WILD NORWAY 383 



It is possible then at the present moment to indicate : 



(a) Various characters in which the wild Norway differs from 

 the domesticated Albino. 



(b) Those characters which in the caged or domesticated Nor- 

 way tend to become like those of the domesticated albino and 



(c) Those which — when the Albino is given some of the condi- 

 tions of the wild life — exercise for instance — tend to return to 

 the Norway type. 



(a) Characters in which the wild Norway differs from the do- 

 mesticated Albinos. The wild Norway is more excitable and 

 much more savage. They gnaw their cages. The body weight is 

 less for a given body length, hence it is a slighter animal. The 

 skeleton is relatively heavier, also the suprarenals (both sexes) 

 and the testes and ovaries. On the other hand the thyroid is of 

 like weight and the hypophysis distinctly lighter, in both sexes — ■ 

 this difference being most marked in the female. The brain and 

 the spinal cord are both heavier than in the Albino. The rela- 

 tions are illustrated by the data in table 212. 



Table 212 shows that for a given body weight the wild Norway 

 has a heavier brain both in males and in females. In all groups 

 the difference is more marked in the males, and increases with 

 body weight. All the foregoing relations are found in the case 

 of the spinal cord, only the difference between the sexes is in 

 each group more marked than in the case of the brain. 



In the Norways, as compared with the Albinos, the absolute 

 differences in weight between the sexes is distiactly greater in the 

 case of the brain, but much less in the case of the spinal cord. 

 This brings it about that while the cord in the Norway differs 

 but slightly in weight according to sex, there is in the Albino a 

 distinct sex difference — the female albino having a heavier cord 

 than the male. 



As a result of these relations it is evident that the reduction 

 in weight due to domestication has in the Albino affected the 

 male more than the female in both the brain and spinal cord, 

 and that in the latter case the reduction in the male has been 

 carried so far that the female cord is the heavier. This reduction 

 in the weight of the brain and cord is accompanied by a slight 



