foundations of animal chemistry. Boerhaave saw in milk the most perfect food, and to him it was a fluid containing, wrapt up in mystery, all the elements of the body. Hence he laid the greatest stress on the importance of its study, and without doubt his example and teaching were the immediate cause of the numerous experiments carried out by his disciples, Vullyanoz, Doorschodt, and others. Boerhaave says * "An animal is composed of matter which was not that animal before, but is changed into it by the vital power of the animal. . . . Milk, therefore, appears to be the first thing to be examined, for this is a true chyle, and much less diluted with the lymph than the chyle when poured into the subclavian vein, and therefore approaches nearer to the aliment. It has flowed through the veins, the heart, the lungs, and the arteries, and therefore has been mixed with all the juices, and being afterwards separated by the particular structure of the breasts, it may be collected and examined apart. Milk is a liquor prepared from the aliment chewed in the mouth, digested in the stomach, perfected by the force and juices of the intestines, and elaborated by means of the mesentery and its glands and juices, and the juices of the thoracic duct; it has undergone some actions of the veins, arteries, heart, lungs, and juices, and begun to be assimilated, yet may be had separate and discharged out of the body. And thus, by their own milk prepared from the proper matter of the chyle, all the known animals that have milk are nourished, both male and female; for milk is always prepared from the chyle as well in men as in women, as well in virgins and barren women as in mothers and nurses. Whence every such animal consists, is nourished, and lives on its own proper milk, and from this alone prepares all the other parts, both the solid and fluid, by means of the vital actions. It is now certain that men may live for years upon milk alone, and perform all the actions of life, and have all the solid and fluid parts of their bodies perfectly elaborated thereby. The serum, therefore, the blood, the lymph, the spirits, bones, cartilages, membranes, and vessels, proceed from milk, and if a man may live for years upon milk alone, milk must contain in itself the matter of all the parts of the human body.” Boerhaave appears to have tested milk with a great variety of reagents, and found that it was curdled by all acids, whether nitric, acetic, hydrochloric or sulphuric, or by acid vegetable juices. He also distilled milk, and found that it gave no spirit on distillation. "It also appears not to contain any trace of saline matter, being inodorous and perfectly insipid, and causing no pain if dropped into the eye." On boiling milk with alkalies, Boerhaave was the first to notice the yellow colour caused by the decomposition of the sugar. He thought that a similar change took place in fevers, for he notices the yellow milk of feverish women, and warns the physician that he must not suppose the yellowness to be caused by an acid, but rather by an alkaline tendency, and by too much heat. Boerhaave paid # "The Practice of Chemistry," translated from Boerhaave's Elementa Chemica. By Peter Shaw, M.D., 2nd ed. Lond. 1741, 2 vols., 4to. particular attention to the state of the milk in fevers and infectious diseases; "and in the last contagion among the cows, whilst their meat remained in the stomach, and was neither discharged upwards by ruminating nor expelled downwards, and therefore truly putrefied with the violent degree of heat, so that the stomach was almost scorched with heat, as we explained the thing Then the milk grew sharp, yellow, somewhat fœtid, and thin in the dug, and in this form was either milked out or dropped spontaneously." He also condemned the use of milk from heated or improperly fed animals, or those suffering from fever, and remarked that it would be found of a fœtid urinous odour, yellow in colour, thin, of a saline ungrateful taste, and acquiring, after a time, an odour of rancid cheese.* § 106. Boerhaave, so far as is known, made no quantitative determination of any of the constituents of milk; but a very early attempt is found in a research undertaken by Geoffroy, published in 1737.