402 PARTURITION. [BOOK iv. 



much as takes place independently of the will, is, in contrast to that 

 of the uterine muscles, obviously a reflex act of a more ordinary 

 kind carried out by means of the spinal cord ; and we may suppose 

 that, though the mere contractions of the uterus may serve as a 

 possible source, the necessary stimulus is supplied by the pressure 

 of the fcetus in the vagina ; in support of this it may be noted that 

 the action becomes much intensified towards the end of labour 

 as the stress and strain caused by the advancing head tell more 

 and more on the external skin. 



971. Hence as we have said the whole act of parturition 

 may with reason be considered as a reflex one. Whether it be 

 wholly a reflex or in a certain sense an automatic one, the act can 

 readily be inhibited by other contemporary actions of the central 

 nervous system. Thus emotions very frequently become a hind- 

 rance to the progress of parturition ; as is well known, the entrance 

 into the bedroom of a stranger often causes for a time the sudden 

 and absolute cessation of 'labour' pains, which previously may 

 have been even violent. Judging from the analogy of micturition, 

 we may suppose that this inhibition of uterine contractions is 

 brought about by an inhibition of the centre in the lumbar cord 

 leading to a sudden cessation of the augmentor action of which 

 we spoke above as far as the uterus itself is concerned, and in a 

 more direct way to a cessation of the contractions of the abdominal 

 muscles. Some observations tend to shew that a region of the 

 bulb exerts such an inhibitory influence ; but the matter needs 

 fuller investigation. 



