252 
SCIENCE. 
3d. A longitudinal section nearly parallel with 
the former, running from the anterior prolongation 
of the olfactory bulb through the middle of eac/i 
cerebral and optic lobe, and striking the lateral con- 
voluted mass of the medulla oblongata, could be 
made from the same brain, as a supplement to the 
elucidation of the internal contours. 
4th. One horizontal dissection exposing the ven- 
tricular floors, from above, and another exposing 
the ventricular roofs from below, will still further 
clear up these relations. 
5th. A series of transverse sections, taken per- 
pendicularly to the peduncular axis, will be es- 
sential to a comprehension of the relations of the 
ventricles anti deeper parts for each altitude. The 
sections should be taken at distances of from one to 
three millimetres apart, according to the size of the 
brain, then preserved in separate bottles and labeled 
in numerical order. 
All these preparations should be made from 
brains hardened in absolute alcohol, and the dissec- 
tions should be made after the brain has been kept 
thus for one month, if the working season is in 
summer, and one or two weeks or even a few days, 
if the season is winter. 
My plan, when engaged in this and similar work, 
has been to expose the cranial cavity by cutting 
away the surrounding parts with a strong knife 
until the brain level is reached. This requires very 
little practice. Then the lateral walls are broken 
away with a forceps, or cut away the same knife, 
and the student may then clear up the tracks of the 
cranial nerves for a short distance. The brain is 
not to be removed from the skull base, but left in 
contact with it, a smooth round head of a needle 
may be employed to bread up the arachnoid attach- 
ments there, and facilitate the penetration of alcohol 
to the basilar parts, but this is all that should be 
done. The brain must be immersed in alcohol, 
with the base of the skull in connection therewith, 
at least by means of the emerging nerve roots, else 
the topography may become disturbed. 
The membranes (excepting the dura of the con- 
vexity) should not be touched, for it is desirable to 
trace their connections with plexiform structures 
penetrating the fissures and cavities of the encepha- 
lon, as these may be of service in explaining certain 
homologies. 
Alcohol is selected as the preserving fluid for the 
reason that it does not render the specimens too 
brittle for coarse dissection, which the chromic salts 
do, nor distorts the contours as does glycerine. 
The transverse sections can be made in a micro- 
tome, moving the piston the distance of the thick- 
ness of the required section, before each section is 
cut. Previous to each cutting, the imbedding 
matrix should be removed to a little below the level 
of the section. All other sections can be made 
without a microtome, it being well, however, to fix 
the brain in a wax or a paraffine layer, poured on 
a glass plate. Adherent particles of the material 
thus used can be subsequently removed with tur- 
pentine, when the specimen is prepared for perma- 
nent preservation. It is needless to add that ail 
sections and dissections can be done a hundredfold 
better under the surface of a fluid like alcohol or 
water, than by simply wetting the knife with these 
fluids, as textbooks direct. 
All the work so far mentioned is only preparatory 
however. It is merely destined to furnish on the 
one hand a topographical guide to the more impor- 
tant work which is to follow, on the other to sup- 
plement the ascertained relations of ganglionic 
masses and fascicular tracts by a plastic conception 
of the encephalic segments which contain them. 
The work which is to follow is far more tedious, 
but also far more important ; its methods are those 
employed in studying the microscopic anatomy of 
embryos. 
For the purposes of microscopic anatomy the 
brains of smaller species are as preferable, as those 
of the larger species are desirable for the coarse 
anatomy. The brain of a sturgeon twelve inches 
long, will show all the microscopical details as 
well, and be easier of manipulation than that of one 
twelve feet long. The latter’s had best be devoted 
to naked eye study. 
If the weather is cold, the animal perfectly fresh, 
and the specimen can be kept in a temperature near 
the freezing point (it should never reach or drop 
below the latter,) the brain can be immediately 
transferred to a solution of chromic acid of a light 
sherry color. In my experience this tint, tested in 
a two ounce graduate, is a far more reliable gauge 
than any weighing by so many grains to so many 
ounces, that is ordinarily recommended. After 
staying a week in this solution, it is transferred to 
one of bichromate of potash, having the same color. 
Here it remains, care being taken to have always 
at least one hundred times as much fluid volume as 
specimen volume, until the desired degree of hard- 
ness is attained. The latter is hard to describe in 
words, but an adequate conception can be best con- 
veyed by saying that the specimen should be un- 
yielding to pressure, and yet not altogether inelas- 
tic. The membranes will now separate readily, 
and the specimen, first washed in water, is trans- 
ferred to a neutral (long stood, and repeatedly fil- 
tered and mouldless) carmine solution, so concen- 
trated as to appear black in a depth of six inches. 
Here the specimen is left for from one to three 
weeks, according to the size of the brain. Then it 
is again washed, put in water containing two per 
cent, of glacial acetic acid for twenty-four hours, 
washed again, transferred to proof spirit for a day, 
then finally to absolute alcohol, until such time as 
the obsen/t r is ready to make his sections. 
When this time arrives (and it is best not to defer 
it over a month) the brain stained and hardened as 
it is, is transferred to clove oil, which penetrates and 
drives out the alcohol in a few days. The trans- 
lucency of the specimen is a sign that this has been 
accomplished. It is then taken off, the superfluous 
clove oil drained from the surface, and imbedded in 
a microtome with paraffine. T. he superfluous 
matrix being removed with each section, the cutting 
is done with turpentine, and each section, stained 
and transparent, can be transferred to its appropri- 
ate slide and mounted, so that the order in which 
each section belongs is preserved. This is an im- 
portant advantage. 
If the weather is warm, the brain should be sub- 
