BREASTS AND MILK. 381 



When secretion has actually begun, the moulting of the glob- 

 ules is complete, and it is difficult to find in the milk any trace 

 of its cellular origin. The quantity secreted varies, but may be 

 generally estimated at 1.300 litre in 24 hours: the quantity 

 of bile produced is about the same, but the milk contains 

 more solid elements than this latter fluid, the proportion 

 being 12 parts in 100 (while it is only 5 parts in 100 in the 



Fig. 100. Mammary gland during lactation. Milk.* 



bile). These 12 parts are composed nearly in the following 

 manner, at least in the case of women: first, 1.5 grin, of 

 various salts (in 100 grms. of milk), being for the most part 

 baits of the blood, and especially phosphates of lime and 

 potash (a little soda), and a certain quantity of iron; 2 

 grms. of fat or butter ^uiargarine, oleine, etc.) ; this fat is the 

 only physical element in good milk, and appears under the 

 form of small drops of various size, which impart its peculiar 

 white appearance to the milk (emulsion) 3 grms. (in 100 

 grms. of milk) of caseine^ an albuminoid substance 1 , which is 

 coagulable, not by heat, but by the gastric j uice, or by pep- 

 sine, as we saw when studying digestion. The principal 

 element (in woman's milk) is, finally, the sugar of milk, 

 which is in the proportion of 4 parts in 100, or a little more. 



motionless for a considerable time, they pass into a granular state, 

 becoming three or four times larger than when in their normal con- 

 dition; they also absorb fatty globules, more or less 'considerable 

 in size, exactly as the epithelial cells and the leucocytes of the 

 larynx and the trachea are filled, simply by penetration, with 

 granules of lamp-black or other dust. The globules of the colos- 

 trum are formed in a similar manner, but very rapidly. 



* A. Glandular lobule of the mammary gland, with the milk flowing from 

 it. 13, Milk-globules. C, Colostrum, a, Cells with very distinct fatty gran- 

 ules. b t The same, whose nucleus has disappeared. 280 diain. (Virchow.) 