+ This experimenter took 12 lbs. of milk, and after coagulating the fluid, heated it gently over the fire, in order to separate the coagulum more completely. The liquid was now filtered, and the serum and coagulum both weighed. The serum weighed 8 lbs., the coagulum 2 lbs. 7 ozs. The serum was then evaporated to dryness, and left a residue weighing 7 ozs. 24 grains; in other words, it amounted to 5.2 per cent.; and since it must have been mainly composed of milk-sugar and salts, the determination is almost as exact as that of any analysis of the present day. He now appears to have distilled the residue, and obtained empyreumatic products, and a caput mortuum," from which he extracted soluble salts by lixiviation, and among these salts he recognised chloride of sodium by its cubical crystals. 66 + Doorschodt § experimented on milk, possibly under the immediate superintendence of Boerhaave; for he distilled it, and noticed that the distillate was neither acid nor alkaline, concluding, hence, that water alone was condensed, and that there was no other volatile principle. He also boiled the milk with alkalies, and details with great precision the successive changes of colour. He appears to have been the first to notice that alcohol coagulates * A work by Dumonchaux, about the period of the Boerhaave school, De Lacte Mammarum et Pinguidine, Petrus J. Dumonchaux, Duaci, 1754, contains nothing new about the composition of milk, but merely cites the opinions of others. + Commercium Literarium ad Re Medica et Scientiæ Naturalis Incrementum Institutium, &c., 1737. The caput mortuum was the name of any residue left after distillation in the retort. § Henricus Doorschodt: De Lacte, 1737. milk, and also that it may be preserved by borax and other antiseptics. § 107. M. Vullyanoz, another disciple of Boerhaave, published a tract, in 1756, on the essential salt of milk, which tended greatly to spread a knowledge of the substance discovered by Bartoletus, and described so fully by Testi the Italian. It would appear from his treatise that sugar of milk was then an article of commerce, but that there was great difficulty in preparing it white and pure. "There is in Switzerland a chemist named Creuzius who has composed the salt admirably, but unfortunately he will not impart his secret to any one. This is the more vexatious, because the salt he is proprietor of is infinitely finer than the others; it is whiter, sweeter, and dissolves better on the tongue." The method used in the time of Vullyanoz was simple evaporation, but he complains that the product was often "sour," and was not the same as the Swiss sugar. Vullyanoz established the fact that all herbivorous animals, as well as women, gave sugar of milk; he also investigated the solubility, and found it insoluble in hot alcohol, in spirits of ammonia, and in very pure aqua fortis, &c. Noticing that it effervesced with nitric acid, he made experiments which proved it to be a neutral salt, and thence drew an analogy between milk-sugar and soap, concluding that the latter contained an oil and also an acid, that it could be fermented, and that on distillation it yielded an acid, and was decomposed by sulphuric acid.† § 108. The next important paper on milk in order of time, is that of Voltelenus, important because his experiments were quantitative. He took 42 ozs. of cows' milk and distilled it. The process was conducted very carefully, and occupied many days, and, as may be expected, was very troublesome, from the irregular bursts of ebullition. By the fifth day he obtained 29 ozs. of distillate " Aqua Lactis Destillata;" in other words, his determination of water was 69 per cent., much below the truth. The residue in the retort weighed 2 ozs. 3 drms., and effervesced with alkalies. He now increased the fire, and obtained an unctuous oil, weighing 14 drms., mixed with what he calls an oily *"'Sur le sel essentiel de Lait." Par M. Vullyanoz, Docteur en Médecine a Lauzaume. Recueil Périodique, Observations de Médecine, Chirurgie, Pharmacie," &c. Par M. Vandermonde, 1756. + Subsequent to the work of Vullyanoz appeared a treatise on milk-sugar, "Abhandlung vom Milch-Zucker," Braunschweig, 1772, by G. R. Lichenstein, who considered it an earthy salt, and called it terra-oleosum sal mediam. Floris Jacobi Voltilenii: De Lacte Humano ejusque cum Asino et Ovillo Comparatione, &c. Lipsiæ, 1779. spirituous matter, acid, acrid, and like the spirit from guaiacum wood. The carbon in the retort weighed 10 drms., but on burning to an ash it weighed 3. The ash, boiled with water, left 2 drms. insoluble. In other words, he determined the ash to be '89 per cent., and the soluble portion 31 per cent. Hence, Voltelenus most certainly made a correct determination of the amount of saline matters in milk, and was probably the first who did so. Voltelenus next made a similar experiment with women's milk, taking 32 ozs., from which, in thirteen days, he had distilled over 31 ozs. 6 drms. of odourless