PREGNANCY IN ANIMALS 123 



Pregnancy and impregnation. The -character of the 

 food fed not only influences the season for mating, but it 

 also influences what may be termed the degree of the 

 impregnation. This means that the character of the de- 

 velopment in utero is influenced more or less by the physi- 

 cal condition of the parents at the time of mating. It 

 means also that with animals which produce more than 

 one at a birth, the relative number of the progeny will be 

 influenced by the same condition. 



That the first influence referred to is operative has 

 been determined by observation. Similarly it has been 

 ascertained that this influence extends to the male, how- 

 soever the female impregnated may be fed subsequently. 

 It is fair to infer, therefore, that the same is true of the 

 influence of the female at the time of mating. 



But it would seem reasonable to suppose that the 

 sum of the influence exerted by the female prior to the 

 birth period, would be greater than that from the male, 

 not in determining form and other inherited qualities, but 

 in influencing the size of the young animal or animals 

 when born, the relative degree of bone and muscle pos- 

 sessed, and also the vigor of the young animal at that 

 time since these are of necessity influenced by the food 

 fed to the dam while the foetus is in process of de- 

 velopment. 



. That the condition of both parents at the time of 

 mating does influence the numbers of the progeny where 

 more than one is very commonly produced at a birth has 

 also been ascertained by observation. If either parent is 

 reduced in physical vigor, whether from want of sufficient 

 nourishment or from excess of the same, the influence is 

 adverse to relatively numerous progeny. The influence of 

 a diet lacking in succulence acts in the same direction, 

 though sufficiently nourishing. These, of course, are not 

 the only influences that affect prolificacy, but they are 

 among the most potent, though not so potent as inheri- 

 tance. 



