INNERVATION OF THE GENERATIVE ORGANS 565 



stimulation of the medulla caused the movements of the uterus 

 to cease. Moreover, it is to some extent borne out by the fact that 

 the " pains " of labour can often be inhibited by emotions and other 

 contemporary actions of the central nervous system (see below, p. 572). 



It is well known that' uterine contraction can be induced by the 

 presence of a foreign body in the uterus, by injections into the 

 rectum, by the application of the child to the breast, and by various 

 other means. . According- to Kurdinowski^ the sensation of any 

 violent pain may cause uterine contraction in animals, and the organ 

 may respond to remote stimulation (e.g. in the ears). These observa- 

 tions alone are sufficient to show that the contraction is often a reflex 

 act. The experimental evidence cited above shows no less clearly 

 that the controlling centre is in the lumbar portion of the spinal 

 cord. Nevertheless there are many indications, as just mentioned, 

 that the movements of the uterus can be brought under the influence 

 of a higher centre situated in the brain. On the other hand, the 

 fact that rhythmical contractions can continue to occur in the absence 

 of all nervous connections is a certain proof that they are primarily 

 independent of • the central nervQus system, although normally they 

 are to a large extent influenced by it. It must be concluded, 

 therefore, that the power to contract and relax rhythmically is an 

 inherent property of the uterus. 



The question as to the nature of the mechanism involved in 

 uterine contraction is inseparably connected with the further 

 problem concerning the part played by nervous influence in 

 controlling the course of parturition. This subject is dealt with 

 below (p. 570). 



The Normal Course of Parturition in the Human Female 



The increased size of the foetus, together 'with the accumulation of 

 the amniotic fluid, causes the uterus towards the end of pregnancy to 

 become considerably distended. The enlargement is still further 

 increased by, the growth of the uterine wall itself. Partly as a 

 consequence of this enlargement the waves of contraction which 

 were present at the ^beginning of pregnancy, or even previously, as 

 above described, become much more marked, but are still unaccom- 

 panied by painful sensation. With the onset of labour, however, 

 these unconscious painless contractions are replaced by others of 

 increasing intensity, and in the human subject distinctly affecting 

 consciousness and giving rise to severe suffering. These are the 

 " labour pains " which bring about the dilatation of the cervix uteri 

 and lead to the expulsion of the child followed by the placenta. 



^ Kurdinowski, " Ueber die Eeflectorische Wechselbeziehung zwischen den 

 Brustdriisen und dem Uterus," Arch. f. Gynak., vol. Ixxxi., 1907. 



