Fig. 79.—Spheroids typicus (from Sergi's collection).
Fig. 80.—A child six months old.
Fig. 81.—The same child a year and a half old.
It follows from these figures that by the end of the sixth month the weight of the brain is already very nearly doubled; but the maximum growth takes place between the ages of one month and three, after which it shows a notable diminution of rate.
But while the weight of the whole body is increased threefold by the end of the first year, that of the brain is very far from being tripled, since the rate of growth is still further diminished during the second six months; in fact even according to Welcker the weight at the end of the first year has little more than doubled.
Accordingly the rhythm of cerebral growth is not identical with that of the increase in weight of the body taken as a whole.
According to Massini, the relation between the cerebral weight and the weight of the body, at the various successive ages, is as follows: