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XX. Contributions towards determining the Weight of the Brain in different Races of 
Man. By Joseph Barnard Davis, M.I ). , &c. Communicated by J. Marshall, Esq., 
F.RS. 
Received November 30, 1867, — Read January 23, 1868. 
The Brain being the most essential and characteristic portion of the human organiza- 
tion, as connected with intelligence and mental manifestations, it would naturally be 
expected to have absorbed great attention. Still, comparatively little has been done to 
ascertain its relative magnitude in the different races of mankind. Opportunities for 
the examination of exotic brains are very rare ; and it is only by gauging the capacities 
of trustworthy skulls of different races, and thence deducing the volume of the ence- 
phalon that extended and reliable data are to be obtained. That an accumulation of 
observations of this kind is required for dny results deserving confidence, ensues from the 
manifest diversity of volume and weight which pervades all individual organs of the body. 
These skulls are but seldom met with in such variety and such number as to yield satis- 
factory data. Hence it seems to be very desirable to place on record the averages cal- 
culated for a considerable collection of human crania, embracing most of the chief divi- 
sions of mankind. 
It may be supposed that this method is inferior to that of ascertaining directly the 
weight of the brain. This, however, is itself subject to considerable fluctuations, depen- 
dent upon sex, age, the kind of disease with which the person has been affected, and the 
condition of the organ at the period of death *. These all influence the determination, 
and complicate the deduction of any average weight and volume of the brain when sub- 
jected to the manipulation of the observer. It has been asserted “that the actual 
weights of human brains can alone form just data for conclusions; and that it seems 
scarcely possible that any method of ascertaining the size of the brain from examination 
of the skull can be free from fallacy ”f. Without undervaluing the views of so excellent 
an observer as Dr. Peacock, it may be said that, if this be allowed to be correct in refer- 
ence to any individual case, since the disease which terminates the life of a person itself 
alters the relation of the solid to the fluid contents of the cranium, it may yet with con- 
fidence be affirmed that the examination of a large series of skulls in ascertaining their 
* Chronic diseases tend to change the proportions between the weight of the brain and the fluids of the cra- 
nium. These fluids are abundant at an early period of life, diminish from birth to a mature age, from twenty 
to thirty years of age, after which they again increase. Dr. A. AVeisbach, in his careful observations, found 
the fluids more abundant in the brains of men than in those of women. 
t Dr. Thomas B. Peacock, ‘ Tables of the AVeights of the Brain and of some other Organs of the Human 
Body,’ 1861, p. 22. Reprinted from the ‘ Monthly Journal of Medical Science,’ vol. vii. 1847. 
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