When ovaries and testes were transferred in guinea pigs a few days old, he found, in general, that through the influences of the hormones from these glands the character of each sex underwent “slow but radical transformation over toward the other.”[181] In the one case the male organ atrophied and the breasts were developed, with a disposition to nurse, the hair became finer, the method of growth was transformed into that of the other sex; and the converse occurred when the transplantation was in the reverse direction. The change was thus both morphological and functional and Steinach believes that there is a distinct antagonism of the sex hormones due to transplantation of a heterological gland and that this is not due to biochemical differences of blood but to a distinct antagonism between male and female hormones, which have a sex specificity that is the main factor in directing growth. He distinguishes between the specific sex influence and the antagonism that brings about heterological sex signs, which favor the development of other pubertal glands and control growth, even to the dimensions of the skeleton, both stimulating and inhibiting it. The transplantation can be so effected that the glands of both sexes, in a sense, inhibit each other, so that something like experimental hermaphroditism can be caused. These changes last sometimes through life and occasionally there may be periodic milk secretions in males. Each element checks and may throw the other out of function.