Page:The American Cyclopædia (1879) Volume XI.djvu/560

 542 MILK 1-045. According to Simon, the average spe- cific gravity of human milk is 1-032. There is a difference of opinion among chemists as to whether normal milk has an acid or an alkaline reaction. According to Berzelius, Peligot, and Lassaigne, it is acid ; Simon and others regard it as alkaline, and attribute the acid reaction found by others to its having ac- quired acidity by standing, or to disease. Nu- merous examinations, however, seem to indi- cate that healthy milk may be alkaline, neutral, or acid, according to the food of the animal. D'Arat and Petit say that the milk of stall- fed animals is always acid, and becomes alka- line only when they are turned out to grass. Hermbstiidt found milk that had remained long in the udder acid. Fraas had a cow milked six times a day, and found the milk at each time feebly alkaline. After an interval of 24 hours she was again milked, when the first portion of the milk was found alkaline and the last portion acid. The opacity of milk de- pends upon numerous yellow microscopic glob- ules of a fatty substance from y^Vrnr to ^Vff of an inch in diameter, shown in fig. 1. Ac- cording to Chevreul, cow's butter is composed of stearine, margarine, and oleine, with small quantities of buty- rine, caproine, and ca- prine ; but late analy- ses by Heintz and others deny the ex- istence of margarine, saying that it con- sists of palmitine and a small quantity of stearine, together with small quantities of glycerides, yielding by saponification myris- (See BUTTER.) In regard to the size of the butter globules observers differ. Dr. Carpenter gives their diameter as Tgfax to srJVfr, an< l Dr. Dunglison adopts this measure. Dr. Dalton says: "The largest of the globules are not over ^Vu, the greatest number of them being about T^Vrrff of an inch in diameter." According to Dr. Bennett, their diameter varies from -^j^ to y-^ f an inch- There has recently been considerable discus- sion as to the existence of an envelope, or " membrane " as some term it, around the globules. Dr. Von Baumhauer and F. Knapp assert that they have none, and others concur with them. Dr. Bennett and others maintain that either a caseous or an albuminous enve- lope exists, and experiments are cited as sus- taining this opinion. The taste of milk is bland and sweetish, and it has a peculiar animal odor, depending somewhat upon the animal, but perhaps still more upon the food. Gar- lic, even if the plant is partaken of in very small quantities, is distinctly perceptible by the smell as well as by the taste. Milk has al- ways been an article of man's diet, and forms the entire nourishment of the early existence FIG. 1. tic and butic acids. CONSTITUENTS. Cow. AM. Goat. Ewe. Woman. Woman. Water Butter Sugar of milk. . Caseine Various salts. . . Total 86-28 4-38 5-27 3-80 0-27 91-65 0-11 6-08 1-82 0-84 86-80 8-32 5-28 4-02 0-58 85-62 4-20 6-00 4-50 0-68 87.98 8-55 6-50 1-52 0-45 100-00 89-20 2-60 6-00 2-00 0-20 100-00 100-00 100-00 100-00 100-00 of all mammals ; and it contains all the ele- ments necessary for the growth of the animal framework. In comparing milk of the same animal under different conditions of age, health, food, length of time after parturition, &c., as remarkable differences in the proportions of the ingredients will be observed as when samples of the average milk of several different species of mammalia are compared. The following table exhibits the composition of several kinds of milk, the first column presenting the aver- age result of ten analyses by Prof. Poggiale, the next four being furnished by Messrs. Henri and Chevalier, in the Journal de Pharmacie, vol. xxv., and the last by Dr. Samuel K. Percy of New York as the composition of the milk of a healthy woman. The albumen in these analyses is reckoned with the caseine. An analysis by Volcker is given in the article CHEESE, and also one of the cheese made from the milk. Of tnese constituents the most uni- form in its proportions is the sugar, but this may be materially increased by the use of sac- charine food, as is found in feeding cows upon carrots and beets. The sugar of milk is crys- tallizable, but it is less sweet and less soluble in water than cane sugar. Milk from unhealthy animals often exhibits an increased proportion of phosphate of lime in* the ash. When milk is exposed to a warm temperature it ferments, and lactic acid is generated, which has the same ultimate composition as sugar of milk. Under certain conditions the vinous fermentation may now take place, the sugar of milk be converted into grape sugar, and a spirituous liquor be produced, as is practised by the Tartars. (See KUMISS.) Various circumstances affect the quality and composition of milk. That called colostrum, given by the cow immediately after calving, is yellowish, thick, and stringy; for several days it is unfit for use. Examined by the microscope, it is seen to contain numerous large and granular corpuscles. Milk drawn from the cow in the morning is thought to be better than that of the afternoon ; and a re- markable difference is perceived in the propor- tion of cream in the first and last portions of the milking, the latter containing twic.e as much cream as the same quantity of milk of the for- mer. In the udder of the cow the cream seems to rise as it does when the milk is collected in a vessel. Some of the methods of testing the quality of milk are noticed under GALACTOM- ETER. By this the specific gravity is ascer- tained both of the whole milk and skimmed milk ; but as these data are of little value with- out a knowledge of the proportion of cream,