Museum LIBRARY.

MICROSCOPIC STUDIES

ON THE

CENTRAL NERVOUS SYSTEM

Leptiles antl Patrachians.

THE. SPINAL CORD OF THE FROG-RANA
PIPIENS, RANA HALECINAZ,
é

ae | By JouN ae Mason. Mes Dc
ees y

CHICAGO:

J. J. SPALDING & Co., PRINTERS, 158 CLARK Sr,’
1880.

3 BR oy
SEES PS) 2
eee ae tak
Eee epee yaa
sae oe eS

We

nica
Thigeck

tts ty Ph
ake

/QG\ONAL MUSEUM

PAY a
Z “ flicroscoy e Studies on the Central Nervous

2 SMITHS. AN

“System of Reptiles and Batrachians.

By Joun J. Mason, M. D.

ARTICLE I1.—TIIE SPINAL CORD OF TIE FROG

RANA PIPIENS,
RANA ILALECINA

[Reprinted from the JouRNAL oF NeRvous AND MENTAL Diskase, Jan., 1880. ]

T is not intended in these articles to give, in detail, an ana-
tomical description of the nervous system of this class of
animals. So far as the anourous group of batrachians is con-
cerned, one could hardly effect such a purpose better than by
translating the works of either Reissner * or Stieda,+ which
together an those of Wymant and Ecker § are in the hands
aa most comparative SAR Only in writing of species,
the nervous system of which may not previously have been
studied, will a full description be attempted, the main object
being to present from time to time facts observed by the au-
thor, and regarded by him as supplementary. The form of
the spinal cord and especially that of its enlargements; the
nuclei of the nerve cells, and variations in their shape, size,
ete., in the same individual; the number of ganglionic bodies
in the spinal cord, and Tee relations to the roots of the spinal
nerves, and the differences, if any, which may be determined
by sex: these, among others, seem to me to be subjects of

*Der Bau des Centralen Nervensystems der Ungeschwinzten Batrachier.
Dorpat, 1864.

+Studien ueber das Central Nervensystem der Wirbelthiere. Leipzig, 1870.

t Anatomy of the Nervous System of Rana pipiens. Washington, 1853.

Sleones Phystologice, 1851-59. Liepzig. ‘Die Anatomie des Frosches
des physiologischen Thieres, ist fur den Physiologen, kaum minder wichtig,
als die Anatomie des Menschen.”

2 Mason— Central Nervous System of Leptiles, ete.

much interest, many of which can be examined remarkably
well in cold-blooded animals.

Before describing the method of making preparations which
I employ, a few features of the process of Stieda will be no-
ticed. This observer places the entire brains of small animals,
first in a solution of 80-90 per cent. alcohol, which has been
tinted yellow by iodine. As soon as the piece feels firm to the
touch (one to four days according to the size of the specimen)
it is placed in a dark yellow solution of bichromate of potash,
care being taken to use a large excess of the solution. After
a time varying from three weeks to three months, the hard-
ened part is placed in strong ammoniacal carmine, and is
removed after from one to five days, placed in alcohol, and
atter all excess of carmine has been removed, is ready for
section.

By this process Stieda has been able to prepare sections in
a long unbroken series, of the brains of inice, frogs, ete., sav-
ing thereby the risks of several transfers.

My own method is the old one, except in regard to the
solutions for hardening. A two per cent. solution of bichro-
mate of potash has given me excellent preparations, also the
solution of Clarke, which consists of a solution (1-800) of
chromic acid, to each ounce of which a grain of bichromate of
potash is added. So far I prefer to stain after cutting. At
least two transfers may be avoided by using a siphon tube, to
remove alcohol or water, and with the flattened spoons of Se-
guin, there is but little danger of injuring the sections. After
the piece has remained from three to five weeks in the two per
cent. bichromate solution, which it is well to renew every two
weeks at least, it is placed in Ivanoft’s modification of Miller’s
fluid, which consists of one or more parts of sulphate of soda,
until ready for section, when it is transferred to alcohol for a
few minutes.

The membranes of the cord ought not to be removed
until just before making the sections, or until the part is
thoroughly hardened, otherwise deformity will surely result,
showing itself in an oval instead of circular central canal.
When an unbroken series is not desired, it is better to make
sections with the membranes on. After cutting, the sec-

Mason—Central Nervous System of eptiles, ete. 3

tions are stained in Beale’s glycerine and water solution
of ammoniacal ecarmine, for which I often substitute the
borax carmine of J. W.S. Arnold, after adding to it some
ammonia, which rather improves the color. Transparency is
effected by oil of cloves, after absolute alcohol has expelled
the water, and the mounting is done in Canada balsam dis-
solved in chloroform. A short piece of copper wire hammered
flat at one end and bent at right angles is a good substitute for
the steel spoon, as it can be quickly made of any size, and its
outline changed by scissors when desired.

