CHAPTER 12 



GROWTH IN WEIGHT OF PARTS AND SYSTEMS OF 



THE BODY 



1. Growth of parts. 2. Growth of systems. 3. Weight of cranium. 



1. Growth of parts of the body. For the general conditions 

 under which these observations were made by Jackson and 

 Lowrey ('12), see pp. 73-74. 



Five Norways only were examined, these having been trapped 

 in barns at the University of Missouri. They were probably 

 living on grain. As will be seen by reference to table 82 the 

 smallest of these, a male, weighed 65 grams and was therefore 

 probably from three to five weeks old. The percentage rela- 

 tions of the several parts of the body are given in table 82. 



TABLE 82 



Norway rat — Percentage weights of head, trunk and extremities. 

 (Jackson and Lowrey, '18) 



Sexes combined 



' Including gravid uterus, which weighed 13.76 grams. 



On comparing the relative values here given with those for the 

 albino rat (see p. 74) it appears that for corresponding body 

 weights the average values for the fore limbs and hind limbs are 

 low, while those for the trunk are high — a relation which might 

 be expected in view of the greater body length of the Norway — 

 see tables 49 and 82. 



195 



