TI-iV. EFFECT OF TESTICLE EXTI~ACT ON ~HE RATS OF G~OWTH OF CHICKEN TUMOR I* BY ERNEST STURM AND F. DURAN-REYNALS, M.D

The observation that testicle extract markedly enhances the infectivity of certain viruses and bacteria, reported by one of us (DuranReynals (1)) has been confirmed and extended by a number of investigators (2). I t has been further shown that testicle extract exerts an inhibitory influence on the growth of a transplantable epithelioma of the rabbit (3) and to a less extent on a sarcoma of the mouse (4). I t is of interest to know what effect testicle extracts will have on the chicken neoplasms, transmissible by cell-free extracts. Recently Hoffman, Parker and Walker (5) have published the results of a similar investigation in which they report evidence of the enhancement of the chicken tumor agent by rabbit testicle extract, but none by that from rooster testicle. This evidence is based on two positive experiments, but the same testicle extract was used in both tests. They draw no conclusions as to the nature of the tumor agent from these results, but give the impression that further investigation with the method might lead to some conclusions on the question. During the last 3 or 4 years a considerable amount of data had been accumulated in this laboratory, but had not been published at the time the article referred to appeared. Since our results dif" fered from those reported by the above authors, we deferred publication until additional tests could be made with certain minor modifications in technique suggested by their paper.