42 



CHAPTER IV. 



MILK. 



THE milk is a white,, fatty, and rather thick fluid, which is 

 secreted by the female breasts during pregnancy and after 

 delivery. A metastatic or vicarious secretion of milk from 

 the skin, the navel, the groin, the stomach, the intestines, the 

 mucous surface of the genital organs, or the axilla, is by no 

 means rare : it has also been observed in the breasts of men. 



General physico-chemical characters of the milk. 



Perfectly fresh milk has always a decidedly alkaline reaction, 

 and it retains this property for a longer or shorter time : the 

 milk of women retains its alkaline reaction longer than that of 

 cows ; and the milk of healthy women longer than that of in- 

 valids. 



On examining the milk under the microscope we perceive a 

 great number of fat-vesicles of very different sizes swimming in 

 a clear fluid, and occasionally epithelium-cells. From repeated 

 comparisons I have found that the fat-vesicles in the milk of 

 woman are generally rather larger than those in the milk of 

 the cow. In addition to these fat-vesicles, we observe, under 

 certain circumstances, other microscopic objects, of which I shall 

 treat subsequently. The fat-vesicles have, as Raspail declared, 

 a solid envelope, a point which has been confirmed beyond dis- 

 pute by Henle and myself. Easpail considers that it is com- 

 posed of coagulated albumen ; it is, however, more than probable 

 that it consists of coagulated casein. Henle 1 has shown that 

 this capsule may be dissolved by acetic acid, and that butter 

 then issues from it ; it is probable, however, that this fluid fat 

 becomes inclosed in a new envelope, for Ascherson 2 has observed 



1 Froriep's Notizen, 1839, No. 449. 



2 Ueber die Hautdriisen der Frosche und iiber die Bedeutung der Fettstoffe, 

 Miiller's Archiv. 1840. 



