on this basis of calculation is directly due to the fact that total

TABLE 5

Chemical composition of cerebrum and cerebellum-medulla of normal and atazic
pigeons (in per cent of solids)

CEREBRUM CEREBELLUM AND MEDULLA

Syh ghee whe hae Ve eae

E ao K Ae A Bo ‘Gala ie

Younger Older Younger Older
Water in, perveent 25's: ciceian = ae 81.0} 80.3] 79.7) 79.6) 77.9] 78.0) 77.9) 77.8
PEOUCIAD isos hs PRA ee 52.1) 51.3] 49.9} 50.3) 46.3) 46.8) 45.8) 46.2
MN OUAS 95 cheat ier Seta eds patch Secon e 34.4} 35.3] 35.8} 35.0) 40.7) 41.4) 41.9) 41.8
BxXtTACbives...< s...<25) enyoess waaess on] 20.0) a4) 1473/1147] doeO | Sle ee
Cholesterol. 2h. a aektns lise Th V5) Tl TAO T 31) 1828/5 S58) OSLO eas
Phospbatidscrcscee ps leslie 4 eee 22.5) 22.5]°22.3] 20.2) 24.6) 23.4) 22.5] 23.0
Sulph aids tos ot. tan coat it os dae cage 8.4) 8.4) 6.8) 5.6) 13.3) 11.3} 11.8) 15.9

Distribution of sulphur in per cent of total sulphur

Protein-sulphur...................]| 65.3] 69.7] 66.6) 69.9) 55.8) 54.5) 56.8) 49.6
Lipoid-sulphur....................] 18.1] 16.5) 18.9} 15.3) 26.6] 23.5) 27.2) 32.1
Extractive-sulphur.)........:..5.. 16.6} 13.8} 14.5) 14.8] 17.6} 22.0} 16.0) 18.3

Total sulphur (in per cent of solids)| 0.93] 1.02} 0.72) 0.76) 1.00) 0.96) 0.87} 0.97

Distribution of phosphorus in per cent of total phosphorus

Protein-phosphorus...............-| 17.7| 20.1} 13.9] 16.0) 18.7) 18.0) 17.9) 20.4
Lipoid-phosphorus...............-| 63.0] 59.8} 67.5) 62 1} 61.7) 60.2) 61.2) 59.3.
Extractive-phosphorus............| 19.3} 20.1] 18.6} 21.9} 19.6) 21.8) 20.9) 20.3

Total phosphorus (in per cent of
SOLIGS) 02.6 dicccsa scenes epee a omeee| £80) 2-46) 1.28) 1.26) Dl Gort ce) ieee idee

phosphorus and total sulphur are reduced in the brains of about
600 days. Calculated thus, lipoid-phosphorus is in greater
amount in the 598-day normal than in the 205-day normal.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 97

Also, lipoid-sulphur is in greater amount in the 598-day than in
the 205-day brain. In the comparison of the brains of these
ages soon to follow (table 5), we shall therefore use the figures
obtained for lipoid-phosphorus and lipoid-sulphur (table 6) and
ignore the figures for phosphatids and sulphatids which are eal-
culated by factor and in terms of per cent of solids.

The other fractions (protein and extractive) of sulphur and
phosphorus may next be considered. They, too, are calculated
(table 7) in per cent of total sulphur and of total phosphorus.

TABLE 6

Distribution of sulphur and phosphorus in cerebrum and cerebellum-medulla
(calculated in per cent of solids)

CEREBRUM CEREBELLUM AND MEDULLA

GROUP Sulphur

Protein} Lipoid seniree Total | Protein} Lipoid raed Total

hate Ataxics 0.528] 0.111] 0.116] 0.755] 0.481] 0.310] 0.177] 0.968
ae Normals | 0.479] 0.136] 0.104] 0.718] 0.494] 0.235| 0.139] 0.868
Pic. Ataxics 0.708] 0.167| 0.140] 1.015] 0.526] 0.226] 0.213! 0.964
BeT.--- ) Normals 0.609] 0.169] 0.155] 0.933] 0.559] 0.267| 0.177] 1.003
Phosphorus

ate Ataxies 0.202] 0.783] 0.276] 1.262] 0.308] 0.894] 0.307) 1.509 |
“--** ) Normals 0.178] 0.867] 0.239] 1.284] 0.256] 0.874] 0.298] 1.428

= ee Ataxics 0.293] 0.872} 0.293] 1.458] 0.272] 0.910] 0.330) 1.512
ounser.--- \ Normals *— |-0.245| 0.873] 0.268] 1.387| 0.288] 0.956] 0.304] 1.548

Protein-sulphur is present in largest amount in brains 166 and
183 days old, and in lowest amount at 205 days. It is lower in
the three oldest groups than in the three youngest groups;!! but
the irregularity just noted makes it impossible to use this fraction
as an index of age. LHxtractive-sulphur and total sulphur plainly
do not vary consistently with age.

1 Protein sulphur is lower in both cerebrum and cerebellum-medulla of nor-
mals of 598 days than in normals of 205 days.

98 MATHILDE L. KOCH AND OSCAR RIDDLE

Protein-phosphorus decreases wholly consistently with age in
all of the normals. Extractive-phosphorus decreases progres-
sively with age. This rule fails, however, in the very old (2,021-
day) brain. Total phosphorus also progressively decreases with
age.

In the comparison of the normal and ataxic brains, the younger
age is characterized, therefore, by higher values for water, pro-
tein, protein-phosphorus, extractive-phosphorus, and total phos-
phorus; and by lower values for lipoids, cholesterol, lipoid-phos-
phorus, and lipoid-sulphur. A comparison, on the basis of these
nine constituents, of corresponding parts of the brain of normals
and ataxics will be made first. That of the whole brain of all of
the normals and ataxics can be better done later.

Results of analysis of cerebrum and cerebellum-medulla of normals
and ataxics (table 5)

The cerebrum of the younger (less) ataxic group gave lower
figures for moisture, protein (extractives),!2 cholesterol, lipoid-
sulphur, and lipoid-phosphorus than the younger normals with
which they should be compared. Higher figures were obtained
for lipoids, protein-phosphorus, extractive-phosphorus, and total
phosphorus. Six of these figures indicate that the cerebrum of
the younger ataxics (206 days) were less differentiated than those
of the younger normals (205 days); three figures point to the
opposite conclusion.

The cerebellum-medulla of the younger ataxics show smaller
values for lipoid-sulphur, protein-phosphorus, lipoid-phosphorus
(phosphatids, sulphatids, extractives), and total phosphorus;
greater values for moisture, protein, lipoids, and extractive-phos-
phorus. Five of these figures point to the (less) ataxic cerebel-
lum-medulla as the younger stage, while three are opposed.
Cholesterol shows no difference. Summarizing this comparison
of parts of the brain of younger normals and younger (less) atax-
ics, it may be said that the results show but little of chemical

Substances which are not really distinctive of age will sometimes be
included in the summaries or comparisons which follow, but to distinguish them
they will be included in parentheses.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 99

difference which is consistently interpreted on the basis of age.
The differences found, however, favor the view that both the
cerebrum and cerebellum-medulla of the ataxics were somewhat
younger than the normals with which they are compared. In
reality, our observed moisture differences of 0.1 per cent are
insignificant.

The cerebrum of the older (strongly) ataxic group show de-
creased water, lipoids, cholesterol (phosphatids, sulphatids),
lipoid-sulphur, lipoid-phosphorus, and total phosphorus, when
compared with the amounts found in the older normal group.
Increased values are shown for protein (extractives), protein phos-
phorus and extractive-phosphorus. Seven of these figures indi-
cate juvenility or chemical under-differentiation of the ataxics
as compared with the normals of equivalent age. Two figures,
those for the very nearly equivalent water and total phosphorus,
oppose this interpretation. Reference to table 4 will show that
the cerebrum in this group of ataxics was below normal size.

The cerebellum-medulla of the older ataxics show decreased
amounts of water, lipoids (extractives), cholesterol, lipoid-phos-
phorus, and extractive-phosphorus, and increased amounts of
protein (phosphatids, sulphatids), lipoid-sulphur, protein-phos-
phorus, and total phosphorus. Of these figures, six are in favor
of, and three are opposed to, the view that the cerebellum-
medulla of the ataxic group is more juvenile than that of the
normal group..

Most of the chemical evidence which is distinctive of age indi-
cates, therefore, that both parts of the brain of the older group
of strongly ataxic birds (600 days) were somewhat less old than
the older normal brains (598 days) with which they must be com-
pared. Similar evidence was found for both cerebrum and
cerebellum-medulla of the younger (less) ataxic group.

Concerning the whole of the new evidence obtained by a com-
parison of the chemical composition of the parts of the brain of
normals and ataxies, it can be said that all of the four tests made,
support the interpretation which was given to our previous re-
sults. Most of the evidence indicates that the cerebrum and
cerebellum-medulla of both ataxic groups are chemically less dif-

100 MATHILDE L. KOCH AND OSCAR RIDDLE

ferentiated, or less old, than are these parts of the brain in nor-
mals of equivalent age. Further, the evidence obtained from
the older strongly ataxic brains is more decisive than that
obtained from the younger less ataxic brains.

Distribution of sulphur and phosphorus in cerebrum and
cerebellum-medulla

In table 6 are given the data. on the distribution in cerebrum
and cerebellum-medulla of sulphur and phosphorus calculated
in per cent of solids. That method of calculation scarcely
changes the description already given above in terms of total
sulphur and total phosphorus. Particular attention may be
directed only to differences in distribution of these elements in
the cerebrum and cerebellum-medulla. These data are the
first thus far obtained for any bird.

Protein-sulphur is more abundant in the cerebrum than in the
cerebellum-medulla. Lipoid-sulphur and extractive-sulphur is
distinctly less in the cerebrum. ‘The older birds (598 and 600
days) have markedly less sulphur in all fractions of the cerebrum
than have the younger birds (205 and 206 days). In the cere-
bellum-medulla there is less of difference due to age. This prob-
ably indicates that the maximum sulphur content of the pigeon
cerebrum is reached at nearly 206 days and thereafter decreases
in relative amount (table 7). The sulphur of the cerebellum-
medulla suffers no marked decrease during this period (206 to
600 days). Most of the sulphur of cerebrum and cerebellum-
medulla is protein-sulphur.

The phosphorus of both the cerebrum and the cerebellum-
medulla is chiefly lipoid-phosphorus. Protein-phosphorus and
extractive-phosphorus are present in almost equal quantity in
both parts of the brain. All three fractions of phosphorus’ are

13 Only two of the figures compared above show a different relation to each
other under the two methods of calculation. These occur in the lipoid-phos-
phorus and extractive-phosphorus of the cerebellum-medulla of the older ataxic
group. Both became higher in the ataxic than in the normal. The numerical
result is the same as before: six figures still indicate the rele Ye immaturity of
the organ and three figures are opposed.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 101

present in slightly greater amounts in the cerebellum-medulla
than in the cerebrum.

The distribution of sulphur and phosphorus, calculated for
the entire brain of the four bird groups considered above, is shown
in table 7. These figures are of course based upon the original
actual weights. Similar figures for brains of 45 days and 2,021
days of the present series of analyses, besides corresponding fig-
ures from our five previous analyses, are included for comparison.
Reference to the data of this table has already been made.

TABLE 7

Distribution of sulphur and phosphorus in per cent of total sulphur and total
phosphorus for whole brain of all analyses

SULPHUR PHOSPHORUS

NUMBER GROUP AGE
Protein| Lipoid Bava, Total! | Protein| Lipoid | Extrac- TotalA

days
il Normal 2021 | 60.2"|+23:5 ||) 16.3"), 0:84) 14.1 | 61.7 | 24.2) 1.40
Be Ataxic COORG SHON POT OM IGE ORL ideo nl Olen elem So:
3 Normal 598 | 68.8 | 21.3 | 14.9 | 0.76 | 15.0 | 65.9 | 19.1 | 1.32
4 Ataxic 206 | 66.0 } 18.2 | 15.8 | 1.00 | 19.5 | 59.9 | 20.5 | 1.47
5 Normal 205 | 62.6 | 20:5 | 16.9 | 0.95 | 18.0 | 62.6 | 19.4 | 1.48
6 Normal 183 | 69.6 | 18.2 | 12.1 | 0.69 | 19.0 | 60.8 | 20.3 | 1.50
a Ataxic LGGHRGOZON S225 Socom mOs (onl loalel|5O sen 22 adele ih
8 Ataxic LES OTRO WANG TN Loe WORT NLS. 84) 88a9> | 22.56) | eee
9 Ataxic 133 | 65.1 |(21.2)| 18.7 |(0.76)| 19.5 | 58.4 | 22.1 | 1.49
10 Normal 106 | 65.8 |} 19.4 | 14.8 | 0.67 | 19.3 | 58.2 | 22.5 | 1.53
ital Mixed AD 65629) 145) 23.4 Ob3, | 20:2) 55.10 2428" | 161

1 In per cent of total solids.
Nore.—Nos. | to 5 and 11 are new data; nos. 6 to 10 are our earlier data (’18).

Summary of present and earlier data on chemical differences in
ataxic brains

In tables 7 and 8 are given for the whole brain the principal
analytical figures obtained by us in the present and former
series of analyses. Samples V and VI (nos. 1 and 11 in these
tables) and samples I-IV and Ia-IVa (nos. 2 to 5) of the present
series are there calculated for the whole brain.

In these tables the composition of the most ataxic brains of the
present and former series, nos. 2 and 8, respectively, may be

102 MATHILDE L. KOCH AND OSCAR RIDDLE

readily compared (figures for both placed in italics) with the
brains of similar ages. It is in these two series in which the ab-
normality was most marked that the clearest evidence for a
chemical under-differentiation or relative immaturity of the
ataxic brains is found. It is notable that in both of these groups
the amount of water is either equivalent to or more than is indi-
eated for their actual age; protein is present in excess in both;
lipoids are deficient in both; cholesterol is lowest in both; phos-
phatids and sulphatids™ are also low in both; total phosphorus

TABLE 8
Chemical composition of the whole brain of normal and ataxic pigeons (in per cent
of solids). Arranged according to age

AVERAGE SOLIDS
E BOW OF WATER CHOLES, ean pen eet
BRC uEES edhe! aay eae Bes tinea ee
days grams | grams

1 | Normal!) 2021 351 | 2.001] 78.4 | 47.4 | 39.4 | 13.2 Salk | AY8} 9.9
2 | Atazxic 600 809) 1.799 7923 | 49.2.) 86.8 | 1420 7.7 | 20.8 8.0
3 | Normal 598 334 | 1.903) 79.3 | 48.8 | 37.4 | 13.8 CaS |e22e4 8.0
4 Ataxic 206 304 | 1.852] 79.8 | 50.2 | 36.8 | 13.0 LAs |) Peat Out
5 | Normal! 205 297 | 1.888) 80.2 | 5).6 | 36.0 | 13.4 flac) |) 233511 9.8
6 | Normal 183 362 | 1°879) 79.8 | 50.7 || 37-1 | 1252 Up)\) 23.5 6.3
7 | Ataxic 166 S14 W784 79ED | 49e7 | ove2 | ool 7.4 | 23.0 6.1
8 | Atazxic 158 326 || 1.789) 80.2 | 52-1 | 34.9 | 12°59 6.8 | 21.9 G23
9 | Ataxic 133 331 | 1.900) 79.6 | 50.9 | 36.4 | 12.7 C22 Aa (Seo)
10 | Normal 106 SOOM 1. 92228020 "50LON S6r8 3.2, (002229 6.5
11 Mixed? 45 2AT | MeATSINS2 26 ole ON| sod 4 6.5 | 22.8 4.1

1 Birds not of ataxic strain, but of nearly similar variety.
2 A mixed group, probably normals and atax cs, all from ataxic strain.
Norr.—Nos. 1 to 5 and 11 are new data; nos. 6 to 10 are our earlier data (’18).

is low in both; extractive-phosphorus and protein-phosphorus
are high in at least one case. In all of these fractions these two
ataxic brain groups are less differentiated chemically than brains
of their calendar age should be. Extractives are not distinctive
of age for the ages actually considered and one ataxic shows a
high the other a low figure for this fraction.

It thus appears that of those nine chemical fractions (eighteen
for the two groups) which ean be relied upon to reflect age differ-

4 Confirmed by lipoid-phosphorus and lipoid-sulphur, table 7.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 1038

ences in the whole brain of the two most strongly affected groups,
two or three fractions indicate equivalent age, two indicate older
age, and thirteen fractions indicate younger age than was actu-
ally theirs. It is difficult to believe that such results would have
been obtained on two groups of brains not actually unlike in de-
gree of chemical differentiation. Similar differences in smaller
degree and of less definiteness occur in the one strongly ataxic
cerebrum and cerebellum-medulla group analyzed. The whole
brains of two additional groups of birds showing relatively little
ataxia gave nearly indifferent figures in respect to age. It seems
necessary to conclude that the result of the two series of brain
analyses indicates that chemical differentiation does not proceed
as rapidly in the brain, perhaps more particularly in the cerebel-
lum-medulla of ataxie birds as in the brain of normal birds.
Moreover, chemical under-differentiation of the ataxic brain
certainly may persist into very mature age.

DISCUSSION
Analyses and materials

In our analyses we have been obliged to deal with groups of
brains and not with individual brains. This fact has a bearing
on the results obtained. The ages of some of the birds of an
older group were not very dissimilar to that of some of the birds
placed in a younger group. The material entering into the sam-
ples is further complicated by the possibility that some among
the birds considered as normal might later have shown obvious
ataxia. The ataxia manifests itself in various degrees and be-
comes evident at various ages. Ataxia exhibited in early life
may later wholly disappear. Some of the ataxics selected may
have been well under way to recovery. It seems probable that
the observed differences in chemical composition between ataxic
and normal brains would have been greater if it had been possible
to analyze single brains instead of groups of brains. In connec-
tion with these remarks, we would ask that it be borne in mind
that unlimited numbers of ataxic birds have not been available
to us, since the derangement, though hereditary, behaves rather
as a recessive than as a dominant (Riddle, ’18).

104 MATHILDE L. KOCH AND OSCAR RIDDLE

Our data concerning the localization of the derangement in the
brain are still imperfect, because in our analyses the brain was
separated into anterior and posterior parts only. It has been
made clear that the chief size reductions occur in the posterior
brain; and the evidence indicates that the deviations in chemical
composition are accentuated in this same region.

Whether analyses of medulla and cerebellum separated from
each other would have shown that all of the size and chemical
changes occurred in one only of these organs is a question quite
unanswered by our data. Nevertheless, the fact that changes
were also found in the cerebrum would seem to indicate that the
derangement is not absolutely confined to either of the chief
divisions of the brain. It is possible, however, that localized
affected areas are present and that these were ‘diluted’ by much
normal material in our samples as prepared for analysis. If this
were true, these particular localized areas would necessarily have
a much greater degree of chemical under-differentiation than is
indicated by the figures obtained by us.

The sex of the ataxic birds deserves a further statement.
Those who may have carefully examined the character of the
samples obtained from ataxic pigeons, in both the earlier and pres-
ent series, will have noted that more female brains than male
brains are found in these samples as prepared for analysis. In
the earlier series (of ataxics) the proportion was ten females to
five males; in the present series twelve females to eight males.
This disproportionate representation of the two sexes in these
samples was not consciously effected by us, since the sex of most
of the individuals selected for the purpose was not known until
after the birds were killed. In most cases they were selected
chiefly because they were ataxic in one or another degree. Equal-
ity of the sexes was desired in our present samples, but could not
always be obtained.

The excess of females in the two series of ataxics has led us to
examine a segment of the breeding data in an effort to learn
whether the ataxia more often occurs in females than in males.
The data given below were obtained from a tabulation’ of the

All groups of offspring of ataxic blood or strain were included in the sum-
mary. The matings which had yielded no ataxic offspring were excluded.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 105

offspring (to the fourth generation) of the original ataxic female.
These data indicate that the ataxia does occur more frequently
among females if the computation be made upon offspring which
live long enough to permit a reasonably accurate prognosis of
ataxia or normality. Obviously, no other method of computa-
tion is practicable.

Necessary to a full consideration of these particular figures are
the facts, published earlier by one of us (Riddle, ’18), that the
ataxia does not behave as a sex-limited character in heredity,
and that probably more affected than unaffected individuals die
early—hefore definite classification as ataxic or normal is pos-
sible. Also, fully as many females as males die early. Included
in the group of birds that were properly classified for the above
purpose are a total of seventy-seven males and seventy-five
females. Among these there were, however, only fifteen ataxic
males to twenty-nine ataxic females. It is therefore quite prob-
able that females are more subject to the derangement than are
males.

Comparison of constituents of parts of human and pigeon brain

As a result of our separate analysis of anterior and posterior
parts of the brain, it is now possible to make a comparison of these
with similar parts of the human brain. So far as we are aware,
there are no data for other animals which permit a similar com-
parison with the parts of the human brain. The comparison is
best made by reference to table 9. A study of the figures ob-
tained brings to light the rather surprising situation stated below.

The human cerebrum has, of course, higher values for certain
chemical components and lower values for certain other compo-
nents than the human cerebellum-medulla. The same is true for
the corresponding parts of the pigeon’s brain. The singular
fact to which attention is directed lies in the circumstance that
in the pigeon the direction of the difference is the reverse of that
for man in the case of every chemical fraction shown in the table.

Perhaps this incongruity will not be made less intelligible by
the immediate statement of another peculiarity of the figures of

106 MATHILDE L. KOCH AND OSCAR RIDDLE

this table. These show that (from the standpoint of relative
amounts of the various chemical constituents) the cerebellum-
medulla of the pigeon is chemically an intermediate of the pigeon
cerebrum and the human brain (both of cerebrum and of cere-
bellum-medulla). Only the sulphatids of the seven fractions
from the pigeon cerebellum-medulla fail to take an intermedi-
ate place between the pigeon cerebrum and human cerebrum.

TABLE 9
Comparison of the chemical composition of the adult cerebrum and cerebellum-
medulla of man and of the pigeon (in per cent of solids)

WATER PRO- peel asad CHOLES- EC: CERE-
S| pains | SER prove) OE [eco] eel

(Part 1)

Cerebrum
Pamdan* (2032. BOS 76.9 | 37.7 | 7.9 | 54.4 | 28.3 | 10.0} 9.6 |. 6.6
Pigeon? bi esis mabopones hi 80:3 | 51/0.| 13.9) | 35g] | 22.4) 7.5,)) 7.6 |e 3

Cerebellum-medulla

BUTT ET S17 CA aie Sin eee a 7 2a 78.1 | 40.4 | 8.7 | 50.9 | 25.0] 6.4) 9.0) 7-4
Piglet eee. oes oe sae W629) WAG | 12267-43232 00| oson el2zon

(Part 2)

Rearrangement of above figures in terms of decreasing (ontogenetic) age
Human cerebrum.......... 1629 AWe3ded olind 94) 04-4.) 023530] LOS05 FEO FGs Gro
Human cerebellum........| 78.1 | 40.4 | 8.7 | 50.9 | 25.0} 6.4) 9.0] 7.4
Pigeon cerebellum........ A de9)| 4650 1) 1256) 4103 2325) | Ss eoni2eonle-
Pigeon cerebrum..........| 80.3 | 51.0 | 13.9 | 35.1 | 22.4] 7.5) 7.6) —#

1 Average of two analyses by Koch and Voegtlin (’16) of cerebrum and cere-
bellum-medulla.

2 Average of two analyses (I-Ia and II-IIa of this paper).

3 Cerebrosides have not been determined in the pigeon brain.

If, now, the figures found in part 1 of table 9 be arranged in ~
such an ‘age series’ as was prepared for the several pigeon brains of
various ages (table 8), the result may be seen in part 2 of table 9.
According to the places taken by cerebrum and cerebellum-
medulla of man and the pigeon in this arrangement, the human
cerebrum would seem to be the oldest—i.e., the most fully differ-
entiated ‘brain tissue;’ the human cerebellum-medulla nex! in
order; the pigeon cerebellum-medulla next. The pigeon cere-

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 107

brum would seem to be the least differentiated, or youngest, of
these ‘brain tissues.’ Not quite all of the figures agree in the
assignment of a particular brain type to its place in the series.
Certainly, however, there is an interesting agreement.

Do these figures have any phylogenetic meaning? Does the
known sequence of chemical differentiation in ontogeny have
any relation to phylogenetic facts? As the types of brains stand
in the series, the human cerebrum shows the highest chemical
differentiation; the pigeon cerebrum is the least differentiated.
The cerebella occupy intermediate positions, that of the pigeon
being lower than the human."

Of course, differences in proportion of white and gray sub-
stance are involved, but possibly neurologists may have at hand,
or may later note, other facts which have a relation to these com-
parisons of chemical composition and to this grouping of chemical
types of brain on the basis of age. It has already been shown by
Donaldson (’08, 710) that two main phases of brain growth in
man and the rat are similar at corresponding ages and that the
percentage of water in the brain agrees at equivalent ages.
Hatai (’17) concluded ‘‘that the percentage of water (in body of
different mammals) is an indicator of the chemical alteration in
different species, while neither the calendar age nor body weight
of the animals can be used for this purpose.”

16 It should be shown that the relative position of these brain parts is not a
fortuitous result of the particular ages of the human and pigeon brains selected
for comparison. The human brains were aged 20 and 54 years; the pigeons were
of 205 and 598 days. These pigeons are sexually mature at 180 days. Five
hundred and ninety-eight days is more than three times the period preceding
sexual maturity. By this method of computing age, the two groups seem compa-
rable. If, moreover, the figures for either the 205-day or 598-day birds be taken to
represent properly the composition of the pigeon brain, none of the figures of the
two parts of table 9 are changed or misplaced in relation to the other figures. If
the 20-year human alone be made to serve as a basis of comparison, the order of
none of the figures is changed. If the 54-year human be made to represent the
human, then the only changes of order concern the moisture of the human cere-
bellum-medulla which falls slightly below (initially it is only 0.2 per cent above)
that of the pigeon cerebellum-medulla, and thus makes the series more perfect
for the water fraction than it stands in the table. One slight additional change
results: The extractives of the human cerebellum-medulla fall very slightly
below the extractives of the human cerebrum.

108 MATHILDE L. KOCH AND OSCAR RIDDLE

The ‘age series’ of pigeon brains

It has earlier been stated that it is only on the brains of man
and the rat that we have had fairly adequate data for the pro-
gressive change of the various proximate chemical constituents
during growth, or, more properly, as related to growth and age.
The present work supplies such an ‘age series’ for the pigeon
brain, and this series is now as extensive as are those now known
for man and the rat. Each of these latter series includes obser-
vations on one or more relatively younger stages than we have
studied in the pigeon. On the other hand, the data for the pigeon
include one relatively older stage than has been obtained on
either of the other two forms.

Except for differences which appear because of a lack of paral-
lelism of age, the three ‘age series’ show that quite the same course
of chemical differentiation is followed in the brain of man, the
rat, and the pigeon. It is not our purpose to discuss these three
series here. The essential similarity of results obtained on mate-
rial from sources so unlike should, however, be noted as additional
evidence for the trustworthiness of the methods developed by W.
Koch (’09) for brain analysis. The brains of the three ‘age
series’ mentioned above have all been analyzed according to
Koch’s method. 7

Since the above was written, we have had an opportunity to
learn something of the results of the neurological studies made
by Hoshino (’19) of the brains of some of this same family of
ataxic pigeons. Although the present study was completed and
fully described before we were aware of Hoshino’s results,'” it
seems well to add here that the neurological and chemical studies
support an essentially similar view. The bearing of Hoshino’s
summary statement is self-explanatory: “This may be regarded
as a hypoplasia or developmental inhibition in the propriocep-
tive system, part of the motor system, and some structures con-
necting the medulla oblongata and cerebellum, occurring during
growth, with seareely any definite degeneration or secondary
increase of neuroglia tissue.”

‘7 The courtesy of Doctor Hoshino has made it possible for us to read his com-
pleted manuscript prior to its publication.

COMPOSITION OF BRAIN OF ATAXIC PIGEONS 109

SUMMARY

1. The brains of birds which have lost a very large amount of
the normal control of the voluntary movements (ataxia) show
deviations from the normal brain in size and in chemical compo-
sition. These deviations are more pronounced in the cerebellum-
medulla.

2. The brains of the ataxics are smaller. The cerebrum is
either not reduced or is reduced in very small amount. ‘The cere-
bellum-medulla (weighed together) is certainly reduced in size.

3. Possibly the somewhat smaller brain size of the (mature)
ataxics is necessarily associated with a relatively less amount of
white substance. If this is true, some, but not all, of the ob-
served inequalities in chemical composition may be associated
with this circumstance. The whole of the results would never-
theless emphasize the existence of some retarding influence on the
completion of growth in the ataxic brain.

4. Eight analyses were made of anterior and posterior parts
of the brain. Four of these were from ataxic birds and four
from normal birds. The chemical changes found are more defi-
nite and pronounced in the cerebellum-medulla than in the cere-
brum. The results support our previous conclusion that the
differences ‘‘suggest a chemical under-differentiation or imma-
turity of the ataxic brains.”

5. The pigeon cerebrum and cerebellum-medulla strongly con-
trast with the human cerebrum and cerebellum-medulla in the
distribution of the several chemical constituents.

6. Entire brains of very young and of very old birds were
analyzed. Data for the chemical changes in the brain which
accompany age have been obtained for a series of ages in the
pigeon. Examination of this more extensive ‘age series’ of pigeon
brains has enabled us to evaluate much better than in our previ-
ous work the relation borne by the various chemical fractions to
age and has also drawn attention to the relatively greater abso-
lute brain weight in the males and the relatively greater weight
of the cerebellum-medulla as compared with the cerebrum in the
females.

110 MATHILDE L. KOCH AND OSCAR RIDDLE

7. The significance of the results obtained in the present and
former series of analyses has been reviewed. The evidence war-
rants the conclusion that chemical differentiation, probably rep-
resented largely by the relative abundance of the myelin, does
not proceed as rapidly in the brain, and more particularly in the.
cerebellum-medulla, of .ataxic birds as in the brain of normal
birds.

LITERATURE CITED

Donatpson, H. H. 1908 A comparison of the albino rat with man in respect
to the growth of the brain and of the spinal cord. Jour. Comp.Neur.,
vol. 18, p. 345.
1910 On the percentage of water in the brain and in the spinal cord
of the albino rat. Jour. Comp. Neur., vol. 20, p. 119.
1916 A revision of the percentage of water in the brain and in the
spinal cord of the albino rat. Jour. Comp. Neur., vol. 27, p. 77.

Hatat, 8. 1917 Changes in the composition of the entire body of the albino
rat during the life span. Am. Jour. Anat., vol. 21, p. 23.

Hosuino, T. 1919 A study of brains and spinal cords in a family of ataxic
pigeons. Jour. Comp. Neur., vol. 31, pp. 111-161.

Kocu, W. 1909 Methods for the quantitative chemical analysis of animal
tissue. Jour. Amer. Chem. Society, vol. 31, p. 1829.

Kocu, W., anp Kocu, M. L. 1913 Contributions to the chemical differentiation
of the central nervous system. III. The chemical differentiation of the
brain of the albino rat during growth. Jour. Biol. Chem., vol. 15,
p. 428.

Kocu, W., AnD Mann, 8. A. 1907 A comparison of the chemical composition
of three human brains of different ages. Jour. Physiol. (Proc. Phys.
Society), vol. 36.

Kocu, M. L., anp Rippue, O. 1918 The chemical composition of the brain of
normal and ataxic (?) pigeons. Am. Jour. of Physiol., vol. 47, p. 124.

Kocu, M. L., anp Voratiin, C. 1916 II. Chemical changes in the central nerv-
ous system in pellagra. Bull. No. 103, Hygienic Laboratory, Wash-
ington, p. 51.

Rippie, O. 1917-1918 A case of hereditary ataxia(?) in pigeons. Proc. Soc.
for Exp. Biol. and Med., N. Y., vol. 15, p. 56.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO 2

Resumen por el autor, Teiji Hoshino.

Estudio del cerebro y médula espinal de una familia de palomas
ataAxicas.

El autor ha estudiado funcional y anat6Omicamente cuatro
palomas que presentaban ataxia hereditaria y tres palomas nor-
males de la misma familia, las cuales le fueron enviadas por la
Estacion de Evolucién Experimental de la Instituci6n Carnegie.
Incluye en el presente trabajo la historia completa de la familia
aludida con los datos de anatomia gruesa y microscépica refer-
entes a los individuos atdaxicos y a los normales que sirvieron
como tipo de comparacién. Los cambios encontrados en el
sistema nervioso central consisten principalmente en una reduc-
cidn del tamafio del cerebro y médula espinal, especialmente en
el cerebelo y las partes directamente relacionadas con él. Esto
puede considerarse como una hipoplasia o inhibicién del desar-
rollo del sistema propioceptivo, parte del sistema motor y
algunas de las estructuras que unen a la médula oblonga con el
cerebelo, la cual tiene lugar durante el crecimiento, con una
degeneracién apenas marcada o aumento secundario del tejido
neurdglico. Después de revisar someramente la ataxia de Fried-
rich y la hérédo-ataxia cérébelleuse de Marie, el autor interpreta
la condicién de las aves examinadas como una combinacién de
las dos afecciones humanas mencionadas.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTFOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 17

A STUDY OF BRAINS AND SPINAL CORDS IN A
FAMILY OF ATAXIC PIGEONS

TEIJI HOSHINO
Hull Laboratory of Anatomy, University of Chicago

THREE FIGURES

Although it is said that hereditary disturbances of coérdination
in man are very rare, still not a few reports have been published,
especially since Friedreich (’63, ’75) and Marie (’93) described the
disturbances from both an anatomical and clinical point of view.
Of similar conditions in lower mammals, three cases have been
reported: in the kitten by Krohn (’92), Langelaan (’07), and
Jelgersma (718).

So far as I could find no authors have hitherto investigated
hereditary incoérdination in birds. Such a study might throw
some light on the comparative and pathological anatomy of this
condition.

The birds which form the foundation of this report were pre-
sented by Dr. Oscar Riddle, of the Carnegie Station for Experi-
mental Evolution, Cold Spring Harbor, Long Island, New York,
to Dr. C. J. Herrick, Professor of Neurology in the University of
Chicago, who was good enough to turn them over to me to study
the changes in the central nervous system. I am indeed very
much indebted to these gentlemen for giving me such an oppor-
tunity, and in particular to the latter who has given me valuable
suggestions in the course of the investigation. I also wish to
thank the members of the anatomical department who so kindly
made it convenient for me to carry on this work.

Doctor Riddle has sent us a very exact and complete family his-
tory of the birds. He has studied heredity in pigeons for several
years, continuing the work of Professor Whitman. The history
will be interesting, for in man we seldom find such an exact and

111

1 a 2 TEIJI HOSHINO

reliable record of hereditary diseases over a period of several gen-
erations. ‘Therefore, it will undoubtedly be interesting to copy
from his notes and from one of his reports (’18) the remarkable
parentage of these pigeons. The following is a brief summary of
this history.

From an egg produced by the weakening influences of ‘repro-
ductive overwork’ a female pigeon no. 151 was hatched in 1914
which showed a marked lack of power over the voluntary move-
ments of the head and body. ‘This lack of codrdination was prac-
tically completely lost in the adult bird. The affected female
was bred to two normal males, A126 scraggly and C-B9. The
derangement has been inherited through four generations de-
scended from either male.

The parents of no. 151 were raised by Professor Whitman.
The male parent, a two-barred homer H-A, had no ataxic symp-
tom nor did his sire or dam. H-A homer was an inbred, for its
parents were brother and sister. The dam of no. 151 was of the
homer-carrier type, normal and without ataxia. ‘These parents
of no. 151 laid for the last time in 1914 on about October 12th
to 14th, and one of these eggs hatched the ataxic female. This
female (no. 151) was thus hatched at the end of the season from
a pair of birds which had been kept constantly at work and from
parents one of which was an inbred.

When first out of the nest the abnormality of no. 151 was noted,
and therefore the next pair of eggs produced by parents of no. 151
were also incubated. The two birds hatched from these eggs
.cesembled no. 151, but were not ataxic. There is no record of
ataxia in any of the other descendants of the parents of no. 151
during the entire previous four years. ‘There is reason to believe
that this character arose within the germ that produced no. 151
and that the weakening effects of abnormally rapid egg-laying
and possibly the inbreeding of the male parent were causally
related to the appearance of the character.

The sire (A428) of the ‘scraggly’ male no. A126 was a checkered
‘Columba livia domestica, which had the tips of the wings white.

, As is well known, white is apt to appear in these outmost wing-
feathers in many breeds of the domestic pigeons. This restricted

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS als

sort and placement of white seems to be the only trace of white
that could be carried by either the ‘scraggly’ male or the ‘ataxic’
female. The dam (545) of no. A126 was not very accurately de-
seribed for color, but was probably of medium slate color and two-
barred. The possibility of some white primaries is not excluded,
but is wholly improbable. Her sire was of slate color and two-
barred; her dam was wholly black. Her brothers (of whom one
was a ‘seragely,’ from an ‘aleoholized’ egg) and sisters bear no
record for white in any case. Her offspring, the several brothers
and sisters of A126, ranged in color from light slate with two bars
to black; no white appeared in any birds of this fraternity.
The dam of ‘scraggly’ A126 also threw a ‘scraggly’ female (A339)
from an ‘etherized’ egg. The dam, no. 545, was herself hatched
from an ‘alecoholized’ egg, and from the eighteenth egg laid within
a period of ninety-two days. No. A126 was produced out of
season, February 1, from the tenth egg in life, these ten eggs being
produced in the very short period of forty-seven days.

The above records for ‘scraggliness’ in connection with the
mother of ‘scraggly’ no. 126 would raise a question as to whether
‘scraggliness’ were not carried by the mother, and thus did not
originate in the germ that produced A126. This is a question
that cannot, of course, be definitely settled. It is of importance
to note, however, that the ‘scraggliness’ in this fraternity is found
only in ‘treated’ germs (alcohol, ether), or in the offspring (A126)
of a bird from a treated germ, and also in all cases in connection
with weakening influences of reproductive overwork. Scraggli-
ness had appeared earlier several times in birds of various strains
in the long history of our collection of pigeons, but it had been
observed that such birds arose more frequently or entirely from
‘weakened germs’—of late season or out of season, and from par-
ents ‘worked’ more rapidly than normal. To us it therefore
seems more probable that the germ which gave rise to A126, if
developed, grown, and liberated under wholly favorable condi-
tions instead of the reverse, would probably have produced a
normal bird; and if, then, in turn, the germs produced by this
normal bird had been favored by the best and most normal condi-
tions the character would probably not have been exhibited in
its offspring.

114 TEIJI HOSHINO

Male C-B9, with which the ataxic female (151) was mated for
a short period prior to her mating with the scraggy male, was
a pure wild rock pigeon (Columba livia). It was hatched in
1910 from parents obtained (1908) from the caves of Cromarty,
Scotland. The three offspring of this very strong and vigorous
male and the ataxic female were normal in appearance and be-
havior; but in the next generation a portion of the offspring ex-
hibited ataxia. No white color has thus far appeared in any of
their descendants.

Ataxia, secraggliness, and white color have all appeared in three
generations derived from the mating of the scraggly male and
ataxic female. Without here entering into full considerations of
the proportions of abnormals to normals for each of these three
characteristics in the different generations, it can be said that the
first generation showed relatively few abnormals—ataxics, scrag-
glies, or whites. Later generations have shown higher propor-
tions of affected individuals, and the combination of ataxia and
scraggliness has there been obtained.

The ataxia of the original ataxic bird (no. 151) disappeared
some time after she became adult. When she died recently, she
seemed quite normal. This is not true of many or most of later
ataxics, which show much more extensive lack of codrdinations,
and maintain them till the end of life. Of course, the extreme
ataxics do not live long. Doctor Riddle describes the scraggli-
ness as follows: This, he says, is a plumage defect; the feathers
lack barbules and hooklets, and as a result the barbs of all feath-
ers of all these birds hang loosely apart so that the wing feathers
give no resistance to the air, and the birds cannot fly. Such
feathers present a very peculiar and bristling appearance.

The statement concerning pedigree, and behavior of each of
the four birds, which were sent us runs as follows:

No. K137. Young of cage 131. Second generaon hybrid (not
counting original ataxic and scraggly as first generation). Parents:
male A456 and female A446 (neither of which showed ataxia or scraggli-
ness). The parents of these latter: original ataxic female 151 and
original scraggly male A126, from eggs laid 4/8/17. Ataxic—gait un-
steady; flies very little or not at all; tips backward, and also tends to
tip sidewise.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS PS

No. K172. Young of cage 269a. Third generation on one side;
second generation on other. Side of third generation is through a
normal brother of no. K131, described above. Side of second genera-
tion is through ataxic female no. B661, which is offspring of original
ataxic female no. 151 mated to pure wild rock pigeon male C-B9.
From egg of 5/19/17. Ataxic—tips backwards.

No. K158. Young of cage 130. Second generation from two normal
voung of the two last-named birds: ataxic 151 and normal C-B9. From
ege of 6/17/17. Ataxic—tips or nods head sidewise; tips backward,
and sometimes flies sidewise.

No. K207. Young of cage 123aa. Second generation, from two
normals, male B533 and female B548; these latter were offspring of
original ataxic female 151 and scraggly male A126. From egg of
6/22/17. Ataxic—somersaults backward, occasionally falling side-
wise; twists neck and head; does not fly; no codrdination In any move-
ments observed.

No. K167. Normal, is of same fraternity as K137. From egg of
6/19/17.

No. K199. Normal, is of same fraternity as K207. From egg of
6/9/17.

No. B473. Normal, otder bird, is of same fraternity as K158.
From egg of 12/21/16.

With the above detailed records we received the four ataxic
and three normal birds in good condition on October 26, 1917.
We observed them for more than three months, during which
time all of the four ataxic pigeons slowly became worse, while
the three normal ones seemed quite healthy and in good condi-
tion, living a very active life.

The affected birds apparently are backward in their develop-
ment, they look smaller, their feathers are scanty; they have lost
the characteristic briliant color, and appear lusterless. The
muscles are flabby. The birds maintain one position quietly
almost constantly. To support the body they stretch their
legs wide apart and a little forward with the tail braced against
the bottom of the cage and the trunk partly lowered to the floor,
so as to avoid falling forward, backward or to the side. The
pigeons, then, maintain their position while standing with three
supports Just like a three-legged stool; two widely spread legs
and a tail braced against the floor. The affected birds do not
stand on the limb of a tree as normal pigeons usually like to do,
but remain on the floor of the cage, often supporting themselves

116 TEIJI HOSHINO

on one side of the body with the wall of the pen. If food or water
is placed in the middle of the cage on the floor, they have great
difficulty in reaching it. Food is really the only thing which will
make them attempt to walk, except when they are frightened or
excited. In their attempts to walk they fall forward or sideways
or just stumble along reeling like a drunken man, ‘démarche
ébrieuse.’ When they fall forward they try to get up with their
bills against the floor pushing back the body and flapping the
wings with much effort. When they fall to the side they usually
roll over once or twice. Sometimes they fall to the right, while
at other times they fall to the left and then roll until they reach
some obstruction which helps them to get up with the aid of
flapping the wings. Flying is practically impossible in all birds;
if they are thrown free in the air, they flap their wings irregularly
and cannot fly above the height they are thrown, but go directly
down to the floor notwithstanding that their flapping efforts are
much more intense than those of normal birds. When the birds
are excited or frightened, the disturbances of the irregular move-
ments stated above are much more apparent. Such a movement
as the so-called “tremulance” or oscillatory movements cannot
be observed either when the birds are excited or at rest. Ocular
movements are free, no deviation and no nystagmoid jerking can
be substantiated. The reflexes which may be elicited from the
cornea are normal. When they are put on a rotating chair
they show the head nystagmus characteristic of normal pigeons.
If they are rotated more than five or six times they lean against
the cage wall or lie down, exhibiting regular head nystagmus.
When blindfolded the birds reveal no increase of the disturbances
of coordination.

As far as can be determined, sight and hearing are normal; the
birds can recognize food and an observer who may be approach-
ing; they also react to a sudden sound by raising the head and
trunk suddenly, but immediately lower them again. Pupils are
equal and react to light promptly. The sensibility to touch as
well as to pain appears unaffected in the skin; the birds react to
stimulation with direct movements, but all these movements are
quite sluggish. The toes of three affected pigeons are more or

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS Male

less flexed and widely abducted, so that the web spaces appear
quite large and toes show so-called hollow-foot. They do not
‘coo’ or make any other noise. ‘To observe the intelligence of a
bird is of course always difficult. So far as we can see from
the behavior of the birds, the intelligence seems not to be far
different from that of the healthy birds; they show movements
of uneasiness and fear, if one approaches them or tries to catch
them then they begin to move away as one approaches. ‘They
distinguish food from uneatable objects, and show a preference
for the place in the cage where the body is most conveniently
supported.

No bird shows a limitation to a particular kind of incoérdinated
movement; all of them have a nodding head and neck and even
a swaying trunk, tipping forward and backward and falling to
either side. The unsteady staggering gait, tipping head, and
swaying trunk are the common symptoms in all affected birds
with of course variations in degree. A weakness of the sphincter
of rectum or bladder cannot be detected in any bird.

Pigeon no. K207. Keeps body quiet; stretches the legs forward
and widely apart laterally, the head and neck pulled a little backward.
The bird tips to one side twelve to fifteen times when standing without
leaning against the wall or on any support. When excited the head
and neck move at first clonically upward, then backward so that the
head eventually touches the back. To coérdinate this forced position
of head and neck the bird flaps the wings excitedly, but in vain, to
restore the right position. Often the bird turns a somersault backward
several times to regain its position. If we catch the bird by the wings,
we feel a strong resistance in the wing muscles when the forced move-
ments are occurring. No rigidity or paralysis, however, was recog-
nized (fig. 1). The pigeon was killed January 28, 1918.

Pigeon no. K137. Remains on the floor with widely spreading legs
and with tail braced against the bottom of the cage. When walking
the bird tips to one side or the other. When excited this movement
occurs twelve times a minute. Usually always when two or three steps
are taken the bird stops and braces the tail against the floor to regain
its equilibrium. Reacts normally to light and sound. No spon-
taneous nystagmus in head or eyes. As time progressed the swayings
of the body increased so that before it was killed (February 2, 1918)
they occurred eighteen times a minute. The legs react to touch and
pain, though slowly. The nails and phalanges of the toes were flexed
and the toes turned toward the midline of the body resulting in a sort
of talipes cavus or hollow foot. The tail, owing to constant use as a

118 TRIJI HOSHINO

Fig. 1 Pigeon K207. Most ataxic, the head and neck twisted and turned
backward, the lower part of the body braced on the floor, legs stretched laterally
and forward, phalanges of toes flexed resulting in hollow foot.

Fig.2 Pigeon K137. Body swaying forward with flapping wings. The
wings and tail are shortened.

Fig. 3 Pigeon K172. The tail and wings are short, owing to frequent use
as supports of the trunk; the feathers are worn down and appear as if ,they had
been cut off with scissors.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 119

support of the trunk, is short and the feathers are worn down, and
appear as if they had been cut off with a scissors (fig. 2).

Pigeon no. K172. Keeps quiet and still as if sleeping, swaying
only the head and neck toward the side and a little backward. The
bird assumes the same position as the two previous ones. A wink of
eyes is often observed. No spontaneous nystagmus in head or in
eyes can be seen. The bird reacts to sounds. The most lateral of the
three front toes of the right foot is bent backward rather than forward.
The tail is shortened and has only rough feathers. This bird cannot
fly at all. When excited the bird rises up and a little to the side and
then bends backward slowly in clonic contraction till the forehead
touches the back; with flapping wings a somersault is made backward
or the bird falls to the side. From December 18th, the pigeon could
not maintain the body in a standing position, but fell every five seconds
to the side and backward. When it fell on the back it could hardly
restore its normal position. On January 14, 1918, the bird was killed
(fie23):.

Pigeon no. K158. Is the most slightly affected one. Owing to the
tipping or swaying of the head and neck toward the side or forward,
the rapid codordinated movements of feet and legs forward or to side
can be observed. Sometimes to maintain equilibrium in these irregular
movements the bird flaps the wings. These movements occur about
twelve times a minute, but the movements are slight and the restora-
tion of the body position occurs quickly. During the whole period of
observation, it never tipped or swayed backward. Bird walks swaying
from side to side just as is done on board ship in a rough sea. It will
not fly alone, but if set free in the air, it will fly to a higher level than
the position where it is set free. At rest the body is supported on for-
ward stretching legs with tail on the floor. Only a slight deformity
of the toes on both sides is seen. Killed February 18, 1918.

As for the three healthy birds, they never revealed any abnor-
mality of movement during more than three months of observa-
tion, but lived a lively life, cooing, flying, or else perching on the
limb of the small tree in the cage.

METHODS OF PREPARATION

In reference to the examination of the central nervous system
of the birds, we must remember that the anatomy of the normal
tracts and nuclei of the pigeon is yet much in the dark, notwith-
standing the works of Stieda (’69), Turner (91), Brandis (?93—
96), Friedlaender (’98), Wallenberg (’98-’06), Edinger (?03—
708), Ramon y Cajal (’08), Frenkel (09), Kiithn and Trendelen-
berg (11), Shimazono (712), Ingvar (’18), and others (Kreis,

120 TEIJI HOSHINO

Winkler, Dogiel, Miinzer and Wiener, Boyce and Warrington,
Murphy, Ziehen, Williams and Brouwer). It is not easy, there-
fore, for any one to study accurately any changes that have
occurred in the nervous system of the pigeon. For this reason
each section of the affected birds was treated quite the same way
as a corresponding control section. This not only gives us a
comparison with the normal structure, but also serves to show
us any artefacts that may be present.

The birds were narcotized with ether, while I opened the cranial
cavity and spinal canal to take out the whole brain and spinal
cord. During the time of the removal the brain and cord were
both rinsed in physiological salt solution, and before fixation,
measured and weighed. The brain stem, cerebellum, and the
spinal cord of both the normal and affected birds were used for
microscopic examination. The brain was cut through proxi-
mally at the level of the posterior third of the optic lobes and dis-
tally at a point separating the medulla oblongata from the spinal
cord. Half of the cerebellum was left attached to the medulla
and the whole fixed in 10 per cent neutral formalin solution, while
one portion of the half of the cerebellum removed was fixed in
Zenker’s formalin solution and the other in alcohol. The fol-
lowing is the formula for Zenker’s formalin solution used:

Bichromatexol poudssilimenr sae siete eee eee rea Ora ce nS
BichromaAte sor MereuLyees Meco eee ee ceteris Ore cals
OCU SUP AES eae cis cretietere, Seveie rei ee eherelene are er oevaee rier anaes 1 gram
[oye cctsH Vial, Gee aun ooh oreo oma e roto G nom omiCrianod ocr tao 6 Obie 6 10 ce.
Distilled: water swicere secretes aisiere cle systole ane store ato cretsbade oye rave ctor harresetel® 100 ce

From the spinal cord two parts were taken, one from the cervi-
cal region and the other from the lumbar region. Each piece was
cut into three divisions, one put in Zenker’s formalin, one in 10
per cent neutral formalin, and the third in alcohol. Each speci--
men had a control piece from the normal bird and both were
treated the same way in the same bottle. After fixation, regular
dehydration followed with both pathological and control speci-
mens. Both pieces were imbedded in the same block of paraffin
and cut with the microtome at the same time. With each stroke
of the blade, then, two sections would be made, one pathological

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 121

and the other normal, and both having the same thickness.
The two corresponding sections were then put on the same slide |
and stained at the same time. This does away with any varia-
tion that could arise from the dye. In reference to the stains,
Weigert and Pal’s modification, toluidin-blue-erythrosin, Mann’s
eosin-methyl-blue, haematoxylin-eosin, and Mallory’s neuroglia
method were employed.

- Thus, each affected section and normal control section has been
treated in exactly the same way from fixation to cutting and
staining, and we are able to compare any slight pathological
changes which might have taken place with much reliability. If
there are any artefacts or postmortem changes, which must oc-
cur to some extent, they will be present in both the affected and
normal specimen to the same degree. ‘The findings observed in
each of the sections of all the birds will be here recorded tcgether,
for the changes found are almost the same in all four affected
pigeons.

MACROSCOPICAL FINDINGS

The small size of the brain and spinal cord in all affected birds
can be recognized at a glance without any hesitation, especially
in the spinal cord, cerebellum, and medulla oblongata. The
length of the spinal cord and the weight of the different parts of
the brain and cord may be seen in tables 1 and 2.

As is seen in the tables, the weights of the brain and spinal
cord are not only absolutely less in the affected pigeons, but less
in proportion to their body-weights. In the affected pigeons,
moreover, there is much more reduction in weight of the distal
portion of the brain which includes the cerebellum and medulla
oblongata chiefly, but also a part of the midbrain and the lower
third of the optic lobe than of the proximal part of the brain which
is the cerebrum chiefly. Again, the ratio between the weight of
the distal portion of the brain to the whole brain in the affected
pigeon is always less than the ratio between the weight of the
distal portion of the brain to the whole brain in the normal
pigeon. ‘The same relation holds for the spinal cord.

TEIJI HOSHINO

122

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a a ee

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eip'z | scu'z | s2g'a | eee | ape's | eels | 680% | TOs | Ise | p1oo jeurds pus ureiq Jo 443.0\\
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Bein te le re ee ele A Se eS eee Se

pi0o qourds pun urpig fo 74629 M4
1 HIGVL

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 123

The spinal cord is shortened in the affected subjects. None of
the cases presents either a scoliosis or kyphosis of the vertebrae.
The medulla oblongata is reduced in size in both the ventrodor-
sal and transverse diameters. Nowhere in the brain or spinal
cord can there be observed a defect of any region with the naked
eye or with a lens. The cerebellum viewed from a cut surface
in sagittal section, after fixation, exhibits a rather round outline
in the affected specimen, while in the normal the anterior, dorsal,
and postericr margins are easily distinguishable, the whole ap-

TABLE 2

Length of spinal cord

K137|K 167] K158) B473/K207 | K199) K172
(A) | CN) | (A) | CN) | (A) | GN) | A)

AVERAGE
NORMAL
AVERAGE |
AFFECTED |

|

Length of the whole spinal cord in
PEMINELeLS's. =. Sete os 3 5 163] 173} 160| 171] 151) 178) 169] 174) 161
Length from the upper part of the
cervical cord to the beginning of the
upper intumescent a................ .| 59] 63} 57| 62) 55) 63] 60/62.7/57.8
Length from the upper part of the
cervical cord to the beginning of the
lower intumescentia......... fy ae ea 120) 129) 118} 127) 111) 131] 125] 129) 118

pearing as a five-angled polygon. All the lobuli and sulci of the
cerebellum are sharp and well defined in the normal specimens,
while in the affected specimens the lobuli are thin and flat and
the sulci shallow, the whole appearing much more indistinct.
In each, however, the total number of lobuli is the same.

The consistency of the brain substance is the same in both the
affected and normal birds; one can feel no sclerotic hardness in
the affected brains.

The visceral organs in all affected birds reveal no abnormal
conditions except that the testes in pigeon no. K172 are somewhat
rudimentary (one-third of normal size).

124 TEIJI HOSHINO

MICROSCOPICAL FINDINGS
1. Spinal cord

The spinal cord of the pigeon has two enlargements, the upper
and lower intumescentia. The upper enlargement is located far
posteriorly, owing to the bird’s long neck, and hence there is a
very short thoracic cord between the upper and lower enlarge-
ments (cervical vertebrae, 14, thoracic 4, lumbosacral 7 or 8,
coccygeal 5). The upper enlargement has a larger diameter than
any other part of the cord. At the lower enlargement, the cord
is divided into two halves by the ‘sinus rhomboidalis,’ as named
by Kolliker (02). The two halves of the cord are connected
at the lower part of the intumescentia only by the anterior white
commissure. According to Koélliker, this sinus is formed by ex-
tensive development of the sulcus dorsalis medialis in which
there is a gelatinous glial tissue. The ligamentum denticulatum,
a band of connective tissue which supports the cord from the
lateral edges of the vertebral bodies, appears at the level of the
lower enlargement well developed in the anterolateral portion of
the cord.

White matter. All the sections of the spinal cords at the differ-
ent levels in the four affected pigeons are decidedly small in ref-
erence to both the white and gray matter as seen with the micro-
scope as well from the exact measurements, compared with the
sections from the corresponding levels of the normal control
birds. The myelin sheaths stained by the Pal-Weigert are gen-
erally slightly paler, so that each section of the affected .speci-
mens looks as if it were cut much thinner than the normal
section, whereas, in fact, they are both exactly the same in
thickness, as already indicated. Nevertheless, there is not found
any area in the funiculi totally without color by Pal’s method.

Throughout all levels of the spinal cord there is a relatively
pale area in the median portion of the anterior funiculus and in
the dorsolateral periphery of the lateral funiculus, while cn the
other hand the whole dorsal funiculus is pale. The other
portions of the different funiculi do not exhibit any marked
color change.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 125

The one. in the medial portion of the funiculus ventralis is
shaped like a right triangle with the right angle in the corner be-
tween the edge of the cord and ventral sulcus. The triangle is
elongated ventrodorsally and narrow frcm side to side in the
upper cervical region, but it is broad from side to side and narrow
ventrodorsally in the lower eniargement. ‘This area is present
in both normal and affected specimens, but in the affected ones
the boundaries are quite indistinct. The normal has fibers of
almost uniform caliber in this area, but in the affected one the.
fibers are small on the average and vary in size (tables 3 and 4).
In addition to this, there are many small fibers under 2.8 » in
caliber in the affected birds. So many small fibers in this area
are not observed in the normal preparations. They have all
about the same size and their myelin sheaths stain deeply.
These differences of the myelin sheaths and the variable caliber
of fibers of the affected specimens no doubt give rise to the pale
appearance and to indistinct boundaries of this area. The great-
est transverse breadth cf the funiculus anterior is reduced in all
the affected specimens. Nowhere is there any apparent sign of
the degeneration of the fibers, however. At the lateral portion
of the anterior funiculus of pigeon no. K172, just at the place
where the anterior rootlets pass through the white matter, from
the ventral horn, the longitudinal fibers are arranged loosely.

The second area at the lateral periphery of the lateral funiculus,
just dorsal to the dorsal horn, is long and crescent-shaped with
its base toward the periphery. At its median side, it is bounded
by an area of fibers of large caliber. This portion in the affected
specimens is reduced in both the transverse and ventrodorsal di-
ameters and is light blue in color; the myelin sheaths are thinner
and the caliber of fibers is much smaller than normal, as is seen
in tables 3 and 4. In the lower enlargement the fibers measure
2.9 to 7.1 » in the normal and in the affeeted specimen 2.2 to
5a ig:

The third area indicated as being the funiculus dorsalis, in
addition to its pale color, has a brownish to red. color when count-
restained by erythrosin, instead of the deep blue-black of the
normal section. It must be noticed here that usually the funic-

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 2

126 TEIJI HOSHINO

ulus posterior in the normal pigeon stains a deeper blue to
purple-black by Pal-Weigert than any of the other funiculi. In
the affected specimens the median part of the funiculus posterior
contains fibers of smaller caliber than normal and the fibers have
poorly developed myelin sheaths though even the normal fibers

TABLE 3!

The upper cervical region of the spinal cord

AVER-| AVER-
K207 | K199 | K137 | K167| K158} B473 | K172| ace | ace
(A) (N) (A) (N) (A) (N) | (A) | Nor- |AFFEc-

MAL | TED

Transverse diameter of cord

rhe) ia Ubuaveids, -5a5 5006000 2.738 3.340)2.137|2.204/1.970 3.206/1.870)/2.595|2.097
Ventrodorsal diameter.......|1.903/2.171]1.753/1.887/1.118)2.004/1.720,2.020]1.745
Greatest breadth of ventral

OTT eee aa tere 0.217|0.283 0.250/0.350,.0.317|0.334)0.217|0.322/0.250

Distance from the central
canal to the latero-anterior .
periphery of the ventral

NOLEN Ack oe emacs 0.417/0.417|0. 45010. 534\0. 467/0.534/0. 450)0. 495/0. 442
Grea‘est breadh of the dor-
Sa lUhOTR Ese pie pee eee ne 0.133 0.183 0.233 0.301 0.233 0.300.0.150 0.272 0.188

periphery of the dorsal
horn tovits*base:/.\-..0.5 4.2 0.300 0.300 0.384 0.417 0.417

Ga bali

0.484,0.384 0.3840.370
Greatest breadth of the | | | |
funiculus ventralis......... 0.417,0.450 0.450 0.534.0.501
Greatest breadth of the | | | | | |
funiculus dorsalis.........|0.2500.3500.384.0.417,0.334 0.417\0.300 0.395 0.317
1) Number, and 2) size of
large ganglion cells in }1] 8 | 16 3.5
the anterior portion of |2 | 19.9} 37.1] 25.7
the ventral horn (uz)...
Caliber of the fibers at the
media! portion of the funic-
WINSPANteLlors (A) eeEeee eer 7.9) 1129), 825) 114) (82510225 fee oe
Caliber of the fibers at the ,
dorsolateral portion of the
funiculus lateralis (u)...... 5a) Sb) 22h) Vall) VAL 216 Si) (555) ago eee:
Caliber of the fibers of
the funiculus dorsalis } 1
(u) 1) medial portion; | 2
2) Lateral portion.....

0.584 0.501 0.522 0.467

Distance from the dorsal |

8.5} 4.5} 11 6) Well. Sietbeo
28.5) 28.5) 42.7) 28.5] 36.2} 25.6

co "<S
o1 0
woe
CO oO
Ww bd
NI
wh
ob
oo
No 0

ET per A 6)
2.2| 2.8

Noe
es

1The numbers given in each column in Tables 3 and 4 indicate the average
obtained from twenty sections.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 127

TABLE 41
The upper enlargement

AVER-| AVER-
K207 | K199 | K137 | K167 | K158 | B473 | K172| ace | aag
(A) (N) (A) (N) (A) (N) (A) | NoR- |AFFEC-
MAL | TED

Transverse diameter in milli-

IMCtCTS so on ae eons. 2.839 3.173 2.5713. 106 2. 839 3. 106 3.206 3. 129 2. 859
Ventrodorsal diameter....... 2.3212. 388 2.120: 2.1202" 5212: 338 2. 321, 2. 398 ‘2. 274
Greatest breadth of the | |

WOMEN. 5 cc5sne canadse 0.668 0.801,0.551,0.701 0.668 0.734,0.734 0.746 0.654
Distance from the central

canal to the latero-anterior

periphery of the ventral

LOTS eee eS Oe 1.052/1.302/1.068}1.169)1.002/1.169|1.052/1 .214/1.043
Greatest breadth of the |
Gonsalhorme. one eeeeeeee 0.367)/0.400 0.283 0.417,0.233 0.350.0.350 0.389:0.300

Distance from the dorsal
periphery of the dorsal
hornytonts base... eeeeeEoe 0.835|0.801 0.851 0.7510.751

Greatest breadth of the | |
funiculus ventralis......... 1.002/1.252}1.068

Greatest breadth of the | |
funiculus dorsalis.......... 0.384/0.501,0.384 0.584 0.584 0.751 0.584 0.612,0.486

1) Number, and 2) size of
the large ganglion cells
in the latero-anterior
portion of the ventral
ROTI )n5< 2 o.. 3 eee

Size of Clarke’s column:

0.7840.751,0.779, 0.798

i sa ike 252/1.290/1.122

—_

PON A 2 28. TS: S226. 28. ee
31.3] 48.4) 29.9) 44.1) 32.7] 45.6] 31.3) 46.0} 31.3

iw)

="

a ne 0.384)0.384,0. 301 0.367 0.251 0. 401/0.284 0.384 0.271

1) Broad diameter; 2)) 9 |g 917/9.334'0.2000.334'0.20010.334.0.234'0.334'0.214
narrow diameter......

1) Number, and 2) sizeof [7 | 7 |o, | 7 |415 | 4.8117 | 4.5'17.66] 5.56

the cells in Clarke’s )9 | 99 9| 49.1] 24.2| 30.2/ 24.2] 34.2] 19.9'34.8 [18.6
Column (W)ee eee eee

Caliber of the fibers at the
medial portion of the
funiculus anterior (u)......| 9.1] 9.9} 6.5] 7.8] 5.7) 9.9} 8.0] 9.3] 7.8
Caliber of the fibers at the
dorsolateral portion of
the funiculus lateralis (u).| 2.8) 3.4] 3.1] 5.7) 2.2) 3.4) 2.5) 4.1] 2.8
Caliber of the fibers of the
funiculus dorsalis (u) }1
1) Medial portion |2
2) Lateral portion.....

iw)

@ 2.2) 2.9) 3S.) 2.4
4, 7.1) 3.4) 6.8) 3.6

Co

1The numbers given in each column in Tables 3 and 4 indicate the average
obtained from twenty sections.

128 TEIJI HOSHINO

here are small in caliber, yet the difference between the affected
and normal is well defined. The lateral area of the funiculus has
a slightly larger caliber of fibers than the median pcrtion, but
even so they are smaller than those in the normal. In the upper
enlargement, the medial triangular area in this funiculus along
the median sulcus stains a deep blue to black in the normal,
while in the affected one it shows a paler color and reduced
breadth. The measurements of fibers are given in table 38. In
the lower enlargement, the funiculi posteriores are not attached
to each other, but they are separated by a wide space, the sinus
rhomboidalis; the sinus side of each funiculus is convex, while
the other side is closely applied to the dorsal horn. The funiculi
in the affected specimens are not reduced ventrodorsally, but do
show a diminution transversely. There appear to be two kinds
of fibers in the funiculus in the normal pigeon. One occupies
the medial fourth and measures 3.1 » on the average, while the
other group occupies the lateral three-fourths and has fibers of
much larger caliber, 5.1 u. In these two areas of fiber groups, in
the affected specimens, the fibers have a smaller caliber and thin-
ner myelin sheaths; the average caliber of the fibers in the medial
portion is 2.2 », while those in lateral portion measure 4.2 uz.
Moreover, the arrangement of the fibers is looser.

No segmentation or decoloration in the myelin sheaths of the
nerve fibers is seen.

Gray matter. The gray matter of the spinal cord of the af-
fected birds shows a reduction in both the anterior and posterior
horns and in the central gray matter. Both horns are reduced
especially in width, as shown in the tables (3 and 4), but there is
not much reduction in length. There is, then, only a decided
meagerness of both horns. Besides these changes, other condi-
tions may be pointed out.

In the anterolateral portion of the ventral horn, the ganglion
cells are only half the normal in number and the large cells present
in the upper and lower enlargements are decidedly reduced in
size (table 3), and usually have a slender shape, but are seldom
shrunken. In both enlargements, a small area of ganglion cells
at the medio-anterior portion of the ventral horn protrudes into

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS ~ 129

the funiculus proprius anterior in the normal, but in the affected
birds, it does not protrude or is quite indefinite and contains
fewer and smaller cells. Fibers which run in the anterior horn
are few, especially those which run toward the central gray
matter.

The nerve cells in the base of the posterior horn with their
fiber network are changed strikingly, about which further
description will be given later under the title of Clarke’s column.

The dorsal horn shows a marked reduction in its breadth in all
the pigeons, especially at its base, notwithstanding the fact that
it is almost as long as the normal.

In the normal specimen, at the enlargements, especially in the
lower, there are usually a few large polygonal ganglion cells 22.8 y
on the average at the lateral border of the central gray matter,
and sometimes they are even in the reticular formation of the
lateral funiculus near the border. These cells are rarely found
in the affected birds or, if present, are small and few in number.
The anterior commissure which connects both halves of the cord
at the level of the lower enlargement is scant, and consequently
the fibers running into the anterior horn and central gray matter
seem to be very few in number.

The column of Clarke. In the spinal cord of the pigeon, es-
pecially at the level of the upper and lower enlargements, we find
a large group of ganglion cells with an interlacement of fiber retic-
ulum at the base of the dorsal horn, symmetrically located and
adjoining the funiculus posterior. This structure corresponds to
the so-called Clarke’s column in the thoracic cord of mammals.
It may be well to describe a little more thoroughly this column
of cells in the normal pigeon’s cord, for only a few observations
have been hitherto made on this structure in pigeons and other
birds.

In the cervical region above the upper enlargement, there can
hardly be found a well-developed structure analogous to this
column; the narrow H-shaped gray matter exhibits no marked
thickening at the base of the posterior horns. Only a few small
round cells 5.7 to 7.1 uw in diameter not well defined from the
cells in the central gray substance are visible, and the network

130 TEIJI HOSHINO

of fibers around the cells is not pronounced, though a few tiny
bundles enter from the dorsal roots and from the funiculus pos-
terior. Schacherl (’02) says the small size of this column in the
pigeon makes it difficult to study the internal structure of the
individual cells, and he says that the cell group in the upper
cervical cord which corresponds to Clarke’s column cannot be
distinguished.

In the upper enlargement, cervical intumescentia, is found an
analogous structure to Clarke’s column in full development, but
this is different from the arrangement in man and other mammals,
for in these it does not appear at this level. It has a large spheri-
cal form on each side at the base of the dorsal horn, having its
larger diameter from the medioventral to the laterodorsal side
and its shorter diameter from the mediodorsal to lateroventral
side. Its huge structure, 0.334 to 0.384 mm. in diameter in
the average normal pigeon, occupies almost the whole space of
the gray matter at the base of the dorsal horn. The marked pro-
trusion into the white matter of the posterior funiculus as seen
in man does not occur in the pigeon; the whole group of cells is
within the horn or in the central gray matter and causes no
bulging.

