78 SCIENCE AND PRACTICE OF DAIRYING. 



the external conditions under which milk is obtained are similar, and the 

 single consignments of milk differ comparatively little in their relative 

 percentages of fat, it is not worth the trouble of introducing this costly 

 and inconvenient method of milk valuation. 



If all parties are agreeable, the lacto-butyrometer may be used for 

 investigating the milk. The Soxhlet method, however, is by far the 

 better one. Where it is impossible to overtake the number of milk inves- 

 tigations that are required to be made by this method, the lactocrit may 

 be used. This process, even where a large number of investigations have 

 to be made, is not likely to give unreliable results. According to the 

 author's experience, where the number of fat determinations amounts to 

 30 per week, or to 15 determinations twice a week, it is almost as cheap 

 despite the high price of the apparatus as the Soxhlet method; and 

 where the number of determinations exceeds this, the cheaper, propor- 

 tionately, does it become. One worker, provided he is supplied with 

 assistance in the cleaning of the apparatus, &c., can easily undertake the 

 determination of fat in more than 100 samples of milk daily, and in over 

 600 samples in a week. The indirect determination of the percentage 

 of fat in milk by means of the thickness of the cream layer, as, for 

 example, by the Fjord milk-control apparatus, is now quite antiquated, 

 especially for the purpose here referred to. 



With regard to the method of fixing the price per kilogram of milk, 

 according to the percentage of fat it contains, reference will be made 

 in 145 



In dairies in which cream cheeses are made out of the milk 

 obtained from different dairies, where any difficulty may occur, the 

 so-called milk-ferment test and the rennet test are useful. 



For the carrying out of the milk-ferment test special apparatus is 

 required. The improved milk-ferment apparatus of Walter, or that of 

 Denkelman, known as the lacto-fermentator, for example, may be used. 

 In the application of this test, the milk of each milk-supplier is set in small 

 quantities, in suitable vessels, for some time (12 hours) at a temperature 

 of 40 C. At this temperature the action of injurious low ferments which 

 may be present is developed more quickly than at the ordinary tempera- 

 ture. Pure milk, under the above conditions, coagulates into a cohesive 

 homogeneous mass, resembling the albumin of a boiled egg, and possessing 

 a pure acid smell. If the milk in any of the vessels has not become 

 coagulated, or presents a ragged, flocculent coagulation, floating in a 

 muddy serum, or occurs in non-homogeneous slimy clots, full of gas-bubbles, 

 and possesses, instead of the purely acid smell, a strange, unpleasant 

 odour, it is to be inferred that the milk which this sample represents is 



