solution by Cream also

Sugar of milk* (saccholactin) is the saccharine principle upon which the sweetness and also the fermenting properties of milk depend. It is held in the whey after the separation of the curd. contains it in the proportion of forty-four parts, and skimmed milk in the ratio of about thirty-five parts of this substance in a thousand. As the process of obtaining this and the other constituents of whey may be interesting to the general reader, we will concisely refer to it.

Take a quart of milk perfectly creamed by repeated skimmings; separate the curd by adding to the milk one table-spoonful of vinegar, or what is a better coagulator, a small quantity of fresh rennet. When the curd is formed, strain it through a fine hair sieve, and afterwards filter the liquor through unsized paper. Now slowly evaporate the whey to the consistence of a viscid syrup, allow it to cool, and it will concrete into a thick gluey mass. Dissolve this mass in water, and the whey will be sufficiently pure for chemical examination. Evaporate a second time as before, and the syrup will be of a faint yellow color, and of rather an agreeable flavor. Upon cooling the fluid in this state, it deposits numerous prismatic crystals, of a darkish yellow color, which are called sugar of milk. If this substance is re-dissolved and purified by means of albumen, it becomes white and semi-transparent. It is inodorous and of a peculiarly sweetish taste, and appears to partake of the properties of both gum and sugar.

* Fabricius Bartholdi, an Italian, was the first European who mentioned this sugar. He described it in his Encyclopædia HermeticoDogmatica, published at Boulognia in 1619; but it seems to have been known in India long before that period. For the best account of its properties we are indebted to Mr. Lichtenstein.— Thompson,

Its crystals are six-sided, or what are denominated regular parallelopipeds, terminated by four-sided pyramids.

The properties of this substance are essentially different from sugar. It requires for its solution five times its volume of cold, or two and a half its volume of hot water. It is insoluble in alcohol and ether, except with the addition of a little sulphuric acid. At the temperature of 55, its specific gravity is 1.543. Great importance appears to be attached by some physicians to the medicinal virtues of this substance, but it has never, we believe, been shown that they are very considerable. In Switzerland and in other places, it is separated in a large way for pharmaceutical purposes.

Near the end of the evaporation of the whey, muriates of potash and soda are deposited, and some phosphate of lime. If the fluid, which on cooling assumes the appearance and consistency of animal jelly, be diluted and slowly evaporated a second time, an additional quantity of the muriate of potash is separated in crystals, and also of the phosphate of soda and lime. Phosphate of lime may be obtained by pouring into the clear whey a little of the oxalate of ammonia, which occasions a precipitate of the oxalate of lime. If the nitrate of lead or the nitrate of mercury is used, the phosphates of lead and mercury are precipitated. The residuum of the whey now consists chiefly of gelatin. If alcohol is poured upon the whey after it is evaporated to the consistence of syrup, a flaky precipitate is formed consisting of gelatin and the sugar of milk, which substances may be separated by a decoction of nutgalls or tannin.

CHAPTER X.

HUMAN MILK.

Pliny's opinion of different kinds of milk.-Artificial ass's milk, its reputed virtues.-Peculiarities of human milk.-Whiter than cow's.-Yields more cream.-In what respects it differs.-Variations of it at different periods.-It is incoagulable.-Less prone to acidity than other milk.-It is affected by mental emotions.— Illustrated by an anecdote.

So far as known, the principal elements in the milk of all other animals are the same as in that of the cow, but so varied in their proportions as to give to each kind of milk its own peculiar characteristics. To the senses, indeed, the difference is so clearly cognizable, that the ancients, who were but little acquainted with analytical chemistry, appear to have entertained nearly as correct notions of the dietetical properties of milk as the moderns, notwithstanding the great improvements in this branch of science. Pliny, the natural historian, was not only a man of learning and observation, but also the chronicler of the wisdom of the ancients, and yet we have not seen his writings quoted on this subject. He says, human milk is sweetest, and camel's is next; cow's milk will yield twice as much butter as the same quantity of goat's milk, and is better than any other for butter. Camel's milk is thickest, and as it regards consistence, mare's milk ranks next. But goat's milk he supposes to be most nourishing, and hence originated the mythical legend of the poets, who feigned that Jupiter was suckled by a goat. Sow's milk was regarded

as an efficacious aperient, and was prescribed for various maladies. But ass's milk, on account of its reputed medical and cosmetic properties, was valued beyond any other kind. Such confidence was reposed in its virtues as a beautifier of the complexion, that the Empress Poppæa, wife of Domitius Nero, used it for this purpose; having five hundred asses continually in her retinue to furnish her with a fresh bath every morning. Artificial ass's milk, reputed to possess similar properties, was prepared as follows:

P. x. limac terrest. contns. xviii. Rasur. C. Cervi. Hordei perlati. Rad. cryngii, sing. unc. i. aquæ puræ lib. vi. coque coni igne in vase singulino vitriato ad lib. iii.; dein cola et adde sympi balsamici seseuncian. Capiat quotidie unc. iv. hujus liquoris mistas cum lactis vaccin. recentis p. æ.†

The milk of the animals named does not, as will appear from modern observations and experiments, essentially vary from the foregoing account.

Assuming cow's milk, because most familiarly known, as a standard of comparison, we propose to refer with some particularity to the milk of other animals.

Human milk is whiter and thinner than that of the cow, and contains more saccharine and oily matter, but less caseum. It contains, indeed, less than a sixth part of the curd that is yielded by cow's milk, and it is imperfectly coagulable either by rennet or acids. Heat does not increase its coagulability; but when it is boiled a pellicle is thrown up to the surface, which has the properties of caseum. The difficulty in forming the curd, is attributed by Thompson and others chiefly to the superabundance of * Pliny's Natural History, Lib. XXVIII. c. 11. + Med. Trans., Vol. II. p. 341,

water with which the curd is diluted. As it contains, however, less than one per cent. more water than cow's milk, which so readily coagulates, this reason is evidently inconclusive.

Woman's milk yields abundance of cream, which is generally whiter than cow's, and after it is separated, the milk is extremely thin, and of a pale bluish color. No butter can be obtained from the cream. After long churning, a viscid unctuous matter is separated, but it cannot be changed into perfect butter. If it is allowed to remain at rest a day or two after the agitation, it spontaneously separates into two parts; the one a colorless, pellucid fluid, which occupies the inferior part of the vessel; and the other a thick, white, oily fluid, which floats upon the surface. The lowermost fluid contains sugar of milk and some curd; the uppermost does not differ from cream, except in consistence. But as the oily part of this cream cannot be separated by agitation from the curd, it is found extremely difficult to determine the relative proportions of the component parts of human milk.* When the whey, after the curd is separated from it, is slowly evaporated, it yields crystals of sugar of milk, and of muriate of soda. The quantity of sugar is greater than in cow's milk. According to Haller, the sugar obtained from cow's milk is to that obtained from an equal quantity of woman's milk, as 35:58, and sometimes as 37:67, and in all the intermediate ratios.

Woman's milk appears, therefore, to differ from that of cow's in three particulars.

I. It contains a much smaller quantity of curd.

II. Its oil is so intimately combined with its curd, that it does not yield butter.

* Parmentier. Jour. de Phys., XXXVIII. 419.