296 



THE COMPLETE GRAZIER. 



BOOK II 



and in extreme instances it may vary from : 



87-05 

 3-50 

 3-70 

 4-60 

 0-40 

 075 



100-00 



Water . 

 Casein . 

 Butter . 

 Milk sugar 

 Albumin 

 Ash 



80-00 to 90 -00 per cent. 



3-00 

 1-80 

 3-00 

 0-30 

 070 



5-00 

 5-20 

 5-50 

 0-55 

 0-80 



"Neither casein nor butter is in solution in milk, but rather in 

 suspension the butter-fat expressly so. Casein appears to be in the 

 form of an extremely attenuated jelly, owing to lavish absorption of 

 water ; but it is not dissolved, or it would pass the membrane of a 

 dialyser. It is soluble in diluted hydrochloric acid, or carbonate of 

 soda, and it is coagulable by rennet, and by lactic acid, and may be 

 precipitated by various acids. Coagulation by rennet, which is the 

 active agent of digestion in the fourth stomach of a calf, is the only 

 form of coagulation that can be employed in cheese-making, for it is 

 the digestive agent alluded to which has so much to do with ripening 

 and mellowing the cheese after it is made. 



" Butter-fat, in the form of cream-globules, is easily seen by the aid 

 of a microscope to be in suspension in milk, and each globule is a 

 separate entity. These globules belong to the ' infinitely little ' in 

 Nature, for a single pint of milk, containing 4 per cent, of cream, has 

 been estimated to contain no less than the prodigious number of forty 

 thousand millions of them ! The diameters of the globules vary a good 

 deal in all milk, and in the milk of different breeds of cows, or in that 

 of different cows of the same breed, sometimes.,. Sturtevant gives 

 them at 44 \ to -g-gV^j- f an inch. Milk, indeed, is an emulsion, in 

 which the most valuable ingredient is butter-fat. The specific gravity 

 of milk containing all its cream is about 1*032, whereas that of butter- 

 fat is about '90, water as a standard being 1*00 ; and it is this difference 

 in specific gravity which causes cream to rise to the surface of milk 

 that is at rest. Some of the cream-globules, however, have the 

 peculiarity of being stationary, while others appear to gravitate slowly 

 downwards, and hence it is that the whole of them never succeed in 

 reaching the surface of the milk." l 



Milk from which the supernatant fluid or cream has been removed, 

 is termed skim-milk, and still retains a considerable quantity of 

 coagulable or caseous matter, which may be separated from the serum 

 or whey, by means of a rennet or some acid. This coagulated portion 

 constitutes the curd, and is the basis of cheese. If a rennet be used, 

 and all the portion coagulated by its means be separated, the addition 



" The Farm and the Dairy," by J. P. Sheldon, pp. 59, 60. 



