312 MATSUZIRO TAKENOUCHI 



able to verify these findings in part, but Swdngle ('17), Uhlenhuth 

 ('18), and Hoskins ('16) report negative results. 



Uhlenhuth in his latest paper ('19), however, states that 

 the metamorphosis of the salamander larva is retarded when 

 thymus gland is fed. 



The theory of the relation of the thymus to general metabo- 

 lism also lacks definite proof (Jackson, 15, '15 a; Stewart, '18), 

 and the theory that rachitic changes in children are caused by 

 disturbances of the thymus cannot be proved by any known 

 facts. 



The cells which make up thymic tissue belong to the vascular 

 system (Danchakoff, '16), and Adami ('14) states on page 563 

 of his text-book that "To all intents and purposes it (the thymus) 

 is a lymphoid organ," and the formation of an internal secretion 

 is no more likely to be the function of the thymic cells than of 

 the cells of similar appearance in other lymphoid tissues. Sum- 

 ming up all the physiological, anatomical, and experimental facts, 

 E. R. Hoskins ('18) says that whatever be the real function of the 

 thymus, certain it is that the production of an internal secretion 

 by it has not been proved. 



Among other experiments with the thymus which cannot be 

 placed under the headings, extirpation or administration of thy- 

 mic tissue or extracts, there are two ; one, which aims to destroy 

 the thymic tissue in vivo by x-ray irradiation, while the other 

 seeks to do the same by some serological method. To the first 

 category belong the experiments of Regaud and Cremieu ('12). 

 They made the thymus atrophic, especially the cortical portion 

 of it, by x-ray irradiation, but they did not observe any abnor- 

 mality in the health and growth of the animals so treated. 

 Hewer ('16), however, reports that injury to the thymus by 

 x-ray irradiation results in injury to the function of the testes. 

 "Since complete removal of the thymus has no such effect, and 

 since unhealthy animals never breed well, Hewer must prove 

 that her treatment did more than injure the health of her 

 animals" (Hoskins, '18). 



Under the second category, namely, the action of thymotoxic or 

 thymolytic serum, there are many reports on record. Gilberti 



