660 REPRODUCTION. 



sels, to be afterward discharged by the excretory organs of the mother. 

 The mother may therefore be affected by influences derived from the 

 foatus. It has been observed in animals, that when the female has two 

 successive litters of young by different males, the young of the second 

 litter will sometimes bear marks resembling those of the first male. In 

 these instances, the influence which produces the mark is transmitted 

 by the first male to the foetus, from the foetus to the mother, and from 

 the mother to the foetus of the second litter. 



It is probably through the placental circulation that shocks or injuries 

 inflicted on the mother produce disturbances in the nutrition of the foetus. 

 There is little room for doubt that various deformities and deficiencies 

 of the foetus, conformably to the popular belief, may originate from ner- 

 vous impressions experienced by the mother. The mode in which these 

 influences are conveyed is not always easy of explanation. But it is 

 well known that nervous impressions in the adult will often cause local 

 derangement of the circulation, through the vasomotor system, in the 

 brain, the lungs, or the skin. The uterine circulation is peculiarly sus- 

 ceptible to similar influences, as shown in cases of amenorrhoea and 

 menorrhagia. If a nervous shock to the mother may excite premature 

 contraction in a pregnant uterus and consequent abortion, it is un- 

 doubtedly capable of causing partial or temporary disturbances of its 

 vascularity. But the foetal circulation is dependent, in great measure, 

 on the maternal ; and, as the nutrition of the foetus is provided for by 

 the placenta, it will suffer from derangement of the placental circula- 

 tion. These effects may be manifested either in the general atrophy 

 and death of the foetus, or in the imperfect development of particular 

 parts ; as in the adult a morbid action may either operate on the entire 

 system, or be limited to some organ especially sensitive to its influence. 