The cells are generally round, oval, sometimes polygonal; they
vary in number from ten to eighteen, and among them there are
three to six large cells in each average section. The size of these
large cells in the normal varies from 31.3 to 51.3 » in diameter.
The area of this cell group is filled and surrounded by a mass of
fine network of fibers which is mainly composed of fibers from
the posterior roots and fiber bundles from the funiculus dorsalis.
This network of fibers gives the dorsal and medial borders of the
column a clear definition from the surroundng tissues. The
ventral and lateral borders, however, are not quite so well
defined, owing to the diffuse transition into the lateral proprial
fasciculus or into the fiber network of the lateral portion of
the central gray matter.

In the thoracic region the column decreases in size, the con-
tained cells are less numerous and the network not so luxuriant,
but in the lower enlargement, intumescentia lumbosacralis, it

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 131

appears again in good development and almost equal to that in
the upper enlargement. Here in the lower enlargement the
structure is less distinct than in the upper, especially in its lateral
and ventral borders; its border adjacent to the central gray mat-
ter is somewhat diff cult to distinguish. In the sacral region
the typical columnal feature is lost, but there often remain one
or two large round or oval cells at the corresponding place.

In the affected birds, at the level of the upper cervical cord,
the nerve cells in the base of the dorsal horn and in the central
gray matter are small and measure on the average 6.4 y, while
in the normal they measure 8.6 u in size; they are also reduced in
number. The small size of the cells makes it hardly possible to
describe their internal structure, but the striking narrowness of
the posterior horn at its base must be remembered. In the upper
enlargement, Clarke’s column, which is at its maximal thickness
at this level, has a decidedly small size, fewer cells and less reticu-
luminallaffectedspecimens. Thecellshave a spindle-like slender
shape and are rarely shrunken and are not at all like the large
round or oval normal cells. The fibers around and in the col-
umn are few, stain weaker, are thin and short, and often they
seem as if they were cut off in pieces. They run into the dorsal
horn from the funiculus dorsalis or from the dorsal roots, and in
the normal they may follow into the central gray matter or
reticular formation in the lateral funiculus, but in the affected
birds they are usually quite thin and show a short course.

At the level of the lower enlargement, Clarke’s column meas-
ures, though not exactly determined, about 0.317 to 0.384 mm.
in the normal and 0.200 to 0.251 mm. in the affected birds. The
cells in the affected sections are small and few in number, measur-
ing 14.2 ,.indiameter. In the affected specimens these cells are
really quite rare, only one to three are found in a field at the most,
while in the normal three to five are found in one field, and these
measure 39.9 to 51.1 » in diameter. The cells in the affected
birds have usually a slender shape and sometimes, though rarely,
seem to be slightly shrunken. Fibers which go from the end of
the posterior horn or into the central gray matter in the normal
take a path in a direction ventrolaterally or transversely at the

132 TEIJI HOSHINO

lateral edge of Clarke’s column. These fibers enter apparently
into the lateral funiculus, while others run into the ventral horn
along the lateral edge of the central gray matter. The fibers of
this reticulum are fewer and shorter than normal and are hence
quite difficult to make out. They do not exhibit long strands,
but appear as if they were cut in short fragments. The group
of fibers which run at the lateral edge of the central gray sub-
stance at this level is not present or else quite indistinct.

All the above changes of ganglion cells, however, never prcgress
as far as total destruction or degeneration and the cell nuclei are
well preserved.

Hofmann’s nucleus. This was called by Brandis (’93) merely
‘faserarmes Randfeld’ and by Kolliker (’02) it was fully described
in the spinal cords of birds and reptiles. It is located in the
pigeon at the lateroventral periphery of the lateral funiculus in
the shape of a crescent, having a maximal transverse diameter
0.084 mm. and a ventrodorsal diameter 0.284 mm., and contains
two to four large cells of 14.7 u in each section of the upper
cervical region in our normal birds. At the level of the enlarge-
ments it varies from 0.067 to 0.084 mm. in breadth and 0.301 to
0.334 mm. in length. This structure shows almost the same
condition in the affected as in the normal.

Gowers’ tract. Morphologically, with the methods we used,
we could hardly distinguish a tract which corresponds to the
Gowers’ bundle of mammals independently in the spinal cord
of either the normal or affected specimens. Brandis did not
exactly make the differentiation of both tracts of Gowers and
Flechsig, but always considered them as the ‘Kleinhirnseiten-
strangbahn’ in the birds. Friedlander (’98) describes these
tracts in the pigeon as quite analogous to mammals in regard
to their positions. One can see, however, in his illustration
that only a few scattered Marchi’s small black globules exist
in the anterolateral area of the funiculus lateralis, while many
apparent Marchi’s black globules are present in the dorsolateral
portion. Kiihn and Trendelenburg (711) report that the two
direct cerebellar tracts can only be well distinguished at the
places near to their origins and not in their paths up the cord.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 133

If this tract runs through the anterior commissure, as Kuhn
and Trendelenburg contend, our findings of a decided reduc-
tion in the anterior commissure with a decreased number of cells
in the central gray substance must show the defective develop-
ment of this tract, at least at its origin.

Nissl preparations. ‘The section at various levels of the cord
which were stained ‘with toluidin blue and counterstained with
erythrosin give almost the same results as indicated in reference
to the general conditions of the ganglion cells. The cells in
the anterior horn and in the base of the posterior horn (Clarke’s
column) in the upper and lower enlargements reveal a marked
reduction, from one-half to two-thirds the normal, both in
reference to size and number. ‘The Nissl bodies stain a relatively
light purple color in all ataxic birds, so that although the bodies
can be easily distinguished they usually appear more or less
diffuse and indistinct as the result of a less number and weaker
staining properties when compared with the normal numerous
Nissl bodies of a deep purple color. At different levels of the
cord, in all affected specimens, this is observed and easily recog-
nized in both the enlargements, where the cells are large enough
for minute examination of intracellular conditions. Complete
destruction, disappearance, and disintegration of Nissl bodies
or the typical grouping of this substance in one part of the
cell body could not be found in any of the cells. This, then,
indicates that the Nissl bodies are reduced throughout the
affected birds, but further than this there is nothing which
resembles new or old degenerative processes.

Pia mater, blood-vessels and spinal roots. The pia mater is
not thickened, but sometimes it is slightly thinner in the
affected birds; the blood-vessels in the periphery of both the
anterior and posterior medial sulci have a smaller caliber than
normal (the largest diameter is 0.050 mm. in the affected and
0.0835 mm. in the normal on the average), but their coats show
no thickening or infiltration. The capillaries and small blood-
vessels appear in cross-section of the cord definitely in less
number in the sections of the affected pigeons than in the normal.
This may indicate an insufficient supply of blood to the spinal
cord of the affected pigeons.

134 TEIJI HOSHINO

No round-cell infiltration is seen surrounding the central
canal. Sometimes there seems to be a slight increase -of
neuroglia at the periphery along the medial sulcus in the funic-
ulus posterior in a few sections; however, this is not seen in
successive series of preparations. Lissauer’s zone and both
spinal roots in all the affected birds show no evident difference
from the normal. ;

2. Cerebellum

The cerebellum of the pigeon lies as a dorsal cover of the
fourth ventricle and anteriorly it is attached closely to the
large optic lobes. It has a spherical shape and is supported
on both sides by a stalk, the crus cerebelli ad medullam (Stieda,
69). This is the only cerebellar peduncle the pigeon has, any
independent structure corresponding to the other two peduncles
in mammals is not defined, at least macroscopically. The
lamellae of the cerebellum, which run transversely on the sur-
face, converge in the crus cerebelli, fan-shaped at the lateral
part of the cerebellum. ‘The lateral hemisphere is not present
in the pigeon. As to the division of the vermis, Shimazono
(’12) divided it into two parts, the vermis anterior and posterior;
Ingvar (718) lately divided it into the lobus anterior, medius,
and posterior. The anterior, Ingvar divides from the medius
by fissure primarius and the posterior from the medius by the
fissure prepyramidalis. He came to this division as a result
of his phylogenetic and ontogenic studies. The lobus anterior
is divided into four lobuli; lingula, lobus centralis, and culmen,
and the lobus posterior into three lobuli; uvula, nodulus, and
pyramis. The interplaced lobuli between the anterior and
posterior comprise the lobus medius which consists of three
lobuli.

A small appendix from the posterolateral portion of the cere-
bellum turns up, making a furrow between it and the cerebellar
body; it is shaped like an auricle, and is called the lobus lateralis
or auricle. Many authors agree that it corresponds to the
floccular body in mammals. The auricle consists of two main
lamellae, the one large anterior, the paraflocculus, the other

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 135

small posterior, the flocculus. The former is continued from
the uvula and one part of pyramis, while the latter comes from
the nodulus.

A majority of the specimens were cut transversely and there-
fore at first there appears in the sections the lobuli of the lobus
posterior, then the middle part of the vermis and the medullated
cerebellar body, and at last the lobus anterior comes into view.
Here it must be noticed that in the affected cerebellum, owing to
its small size, when we start to cut sections from the same sur-
face at the same time with a normal cerebellum, both being at
the same level in a piece of paraffin mounting, we reach the white
substance of the affected cerebellum with the knife before we
reach to the same white substance of the normal.

Each lobule of the cerebellum of all the affected birds was
measured and compared with that of the normal birds. The
chief result is the greater or less reduction of the cortex cere-
belli, especially of the molecular layer in almost all parts of the
cerebellar surface. This is found to be true in all the affected
pigeons. The reduction of this molecular layer is general;
the vermis anterior, medius, posterior as well as auricle are
generally affected. We can hardly deduce any rule concerning
the situation of the reduction of this layer except that in all
cases it is somewhat marked and constant in the lateral gray
matter of the central medullary substance (Kleinhirnkérper)
which will be described later. In none of the affected birds
is there ever found any place where the molecular layer is totally
absent.

The granular layer and the medullated layer are usually
slightly narrower than normal, but the difference is not so
striking as in the molecular layer. The granule cells present
normal character. The Purkinje cells show generally no change
either in size or in number. No cell is seen that has undergone
any process of disintegration. The arrangement of the Nissl
substance in the cell is almost normal, though it appears in
much less quantity when compared with that of the normal.

The nucleus cerebellaris lateralis appears in the section of
the cerebellar body at the level where the intrabulbar vestibular

136 TEIJI HOSHINO

fibers appear in the medulla oblongata. ‘This nucleus is com-
posed of many large and small groups of cells and is supposed
to correspond to the nucleus dentatus of mammals (Wallen-
berg, 798). We may divide this into five groups, according
to Shimazono, though each division is not sharp, and some-
times it is difficult to define each part exactly, especially the cell
group located ventrally near the base of crus cerebelli, where
the arrangement of cells becomes diffuse and they pass over
into the cell group in the dorsal area of the acoustic field. No
remarkable differences of these nuclei in the affected birds
can be detected from the normal.

The nucleus cerebellaris medialis which is located proximal
to the former nucleus shows a large round form at its maximal
development. ‘This is said to correspond to the nucleus fastigii
of mammals and is said to give origin to the efferent cerebello-
spinal tract (Shimazono, 712). It measures 1.035 mm. in trans-
verse and 1.202 mm. in the dorsoventral diameter; the size
of the ganglion cells varies from 26.5 to 35.3 » in the average
normal pigeon. The measurements of the same in the affected
birds show no changes. It is of the same size and contains
just as many cells.

At the level of these cerebellar nuclei, the medullated cere-
bellar body appears distinctly and it has a direct connection
with the medulla oblongata, through the cerebellar peduncle.
The lateral portion of the cerebellar body, notwithstanding the
normal size of the cerebellar nuclei as already stated, is reduced
in area both in reference to fibers and gray substance. The
myelinated fiber mass just lateral to the nuclei measures 0.418
to 0.585 mm. on the average in the affected birds, while in the
normal it measures 0.668 to 0.752 mm. Individual fibers stain
a more or less light blue color in the affected birds, while in the
normal they stain a deep purple-black; the myelin sheaths
themselves are also thinner. This is true in all the affected
specimens. Nevertheless, no positive proof of degeneration of
the processes can be made out.

The molecular layer at this ventrolateral part of the vermis
is reduced in breadth in all affected birds sometimes one-half

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 137

to two-thirds or even one-third of the normal and often shows
an irregular breadth, so that it forms a wave-like layer. Measure-
ments of this layer here vary from 0.150 to 0.251 mm. in affected
and 0.167 to 0.418 mm. or sometimes even to 0.501 mm. in the
normal. The granule cells reveal no changes save in some
cases they seem to be rather loosely arranged. The Purkinje
cells here, though they have generally almost the same appear-
ance as in the normal specimen, yet show a slight difference.
They are 26.5 to 29.4 uw long and 14.7 to 17.6 mm. wide in the
normal on the average, but in the affected birds they are usually
a little smaller and slender in shape. In pigeon no. K207 they
are 20.5 to 26.5 » in length and 11.8 to 14.7 » in width. The
processes or dendrites of the Purkinje cells which run perpen-
dicularly to the surface of the cortex, having a measurable
length of about 58.8 to 73.5 » in the normal specimens, while
they are short and very often difficult to make out in the affected
birds.

In the sections which were cut horizontally, we can see that
the affected birds have not only a narrow molecular layer, but
also shallow sulci, and consequently the depth of the gyri is
often reduced to one-half to two-thirds of the normal. In
addition to this, when sections were being cut it could be observed
that in the affected specimen one reaches the base of the
myelinated layer where it branches to go to the different gyri
sooner than in the normal birds.

There is no abnormal increase in cells in the cortex, especially
in the molecular layer. No thickening of the pia mater is recog-
nizable; the capillaries in the cortical layer seem not to be as
numerous as in the normal.

From the above findings in the cerebellum we may easily
conclude that the nucleus cerebellaris medialis and lateralis
do not play a very important part in the affection observed in
the birds. The chief changes consist, however, in a diffuse
reduction of the molecular layer on the whole surface of the
cerebellum and especially in a reduction in the lateral myelinated
portion of the cerebellar body with its cortical layer near the
cerebellar peduncle. In reference to the cerebellar peduncle,
further description will be given later.

138 TEIJI HOSHINO

3. Brain stem

The medulla oblongata of each of the pigeons, both affected
and normal, with the attached half of the cerebellum was studied
in the successive serial sections from the distal end up to the
height of the oculomotor nucleus in the midbrain. Since the
normal structural relations of nuclei and tracts are not very
well known, I have described, of necessity, the normal structure
first before attempting to point out any alteration or difference
in the affected birds.

The distal portion of the medulla oblongata. At this level of
the medulla oblongata, the gray substance of the posterior horn
increases in its horizontal width, the axis of the horn is directed
laterally, and it contains many myelinated fibers. The myelin-
ated fibers in the posterior horn converge ventromedially at
the neck of the horn, whence they run either into the funic-
ulus lateralis, or the anterior horn, while more proximally they
also enter the anterior commissure.

The anterior horn is narrower than in the cervical cord; its
axis nears the midline, and it contains an abundance of fibers
which go to form a part of the thick anterior commissure. The
anterior commissure also receives fibers from the lateral fu-
niculus and from the posterior horn. These fibers in the anterior
commissure disappear in the opposite medial edge of the fu-
niculus anterior. Going more proximally, the anterior horn
becomes smaller and there appears the nucleus hypoglossus,
while laterodorsally to the central canal the beginning of the
vagus nucleus is seen.

The fibers in the anterior funiculus correspond to the
fasciculus longitudinalis medialis of mammals. This has been
established by the early formation of myelin sheaths and the
pathway taken by these fibers to the midbrain (Brandis, ’93).
Many fibers in the funiculus anterior and lateralis, which cross
in the raphé and run laterally and dorsally, correspond to the
internal arcuate fibers of mammals. The thick fiber bundle
which runs along the ventral periphery of the medulla forms
the external arcuate fibers and makes one of the important con-
nections with the cerebellum.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 139

In the affected birds, the gray matter of the posterior horn
is small, both the transverse and ventrodorsal diameters being
reduced. Moreover, it contains few cells and few and thin
myelinated fibers. The fibers in the posterior horn run to the
reticular formation in the lateral funiculus, while those to the
anterior commissure are diminished in number, and are often
hardly distinguished in the affected specimens. The two small
areas of gray matter in the ventral base of the posterior funiculus,
the one lying medially and the other laterally, also are reduced
and contain fewer and smaller cells in all ataxic sections by
exact measurement. These areas which were called by Brandis
merely as ‘faserfreie Stellen,’ in all probability correspond to
the nuclei funiculi posteriores of mammals from their similar
localization and form. ‘The fiber bundles dorsal to the posterior
horn and the two small areas noted above are reduced; the
fibers have a small caliber, thin myelin sheaths, and stain lighter
in all affected sections. No positive degenerative processes
are exhibited.

The fiber area of the ventrolateral portion to the posterior
enlarged horn in the funiculus lateralis has not a distinct
boundary from the neighboring fiber bundles at this level even
in the normal pigeon, although it seems to be reduced in area
and in the ealiber of the individual fibers in the affected birds.
In the anterior funiculus the gray matter becomes smaller as
one passes proximally. The nuclei hypoglossi do not exhibit
much difference from the normal.

A little further proximally, laterodorsal to the central canal,
there appears the vagus nucleus, which shows its structure at
the inferior portion of the floor of the fourth ventricle where the
central canal opens into the ventricle. This nucleus is well
developed as well as its transversely running intramedullary
fibers in both the affected and the normal specimens. The
fasciculus solitarius is quite the same in both.

In the ventral area of the medulla oblongata, along the mid-
line there appears a long triangular area of longitudinal fibers,
its base directed dorsally. This is nothing but the fasciculus
longitudinalis medialis and predorsalis or ‘Vorderstrangrest’

140 TEIJI HOSHINO

(Brandis, ’993a; Winkler, ’91; Wallenberg, ’03). This area
of fiber tracts is not so well defined in regard to the separate
fibers as in the normal, owing to the poor development of the
myelin sheaths and small size of the fibers. This is one of the
striking differences in all affected birds from the normal. The
internal arcuate fibers which appear more proximally in the
medulla oblongata are less distinct than those of the normal;
this is especially easy to see at the raphé, where they decussate.
The thickness of the external ventral arcuate bundle, which
runs ventrally along the periphery of the medulla, gathering
fibers from the posterior and also lateral funiculus, is reduced
by one-third of the normal; the individual fibers are much
thinner in reference to the myelin sheaths and are also reduced
in number. This finding makes another striking difference in
all affected birds not only at this level, but also at other levels
of the medulla.

The level of the nucleus olivaris inferior. The nucleus olivaris
inferior in the pigeon appears at the level of the hypoglossal
root and lateral to it, but it is partly pierced by this nerve in
the ventral region of the medulla oblongata. It lies in a trans-
verse position, having a thick gray mass at the lateral end.
Brandis only described ‘‘ein grosses fast faserfreies Feld’’ at this
level without paying any further attention to the olivary nucleus.
Yoshimura (710) found experimentally that by injury to the
cerebellum this nucleus degenerated almost totally contra-
laterally. The olivary nucleus is connected by way of the
arcuate fibers to the cerebellum homo- and contralaterally and
has a direct connection with the spinal cord. The median
part of this nucleus contains a rich fiber network with few cells.
Shimazono infers from his experimental and embryological
study that almost certainly fibers from the olivary nucleus
cross in the raphé and go dorsally to the cerebellum.

In all our preparations except only the case of the pigeon
no. K207, the nucleus olivaris inferior is poorly developed;
the nucleus is small; the normal measures transversely 0.668
mm. and ventrodorsally 0.367 mm., while the affected specimens
measure 0.418 mm. transversely and 0.117 mm. ventrodorsally.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 141

The number of contained cells is reduced, forty in each section
on the average in the normal, twenty-five on the average in
the affected; the size of the cells is below normal, the normal
cells measuring 19.9 to 22.8 uw in diameter, but the Nissl bodies
show no difference from the normal. The interolivary fiber
bundle is markedly reduced; in the affected pigeon no. K158,
its ventredorsal thickness measures 0.0835 mm. instead of
0.2505 mm. as in the normal. This fiber bundle, therefore,
is one-third the normal thickness. In other affected birds this
reduction is also seen, but not so markedly. In the normal
specimen the fibers surrounding the olivary nucleus, the cir-
cumolivary fibers, especially those dorsal and lateral to it, are
thick and well developed. We see also a fiber bundle which
runs from the olivary body or from its surroundings, dorsally
and laterally to the spinal root of the trigeminal nerve.
Further proximally this bundle appears at the medial part
of the tractus spinocerebellaris and enters the cerebellum with
it. This fiber mass appears less definite and stains lighter than
the normal deep color, so that the distinctness of the boundary
of the gray matter of the olivary nucleus seems to be less defined
in the affected Weigert preparation than in the normal sec-
tions. ‘This is due to the scantiness of fibers and thin myelin
sheaths around the nucleus. The fibers which are seen within
the nucleus are also diminished in number.

The internal arcuate fibers are few in number and do not
stain as deeply as the normal, and the scattered ganglion cells
in the reticular formation are small and not nearly as numerous
as in the healthy birds. The restiform body is markedly re-
duced, 0.200 to 0.251 mm. in the affected and 0.367 to 0.418 mm.
in the normal. The fiber mass which runs longitudinally at the
ventromedial region of the restiform body is not stained as well
as in the normal and contains fewer fibers. No difference is
recognizable in the spinal roots of the trigeminal nerve in either
its staining qualities or its dimensions. Fibers of the hypo-
glossus and the cells in the nucleus n. hypoglossi have all a
normal structure.

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142 TEIJI HOSHINO

The zone of fibrae arcuatae externae ventrales is extremely
thin and contains only a few fibers and stains less intensely
than normal. The area of the fasciculus long. med. and pre-
dorsalis shows diminished transverse as well as ventrodorsal
dimension, especially the former. In the distal portion of the
medulla oblongata, this fasciculus long. med. cannot be sepa-
rates from the fiber tract which lies ventrally to this fasciculus.
The area of this fasciculus contains many smaller fibers, all
more variable in size than the normal; the average caliber is
5.7 » in the ataxic and 8.6 uw in the normal; the staining also
not so deep as in the normal. Nucleus of the ala cinerea and
the fibers of the vagoglossopharyngeus are normal.

All above findings are quite uniform in all affected pigeons,
there being only a difference in degree.

The level of the cochlear nuclei. The acoustic nerve enters
the medulla oblongata in two roots as in mammals; the one is
the dorsal, distal, or lateral root, the nervus cochlearis; the
other is the ventral, proximal, or medial root, the nervus vestib-
ularis. The nuclei of the acoustic nerve are divided into
three main groups: One, the nucleus angularis, ‘Eckkern,’
located at the dorsolateral portion of the medulla, into which
the cochlear root enters; this corresponds to the tuberculum
acusticum of mammals (Brandis, ’94; Winkler, ’91). The
second nucleus appears in the lateral wall of the fourth ventricle,
crescent-shaped, surrounded by a medullated fiber mass, and is
named the nucleus parvo-cellularis, ‘der kleinzellige Kern.’
The third one, the largest, occupies the space between the above
two nuclei, nucleus magno-cellularis, ‘der grosszellige Kern.’
The magno-cellular nucleus is supposed to be analogous to the
nucleus Deiters in mammals.

The nucleus angularis as well as the cochlear stem in all four
ataxic birds are almost the same in the normal in reference
to their developmental conditions. The nucleus parvo-cellu-
laris has sometimes a little narrower shape and the medullated
fibers around it appear to be slightly reduced. The nucleus
magno-cellularis, though it appears almost the same as normal,
seems to be diminished at its proximal dorsal portion in the

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 143

base of cerebellar peduncle, the size of each cell, however, is
not changed; the large cells in this area are 39.9 » in diameter
in both the normal and affected. These reductions of two
nuclei, nevertheless, are by no means striking. The so-called
‘Bogenzug’ of Brandis or the dorsal fiber system of the n. octavus
in the acoustic area runs from or around the nucleus parvo-
cellularis partly to the raphé and partly dorsally to the cere-
bellum. Both fiber paths of this bundle are sometimes slightly
thinner in the affected cases, though there is no striking varia-
tion from the normal. The fibers that are around or come from
the nucleus magno-cellularis and that run dorsally to form
the medial part of the cerebellar peduncle and that then pass
across the peduncle obliquely to enter the cerebellar cortex
exhibit no differences from the normal.

A fiber bundle which runs dorsomedially to ventrolaterally,
from the ventrolateral border of the nucleus parvo-cellularis
to the small round nucleus medial to the spinal root of the n.
V. appears plainly at the more proximal level, where the sensory
nucleus of the trigeminal nerve appears. This fiber bundle
and nucleus appear quite the same in both the affected and
healthy birds. They seem to correspond to the beginning
portion of the ventral system of the central acoustic nerve,
as was brought out by Wallenberg (’98). The further cerebral-
ward course of fibers from this nucleus which cross the abducens
root at its ventral two-thirds is not easily differentiated
from internal arcuate fibers in any of our normal or ataxic
preparations.

The restiform body at this level is much more apparently
reduced; its size is often one-half the normal, on the average
the transverse diameter is 0.200 to 0.251 mm. in the affected,
and 0.334 to 0.418 mm. in the normal. The fiber mass cross-
sectioned just medioventral to the restiform body is not as large
as in the normal section. The cerebellar peduncle appears at
this level connecting the cerebellum and medulla oblongata
in frontal section. The peduncle is markedly reduced in its
whole transverse breadth; 1.336 mm. in the affected and 1.754
mm. in the normal. This reduction is due to the thinness of

144 TEIJI HOSHINO

the spinocerebellar tract and bundles from the arcuate fibers
which form the main portion of the restiform body, and is
observed in all serial sections in all the affected birds.

The fiber bundle along the ventral periphery of the medulla
is quite thin in all affected pigeons. This is indeed very striking;
the ventrodorsal thickness of this bundle measures 0.100 mm.
in the normal and 0.043 mm. in the affected bird—a dimension
of less than one-half the normal. There is not only a reduc-
tion of thickness of the bundle, but each individual fiber is
smaller and stains weakly owing to its thin myelin sheaths.
The above condition of this bundle throughout its course is
common in all affected birds and it constitutes one of the most
decided changes in the medulla.

The internal arcuate fibers are less prominent and quite indis-
tinct, owing to the reduction in fibers, their poor staining proper-
ties and the small size of the individual fibers; the scattered large
ganglion cells between the fibers in the reticular formation are
not only few in number, but also small in size, the average size
of the large cells being 22.8 to 37.5 » in the affected and 28.5 to
57.0 » in the normal. The area of the reticular formation is
apparently reduced.

The tall triangular area of the longitudinal fiber bundle along
the raphé with its base directed dorsally to the floor of the fourth
ventricle, that is, the area of the fase. long. med. and predorsalis is
smaller, especially in its transverse diameter, this measuring 0.638
mm. in the affected and 0.985 mm. in the normal. ‘The fibers
which cross the raphé from side to side and the fibers which run
ventrodorsally in the raphé in this area are quite scant. The
fibers, both the longitudinal and transversal, are thin, indistinct,
and do not stain a deep black by Weigert. The spinal root of
the trigeminal nerve shows a good development in both the
healthy and unhealthy birds.

The level of the vestibular nerve. Proximal and a little ventral
to the cochlear stem, the nervus vestibularis appears as a large
bundle entering the medulla oblongata. A part of the fibers
runs dorsally to the acoustic area, to the nucleus magno-cellu-
laris, while the other and greater part of the fibers runs medially

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 145

to the raphé, where it enters into the fase. long. med. Some of
the fibers of the first group disappear into the fiber group sur-
rounding the nucleus parvo-cellularis, giving apparently fibers to
this nucleus, while others run dorsally and laterally and enter
into the cerebellar peduncle. The second group of the vestibular
fibers runs transversely, as already seen, toward the raphé, be-
neath the nucleus parvo-cellularis and the so-called ‘Bogenzug’
of Brandis, to enter the raphé.

The breadth of the stem of the n. vestibularis just outside of
the medulla oblongata in all affected birds has the normal dimen-
sion, both being 0.585 mm. The nucleus of this stem which is
analogous to the ganglion of Scarpa in mammals shows no dif-
ference from the normal. At the lateral portion of the medulla,
after passing through the restiform body, the intrabulbar vestib-
ular fiber bundle increases in its dimension; it measures on the
average 0.835 mm. in the affected as well as in the normal birds.

When we pursue the vestibular fibers transversely from the
periphery toward the raphé, however, we find differences in the
floor of the fourth ventricle at the place where the vestibular fibers
meet the fasciculus long. med. In the ataxic, the bundle of fibers
which goes from a connection with the vestibular nerve fibers
and the ‘Bogenzug’ just at the lateral side of the fase. long. med.,
where they leave this fasciculus, is markedly reduced in dimensicn,
being about two-thirds that of the normal. Both of the fasciculi
long. med. in their transverse diameter measure 0.835 mm., while
in the normal they measure 1.086 mm. on the average. In pigeon
no. K137 the transverse diameter is only 0.718 mm. ‘The ven-
trodorsal diameter of the fasc. long. med. including fase. predor-
salis, on the contrary, is not very much reduced, 1.002 mm. in
the normal and 0.919 mm. in the ataxic; often both measure the
same. In the area of the fase. long. med., the fiber bundle along
the raphé, running ventrodorsally, is reduced in its transverse
diameter; in the affected pigeon it measures 0.08 mm., while in
the normal it measures 0.167 mm. The fibers crossing trans-
versely in the triangular area of this fasciculus are also apparently
diminished in number. The longitudinal fibers are diminished
and the average caliber of each fiber is 5.7 » in the affected and

146 TEIJI HOSHINO

8.6 » in the normal; the staining properties of the fibers here
are poor.

The fiber groups which go dorsally and to the ventral portion
of the acoustic area and which pass into the ventral part of the
nucleus parvo-cellularis are slightly smaller than normal. In the
ventral region of the cerebellar peduncle, between the medial
edge of the spinocerebellar tract and the lateral region of the
‘Bogenzug,’ we find an area of large ganglion cells which is the -
proximal process of the nucleus magno-cellularis. The trans-
verse breadth of this nucleus here measures 0.835 mm. in the
affected and 1.084 mm. in the normal; its dorsoventral boundary
is somewhat difficult to make out because of the close relation
to the ventral cells of the nucleus cerebellaris lateralis. The cere-
bellar peduncle has a small breadth and the lateral fiber mass in
this peduncle which is composed of fibers that come mainly
from the medulla oblongata has a breadth of 0.834 mm. in the
affected and 0.835 mm. in the normal, or a ratio, therefore, of
132.5.

The difference of the external ventral arcuate fibers between
the normal and affected becomes more prominent than ever at
this point, 0.100 mm. in normal and 0.066 mm. in the affected
birds. The staining properties, caliber, and other conditions of
each individual fiber are the same as described before. It is
clearly seen that the fibrae arcuatae externae ventrales run latero-
dorsally and enter the restiform body and with the tractus spino-
cerebellaris pass dorsally up to the lateral edge of the cerebellar
peduncle. ‘The fibers in the reticular formation have the same
changes as noted at the former level. ‘The changes in the fase.
long. med., the external ventral arcuate fibers, the lateral portion
in the cerebellar process, and the restiform body are the main
important differences in the affected pigeons at this level with,
however, no apparent degenerative processes in either fibers or
nuclei. ;

The facial nerve and its nucleus appear normal.

The level of the sensory trigeminal nucleus. The spinal root of
the trigeminal nerve is pierced ventrodorsally by a few fibers
which come from the reticular formation and pass toward the

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 147

cerebellar peduncle dorsally. These fibers can be easily seen in
the normal section, while in the affected section they cannot be
seen distinctly at all. The area and staining properties of the
spinal root of the nervus trigeminus are normal. In the ventral
region of the cerebellar peduncle, more proximally than the
acoustic area and the vestibular fibers, there appears a large
oval nucleus, with the long axis from the mediodorsal to the
ventrolateral portion of the brain stem. This is the sensory
nucleus of the trigeminal nerve (nucleus magnus nervi trigemini,
Wallenberg). In the lateral area of this nucleus there runs a
thick bundle from the brain stem laterally to the cerebellar pe-
duncle, but there are also fiber groups which run to the medial
side of the cerebellum. The fiber bundles which surround this
nucleus at its medial side run chiefly to the medial region of the
cerebellar body, some of them, however, cross in the midline at
the base of the cerebellar body. From the sensory nucleus of
the trigeminal nerve fibers emerge at its ventrolateral border and
pass out of the brain stem.

The nucleus with its contained cells as well as its peripheral
fibers when compared with the normal reveals no abnormalities.

The three nuclei of the motor VY. described by Brandis (’95)
with their cells and fibers appear perfectly normal.

The fase. long. med. and external ventral arcuate fiber bundle
in all affected specimens are less well developed as at the former
level. The eminences of the fase. long. med. in the floor of the
fourth ventricle are much flatter than normal. In pigeon no.
K207, the fiber bundle at the ventral periphery of the brain stem
is almost absent.

At the ventral part of the brain stem there is a symmetrical
small nucleus, directly dorsal to the external ventral arcuate
bundle. This nucleus lies medial to the intracerebral roots of
the nervus abducens; it is round in shape and contains about
eighteen small round cells. Surrounding this nucleus there are
some fibers which cross the raphé tranversely to the other nu-
cleus. In the ataxic specimens except pigeon no. K172, this
nucleus is rather flat than round, contains smaller and fewer cells
and the interspersed fibers are few; the fibers around it are ap-

148 TEIJI HOSHINO

parently diminished in number. This nucleus appears in frontal
section, and proximally disappears at the level where the troch-
lear nucleus shows its largest size. In the affected preparation,
on the other hand, the nucleus disappears at the level just prox-
imal to the place of appearance of the sensory nucleus of the
trigeminal nerve.

This nucleus has never been exactly described, even though it
seems to be similar to the oliva in Friedlinder’s illustration (98)
or the medial «<-nucleus (‘Trapezkern,’ Westphal) of Wallenberg
(04) in reference to its localization. The inferior olivary nucleus
of the pigeon lies, however, far distal and lateral to the hypo-
glossal root, while the superior olivary nucleus lies more dorsal-
ward, as already described. If this nucleus had a connection
with the fiber bundle of the ventral system of the eighth nerve,
like the superior olivary nucleus and the nucleus isthmi, it would
be normal as these are. Thomas (711) reports the atrophy of the
arciform nucleus in cerebellar atrophy, and contends from his
experiments that the arciform nucleus has close relation with the
pontine nucleus. It seems to me rather, therefore, that this
nucleus may have some close physiological relation to the already
described ventral fiber bundle or to the arcuate fibers than to
the ventral system of the eighth nerve.

The internal arcuate fibers in the reticular formation are fewer
and paler; differences especially marked in the fibers which cross
at the raphé. At the lateral edge of the brain stem, a fiber mass
runs toward the cerebellum passing through the cerebellar pe-
duncle, which measures 0.25 mm. in the normal and 0.08 mm. in
the affected birds. Going more proximally from this level, the
fasc. long. med. becomes more and more round in section and the
cerebellar peduncle decreases in breadth.

At this point it will be well to describe more thoroughly the
cerebellar peduncle, from its distal to proximal end, for reduction
of this peduncle is one of important differences in the affected
birds.

The distal connection of the medulla oblongata to the cere-
bellum in frontal sections begins at the level of appearance of
the cochlear nerve. The spinocerebellar tract at the lateral

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 149

edge of the medulla oblongata which hitherto ran longitudinally,
changes its direction dorsalward. As one goes cerebralward,
the peduncle increases in its thickness, gathering fibers from the
medulla oblongata. When the wide bundle of the nervus vestib-
ularis appears, one sees a large fiber mass running dorsally from
the lateral edge of the medulla oblongata to the lateral portion
of the cerebellar peduncle whose fibers go chiefly to the cortex
on thesame side. This fiber mass gradually increases in breadth,
receiving fibers from a bundle which runs on the ventral periph-
ery of the medulla oblongata from one side of the cerebellar
peduncle to the other. ‘This ventral fiber bundle shows its maxi-
mal thickness at the level where the cerebellar peduncle has its
greatest thickness, i.e., at the proximal portion of the vestibu-
lar nerve. Regarding this fiber bundle, from its relation to the
cerebellum, from its anatomical localization, and especially from
its striking diminution in size (one-third to one-half the normal
breadth in all the affected birds), it will not be a great mistake
to indorse Stieda, who suggests that this fiber bundle in large
part, if not wholly, is comparable with the pons varolii of
mammals.

At the region where the facial nerve fibers appear in the
medulla and the nucleus cerebellaris medialis forms a large round
nucleus in the cerebellum, the fibers in the peduncle become
more and more numerous, and go not only to the lateral portion,
but also to the median portion of the cerebellar body, some of
them crossing the midline to the opposite side. The fibers of
the brachium conjunctivum appear at the medial edge of the
peduncle. Then at the ventrolateral base of the peduncle, tak-
ing the place of the position of the large cell area of the acoustic
field, the oval sensory nucleus of the trigeminal nerve appears,
well surrounded by medullated fibers, as indicated before. We
see here nothing but a rich mass of fibers in the peduncle which
run to the lateral and medial parts of the cerebellar body. Far-
ther proximally, the fibers which go from the dorsal portion of
the brain stem into the velum medullare appear. At the location
where the massive bundle of the sensory V. root appears, the
connection between the cerebellum and brain stem is lost. After

150 TEIJI HOSHINO

separation of the cerebellum and brain stem in frontal sections,
in the dorsolateral part of the brain stem, a thick fiber group
runs up to the median line. Laterally, there is seen, outside of
the brain stem, the peripheral trochlear nerve which is cut paral-
lel to the fibers. Proximally to the trochlear nucleus, we see a
massive fiber bundle which forms the ventrolateral part of the
brain stem to the optic lobe.

The breadth of the cerebellar peduncle in the affected birds
at different heights shows a marked reduction in its distal and
middle region, with only a slight reduction, however, in its proxi-
malregion. If we measure the cerebellar peduncle at its narrow-
est place, namely, from the lateral edge of the cerebellar ventricle
to the place where the external lateral surface bends and turns
medially, we obtain the following measurements: At the distal
region of the cerebellar peduncle, its breadth measures 1.837
to 2.004 mm. in the normal and 1.253 to 1.336 mm. in the
affected specimen; in the middle portion of the peduncle, 1.921 to
1.754 mm. in the normal and 1.320 to 1.253 mm. in the affected,
and in the proximal portion, 1.169 mm. in the normal and 1.002
mm. in the affected pigeon. Moreover, this reduction is chiefly
seen in the lateral fiber bundle of the cerebellar peduncle, espe-
cially in the distal and middle portions of the peduncle.

In the cerebellar peduncle there are many other fiber bundles
besides those already described. These were studied by Frenkel,
Wallenberg, and Shimazono and will be briefly discussed.

The tractus octavo-cerebellaris goes up directly from the acous-
tic area, passing through the cerebellar peduncle to the lateral
region of the cerebellar body and enters the cortex of the cere-
bellum. The tractus octavo-floccularis runs from the large cell
nucleus and nucleus parvocellularis to the medial part of the
peduncle, forming an are obliquely to the peduncle, and enters
the lobus lateralis.

The fibers in the tractus octavo-floccularis in the affected sec-
tion are separated into a few small fiber groups, while in the nor-
mal they run as one solid bundle in the ventral part of the pe-
duncle; asa result of this, the fibers in the affected specimen are
reduced in volume without showing any kind of distinct degener-

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 1

ative processes in their myelin sheaths. The nucleus parvo-
cellularis, as already indicated, does not seem to have quite the
same semilunar shape as the one in the normal section and the
cells appear to be a little smaller, even though the difference is
not striking.

The tractus octavo-cerebellaris is seen best a little proximal
to the above section of the tractus octavo-floccularis. Here the
tract runs from the acoustic area dorsally, crossing the tractus
octavo-floccularis, and then passes through the ventral group of
the lateral cerebellar nuclei in separated small bundles to reach the
dorsal part of the cerebellar body. ‘This bundle diverges into
ten to twelve fiber groups in both the affected and normal sec-
tions; the whole breadth of the bundle in the affected pigeon
measures 0.114 mm., while in the normal it is 0.151 mm. No
degenerative processes, however, could be seen.

The tractus quinto-cerebellaris emerges from the sensory tri-
geminal nucleus, passes the cerebellar peduncle medial to the
spinocerebellar tract to the cerebellar body. ‘This tract is well
seen in both birds and there is no recognizable difference between
them. The sensory nucleus of the trigeminal nerve in the
affected birds is in good condition, as already observed.

The tractus bulbo-cerebellaris runs from the nucleus lateralis,
located ventral to the facial nerve stem in the peripheral border
of the medulla, to the lateral side of Deiter’s nucleus dorsalward
to disappear in the tractus spino-cerebellaris in the cerebellum.
This tract is not easily differentiated in either our normal or
affected sections, but it must be included in the reduced lateral
fiber groups of the medulla or the cerebellar body. The tractus
cerebello-spinalis, an efferent tract, which should be in the cere-
bellar peduncle, is difficult to define, but so far as the cerebellar
nucleus (medialis) is concerned, which is supposed to be the
nucleus of origin, there is no change in it whatever.

The tractus cerebello-mesencephalicus enters the brain stem
at the ventral region of the cerebellar peduncle and runs median-
ward. Wallenberg and Shimazono proved this by injury of the
nucleus cerebellaris lateralis. In our sections this tract, which
is the brachium conjunctivum, appears medial to the sensory

52 TEIJI HOSHINO

nucleus of the trigeminal nerve as a fiber mass running from the
ventral part of the cerebellar peduncle to the medial part of the
medulla. This brachium is perfectly normal in the affected
specimens. The decussation of the brachium as well as the nu-
cleus ruber at the proximal region of the oculomotor nerve are
well developed.

As to the connection of the cerebellum to the fasciculus longi-
tudinalis medialis, no definite structure could be identified.

The levels of the trochlear and oculomotor nuclei. The troch ear
nucleus, its size, shape, and number of cells, together with the
fibers coming from the nucleus in the affected specimens, all ap-
pear as in the normal sections. The whole dorsoventral diameter
of the brain stem at this level of the nucleus trochlearis measures
in the midine 3.507 mm. in the normal and 2.922 mm. in the af-
fected section. ‘The entire width of the brain stem from side to
side measures 5.511 mm. in the normal and 4.843 mm. in the
affected. ‘These measurements show a reduction of the brain
stem at this level, but the small size is chiefly due to a diminu-
tion in area of the reticular formation. The ventral arcuate
bundle has already disappeared.

The oculomotor nucleus appears proximal to the trochlear
nucleus as its continuation, medial and slightly dorsal to the fase.
long.med. ‘The dorsolateral centers of this nucleus contain small
well-defined cells, but the other centers have large cells. From
the nucleus fibers emerge passing ventrally, part of them crossing
the raphé, where they form the internal fibers of the opposite
oculomot or nerve. At the point of emergence of the nerve fibers
from the brain stem, there appears in the nerve stem a half-
moon-shaped, colorless line in the Weigert preparation. This
condition may be a structure analogous to that already discussed |
in the cranial nerve roots in the human by Thomsen (’87), Hulles
(06) and Staderini (’90). No pathological or defective devel-
opment in the oculomotor nerve fibers or in its nucleus is visible
in the affected pigeons.

The fase. long. med. in this region is small and appears less oval
than the normal, but the reduction is not as marked as at the
former levels; it measures transversely 0.317 mm. in the affected,

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 153

0.367 mm. in the normal and 0.334 mm. in the affected, 0.468
mm. in the normal dorsoventrally. The nucleus ruber with the
decussation of the brachium conjunctivum, are both quite normal
in size and in number of cells. The cells in the red nucleus meas-
ure on the average 28.5 » in both the normal and affected sections.

In the nucleus isthmi in the brain stem and nucleus mesenceph-
alicus lateralis in the optic lobe, no distinct difference from the
normal can be detected.

SUMMARY AND DISCUSSION

We may summarize here the chief differences observed in the
affected birds. Macroscopically, the central nervous system
especially, cerebellum, medulla oblongata, and spinal cord are
reduced in size in all the affected birds. A reduction in weight,
chiefly in the distal portion of the brain, is present both absolutely
and relatively in reference to the body weight and the weight of
the whole brain in comparison with those of the normal.

In the cerebellum, the molecular layer is decidedly reduced in
its thickness, showing microgyri throughout. ‘Though it is es-
tablished that the direct spinocerebellar tract distributes its
terminals in the ventral lobuli of the anterior lobe (Ingvar, 18),
no localization in regard to the reduction in the cortex of the cere-
bellum in our cases could be seen. The reduction of the cortex
in the lateral part of the cerebellar body, however, is relatively
striking and also is constant in all affected birds. The Purkinje
cells, even though they exhibit sometimes a little more slen-
der shape and shorter dendrites, show no decided regressive alter-
ations. Neither is there scen a total defect or any increase in
the nerve elements in the cortical layer. The medullated layer
is paler by the Weigert, owing to the thin myelin sheaths of each
fiber, but not from swelling or segmentation. The large nuclei
in the cerebellum, the nucleus cerebellaris medialis and lateralis,
as well as the tractus cerebello-mesencephalicus, are in as good
condition as in the normal. The pedunculi cerebelli show strik-
ing reduction, sometimes to one-half the normal. Thus is well
seen in the inferior and middle portion of the peduncle, but not so

154 TEIJI HOSHINO

marked in the anterior portion. The fibers from the reticular
formation to the peduncle are hardly recognizable.

In the medulla oblongata, the most conspicuous and constant
changes in all affected birds are the reduction of the fiber bundles
in the ventral periphery of the brain stem, the fasciculus longi-
tudinalis medialis, the cerebellar peduncle, and the reticular
formation, including the internal arcuate fibers and ganglion
cells. Other differences, though not so considerable as in the
above structures, and sometimes not constant, may be pointed out:
the reduction of the nuclei funiculi postcriores, nucleus olivaris
inferior with its inter- and circumolivary fibers, and a sym-
metrical nucleus which is located at the ventral periphery in the
middle portion of the brain stem. All the cranial nerves are nor-
mal in nuclei and fibers in all affected birds. ‘The nucleus ruber,
the brachium conjunctivum, the nucleus isthmi (nucleus lemniscus
lateralis) in the midbrain, and the nucleus mesencephalicus lat-
eralis in the optic lobe appear in good condition.

In addition to the small size of the gray and white matter in
the spinal cord en masse, there is decidedly poor developmen of
cells in Clarke’s column, the anterior horn, and the central gray
matter, all those present being small in size, often one-half the
normal, few in number, with scanty processes. The median
portion of the funiculus anterior, the direct spinocerebellar tract,
and the posterior funiculi are reduced in area and also show indis-
tinct borders owing to the intermingling of abnormally small and
delicate fibers which show a diminution of caliber. The fiber
network in all the gray matter, especially, in Clarke’s column is
scant. The capillaries and small blood-vessels in the substance
of the spinal cord and cerebellar cortex are apparently greatly
reduced. None of the spinal roots or Lissauer’s zone show any
variations. In all cases there is never seen a definite degen ra-_
tive or regressive process, such as segmentation of myelin sheaths,
or increases of the neuroglia or interstitial tissues. No thicken-
ing of the pia mater, the coats of the blood-vessels, or abnormal
cell infiltration is observed.

Thus, the changes in the central nervous system in the affected
pigeons may be regarded as a hypoplasia or developmental inhi-:

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 155

bition in the proprioceptive system, part of the motor system, and
some structures connecting the medulla and cerebellum, occur-
ring during growth with scarcely any definite degeneration.

It is not an easy problem to explain from our specimens what
part of the cerebellum or spinal cord may have been primarily
interfered with in its growth. Again, it is more difficult to ex-
plain why just those neurons are especially affected. William-
son (711) holds the opinion that a tendency for alteration in the
peripheral parts of the cord may result from the fact that this
area has a poorer blood supply than the central. Pitt says there
is an inherited tendency toward general early vascular deteriora-
tion in certain cases, while Gowers suggests that abiotrophy, or
an inherited tendency toward early death of the nerve fibers may
occur in this condition (Turner, 710). Though these explana-
tions have been given to account for the changes observed in
hereditary ataxy, none quite fit in with our cases. The apparent
scantiness of the blood-vessels and the capillaries in the cerebel-
lar cortex and in the spinal cord in our cases might possibly have
some relation to this question, yet this condition of the vessels
is far from sufficient to explain all. We are, therefore, as yet
entirely ignorant as to why just these systems should be picked
out.

The question then arises as to how these symptoms could de-
velop without any degenerative or regressive processes. Since
certain groups of neurons in the central nervous system are im-
properly developed while others are almost normally developed,
there results an unbalanced arrangement in their functions in
the early life of the bird which may appear as a disturbance of
coérdination. In this, our cases seem to be similar to some ex-
tent, but not quite the same as the case of Noune (’05), who re-
ported a congenital small central nervous system in the human
without degeneration, associated with cerebellar symptoms which
Holmes (’07, ’07 a) classified as his sixth type of hereditary
ataxia from the standpoint of pathologic anatomy. The fact
that the original ataxic pigeon no. 151, according to the record
(Riddle), recovered from the disturbance when an adult, seems
to me to give a sort of confirmation to the above view.

156 TEIJI HOSHINO

Under the name of hereditary ataxia, we understand a condi-
tion of congenital disturbance of codrdination of movements
or even in standing, static ataxia. This disease is generally
classified into two types: one is the Friedreich’s ataxia and
the other is the L’hérédo-ataxia cérébelleuse. The former
was first described by Friedreich in 1863, who noticed a
typical hereditary form of a chronic degenerative atrophy
in the posterior and lateral funiculi of the spinal cord. The
affection is characterized clinically by a disturbance in the
coérdination of movements, as he says: ‘‘Die Krankheiten
diirfte vom klinischen Gesichtspunkte aus als chronische pro-
gressive Lihmung der Combination der Bewegungen, von pathol-
ogisch anatomischen Standpunkte aus als chronische degener-
ative Atrophie der spinalen Hinterstringe zu bezeichnen sein.”
After his discovery of this affection, similar cases were reported
by Carpenter (71) and Gowers (’80) in England, and Brousse in
France (’82), who had proposed to call the affection by the name
of Friedreich’s disease (Marie, 792). The chief changes in this
disease are usually a thin small cord, with degeneration or atro-
phy, and, consequently secondary sclerosis of the lateral and
posterior columns, and thickening of the pia mater. The fre-
quently affected tracts are in the proprioceptive systems in the
cord, namely. the direct spinocerebellar tracts and the columns
of Goll and Burdach, but sometimes the lateral pyramidal tract
is also involved. Occasionally there is more or less diminution
in the number of fibers in the anterolateral column, and also
atrophy of the cells in both the anterior and posterior horns
(Blocq and Marinesco, ’90; Barker, ’03). The cells of the col-
umn of Clarke are notably degenerated or else very poor in devel-
opment. All authors agree in that this disease is due to an ar-
rest of development or growth of the various systems of fibers in
the spinal cord (Menzel, ’91).

Under the title of L’hérédo-ataxia cérébelleuse, Marie (93)
reported two cases of a familial ataxia, and collected from the
literature a series of similar cases, in which atrophy of the cere-
bellum was found. He has established asymptom-complex dis-
tinct from Friedreich’s ataxia. Marie’s disease is believed to be

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 157

due to the congenital atrophy of the cerebellum, mostly a malde-
velopment of the cortical layer, often with atrophy of the molecu-
lar, granular layers and also Purkinje cells. The. reduction or
degeneration of the inferior and middle cerebellar peduncles is
usually cited (Menzel, 791).

Many transitional types of these two diseases, however, have
been reported afterward in reference not only to symptomatology,
but also to pathological anatomy (Mingazzini, ’05). Many
authors (Oppenheim, 00; Holmes, ’07; Jendrassik, ’11, and
others) at present believe these two diseases to be merely one
type of hereditary ataxia in which there may at times be a prom-
inence of spinal-cord involvement while at another time the cere-
bellar involvement predominates, according to the main locali-
zation of the affection.

It is evident from the indicated pathological findings found in
the central nervous system, as. well as from symptoms exhibited
during life and from the detailed family history, that the disease of
our pigeons is familial and congenital and that it comes quite in
accordance with the so-called hereditary ataxia of man.

The condition of static ataxia and the modes of gait from
‘démarche ébrieuse’ to somersault may be considered as a cere-
bellar disturbance or, if not, they must have at least a close rela-
tion to some important tracts, such as the direct cerebellar tracts,
which anatomically have a connection with the cerebellum. On
the other hand, the deformity in the toes found in three affected
birds seems rather to point to the so-called Friedreich’s foot or
pes cavus which has never been recorded in a case of simple
atrophy of the cerebellum (Marie’s disease), but is no doubt a
symptom arising from a lesion in the spinal cord.

Thus our subjects are a type in which the spinal cord and the
cerebellum as well as the medulla oblongata are involved, pre-
senting on one hand Friedreich’s ataxia and on the other hand
Marie’s disease at the same time from both the symptomatical
and pathological points of view. Had we examined the spinal
cord only, it might have been a typical case of Friedreich’s ataxia,
whereas the study of the cerebellum alone would have given us
that of Marie’s disease. This combination of the symptoms and

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 2

158 TEIJI HOSHINO

pathological changes accords with the authors who believe in the
similarity of these two kinds of hereditary ataxia in human cases.

As to the real etiology of this disease, it has been assumed
that many factors may play a part, such as idiocy, epilepsy, alco-
holism, acute infectious diseases, and consanguinity of the par-
ents (Oppenheim, ’00; Starr, 09), but none of these have much
real value. The connection cannot be made. They lack posi-
tive proof as etiologic factors.

As circumstantial pedigrees show, all our cases descend from
an original egg (pigeon female, no. 151) produced by the weaken-
ing influence on a reproductively overworked normal parent (from
records of Dr. Oscar Riddle). Whether or how this overwork has
a direct influence on the central nervous system on exerts some
secondary effect on this system as a result of some nutritional
changes is a further difficult problem. Nevertheless, we feel
that we can deduce the very interesting fact that some disorder
or disturbance caused by ‘reproductive overwork’ was at least
an important etiological factor of this disease, and that the basis
for such a conclusion in the present case does not rest on uncer-
tain observations, as has often been done previously, but upon a
practical and experimental foundation.

BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 159

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THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 3
FEBRUARY, 1920

Resumen por el autor, Fred W. Stewart
Universidad Cornell, Ithaca.

El desarrollo de los ganglios craneales del simpatico en la rata.

El presente trabajo trata especialmente de los ganglios del
simpdtico que se relacionan dirante el desarrollo con los ner-
vios craneales situados mas caudalmente (nervios facial, gloso-
faringeo, y vago), tratando el autor de llenar el aparente vacio
que existe en la cadena morfolégica de los ganglios craneales de
esta region. Las interpretaciones antiguas se discuten con algun
detalle. Los resultados de este estudio indican el origen total
o, al menos parcial, de los nervios del simpatico: cardiaco, eso-
fagico, traqueo-esofigico, pulmonar, gastrico e intestinal, a ex-
pensas del vago. Las células nerviosas de origen glosofaringeo
originan los ganglios del tercio posterior de la lengua, ganglios
faringeos, ciertos ganglios del plexo timpanico y el ganglio 6tico.
El ganglio esfeno-palatino es un ganglio del ramo palatino VII
(nervio petroso superficial mayor). Se nota por esta causa una
estrdcha relacién entre el modo de origen de los ganglios 6tico y
esfeno-palatino y el curso de sus fibras preganglionares. Las
pruebas acumuladas por el autor estan en favor de la interpre-
tacion de los ganglios submaxilaries y sublinguales, juntos con
los pequenos ganglios de los dos tercios anteriores de la lengua,
como originados a expensas del facial por medio de la cuerda
del timpano. El ganglio ciliar se deriva exclusivamente de ele-
mentos del trigémino. Las células ganglionares del nervio ter-
minal se originan por proliferacién de las células de la fosa olfa-
toria. Las células ganglionares del simpdtico presentes en el
plexo carotideo interno y plexos aliados, junto con ciertos gang-
lios del plexo timpdnico, son crecimientos anteriores del ganglio
cervical superior del simpatico.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR'S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 28

THE DEVELOPMENT OF THE CRANIAL SYMPATHETIC
GANGLIA IN THE RAT

FRED W. STEWART
Department of Histology and Embryology, Cornell University, Ithaca, New York

THIRTY-SIX FIGURES

CONTENTS
MOC C ETO tee <M Meats ee orc eyes Meyer a azieucl yas alah ereen osu 163
TEIIGICOLCI Se AR Orn... & Oo) Sia RO SiMe Ise ana ee ec te Soin oe os, ee Re 164
Nationals ainda ethod Saappeiants (Heep ices sos ds. - Baca ti oeglels Sate bine ee orate 171
Observations
Forward growth of the sympathetic of the cervical region.............. 172
Valcus porwon ofbhetsympathetic. -sis5+.ctese. cesar: oe ee ee oer 174
Glossopharyngeus portion of the sympathetic........................-- 188
Hacialis; portion jomtbevammpat netic 2c oc... hfe gah oe. 84 eee tell och 195
hricemmalbporvionsorwhessvimpatheticn. epee ss eae crane eee 200
iheranelionreelisiof themervus terminaliss...25..0.5....2<.02-..-+0-- 201
SUMING Tayi. se Se Snes OREN S COLL LAs, t RE MOM MPA AE ns BEAN LETS Oy Reds St 205
INTRODUCTION

The developmental history of sympathetic ganglia, associated
with the various cranial nerves, has hitherto been little studied.
The attention of embryologists has been almost entirely directed
toward determining the origin of the larger sympathetic gangli-
onic masses, namely, the ciliary, sphenopalatine, otic, and sub-
maxillary ganglia. The general consensus of opinion would seem
to assign to the last three ganglia a trigeminus origin, at least
in mammals. Investigation of the origin of the ciliary ganglion
has been productive of varying results. Practically nothing is
known concerning the development of sympathetic ganglia re-
lated to the more caudally situated cranial nerves, the facialis,
glossopharyngeus, and vagus. The tendency is to consider
definitive sympathetic ganglionic masses absent. The neural
crest, however, is continuous throughout the region of the cranial

163

164 FRED W. STEWART

nerves, at least as far anteriorly as the trigeminus. Since sympa-
thetic ganglia are known to be developed in relation to each
segmental spinal nerve and likewise possibly in connection with
the trigeminus of higher forms, their apparent absence in the
case of facialis, glossopharyngeus, and vagus leaves a curious
break in the morphologic chain of ganglia. With these facts
in mind, the writer undertook, some three years ago, a reinvesti-
gation of the origin of sympathetic ganglia in connection with
the cranial nerves, the facts ascertained being embodied in this
paper.
HISTORICAL

Numerous efforts have been made to account either for the
presence or absence of sympathetic ganglion cells developmen-
tally related to the facialis, glossopharyngeus, and vagus nerves.
Previous works dealing with the subject may be classified under
two general headings: first, those admitting and explaining the
absence of such cells; secondly, those seeking to recognize either
in the cerebrospinal ganglion or in the central nervous system,
a representative of the absent sympathetic ganglion. These
two general groups of interpretations obviously overlap.

Perhaps the sole representative of the first of these groups
consists in a brief paper by Ariéns Kappers (08). If I am
correct in my interpretation of Kappers, his reasoning 1s
as follows: From numerous studies, both developmental and
comparative, Kappers has concluded that there exists in the
central nervous system some relation between the direction of
migration of the cell body of the neuron and the source of maxi-
mum stimulation; the cell body tends, namely, to move in the
direction whence maximum excitation proceeds. In the sympa-
thetic nervous system we are dealing with a migration of cell
bodies in a direction apparently exactly the reverse of the direc-
tion-type observed in the central nervous system. This vari-
ation is to be explained through the observations of Langley
and Anderson (’94) and afterward Langley alone (numerous
papers, ’99, ’00, 03) on the physiology of the axon-reflex. Kap-
pers ventures to suppose that the axon type of stimulation is

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 165

the type most prevalent in the sympathetic nervous system, and
that consequently the direction of migration of cell bodies of
sympathetic neurons forms no exception to the expressed
generalization.

In the application of this principle to the problem of the head
sympathetic, Kappers draws certain conclusions: In fish forms
the possibility of stimulation of sensory endings of cranial visceral
nerves is in excess of the possibility of stimulation of spinal
visceral branches, at least so far as concerns nerves VII, IX, and
X. Sensory branches are spread over gills and adjacent regions
exposed to strong stimuli, while branches to the viscera them-
selves, hidden as they are, are much less open to stimulation.
In higher vertebrates the visceral territory of the sensory VII,
IX, and X components is relatively less open to powerful stimu-
lation than is the corresponding territory in lower forms, since
gills are absent and feeding methods vary. Furthermore,
throughout the alimentary tract, sensory terminations are in-
ferior in numbers to motor terminations. Kappers therefore
infers that, in the absence of true sensory (reflex) stimulation,
the axon type has dominated the system. As an expression of
this increasing want of adequate sensory stimulation in the head
region of higher forms and the consequent domination of the
axon type would come, I should suppose, the development of such
structures as the otic, sphenopalatine, and submaxillary ganglia.
The factor, according to Kappers, influencing the development
of a series of cranial sympathetic ganglia in teleosts, is probably
the protecting value of the operculum. In criticism of this
largely theoretical work, numerous objections may be raised:
first, while it might possibly explain the absence of cranial sympa-
thetic ganglia developed in connection with cranial nerves in
general, it could scarcely account for the fact that when sympa-
thetic ganglia do appear, they are developed in connection with
the trigeminus—should such be the conclusion eventually reached;
secondly, quantitative estimations for relative possibilities of
stimulation are little more than suppositions, and Kappers must
certainly consider, in this connection, the difference between
strength of stimulus and adequacy of stimulus; thirdly, there is

166 FRED W. STEWART

the obvious logical difficulty in arguing from the incompletely
demonstrated ‘law of neurobiotaxis’ to the likewise physio-
logically undemonstrated ‘law of prevalence of the axon-reflex.’

The second group of interpretations, i.e., where it is sought
to recognize in certain cerebrospinal ganglia, or in the central
nervous system, representatives of sympathetic ganglion cells, has
become quite prevalent. Perhaps the most emphatic advocate
of this belief is C. K. Hoffmann (’00). Hoffmann’s conclusions
may be briefly summarized in the following statements:

1. The formation of the sympathetic ganglion in the trunk
region is contingent upon the union of posterior and anterior
nerve roots to form a mixed trunk.

2. In the majority of head segments this union does not occur.

3. The ramus ophthalmicus V, constituting a purely dorsal
sensory nerve, unites with a purely ventral motor nerve, the
oculomotor and, as a result of the union, the ciliary ganglion
is formed.

4. Since, however, motor and sensory portions of the tri-
geminus, facialis, glossopharyngeus, and vagus nerves unite
within the central organ, they issue therefrom as mixed nerves,
and may, therefore, at their origin give rise to sympathetic
ganglia. The great peripheral ganglia of these nerves are con-
sequently mixed cerebrospinal and sympathetic, these including
jugular, nodose, petrosal, geniculate, sphenopalatine, otic, and
submaxillary. The ciliary ganglion alone is purely sympathetic.

The interesting fact in Hoffmann’s interpretation is that the
single ganglion he has concluded to be entirely sympathetic in
nature, the ciliary, is the only one about which serious doubt
regarding its single value has definitely existed.!

1 Krause (’81) advocated the double nature of the ciliary ganglion. Retzius
(81) described bipolar cells in the ciliary ganglion of the chick, but believed that
of the cat purely sympathetic; in 1894 Retzius confirmed his observations. Holtz-
mann (’96) found bipolar cells in the ciliary ganglion of the frog, the chick, and
the dog; he considered the ganglion mixed cerebrospinal and sympathetic. Car-
penter (’06) believed that the ciliary ganglion of the chick consisted of two por-
tions, one of bipolar cells and the second of cells typically sympathetic in charac-
ter. Carpenter’s later work (11) failed to confirm the observation. Galvao
(17) described the ciliary ganglion of ophidians as consisting of strictly unipolar
cells.

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 167

The portion of Hoffmann’s explanation most deserving of
attention is the part concerned with the possible double nature
of those cranial ganglia which have generally been considered
similar in structure to the posterior root ganglia of the trunk
region. Histological evidence would seem to rest on the recog-
nition of multipolar cells, possibly bipolar cells in the ganglia
concerned. Such evidence is apparently scanty (Cajal and
Oloriz, 98; Cajal, 06) in the case of the cranial sensory ganglia,
but there exists considerable evidence for the presence of multi-
polar cells in the posterior root ganglia of the spinal nerves.
Such, for example, is the contention of Kolliker (96) (quoting
Disse, ’93), Lenhossék (’94), Spirlas (96), Dogiel (97), Hardesty
(05), and Ranson (12). Dogiel (97) examined hundreds of
ganglia, finding only occasionally those containing multipolar
elements, and then but one, two, or three cells per series. Of
the numerous minutely described cell-types indicated in Dogiel
(08), his type XI most nearly approaches our ordinary notion
of a sympathetic ganglion cell, but in the absence of any knowl-
edge as to the termination of the so-called ‘Hauptfortsatz’ and
considering the doubtful nature of the ‘Dendritenihnliche
Fortsitze,’ an assignment of these cells to the sympathetic would
be premature. Cajal (06) did not consider bipolar cells found
in the vagus ganglion as sympathetie.

Despite the lack of adequate histological evidence, certain
morphologists still prefer to interpret the geniculate, petrosal,
and nodosal ganglia as in part sympathetic. Such is the econ-
clusion of Hardesty (14). F. T. Lewis (’13) states that since
upon the glossopharyngeal and vagus nerves two ganglia exist—
a ganglion of the root and a ganglion petrosum (IX) or nodosum
(X), the latter ganglia occupying a position somewhat comparable
in relation to the root ganglia as do ganglia of the sympathetic
chain to dorsal root ganglia in the spinal region—his tentative
attitude is to regard these inferior ganglia (petrosal and nodose)
as sympathetic ganglia. Professor Hardesty has been so kind
as to furnish me with certain physiological references bearing
particularly on the vagus ganglia (Garrey, ’12), possibly indicat-
ing a vagus influence on the heart independent of cardiac ganglia,

168 FRED W. STEWART

or in other words suggestive of a higher synapse. The reader
is referred to the paper in question for discussion. Langley (’03),
in discussing the sympathetic action of the vagus, concludes
that the ganglion nodosum is not concerned with efferent
impulses.

Earlier advocates of the interpretation that some portion of
the sympathetic remains behind incorporated into the substance
of the cerebrospinal ganglion, may have derived evidence from
Gaskell (86). The latter inferred the presence of non-medul-
lated fibers in the vagus trunk, but failed to find them in the
root; his consequent conclusion was that these non-medullated
fibers of the vagus trunk were postganglionic fibers arising from
small cells of the nodose ganglion. Dogiel (’08), however, de-
scribed non-medullated axons associated with small cells in
spinal ganglia; Cajal (06) confirmed Dogiel’s observations and
furthermore showed the axons to be of the T- or Y-shaped variety,
and Ranson (11, 714, and ’15) has shown that the axons of these
small cells constitute the non-medullated fibers of the peripheral
branches of the spinal nerves, and has proved them present both
in the trunk and the root of the vagus.

Streeter (712) suggests that representatives of the sympathetic
ganglia of the facialis, glossopharyngeus, and vagus nerves may
be present in cells which have remained within the confines of
the neural tube or of the sensory ganglion. This possibility is
again suggested in connection with the failure of cells of oculo-
motor origin to contribute to the ciliary ganglion of human
embryos.

In certain lower forms there is good evidence for believing that
cranial sympathetic ganglia are present in connection with the
facialis, glossopharyngeus, and vagus nerves. Anatomical or
histological studies show them present at least in teleosts (Stan-
nius, ’46, ’49, ’54; Herrick, ’99, 00; His, Jr., ’93). Neumayer
(06), in Hertwig’s Handbuch, states that in selachians cranial
sympathetic ganglia other than the ciliary are absent. Johnston
(06) states that the development of cranial sympathetic ganglia
reaches so great a magnitude in teleosts that it is to be hoped
that it will be discovered in selachians. His, Jr., (93) found

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 169

sympathetic ganglion cells, or small cells which he considered
as sympathetic, in connection with the ganglia of the trigeminus,
facialis, glossopharyngeus, and vagus in selachians. Similar
observations were made in the case of teleostome fishes and
Anura. Since His’ work appeared before the account of Neu-
mayer, and since it is quoted by Neumayer in other respects,
but ignored in this particular, I assume that His’ results have
not been confirmed. Even the ciliary ganglion seems absent
to a large extent in Amphibia. Herrick (’94) found no evidence
of a ciliary ganglion in Amblystoma punctatum. Coghill states
that the ciliary ganglion of Amblystoma tigrinum is transitory
and probably at no time functional. Norris (’08) reported the
absence of a ciliary ganglion in Amphiuma, and McKibben (13)
has been unable to discover it in Necturus. Kuntz (’14) pre-
- gents what is perhaps evidence for a transitory ciliary ganglion
in Amblystoma and for a definitive ciliary ganglion in the frog.
Kuntz (14) reports the presence of both a sphenopalatine and
a ciliary ganglion in turtles (Thalassochelys and Chelydra) and
the presence in the chick of four sympathetic ganglia—ciliary,
otic, sphenopalatine, and submaxillary.

Although the facts point quite clearly to the presence of
sympathetic ganglia in connection with cranial nerves in lower
forms, little has been done in determining their origin. His, Jr.
(93) observed the forward growth of the sympathetic chain
from the trunk region in the trout and described it as consisting
of cell-free fibers having primitively no connection with cranial
nerves. Subsequently, connections with trigeminus, glosso-
pharyngeus, and vagus were formed, and at a slightly later stage
these connecting strands were found rich in sympathetic ganglion
cells. The inference would be that the cells were derived from
the respective cranial ganglia. Johnston (’05) states casually
that in the teleosts a sympathetic ganglion is present with each
cranial ganglion from which same it is presumably derived.
Kuntz (14) has made a detailed study of the development of
cranial sympathetic ganglia in the toadfish, but has obtained
rather indefinite results.

