STUDIES ON THE PHYSIOLOGY OF REPRODUCTION IN BIRDS

Abstract

Thymus and bursa Fabricii were completely extirpated (thymobursectomy) from 17 common pigeons at a 1st operation performed about 42 days after hatching, or at a 2nd operation 3-4 wks. later; 15 brothers of the 7 operated[male][male], and 26 sisters of the 10 operated [female][female], served as control. Birds were reared to or beyond maturity (3-16 mos. after operation). That part of the body growth (14% of total) which occurred after the operation was not affected by the loss of these 2 organs. No clear and consistent difference was found in wt. of testes, ovaries, thyroid, liver or spleen in operated and control. No difference was observed in bone abnormalities, basal metabolism, health and appearance. The operation had no effect on the time or age at which the [female][female]became sexually mature. The operated [female][female]produced eggs (88) whose envelopes were quite normal, with only 1 exception; there were no soft-shelled eggs. These data and the more crucial data of Greenwood strongly question Stoli''s report of soft-shelled eggs as a result of thymectomy in mature fowls, unless the particular race of fowl used really determines the result. The authors conclude that tissue with "thymic function" is probably widely scattered in the body of vertebrate animals generally. This condition is now rather more evident in birds than in other groups. In birds such tissue is probably regularly represented in the 2 thymi, the bursa Fabricii, the 2 post-branchial bodies, in the lymph glands and perhaps in other lymphoid organs; occasionally it is undoubtedly present in still other areas adjacent to the thymus. An extensive examination of the literature leads to the conclusion that theymectomy has almost everywhere and completely failed to reveal or to confirm those functions of the thymus which have been rather clearly indicated by various other methods of investigating this organ. The explanation of the failure of theymectomy to produce effects probably rests upon the existence and hyperplasia of other widely scattered tissue having thymic function. No result ever obtained from simple thymectomy is usable as evidence against the existence of an endocrine or other function of the thymus.