not fat in pure milk (which is generally considered as too low) and adopt the formula :

in which

100 S = x,

9

represents the percentage of genuine milk, and

S the solids not fat.

In skimmed milk the percentage of fat removed (x) can be ascertained by the formula:

in which S solids not fat, and f = the fat found. In case the sample has been subjected to both skimming and watering, the water added (x) can be calculated from the formula* :

The addition of mineral salts to milk is detected by the increased proportion of ash found; the presence of an abnormal amount of common salt by the high proportion of chlorine present in the ash, which in pure milk should never exceed o⚫ 14 per cent. The use of sodium bicarbonate, borax, etc., is also detected by the analysis of the ash. Glycerine, salicylic acid, flour, and starch, if added, can be extracted from the milk-solids and their identity established by the usual characteristic reactions.

The microscope is of great service in the determination of the quality of milk, and especially in the detection of the presence of abnormal bodies, such as pus, colostrum cells, and blood. In pure cow's milk the globules are in constant motion; their usual size is of an inch, but this depends upon the nature of the food used. Plates IV. and V., which represent cream, pure milk, skimmed milk, and milk containing colostrum cells, were taken from photomicrographic negatives furnished through the kindness of Mr. Martin.

Blyth.

Numerous cases of severe illness have from time to time been developed by the use of milk which was apparently free from any of the usual adulterants. In a recent issue of the Philadelphia Medical News' (Sept. 1886) an instance of wholesale milk poisoning at Long Branch is described, and the results reached by a careful study of the epidemic are given. It was demonstated that warm milk, fresh from the cow, if placed in closed cans under conditions which retarded the dissipation of its heat, may suffer fermentation resulting within a few hours in the genesis of a sufficient quantity of a poisonous ptomaine (termed tyrotoxicon) to produce dangerous toxic effects in those drinking it.

Tyrotoxicon was isolated from the milk, and obtained in needle-shaped crystals, which reduced iodic acid and gave a blue coloration when treated with potassium ferricyanide or ferric chloride. Prof. Victor C. Vaughan discovered the same alkaloid in poisonous cheese, and has also detected its presence in ice-cream that had been the cause of sickness. In this connection it is of importance to note that the addition of gelatine to ice-cream is occasionally practised : in case this substance is used while in a state of incipient decomposition, the danger of the bacteria and other organisms present subsequently resuming activity is considerable. It has been repeatedly and conclusively demonstrated that milk from cows affected with tuberculosis and other complaints, is capable of propagating the seeds of disease, especially in children. The presence of impure water in milk constitutes another source of danger. A test based upon the fact that water which has received sewage contamination often contains nitrites, is applied by first coagulating the suspected milk with acetic acid, then filtering and adding to the filtrate a few cc. of an equal mixture of sulphanilic acid and naphthylamine sulphate, when, in presence of nitrites, a rose-red colour will be produced.

"Ein Ptomain aus giftigem Käse," Zeit. f. Phys. Chem., x. p. 2, 1886.