574 THE PHYSIOLOGY OF REPRODUCTION 



uterine segment) upon the surrounding nerve ganglia. Supposing 

 this conclusion to be correct as applied to the bat, it is not quite 

 clear that it is equally applicable to the human female and to other 

 animals. 



(5) Simpson 1 and others were of opinion that the " pains " of 

 labour were the indirect result of a partial separation of foetus and 

 decidua, brought about by the fatty degeneration of the latter in 

 the last stages of pregnancy, so that the foetus became virtually 

 converted into a foreign body, which caused the uterus to respond 

 accordingly. It is true that part of the maternal placenta undergoes 

 degenerative changes towards the end of pregnancy, but there is no 

 evidence that this by itself is sufficient to cause a separation of the 

 foetus from the uterine wall. 



(6) There is no evidence in support of the theory that the 

 exciting cause of parturition is an accumulation of carbon dioxide 

 in the blood, beyond the fact demonstrated by Brown-Se'quard, 2 

 Keiffer, 3 and others, that uterine contractions can be induced 

 experimentally by this means. 



(7) Spiegelberg 4 put forward the theory that parturition was 

 brought about through the action of substances secreted by the 

 foetus and passed into the maternal blood. These hypothetical 

 substances, which appear to have been comparable to Starling's 

 hormones, were supposed to act on the uterine centre in the spinal 

 cord. Spiegelljerg suggested, further, that the exciting substances 

 were elaborated as a result of an insufficiency of nutrition, and were 

 an indication that the mature foetus required other sustenance than 

 that supplied to it through the placenta. This theory appears to be 

 devoid of all experimental basis, but it is not opposed by any of the 

 known facts. 5 



(8) Tyler Smith, 6 Minot, 7 Beard, 8 and others have held the view 

 that there is a connection between parturition and menstruation, the 

 two processes being physiologically homologous. According to this 

 theory, there is an increased tendency towards uterine contractions 



1 Simpson, loc. cit. 



2 Brown-Sequard, Experimental Researches, English translation, London, 

 1853. 



3 Keiffer, loc. cit. 



4 Spiegelberg, "Die Dauer der Geburt," Lehrbuch der Geburtshiilfe, vol. ii., 

 1891. 



6 Van der Heide states that he induced labour pains at full term in 

 pregnant women by injecting foetal blood-serum. According to the same 

 author the maternal blood of rats in late pregnancy contains -substances toxic 

 to non-pregnant animals (Jour, ^fed. Research, vol. xxix., 1914). 



6 Tyler Smith, Parturition and the Principles and Practice of Obstetrics, 

 London, 1849. 



7 Minot, "Uterus and Embryo," Jour, of Morph., vol. ii., 1889. "Human 

 Embryology." 



* Beard, The Span of Gestation and the Cause of Birth, Jena, 1897. 



