OF VITAL MOTION. 67 



long is there an absence of contraction in these 

 muscles. 



Nor can the germ be supposed to excite contraction 

 in the uterus, for if so, how is it that these phenomena 

 are deferred to the close of the period of gestation ? 

 The fact is, that the uterus has grown and expanded, 

 so as to adapt itself to the increased size of its con- 

 tents, so long as the mother was able to provide food 

 for the development of her offspring, without pre- 

 judicing the supply necessary for her own system; 

 but when this bound is passed, and the foetus has 

 attained to such a magnitude as to become a source of 

 exhaustion to the mother, then the walls of the uterus 

 begin to contract. The immediate effects of this 

 change will be to constrict the vessels connected with 

 the placenta, and to lower in a proportionate degree 

 the vitality of the foetus, by this check upon its respira- 

 tion. And this lowering of the vitality of the foetus 

 may be supposed to give rise to further contraction in 

 the uterus, for if during the previous nine months, 

 the increase of the womb has been proportionate to the 

 increasing vitality of the foetus, and to all appearance 

 consequent upon this increase, so we may infer that 

 contraction will be commensurate with the decrease. 

 By this uterine contraction, the placental vessels will 

 suffer constriction, and the vitality of the foetus be 

 proportionately reduced, while this reduction will 



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