12 MILK- ANALYSIS. 



nearly neutral to test-paper, but is very apt to turn sour 

 from very slight causes. 



Milk exhibits great constancy of composition ; the effect of 

 variations in the diet of the cow showing itself in the amount 

 of the secretion rather than in its quality. This is very 

 strikingly manifested on making a comparison of the milk 

 yielded by the poor and ill-fed Bengali cow in India with 

 that given by our own highly-fed beasts in this country. 

 Dr. Macnamara's analyses of the milk of the Bengali cows 

 show that it hardly differs from the milk of English cows in 

 quality, whereas in quantity it differs greatly, the yield of 

 milk from the former being a small fraction only of that 

 from the latter. The milk of an animal has probably very 

 much the same constancy of composition as the blood of the 

 animal. It is well known that, by administering water to an 

 animal, we are not able to dilute its blood to any considerable 

 extent. Instead of telling on the blood, the water tells on 

 the perspiration or on the urine, so that from containing four 

 or five per cent, of solids, the urine may become so dilute as 

 to contain only one per cent, of solids. The milk resembles 

 the blood in this respect, and is in contrast with the urine ; 

 and by giving an animal an excess of water we do not dilute 

 its milk, but its urine. 



As will be readily comprehended, this constancy of com- 

 position is a cardinal fact in milk analysis. If milk were 

 variable in strength, as urine is, chemical analysis would fail 

 to detect the watering of milk. That milk is a secretion of 

 constant, or only slightly varying composition, lies at the 

 very root of the subject of this treatise. 



In Chapter JfX., on " The Ailk Supply of the London 

 Workhouses" the experimental evidence bearing upon this 

 question is minutely entered into. 