The sections of the alligator’s spinal cord, which were
shown with photo-micrographs at the last annual meeting of
the American Neurological Association, measured about 9-10
mm. through the brachial and crural enlargements, and were
made from specimens lardened by the same process as that
recommended by Seguin* for the human cord.

To prepare isolated nerve-cells, there is perhaps no better
method than that employed by Karabanowitsch, viz.: macera-
tion for forty-eight hours in a weak solution of bichromate of
potash (2-100) mixed, equal parts, with a (1-100) solution of
caustic soda and ammoniacal carmine.

It is possible, however, to make beautiful preparations of the
nerve-cells of the frog, by simple agitation, with some teasing,
in a drop from a solution of glycerine, water and carmine.
Agitation in osmic acid is another common means of isolation,
but the preceding methods are generally to be preferred.

The large cellular structures which form such a prominent
group in the inferior horns of grey matter are composed of
large, sharply defined nuclei, surrounded by protoplasmic
masses which, under the action of certain re-agents, look as if
they were composed of fibrillae, which unite in bundles to form
what are called the cell processes. The nuclei seem to be
but slightly affected by these re-agents, but by prolonged
action, seem to be compressed by the surrounding mass. In
the cells of medium size the nuclei are rarely if ever changed
from the spherical form or circular appearance. These nuclei
which contain a distinct nucleolus, are not too numerous to be
counted in the frog. For example, in an unbroken series of

®Stricker’s Handbook, p. 646, . i

4 Mason—Central Nervous System of Leeptiles, ete.

twenty-four sections, from the middle of the brachial enlarge-
ment of Rana halecina, I counted in both inferior horns 540
large and medium-sized nuclei, and in an unbroken series of
twenty-four sections from the middle of the crural enlarge-
ment I counted in both horns 390 nuclei. Ieissner * esti-
mated the length.of the brachial enlargement as standing to
that of the crural enlargement in the ratio of 6-10, and this
proportion is true of the American species, as would be sup-
posed. It seems fair to conclude therefore, that while the
erural enlargement in frogs has a smaller transverse diameter
than that of the brachial enlargement, still, by its greater
length it contains as many if not more ganglion cells than the
latter. It is then, perhaps, the larger of the two swellings
and corresponds, as it ought, with the larger size of the poste-
rior extremities.

The preponderance of the lumbar enlargement in birds, and
the equality of the two which I have observed in the alligatort
and in several species of lizards can undoubtedly be explained,
by regarding the amount of grey matter, or possibly the num-
ber of nerve-cells, as the surer indication of importance of
function in different regions of the cord.

The large crural nerve cells, as well as their nuclei, are
larger than those of the brachial reqion.

This fact I have established by numerous measurements,
which may be condensed into the following average diameters
for Rana halecina: Brachial nuclei, long diameter, 7; crural
nuclei, long diameter, 8; brachial nuclei, short diameter,
6.5; crural nuclei, short diameter, 7.5. The numbers denote
divisions of the micrometer eye-piece, each division with the
objective used representing .002 mm.

After a thorough comparison of sections from the brachial
region of twenty large specimens of Rana pipiens, of which
seven were males, J have been unable to detect any difference
either in the arrangement, size or structure of the elements,
that could reasonably be referred to as explaining the remark-

* Loc. cit.—Length of intumescentia anterior, 6 mm.; that of intumes-
centia posterior 1U mm.

+See “ Transactions of American Neurological Association,” in preceding
number of the JouRNAL.

Mason—Central Nervous System of Reptiles, etc. 5

able and purely reflex energy displayed by the male frog dur-
ing the embrace of copulation.* The group of cells with
nuclei of medium size, described by me in the Mew York
Medical Journal, of December last, is present in the “pars
media” of cords from both sexes in three species which I
have examined with especial reference to this point.

The distribution of the inferior root fibres in the inferior
horns of grey matter, among and to the ganglion cells.

Wyman,+ whose memoir appeared at the time Ecker was
preparing his /eones Physiologice tor publication, states, page
20: ‘* Atter the most careful examination, I have not detected
any direct connection between these caudate appendages and
nerve tubes;” while the latter anatomist prints an illustration
after Kupfer + which represents, in a cross section made
through the middle of the brachial enlargement, four large
nerve cells, with processes running downwards and outwards,
as far as the periphery, and two other large cells, from the
same group, with processes continuous with the superior:
(posterior) roots!

