OF LABOUR AND ITS SEQUELtE. 383 



the approach of labour, is contracted, and, as it were, 

 prepared for its separation from the uterus. 



What is usually urged respecting the utmost expan- 

 sion of the uterus, and other similar excitements to 

 labour, is refuted by many circumstances, and, among 

 the rest, by the numerous examples of extra-uterine, 

 whether tubal or ovarian, conceptions, in which, at 

 the expiration of ten months from impregnation, the 

 uterus, notwithstanding its vacuity, is seized with the 

 customary, though indeed fruitless, pains.* 



598. Besides this exciting cause, other very power- 

 ful efficient causes are requisite, as must be manifest 

 from the relation of the ovum to the uterus. 



We are persuaded that the proximate and primary 

 cause, is solely the vita propria of the uterus. (42, 547.) 



Among the remote, the most important appears to be 

 the respiratory effort excited principally by the great 

 connection^ of the intercostal nerve with the rest of the 

 nervous system. 



599. We formerly noticed (582) that, in the latter 

 periods of pregnancy, the uterus somewhat subsided, by 

 which circumstance the form of the abdomen is a little 

 changed and the inconveniences induced during ad- 

 vanced pregnancy in the function of respiration are 

 relieved. At the same time, the vaginal mucus (543) 

 is secreted more abundantly, the vagina itself is re- 

 laxed, the columns of rugae are almost obliterated, 

 and the labia pudendi swell; finally, near the approach 

 of labour, the os uteri gradually dilates into a circular 

 opening. 



* I have recorded a remarkable instance of this kind in the Comment. Soc 

 Scifnt. Gottingent. Vol. viii. 



t v. Camper, Tiemomt. (mat. pathol. L. H. p. 9. 



