Response of the Sparrow Testis to Various Kinds and Amounts of Gonadotrophins *

It has been known ever since the early investigations with gonadotrophins that the response of the bird to these substances is different from that of the mammal. In the bird, the testis is much more responsive to any type of stimulation than is the ovary, while in the mammal the reverse seems to be true. It was also shown relatively early that the chorionic gonadotrophins secreted in the urine of pregnant women brought about only slight response in birds, ""6, while another chorionic gonadotrophin, which is found in the blood of the pregnant mare (PMS) but is not secreted in the urine, is one of the best gonadotrophic substances for stimulating the gonads of birds.' There does not seem to be an adequate explanation of the above differences in response. The present experiments are an attempt to analyze the response of the sparrow testis to some of the gonadotrophins that have been used to stimulate this organ, with the aim of determining, if possible, the underlying principle responsible for the observed differences.