Dr. Lyon Playfair on the Milk of the Cow. 295 



minished the amount of oxygen respired, and was then fed 

 upon gruel (oatmeal and water). On the 21st sufficient milk 

 for analysis was procured. 



23*9450 100*00 

 The butter in this milk was therefore quite equal to that 

 in the milk of a cow. As the diet thus influences the compo- 

 sition of the milk, may not the frequent occurrence of ricketty 

 children in the higher classes of life be due to the circum- 

 stance of the mothers living principally upon white bread — 

 bread, therefore, from which phosphates have been in a great 

 measure removed ? Had the woman been at her usual ex- 

 ercise, it must of course have diminished. The milk of a 

 woman possesses a very sweet taste, and is remarkable for its 

 great amount of sugar of milk. In this and in other respects 

 it closely resembles that of the ass. The following analyses 

 exhibit the composition of the milk of various animals : — 



Woman. Ass. Cow. 



Before concluding this paper, I take the opportunity of 

 making a few remarks to practical men on the mode of pre- 

 serving milk, as this is a subject on which questions have been 

 often sent to me. 



Milk consists of casein, of sugar of milk, and of certain 

 salts dissolved in water, in which are suspended little globules 

 of fat or butter. These globules are surrounded by a shell or 

 skin, which is supposed (by Otto) to be coagulated casein. The 

 soluble casein, being a nitrogenous body, is very apt to run into 

 putrefaction. In summer it does not do so readily, because 

 the temperature being elevated, the sugar of milk is converted 

 apparently into grape sugar by the agency of lactic acid, then 



* Journal de Pharmacie, xxv. 333 et 401. f Supra. 



X Ann. de Ch. et de Phys. Ixii. 432. 



j| Ann. de Ch. et de Phys- lxxi. 65, 



§ Average of analyses of the milk of a cow in the field. 



