376 E. G. HOSKINS 



were reported by Basch, Klose and Matti. Pappenheimer (1914) re- 

 ported the results of a careful research upon rats. In order to prove 

 that the thymus was completely removed, the tissues of the neck and the 

 upper half of the thorax were sectioned serially and examined micro- 

 scopically. The results were purely negative, definitely proving that 

 in .the rat, at least, the thymus gland plays no vital part. 



Park and McClure in 1919 published an admirable resume and 

 analysis of the literature on thymectomy up to that date. To those who 

 are desirous of a more extensive discussion than that herein presented, 

 Park and McClure's paper is especially commended. These investiga- 

 tors added the results of an extensive series of thymectomies of their 

 own. Dogs served as subjects. The thymus was removed from 75 puppies 

 varying in age from 9 days to 7 weeks. The early post-operative mor- 

 tality was high, so that the series was soon reduced to 24 thymectomized 

 and 19 control dogs from 14 different litters. Each experimental animal 

 had a litter control and, in all but three of the 14 litters, an individual 

 control animal was available. The animals were observed for a period 

 of from 1 to 15 months. Especial attention was devoted to diet and to 

 hygiene. In the whole series of 75 animals the mortality was 13 per 

 cent greater in the experimental than in the control dogs. Of the thy- 

 mectomized dogs that failed to survive, 82 per cent died within two months, 

 i. e., within Klose' s "latent period" when thymectomy per se was supposed 

 to give no serious results. Considering the necessary severity of the 

 operation, the striking feature of these findings is that the mortality 

 was so nearly the same in the experimental and in the control animals. 

 With one possible exception, the authors were able to offer plausible ex- 

 planations other than deprivation of the thymus gland for the sickness 

 and death of all the thymectomized dogs. Ten of the thymectomized ani- 

 mals remained well throughout the course of the experiment ; they were 

 observed from 7 to 15 months. The authors were unable to determine 

 that the operation resulted in any significant depression of growth or 

 development. Neither did the thymectomy result in rickets or any skele- 

 tal disorder. The thyroid, suprarenals, and testes or ovaries were es- 

 sentially alike in both the normal and control series. The authors con- 

 chide definitely that the thymus gland is not essential to life. Thymus 

 function plays no necessary part in the process of ossification. Neither 

 is it essential for the normal growth and development of the hair, teeth, 

 and muscles, nor for normal intelligence. The possibility, however, that 

 thymectomy may cause delayed closure of the epiphyses was not entirely 

 excluded. 



As a result of their own studies and of the analysis of the literature, 

 Park and McClure point out that "there are other explanations than de- 

 privation of thymus function for the symptoms and pathologic changes 

 which have been reported in thymectomized animals, and that those ex- 



