254 PHYSIOLOGY CHAP. 



subject, published by Silvansky (1897), D'Erchia (1898), and 

 Raineri (1903), were followed by a more complete account by 

 Stolper and Hermann (1904), who endeavoured to explain the 

 origin of the proliferation of the intima which causes the 

 puerperal involution of the uterine arteries in guinea-pigs. 



Almost at the same time Piana (1903), when treating of the 

 same subject, enunciated views diametrically opposed to those 

 of the above-named authors. According to him, tKe enormous 

 enlargement of the uterine arteries in the guinea-pig during 

 pregnancy is not due to dilatation of the lumen of the vessel, but 

 to cellular proliferation of all the strata of its walls, more especially 

 of the intima and the endothelium, from which large lymphoid 

 cells are developed, some by karyokinesis, having numerous smaller 

 elements with nuclei staining deeply which gradually become 

 detached and mingle with the circulating blood. On the ground 

 of these discoveries he set up the hypothesis that the uterine 

 arteries of the guinea-pig assume during pregnancy a haemopoietic 

 function, which gradually comes to an end during the puerperium 

 in proportion as the process of involution in the vessels advances, 

 and the uterus returns to its ordinary pre-gravid state. 



La Torre (1907) repeated Piana's investigations with the 

 greatest care, verified the results, but did not consider Piana's 

 theories proved by them. Thus with reference to this interesting 

 subject we have not a few facts of uncertain significance which 

 have still to be explained by research work differing in method 

 or made on other animals. 



Lactation is of considerable assistance to the regular puerperal 

 involution of the uterus, perhaps because the mammary gland 

 utilises the organic materials formed by the retrogressive process 

 of the genital apparatus. 



The lacerations and contusions of the perineum, the vagina 

 and the cervix, caused by the passage of the infant through the 

 relatively narrow channel, heal during the first few days of the 

 puerperium. The large wound in the endometrium, which is due 

 to the detachment of the after-birth, and on account of which 

 the condition of the recently confined woman has frequently been 

 compared to that of a patient who has undergone an amputation, 

 is completely healed in about three weeks by a special process of 

 repair. We mentioned that the superficial stratum of the decidua 

 is detached and expelled during the after-pains. For the restitutio 

 ad integrum of the large wound resulting from this, a real re- 

 generation of the uterine mucosa and of its epithelial covering 

 must take place. 



During the first period of the puerperium, the residua of the 

 old niucosa are invaded by a great number of leucocytes, which 

 form a barrier of granulation tissue towards the surface. The 

 external strata of the decidua become necrosed, are eliminated 