Such an exaggerated illustration could never have been
made by photography.

Reissner,§ ten years later, in a work than which there are
few more perfect memoirs, writes: ‘In regard to the inferior
roots, I must premise, that the spinal cord of anourous batra-
chians, which have been at my disposal, is very little suited
for observing the entrance and course of the fibres in the grey
substance. * * * * As before stated, a nerve cell may
lie near the point of entrance of a bundle, and send one of
ise processes’ into the same.: (Fig: M.) *. * * .*- The
remainder of the nerve root fibres which run upwards or out-
wards in the grey matter, unite either wholly or in part with
large nerve cells.”

Stieda, || after contending for the true cell structure of the
protoplasmie mass which contains the nuclens, and the struc-

* Goltz.—_Beltrige zur Lehre von den Functionen der Nervencentren des
Frosches. Berlin, 1869.

+ Loc. cit.

t Diss. de Medulle Spinalis Tertura in Ranis. Dorpat, 1854,

§ Loe. cit. pp. 19, 20.

|| Loe. cit. p. 150, et seq.

6 Mason— Central Nervous System of Reptiles, ete.

tureless state of the axis cylinder, against the views of those
who believe in their fibrillary composition, enquires: “ How
is it now with the connection between nerve-cells and nerve-
fibres? * * * * From my observations on fresh as well
as on hardened ganglia of the spinal nerves in fishes, amphi-
bia, warm-blooded animals and man, the union is of this
nature: the axis cylinder of the nerve fibre is the direct con-
tinuation of the cell substance;”’ and two pages further on,
“Tt seems to me impossible to see such a connection in sec-
tions of the brain and spinal cord; it can only be done with
the help of isolating methods, as we are taught by the latest
observations of Koschewnikoff.’* It will be observed that
although Stieda has not seen such a connection in a section,
he nevertheless considers it as a fact, while Reissner, in 1864,
claimed to have seen it; and it was figured by Mcker and
Kiipfer. Dean+ has also a plate showing, in the rabbit, a
nerve process joining a nerve-fibre of an anterior root, and
passing out as far as the periphery. The frequency with
which I have obtained sections from the brachial enlargement
of the frog, which show in the clearest manner what becomes
of by far the greater part of the inferior root fibres of this
region, leads me to give here my manner of procedure.

In the first place, I must assert, contrary to the opinion of
Reissner given above, that I know of no other animal so well
suited, and for so many reasons, as is the frog, for the study
of this point. It is true that the root-fibres in each section are
comparatively few; but this seems to me an advantage rather
than an impediment, and if more nerve-fibres are desired, it
is quite easy to obtain them by making more sections. The
supply ot frogs is ample; and their spinal cords almost come
out of the spinal canal of themselves, so easy is their removal,
when the operation is done upon the abdominal side. As the
chiet cause of failure lies in the division by the razor of the
nerve-tube somewhere between the cell and the periphery of
the cord, it follows that, cwteris paribus, the smaller the
diameter of the cord, the greater the chance of success. In

* Archiv fiir Microsk. Anat. Bad. V. 1869.
tJ. Dean.— Microscopic Anatomy of the Lumbar Enlargement of the Spinal
Cord. 1861,

Mason—Central Nervous System of Leptiles, ete. 7

the brachial enlargement, many fibres from the inferior roots
enter the cord at right angles, and remain in the same vertical
plane while describing a curve laterally, the convexity of which
lies towards the inferior median fissure. This is why longitu-
dinal sections are useless for showing this connection; while
aseries of transverse sections, made in the section cutter, in-
cluding the roots of the second pair of nerves, will often
show, in well stained specimens, the greater portion, if not
all, the root fibres passing through the white substance, and,
after entering the grey substance, branching outwards among
the cells. Most of the fibres lose themselves among the larger
external group of cells, while a few are seen to unite with the
upper group. In several instances I have traced a connection
between cell process and nerve-fibre, with so much certainty,
confirming the observation by using a binocular instrument,
that I am forced to believe not only in the possibility, but the
facility of demonstrating in this way an important fact.

It is always advisable to submit the transparent section to
microscopic examination before it is covered, as the weight of
the cover is often sufficient to sever fibres. Good objectives,
of considerable power, can be used in studying uncovered
preparations; and I have succeeded in obtaining satisfactory
photographs of some of these.

CONCLUSIONS.

1. The central canal of the spinal cord of frogs is more
nearly cylindrical in shape than has been generally supposed.
The oval contour is not seen in cross sections below the
second pair of nerves, when the membranes are not removed
before hardening.