170 FRED W. STEWART

The impression is gained from Kuntz’ work on the toadfish
that he regards the cranial sympathetic ganglia of this form as
taking origin both from the cranial ganglia and from the neural
tube. According to Kuntz, the sympathetic trunk may be .
traced forward to the Gasserian ganglion in embryos of from 5
to 6mm. At this early stage the primordia of cranial sympa-
thetic ganglia are to be recognized. The sixth sympathetic
ganglion arises in contact with the medial aspect of the first
spinal ganglion and of the ganglion jugulare X. Kuntz believes
that the ganglion cells of this sixth sympathetic ganglion take
origin from the first spinal ganglion, the neural tube, and the
jugular ganglion. The fifth sympathetic ganglion arises and
perhaps likewise the fourth from cells which have migrated
forward from the anlage of the sixth ganglion. The third sympa-
thetic ganglion is derived ‘more or less’ from the geniculate. The
second sympathetic ganglion may be related genetically to both
the fifth and seventh nerves, the majority of its cells being doubt-
less derived from the Gasserian ganglion, and the first sympa-
thetic ganglion is intimately associated with the anterior portion
of the Gasserian.

In the turtle Kuntz has suggested a forward extension from
the cervical sympathetic ganglion contributing to the formation
of both the sphenopalatine ganglion and the otic ganglion.
According to this writer, the Gasserian and geniculate gangla
are both associated with the formation of the sphenopalatine
ganglion, in the turtle; the geniculate contributes cells to the
otic ganglion. The development of the larger cranial sympa-
thetic ganglionic masses in mammals has been followed by Kuntz
(13). Kuntz (09) has discussed the contribution of the vagus
to the sympathetic system. His findings may best be considered |
somewhat later. Hardesty (’14) states that certain small ganglia
of the cephalic sympathetic plexus arise from the semilunar,
geniculate, glossopharyngeal, and vagus ganglionic masses.

In no form, apparently, is it clear how much of the cranial
sympathetic belongs to the head proper, i.e., with the cranial
nerves developmentally, and how much is to be regarded strictly
as a forward extension from the cervical or trunk region. Not

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 171

until the entire developmental history of the cranial sympathetic
ganglia of lower forms has been made a subject for reinvesti-
gation will we be enabled to make any sort of generalization
or homology.

MATERIAL AND METHODS

The present study is concerned entirely with the development
of the cranial sympathetic ganglia in the mammals. The ma-
terial used consisted largely of rat embryos. Both albino rats
and gray rats were employed, the two series serving to supple-
ment one another. The material available from the depart-
mental collection at the beginning of the work consisted in fifteen
series, covering a fairly large range. During the study forty-four
series were added to the collection. The latter embryos were
obtained from The Wistar Institute of Anatomy and were pre-
pared by the writer with methods especially suited to the type
of study demanded. Litters ranging in age from ten and one-
half to seventeen days were employed, material being removed
at approximately half-day intervals. For general purposes,
embryos were fixed in Carnoy’s 6-3-1, Zenker’s fluid, and Bouin’s
fluid. In addition silver impregnations were obtained by the
Ranson pyridine-silver technique (Ranson, 712). Vom Rath’s
picro-acetic-osmic-platinic chloride technique, following the pro-
cedure of Neal (’14), was used with excellent results in some
stages. Where staining was necessary, hematoxylin and orange
G. or eosin were generally employed, once Held’s erythrosin-
methylene blue. Several impregnations of heads of young rats
ranging in age from twelve hours to fourteen days were obtained,
using the Huber-Guild technique as modified by Larsell (718).
In two cases the glossopharyngeal nerve was dissected out into
the tongue and the region removed and stained by the Nissl
technique. In order to have some check on the observations
of Kuntz (13), seven pig embryos were examined for the early
stages in the formation of the sphenopalatine and otic ganglia.
The writer wishes at this point to express his gratitude to Prof.
B. F. Kingsbury for originally suggesting the study and for
assistance during its progress. Additional expenses incurred

12 FRED W. STEWART

during the investigation have been met through the Mrs. Dean
“age Research Fund. The writer wishes to acknowledge the
assistance granted.

OBSERVATIONS
Forward growth of the sympathetic of the cervical region

The first problem for consideration in the study of the origin
of the cranial sympathetic ganglia? is that of the forward growth
of the sympathetic of the cervical region into the head. Thir-
teen-day stages in some cases give no evidence of a superior
cervical sympathetic ganglion, and therefore, of course, no
internal carotid nerve. In others a sympathetic ganglion is
present in connection with the first cervical nerve, but no fusion”
of cervical sympathetic ganglia has occurred as yet. In embryos
thirteen and one-half days old, a tendency toward fusion is
noted in the cervical sympathetic ganglia, as evinced by the more
scattered arrangement of cells and the establishment of a longi-
tudinal connecting strand. In some cases a complete fusion has
occurred. Simultaneously with the formation of the longitudinal
connecting strand, a forward extension is noted. This anterior
extension may be traced forward along the internal carotid
artery to a region just dorsal to the pharynx at about the level
of the second pharyngeal pouch. The ganglion itself has like-
wise grown forward to approximately the third-pouch region,
whereas in the earlier stage, the most anterior of the cervical
sympathetic ganglia lay somewhat caudal to the fourth-pouch
region. This more anterior position of the superior cervical
sympathetic ganglion seems the result of a large cell increase in

2In this paper the term ‘sympathetic’ is used in a broad sense to include
ganglia of the sympathetic chain, prevertebral ganglia, such as the coeliac, and
smaller masses of sympathetic ganglion cells such as are found in the myenteric
and submucous plexuses of portions of the alimentary canal and in the various
viscera; likewise, the larger ganglionic masses of the head and the so-called
ganglionated cephalic plexus (Hardesty, 714). In view of the appointment of a
committee, at the 1916 session of the American Association of Anatomists, to
examine and revise if necessary the present terminology used in designating these
portions of the peripheral nervous system, no more elaborate terminology has
been employed by the writer in the present paper.

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 173

the interval between the two stages, and is not to be thought of
as in the nature of a general forward extension along the internal
carotid of cells from the ganglion. The superior cervical sympa-
thetic ganglion ceases abruptly anteriorly; its cells do not ‘shade
off’ among the fibers of the internal carotid nerve.

Erpecially in early stages, complementary pictures are of
value. The commoner methods of technique are more. useful
in demonstrating cell elements than is the pyridine silver. While
the latter method has been very effective in demonstrating fibers,
it is of only occasional value, in early stages, in furnishing good
pictures of the cell bodies. The value of the pyridine-silver
technique improves with the increase in cytoplasm of the develop-
ing cell body, but even in later stages isolated cell elements
tend to be obscured by a wealth of heavily impregnated fibers.
At fourteen days little change is indicated, but in fourteen and
one-half day stages the pyridine-silver technique gives very
excellent pictures of neuroblasts—at this stage unipolar elements
—among the fibers of the internal carotid nerve, slightly isolated
from the superior cervical sympathetic ganglion. Between this
stage and the fifteenth day the outgrowth from the cervical
sympathetic ganglion extends sufficiently far forward to join the
great superficial petrosal nerve, and from this time on the great
petrosal nerve may be definitely recognized. Ganglion cells
found in the course of the strands vary greatly in number.
In one embryo (pyridine-silver technique) only a single cell was
observed between the superior cervical sympathetic ganglion
and the point of junction of great superficial petrosal and great
deep petrosal to form the Vidian nerve. In others cell masses
of considerable size have been encountered, frequently though
not always near the origin of the Vidian nerve (fig. 22). The
Vidian nerve may be followed into the sphenopalatine ganglion
and with it apparently go fibers from the superior cervical
sympathetic ganglion. In sixteen-day embryos the internal
carotid nerve may be traced as far forward as the carotid canal;
ganglion cells are encountered throughout its entire extent. At
seventeen days the internal carotid nerve, after giving a branch
to the hypophysis, fuses intimately with the abducens; the latter,

174 FRED W. STEWART

soon after, gives a fine anastomotic branch to the trigeminus,
and ganglion cells are found along these fibers. These are,
reedless to say, of scanty number. Koch (’16) and Rhinehart
(18) have reported the presence of sympathetic fibers in the
abducens nerve. As regards other outgrowths from the cervical
sympathetic, we must consider those fibers passing toward the
‘erritory of the middle ear and entering into the formation of
the tympanic plexus. They have been given especial attention
in view of their later involvement with fibers of the glossopharyn-
geal nerve, and in view of the possibility of confusing ganglion
cells originating from different sources. In fifteen-day embryos
strands from the internal carotid nerve, cephalad of the superior
cervical sympathetic ganglion, enter the dorsal pharyngeal region
and become lost in the mesenchyme over the region of the first
pharyngeal pouch. The strands are two in number, and both
have been seen to contain ganglion cells, in each case near the
origin of the strand. ‘These strands are recognized as the earliest
appearance of the superior and inferior caroticotympanic nerves.
In sixteen-day embryos the posterior of the two strands has
become relatively much larger and numerous ganglion cells are
to be noted (fig. 1); seventeen-day embryos show a vomplete
sympathetic anastomosis about the cartilaginous otic capsule.
Subsequent to sixteen-day stages there apparently occurs some
mixing of glossopharyngeal fibers with fibers from the cervical
sympathetic, but the origin of certain ganglion cells of the
tympanic plexus apart from any contribution via the glosso-
pharyngeal seems clear. In concluding this section we may
state that in addition to the ganglia of the carotid plexus and
its extensions, a portion of the ganglia of the tympanic plexus
belong with forward extensions from the superior cervical sympa-
thetic ganglion.
Vagus portion of the sympathetic

Coming now to the question of sympathetic ganglia related
developmentally to the cranial nerves, it is perhaps most con-
venient to consider first the vagus group. Previous attempts
have been made to show that the vagus plays a part in the

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 175
development of sympathetic ganglia. Kuntz (’09) traced the
origin of the ganglion cells of the esophageal, gastric, intestinal,
pulmonary, and cardiac plexuses to cells which migrated outward
from the hindbrain and from the vagus ganglionic masses periph-
erally along the vagus trunk. From Kuntz’ figures, however,
I must confess some doubt as to the complete accuracy of his
observations. With special techniques and a large series of

Fig. 1 Rat embryo, 16 days, Carnoy’s 6-3-1. Neuroblasts among fibers of
the inferior caroticotympanic nerve. Projection drawing, x 4500.

ABBREVIATIONS

A.C.N.IX., accompanying cells, nerve
IX

B. bronchus

C.P., coeliac plexus

C.S.S., ganglion cells of cerebro-spinal
type

C.T., chorda tympani

E., esophagus

G.VII, ganglion geniculi

G.C., ganglia eardiaca

G.N.V., ganglion Gasseri

G.N.X., ganglion, nerve X

G.O., ganglion oticum

G.p.t., ganglion of plexus tympanicus

G.S., sympathetic ganglion cells

G.symp., ganglion sympathicum

G.S.NJIX, ganglion sympathicum,
nerve IX
G.S.N.X, ganglion sympathicum,

nerve X

G.sph., ganglion sphenopalatinum

G.T.E., tracheo-esophageal ganglion

Gang. ling., lingual ganglia

I., intestine

M., ramus mandibularis V

N.IX, glossopharyngeal nerve

N.C.I., nerve cells of the intestinal
coat

N.C.R.O., nerve cells of the ramus
ophthalmicus V

N.C.N.T., nerve cells of the nervus
terminalis

N.R., nervus recurrens

N.T., nervus terminalis

O., optic cup

Ph., pharynx

R.P.VII, ramus palatinus VII

R.P.IX, ramus palatinus IX

Tr., trachea

176 FRED W. STEWART

embryos, I am free to admit that I have been totally unable
to follow Kuntz’ ‘indifferent cells’ back to their ultimate origin,
that is to a neural-crest origin as opposed to a neural-tube origin
—either one or both. The problem of the origin of the sympa-
thetic ganglia of the trunk region is less difficult. The path of
migration is for the most part shorter in the case of the sympa-
thetic ganglia which originate in relation to the spinal nerves
than it is for the cranial sympathetic ganglia; one must be
exceedingly cautious in accepting statements as to the definite
origin of neuroblasts apparently migrating along cranial nerve
trunks. We must for the time be satisfied in basing our interpre-
tation largely on future relationships, for at no time apparently
does one find a continuity en masse between the sensory ganglion
of the vagus and its sympathetic cells such as Held (’09), for
example, has figured for the trunk sympathetic. In addition to
Kuntz, Streeter (12) indicates diagrammatically sympathetic
neuroblasts migrating peripherally along the vagus into the
cardiac plexus.

In thirteen-day rat embryos the vagus has been traced caudad
to a point slightly below what has been considered the origin
of the superior laryngeal nerve. Within the next half-day the
vagus undergoes a rapid caudal extension and may be followed
into the condensing mesenchyme about the developing stomach.
Small but easily distinguishable neuroblasts are found massed
about the growing stump of the nerve and may be traced out.
into a narrow strand of single cell thickness into the gastric
mesenchyme. The first distinguishable phase in the develop-
ment of the vagus portion of the sympathetic seems, then, the
grouping of neuroblasts about the growing tip of the vagus in
the lower esophageal region. In addition to these cells, an
occasional cell of larger proportions is encountered along the
vagus trunk; these elements will be considered in later stages.

For a considerable time the writer was at a loss to account
for the rapid increase in the number of neuroblasts along vagus
fibers and was inclined to search for large additions from the
trunk sympathetic ganglia. Careful search, however, failed to
reveal any trace of such contribution, and the true explanation

CRANIAL SYMPATHETIC GANGLIA IN THE RAT VIG

did not become apparent until later, when the glossopharyngeal
nerve was studied. In examining cells in and along the vagus
trunk, one finds numerous shapes and sizes which are apparently
intermediate between the elongate type of cell and the cell in
which cytoplasmic development and general nuclear shape pre-
sent clearly the characteristics of a neuroblast. These cells
possess nuclei showing bendings, constrictions, and tendencies
toward the assumption of a spherical shape, apparently corre-
lated with cytoplasmic increase. Vagus fibers are very rich in
these elongate elements and their apparent modifications, and
it is seemingly through transformation of this indifferent type
of cell that the majority of neuroblasts along the vagus trunk
arise. In recognizing these elongate cells as elements closely
resembling the ‘indifferent cells of Schaper’ the writer agrees
with the interpretation of Kuntz. Only occasionally does one
encounter a neuroblast, other than large elements—seemingly
aberrant sensory cells—in the upper portion of the vagus trunk;
elongate cells and their earlier types of modification are found,
however, throughout. The more definitive neuroblastic cells
occur lower down, particularly at and below the origin of the
inferior laryngeal nerve, in the lower esophageal and upper
gastric regions. Here the differentiation process apparently is
at a maximum, and in later stages—fifteen-day embryos—large
accumulations of neuroblasts may be found along the vagus
trunk in the lower esophageal region (fig. 23). This ganglionic
mass figured is alone larger than any definitive ganglion of the
sympathetic chain at this stage. A similar ganglionic mass has
been described by Abel (’09) in a five-day chick embryo. Miss
Abel likewise noted similar cells higher up in the vagus trunk,
but failed to interpret them of vagus origin; she derived the
ganglia of the alimentary canal entirely from the trunk sympa-
thetic ganglia. .

Embryos of fifteen and three-quarter days, especially those
in the preparation of which special techniques have been em-
ployed, have been most ‘useful. It is quite advantageous to
compare pyridine-silver preparations, which give excellent fiber
pictures, with the results of some excellent cytoplasmic fixer,

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 3

178 FRED W. STEWART

such as the v. Rath picro-acetic-osmic-platinie chloride. If we
take first the fiber picture alone, we find the superior laryngeal
nerve present as a large, well-developed strand. Passing caudad,
the vagus gives off fine branches to the developing esophagus,
these twigs forming a plexiform mass of fine, often single fila-
ments in the condensing mesenchyme of the future muscularis; no
fibers can be traced into the region central to the muscularis.
The larger branches anastomose with similar fibers entering from
the inferior laryngeal nerve. At the junction of the inferior
laryngeal nerve with the vagus trunk there is an accumulation
of ganglion cells; their nature will be discussed later when they
may be examined to better advantage. Both vagi give off
esophageal branches below the level of the bifurcation of the
bronchi and send strands into the deeper portion of the cardiac
plexus anterior to the bifurcation of the bronchi and above that
of the Aa. pulmonales. Plexiform fibers connect the deeper
portion of the cardiac plexus with a more superficial portion,
with pulmonary branches, and with branches to the lower portion
of the vena innominata sinistra. This study does not concern
itself with the morphogenesis of the cardiac plexus save as refer-
ences to it are necessary in general description. The develop-
ment of the cardiac plexus deserves additional attention; even
after my rather superficial examination, it is quite evident to
me that the work of His, Jr. (’91), on the development of the
cardiac plexus of the chick, needs careful checking. In the
abdomen the vagus spreads out over the developing stomach
much as in the adult. Just before so doing the left vagus and
shortly afterward the right, communicate directly by large
branches with the coeliac plexus and indirectly by fine fibers
along the gastric branches of the coeliac axis. Due to additions
from other sources, above mentioned, it is quite impossible
henceforth to determine histologically how far caudad the vagus
extends.

Other similarly prepared embryos of fifteen and three-quarter
days have furnished quite excellent impregnations of developing
neuroblasts in the gastric and intestinal plexuses. Neuroblasts
are found in large numbers in the condensing mesenchyme about

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 179

the stomach and in still larger quantities (perhaps due to its
smaller diameter) in the developing intestinal coat (fig. 2). As
regards their origin, the possibility of the addition of elements
originating from the trunk sympathetic proper, and migrating
outward along the sympathetic branches accompanying the
divisions of the coeliac axis, or the superior mesenteric artery,
or along direct strands connecting the vagus with the coeliac

f}

~- Wg

Fig. 2 Rat embryo, 15} days. Neuroblasts of intestinal plexus. Projection
drawing from pyridine-silver preparation, X 500.

plexus, must be considered. Study of fibers joining the enteric
nerve plexus with the coeliac convinces me that any addition
from the latter at this stage is small. Later stages have not
been examined in search of such additions since the scope of the
present paper included merely the demonstration of a ganglion
cell contribution of vagus origin. What is perhaps a slight
addition from the coeliac ganglionic mass is indicated in the figure
to which reference has just been made. In addition, there is

180 FRED W. STEWART

some evidence of an increased number of neuroblasts in the
developing intestinal coat at the point where additions from the
coeliac ganglion would seem probable. This may, however, be
purely physiological (Kappers, numerous papers on neurobio-
taxis). It will be noted hkewise from the figure that there is
some slight indication of a splitting of the enteric plexus into
two concentric rings. This division of the plexus is not found
continuously; it is scarcely at all evident in the stomach wall,
largely so in the upper intestinal tract, and the condition grows
progressively less marked in the’ more caudal loops of the intes-
tine. The doubling of the ring of neuroblasts apparently bears
no relation to possible additions from the coeliac. A morpho-
genetic factor might be suggested as responsible for the late
separation into two plexuses—intermuscular and submucous—
in the stomach region; for example, the large increase in the
lumen of the digestive tube and consequently greatly increased
wall surface. |

Before discussing in further detail cell types and distribution,
it will be necessary to turn to still younger stages in order to
determine whether or not neuroblasts are present along the
gastro-intestinal tract before any confusion exists between vagus
branches and those from the coeliac plexus. Pyridine-silver °
preparations of fourteen and one-half day embryos show develop-
ing neuroblasts in the gastric mesenchyme and in the mesenchyme
surrounding the intestine proper. Although nerve fibers are
beginning to grow outward along the coeliac axis and’ superior
mesenteric artery, no connection between them and the fibers
of the vagus can be made out; they do not enter into gastric
or intestinal territory and no cellular contribution to the enteric
plexus is indicated. A similar condition has been noted by
Kuntz (’09) for pig embryos of from 6 to 7 mm.

When this study was begun it was my belief that all migrant
cells—all neuroblasts which had wandered peripheralward from
the cerebrospinal ganglionic masses or neural tube (depending
on the interpretation assumed)—partook of the nature of sympa-
thetic elements, and I was rather at a loss to account for my
ability to quite early classify the neuroblasts into two distinct

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 181

types. It was not until some time later when reviewing a paper
by Weigner (’05) that the picture became clear. Weigner, in a
study of the nervus intermedius, both in man and in the marmot,
showed conclusively the presence of T-cells, typical cerebrospinal
ganglion cells, on the nervus petrosus superficialis major, the
chorda tympani, and especially at the exit of the nerve to the
stapedialis muscle. Bipolar cells were likewise encountered.
Weigner used material prepared by the Cajal method and there
was small chance for error. Rhinehart (’18) mentions a small
ganglion at the point where the chorda tympani leaves the
facialis trunk, probably of the same nature as the cells described
by Weigner, although this is not so stated. This point will be
considered later in connection with the facialis.

In the case of the vagus, the two types of peripherally situated
neuroblasts are readily distinguishable. One possesses a large,
rather clear nucleus and a relatively large amount of deeply
staining cytoplasm; the cell seems comparable in every way with
elements of the ganglion nodosum; these cells are, in some cases,
unipolar, but in the majority of instances, bipolar. In some
embryos they are to be found in continuous rows (fig. 24) all
the way from the ganglion nodosum to the origin of the inferior
laryngeal nerve. I have been able to differentiate them most
easily in v. Rath preparations, where the cytoplasm is intensely
blackened. The second type of cell, the type which the writer
recognizes as a sympathetic neuroblast, is distinguishable by its
smaller nucleus, more granular and grayish in its staining capacity,
and by the markedly smaller amount of cytoplasm. It seems
convenient for future reference to refer to the two cell types
as the ‘large-cell’ and the ‘small-cell’ type, respectively. The
recognition of the small-cell type as sympathetic in nature is
based on the following: 1) the cells resemble those elements
encountered in the superior cervical sympathetic ganglion and
its branches, notably the internal carotid nerve; 2) the cells
tend to group themselves in masses, and in these groups the
large-cell variety is usually absent; 3) the cells are found particu-
larly in those regions of the vagus trunk where available descrip-
tions of future conditions do not lead us to suspect the presence

182 FRED W. STEWART

of the spinal ganglion cell type; 4) they resemble similar elements
in other nerve trunks considered in this study where subsequent
observation has shown the cells to be sympathetic, and they are
to be found in regions of the vagus where other techniques have
indicated sympathetic neuroblasts.

3

Fig. 3 Rat embryo, 15} days, vom Rath’s technique. Neuroblasts of vagus
trunk, below bifurcation of the bronchi. 1, 2, 3, types of cell, intermediate be-
tween elongate accompanying cell and definitive neuroblast. Projection draw-
ing, * 500.

As regards the distribution of the two types, it may be remarked
that the large-cell type tends to be found along the main vagus
trunk, sometimes, as has been said, in a continuous row from the
ganglion nodosum to the origin of the interior laryngeal nerve,
at other times more scattered, There is a quite constant aggre-

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 183

gation of these cells at the origin of the superior laryngeal nerve
and another at the origin of the recurrent nerve. Caudal to
the origin of the latter nerve the large cells are but rarely en-
countered. The small-cell type is of much more general occur-
rence. They are found in large numbers in and along the vagus
trunk (fig. 3); they are likewise found in especially large aggre-
gates at the origin of the recurrent nerve (fig. 4); they are dis-
cernible in the cardiac branches of the vagus, in the pulmonary

Fig. 4 Rat embryo, 15¢ days, vom Rath’s technique. Neuroblasts of vagus
trunk, at origin of N. recurrens. Projection drawing, X 500.

branches, on vagus fibers in the mesenchyme between trachea
and esophagus continuous with similar aggregates in the main
trunk, and in the gastric and intestinal mesenchyme (figs. 5
and 6). The entire vagus has become in fifteen and three-
quarter day embryos the site of neuroblastic differentiation.
Attention may be called at this time to the fact that no such
pictures as are indicated in the figures of Kuntz (’09), for the pig,
have been obtained in the case of the rat. Although fifteen and

184 _FRED W. STEWART

three-quarter day rat embryos are relatively much farther ad-
vanced than the 6-mm. pig embryos figured by Kuntz (the period
of gestation in the rat averaging but twenty-one days), neither
silver impregnations nor v. Rath preparations give any indication
of the presence of neuroblasts surrounding the esophagus, as

5

Fig. 5 Rat embryo, 15} days, vom Rath’s technique. Neuroblasts along
gastric branches of the vagus. Projection drawing, X 500.

the anlage of myenteric and submucous plexuses. The fibers,
to be sure, are present, but up to the present nerve cells have
not been encountered in any such relation. Considering the
excellent impregnations which have been obtained of the corre-
sponding gastric and intestinal plexuses, there is little reason
for supposing that the failure to demonstrate them in a peri-
esophageal position is due to faulty technique.

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 185

An examination of later stages—sixteen- and seventeen-day
embryos—affords some few additional facts. The ganglionic
mass at the origin of the recurrent nerve has increased somewhat
in size. Ganglia on the branches of the inferior laryngeal nerve
and on small vagus branches below the exit of this nerve have
assumed a constant position as regards the trachea and esophagus.
They are situated between the trachea and the esophagus; their
number is not constant, averaging perhaps eight per side; as

Fig. 6 Rat embryo, 15{ days, vom Rath’s technique. Neuroblasts along
duodenal branches of vagus. Projection drawing, X< 500.

one might assume from their origin, they are bilaterally sym-
metrical. The ganglia tend to be irregular in shape, rather
diffuse groups of cells shading into one another; occasionally
they are well formed, compact masses. They possess transverse,
intercommunicating strands and give off branches to the develop-
ing musculature of the trachea. Apparently the occasional
neuroblasts which may now be encountered in the developing
muscularis of the esophagus and were not found in earlier stages
owe their origin to cells found in vagus and inferior laryngeal
strands independent of these so-called tracheo-esophageal gan-

186 FRED W. STEWART

glia. These cells together with a tracheo-esophageal ganglion
are indicated in figure 7. Below the bifurcation of the trachea,
ganglia are found between the bronchi; the most caudal of these
fuse with the large masses of ganglion cells constituting the

°
4

Fig. 7 Rat embryo, 17 days, Carnoy’s 6-3-1. Neuroblasts of vagus trunk, a.
tracheo-esophageal ganglion, and developing ganglion cells of the esophageal
plexus. Projection drawing, X 500.

deeper portion of the cardiac plexus. Subsequently this gan-
glionic mass gives rise to four (two bilaterally symmetrical) off-
shoots (fig. 25) related apparently to the bronchi and seemingly
reminiscent of the same fundamental plan of arrangement as
that found higher up. Branches from the vagus proper and from

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 187

the cardiac plexus, all rich in ganglion cells, enter the hilus of
the lung in association with the bronchi, and the pulmonary
artery and vein.

A large number of ganglion cells are encountered along the
branches of the superior laryngeal nerve. Certain of these near
the vagus trunk are apparently sensory cells continuous with
those of the ganglion nodosum. Others (fig. 8) I have considered
as sympathetic. Apparently fairly late material is necessary to
fully follow the development of the small ganglia of the esopha-

Fig. 8 Rat embryo, 17 days, Carnoy’s 6-3-1. Neuroblasts among fibers of
the nervus laryngeus superior. Projection drawing, X 500.

geal and pharyngeal plexuses. The writer hopes to undertake
the investigation as time and material become available. Some
attention, however, has been paid to the ramus pharyngeus
vagi. The ramus pharyngeus vagi is in later stages so closely
related to branches from the cervical sympathetic ganglion and
to glossopharyngeal branches, that the study of these older
embryos is rather unproductive of definite results. In sixteen-
day embryos the ramus pharyngeus vagi may be traced fairly
separately into the developing muscularis of the pharynx; at
this time no neuroblasts have been found among its branches.

188 FRED W. STEWART

Shortly afterward the intermingling of fibers from other nerves
so complicates the region that nothing may be ascertained. The
ramus pharyngeus vagi is considerably smaller at this stage than
the corresponding glossopharyngeal branch. The latter will be
considered in a subsequent connection.

In briefly concluding the section on the vagus, the statement
may be reiterated that, far from finding that the vagus plays

om SEZ

Fig. 9 Rat embryo, 15 days, Carnoy’s 6-3-1. Elongate cells massed along
fibers of the ramus lingualis IX as it enters the tongue. Projection drawing,
x 500.

no part in the development of sympathetic nerve cells, the
author’s results seem to indicate that part if not all of the nerve
cells found in the cardiac, gastric, tracheal, esophageal, pulmo-_
nary, and upper intestinal plexuses are of vagus origin.

Glossopharyngeal portion of the sympathetic

An examination of the glossopharyngeal nerve for developing
sympathetic neuroblasts must include the study of three branches,
namely, the lingual branch, the pharyngeal branch, and the

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 189

ramus palatinus (ramus tympanicus or Nerve of Jacobson),
These divisions will be considered in the order named.

In 5.5-mm. embryos (gray rat) the lingual division of the
glossopharyngeus may be traced into the floor of the pharynx
as an exceedingly cell-rich strand (fig. 26). It is composed of
cells quite closely resembling elements found within the ganglion
petrosum, and some difficulty is experienced in distinguishing
the exact limits of the ganglion. The contrast between the
glossopharyngeal nerve and the hypoglossal, a purely motor

Fig. 10 Rat embryo, 15} days, vom Rath’s technique. Similar cells along
finer branches of the ramus lingualis IX inthe tongue. Projection drawing, X 500.

nerve, is very marked (fig. 26). The latter nerve is practically
free from accompanying cell elements. Slightly later stages
(fourteen and one-half and fifteen-day albino rats) show cluster-
ings of elongate cells, similar to those found in the early vagus
trunk, along the glossopharyngeal nerve as it enters the tongue
(fig. 9), and shortly afterward they are evident in the finer
lingual branches of the nerve (fig. 10). As yet no definitive
neuroblasts are evident; the writer believes that the definite
test for the presence of a developing ganglion cell must be, as
in the case of the vagus, the development of the characteristic

190 FRED W. STEWART

cytoplasm. This cytoplasmic increase is little marked in sixteen-
day embryos, but the branches of the glossopharyngeus in the
tongue show such well-marked clusters of elongate and rounded
cell elements (fig. 27) that their neuroblastic character is no
longer a matter of doubt. Definitive neuroblasts are found in
seventeen-day embryos (fig. 11). They apparently arise, as in
the case of the vagus, through a rounding out of the nucleus and
through an increase of the cytoplasm in certain of the elongated

(ojos
e

ia

Fig. 11 Rat embryo, 17 days, Carnoy’s 6-3-1. Neuroblasts along fibers of
ramus lingualis 1X in tongue. Projection drawing, X 500.

accompanying cells. Rhinehart (’18) has observed sympathetic
ganglion cells on fibers of the glossopharyngeal nerve within the
tongue. In order to confirm the observations of Rhinehart and
to have some check upon my own observations, to establish
continuity between the embryonic and the adult condition, four
pyridine-silver series through heads of young rats were prepared.
In each case it has been possible to locate the constant ganglionic
mass described by Rhinehart on the glossopharyngeal nerve
near the hyoid bone. It has likewise been discovered in Nissl
nreparations and the sympathetic character of its cells verified.

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 191

In connection with some previous observations of the writer on
changes occurring in the foliate papilla of the rabbit after section
of the glossopharyngeal nerve, opportunity has existed to observe
any changes in ganglion cells of this region (undoubtedly IXth
territory) following section. No change and no decrease in
ganglion cells has been noted after complete disappearance of
taste buds. Circumstantial evidence then would seem to indicate
that the general arrangement of these ganglia followed somewhat
the scheme of those of the intestinal plexuses, and that they are
not entirely dependent on external (cerebrospinal) stimuli. This
observation accords with that of Prentiss (’04). The latter
noted no changes in cells or fibers (aside from large medullated
fibers) in the perivascular and subepithelial networks in the oral
epithelium of the frog after section of the palatine branches of
the facialis. Prentiss’ observation as to the existence of such
networks is interesting in connection with the reported absence
of cranial sympathetic ganglia—save perhaps a ciliary ganglion—
in anura.

The ramus pharyngeus IX, as previously stated, is much larger
than the corresponding vagus branch. Although anastomoses
with the ramus pharyngeus vagi occur at early stages, I have
been able to trace the respective branches quite clearly up to
and including sixteen-day stages. At this time certain elongate
elements are found in a ganglion-like cluster; a rounding out of
the nucleus is to be noted together with the development of a
scanty but characteristic cytoplasm, and in seventeen-day
embryos large numbers of ganglion cells are to be found in the
nerve trunk and among its peripheral terminations (fig. 12);
these cells are evident throughout the entire trunk from the
ganglion petrosum peripheralward, and one is consequently
forced to assume that they originate from migrating cells of the
glossopharyngeus. A sympathetic anastomosis is, to be sure,
present at this time, but the position of the developing nerve
cells of the ramus pharyngeus IX forces one to exclude this
anastomosis as a factor in their production.

The adult nervus tympanicus or nervus palatinus IX is quite
closely associated with fibers from the internal carotid nerve;

192 FRED W. STEWART

these fibers are ganglionated in later stages. Accordingly, some
effort must be made to rule out these neuroblasts migrating from
the internal carotid nerve if any contribution along fibers of the
glossopharyngeal to the small ganglia of the tympanic plexus
is to be shown. If the otic ganglion were of trigeminus origin,

Fig.12 Rat embryo, 17 days, Carnoy’s 6-3-1. Neuroblasts of ramus pharyn-
geus IX. Projection drawing, X 500.

it too would have to be considered as a possible source of the
neuroblasts of the tympanic plexus, which might then arise
through a caudal migration of cells via what in the adult is known
as the lesser superficial petrosal nerve. My personal observations
have failed to show any developmental relationship between the
otic ganglion and the Gasserian ganglion, and I have been forced
to the conclusion that the otic ganglion is entirely a ganglion

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 193

of the ramus palatinus IX. Kuntz (13) has derived the otic
ganglion of the pig from the Gasserian ganglion and the rhomb-
encephalie wall. Kuntz states that the otic ganglion is well devel-
oped before there is any trace of a ramus palatinus IX. In the
rat this is certainly not the case. In 5.5-mm. embryos of the
gray rat (fig. 13) the first trace of the otic ganglion is to be found
as an enlargement in the growing tip of the ramus palatinus IX.
In fourteen and one-half day embryos of the albino rat, a large

ie

Le,

Fig. 13 Rat embryo (gray), 5.6 mm., Zenker’s fluid. Anlage of the otic
ganglion; marked thickening at tip of ramus palatinus IX. Projection drawing,
X 333.

ramus palatinus IX is present, and a few scattered neuroblasts
(fig. 14) are present among its terminal fibers. The ramus
palatinus IX ends immediately below the ganglion geniculatum
VII well posterior to the Gasserian ganglion. No evidence has
been found for a migration of cells from the geniculate ganglion
into the anlage of the otic ganglion. J am unable to reconcile
my observations on pig embryos with the statement of Kuntz.
It is difficult to Judge when, exactly, he would consider the otic
ganglion as ‘well established.’ Since his first descriptions of the
anlage of the otic ganglion are of pig embryos of from 12 to 15

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 3

194 FRED W. STEWART

mm. in length, I should scarcely think that at this stage the otic
ganglion would be ‘well established.’ I have found a fairly large
ramus palatinus IX in 11-mm. pig embryos and a smaller one in
an 8-mm. pig. There seems to be no trace of an otic ganglion,
nor have I been able to discover the structure before it was
noted as a diffuse collection of cells amid the fibers of the ramus

Z
=
N.VII
G.O.
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65d se

Fig. 14 Rat embryo, 144 days. Early neuroblasts at tip of ramus pa!atinus
IX. Projection drawing from pyridine-silver preparation, X 500.

palatinus IX, well posterior to the semilunar ganglion and ramus
mandibularis V. This is the condition noted in 15- and 16-mm.
pig embryos. In 17-mm. embryos the otic ganglion is quite a
well-marked structure, but has lost none of the diffuseness which
characterizes its earlier stages. The pig embryos which I have
examined in this connection form a rather close series (15, 16,
17, 17.5, and 18 mm. total length). The status of the otic
ganglion in the 18-mm. pig embryos resembles quite closely that
apparent in fifteen-day rat embryos (fig. 28). In the rat, nerve

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 195

strands connecting the trigeminus with the otic ganglion are
to be noted in sixteen-day embryos. The sympathetic root is
likewise apparent. Neither of these have the appearance of
migration paths. In the pig, 17.5-mm. stages have shown small
aggregates of ganglion cells along the ramus palatinus IX well
posterior to the otic ganglion. Although no attempt has been
made to follow these in the pig, they are probably to be thought
of as belonging to the glossopharyngeal contribution to tympanic
plexus. |

In sixteen-day rat embryos, the ramus palatinus IX contains
numerous neuroblasts throughout its course from the ganglion
petrosum to the otic ganglion; some tendency toward the for-
mation of cell aggregates is noted, and in two seventeen-day
embryos examined the ganglion cells on the ramus palatinus
IX were found to consist of three bilaterally symmetrical groups.
The first ganglion appears at the point of origin of the ramus
palatinus IX (at this stage slightly distant from the ganglion
petrosum); the second (fig. 29) appears at the junction of ramus
palatinus IX with the inferior caroticotympanic nerve, and the
third at the point of union with the superior caroticotympanic
nerve (fig. 30). Were it not for the general distribution of
neuroblasts throughout the ramus palatinus in earlier stages,
examination of seventeen-day embryos might convey the impres-
sion that all of the neuroblasts within the tympanic plexus
originated along the caroticotympanic nerves from the superior
cervical sympathetic ganglion. In view of this more general
distribution, however, the writer is inclined to believe that the
cells are of double origin, along the glossopharyngeal and from
the superior cervical sympathetic ganglion.

Facialis portion of the sympathetic

Kuntz (13) has concluded that in the pig the sphenopalatine
ganglion arises along the medial surface of the maxillary division
of the trigeminus, from cells which wander peripherally from
the semilunar ganglion. Streeter (712) likewise derives the
sphenopalatine ganglion from the semilunar ganglion, calling

196 FRED W. STEWART

attention, however, to the closeness of its relation to the great
superficial petrosal nerve. Kuntz states that the possibility of
a few cells reaching the sphenopalatine ganglion via the great
superficial petrosal nerve is not precluded; connection is not
made, however, with the latter nerve until the anlage of the
sphenopalatine ganglion is well established. On the basis of my
own preparations, I have been forced to conclude that the
sphenopalatine ganglion is a ganglion of the ramus palatinus VII
(the great superficial petrosal nerve). In view of the discrepancy
existent in the findings of Kuntz and myself, I have examined

Fig.15 Rat embryo, (gray), 5.6 mm., Zenker’s fluid. A portion of the ramus
palatinus VII. Projection drawing, X 500.

a large number of early stages in the formation of the spheno-
palatine ganglion, in all twenty-seven series. Of these, seven
are of pig embryos of favorable stages. The intensely cellular
character of the ramus palatinus VII is apparent in 5.5-mm. rat
embryos (fig. 15). The main trunk of the ramus ends anteriorly
in cell-rich strands. In fourteen-day rat embryos, the nerve
trunk, contrary to the appearance of others, such as the hypo-
glossus where cell content is apparently restricted to sheath cells,
shows toward its growing tip, irregular swellings due to local
clusterings of accompanying cells; a considerable extension out-
ward toward the trigeminus is generally noticeable (fig. 31);

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 197

the nerve ends anteriorly in a rich, though diffuse, plexus of
strands. Similar conditions are approached in 15- and 16-mm.
pig embryos. As the number of neuroblasts among the fibers
of the ramus palatinus VII is increased, the forward and outward
growth of the sphenopalatine ganglion brings it into relation
with palatine branches of the maxillary nerve; these branches
never, so far as I am able to determine, possess the appearance
of a migration path. The palatine branches of the maxillary
nerve traverse the sphenopalatine ganglion in fourteen and one-
half day rat embryos; the main mass of the ganglion lies posterior
to these palatine branches, diffusely scattered along the entering
fibers of the ramus palatinus VII. In fifteen-day rat embryos
(fig. 32) the sphenopalatine ganglion is an elongated, very diffuse
structure, and at slightly later periods, its growth brings it into
direct contact with the main trunk of the maxillary division of
the trigeminus; with the ganglion well formed, it is difficult to
judge whether or not it receives subsequent additions from the
semilunar ganglion; so far as I am able to determine, it does
not. Still later stages find the sphenopalatine ganglion directly
continuous with the semilunar ganglion (fig. 33), with, neverthe-
less, a clear line of division between their respective cell elements.
The development of the sphenopalatine ganglion in the pig is
very similar in its early stages (15 to 18 mm.) to that of the rat;
later stages have not been followed. It has been traced from a
diffuse collection of neuroblasts amid the anterior terminations
of fibers of the ramus palatinus VII (figs. 34 and 35) to a relatively
compact structure in contact with the main ramus maxillaris V.
Its first appearance is well mediad to the palatine branches of
the maxillary nerve. In concluding this section on the develop-
ment of the sphenopalatine ganglion, the fact should be empha-
sized that in the turtle and in the chick Kuntz (’14) has derived
the ganglion from cells migrating outward along the great super-
ficial petrosalnerve. The early diffuse character of the ganglion
which.he describes in these forms is quite suggestive in view of
my own observations on conditions found in the rat and the pig.
Certainly, one would suppose that such a structure as the spheno-
palatine ganglion would possess fundamentally the same mode
of origin in all forms in which it occurs.

198 FRED W. STEWART

Weigner (’05) reported the presence of nerve cells, resembling
those of posterior root ganglia, along branches of the chorda
tympani and the great superficial petrosal nerve. In the rat
I have found them in very small numbers along the chorda
(fig. 16), but more regularly along the great superficial petrosal.
In addition to an occasional isolated cell, there occurs regularly
a small ganglion at the junction of the great superficial petrosal
and lesser superficial petrosal nerves; the cells comprising it
are typical T-cells. The presence of supposedly sensory cells
along fibers of the great superficial petrosal nerve is interesting
in view of the assertion of Hoffmann (’00) that the sphenopalatine

Fig. 16 Rat embryo, 17 days, Carnoy’s 6-3-1. Large ganglion cell (cerebro-
spinal type) among fibers of the chorda tympani. Projection drawing, X 500.

ganglion was in part sensory. While I have never observed these
cells as far anteriorly as the sphenopalatine ganglion, it does not
seem impossible that a migration, sufficiently extensive, would
bring them to this position. The sphenopalatine ganglion might
then occasionally (in some forms) contain typical sensory cells.
In the case of the submaxillary ganglion, I have been unable
to substantiate the findings of Kuntz: Kuntz (’18) derives the
submaxillary ganglion from cells which wander out from the
semilunar ganglion, and from the wall of the rhombencephalon,
along the mandibular division of the trigeminus. He finds the
ganglion in connection with the lingual nerve before the union
of the latter with the chorda tympani. His earliest description

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 199

of the ganglion refers to pig embryos of 13- to 16-mm. length.
Kuntz’ observation on the time of union of the chorda with the
lingualis would agree with my own findings in the pig; the two
strands have not yet united in an 11-mm. embryo, but from the
relative positions of the nerves, the fusion must occur very soon
after. In my next available series (15 mm.) the union has oc-
curred and the ganglion is present, at least as closely related to
the chorda as it is to the lingualis. In the rat, the submaxillary
ganglion does not make its appearance until after the fusion of
the chorda and lingualis has occurred. I have been able to
examine nine series showing the chorda tympani previous to
this period. It resembles closely in structure the early palatine
rami (VII and IX) and is proportionally more cellular in character
than is the ramus maxillaris. In fourteen-day rat embryos the
chorda has united with the lingualis, although at this period the
combined trunk is more largely chorda; the submaxillary ganglion
has not been found at this stage. Later, when the structure does
appear, it lies on that aspect of the combined chorda-lingualis
trunk where one would from previous relations recognize
mostly chorda fibers. In fifteen-day embryos the ganglion sur-
rounds the combined trunk, but again is mainly on the chorda
side; the evidence is of course purely circumstantial, and some
account must be taken of the fact that the ‘chorda side’ of the
nerve is likewise that aspect nearest the developing submaxillary
gland. Nevertheless, the similarity between the chorda and the
ramus lingualis IX and the fact that the more posterior lingual
ganglia arise in connection with the latter are strongly suggestive
of a chorda origin of the submaxillary ganglion. The greater
proportion by far of the small sympathetic ganglia of the tongue
are formed as a continuance of the same migration which gives
rise to the submaxillary ganglion and the closely allied sublingual
ganglion. This formation of small lingual ganglionic masses
apparently occurs fairly late; in seventeen-day rat embryos
ganglion cells are found in virtually continuous strands, from
points on the entering chorda-lingualis trunk into the mesen-
chyme surrounding submaxillary and sublingual glands, along
the submaxillary duct, and upward into the tongue, where they

200 PRED W. STEWART

may be found arranged in a definite row as in figure 36. Rhine-
hart (18) has called attention to the presence of ganglion cells
along fibers of the hypoglossal nerve in the tongue. Save where
fibers of the chorda-lingualis trunk are associated with those of
the hypoglossal, no such cells have been encountered in the rat;
the main hypoglossal trunk has never been found to contain
ganglion cells. Roughly speaking, the ganglia of the anterior
two-thirds of the tongue belong with the chorda-lingualis migra-
tion, those of the posterior third belong with the lingual division
of the glossopharyngeus. Could it be shown that ganglion cells
enter the tongue by way of the hypoglossus, it might be most
interesting in connection with the transient hypoglossal ganglia
deseribed by Prentiss C10) and others.

Trigeminal portion of the sympathetic

Thus, the possibility of a contribution of trigeminal elements
to the submaxillary ganglion cannot be denied, nor have I been
able to verify its occurrence. Likewise, I have little to add to
the controversy regarding the morphology of the ciliary ganglion.
The reader is referred to papers dealing more especially with the
ciliary ganglion or with general aspects of cranial nerve mor-
phology for more complete discussion, particularly v. Kupffer
(95), Hoffmann (’96, ’97, 799), Johnston ’(05), Carpenter (’06),
Belogolowy (710), and the recent paper of Neal (14). Kuntz
(13) has studied the development of the ciliary ganglion in the
pig, and believes it to arise from cells migrating peripheralward
from the neural tube along the oculomotor nerve, and from others
migrating from the semilunar ganglionic mass along the ophthal-
mic division of the trigeminus. Streeter (12) assigns the
ciliary ganglion in human embryos to cells which apparently arise
from the semilunar ganglion. In this respeet my own observa-
tions on the development of the ciliary ganglion in the rat accord.
The facts to be emphasized are the following: first, the anlage of
the ciliary ganglion is to be found in a direet anterior extension
over the optic stalk of cells continuous with, and apparently
similar to those found in the semilunar ganglion (fig. 17); secondly,

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 20)1

the growth in length of the ramus ophthalmicus V tends toward
an isolation of the more anterior elements and a seattering of
others along the ramus between its termination and the senilunar
ganglion (fig. 1%); thirdly, additions to the ciliary ganglion seem
to arise from cells which migrate outward along the ophthalmic
division of the trigeminus; fourthly, theee additions to the ganglion
arise as differentiations of elongate celle in the ramus ophthal-
micus, and the resulting cell type is constantly smaller than

wn 4
o> 8

g

Vig. 17 Rat embryo, 14 days, Carnoy’s 6-3-1, Neuroblasts in the growing
tip of the ramus ophthslmicus V (trans.). Projection drawing, %~ S00,

the first type observed in the ophthalmic division. The identity
of the first type of cell is maintained up until the fifteen and
three-quarter stage; after that it has not been distinguished.

The ganglion cella of the nervus terminalia

realizing that the present tendency of histologists is to regard
the ganglion cells of the nervus terminalis ae sympathetic in
character, some brief attention has been paid their origin. The
writer’s series is not complete in early stages in the development

202 FRED W. STEWART

of the olfactory sac, and statements made in this regard are
admittedly on the basis of limited material. In the rat no
evidence of a neural-crest origin for cells of the nervus terminalis,
as presumed by Johnston (’09), has been obtained. They,
instead, apparently arise from a proliferation of cells of the septal

Fig. 18 Rat embryo, 13} days, Bouin’s fluid. Neuroblasts scattered along
the ramus ophthalmicus V. Projection drawing, X 500.

aspect of the olfactory sack, including the epithelium of the
vomeronasal organ (fig. 19). The possibility suggested by
Hardesty (’14), that the ganglion cells of the nervus terminalis
may arise as a forward extension from the cervical sympathetic,
is searcely tenable. Cells appear among the fibers of the nervus
terminalis (of course, not differentiated from olfactory fila) before
there is any forward extension whatever from the cervical sympa-

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 203

thetic, and reach large size (fig. 20) much in advance of neuro-
blasts in the nearest cranial sympathetic ganglion, the spheno-
palatine. Despite the apparent sympathetic character of the
cells, it must be realized that where the central course of the
fibers has been studied, their afferent nature has been strongly

!

Com
x C.N.T.

20

Fig. 19 Rat embryo, 14 days, Carnoy’s 6-3-1. Cells of the nervus terminalis,
in process of proliferation from the epithelium of the vomeronasal organ. Pro-
jection drawing, X 500.

Fig. 20 Rat embryo, 15% days, vom Rath’s technique. Neuroblasts among
fila olfactoria. Projection drawing, x 500.

suggested, and although many excellent papers on the nervus
terminalis exist, no one person has followed both central and
peripheral course in a single form.

204 FRED W. STEWART

»

1
ae a

i ‘NS

Fig. 21 Schema to illustrate the writer’s interpretation of the origin of sympa-
thetic ganglia along the various cranial nerves. 1, The ciliary ganglion. 2, The
sphenopalatine ganglion. 3, The submaxillary and sublingual ganglia, together
with certain small ganglia of the anterior two-thirds of the tongue. 4, The otic
ganglion and certain ganglia of the plexus tympanicus. 4, Pharyngeal ganglia.
6, Small ganglia of the posterior third of the tongue. 7, Ganglia of the internal
carotid plexus, its allied plexuses, and certain ganglia of the tympanic plexus.
8, Ganglia along branches of the superior laryngeal nerve. 9, Cardiac ganglia.
10, Esophageal, tracheo-esophageal, gastric, pulmonary, and intestinal ganglia.

CRANIAL SYMPATHETIC GANGLIA IN THE RAT 205

SUMMARY

1. Large numbers of cells of vagus origin reach the cardiac,
intestinal, gastric, tracheal, esophageal, and possibly pharyngeal
plexuses.

2. Cells of glossopharyngeus origin give rise to certain small
ganglia of the pharyngeal wall, the posterior third of the tongue,
the tympanic plexus, and, in addition to these, to the otic ganglion.

3. The sphenopalatine ganglion is a ganglion belonging de-
velopmentally to the ramus palatinus VII (great superficial
petrosal).

4. The sphenopalatine and otic ganglia are therefore developed
from cells migrating along those nerve trunks which, in the
adult, carry preganglionic fibers to the ganglia.

5. Circumstantial evidence favors the interpretation that the
submaxillary and sublingual ganglia, together with certain small
ganglia of the anterior two-thirds of the tongue, are of facialis
origin, the path of*migration being the chorda tympani.

6. Neuroblasts giving rise to the ciliary ganglion reach the
orbit by way of the ramus ophthalmicus V.

7. The ganglion cells of the nervus terminalis originate in a
proliferation of cells of the olfactory sac.

8. Ganglion cells of the carotid plexus and its allied plexuses,
together with a portion of the cells of the tympanic plexus,
arise as extensions forward from the superior cervical sympa-
thetic ganglion.

206 FRED W. STEWART

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823-871.

LARSELL, OLor 1918 Studies on the nervus terminalis: mammals. Jour. Comp.
Neur., vol. 30, pp. 3-68.

Lennwosséxk, M. v. 1894 Zur Kenntnis der Spinalganglien. Beitrige zur
Histologie des Nervensystems und der Sinnesorgane. Bergmann,
Wiesbaden.

McKrispen, P. S. 1913 The eye-muscle nerves in Necturus. Jour. Comp.
Neur., vol. 23, pp. 153-172.

Nea, H. V. 1914 The morphology of the eye-muscle nerves. Jour. Morph.,
vol. 25, pp. 1-188.

208 FRED W. STEWART

Norris, H. W. 1908 The cranial nerves of Amphiuma means. Jour. Comp.
Neur., vol. 18, pp. 527-568.

Prentiss, C. W. 1904 The nervous structures in the palate of the frog; the
peripheral networks and the nature of their cells and fibers. Jour.
Comp. Neur., vol. 14, pp. 93-117.

1910 The development of the hypoglossal ganglia of pig embryos.
Jour. Comp. Neur., vol. 20, pp. 265-282.

Ranson, 8. W. 1911 Non-medullated fibers in the spinal nerves. Am. Jour.
Anat., vol. 12, pp. 67-88.

1914 The structure of the roots, trunk, and branches of the vagus
nerve. Jour. Comp. Neur., vol. 24, pp. 31-60.

1915 The vagus nerve of the snapping turtle (Chelydra serpentina).
Jour. Comp. Neur., vol. 25, pp. 301-316.

Rerzius, G. 1881 Untersuchungen iiber die Nervenzellen der cerebrospinalen
Ganglien und der iibrigen peripherischen Kopfganglien mit besonderer
Riicksicht auf die Zellenausliufer. Arch. f. Anat. u. Phys., Jahrg.
1880, Anat. Abth., 8. 369-402.

1894 Uber das Ganglion ciliare. Anat. Anz., Bd. 9, S. 633-637.
1894 a Ganglion ciliare. Biol. Unters., n. f., Bd. 6, 8. 37-40.

RuiNeEwART, D. A. 1918 The nervus facialis of the albino mouse. Jour. Comp.
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Spirutas, A. 1896 Zur Kenntnis der Spinalganglien der Saéugetieren. Anat.
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Srannius, H. 1846 Lehrbuch der vergleichenden Anatomie. Rostock.

1849 Das periphere Nervensystem der Fische. Rostock.
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Srreeter, G. L. 1912 The development of the nervous system. Human
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Weicner, K. 1905 Uber den Verlauf der Nervus intermedius. Anat. Hefte,
Bd.29, 8. 97-163.

PLATES

ABBREVIATIONS

B., bronchus G.S.N.IX, ganglion sympathicum,
G.C., ganglia cardiaca nerve IX

Gang. ling., lingual ganglia G.sph., ganglion sphenopalatinum
G.N.X., ganglion, nerve X G.T.E., tracheo-esophageal ganglion
G.O., ganglion oticum M., ramus mandibularis V

G.p.t., ganglion of plexus tympanicus N.IX., glossopharyngeal nerve

209

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 3

PLATE 1
EXPLANATION OF FIGURES

22 Rat embryo, 15 days, Carnoy’s 6-3-1. Neuroblasts massed along the
internal carotid nerve. Photograph, X 105.

23 Rat embryo, 15 days, Carnoy’s 6-3-1. Large aggregate of neuroblasts
along vagus trunk, level of cardia. Photograph, X 65.

24 Rat embryo, 15 days, Carnoy’s 6-3-1. Ganglion cells continuous with
those of the ganglion nodosum, as far caudad as the origin of the inferior laryngeal
nerve. Photograph, X 50.

210

PLATE 1

CRANIAL SYMPATHETIC GANGLIA IN THE RAT

FRED W. STEWART

211

PLATE 2
EXPLANATION OF FIGURES

25 Rat embryo, 17 days, Carnoy’s 6-3-1. Continuation of series of tracheo-
esophageal ganglia along bronchi, and into cardiac plexus. Photograph, X 145.

26 Ratembryo (gray), 5.6 mm., Zenker’s fluid. Ramus lingualisIX. Photo-
graph, X 180. { fie |

27 Rat embryo, 16 days, Carnoy’s 6-3-1. Clusters of neuroblasts along fibers
of ramus lingualis 1X in tongue. Photograph, X 142.

212

CRANIAL SYMPATHETIC GANGLIA IN THE RAT PLATE 2
FRED W. STEWART

PLATE 3
EXPLANATION OF FIGURES

28 Rat embryo, 15 days, Carnoy’s 6-3-1. Gasserian ganglion geniculate
ganglion, and otic ganglion. Photograph, X 55.

29 Rat embryo, 17 days, Carnoy’s 6-3-1. Ganglion of the plexus tympanicus.
Photograph, X 130.

30 Same.

31 Rat embryo, 14 days, Carnoy’s 6-3-1. Ramus palatinus VII; a marked
lateral extension near its anterior extremity indicates the anlage of the spheno-
palatine ganglion. Photograph, X 360.

32 Rat embryo, 15 days, Carnoy’s 6-3-1. A still rather diffuse, elongated
sphenopalatine ganglion. Photograph, X 92.

214

CRANIAL SYMPATHETIC GANGLIA IN THE RAT PLATE 3
FRED W. STEWART

PLATE 4
EXPLANATION OF FIGURES

33 Rat embryo, 17 days, Carnoy’s 6-3-1. A late stage showing the spheno-
palatine ganglion in contact with the Gasserian ganglion. Photograph, x 55.

34 Pig embryo, 15 mm., Zenker’s fluid. Diffuse cell strands, extending out-
ward from the ramus palatinus VII. Photograph, X 175.

35 Pig embryo, 17.5 mm., Zenker’s fluid. A fairly large but still exceedingly
diffuse sphenopalatine ganglion. Photograph, X 80.

36 Rat embryo, 17 days, Carnoy’s 6-3-1. Developing lingual ganglia.
Photograph, X 55.

216

CRANIAL SYMPATHETIC GANGLIA IN THE RAT PLATE 4

FRED W. STEWART

. Ra.
: Mole Lae os al

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL, 31, no. 4
APRIL, 1920

Resumen por el autor, Henry Carrol Tracy.
Escuela de Medicina Marquette.

El laberinto membranoso y su relacién con el diverticulo pre-
celémico de la vejiga natatoria en los cupleoideos.

En los peces cupleoideos existe alrededor del laberinto y el
cerebro un sistema de canales perilaberinticos formados a ex-
pensas de tejidos condensados y espacios intercelulares dife-
renciados en el tejido perimeningeo. Los cambios en la presién
hidrostatica pueden transmitirse directamente a la endolinfa
mediante este sistema de canales. El piso del receso utricular
esta unido a los bordes de la ventana existente en la cdpsula
del hueso prodético, la cual contiene a la vesicula membranosa
de paredes delgadas de la vejiga natatoria. La mancha del
receso utricular esta subdividida en tres partes, de las cuales
la anterior esta situada a lo largo de la linea de insercién del
piso utricular en el borde fenestral anterior, mientras que la
porcién media esta colocada a lo largo de la insercién en el borde
posterior. Entre estas dos porciones maculares se extiende la
membrana otolftica a través de la endolinfa. Esta membrana
presenta una estructura multilocular, en cuyos espacios se pro-
yectan las pestanas de las células maculares; se desarrolla prob-
ablemente a expensas de la cuticula situada sobre dichas células
a la cual se une la secreccién producida por estos ultimos ele-
mentos. Las células maculares’ probablemente forman un
receptor estimulado por cambios en la presién hidrostdtica.
Estos cambios.se transmiten por los canales perilaber nticos
hasta la endolinfa y desde esta por la ventana (estimulando de
este modo a las células de la macula) a la vesicula membranosa
de la vejiga natatoria. La estimulaci6én de las células maculares
probablemente produce reflejos que rigen el mecanismo regulador
de los gases contenidos en la vejiga natatoria 0, produciendo
movimientos compensadores en la nataci6én, tiende a mantener
al pez cerca de ciertos niveles del agua.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 2

‘THE MEMBRANOUS LABYRINTH AND ITS RELATION
TO THE PRECOELOMIC DIVERTICULUM OF
THE SWIMBLADDER IN CLUPEOIDS

HENRY C. TRACY

Department of Anatomy, University of Kansas

TWENTY FIGURES

CONTENTS

NAO MUG EVO MAT FFss-.c armas oe eateries each sere: # o's sia) © nfs Stossherehoteevane ayerh aisyes fore cuarerayevecopatere 219
Nacermnnaad "Met HOUS hs sre eeeae tars tas seid 24 cee eitoieeaees semtiee@uencie cnlee ew hee 220
ATO TMNTTN OL O Daye: erste esiceedee cea Tesi chcte sahara: Sie 2 care, coftopenaet area a epe ala roids tesphaTSia ene) oe 220
General histological structure of the swimbladder and the precoelomic

Givier-ticulurm skh see tree eras & la) «jt sic Gigs tiede @ em ebebs iste tel Rawte “veh at anstsindel eters 222
The perimeningeal tissue and the perilabyrinthine spaces.................. 224
Aer mem DCAM GUS Ab AIM ule ete). vice eR aielavg.c See yee ins, 310 Gabe w Syed ele whe 229
The function of the ear-swimbladder relation in Clupeoids................. 233
OLUATN OTT ie Ae aienes S a alot. CAoke oO COE eC LTO CO OOo Emre oe 241

INTRODUCTION

In a recent paper (Tracy, ’20) I have described the Clupeoid
skull and cranial nerves from the point of view of their rela-
tions to the precoelomic diverticulum of the swimbladder. In
that paper is also included a summary of previous investigations
on the ear-swimbladder relation in Clupeoids. This present
paper is concerned primarily with the swimbladder diverticu-
lum and the membranous labyrinth and their relations to each
other and to the skull. Of particular interest is the macula acus-
tica utriculi, which has not been previously described and which
in Clupeoids is different in structure and relations from that in
other groups of animals. The probable physiological signifi-
cance of these structures is also discussed in this paper.

The drawings were made by Mr. Leo Massopust, the depart-
ment artist at Marquette School of Medicine.

219

220 HENRY C. TRACY

MATERIAL AND METHODS

Adult specimens of the following common American species of
Clupeoids were examined: Alosa sapidissima (shad), Pomolobus
pseudoharengus (alewife), Pomolobus aestivalis (summer her=
ring), Pomolobus mediocris (hickory shad, fall herring), Bre-
voortia tyrannus (menhaden). The shad specimens were
bought in local markets; specimens of the other species were
obtained from the Marine Biological Laboratory where they had
been preserved in 10 per cent formalin.

In addition to the ordinary dissection methods, decalcified
heads of Pomolobus pseudoharengus were embedded in celloidin
and cut in various planes in sections 50, in thickness. This
method was particularly useful in the study of the condensed,
perilabyrinthine tissue and the canals contained within it. For
the study of these structures by dissection, A. sapidissima is the
most favorable of these species, because the perilabyrinthine
structures are larger and better defined than in the smaller species.
For the demonstration of the perilabyrinthine spaces, some use
was made of the cedar oil and chloroform method (Locy, ’16,
p. 542).

In addition to adult specimens of the above-named species,
there were also available a few young specimens of Brevoortia
tyrannus and about thirty stages of Stolephorus mitchilli (an-
chovy) ranging from 3 mm. up to half-grown specimens. These
were sectioned in various planes and stained by standard methods.
Most of these specimens I obtained some years ago from the
lobster rearing cars at the Experiment Station of the Rhode
Island Commission of Inland Fisheries, then under the director-
ship of Dr. A. D. Mead, of Brown University.

TERMINOLOGY

The remarkable series of spaces and differentiated tissues
which are described in detail in the body of this paper are un-
doubtedly modifications of the perimeningeal tissue which per-
vades the intracranial region outside the meninx primitiva. In
discussing them, it is not easy to select terms which have an

EAR-SWIMBLADDER RELATION IN CLUPEOIDS vt

accurate morphological value. The term ‘perimeningeal’
must be retained for the undifferentiated tissue around the
brain and labyrinth, and cannot, therefore, with definiteness be
applied to structures differentiated from it. The term ‘peri-
lymph’ or ‘perilymphatic’ which has been used by previous
writers in this connection is subject to the same objections which
Streeter (17) has advanced in discussing the somewhat analo-
gous structures around the membranous labyrinth in higher
vertebrates.

The term ‘periotic,’ or ‘perioticular,’ as it has been applied to
the tissues and spaces around the membranous labyrinth of
higher vertebrates is also objectionable in the case of the Clupe-
oids. Only a small part of the labyrinth in these fishes is en-
closed in an auditory capsule. The tissues and spaces around
the labyrinth are, therefore, continuous with, and never dif-
ferentiated from, the corresponding structures around the
brain, but they form a part of an extensive system of differen-
tiated tissues and spaces which extend through the perimenin-
geal tissue both above and below the brain and which reach out
through the lateral recess of the skull to the lateral-line canals.
These relations are obviously different in many respects from
those of the spaces around the membranous labyrinth of higher
forms to which Streeter applied the term ‘periotic’ or ‘perioticu-
lar.’ The use of this term in the case of the Clupeoids implies
an homology which is certainly not complete and which prob-
ably has little, if any, morphological significance.

The term ‘perilabyrinthine’ has therefore been chosen to
apply to all the specialized, condensed tissue and the spaces in
it, which are developed around the membranous labyrinth and
their extensions over and under the brain. ‘Perimeningeal’
will be used as is customary (following Sterzi) to designate all
the undifferentiated tissue between the meninx primitiva and the
cranial wall. It may be noted here that in certain regions of the
Clupeoid skull this tissue extends through large apertures in the
cranium and becomes continuous with the subcutaneous tissue,
particularly in the neighborhood of certain parts of the lateral-
line canals. Here accurate use of terms may be sometimes diffi-

222 HENRY C. TRACY

cult, but perimeningeal will apply to all this tissue except that
which is obviously subcutaneous.

The term ‘marginal membrane’ (used by Streeter for the
membrane limiting the developing periotic spaces of the human
embryo) seems appropriate for the incomplete connective-tissue
walls found around some of these spaces.

THE GENERAL HISTOLOGICAL STRUCTURE OF THE SWIMBLADDER
AND THE PRECOELOMIC DIVERTICULUM

The wall of the swimbladder is composed of a lining mucosa
(tunica interna) and an outer strong connective-tissue layer
(tunica externa). A thin layer of loose connective tissue (sub-
mucosa) joins these two layers. The histological details of
these layers in the Clupeoids have not been investigated com-
pletely. The epithelium in most parts of the organ is simple
squamous; in some places, however, and particularly in the
pneumatic duct, it is cuboidal or columnar, and in Alosa sapi-
dissima is thrown up in complicated folds which possibly form
a primitive type of ‘red gland.’ The tunica propria of the
mucosa seems to consist of a delicate connective or reticular
tissue, with a network of fine elastic fibers in a layer under the
epithelium; in the outer part of the mucosa is a second layer of
elastic tissue. In Stolephorus a thick band of circular smooth
muscle occurs in the tunica propria at the constriction between
the two parts of the swimbladder, in the walls of the pneumatic
duct, and at the entrance of the precoelomic diverticulum into
the cartilage tube.

The tunica externa is much thinner in the Clupeoid swim-
bladder than in that of many other teleosts. It is composed
almost wholly of coarse bands of connective tissue running cir-_
cularly in a compact layer around the organ. The only elastic
elements shown in my sections are fine fibers running in a radial
direction through this layer.

The precoelomic diverticulum of the swimbladder is formed
in the embryo by an anterior outgrowth from the forward end
of the anlage of the primitive swimbladder which pushes cephalad
into the cranial cavity. As might be expected from the manner

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 223

of its development, the diverticulum is structurally a continu-
ation of the mucosa (tunica interna) of the swimbladder, and is
made up of corresponding layers. The epithelium of the swim-
bladder continues from its anterior end (here simple squamous)
into the diverticulum, where it becomes columnar and is thrown
up into simple folds which suggest a glandular structure (fig. 1).
In the parts of the diverticulum inside the bones of the skull,
the epithelium becomes low cuboidal or squamous and is not
thrown up in folds (Stolephorus and Pomolobus). The epithe-
lium of the membranous vesicles is simple squamous (fig. 17).
The tunica propria in the tubular part of,the diverticulum is
thin but dense and at the beginning of the diverticulum in
Stolephorus contains a layer of circular smooth muscle. Very
loose, sparse connective tissue (submucosa) suspends the tube
in the cartilage canal (fig. 1). The connective tissue attach-
ing the membranous vesicles to the inner surface of the osseous
capsules is very loose; here the tunica propria and submucosa
blend into each other.

The posterior membranous vesicle of the swimbladder diver-
ticulum, which lies in the posterior osseous capsule, is practi-
cally the same in structure as that of the anterior membranous
vesicle. Since the posterior vesicle has no apparent relation to
the labyrinth or other structure outside the bony capsule, it will
not be discussed further in this paper.!

The cartilage tube around the diverticulum is continuous
with the tunica externa of the swimbladder and is probably the
morphological representative of that layer. The cartilage in
Stolephorus and Pomolobus presents, in sections, a somewhat
peculiar microscopic appearance, since the cartilage cells are
larger than usual in comparison with the amount of intercellular

1 The development of this vesicle is almost unknown. It is not formed until!
comparatively late stages. It is not present in Stolephorus or Brevoortia in
specimens earlier than 30 mm. in length. It is, however, fairly well developed’
in a young Stolephorus 38 mm. in length. The relations shown in this specimen
indicate that it develops by the formation of an outgrowth from the main branch
of the precoelomic diverticulum. This outgrowth pushes up into the space
within the canal for the diverticulum in the otic capsule (indicated by the end of.
the reference line CSD in fig. 15).

224 HENRY C. TRACY

matrix. A peculiarity of the tube in the shad (fig. 2) is the
indefiniteness of the perichondrium; the transition from fibrous
tissue to cartilage matrix is gradual and matrix formation has
proceeded’ into the surrounding connective tissue in a very
irregular manner. There is therefore an intimate connection
‘dorsally and at the sides of the tube with the muscular aponeuro-
sis on which it lies. These conditions produce the roughness
which is characteristic of the surface of the tube as seen in dis-
section. It is attached to the aponeurosis by strong threads of
connective tissue. The dimensions of this tube in one adult
specimen of Alosa, measured from the section by micrometer
methods, is as follows: outside diameter, 0.85 mm. in one dimen-
sion, 0.6 mm. in the other; least inside diameter, 0.12 mm.;
greatest inside diameter, 0.19 mm.; diameter of the membranous
diverticulum, 0.05 mm. In Stolephorus, outside diameter, 0.14
mm.; inside diameter, 0.075 mm.; diameter of the diverticulum,
0.03 mm.

