52 SCIENCE AND PRACTICE OF DAIRYING. 



of milk has become common, and the necessity of taking suitable 

 precautions has become recognized, the more rarely have such milk 

 defects shown themselves. They still exist in various places in 

 small dairies, but in large dairies in which intelligent and clean 

 methods of working are followed, they no longer, and, indeed, 

 should no longer exist. 



Although the changes which milk in certain cases undergoes 

 have not been fully elucidated, we know, nevertheless, that the causes 

 are for the most part not to be found, as was formerly surmised, in 

 the chemical condition of the food, the condition of the soil or 

 pasture-land, the illness of animals, &c., but are to be sought for in 

 the activity of lowly organized forms of life. Only a few diseases 

 are traceable to other sources. 



It was not uncommon in the past, for milk which had been standing 

 for about two days for the purpose of creaming, to become subject to putrid 

 fermentation, to curdle prematurely, to assume a bitter taste, to become 

 red or yellow in colour, stringy, slimy, or soapy in texture; or for the 

 cream, after 24 hours' standing in the cream-vat, to become curdy, stringy, 

 and bitter in taste; or such difficulties might only show themselves in 

 the butter. Such undesirable phenomena rarely occur now in the larger- 

 dairies, and if so, only in the case of the cream. Should they threaten to 

 manifest themselves, it is now easy to combat them if the desire and 

 requisite knowledge are possessed by the dairyman. 



With regard to changes commonly occurring in milk or cream, which 

 are not caused by ferments, the following may be mentioned : 



Milk in which Cream Rises Slowly (Lazy or Dead Milk). This fault 

 is only found to any extent when milk is treated with ice. It manifests 

 itself in a striking diminution of the yield of butter under ordinary 

 treatment, even when there is an equal, perhaps even an increased, 

 percentage of fat in the milk. In order to prevent its development the 

 milk should be creamed by centrifugal force, or by the Holstein process, 

 or should be churned as whole milk. The milk of cows which have been 

 long milked is often subject to this unwelcome fault. It not merely occurs 

 in autumn, as has been asserted, when the cows are for the most part 

 becoming dry, but also in the spring, shortly before they receive green 

 food, or are turned out to pasture. Undoubtedly it arises from the fact 

 that the original condition of the nitrogenous matter of the milk becomes 

 changed in an abnormal manner, so that a large portion of the fatty 

 globules experiences an opposition which prevents them from rising freely. 

 It has been noticed that milk which exhibits a difficulty in creaming con- 

 tains less calcium phosphate than ordinary milk. 