2. The nuclei of the large nerve-cells are more generally
oval in form than are those of the smaller cells. I have con-
firmed this in a few fresh preparations only. It is-possible
that the re-agents employed have a different effect upon the
two classes of nuclei, but it seems more reasonable to con-
clude that they have a different form anatomically.

3. The nerve-cells of the crural enlargement are as abundant
as those of the brachial enlargement, if not more so. Their
nuclei are larger, as are also the surrounding masses of pro-
toplasm or cell bodies.

8 Mason—Central Nervous System of Leptiles, ete.

4. No difference in structure can be made out in the upper
portion of the cord, corresponding with the sexual function
in the male. The long-continued and violent tonic spasm of
the anterior extremities, must be explained by local hyper-
emia influencing the same structures as those which exist in
the female.

5. The relation which is generally believed to exist be-
tween the so-called motor-cells and the inferior (anterior)
roots, can be demonstrated in the frog more readily than in
any other animal.

Sorin

ee

oe

MICROSCOPIC STU DIES

CENTRAL NERVOUS SYSTEM

Aeptiles antl Patrachians,

ARTICES LL.

By Joun J. Micon M.D.

CHICAGO:
DING & Co., PRINTERS, 158 CLARK S

1880.

Re

Keon

y
Pe

\ : ; =
/ Microscopic Studies on the Central Nervous
_ System of Reptiles and Batrachians.

»

By Joun J. Mason, M. D.

ARTICLE II.—DIAMETERS OF THIE NUCLEI OF NERVE CELLS IN THE
SPINAL CORD. RANA s IEMYS FLORIDANA 5 'TKS-
TUDO POLYPHEMUS.

(Reprinted from Vuk JOURNAL OF NeRyous AND MENTAL DisEase, -Ju/1/, 1880.)
Ae early as 1875, while studying the histology of the frog’s

“spinal cord, with special reference to the effect pro-
duced by poisons, 1 was often impressed by what appeared
to be an inequality between the size of the nerve-cells in the
brachial and those of the crural enlargement. This diftfer-
ence was most striking in longitudinal sections, where a long
column of cells was under observation. They appeared to be
larger in the crural than in the brachial region. The idea of
ascertaining by actual measurement whether the incquality of
size were real or apparent, was not then entertained, because
it seemed to me that measurements of the body of the cell
must be unsatisfactory, owing to the great and constant diver-
sity in its form and in the number, size, and length of its
prolongations or processes. Later I was led to measure the
nuclei, and last winter published in the January number of
this journal the fact that there is a considerable difference in
the frog between the two enlargements of the spinal cord, as
to the diameters of the cell-nuclei.

Neither Reissner, Stieda, nor any other anatomist, had, up
to this time, given in their writings comparative measure-
ments of nuclei taken from these two regions of the cord.
‘Whatever shapes the cell-body may assume, or whatever may
be the nature of its substance, the nucleus in these animals
presents itself to us always as a sharply-defined, persistent
anatomical element, easily prepared for microscopical exam-
ination. Readily colored by carmine, ir both fresh and hard-

bo

Mason

Central Nervous System of Peptiles, ete.

ened specimens, it is especially well adapted for measurement,
and its prominence as an object in the microscopic field seems
constantly to invite our efforts to determine more about its
real nature and function. The writer does not claim to have
accomplished much in this direction. The facts, however,
which he has brought to light have been established with so
much care and precision that he feels warranted in formulat-
ing the following law, which he predicts will be found to hold
true in all vertebrate animals, viz.:

The nuclei of the cells in the inferior (anterior) horns, in
the two enlargements of the spinal cord, have average diame-
ters which are proportional to the muscular power of the cor-
responding extremities.

The observations which seem to justify the above law are
briefly the following:

In the frog, which uses almost exclusively its posterior
extremities for locomotion, on land and in water, I find that
the average diameters (for Rana halecina) of the cell-nuclei of
the crural enlargement exceed, by about g4, of a millimetre,
the average diameters (long and short) of the cell-nuclei of
the brachial enlargement. The average size of the former
stands to that of the latter very nearly in the arithmetical
ratio of 7 to 6 divisions of the micrometer eye-piece used with
Nachet’s objective, No. 5.

In the gopher of Florida, testudo polyphemus (Holbrook),
which lives exclusively on land, and digs deep excavations in
the earth with its anterior extremities, the latter become quite
powerful, and attain a development more than double that of
the posterior limbs. The average diameters of the cell-nuclei
in the spinal cord of this animal I have found to have a re-
verse arrangement as to size from that noticed in the frog.
The average size of the brachial nuclei stands to that of the
crural nuclei in the arithmetical ratio of about 7.5 to 7.

