CHAPTER 13 



GROWTH IN TOTAL BODY WEIGHT ON BODY LENGTH 



AND GROWTH IN THE WEIGHT OF PARTS AND 



SYSTEMS OF THE BODY 



1. Total body weight between birth and maturity on body length. 2. Growth 

 of parts. 3. Growth of systems. 4. Weight of cranium. 



1. Total body weight between birth and maturity on body length — • 

 wild Norway rats. Body length on body weight. From the study 

 of 282 male and 318 wild female Norway rats, trapped in Phila- 

 delphia, measurements have been taken for body weight and body 

 length (Donaldson and Hatai, '11). 



The values for body length — sexes combined — on body weight 

 are given by formula (53.) In chart 61 the corresponding graph 

 is given and for comparison the graph for the body length of the 

 Albino is also drawn (see formula 4) . 



At 450 grams the body length of the wild Norway is about 4 

 per cent above that of the Albino. 



It has been found that for a given body weight, the body 

 length is in the male Norway 0.4 per cent above the mean, and 

 in the female 0.4 per cent below (Donaldson and Hatai, '11, p. 

 425). 



Table 187 contains values for body weights and for the tail 

 length and the weights of the brain and the spinal cord computed 

 by the formulas devised by Hatai. 



Body weight on body length. W^hen the formula (53) is trans- 

 formed so as to give the body weight for a given body length and 

 the correction for sex is included, we have for the males formula 

 (54) and for the females formula (55). In chart 62 are given the 

 graphs for both sexes. As in the case of the Albino, the body 

 weight for the male is slightly below that for the female of like 

 body weight. 



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