256 PHYSIOLOGY CHAP. 



through the canal and replaced by connective tissue. At the 

 same time there occurs in the blind ends of the uterine glands 

 a rapid proliferation of epithelial cells which protrude from the 

 glandular orifices in the form of a semi-fluid mass, rich in nuclei, 

 and regenerate' the epithelial covering of the mucosa (Fig. 111). 



The regeneration of the mucosa and of the uterine epithelium 

 may be considered complete at the end of the third week. During 

 this period the exfoliation of the surface of the endometrium is 

 accompanied by the puerperal flux or discharge of the locliia. This 

 during the first days consists of blood coming from the vessels 

 of the decidua serotina (sanguineous lochia). On the third day 

 the lochia become paler (serous lochia), and are composed of serum, 

 erythrocytes, leucocytes, fragments of decidua and epithelium. 

 After the first week the lochia become greyish white (white or 

 creamy lochia) and consist of mucus from the cervical canal mixed 

 with numerous leucocytes. Finally during the third week the 

 lochia gradually diminish and are reduced to the expulsion of a 

 little transparent mucus. 



The lochia coming from the uterus are normally sterile, 

 inodorous, or with a slight smell from the aseptic secretions ; but 

 during their passage through the vaginal canal and vulva they 

 become mixed with numerous microbes which are found there 

 in considerable numbers, as was first pointed out by Doderlein, 

 and are represented by cocci and bacilli of various kinds, and this 

 gives the vaginal lochia an acrid odour of decomposition. These 

 microbes, however, if they do not ascend to the endometrium, are 

 not absorbed, owing to the defence made against them by the 

 pavement epithelium of the vagina ; hence they do not give rise 

 to general infective phenomena or cause any feverish rise of 

 temperature. 



During this progressive involution of the genital apparatus, 

 the mammary glands enter upon full physiological activity. As 

 we saw in Vol. II. Chap. IX., the state of pregnancy causes 

 vigorous development of the alveoli of the glands. We may add 

 here that the development of the mammae is shown in tumefaction 

 and hyperaemia of the organ, shown externally by a cutaneous 

 network of dilated bluish veins, and also by the lancinating pains 

 noticed by pregnant women. As early as the second month of 

 gestation it is possible to squeeze out of the nipple some drops of 

 colostrum, which increases in quantity as pregnancy advances. 



In the colostrum the microscope shows small drops of fat 

 unequal in size, mixed with exfoliated epithelium from the alveoli 

 of the glands and ducts, and with the so-called corpuscles of the 

 colostrum discovered by Donne ; these corpuscles are merely leuco- 

 cytes which have migrated into the alveoli of the glands and act 

 as phagocytes, enveloping the more minute drops of fat (Fig. 112). 



The secretion of the true milk begins on the second or 



