TAIL LENGTH 205 



authors. In gravid females a correction was ' made however 

 by subtracting the weight of the uterus and fetuses from the 

 observed value. The weight of the body on the body length is 

 given hi chart 28. 



The body weight values for each millimeter of body length in 

 each sex are given in table 144. The graphs were computed by 

 formulas (5 a) and (5b), and show that for a given body length 

 the female has a greater body weight. Donaldson '09, Donaldson 

 and Hatai, '11. 



Tail length on body length. The method of obtaining the tail 

 length has been given under body length. The values for the 

 graphs in chart 29 and for table 144 were determined by formulas 



TABLE 139 



Ratio of body length (B) divided by tail length (T) in rats reared at different 

 temperatures (Przibram, '23) 



(7) and (8). The tail is generally shorter than the body but in 

 the female is relatively longer than in the male. It seems prob- 

 able that six or seven of the caudal vertebrae are not formed till 

 after birth. 



The relative length of the tail is modified by external tem- 

 perature which hi turn modules the internal temperature. Low 

 temperatures decrease the growth of the tail while high tem- 

 peratures increase it. Thus the ratio of the body length divided 

 by the tail length is modified as in table 139 (Przibram, '22 A-D). 



It is possible also that the greater relative length of the tail in 

 the female may be related to the higher body temperature in the 

 female (Przibram, '22 B). 