THE PERIMENINGEAL TISSUE AND THE PERILABYRINTHINE
SPACES

The perimeningeal tissue over the top and sides of the brain
is for the most part undifferentiated and consists of a layer of
connective tissue, thick and fatty in most places, but mem-
branous and fascia-like over the lateral cartilage plate (Pomo-
lobus pseudoharengus). This fatty tissue also extends through
the temporal foramen and encloses the large bay of the lateral-
line canal which lies therein. The perimeningeal tissue extends
around the semicircular canals and between the outer side of
the sacculus and the corresponding bony wall of the auditory
recess; it fills the lateral recess and surrounds the expanded
part of the lateral-line canal in the recess. In these latter
situations, however, it apparently does not contain fat, but is
of a very loose, reticular-like structure.

Immediately around the membranous labyrinth and under the
brain, a considerable part of the perimeningeal layer is dif-
ferentiated into a tissue which is similar to that forming the
tunica propria of the epithelium of the labyrinth in other ani-

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 225

mals. This differentiated tissue is compact, elastic, tough, and
translucent, and is apparently composed of flattened bands, or
sometimes of irregular plates of fibro-elastic tissue so closely
held together by a cement substance that in sections it appears
in most places almost as homogeneous as the matrix of cartilage.
Flattened, stellate cells occupy irregular spaces between the
fibrous elements. .

In the Clupeoids, this differentiated tissue is not confined to
the cells and fibers immediately adjoining the epithelium of the
labyrinth, but forms definite processes and extensions which
reach into remote parts of the perimeningeal tissue. These are
the structures referred to as perilabyrinthine plates or processes
to distinguish them from the undifferentiated portions of the
perimeningeal tissue.

The most extensive of these perilabyrinthine structures in-
volves the greater part of the perimeningeal layer under the
brain. It takes the form of a horizontal plate (subcerebral
perilabyrinthine plate) which connects the thickened walls of
the utriculi of the two sides under the brain (figs. 8 and 11, SPP).
Anteriorly it extends a short distance in front of the utriculus
and its edge curves downward to become attached to the peri-
osteum on the surface of the anterior bony capsules of the two
sides and the ridge of bone connecting them (fig. 12, SPP).
The lateral edge of this forward extension of the plate in front
of the utriculus is attached to the arch leading to the lateral
recess of the skull (i.e., to the falciform process of the prootic
bone); over the utriculus, the lateral part of the plate is con-
tinuous with a sharp ridge-like thickening of the differentiated
perilabyrinthine tissue of the utricular roof which is continuous
with the thin perimeningeal tissue which lines the cartilage in
the lateral wall of cranium (fig. 11,*). Posteriorly the plate is
attached to the free anterior edges of the triangular plates of the
two exoccipital bones, so as to roof in the saccular recess on
each side. Thus the plate, with the connected thickening of the
utricular roof, forms a ‘false bottom,’ so to speak, of the cerebral
cavity, and by its continuous attachment with the margins of
the auditory recess completely excludes the latter from direct

226 HENRY C. TRACY

connection with the space around the brain (fig. 8). Over the
brain there is also a perilabyrinthine structure in the form of a
hollow rod or band which arches over the medulla behind the
cerebellum and connects the base of the superior sinus of the
labyrinth with the corresponding structure of the other side
(figs. 12 and 16, PSC).

Less extensive developments of the perilabyrinthine tissue
are found in other places, particularly around the superior
sinus and the superior end of the anterior semicircular canal
(Alosa) where it lies free in the cerebral cavity (figs. 7 and 12).
There is also a plate of this tissue which begins in the roof of
the extreme anterior end of the sacculus and passes laterally
involving the ventral wall of the utriculus; it is somewhat tri-
angular in form and extends under the pterotic segment of the
arch which leads into the lateral recess (figs. 9 and 12, TPP).
This plate is probably the structure which Breschet called the
‘bulbe accessoire; Ridewood describes an expansion of the
utriculus in this position. Tysowski, however, describes it as
merely a three-sided pyramidal thickening of the utricular wall.
A reconstruction of the cavity of the labyrinth definitely proved
that this structure contains no diverticulum of the labyrinth.

Condensed tissue also occurs as a local thickening of the
outer wall of the recessus utriculi and under the divisions of the
maculi acustica utriculi. It is important to note that the floor
of the recessus utriculi between, and on each side of, the anterior
and middle division of the macula acustica utriculi is thin and
contains little or no dense tissue (fig. 17).

Through certain parts of these plates and processes of com-
pact perilabyrinthine tissue, the forms and relations of which
have just been described, and through certain parts of the undif-
ferentiated perimeningeal tissue is an extensive system of
spaces and canals which result from a rarefaction or thinning
out of the tissue elements. In the manner of their develop-
ment, these spaces and canals are probably comparable with the
perioticular spaces of the mammalian ear as described by Streeter
(17). In some of these spaces the rarefaction of the tissue is
merely relative as compared with the compact tissue; in others

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 227

only a few delicate fibers remain in them. These spaces are
merely tissue spaces formed by modification of the perimenin-
geal or perilabyrinthine tissue, and they are probably not
directly homologous with the spaces around the labyrinth in
higher forms.

These canals are in direct connection with tissue spaces in
the lateral recess. The tissue of this cavity is composed of a
meshwork or reticulum of connective-tissue strands or trabec-
ulae. It contains no fat. The spaces of this meshwork are
of varying sizes and communicate freely with each other. One
very large space (in diameter nearly half of the whole width of
the recess) appeared in all specimens which I sectioned and is
probably constant. It lies close to the lateral-line canal. It is
bounded by a very definite marginal membrane of modified
connective tissue. Numerous small deficiencies in the mem-
brane, mostly on the mesial side of the space, allow free com-
munication with the spaces in the reticular network. These
spaces in turn communicate with the perilabyrinthine spaces
mentioned above and, together with them, form a complicated
system of intercommunicating canals which have a definite
relation with the membranous labyrinth and other structures.

These perilabyrinthine spaces and canals may be considered
in three groups, viz., lateral, subcerebral, and supracerebral.

The lateral group of spaces consists of the tissue spaces of the
lateral recess which have been described above. They are
immediately continuous (figs. 11 and 12) with the utricular
subcerebral canal under the recessus utriculi. They also com-
municate with the supracerebral canal through an opening in the
triangular plate (7PP) and the reticular spaces which lie lateral
to the utriculus and the superior sinus.

The subcerebral group comprises two canals, the utricular
subcerebral canal and the saccular subcerebral canal. These
canals are excavated from the lower surface of the subcerebral
perilabyrinthine plate (fig. 11, USC and SSC). The lumen of
both is occupied by an exceedingly sparse network of very deli-
cate connective-tissue fibers. The utricular subcerebral canal
is the more anterior and runs transversely across the floor of

228 HENRY C. TRACY

the skull between the two lateral recesses. It begins on each
side under the utriculus where it occupies the whole space
between the floor of that structure above and the surface of the
anterior osseous capsule below (fig. 12). It is partially sub-
divided into an anterior and posterior part by the projecting
lips of the fenestra on which the utriculus rests (figs. 5, 9, 12,
and 17; USCA, USCP). In the utricular region the roof of the
canal is formed by the floor of the recessus utriculi in which
are located the divisions of the macula acustica utriculi. The
floor of the utriculus is very thin except under the divisions of
the macula.

Laterally the canal connects freely with the tissue spaces
in the lateral recess under the arch made by the apposition of
the falciform process of the prootic bone with the projecting
anterior part of the pterotic bone. Thus, the lateral spaces
of each side communicate freely with each other through the
canal. There appears to be no obstacle to the free transmis-
sion of pressure changes from the outside through the lateral-
line canal and the lateral spaces to the two parts of the utricular
subcerebral canal and thence to the floor of the utriculus on
each side of the lips of the fenestra.

A small blind extension of this canal passes up over the
mesial narrow side of the recessus utriculi in close relation to the
epithelium. From the space between the utriculus and the
anterior osseous capsule, the canal passes medially straight
across the floor of the skull under the brain to become con-
tinuous with the corresponding structure of the other side
(fig. 11).

The utricular subcerebral canal is the best-defined of all the
perimeningeal spaces. It is easily visible to the naked eye and.
has been observed by all investigators from Weber on. Weber
and Ridewood considered it an endolymphatic canal. I have
studied many series of sections of young and adult Clupeoids,
and there can be no doubt whatever that it is a tissue space,
differentiated from the perimeningeal tissue under the mem-
branous labyrinth and brain. Tysowski and de Beaufort, the
only investigators to study the canal with modern technic,
emphatically testify to the same conviction.

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 229

A similar canal short but of larger diameter, connects the
loose tissue on the mesial surfaces of the two sacculi. This
saccular subcerebral canal has previously been mentioned only
by Tysowski.

The supracerebral canal is a space in the hollow band of
compact tissue which arches over the medulla behind the cere-
bellum (fig. 16). As this passes down posterior to the superior
sinus of the utriculus, it divides (figs. 4, 5, 6, and 7; PSCM,
PSCL); one banch passes through the compact perilabyrinthine
tissue mesial to the sinus and connects with spaces mesial to
the sacculus, the other gradually passes behind and then lateral
to the sinus and connects with the lateral spaces above men-
tioned. This branching of the supracerebral canal may per-
haps explain the conflicting views of Breschet and Hasse.
Breschet must have seen merely that part of the supracerebral
canal which passes between the two superior sinuses; Hasse
doubtless traced the branch of the canal which passes down to
the sacculus mesial to the sinus and assumed it to be the endo-
lymphatic duct.

The upper chamber of the anterior osseous capsule contains
only a very sparse connective tissue. It is apparently very
similar in structure to the perilabyrinthine spaces. It will be
observed, therefore, that only a very loose and rarefied con-
nective tissue intervenes between the elastic septum of the
osseous capsule and the thin part of the utricular wall which
bridges the fenestra and connects the anterior and middle
divisions of the macula.

THE MEMBRANOUS LABYRINTH

The form and structure of the membranous labyrinth of the
Clupeoids appear on dissection quite different from those of
other teleosts, because the thickenings of the compact tissue,
as described above, do not conform externally to the shape of
the utriculus and sacculus. Nevertheless, the epithelial part
of the labyrinth is essentially like the teleostean labyrinth in gen-
eral except in the form of the recessus utriculi and the structure
of the macula acustica utriculi.

230 HENRY C. TRACY

The labyrinth lies in the auditory recess suspended there by
the thickenings and processes of the compact perilabyrinthine
tissue. The utriculus occupies the lateral and anterior part of
the recess. The recessus utriculi is enlarged transversely into
a flattened somewhat wedge-shaped chamber. The narrow
part of the chamber extends a little under the brain mesially
while the broader part fits up under the arch made by the falci-
form process and the projecting part of the pterotic bone, and
is thus in relation by its lateral surface to the lateral recess of
the skull; ventrally, the surface of the recessus utriculi rests
directly on the lips of the slit-like fenestra of the anterior bony
capsule (fig. 12). Sections show conclusively that no part of the
labyrinth enters the fenestra. What Weber and Ridewood mis-
took for a utricular diverticulum is merely the tissue space in
the upper chamber of the osseous capsule above the septum.
Under the recessus utriculi is the subcerebral perilabyrinthine
canal, which, as described above, is here subdivided into an
anterior and posterior canal (USCA, USCP) by the projecting
lips of the fenestra as a result of their attachment to the floor
of the utriculus.

The macula acustica utriculi is differentiated into three parts
which run transversely across the floor of the broad wedge-
shaped recessus utriculi; the anterior division (fig. 17, MAA)
lies along the line of attachment of the floor of the recessus
utriculi to the anterior lip of the slit-like fenestra of the anterior
osseous capsule; the middle division (MAM) runs along the line
of attachment to the posterior fenestral lip; the posterior divi-
sion (MAP) lies a little farther back, and in no particular rela-
tion to structures outside the utriculus. These three divisions
slightly diverge laterally; mesially they unite in a common area
which lies in the narrow part of the wedge-shaped recessus
utriculi nearly over the mesial end of the fenestra. Under each
division of the macula, the tunica propria is rather thick and
contains the branches of the eighth nerve which supply the
macular cells. The middle band of the thickened tunica pro-
pria under the middle division of the macula is shaped like a
three-sided prism which is attached by its edge to the posterior

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 231

lip of the fenestra by very delicate connective-tissue strands which
are usually torn off in dissection. This band of tunica propria
‘and its overlying macular cells projects about equally over the
opening of the fenestra and over the posterior division of the
utricular subcerebral canal (fig. 17). The tunica propria of the
anterior division of the macula is thinner and band-like and is
loosely attached to the edge of the anterior fenestral lip.

The anterior and middle divisions of the macula consist of
band-like areas of a two-layered epithelium (fig. 19). The basal
layer is composed of small cells with small round, dense nuclei;
the upper layer is of columnar cells, in which the cytoplasm
distal to the nuclei is densely granular and with indistinct cell
walls. Under the cuticulum of each cell is a small round, dense
body staining heavily with iron hematoxylin. Running out
from this body is a rather long cilium which is quite stout and
stains deeply near its origin.

The anterior and middle divisions of the macula are sepa-
rated by only a slight interval and they lie in planes which
are nearly at a right angle to each other. Bridging across this
angle and connecting the two macular surfaces through the
endolymph, is a structure which in the early and adolescent
stages of development appears as a thick hyaline plate. In the
adult this plate has become transformed into an otolith by the
deposit of caleareous granules within it or on its upper surface.
Hence, I shall refer to the structure as the otolithic membrane
of the macula acustica utriculi. Its shape is determined by the
interval between the two macular divisions, and hence it forms a
long narrow triangle. Its apex is rounded mesially where the
two divisions of the macula unite; laterally it ends in a free edge.
The other edges spread out to cover the two macular surfaces.

The middle part of this plate in the adolescent stages of
Stolephorus appears to be hyaline and structureless with the
exception of some horizontal striations. On each side of the
middle, the membrane appears to contain a great number of
cells or chambers like a honeycomb which end blindly toward the
middle of the membrane, but open onto the macular surfaces.
The plate undergoes much shrinkage during histological prepa-

232 HENRY C. TRACY

ration, and hence is always seen pulled off from one or both of
its surfaces of attachment. There are often, however, attach-
ing strands which extend down to the surface of the macular
cells (particularly in the case of the anterior division).

The relation of the otolithic membrane to the labyrinth epi-
thelium and to the endolymph at once suggests a comparison
with the tectorial membrane of the mammalian ear. According
to the conclusions of Prentiss (’13), the latter is primitively a
cuticular organ of a chambered structure which is secreted
between and at the ends of the cells composing the basal epi-
thelium of the cochlea. The otolithic membrane in Clupeoids
is probably formed by an analogous process.

This chambered structure appears in sections of the organ in
all specimens from about 6 mm. up. In figure 20 is shown a
section through that part of the otolithie membrane which
covers the middle division of the macula; the section passes
nearly parallel to the surface of the latter, and hence at right
angles to the chambers. The section appears as a plate perfor-
ated with round holes. Near its margins the holes become oval
and then elongated and less distinctly visible, due doubtless to
the more oblique angle at which the chambers are sectioned.
When studied by means of the high-power binocular microscope
with oblique substage illumination, a dark rim always appears on
one side of each hole. By rotating the decentered substage
diaphragm the dark rim is seen to move evenly around the mar-
gin of each hole. The only probable interpretation seems to be
that the dark rim is a refractive phenomenon and the holes are
circular, each with a smooth even circumference. I was unable
to demonstrate sections of cilia in these holes. If account is
taken of the amount of shrinkage which the membrane under-
goes in preparation, it is fair to assume that these chambers
have been considerably enlarged by the shrinkage process. This
consideration and the circular shape of the sections of the cham-
bers suggest that they may in life be just large enough to accom-
modate the cilia. Probably, then, the substance of the mem-
brane begins as a cuticulum, and is further developed by secre-
tion from the tops of the macular cells, and in this secretion the

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 233

cilia are embedded. The chambers as they appear in fixed
material are produced by shrinkage of the membrane substance
away from the cilia.

De Beaufort has briefly mentioned the macula acustica in
the Clupeidae. He says (’09, p. 619): “Mit dem utriculus
existiert daher keine Verbindung, wohl liegt aber seine ventrale
Fliche mit der Macula acustica oberhalb der erwahnten Off-
nung der Bulla.” Tysowski gives a figure (’09, fig. 1) in which
the macula is shown lying over the fenestra of the bulla. His
figure seems to show the division of the organ into three parts,
but he makes no mention of it in his text.

THE FUNCTION OF THE EAR-SWIMBLADDER RELATION IN
CLUPEOIDS

The swimbladder has a complexity of function correlated
with the diversity of its anatomical structure. Bridge and
Haddon (93) thus summarize the functions which have been
attributed to the organ in different species of fishes: 1) phona-
tion, 2) respiration, 3) accessory to audition, 4) purely hydro-
static. The swimbladder of many species probably has more
than one of these functions, but different functions in varying
degrees. Hence, its physiology is a complicated problem which
requires for complete solution a separate investigation in each
of the structural types of the organ. Results of experimental
work on fishes with a certain type of the organ can hardly be
assumed to apply in every case without modification to fishes
having a different type. Moreau (’76) and Baglioni (’08) have
laid the foundation of our knowledge of the general physiology,
but on the function of the specialized types of the swimbladder
very little recorded experimental work can be found. An ex-
ception to this statement is the work of Tower (’08) on the
sound-producing function of the organ in certain groups of
fishes.

The ear in fishes is also an organ of complicated physiology.
Audition and equilibration are functions usually assigned to
this organ, but experimental evidence on the differentiation of
functions in the different parts of the membranous labyrinth is
incomplete (Lee, 98; Parker, ’08).

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 4

234 HENRY C. TRACY

The physiological problem is even more complicated when
it is a question of the function of these two organs, brought
into relation to each other by a definite mechanism. Is one
‘organ accessory to the other, and, if so, which of the several
functions of one organ does the other subserve? Or, is some
entirely new function evolved as the result of their interrelation
by the development of a connecting mechanism?

Most of the anatomical papers on the ear-swimbladder rela-
tion offer suggestions and sometimes extended discussions on
the physiology of the mechanism, but it seems remarkable that
in a century since Weber no experimental work on this unique
relation has been recorded. The theories suggested cannot be
discussed here in detail, but the most important of them may be
summarized as follows: 1) accessory to hearing (Weber); 2)
perception of hydrostatic pressures (Hasse); 3) appreciation of
changes in barometric pressures (Sagemahl). Bridge and
Haddon (’93), in an important paper on the Weberian ossicles,
have shown that the anatomical structure of this mechanism is
not consistent with the first or third theory, but is adapted to
perception of changes in hydrostatic pressures. Wright (’84)
came to the same conclusion.

With regard to the physiology of the Clupeoid type of the
ear-swimbladder relation, little has been written. At the pres-
ent time, however, the anatomical relations of these structures
are perhaps sufficiently well known to justify the statement of a
physiological theory, which it is to be hoped may be confirmed
or modified later by experimental work.’

* The lateral recess of the skull would appear to furnish an easy means of
reaching the ear-swimbladder mechanism in Clupeoids in experimental work

(fig. 12). This recess is separated from the outside only by the lateral wing of
the frontal bone which is quite superficial. The Clupeoids, however, or at least
the American species, seem in general unfavorable for physiological experimenta-
tion. They are free-swimming in their habit and hence do not thrive when con-
fined in small enclosures. They are delicate and of a ‘nervous temperament,’
so to speak, and they do not easily adjust themselves to handling and to opera-
tive procedures. Fishes with the Weberian ossicles, e.g., siluroids and certain

cyprinoids, would appear to be much more favorable for experimental study of
the ear-swimbladder relation.

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 235

The mechanical relation of the swimbladder to other struc-
tures is shown diagrammatically in figure 8. The swimbladder
is a tube of very small diameter in comparison with the size of
the body of the fish and with the thickness of its muscular wall;
it has no direct connection with the skin or other superficial
structures, as is the case in many other groups of fishes (with
the exception in some species of a postanal connection with
the exterior, which will be discussed below). It may there-
fore be assumed that the thick muscular wall of the body, sup-
ported by vertebrae, ribs, scales, spines, etc., interferes with the
direct and immediate transmission of changes in hydrostatic
pressure from the surrounding water to the swimbladder. In the
head, however, the anatomical structure indicates that there
exists a pathway for the transmission directly to the anterior
membranous vesicle of changes in the outside pressure resulting
from movement of the fish from one water level to another.

The pressure transmission from the outside to the walls of the
vesicle may be assumed to take the following pathway (indi-
cated by the arrows A, A1, A2, fig. 8): from the lateral-line
canal in the lateral recess to the lateral perilabyrinthine spaces,
thence to the whole system of perilabyrinthine canals, particu-
larly to the utricular perilabyrinthine canal (with which the
lateral spaces are in direct connection), thence through the two
parts of that canal, around the lips of the fenestra, to the floor
of the recessus utriculi, then through the endolymph down
through the fenestra— and through the superior chamber of the
osseous capsule and the elastic septum to the wall of the anterior
membranous vesicle. Since the walls of the gas-filled vesicle
beneath the septum are thin and loosely attached to the sides
of the inferior chamber of the bony capsule, the vesicle easily
expands and contracts, and hence pressure transmission from
the outside to it will cause a mass movement of fluid along the
pathway indicated. The parts of the utricular wall immedi-
ately adjacent to and in between the anterior and posterior
divisions of the macula are thin with little or no condensed
tissue. The thin floor of the utriculus between the two divi-
sions of the macula overlies the fenestra, and hence is in the

236 HENRY C. TRACY

direct pathway of the transmission of pressure. Since each of
the macular divisions is very loosely attached to the edge of
the fenestral lips, the fluid movement resulting from the trans-
mission of force through the fenestra may cause a slight motion
of the divisions of the macula which will result in a stimulation
of the macular cells by the cilia embedded in the otolithic
membrane.

A possible objection to this theory of the mechanics of these
structures as stated above may be alleged, owing to the fact
that in some of the Clupeoid species the caudal end of the
swimbladder opens directly to the exterior just behind the anal
opening. In the majority of the Clupeoids and allied forms,
however, the postanal connection of the swimbladder with the
exterior is not present. De Beaufort (09) names nine species
with an opening near the anus and fifteen without such an
opening. Of the American species (not included in the list of
de Beaufort), Alosa sapidissima, Brevoortia tyrannis, and
Stolephorus mitchilli have no anal communication. In species
in which the opening is present the communication takes place
through a slender thin-walled tube which curves around to the
left between the genital and kidney ducts to the left body
wall and opens to the exterior between the genital opening and
the anus (de Beaufort, ’09, described in Clupea harengus). It
might be said that the expansion or compression of the gas in
the swimbladder may take place directly through the postanal
opening (in those species in which it exists) and thereby bal-
ances the pressure transmitted to the wall of the anterior mem-
branous vesicle along the pathway indicated above to such a
degree that pressure transmission through the head would not
be effective in originating a stimulus in the divisions of the
macula. Possibly this may be true to some degree for extreme
and very sudden changes in the hydrostatic pressure of the
surrounding medium. It seems hardly probable, however, that
the transmission of changes in hydrostatic pressure through a
slender, curved, thin-walled tube could be as direct or as imme-
diate as through the perilabyrinthine spaces. The possibility
of the transmission of changes in hydrostatic pressure to the

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 234

body of the swimbladder either directly through the anal region
or even indirectly through the fluid-permeated tissues of the body
of the fish cannot be denied. But the requirements of the
theory as stated above are sufficient if it can be shown that
transmission of the pressure changes through the lateral recess
and the perilabyrinthine canals to the anterior membranous
vesicle is more direct, more immediate, and more sensitive to
slight variations than the transmission of pressure changes
through the body walls or through the postanal opening to the
body of the swimbladder.

An auditory function may possibly be attributed to this
mechanism. This was the view expressed by most of the older
anatomical writers. Weber (1820), for example, considered that
the septum in the anterior osseous capsule functions as a tym-
panic membrane. The anatomical structure of this mechanism
hardly appears to support this view. To be effective as an
aid to hearing, it must be constructed so as to transmit molecu-
lar vibrations from the outside to the membranous labyrinth
more quickly or more efficiently than they can be transmitted
by other existing structures in the head of the fish. Whereas,
it would appear that the molecular vibrations of sound waves
would pass more easily to the membranous labyrinth directly
from the water through the bones and fluid-permeated tissues of
the head. This apparatus is so constructed that we have a
pathway adapted for a mass motion of fluid; it can hardly be
considered as a means of increasing efficiency of transmission
of the molecular motion of sound waves. These considerations
are similar to those which lead Bridge and Haddon to conclude
that the Weberian ossicles are for the transmission of hydro-
static pressures and not accessory to audition.

If the functional significance of these structures can be shown
to be essentially as stated above, the anterior and posterior
divisions of the macula acustica utriculi are together to be con-
sidered as a ‘depth sense organ’ or, more accurately speaking, a
receptor which is stimulated by changes in hydrostatic pres-
sure which usually, or perhaps always in the normal life of the
fish, result from movements from one water level to another.

238 HENRY C. TRACY

The anterior membranous vesicle enclosed in the osseous capsule,
the enlargement of the lateral-line canal in the lateral recesses,
the lateral recess of the skull, the perilabyrinthine canals, and
the otolithic membrane are to be considered as accessory struc-
tures by which the stimulus is brought to bear on the receptor.

This mechanism as a whole may be conceived to function in
one of the following ways:

1. Merely as a sense organ which acquaints the fish with
changes in water level.

2. As a part of a reflex mechanism actuated by changes in
water level, originating nerve impulses which pass out by effer-
ent fibers of the spinal nerves to the skeletal muscles, thereby
producing compensatory movements which tend to maintain the
fish at a nearly constant water level.

3. As a part of a reflex mechanism which through efferent
visceral nerves transmits nerve impulses to the secretory cells
and smooth muscle fibers in the swimbladder wall and which
thus adjusts the swimbladder to changes in hydrostatic pressure.

4. By some combination of two or possibly of all three of
these functions. ,

To consider this ear-swimbladder mechanism ‘merely as a
sense organ” (whatever that term may mean) is hardly adequate
in view of our present conceptions of the nervous system in gen-
eral and the nerve connections of the membranous labyrinth
in particular. In all vertebrates the maculae and cristae seem
to function primarily (and possibly exclusively) through reflex
mechanisms. It is probably safe to affirm this positively in
case of the lower vertebrates. It is therefore almost certain
that this apparatus acts reflexly according to the second or
third possibility as stated above or by combination of the two. —
We know, through the work of Moreau, Baglioni, and others,
that in the case of the Physoclisti the gas pressure inside the
swimbladder is adjusted to changes in the outside water pres-
sure as a result of an interaction between the absorptive and
secretory mechanisms in the wall of the organ. In the Clu-
peoids there is an epithelium, apparently secretory, in the
pneumatic duct and probably in the tubular portion of the

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 239

precoelomic diverticulum; smooth muscle surrounds the open-
ing of the diverticulum to the body of the swimbladder and is
also found in the walls of the pneumatic duct which opens into
the stomach. Apparently, therefore, a mechanism for the ad-
justment of the gas pressure in the swimbladder exists; the
nerve impulses controlling it are doubtless of a reflex nature and,
in the absence of experimental evidence to the contrary, it seems
a reasonable hypothesis that the source of the afferent impulses
of this reflex is in the divisions of the macula recessus utriculi.

That this mechanism is effective in maintaining the fish at a
nearly constant level is scarcely consistent with what little is
known regarding the habits of these fishes.

It is known that herring and menhaden, within a few minutes,
will dive below the surface to depths greater than the bottom of
the purse seines of the fishermen. Possibly, however, while
this mechanism may not suffice to force the fish to remain
near one level, it may by compensatory motions of fins and body
musculature tend to prevent the fish from departing far from a
certain level except in extreme cases.

This apparatus, however, may be effective in maintaining
the fish at certain water levels within certain wide limits. The
mechanism of secretion and absorption of gas in the body of
the swimbladder probably has its physiological limits; it is
possible that the mechanism described may prevent the fish
from descending to depths greater than those at which the fish
is able to adjust the gas pressure in the body of the swim-
bladder to the hydrostatic pressure.

Anatomical work, however, can hardly go further than the
statement of the problem and the discussion of its possibilities.
Further analysis of the function of this mechanism can only be
attained by experimental work.

240 HENRY C. TRACY

SUMMARY

1. The swimbladder in Clupeoids is composed of a mucosa
(tunica interna), a submucosa, and an outer dense connective-
tissue layer (tunica externa).

a. In the body of the swimbladder and in the membranous
vesicles, the lining is simple squamous epithelium, but in the
pneumatic duct and in the precoelomic diverticulum the epi-
thelium is columnar and apparently glandular in structure.

b. A circular layer of smooth muscle is found around the
pneumatic duct and at the beginning of the precoelomic
diverticulum.

c. The glandular cells and the smooth muscle probably regu-
late the gas pressure in the swimbladder.

2. The perimeningeal tissue is differentiated in certain places
into a compact elastic tissue (perilabyrinthine) which extends
away from the walls of the labyrinth under the brain (subcere-
bral plate) and in a band over the medulla just behind the cere-
bellum (supracerebral band). Less extensive developments of
this tissue are found in relation to other parts of the labyrinth.

3. A complicated system of intercommunicating canals and
spaces of rarefied connective tissue extends through the peri-
labyrinthine tissue around the brain and labyrinth. These
spaces may be grouped in three divisions:

a. Lateral, spaces in the tissue in the lateral recess near the
lateral-line canal and lateral to the labyrinth.

b. Subcerebral, two canals traversing the under surface of
the subcerebral perilabyrinthine plate; the posterior of these
canals (saccular subcerebral canal) connects the saccular por-
tions of the auditory recesses of the two sides; the anterior canal
(utricular subcerebral canal) connects the lateral recesses of the
two sides of the skull by passing under the utriculus where it is
partially subdivided into two canals by the projection of the
lips of the fenestra of the anterior osseous capsule.

c. Supracerebral, the canal in the supracerebral perilabyrin-
thine band over the medulla.

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 241

4. The floor of the recessus utriculi rests on the lips of the
fenestra and is attached to them by delicate connective-tissue
strands. The utriculus does not send a diverticulum into the
superior chamber of the anterior osseous chamber.

5. The upper chamber of the anterior osseous capsule con-
tains very sparse connective tissue and is similar in structure to
the perilabyrinthine spaces.

6. The macula recessus utriculi on the floor of the recessus
utriculus is subdivided into three parts (anterior, middle, and
posterior). The anterior and middle parts of the macula are so
situated that they lie along the line of attachment of the floor
of the recessus utriculi to the anterior and posterior fenestral
lips, respectively.

7. The space between the anterior and middle divisions of the
macula is bridged by the otolithic membrane in which the cilia
of the macular cells are probably embedded.

8. The otolithic membrane originates from the cuticulum over
the macular cells. Probably its further development takes
place by the secretion of substance from the surface of the
macular cells.

9. The perilabyrinthine canals form a system of spaces
through which changes in hydrostatic pressure of the water are
transmitted to the thin walls of the anterior membranous vesicle.
The mechanical relations are such that this transmission of pres-
sure causes a slight motion of the anterior and middle divisions
of the macula acustica utriculi, and a consequent stimulation
of the cells by means of the cilia embedded in the otolithic
membrane.

10. The anterior and middle divisions of the macula acustica
utriculi constitute a receptor stimulated by changes in hydro-
static pressure resulting in the movement of the fish from one
water lével to another.

11. Impulses arising from this receptor probably originate
the reflex which controls the gas-regulating mechansim in the
swimbladder. They may also give rise to reflexes which produce
compensatory movements of the swimming musculature and
thereby maintain the fish within certain water levels.

242 HENRY C. TRACY

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Weser, E. H. 1820 De aure et auditi hominis et animalium, De aure ani-
malium aquatilium. Lipsiae, Pars 1.

Wricut, Ramsay 1884 The relationship between the airbladder and audi-
tory organs in amiurus. Zool. Anz., vol. 7.

Wricut, Ramsay 1884 The nervous system and sense organs of amiurus.
Proc. Canadian Institute, Toronto. Series III, vol. 2.

FIGURES

ABBREVIATIONS

A, A, A®, arrows in figure 8 to show
the probable direction of transmis-
sion of hydrostatic pressure from the
outside to anterior membranous
vesicle

AO, aorta

AOC, anterior osseous capsule

ASCA, ampulla of anterior semicircu-
lar canal

ASCL, ampulla of lateral semicircular
canal

ASP, alisphenoid bone

AV, anterior membranous vesicle

BAOC, bone of anterior osseous cap-
sule

BR, brain

BSO, basioccipital bone

CA, crista acustica in ampulla of the
anterior semicircular canal

CC, cartilage of the canal of the swim-
bladder diverticulum

CI, inferior chamber of anterior osseous
capsule

COC, cartilaginous otic capsule

CS, superior chamber of anterior osse-
ous capsule

CSD, canal of the swimbladder diver-
ticulum in the cranium

E, eye

EMV, Epithelium of the membranous
vesicle of the swimbladder

EPO, epiotic bone

EXO, exoccipital bone

F, fenestra

FB, fusiform bulla of the pre-coelomic
diverticulum of the swimbladder

LC, lateral-line canal

LF, lip of the swimbladder of the
fenestra

LR, lateral recess of the skull

MAA, anterior division of macula
acustica utriculi

MAM, middle division of the macula
acustica utriculi

MAP, posterior division of the macula
acustica utriculi

MD, medulla

MV, embryonic membranous vesicle of
precoelomie diverticulum

NAM, nerve of the anterior division of
the macula acustica utriculi

NPM, nerve to the posterior division of
the macula acustica utriculi

OM, otolithic membrane

P, periosteal lining of the anterior
osseous capsule continued on the
surface of the septum

POC, posterior osseous capsule

PRO, prootic bone

PSB, precoelomic diverticulum of the
swimbladder

PSC, supracerebral perilabyrinthine
canal

PSCL, branch of supracerebral peri-
labyrinthine canal which connects
with the perilabyrinthine spaces of
the lateral recess

PSCM, branch of the supracerebral
perilabyrinthine canal which opens
medially to the sacculus

PV, posterior membranous vesicle

RU, recessus utriculi

243

244

RX, recurrent ramus of vagus nerve

S, sacculus

SB, body of the swimbladder

SC, septum of anterior osseous capsule

SCA, anterior semicircular canal

SCL, lateral semicircular canal

SCP, posterior semicircular canal

SPA, sphenotic bone

SPP, subcerebral plate of perilaby-
rinthine tissue

SS, superior sinus of the utriculus

SSC, saccular subcerebral perilaby-
rinthine canal

TPEXO, triangular plate of the exoc-
cipital bone

TPP, triangular plate of perilabyrin-
thine tissue lateral to utriculus and

HENRY C.

TRACY

sacculus (‘accessory bulb’ of Bres-
chet)

USC, utricular subcerebral perilaby-
rinthine canal

USCA, utricular subcerebral perilaby-
rinthine canal anterior to the lips of
the fenestra

USCP, utricular subcerebral canal
posterior to the lips of the fenestra

VN, vein

VT, vertebral column

VI, abducens nerve

VIII, acustic nerve

IX, glossopharyngeal nerve

*, ridge in thickened roof of utriculus
which is continuous with the peri-
meningeal tissue lining the lateral
wall of the cranium

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 245

Fig. 1 Section through the cartilage canal and the precoelomic diverticulum
of the swimbladder of Stolephorus mitchilli.

Fig. 2 Section through the cartilage canal and the precoelomic diverticulum
of the swimbladder of Alosa sapidissima.

246 | HENRY C. TRACY

Fig. 3 Diagram of the right membranous labyrinth and supracerebral peri-
labyrinthine canal of Alosa sapidissima, based on figure 12; orientation diagram
of the approximate planes of the sections shown in figures 4, 5, 6, and 7.

Figs. 4, 5,6, and 7 Sections through the right labyrinth and supracerebral
perilabyrinthine canal at levels shown in the orientation figure (fig. Be

EAR-SWIMBLADDER RELATION IN CLUPEOIDS 247

TRACY

HENRY C.

248

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-dal1Ip oy} MOYsS ‘ZY pue ‘TY ‘VY ‘sMOLIV oY, ‘Sploodn[y oy} ul pvay pus Apoq
aq} 0} LOppR[quUIIMS OY} JO UOIZRIAI OY} MOYS 0} SUIMBIP OIVUIUIBIZBIG: g “BI

249

THE JOURNAL OF COMPARATIVE NEUROLOGY, vou. 31, No. 4

250 HENRY C. TRACY

Fig. 9 Dissection from the right ventrolateral side of the skull to show the
relation of the membranous labyrinth to the anterior osseous capsule, also the
relation of the anterior and middle divisions of the macula acustica utriculi
to the lips of the fenestra. Pomolobus pseudoharengus.

Fig. 10 Drawing of the ventrolateral side of a reconstruction model of the
left labyrinth and of the single embryonic membranous vesicle. Stolephorus
mitchilli, 28 mm. in length. The three cristae acusticae in the ampullae of the
semicircular canals are shown. The membranous vesicle is drawn transparent,
and through it can be seen the three divisions of the macula acustica utriculi.
The sacculus projects downward and backward.

51

USCP

PRO

hae M77.

a

BARS HENRY C. TRACY

Fig. 11 Drawing to show the membranous labyrinth and the subcerebral
perilabyrinthine plate and canals in relation to the floor and side of the skull.
Drawing somewhat diagrammatic, based on dissections and a model. The
upper half of the cranial wall and of the semicircular canals have been dissected
away. The specimen is cut in the median sagittal plane which shows at the right
side of the figure; a second cut parallel to this and about half-way to the outside
separates the specimen into two parts which are represented as being slightly —
separated. In the median plane are shown the utricular and saccular sub-
cerebral canals; in the second plane are shown the relations of the utricular
subcerebral canal where it is divided into two parts by the lips of the fenestra
of the anterior osseous capsule; the two parts of the canal connect laterally
under the utriculus with the lateral recess of the skull (fig. 12). The relation
of the recessus utriculi to the fenestral lips and to the two chambers of the
anterior osseous capsule are also shown. The canal for the precoelomic diverti-
culum is cut obliquely just before its entrance to the capsule. The cavity of
the posterior osseous capsule is cut into slightly on its median side. Pomolobus
pseudoharengus.

Fig. 12 Lateral dissection of the labyrinth and perilabyrinthine structures.
The utriculus rests on the lips of the fenestra with a division of the utricular
subcerebral canal (USCP, USCA) on either side. These relations are those seen
on looking medially toward the utriculus when the lateral recess of the skull is
opened up from the outside. Posteriorly in the drawing, the supracerebral
perilabyrinthine band springs from the base of the superior sinus. Accessory
plates of perilabyrinthine tissue can be seen applied to the outside of the utricu-
lus, the ampullae, the superior sinus, and the upper end of the anterior semi-
circular canal. The triangular projection of perilabyrinthine tissue (77PP) is
probably the ‘bulbe accessoire’ of Breschet. An opening through this (not
shown in the figure) puts the lateral recess in communication with tissue spaces
lateral to the superior sinus and hence with the supracerebral canal (PSC)
through its irregular opening.

Fig. 13 Diagram of a sagittal section of the anterior osseous capsule and
septum: orientation figure for figure 14. Pomolobus pseudoharengus.

Fig. 14 Drawing to show the histological detail of the septum and its attach-
ment to the wall of the anterior osseous capsule. The elastic plates of which the
septum is made up anastomose freely as they approach the bone and are attached
by white connective-tissue fibers which pass into irregular radial canals in the
bone. The periosteum of the two chambers is reflected onto the surfaces of the
septum.

253

254 HENRY C. TRACY

Fig. 15 Microscopie section of the head of Stolephorus, 28 mm. in length.
The section is sagittal and is taken about one-third the distance between the
median plane and the lateral side of the head. The otic capsule is still cartilag-
inous, though membrane bone formation has begun on the surface. There is
only one membranous vesicle (MV) at this stage. The canal (CSD) for the pre-
coelomic diverticulum passes through the cartilage of the otic capsule. The
diverticulum itself is cut obliquely (PSB) just before its entrance to the mem-
branous vesicle. The vesicle occupies a space excavated from the cartilage of
the otic capsule; beginning of bone formation in the connective tissue around
the vesicle has taken place.

Fig. 16 Dissection of the occipital region of the skull to show the position
of the supracerebral perilabyrinthine band. Pomolobus pseudoharengus.

ertassgeds& IT.

& 255

|

256 HENRY C. TRACY ~

Fig. 17 A drawing from the same section shown in figure 15, but with higher
magnification to show the relations of the three divisions of the macula acustica
utriculi. The plane of section passes at the extreme lateral end of the posterior
division of the macula. The septum of the anterior osseous capsule is only
slightly developed at this stage and is not visible in this section. The relation
of the anterior and middle divisions of the macula to the two divisions of the
utricular subcerebral canal are well shown.

Fig. 18 Section of the anterior and middle divisions of the macula to show
the structure of the otolithie membrane. Stolephorus mitchilli, 8 mm. in
length. At this stage the divisions of the macula are in the process of differen-
tiation from a single sensory spot. Section drawn as viewed through the binocu-
lar microscope, 1/12 oil-immersion lens. The otolithic membrane is slightly
diagrammatic.

Fig. 19 Drawing from the same slide as figures 15 and 17 to show the details
of the anterior and middle division of the macula acustica utriculi and of the
otolithic membrane; 1/12 oil-immersion lens.

Fig. 20 Section of the otolithie membrane approximately parallel to its
surface. Brevoortia tyrannis, 25 mm. in length, 1/6 objective. This shows the
sections of the ‘cells’ or chambers in the membrane. They are cut transversely
in the middle of the section, but appear oblique at either end owing to their
change in direction.

257

Resumen por el autor, O. Larsell.
Universidades de Chicago y Wisconsin.

El cerebelo de Amblystoma.

El] autor describe el cerebelo de Amblystoma con especial
mencién de sus progresos sobre la estructura y organizacion del
cerebelo de los Urodelos inferiores. En Amblystoma existe una
estructura mucho mas diferenciada, que corresponde a la posicién
mas elevada de este género en la serie de los anfibios. El cerebelo
aumenta de tamafio y también en la complejidad de su estructura.
Existe una capa de células de Purkinje, y lo mismo sucede con
las células de los granos y otros rasgos tipicos del cerebelo de
los vertebrados mas superiores. Las conexiones de los tractos
fibrosos se conservan relativamente simples.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 23

THE CEREBELLUM OF AMBLYSTOMA

O. LARSELL

Anatomical Laboratories of the University of Chicago and of the University of
Wisconsin

TWENTY-ONE FIGURES

The cerebellum of the Amphibia is recognized as being of very
primitive type. This is particularly true of the organ in the uro-
deles, in certain forms of which it is said by some authors to be
entirely absent. Because of this primitive structure, a compara-
tive study of the organ in various representative types of Amphi-
bia should prove instructive. Such a study was made by Her-
rick (714), with particular reference to Necturus maculosus,
although Amphiuma means and Cryptobranchus alleghaniensis
were also included, and some observations were made on the
cerebellum of Amblystoma tigrinum.

It was at the suggestion of Professor Herrick that the present
study was begun. It isa pleasure for the writer to acknowledge
his sense of indebtedness to Professor Herrick for his interest and
his generosity in making available every facility for the prose-
cution of the work, including a wax model of the hind-brain of
larval Amblystoma, a series of sketches on cardboard of the brain
stem of adult Amblystoma tigrinum, which had been cut to cor-
respond with the outlines of the serial sections from which the
plots were made, and loans of prepared slides. Acknowledgment
should also be made to Dr. Paul 8. McKibben for permission to
use an extensive series of microscopical preparations, including
brains of Amblystoma, both adult and larval, prepared by the
Golgi, Weigert, Cajal, and other methods and mounted as serial
sections. ‘These preparations were made by Doctor McKibben
and are his property. The opportunity to use them has very
greatly facilitated the work on the cerebellum. In addition to
these, a number of series of sections have been prepared by the

259

260 O. LARSELL

writer by various methods especially for this study. The macro-
scopic form and relations of the cerebellum have been determined
by dissections under the binocular microscope. Three species of
Amblystoma, namely, tigrinum, punctatum, and opacum, were
employed in the study. The greater part of the description is
based on Amblystoma tigrinum (Green).

The external form of the cerebellum of Necturus has been de-
scribed and figured by Herrick in the paper previously cited.
Kingsbury (’95), Miller (00), McKibben (713), and others, in
descriptions or figures of the entire brain of this form, have also
figured and described the cerebellum in greater or less detail.
Other urodeles have received some attention in this respect, but
so far as the writer is aware, but little description has been given
of the cerebellum of adult Amblystoma. Stieda (’75) gives a
brief description of this organ and a figure of the entire brain,
including the cerebellum, in connection with his work on the
central nervous system of Siredon (Amblystoma mexicanum).
Osborn (’88) also figures the entire brain, with the cerebellum, of
the Mexican axolotl, in a study of the internal structure of the
brains of various urodeles, and Herrick (714 a) figures it in con-
nection with a detailed study of the medulla oblongata of larval
Amblystoma tigrinum.

As compared with the cerebellum of Necturus, which has been
described in greatest detail, this organ in Amblystoma is much
more massive. This massive structure continues across the mid-
plane, as pointed out by Herrick (714). It forms a well-defined
ridge which projects dorsocaudally, from the anterior end of the
medulla oblongata, and which lies posterior to the points of emer-
gence from the brain of the IV nerve (figs. 1 and 2). Below this
ridge the IV ventricle extends laterally on either side to form the
recessus lateralis. This recess continues forward, forming a blind
sae which extends rostrad into the auricular lobe. This sae (fig.
3, d.a.) Herrick has called the anterior diverticulum. As com-
pared with Necturus and Amphiuma and with larval Ambly-
stoma, it is relatively small in the adult of the latter species.
It is surrounded on all sides except posteriorly by massive tissue;
mesally by the corpus cerebelli and auricular lobe; dorsally and

THE CEREBELLUM OF AMBLYSTOMA 261

laterally by the auricular lobe, so that it forms in reality a con-
tinuation of the IV ventricle into the auricular lobe. The re-
cessus lateralis is also covered, in adult Amblystoma, by massive
tissue on all sides except caudodorsally, where the membranous
chorioid plexus forms its roof. This is in contrast to the con-
dition present in larval Amblystoma, in which the covering of
the lateral recess is almost entirely membranous.

Laterally the main mass of the cerebellum is continuous with
the auricular lobe and the rhomboidal lip of the medulla oblon-
gata (figs. 1,2, and 3). As pointed out by Herrick (14) for uro-
deles in general, the relation of the cerebellum to the rhomboidal
lip is very similar to that found in early embryonic stages of
mammals. In Amblystoma there is relatively more massive
structure than in lower forms of urodeles. The auricular lobe is
closely related to the corpus cerebelli rostrally and dorsally.
Johnston (’06), in summarizing the vertebrate cerebellum, states:
‘‘In most vertebrates the lateral walls bulge outward and for-
ward as the auricular lobes, the floccular lobes in man.” This
describes the relation of the auricular lobe to the rest of the cere-
bellum in Amblystoma, with the reservation that, the bulging is
quite limited.

Herrick has defined the corpus cerebelli in Necturus as the
cerebellar tissue which forms the anterior wall of the lateral re-
cess and corresponds to the chief mass of the cerebellum in higher
Amphibia and Reptilia, and the eminentia ventralis cerebelli as a
forward extension of the eminentia trigemini which is continuous,
in front of the lateral recess, with the corpus cerebelli. In Ambly-
stoma there is apparent a pronounced eminence which projects
posteriorly and downward into the ventricle, in the region corre-
sponding to the corpus cerebelli of Necturus. This eminence
(which represents only a part of the body of the cerebellum as
Herrick used this term) is located medially of the anterior di-
verticulum (fig. 3, c.cb.). It is continouus with the eminentia
cerebellaris ventralis, which in Amblystoma extends laterally and
upward in such a manner as to form the principal part of the
anterior wall of the lateral recess. As compared with Necturus,
this entire region of the brain of Amblystoma appears telescoped

THE JOURNAL OF COMPARATIVE NEUROLOGY. VOL. 31, NO. 4

262 O. LARSELL

together anteroposteriorly, with upward displacement of cere-
bellar structures.

As will be more fully indicated later, the eminence formed by
the corpus cerebelli contains a group of cells which appear to
represent the foreshadowing of the nucleus dentatus of higher
vertebrates. These cells are located in the anterior and ventral
portion of the eminence, just medial to the dorsoventral plane of
the anterior diverticulum. Because of the massive structures
surrounding it on all sides except posteriorly, the anterior end
of the fossa rhomboidea is greatly reduced in size, particularly in
the region of the corpus cerebelli. Lateral to the anterior di-
verticulum the cerebellar structure is less massive and is contin-
uous with the rhomboidal lip (fig. 3).

ABBREVIATIONS

ax., axone

br.conj., brachium conjunctivum

caud., caudad

cb., cerebellum

c.cb., corpus cerebelli

ceph., cephalad

com.cb., commissura cerebelli (myelin-
ated component)

com.cb.l., commissura cerebelli later-
alis (unmyelinated component)

d.a., diverticulum anterior of recessus
lateralis

f.l.m., fasciculus longitudinalis medialis

gr.c., granule cell

lat., lateral

l.aur., lobus auricularis

lm., lemniscus

mes., mesencephalon

mes.V, radix mesencephalica trigemini

m.fi., moss fibers

m.s.p., midsagittal plane

n.III, neryus oculomotorius

n.IV, nervus trochlearis

n.V, nervus trigeminus

n.VII + VIII, nervi facialis et acusti-
cus

n.IX,nervus glossopharyngeus

nuc.dent., nucleus dentatus

nuc.mes.V, nucleus mesencephalica tri-
gemini

Pur.c., Purkinje cell

r.l., recessus lateralis

r.P.c., reduced Purkinje cells

r.VII 1.l.d., radix lateralis facialis dor-
salis

r.VII l.l.m., radix lateralis facialis me-
dius

r. VII 1.l.m’., radix lateralis facialis ven-
tromedius

r. VII l.l.v., radix lateralis facialis ven-
tralis

r.VIII, radix nervi acustici

str.gr., stratum granulare

str.mol., stratum moleculare

str.Pur., stratum of Purkinje cells

t.f., terminal fibers

tr.a., dorsal longitudinal tract of area
acustica

tr.b., ventral longitudinal tract of area
acustica

tr.m.cb., tractus mammillocerebellaris

tr.sp.cb.d., tractus spinocerebellaris
dorsalis

tr.sp.cb.v., tractus spinocerebellaris
ventralis

tr.sp.t., tractus spinotectalis

tr.v.a., tractus visceralis ascendens
(secondary gustatory tract)

v.m.a., velum medullare anterior

THE CEREBELLUM OF AMBLYSTOMA 263

nV

nV+VIr

c.cb. 3
Fig. 1 Dorsal view of mesencephalon, cerebellum, and medulla oblongata of
Amblystoma punctatum.
Fig. 2 Same as figure 1, viewed from the left side.
Fig.3 Right half of rhombencephalon of Amblystoma punctatum, from which

part of the cerebellum has been removed so as to expose the corpus cerebelli and
the recessus lateralis. Dorsal view.

264 O. LARSELL

Histological structure

Histologically, the cerebellum of Amblystoma consists of three
layers which may be distinguished by the size of their cells and
the relative abundance of their nerve fibers. Two of these
layers were recognized long ago by Stieda (’75) in the larval form
of Amblystoma (Siredon). He considered them to correspond to
the granular and the molecular layers, respectively, of the cere-
bellum of higher vertebrates. This is in agreement with the

Fig. 4 Horizontal section through part of cerebellum of Amblystoma tigri-
num. Series CLXXXYV, sl. 2, sect. 29. Cajal method. X 125.

findings of the present writer. To these two should be added
in adult Amblystoma a third layer which consists of Purkinje
cells. This layer occupies a position between the granular and
the molecular layers (fig. 4, str.Pur.) and is composed of relatively
large cells which resemble Purkinje cells of somewhat reduced
type. '
These layers correspond in a general way to those of the mam-
malian cerebellum, not considering the medullary layer of white
matter, and will be designated as molecular layer, Purkinje cell

THE CEREBELLUM OF AMBLYSTOMA 265

layer and granular layer, respectively. There are important dif-
ferences of detail, as compared with the corresponding layers of
the higher vertebrates, which will be set forth in the description
of the different zones.

Fig. 5 Sagittal section through cerebellum of Amblystoma tigrinum near
median plane. Series CLXXXVI, sl. 5. Cajal method. > 125.

Fig. 6 Sagittal section through cerebellum of Amblystoma tigrinum. Most
medial section but one. Series CLXXXVI. Cajal method. x 125.

The outermost or molecular layer (figs. 4, 5, 6, 7, str.mol.), which
Stieda described as being composed of a granular ground substance
with but few nuclei, consists chiefly of fibers with but few cells.
The larger fibers are myelinated, but Cajal sections reveal a

266 O. LARSELL

much larger number of fine unmyelinated fibers and their term-
inal branches. Most of the fibers of this layer are scattered
without definite arrangement, but a few definite bundles are
present, especially in the lateral portions of the cerebellum.
These bundles are located posteriorly and near the layer of
Purkinje cells, next to be described. Only two of them could be
followed with any degree of certainty as to their relationship.
These were the dorsal portion of the cerebellar commissure and
the lateral cerebellar commissure (figs. 5, 6, and 15, com.cb.,
com.cb.l.). The few cells present in this layer (fig. 7) are irreg-
ularly scattered and of medium size. They are multipolar, but
so far as the preparations available indicate, bear no resemblance
to the basket cells of the corresponding layer in the mammalian
cerebellum. ‘There is a closer similarity to the superficial stellate
cells, both in the arrangement of their processes and in the posi-
tion of the cells near the surface of the molecular layer.

The layer of Purkinje cells is represented in Amblystoma by
cells of relatively large size. They are arranged in a fairly uni-
form layer from one to three cells deep (fig. 4. str.Pur.). Their
dendritic processes, of which from one to three or four may be
counted, extend outward into the molecular layer. The branch-
ing of these processes is very simple and limited. As revealed
by Golgi preparations (figs. 8, 9, 10, and 11), each of the primary
dendrites may give off two or three secondary branches, and these
in turn may ramify, but beyond this no divisions were observed.
In some of the preparations gemmules are present on the secon-
dary and tertiary branches. The primary branches are dis-
tributed both horizontally and dorsoventrally, i.e., their distri-
bution is not confined to a narrow zone of relatively wide area,
but rather they radiate in such a manner as to outline roughly -
a pyramid, with the cell body at its apex. The Purkinje cells of
this layer are especially numerous in the lateral portions of the
cerebellum (corpora cerebelli). Some of their processes from this
region extend forward and laterally toward the tectum of the
midbrain, and some of the smaller branches appear to enter the
tectum (figs. 10 and 11).

|
ceph Le

str mol “a oS
= eens
Bee Pole re
SS se |
= a

mee 5007 4

msp

“Scr gr

mii caud.

comcb

str mol.

Ye kiss eo
3c 5 a = ae
a :

Fig. 7 Horizontal section through the cerebellum of Amblystoma tigrinum,
showing typical fibers and cells in the molecular layer, and granule cells and a
moss fiber in the granular layer Series CCIV, sl. 3. Golgi method. X 196.

Fig. 8 Horizontal section through cerebellum of Amblystoma tigrinum,
showing a Purkinje cell, several reduced Purkinje cells, and several other nerve
cells. Series CXVII, sl. 3, sect. 1. Golgi method. x 60.

267

268 O. LARSELL

| aise 2a

str mol

str mol..

THE CEREBELLUM OF. AMBLYSTOMA 269

The axones of the Purkinje cells (figs. 9, 11, and 14) have their
origin either from the cell body or,,more commonly, from one
of the primary dendrites close the the perikaryon. They pass
into the molecular layer where they become lost among the num-
erous fibers there present. From many of the cells axone-like
processes pass into the granular layer, but turn upward to enter
the molecular zone, in the majority of cases observed. A similar
passing of the axone of the Purkinje cells into the molecular layer
was found by Johnston (’01) in Acipenser.

Other cells of somewhat smaller size were observed in Golgi
preparations along the posteroventral border of the cerebellum
and at various levels within the granular layer (figs. 8, 10, 12,
and 13, r.P.c.). Typically the cell body is elongated, giving a
pear-like form to the cell, but some of fusiform outline were ob-
served. The dendrites extend toward the molecular layer and
appear to terminate for the most part within the more posterior
and ventral region of this zone, although many do not reach the
molecular layer, but end within the granular layer. Some of the
processes are studded with gemmule-like projections (figs. 12
and 13).

From the position of most of the cells of this type, along the
border of the cerebellum, they might be considered as ependymal
cells, related to the peculiarly elongated type characteristic of
the cerebellum of other vertebrates. In their morphological
characteristics, however, they resemble nerve cells. The den-
dritic branches do not have the arrangement or appearance of
the long processes of the ependymal cells. In connection with
many, an axone-like process was observed. This is of simple
type, without profuse branching near the cell body, and extends
into the molecular layer. In some respects these cells resemble

Fig.9 Horizontal section through cerebellum of Amblystoma tigrinum, show-
ing Purkinje cell and granule cells. Series CCIV, sl. 3, sect. 84. Golgi method.
x 196.

Fig. 10 Sagittal section through cerebellum of Amblystoma tigrinum. Series
CCV, sl. 1, sect. 39. Golgi method. x 125.

Fig. 11 Sagittal section through cerebellum of Amblystoma tigrinum. Series
CCV, sl. 1, sect. 30. Golgi method. X 125.

270 O. LARSELL

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THE CEREBELLUM OF AMBLYSTOMA 271

the Golgi cells of Type II, but the sparsely branched axone would
exclude them from this group.

In position and size as well as in general characteristics, these
cells appear to correspond more closely than do the larger ones
first described to the reduced Purkinje cells found by Herrick in
Necturus. Various transitional stages between these reduced
cells and the more highly differentiated ones were observed. The
degree of morphological differentiation appears to correspond
roughly with the position of the cell. Those located at the cere-
bellar border are the most simple in type; cells at various levels
in the granular layer appear to be somewhat more advanced,
while the cells composing the Purkinje cell layer most closely
resemble Purkinje cells of higher forms (figs. 8 to 13). Not all
preparations revealed the presence of these reduced cells, but
this was probably due to the idiosyncrasy of the Golgi technique.
When present in a given series of sections they were more numer-
ous than the larger cells more deeply placed. They were found
in greatest number along the cerebellar border about midway
between the median line and the lateral border of the cerebellum,
but many were observed quite close to the median plane and
also laterally, and at various levels between the cerebellar border
and the Purkinje cell layer. They might be considered to belong
to the granular layer of the cerebellum, but because of their ap-
parent relation to the cells of the Purkinje cell layer they are
described at this point.

The granular layer, in addition to the reduced Purkinje cells
just noted, consists of numerous small rounded cells, among which
are interspersed myelinated fibers. In Golgi preparations these
cells are seen to possess several relatively short, tortuous processes
which give a stellate appearance to the cell. Many of these

Fig. 12. Horizontal section through cerebellum of Amblystoma tigrinum.
Series CXVII, sl. 3, sect. 2. Golgi method. X 60.

Fig. 138 Horizontal section through cerebellum, deeper than that of figure 12.
Series CXVII, sl. 3. Golgi method. X 60.

Fig. 14 Horizontal section through cerebellum of Amblystoma tigrinum,
showing various elements of granular layer. Series CCIV, sl. 3, sect. 83. Golgi
method. X 196.

Zi2 O. LARSELL

processes terminate in short twigs which resemble the claw-like
telodendrites of the granule cells of more highly developed cere-
bella (figs. 7 to 14). In only a few instances was an axone ob-
served to pass from such cells (figs. 11 and 14). When present it
is directed toward the molecular layer, but becomes lost among
the numerous fibers of fine caliber there present. No certain in-
dication of bifurcation within the molecular zone was noted.

The fibers of the granular layer appear to be all myelinated,
except for the terminal branches which end within it. A well-
marked bundle of myelinated fibers passes through the layer from
one side of the cerebellum to the other. This includes the cere-
bellar commissure and, for part of its course, the tractus spino-
cerebellaris ventralis, although the latter is independent through-
out much of its course within the cerebellum (fig. 16, tr.sp.cb.v.).
Fibers from this large bundle are given off at short, irregular
intervals and terminate among the cells of the granular layer.
Some of these fibers (figs. 7 and 14, m.fi.) appear to be related
to the moss fibers of the more highly developed cerebellum. In
Golgi preparations they are seen to terminate in short, stout
twigs, and along their course, especially at the points of branch-
ing, are found the nodosities characteristic of moss fibers. Other
terminations within the granular layer consist of long slender
processes (fig. 15, ¢.f.) with fine varicosities here and there along
their course, but without the stout terminal twigs just noted.
These appear to come from the tractus spinocerebellaris ventralis,
but this was not determined with certainty. According to Ram6én
y Cajal, the moss fibers in mammals are the terminal arborizations
of afferent fibers which enter the cerebellum through the inferior
peduncle, while the climbing fibers, which the last described
type of ending most closely resembles, enter from the brachium
pontis. It is difficult to apply this statement to the cerebellum
of Amblystoma, as the brachium pontis is altogether lacking.
The moss fibers may be the terminal arborizations of the tractus
spinocerebellaris dorsalis, thus passing into the cerebellum
through the region which in the more differentiated cerebellum
is the inferior peduncle. If the second type described are term-
inal fibers of the tractus spinocerebellaris ventralis, as they ap-

THE CEREBELLUM OF. AMBLYSTOMA 273

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Fig. 15 Sagittal section through cerebellum of Amblystoma tigrinum, show-
ing terminal fibers within granular layer. Series CCV, sl. 1. Golgi method.
xX 196.

Fig. 16 Reconstruction from five sagittal sections through lateral part of
cerebellum of Amblystoma tigrinum. The outline and the position of the cells

were drawn from section 26 of slide 4, series CLX XXIV, the fibers were drawn in
from sections 26 to 30. Cajal method. X 60.

274 O. LARSELL

pear to be, they enter the cerebellum through the region which
becomes in higher forms the superior peduncle.

Fibers are present everywhere in this layer, from one side to
the other of the cerebellum. In the more medial region many
run anteroposteriorly (fig. 5) rather than transversely, as is the
case more laterally in the organ. Close to the median line most
of the longitudinal fibers, as seen in sagittal sections, disappear,
and the majority of fibers present are cut transversely. These
belong for the most part to the cerebellar commissure, but some
are fibers of the tractus spinocerebellaris ventralis.

The granule cells are entirely absent in the median plane (fig.
6), but appear as a few scattered cells very close on either side
of this plane. The granular layer therefore increases in thick-
ness laterally, from a very thin zone containing only a few fibers
in the median plane, to a layer which occupies nearly half of the
thickness of the lateral portion of the cerebellum. In the last-
named region it consists, in addition to numerous fibers, of from
twelve to fifteen layers of cells. The few cells present near the
median line are located in the posterodorsal portion (fig. 5) of
the cerebellum. As the corpus cerebelli is approached, the gran-
ule cells not only increase in number, as above noted, but also
extend toward the more ventral portion of the cerebellum, until
this becomes the thickest portion of the granular layer. This
cell layer is continuous with the gray matter of the medulla
oblongata.

In each lateral half of the cerebellum there is present an en-
largement of this gray matter which, from its position and from
the origin within it of fibers of the brachium conjunctivum, ap-
pears to represent the primitive nucleus dentatus (fig. 16, nue.
dent.) already noted in the description of the external form of
the cerebellum.

The fiber tract systems of the cerebellum of Amblystoma corre-
spond in general with those of Necturus, but with some modi-
fications. The efferent fibers consist of internal arcuate fibers
which pass forward and downward into the medulla oblongata
and into the midbrain. These are chiefly unmyelinated. They
evidently represent the cerebellotegmental system. Only in the

THE CEREBELLUM OF AMBLYSTOMA 275

case of those passing forward into the midbrain is there any def-
inite grouping of fibers to form a bundle. This bundle (fig. 16,
br.conj.) is loosely arranged and has relatively few myelinated
fibers. Those present are of small diameter. The unmyelinated
fibers are more numerous, so that the bundle is more evident in
favorable Cajal preparations than in those stained by the Weig-
ert method. The majority of fibers which enter into this bundle
appear to arise from the cells composing the group which has
been described as the primitive nucleus dentatus. Some appear
to come from the molecular layer, but could not be traced for
any distance within this layer. These may possibly represent
axones of the Purkinje cells, which, as described above, pass into
the molecular zone to be lost within it among the numerous
fibers there present. No other efferent cerebellar tracts were
recognized, if present.

The afferent fibers which terminate within the cerebellum are
definitely grouped into tracts of greater or less size. They are
for the most part composed of myelinated fibers.

The tractus spinocerebellaris ventralis is the largest of the affer-
ent tracts. It les dorsally and laterally of the bulbar lemniscus,
and is closely associated, as pointed out by Herrick in both Nec-
turus and larval Amblystoma, with the tractus spinotectalis.
Just before reaching the level of the superficial origin of the V
nerve, the two tracts separate to some extent, but not entirely.
They continue forward as far as the ventral and anterior portion
of the corpus cerebelli (fig. 16, tr.sp.cb.v., tr.sp.t.). Here the
ventral spinocerebellar tract is completely separated from the
mixed bundle and turns dorsally and medially to pass into the
body of the cerebellum (figs. 16 and 21, tr.sp.cb.v.). Its fibers
remain distinct from those of the cerebellar commissure for some
distance, then it becomes part of the commissural bundle; but
in sagittal sections the tract, somewhat reduced in size, is seen
to separate again from the commissure on its dorsal side (fig. 16).
Its fibers pass among the cells of the granular layer a few at a
time as the median plane is approached, but many cross to the
opposite side of the cerebellum. The bundle is therefore not
greatly reduced in size as it also receives fibers from the corre-
sponding tract of the opposite side.

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THE CEREBELLUM OF AMBLYSTOMA Ad

The tractus spinocerebellaris dorsalis offers considerable diffi-
culty in identification. As seen in Weigert preparations (figs.
17 to 21, tr.sp.cb.d.), a bundle of myelinated fibers emerges from
the cerebellar commissure near the ventrolateral extremity of the
latter and assumes an independent course ventrally and caudally.

Figs. 17 to 21 Five transverse sections through medulla oblongata and cere-
bellum of Amblystoma tigrinum, arranged in series from the level of the super-
ficial origin of the V nerve to the level of the superficial origin of the IV nerve,
showing the arrangement of the fiber tracts of the cerebellum and some of the
tracts of the medulla oblongata for orientation. Series IIC, sects. 574 (fig. 21),
585 (fig. 20), 595 (fig. 19), 603 (fig. 18), and 605 (fig. 17). Weigert method. 28.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL 31 NO. 4

Dis O. LARSELL

Within the commissure the bundle is distinguishable for a short
distance toward the median plane by reason of the smaller diam-
eter of its myelin sheaths, but it soon becomes lost among the
numerous fibers of various size which compose the commissure.
Caudad this bundle runs mesial to the VIII tract, but before
reaching the superficial root of the V nerve, it turns ventrally
to pass beneath the latter. Cephalad of this point, however, it
becomes so intermingled with other fibers as to be very difficult
to follow. It takes its further course ventrally of the spinal V
tract for a short distance, but before reaching the level of the
VIII root it becomes lost among other fiber bundles.

Some of the fibers of the mixed bundle cephalad of the V root
pass as far caudally as the superficial origin of the trigeminus.
At this pot many of them pass ventrally just anterior to the V
root fibers, others find their way ventrally through the V root ~
bundle, and the two groups reunite below the spinal V tract.
These constitute the ascending gustatory tract (figs. 17 to 21,
tr.v.a.). Cephalad this tract passes through the auricular lobe,
and appears to come into relation with a group of cells just
rostrad of the lobe, but which are evidently a part of the mid-
brain. In adult Amblystoma this group of cells is more obscure
than in the larval form, in which they stand out very clearly.
The ascending gustatory tract does not appear to have any direct
connection with the cerebellum.

A small bundle of myelinated fibers of reduced diameter from
the trigeminus shows bifurcation of the fibers just before the
nerve enters the medulla oblongata, or just within the latter.
One branch of these bifurcated fibers may be observed in Golgi
and Weigert sections to take its course ventrally of the VIII
tract to the auricular lobe, but some of these fibers appear to
pass into the cerebellar commissure in company with the dorsal
spinocerebellar tract. The other branch of the bifurcated fiber
passes posteriorly into the medulla and possibly into the cord.
This is the only indication of trigeminal fibers which appears to
terminate within the cerebellum.

In Golgi sections cut sagittally a few fibers were observed to
pass between the pars dorsalis hypothalami and the lateral por-

THE CEREBELLUM OF AMBLYSTOMA 279

tion of the cerebellum. The cells of origin appear to lie in the
pars dorsalis hypothalami. The fibers pass from this region
dorsocaudad and toward the midplane. After passing dorsal to
the region of the interpeduncular nucleus, they dip ventrally be-
_ hind this nucleus, then assume a more dorsal course and pass
through the midbrain into the tegmentum and the cerebellum.
Within the cerebellum (figs. 11 and 13, tr.m.cb.) they are scattered
loosely in the dorsolateral region, and show characteristic vari-
cosities. They appear to come into relation with dendritic pro-
cesses of the larger Purkinje cells (fig. 11) above described, which
extend toward the midbrain. These fibers correspond to the
tractus mammillocerebellaris which appears to be present in
Necturus also. From the interpeduncular region, in Amblys-
toma, a number of fibers accompanies the mammillocerebellar
’ tract in its course toward the cerebellum, lying ventral and par-
allel to it. The fibers appear to have their origin from cells in
in the interpeduncular nucleus. They pass dorsally and caiidad
into the tectum mesencephali, where many of: them appear to
end. Others, however, appear to continue caudad into the
cerebellum in company with those of the tractus mammillo-
cerebellaris. This appearance was chiefly due to the greater
numbers of fibers in the region of the cerebellum occupied by
the tractus mammillocerebellaris, as compared with the num-
ber constituting this tract rostrad of the nucleus interpeduncu-
laris. ‘The number within the cerebellum appears to correspond
more closely with that of the combined tracts in their course
between the interpeduncular region and the mesencephalon, but
this greater number within the cerebellum may be due to pro-
fuse terminal branching of the mammillocerebellar fibers. This
point could not be determined in the material available. It is
possible that some are fibers of the secondary gustatory tract
which pass through the lateral region of the cerebellum. Her-
rick (’17) believes that the mammillocerebellar tract which he
had previously tentatively established in his description of the
cerebellum of Necturus ‘includes the combined secondary and
tertiary visceral tract, with perhaps mammillotegmental fibers
mingled with them.” Jn the Golgi preparations of Amblystoma,

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO 4

280 -O. LARSELL

it appears quite evident that some of the fibers of the combined
tract terminate within the cerebellum, so that the designation,
tractus mammillocerebellaris, is employed.

