THE EXAMINATION OF MILK 421 



principle as that laid down by Lehmann, which regards as 

 adulteration anything which does not normally belong to 

 the food in question, it is proper that milk having these 

 appearances should be rejected, and steps taken to prevent 

 them. A rough-and-ready, but very useful and effective 

 test, is the rate at which milk goes sour. For practical 

 purposes, it may be said that any milk which goes sour 

 rapidly is a bad milk, although the converse is not neces- 

 sarily true. According to Schatzmann, if a sample of milk 

 be kept for twelve hours at 40° C, and within that time 

 coagulates, it is to some extent defective ; and in nine hours 

 no change whatever should appear to have occurred. The 

 presence of colostrum is a ground for the immediate con- 

 demnation of milk; it can usually be detected by the 

 presence of long elastic yellowish threads. 



The remedy for almost all of these diseases lies above all 

 in cleanliness, both as to the udders and body of the cow, 

 the stable, and the hands of those employed in milking. 

 Clean milk-pans, pure water, and a cool, odourless and 

 clean store-room, are absolutely indispensable. The milk- 

 cans or other utensils are best made of earthenware or 

 well-tinned copper or iron, and they should be thoroughly 

 scalded and cleaned between each change of milk. 



In addition to the faults which arise from specific 

 bacterial causes, milk may be watery in the case of ill-kept 

 and ill-fed cows. Salty milk may be watery (1027 to 1029 

 specific gravity). Salty milk is stated to occur only in 

 connection with inflammation of the udder. It is to be 

 detected not only by its taste and its high percentage of 

 ash, but by its low percentage of milk-sugar. According to 

 Klenze, 2*4 per cent, of small deposits of calcium carbonate 

 in the milk glands may give rise to sandy milk. 



The faults mentioned so far are those which arise for the 

 most part through causes external to the cow, and are 



