840 MILK. 



Free gases, and more especially carbonic acid, can always be 

 shown to be present in fresh milk, according to the method already 

 described at p. 330. 



Abnormal constituents have in general been but rarely found 

 to exist in the milk, although our daily experience of the injurious 

 influence exerted by the milk of some women on the children 

 they suckle, and frequently by that of cows on the life of their 

 calves, clearly indicates the existence of chemical metamorphoses 

 in the milk, and the presence within it of certain abnormal 

 substances. Albumen is the most frequent of these abnormal 

 constituents of the milk ; it is present in inflammatory affections 

 of the mammary glands, when the milk contains blood and pus ; 

 and it is perhaps normally present in the contents of the lactiferous 

 ducts in all periods except during lactation ; at all events, Simon 

 found 19'834 of a substance coagulable by heat in the fluid 

 secreted by the udder of an ass, fourteen days before foaling. The 

 colostrum of the cow coagulates on being boiled, but not when 

 treated with rennet. We must not, however, assume that when 

 the milk coagulates on being heated it necessarily contains 

 albumen, for Scherer has obtained a casein from normal milk 

 which coagulated by heat, while both Dumas and Bensch found 

 that the milk of the bitch became pulpy and was even almost 

 completely coagulated on being heated, when the animal had been 

 kept on vegetable food as well as when it was fed on animal matters, 

 while on cooling it very frequently again became thinly fluid. 



Marchand * found dissolved hcematm in the milk of a diseased 

 cow, without, however, being able to detect any blood-corpuscles 

 under the microscope. 



Fibrin occurs in the milk only when the latter contains hlood ; 

 at least, as far as my own experience extends, it is never present 

 except simultaneously with blood-corpuscles, or at least with 

 haematin. 



Reesf has found urea in the milk in Bright' s disease. 



Much was formerly written regarding the passage of foreign 

 substances, as pigments, medicines, and poisons, into the milk, 

 but we have no certain knowledge of any excepting iodide of 

 potassium, which has been found in the milk of women by Peligot 

 as well as by Herberger. 



As in the case of the blood, it will hardly be irrelevant if after 

 this notice of the normal and abnormal constituents of the milk, 



* Journ. f. pr. Chem. Bd. 47, S. 130134. 



t Guy's Hospital Reports. New Series, vol. i., p. 328. 



