QUAXTITATIVE STI-DIES 0s THE SESSONAI, DEVELOP,\lENT OF THE DEFERENT DI'C'TS IS PASSEKINE BIKDS I EM I L 11'1 TSCH I Zoo~ogicnl L a b o r o f o r y , l'lrc. State C?fiwrsif!/ of I o ~c ~n , I o w a City.
TEN FIGURES
Tlie spectticular seasonal variation iii size of the s e s organs of male hirtls (table l ) , was already described by Aristotlc. It is now well known that ciidoci.inologicHl1~ the entire complex of changes rests primarily on an aiinual cycle of hypopliyseal activity. During the noii-breediyg or cvlipse season the output of gonadotropic liornioiies descends to the low levels otherwise characteristic for the juvciiilc stage. Consequcntly the sex glaiids regress and return to a quasi-immature state. The testes shrink, and in the seminal tubules there wmain 110 germ cells other than primary spermatogonia. The seasonal rhythm of hppophyseal activity persists even after castration (Witschi, '35).
C: rowtli and regression of the gonoducts, which follow the cycle of the gonads (table l), are generally assumed to depend entirely on the quantity of the s e s lioimioiies that circulate in the blood. But when attcinpt iiig to determine the minimal amounts of various aiidrogens that n.onld restore the breeding coiiditioii of the dcfcreiit cliicts in castrated starlings, it was found that in the male, full size is nevc~' attained, even with vcrj-large closages (table 2 ; cf. figs. 1 and 2 with 3 ) .
This result is at variaiice with previously reported data (Witsclii and Fiigo, '40) 011 the vestigial deferent ducts of the female. Hew, a single duct, from the lowci* edge of the kidney to tlir cloaca, was fouiid to weigh between 1.0 and 1.5 mg. in castrates and in females of the inactive phase. During tlic bweding season it increases to from 4 to 6 ii11(1 in exceptional cases to as high a s 9 rng. In castrates, daily injections into the breast muscles of 0.0.5 to 0.1 mg. of testosterone propionate rcstore the breeding weight, and dosages of 1.25 mg. produce ducts that cxcced the normal size by at least 507.. This iiirestigation was supported b~ n grant from the Committee f o r Resenrcll in Problmls of Scs, National Reuearclr Council. Testostcrone propiouate (Perandrcn) was generousl?-supplied by Cilia P1inrm;rceutical Products, Inc., and pregnnl1t mare serum (Gonadill) 1~7 the Cutter Laboratories.