liquid. Here, unfortunately, his retort broke; but he concluded that human milk is resolved by fire into much water and spirit; a double oil, a double salt, fixed and warm alkali and earth, to which may be added a "spiritus sui generis." He refers to sugar of milk, and affirms that he has separated a similar substance from human milk. The same process was applied to asses' milk, 32 ozs. being distilled over a sand-bath in three days. On the first day a lactescent distillate came over, in quantity amounting to 1 oz. 17 drms. 1 scr.; on the second day, a more limpid liquid, amounting to 19 ozs. 4 drms. ; and on the third day there came over 6 ozs. 1 drm. 1 scr., of a feebly acid liquid; by the fourth day he had to increase the heat, and obtained a black opaque oil, which separated on standing into three parts-a thick substance, a thinner, and what he calls a spirit. The carbon in the retort was weighed and then burnt. The ash weighed 3 drms., and on lixiviation the insoluble portion weighed 2 drms. 1 scr. He made precisely similar experiments on the milk of the sheepidentified salt, determined the amount of ash, &c. He thus came to the conclusion that all milk had the same constituents. § 109. Schoepff, in a very learned paper,* containing full references to the works of his predecessor, was the first who noticed the yellow colour of the whey-" liquidem colore diluti citrinum." He crystallised milk-sugar, and determined its amount with fair accuracy; but did not know exactly what it was, for the crystals were of a yellow colour, and reddened syrup of violets; hence they were probably contaminated with lactic acid and colouring-matter.† One of the last workers on the chemistry of Specimen Inaugurale Chemico-medicum de Variis Lactis Bubuli Salibus aliisque Substantius in ejusdem parte Aquosa Contentis, &c. Ludovicus Augustus Schoepff, 1784. + Previous to Schoepff, Beaumé appears to have made an accurate determination of the amount of salt in milk, saying that the third evaporation yielded crystals of sea salt, in the proportion of 7 to 8 grains per pint. Beaumé: Dict. de Chimie, ii., 1778, 498. Rouellium denied that the crystals were those of sea-salt, but considered them "salis febrifugi sylvii." milk, prior to the nineteenth century, was Scheele, who discovered lactic acid, and established that phosphate of lime was always present in the casein. He considered, in fact, that the casein formed with lime a true combination, the proportion between the two being from 1 to 15 per cent. of calcium phosphate to every 100 parts of dried casein.* Experiments similar to those recorded were undertaken by Hoffman, who determined the total solids of cows' milk to be 13.5 per cent. ; of asses, 9.5; goats about 10 per cent.; and of human, 9. He exhausted the total solids by water, and evaporated and weighed the soluble matter thus extracted, but no accurate result followed; and, indeed, it is very difficult to dissolve out milk-sugar and salts fully from the milk solids, unless they have been previously deprived of their fat. Caspar Neumann repeated and enlarged the experiments of Hoffinan; he made out that cows' milk contained 14 per cent. of total solids, and he also distilled milk as well as butter. From 16 ozs. of fresh butter, distilled in a retort, at first over a sand-bath, and afterwards over an open fire, there arose 1 oz. of liquor of no remarkable smell or taste; 1 oz. and half a drm. of a reddish acidulous liquor, which smelt like burnt butter; 1 drm. of a brownish-yellow oil; 3 ozs. 3 drms. of a yellow oil; 1 oz. 6 drms. of a white, and 5 drms. of a yellowish-brown oil-all of a thick butyraceous consistence, and a volatile smell like that of horse-radish; and 1 oz. 6 drms. of a thin empyreumatic oil, which smelt like the Oleum philosophorum, that is, old olive oil distilled over from bricks. There was not the least mark of any volatile alkali in the whole process. The caput mortuum weighed 3 drms.t THE COMPOSITION OF COWS' MILK. § 110. Up to the present time the milk of the mammalia alone has been fully analysed. This has been found to consist of water, a peculiar sugar, albuminous bodies, a small amount of saline matter, and an emulsified fat. The milk of every class of animals has not, however, yet been examined completely; and although it may be presumed, on physiological grounds, that all milks contain qualitatively identical or analogous ingredients to those * De Lacte ejusque Acida: Nova Acta Acad. Reg. Sued. Anni 1780; Opuscula Chemica., vol. ii., p. 101-118. +"The Chemical Works of Caspar Neumann," abridged and methodised, by Wm. Lewis. Lond. 1773. |