William O. Reinhardt 



491 



Results 



The data obtained in this study of the growth of thymus, spleen, and lymph 

 nodes are summarized in tables 1 and 2. A total of 284 animals were em- 

 ployed, divided equally between males and females. Seven age groups were 

 studied, consisting of about 20 animals of each sex. The lymph nodes were not 

 dissected in the newborn animals because of practical difficulties. Study of 



TABLE 1 

 Mean Weights of Thymus, Lymph Nodes, and Spleen of Male Rats 



* Mean weights in milligramsistandard error of the mea 

 integer. 



"(^)- 



All figures expressed to the nearest 



TABLE 2 

 Mean Weights of Thymus, Lymph Nodes, and Spleen of Female Rats 



* As in Table i. 



the standard errors in relation to the number of samples and the size of the 

 means provides an estimate of the amount of variation in these tissues. Such 

 analyses, however, are not to be considered as standards in application to 

 other experiments. They are included here for the purpose of indicating the 

 extent of observed variation in this series of animals and under the conditions 

 employed. 



Figure 1 shows the growth in weight of the thymus gland in both males and 

 females in this series of animals. Each of the points on the curves represents, 

 on the average, the mean of the thymus weights of 20 animals at the various 

 ages indicated. 