In other words, there was a difference in the diameters of
about 54, of a millimetre, the nuclei of the cells of the an-
terior or brachial enlargement being larger than those of the
posterior or crural enlargement.

Again, in the so-called terrapin of the St. John’s river, Flor-

Mason—Central Nervous System of Reptiles, ete. 3

ida, Emys Floridana (Holbrook), which uses the posterior with
much greater effect than the anterior extremities in swimming,
and which has correspondingly large hind legs, the arrangement
of nuclei as to size is reversed in accordance with the law. The
difference in the average diameters I here found to be less than
in the nuclei of the gopher; but, whereas in the latter animal
the brachial nuclei were found to be larger than the erural
nuclei, in the emys the nuclei from the crural enlargement
were the larger.

I have also measured these nuclei in the spinal cord of
alligators; red-headed lizards, Scincus erythrocephalus (Hol-
brook); horned toads, Phrynosoma cornutum ; and the chamele-
ons of the South, Anolius Carolinensis, without being able to
detect constant differences in average diameters between these
elements from the two enlargements. Only in the frog and
the two species of chelonia referred to, have I found a marked
disparity between the brachial and the crural nuclei. This
equality of the nuclei in lizards seems, therefore, confirmatory
of the law which I hope to have established, for of all the
animals above enumerated, frogs and turtles present the
greatest inequality in the extremities as to size and especially
as to power.

In the alligator and lizards, while the posterior are consid-
erably larger than the anterior extremities, the difference, if
there be any, in the power which can be exerted by the two
sets of limbs in running or climbing, is inconsiderable when
compared with the marked contrast in their functions to be
observed in the frog, gopher and emys.

The diameters of the nuclei of the nerve-cells vary in difter-
ent individuals of the same species, in accordance with the age
of the animal. Thus, in a very small but well-developed and
active specimen of Rana halecina, I found the average diame-
ters of inferior horn groups from all parts of the cord to be
less than those in another specimen of this species, about
three times as large. The crural nuclei, however, were found
to be larger than the brachial nuclei in both animals. In a
young gopher, which had not yet used its anterior limbs for
burrowing, the nuclei in general were smaller than those of a
full-grown animal, while I could discover no difference in size

+ Mason—Central Nervous System of Leptitles, ete.

between the brachial and crural nuclei. It might seem fair to
infer, therefore, that the nucleus of a motor cell grows with
the muscular substance which it is supposed to innervate. If
farther research confirm this inferenee, a conclusive reason
will be furnished for the now common division of nerve-cells
into motor and sensitive; for if the nuclei of a definite cell-
group are found to increase in size along with the develop-
ment of muscular power in the related extremities, and to
have no such connection with the function of sensation, such
nuclei may certainly be regarded as belonging to the motor
apparatus.

A word as tothe manner of making permanent preparations
for counting and measuring nuclei. During the past winter
I have tried the method recommended by Stieda* for hard-
ening the brains and cords of small animals, and have found
it to be superior to any other that I have yet met with. In
transparent carmine-colored sections the nuclei are shown
with remarkable distinctness, and can be :measured with
great ease and accuracy. My custom has been to make an
unbroken series of transverse cuts through both the enlarge-
ments; mount all the sections, and carefully label all the
slides so that all the preparations from the same individual
may be kept together by themselves. Longitudinal sections
are particularly well adapted for showing a large number of
nuclei in the same field.

It is always desirable to measure fresh nuclei when possible.
This I have done in the frog and alligator, confirming what was
observed in sections. Great care must be taken here to avoid
compressing the nucleus between the cover and slide, and tor
this purpose it is always better to use bits of softened wax to
support the cover under its four corners.

When the sections are mounted and the Canada balsam
has become sufficiently hard the slide is placed under the No.
5 objective (better to have a movable stage) with micrometer
eye-piece + and the group of large cells in one of the inferior
horns is readily found. The nuclei of these cells are then

*See this journal for January, 1880.
+ Vid. Robin—Traité du Microscope, \). 208.

Mason—Central Nervous System of Reptiles, ete. 5
counted, and the eye made familiar with their relative position
in the field, in order to avoid measuring the same nucleus
twice. The measurements as taken are noted down for this
horn, and then the horn of the other side of the section is
brought into the field, and so with each section on the slide.*
The process is somewhat laborious, but by properly dividing
the work it may be gone through with without much fatigue.
After all the measurements that are desired are taken, they
are added together and the sum is divided by the number of
nuclei measured. This gives the average diameter.

oO
to)

EXAMPLE.

MEASUREMENTS OF NUCLEI FROM THE SPINAL CoRD OF TESTUDO POLY-
PHEMus No. 1. May 151, 16TH AND 177TH, 1880.

