REPRODUCTION. 4*1 



membrane of the uterus from the placenta outward and for a considerable 

 depth is gradually torn free from the deeper parts through the spongy layer, 

 and with the attached chorion and amnion follows the placenta. As a rule, 

 this after-birth appears at the vulva within fifteen minutes after the expulsion 

 of the child; it consists of the placenta, the amnion, the chorion, the deddua 

 reflexa, and a considerable portion of the <le<-i<ln<t r<r<t. 



Previous to the third stage slight bleeding from laceration of the passages 

 occurs. But with the loosening of the placenta and the accompanying rupture 

 of the placental vessels the maternal blood flows freely and continue- to flow 

 from the uterine wall, chiefly from the placental area, until the after-birth is 

 discharged. The average loss of blood amounts to about 400 grams. At the 

 close of the third stage of labor the uterine contractions have so far proceeded 

 that the organ is compressed into a hard compact mass, the ruptured vessels 

 are contorted and compressed, and the bleeding is thereby largely stopped. 

 For several hours, however, slight hemorrhage continues as an accompaniment 

 of the post-partum contractions, but finally this ceases with the formation of a 

 blood-clot over the wounded surface. 



The third stage of labor may continue through one or two hours. It is 

 customary, however, for the obstetrician speedily to put an end to it by assist- 

 ing the removal of the after-birth. 



Nature of Labor. — Our knowledge of the nature of the muscular phe- 

 nomena of labor is incomplete. The uterine contractions are in part automatic 

 and in part reflex, but to what extent the former, and to what the latter, is not 

 known. Rein 1 found that in the rabbit after section of all uterine nerves 

 normal conception, pregnancy, and birth may occur, [n some animal- uterine 

 movements may continue after removal of the organ from the body. Such 

 and other observations indicate the existence of an automatic contractile power 

 resident in the organ itself. Since nerve-cells are not found in its walls, it 

 seems probable that the automatism resides in the muscle tissue. The uterus 

 is, moreover, very sensitive to direct stimulation, even after excision. In ani- 

 mals higher than rabbits a connection with the lumbar spinal cord seems 

 essential to normal labor. Goltz 2 obtained in dogs conception, pregnancy, and 

 delivery after section of the spinal cord at the height of the first lumbar 

 vertebra. In paraplegic women, with conduction in the cord broken in the 

 dorsal region, delivery is possible. A centre tor uterine contraction must 

 hence be supposed to exist in the lumbar cord. Centripetal and centrifugal 

 fibres exist in both sympathetic and spinal uerves, and reflex uterine contrac- 

 tions are readily obtained by stimulation of the central end- of the divided 

 nerve-trunks. According to Langley and Anderson, 3 in the cat :nid the rab- 



bit both the longitudinal and the circular muscular coats and the arteries of 

 the uterus are supplied with motor nerve-fibres mainly by the third, fourth, 

 and fifth lumbar nerves; the fibres pas- to the sympathetic system, and 



'<;. Rein: PfiUger'B Archiv fur die gesammte Physiologic, 1880, \.\iii. 

 2 Fr. Goltz: Ibid., 1874, ix. 



8 Langley and Anderson: Journal of Physiology, 1895 96, six. p. 122. 

 Vol. II.— 31 



