Dr. Lyon Playfair on the Milk of the Cow. 293 



either perform some new functions in the system, or are sepa- 

 rated from it; but we are entirely ignorant how these secre- 

 tions are produced. Scherer has indeed pointed out that al- 

 bumen may be converted into casein by digestion with caustic 

 potash ; and it is possible that this may be the process em- 

 ployed to form it in the organism. On this view, we might 

 suppose that the waste of the tissues operated indirectly in its 

 production. By their waste their alkaline constituents are libe- 

 rated, and might act upon the albumen of the blood by con- 

 verting it into casein. Be this as it may, there are many facts 

 which induce us to believe that the waste of the tissues does 

 favour the production of casein in the milk. The milk of a 

 cow, fed in the stall, is not only absolutely but relatively 

 poorer in casein than one fed in the field, where exercise in- 

 creases the transformation of its tissues. During parturition 

 all the muscles are thrown into a violent state of action. As 

 the labour in a cow continues for many hours, there must be 

 a great waste of tissues in the production of the force neces- 

 sary to occasion these muscular exertions. Such being the 

 case, if our view be correct there ought to be in the milk of 

 a cow, immediately after parturition, an abundance of casein : 

 and every one knows that such milk is quite thick with 

 cheese. We are indebted to Boussingault for an analysis of 

 the milk of a cow before the calf had been allowed to suck. 

 He found it to contain as much as 1 5 per cent, of casein, while 

 the milk of the same cow analysed a few days after its calving 

 contained only 3 per cent, of the same substance ; therefore 

 only one-fifth the quantity*. If then the waste of the tissues 

 tends, directly or indirectly, to increase the amount of casein 

 in the milk, then we are at no loss to understand why the milk 

 of the second day should be unusually rich in casein. 



Beans contain 31 per cent, of casein ready formed. Hence 

 it is that they have been found so practically useful in aiding 

 the formation of the milk. 



The conditions necessary for the production of casein in 

 the milk, are different from those which are favourable to the 

 formation of butter. When butter is the principal object 

 desired, the cow cannot be put upon too rich pastures. But 

 in all cheese districts, it is agreed that poor land is best 

 adapted for cheese. Land is called poor, not when the grass 

 is deficient in nitrogenous bodies, but in constituents desti- 



* It might be objected to the view given, that the analysis of this milk 

 indicates a very small amount of inorganic ingredients. Boussingault found 

 only 0-3 per cent. To this it may be answered, that the alkalies which 

 favoured the formation of casein are soluble, and therefore were neglected 

 in Boussingault's analysis, by being included along with the sugar of milk. 

 {Ann. de Ch. et de Phys. lxxi. p. 72.) 