The mesencephalic V tract (figs. 19 to 21, mes.V) has not —
been studied by the writer except in its relation to the cerebel-
lum. It is composed of coarse myelinated fibers which form a
well-defined bundle of characteristic appearance. This bundle
passes dorsorostrally and mesad from its origin at the superficial
roots of the trigeminus toward the mesencephalon. In its
course it traverses the cerebellum and for a short distance is
more or less intermingled with the cerebellar commissure (fig.
19). The fibers of the mesencephalic V tract, however, may be
distinguished from those of the commissure. They merely pass
through the latter in their course between the midbrain and V
nerve. In the boundary region between the cerebellum and
the tectum, however, the mesencephalic V fibers become inter-
mingled with others, especially those of the IV nerve, in such a
manner that they are difficult to follow in Weigert preparations.
Their further course has not been studied. So far as observed,
they have no immediate functional relation to the cerebellum.
The trigeminal fibers previously noted which appear to pass into
the cerebellum have no relation, so far as could be determined,
to the mesencephalic V tract.

There are some indications of tectocerebellar fibers, but they
do not form a distinct tract and are so intermingled with other
fibers in this region that a clear analysis was not possible.

The fiber tracts which pass into the auricular lobe have much
the same relationship in adult Amblystoma as they have in the
larval form, so far as the available material indicated.

The VIII tract forms a well-defined bundle of fibers which lies
close to the lateral margin of the area acustica. From its origin
at the level of the VIII nerve to a point slightly rostrad of the V
root, two bundles, a dorsal and a ventral, may be observed in
adult Amblystoma. This is the condition observed by Herrick
in the larval form, except that the two tracts are distinct only
as far as the superficial origin of the V root in the latter. The
fibers continue forward from this point as a single tract which

THE CEREBELLUM OF AMBLYSTOMA 281

passes into the lobus auricularis. Within the’ auricular lobe
fibers pass dorsally and mesad from the main bundle (figs. 17 to
21, 7r.VIII). Most of these disappear among the cells and fibers
of the auricular lobe, but many appear to pass into the corpus
cerebelli. The VIII tract continues forward, diminished in
size, to the most rostrad region of the auricular lobe, where its
fibers disappear in a manner similar to those in the more caudad
portion of the lobe.

The lateral-line roots of the VII nerve can be followed as small
bundles of myelinated fibers forward into the auricular lobe.
Four distinct bundles can be recognized in the adult Ambly-
stoma at most of the levels between the superficial roots of the
facialis and the auricular lobe. These apparently are the con-
tinuation of the four roots of the lateral-line component of the
VII nerve described by Coghill (02). The three more dorsally
located (figs. 17 to 20, 7r.VIT LL.d., r.VII Ul.m., and r.VIT 1.l.m’.)
could not be followed with certainty beyond the posterior region
of the auricular lobe, but the ventral tract (fig. 21, r.V/TI L.l.v.)
continues dorsal to the VIII tract to terminate in the rostral
end of the auricular lobe.

SUMMARY

The cerebellum of Amblystoma has the general characteristics
of this organ as described in other urodeles, but it shows some
advances of structure and organization not present in the lower
forms of this group of vertebrates.

The more important of these advances are: 1) increased size of
the corpus cerebelli; 2) the presence in the corpus cerebelli of a
group of cells which appear to foreshadow the nucleus dentatus;
3) the presence of a definite zone of Purkinje cells, the cells of
which have the general characteristics of this type of neurone as
present in higher vertebrates; 4) the presence of granule cells
and moss fibers within the substantia grisea, which corresponds
to the stratum granulare of higher forms.

The principal fiber-tract connections, with modifications of
detail, are similar to those of lower urodeles. These include the
tractus spinocerebellaris ventralis, the tractus spinocerebellaris

282 O. LARSELL

dorsalis, and the tractus mammillocerebellaris, on the afferent
side. To these, in Amblystoma, should be added some fibers
from the trigeminus and also fibers of the VIII tract which
pass into the body of the cerebellum from the auricular lobe.
There are evidences of a tectocerebellar tract, but the fibers are
diffuse and are intermingled with other fibers in the region of
the entrance into the brain of the IV nerve in such a manner as
to be difficult of separation from the others.

The efferent fibers include the brachium conjunctivum and
numerous arcuate fibers which are not aggregated into definite
tracts, but which appear to correspond to the cerebellotegmental
system.

LITERATURE CITED

Cocuitt, G. E. 1902 The cranial nerves of Amblystoma tigrinum. Jour.
Comp. Neur., vol. 12, pp. 205-289.

Herrick, C. Jupson 1914 The cerebellum of Necturus and other urodele Am-
phibia. Jour. Comp. Neur., vol. 24, pp. 1-29.
1914a The medulla oblongata of larval Amblystoma. Jour. Comp.
Neur., vol. 24, pp. 343-427.
1917 The internal structure of the midbrain and thalamus of Necturus.
Jour. Comp. Neur., vol. 28, pp. 215-348.

Jounston, J.B. 1901 The brain of Acipenser. A contribution to the morphol-
ogy of the vertebrate brain. Zool. Jahrb., Bd. 15, S. 1-204.
1906 The nervous system of vertebrates. Philadelphia.

Kinessury, B. F. 1895 On the brain of Necturus maculatus. Jour. Comp.

Neur., vol. 5, pp. 139-205.

McKipsen, Pav 8. 1913 The eye-muscle nerves in Necturus. Jour. Comp.
Neur., vol. 23, pp. 153-172.

Mituer, W.S. 1900 The brain of Necturus maculatus. Bul. Univ. Wisconsin,
no. 33, Science Series, vol. 2, pp. 227-234.

Ossorn, H. F. 1888 A contribution to the internal structure of the amphibian
brain. Jour. Morph., vol. 2, pp. 51-96.

Sriepa, L. 1875 Ueber den Bau des centralen Nervensystems der Amphibien
und Reptilien (I. Axolotl; II. Schildkréte). Zeits. fir wiss. Zool.
Bd. 25.

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Resumen por los autores, Swale Vincent y A. T. Cameron.
Universidad de Manitoba.

Nota sobre un reflejo inhibidor de la respiracién en la rana y
otros animales.

En todos los animales existen mecanismos reflejos que inhiben
los movimientos respiratorios cuando la cabeza se sumerje en
el agua. Los receptores de tales reflejos estén situados proba-
blemente en el epitelio de la membrana mucosa nasal. En
adicién los autores han encontrado algunas pruebas que demu-
estran que en la rana existe un mecanismo reflejo accesorio que
depende de la oelusién de los orificios nasales externos y la ce-
sacién de la corriente de aire en los pasajes respiratorios. Ambos
reflejos pueden entrar en accién cuando la rana esta sumerjida.

Translation by José F. Nonidez
Carnegie Institution of Washington

AUTHORS’ ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 23

A NOTE ON AN [INHIBITORY RESPIRATORY REFLEX
IN THE FROG AND SOME OTHER ANIMALS

SWALE VINCENT AND A. T. CAMERON

Department of Physiology, Biochemistry, and Pharmacology, University of
Manitoba, Winnipeg, Canada

Some of the results stated for the frog in the present commu-
nication were read to the Scientific Club of Winnipeg on February
24, 1914. At that time we were not acquainted with any pre-
vious account of the phenomenon, but subsequently discovered
Axenfeld’s paper,' published in 1911. This appears to be a
preliminary communication and contains no references to litera-
ture. We have failed to find any subsequent communication by
Axenfeld or any other author upon this reflex in the frog, and
since Axenfeld does not appear to state fully the facts of the case, -
we have decided to make a brief communication at the present
time.

Moreover, the observations on other animals made by several
previous observers seem to have been overlooked by the most
recent writers. Starling, writing in Schiéfer’s Text-book," says:

A pure expiratory reflex may also be brought about by gentle stimu-
lation of the nasal mucous membrane of the rabbit, as by application
of chloroform vapor. A similar expiratory pause is caused in many
animals by dipping the nose into water, or even by plunging the lower
half of the body into water (Tauchreflex). The temperature of the
water is of no influence on the results of the experiment. Frédericq?
has shown that a specially long expiratory pause may be produced in a
diving animal, such as the duck, by allowing a stream of water to flow
on its beak. The teleological importance of these reflex cessations of
respiration, which have been classed together by Miescher-Riisch!* as
apnoea spuria is obvious.

We have found other references to the authors here quoted,
including a paper by Foa’ modifying Miescher’s classification of
apnoeal reflexes. We have, unfortunately, not been able to

283

284 SWALE VINCENT AND A. T. CAMERON

consult the original papers of these authors, and from the refer-
ences we cannot be certain how far they have dealt with the
precise points with which we are most concerned.

A. THE FROG

The normal respiration of the frog has been fairly completely
studied. A summary of the known facts is given by Baglioni.*
It is sufficient to remark here that a large share in the function
of respiration is borne by the skin, the lungs providing an acces-
sory mechanism consisting of two separate movements, a) that
of the mouth with the lungs closed off and, b) the true lung
movements, the latter only occurring at certain intervals. The
movements with which we are concerned in this paper are those
occurring in the throat and nostrils. (For an account of the
normal respiration compare also Willem."*)

Two different kinds of external influences have been described
as affecting the movements in question. Graham Brown,® who
gives a good account of the literature, deals chiefly with the
influence of the nervous system and the labyrinth, but mentions
certain external factors producing inhibition, such as shaking of
the animal, a blow on the nose, stimulation of the skin, etc.
He does not mention the effect of immersion in water or of plug-
ging the nostrils. Axenfeld,! who seems to have been the first to
describe specifically the immersion apnoea in the frog, attributes
the phenomenon to a definite stimulation of the nerve endings
of the nasal mucous membrane by means of water. Some of
the earlier observers referred to by Graham Brown describe an
apnoeal reflex in the frog due to various afferent impulses arising
from different parts of the body surface.

The immersion apnoea is one which must have been familiar
to naturalists for a long time. The moment that a frog becomes
completely immersed in water, the respiratory movements cease,
and remain in abeyance as long as the animal continues to be
immersed. The most elementary observation shows that cessa-
tion of breathing occurs at the moment that both nostrils touch
the water. Our observations were directed chiefly toward
determining the nature of the stimulus which inhibits the respi-
ratory movements.

INHIBITORY RESPIRATORY REFLEX IN FROG 285

Axenfeld comes to the conclusion that the nasal mucous
membrane is stimulated specifically by air and by water, and
that the stimulation calls forth in one case movements of breath-
ing, and in the other inhibition of these. He states that 20
per cent acetic acid destroys the reflex by damaging the mucous
membrane of the nostril; if a frog is immersed after such treat-
ment it continues to breathe, filling its mouth with. water.

He also states that the inhibitory reflex is not altered after
section of the first division of the fifth nerve with its nasal branch.

We have carried out the following series of experiments:

1. Several frogs were treated with 20 per cent acetic acid,
following Axenfeld’s directions, and using his precaution of
plugging the mouth with absorbent cotton while the nostrils
were being treated with the acid, in order to prevent more exten-
sive damage. We found that the proceeding interferes with the
normal respiration. The animal can no longer breathe properly,
even in air. When such an animal is placed in water it is true
that it continues the movements of respiration, but this is ren-
dered possible by the opening of the mouth to some extent and
not through true nasal breathing. The interference with breath-
ing in the air is probably due to swelling of the epithelium and
excess of mucus in the nasal cavity, and in this case also the
animal breathes through the mouth.

We have repeatedly observed that during free-air breathing
when through any cause the nasal passages become obstructed,
after a while the animal will continue breathing by occasionally
opening and closing the mouth.

2. More complete destruction of the epithelium of the nasal
passage can be produced by the actual cautery. We have done
this with several frogs, and if the passage of the nose be kept
free something approaching a regular respiration will go on for
some time. ‘This, however, ceases instantly on immersing the
animal in water. It has been pointed out to us that the cautery
will not destroy the epithelium of the deep recesses of the nasal
cavity.

3. Early in our experiments it was noticed that plugging the
nostrils with blunt seekers or by placing the fingers over the

286 SWALE VINCENT AND A. T. CAMERON

nasal apertures, immediately stops the movements of the floor
of the mouth. The inhibition is temporary, and lasts from eight
to fifteen seconds. Mechanical stimulation of the interior of the
nostril does not produce this effect, nor does mechanical stimu-
lation of the skin in the neighborhood of the nostril. A weak
electrical stimulation in the same neighborhood produces no
effect, but a strong stimulation with induced current causes the
animal to throw back its head, and this type of action, as ob-
served by Graham Brown and others, checks the respiratory
movements. But it is interesting to note that when the head is
thrown back or pushed back by the hand, in either case there
occurs closure of the nostrils concurrently with cessation of
respiration, and stimulation of the skin of the back will induce
throwing back of the head, closing of the external nares, and
stoppage of respiration. |

These changes in some ways simulate the posture reflex ob-
served in the duck by Huxley (see below). It should therefore
be pointed out here that when a frog is immersed in water or
when the nostrils are plugged, no such change of posture need
necessarily occur, and does not usually so occur, so that the
reflex is not due to this cause.

4. The following experiment was carried out with two frogs:
Fine, accurately fitting cannulae were inserted into the nostrils
after cauterizing. The animal was then immersed with the
extremities of the cannulae communicating with air; so long as
the cannulae were not plugged by mucus, and did not by pres-
sure mechanically occlude the nasal passages (these errors were
specifically guarded against in the cases observed), respiration
went on normally, and no inhibition could be induced such as
those described as similar to the postural reflex (it being no
longer possible to close the nares). On removing such tubes
from the nostrils while the frog was under water, breathing
stopped immediately.

Repetition of this experiment with a number of other frogs
gave less satisfactory results, owing to the difficulty of keeping
the cannulae free from mucus, etc. In some cases where the
cautery had enlarged the aperture of the nostril considerably so

INHIBITORY RESPIRATORY REFLEX IN FROG 287

that the cannulae did not completely occlude it, immersion of
the animal, snout-end last, caused immediate cessation of respi-
ratory movements, apparently through the entry of water into
the nostrils round the outside of the cannulae.

In all the above experiments similar effects were produced by
immersion in water, whether the animal was immersed snout
first or snout last, except in cases where the mucous membrane
of the nostrils had been damaged, when change of posture pro-
duced an effect in some animals, this being almost certainly due
to increased or decreased plugging of the nostrils with mucus.

5. Cannulae were inserted into the nostrils of an intact animal;
the respiratory movements were seriously affected, but after
some minutes an imperfect kind of respiration began. The free
ends of the cannulae were then immersed in water, and after
several seconds the same imperfect respiratory movements
recommenced, although only water could be taken in. This
occurred even when the nostrils were also submerged.

All these experiments were carried out with R. pipiens from
Ilinois.

Conclusions

Apparently Axenfeld is right in supposing that the most
important factor in the submersion stoppage of respiratory
movements is a specific stimulation of the nasal mucous mem-
brane by contact with water. This is supported by our experi-
ments nos. 4 and 5, and is not definitely contradicted by no. 2.
It may be observed in this place that this inhibition of the
respiratory movements is more pronounced and permanent in
the frog than in other classes of animals, since, as shown by
experiments carried out in this laboratory,’ the animal can live
for many weeks under water, and during this time makes no
attempt at respiratory movements, the floor of the mouth
remaining permanently in the expiratory position.

In addition to the reflex described above, there appears to be
another and quite separate one, caused by plugging the nostrils
(cf. experiment 3). We are tempted to suggest that the sense
of resistance brought about by the impeded air flow and experi-

288 SWALE VINCENT AND A. T. CAMERON

enced through the muscular sense of the throat muscles acts as
the afferent stimulus for the reflex.

B. BIRDS

The respiratory reflexes in the duck have been dealt with in a
series of papers by Frances M. Huxley.!°!2 This observer,
who makes no reference to the work of Frédericq, noted that
respiration in the duck always ceased when the head and neck
were immersed in water. In her conclusions she says (2°, p. 152):

Thus submersion of a duck’s head gives rise to complete apnoea
followed by a compensatory hyperpnoea. Submersion of the end of
the bill does not produce this; submersion of the external nares does so
only to a certain degree. For its complete production entire immersion
of the glottis, the anterior portion of which lies 2.5 em. behind the
posterior border of the external nares, is required.

In her second paper published on the same date she seems to
have somewhat altered her opinion. Here she states: ‘‘As soon
as the mucous membrane of the nostrils, etc., comes in contact
with the water, a reflex apnoea is produced” (11, p. 174).

Her detailed description of experiments points to the latter
view as being the more correct. Both with immersion of nostrils
and immersion of the whole head there was a comparable per-
centage of cases where one or two respiratory movements were
made after immersion.

We have made several immersion experiments with the duck,
and we believe complete immersion of the nostrils (and not
necessarily of the whole head) is sufficient to induce apnoea.

Doctor Huxley appears to assume that the mechanism is a
reflex from the mucous membrane of the nostril, as Axenfeld
assumed in the case of the frog, but her experiments did not
eliminate the possibility of a mechanical factor, such as we have
stated to be efficient in the latter animal. Such a mechanical
factor, however, does not appear to be in operation in the case
of the duck.

Plugging the nostrils does not interfere with the normal
breathing in the duck, but this is partly due to the fact that the

INHIBITORY RESPIRATORY REFLEX IN FROG 289

animal breathes through the mouth. Surrounding the mouth
cavity with water and subsequently plugging the nostrils, does
not interfere with respiratory movements. Further, immersion
of the head in water while the nostrils are plugged with the
fingers has no effect, although on removing the fingers from the
nostrils while the head is still under water all respiratory move-
ments are immediately inhibited. This seems to us conclusive
evidence that in the duck a fluid contact with the mucous mem-
brane of the nostril is essential to the reflex.

We can fully confirm Frédericq’s observation that pouring
water over both the nostrils will bring about the apnoea, although
the mouth is freely exposed to air. Further, we find that a
stream of water directed through the nostrils produces the same
effect. Plugging one nostril with the finger and directing a
stream of air (under pressure) against the other induce the
reflex, but this may be due to distention of the air sacs, which
produces apnoea, according to Baer.? Stimulation by introduc-
ing a solid object into the nostril (such as wires, india-rubber
tubing, etc.) is not effective.

It thus appears that the apnoeal reflex in the bird is of a
similar nature to the more important one in the frog.

The postural reflex fully described by Huxley and by Paton"
in the duck may be easily demonstrated, and we have no further
observation to offer upon this phenomenon. Whether there is
a similar reflex in the frog we cannot yet be sure. What we at
first thought to be a postural reflex in that animal seems con-
nected with closure of the nostrils, and is probably something
different.

We have carried out a series of experiments upon the pigeon.
Immersion of the nostrils in water or direction of a stream of
water upon the nostrils immediately stops the respiratory move-
ments. A stream of air under pressure produces the same effect
as in the duck, but this may be due to distention of air sacs
(see above). On the other hand, plugging the mouth and nos-
trils and mechanical and electrical stimulation are not effective.

290 ‘“.SWALE VINCENT AND’ A. T.: CAMERON
C. MAMMALS

According to Huxley, Beau‘ in 1860 observed that when a
dog is immersed in water it immediately ceases breathing, and
this was confirmed by Paul Bert® in 1870. Beau attributed the
cessation to reflex action from contact of water with the respi-
ratory orifices, while Bert considered it due to voluntary move-
ment.

We have found that the reflex can be readily demonstrated
in the white rat.

We have shown that if the snout of the non-anaesthetized
animal be immersed in water at body temperature (to avoid
effect of cold), even if part of the mouth remains in contact with
air, immediately the nostrils are immersed they are closed and
respiration ceases.

Precisely the same occurs with the anaesthetized animal, and
the result can easily be recorded by the graphic method. The
reflex is very definite, and—with a short immersion lasting a few
seconds only—appears to persist for some seconds after removal
of the snout from water.

The observation upon the anaesthetized animal is sufficient
to negative any suggestion of voluntary action.

Further observations showed that a stream of air under slight
pressure stops the respiration, while plugging the nostrils and
mouth and mechanical and electrical stimulation do not do so.

The same results are obtained with the anaesthetized rabbit.

Although we are not yet prepared to discuss fully the nature
of the reflex in mammals, we think that it is probably of the
same nature as that in the duck.

GENERAL SUMMARY

In all vertebrates there appear to be reflex mechanisms which
inhibit the respiratory movements when the animal’s head is
submerged beneath the surface of water. The receptors for
these reflexes are probably situated in the epithelium of the
nasal mucous membrane. In addition we have adduced some
evidence that in the frog there is an accessory reflex mechanism

INHIBITORY RESPIRATORY REFLEX IN FROG 291

depending upon the plugging of the nostrils and stoppage of the
flow of air through the respiratory passages. Both these may
come into play when the frog is submerged.

Doctor Herrick has pointed out to us that there are ‘four
different types of innervation of the nasal region, the functional
limitations of no one of which have been clearly shown. These
are:

1. Trigeminal nerve endings.

2. Olfactory nerve.

3. The vomeronasal nerve, with the same type of peripheral
endings as the olfactory, but limited to the vomeronasal organ
(Jacobson’s organ) peripherally and with a special part of the
olfactory bulb (the bulbus accessorius) centrally.

4. The nervus terminalis—peripheral endings unknown and
central endings independent of the olfactory bulb.

“Ayers (Jour. Comp. Neur., June 15, 1919, vol. 30, 323) has
suggested some of the physiological problems here. The ter-
minal nerve is found in all vertebrates from fishes up and is
therefore probably not specifically concerned with air breathing.
On the other hand, Jacobson’s organ and its nerve are well
developed in air breathers. Their reduction in birds may
account for some of the peculiarities of these animals.”’

Since we shall find it impossible to pursue this line of investi-
gation any further, we can only hope that. the above observa-
tions may at any rate serve the purpose of suggesting a field for
comparative physiological research.

Some of the experiments above described were carried out by
Mr. K. J. Austmann under our direction.

292 SWALE VINCENT AND A. T. CAMERON

15

16

LITERATURE CITED

AXENFELD, D. 1911 Die Bedeutung der Nasenschleimhaut fiir den Respi-
rationsakt der Amphibien. Zentralb. f. Physiol., Bd. 25, S. 329-31.

Barr, M. 1897 Zur physiologischen Bedeuting der Luftsicke bei Végeln.
Biol. Zentralb., Bd. 17, S. 282, quoted by Baglioni, Ergeb. d. Physiol.,
1911, Baril, (8: 558.

Bacuioni1, 8. 1911 Zur vergleichenden Physiologie der Atembewegungen
der Wirbertiere. Ergeb. f. Physiol., Bd. 11, 8. 526.

Brau 1860 Recherches sur la mort par submersion. Arch. gén. de méde-
cine, 5° série, T. 16, quoted by Huxley, Quart. J. Exp. Physiol., 1913,
vol. 6, p. 147.

Bert, Paut 1870 Physiologie de la Respiration, quoted by Huxley (ibid.)

Brown, T. Grauam 1909 Die Atembewegungen des Frosches und ihre
Beeinflussung durch die nervésen Zentren und durch das Labyrinth.
Arch. f. d. ges. Physiol., Bd. 130, S. 193.

Cameron, A. T., anD BRowNLEE, T.I. 1915 On an accumulation of gas in
the tissues of the frog as a result of prolonged submersion in water.
Quart. J. Exp. Physiol., vol. 9, p. 231.

FoA, C. 1911 Nuove ricercho sull’ apnea e sull’ automatismo del centro
respiratorio. Arch. di. Fisiol., vol. 9, pp. 453-76, quoted by Baglioni,
q. V., p. 581.

FrépERIcQ 1893 Arch. f. Physiol., Leipzig, Suppl. 8S. 65, quoted by Star-
ling (q. v.).

Huxtey, Frances M. 1913 On the reflex nature of apnoea in the duck in
diving: I, The reflex nature of submersion apnoea. Quart. J. Exp.
Physiol., vol. 6, pp. 147-57.

Ibid., II. Reflex postural apnoea. Ibid., pp. 159-82.
On the resistance to asphyxia of the duck in diving. Ibid., pp. 183-96.

Mirscuer-Riiscu. 1885 Arch. f. Physiol., Leipzig, 1885, S. 355, quoted by
Starling (q. v.).

Paton, D.N. 1914 The relative influence of the labyrinthine and cervical
elements in the production of postural apnoea in the duck. Quart.
J. Exp. Physiol., vol. 6, 197-207.

Srartine, E.H. 1900 Mechanism of the respiratory movements. Schiifer’s
Text-book of Physiology, vol. ii, p. 305.

Witty, V., 1919 Les mouvements respiratoires de la grenouille. Arch.
néerl. de physiol., vol. 3, pp. 315-48, through Physiol. Abstracts, vol.
4, pp. 265-6.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 5
JUNE, 1920

Resumen por los autores, H. W. Norris y Sally P. Hughes,
Colegio Grinnell.

Los nervios craneales, occipitales y espinales anteriores de
Squalus acanthias.

El presente trabajo es una descripcién del origen central,
ganglios, trayecto y distribucién periférica de los nervios craneales,
occipitales, y tres primeros nervios espinales de Squalus acanthias,
los cuales se comparan con los correspondientes de Mustelus
californicus e incidentalmente con los de Raja radiata. También
se incluye una descripcién detallada del plexo ciliar del simpatico
y una descripcién mas breve de los ganglios del simpatico hallados
en los nervios branquiales. Se describe asi mismo el origen del
nervio hipobranquial (hipogloso) a expensas del nervio occipital
y dos primeros nervios espinales. Los elementos sensorios
somaticos faltan en los nervios glosofaringeo y vago. En el
glosfarfngeo existe un constituyente lateral provisto de rafces y
ganglios distintos. Hay una _ diferencia marcada entre los
nervios constituyentes del complejo del vago. Los 6rganos sen-
soriales de la linea lateral y su inervacién se revisan brevemente.
Existen tres (o cuatro) tipos de 6rganos sensoriales de la Ifnea
lateral, a saber: 1) 6rganos canaliculares; 2) 6rganos en forma
de fositas; 3) ampollas de Lorenzini; 4) el 6rgano sensorial
espiracular etc, que esta probablemente formado por ampollas
de Lorenzini modificadas. Se describe la inervacién de todos
estos Organos.

Translation by José I’. Nonidez
Cornell University Medical College, N. Y.

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, MARCH 8

THE CRANIAL, OCCIPITAL, AND ANTERIOR SPINAL
NERVES OF THE DOGFISH, SQUALUS ACANTHIAS

H. W. NORRIS AND SALLY P. HUGHES
The Zoological Laboratory of Grinnell College

FIFTY-THREE FIGURES

CONTENTS

lGahertoys WICCIa op Grok Dens DAU en Onc tC on OM anemo ocd aaa mane mete opck 294
Matenralgandemetiodsn ractrcyte - + 2.00) cis steele stare oo cetisert ore te cies 296
PRM ETOMCHOLYATM ELV. sca yeep ciscaess sisi slo Sc siclicde ls «Sewer aa Bho tics 918 MLA 296
The optic andthe eye=muscle nerves...: ..- 2.52.2... bs Oe ee eS 306
(Rhentrmeniinalmenve rig et: ait ).(3.5- 05% tenes odes ca tldtee sans). LS iced 320
1. The roots and ganglia of the trigeminal complex....... 320
PeeWee A Cixi CSEMCE MIM ALIGHT Vises ciacosims ci eveaveeeetocises orion. Sas tes 327

5. the ramusiophphalmicus profundus V.. +). 25.040... on.'8 62-2 330

4. The ramus ophthalmicus superficialis V...................:. 332

ie Moe TON TMaScUEHOIS) We eee pe Gele bono olue0 cad Om em picatas aor 336

Or, Weqnanatae surety DONATES: Vis ok os 2 ss-p fh eal a ees a, Se « «ps ag ae 337
MNNELTACTA ET CLV.C aamwPeter ee tear ne sas ooo. has sk atone seeks sigua Seatnoiare cusrelatte aerate 339
1. The lateral-line roots and ganglia of the facial nerve..... . 339

2. The roots and ganglia of the facialis proper.................. 346

3. The ramus ophthalmicus: superficialis VILs 00% 35.55 cee. ec e cece es 347
APUG LAMNUSHOUCCA Smet snd he nic nh erst Mein Laisa: aire 348

5. ANE TAMU SPOR MAUMVRULR Forts tk ohle o/s hg acta teas heaeea Bidets ote sie tua 348

65 Dhe truncusthyomendibulanis; VillS sepa ce foc desc scree soe 350
The ramus mandibularis externus VII................6.. 350

The ramusaaandibularis:internus) VIL. so sc. 22 5 ho cin sani 352

Lhe rami smmyord ens: VALDES > oar een sre: 200). 0 cca ke ene ae ean 352

7, The ramustpalatimus VEL. 2)... . 02s... 02 Hid 8 aoe deco 353

8. General reflections upon the facial nerve...................-- 353

AD CUP FDIS ITH aS AVDS, ction Oued DE CO CRETE e DEIOIG co Lc ane RnR one oc 355
ie elossoplaryigeaemenyen F-15506. ssa os « « swudueled si sla sie cede cna vale 356
1. The roots and ganglia in the glossopharyngeal nerve........ 356

2. The lateral-line elements in the glossopharyngeal nerve 356

oo Lhe Tams Supra vempOrals doko... ...2 dak aceas on vce eeseesss 308
AUS Hist DTAMe Mi AMMEN VC) a5 </2/<!x.<s/a/s:0 sie eeevehe «© b eaieseae e's a0 358
WHE VAGUS NER VEN ees see eR ae aa ore abe ci caih RRs bc oe red celtoides Sue es 360
1. The lateral-line roots and ganglia of the vagus nerve...... . 360

2. The roots and ganglia of the vagus nerve proper.............. 362

On Lhe TaMUS SUprA LEMP ORAlISON: %.c:2< a..cue es sei Aeias a ee Sails © 366

294 H. W. NORRIS AND SALLY P. HUGHES

4-'The ‘ramus Monsaligs oxo \cere yen cteye se misecoeeis ete oe eres ore rare erate tetera eee 366
5. General cutaneous elements in the vagus nerve of elasmobranchs... 367
6) Rherramusslatenaliisexevacae eric rrccssicicie cee vier rete teaersiterereneloretekereicroeiets 369
7helsecond to thesnithy branch alemenyes seer eee citi iiteriaeticir 369
8) The ramus) imtesbino-accessOnlus exper). eieie cis settee eects 372
The oecipital mervess a An fee seek ae as toe reteencho aie olecrats = = = hate orate raters ers 373
The first three spinalimetved: eke, Lage aeleeite Modstsee & aike wie aarti Ae eoeraear 375
The Mypobranchial Merve. ict. te: <7:-15 ciety oralas wieleide Fyne mies sss hela ielahe see 376
Sympathetic ganglia connected with cranial nerves...............+.0-+--- 381
i "Ehe ciliary sympatheuile plexus... se ssc. =o tes oles ieee acer 382
2. Branchial sympathetic ganglia................. Sea Es cae cae BOO
TeniGer ature Cubed eye yicnicrcve ectets ere oice Ola ere terete ecu stekeraint eke te favatlorchvexsrererersneracaees 392
INTRODUCTION

The common dogfishes of Europe and America have long been
used in biological laboratories as types introductory to courses
in the comparative anatomy of vertebrates, neurology, etc. An
exact knowledge of the structure of these forms, particularly of
the head, has, strangely enough despite their general use, not
yet been gained, except in reference to certain parts. Marion
(05) has described the muscles of the head in Squalus acanthias.
The skull of the same form has been accurately described and
figured by Wells (17). Neal’s (’97, ’98, 714, ’18) studies on the
development of the nervous system, the metamerism of the
head, and the innervation of the hypoglossal musculature have
thrown much light upon adult conditions. It has long been
customary to regard the cranial nerves of the selachians as a
pattern to which may be referred the cranial nerves of all other
vertebrates. Without doubt, this practice has been justified,
but it is a matter of regret that so little has been positively known
of the exact composition, origin, and distribution of the main
nerves, to say nothing of the smaller divisions.

There is a vast and bewildering literature upon the cranial
nerves of the elasmobranch fishes. Much of it is based upon
inexact observations, much of it has been published in support of
theories that have little basis in fact. Doubtless, our knowledge
of cranial anatomy had to be exploited in the interests of now
generally abandoned theories of the metamerism of the head.
Unquestionably, there is a fundamental segmentation of the

NERVES OF THE DOGFISH 295

head, but in seeking to establish a theory we have too often over-
looked the obvious facts. A review of the extensive investiga-
tions into the anatomy of the selachian nervous system would be
of littie value in the present research, for, notwithstanding the
voluminous literature, few attempts have been made in an exact
analysis of the cranial nerves of these forms. Strong (’03, ’04)
published very brief abstracts of very extensive and thorough-
going analyses of the cranial-nerve components in Squalus acan-
thias. Landacre (’16) described the embryonic condition of the
cranial ganglia and nerve roots in the same species. Houser
(01) made a careful study of the neurones of the selachian brain,
using chiefly Mustelus canis. Allis’ (01) studies upon Mustelus
laevis have made valuable contributions to our knowledge of the
selachian nervous sytem, but the writers are unable to follow
him in many of his conclusions.

It is in the hope of clarifying our present knowledge of the basic
structures that constitute the peripheral portions of the cranial
nerves of the elasmobranch fishes that the writers have under-
taken an analysis of the composition of these nerves. At the
very outset of the presentation of our results, it may be said
that there has been throughout the investigation a remarkable
clearness as to the certainty of the facts. Long and wearisome
tracing out of details has characterized the progress of the re-
search, but there has been a satisfying certainty about all the
minutiae that has made the task a pleasant one. Probably in
no other vertebrates are the nerve components more distinct
histologically than in the selachians. Given the proper tech-
nical treatment, there need be little uncertainty about the
findings.

For general bibliographies on the cranial nerves of the selach-
ians the reader is referred to the papers of Allis (’89, 797, ’01),
Cole (’98), and Neal (’98, 714).

The writers are greatly indebted to Prof. H. V. Neal, of Tufts
College, for embryos of Squalus acanthias, to Prof. J. F. Daniel
and Mr. F. H. Ballou, of the University of California, for em-
bryos of Mustelus californicus, and to Mr. Fred T. Lane, of Rock-
port, Massachusetts, whose kindly cooperation has been that of a

296 H. W. NORRIS AND SALLY P.. HUGHES

friend rather than an agent. For the loan of literature and the
freedom of access to his private library the writers are under
lasting obligation to Prof. J. S. Kingsley, of the University of
Illinois.

Acknowledgment is made of a grant from the Bache Fund of the
National Academy of Sciences, which has made possible the early
completion of this research.

MATERIAL AND METHODS

Heads of Squalus acanthias and of Mustelus californicus, in
the ‘pup’ stage, were fixed in vom Rath’s picric-acetic-osmic-
platinic mixture and sectioned by the celloidin method. The
best results were obtained by fixing in a 10 per cent solution of
neutral formalin, followed, after thorough washing, by the vom
Rath treatment. Where the latter is applied to fresh material
(dogfish), many kinds of structures are blackened; but when
preceded by formalin fixation, only nerves and muscles are thus
affected and stand out distinctly, on a nearly-colorless background.
Material long preserved in formalin does not seem to react as
favorably as that which has been recently fixed. The sections
were cut 15u and 20 thick, mounted in balsam on lantern-slide
covers, and covered with large sheets of mica. In most instances
the sections were counterstained on the slide in Van Gieson’s
picrofuchsin. By this treatment the most faintly stained nerve
fibers could be distinguished readily from connective tissue. Pro-
jections of the nerves were made upon the sagittal and horizontal
planes. A wax model was made of one half of the medulla
oblongata, especial attention being given to an analysis of the
ganglia. A model of some of the structures found in the orbit
has served to make clear some of the relations of the ciliary
ganglia.

THE OLFACTORY NERVE

The writers see no good reason for disagreeing with Brookover
(10, 711, 714, 715) in the opinion that the nervus terminalis is
in origin and structure related to and a part of the olfactory
nerve. Belogolowy (’11), from his researches upon the develop-

NERVES OF THE DOGFISH 297

ment of the nervus terminalis in Selachians (Acanthias, Raja,
Torpedo), concludes that the olfactory nerve develops out of and
supplants a primary ganglionic nerve of the olfactory vesicle.
The nervus terminalis of selachians, according to him, is but a
persisting remnant of the primary nerve. The primary olfactory
nerve is a derivative of the olfactory placode. The secondary
olfactory nerve (olfactory nerve proper) is then but a derivative
of the nervus terminalis. Brookover agrees with Belogolowy,
except that he does not see any need or propriety in calling the
ganglion a primary olfactory ganglion.

To the account given by Locy (03) of the nervus terminalis
of Squalus acanthias the writers have nothing of importance to
add. In the words of that writer:

Starting deep in the median furrow, it passes forward across the
anterior surface of the forebrain; it then curves in the angle formed by
the union of the olfactory tract and the forebrain, and finally passes
along the inner margin of the tract to reach the median division of the
fila olfactoria. It crosses this obliquely and enters the fissure between
the two divisions of the fila.

For a review of the literature relating to the nervus terminalis,
the paper by Larsell (18) should be consulted.

To quote further from Locy (’99): ‘‘The olfactory nerve in
selachians has for a long time been represented as double, but
very little has been said about it in descriptions of figures or in
texts.”’ Locy (’99, 703) has described the development of the
olfactorius in Squalus acanthias, showing that in its earlier stages
it is distinctly double. Those who have figured the double char-
acter of the olfactory nerve in selachians have for the most part
concerned themselves with the olfactory bulb. Miklucho-Maclay
(70), in many excellent figures of the brains of various selach-
ians, has shown very plainly that the olfactory bulb is distinctly
double. Locy draws a sharp distinction, as most of his prede-
cessors have not done, between the olfactory fila (olfactory nerve)
and the olfactory bulb and tract.

As Locy observes in the 150-mm. stage of Squalus, a distinc-
tion externally between bulb and tract can hardly be made. In
section, however, there may be distinguished in the olfactory

298 H. W. NORRIS AND SALLY P. HUGHES

lobe a posterior fibrous portion at whose periphery the olfactory
glomeruli gradually appear, in passing anteriorly section by sec-
tion. In the posterior part of the field of their appearance in
the sections an anatomical distinction between lateral and ventral
groupings of the glomeruli does not seem apparent, but proceed-

= ie
NSE SS SS 4 Sy
cspro. tee ;

a Wa
s

S\_(

Fig. 1 A cross-section of the right half of the head through the olfactory
bulb and the extreme posterior border of the olfactory lamellae. Section 429
(fig. 51). X15.

ing anteriorly there are soon seen three bands of glomeruli,
dorsal, lateral, and ventral. Anterior to the level where the
olfactory bulb appears separate from the brain in cross-sections,
the dorsal and ventral areas unite mesially into one, ventro-
mesial in position (fig. 1, glm.).

NERVES OF THE DOGFISH

299

ABBREVIATIONS

a., nerves supplying ampullae of Loren-
zinl

abas., basilar artery

abuc., buccal ampullae of Lorenzini

ac., acusticum (tuberculum acusticum)

admd., m. adductor mandibulae and its
innervation

an., ala nasalis

aoph., ophthalmic artery

apsdbr., pseudobranchial artery

apsic., posterior cerebral artery

aspro., supraorbital ampullae of Loren-
zini

auc., auditory capsule

ba., basal portion of cranium

bolf., bulbus olfactorius

bolfl., lateral portion of the olfactory
bulb

bolfm., mesial portion of the olfactory
bulb

br.plx., brachial plexus

br.X 1-4, branchial nerves of the vagus

buc., buc.VII, ramus bucealis VII

bv., unnamed blood-vessels

c., nerves supplying canal organs

care., external carotid artery

cari., internal carotid artery

cbl., cerebellum

cbr.1, first ceratobranchial cartilage

cd., chorda dorsalis

chm., hyomandibular lateral-line canal

chmd., hyomandibular cartilage

cil., ciliary nerves

cila., anterior ciliary nerve arising
from the r. oph. prof. V

cilp., posterior ciliary nerve arising
from the r. oph. prof. V

cilrl., radix longa of the ciliary plexus

cinfro., infraorbital lateral-line canal

clat., main lateral-line canal of the
trunk

cmd., mandibular lateral-line canal

cplx., chorioid plexus

cr., cranial wall

crtf., corpus restiforme

csp., chorda spinalis

cspro., supraorbital lateral-line canal

esproe., ethmoidal section of the pre-
ceding

cspt., supratemporal lateral-line canal

ctm., temporal lateral-line canal

cv.1, first ventral constrictor muscle

dors.X, ramus dorsalis X

dlpo., dorsolateral series of pit-organs

dpo., dorsal series of pit-organs

eth., branch of r. oph. spf. VII inner-
vating the ethmoidal section of the
supraorbital lateral-line canal

jfim., fasciculus longitudinalis medialis

folf., fila olfactoria

folfl., lateral division of the olfactory
fila

folfm., mesial division of the olfactory
fila

folfm.ad l., mesial olfactory fila distrib-
uted laterally

gac., ganglion acusticum

gacs., saccular portion of the auditory
ganglion

gacv., vestibular portion of the audi-
tory ganglion

gbr.X1-4, ganglia of the
nerves of the vagus

gbuc., ganglion of the ramus buccalis
VII

gbuca., small accessory ganglion on the
preceding

gcil.1—9, ganglia of the ciliary plexus

gg., ganglion Gasseri

ggen., ganglion geniculi

ggl., ganglion glossopharyngei

gll.X, lateral-line ganglia (in entirety)
of the vagus nerve

gll.Xa, b,.c, the three lateral-line gang-
lia of the vagus nerve

glm., glomeruli olfactorii

gmde., ganglion of the ramus mandib-
ularis externus VII

gop., ganglion of the ramus oph. pro-
fundus V

branchial

300 H. W.

gos., gos.VII, ganglion of the ramus
oph. superficialis VII

gos.V, ganglion of the ramus oph. su-
perficialis V

got., ganglion of the ramus oticus VII

gspt.IX, lateral-line ganglion of the
glossopharyngeal nerve

gsy., sympathetic ganglia

gv., ganglion vagi

g.IX, combined ganglia of the glosso-
pharyngeal nerve

hybr., nervus hypobranchialis

hy., hy.VII, ramus hyoideus VII

ical.1, first interealary cartilage

lat.X, ramus lateralis X

lbinf., lobi inferiores

lbll., lobus lineae lateralis

lbus., lobus visceralis

lolfa., anterior olfactory lamellae

lolfp., posterior olfactory lamellae

lup-q., m. levator palato-quadrati and
its innervation, including that of the
m. spiracularis

md., md.V, ramus mandibularis V

mde., mde.VIT, ramus mandibularis ex-
ternus VII

mdea., mdep., anterior and posterior
divisions of the r. mde. VII

mdi., mdi.VII, ramus mandibularis in-
ternus VII

mdobl., medulla oblongata

mdpo., mandibular series of pit-organs
and their innervation

mes., raesencephalon

mes.V, radix mesencephalica V

mx., mx.V, ramus maxillaris V

mxpc., a posterior cutaneous branch of
the ramus maxillaris V

mzph., pharyngeal branch of the ramus
maxillaris V

nas.d., anterior dorsal division of the
nasal chamber

nas.v., posterior ventral division of the
nasal chamber

ne., nasal cartilage and eapsule ©

nflv., nasal flap valve

nt., nervus terminalis

oc., eyeball

NORRIS AND SALLY P. HUGHES

occ., occipital condyle

oce. y+z, occipital nerves y and z

oi., m. obliquus inferior and its inner-
vation

op., op.V, ramus ophthalmicus pro-
fundus V

opch., optic chiasma

os.V, ramus ophthalmicus superficialis
Vv

os.V1—-4, branches of the preceding

os.VII, ramus ophthalmicus superfici-
alis VII

ospr., spiracular sense organ

ot., ot. VII, ramus oticus VII

pa., processus antorbitalis

pal., pal.VII, ramus palatinus VIT

pch., parachordal region of cranium

ped., optic pedicel

ph.IX, ph.X1-4, pharyngeal rami of
the glossopharyngeal and vagus
nerves

pmn.V, portio minor and its rootlets of
the trigeminal nerve roots

pmj.V, portio major of the trigeminal
nerve roots

p-q., palatoquadrate cartilage

pro., m. preorbitalis and its innerva-
tion

prt.VII, prt.IX, prt.X1-4, pretrematic
rami of the facial, glossopharyngeal
and vagus nerves

pst.IX, pst.X1-4. posttrematic rami
of the glossopharyngeal and vagus
nerves

pst.IXa, pst.Xal-4, accessory post-
trematic rami of the glossopharyn-
geal and vagus nerves

r., rostrum

rbuc., root fibers of the ramus buccalis
VII

rc., rostral carina

rext., m. rectus lateralis (externus) and
its innervation

rinf., m. rectus ventralis (inferior) and
its innervation

rint., m. rectus internus and its inner-
vation

rot., root fibers of the ramus oticus VII

NERVES OF THE DOGFISH

rs., m. rectus dorsalis (superior) and
its innervation

sac., sacculus

sacus., saccus vasculosus

sbsp., m. subspinalis and its innerva-
tion

sca., anterior semicircular canal

scl., sclerotic coat of the eyeball

so., m. obliquus dorsalis (superior) and
its innervation

sp.1—6, first six spinal nerves

sp.1m., motor portion of the first spinal
nerve

sp.irm., motor root of the first spinal
nerve

sp.1s., sensory portion of the first spinal
nerve

sp.8m., motor portion of the third spi-
nal nerve

sp3s., sensory portion of the third
spinal nerve

spr., spiracle

sptpo., supratemporal pit-organs

spt.IX, ramus supratemporalis IX

spt.X, ramus supratemporalis X

sp.V, tractus spinalis trigemini

sp.Va, anterior continuation of the pre-
ceding

sy., Sympathetic nerves

tm., tectum mesencephali

trap., m. trapezius and its innervation

tr.kmd.VII, truncus hyomandibularis
Vil

tr.io.V+VII, truncus infraorbitalis
(mx. V+bue. VII)

trm., trunk muscles

utre., utriculus

v, W, x, y, 2, the five occipital nerves

v.1, first vertebra

vise.X, ramus visceralis X

vpo., ventral series of pit-organs and
their innervation

301

I, nervus olfactorius

IT, nervus opticus

III, nervus oculomotorius

IIId., dorsal division of the oculomotor
nerve

IIIv., ventral division of the oculo-
motor nerve

IV, nervus trochlearis

IVch., decussation of the trochlear
nerve

IVndl., nidulus of origin of the troch-
lear nerve

IVr., root of the trochlear nerve

Vrm., motor root of the trigeminal
nerve

VI, nervus abducens

VII, nervus facialis

ViIril., lateral-line roots of the facial
nerve

VIIrlid., dorsal lateral-line root of the
facial nerve

VIIrllv., ventral lateral-line root of
the facial nerve

VIlIrm., motor root of the facial nerve

VIIrvs., visceral sensory root of the
facial nerve

VIII, auditory nerve

VIIIr., root of the auditory nerve

VIIIs., saccular division of the audi-
tory nerve

VIIIv., vestibular division of the audi-
tory nerve

IXr., root of the glossopharyngeal
nerve

Xr., roots of the vagus nerve proper

Xr.br.1-4, roots of the four branchial
nerves of the vagus

Xrll., lateral-line roots of the vagus

Xrm., motor rootlets of the vagus

Xrvs., visceral sensory rootlets of the
vagus

302 H. W. NORRIS AND SALLY P. HUGHES

Locy has stated that the olfactory cup in selachians is imper-
fectly divided by the development of a membranous fold from
the ring surrounding the entrance to the cavity, there resulting
two parts in the chamber, a mesial and a lateral. These two

folfm.ad |.
> \

SG)

Fig. 2 A similar section slightly anterior to the preceding, and immediately
anterior to the olfactory bulb, through the two masses of olfactory fila. Section
412. X\15.

divisions in the olfactory cup are the result, as Berliner (’02) has
shown, of the early differentiation in the embryo of two groups
of Schneiderian folds or lamellae. These, however, have no
exact relation to the double nature of the olfactory nerve. Sund

NERVES OF THE DOGFISH 303

(04, ’05) finds in Spinax niger that the olfactory nerve in its
development is at first single, connecting the anterior ventral
part of the olfactory placode with the brain. Later by shifting
and extension of the olfactory pit the nerve becomes connected
with the dorsal part of the placode. Longitudinal Schneiderian

t
f
|
\

is
%

Fig. 3 A similar section through the nasal capsule, cutting the extreme pos-
terior edge of the lamellae of the anterodorsal part of the olfactory cup. Sec-
tion 387. X15.

folds appear, most complete near the nerve. Later a secondary
group of the folds appears and a secondary nerve connection with
the anteroventral part of the placode occurs. There results a
double chamber—one posterior, containing the primary folds and
related to the primary nerve, the other anterior, containing the

304 H. W. NORRIS AND SALLY P. HUGHES

secondary folds and related to the secondary nerve. Sund sug-
gests that the anterior secondary chamber corresponds to Jacob-
son’s organ. Asai (713) shows in models of the olfactory organ
of Mustelus laevis that the olfactory cup is divided by the mem-
branous fold into a posteroventral and an anterodorsal chamber,

aspro.

Fig. 4 A cross-section through the right olfactory cup, cutting through the
nasal opening and the extreme anterior edge of the lamellae of the posteroventral
part of the olfactory chamber. Section 346. X15.

but that the two series of Schneiderian folds are continuous with
each other around the ends of the septum.

In Squalus acanthias in the 150-mm. stage these two parts of
the olfactory cup are posteroventral and anterodorsal in position.
The olfactory fila entering the mesial (dorsal, mesial, ventral)
group of glomeruli in the olfactory bulb are related to the larger

NERVES OF THE DOGFISH 305

part, mesial and lateral of the olfactory lamellae in the antero-
dorsal portion of the olfactory cup, and to a smaller mesial por-
tion of the lamellae in the posteroventral part. The fila enter-
ing the lateral group of glomeruli are from the larger lateral part
of the lamellae of the posteroventral portion of the cup, and from
a smaller number of the lateral lamellae of the anterodorsal part
of the cup. In brief: the lateral olfactory glomeruli are related to
the lateral olfactory lamellae in the olfactory cup; the mesial glo-
meruli are connected with mesial lamellae and with some of the
lateral ones. Thus there are two olfactory nerves: a ventro-
mesial olfactory nerve, related on the one hand to dorsal, mesial,
and ventral glomeruli, and on the other to mesial and lateral
lamellae in both parts of the olfactory cup; and a lateral olfactory
nerve, related to lateral glomeruli and to lateral lamellae in both
parts of the cup. Hence the two divisions of the olfactory cup
are not in exact correspondence to the two olfactory nerves, as
Locy supposes. The lateral division of the olfactory fila evi-
dently corresponds to Sund’s primary olfactory nerve, and the
mesial division to the secondary nerve, but later distributions of
fibers have obscured the original sharp distinction between the
two nerves. In Mustelus the relations of the olfactory fila to
the olfactory cup and parts of the olfactory bulb are essentially
as In Squalus.

In figure 1 is shown a cross-section through the anterior por-
tion of the olfactory bulb, where the olfactory glomeruli are seen
arranged in two groups: a dorsal-mesial-ventral series and a lat-
eral series. ‘The two large masses of olfactory fila, ventromesial
and lateral, give a distinctly double appearance to the anterior
part of the bulb (figs. 35, 51, 52, 53, bolfm., bolfl.). Figure 2 is of
a cross-section through the two olfactory nerves slightly posterior
to the transverse level where the nervus terminalis passes across
the mesial olfactory fila. Some of the lateral olfactory fila are
seen passing mesially into the mass of mesial fila (folfm. ad l.).
In figure 3 the posterior edge of the anterodorsal olfactory lam-
ellae is shown, and in figure 4 the anterior extremities of the
posteroventral lamellae. The position of the septum between the
two parts of the olfactory cup is indicated in figures 35 and 51.

306 H. W. NORRIS AND SALLY P. HUGHES

THE OPTIC AND THE EYE-MUSCLE NERVES

The thoroughgoing descriptions and discussions by Neal (’98,
14, °18) of the origin, histogenesis, homologies, and general
topographical relations of the eye-muscle nerves, with especial
relation to the condition in Squalus acanthias, make any extended
treatment of the subject by the present writers quite superfluous.
For a review and list of the literature upon this subject the reader
is referred to the second (’14) of these papers by Neal.

From the eyeball the optic nerve runs posteromesially into
the optic foramen, and thence anteriorly into the chiasma. The
anterior dorsal part of the chiasma is formed from fibers situated
dorsally in the nerve, and the ventral posterior part from the
ventral portion of the nerve. Near the brain a cross-section of
the nerve shows a deep notch on its posterior border; near the
eyeball a similar section reveals four such deep indentations (figs.
15 and 34).

The nidulus of origin of the oculomotor nerve is situated im-
mediately dorsal to the ventral motor columns, slightly posterior
to a transverse level where the cavity of the midbrain communi-
cates ventrally with that of the inferior lobes. Numerous strands
of fibers, many of which decussate, pass posteroventrally from
the nidulus, emerging immediately posterior to the point where
in cross-section the inferior lobes separate externally from the
midbrain. After being collected into the external nerve, the
rootlets pass posteriorly in the angle between the midbrain and
the inferior lobes, the nerve lying at first at the dorsolateral
angle of the inferior lobes, farther posteriorly in the same relation
to the saccus vasculosus, finally passing laterally across the dor-
sal border of the latter to reach its exit from the skull (figs. 5, 6,
12 to 14, and 21). An intracranial ganglion on the oculomo-
torius, as reported by Nicholls (15) in Seyllium, is not found by
the writers in Squalus. Entering the orbit the third nerve, turn-
ing sharply anteriorly, almost immediately divides into two
branches. An anterior dorsal division (I//d.) passes at once
into contact with the dorsal rectus muscle, and running along
its anteromesial border between it and the internal rectus muscle

NERVES OF THE DOGFISH 307

Figs. 5 to 11 Parts of cross-sections through the orbit of the right eye. To
show the interrelations of the oculomotorius, the trigeminal and facial trunks in
the orbit, the ciliary plexus and the ocular muscles. . X25. Fig. 5, section 859.
Fig. 6, section 869. Fig. 7, section 889. Fig. 8, section 893. Fig. 9, section 895.
Fig. 10, section 901. Fig. 11, section 906.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 5

HUGHES

NORRIS AND SALLY P.

\nWe

Jele

308

NERVES OF THE DOGFISH 309

innervates both muscles (figs. 5 to 7, 15 to 17, and 21). The
posterior ventral division of the nerve turns posteriorly and then
sharply ventrally around the origins of the rectus dorsalis and
rectus internus on the optic stalk, passing between the ganglion
of the ramus ophthalmicus profundus and the rectus dorsalis

muscle (fig. 31, [/Jv.), then between the optic stalk and the
rectus lateralis muscle, farther ventrally between the latter and
the origin of the rectus internus, and still farther ventrally be-
tween the rectus lateralis and the rectus ventralis (figs. 8 to
11, 15 to 17, 20, and 21). In thus passing ventrally it divides
into an anterior and a posterior branch, both divisions turning

310 H. W. NORRIS AND SALLY P. HUGHES

anteriorly around the posterior border of the rectus, ventralis,
the anterior one entering and innervating the muscle and the
posterior one running across the ventral border of the muscle
and parallel to the truncus infra-orbitalis (figs. 7 to 9, 15 to 17,
and 21). This relation to the latter nerve is maintained “until

a

®
cilrl7

apsdbr. sex

the oculomotor branch terminates in the obliquus ventralis
muscle (figs. 5 to 9, 15 to 17, and 21). In this anterior course
the nerve passes ventral to the optic nerve. The relations of
the oculomotor nerve to the ciliary plexus will be described later.

The trochlear nerve leaves the brain in the fashion character-
istic of selachians: on the dorsal wall of the midbrain just an-

NERVES OF THE DOGFISH 311

terior to the cerebellar stalk, and ventral to the cerebellar crest
(figs. 18 and 24). At its decussation in the velum it beeomes
closely associated {with other fiber tracts: the decussatio veli,
the tractus tectocerebellaris, and the radix mesencephalica tri-
gemini. jThe relations of these various tracts to each other have

been described by Johnston (’05, ’09) and by van Valkenburg
(11) in Seyllium canicula and stellare. As stated by these
authors, the relations in Squalus acanthias (Acanthias vulgaris)
are essentially similar to those in Scyllium. From the decus-
sation the trochlearis fibers pass anteroventrally around the
lateral angle of the fourth ventricle to their origin in the troch-

S12 H. W. NORRIS AND SALLY P. HUGHES

lear nidulus dorsal to the ventral motor fiber columns immediately
posterior to the oculomotor nidulus (figs. 12 to 14, 18, and 19).
Near the decussation the trochlear fibers pass by and interlace
with the fibers of the radix mesencephalica V, which here con-
sists of numerous small tracts near their termination in the mesen-

a

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apsdbr,

=

cephalic tectum. Peripherally, the nerve runs anteriorly along
the dorsolateral border of the midbrain, in the anterior part of
its intracranial course pressed closely between the brain and the
skull. At its foramen it passes ventrolaterally through the
cranial wall and comes into intimate relation with the mesial
border of the ramus ophthalmicus superficialis facialis. ‘Thence

NERVES OF THE DOGFISH as

passing anteroventrally around the ventral border of the latter,
it turns abruptly anterodorsally across the orbital cavity and
soon reaches the dorsal oblique muscle which it innervates.
The posterior rootlets of the abducens nerve appear emerging
from the ventral motor column of the medulla oblongata at the
transverse level of the anterior border of the internal opening of
the spiracle (fig. 20). There are about eight large rootlets that

Rie Sa

=
Set ee ETS
SS

contribute to its formation, all arising in the ventral motor col-
umn. Peripherally, the nerve runs anteriorly intracranially, at
first at the ventrolateral border of the medulla; farther anteriorly
at the transverse level of the posterior border of the gasserian
ganglion, it enters a canal in the ventral floor of the cranium and
runs anterolaterally toward the orbit. Emerging from the canal
mesial to the maxillary ramus of the trigeminal nerve, it passes

H. W. NORRIS AND SALLY P. HUGHES

314

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NERVES OF THE DOGFISH

315

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HUGHES

NORRIS AND SALLY P.

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NERVES OF THE DOGFISH 317

318 H. W. NORRIS AND SALLY P. HUGHES

around the anterior border of this nerve, turns laterally into the
orbit, and divides into two branches, one of which immediately
enters the anterodorsal part of the rectus lateralis muscle, the
other the anteroventral part (figs. 10, 11, 15 to 17, and 20).

Fig. 18 A horizontal section through the trochlear decussation, showing the
relations of the trochlear roots and the radix mesencephalica V. Section cut
somewhat obliquely. X25.

Fig. 19 A horizontal section through the trochlear nidulus, showing the rela-
tions of the trochlear root and the radix mesencephalica V. X25.

NERVES OF THE DOGFISH 319

Fig. 20 A horizontal section through a portion of the base of the cranium
from the optic commissure anteriorly to the anterior portion of the ear capsule
posteriorly, cutting the optic chiasma, the roots of the abducens nerve, the in-
ferior lobes, the saccus vasculosus and the anterior part of the medulla oblongata.
X15.

320 H. W. NORRIS AND SALLY P. HUGHES

THE TRIGEMINAL NERVE
1. The roots and ganglia of the trigeminal complex

According to Landacre (’16), the roots of the trigeminal nerve
in 22-mm. embryos of Squalus acanthias are in two groups: (I)
an anterior portio minor of three roots: 1) sensory fibers by which
the profundus ganglion connects with the tractus spinalis tri-
gemini; 2) motor fibers; 3) sensory fibers, presumably belonging
to the maxillomandibular division of the fifth nerve; (II) a pos-
terior portio major, consisting of sensory fibers entering the
spinal V tract. At the stage examined by the writers there are
found in the portio minor four or five rootlets: 1) an anterior
dorsal rootlet of motor fibers, with which are possibly associated
sensory elements; 2) motor fibers; 3) fibers ending in the spinal
V tract, and presumably sensory; 4 and 5) motor fibers (figs. 12
to 14, 21, 22, and 25 to 30, pmn.V, 1-5). - The portio major con-
sists of a large number of sensory rootlets entering the spinal V
tract, with which are mingled a small number of motor fibers
(figs. 12 to 14,°21,,22,:29, 30; and’32, pm7.V):

That the first rootlet of the portio minor is largely motor is
beyond question, but its exact composition the writers have found
well nigh impossible to determine. That fibers from the pro-
fundus ganglion enter the brain through this first rootlet seems
- possible; they appear to do so. In fact, the relations in the gas-
serian ganglion would justify the supposition that all the rootlets
of the portio minor contain sensory elements, but their course
in the brain does not warrant such a conclusion. The first
rootlet passes directly into the anterior continuation of the spinal
V tract, where it divides into two parts, one continuing on di-
rectly into the lateral motor column, the other turning abruptly
anteriorly and becoming the radix mesencephalica V. Appear-
ances permit the assumption that some fibers of this first rootlet
may end in the spinal V tract. The second rootlet seems to be
exclusively motor. It passes through the spinal V tract, but
shows no indications of ‘giving fibers to it. The third rootlet is
very small. It arises immediately posterior to the second root-
let, and in some specimens cannot be recognized, probably being

NERVES OF THE DOGFISH 321

united with the preceding rootlet. It ends in the spinal V tract.
It seems to come from the profundus ganglion rather than from
the gasserian. The fourth and fifth rootlets may possibly con-

i 1000 2

4
Y)

Vilrlid. Z:

Fig. 21 A projection upon the sagittal plane of the roots and ganglia of the
V-VII-VIII nerve complex, together with the oculomotor nerve and the ciliary
sympathetic nerve plexus. Represented as seen from the left side. X20.

tain sensory fibers, but motor elements predominate. From a
study of cross, sagittal, and horizontal sections the impression
is gained that the portio minor is overwhelmingly motor in com-
position, and that the greater part of the profundus fibers enter

O22 H. W. NORRIS AND SALLY P. HUGHES

the portio major. The latter contains only a very small per-
centage of the motor elements in the trigeminal nerve. The
sensory fibers of the portio major on entering the brain pass by

Vilrild.

Fig. 22 A projection upon the sagittal plane of the roots and ganglia of the
V-VII-VIII nerve complex, portions of the lateral-line roots and ganglia being
represented as cut away to expose the gasserian ganglion with its roots and the
roots of the facialis proper. Of the auditory nerve only the root is shown. Left
view. X20.

a broad sweeping curve into the tractus spinalis trigemini, run-
ning ventral to the motor and visceral sensory roots of the fa-
cialis. The condition in Squalus gives no justification for the
statement that ‘the fibers of the ophthalmicus profundus are

NERVES OF THE DOGFISH a2

traced into the midbrain.”’ The relations of the roots of the
fifth nerve in Mustelus are essentially as in Squalus.

Marshall and Spencer (’81), summarizing the studies of other
investigators, state for the trigeminal nerve in adult selachians

ay
~~ U;
Vilrlid. &

Fig. 23 A projection upon the sagittal plane of the roots and ganglia of the
V-VII-VIII nerve complex of Mustelus californicus. Left view. X20.

two roots: 1) an anterior one [portio minor] arising from the
brain by two non-ganglionated rootlets; 2) a posterior ganglion-
ated root [portio major]. Van Valkenburg’s more recent descrip-
tion of the roots of the trigeminus in Scyllium (’11 a and b) indi-
cates that the roots of the fifth nerve in that form are essentially

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 5

324 H. W. NORRIS AND SALLY P. HUGHES

as in Squalus. Van Wijhe (’82) finds in stage L of the embryo of
Seyllium that the trigeminal nerve connects with the brain by
two roots, an anterior non-ganglionated part, which he regards
as belonging to the ramus ophthalmicus profundus, and a pos-
terior ganglionated root. Mitrophanow (’92) antagonizes the
views of van Wijhe, and while controverting the opinion that the
ophthalmicus profundus is an independent nerve asserts that in
Acanthias vulgaris the anterior trigeminal root [portio minor]
belongs with the maxillomandibular trunk, the ophthalmicus
profundus sending its fibers chiefly into the posterior root [portio
major]. Ewart (89) states that in Laemargus the ramus oph-
thalmicus profundus arises by two to five rootlets immediately
in front of the main trigeminal root; but this is doubtless an error,
for the probability is that the relations that obtain in Squalus,
Scyllium, and Mustelus are typical. The discrepancy between
this account of the roots of the trigeminus in Squalus and the
description by Landacre is doubtless to be explained as due
largely to a later and more extensive development of motor fibers
in the stages studied by the writers.

The ganglia of the two divisions of the trigeminal nerve are
sharply distinct in Squalus, both in embryo and adult. The pro-
fundus ganglion (gop.), wholly extracranial in position, is in
contact dorsally with the anterior (dorsal) lateral-line ganglion,
which sweeps out in a semicircle laterally, nearly hiding the
trigeminal ganglia (figs. 10, 11; 16, 17, 21, 22, 24, 31, 32, 35, 51,
and 52). The profundus ganglion in the ‘pup’ stage is about
500u long and oval in shape. Its root fibers pass posteriorly at
the lateroventral border of the anterior portion of the lateral-
line ganglion, accompanied on its mesial border by fibers of the
ramus ophthalmicus superficialis trigemini (figs. 10, 11, 22, and -
35, os.V1). It is difficult to distinguish sharply between the
two nerves in the common mass which they form as they ap-
proach the brain, but as they pass toward the brain wall the
profundus fibers shift from a ventrolateral to a dorsomesial po-
sition (fig. 22). Reaching the anterior dorsal tip of the gasserian
ganglion, the profundus fibers pass through to enter largely if
not wholly the portio major, as described above, while the fibers

325

OF THE DOGFISH

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326 H. W. NORRIS AND SALLY P. HUGHES

of the ramus ophthalmicus superficialis V enter the gasserian
ganglion to become ganglionated. The further destination of
the latter fibers is uncertain.

The gasserian ganglion is partly extracranial, extending out
ventrolaterally from the brain wall, and in consequence is dumb-
bell or hour-glass in shape, the intracranial part being somewhat
larger (fig. 33, gg., gmx.). This peculiar shape of the ganglion
is due to the proximity of the lateral-line ganglion and the
rectus lateralis muscle. From the proximal intracranial portion
the mandibular and superficial ophthalmic rami arise, and from
the distal portion the maxillary ramus (figs. 21, 22, and 24).
Whether any of the sensory fibers of the portio minor belong to
the gasserian ganglion is uncertain, but Landacre believes those
of the third rootlet do. The gasserian ganglion is in contact
anteriorly with the base of the profundus ganglion and the rectus
lateralis muscle (figs. 16, 31, and 33), dorsally with the lateral-
line roots of the facialis nerve (figs. 16 and 24), laterally with the
dorsal lateral-line ganglion and root (fig. 16), and dorsolaterally
with the dorsal lateral-line ganglion. Unlike the condition in the
22-mm. embryo, as described by Landacre, the emergence of the
fibers of the ophthalmicus superficialis V does modify the form
of the gasserian ganglion. Distal projections of small ganglionic
masses are seen to be related to parts of the ramus ophthalmicus
superficialis V (figs. 16 and 31).

In Mustelus the fifth nerve possesses three ganglia, merged
posteriorly, as Allis finds, but nevertheless distinct: a dorsal
ganglion of the r. oph. spf. V, a lateral profundus ganglion,
and a ventral maxillomandibular ganglion. The first two of
these are intracranial; the maxillomandibular ganglion is largely
intracranial, but a considerable portion, as in Squalus, extends |
out through the trigeminal-facial foramen into the ventral por-
tion of the orbit. Figure 23 is a projection upon the sagittal
plane of the ganglia of the V-VII-VIII complex in Mustelus
californicus, showing the relative independence of the several
ganglia. At no place is there any difficulty in distinguishing
between the trigeminal and facial ganglionic elements.

NERVES OF THE DOGFISH a20

2. The radix mesencephalica V

The radix mesencephalica V is formed in Squalus from the
anterior rootlet. of the portio minor of the trigeminus roots.
This anterior rootlet passes in through the brain substance al-
most exactly at a right angle to the longitudinal axis of the med-
ulla (fig. 25, pmn.V1). In it can be distinguished two constitu-
ents, a dorsal and a ventral (fig. 13, pmn.V1, mes.V). On reach-
ing the anterior continuation of the tractus spinalis trigemini, the
dorsal fibers turn abruptly within the latter as the radix mesen-
cephalica V, and the ventral fibers pass directly mesially into
the lateral motor column. The mes. V continues anteriorly and
dorsally, ventrolateral to the lateral angle of the fourth ventricle.
Before the posterior peduncle of the cerebellum is reached, the
fibers of the mes. V- have separated from those of the spinal V
tract, and curving around the lateral angle of the ventricle ascend
rapidly in the base of the cerebellum, in their passage losing their
compact arrangement and taking the form of a diffuse fibrous
band as they pass along the lateral wall of the ventricle (fie, 2)
Reaching the transverse level of the posterior border of the mid-
brain, the radix curves around the lateral border of a fissure-like
at eral extension of the fourth ventricle in the lateral wall of the
cerebellar segment (fig. 19), dividing into two limbs, of which a
lateral one sends out branches into the lateral substance of the
cerebellum. The mesial limb of the radix meets the root of the
trochlearis rising from its nidulus situated anteriorly and ven-
trally (figs. 12 to 14, 18 and 19). The two tracts pass through
each other, interlacing in a manner difficult of analysis, the
trochlearis passing posteriorly and dorsally from the place of
crossing to its decussation in the posterodorsal wall of the mid-
brain. The radix after passing through the trochlearis divides
diffusely and is distributed to the mesencephalic tectum, presum-
ably to the nidulus magnocellaris (figs. 14 and 18).

