316 E. R. HOSKINS 



rant, Gudernatsch, Cotroni, Hewitt, Romeis, Lenhart), is in many 

 cases possibly a general toxic effect, which is produced whenever 

 the dosage is too high. Even a high protein diet, e.g., an ex- 

 cessive meat diet, may likewise be detrimental to growth, as 

 has been shown for the albino rat by Chalmers Watson ('06). 



2. Head 



Data for percentage weights of head (and other organs and 

 parts) are found for females in table 8, and for males in table 

 9. Absolute weights are given in tables 6 and 7. 



a. Controls. The head forms an average of 9.5 per cent of 

 the body weight in the females and 8.3 per cent in the males 

 among my younger control rats. In the older groups, the head 

 averages 10.3 per cent in the females, and 8.4 per cent in the 

 males. These results are in general somewhat lower than those 

 obtained by Jackson ('13, '15). 



h. Thyroid group. The head averages very slightly heavier 

 in both females and males to which thyroid was fed. The dif- 

 ference is probably insignificant. 



c. Thymus, hypophysis and pineal groups. The head in these 

 groups shows no constant variation from the controls in either 

 direction. The few small differences are probably not significant. 



3. Eviscerated Body {Tables 6 to 9) 



a. Controls. The eviscerated body forms an average of 80 

 to 84 per cent of the net body weight in both males and females. 

 This part of the body contains the muscles, skin, skeleton, body- 

 fat, great vessels, lymph nodes, and spinal cord. 



h. Thyroid group. The eviscerated body in all rats of both 

 sexes (excepting 3 old males, in which the dosage was slight) 

 is about 4 per cent less in relative (percentage) weight than 

 that of the controls. This loss is due probably to loss of fat, 

 which is a well-known effect of thyroid-feeding, especially with 

 high dosage. A comparison of the body weights and body 

 lengths in the control (muscle-fed) and thjrroid groups shows a 



