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[25] 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. PLATE V. [Illustration: Skimmed Cows Milk × 420.] [Illustration: Colostrum in Cows Milk × 420.] ARTOTYPE. E. BIERSTADT, N. Y. FOOTNOTES: [18] In 1885, out of 2024 samples tested, 880 fell below the standard of 13 per cent. total solids. [19] Second Annual Report of the New York State Dairy Commissioner, 1886. [20] Dammer’s ‘Lexikon der Verfälschungen,’ 1887, p. 592. [21] 3·50 per cent. should be deducted for chlorine and oxygen. [22] For description of the “Lactocrete,” see ‘Analyst,’ Jan. 1887. [23] ‘Analyst,’ x. pp. 46-54. [24] Blyth. [25] “Ein Ptomain aus giftigem Käse,” Zeit. f. Phys. Chem., x. p. 2, 1886. BUTTER. Butter is the fat of milk, containing small proportions of caseine, water, and salt (the latter mostly added), and possessing a somewhat granular structure. In its preparation the fat-globules of cream are made to coalesce by the process of churning, and are removed from the residual buttermilk. Its colour, due to lactochrome, varies from white to yellow, according to the breed and food of the cow. The fatty constituents of butter are butyric, caproic, caprylic, capric, myristic, palmitic, stearic, and oleic acids, which are combined with glycerine as ethers; the first four are soluble in hot water, the remainder insoluble. It is very probable that butter fat is composed of complex glycerides, _i. e._ tri-acid (presumably oleic, palmitic, and butyric) ethers, of the following character:-- {O.C_{4} H_{7}O C_{3} H_{5} {O.C_{16}H_{31}O {O.C_{18}H_{33}O The table on p. 64 exhibits a summary of the results obtained by various chemists by the analysis of numerous specimens of genuine butter.