According to Neal and others, the radix mesencephalica V in
Squalus is a motor tract originating in the nidulus magnocellaris
and passing out of the brain peripherally through the maxillo-
mandibular division of the trigeminus. The writers agree with

HUGHES

NORRIS AND SALLY P.

H. W.

328

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NERVES OF THE DOGFISH 329

Landacre to the extent that the first rootlet of the portio minor
may contain sensory elements from the profundus ganglion.
But the first rootlet also contains motor fibers that pass directly
into the lateral motor column. The mesencephalic V tract may
contain sensory fibers, but sensory fibers entering through the
first rootlet of the portio minor may possibly all enter the spinal
V tract. Johnston (05, ’09), who argues for the sensory nature
of the radix, says that it passes out of the brain by the sensory

root, portio major. This is certainly an error, for both in
Squalus and Scyllium (van Valkenburg) it passes by way of the
first rootlet of the portio minor. The portio minor is pre-
eminently the motor root of the trigeminus in the selachians.
Though the material used by the writers does not warrant the
statement that there are no sensory elements in the radix, it
does lend support to the view that the radix is an efferent tract,
at least in part. As Allen (’19) has recently concluded, the radix
mesencephalica trigemini is possibly concerned functionally
with the muscle sense.

330 H. W. NORRIS AND SALLY P. HUGHES

3. The ramus ophthalmicus profundus V

The profundus nerve leaves its ganglion slightly posterior to
the distal tip of the latter, on its dorsolateral border (fig. 10).
Leaving the ganglion, it swings out dorsolaterally in a ‘gradual
curve through the orbit anteriorly, passing ventral to the dorsal
rectus muscle (figs. 5 to 7), grazing the mesial wall of the eye-
ball, again approaching the ramus ophthalmicus superficialis
VII so as to pass along the ventral border of the latter close
to the skull (fig. 15). Anterior to the emergence of the
trochlearis nerve the profundus separates from the facial super-
ficial ophthalmic, passes ventral to the dorsal oblique muscle
(fig. 15), then rising dorsally, at the level of the anterior wall
of the eyeball passing through a long narrow canal in the cranial
wall, it emerges on the dorsal side of the skull, just dorsal to the
olfactory bulb (figs. 35 and 51). .It divides within the canal
into two portions, and on emerging is distributed to the skin of
the snout dorsally and laterally. In its course from the ganglion
to its final distribution the ophthalmicus profundus gives off
three branches, the posterior two of which are the anterior and
posterior ciliary nerves (figs. 21, 22, 35, and 51, cila., cilp.).

As the ramus ophthalmicus profundus leaves its ganglion
there may be recognized at its lateral border a small but dis-
tinct bundle of fibers, which may be traced back within the
ganglion (figs. 6 to 11, cilp.).. At no place does this small bundle
appear to be closely associated with the other fibers of the nerve.
Near the level of the exit of the oculomotor nerve, as the pro-
fundus nerve is passing ventral to the dorsal rectus muscle and
near the posteromesial border of the eyeball, this small strand
of fibers separates spatially from the main nerve (fig. 6, cilp.).
The fibers of this small strand are all well medullated. At the
point of emergence from the profundus, however, non-medul-
lated fibers appear as a distinct tract. In some specimens these
fibers can be traced back into the ganglion. On leaving the
profundus nerve the non-medullated fibers pass ventrally and
posteriorly to join the ciliary plexus (figs. 6 to 8, cilrl.). Their
subsequent course will be described in the account given later

NERVES OF THE DOGFISH ool

of the sympathetic system. The medullated fibers are dis-
tributed to the wall of the eyeball, passing into the interior by
small foramina through the sclerotic cartilage. Although di-
verse in character and distribution, these fibers given off from
the posterior region of the ramus ophthalmicus profundus may
be termed the posterior ciliary nerve. The medullated ones
seem to represent the ciliares longi in part.

At the level where the trochlear nerve is passing ventrally
around the ramus ophthalmicus superficialis VII the ramus
ophthalmicus profundus running a little. ventral to the other
nerves gives off a small branch distributed to the external mem-
branous portion of the sclerotic coat, a small twig passing intern-
ally through the cartilaginous portion (figs. 35 and 51, cvla.).
This anterior branch may be termed the anterior ciliary nerve.
Between the anterior and posterior ciliary nerves a very minute
twig is sent from the r. oph. prof. into the sclerotic coat. The
branches of the profundus distributed to the eyeball appear to
be the equivalent of the long ciliary nerves of higher forms.

Slightly anterior to the origin of the anterior ciliary nerve
another branch leaves the ramus oph. prof. Itruns anteriorly
across the dorsal oblique muscle on the ventrolateral face of the
latter, then at the anterodorsal border of the same muscle turns
mesially and dorsally, and at the anteromesial border of the
foramen by which the r. oph. spf. VII passes to the dorsal bor-
der of the skull, runs by its own small foramen to the dorsal
side of the cranium. Passing anteriorly, it is distributed to the
skin lateral to the supraorbital canal.

The ramus ophthalmicus profundus in Mustelus on entering
the orbit gives off a posterior ciliary nerve, also a ciliary branch
that unites with the ventral division of the oculomotorius. It
then passes through the Y-shaped fork of the rectus internus
muscle, meeting the oculomotorius passing in the reverse direc-
tion. Anteriorly the profundus passes at the ventral border of
the rectus internus, becoming closely applied to the mesial wall
of the eyeball. It gives off an anterior ciliary nerve that enters
the eyeball on its anterior border. At the level of the origin of
the dorsal oblique muscle it passes through the posterior part of

aoe H. W. NORRIS AND SALLY P. HUGHES

the levator palatoquadrati muscle and enters a foramen in the
lateral wall of the cranium, passing into the cranial cavity. At
the level of the posterior wall of the nasal capsule it enters a
foramen of exit in the dorsolateral wall of the cranium, emerging
just ventral to the supraorbital lateral-line canal, lateral to the
ramus oph. spf. VII. As it runs anteriorly in this position it
divides first into two main branches, then into smaller ones
farther on. As described by Allis, most of its terminal branches
curve ventrally and then posteriorly around the anterior wall
of the nasal capsule, supplying the skin on the ventral side of
the snout. The distribution of the profundus in Mustelus is
thus in sharp contrast to that in Squalus, since in the latter the
final terminations are dorsal and lateral, reaching anteriorly to
the tip of the snout.

4. The ramus ophthalmicus superficialis V

Under this designation are included certain small nerves of
somatic sensory composition that have a common central origin
and a special peripheral distribution, i.e., to the skin dorsal to
the orbit. Under this heading we may recognize in Squalus
three groups of fibers: 1) in a cross-section of the head immedi-
ately anterior to the thin anterior part of the profundus ganglion
there is seen a small but distinct band of fibers on the ventral
border of the ramus ophthalmicus superficialis VII, in size less
than one-fifth of the profundus nerve (fig. 10, os. V 1); 2) in the
same section there may be seen on the mesial dorsal border of
the same nerve trunk a smaller band (os. V 2); 3) dorsolateral
to the r. oph. spf. VII may be seen one or more small nerves
(os. V 3). Proximally the fibers of 1) may be followed in the
angle between the ramus oph. spf. VII (ganglion) and the pro-
fundus ganglion (figs. 11, 22, 32, and 35). As the profundus
root fibers emerge from their ganglion, the two nerves run side
by side, the superficial ophthalmic fibers dorsal in position, but
so completely merged are the two nerves that it is difficult in
many instances to distinguish between them. But as_ pre-
viously stated, the fibers of the r. oph. spf. V, which at first lie

_NERVES OF THE DOGFISH Bee

dorsomesial to the profundus fibers, shift their position so as to
run ventral, and enter the dorsomesial part of the gasserian
ganglion. Distal to the level of the profundus ganglion this
first division of the ramus oph. spf. V. runs at first along the
ventral border of the r. oph. spf. VII, then shifts to its lateral
border. The final distribution of the terminal branches is
around the ventral edge of the supraorbital crest of the skull to
the skin dorsal to the eyeball (figs. 5 to 9, 15 to 17)... The fibers
of 2) may be traced proximally, soon curving ventrally around
the mesial border of the r. oph. spf. VII to join the fibers of 1).
The two nerves do not always unite, but fibers of 1) may pass
into 2) and the reverse. The fibers of 2) end in a mass of large
cells on the dorsal border of the gasserian ganglion. Distally
2) passes anteriorly between the r. oph. spf. VII and the lateral
cranial wall, and rising to the dorsal border of the nerve trunk
divides into a few small branches that pass along with lateral
line branches of the r. oph. spf. VII through the supraorbital
crest of the cranium to the top of the head, where they are dis-
tributed to the skin dorsally, mesial and lateral to the supra-
orbital canal. If any fibers of this second division of the r.,
oph. spf. V remain with the main trunk of the r. oph. spf. VII,
they become indistinguishly blended with its branches. A num-
ber of small nerves, which from their distribution must be re-
garded as functionally a part of the r. oph. spf. V, pass into the
anterior end of the gasserian ganglion in the vicinity of the en-
trance of nerves 1) and 2). Peripherally, they are distributed
to the skin dorsal to the orbit. They pass into special cell masses
on the lateral border of the gasserian ganglion (figs. 7 to 11, 22,
31, 32, and 35, os. V 3, gos. V). The distribution of the ramus
ophthalmicus superficialis V in its entirety is on the dorsal side
of the head posterior to the area of distribution of the ramus
ophthalmicus profundus.

In one specimen a few fibers were found to join intracranially
the extreme anterodorsal tip of the gasserian ganglion, Just ante-
rior to the root of the portio minor (figs. 21, 22, and 35). Traced
peripherally, the fibers are found to pass anteriorly and dorsally
intracranially, then through a canal in the anteromesial wall of

334 H. W. NORRIS AND SALLY P. HUGHES

the ear capsule, where a small ganglion occurs, thence to the dor-
sal side of the head, where they are distributed to the skin poste-
rior to the area of distribution of the third division (os. V 3)
of the ramus oph. spf. V. Because of its distribution, this small

Fig. 31 A horizontal section through the ganglia of the V-VII-VIII complex
of the right side, an especial feature being the accessory ganglia of the ramus
ophthalmicus superficialis trigemini (gos.V). 25.

nerve is here tentatively designated as a fourth division of the
superficial ophthalmic ramus (0s. V 4).

The striking differences between Squalus and Mustelus in
respect to the origin, relative size, course, and distribution of
the rami ophthalmicus profundus and ophthalmicus superficialis

NERVES OF THE DOGFISH 200

V merit especial consideration. The writers reserve this topic
for future discussion, believing that only by a comparative study
of many elasmobranch forms can any satisfying conclusions be
reached in this particular subject.

Fig. 32. A horizontal section through the V-VII-VIII ganglia of the right
side, showing the distinct root of the ramus oticus VII. X25.

The ramus ophthalmicus superficialis V of Mustelus arises, as
previously stated, from a distinct intracranial ganglion. It
passes out of the skull as a large compact nerve on the ventral
border of the r. oph. spf. VII. It accompanies the latter ante-
riorly, sending off several small branches that combine with

336 H. W. NORRIS AND SALLY P. HUGHES

small branches of the latter. Anteriorly it is distributed to the
skin of the dorsal side of the head, dorsal and anterior to the
eye (fig. 23).

In those amphibians in which somatic sensory fibers are asso-
ciated with the r. oph. spf. VII, they occur in a diffuse arrange-
ment, and are given off from the ganglion or near the base of
the supraorbital trunk, in a fashion suggestive of the mode of
occurrence in Squalus.

5. The ramus macillaris V

This nerve arises from the smaller extracranial portion of the
gasserian ganglion as a large mass of fibers that joins the ramus
buecalis VII to form the infraorbital trunk. At first somewhat
triangular in cross-section (figs. 7 to 10 and 20, mz.) on the mesial
border of the infraorbital trunk, farther anteriorly it becomes a
flattened band curved around the ventromesial border (figs. 5,
6, 21, and 22). Still farther anteriorly it covers the infraorbital
trunk dorsally, mesially, and ventrally (fig. 24), thence sepa-
rating into a dorsal, a mesial, and a ventral band. With the
giving off of certain small branches to the ventral surface of the
head anterior to the mouth, some of which run posteriorly from
their origin from the main nerve, the ramus maxillaris together
with the ramus buccalis divides into three groups of nerves, the
largest mesial one running anteriorly and supplying the ventral
surface of the snout mesially and anterior to the level of the
eyes. The other two divisions supply the ventrolateral epithe-
lium of the snout. One of the small posteriorly directed branches
runs far back at the lateral angle of the mouth, terminating at
the lateral border of the oral epithelium between Meckel’s car-
tilage and the palatoquadrate bar (fig. 35, maph.). This small —
nerve evidently corresponds to Cole’s (’96) pharyngeal branch of
the ramus maxillaris in Chimaera.

The association of the maxillaris with the buccalis is every-
where very intimate, even into the small branches. The large
nerves commonly break up into their smaller divisions long be-
fore the latter leave the vicinity of the main nerves (figs. 1 to 4
and 34). In.consequence their representation in the illustrations
is somewhat diagrammatic.

NERVES OF THE DOGFISH Bat

6. The ramus mandibularis V

This ramus of somatic sensory and visceral motor fibers de-
rives its sensory elements mostly from the mesial end of the
gasserian ganglion. Most of its ganglion cells are intracranial.
Its fibers pass directly laterally through and around the poste-
rior border of the maxillary part of the ganglion, and bending
posteroventrally around the dorsolateral border of the palato-
quadrate bar break up into two divisions, a large dorsal motor
branch supplying the adductor mandibulae muscle, and a ven-
tral division that divides into an anterior branch supplying the
skin of the ventral side of the lower jaw anteriorly, and a poste-
rior branch that innervates the first ventral constrictor muscle
and supplies the skin ventral to this muscle (figs. 15 to 17, 20
to 22, 24, 33, 35, 51 to 53, md.). The anterior part of the first
ventral constrictor muscle is innervated exclusively by the
ramus mandibularis V, but in the posterior part where its fibers
mingle indistinguishably with those of the second constrictor
muscle, there is evidently innervation also from the truncus
hyomandibularis VII. This ventral motor branch of the man-
dibularis also innervates a part of the adductor mandibulae.

From the dorsal border of the main trunk of the ramus man-
dibularis shortly after leaving the ganglion there are given off a
few (three or four) small branches, which break up into numerous
small twigs, motor elements supplying the levator palatoquad-
rati and spiracular muscles and sensory fibers supplying the skin
dorsolaterally in the region of the spiracle (fig. 35, lup-q.). From
the main mandibular trunk, as it is passing around the lateral
border of the palatoquadrate bar, there is given off from its
ventral side a small nerve. This follows the main nerve around
to the ventral border of the bar of cartilage, but as the man-
dibular trunk turns posteriorly this small nerve bends antero-
ventrally along the lateral border of the palatoquadrate bar,
entering the lateral border of the posterior part of the pre-
orbital muscle, and furnishing the innervation of the latter (figs.
35 and 51, pro.). The writers do not find in any of the many
series of sections examined any anastomosis between the ramus

338 H. W. NORRIS AND SALLY P. HUGHES

mandibularis and the ramus maxillaris such as Landacre de-
scribes. But during the progress of this research attention was
called to a laboratory dissection of an adult Squalus in which
there is a large anastomosis between the ramus mandibularis
and the infraorbital trunk. It arises from the ramus mandibu-
laris, as the latter is passing around the palatoquadrate bar, and
runs anterolaterally, then anteromesially, over the preorbital
muscle across the floor of the orbit to join the infraorbital trunk

Fig. 33 A horizontal section through the trigemino-facial foramen, showing
chiefly the gasserian and geniculate ganglia. X30.

at the region where the latter breaks up into its chief large
branches destined to the skin and lateral-line organs. It seem-
ingly joins a maxillary branch, and probably consists of somatic
sensory fibers that belong primarily to the ramus maxillaris.
As the ramus maxillaris is leaving its ganglion it gives off a
minute twig which passes ventrolaterally around the ventral
border of the ramus bucealis VII out to the ramus mandibularis
V as the latter is passing around the lateral border of the palato-
quadrate bar. The small nerve in question does not unite with

NERVES OF THE DOGFISH 339

the ramus mandibularis, however, but passes along the anterior
border of the latter, thence ventrally, laterally, and anteriorly,
to the base of the eyelid, then turning posteriorly it passes along
the internal border of the jugular group of ampullae of Loren-
zini, becoming smaller and smaller as it is distributed to the
cutaneous tissue (fig. 35, mxpc.).

Fig. 34 <A cross-section through the optic chiasma, showing structures in the
angle between the ventrolateral brain wall and the ventromesial wall of the eye-
ball. Section 692. X15.

THE FACIAL NERVE

1. The lateral-line roots and ganglia of the facial nerve

The roots of the lateral-line component of the facialis enter
the medulla in two divisions: a dorsal root passing into the 'at-
eral-line lobe and a ventral root entering the acusticum (figs.
36, 12 to 14, 21, 22, 35, and 51, ViJrild., VIIrllv.). A horizontal

THE JOURNAL OF COMPARATIVE NEUROLOGY VOL. 31, NO. 5

340 H. W. NORRIS AND SALLY P. HUGHES

section through the dorsal root at its point of entrance into the
brain shows that its fibers pass into the brain substance on each
side of a vertical internal furrow or sulcus in the lateral-line
lobe (fig. 39), in this way spreading fan-shape in the brain wall.
In a similar fashion the ventral root fibers spread anteriorly and
posteriorly in the acusticum (figs. 25 to 30). According to
Strong (03), the dorsal root is formed by the union of fibers
from the truncus hyomandibularis and ramus buccalis, but the
ventral root fibers are derived from the ramus ophthalmicus
superficialis VII and pass through the dorsal root in order to
reach the acusticum. Cole (’96) and Cole and Dakin (’06) state
that in Chimaera the rami ophthalmicus superficialis, buccalis
and hyomandibularis each connects with the brain by a dorsal
{lateral-line lobe] and a lateral [acusticum] root. Allis (01) states
that in Mustelus the dorsal (superficial ophthalmic) and ventral
(buceal-hyomandibular) roots of the ‘trigeminus II’ [lateral-line
conponent of the facialis] each connects with the ‘lobus trigemini’
flateral-line lobe] and with the tuberculum acusticum. This
account of Allis the writers corroborate, but would add that in
Mustelus both the hyomandibularis and the buccalis send fibers
into the lateral-line lobe and also into the acusticum. In brief,
the relations in Mustelus are exactly like those in Chimaera.
It seems highly improbable that the conditions in other elasmo-
branchs are different from those in Mustelus and Chimaera.
In Squalus the interweaving of the root fibers makes it well nigh
impossible to determine with accuracy their peripheral distribu-
tion, although from a study of Squalus material alone the writers
would agree with Strong. As Cole and Dakin state for Chimaera,
so for Mustelus it may be said that the truncus hyomandibularis
sends but few fibers into the acusticum.

Hawkes (’06) states that in Chlamydoselachus the hyo-
mandibular trunk arises from the brain at the same level as the
root of the trigeminus and facialis proper, and that the super-
ficial ophthalmic VII and buccal arise by two roots situated
more dorsally. It seems to the writers more probable that the
so-called hyomandibular roots in Chlamydoselachus are the vis-
ceral sensory and motor, and that the ‘rami communicantes’

341

OF THE DOGFISH

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Fig. 36 A cross section through the roots of the facial and auditory nerves
of the right side. Section 998. 25.

NERVES OF THE DOGFISH 343

between the gasserian ganglion and the anterior hyomandibular
root are really the lateral-line root of the hyomandibularis, de-
rived not from the gasserian ganglion, but from the more dorsal
lateral-line roots, those of the lateral-line lobe and the acusticum.

Fig. 37. A cross-section through the roots of the left facial nerve of Mustelus
californicus. X25.

The dorsal (anterior) and ventral (posterior) lateral-line
ganglia in Squalus are sharply distinct from each other, as Land-
acre has shown in the 22-mm. embryo. The anterior ganglion,
owing to its development around the posterior border of the

344 H. W. NORRIS AND SALLY P. HUGHES
origin of the rectus lateralis (externus) muscle, is crescentric,

dumb-bell shaped, an anterodorsal superficial ophthalmic por-
tion and a posteroventral buccal portion, the two parts being

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a S.

Fig. 38 <A cross-section through the roots of the left facial nerve of Mustelus
californicus, slightly anterior to that shown in the preceding figure. The dorsal
lateral-line root in its passage ventrally is seen ‘straddling’ (to use the expression
of Allis) the ventral lateral-line root. The section cuts the posterior end of the
buccal ganglion (gbuc.) and the anterior end of the ganglion of the ramus man-
dibularis externus VII (gmde.). X25.

continuous through a narrow ganglionic neck (figs. 15 to 17, 21,
and 24, gos. VII, gbuc). The anterior portion, from which
arises the ramus ophthalmicus superficialis VII, extends forward
some distance as a central core in the superficial ophthalmic

NERVES OF THE DOGFISH 345

trunk, being covered externally by nerve fibers (figs. 5 to 11).
Where the two parts of the ganglion are confluent, fibers pre-
dominate in the ophthalmic portion. The ventral (posterior) or
external mandibular ganglion is situated out on the truncus
hyomandibularis (figs. 20, 24, 33, and 51, gmde.). It is a round
column of cells that does not appreciably modify the form of
the nerve trunk. Its root fibers run in toward the brain dorsal
to the root of the geniculate ganglion and ventral to the vestibu-
lar division of the auditory nerve (figs. 17, 31, 32, and 36, rmde.),
and turning dorsally around the anterior border of the vestibu-
lar part of the auditory ganglion (figs. 12, 21, 22, and 24), join
the main lateral-line roots.

The superficial ophthalmic and buccal portions of the dorsal
ganglion in Mustelus are not confluent, as in Squalus, but widely
separated. Both are extracranial (fig. 23).

The shape of the anterior ganglion (oph. spf. and buc.) in
Squalus is modified by certain groups of cells that almost merit
the designation as distinct ganglia. At the dorsolateral border
of the buccalis portion of the anterior lateral-line ganglion, just
ventral to the ampulla of the anterior semicircular canal, is a
small conical collection of cells protruding from the general
mass (fig. 35, gbuc. a.). From this there pass out three small
nerves (only two shown in fig. 35) that supply fourteen ramuli
to the neuromasts of the postorbital section of the infra-orbital
canal. A little farther posteriorly (figs. 32 and 35), on the ex-
treme posterior border of the lateral-line ganglion, a more con-
Spicuous mass of cells (got.) extends in a fashion similar to the
preceding. From it there pass out through a canal in the lat-
eral portion of the ear capsule to the top of the skull fibers that
supply the first five or six ramuli to the neuromasts of the main
lateral-line canal of the trunk. From its origin and distribution
this latter nerve must be regarded as the equivalent of the
ramus oticus of various authors. Besides innervating the lateral-
line canal, it supplies a peculiar tubular organ on the anterior
median border of the spiracle (fig. 20, ospr.). Its root fibers can
be traced into the acusticum by a small bundle that enters the
brain immediately posterior to the visceral sensory root of the
facialis (fig. 32, rot).

346 H. W. NORRIS AND SALLY P. HUGHES

In Mustelus there is a large posterodorsal extension of the
buccal ganglion within the orbit, from which a number of small
nerves emerge, one of which, from its distribution to the poste-
rior horizontal portion of the infraorbital canal, Allis correctly
considers as the equivalent of the ramus oticus. The rest of the
small nerves from the otic portion of the ganglion supply the
postorbital section of the infraorbital canal and the spiracular
organ which in Squalus is innervated by the ramus oticus proper.
In Mustelus the hyomandibular trunk does not lie in a canal in
the ventral wall of the ear capsule, but in the ventral portion of
the orbit. The ganglion of the ramus mandibularis externus
VII is not such a long slender column of cells as’in Squalus,
confined to the narrow hyomandibular canal, but lying free in
the ventral part of the orbit assumes a more globular form (figs.
23 and 37, gmde).

2. The roots and ganglia of the facialis proper

The geniculate ganglion is situated upon the hyomandibular
trunk in the larger proximal part of the hyomandibular canal, in
the cranial wall ventral to the vestibular portion of the ear (figs.
17, 24, and 33, ggen.). The geniculate ganglion is everywhere -
distinct from other ganglia, even where in contact with them.
From the ganglion proximally the visceral sensory root fibers,
accompanied by groups of motor fibers, pass into the cranial
cavity, and curving around the anterior ventral border of the
auditory ganglion, between its cells and the root of the ventral
lateral-line ganglion, enter the medulla and pass directly to the
visceral sensory column in the latter (figs. 12 to 14, 26 to 29,
31, 32, and 36, VII rvs.). The slightly medullated character
of its fibers renders them especially easy to distinguish from other
fiber tracts. The motor root passes through the brain sub-
stance immediately ventral to the sensory fibers, from the periph-
ery to the lateral motor column. Some of the motor root fibers
have the appearance of arising in the ventral motor column.
Within the brain the sensory root divides, one part passing
directly into the visceral lobe, there to curve posteriorly along

NERVES OF THE DOGFISH 347

the latter; the other part passes posteriorly some distance be-
fore entering the visceral lobe (figs. 26 and 27). Within the
brain these two roots, sensory and motor, lie ventral to the ven-
tral-line root and dorsal to the anterior border of the great audi-
tory root (figs. 22 and 36). Outside the brain, accompanying
and dorsal to the motor and visceral sensory roots of the facialis,
is the posterior (ventral) lateral-line root, whose ganglion is situ-
ated on the hyomandibular trunk mostly distal to the geniculate
ganglion (fig. 24).

3. The ramus ophthalmicus superficialis VII

This large nerve is related to the anterior part of the dorsal
(anterior) lateral-line ganglion. As already stated, the ganglion
is so overgrown with fibers that few of the cells appear on the
exterior, but for the most part form a core that extends far out
in the nerve (figs. 5 to 11, 15 to 17, gos. VIZ). The nerve passes
anteriorly through the dorsal portion of the orbit, giving off
small nerves that pass dorsally through small foramina in the
supra-orbital crest of the cranium to supply supra-orbital canal
organs (fig. 50, os. VIZ). Rising higher in its anterior course
the main nerve at the anterior part of the orbit passes by its
own large foramen through the crest of the cranium to the top
of the head, where it courses anteriorly supplying supra-orbital
canal organs and the supra-orbital group of ampullae of Loren-
aini. ‘The superficial ophthalmic has few large branches. The
largest one of these, given off shortly after the main nerve emerges
from the cranium, runs anteroventrally to supply the canal
organs situated in that part of the supra-orbital canal that runs
from the tip of the snout posteroventrally around to the ventral
side of the head to join the infra-orbital canal (figs. 35, 50 to 52,
eth.). Anteriorly the main nerve breaks up into numerous small
branches that supply canal organs and ampullae of Lorenzini
(figs. 1 to 4, os. VIZ). Accompanying the superficial ophthalmic
VII are two of the divisions (os. V 1 and os. V 2) of the super-
ficial ophthalmic V. These are so closely applied to the facialis
ramus as to appear like branches of the latter when given off.

348 H. W. NORRIS AND SALLY P. HUGHES

Their destination has been described. Arising from the ganglion
near the base of the r. oph. spf. VII are a few small much elongate
nerves that innervate the posterior part of the supraorbital canal.
Branches of the r. oph. spf. V (os. V 3) are closely associated with
some of them.

4. The ramus buccalis VIT

The intimate association of this ramus with the ramus maxil-
laris V to form the truncus infra-orbitalis has been described.
Its distribution is to the sense-organs of the infra-orbital canal
and the associated ampullae of Lorenzini. From the ganglion
near the base of the ramus buccalis are given off a few small
nerves (fig. 50). One of these supplies the anterior portion of
the main lateral-line canal. Its distribution and relations will
be discussed under the head of the ramus oticus VII. The other
small nerves just mentioned collectively innervate the canal
organs of the postorbital section of the infra-orbital canal. The
ramus buccalis proper gives off few branches until it breaks up,
with the ramus maxillaris, into three main branches or rather,
three loose collections of small branches. Some of these supply
ampullae of Lorenzini only, but the most of them are distributed
to canal organs and ampullae indifferently.

In Mustelus, as Allis has shown, the maxillary and mandibular
rami run for some distance with the ramus buccalis in a common
infra-orbital trunk. In this trunk the maxillary and mandibu-
lar sensory elements are completely merged, but always distinct
from the buccalis.

5. The ramus oticus VII

The ramus oticus, as mentioned in a preceding section,
enters a distinct ganglionic mass on the posterior distal part of
the buccal ganglion. The root fibers, however, unlike those of
the buccalis, seem to connect with the acusticum only, and not
with the lateral-line lobe. The canal organs which it supplies
lie in that part of the canal system which is the immediate pos-
terior continuation of the supra-orbital canal, between the latter

NERVES OF THE DOGFISH 349

and the section of the canal innervated by the glossopharyngeus.
About five ramuli are contributed to canal organs (fig. 50,
ot. VII) ;

Hawkes finds a ramus oticus in Chlamydoselachus that sup-
plies the postorbital section of the infra-orbital canal, and the
horizontal section of the infra-orbital canal (anterior end of the
main lateral-line canal), and also sends two small branches to
the skin. These latter she interprets as general cutaneous.
But comparison with Squalus would suggest that in Chlamydo-
selachus these cutaneous branches may possibly innervate
spiracular organs as in Squalus, or isolated neuromasts, pit-
organs.

Besides innervating canal organs in Squalus, the ramus oticus
supplies a peculiar tubular organ on the anterior mesial wall of
the spiracle (fig. 20, ospr.). This is apparently a modified
ampulla of Lorenzini.

Landacre describes in the 22-mm. embryo a lateral-line pri-
mordium which he regards as corresponding to the most poste-
rior sense-organs of the infra-orbital canal. This receives two
small branches from the buccalis ganglion, arising in the angle
between the buccalis and the r. oph. spf. VII. He describes
a second small twig arising more posteriorly, which innervates
_a lateral-line primordium that he believes gives rise to lateral-
line organs near the junction of the supra-orbital and infra-
orbital canals. He considers this the ramus oticus auctorum.
He notes that this ramus after supplying twigs to the lateral-
line primordium sends a branch more posteriorly, ending in the |
anterior wall of the spiracle.

As stated in a preceding section, the ramus oticus VII in Mus-
telus arises from a ganglionic mass In common with the small
nerves that innervate the postorbital section of the infra-
orbital canal. An account of the occurrence, innervation, and
homologies of the spiracular organ of elasmobranchs, ganoids,
and dipnoans has been given elsewhere by the writers (’20).

Herrick (’99) considers the ramus oticus of Menidia as primi-
tively a general cutaneous dorsal ramus of the facialis to which

350 H.. W. NORRIS AND SALLY P. HUGHES

lateralis elements have been added secondarily. In Squalus,
Mustelus, and Raja, and presumably in all elasmobranchs, it is
wholly lateralis.

6. The truncus hyomandibularis VIT

There are three chief constituents of the hyomandibular
trunk: a) lateral line, ramus mandibularis externus, whose root,
as already described, enters the lateral-line lobe and the acusti-
cum together with the buccalis root, and whose ganglion occurs
mostly distal to the geniculate ganglion as an elongated column
which scarcely affects the size or shape of the hyomandibular
trunk (figs. 17, 20, 24, 48, 51 to 53, mde., gmde); b) visceral sen-
sory, ramus mandibularis internus, whose fibers arise in the geni-
culate ganglion (figs. 48, 51 to 53), mdv.); c) visceral motor,
ramus hyoideus, the motor constituent of the facial nerve (figs.
48, 51 to 53, hy.).
bs Emerging from the hyomandibular canal, the hyomandibular
trunk passes posterodorsally without branching, at the lateral
border of the ear capsule, around the mesial dorsal border of the
spiracle to the lateral border of the anterior part of the second
dorsal constrictor muscle and at the lateral border of the hyo-
mandibular cartilage. Thence it passes posteroventrally along
the anterior lateral border of the same muscle and posterior
border of the spiracle (figs. 48, 51 to 53, tr. hmd.).

In Mustelus the lateralis component of the hyomandibularis
is relatively smaller than in Squalus, due probably to the. lack
of the hyoidean group of ampullae of Lorenzini in the former.

The ramus mandibularis externus VII. The first branch of
considerable size given off from the hyomandibular trunk is the
anterior division of the ramus mandibularis externus. It leaves
the main trunk at the horizontal level of the ventral end of the
hyomandibular cartilage and runs anteroventrally, dividing
into a dorsal branch that supplies the jugular or hyomandibular
canal and a ventral branch that innervates the mandibular canal
(fig. 50). After giving off the last twig to the mandibular canal
organs, this ventral branch sends a twig into a tubular structure

9

NERVES OF THE DOGFISH 351

that contains a well-developed sense-organ in its posterior end.
The tubular organ in question lies anteroventrally to the man-
dibular canal, opening to the exterior at its own anteroventral
end. Itis about 0.7 mm. in length. It is apparently a modified
ampulla of Lorenzini. From this tubular organ the anterior
branch of the ramus mandibularis externus continues in an
anteroventral direction, in close proximity to the anterior sen-
sory division of the ramus mandibularis V, and finally comes to
a series of tubular organs ventral to the lateral border of Meckel’s
cartilage, between the latter and the skin. These tubular organs
all open upon the mucous membrane, or near the line of junction
of the mucous membrane with the epidermis at the lateral angle
of the mouth. In the single specimen in which they were care-
fully examined they are eleven in number, and are evidently the
rudiments of a group of ampullae of Lorenzini. All these
tubular organs are innervated by the nerve branch mentioned
above.

The main part of the posterior division of the ramus mandibu-
laris externus supplies the hyoidean group of ampullae. It
passes posteroventrally from the point of division as a stout
nerve that suddenly breaks up into its terminal twigs for the
rosette of hyoidean ampullae. From the base of the posterior
division of the ramus mandibularis externus there runs anteriorly
along the lateroventral border of the adductor mandibulae
muscle a small nerve whose destination is a series of pit-organs
in the jugular region, lying mostly ventral to the hyomandibular
canal. There are about twenty-five of these pit-organs. Farther
dorsally is another series of pit-organs innervated by small
twigs from the main hyomandibular trunk before the branching
of the latter. There are about eight pit-organs in this second
group. ‘The two groups constitute a single series almost in the
shape of a semicircle, extending from the spiracle nearly to the
midventral line.

Hawkes finds in Chlamydoselachus three branches of the ramus
mandibularis externus which seem to correspond in a general way
to the dorsal and ventral branches of the anterior division and the
entire posterior division in Squalus. She notices several branches

302 H. W. NORRIS AND SALLY P. HUGHES

which are interpreted as somatic sensory. It may be suggested
that microscopical examination will show that these supposed
general cutaneous nerves end in pit-organs or similar structures,
as in Squalus.

Cole (’96) describes in Chimaera “‘two groups of ampullae,
situated behind the lower jaw,” and innervated by the ramus
mandibularis externus. These ampullae are small and simple
in structure, and probably correspond to the small rudimentary
ampullae and the near-by larger tubular organ in Squalus, inner-
vated by branches of the ramus mandibularis externus VII.

The ramus mandibularis internus VIT. Slightly posterior and
dorsal to the origin of the anterior division of the ramus man-
dibularis externus from the hyomandibular trunk the ramus
mandibularis internus is given off (figs. 48 and 51), and as the
visceral sensory terminal branch of the hyomandibular trunk
passes transversely around the lateral edge of the hyoid cartil-
age, into the interval between the latter and Meckel’s cartilage,
and turning anteriorly runs along the dorsomesial border of the
latter between it and the hyoid cartilage, as far as the anterior
end of the latter. Thence it continues anteriorly between the
ventrolateral edge of the basihyal and Meckel’s cartilage, now
dividing into a number of small branches. Its area of distribu-
tion is the lower jaw and the ventrolateral floor of the mouth
mesial and anterior to the chorda tympani.

The ramus hyoideus VII. As the hyomandibular trunk
passes along the lateral border of the second dorsal constrictor
muscle, it gives off numerous small twigs to the muscle (fig. 49).
Farther ventrally the remaining motor fibers separate from the
lateral-line elements, which form the posterior branch of the
ramus mandibularis externus, at the lateral border of the hyoid
cartilage, as described above. Thence as a compact nerve they
pass ventrally around the hyoid cartilage to the ventral side of
the lower jaw, and turning anteriorly between the first and sec-
ond ventral constrictor muscles are distributed to the second
ventral constrictor and the posterior part of the first constrictor.

NERVES OF THE DOGFISH 353

7. The ramus palatinus VIT

From the enlarged proximal portion of the geniculate ganglion
there passes out through the wall of the hyomandibular canal
ventrolaterally a nerve of visceral sensory composition, that on
emerging turns anteroventrally soon dividing into an anterior
and a posterior branch (figs. 21, 22, 48, and 51, prt. VII, pal.).
The anterior division passes anteriorly, situated between the
base of the cranium and the palatoquadrate bar, dorsal to the
roof of the mouth. It continues anteriorly in this position, giv-
ing off branches to the dorsal oral epithelium: ramus palatinus
VII. The posterior branch passes posteriorly at the mesial
ventral border of the palatoquadrate bar, giving off branches to
the dorsolateral oral membrane, until the level of the anterior
wall of the spiracle is reached. Here it turns ventrally and
anteriorly and runs along the dorsolateral surface of Meckel’s
cartilage, farther anteriorly breaking up into small branches
supplying the ventrolateral oral surfaces—the so-called chorda
tympani. From the geniculate ganglion slightly posterior to
the point of origin of the ramus palatinus, there are given off
two or three small nerves that supply the pseudobranch and the
anterior wall of the spiracle (figs. 21, 22, 48 and 51). These
have been termed ramus pretrematicus by various authors.

&. General reflections upon the facial nerve

Excluding the lateral-line elements, the facial nerve exhibits
the three characteristics of a branchial nerve: ramus pharyngeus
(palatinus), ramus pretrematicus (so-called chorda tympani) and
ramus posttrematicus (hyomandibularis). The hitherto so-
called rami pretrematici are to be regarded as twigs that belong
to the palatinus and pretrematicus proper, but are given off
separately. The anastomoses that occur between these so-
called pretrematic rami and the ramus pretrematicus proper
support the view of their common origin. The rami hyoideus
and mandibularis internus may be regarded as the visceral
motor and visceral sensory constituents of a ramus posttrema-
ticus. Divergent opinions have been expressed as to the homol-

354 H. W. NORRIS AND SALLY P. HUGHES

ogies of these rami of the facialis. Regarding the ramus palati-
nus in a narrow sense, there can be little question. The so-called
chorda tympani is plainly prespiracular or pretrematic and does
not correspond to the chorda tympani of higher forms.

The ramus alveolaris or mandibularis internus of amphibians
is variously interpreted as pretrematic or posttrematic. Driiner
(01, ’04), who has exhaustively studied this subject, regards the
ramus alveolaris of the urodele amphibians as pretrematic. In
that case the posttrematic VII in amphibians lacks a visceral
sensory element. In Siren (Wilder, ’91; Norris, 713) the palatine
and alveolar rami arise from the ganglion by a common trunk,
as do the palatine and pretrematic rami in Squalus. In most
amphibians the ramus alveolaris leaves the geniculate ganglion
in the hyomandibular trunk, in some separately as an indepen-
dent nerve. In its distribution the ramus mandibularis internus
of Squalus resembles more closely the ramus alveolaris of am-
phibians, i.e., it runs along the mesial border of the lower jaw
(or even within the dentary bone in amphibians), while the ramus
pretrematicus of sharks runs along the lateral border. In con-
sidering the homology of any nerve its peripheral distribution as
well as its origin should be taken into consideration, as Strong
(90, ’92) has so clearly pointed out. May it not be that the
ramus alveolaris of amphibians is a combined nerve, i.e., a
fusion of pretrematic and posttrematic visceral sensory elements?
Herrick (’99), indeed, suggests ‘‘that the amphibian ramus
mandibularis internus VII may represent both pre- and post-
spiracular communis elements.”

The facial nerve proper in Squalus, and presumably in all
sharks, is completely free from anastomoses with other nerves.
Jacobson’s commissure, ramus communicans X ad VII, anasto-
moses with the ramus ophthalmicus profundus V or other parts
of the trigeminal nerve, are wholly absent. General cutaneous
elements are absent both in root and branches. It is a typical
facial nerve, containing only visceral sensory and visceral motor
components.

The double condition of the ramus mandibularis externus VII
is possibly to be regarded as foreshadowing the condition in the

NERVES OF THE DOGFISH BOYD)

amphibians, where it divides into rami mentalis externus and
internus. Or if the condition in Chlamydoselachus, as described
by Hawkes, is primitive, the amphibian condition may have
been derived from that.

Four varieties of lateral-line sense-organs occur in Squalus:
canal organs (neuromasts in canals), pit-organs (naked neuro-
masts in the skin), ampullae of Lorenzini, and certain peculiar
tubular organs (on anterior wall of spiracle, on lower jaw near
mandibular canal), probably modified ampullae.

THE AUDITORY NERVE

The root fibers of the auditory nerve pass from the ganglion
into the acusticum as a single large, broad root, slightly posterior
to the facialis roots (figs. 12 to 14, 31, 82, and 36, ViIIr.). It
is well-nigh impossible from a study of cross-sections alone to
draw a sharp line of distinction between the auditory fibers and
the ventral lateral-line root. But in sagittal and horizontal
sections they are seen to be distinct (figs. 27 to 30, VJJI/r.,
rllv.). On entering the acusticum the auditory root is seen to
divide into anteriorly and posteriorly directed tracts, the poste-
rior tract being the larger (fig. 28, V/JIr.).

The auditory ganglion at its anterior vestibular end is large
and globular, but posterior to the root fibers the ganglion cell
mass assumes the form of a vertical plate, though farther poste-
riorly it becomes a rounded column, the saccular ganglion (figs.
12, 31, and 32). The anterior end of the auditory ganglion is
wholly intracranial; but gradually passing out laterally and pos-
teriorly through the cranial wall, its posterior portion becomes
situated in a recess in the ventral part of the ear capsule. Near
the anterior end of the ganglion a large vestibular nerve passes
into the ear capsule, supplying the utriculus and the ampullae
of the anterior and horizontal semicircular canals. Succeeding
this large vestibular branch there follow numerous branches
dorsally and ventrally supplying the saeculus and finally the
ampulla of the posterior canal (figs. 12, 21, 31, and 32).

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL, 31, NO. 5

306 H. W. NORRIS. AND SALLY P. HUGHES
THE GLOSSOPHARYNGEAL NERVE
1. The roots and ganglia in the glossopharyngeal nerve

The ganglion of the ninth nerve is farther removed from the
brain wall than that of any other cranial nerve. It is situated
in the ventrolateral part of the ear capsule, near the posterior
end of the latter, in a large chamber hollowed out of the cartilage.
Its root, composed of lateral-line, visceral sensory, and visceral
motor fibers, passes anteriorly and mesially from the ganglion
to its entrance into the medulla at a point about opposite the
middle portion of the spiracle. At the anteromesial end of the
visceral sensory ganglion and extending mesially upon the root,
is a small mass of cells, the ganglion of the lateral-line compo-
nent (figs. 24 and 48, gspt. IX). The visceral sensory root
enters the medulla and passes anteromesially into the visceral
lobe. The lateral-line component enters the brain immediately
dorsal to the anterior part of the visceral root, ventral to the
extreme anterior end of the lateral-line root of the vagus nerve
(fig. 24). Within the brain the lateral-line root of the ninth
nerve runs anteriorly ventral to the mesial border of, and nearly
parallel with, the root fibers of the lateralis X, but always dis-
tinct from them. Anteriorly, the lateral-line element of the
ninth approaches that of the tenth, and finally takes a position
at the mesial border of the other lateral-line tracts, just lateral
to the visceral lobe. The motor elements in the glossopharyn-
geal root occur in scattered bundles. In similar fashion they
connect with the brain by a number of minute rootlets, in position
anterior to the other roots.

2. The lateral-line elements in the glossopharyngeal nerve

Various writers have recognized lateral-line elements in the
ninth nerve of fishes, although their presence there has been gen-
erally overlooked or ignored. Allis (’89, ’97) describes and figures
a lateral-line component of the glossopharyngeus of Amia, inner-
vating one canal organ and a line of pit-organs. Ewart (’92)
and Ewart and Cole (’95) found a lateral-line component in the

NERVES OF THE DOGFISH 207

ninth nerve of Laemargus, which innervates ‘‘three sense organs
of the lateral line lying immediately posterior to the eommis-
sural canal,” besides sending branches to the skin. It may be
suggested that these latter branches possibly supply pit-organs,
as in Amia. In Chimaera Cole (’96) finds that from the ninth
“ganglion a very fine dorsal branch is sent up to the skin, but
this does not innervate any sense organs of the lateral line.”
Hawkes (’06) describes a small ganglion upon the root of the
glossopharyngeal nerve in Chlamydoselachus from which a small
dorsal branch proceeds, innervating two neuromasts of the lat-
eral line, besides sending twigs to the skin. Allis (01) is not
certain of the presence of this element in the ninth nerve of
Mustelus. Johnson (’17) figures various stages in the develop-
ment of Squalus acanthias, showing an unnamed dorsal branch
of the ninth nerve. In the 22-mm. stage of Squalus Landacre
(16) finds in the glossopharyngeal nerve a lateral-line ganglion
related to two primordia and a branch of uncertain distribution.
Stannius (’49, p. 79) finds in Spinax acanthias and Carcharias
glaucus a dorsal branch whose origin, course, and distribution
answer to the dorsal lateral-line ramus of the ninth in Squalus.
He fails to find such a ramus in the rays, although a fine nerve
in Raja batis, a branch of the glossopharyngeus, was traced to
the region of the external acoustic pore. The writers confirm in
part the statement of Stannius that no dorsal lateral-line branch
of the ninth nerve occurs in the rays. In Raja radiata there is
no lateral-line element in the ninth nerve, nor any dorsal branch
of the latter. Van Wijhe (’82) states that in stage K of the em-
bryo of Scyllium the ninth nerve differentiates into a dorsal and
a ventral ramus, of which the former unites with an epidermal
thickening which is the anlage of that portion of the canal-organ
system innervated by the glossopharyngeus. In stage L the
glossopharyngeal ganglion begins to divide into a ganglion at
the base of the dorsal ramus and another on the ventral ramus.
Klinkhardt (05) finds in embryos of Spinax niger a dorsal
cutaneous connection on the glossopharyngeus. Wright (’85)
mentions a dorsal lateral-line branch of the ninth nerve in Mus-
telus. Panschin (’10) describes a lateral-line component in the

358 H. W. NORRIS AND SALLY P. HUGHES

ninth nerve of Lota. Herrick (01) describes a lateral-line com-
ponent in the glossopharyngeus of Amelurus melas, derived,
however, from the vagus, which supplies one canal organ and
two pit-organs. The writers find in Mustelus californicus a
small lateral-line ganglion upon the ninth nerve in essentially
the same position as the one in Squalus, from which a nerve
proceeds dorsally, contributing two ramuli to the lateral-line
canal. In one specimen examined a single ramulus occurs.

Cole (98) says that the glossopharyngeus takes ‘‘no part in
the innervation of the system [lateralis] either in Gadus or mor-
phologically in any other form.’ Kingsbury (’97) finds a lat-
eralis constituent in the ninth of Amia, but derived from the
main lateral-line nerve. Allis (97) says that the lateral-line
element in the glossopharyngeal nerve of Amia is derived from
the root of the lateral-line nerve of the vagus, but in the larva
bears a distinct ganglion.

3. The ramus supratemporalis IX —

From the small lateral-line ganglion on the root of the glosso-
pharyngeus all the fibers pass dorsoposteriorly as a single minute
nerve, through a short canal in the lateral wall of the ear cap-
sule, to the dorsal side of the head. Thence running anteriorly,
they are distributed through three terminal ramuli to that part
of the main lateral-line canal between the distribution areas of
the ramus oticus VII and the ramus supratemporalis X. No
pit-organs are connected with the ninth nerve, nor are somatic
sensory elements found in it. Houser (’01) mentions and figures
general cutaneous fibers in the ninth nerve, and also states their
occurrence in the tenth nerve, of Mustelus canis.

4. The first branchial nerve

The glossopharyngeal nerve in Squalus may be taken as an
example of a typical branchial nerve. It consists of four rami:
lateralis, pharyngeal, pretrematic, and posttrematic. ‘The post-
trematic, however, is itself distinctly double. All but the lat-
eralis contain visceral sensory elements, the posttrematic dif-

NERVES OF THE DOGFISH 359

fering from the pharyngeal and pretrematic in possessing visceral
motor fibers in its main portion.

Within its canal in the ear capsule the ninth nerve emerges
from the posterior end of the visceral ganglion in two portions, a
smaller lateral visceral sensory part, and a large mesial portion
of sensory and motor composition (figs. 24, 48, 51, and 52). On
emerging from the canal in the ear capsule, the smaller portion
divides into two chief branches at the ventromesial border of the
thymus gland. The mesial one of these divisions turns anteriorly
along the roof of the pharynx and mouth dorsally: ramus pharyn-
geus IX (figs. 48, 51 and 52, ph. IX). The lateral branch of the
lateral sensory division of the glossopharyngeus turns antero-
ventrally from its point of separation from the mesial branch
and runs along the anterior wall of the first gill cleft—ramus
pretrematicus IX (figs. 48 and 51, prt. IX). »

After giving off the rr. pharyngeus and pretrematicus, the
remaining fibers of the ninth nerve constitute a large nerve lying
dorsal to the mesial end of the first epibranchial cartilage.
Along the anterolateral face of this cartilage it runs ventrally,
curving at first posteriorly and then ventrally as it shifts over
to the first ceratobranchial cartilage. It runs along the dorso-
lateral border, later along the ventrolateral border of this car-
tilage. Shifting to the mesial border, it runs to the extreme
anterior tip of the cartilage and farther anteriorly at the dorso-
lateral border of the coracobranchialis muscle, beyond the ante-
rior end of which it runs at the dorsomesial border of the poste-
rior horn of the basihyal. _ Farther anteriorly it passes along the
dorsal border of the lateral portion of the main part of the basi-
hyal cartilage, supplying the mucous membrane of the floor of
the pharynx and mouth. Besides the chief portion of the ramus
posttrematicus there are some secondary parts given off as
small visceral sensory branches (fig. 48, pst. 7Xa) that run
more directly anteroventrally across the anterolateral face of the
epibranchial cartilage, thence along the ceratobranchial bar a
little dorsal to the main ramus. The general course of the
ramus posttrematicus IX is thus seen to be along the mucous
membrane of the posterior wall of the first gill-cleft.

360 H. W. NORRIS AND SALLY P. HUGHES

THE VAGUS NERVE
1. The lateral-line roots and ganglia of the vagus nerve

The roots of the vagus nerve in their entirety when seen in a
lateral view (figs. 24, 48, and 51) form a wedge-like sheet of
fibers on the side of the medulla. Converging at the postero-
ventral angle of the wedge, the combined fibers form a compact
column that produces a hollowing out of the mesial wall of the
ear capsule and forms a recess, the beginning of a canal or cham-
ber in the extreme posterior portion of the ventromesial part of
the ear capsule. This chamber in which the combined lateral-
line and visceral sensory ganglia for the greater part lie, opens
posteriorly at the border of the occipital condyle.

As indicated in a previous section, the lateral-line element in
the ninth nerve enters the brain immediately anterior and ven-
tral to the anterior lateral-line roots of the vagus (figs. 24 and
51). Within the brain the vagus lateral-line fibers may be traced
far anteriorly as a wedge-shaped (in cross-section) tract reaching
from the periphery of the brain inward as far as the lateral border
of the visceral lobe. On entering the brain the lateral-line fibers
of the vagus all turn anteriorly (fig. 40). Farther anteriorly the
tract appears to be made up of scattered bundles and finally
becomes indistinguishable from the other medullated tracts of
the acusticum. Peripherally, the root fibers form a _ broad
ribbon-like band lateral to the brain, covering the anterior roots
of the vagus proper lying mesially. Farther posteriorly, the
lateral-line root drops ventrally so that the more posterior roots
of the vagus are exposed. Still farther posteriorly and ending
in the ganglion, the root becomes more compact covering merely
the ventral border of the vagus roots (figs. 24, 48, and 51).

The lateral-line ganglion of the vagus shows evidence of a
segmentation into three parts. The first is the more anterior
part of the vagal ganglionic complex, a slender column of cells
that gives rise to the supratemporal ramus. Just posterior to
this first cell mass and for some distance in contact with it lies
the major part of the ganglion, two scarcely separable masses of
cells, from the anterior of which arise the fibers of the ramus

NERVES OF THE DOGFISH 361

oer
3 gbr.X 2 gbr.X fee

Fig. 39 A horizontal section through the dorsal lateral-line root of the facial
nerve. X30.

Fig. 40 A horizontal section through the lateral-line root and a visceral
sensory root of the vagus nerve, showing that the lateral-line root fibers all pass
anteriorly on entering the brain. A composite of three sections. X25.

Fig. 41 A parasagittal section through the right vagal ganglionic complex,
showing the segmental arrangement of the branchial ganglia. X31.

Fig. 42 A cross-section through the roots of the right vagus nerve, showing
the distinctness of the individual roots and ganglia. Section 1279. X31.

362 H. W. NORRIS AND SALLY P. HUGHES

dorsalis. Fibers from the third ganglion together with the
remaining fibers from the second form the ramus lateralis of the
trunk. In a horizontal section through the ganglionic com-
plex (fig. 45) there are seen external swellings indicating these
three ganglia. In a sagittal section the ganglion of the supra-
temporal ramus is seen to be anatomically distinct from the
others.

In the 22-mm. embryo Landacre finds three lateral-line ganglia
upon the vagus. From the first the supratemporal ramus
emerges connecting with three lateral-line primordia; from the
second ganglion a ramus, evidently ramus dorsalis, connects
with a large lateral-line primordium, and from the third ganglion
proceeds the ramus lateralis.

In Mustelus the ganglion of the supratemporal ramus is ana-
tomically distinct from the other vagal ganglia, not even in con-
tact with them. A similar condition occurs in Raja radiata.
In Mustelus the ganglion is sometimes very much elongate,
partly intracranial and partly extracranial.

2. The roots and ganglia of the vagus nerve proper

The visceral sensory roots of the vagus extend for a long
distance posterodorsally from the origin of the lateral-line roots
(figs. 24 and 51). There are thirty or more of the visceral roots
of the vagus. The majority of them are mixed, each comprising
a wide sensory band and a small motor element. The poste-
rior six or more are exclusively motor in composition. The
extreme posterior three or four rootlets arise from the dorsal
side of the medulla. Figure 43 is of a parasagittal section
through the lateral wa'l of the medulla cutting most of the vagus
rootlets. It will be seen that these enter the brain in an almost
straight line, rising gradually from anterior to posterior. As the
rootlets enter the brain, the motor element in each of the mixed
rootlets is usually ventral in position. As they pass inward the
sensory elements ascend into the visceral lobe, and the motor
fibers turn ventrally into the lateral motor column. At the
brain wall there is little evidence of a segmental arrangement

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Fig. 43 A parasagittal section through the left lateral border of the medulla
oblongata, cutting the rootlets of the vagus nerve. Four groups of rootlets are
shown somewhat indistinctly, corresponding to the roots of the four branchial
nerves. X25.

Fig. 44 A horizontal section through the ear capsules and parachordal region
of the cranium, showing five occipital nerves and the segmental arrangement of
the four vagal branchial ganglia. A composite of three sections. X15.

363

H. W. NORRIS AND SALLY P. HUGHES

364

NERVES OF THE DOGFISH 365

of the roots. Figure 48 shows that the arrangement of the root-
lets is in an almost uninterrupted series from anterior to posterior.
But in the sheet of fibers at the lateral border of the medulla,
formed by these rootlets, the individual branchial nerves soon
begin to differentiate, and in cross-section the segmental char-
acter of this sheet-like root of the vagus becomes very evident
(fig. 42). The four branchial and the single intestinal rami be-
come differentiated successively anteriorly posteriorly, the last
branchial and the intestinal, in the roots as well as peripheral
to the ganglion, being closely related. Without doubt there is
individual variation in the arrangement of the rootlets. In a
study of cross-sections it is often difficult to distinguish be-
tween the individual rootlets, but comparisons between cross-
sections and parasagittal sections shows that the variations in
the roots of the vagus are very few indeed.

The visceral vagal ganglionic mass shows a segmentation into
four branchial and one intestinal divisions, all more or less in
contact, and the last two closely fused. Horizontal and para-
sagittal sections show very clearly this segmental arrangement
(figs. 41 and 44). The common ganglion of the fifth bran-hial
and the intestinal nerve is larger than the others and plainly
double. Proximal to this last ganglion and related to it there
are two distinct roots. One the branchial root, connects with
the ganglion more anteriorly and ventrally than does the intes-
tinal root. Distally there emerge from the ganglion two nerves,
a ventral branchial and farther posteriorly a dorsal intestinal.
The motor fibers that pass through this fourth ganglion mass
belong to the intestinal division and are of two kinds: coarse
ones to the trapezius muscle, and finer, less medullated ones to
the wall of the digestive tract.

Fig. 45 A horizontal section through the roots of the right vagus nerve,
showing the four vagal branchial roots and the segmented condition of the lat-
eral-line ganglion. 30.

Fig. 46 A section of the left truncus hyomandibularis VII, cut horizontally
through the head, but obliquely to the nerve, showing the components of the
truncus and a sympathetic ganglion on the posterior border of the nerve. 30.

Fig. 47 A section of the left truncus hyomandibularis VII, cut transversely
through the head, but obliquely to the nerve, showing the components of the
nerve and a sympathetic ganglion on the posterior border of the nerve. Corre-
sponds approximately to section 1188 in figure 48. 30.

366 H. W. NORRIS AND SALLY P. HUGHES

3. The ramus supratemporalis X

This nerve is exclusively lateralis in composition. It leaves
the ventrolateral border of the anterior division of the lateral-
line ganglion, and after running posteriorly for some distance in
the vagal canal passes out dorsolaterally through a small canal
in the posterior wall of the ear capsule (figs. 41 and 42, spt. X).
It divides within the canal, an anterior branch passing dorsally
and anteriorly along the dorsolateral border of the ear capsule
and finally to the periphery to supply the sense-organs of the
commissural canal and the two pit-organs situated just anterior
to the external opening of the endolymphatic duct (fig. 50,
spt. X). A posterior branch passing dorsally and posteriorly
supplies ramuli to the neuromasts of the main lateral-line canal
immediately following those supplied by the ramus _ supra-
temporalis IX. In the specimen used in the plotting of figure
51 there are six of these ramuli supplied to the main canal; in a
second specimen only four.

4. The ramus dorsalis X

The term ramus dorsalis is here used as a non-committal
designation of a ramus exclusively lateralis in composition, that
arises from the second of the three divisions of the lateral-line
ganglionic mass of the vagus, and is distributed in part to neuro-
masts in the main lateral-line canal, but mostly to pit-organs
in the occipital and dorsal anterior trunk regions. It evidently
comprises a number of nerves, which, however, have a com-
mon origin from the ganglion and a similar distribution. There
emerge from the ventrolateral border of the ganglion three bands
of fibers. The two anterior may unite loosely into a common °
nerve, the third runs almost directly posteriorly and soon sepa-
rates from the other two, rejoining them only through anasto-
moses. <A large tract of one of the anterior bands may rejoin
the main lateral-line nerve. There is a tendency in the origin
of all of them for small tracts of fibers from the ganglion to join
the larger ones some distance from the origins of the latter,
forming in this manner a kind of plexus. A single nerve finally

NERVES OF THE DOGFISH 367

results from the plexus, extending posteriorly nearly to the first
dorsal fin.

Fibers of the ramus dorsalis are distributed through a vari-
able number of nerve ramuli to the section of the main sensory
canal immediately posterior to that innervated by the ramus su-
pratemporalis X. In one specimen there are eight of these ramuli;
in a second specimen eleven. It should be noted, however, that
in the first one the ramus supratemporalis X has six ramuli,
and in the second four. That is, there seems to be a sort of re-
ciprocal arrangement of ramuli between the rami supratemporalis
and dorsalis. Besides innervating the sensory canal, the ramus
dorsalis supplies a dorsal series of pit organs extending from im-
mediately posterior to the commissural canal nearly to the first
dorsal fin. In the specimen from which figure 50 was made there
are twenty-five of these pit-organs on the left side. It is a debat-
able question whether the ramus dorsalis as here defined is a
single nerve, but the presence of anastomoses between its divi-
sions precludes any exact separation between them. In Mus-
telus the ramus dorsalis is formed in a similar fashion from two
or three small nerves.

5, General cutaneous elements in the vagus nerve of elasmobranchs

It has been quite generally assumed that the vagus nerve of
selachians contains somatic sensory elements. The rami supra-
temporalis and dorsalis have been commonly designated as dor-
sal cutaneous branches of the vagus. The writers confess to
being seriously misled by this general assumption in the early
part of this research.

Stannius finds a single dorsal branch of the vagus in selach-
ians, which he regards as lateral-line exclusively. Ewart and
Cole believe that the supratemporal branches of both the glosso-
pharyngeus and the vagus of Laemargus contain cutaneous as
well as lateralis elements. Cole finds in Chimaera a dorsal
branch of the ninth nerve supplying the skin, but not special
sense-organs. A dorsal branch of the vagus, on the other hand,
innervates canal organs. Kappers (’14) finds cutaneous con-

368 H. W. NORRIS AND SALLY P. HUGHES

stituents in the seventh, ninth, and tenth nerves of Hexanchus
and Heptanchus, but not in other selachians. Houser describes
and figures general cutaneous fibers in the vagus nerve of Mus-
telus canis. Landacre describes in the embryo of Squalus acan-
thias a ganglion, which he regards as general cutaneous, on the
vagus nerve together with a nerve which he believes to be the
equivalent of a ramus auricularis. In a figure prepared for the
first edition of Herrick and Crosby’s Laboratory Outlines in
Neurology (’18), the writers represented the ramus dorsalis of
Squalus as containing somatic sensory fibers. The true relations
are shown in the second edition (’20, fig. 5). Besides fibers term-
inating in canal organs, there were other constituents of the ramus
dorsalis that ended in the skin, losing for the most part their
myelin near their termination. More careful examination has
shown that in every instance such fibers of the ramus dorsalis
terminate in pit-organs. The writers are forced to the conclu-
sion that in Squalus acanthias there is no general cutaneous com-
ponent in the vagus nerve of the adult and late embryonic con-
dition. Careful search has revealed no connections between the
tractus spinalis trigemini and the vagus nerve. Nor can there
be found any ganglia in the vagus nerve of Squalus except the
three lateralis ganglia and the four (five) ganglia on the branchial
and intestinal nerves.

The occurrence of well-defined somatic sensory components in
dorsal branches of the vagus nerve in ganoids and teleosts (Her-
rick, ’99, ’00, ’01; Allis, 97; Panschin, ’10) leads to the expec-
tation of finding them in the selachians. It may be that the
condition in Squalus is not typical. The finding of a somatic
sensory ganglion by Landacre in the embryo suggests that its
occurrence may be general.

Hawkes notes that two kinds of fibers are found in the dorsal
branches of the ninth and tenth nerves of Chlamydoselachus:
coarse fibers, interpreted as lateral-line, and “smaller medullated
fibers probably general cutaneous.’’ The writers have observed
that the pit-organs in Squalus are innervated by fibers of notice-
ably smaller caliber and less dense medullation than those supply-
ing the canal organs.

NERVES OF THE DOGFISH 369

General cutaneous elements in the vagus of amphibians, with
the exception of the caecilians (Norris and Hughes, 718), have
long been recognized.

6. The ramus lateralis X

This large nerve runs out of the posterior ventral border of the
lateral-line ganglion. Its fibers are derived from the second and
third divisions of the latter. Its fibers are distributed to the
canal organs of the main lateral line and to the series of dorso-
lateral pit-organs situated dorsolaterally above the lateral-line
canal of the trunk, termed by Johnson (’17) the accessory pit-
organs (fig. 50).

7. The second to the fifth branchial nerves

The branchial nerves derived from the vagus, in their relations
to the branchial clefts and arches are essentially similar to the
glossopharyngeal nerve in its relations to the structures of the
first branchial cleft and arch. Each nerve may be traced to a
distinct root far anterior toits own ganglion, suggesting the elongate
root of the ninth. Peripherally to the ganglion each nerve divides
into threerami: pharyngeal, pretrematic and posttrematic, with dis-
tributions similar to the corresponding rami of the glossopharyngeus.
The posttrematic, consisting of a main and a secondary portion,
as in the ninth, with similar courses, innervates the corresponding
interarcual, adductor arcus branchialis, interbranchial, and ven-
tral-constrictor muscles. The innervation of the adductor arcus
branchialis is in each instance by small nerves that pass through
foramina in the epibranchial cartilage.

The fifth branchial nerve contains only visceral sensory fibers
(sympathetic elements being ignored). It leaves the ganglion
common to it and the ramus intestinalis farther anteriorly than
the latter. After the separation of the other branchial nerves,
the fifth continues its position at the ventral mesial border of the
ramus intestinalis until it reaches the transverse level of the
extreme posterior border of the fourth adductor muscle, where it
gives off a ramus posttrematicus. The latter runs posteriorly

370 H. W. NORRIS AND SALLY P. HUGHES

across the dorsal border of the fourth interarcual muscle, then
farther ventrally along and across the elongate fifth epibranchial
bar, near the ventral end of the latter turning anteriorly to run
at the lateral border of the muscular wall of the digestive tract,
where it enters a ganglion (fig. 48). From the ganglion several
nerves pass anteriorly, apparently distributed to the wall of the
pericardial chamber. This anterior end of the ramus posttre-
maticus forms a so-called ramus cardiacus.

As the fifth branchial nerve is passing across the interarcual
muscle a ramus pretrematicus is given off running posteriorly,
ventrally, and finally anteriorly along the anterior wall of the
fifth branchial cleft. Near the posterior border of the inter-
arcual muscle a ramus pharyngeus passes through the muscle
to the roof of the pharynx and has the usual distribution.

Where the main lateral-line ganglion is in contact with the
visceral ganglion of the fourth branchial nerve (X3), a tract of
fibers passes from the former into the latter, thence out of the
ganglion along with the motor constituent and through the main
fourth branchial nerve into its posttrematic ramus. It contin-
ues in the latter around to the ventral part of the fourth branchial
arch. On the posterior border of the fourth ceratobranchial car-
tilage it leaves the posttrematic ramus through a small sympa-
thetic ganglion and passes anteriorly, ventrally, and mesially in
the fleshy connections of the fourth branchial arch with the
lateral trunk wall. It then turns posteriorly at the lateral
border of the coracobranchialis group of muscles, then farther
posteriorly runs along the lateral border of the coracoarcualis
muscle, and continues in this position, descending ventrally in
its course until the posterior lateral border of the pectoral girdle
is reached. Here it turns mesially around the pectoral girdle
and runs posteriorly in the ventral body wall, breaking up into
small twigs distributed to a small group of pit-organs situated
posterolaterally to the base of the yolkstalk of the embryo (figs.
48 and 50, upo.).

Of the occurrence in Squalus of ‘rami pretrematici interni,’ such
as are stated by Sewertzoff (11) to be found in Scyllium, Acan-
thias, Raja, and Trigon, the writers find little evidence. Sew-

371

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NERVES OF THE DOGFISH

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ertzoff gives no figures or exact descriptions of these nerves in
Acanthias, and his citation of Bender (’06) as an authority for
their occurrence in the latter form is of little weight, since Bender
gives neither figures nor description of them in Acanthias. After
an examination of the figures of Sewertzoff and Bender there can
be little doubt of the presence of these so-called rami pretre-
matici interni in Heptanchus, Scyllium, Raja, and Centrophorus,
but in Squalus acanthias the ramus pharyngeus of the branchial
nerves does not divide into a dorsal pharyngeus and a latero-
ventral ramus pretrematicus internus. The entire ramus phar-
yngeus is distributed dorsally. The pharyngeal rami of the third
and fourth branchial nerves of the vagus do divide immediately
on emerging from the main nerve, but into anterior and posterior
divisions, both distributed dorsally and not laterally. Pharyn-
geal, pretrematic and posttrematic rami occur in all the branchial
nerves including the facialis proper. Bender regards the ramus
palatinus of selachians as a combination of a ramus pharyngeus
with a ramus pretrematicus. In quite similar fashion the ramus
pharyngeus of the glossopharyngeal nerve unites for some dis-
tance with the ramus pretrematicus. In both the facialis and
the glossopharyngeus of Squalus the ramus pretrematicus near
its dorsal end gives off small twigs, in one case to the pseudo-
branch, in the other to the wall of the first gill cleft. In the vagal
branchial nerves the pharyngeal and pretrematic rami arise from
the main nerve sharply distinct from each other. The accessory
posttrematic rami occur in a double condition in the glossophar-
yngeus and fourth vagal branchial (fig. 48).

