:J82 J 



SECT. XLI. 



OF LABOUR AND ITS SEQUELAE. 



594. THE foetus, formed by the powers already de- 

 scribed, and having reached the period of full maturity, 

 has to come into the world by means of labour.* 



595. This critical period occurs naturally (and phy- 

 siology treats solely of natural occurrences) at the end 

 of the tenth lunar month from conception, i. e. about 

 the 39th or 40th week. 



596. At that time, the pregnant woman is impelled 

 to bring forth by an absolute necessity, less under the 

 influence of the will than any other voluntary function 

 (287). 



597. Physiologists have differed in their explana- 

 tions of the causes of so determinate and sudden an 

 event. After all, the exciting cause of labour must 

 be ascribed to an established law of nature, hitherto 

 equally inexplicable as so many other periodical phe- 

 nomena; v. c. the metamorphosis of insects, the stages 

 of exanthematic fevers, crises, &c. &c. nor has the 

 mature ovum been inaptly compared, cceteris paribus, 

 to fruit, which, when ripe, falls almost spontaneously 

 to the ground, from the constriction of those vessels 

 which previously conveyed its nourishment. And in 

 fact it has been remarked that the human placenta, at 



* J. J. Homer, Pnrtus naturalis bre vis expositio. Getting. 1786. 8vo. 



