Sir W . Hamilton adds, that in the male about one brain in seven
is found above four pounds Troy; in the female hardly one in an
hundred.
These results are highly instructive, and furnish the average weight
of the cerebral organs at the time of death; hut whoever will examine
the valuable tables of Dr. Sims, will observe that various circumstances
may affect the weight of the brain, without, at the same time,
modifying its size; viz.: extreme sanguineous congestion; fluids
contained in the ventricles; interstitial effusion; extravasation of
blood, and softening and condensation of structure. These morbid
changes sometimes take place rapidly, while the absolute bulk of the
brain remains unaltered. Again, the plan of weighing the encephalon
must always be a very restricted one; and is not likely ever to be
practised on an extensive sca|p, except in the Caucasian and Hegro.
3. Another, but indirect, mode of ascertaining the weight |of the
brain, has been practised by Sir William Hamilton, who “ examined
about 300 human skulls, of determined sex, the capacity of which,
by a method he devised, was taken in sand, and the original weight
thus recovered.” *
Respecting the process employed in these experiments I am not
informed; and I agree with Dr. Sims, that the weight of the brain
cannot be determined by ascertaining the capacity of the cranium, by
any method, however accurate in itself.
More recently, Prof. Tiedemann has performed an elaborate series
of experiments to determine the comparative weight of the brain in
the different human races.
“ For this purpose,” he observes, “ I filled the skull through the foramen magnum with
millet-seed, taking care to close the foramina and fissures,, sp as to prevent the esoape of
the seed, and at the same time striking the cranium with the palm of the hand, in order to
pack its contents more closely. I then weighed the skull thus filled, and subtracted from
it the weight of the empty one, and I thus determined the capacity of the cranium from
the weight of the seed it was capable of containing.” "j-
The results obtained by Prof. Tiedemann, like those of Sir William
Hamilton, possess a great value in researches of this kind; yet, unfortunately,
they are not absolute either as respects the size or weight
of the brain; for it is evident that the second of these, objects could
only be obtained by employing a medium of the same density as the
brain | and as to capacity, no method had, at that time (1837), been
devised for obtaining it in cubic inches.
4. Seeing, therefore, that the several processes just described are
not absolute, but only comparative in their results, without affording
* Essays and Heads of Lectures: by Dr. A. Monro, xxxix.
•j- Das Hein des Negers, &c. p. 21.
either the true weight or true bulk of the brain, I solicited my friend,
Mr. John S. Phillips, to devise some more satisfactory method of obtaining
the desired object; and this has been entirely successful in
the following manner.
A tin cylinder was made, about two inches and three-fourths in
djameter, and two feet two inches in height, standing on a foot, and
banded with swelled hoops about two inches apart, and firmly soldered
to prevent accidental flattening. A glass tube, hermetically
sealed at one end, was cut off so as to hold exactly five cubic inches
of water by weight, at 60° Fahrenheit. A float of light wood, well
varnished, two and one-fourth inches in diameter, with a slender rod
of the same material fixed in its centre, was next dropped into the
tin cylinder. Then five cubic inches of water, measured in the glass
tube, were poured into the cylinder, and the point at which the rod
on the float stood above the top of the cylinder, was marked by the
edge of a file laid across its top. And, in like manner, the successive
gradations on the float-rod, indicating five cubic inches each, were
obtained by pouring five cubic inches from the glass tube gradatim,
and marking each rise on the float-rod. The gradations thus ascertained
were transferred to a mahogany rod, fitted with a flat foot, and
these were again subdivided by means of compasses to mark the cubic j
inches and parts.*
In order to measure the internal capacity of a cranium, the larger
foramina must be first stopped with cotton, and the cavity then filled
with leaden shot one-eighth of an inch in diameter, poured into the
foramen magnum. This process should be effected to repletion; and
for this purpose it is necessary to shake the skull repeatedly, and, at
the same time to press down the shot with the finger, or with the end
of the funnel, until the cavity can receive no more. The shot are
next to be transferred to the tin cylinder, which should also be well
shaken. The mahogany rod being then dropped into the tin cylinder,
with its foot resting on the shot, the capacity of the cranium will he
indicated by the number observed on the same plane with the top of
the tube. .
I thus obtain the absolute capacity of the cranium, or bulk of the brain
in cubic inches; nor cam I avoid expressing my satisfaction at the
singular accuracy of this method; inasmuch as a skull of 100 cubic
inches capacity, if measured any number of times with reasonable
care, will not vary a single cubic inch.
On first using this apparatus, I employed, in place of shot, white-
pepper seed, which possessed the advantage of a spheroidical form
* Crania Americana, 1839, p. 253.