330 E. R. HOSKINS 



of the spleen in the rat very high (coefficient of variation aver- 

 aged about 35). His relative (percentage) values for the nor- 

 mal spleen (including all specimens) are also somewhat above 

 the curve derived from Hatai's formula (excluding enlarged 

 specimens), but are considerably lower than mine, excepting 

 the old male group (tables 8 and 9). It is evident that my con- 

 trol spleens are relatively larger than that which is usually con- 

 sidered normal, but it is impossible to say whether or not this 

 is due to normal variability. A study of individual data shows 

 that the weight of the spleen in most rats varies in the same direc- 

 tion as that of the liver. Dr. Hatai of the Wistar Institute 

 has told me that he also has noted such correlation. This fact 

 is in agreement with the doctrine that the spleen functions in 

 furnishing certain materials to the liver for use in general meta- 

 bolism. Sweet and Ellis ('15) state that where digestion is 

 interfered with greatly by removal of the external function of 

 the pancreas, the spleen undergoes marked simple atrophy. 



b. Thyroid groups {tables 6 to 10). In relative weight where 

 the averages of the thyroid groups are compared with the entire 

 control group it is seen that there is an increase in the weight 

 of the spleen of about 25 per cent. According to Donaldson's 

 method of comparison the increase in absolute weight amounts 

 to 41.3 per cent and 15 per cent in the older and younger female 

 groups, and of 86 per cent and 6.4 per cent in the corresponding 

 male groups (table 10). The apparently small increase shown 

 by the younger group of males is due to an unusually large spleen 

 in the control group, in which the liver was also unusually large 

 (as above mentioned). 



c. Thymus, hypophysis, and pineal groups. As might be ex- 

 pected, the spleen in these groups shows considerable variability, 

 but it is probably within the limits of normal variation. There 

 appear decidedly smaller spleens in the thymus-fed male group, 

 but the results are not constant, and of doubtful significance. 



