64: PROTEINS. 



O01 or less, according to Osborne and Wakeman, per cent, of 

 phosphorus, while the vegetable fats which largely compose 

 margarine are free from phosphorus. 



The phosphorus of casein is not in a form which is an index 

 of vitamines. 



Funk finds that the vitamines may be precipitated by phospho- 

 tungstic acid after removal of proteins, and that about one-half 

 is removed with the fat. 



Enzymes of Milk. Babcock and Kussell have described a 

 proteolytic enzyme, to which they attribute a portion of the 

 ripening of cheese (q.v.) ; this is carried down by any finely 

 divided precipitate, and appears in the " separator slime " 

 (q.v.). If milk is preserved with chloroform or any bactericide 

 which does not affect the enzyme, the milk is gradually pepton- 

 ised in the cold ; the enzyme is, however, destroyed by heat. 



A peroxydase, shown by developing a colour by the oxidation 

 of many organic substances when hydrogen peroxide is added 

 to milk, is always present in cow's milk, though not in human 

 milk. It probably has a connection with the minute traces of 

 manganese present in milk. It is destroyed at 80 C. Catalase, 

 which rapidly splits hydrogen peroxide into water and oxygen, 

 is always present, and probably passes into the milk from the 

 blood in the blood-vessels of the udder ; the catalase of milk 

 is much less than that present in blood, lymph or pus, and a 

 high catalase content may indicate an unhealthy condition of 

 the udder permitting more than the usual amount of catalase 

 to enter. 



A reductase, an enzyme which has a reducing action, and which 

 is best shown by the decolorisation of dyes such as methylene 

 blue, is present to a small amount in milk, but is frequently 

 enormously increased by the secretion of a reductase by micro- 

 organisms which grow in milk. The estimation of the rate at 

 which colouring matters are decolourised is a very useful index 

 of the bacterial contamination of milk. 



Cellular Elements. In connection with enzymes, it may be 

 mentioned that milk contains cellular elements, which bear 

 some resemblance to the white corpuscles of blood, lymph and 

 pus, and which are shown by the addition of a stain such as 

 rosaniline to milk ; the cellular elements take up the dye and 

 can be distinguished under the microscope ; they, as well as 

 structures which have the appearance of empty milk sacs, are 

 removed on centrifuging, and are found in the separator slime 

 (q.v.), and probably consist of Storch's mucoid protein. They 

 have been mistaken for pus cells, and allegations have been 

 made that milk contains pus or is unhealthy simply on the evidence 

 of the presence of cells, which stain differentially when treated 