8. The ramus tntestino-accessorius X

As this nerve trunk leaves the ganglion posteriorly, its coarse
motor constituents form a narrow band along its dorsal border.
These soon separate as a distinct nerve that passes posteriorly
along the dorsal border of the visceral sensory elements of the
nerve trunk, finally rising in a few divisions into the trapezius
muscle which it innervates (figs. 48 and 51, trap.). The fine
motor and the sensory elements of the ramus continue straight

NERVES OF THE DOGFISH oie

posteriorly nearly to the posterior border of the fifth branchial
arch. Then it divides into three mainbranches whose subdivi-
sions are distributed chiefly to the wall of the digestive tract.

THE OCCIPITAL NERVES

The occipital nerves in Squalus acanthias are variable in num-
ber. Two seems to be the more constant number, but in some
instances two well-developed and one or more rudimentary ones
may be found. In the same head there may occur a difference
in number between the two sides. Firbringer (97) reports two
or three occipital nerves in Acanthias vulgaris. Following the
method of Fiirbringer, the writers designate the occipital nerves
from posterior to anterior by the letters z, y, x, ete.

The anterior rootlets of the occipital nerve y may be discerned
somewhat anterior to the transverse level of the posterior motor
roots of the vagus (fig. 51, y). They arise, in marked contrast
to the visceral motor roots of the vagus, from the ventral motor
column. About six rootlets contribute to the formation of the
nerve. After its formation the nerve passes at once into the
vagal canal, sometimes by a distinct foramen. Within the canal
(fig. 42, y) it passes back with the vagal complex and divides into
a larger ventral and a smaller dorsal portion. The smaller divi-
sion, in passing out dorsally through a small canal in the roof of
the ear capsule (figs. 49 and 51), is accompanied by a correspond-
ing branch of the occipital nerve z, the two being distributed to
dorsal trunk muscles. The main portion of the nerve y continues
through the vagal canal accompanied by the main part of nerve
z. As the two nerves pass into the firstinterbasal (subspinalis)
muscle, or more correctly stated, between its dorsal and ventral
portions, they are joined by a ventral branch of the first spinal
nerve. This latter nerve contains somatic sensory as well as
somatic motor fibers. The three nerves pass back through the
muscle and at its lateral border merge into a single trunk, in
which, however, the individuality of the contributing nerves is
not lost.

3/4 H. W. NORRIS AND SALLY P. HUGHES

Occipital nerve z originates by four or five rootlets from the
region where the spinal cord merges into the medulla. It passes
at once through:a small foramen into the vagal canal, almost im-
mediately on entering giving off the small dorsal branch that
passes out dorsally with a corresponding branch of the nerve y.
As stated above, it accompanies the preceding occipital nerve
posteriorly and finally unites with it and a branch of the first
spinal nerve. It gives off small branches to the first interbasal
muscle.

The occipital nerve x, when present, is very small. In the
single instance in which it was traced from origin to innervation,
it was found to leave the brain wall some distance anterior to
the exit of y. Passing back ventral to the vagus roots it enters
a minute canal in the base of the cranium, merging into the vagal
canal, where it runs posteriorly at the ventral border of the bran-
chial ganglia (fig. 42). On leaving the vagal canal, it takes a
position at the lateral border of the basal plate, soon joining the
nerve y, with which it passes back some distance, finally turning
mesially into the mesial portion of the first interbasal muscle,
which it innervates. Figure 44 is a horizontal section through
the cranial basis of a specimen with five occipital nerves. The
destinations of nerves v and w were not traced.

According to Fiirbringer, there are usually three nerve branches
supplying the interbasal muscles in selachians. One or two of
these, derived from y or y and z, innervate the first interbasal
(subspinalis). One or two branches derived from y and z supply
interbasals 2-3. The writers find in Squalus acanthias five nerve
branches supplying the first interbasal muscle: one derived from
nerve x, two from y, one from z, and one from the first spinal
nerve. That the other interbasal muscles are innervated as
Firbringer describes is probable, but the writers are unable to
confirm his statements.

The small foramen of exit of the nerve z into the vagal canal
is designated by Wells (17) as a secondary foramen of the vagus
nerve.

NERVES OF THE DOGFISH aD

THE FIRST THREE SPINAL NERVES

The more anterior motor rootlets of the first spinal nerve ap-
pear a short distance posterior to the last rootlets of the occipital
nerve z, at a level slightly posterior to that of the posterior bor-
der of the roof of the cranium. The motor root thus formed
passes out at once through a foramen between the first vertebra
and the occipital condyle (fig. 48, sp.Jrm.). On emerging, it
divides into a ventral and a dorsal ramus, the latter passing post-
eriorly and then anteriorly around the antero-lateral border of
the first spinal ganglion, apparently without receiving any sen-
sory elements from it, and gives off branches to the dorsal trunk
muscles. The ventral motor ramus, after sending off one or
more branches that run posteriorly in the ventral portion of the
dorsal trunk muscles, is joined by a sensory ramus from the first
spinal ganglion, the two forming a nerve which running poster-
iorly at the lateral border of the occipital condyle joins the two
occipital nerves as previously described (fig. 49).

The sensory root of the first spinal nerve enters the dorsal
portion of the spinal cord somewhat posterior to the posterior
rootlets of the motor root. Its course from the spinal cord to
its foramen of exit through the first intercalary cartilage is pos-
teriorly directed, then anteriorly into the ganglion situated imme-
diately outside the foramen. From the extreme posterior end
of the ganglion a branch runs ventrolaterally to join the ventral
motor ramus as described above. One or more (usually two)
sensory nerves connect with the anterior end of the ganglion
(fig. 49).

The anterior rootlets of the second spinal nerve begin to emerge
as far anteriorly as the level of the sensory root of the first spinal
nerve. Numerous rootlets converge to form a root that passes
out at the level of the posterior rootlets through a foramen in
the first vertebra, dividing immediately on exit into a dorsal
and a ventral branch. In the number and arrangement of its
parts the second spinal nerve is almost a duplication of the firs*
spinal. Its ventral ramus of motor and sensory composition
runs posteriorly at the lateral border of the first and second ver-

376 H. W. NORRIS AND SALLY P. HUGHES

tebrae, and just posterior to the origin of the third spinal nerve
fuses with the trunk formed by the union of the occipital and
first spinal nerves, forming what is known as the cervical plexus
(figs. 49 and 51). It will be seen that this account of the main
branches of the anterior spinal nerves in Squalus acanthias is
not wholly in agreement with the description given by Allen (717)
of the corresponding parts of a posterior abdominal spinal nerve
in the same species.

The form and branches of the third spinal nerve repeat with
little variation those of the two preceding nerves. The ventral
ramus passes out through a foramen in the second vertebra, and
after running posteriorly some distance comes into intimate re-
lations with the combined mass of the ventral rami of the occip-
ital and first and second spinal nerves. Only with extreme care
can it be followed in sections through the cervical plexus. It is
seen to receive a motor branch from the second spinal nerve,
but all its own motor fibers pass into the brachial plexus. It
sends anteroventrally one or more large sensory branches closely
paralleling the great hypobranchial nerve formed from the cer-
vical plexus (figs. 49, 51, and 53). This account is in close agree-
ment with that of Fiirbringer for Acanthias, but he states that
in some instances the third spinal nerve contributes to the cer-
vical plexus a sensory branch.

Miiller (’11) states that in Acanthias vulgaris there are three
occipital nerves, later in development two. In seventeen ex-
amples he finds that the third spinal nerve forms the first bra-
chial nerve; in six instances it is the second spinal, and in four
instances, the fourth spinal.

THE HYPOBRANCHIAL NERVE

The great nerve trunk formed by the union of the ventral rami
of the occipital and first two spinal nerves is composed of somatic
sensory and somatic motor fibers. Visceral sensory and motor
fibers, if present, are not in evidence. Careful examination of
cross-sections of the nerve shows that it is possible to distinguish
with considerable accuracy the parts contributed by the various

NERVES OF THE DOGFISH BT

nerves. As the nerve trunk approaches the place of its sepa-
ration into the chief branches of distribution, these elements be-
come more distinct. The derivative of the third spinal nerve
retains its individuality throughout, and never actually unites
with the others. The sensory elements of the spinal-nerve con-
stituents are coalesced and become intimately associated with
the occipital-nerve derivatives. The motor elements of the first
and second spinal nerves are distinct.

In this condition the hypobranchial nerve forms a flat hori-
zontal band at the ventral border of the dorsal trunk muscles,
mesial to the ramus intestinalis X. Gradually it shifts laterally
dorsal to the ramus intestinalis, and finally, passing ventrally
around the lateral border of it, breaks up into its chief branches.
There are three of these branches, two directed anteriorly and
one posteriorly. In the readjustment of the constituent ele-
ments to form the peripheral divisions, the sensory elements from
the first and second spinal nerves combine with the motor con-
stituents of the occipital and second spinal nerves to form a
trunk that sends a small motor branch posteriorly into the third
spinal nerve and thence into the brachial plexus, and a large
branch anteriorly along the mesial dorsal border of the limb-
girdle (fig. 49).. When the posterior end of the fifth epibranchial
cartilage is reached, the nerve runs along its mesial border, then
shifting to the ventral border of the fifth ceratobranchial bar
and dividing into two or three divisions that later reunite, it
finally unites with the second anterior division of the hypobran-
chial nerve, just outside the ventrolateral wall of the pericardium,
on the dorsal border of the coraco-arcualis communis muscle,
which it innervates. In its course along the border of the coraco-
arcualis muscle the motor hypobranchial trunk divides into a
dorsal and a ventral branch. The latter, the larger, turns sharply
through the muscle ventrally, sends branches into the coraco-
mandibularis and enters and passes anteriorly within the coraco-
hyoideus muscle. The dorsal branch runs along the dorsomesial
border of the coraco-arcualis communis, and after passing
through this muscle, between the first and second divisions of the
coracobranchialis muscle, is distributed to the latter.

H. W. NORRIS AND SALLY P. HUGHES

378

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380 H. W. NORRIS AND SALLY P. HUGHES

The second division of the hypobranchial nerve, derived from
the motor constituent of the first spinal nerve, runs anteriorly
somewhat dorsal to the first division. At first it passes along
the lateral border of the esophagus, just outside its muscular
wall, farther anteriorly ventral to the lateral part of the pharynx,
then at the mesial dorsal border of the fifth ceratobranchial
cartilage, and still farther anteriorly ventral to it. It then unites
with the first branch, as already described. At the union of the
two nerves apparently all of the sensory elements of the first
division have been given off in minute nerves to the ventral and
ventrolateral skin in the branchial and postbranchial region, and
from this point onward the hypobranchial nerve is exclusively
motor. Anterior to the shoulder girdle, the motor hypobran-
cbialis innervates the coraco-arcualis communis, coracomandibu-
laris, coracohyoideus, and coracobranchiales muscles.

Neal (97) derives the hypoglossal musculature of Squalus
from the fourth to the eighth postotic somites. The second and
third postotic somites are present; the second is rudimentary,
and the third is without a ventrally growing bud, but with a
nerve. From the fourth somite comes the coracomandibularis
muscle, apparently. The fifth to the eighth somites produce
muscles between the hyoid and procoracoid cartilages. The
seventh and eighth somites also contribute to the pectoral plate.
If one takes into account the occurrence of as many as five pairs
of occipital nerves in the pup stage, it is seen that there is slight
discrepancy between the account given by the writers and that
of Neal relating to an earlier stage.

According to van Wijhe, the hypoglossus nerve is derived from
three (apparently four) ventral roots of the seventh, eighth, and
ninth somites, on the last of which is a sympathetic ganglion.
In Squalus the writers find a small sympathetic ganglion on the
ventral root of the third spinal nerve.

Individual variation in the derivatives of the somites and their
corresponding nerves probably explains the minor discrepancies
between the accounts of various writers.

Comparing the hypobranchial nerve of selachians with the
hypoglossal nerve of amphibians, we see some suggestive re-

NERVES OF THE DOGFISH 381

semblances. The hypoglossal nerve of the urodele amphibians
is formed from the ventral branches of one or more spinal nerves.
In some forms, as Siren, sensory elements are contributed at the
origin of the nerve, to be given off before the true hypoglossal
nerve is reached. In the caecilians sensory elements are like-
wise found at the origin of the nerve, and in some species of cae-
cilians an occipital nerve forms part of the hypoglossal. The
ventral musculature supplied by the hypobranchial nerve in
selachians undoubtedly corresponds in a general way to the ven-
tral musculature anterior to the shoulder-girdle in amphibians.
In Siren, for example, where the hypoglossus is derived from two
or three spinal nerves, it Innervates not only the geniohyoid
muscle, but also in part the sternohyoideus, abdominohyoideus,
and other trunk muscles. In the caecilians, in which it is de-
rived from the first and second spinal and sometimes from the
occipital as well, it innervates not only the geniohyoideus and
hyoglossus, but also parts of the thoracicohyoideus and ab-
dominohyoideus and other trunk muscles.

In general the hypobranchial nerve and musculature of se-
lachians corresponds to the hypoglossal nerve and musculature
of amphibians. There would seem little difficulty in deriving
the amphibian hypoglossal from the selachian hypobranchial.

SYMPATHETIC GANGLIA CONNECTED WITH CRANIAL NERVES

The writers frankly disclaim any attempt at a description of
the sympathetic nervous system in Squalus. Rather, there fol-
low notes on the occurrence of certain ganglia, observed some-
what incidentally during the preparation of the main body of
this research. Some of these ganglia have been seen and men-
tioned by previous writers, but as far as the writers know there
has been no comprehensive treatment of the subject, as far as
it concerns the selachians. These fragmentary observations are
about all that could be made upon the material available. A
special research upon material prepared especially for the invest-
igation of sympathetic nervous tissue in the elasmobranch fishes
should yield valuable results. The results of somewhat desultory

382 H. W. NORRIS AND SALLY P. HUGHES

observations are here recorded in the hope that they may serve
as a stimulus to more fruitful research.

The descriptions fall under two heads: 1. The ciliary sympa-
thetic plexus; 2. The sympathetic ganglia upon the branchial
nerves.

1. The ciliary sympathetic plexus

An extensive and confusing literature has developed around
the subject of the ciliary ganglion. A misinterpretation of de-
velopmental conditions in the selachians has been responsible
for much of the confusion. It is probable that some of the un-
certainty is also due to the double or even multiple character of
the ganglion in some selachians.

For recent reviews and discussion of the literature upon this
subject the reader is referred to papers by Carpenter (’06) and
by Neal (714).

Keeping in mind the fact that in many selachians the ciliary
ganglion because of its multiple character is in such minute
parts as to escape ordinary notice in dissections, we see that
Stannius (’49) has described with surprising accuracy the ciliary
nerves and their relations to the oculomotor and trigeminal
nerves. In the plagiostomes, according to him, there are usually
two to four ciliary branches (long ciliary) arising from the ramus
ophthalmicus profundus V (nerve or ganglion). Two of these
enter the eyeball between the insertions of the rectus externus
(lateralis) and rectus superior (dorsalis) muscles, and another,
single or double, enters dorsal to the insertion of the rectus in-
ternus. <A ciliary ganglion is lacking (in the opinion of Stannius)
together with anastomoses between the ciliary branches of the
oculomotorius and trigeminus. A ciliary branch of the oculo-
motorius arises from the ventral branch of the latter and accom-
panies a small artery to the eyeball, entering with it at a point
between the insertion of the rectus internus and rectus inferior
(ventralis). If Stannius had not overlooked the ciliary ganglia,
his descriptions would fit very closely into the actual relations
as found in Squalus. With the exception of the ciliary nerves,
Stannius finds no definite sympathetic in the head of plagios-

NERVES OF THE DOGFISH 383

tomes, but believes that the sympathetic elements are in these
forms bound up with the cerebral nerves, going directly to their
destinations without formation of special sympathetic trunks.

Schwalbe ('79) made an extensive study of the ciliary ganglion
in the elasmobranchs. In Scyllium catulus he found three cili-
ary ganglia, one where the oculomotorius divides for the rectus
inferior and obliquus inferior muscles, a second double in char-
acter situated approximately where the nerve crosses the oph-
thalmic artery, and a third found farther peripherally where the
nerve breaks up in the inferior oblique muscle. In Mustelus
he finds two ganglia, one where the branch to the rectus inferior
is given off and the other farther peripherally on the branch
to the obliquus inferior. In Mustelus a ciliary nerve from the
ramus ophthalmicus profundus V runs to the eyeball, so close to
the oculomotor nerve as to appear to be a branch of it. At about
the same plane the oculomotorius sends a ciliary branch to the
eyeball. In Chimaera he finds one ciliary ganglion, corresvond-
ing to the second one in Mustelus. He recognizes three classes
of ciliary nerves: 1. motor, from the oculomotorius; 2. sensory,
ciliares longi, from the ramus ophthalmicus profundus V; 3. vas-
cular, ciliares breves, from the ciliary ganglion.

Ewart (89) finds no ciliary ganglion in Laemargus, but one or
two ciliary branches of the oculomotorius which, after joining
ciliary branches of the ophthalmicus profundus, enter the eye-
ball. He states (90) that occasionally two well-developed ciliary
ganglia occur in Acanthias, connected usually with the inferior
branch of the oculomotorius. In some instances ganglion cells
have wandered along the ciliary nerves toward the eyeball. He
finds no ganglion cells in the trunk of the third nerve or its
branches. The ciliary ganglion has in all cases at least two roots,
one from the oculomotorius and one or two from the ophthalmicus
profundus. In addition to the ciliary nerves from the ciliary
ganglion, there are ciliary nerves from both nerve and ganglion
of the ophthalmicus profundus.

Hoffmann (’99) recognizes two ciliary ganglia in 48- to 50-
mm. embryos of Acanthias, one situated approximately where
the ophthalmic artery is crossed by the third nerve, the second

384 H. W. NORRIS AND SALLY P. HUGHES

occurs laterally on the upper surface of the oculomotorius oppo-
site the origin of the branch for the rectus internus. The second
is connected directly with the ophthalmic ganglion through a
nerve. The relation of the first ciliary ganglion to the ganglion
of the ophthalmicus profundus is not evident. Gast (’09) fig-
ures in Scyllium catulus embryos of 39-mm. length at least five
cilary ganglia, the three most important of which he terms: 1)
rectus ganglion, situated near the division of the third nerve into
its dorsal and ventral branches; 2) ciliary ganglion, near where
the branch to the rectus inferior is given off; 3) distal ganglion,
apparently on the branch to the obliquus inferior. In Mustelus
laevis of 22 mm. he finds three ciliary ganglia, rectus ganglion,
distal ganglion, and ganglion on the ‘infundibular nerve.’ Allis
CO1) recognizes a single ciliary ganglion in Mustelus laevis,
which is connected with the ophthalmicus profundus by two
branches (radix longa) and with the oculomotorius by a single
branch (radix brevis).!

In pointing out the fact that the so-called ciliary ganglion of
many writers is the ganglion of the ophthalmicus profundus,
Beard (’87) cleared up much of the prevalent confusion. The
ganglion of the ramus ophthalmicus profundus he terms the
mesocephalic ganglion, reserving the name ciliary for the gang-
lion intimately associated with the oculomotorius, which Schwalbe
called the ganglion oculomotorii. Van Wijhe (’82) distinguishes
between ciliary and oculomotor ganglia in Seyllium, but applies
the former name to the profundus ganglion. He finds a nerve
arising from the oculomotor (ciliary) ganglion and accompany-
ing the opthalmic artery to the eyeball. Marshall and Spencer
(81) and Marshall (’81) evidently confuse the ciliary with the
profundus ganglion in the early embryos of Scyllium, and regard —
the profundus nerve as a part of the third nerve in origin. They
report that ganglion cells of the ciliary in the later stages of de-
velopment are found ‘‘in small scattered patches at different parts
of the nerve” (’81, p. 89). The intimate relations of the meso-

1 At the 1912 meeting of the American Association of Anatomists Dr. H. D.

Senior, in a paper on the eye-muscle nerves of Squalus acanthias, stated that
no ciliary ganglion occurs in that species.

NERVES OF THE DOGFISH 385

cephalic and ciliary ganglia were recognized by Beard and by
Onodi (01). The latter examined the structures in the orbit of
many selachians and came to the conclusion that the oculomotor
ganglion (ciliary) of Schwalbe is a definite isolated ganglion in
some spceies, a loose network of cells and fibers in others, and in
others still in a form intermediate between these two extremes.
In Galeus he finds a loose network; in Mustelus laevis two ciliary
ganglia. These two ganglia are connected with each other by
two branches, and each sends a ciliary nerve anteriorly, and a
branch posteriorly into the ophthalmic nerve. From the larger
of the two ganglia two branches with an oculomotor branch supply
the ventral oblique muscle. As recently as 1905 Klinkhardt des-
ignated the profundus ganglion in Spinax as ciliary.

Connected with the oculomotor nerve in Squalus are a number
of ganglia, varying in size from a half-dozen cells to many in
number. These ganglia are situated on the courses of small
non-medullated nerves which as a whole form a plexus.’ It is
not possible in every instance to distinguish the fiber tracts upon
which the ganglia are situated, being when in a loose structure
so little differentiated from connective tissue. The number and
arrangement of the ganglia is subject to individual variation.
Moreover, the ganglion cells often occur seattered along their
courses instead of being compacted into definite ganglia. There
can, however, be distinguished the following general plan of
arrangement and number.

Nothing but densely medullated motor fibers are detected in
the intracranial portion of the oculomotor nerve. No _ intra-
cranial ganglion cells, such as Nicholls (715) finds in Scyllium,
are found on the third nerve in Squalus or Mustelus. As the
oculomotorius enters the orbit it divides at once into dorsal an-
terior and ventral posterior branches. At the point where this
forking takes place a small ganglion occurs (figs. 8 and 21, gcil.1).
sometimes of only about a half-dozen cells, sometimes within the
oculomotor nerve sheath, more often just outside. Regarding
the fiber connections of this ganglion there is some uncertainty.
Possibly fibers run anteriorly along the anterior division of the
oculomotor nerve together with blood-vessels; apparently they

386 H. W. NORRIS AND SALLY P. HUGHES

do. Fibers can be traced from the ganglion or its vicinity an-
teriorly into the main nerve as it passes through the foramen in
the cranial wall (fig. 6). From ganglion | there runsventrally
a fiber tract along the lateral border of the posterior (ventral)
division of the III nerve, into a ganglion situated on the antero-
lateral border of the latter (figs. 9, 16, 17, 21, and 31, gcil.2).
As described in the account of the ramus ophthalmicus profundus
V, the posterior ciliary nerve includes a non-medullated constit-
uent that turns ventrally and posteriorly to join the ciliary plexus.
This non-medullated nerve passes, as stated, ventrally and pos-
teriorly between the rectus dorsalis and the rectus lateralis muscles
and enters ganglion 2. In some instances there is a small gang-
lion imbedded in the rectus dorsalis muscle between ganglion 2
and the ramus ophthalmicus profundus. Farther ventrally on
the mesial posterior border of the third nerve at the point where
the ventral division separates into branches, one for the rectus
ventralis and the other for the obliquus ventralis muscle, there
occurs another ganglion (ganglion 3) (figs. 10, 15, 17, and 21,
gcil.3). Fibrous connection between ganglion 2 and ganglion 3
is plainly discernible as a flat band between the third nerve and
the rectus lateralis muscle (fig. 20, cil.), as it passes around to the
posterior mesial border of the third nerve. In some instances
ganglion 2 and ganglion 3 are almost confluent (fig. 17); in other
instances there seems to be another ganglion (ganglion 3a), dis-
tinct from ganglion 3, and situated in the forking of the nerve
(fig. 10).

Ganglion 1 seems to correspond to Gast’s ‘rectus’ ganglion,
though possibly the latter also includes ganglion 2. Gast’s ‘cil-
iary’ ganglion seems to correspond to ganglion 3. Hoffmann’s
two ciliary ganglia in Acanthias are evidently ganglia 2 and 3.

Ventral to ganglion 3, in the region of the ophthalmic artery,
the ciliary sympathetic cord divides into two branches. One of
these passing laterally around the posterior border of the oculo-
motor branch which supplies the ventral rectus muscle and then
between the two oculomotor divisions, follows the ophthalmic
artery out to the eyeball. On the way a ganglion (ganglion 6)
occurs from which a small nerve runs anteriorly along the ventral

NERVES OF THE DOGFISH 387

border of the ventral rectus muscle. Farther laterally, near the
eyeball, occurs another ganglion (ganglion 7) from which the nerve
passes into the eyeball (figs. 5, 7, and 21, gcil.6, gcil.7). This
nerve running from ganglion 3 out to the eyeball is what is usually
termed the ciliaris brevis. The second branch ventral to gang-
lion 3 extends posteromesially along the same small artery, but
toward the origin of the latter from the pseudobranchial artery.
At the dorsomesial border of the base of the infraorbital trunk
(mx.V +buc.VIT) a ganglion (ganglion 4) is found on this second
ciliary branch (figs. 16 and 21, gcil.4).. From this ganglion the
ciliary branch runs posteriorly along the ophthalmic artery to
the junction of the latter with the pseudobranchial artery, and
farther posteriorly finally joining a twig of the ramus palatinus
VII (fig. 21). Gast shows ‘vascular nerves’ in Seyllium which
possibly represent in part this palatine anastomosis in Squalus.
His infundibular nerve with ganglion in Mustelus seems to be
the same nerve. Two or three small ganglia (ganglion 5) in
Squalus on the ventral border of the rectus ventralis muscle near
the ophthalmic artery are closely related to ganglion 3 (fig. 15,
gceil.5). The small nerve from ganglion 6 running anteriorly
along the ventral surface of the rectus ventralis muscle was not
found in all specimens. When present it passes into a double
(or single) ganglion (ganglion 8) imbedded in the oculomotor
nerve branch destined to the ventral oblique muscle (fig. 21,
gcul.8). Farther anteriorly, near where the third nerve breaks
up in the ventral oblique muscle, a few ganglion cells (ganglion
9) are found, presumably connected by fibers with ganglion 8.
Schwalbe’s three ciliary ganglia in Scyllium are evidently ganglia
3 (with 3a or 6), 8 (double) and 9. His two ganglia in Mustelus
seem to correspond to ganglia 3 and 8.

The writers would not be understood as laying much stress
upon homologies between the ciliary ganglia of different species.
There is too much individual variability to insist upon homolo-
gies based merely upon the situation of ganglionic masses.

The ciliary plexus in Squalus thus consists fundamentally of
ganglionic masses in the orbit, related by non-medullated fibrous
tracts to three distinct nerves: oculomotorius, ramus ophthal-

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL, 31, No. 5

388 H. W. NORRIS AND SALLY P. HUGHES

micus profundus V, and ramus palatinus VII. The medullated
fibers given off from the ramus ophthalmicus profundus for the
innervation of the eyeball, and passing to their distribution
through the branches tentatively designated by the writers as
anterior and posterior ciliary nerves, are apparently the equiv-
alent of the ciliares longi of the higher vertebrates. They have
nothing to do with the ciliary ganglion. The non-medullated
constituent of the posterior ciliary fibers is the equivalent of the
radix longa of human anatomy. Just where the oculomotorius
gives its limited contribution to the ciliary nerve is difficult to
determine, probably in the region of ganglion 1. A radix brevis
is not clearly in evidence. The nerve that runs to the eyeball
from ganglion 3 is without doubt the short ciliary nerve.

In Mustelus californicus there occurs a small group of ganglion
cells where the oculomotor branch for the rectus superior muscle
separates from the main nerve, corresponding apparently to
ganglion 1 in Squalus. The ramus ophthalmicus profundus gives
off a posterior ciliary branch as in Squalus, a medullated com-
ponent of which passes posterolaterally to enter the posterior
wall of the eyeball by two terminal branches, and a non-medul-
lated part passes into the ventral division of the oculomotorius,
but not through a small ganglion (ganglion 2) as in Squalus.
The non-medullated element passes with the third nerve around
the posterior border of the rectus inferior muscle and with the
nerve runs anteriorly. A small ganglion occurs on the non-
medullated element shortly after turning in the anterior direc-
tion. From this ganglion there pass three ciliary branches. One
of these runs posterolaterally along the ophthalmic artery to the
eyeball, entering the latter in a few small branches, near the en-
trance of the artery. This branch bears a ganglion, having also
a small ganglion near its origin. A second branch from the gang-
lion passes posteromesially with the ophthalmic artery to the
junction of the latter with the pseudobranchial artery and along
the latter posteriorly to a junction with a branch of the ramus
palatinus VII. From the relation of these two ciliary branches
to the ganglion it would seem that the latter represents in a gen-
eral way ganglion 3 in Squalus. The small ganglion on the

NERVES OF THE DOGFISH 389

branch running out to the eyeball is possibly ganglion 7; the small
ganglion near the beginning of the second nerve seems to be
ganglion 4 of Squalus. A short distance anterior to ganglion
3 there occurs a large ganglion on the ventral branch of the oculo-
motorius, the one usually termed the ciliary ganglion of Mustelus.
t seems in some respects to answer to ganglion 6 in Squalus.
As in the latter, a nerve runs anteriorly from the ganglion con-
necting with small ganglia upon the branch of the third nerve
which supplies the ventral oblique muscle. Two such small
ganglia are found more anteriorly near where the oculomotorius
branch enters the oblique muscle. These anterior ganglia pos-
sibly correspond to ganglia 8 and 9 in Squalus. As in Squalus,
an anterior ciliary nerve runs from the ramus ophthalmicus pro-
fundus to the eyeball. The arrangement of the ciliary ganglia
and nerves in Mustelus is seen to be fundamentally similar to
the conditions in Squalus. Gast’s ‘rectus’ ganglion in Mustelus
embryos of 22 mm. seems to be ganglion 1. His ‘distal’ ganglion
is probably the large ganglion (ganglion 6), and his ganglion upon
the ‘infundibular nerve’ is probably ganglion 4. Schwalbe’s
two ganglia in Mustelus occur upon the ventral branch of the
third nerve. One is evidently the large ciliary ganglion (gang-
lion 6 or 6 and 3) and the other probably ganglion 8 or 9. Allis
shows only one large ciliary ganglion in Mustelus.

2. Branchial sympathetic ganglia

From Stannius down to the present the opinion seems to have
prevailed that the sympathetic system is represented in the head
of selachians solely by the ciliary ganglion and its connections.
The common opinion has been that the sympathetic elements,
except for the ciliary, are contained indistinguishably in the
cranial nerve trunks.

The writers find definite sympathetic ganglia on all the post-
trematic rami of the branchial nerves, including the ramus hyo-
mandibularis VII. With the exception of the latter, the typical
number of these ganglia seems to be four for each posttrematic
ramus, two on the dorsal region of the nerve as it passes across

390 H. W. NORRIS AND SALLY P. HUGHES

the epibranchial cartilage, and two on the ventral region along
the ceratobranchial cartilage. This number is subject to varia-
tion. The ganglia vary greatly in size and distinctness. In
most instances they are situated on the bases of small branches
of the posttrematic ramus, these small branches almost always
containing motor fibers, so that motor nerves seem to arise from
the ganglia. Non-medullated fibers connect with the ganglia
and form conspicuous components of the nerve branches con-
nected with the ganglia. In some instances non-medullated
fibers connect adjacent ganglia external to the post-trematic
ramus, forming semblances of plexuses. The non-medullated
fibers, when they occur in large enough numbers, are in marked
contrast to the medullated (lightly) fibers of visceral sensory
nature. But in general the sympathetic fibers cannot be traced
far from their ganglia because of the diffuse arrangement. No
sympathetic ganglia were found by the writers on the pretre-
matic and pharyngeal rami of the branchial nerves.

The only reference the writers have found mentioning sympa-
thetic ganglia upon branchial nerves is one by Allis (’01), who
finds on the hyomandibular trunk of Mustelus a ganglion of
small cells, from which pass four small nerves into the second
dorsal constrictor muscle. The writers find this ganglion in
Mustelus as Allis has described it; also other small ganglia on
the more ventral branches of the same nerve.

As the hyomandibular trunk of Squalus passes dorsolaterally
at the anterior wall of the spiracle the visceral sensory fibers are
seen collected at the dorsolateral border of the nerve, the motor
element at the ventrolateral edge, the main portion of the trunk
being lateral line. In the transition from the anterior wall of
the spiracle over to the posterior wall some of the visceral sens-
ory fibers of the nerve are seen to pass around on both sides to
the region of the motor fibers. Slightly farther ventral to this
appear the sympathetic ganglia on small motor branches given
off to the second dorsal constrictor muscle. Upon some of these
branches (five or six) there are small ganglionic masses, the cells
of which are much smaller than the smallest cells of the ordinary
cranial nerve ganglia. Non-medullated strands, external to the

NERVES OF THE DOGFISH 391

nerve trunk, connect some of these ganglia. The most ventral
of this group on the main hyomandibular trunk is sometimes
much larger than the others (figs. 46 and 47, gsy.).

After the hyomandibularis has divided into its chief rami, there
may be found on the ramus hyoideus three or more of these small
sympathetic ganglia. As the ramus hyoideus turns mesially
around the lateral border of the hyoid bar to pass between the
first and second ventral constrictor muscles, a small branch is
given off to the second ventral constrictor. At the base of this
nerve branch is a ganglion. Farther mesially, just ventral to the
lateral border of the second ventral constrictor, is another gang-
lion, this also near the branching of the nerve. A distinct non-
medullated nerve runs from this ganglion into the ramus hyoid-
eus, and another non-medullated strand, accompanied by one or
two medullated fibers runs from the ganglion anterodorsally into
the constrictor muscle. Farther mesially still another small
ganglion is situated at a branching of the ramus hyoideus, send-
ing a non-medullated twig into the muscle. Scattered ganglion
cells also are found upon the smaller divisions of the ramus
hyoideus (fig. 48).

On the posttrematic rami of the glossopharyngeus and the
first three branchial nerves of the vagus the arrangement is essen-
tially as stated previously: two small ganglia on the ramus dor-
sally and two ventrally. Figure 48 shows striking variations
from this arrangement, but the statement above holds true of
most specimens. The ganglia are sometimes little more than
scattered cells. Invariably they occur on small branches of
mixed constitution. In the fourth branchial nerve of the vagus
there are no motor elements, and ganglia are wanting on those
portions of the posttrematic ramus passing over the epibranchial
and ceratobranchial cartilages. The single elongate ganglion
upon the posttrematic ramus is situated at the ventral border
of the anterior muscular wall of the esophagus. Its cells are

-larger and of very different appearance from the cells of the
ganglia on the other branchial nerves (fig. 48).

392 H. W. NORRIS AND SALLY P. HUGHES

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401

aA

Resumen por el autor, N. E. MacIndoo,
Bureau de Entomologia, Washington.

El sentido del olfato en los Ortdépteros.

Poros olfatorios: El estudio comparativo de la disposicién de
los poros olfatorios de los Ortépteros se ha basado en el estudio
de ambos sexos en veintiuna especies, pertenecientes a veinte
géneros y representando seis familias. Se encontraron siempre
poros olfatorios en las patas, antenas y estiletes anales; general-
mente también en las alas (cuando existen), segmentos abdomin-
ales, cercos, cabeza y en todas las partes bucales y a veces también
en los segmentos tordcicos y oviscapto. En el primer segmento
antenal generalmente existen unos pocos, pero hay siempre
muchos de ellos en el segundo segmento. Los Mantidos y
Fasmidos poseen el menor ntimero de poros, ciertos acrididos

presentan el mayor nimero, mientras que las especies restantes
‘tienen un numero medio. Los poros en las seis mudas de los
saltamontes aumentan gradualmente desde el 46 por ciento en
la primera muda hasta 100 p.c., en la hembra adulta. Exterior-
mente estos 6rganos son oblongos generalmente, a veces casi
presentan forma de hendidura, pero el tipo de poro en forma de
ojo es el mas comtin. Interiormente cada uno de estos 6rganos
posee una célula sensorial fusiforme cuyo extremo periférico se
une con el orificio del poro en la quitina. Experimentos sobre
las antenas: Se llevaron a cabo experimentos sobre los salta-
montes y grillos para determinar si los llamados organos olfatorios
de las antenas reciben estimulos olfatorios. Puesto que se
cortaron las antenas por encima de los poros olfatorios del primer
y segundo segmento, parece probable, a juzgar por tos tiempos
de reaccion obtenidos, que el resto de las antenas, que poseen
los lamados poros olfatorios, no sirven como receptores olfa-
torios, en contra de lo supuesto por otros investigadores.

Translation by José F, Nonidez
Cornell University Medical College, N. Y.

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SHRVICE, APRIL 5

THE OLFACTORY SENSE OF ORTHOPTERA

N. E. McINDOO
Bureau of Entomology, Washington, D. C.

NINETY-TWO FIGURES

CONTENTS

Imtroductronkandymethodsstcccecanae cs ae bie aise cee oe ete a oa oe 405
Mornpholocyzor the olfactory poressesssee ice aa een ace eee 407
Wispositveniof pores\mla) grasshoppers()LA).\sth 2A). sb annette acre ete 407
d-,Pores onsheady oct cbt sages dG INTEL: HELGE Tas RE 407

bs Porésxonvthoramsey. sacks ss sorsia cig ecient Go cia poker eee eee 409

€. IPOTESHOMY Alo OMMEMUA wots Seyeiard ci nie ccs siegepnlola Seqarie teeth cee ore teeta 411

GF JPOres+ on wall sixinstars tes. Sac Aree ces ote ee + See een 412
Disposition-of pores:inother Orthoptera 42. f1394206.01: >: BUS: 412

G4 Poressone hea dieicca 8 ese ooecegevolneyd Go ieee eR era Pants eo ee 413

Dis Poresronnt ho raxcetcates «dente toe se sel cate nea hie aay San ciea he ome eye 413

Gr Poresvon! AA OMEN 456 ee cisee ecco sce eee eres, soe ai oe oe 414

d. Pores on first and last instars of croton-bug..................... 414

e. Family, generic, specific, and sexual variations.................. 414
StLetUres Of POKES Wns, CASS MOPED a. c:nt..< sheets 2p <a oye le, city Pe Soups cee 415
Qeslixtermalestru ChURer case. «isco > scratin rete tier kc POEMS SE 55 amin 415
orilmnternalustructunmeyss-1s2'i3.'-c. soar aac ast en 2 419
‘Rhevantennaleoreanss-. see se. cake’. 4 hele eens see as tae tenes 421
imesponses: to chemical stimmllit 6 \-.<88 seksi cons 2 dee ee 423
HxperimentSawith: PEASSHOWPCES ... .2.ckirr = eres kote +. <a oles aa ms earn 423

a. Unmutileited @rasshoppers.. 05.1 seems: 04. > onc cree er eine 423

b. Grasshoppers with antennae severed through third segments.... 425
Experimentsswathyonteketses.-. nea. ste seer. era ieee 425

a. cUnmutilatedventiGkets oss 445.53 oe ee eee eee ees eek 425

b. Crickets with antennae severed through third segments......... 425
RSUUTLAa NG 142 IN Gh ee ASI PREC 3 ocr c A RR ARE SS 5 0-00 Shura MeO ERG Gea Cet na nate hb ieee 426
GG ET a LUTES CLC Gs oe se yccncsaes PRAY he ees RTE Oe NO OT Pe oe ek ere FRG rey = 427

INTRODUCTION AND METHODS

The results herein recorded are a continuation of the writer’s
investigations concerning the olfactory pores of insects. Up to
date, including the present results, these organs have been care-
fully studied in Hymenoptera, Coleoptera, Lepidoptera, Diptera,

405

406 N. E. McINDOO

and Orthoptera; also in one coleopterous larva and in thirty spe-
cies of lepidopterous larvae. All of these orders, except Orthop-
tera, have complete metamorphoses, and consequently it was
more convenient to study the olfactory pores in the adult forms
than to use both immature and mature forms at the same time;
but in regard to insects having incomplete metamorphoses, it
is expedient to use all instars of at least one insect in the same
study. For this reason and in order to determine what effect
metamorphosis has on the olfactory pores, a careful study of the
disposition of these organs in all six instars of a certain grass-
hopper has been made.

The two chief objects of the present investigation are: 1) to
determine whether the olfactory pores are better adapted ana-
tomically to receive olfactory stimuli than are the so-called ol-
factory organs on the antennae, and 2) to ascertain experimen-
tally the effects on the olfactory sense when the so-called olfac-
tory organs on the antennae are removed.

To obtain material for the study of the disposition of the ol-
factory pores, dried museum specimens were mostly used; these
were obtained of Mr. A. N. Caudell, who also kindly identified
all of the species used in this study. Fresh material was fixed
in the modified Carnoy’s fluid, and was embedded in celloidin
and paraffin. The sections were cut 5 in thickness, and were
stained in Ehrlich’s hematoxylin and eosin. All the drawings
were made by the writer and all are original, except figures 90
to 92; these represent the so-called olfactory organs (pit pegs)
and pegs on the antenna of a grasshopper (Tryxalis nasuta L.),
and were copied from Rohler (’05).. The drawings were made
at the base of the microscope with the aid of a camera lucida.

THE OLFACTORY SENSE OF ORTHOPTERA 407

MORPHOLOGY OF THE OLFACTORY PORES
Before making a study of the anatomy of the olfactory pores,
the distribution and number of them were first investigated.
Disposition of pores in a grasshopper

From the eggs of Melanoplus femur-rubrum DeG., all six in-
stars were reared, and since the fifth instar was most favorable
in size and in condition of the integument for a critical study, the

Figs. 1 and 2 Disposition of olfactory pores on the first and second antennal
segments of female grasshopper (Melanoplus femur-rubrum, no. 18 in table 1)
in fifth instar. Fig. 1, dorsal surface, and fig. 2, ventral surface of same segments;
the inner edges of the antenna face one another. X53.

pores on a female of this stage were studied and drawn in detail
as follows.

a. Pores on head. Pores were found on the head capsule and
on all of the head appendages; on the former 7 scattered pores
were observed, but on the head appendages they are more or
less constant in position.

The first antennal segment bears 4 scattered pores, 2 being on
the dorsal side and 2 on the ventral side (figs. 1 and 2, a—d); the
second antennal segment bears 2 isolated pores (e and f), besides
a group of 43 (g and h) which completely encircles the extreme
distal end of the segment.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 5

408 N. E. McINDOO

The mandible bears two groups of pores (figs. 8 and 4, a and
b), one being on the outer side and the other on the inner side,
and also several isolated pores. The labrum bears one group of
4 pores (fig. 5, a) on the ventral side. At the base of the hypo-
pharynx there are two groups of pores, one of 32 (fig. 6, a) being
on the left side and one of 27 pores (7, b) on the right side, besides

Figs. 3 to 9 Disposition of olfactory pores on mouth-parts of same grass-
hopper as mentioned in figures 1 and 2. Fig. 3, outer surface, and fig. 4, inner
surface of same mandible; fig. 5, dorsal surface of labrum; fig. 6, outline of left
side, and fig. 7, outline of right side of hypopharynx; fig. 8, ventral surface of one-
half of maxilla and labium, and fig. 9, dorsal surface of same half of maxilla and
labium. Figs. 3, 4, 5, 8, and 9, X13; figs. 6 and 7, X21.

many isolated pores on either side about midway between the.
base and top of the appendage. Every portion of the maxilla
and labium bears pores, 176 being found on the ventral side and
84 on the dorsal side; most of them are scattered, but four groups
are present, two of these being on the ventral side of the lacinia
(fig. 8, c and d), one on the dorsal side of the lacinia (fig. 9, 7), and
one on the dorsal surface of the third segment of the maxillary
palpus (fig. 9, 4). The scattered pores are represented in the

THE OLFACTORY SENSE OF ORTHOPTERA 409

figures by widely separated dots, a few being present on each
the palpifer (fig. 8, @) and the maxillary palpus, several on each
the galea (fig. 8, b) and the lacinia (e), and a few on each the lab-
ial pulpus (f) and the ligula (fig. 9, 7). The mentum bears 10
scattered pores (fig. 8, g).

b. Pores on thorax. Most of the pores found belonging to the
thorax lie on the legs and wings and only a comparatively few are
present on the thoracic segments. On each front and middle leg
there are ten groups and several isolated pores, but on each hind
leg there are only six groups besides several isolated pores (figs.
10 to 15). On each wing there is one group and several isolated
pores (figs. 16 to 19).

The pores are located more definitely as follows: Groups nos.
1 to 5 (figs. 10 to 15) lie on the trochanter; nos. 6 and 7 on the
femur; and nos. 8 to 10 on the tibia. All of these on the front
and middle legs are constant in position, although slight varia-
tions may be observed owing to the degree in which the leg is
rotated. On the smaller portion of the trochanter of the hind
leg (figs. 14 and 15) there are only four groups, probably nos.
1, 2,4, and 5. This part of the trochanter, partially hidden by
the femur, is comparatively small and is found with difficulty.
The groups on it are shifted in position and no. 1 has 8 pores
instead of 3 as on the other legs; no. 2 has 9 pores instead of 10;
no. 3 is absent, but on the other legs it has 9 pores; no. 4 has 5
pores instead of 8 or 10; no. 5 has 13 pores instead of 10.
Groups nos. 6 and 7 on the front and middle legs lie at the prox-
imal end of the femur, but at the same place on the femur of the
hind leg there are no pores; no. 7 is wanting, but on the other legs
it has 10 or 11 pores. No. 6 is either absent or has migrated
down the femur (fig. 14) one-third the distance from the trochan-
ter; however, at this position there are 3 pores, but no. 6 on the
other legs has 13 pores. Groups nos. 8 to 10 lie near the prox-
imal end of the tibia; nos. 8 and 10, having 8 and 5 pores, respec-
tively, on the front and middle legs, are wanting on the hind leg,
and no. 9 has 4 pores instead of 5.

A few of the isolated pores are constant in number and position,
while most of them are variable in disposition. The base of each

410 N. E. McINDOO

5

Figs. 10 to 15 Disposition of olfactory pores on legs of same grasshopper as
mentioned in figures 1 and 2. Figs. 10 and 11, inner and outer surfaces, respec-
tively, of front leg; figs. 12 and 13, inner and outer surfaces, respectively, of
middle leg; figs. 14 and 15, inner and outer surfaces, respectively, of hind leg.
The claws and pulvilli in figs. 10, 12, and 14 are shown from ventral view, and in
figs. 11, 13, and 15 from dorsal view. AntM and PostM stand for anterior and
posterior margins. 6.

THE OLFACTORY SENSE OF ORTHOPTERA 411

pseudospine on the tibia (fig. 15, ¢) usually bears 1 pore, but occa-
sionally 2 pores, and the base of each spine (fig. 14, &) always
bears 1 pore. The following pairs of pores are always constant
in position: 1 pair on each tibia (figs. 10, 13 and 15, d); 1 pair on
the first tarsal segment (figs. 10 and 13, g) of the front and middle
legs and 2 pairs on the same segment of the hind leg (figs. 14 and
15, g and 1); 2 pairs on the third tarsal segment (figs. 10 to 15,
h and m) of each leg, and 2 pairs on the dorsal surface of each
claw and pulvillus (fig. 15, 7 and J).

The other isolated pores are represented in the figures by dots
(fig. 15, a, b, and c); these are very variable in disposition and
are much smaller than the other ones. All parts of the thoracic

Figs. 16 to 19 Disposition of olfactory pores on wings of same grasshopper
as mentioned in figures 1 and 2. Fig. 16, dorsal surface, and fig. 17, ventral sur-
face of front wing; fig. 18, dorsal surface, and fig. 19, ventral surface of hind wing.

x6.

segments were not critically examined, but 39 minute pores
(fig. 15, a) were counted on fragments of these segments.

Groups nos. 11 and 12 lie on the dorsal surface of the front
and hind wing (figs. 16 and 18); no. 11 consisting of 15 pores and
no. 12 of 19 pores. Several scattered pores are also present on
both surfaces of each wing (figs. 16 to 19).

c. Pores on abdomen. In all, 45 pores were found on the ab-
dominal segments. Roughly speaking, most of these lie in four
rows extending the full length of the abdomen; two of these rows
lie on the tergum and two on the sternum, the latter two near the
midline, but the former two far from the midline. Each segment
usually has at least 2 large pores and one or more minute ones,
which may or may not be in the rows just mentioned. The ovi-
positor bears 53 scattered pores.

412 N. E. McINDOO

d. Pores on all six instars. A careful study of the pores on all
six instars shows very little difference in regard to their distribu-
tion, but the total number of them on the different instars varies
from 727 in the first instar to 1571 in the sixth instar (adult fe-
male). The first four instars are wingless while the wings of the
fifth instar are comparatively small, as already shown in figures
16 to 19; nevertheless, the groups of pores on the adult wings are
the same in number and position as are those of the fifth instar,
but the adult wings bear only a few isolated pores. A few pores
were found on the cerci of the first four instars, and many widely
scattered ones lie on the ovipositors of the adult female and of
the fifth instar (table 1). Now, since it is not expedient to tabu-
late the numbers of pores found on the various parts of the in-
tegument, they will be presented for the six instars in the follow-
ing order: first, second, third, fourth, fifth, and six instar ( 9
and 0). Mandibles: 71—74—86—92-92- 986-7108; maxillary
palpi: 11-10—7—-21—28- 9 56-24; galeae: 51-48-43-48-72- 9 56
—o'62; laciniae: 52-48-48-56-104— ¢ 128-7108; hypopharynx:
42-—50—-50-82-101— 9110-7108; labial palpi: 12-10—12—16—20-

2 44—- 720; ligula: 17—24—22-18-36- ? 26— 738; labrum: 4-4-5- -
5-4- 94-94; mentum: 12-8-6-6-10-— ? 10-710; total number of
pores on mouth-parts: 272—276—-279-344-467- 9? 520— 482; head
capsule: 9—11-9-14-7- 95-07; antennae: 22—28-42-56-98-

2106-110; abdominal segments: 54-45-54-50-45-— 9 45-36;
cerci: 3-4-3-5-0—- 20-70; ovipositor: fifth instar 9 53—adult-
355; legs: 367-429-449-485-660- 9718-720; front wings:
fifth instar 84— 9 84-786; hind wings: fifth instar 66— 9? 38-740;
total number of pores found on entire integument: 727—793-836—
954-1480—- 21571-71481. In obtaining these figures, the mi-:
nutest and the most difficult pores to be found on the fifth instar
have not been counted, nor have those found on the thoracic
segments of the fifth instar been counted.

Disposition of pores in other Orthoptera

In making a comparative study of the disposition of the ol-
factory pores in Orthoptera, both sexes of twenty-one species,

THE OLFACTORY SENSE OF ORTHOPTERA 413

belonging to twenty genera and representing the six families,
have been examined. Since the pores on only one specimen for
each sex in a species were counted, the total number of pores
recorded cannot be a fair average.

a. Pores on head. Pores were found on all the head capsules
examined, except on four locustids (table 1, nos. 37, 38, 41, and
42) and on the five crickets examined (nos. 48 to 47). The num-
ber varies from 0 to 40; the highest number being found in the
American roach (no. 6).

The number of pores on the antennae vary from 16 (no. 24)
to 124 (nos. 33 and 34). Pores are always present on the second
antennal segments, and the numbers found on the first antennal
segments are as follows: no. 1, 9; no. 2, 14; no. 3, 8; no. 4, 15; no.
Seno: OF Deano. isha; noe. 6, 4no05.9.i leno. 16, Zane. iit:
no. 18 (figs. 1 and 2), 8; no. 48, 2; no. 44, 4, and none on all the
others. No pores were observed on the remaining antennal
segments.

Relative to various portions of the mouth-parts of the adult
specimens, the number of pores varies as follows: mandibles 8
(no. 9) to 110 (mo. 2); maxillary palpi 0 (nos. 8, 10 to 13) to 77
(no. 6); galeae 0 (nos. 9 and 11) to 99 (no. 6); laciniae 2 (no. 9)
to 166 (no. 34); hypopharynx 0 (nos. 10 to 13) to 216 (no. 39);
labial palpi 0 (nos. 10 to 13) to 52 (no. 33); paraglossae (common
to all except Acrididae) 0 (nos. 8, 9, 11, 46 and 47) to 89 (no. 4);
glossae (common to all except Acrididae) 0 (nos. 8, 9, 11, 37 to
42, 44 to 47) to 18 (no. 5); ligula (common to only Acrididae)
0 (no. 15) to 56 (no. 24); labrum 0 (nos. 8, 9, 10, 12 and 13) to
31 (no. 39); mentum 0 (nos. 8 to 13, 37 and 38) to 35 (no. 43);
and total number of pores on mouth-parts 30 (no. 11) to 605
(no. 43).

b. Pores on thorax. Relative to the legs and wings of the adult
specimens, the number of pores varies as follows: legs 197 (no.
11) to 774 (no. 33); front wings 0 (nos. 23 and 24) to 134 (no. 33);
and hind wings 0 (nos. 8, 9, 39 and 40) to 284 (no. 44). The
front wings of nos. 23 and 24 are much reduced, about as long as
the abdomen; they have grown together and are rigid like the
elytra of beetles. The front wings of nos. 39 and 40 are much

414 N. E. McINDOO

reduced, and the hind wings are only rudimentary. The wings
of the mole-cricket (no. 43) are very small, about one-half the
length of the abdomen. The hind wings of the common cricket
(nos. 44 and 45) are very small and the pores on them are
minute. Only occasionally were a few pores observed on the
thoracic segments.

c. Pores on abdomen. Relative to the pores on the abdomens
of adult specimens, the number varies as follows: abdominal
segments 0 (nos. 8 to 18, 35 to 47) to 178 (no. 1); cerci 0 (nos. 8
to 18, 24, 29, 32, 34, 35, 36, 38 to 42, 44 to 47) to 130 (no. 48);
and ovipositor 0 (nos. 36, 42, 45 and 47) to 116 (no. 24). The
male of Blatta orientalis (no. 4) and of Periplaneta americana
(no. 6) has a pair of anal stylets which bear 42 pores, most of
which lie on the dorsal surface. The cerci of these two species
bear 51 pores, nearly all of which le on the ventral surface at
the extreme distal ends of the segments; however, in the grass-
hoppers and crickets the pores are widely scattered over the sur-
face of the cerci. The pores on the cerci and anal stylets of nos.
4 and 6 have been added and then recorded under cerci.

The total number of pores found on the entire integument
varies from 271 (no. 11) to 1616 (no. 33); the mantids and phas-
mids have the smallest number, certain acridids the largest
number, while most of the remaining ones have a medium number.

d. Pores on first and last instars of croton-bug. Comparing the
number of pores on the first instar (no. 3, recently hatched)
with the number on the adult male (no. 1), we have the following
figures: mandibles 31-68; maxillary palpi 5-14; galeae 15-74;
laciniae 7-69; hypopharynx 8-40; labial palpi 7-13; paraglossae
4-45; glossae 0-9; labrum 7-15; mentum 7-6; total number on
mouth-parts 91-353; head capsule 25-22; antennae 26-41; ab-
dominal segments 126-178; cerci 11-82; legs 192-354; no front
wings-47; no hind wings-11; and total number of pores found
on entire integument 471-1088. Hence, the first instar has less
than one-half the number of pores possessed by the adult; this
was also found true for the grasshoppers.

e. Family, generic, specific, and sexual variations. Relative to
these pores, the family variations may be small or large, depend-

THE OLFACTORY SENSE OF ORTHOPTERA 415

ing on what families are compared; comparing the Acrididae,
Locustidae, and Gryllidae with one another, the variations are
small, but if these families are compared with the other three
families or if Blattidae is compared with Mantidae and Phasmi-
dae, the variations are large. The chief variation pertaining to
the genera, species, and sexes is in the number of pores present;
however, the pores may occasionally differ a little in external
structure. For example, those on the legs of the mole-cricket
(no. 43) are almost slit-shaped, while in the other genera they
are more or less eye-shaped. Twelve of the twenty males exam-
ined bear more pores than do their respective females, but, as a
rule, there is not much sexual variation in the number of pores.
For further details the reader is referred to table 1.

Structure of pores in a grasshopper

The preceding pages deal with the disposition of the olfactory
pores, and now a discussion of their anatomy will be given.

a. External structure. When the superficial ends of the pores
are examined under a high-power lens with a strong transmitted
light, these organs appear as small bright spots, each of which
is surrounded by darker chitin, the pore border (figs. 20 and 52,
B), and by the pore wall (W). Sometimes the borders are
searcely discernible, as for example, those on the abdominal seg-
ments (fig. 33) and those of the smallest isolated pores on the
legs (fig. 61); occasionally the borders and walls are very dark
(figs. 15, d, and 52) and the wall is wide; a few of the pores have
double borders (figs. 15, f, and 63), the outermost one being only
a little darker than the surrounding chitin and the innermost one
considerably darker; and occasionally the borders resemble some
of those on coleopterous and lepidopterous larvae (MeIndoo,
’19) in that they have radial streaks (figs. 15, g, and 53). The pore
wall may be round (fig. 55), oblong (fig. 51), but it is usually
eye-shaped (figs. 20 and 22), and this is the first time for an eye-
shaped type to be described; this type is common to all the Or-
thoptera examined; however, on the legs of the mole-cricket,
the walls are almost slit-shaped, and in this respect somewhat
resemble the lyriform organs of spiders.

McINDOO

N. E.

416

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aon labrum; fig. 32, a pore and 2 hairs near a spiracle on fourth abdominal seg-

THE OLFACTORY SENSE OF ORTHOPTERA 419

Inside the wall the chitin is lighter in color and near the center
usually may be observed a round or oblong transparent spot,
the aperture (figs. 20 and 52, Ap).

b. Internal structure. As in Lepidoptera and Diptera (Mc-
Indoo, 718), some of these pores belong to the dome-shaped
type (figs. 68 to 70), because the chitin around the aperture is
dome-shaped; most of them, however, belong to the hymenop-
terous type in that the chitin around the apertures is slightly
depressed (figs. 77 and 82), and only occasionally is one (fig. 79)
found approaching the coleopterous type, in which case the chitin
is deeply depressed. Internally, these pores differ from all the
others yet described by the presence of a cavity or indentation
(fig. 77, Z) encircling the base of the chitinous cone (fig. 79, Con).
In cross-section this indentation resembles two horns which run
from the pore canal (fig. 70, Can) outwardly into the pore wall
(fig. 67, W); it is sometimes very shallow (fig. 71) and some-
times very deep (fig. 84), and since it is nearly always present in
the grasshopper, we may regard these pores as constituting the
orthopterous type.

The pore canal (fig. 70, Can) may be short (fig. 72) or long
(fig. 67), but in the base of the pseudospines (figs. 15, e, and 84)
on the tibia it passes only about one-half the distance through
the integument, therefore, causing the pore aperture to be long.

ment; fig. 33, largest and smallest pore on last abdominal segment; fig. 34A, a
pore from cercus (fourth instar) ; fig. 34B, a pore from cercus and fig. 34C, a pore
from anal stylet of Blatta orientalis; fig. 35, 2 pores from ovipositor; fig. 36, one
of largest pores, smallest and medium-sized hair from metathorax. Figs. 37 to
46, groups of pores on middle leg, and figs. 47 to 51, groups on hind leg (figs. 12
to 15); fig. 37, no. 1; fig. 38, no. 2; fig. 39, no. 3; fig. 40, no. 4; fig. 41, no. 5; fig. 42,
no. 6; fig. 43, no. 7; fig. 44, no. 8; fig. 45, no. 9; fig. 46, no. 10; fig. 47, no. 1; fig.
48, no. 2; fig. 49, no. 4; fig. 50, no. 5; fig. 51, no. 6. Figs. 52 to 58, paired pores
on legs; fig. 52, pair d on hind leg; fig. 53, pair g on middle leg; fig. 54, pair e on
hind leg; fig. 55, pair h on hind leg; fig. 56, pair m on middle leg; fig. 57, 1 of pair
7 on claw of hind leg; fig. 58, pair 7 and a hair on pulvillus of hind leg. Fig. 59,
largest and smallest pore on metathorax at a (fig. 15); fig. 60, largest and smallest
pore at b on trochanter; fig. 61, largest and smallest pore at c on femur; fig. 62,
pore on base of pseudospine at e on tibia; fig. 63, pore at f on tibia; fig. 64, pore on
base of spine at k on tibia. Fig. 65, 6 of pores in group no. 11 on front wing; and
fig. 66, 6 pores in group no. 12 on hind wing. Ap, pore aperture; B, pore border;
W, pore wall. X820.

420 N. E. McINDOO

The chitin in sections usually did not take the stain, but re-
mained a naturally dark color; however, in the labrum and at the
tips of the labial palpi the outer stratum and pore walls are dark
yellow (represented by black in figs. 75 and 89), while the re-

Figs. 67 to 89 Sections showing internal anatomy of olfactory pores of adult
grasshoppers (Melanoplus femur-rubrum), soon after having molted the last
time. Fig. 67, pore from mandible; fig. 68, pore from maxillary palpus; fig. 69,
pore and sense cell from galea; fig. 70, pore from lacinia; fig. 71, pore from hypo-
pharynx; fig. 72, pore from labial palpus; fig. 73, pore from ligula; fig. 74, pore
from mentum; fig. 75, 3 pores from labrum; fig. 76, pore from head capsule; fig.
77, pore and sense cell from two sections through second antennal segment) fig.
78, pore from abdominal segment; fig. 79, pore from ovipositor; fig. 80, apie
and 3 sense cells from four consecutive sections through trochanter; fig, 81, 2
pores from femur; fig. 82, pore in group from tibia; fig. 83, isolated pore from tibia;
fig. 84, pore and sense cell from base of pseudo-spine on tibia; fig. 85, pore from
claw; fig. 86, pore from pulvillus; fig. 87, pore in group from front wing; fig. 88,
isolated pore from hind wing, and fig. 89, gland pore and gland cell (G/C) from
labrum. Ap, pore aperture; Can, pore canal; Con, chitinous cone; Hyp, hypo-
dermis; J, indentation encircling chitinous cone; SC, sense cell, and W, pore wall.
* 500.

THE OLFACTORY SENSE OF ORTHOPTERA 421

maining portions of the integument are semitransparent (repre-
sented by lines).

Many hypodermal gland pores (fig. 89) were observed on the
ventral surface of the labrum; at first sight they may be mistaken
for the 4 or 5 olfactory pores found on the dorsal surface of the
labrum, but a careful study of them shows that they differ consid-
erably in structure. The narrow aperture leads into the spher-
ical reservoir, which connects with the gland cell (GIC); about
one-half of the space in the peripheral end of this cell is occupied
by the ampulla, in which the secretion apparently collects, and
then this substance runs into the reservoir. The gland cell has
only one pole, while the sense cell (fig. 77, SC) has two; and the
olfactory organ has neither a reservoir, nor an ampulla. As far
as known to the writer, these glands in the labrum of the grass-
hopper have never been described before, although the literature
pertaining to hypodermal glands has not been consulted.

THE ANTENNAL ORGANS

Several investigators have studied the morphology of the an-
tennal organs in Orthoptera, but since certain drawings of the
acridid Tryxalis nasuta L., by Rohler (05) best illustrate these
organs, the following discussion will be taken only from his work.

The antenna of either a male or female of the preceding grass-
hopper consists of seventeen segments, which bear three types
of sense organs as follows: The slender, strongly chitinized
bristles are found on the first to eighth segments, but most of
them le on the third segment; the pegs (fig. 90, Pg) lie on
all the segments, but most abundantly on the middle seg-
ments, and the so-called olfactory organs, pit pegs (PPq), lie
on the third to seventeenth segments, -but most abundantly
on the tenth to fifteenth segments. The total average number
of each type on one antenna is as follows: For males—77 bristles,
3738 pegs, and 1718 pit pegs, and for females—83 bristles, 2330
pegs, and 1362 pit pegs. From a superficial view, a pit peg re-
sembles a small circle (fig. 90, PPg), but when viewed in section
it is observed that a minute hair (fig. 91, PPg) with heavy walls
arises from the bottom of the pit, and a peg (fig. 92, Pg) arises

422 N. E. McINDOO

from the outer surface of the chitin (Ch). Each of the three
types of organs is supplied with a sense-cell group (SCG).
Rohler performed no experiments, but judging merely from
the anatomy of these structures, he-regards the bristles as tactile
organs which probably regulate the movements of the antenna.
He considers the larger or stronger pegs as tactile organs which
protect the body from solid objects, and the smaller or weaker
pegs are tactile organs which serve for the perception of wind
drafts. After a long discussion, he concludes that the pit pegs
are the olfactory receptors, and since the males have more pegs

Figs. 90 to 92. Structure of other antennal organs of a grasshopper (Tryxalis
nasuta), copies from Rohler (’05); magnification not given. Fig. 90, one side of
next to last antennal segment (16th), showing pegs (Pg) and pit pegs (PPg), the
so-called olfactory organs; fig. 91, internal anatomy of pit peg, and fig. 92, same
of peg. Ch, chitin, and SCG, sense cell group.

and pit pegs than have the females, he thinks that the former
are better equipped for finding the latter than vice versa.

Rohler also found the sense bristles and pegs on the mouth-
parts, but entirely overlooked the olfactory pores on the second
antennal segments and on the mouth-parts.

According to Rohbler (pp. 248 and 249), the following men stud-
ied the antennae of Orthoptera and report the following: In
Stenebothrus, Kraepelin found pegs and pit pegs and in Blatta
only olfactory hairs (probably pegs). In Gryllidae, Locustidae,
and Acrididae vom Rath found both pegs and pit pegs, but in
Blatta and Periplaneta americana only pegs. Graber concluded
from his experiments that the antennae ‘of Blatta function as
olfactory organs. While searching for the Johnston’s organ on
the second antennal segments of Locusta and Stenebothrus,

THE OLFACTORY SENSE OF ORTHOPTERA 423

Child saw the olfactory pores, described by the present writer,
but he did not make a study of them; he soon decided, however,
that they did not belong to the Johnston’s type and did nothing
further with them.

RESPONSES TO CHEMICAL STIMULI

In table 1 it is shown that an adult male or female (no. 16 or
17) of Melanoplus femur-rubrum has about 1500 olfactory pores,
108 of which he on the second antennal segments; also, that an
adult male or female (no. 44 or 45) of Gryllus pennsylvanicus
has over 1000 pores, 75 of which lie on the second antennal seg-
ments. Using a pair of fine-pointed scissors, it was ascertained
that the antennae could be cut off not nearer the head than
through the third segments, therefore, five normal males and
five females of each of the preceding species were selected for
experimental purposes. Before mutilating them each one was
placed in an experimental wire-screen case and was tested with
the following sources of odors: chemically pure oils of pepper-
mint, thyme, wintergreen and lemon, dried leaves of pennyroyal
(odor very weak), and bran mash. The bran mash was made
by using wheat bran, cheap molasses, lemons cut into fine pieces,
and water; this mixture with arsenic added is the well-known
poisoned bran mash, used for the control of grasshoppers, which
are very fond of it either in the fields or in captivity, but crickets
prefer bread or certain fruits to it.

Experiments with grasshoppers (Melanoplus femur-rubrum)

The following records include only the first responses and their
reaction times:
a. Unmutilated grasshoppers. These individuals were appar-
ently normal in all respects.
Oil of peppermint:
3 moved body slightly.
2 raised front legs.
2 moved backward slowly.
1 raised hind leg and turned around slowly.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 5 -

424 N. E. McINDOO

1 turned around and worked mouth-parts.

1 turned to one side quickly.
Reaction time, 4 to 8 seconds; average, 5.8 seconds.
Oil of thyme:

5 raised front legs quickly and moved antennae.

3 moved away slowly.

1 arose quickly.

1 turned around slowly.
Reaction time, 3 to 15 seconds; average, 7 seconds.
Oil of wintergreen:

4 moved away slowly.

2 arose quickly.

2 moved backward slowly.

1 raised front leg.

1 moved body slightly.
Reaction time, 4 to 15 seconds; average, 7.3 seconds.
Oil of lemon:

3 moved backward quickly.

2 moved away slowly.

2 tried to get at source of odor through wire-screen.

1 raised front legs slowly.

1 arose slowly.

1 turned to one side quickly.
Reaction time, 3 to 10 seconds; average, 4.3 seconds.
Dried leaves of pennyroyal:

4 moved away slowly.

3 moved body slightly.

1 arose slowly.

1 moved front leg.

1 moved to one side.
Reaction time, 5 to 25 seconds; average, 14.8 seconds.
Bran mash (their food in captivity) :

4 moved away slowly.

3 arose quickly.

1 moved to one side quickly.

1 moved body slightly. .

1 tried to get at source of odor through wire-screen.
Reaction time, 5 to 20 seconds; average, 11 seconds.

THE OLFACTORY SENSE OF ORTHOPTERA 425

The average reaction time of the males to the above six sources
of odors is 7 seconds, and of the females 9.7 seconds, making a
total average of 8.4 seconds for both sexes. The females were
less responsive to all the odors, except to that of the bran mash,
than were the males; but to bran mash each sex responded in
11 seconds.

b. Grasshoppers with antennae severed through third segments.
These are the same insects used above; their antennae were cut
off and twenty-four hours later were again tested with the same
odors. As usual the females responded more slowly than did
the males, and the total average reaction time of both sexes is
9 seconds, whereas it was 8.4 seconds before they were mutilated.
They often tried to get at the bran mash and occasionally at the
oil of lemon when these substances were held under the cases
for a period of a minute or more. They were removed from the
cases to a large cage where they ate bran mash, drank water,
copulated, and lived just as long as did other individuals not
mutilated.

Experiments with crickets (Gryllus pennsylvanicus)

The preceding experiments were repeated by using the com-
mon black cricket.

a. Unmutilated crickets. Since most of these ten insects failed
to respond to the dried leaves of pennyroyal and to the bran
mash, only the four essential oils were used as sources of odors.
The average reaction time of the males to these odors is 10 sec-
onds, and of the females 7.5 seconds, making a total average of
8.8 seconds.

b. Crickets with antennae severed through third segments. The
antennae of the preceding crickets were cut off and two days
later these insects were again tested with the same odors. The
average reaction time of the males to the four odors is 7.5 seconds
and of the females 12.9 seconds, making a total average of 10.2
seconds. Confined in battery jars containing moist sand, these
mutilated crickets lived as long as others not mutilated; they
ate bread and pieces of apples; the males chirped, and the fe-
males oviposited eggs in the sand as usual.

