WEIGHT OP THE BRAIN. 325 



same conclusion is arrived at from well-known facts connected with in- 

 sanity, in which it very frequently happens that some of the faculties 

 alone are deranged, while the others retain their power, and some may 

 even become more perfect than before ; so, likewise, in dreaming, some 

 of the faculties retain their activity, while others have become torpid ; 

 and so, likewise, when different individuals are compared, some exhibit a 

 superiority in one, and some in another mental particular ; and it is as- 

 serted that where the same peculiarity has predominated in different in- 

 dividuals, it has always been attended by an unusual development of a 

 special locality of the brain. Nor is there, in these views, any thing that 

 stands in contradiction to the general plan upon which the nervous sys- 

 tem itself is constituted, as is manifested by the different sensory gan- 

 glia for vision, hearing, or smell, or the arrangement for motion or sensa- 

 tion presented by the spinal cord ; and, moreover, they are supported by 

 the comparative anatomy of this system ; for, whatever grade of animal 

 life we may consider, the appearance of a new function or of a new in~ 

 stinct is certain to be connected with a new and contemporaneous devel- 

 opment of some part of the nervous system. 



The facts which have been observed in cases where one cerebral hem- 

 isphere has either suffered lesions or lost its functions, do not present 

 any contradiction to the preceding doctrines ; for, though the remaining 

 hemisphere may seem to act equally well alone, as did both together, we 

 are very apt to deceive ourselves as regards the actual facts, a statement 

 which may be illustrated by recollecting how easily we persuade our- 

 selves that we see with one eye as well as with two. No doubt, in many 

 of the ordinary cases, one hemisphere of the brain may, like one eye, seem 

 to act well enough, but a more critical examination proves that in other 

 cases this is far from being true. That the two hemispheres act sever- 

 ally and separately is clear from what sometimes ensues in diseased con- 

 ditions of one of them, or when, perhaps, there is a want of symmetry 

 between them, those remarkable forms of mental derangement, some- 

 times known under the designation of double life or duality of mind, 

 then ensuing. 



In man, the weight of the brain averages about fifty ounces ; in fe- 

 males, about forty-five ; the maximum being about sixty-four, weight of the 

 and the minimum about twenty ; in the case of idiots, the brain - 

 mean specific gravity of the gray matter is stated by Dr. Sankey to be, 

 in both sexes, 1.034, but somewhat less early and late in life. The 

 specific gravity of the white is 1.041, and this varies less with sex and 

 time of life than the former. 



The functional activity of the brain depends on the copious supply of 

 arterial blood. It is computed that one fifth of the whole quantity in 

 the circulation is sent to this organ. It is delivered through the two 



