THE FEMALE GENERATIVE ORGANS 537 



The Nervous Mechanism of Parturition 



Parturition may be considered as being normally a reflex 

 act, the centre of which is situated in the lumbar region of the 

 spinal cord. On the other hand, it has been shown from experi- 

 ments upon animals that the transmission of impulses through 

 the cord is not absolutely essential to the occurrence of par- 

 turition. 



Simpson (Sir James) ^ removed the spinal cord from the first 

 dorsal vertebra downwards from a number of sows a few days 

 before parturition was due. Some of the animals died as a 

 result of the operation, but in others parturition proceeded 

 normally, excepting that in each case the last foetus of the 

 series was not born. " The uterine contractions proceeding 

 from fundus to cervix were sufficient to expel the foetuses from 

 the uterus ; and each foetus as it came into the vagina was 

 thence extruded by the force transmitted from the foetus behind 

 it ; but when the last foetus came into the vagina it remained 

 there, because there was nothing to transmit the uterine ex- 

 pulsive force, while the vaginal and abdominal muscles, being 

 under the influence of the spinal nerves, had been rendered 

 powerless by the removal of the spinal cord." 



Riemann ^ states that after the destruction of the cord of a 

 cat from the third dorsal vertebra downwards the animal gave 

 birth to a kitten two days subsequently, shortly before its death. 



Rein ' describes experiments upon rabbits in which he 

 severed the uterus from all nervous connection with the cerebro- 

 spinal system, and found afterwards that the mechanism of 

 labour was not destroyed. 



Furthermore, Oser and Schlesinger,* as a result of experi- 

 mental evidence, state that parturition can occur in animals 

 after the severance of the sympathetic nerves which pass to 

 the uterus, but it is difiicult to understand how this operation 



1 Simpson, Selected Obstetric Works, edited by W. H. Black, Edinburgh, 1871. 

 ^ Riemann, " Einige Bemerkungen iiber die Innervation der Gebar- 

 mutter," Arch. f. Oynak., vol. ii., 1871. 



* Kein, "Beitrag zur Lehre von der Innervation des Uterus,'' Pfliiger'a 

 Arckiv, vol. xxiii. 



* Oser and Schlesinger, " Experimentelle Untersuchungen iiber Uterus- 

 bewegungen," Strieker's Med. Jahrbiicher, 1872. 



