There is, however, also the possibility of difference in the quality of gonad secretion, and of recent years Steinach and his followers have been claiming that this may be at the bottom of many cases of so-called “perversion of sexual instinct.” The latest claim of this school is that homosexual men may be rendered heterosexual in instinct by removal of their testes and implantation of a testis from a sexually normal person--from a man, for example, who is being operated on for cryptorchidism. It is frankly impossible as yet to say whether their conclusions are well founded: a very much larger series of cases will be necessary, and the possibility of suggestion’s action must be eliminated. It is well to remember, however, that there is no theoretical objection to the possibility. We know that in various lower animals, such as moths and flies, the balance between the male- and female-determining factors in the chromosomes may be altered in certain crosses, and that this altered balance in the constitution is reflected in some cases in a state permanently intermediate between male and female, in others by a reversal of sex at some point during development. For various reasons we should not usually expect reversal in mammals; but if such abnormal balance should exist in the constitution, as it well might, we should expect a gonad secreting an abnormal, intermediate secretion. This we might also expect as the result of certain accidents of embryonic life, as actually happens in the abnormal female cattle known to farmers as free-martins. These animals are always born co-twin to a male, and their abnormality is due to the blood-systems of the embryonic membranes of the twins having fused, so that the secretion of the developing male’s gonad acts upon the developing female.