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folds, so as to produce what is known as the convoluted surface of the hemispheres." "In the higher orders of Mammalia, the convolutions are well marked; but we do not find them either numerous or complex in their arrangement till we approach Man."* " While the brain in man is about one-fortieth of the weight of the body, it receives from one-fifth to one-sixth of the whole circulating blood.+

In the position of the cerebrum, superincumbent and external, in its enlarged size and greatly enlarged activity, we have a plain physical expression of the degree in which in man the conscious life overshadows, envelops, and takes in charge the organic life. "It may be doubted whether a healthy human adult brain ever weighed less than thirty one or thirty-two ounces, or whether the heaviest brain of a gorilla has exceeded twenty ounces."^ Yet the gorilla with a brain of twenty ounces would weigh twice as much as the man with a brain of thirty-one ounces. The largest human brain weighs sixty-five or sixty-six ounces.

That the two functions of the brain, its motor function and its reflective function, are somewhat separate from each other, and somewhat exclude each other, is plain. Great power of reflection is attended by an indisposition to activity, and great muscular activity by a like indisposition and inability for reflection. A small and active bird, like a snow-bunting, demands relatively a very large nervous system to .maintain the heat and intense life needful to meet its circumstances. Such size, therefore, does not indicate corresponding intelligence. Though our knowledge is not sufficient to enable us to say, that muscular activity is always accompanied with a predominance of white matter, and reflective activity with the predominance of grey matter, yet the relations of the two parts of the nervous system

*Mental Physiology, p. 93. + Ibid p. 89.

^Man's Place in Nature, p. 120