The Brain being the most essential and characteristic portion of the human organization, 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 encephalon that extended and reliable data are to be obtained. That an accumulation of observations of this kind is required for any 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 satisfactory data. Hence it seems to be very desirable to place on record the averages calculated for a considerable collection of human crania, embracing most of the chief divisions 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, dependent 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 subjected 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". 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 reference 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 confidence be affirmed that the examination of a large series of skulls in ascertaining their capacities and deducing from those capacities the average volume of the brain, affords, in some respects, more available data for determining this relative volume for any particular race than the weighing of the brain itself. It might be less easy in this way to fix the exact weight of any individual encephalon, which might be much changed by some lingering and wasting disease (a large portion of Dr. Peacock’s cases died of Phthisis); but, practically, this method is more sure to yield an accurate average size of the organ, because we have it in our power to use an unchangeable substance with which to gauge the capacity of the skull. And we thus arrive at conclusions the same in result as if we had the brain in all skulls at a uniform density, which, in fact, is the true basis of comparison.