PARTURITION— PUERPERIUM— LACTATION S>s 



existence as well as a large number of new ducts. After the 

 second month the breasts are said to offer a nodular sensation 

 on palpation, this being due to the growth of the mammary 

 alveoli. The nipples also enlarge and become more erectile and 

 are often pigmented, while the tissue surrounding the nipples 

 becomes broader and likewise pigmented. The hypertrophy 

 of the sebaceous glands in the immediate vicinity results in the 

 formation of the so-called glands of Montgomery, which appear 

 as small rounded elevations. A slight amount of milky fluid 

 may occasionally be secreted even in the earlier months of 

 pregnancy, but true milk is not produced until after parturition 

 (see above, p. 74). On the first two or three days after parturi- 

 tion the fluid is thick and of a yellow colour. It is said to have a 

 purging effect on the infant, who consequently loses weight, to 

 be made up for a week or two later, when the mammary secretion 

 has all the properties and composition of normal milk. 



The fluid which is obtained from the breasts on the first 

 two or three days after parturition is called colostrum. It is 

 produced in only small quantities. The yellow colour is due 

 to fat globules (which, if the fluid is permitted to stand, form 

 a layer on the top) along with multinucleated cells loaded with 

 fat particles and know^n as colostrum corpuscles. These cells 

 are probably phagocytes which have made their way into the 

 mammary alveoli, but some may be desquamated epithelial 

 cells. Colostrum is similar to milk in composition, but contains 

 little or no caseinogen, which is the chief protein of milk, and 

 in the presence of the rennet ferment of the stomach, together 

 with lime salts, becomes converted into the insoluble casein 

 or curd of milk. (The curd also contains the fat globules which 

 are enclosed in its meshes.) 



Two other proteins are also present in milk — lactalbumen 

 and lactoglobulin. The sugar in the milk is lactose. In addition 

 to the fat globules, which are held in suspension, the milk con- 

 tains various salts, such as calcium, sodium, and potassium as 

 chlorides and phosphates. Broadly speaking, the milk of each 

 species contains all those constituents which are necessary for 

 nourishing and supporting the growing young. Thus Bunge 

 has shown that the proportion of inorganic salts present in milk, 

 while differing from those found in the blood plasma, are almost 

 identical with those occurring in the new-born animal. 