No. of Sum of Average

Nuclei. Diameters. Diameters.
a geet ( Long Diameters, 1544 6.89
s et | Short Diameters, 1319 5.87
a i ae ( Longe Diameters, 1448 6.58
2 ata |. Shore Diameters, 1198 5.44

The above diameters are in divisions of the micrometer eye-piece with
Nachet No. 5—7 divisions being equal to .0175 m.m.

* It is often possible to mount as many as twelve sections on the same slide,

MICROSCOPIC STUDIES GN FHE CENTRAL
NERVOUS, SYSTEM GE-REPTILES
AND BATRACHIANS

ARTICLE IIl

DIAMETERS OF THE NUCLEI OF. THE LARGE NERVE CELLS IN
THE SPINAL CORD (continued), ALSO OF THOSE WHICH
GIVE ORIGIN TO THE MOTOR FIBRES OF THE
CRANIAL NERVES

JOHN J. MASON, M.D.

NEWPORT, R. I.

[Reprinted from the JOURNAL OF NERVOUS AND MENTAL DiIsEAskE, Vol. viii,
No. 1, January, 1881}

\ WITH THE AUTHOR'S COMPLIMENTS.

vag an
Pic ete
irk Be

THE WRITER DOES NOT MAKE ANY REFER-
MNCE UN Es ARTICLE BO rHE TEEORY: WHICH
EPReEENDS LTO DISTINGUISH BETWEEN MOTOR
EID SoM NSORY CELES, NOR IAS HE EVER EN=
DORSED SUCH A THEORY, EVEN BY INFERENCE,
BUT-HAS DISTINCTLY STATED THAT SENSATION
BAD NOLTRING TO DO WHEE HIS SUBJECT.

\WMHICROSECOPIC STUDIES ON THE CENTRAL
NERVOUS SYSTEM OF REPTILES AND
BATRACHIANS.

By JOHN J. MASON, M.D.,
NEWPORT, R. I.

ARTICLE III.

DIAMETERS OF THE NUCLEI OF THE LARGE NERVE CELLS IN THE
SPINAL CORD (continued), ALSO OF THOSE WHICH GIVE
ORIGIN TO THE MOTOR FIBRES OF THE
CRANIAL NERVES.

INCE writing article II of this series, I have met with
S nothing which could fairly be regarded as an_ objec-
tion to the law then presented, but have, on the contrary,
noted many new facts which tend to strengthen it and
widen its application. Nuclei which, by means of the pro-
longations of their surrounding cell masses, are related to
muscles, have been carefully measured throughout the
entire nervous system.

Scattered cells, like those found singly or in pairs near
the course of the abducens nerve, with those which I have
elsewhere described as existing in the meshes of the raphe
of the alligator, and certain large cells in lizards, serpents,
and turtles which appear to be connected with the acoustic
or facial nerves, may all be classed as of doubtful function.
Although the diameters of their nuclei may in some cases
seem to furnish exceptions to the rule, so long as their
anatomical relations remain obscure nothing can be defi-
nitely affirmed about them in this connection.

Reprinted from the JOURNAL OF NERVOUS AND MENTAL DISEASE, Vol. viii
No. 1, January, 1881.

2 NERVOUS SYSTEM OF REPTILES AND BATRACHIANS.

I would suggest, however, to those who may feel dis-
posed to regard these cells as connected with the sense of
hearing, that such a view involves giving to this apparatus,
in its central portion, a structure almost identical with one
universally admitted to be motor, like, for example, that
concerned in raising the lower jaw; whereas in the central
structures for vision and olfaction the cells are all very
small.

Moreover, these large cells, found in the vicinity of the
acoustic nerve in some lizards, turtles and serpents, are not
found at all in the frog, while in the alligator their posi-
tion indicates that they may be related to the motor
branch of the fifth pair or possibly to the branch which
supplies the depressor muscles of the lower jaw. The em-
inentia acoustica in the latter animal swarms with uniformly
small cells and nuclei which are very probably the sole cen-
tres for the acoustic nerve, and in the same relative plane
the same numerous groups of small cells can be seen in
frogs and some lizards. .

During the past summer, through the kindness of Prof.
S. F. Baird, of the Smithsonian Institution, quite a num-
ber of valuable specimens have been placed at my dis-
posal, among which may be mentioned Heloderma Suspec-
tum, several serpents and one large example of Chelydra
Serpentina.

