Tumor Inoculation 



475 



of widespread metastases, all of the organs enumerated above 

 showed a sharp reduction in weight suggesting an exhaustion. 

 This occurred before the animal exhibited any clinical signs 

 of physical deterioration. 



If, on the other hand, the disease terminated in recovery, the 

 picture presented was quite different. The thyroid invariably 

 showed a hypertrophy which persisted through the early stages 

 of resolution; it then diminished in size but increased again as 

 healing was completed. The suprarenals showed a similar series 

 of changes except that the reduction in size and the secondary 

 increase occurred earlier than the corresponding changes in the 

 thyroid. In these animals, the thymus showed an increase in 

 weight which was proportional to the extent of the growth at 

 the time regression set in and this was a striking feature of the 

 reaction seen in animals capable of controlling the growth of 

 the tumor as compared with those in which the reaction was 

 ineffectual. 



Again, in recovered animals and in animals that had been 

 subjected to repeated inoculations of tumor emulsions (immune 

 animals), the weights of the thyroid, the parathyroids, the 

 thymus, the suprarenals, and the hypophysis were all found to 

 be greater than in normal controls and they apparently retained 

 this increased size indefinitely. 



Finally, a similar series of changes occurred in the super- 

 ficial lymphnodes and in the spleen. The lymphnodes showed 

 an initial hyperplasia and enlargement followed by a terminal 

 atrophy in acutely fatal cases. The spleen, on the other hand, 

 showed comparatively little change during the early stages of 

 the disease but later became enlarged. It was a notable fact that 

 the enlargement was usually proportional to the atrophy of the 

 thymus except in cases of fulminating malignancy where both 

 organs not infrequently showed a reduction in size. 



The alterations described showed clearly that there was an 

 intimate relation between the reaction that occurred in these 

 organs and the malignancy displayed by the tumor or the ability 

 of the animal to control or suppress its growth. Viewed from 

 another standpoint, a similar relation was found to exist be- 

 tween the occurrence of periodic variations in malignancy and 

 the prevailing state of the endocrine mechanism as indicated by 

 the weights of the glands of normal rabbits. For example, 



