Samuel S Fels Fund

THIS REPORT on the growth of white rats treated over a long period with tes-tosterone propionate is offered because the material already published (1–9) on the subject is somewhat contradictory and because considering the in-hibition of such growth by estrogen, any influence by the male sex hormone in this direction is of definite interest. Rats of our own inbred colony, originating from Wistar rats, were treated with testosterone propionate from the first day of life as described in previous papers (14–16). One mg. was injected subcutaneously 3 times per week. Litter-mate controls were used in every experiment. The first group comprised 14 males and 46 females treated with testosterone propionate and 13 male and 18 female controls who received nothing. The second group comprised 14 males and 13 females treated while the controls, 11 males and 8 females, received sesame oil in amounts equal to the injections received by the testosterone treated animals.