Nuclei of the cells of the inferior (anterior) horns of the
caudal, lumbar, dorsal, cervical and upper cervical regions
of the spinal cord, in a large number of frogs of three
species, two species of emys and two of land turtles, and
in several alligators and lizards, including heloderma,
have been measured. Of those found in the cervical and
lumbar enlargements enough has been written already in
the two preceding papers. The preponderance in average

size is here in striking accord with that of the power of the

FOHN $F. MASON. 3

related extremities, and has since been repeatedly con-
firmed in frogs,* especially in longitudinal sections.

The caudal region in turtles and in those lizards which
have few and delicate caudal muscles furnishes an inter-
esting fact for consideration. In turtles the cell nuclei
gradually diminish in size from before backward, and
finally disappear altogether near the posterior portion,
where the horns of gray matter present much the same
appearance, as to structure, as that of the same parts in
the dorsal region.

While in the alligator some of the largest cell nuclei are
met with in this part of the cord, in those saurians, helo-
derma especially, which have comparatively little power in
the tail, these elements are reduced gradually in size in the
same sense as are those in the turtle. The same gradual
transition is well marked in the caudal region of Scincus
Erythrocephalus.

Stieda* gives measurements of nerve cells and their
nuclei from the various parts of the spinal cord in Testudo
Greca and Emys Europea, agreeing with my own made
later, and concludes as follows:

“T guard myself expressly against the supposition that
the great differences in size between these three (large,
medium-sized, and small) classes of cells are evidences of
different physiological importance in these elements. I
wish rather to assert that what is found in the spinal cord
of the turtle can and must be used to support the contrary
view. The fact that in the caudal and dorsal regions no
large cells exist, but only medium-sized and small cells, while

inferior (motor) roots are given out from these same regions,

* In the spinal cord of a bat which I have lately examined, the nuclei of the
cervical region were found to be far more abundant than those of the lumbar
region, and their average diameter somewhat greater. The muscles of the
two pair of extremities bear the same sort of relation to each other.

‘‘Ueber den bau des centralen nerven systems der amphibien und rep-
tilien.” Axoloti and Schildkréte, Leipzig, 1875, p. 4o.

4 MERVOUS SYSTEM OF REPTILES AND BATRACHIANS.

must have great weight against the conclusion that only
the large nerve cells are connected with motor fibres.”
Accepting the passage as it stands I agree with him, but he
has not fairly stated the ordinary view. It does not seem
to me that “only the large nerve cells are connected with
motor fibres,” represents fairly the prevailing belief of
anatomists and physiologists. That all the large nerve
cells are thus connected is more accurately what is thought
to be the fact. Of course, no one has ever claimed that
the cells of origin of the oculomotorius, for example,
were large cells or doubted that they were in connection
with the fibres of the third pair of cranial nerves. Nerve
cells, therefore, may be small and still be connected with
motor nerve filaments. In the dorsal and caudal regions of
the spinal cord of turtles the motor cells are small, because
the muscles which they innervate are small. At the same
time, it may be true that all large cells connect with motor
filaments. To me, this is all in favor of ascribing difference
in energy to different-sized cells or rather nuclei. The
nucleus can be accurately measured, while the body of the
cell can not be, and as the former probably constitutes the
true cell, it has been preferred as an object of study in
my researches.

MEASUREMENTS OF THE DIAMETERS OF THE NUCLEI OF NERVE

CELLS WHICH ARE RELATED TO THE MOTOR FIBRES OF THE CRA-
NIAL NERVES.

1. In four species of turtle, viz.: (1) Emys Floridana,
(2) Emys Terrapin, (3) Testudo Polyphemus, and (4) Chely-
dra Serpentina, the following have been found to be the
comparative dimensions of these nuclei:

The largest nuclei are found in the cells of the spinal
cord and those of the nucleus basilaris of Stieda. Next to
these in size are those of the centre for the motor root of

the trigeminus, supplying with its fibres the elevator mus-

YOHN F. MASON. ' 5

cles of the lower jaw and next those of the centres of the
oculomotorius. This is true of all four species.

In the first three animals weighing about four pounds
each, the nuclei for the respective centres were about equal,
while differing in size in each individual as stated above.
In the Chelydra Serpentina (snapping turtle weighing 24%
pounds) all the motor nuclei were much larger than those
of the smaller specimens. The same rule holds true in
frogs and alligators. The smaller the animal, the smaller
the cell nuclei. I have not seen any mention of this fact
in any works on anatomy.

2. The nervous centres of the alligator are especially

well fitted for sections, and I have obtained three series of
preparations, many hundred in all, showing the nuclei of
the cells of origin of all the motor nerves. In this animal,
the cell nuclei of the motor root of the trigeminus are found
to occupy, as to size, the same middle rank between the
nuclei of the oculomotorius and those of the motor roots
of the spinal nerves, that they do in the turtle. These nu-
clei are remarkably large in both the alligator and snapping
turtle.

