348 TESTS FOR MILK. 



( 150). The proteids are precipitated and the fata extracted with ether. The fats in fresh 

 milk form about 3 per cent., and in skimmed milk H P er cent - The amount of water in rela- 

 tion to the milk-globules is estimated by the lactoscope or the diaphanometer of Donne (modi- 

 fied by Vogel and Hoppe-Seyler), which consists of a glass vessel with plane parallel sides placed 

 1 centimetre apart. A measured quantity of milk is taken, and water is added to it from a 

 burette until the outline of a candle flame placed at a distance of 1 metre can be distinctly seen 

 through the diluted milk. This is done in a dark room. For 1 cubic centimetre of good cow's 

 milk, 70 to 85 centimetres water are required. [Other forms of lactoscope are used, all depend- 

 ing on the same principle of an optical test, viz., that the opacity of milk varies with and is 

 proportional to the amount of butter-fats present, i.e., the oil-globules. Bond uses a shallow 

 cylindrical vessel with the bottom covered by black lines on a white surface. A measured 

 quantity of water is placed in this vessel, and milk is added, drop by drop, until the parallel 

 lines on the pattern at the bottom of the dish cease to be visible. On counting the number of 

 drops, a table accompanying the appliance gives the percentage of fats. This method gives 

 approximate results. In all cases it is well to use fresh milk.] 



Various substances pass into the milk when they are administered to the mother many odori- 

 ferous vegetable bodies, e.g., anise, vermuth, garlic, &c. ; chloral, rhubarb, opium, indigo, 

 salicylic acid, iodine, iron, zinc, mercury, lead, bismuth, antimony. In osteomalacia the amount 

 of lime in the milk is increased (Gusseroiv). Potassium iodide diminishes the secretion of milk 

 by affecting the secretory function. Amongst abnormal constituents are haemoglobin, bile- 

 pigments, mucin, blood-corpuscles, pus, fibrin. Numerous fungi and other low organisms 

 develop in evacuated milk, and the rare blue milk is due to the development of bacillus 

 cyanogeneum. The milk-serum is blue, not the fungus. Blue milk is unhealthy, and causes 

 diarrhea. There are fungi which make milk bluish-black or green. Bed and yellow milk are 

 produced by a similar action of chromogenic fungi ( 184). The former is produced by Micro- 

 coccus prodigiosus, which is colourless. The colour seems to be due to fuchsin. The yellow 

 colour is produced by bacillus synxanthus. Some of the pigments seem to be related to the 

 aniline-, and others to the phenol-colouring matters (Hiippe). 



The rennet-like action of bacteria is a widely diffused property of these organisms ; they 

 coagulate and peptonise casein and may ultimately produce further decompositions. The 

 butyric acid bacillus ( 184) first coagulates casein, then peptonises it, and finally splits it up, 

 with the evolution of ammonia (Hiippe). 



Milk becomes stringy owing to the action of cocci which form a stringy substance [ = dextran, 

 C 12 H lo O 10 (Scficibler)], just as beer or wine undergoes a similar or ropy change. [The milk of 

 diseased animals may contain or transmit directly infectious matter.] 



Preparations of Milk. (1) Condensed milk 80 grms. cane-sugar are added to 1 litre of 

 milk ; the whole is evaporated to ; and while hot sealed up in tin cans. For children one 

 teaspoonful is dissolved in a pint of cold water, and then boiled. 



(2) Koumiss is prepared by the Tartars from mare's milk. After the addition of koumiss 

 and sour milk, the whole is violently stirred, and it undergoes the alcoholic fermentation, 

 whereby the milk-sugar is first changed into galactose, .and then into alcohol ; so that koumiss 

 contains 2 to 3 per cent, of alcohol ; while the casein is at first precipitated, but is afterwards 

 partly redissolved and changed into acid-albumin and peptone. Tartar koumiss seems to be 

 produced by the action of a special bacterium (Diaspora caucasia). 



(3) Cheese is prepared by coagulating milk with rennet, allowing the whey to separate, and 

 adding salt to the curd. When kept for a long time cheese ripens," the caseinagain becomes 

 soluble in water, probably from the formation of soda albuminate ; in many cases it becomes 

 semi-fluid, when it takes the characters of peptones. When further decomposition occurs, leucin 

 and tyrosin are formed. The fats increase at the expense of the casein, and they again undergo 

 further change, the volatile fatty acids giving the characteristic odour. The formation of 

 peptone, leucin, tyrosin, and the decomposition of fat recall the digestive processes. [Cheese 

 is coagulated casein entangling more or less fat, so that the richness of the cheese will depend 

 upon the kind of milk from which it is made. There are, in this sense, three kinds of cheese, 

 whole milk, skim milk, and cream cheese, the last being represented by Stilton, Roquefort, 

 Cheshire, &c. The composition is shown in the following table after Bauer : 



Cream cheese, especially if it be made from goat's milk, acquires a very high odour and strong 

 flavour when it is kept and 'ripens"; the casein is partly decomposed to yield ammonia and 

 ammonium sulphide, while the fats yield butyric, caproic, and other acids.] 



