CHEMICAL COMPOSITION.— The nutri tive ingredients are:— 1. 'Water, constituting from 85 to 90 per cent.
2. Fat, in the form of minute globules held in emulsion by the soluble proteid. If the milk stands, the fat collects at the top as cream. In a good specimen the percentage varies from 3 to 5, the average being about 4.
3. Sugar.—The carbohydrate of milk is lactose, or milk-sugar. Its proportion is remarkably constant: 6 to 7 per cent. during the whole nursing-period.
4. Proteids.—Casein and lactalbumin are the principal forms. The lactalbu min is in solution, and is the more read ily digested and absorbed; its amount is about twice that of casein. The casein is in suspension, and is readily precipi tated; the curd formed by adding acetic acid to breast-milk is in fine flocculi, thus differing from that of cows' milk, which comes clown in dense masses. In a good specimen the proteids vary from 0.75 to 2.0 per cent., the average being about 1.25 per cent.
5. Salls.—The most important salts are calcium phosphate and potassium carbonate. Altocrether the salts amount to about O.?, per cent.
During., the later months of lactation the milk regularly deteriorates, the loss being most marked in the proteids and total solids. At any time, reduction of the proteids is apt to be a sign of failing lactation. V. Adriatic° and J. S. Adrianee (Arehives of Ped., Jan.. Feb., '97).
Analysis of ninety-four samples of human milk, all taken within the puer peral month. shows that wide variations in the several ingredients of breast-milk are met with. Greatest variation was observed in the fat; in one ease its percentage reached S.S2, the lowest being
4.354. Average composition of mother's milk. according to personal analysis: Water, SS.10; fat, 3.0S; sugar, 0.75: proteids, 1.S7; and ash, 0.25. Some variations in fat were probably due to position of mother when milk was with drawn; if in a prone position, cream is drawn off first. There were five deaths among forty-two children, and in each of the fatal cases the percentage of pro teids in the mother's milk was high, ranging from 2.05 to 4 per cent. In all but three eases the milk agreed when proteids exceeded 2.5 per cent. Varia tion in percentage of other ingredients seemed to be more easily borne. Rich mond (Brit. Med. Jour., Jan. 22, '98).
Clinical Examination.—While a com plete chemical analysis of the milk is desirable, this is often impossible; and the physician must depend on his own simple tests.
The QUANTITY may be estimated from the amount which can be drawn with a breast-pump; but the most reliable test is to weigh the infant before and after nursing on scales sensitive enough to record differences of half an ounce. The average result of two or three such weighings will be sufficiently definite.
The QUALITY of the milk, or, at least, whether very rich 07' very poor, can be made out by the following procedures. The specimen taken for examination should be the entire amount of milk that can be pumped from one breast.