123 8 PHYSIOLOGY 



the first two days after birth. The colostrum is formed only in slight 

 quantities. It is an opalescent fluid, often somewhat yellowish, containing 

 fat globules, which, if the fluid be allowed to stand, form a yellowish layer 

 on the top. Under the microscope, in addition to the fat globules, may be 

 seen the so-called colostrum corpuscles, which consist of multinucleated cells 

 loaded with particles of fat. They are probably leucocytes or phagocytes 

 which have wandered into the alveoli and have taken up fat globules. Some 

 of the corpuscles may be desquamated secretory cells. Colostrum is distin- 

 guished from true milk by containing little or no caseinogen. It contains 

 about 3 per cent, of proteins, namely, lactalbumen and lactoglobulin, which 

 coagulate on boiling. Lactose and salts are present in the same proportions 

 as in ordinary milk. It is popularly supposed to have a laxative effect on 

 the child. 



TABLE SHOWING AMOUNT OF MILK SECRETED BY A NURSING WOMAN. 



INCREASE 



DECREASE 



29th-32nd week 916 grm. 



33rd-36th 909 



37th week 885 



PROPERTIES OF MILK 



Fully formed milk presents certain features which are common to all 

 mammals. These have been chiefly studied in the case of cows' milk. We 

 may therefore deal with the composition of cows' milk and point out later 

 in what respects human milk differs therefrom. Milk forms an opaque 

 white fluid with characteristic odour and sweetish taste. Its specific gravity 

 varies between 1028 and 1034. Its reaction to litmus is neutral, to lacmoid 

 it reacts alkaline, and to phenolphthalein, acid. One hundred cubic centi- 

 metres of fresh milk, when treated with lacmoid, requires 41 c.c. w/10 acid 

 for neutralisation. When treated with phenolphthalein the same amount 

 requires 19-5 n/10 alkali for neutralisation. When exposed to the air milk 

 rapidly undergoes changes in consequence of infection by micro-organisms. 

 The most common of these changes is the formation of lactic acid by the 