426 N. E. McINDOO

SUMMARY

In making a comparative study of the disposition of the ol-
factory pores in Orthoptera, both sexes of twenty-one species,
belonging to twenty genera and representing the six families,
have been examined; also, the pores on the first and last instars
of the croton-bug (Blattela germanica) and on all six instars of
the common grasshopper (Melanoplus femur-rubrum) have been
carefully counted. Olfactory pores are more widely distributed
in Orthoptera than in any other order yet studied. They were
always found on the legs, antennae, and anal stylets; usually on
the wings (if present), abdominal segments, cerci, head, and all
the mouth-parts, and sometimes on the thoracic segments and
ovipositor. Relative to the antennae, olfactory pores are pres-
ent on only the first and second segments; occasionally a few lie
on the first segment, but always many on the second segment.
This is the first time that the writer has seen these organs on the
antennae of adult insects, except several on the base of the an-
tenna of the honey-bee and a few on the base of the antenna of
a certain weevil; nevertheless, they are common to the antennae
of all the larvae yet examined. The number of them on the
wings is comparatively few, while the mouth-parts are abundantly
supplied with pores.

The total number of pores found on the entire integument
varies from 271 to 1616; the mantids and phasmids have the
smallest number, certain acridids have the largest number, while
most of the remaining species have a medium number. The
newly hatched croton-bug has 44.5 per cent as many pores as
has the adult female croton-bug; and comparing the total number
of pores found on each of the six instars of the grasshopper (Me-
lanoplus femur-rubrum), we have the following figures: first in-
star 46.3 per cent, second instar 50.5 per cent, third instar 53.2
per cent, fourth instar 60.7 per cent, fifth instar 94.2 per cent,
adult male 94.3 per cent, and adult female 100 per cent.

In distribution and external structure, these olfactory pores
resemble the lyriform organs of spiders more than do the same
organs in any other order yet examined. They are generally ob-

THE OLFACTORY SENSE OF ORTHOPTERA 427

long, sometimes almost slit-shaped, but the eye-shaped type is
the most common. Some of the pore borders are radially stri-
ated; this is the first time for striated borders to be found in
adult insects. The internal anatomy of these pores is similar
to that of those in other orders, but there is one marked differ-
ence: in each of these there is an indentation or cavity which
encireles the bottom of the chitinous cone.

Experiments were performed on grasshoppers and crickets to
determine whether or not their antennae serve as olfactory re-
ceptors. The unmutilated insects were first tested to ascertain
their reaction times to the oils of peppermint, thyme, winter-
green, and lemon and to the dried leaves of pennyroyal and to
bran mash (their food in captivity). Each antenna was then
severed through the third segment, and twenty-four hours later
these mutilated insects were again tested with the above sources
of odors. The average reaction time of the unmutilated grass-
hoppers is 8.4 seconds, and of them after being mutilated, 9
seconds; of the unmutilated crickets 8.8 seconds, and of the
same crickets after being mutilated, 10.2 seconds. In other re-
spects the mutilated individuals seemed normal and lived as
long as others not mutilated. Since the antennae were cut off
just distal to the olfactory pores on the first and second segments,
it appears that the remainder of the antennal segments does not
bear the olfactory organs as other investigators claim.

Compared with the so-called olfactory organs on the antennae
of Orthoptera, the olfactory pores are better adapted anatomi-
cally to receive olfactory stimuli because the peripheral ends
of their sense fibers come in direct contact with the external air,
while those in the so-called olfactory organs on the antennae are
covered with chitin.

LITERATURE CITED

McInpoo, N. E. 1918 The olfactory organs of Diptera. Jour. Comp. Neur.
vol. 29, no. 5, pp. 457-484, 55 figs.
1919 The olfactory sense of lepidopterous eens: Ann. Ent. Soe.
Amer., vol. 12, no. 2, pp. 65-84, 53 figs.

RGOuLER, Ernst 1905 Beitrige zur Kenntnis der Sinnesorgane der Insecten.
Zool. Jahrb. Anat., Bd. 22, s. 225-288, 1 fig. and 2 pls.

Resumen por el autor, Edward Horne Craigie,
Universidad de Toronto e Instituto Wistar.

Sobre la vascularizacién relativa de las diversas partes del
sistema nervioso central de la rata albina.

El autor ha llevado a cabo medidas anatémicas de la riqueza
capilar en veintiuna regiones seleccionadas arbitrariamente en
la médula espinal, médula oblonga y cerebelo de la rata albina.
La parte mas pobre en capilares en la substancia gris es casi
una vez y media mas rica que las zonas mejor dotadas de las
regiones de substancia blanca estudiadas (fasciculo longitudinal
dorsal), mientras que este ultimo presenta mas del doble de
capilares que el fasciculo cuneado. Los centros de la substancia
gris pueden dividirse claramente en dos grupos: el de los nucleos
motores y el de los centros sensorios y de correlacién; estos
ultimos son los mas ricos en capilares. Aunque no existe una
transicion brusca entre estos grupos no existe tampoco una
transicion gradual, excepto en casos individuales. La tnica
excepcion se encuentra en el caso de la substancia gelatinosa.
De todos los centros estudiados el mas rico es el nticleo coclear
dorsal, que presenta una vascularizacién que excede en mas de
la mitad a la de las astas ventrales (el centro motor mas vascular-
izado); en mas de dos veces y media a la de la substancia gela-
tinosa de Rolando (la regién mas pobre de la substancia gris),
siendo asi mismo ocho veces mas rico en vasos sanguineos que
el fascfculo cuneado. Existe muy poca diferencia entre ambos
sexos. La interpretacién de la significacién funcional de los
datos apuntados depende de problemas no resueltos sobre la
naturaleza del proceso nervioso y su relacién con el metabolismo.

Translation by José F. Nonidez
Cornell University Medical College, N. Y.

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, APRIL 6

ON THE RELATIVE VASCULARITY OF VARIOUS PARTS
OF THE CENTRAL NERVOUS SYSTEM
OF THE ALBINO RAT

EDWARD HORNE CRAIGIE

Department of Biology, University of Toronto, and The Wistar Institute of Anatomy
and Biology

FIVE FIGURES AND FOUR CHARTS

The blood supply of the brain has been the object of study on
the part of many anatomists from the time of Galen to the present
day and the relations of the principal vessels have long been
well known. The difference in vascularity between the gray
and white matter in the brain and spinal cord has also been
discussed by numerous authors. So far as the present writer
has been able to discover, however, there does not seem to have
been any attempt hitherto to make an exact quantitative com-
parison of the vascularity of the various structures in the central
nervous system.

Ekker (53)! made some general comparisons of capillary
richness in various parts of the brain, but although he records
some measurements of the diameter of vessels, nothing of im-
portance is noted. According to him, the portion of the brain
which is most richly supplied is the corpus striatum. The
earlier work on this aspect of the subject was not very important.
Guyot, in 1825, succeeded in isolating the vessels of the cerebral
substance with forceps and a stream of water, and reached the
conclusion that the white matter had no blood supply. Upon
this observation he based the opinion that the white matter has
no active function, but is entirely passive. Various writers

1 The writer is indebted for information regarding this paper to Dr. C. Judson
Herrick, who kindly reviewed it for him in the Surgeon General’s Library at Wash-
ington. Later the writer had the privilege of examiming a copy nimself in the
library of the College of Physicians of Philadelphia.

429

430 EDWARD HORNE CRAIGIE

following Ekker (including Luschka, Henle, Frey) reproduced
his account, but added nothing (according to Duret). Gerlach
soon afterward made some similar observations, but without
extending the knowledge of the subject.

The vessels on the surface of the brain and the main branches
which enter its substance were well described in the eighteenth
century by Haller, Willis, Vieq d’Azyr, and others, and their
observations were extended and made more exact by many
later workers.

Heubner (’72, ’74) was ‘‘the first to investigate methodically
the distribution of the different branches of the cerebral arteries”’
(Beevor). He divided the arterial supply of the hemispheres
into basal and cortical, the vessels of the former group being
all ‘end arteries,’ without anastomotic intercommunications,
while those of the latter group anastomose freely in the pia mater.
Cohnheim (’72) concluded that there were a few anastomoses
between the arteries near the circle of Willis, but that the arteries
to the brain were practically ‘end arteries’ in the strict sense,
and that anastomoses within the brain substance were insignifi-
cant when present at all.

About the same time, Duret (’73, ’74) published an extensive
study of the vascular supply of the brain. He found the cells
of the bulbar nuclei to be surrounded by a very fine capillary net,
while the mesh in the white tracts was large. In the cerebral
cortex the outer 0.1 mm. contains large quadrangular meshes
parallel to the surface, forming fine anastomoses between the
arteries which penetrate the convolutions. The next 2 mm.
is filled with rather fine polygonal capillary meshes, formed chiefly
by collateral and terminal branches of the cortical arteries. The
inner 1 mm. has a transitional network, with larger meshes, but
much less elongate than those of the white matter, into which
they pass. In the white matter the length of the meshes is three
or four times the diameter of those in the gray matter, and they
run parallel to the principal bundles, which they seem to surround.
Throughout the central nervous system the cellular regions are
more highly vascular than the rest. Duret remarks upon the
fact that there is a complete correspondence in the vasculari-

VASCULARITY IN THE NERVOUS SYSTEM 431

zation of the whole cerebrospinal axis. The arteries of the bulb
are divisible into median and radicular, corresponding to the
groups supplying the hemispheres, and the same holds true
regarding the spinal cord. He gives a detailed account of the
origin of the vessels supplying each region of the brain.

Krause (’76) finds that the capillary network in the human
spinal cord, in addition to being much wider meshed in the white
matter than in the gray, is widest in the anterior funiculi, closest
(in the white matter) in the posterior funiculi, particularly in
the fasciculus gracilis.

The excess of the capillary supply of the gray matter over
that of the white matter is noted by all succeeding authors who
refer to the capillaries at all (Rudanowsky, Adamkiewicz, Kadyi,
Hoche, Sterzi, Cajal, etc.). Rudanowsky (76) describes the
capillary network in the gray matter as being so fine as to en-
circle a single cell in each mesh. Adamkiewicz (’81) disagrees
with him on this point, but finds evidence of a delicate secondary
net within the primary capillary meshes, which does surround
single cells as Rudanowsky describes.

The vessels of the spinal cord have been subjected to a careful
study by a number of later writers, who have described in detail
their development, arrangement, and distribution (Ross, Adam-
kiewicz, Kadyi, Hoche, Sterzi, Hoskins, ete.). Adamkiewicz
finds the capillaries in the gray matter of the human cord to be
relatively large, the net being densest and the capillaries largest
in the cell groups. The net is poorer in the dorsal horns than
elsewhere in the gray matter, except where these horns are as
large as the ventral ones, in which case the net is alike in both.

Kadyi (’89) observes that the density of the capillary net is
not the same in all parts of the gray matter of the spinal cord.
He speaks, moreover, of ‘true capillaries’ (echte Capillaren)—
those vessels which are interpolated between the final arterial
branches and the first venous tributaries—of which the extent
in the cord is rather small, and ‘precapillaries’ (Vorcapillaren),
arterial and venous,—those vessels which divide into twigs of
a still lower order, but yet resemble the capillaries in their lumen
and in the structure of their walls. Hoche (’99) also makes

432 EDWARD HORNE CRAIGIE

this distinction. Kadyi’s nomenclature for the vessels on the
surface of the cord has been adopted by succeeding workers.

Hoche, whose study is comparative, agrees fairly well with
his predecessors. He finds that the difference in the capillary
supply of the gray and white matter is much less in the rabbit
than in the dog, where the ratio is about 2 or 3 to 1.

The most extensive comparative and embryological investi-
gation of the blood supply of the spinal cord is that of Sterzi
(04), who describes it in all groups of vertebrates, from the
cyclostomes up, and shows how the vascularization improves as
one passes up the series. In studying the horse, he notes that
the capillaries of a single mesh in the gray matter twist greatly,
and that they are smaller at the head of the ventral columns,
where the mesh also is closer. The capillaries of the white matter
he finds to be larger than those of the gray matter, with which
they communicate.

There is a good description of the vessels in the medulla
oblongata due to Adamkiewicz (’90), while those of the midbrain
have been studied by Alezais et D’ Astros (92) and by Shimamura
(94).

The arteries on the surface of the brain have been described
repeatedly, the paper of Hofmann (00) being of particular
interest from the comparative standpoint. The comparative
anatomy of the circle of Willis and its main branches in the
mammalia has been well worked over by Tandler (’99, 702), to
whose observations some interesting additions were made by
Beddard (’04). These vessels were also the subject of an ex-
tensive phylogenetic, ontogenetic, and teratological study by
De Vriese, which appeared soon afterward (’05).

The distribution of the vessels within the brain substance
has also been described by several authors since those already
mentioned. The most important of these are Beevor (’09) and
Stopford (16). The former made a thorough and exact study
of the source of the blood supply of each part of the forebrain
in the human subject, while the latter made a similar investi-
gation of the pons and medulla oblongata. The only paper of
particular interest from the point of view of the present study

99

VASCULARITY IN THE NERVOUS SYSTEM 433

is perhaps that of Aby (99). This investigator made a careful
study of the arrangement and connections of the vessels in the
cerebellum of the cat. He found the granular layer of the cere-
bellar cortex to be the most highly vascular, and observed that
the layer of Purkinje cells was not different in its vascularization
from the rest of the granular layer, as it might have been expected
to be. He draws conclusions regarding the varying metabolic
activity in the different layers based upon the assumption that,
“at a given age, in a given organ, the relative number of blood
capillaries in two regions is a certain index of the relative intensity
of metabolic changes in those regions.” This assumption may
be compared with the observation of various authors that, ‘‘the
richer any region is in nerve cells, the closer is the capillary
network which supplies it’’ (Obersteiner, ’90).

The only other point of interest in the literature which need
be noted is the statement of Obersteiner (’90) that, ‘the corpus
geniculatum laterale, corpus subthalamicum, and nuclei of the
nerves are distinguished from the other gray masses by their
richness in capillary vessels.”’

MATERIAL AND METHODS

The material used in this study consisted of the brains of
nine albino rats and one hooded rat (no. 14), which were selected
from among a great many preparations, their numbers being
12, 14, 16, 23, 24, 26, 31, 55, 56, 58. The animals were killed
with illuminating gas and injected with carmin gelatin by means
of a metal syringe, the cannula being inserted through the ven-
tricle of the heart into the arch of the aorta, and the thoracic
aorta being clamped. The brains were fixed in Bouin’s fluid
or in 10 per cent commercial formalin (nos. 23 and 26), imbedded
in paraffin and cut, one sagittally (no. 12), the others transversely.
The sections were 20 u in thickness in all cases except no. 16,
in which they were 15 u. Only alternate sections were mounted
except in no. 12. The material was stained with picric acid,
either on the slides or in mass, the former being found best and
being used in all the later work.

434 EDWARD HORNE CRAIGIE

Injection with diluted India ink was tried, but gave less satis-
factory results. As soon as injection was completed, the neck
was ligatured and the whole head was cut off and immersed in
chilled fixing fluid until the gelatin had time to set. The top
of the skull was then opened and, if the gelatin was not yet firm,
the head. was returned to the fluid. Finally the brain was re-
moved and left in the fluid for three and a half to five hours more.
The earlier specimens were left longer, but the injection mass
was found to be decolorized by the picric acid, so the time had
to be cut down. For this reason several brains were fixed in
10 per cent formalin for five days, but this method was aban-
doned in favor of the brief treatment with Bouin, the findings
of previous workers, as well as the observations of the writer,
indicating that less distortion would thus be produced.

Bouin’s fluid was used as a fixing agent for two reasons. In
the first place, the strong formalin would give a good hardening
of the gelatin; in the second place, Sugita (17) has shown that
this solution causes less change in volume than do others com-
monly employed.

After fixation the material was rinsed, dehydrated in the
ordinary way with graded alcohols, and imbedded in paraffin.

To determine how much change this treatment produced in
the brain, two specimens were carefully weighed and measured
as soon as removed from the skull, and again after fixation and
after dehydration. There was found to be practically no change
in shape or size during fixation, though there was an increase
in weight, as would be expected. After dehydration the changes
were as follows:

R 57, aGe 352 R58, ace 390
DAYS DAYS
per cent per cent
THORS welght:., ct cas «+ «cone ee eT eae 46.13 48 .36
TOSS WV OLUIMEC; 2. cites sc. o Skate Ree aerate 36.61 37.58

GES In area vol Sections. |! 1) Leese eee ene ee PARC! Bison

VASCULARITY IN THE NERVOUS SYSTEM 435

A considerable number of different stains were tried, but none
were found to give a satisfactory contrast to the carmin gelatin
except the picric acid. Although this gave a rather poor differ-
entiation of the elements of the brain, it was found to be sufficient
for the identification of the various parts and was used entirely.

In studying the sections, a square-ruled disc micrometer was
used in a Leitz ocular no. 3. The objectives employed were
Leitz nos. 3 and 7, and Bausch & Lomb 16 mm. and 4 mm.
The total length of the pieces of capillaries enclosed by the square
ruling (an area of 189 » square under Leitz objective no. 7) in
each of ten sections was determined for each part studied in
every brain, and the ten results were added together, giving the
total length of the capillaries found in a block of tissue measuring
189 x 189 x 200 c. w. In the cases where the thickness of the
sections was 15 » and where the Bausch & Lomb objective was
used, the results were corrected to correspond with this.

There are several sources from which more or less serious
experimental error may arise in this method of investigation.
In the first place, there is the possibility of incomplete injection.
If all brains which show evidence of incomplete injection are
discarded, this source of possible error should not be serious
when a number of brains are used.

While the fixation in Bouin’s fluid causes relatively little
distortion, the complete technique employed does produce a
certain amount of shrinkage, as shown by Sugita and by the
observations recorded above. No effort was made to correct
for this, as it was considered that the relative vascularity of
different regions would not be affected by it, provided that
shrinkage is uniform throughout, as Sugita assumes to be the
case. The material fixed in formalin gave somewhat lower
results on the whole than the average values for the material
fixed in Bouin’s fluid. This is shown graphically in chart 1.

Any absolute determination of the vascularity by this method
is, of course, impossible, and the investigation seeks merely to
establish a set of ratios.

Hill (96) apparently showed that the quantity of blood in
the vessels of the brain when enclosed in the skull is practically

436 EDWARD HORNE CRAIGIE

constant. The distribution of the blood, on the other hand,
may vary in different physiological states, the greater part being
in the arteries under certain conditions, in the veins and capil-
laries under others. The pressure may vary very widely, and
is not necessarily the same as in other parts of the vascular
system. The cerebral venous pressure and the pressure in the

i. ols aes s 7 “a8 sp Nol it 12!) asthielLis “slaty Lies mncomne:
Parte of Brain

Chart 1 Graph showing the relation of the vascularities observed in material
fixed in Bouin’s fluid (Toronto animals only) and in material fixed in 10 per cent
formalin. The break separates white and gray matter. Material fixed in Bouin,
+; in formalin, @. Numbers of regions as in chart 2.

capillaries are always the same, however. <A very careful rein-
vestigation in collaboration with Macleod (’01) merely confirmed
Hill in his previous conclusions, in spite of the histological evi-
dence of the presence of nerve fibers on intracranial vessels which
had been brought forward by Huber (’99) and others. According
to Corin,? the circle of Willis decreases the pressure of the blood
before it reaches the brain.

* Cited by Stopford, quoting Poirer and Charpy’s Traite d’anatomie.

VASCULARITY IN THE NERVOUS SYSTEM 437

Wiggers (’05, ’07, 08) and Weber (08), on the other hand,
maintain that they have definite physiological evidence that the
cerebral vessels are under nervous control, and in a recent paper
(Orr and Rows, ’18) a whole theory of the nature of certain lesions
of the central nervous system is based upon the principle that
the caliber of vessels entering from the pia mater is regulated
by the sympathetic. This would further complicate the problem
of injection, the effect of the injection mass and of the various
experimental conditions upon the vasomotor mechanism being
problematical. The earlier studies of Roy and Sherrington (’90),
moreover, led them to conclude that “the chemical products
of cerebral metabolism contained in the lymph which bathes
the walls of the arterioles of the brain can cause variations of
the caliber of the cerebral vessels,”’ though no evidence of vaso-
motor control was obtained. If this is so, then it is at least
possible that the injection mass may act directly on the walls
of the vessels, causing them to change their diameter, and may
even cause a different amount of change in the vessels of different
regions. The most recent contribution to this problem is that
of Weed and McKibben (’19), who seem to have good ground
for their conclusion that ‘The Monro-Kellie doctrine’ then
requires marked modification. . . . The cranial cavity is
relatively fixed in volume and is completely filled by brain,
cerebrospinal fluid, and blood; variations in any one of the three
elements may occur, compensation being afforded by alteration
in the volume of one or both of the remaining elements.”

It might be thought that if the quantity of blood in the brain
is constant when enclosed in the cranium, as maintained by Hill,
an injection in this state would yield an absolute quantitative
result. This does not appear to be the case, however. It is
difficult to be quite sure that there is absolutely no leakage from
the ligatured neck before the gelatin sets. Also the quantity
of the injection mass remaining in the capillaries will vary with
the varying distribution of the total amount of fluid within the
cranium. The venous sinuses were always found to be largely
filled with the mass, and it might have been expected that the

3 J.e., that the volume of blood in the brain is constant.

438 EDWARD HORNE CRAIGIE

capillaries also would be so, since the capillary and the cerebral
venous pressures are the same, according to Hill. The diameter
of the capillaries in every case, however, was found to be from
about 2 uw to about 4.5 uw, a size which one would not consider
at first sight to be natural. The diameter of the erythrocytes
in the wild Norway rat has been determined by three observers
to be 6.5 or 7 w (Donaldson, 715). Some of the erythrocytes
in the albino rats used in this study were measured (in the fresh
condition) and were found to average about 6 uw in diameter.
The average diameter of the capillaries in the human subject,
where the corpuscles are just a little larger than in the rat, is
stated to be about 12 » (Cajal, ’11: Halliburton, ’14), so that one
would expect those of the rat to measure at any rate 9 or 10 u.
Sterzi (04) finds the capillaries in the spinal cord of the horse
to measure from 70 to 80 ». According to Koelliker, however,
the finest capillaries in the human spinal cord are 5 uv in diameter,
in the brain 4.5, which, like my measurements, would be smaller
than the erythrocytes. Moreover, a recent paper by Krogh
(19 a) makes it appear not improbable that the vessels in the
preparations used for this study are about their natural size.
Krogh finds that in living, resting muscle of the frog, the average
diameter of the capillaries is about 4.5 », while in the guinea-pig
it is only 3.5 y, although the red corpuscles of the frog measure
about 22 x 15 x 4 uw and those of the guinea-pig about 7.2 yu
diameter by 2 » in thickness. In passage, the corpuscles become
greatly deformed and the walls of the capillaries yield somewhat
where the corpuscles lie. Even in working muscle, where the
vessels are found to expand greatly, the average diameter of the
capillaries is still less than that of the corpuscles. It may be
noted in passing that the same author, while demonstrating that
a large number of the capillaries in resting muscle are completely
closed, found that all the capillaries in the brain seemed to
remain permanently open, so that there is not much danger of
error from that source in the present case.

One factor in the apparent small size of the capillaries is the
shrinkage of the gelatin injection mass. An attempt was made
to measure this in some of the larger vessels, but it was found

VASCULARITY IN THE NERVOUS SYSTEM 439

to vary greatly, so that other factors are evidently concerned
also. Where the shrinkage appeared greatest, the diameter of
the mass was only about one-half of the diameter of the vessel
in which it was contained. What changes the reagents may have
produced in the caliber of the vessel itself could not, of course,
be determined.

It was originally intended that the volume of the capillaries
in a given volume of brain tissue should be measured, but it is
evident from the above that measurements of the diameter of
the vessels were of doubtful value. Moreover, there was found
to be generally no very marked difference in the caliber of the
capillaries in different regions, practically all sizes between the
limits mentioned above occurring in each in similar numerical
proportions, so that the ratio would be given just about as well
by considering the lengths instead of the volumes.

Finally, the possibility of error in measuring the vessels is
considerable. It 1s no easy matter to make an accurate estimate
of the length of a vessel which is twisting about in the thickness
of the section and to make correct allowance for foreshortening,
etc. When it is considered, however, that the result for each
part represents the sum of from about 60 to about 350 measure-
ments in each brain studied, this source of error may probably
be neglected.

The particulars regarding the ten animals from which the
results about to be detailed were obtained are as follows: nos.
12 and 16 were female albinos and no. 14 was a female hooded
rat. These animals were obtained from a local dealer in Toronto
and seemed to be in good condition. Nos. 23 and 24 were male
albinos and no. 26 was a female albino. These were procured
from the stock of the Department of Pathology of the University
of Toronto. They were badly infested with lice and did not seem
very healthy. All these animals were adults, not senescent,
but of unknown age. They were not weighed or measured.
Nos. 31, 55, 56, and 58 were albinos from the standard colony
of The Wistar Institute, and full data concerning them were
recorded.

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, No. 5

440 EDWARD HORNE CRAIGIE

RAT SEX AGE WEIGHT BODY LENGTH | TAIL LENGTH
days grams mm. mm.

31 oO 390 228.4 200 158

55 e) 406 159.2 185 177

56 fe) 406 197.4 198 169

58 of 390 | 234.8 210 17?
OBSERVATIONS

The thickness of the sections was such that the complete
capillary mesh did not show, the vessels appearing as short pieces,
which were much more easily measured than they would have
been if they had formed complete meshes within the field. That
this appearance was due only to the thinness of the sections may
be seen by comparing figures 1, 2, and 3, which represent parts
of sections 20 » thick, with figure 4, which represents part of a
50 » section and figure 5, which is from one considerably thicker.
The complete spongy mesh is not illustrated in the figures, as
it was found impracticable to project satisfactorily upon one
plane the complex system of capillaries seen in a section thick
enough to show this, the course of the vessels being much con-
torted. Enough is represented, however, to indicate that such
a condition actually exists, and one complete mesh appears in
figure 5. The figures 1 to 3 were drawn with the aid of a Leitz-
Edinger projecting microscope, while an ordinary microscope
was used for projection in the preparation of figure 4 and figure
5. The illustrations show clearly the evident difference in
vascular richness of the regions represented. In figure 1 and
figure 2 the more conspicuous cell bodies are indicated in gray
to show their relation to the vessels. Nowhere were the meshes
of the capillary net small enough to surround single cells, as
described by Rudanowsky, nor were there any traces of a delicate
secondary network filling the primary meshes (Adamkiewicz,
loc. cit.). The smallest meshes noticed were about 80 y» in
diameter, but no study of this matter was made, as the contorted
course of the vessels caused such measurements to be practically
useless, besides preventing a complete loop from lying in one
section unless this was very thick.

VASCULARITY IN THE NERVOUS SYSTEM 441

Fig. 1 Part of a section of the right chief vestibular nucleus. 160. Thick-
ness, 204. (R223.)

Fig. 2 Part of a section of the right hypoglossal nucleus. 160. Thickness,
20 GREZ35)

442

Fig. 3

Fig. 4
ness, 50 py.

EDWARD HORNE CRAIGIE

Part of a section of the right ventral funiculus of the spinal cord. X
160. Thickness, 20». (R.238.)

Part of a section of the right chief vestibular nucleus. 160.
(R.43.)

Thick-

VASCULARITY IN THE NERVOUS SYSTEM 443

With regard to the diameter of the vessels, while Adamkiewicz
states that those in the gray matter of the spinal cord are rela-
tively large, Koelliker (96) and Sterzi (loc. cit.) find the capil-
laries in the white matter to be larger than those in the gray
matter, while Hoche states that the white matter is supplied
chiefly by ‘Vorcapillaren,’ the gray by ‘echte Capillaren’ in the
dog. The last author found less difference in the rabbit, however.
As indicated above, there was no marked distinction to be seen
in the present case.

Fig. 5 Part of a thick section of the white matter of the cerebellum. 160.
The drawing was made from a rather thick part of a wedge-shaped section, so
that the exact thickness is unknown. (R.14.)

The linear measurements obtained are recorded in the accom-
panying table 1, the actual value for each part being given, along
with its ratio to the respective results for the ventral funiculus
and the ventral cornu of the spinal cord of the same animal.
The various regions are arranged in the table in order of increas-
ing richness of blood supply, as determined by averaging all the
values for each. When this is done, two horizontal lines can be
drawn, one separating the figures for the white matter from those
for the gray, the other separating the results for the motor
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VASCULARITY IN THE NERVOUS SYSTEM 447

a mere glance at the table shows the striking fact that the sensory
centers are more richly supplied with blood-vessels than are
those of which the function is motor, except in the single case
of the substantia gelatinosa Rolandi of the spinal cord.

Among the motor centers upon which observations were made,
the poorest is the motor nucleus of the facial nerve, the richest
the ventral cornu of the spinal cord. The richest of the sensory
centers studied, on the other hand, is the dorsal cochlear nucleus,
while after it come, respectively, the chief vestibular nucleus,
the dentate nucleus, and the granular layer of the cerebellar
cortex. It will be noticed that the last three mentioned are
related to each other, and it may be remarked that these four
richly vascularized regions are ones which are probably in more
or less constant receipt of stimuli, and so may be assumed to
be in almost continuous activity, which may decrease in intensity
at times, but in all probability ceases more rarely than does the
activity of many other centers. It is interesting to observe that
even the molecular layer of the cerebellar cortex, though distinctly
poorer than the granular layer, is more richly supplied with capil-
laries than the motor, and even than some of the sensory centers.
Krause (loc. cit.) remarked that the inferior olive and the dentate
nucleus are conspicuous in their respective regions on account
of their richness in capillaries. The relative vascularity of the
various regions studied is shown graphically in chart 2.

The present data correspond fairly well with the rather in-
definite statement of Hoche (loc. cit.) regarding the relative
vascularity of gray and white matter in the spinal cord. They
do not, however, agree with his statement that part of the dorsal
funiculus is the richest part of the white matter in the dog, nor
with Krause’s findings on the relative richness of the white
columns in the human cord; the results of the present study
indicating that in the rat the pyramidal tract and the lateral
funiculus are richer than the ventral funiculus and the fasciculus
cuneatus, which are about alike.

i ‘The pyramidal tract in the rat is situated in the ventral portion
of the dorsal funiculus of the spinal cord, where it is rather sharply
marked off from the rest Of the white matter. It stains distinctly

448 EDWARD HORNE CRAIGIE

by various methods on account of the fact that it is very in-
completely myelinated in this animal, and that those myelin
sheaths which are present are very thin (Ranson, 713,14). This
tract was found to stand out quite clearly, even with the simple
picric-acid stain, so that it was easy to consider it by itself, which
was fortunate, since the difference in vascularity between it
and the neighboring fasciculus cuneatus was marked. King
(10), observing that very few fibers were shown in this tract by

Vascularit
Tan as eee fan] aff fafa cf af eft ata ef fn of cfs)
BESERESSREBS BHR SBREDEREEeREEDeB BEBERES

4 is 16 Vi7T 18 (Sar20) jal
Parts of Brain

o
1 2 3 + 5 6 i 8 9 io =O 12 13

Chart 2 Graph showing the relative average vascularity of the regions
studied.

Regions

1, fasciculus cuneatus 12, nucleus of Deiters

2, ventral column 13, molecular layer of cerebellar cortex
3, lateral column 14, dorsal horn; spinal cord

4, pyramidal tract 15, inferior olive

§, fasciculus longitudinalis dorsalis 16. superior olive

6, substantia gelatinosa Rolandi 17, chief sensory V nucleus

7, nucleus motorius VII 18, granule layer of cerebellar cortex
8, nucleus XII 19, nucleus dentatus

9, nucleus motorius V 20, chief vestibular nucleus
10, ventral horn; spinal cord 21, dorsal cochlear nucleus
11, spinal V nucleus

VASCULARITY IN THE NERVOUS SYSTEM 449

the Marchi method, concluded that it is probably of only second-
ary functional importance in.the rat. Ranson (13), however,
pointed out that King’s results were in all likelihood due to the
incomplete myelination of the tract, remarking that it was
impossible to say how far this incomplete myelination might
be indicative of functional insignificance. It is interesting to

Vascularity

“ | 4 SBE Pea] een a [
eo oH H H HE Cy

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tt 12 13 14 i5 16 17 16 19 20 2!
Parts of Brain

BEeooao Co
‘4 Pe etfs teat teat ele tet otto
1 2 3 + 5 6 i 6 - ] 10

Chart 3 Graph showing the relation between the results obtained from Tor-
onto and from The Wistar Institute animals. Toronto, @; Wistar Institute, +.
Numbers of regions as in chart 2.

To obviate any possible error in the construction of this graph arising from
the disproportionate number of the two sexes, the figures for the four Toronto
females were added together and divided by two. The quotient was then added
to the figures for the two males and the whole divided by four. In this way the
proportional value of the sexes became equal in each local group.

note the relatively high vascularity of this tract, suggesting great
activity.

As six of the animals studied were obtained in Toronto, while
the remaining four were from the standard colony of The Wistar
Institute, it was thought advisable to group these two sets
separately and compare the results. This is done in chart 3,

450 EDWARD HORNE CRAIGIE

which shows that, in spite of irregularities, there is no evidence
of any definite difference in the material as a whole between the
two stocks.

Chart 4 shows the result of grouping the sexes separately and
comparing them. It will be seen that the females show a distinct
tendency to a richer vascular supply than the males, though the
difference is neither very great nor very constant. .

Se coo ooo
Co

7 is 19 20 2I
Ports of Brain

Chart 4 Graph showing the relation between the sexes in point of vascularity.
Male, @; female, +. Numbers of regions as in chart 2.

DISCUSSION

The attempt to interpret in terms of function the above ana-
tomical observations leads us at once to the question of the
importance of metabolic processes in nervous activity, and so
to the even more fundamental question of the essential nature
of the nervous impulse. Here we find ourselves in a sea of
controversy, of varying opinions, and of contradictory
evidence.

VASCULARITY IN THE NERVOUS SYSTEM 451

Hill and Nabarro (’95) found the oxygen consumption and the
carbon-dioxide production in the brain to be low, while Alexander
and Cserna (713) found it to be very high—so high as to cast
doubt upon their results (Bayliss, 718). The dark color of the
blood in the cerebral veins, as Bayliss points out, suggests that
there has been a very considerable consumption of oxygen, and
Tashiro’s experiments (’17 and earlier papers) lead him to believe
that there is a rather high production of carbon dioxide in nerves
and ganglia. MacArthur and Jones (17), studying ground
tissue, reached a similar conclusion regarding the central nervous
system. There are also two recent papers by Moore (’18, 719)
reporting a high acid production rate in the medulla, but a low
one in the sciatic nerve. It may be noted in this connection
that the total flow. of blood through the brain in a given time
is much greater than that through skeletal muscle and most
other parts of the body (Jensen, ’04). The most generally
accepted view, however, appears to be that respiratory activity
in nervous tissue is low.

Again, A. V. Hill’s investigations (12) are claimed to prove
that the evolution of heat in nerve fibers is so small that any
metabolism is doubtful, while recently Baglioni (17) has shown
that there is a distinct, though not high, production of heat in
the central nervous system of the toad, which, moreover, bears
a definite relation to functional activity.

Whether metabolic activity is high or low, there is still the
question of what relation it bears to functional activity. ‘“The
problem of the essential physico-chemical nature of nerve con-
duction . . . . is still regarded by most physiologists as
unsolved, and apparently by many as insoluble” (Lille, 718).
Probably the most generally accepted opinion regarding the
nervous impulse is that summed up by Bayliss as follows:

That it is a reversible, physico-chemical process, not associated with
loss of material on account of metabolic reactions, is indicated by the
following facts:

Ineapability of fatigue under normal conditions.

Absence of formation of heat.

Absence of decrement in wave.

Low temperature coefficient of rate of conduction.
No conclusive evidence of metabolism of any kind.

452 EDWARD HORNE CRAIGIE

In keeping with this view, several theories as to the funda-
mental nature of nervous activity have been propounded. These
generally postulate some form of electrolytic action as the es-
sential process involved. Macdonald (05) combines this con-
ception with that of a colloidal suspension, about the particles
of which the inorganic electrolytes are largely held in a ‘masked’
condition, from which stimulation causes them to be liberated.
Macallum (712), with experimental evidence in support of his
contention similar to that of Macdonald, believes that the funda-
mental basis of nervous processes 1s surface tension.

Lillie (18) maintains that a process parallel to nervous con-
duction is found in the wave of electrolytic activity which can
be produced by similar means at the surface of a passive metal
wire immersed in an acid solution. He is inclined ‘“‘to regard
the local bioelectric circuits accompanying normal cell activity
as representing primarily some type of oxidation-reduction
element,’ and his description of the process in the metal seems
to involve the elimination of a certain, though probably minute,
amount of waste matter as the impulse passes along.

On the other hand, certain experiments of Adrian (18) suggest
strongly that ‘‘the energy involved in the passage of the impulse
is supplied locally from each point in the fiber through which
the impulse passes, just as the explosion wave in a train of gun-
powder is maintained by the energy in each part of the gun-
powder as the wave reaches it and sets it alight.’”” Johnston
(08) has brought forward certain purely anatomical evidence
in favor of a similar view. Keith Lucas also supports this view,
and after discussing the evidence (up to 1914) as to oxygen
consumption and carbon-dioxide production in the nerve fiber,
concludes: “However, the whole body of evidence is, I think,
sufficient to justify the conclusion that the nerve uses oxygen
and gives off carbon dioxide when it is conducting nervous 1m-
pulses” (Lucas, 717). Adrian himself is less positive. He says
(loe. cit.), regarding the nervous impulse: “Its nature is unknown,
and the only direct accompaniment of it which can be detected
with certainty is the electric response. . . . There is pos-
sibly an evolution of CO, at the same time, but this is still rather
doubtful.”

VASCULARITY IN THE NERVOUS SYSTEM 453

Lucas, then, and probably Adrian, basing their views upon
certain characteristics observed in the conduction of the nervous
impulse, seem to believe that it is chemical rather than physical
in nature.

Direct evidence for this attitude is found in the work of
Tashiro, who supports by strong experimental evidence, seconded
by persuasive arguments against objections and contrary views,
the thesis that every nervous process is accompanied by a definite
change in carbon-dioxide production, indicative of a change in
metabolic activity, and hence that such processes are essentially
chemical in nature. It may be worth while to quote his con-
clusion (Tashiro, 717, p. 107):

Concerning the nature of the material basis of the nervous impulse
we can only say that it appears to involve that part of the chemical
transformations in protoplasm which result in the production of carbon
dioxide. Farther than this we cannot go at present. But it iscertain
that it has a chemical basis. Whether it has also a physical basis,
such as a change in state of the colloidal substratum of the nerve, or
not, we cannot yet say. Who shall write the chemical reaction of the
future, embracing not only the energy exchange, but the change in
psychism as well?

(P. 108.) Three kinds of change occur, then, in our brains when

the nerve impulses are passing —an electric change, a chemical change,
and a psychical change. Which is the fundamental change?

A number of objections have been urged against Tashiro’s
work, which, moreover, seems in some particulars to involve
considerable changes in views hitherto held concerning nervous
action; and in spite of the strength of his evidence and arguments,
the majority of physiologists appear to be disposed to reject it
at the present time. It has received, however, rather striking
support from the work of Baglioni (loc. cit.), who shows that,
despite the earlier evidence to the contrary, there is a definite
production of heat in the central nervous system during activity
which seems to be parallel with the carbon-dioxide evolution
demonstrated by Tashiro in peripheral nerves and ganglia.
Moore, however (loc. cit.), has failed to confirm Tashiro’s obser-
vations and is led to the conclusion that the processes underlying
the nervous impulse do not produce carbon dioxide.

454 EDWARD HORNE CRAIGIE

It is evident that while these questions are in their present
unsettled condition, no final explanation can be formulated to
account for the facts brought out in this study. We may con-
sider briefly, however, the possible bearing upon them of some of
the rival hypotheses.

If nervous activity is of a physical nature, involving no meta-
bolic changes, then all the metabolism present will be the small
amount required to maintain life in the protoplasm. So far as
appears, this should not differ markedly from the rate of meta-
bolism in the neuroglia, which likewise has little else to do,
probably, than simply to perform the ordinary vegetative func-
tions and passively to occupy its place. There will also be a
certain amount of reserve energy available for growth or repair,
a reserve which one may assume to be of rather more importance
to the neuroglia than to the nervous elements themselves, and
which probably will not differ very greatly in different regions.

What, then, is the significance of the differences in vascularity
observed in various centers? With regard to the rather large
difference existing in general between gray and white matter,
this very condition has been brought forward as an argument
in support of the contention that metabolism is practically ab-
sent in nerve fibers, and it certainly seems to agree with it.
The capillaries present in the white matter will in this case be
concerned almost entirely with the needs of the neuroglia. The
richer blood supply in the tract which is largely unmyelinated
may be due to the presence of a greater proportion of neuroglia
surrounding a larger number of much thinner nerve flbers in a
unit volume, space not being occupied by the large bulk of
the myelin sheaths. The myelinated fasciculus longitudinalis
dorsalis, however, is much richer than is this (pyramidal) tract,
so that the significance of the facts is not clear. The observation
that about 50 per cent of the white matter is composed of myelin
(Donaldson and Hoke, ’05; Greenman, 713, ’17; Koch and Koch,
17) would in itself explain the fact that the vascularity of the
more poorly supplied gray regions is in the neighborhood of
twice as great as that of the white matter of the cord.

VASCULARITY IN THE NERVOUS SYSTEM A455

The nourishment of the nerve fibers, according to what seems
to be the fairly generally accepted view, is derived very largely,
if-not entirely, from the cell body. It is difficult to believe,
however, that a fiber a meter long can be nourished entirely
by the activity of a single cell body situated at one end of it,
though the ordinary conception of the functions of the nucleus
would lead one to expect metabolism as a whole to be more
rapid, and perhaps more important in some respects, in that
part of the neurone which contains it. Certain authors state
that the myelin sheath is concerned in the nutrition of the axone,
and if this be true, it is easy to see that myelination may enable
a tract to carry on its functions satisfactorily with a much poorer
blood supply than would otherwise be needed, if activity is not
constant. The arguments in favor of this view are summed up
by Mathews (16). Moreover, the neuroglia itself may perhaps
act as an intermediary between the blood and the nervous ele-
ments. Achtecarro (’15) attributes to the neuroglia considerable
functional activity ‘‘as an interstitial gland which acts on the
nerve elements and on the blood, contributing by means of special
hormones to the endocrinic harmony of the organism.” Cajal
also believes that the neuroglia bears a nutritive relation to the
nerve cells, and acts as a chemical rejuvenator toward them.

It is to be noted that the susceptibility of the reflex are to
anaemia, lack of oxygen, drugs, etc., is much greater than that
of the nerve trunk, which shows that the blood supply is actually
of greater direct. physiological importance to some part of the
neurone which lies in the gray matter than to the axone (Sher-
rington, ’06).

The difficulty is perhaps even greater, and the problem is
of even more immediate interest, when we come to consider the
differences in the vascularity of the various centers of gray matter.
If the functional activities of the neurones involve no metabolic
changes, and the only chemical processes occurring are those
incident to the relatively small amount of assimilation and
respiration necessary to maintain passive life, what is the meaning
of the fact that, for example, the blood supply of the dorsal
cochlear nucleus is from nearly one and a half times to twice as

THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 5

456 EDWARD HORNE CRAIGIE

great as that of the ventral cornu of the spinal cord or that of
the hypoglossal nucleus? While there is no proof that such a
difference in vascularity necessarily implies a corresponding
difference in metabolic activity in the regions concerned, that
assumption, as made by Aby, seems to be the only reasonable
explanation (in so far as it is an explanation) of the facts. More-
over, it is quite in accord with what is known of the blood supply
to other tissues (e.g., Krogh, 719). The considerable individual
variations observed suggest that the correspondence is not very
exact, and no doubt each region is supplied somewhat in excess
of its normal requirements. It is difficult to believe, however,
that there would be any constant and considerable differences,
such as have been demonstrated, if the quantity of materials
used and of waste products given off were about the same in
the various parts compared. Also, the metabolic differences
must really be considerable and regular, as the vascularity sug-
gests, for any small or occasional variations in chemical activity
could probably be satisfactorily dealt with by the cerebrospinal
fluid (Halliburton, 716; Weed, ’17) and, perhaps, the neuroglia,
as suggested above. The observation of Hatai (’17), that “‘the
relation between metabolic products and active cell substance
is quantitatively similar in all parts of the central nervous system
and in both parts of the neurone,” seems to indicate that much
more of these substances must be produced in certain parts, as
otherwise the much greater blood supply in these parts would
cause them to be much poorer in residual products of metabolism,
which are what Hatai measured. His conclusion, that the quanti-
tative relation which he demonstrates between the active cell
substance and the metabolites indicates ‘‘an equality in activity
so far as nitrogen metabolism is concerned,’ does not appear
to agree with the facts regarding the blood supply which are
recorded above.

If the metabolic processes are not much more active in the
richly vascular regions than in the poor ones, we might expect
that the cells in the latter would probably be the first to suecumb
to anaemia. This, however, is by no means the case. The
small pyramidal cells in the cortex survive only eight minutes,

VASCULARITY IN THE NERVOUS SYSTEM A457

while the cells of the spinal cord survive for three-quarters of
an hour or more (Cannon and Burkett, 713).

If it be assumed that the observed differences in vascularity
_ are indicative of corresponding differences in rate of metabolism,
the latter may be accounted for in either of two ways. Provided
that the rate of metabolism is markedly greater in the nervous
elements than in the neuroglia (for which there seems to be no
particular reason if nervous processes are purely physical in
nature), this difference may mean simply that the nerve cells
are packed together more closely in one case than in another—
that there is a greater volume of nervous protoplasm present
in a unit volume of the tissue. This is practically the view
stated by Obersteiner (loc. cit.), who says: ‘the richer any region
is in nerve cells the closer is the capillary network which supplies
it.” There can be no doubt that this factor plays a part, some
of the centers having a considerable admixture of white matter,
and the cells certainly being more numerous in some parts than
in others. The facts, however, do not seem to be adequately
met by this view, and we are impelled to look about for something
else.

The only other explanation which offers itself appears to be
that the difference in rate of metabolism deduced from the differ-
ence in vascularity corresponds to a difference in functional
activity. This implies the acceptance of the view that nervous
processes involve metabolic changes, for which belief, as we have
seen, the physiological evidence is as yet inconclusive. Even
if it be true, one may well wonder why the activity of sensory
nuclei should be greater than that of motor centers and why
there should be such marked differences within each of these
groups. Evidently, our knowledge of nervous processes will
have to advance a long way before these matters can be fully
understood. It may, however, be suggested, with all due diffi-
dence, that sensory centers are in more or less constant receipt
of stimulation, while the activity of motor centers is rather
intermittent. On the other hand, it may be pointed out that
the motor centers which are concerned with muscle tone must
be in a state of more or less continuous excitation.

458 EDWARD HORNE CRAIGIE

There have also been recorded differences in the manner of
growth of certain sensory and motor cells, which seem to be of
such a nature as to demand a larger blood supply for the former.
These differences have been described by Donaldson and Na-
gasaka (’18), who observed that the spinal ganglion cells grow
with the growth of the body, each enlarging ‘‘nearly in propor-
tion to its entire fibers, but less rapidly than the corresponding
axes;’”’ while in the case of the large spinal-cord cell bodies, “‘the
enlargement of the axon to meet the requirements of the increased
muscle mass to be innervated is . . . . not accompanied
by any notable increase in the size or internal arrangements of
the cell.”” The growth of the spinal ganglion cell “is considered
as an adaptation for maintaining the sensory discrimination
despite the extension of the area supplied by a single neuron.”

Finally, one cannot altogether overlook the existence of what
are generally designated ‘psychic’ processes, whatever thesemay
really be, and whatever may be the nature of their relation to
physiological activity. Von Monakow (16) believes “that the
material basis of the sentiments ought to be regarded as chem-
ical.” Cannon and Crile both claim to have found evidence
of endocrine activity in emotions, and Achtcarro believes that
the neuroglia may be involved in such processes. “‘ ‘Evidently,
then,’ as Lagaro remarks, ‘the nervous system and the endocrinic
glands act as one under certain circumstances and constitute
the basis of many changes in normal psychic life.’”’ (Orr and
Rows, 718). Mott (14) states quite decidedly that the physi-
ological basis of all mental activity, whether simple or complex,
is a group of biochemical processes involving oxidation and
hence absolutely dependent upon the blood supply. Thus it
is at least possible that the vascular differences recorded above
may be in part related to ‘psychic’ activities in which the respec-
tive centers are concerned.

VASCULARITY IN THE NERVOUS SYSTEM 459
SUMMARY

No exact quantitative comparison of the vascularity of different
parts of the central nervous system has been published hitherto,
and the present study is an attempt partly to fill this gap. To
that end, anatomical measurements of the capillary richness
have been made in twenty-one regions arbitrarily selected in
the spinal cord, medulla oblongata, and cerebellum of the albino
rat, and the values obtained and their ratios are presented in
tabular and graphic form. It is not claimed that these values
represent the absolute vascularity of the parts concerned, but
it is believed that they do show in a fairly reliable manner the
relative richness of the capillary supply. The results may be
summarized as follows:

1. The gray matter is much more richly supplied with capil-
laries than is the white matter, the poorest part of the gray
being nearly half as rich again as the richest part of the white
among the regions studied.

2. All parts of the white matter are not equally vascular, the
pyramidal tract, the richest part in the spinal cord, being about
twice as rich as the fasciculus cuneatus, while the fasciculus
longitudinalis dorsalis in the medulla is still richer.

3. The gray centers can be sharply divided into two groups,
the motor nuclei and the sensory and correlation centers, of
which the latter are richer than the former. Though the richest
motor region (ventral cornu) is but little poorer than the poorest
sensory one (spinal V nucleus), the two groups do not overlap
in the case of those regions studied, except in a few individuals.
The substantia gelatinosa Rolandi of the spinal cord is the only
part which does not conform with this statement.

4, The richest of the centers observed is the dorsal cochlear
nucleus, which is more than half as rich again as the ventral
cornu, about two and a half times as rich as the substantia
gelatinosa Rolandi (the poorest gray region), and eight times as
rich as the fasciculus cuneatus.

5. Great individual variations occur, and the two sexes do
not seem to show any constant difference.

460 EDWARD HORNE CRAIGIE

6. The interpretation of the functional significance of the
anatomical data recorded depends upon the unsolved problems
of the fundamental nature of nervous processes and their relation
to metabolic activity. ‘he bearing of various theories regarding
these upon the present investigation is discussed.

Special acknowledgments are due to Dr. B. A. Bensley and to
Dr. H. H. Donaldson, as well as to other members of the staffs
in both the Department of Biology of the University of Toronto
and The Wistar Institute. The writer also wishes to express
his indebtedness to Dr. J. J. R. Macleod for helpful criticism
and to the Director of The Wistar Institute for the privileges
which were accorded him in that institution.

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Resumen por el autor, J. M. D. Olmsted,
Universidad de Illinois.

El nervio como influencia formativa en el desarrollo de los botones
gustativos.

En todos los estados de la regeneracién de los extremos de
las barbillas del pez Amiurus nebulosus, el nervio y el cartilago
ocupan practicamente toda la distancia entre la porcién no
extirpada y la membrana basal de la epidermis del extremo
terminal de la barbilla regenerada. Las porciones regeneradas
de escaso tamafio, aun cuando presentan cartilago y el nervio,
no presentan vestigios de botones gustativos. La formaci6n
de las papilas dérmicas, que preceden invariablemente a los
botones gustativos, tiene lugar en la base de las porciones regene-
radas mas largas, como si la capa germinativa de la epidermis
se hundiese en ciertas zonas a consecuencia de la penetracién
de una pequefa rama procedente del tronco nervioso. Puesto
que los botones gustativos degeneran en las barbillas en las
cuales se ha cortado el nervio, y reaparecen con la regeneraciOn
de éste, y ademas, puesto que el nervio aparece en la regién
correspondiente antes de que haya indicio alguno del desarrollo
de un bot6n gustativo, la presencia del nervio puede considerarse
como el factor causal en la formacién de los botones gustativos.

Translation by José F. Nonidez
Cornell University Medical College, N. Y.

AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE, MAY 24

THE NERVE AS A FORMATIVE INFLUENCE IN THE
DEVELOPMENT OF TASTE-BUDS!

J. M. D. OLMSTED
Department of Physiology and Physiological Chemistry, College of Medicine,
University of Illinois, Chicago, Illinois

INTRODUCTION

The influence of one organ upon the development of another
is a fundamental problem in morphogenesis. Embryologists
have rather taken for granted that the differentiation of special-
ized organs, such as the transformation of epithelial cells into
taste-buds, is due to the growth of the appropriate nerve into the
region concerned. Hermann (’84), who first described the de-
velopment of taste-buds in the dog, seems to hold this view, though
he states that one sees the embryonic nerve beneath the germi-
native layer of the epidermis after the dermal papilla appears.
The nerve then passes up to the forming taste-bud, and finally the
characteristic spindle-shaped taste-cells become differentiated.

Marchand (’02), who studied the developing papillae in the
human foetus, states: ‘Vers le cinquiéme mois, certaines cellules
de la couche génératrice commencent alors 4 se différencier pour
donner naissance aux borgeous gustatifs. Les nerfs gustatifs qui
commandent la différentiation sont arrivés au contact de l’épi-
thélium.”

Landacre (’07), in his paper on the place of origin and distribu-
tion of taste-buds in Amiurus melas, says, in regard to the ques-
tion whether the taste-buds appear fortuitously and are later
connected with their gustatory nerves or whether the nerve
fibers take the initiative and produce a bud on the surface, that
the evidence is much more in accord with the latter view. His
best proof is that the smaller subdivisions of the groups of taste-
buds are determined by the number of nerves supplying these
subdivisions, and that buds and nerves appear practically simul-
taneously. ‘‘The assumption . . . that the appearance of

‘From the Department of Physiology and Physiological Chemistry, College
of Medicine, University of Illinois, Chicago, Illinois.

465

466 J. M. D. OLMSTED

the taste-bud indicates the time at which the nerve supplying it
reaches the surface needs verification for taste-buds in Amiurus.”’

There are two cases in which it seems to have been proved that
differentiation of sense organs is dependent upon the nerve,
namely, the formation of the tactile corpuscles of Merkel (Szy-
monowicz, 795) and of Grandry’s and Herbst’s corpuscles (Szy-
monowicz, 796).

The growth of such organs as teeth, however, is claimed to be
absolutely independent of the nervous system (Moral and Hose-
man, 719). But the nerve does exert a regulating influence,
either increasing or decreasing the rate of growth, or causing
changes in color of the tooth.

In another paper (to appear shortly) I have described the de-
generation of taste-buds which occurs after severing the branches
of the seventh cranial nerve leading to the barbels of the catfish,
Amiurus nebulosus, and also the reappearance of taste-buds di-
rectly attendant upon the regeneration of the nerve. ‘The present
paper affords additional evidence that the presence of the nerve
is the formative influence in the development of taste-buds.

MATERIALS AND METHODS

When the end of a barbel (0.5 to 1 cm.) of Amiurus is cut off,
sufficient regeneration takes place under normal circumstances to
become evident to the eye at the end of two weeks. ‘The regen-
erated portion appears as a colorless finger-like projection, having
less than half the diameter of the stump from which it springs.
When prepared with Mallory’s phosphotungstic haematoxylin, ac-
cording to the directions given on page 369 of Mallory and
Wright’s “ Pathological Technique,” the cartilage, pigment cells,
and connective tissue stain a brilliant red; the nuclei of epidermal
cells and of the nervous tissue stain a brilliant blue; while the
nerve fibrils and cytoplasm of the epidermis, especially the cyto-
plasm of the sense cells of the taste-buds, take on a characteristic
lilac hue.

RESULTS

Such preparations show that regeneration is more rapid in the
region near the old stump of cartilage. It is rapid growth in this
region that causes the finger-like appearance of the new part.

THE NERVE IN DEVELOPMENT OF TASTE BUDS 467

A column of large hyaline cells extends from the old cartilage
nearly to the basement membrane of the epidermis at the very
tip of the new portion of the barbel. In the younger specimen
with a regenerated end, i.e., 2 to 3 mm. in length, these precartil-
age cells stain a light blue, but in later stages ofregeneration
they take the typical brilliant red of the old cartilage. These
cells are readily distinguishable by their form and staining prop-
erties. Along the anterior border of this column of precartilage
is always seen, even in the shortest regenerated pieces, a small
amount of fibrous material which stains the characteristic lilac
hue, and which when traced to its origin is always found to be
continuous with the old nerve trunk. Certain sagittal sections
bring out this relationship most favorably in a single section, and
the connection can be readily traced in a series of transverse cross-
sections. These fibers extend in bundles between the rod of pre-
cartilage and the germinative layer of the epidermis throughout
practically the whole length of the regenerated tip of any barbel.

When the regenerated end of a barbel is less than 2 or 3 mm.
in length, the germinative layer of the epidermis extends in a
smooth unbroken sheet around the entire new end. Both trans-
verse and sagittal sections show this unbroken line, and yet the
nerve extends practically throughout the length of the new piece.
But when a length of 3 to 4 mm. is reached, one can see several
indentations in the germinative layer. These appear first in the
region near the junction between the old and new tissue, and par-
ticularly along the anterior border of the new nerve. These
indentations are the beginnings of the dermal papillae, the invari-
able forerunners of the taste-buds. Each papilla is filled with a
small bundle of nerve fibers which stands out from the nerve
trunk like a small button, almost as if they had exerted such
force in their growth out from the nerve that they had indented
the germinative layer at that spot.

Later stages of regeneration showed the presence of fully de-
veloped taste-buds along the whole length of the regenerated end,
mainly concentrated, however, along the edge nearest the nerve.
The development of mature taste-buds after the formation of the
dermal papillae is to be described in a later paper.

468 J. M. D. OLMSTED

CONCLUSIONS

It is evident, therefore, that the growth of the nerve into the
appropriate region precedes the appearance of taste-buds, and
that the formation of dermal papillae, the immediate forerunners
of the taste-buds, is most intimately connected with the growth
into it of the particular branch of the nerve trunk which is to
innervate it.

SUMMARY

1. The nerve and cartilage in all stages of regenerating ends of
barbels of the catfish, Amiurus nebulosus, extend practically the
complete distance from the old stump to the basement membrane
of the epidermis at the very tip.

2. Short regenerated pieces, though possessing cartilage and
nerve, show no trace of taste-buds.

3. The formation of dermal papillae, the invariable forerunners
of taste-buds, takes place at the base of longer regenerated pieces
as if the germinative layer of the epidermis were indented by the
growth into it of a small branch from the nerve trunk.

4. Since taste-buds degenerate in a barbel whose nerve is cut
and reappear when the nerve regenerates, and since the nerve
appears in the appropriate region before there is any evidence of
a developing taste-bud, the presence of the nerve may be said
to be the causative factor in the formation of taste-buds.

BIBLIOGRAPHY

HerMann, F. 1884 Beitrag zur Entwicklungsgeschichte des Geschmacksorgans
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Lanpacrg, F.L. 1907 Ontheplace of originand method of destribution of taste-

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536 pp.
Marcuanp, M. L. 1902 Développement des papilles gustatives chez de foetus
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SUBJECT AND AUTHOR INDEX

CANTHIAS. Thecranial, occipital, and
A anterior spinal nerves of the dogfish,
Squalus
Albino rat. ‘On the relative vascularity of
various parts of the central nervous sys-
GIO LCE Condes Ono Oo BOO cree ete 429
Amblystoma. The cerebellum of............ 259
Anterior spinal nerves of the dogfish, Squalus
acanthias. The cranial, occipital, and.. 293
Ataxic pigeons. A study of brains and spinal
Cordsiinia, tanrilygotseeences coe asi cis as = «07 111
Further studies on the chemical
composition of the brain of normaland... 83

RAIN of normal and ataxic pigeons.
B Further studies on the chemical com-
position of the... -ssstmeceerererre cs goc0g EB
Brain of the rats kept in a state of emotional
and physical excitement’ for several
hours. Metabolic activity of the nervous
system. IV. The content of non-protein
NUCLOLEMMIMaL hese see Sane aie «sce 69
Brains and spinal cordsin a family of ataxic
pireons. vAlstudyofeeeeeereee ees .. 111
Brain stem. II. Comparative study of the
relation of the cerebral cortex to vestibular
nystagmus. Experimentalstudiesonthe 1
——— III. The effects on reflex activities of
wide variations in body temperature
caused by lesions of the thalamus. Ex-
perimental studies on the................ 17

AMERON, A. T., VINcENT, SWALE, AND.
A note on an inhibitory respiratory re-
flex in the frog and some other animals. 283
Cells during hibernation and inanition in the
woodchuck (Marmota monax). The
mitochondnain nerve waar ences ai
Central nervous system of the albino rat.
On the relative vascularity of various
parts of:thes psec ae cei 429
Cerebellum of Amblystoma. The............ 259
Cerebral cortex to vestibular nystagmus.
Experimental studies on the brain stem.
II. Comparative study of the relation of

Chemical composition of the brain of normal
aad ataxic pigeons. Further studies on

t
ta nedds. The membranous labyrinth and

its relation to the precoelomic diverticu-

lum of the swimbladderin............... 219
Composition of the brain of normal and ataxic

pigeons. Furtherstudiesonthechemical 83
Craicizr, Epwarp Horne. On the relative

vascularity of various ‘parts of the cen-

tral nervous system of the albino rat..... 429
Cranial, occipital, and anterior spinal nerves

of the dogfish, Squalus acanthias. The.. 293
sympathetic ganglia in the rat. The
Gevclopment of thesss.-- se eereeereeen nee: 163

EVELOPMENT of taste-buds. The
nerve as a formative influence in the.. 465

Diverticulum of the swimbladder in clupe-
oids. The membranous labyrinth and
its relation to the precoelomic........... 219

Dogfish, Squalus acanthias. The cranial,
oceipital, and anterior spinal nerves of

XCITEMENT for several hours. Meta-
bolic activity of the nervous system.
IV. The content of non-protein nitro-
gen in the brain of the rats kept in a state
of emotional and physical............... 69

ORMATIVE influence in the develop-
ment of taste-buds. The nerveas a... 465

Frog and some other animals. A note on an

inhibitory respiratory reflex in the 283
Gas in the rat. The development

of the cranial sympathetic............. 163

Growth. The logetic character of........... 51

IBERNATION and inanition in the
woodchuck (Marmota monax). The
mitochondria in nerve cells during. . 37

Hosuino, Terr. A study of brains and

spinal cords in a family of ataxic pigeons. 111

Hucues, Satty P., Norris, H. W., anv.
The cranial, occipital, and anterior spinal
nerves of the dogfish, Squalus acanthias. 293

l Pee in the woodchuck (Marmota

monax). The mitochondria in nerve cells

during hibernation and................... 37
Influence in the development of taste-buds.

the nerve as a formative................- 465

Inhibitory respiratory reflex in the frog and
some other animals. A note onan...... 283

Ivy, A. Experimental studies on the
brain stem. II. Comparative study of
the relation of the cerebral cortex to ves-
tibulannystapmssee: eee reer eects 1

APPERS, C. U. Artins. The logetic
characteroterow thee ee eeeee eee ree 51

Kocu, Maruiupre L., anp Rippin, Oscar.
Further studies on the chemical composi-
tion of the brain of normal and ataxic
DISCONS rh. ole eee tee 83

KoMmINE, SHIGEYUKI. Metabolic activ ity of
the nervous system. IV. The content of
non-protein nitrogen in the brain of the
rats kept in a state of emotional and
physical excitement for several hours.... 69

| Bae and its relation to the
precoelomic diverticulum of the swim-
bladder in clupeoids. The membran-

OUB is Sec avert crea 2) oS close elaneis Ghee MEP 219

LarRsELL, O. The cerebellum of Amblystoma 259
Lesions of the thalamus. Experimental
studies on the brain stem. III. The
effects on reflex activities of wide varia-

tions in body temperature caused by.. 17
Logetic character of growth. The........... 51
Meee N. E. The olfactory sense

ot) Orthoptera.. 5. ccdae seem eciecncls ais 405

Membranous labyrinth and its relation to
the precoelomic diverticulum of the
swimbladder in clupeoids. The......... 219

Metabolic activity of the nervous system.
IV. The content of nonprotein nitrogen
in the brain of the rats kept in a state of
emotional and physical excitement for
Severalihoursss cer eae eee moma ae 69

Mitochondria in nerve cells during hiberna-
tion and inanition in the woodchuck
(Manmotamonax)ee ebetenerccesscccecs. 37

470

ERVE as a formative influence in the
development of taste-buds, The........ 465
Nerve cells during hibernation and inanition
in the woodchuck (Marmota monax).
The wmitochondriawn. see ce aac seeiiae 37
Nerves of the dogfish, Squalus acanthias.
The cranial, occipital, and anterior spinal. 293
Nervous system of the albino rat. On the
relative vascularity of various parts of the
Cott: MeN teas yn) Soe Gbomancioacaticte of 429
Nervous system. IV. The content of non-
protein in the brain of the rats kept ina
state of emotionaland physicalexcitement
for several hours. Metabolic activity of 5
Ae eee ee eee nes eames senor D 6

ment for several hours.
tivity of the nervous system.
content of non-protein.................-.- 69
Non-protein nitrogen in the brain of the rats
kept in a state of emotional and physical
excitement for several hours. Metabolic
activity of the nervous system. IV. The
COMCENT Obes ee ee stro cesar natal tema tale 69
Norris, H. W., anp Hucuss, Sauty P.
The cranial, occipital, and anterior
spinal nerves of the dogfish, Squalus
ACANGHIAS Hse Hee eee = crore ve yeeier 293
Nystagmus. Experimental studies on the
brain stem. II. Comparative study of
the relation of the cerebral cortex to
WOMEN Oe nae aencoptiogd oo0.ce cOUOnEDOOuS 1

IV. The

CCIPITAL, and anterior spinal nerves of

O the dogfish, Squalus acanthias. The
(Oe hstt:| ERS AS eee sob 6 SRS eee ee 293
Olfactory sense of Orthoptera. The......... 405

OumsteD, J. M.D. The nerve asa formative
influence in the development of taste-buds 465
Orthoptera. The olfactory sense of.......... 405

IGEONS. A study of brains and spinal
cords in a family of ataxic.............. 111

Pigeons. Further studies on the chemical
composition of the brain of normal and
Ehii> atoits GEER A EOS mab cc UCHR no aaa ae 83

Precoelomie diverticulum of the swimblad-
der in clupeoids. The membranous laby-
rinth and its relation to the.............. 219

ASMUSSEN,A.T. The mitochondria in
nerve cells during hibernation and in-
anition in the woodchuck (Marmota
TROVE ae he recta torent enti sa vletatsee einer ontuets 37

Rat. On the relative vascularity of various
parts of the central nervous system of the

Albino, Hols We Stee iss Scare alaialsverevaretees 429

Rats kept in a state of emotional and physi-

cal excitement for several hours. Meta-

bolic activity of the nervous system. IV.

The content of non-protein nitrogen in the

YHin OL The: tite terete scteeles«. oleiels omhaenpre 69

INDEX

Rat. The development of the cranial sym-
pathetic ganglia in the................... 163
Reflex in the frog and some other animals.
A note on an inhibitory respiratory..... 283
Respiratory reflex in the frog and some other
animals. A note on an inhibitory....... 283
RippLe, Oscar, Kocu, MatTHiInpEe L., AND.
Further studies on the chemical com-
position of the brain of normal and ataxic
DIGCONB: ic hans Ares a eae eRe Ee 83
Rogers, F. T. Experimental studies on the
brain stem. III. The effects on reflex ac-
tivities of wide variations in body tem-
perature caused by lesionsofthethalamus 17

GENSE of Orthoptera. The olfactory..... 405

Spinal cords in a family of ataxic pigeons.

_A study of brains and
Spinal nerves of the dogfish, Squalus acan-
thias. The cranial, occipital, and ante-

Py Misloyeneree cnc a convade dsosbacbRatbosocds 9000 293
Squalus acanthias. The cranial, occipital,

_ and anterior spinal nerves of the dogfish.. 293
Stewart, Frep W. The development of the

cranial sympathetic ganglia in the rat... 163
Swimbladder in clupeoids. The membran-
ous labyrinth and its relation to the pre-
coelomic diverticulum of the.............
Sympathetic ganglia in the rat. The de-

_ velopment of the cranial................. 163
System of thealbinorat. On the relative vas-
cularity of various parts of the central

NEV OUBKS fick eee ware ene enone
'ASTE-BUDS. The nerve asa formative
in the development of.................. 465

Temperature caused by lesions of the thala-
mus. Experimental studies on the brain
stem. III. The effects on reflex activities
of wide variations in body............... 17

Thalamus. Experimental studies on the
brain stem. III. The effects on reflex ac-
tivities of wide variations in body tem-
perature caused by lesions of the......... 17

Tracy, Henry C. The membranous laby-
rinth and its relation to the precoelomic
diverticulum of the swimbladder i1
(hts Baa na andeadoduaMoudenoandposApcet 219

ASCULARITY of various parts of the
central nervous system of the albino

rat. Ontherelative. 3... .j +--+ tan 429
Vestibular nystagmus. Experimental studies
on the brain stem. II. Comparative
study of the relation of the cerebral cor-

32> aa ORD AC Ee aon IRE Secon od on cio ge othe 1
VINCENT, SWALE, AND CAMERON, A. T. A
note on an inhibitory respiratory reflex in

the frog and some other animals......... 283

Wee (Marmota monax). The
mitochondria in nerve cells during hi-
bernation and inanition in the ....... 37

Aa
ons 42

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