OF THE FOETUS. 341 



is alfo very great, in proportion to the abortions 

 in the fouith, fifth, and fixth months ; becaufe, 

 during this middle term of geftation, the pro- 

 dud of generation having acquired llrength and 

 folidity fufficient to refill the adion of the firft 

 four periodic revolutions, a more violent effort 

 than any of the former is neceflary to deftroy 

 the foetus. For the fame reafon, an abortion is 

 more difficult during the fifth and fixth months. 

 But the foetus, v^-hich till now was weak, and 

 could exert its own force only in a feeble man- 

 ner, begins to move vi'ith more vigour ; and, 

 when the eighth revolution takes place, the efforts 

 of the foetus uniting with thofe of the uterus, and 

 facilitating its exclufion, the foetus may come 

 into the world in the feventh month, and be in 

 a capacity of living, whenever it happens to be 

 unufuaily ftiong at this period. But, if the foe- 

 tus be excluded folely from a weaknefs of the 

 uterus, which renders it unable to refifl: the ac- 

 tion of the blood during the eighth revolution, 

 the birth of it is confidered as an abortion, and 

 the child dies. But fuch cafes are uncommon ; 

 for, if the foetus has refifted the firll feven re- 

 volution?, nothing but particular acciilents can 

 prevent it from refifling the eighth, unlcfs it has 

 acquired more vigour than is common at this 

 period. A foetus which has accjuired the iamc 

 degree of ftrength, but at a later period, will be 

 excluded at the ninth revolution; and thofe whicli 

 require nine months in obtaining this degree of 



Y 3 . ilrcngth, 



