528 



DAVID I. MACHT 



Fig. 1. Rana sylvaiica. Ef- 

 fect of prostate feeding from 

 April 20 to May 19. Ram's 

 prostate was used. 



tadpoles weife fed in some cases on weeds and in others on fresh pig's 

 liver, or on both. The only difference in the treatment between the two 

 sets was that the tadpoles in one case were fed on small amounts of 

 desiccated prostate gland mixed with the water, while the control animals 

 were either given no prostate at all or were fed on other desiccated 



glandular substances studied as controls. 

 Thus, for instance, in some experiments as a 

 control to prostate feeding, tadpoles were fed 

 on desiccated parotid substance, or ovarian 

 substance, or corpus luteum, or other glands. 

 For the study of the prostate gland, desic- 

 cated and powdered prostates were used from 

 the following animals: the ram (Armour's 

 preparation), the bull, the steer, and, in some 

 cases, the desiccated hypertrophied prostate 

 of man obtained from the operating room. 



The effect of prostate feeding manifested 

 itself in changes both in growth and differen- 

 tiation of the larvse. As in the case of the 

 thyroid gland, it was found that feeding with prostate tended to hasten the 

 differentiation or metamorphosis of the tadpoles into frogs. This effect 

 was noticeable in some cases even after a few days. While this stimulating 

 effect on metamorphosis was not as rapid as that following the administra- 

 tion of thyroid gland, it was found that feeding with prostate was not as 

 deleterious to the animals, so that prostatic --, 



substance could be administered to the larvae 

 continuously, whereas, as is well known, 

 feeding with thyroid must be carried on at 

 intervals, lest the animals die. Furthermore, 

 unlike the effect of thyroid feeding, prostate 

 feeding did not cause a diminution or shrink- 

 age in size of the tadpoles, but on the con- 

 trary often showed a tendency to stimulate 

 their growth to a size above normal. These 

 effects will be seen in the illustrations. 



The effect upon the size and the metamor- 

 phosis of the larvae was noted in all the frog 

 tadpoles mentioned above, and also in the 

 case of the common toad, Bufo lentiginosus, 

 and in a few salamander larvae which were studied. The stimulation of 

 metamorphosis was, of course, more strikingly evident in the case of those 

 frog tadpoles which normally metamorphose in a short period of time, but 

 was also demonstrable in the case of the bullfrog, Rana catesbiana, which 

 ordinarily takes two years to change from a tadpole into a frog. The sala- 





Fig. 2. Rana palustris. Large 

 tadpoles were fed with some 

 ram's prostate for two weeks, 

 and some with parotid gland. 

 No difference in size and devel- 

 opment. 



