494 Lymph Nodes, Thymus, and Spleen 



animal economy. The relationship may be made clearer by comparative studies 

 of the effects, on lymph nodes and spleen, of endocrine imbalances and dietary 

 disturbances which are already known to affect the thymus gland. 



The Effect of Fasting and Exposure to Cold on the Weights of 

 Thymus, Lymph Nodes, and Spleen 



The following experiments are included to show the extent to which disturbed 

 nutrition will influence the weights of the structures under consideration. 

 Fasting is well known as a stimulus which will cause rapid weight involution 



TABLE 3 

 Effect of Fasting on the Weights of Thymus, Lymph Nodes and Spleen 



IN Male Rats 



* Weight of the tissues in milligrams. Figures in parentheses indicate ranges. 



of the thymus gland. It was thought probable that the lymph nodes might be 

 affected in a similar manner. Normal male rats of this colony, 80 days of age, 

 were subjected to fasting for a period of five days. The animals had access only 

 to tap water for drinking purposes. At the end of this time, normal control fed 

 animals of the same age were autopsied at the same time as the experimental 

 animals. A further group was fasted for five days and then refed the regular diet 

 for three days. Data are given in table 3. The findings have been confirmed 

 in subsequent experiments. The lymph nodes dissected included the com- 

 bined cervical, axillary, mediastinal, and retroperitoneal abdominal nodes, 

 and the mesenteric nodes which are noted separately. 



Thymus, lymph nodes, and spleen, as can be seen by examination of this 

 table, undergo a marked diminution in weight subsequent to a period of 

 fasting. Refeeding restores these structures to an approximately normal weight 

 even though the animals have not regained their original body weight. This 

 contributes direct evidence that not only thymus but also lymph nodes and 

 spleen respond to the withdrawal of food by marked decrease in weight. 



A further experiment to demonstrate the gross reaction of these organs to 

 sudden and profound changes in environment was carried out by exposure of 



