372 K G. HOSKINS 



significance of llis experiments is the demonstration that thymus extirpa- 

 tion is feasible. The details of technique which he worked out have been 

 widely utilized by other investigators. 



The next important contribution was made by Langerhans and Save- 

 liew (1893). They performed thymectomy on 29 rabbits from 3 to 5 

 weeks old and on 2 dogs. Three of the rabbits were discarded from the 

 series because the gland was incompletely removed; 6 died of immediate 

 trauma, and 9 within the first twelve days. Nine of the rabbits remained 

 alive and apparently normal for a considerable period. In none of the 

 animals did significant changes result from the thymus extirpation. 



Tarulli and Lo Monaco (1897) repeated the thymus extirpation experi- 

 ments, using puppies and chickens as subjects. In the dogs they noted 

 a decrease in the number of red-blood corpuscles and hemoglobin per- 

 centage, as well as a slight increase in the number of leucocytes. These 

 changes appeared within a few days after the operation, but in three or 

 four months the blood again became normal. A retardation in growth was 

 apparent for a month or two, and associated with this was a depression 

 of general bodily strength. The nutrition of the hair also appeared to be 

 interfered with. Such conditions might have all resulted directly or 

 indirectly merely from the incidental trauma. In case of the chickens, no 

 symptoms resulted which could be ascribed to loss of the thymus, per se. 



At about this time several investigators made studies of the results of 

 thymectomy in frogs. Abelous and Billard (1896) reported that in 

 their series no frogs survived extirpation of both lobes of the gland for 

 more than two weeks. Within one or two days after the operation the 

 animals showed muscular weakness and gradually developed paralysis, 

 loss of color of the skin, ulcers, progressive anemia, and ultimate edema 

 and death. Transference of blood into a normal animal from an animal 

 reacting to thymectomy caused the development of similar symptoms and 

 ultimate death. Transplantation of a piece of thymus tissue into a 

 thymectomized frog in some cases caused the skin to assume a more 

 normal color but failed to prevent death. Extracts of calf thymus had a 

 similar effect on the skin and resulted in a change from muscular weak- 

 ness to hyperexcitability. The conclusion was reached that in the frog 

 the thymus is essential to life and the theory was advanced that the organ 

 elaborates a substance which protects the animal from toxins formed in 

 the normal metabolic processes. Camia (1900) was the only investigator 

 who was able to confirm the results of Abelous and Billard. 



Ver Eecke (1899) repeated the extirpation experiments and reported 

 the significant observation that proper attention to hygienic conditions 

 prevented the appearance of severe symptoms following the operation.. 

 Animals which had developed a considerable degree of the symptomatology 

 described by Abelous and Billard recovered when kept in frequently 

 changed fresh water. It is probable, therefore, that these latter observers; 



