70 



Mr. Hainan and Dr. Marshall. 



these results for rabbits, but failed to confirm them for guinea-pigs, in which 

 thymectomy is a simple operation. It is not improbable, therefore, that the 

 inhibitory effects of the growth observed by Basch and others were merely 

 post-operative, since they only occurred when the operation of thymectomy 

 was a severe one. 



Gudernatsch states that tadpoles fed upon thymus extract grew to an 

 abnormal size and postponed undergoing metamorphosis. In some cases they 

 did not change into frogs at all, but remained as giant tadpoles. 



Stotsenburg, working upon the effect of ovariotomy on the growth of 

 albino rats, found that this operation caused an increased rate of growth. 

 This appeared to be the case not only after the age of sexual maturity was 

 reached, but prior to the attainment of this age, since the removal of the 

 ovaries appeared to induce an accelerating effect forthwith. 



Lastly, Miss Hewer in a recent paper states that it is possible to induce 

 a hyperthymic condition in rats by feeding these animals upon fresh thymus 

 or upon thymus tabloids, and that this condition is accompanied by partial 

 or complete sterility, the spermatogenetic tissue in the testes ceasing to be 

 active or even undergoing atrophy. It is to be noted that these results are 

 directly contrary to Paton's theory of a compensatory mechanism between 

 the thymus and the testis. 



Record of Experiments with Guinea-pigs. 



The experiments described below were undertaken to put on a more 

 quantitative basis the results obtained by Noel Paton in a previous paper, 

 and form, with a few minor differences, a repetition of his work on the 

 subject. 



In the control thymectomies (pseudo-thymectomies) the thymus glands 

 were exposed without being removed, and the neck afterwards sewn up in 

 the usual way so as to make the operation resemble as nearly as possible an 

 actual thymectomy. In the vasectomy experiments a portion of each vas 

 deferens was removed, but the vascular supply of the testes was not 

 interfered with. 



The guinea-pigs were housed in roomy wire cages and given a liberal diet 

 of oats, bran, and roots, varied occasionally with green food as circumstances 

 permitted. The normal animals were housed in the same cages as the 

 experimental ones, thus ensuring uniformity of external conditions for both 

 sets of animals. With the exception of one experiment all the animals used 

 were males. 



Experiment 1 : Effect of the Removal of the Testes upon the Weight of the 

 Thymus and the Growth of the Animal. — In this experiment, 12 male guinea- 



