Licence: Public Domain Mark
Credit: Physiological chemistry (Volume 2). Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![■which the milk acquires this blue color. When freshly drawn, the fluid is generally perfectly white, asuming this peculiar blue shade of color on the formation of the cream, which exhibits pale blue specks, extending at first scarcely half a line deep, and appearing in detached groups upon the surface of the otherwise white fluid. These specks become darker, and gradually increase downwards and laterally, until they commingle. The curd which separates from the cream is colorless, and the bluish cream contains rod-like, colorless vibriones, similar to those described by Fuchs. I only once observed a distinct formation of byssus. We have already become acquainted with the most important chemical constituents of the milk in our considerations of the organic substrata. This is especially the case with casein and milk-sugar, which have already been very fully treated^f, not only in reference to their chemical properties, but also to their occurrence in variable quantities under different physiolo- gical and pathological conditions (vol i. pages 263, 340). Knobloch1 in- stituted a series of experiments upon one and the same cow in reference to the constitution of the milk at different seasons of the year, and according to the length of time during which each milking was continued. From these observations it would appear in reference to the amount of casein in the milk, in the first place, that its quantity is greater towards the close than at the beginning of each individual act of milking, whilst the quantity of water decreases; and in the second place, that the milk is poorer in casein on winter than on summer fodder. In winter the amount of casein and of salts insoluble in spirit rose during the milking from 7*07^ to 7*08g, whilst in summer it varied from 8-40g to 8#67g. It still remains, however, for us specially to notice the third organic constituent of the milk, namely, the fat or butter. The fat of women's milk has not yet been subjected to any exact qualitative analysis, but the butter of cow's milk has been carefully analyzed by Chevreul,2 and more recently by Bromeis3 and Lerch.4 Pure milk-fat is almost colorless, or at most is but faintly yellow; after being melted it solidifies at + 26°#5. It becomes soft and greasy at a temperature exceeding + 18°. One part of this fat dissolves in 28*9 parts of boiling alcohol of 0-822 sp. gr. It easily be- comes rancid on exposure to the air, and then forms volatile fatty acids ; hence it imparts a somewhat reddish color to moist litmus paper, even when in a comparatively fresh state. It is perfectly saponifiable, and yields, in addition to glycerine, margaric, oleic, capric, caprylic, caproic, and butyric acids, or in place of the two latter, vaccic acid (vol. i. pages 62-74). Bromeis calculated the composition of butter, from the quantity of the acids which he obtained from it, as equal to 68g of margarin, 30$ of olein, and 2% of true butter-fat; but this calculation affords only an ap- proximate representation of the composition of the milk-fat, since its constituents appear to vary considerably under different physiological relations. The quantity of fat contained in milk appears to vary very conside- rably, for Simon* found in women's milk from 2-53 to 3*885] °f butter ; Clemm6 and Scherer found on the fourth day after delivery 4-297{J, on > Kunst und Gewerbeblatt f. d. k. Bayern, 1851, S. 144-147. 2 Recherches sur les corps gras. Paris, 1822 3 Ann. d. Ch. u. Pharm. Bd. 42, S. 4G ff. * Ibid. Vol. 49, p. 212. 6 Die Frauenmilch u. s. w. Berlin, 1838. 6 Handworterb. d. Physiol. Bd. 2, S. 464.](https://iiif.wellcomecollection.org/image/b21136300_0055.jp2/full/800%2C/0/default.jpg)