3. In frogs the rule is even more strikingly illustrated
than in the animals just mentioned. Anatomists have, as
yet, made no centre for the hypoglossus, but it is interest-
ing to note that, the nuclei of the cells forming the “ nu-

’

cleus centralis”’ of Steida, described and figured also by
Reissner (the natural centre for this nerve), have a diameter
just between that of the nuclei related to the oculomotorius
and those related to the motor root of the trigeminus.

The constant variations in the size of these elements
above indicated have been clearly illustrated by photog-
raphy. By employing exactly the same degree of enlarge-
ment—by using the same objective and having the same

distance always between the focusing screen and micro-

6 NERVOUS SYSTEM OF REPTILES AND BATRACHIANS.

scope—for all the nuclei of the same animal, a very accurate
representation of the actual condition is possible.

These photographs can now be examined at the library
of the Academy of Medicine, the New York Hospital lib-
rary, College of Physicians, Philadelphia, Surgeon-General’s
office and Smithsonian Institute, Washington, and at some
university libraries. The same subjects, with over a hun-
dred others, printed by the Artotype process on plate
paper, showing the structure of the central nervous system
of all the North American reptiles, will soon be pub-
lished.

RECAPITULATION OF THE FACTS OBSERVED IN REGARD TO
THE SIZE OF THE NUCLEI OF THE NERVE CELLS IN THE
SPINAL CORD AND BRAIN OF REPTILES AND FROGS.

Ieee OG.

Diameters in divisions of Nachet’s micrometer eye-piece with
objective No. 5:

Spinal cord, brachial enlargement : : a G25 ik oe
: crural - : eR SOP
Centre of motor root of trigeminus. —. é Be OM a6 AE
Possible centre of hypoglossus : ; » AOE
Centre of oculomotorius : : ‘ i BRS CAS

II.—EMYS FLORIDANA.

Spinal cord, cervical enlargement 6. "O55
ie lumbar i Nae
Dorsal region , , Bigs SAC
Caudal, 5° gradually diminishing 6. -2.
Centre of motor root of the trigeminus Sete se
Cerebellum, large cells ; . : to a aa
Centre of oculomotorius : : po a AS
Cerebrum ; : ; ett eke mf a
Optic tubercles : ‘ Ew k Saee one

IlI.—TESTUDO POLYPHEMUS.

Same as emys, except in spinal cord where the conditions are
reversed in the two enlargements. .

YOHN ¥. MASON. 7

IV.—ALLIGATOR MISSISSIPIENSIS.

Spinal cord, cervical enlargement ; : TRE cy
i lumbar si : OS Sek
Centre of motor cord of the trigeminus : nh Guy, Sues
‘motor portion of the vagus. : 2) UG saeacts
“~~ oculomotorius : : : eae. ae
Large cells of the raphe ‘ ; é Egy abe S00
Nuclei of eminentia acoustica ; eae ©
Sensitive cells of the vagus i io SkbExnaeR
Large cells of the cerebellum . ; 5 Oe aUE ARG
Cerebrum and corpus striatum . bet 2us ARS
Optic tubercles ; : Pe tt cee

V.—HELODERMA SUSPECTUM.

With the exception of the caudal region of the spinal cord,
where much the same scarcity and successive reduction of size of
the nuclei exist as in the turtle, the diameters hold the same rela-
tion to each other as noted in the alligator. This remark also
applies to the nuclei of Scincus Erythrocephalus.

V1. ERY PHROCEPHAEUS:

The nerve cell nuclei of small specimens are notably smaller
than the corresponding nuclei of larger specimens of the same
order. This rule only applies to orders, for some of the nuclei of
Rana Pipiens, from the spinal cord, measure as much as those of
the 24-pound turtle. The nuclei of the small lizards are, as a
whole, proportionally larger than those of heloderma or the alligator.

The proposed law, formulated in my last paper, may now
read as follows:

The nuclet of the so-called motor cells of the central nervous
system have, in the same individual, average diameters, which
are proportional to the power developed in the related mus-

cles.

The writer, in conclusion, while admitting the incom-
pleteness of his work, must at least claim to have demon-
strated the fact that a hitherto unobserved relation exists
between the size of a motor nucleus and that of its periph-

eral organ, the muscle.

The spinal cord of
napipienss s,
ina.

the frog - ra
rana halec

5
=|
G
e}
Lap)
é
o}
Y
=

QL
937
M39
Rept.

UTION LIBRARIES

Wii I =

a wp ALIN.
The spinal cord of the frog pipe