CHAPTER 13 



GROWTH OF ORGANS IN RELATION TO BODY 

 LENGTH NORWAY 



1. Length of tail and weights of body, brain and spinal cord in relation to 

 body length. 2. Weight length ratios. 



1) Length of tail, body weight, brain weight and spinal cord 

 weight in relation to body length. Before passing to the tables on 

 the Norway rat, it should be pointed out that the observations 

 used for them have been made on the Norway rat as found in 

 Philadelphia. At the same time it has been shown that the Nor- 

 way rat taken in Vienna, Paris and London is similar in its gen- 

 eral form to that found in the United States, so that the determi- 

 nations in the tables may be applied to the Norway rat in Europe 

 also (Donaldson, '12). 



Table 85 contains values for the several characters named 

 above, computed by the formulas devised by Hatai; these for- 

 mulas being in turn based on series of observations, the number 

 of which is given in each case. 



Body length on body weight. From the study of 282 male 

 and 318 female Norway rats, trapped in Philadelphia, measure- 

 ments have been taken for body weight and body length (Don- 

 aldson and Hatai, '11). 



The values for body length sexes combined on body weight 

 are given by formula (46). In chart 28 the corresponding graph 

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

 the Albino is also drawn (see formula (1)). 



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). 



Body weight on body length. When the formula (46) 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 

 (47) and for the females formula (48). In chart (29) are given 

 the graphs for both sexes. 



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