MILK AS A FOOD 29 



active factory. It takes the fat, the sugar, the albumin, 

 the salts, and other vital elements from the blood and ma- 

 terially changes their physical and chemical nature. Thus 

 the fat is gathered together into little droplets. The sugar is 

 transformed into lactose, which is found nowhere in nature 

 except in milk. The albumin of the blood is transformed 

 into casein, which is also peculiar to milk. Just as a fac- 

 tory receives the raw products at the back door and de- 

 livers the fully formed articles ready for use at the front 

 door, so each little cell receives from the blood certain 

 "raw" products and transforms them into milk. These 

 glandular cells are tremendously active during lactation 

 and soon wear out or die. Large numbers desquamate; 

 that is, they leave the basement membrane of the alveolus 

 to which they are but loosely attached. These cells ap- 

 pear in great numbers in normal milk. 



During milk production there is an increased flow of 

 blood to the gland in order to furnish the materials neces- 

 sary to produce milk. During this congestion some of the 

 white blood corpuscles or leucocytes may leave their capil- 

 laries, squirm into the alveoli, and force their way by virtue 

 of an active amoeboid motion between the secreting gland- 

 ular cells, and thus leucocytes may also appear in the 

 milk. The number of pus cells or leucocytes is greatly 

 increased if the mammary gland is inflamed. The origin, 

 nature, and significance of the cells in milk have consider- 

 able practical importance. In some cities milk containing 

 more than a specified number of "leucocytes" is con- 

 demned, especially if associated with streptococci. This 

 will be discussed later. 



The principal question under dispute is whether the 

 secretion of milk takes place as a result of a considerable 

 destruction of cells and cell nuclei or not. Large numbers 

 of cells appear in normal milk and the consensus of opinion 

 to-day is practically unanimous in considering these cells 

 for the most part as coming from the cast-off glandular 



