ART. VI. Mémoire qui a remporté le premier Prix, &c. i. e. Memoir that gained the first Prize on Feb. 23, 1790, on the following Question propofed by the Royal Society of Medicine, viz. to determine, by a comparative Examination of their Phyfical and Chemical Properties, the Nature of the Milk of Women, that of Cows, Goats, Affes, Sheep, and Mares. By Meff. PARMENTIER and DEYEUX, Members of the College of Pharmacy, &c. Paris. 1791.

THE

HE professed object of philofophical refoarches, is to discover principles which fhall be fubfervient to the ufes of man. Without this object, every inquiry is but the amusement of children. With much fatisfaction, therefore, we contemplate every inftance where fuch purfuits are more immediately applied to the purposes of life; and where facts, which theory may have fuggefted, and which experiments have confirmed, are propofed as the basis of future inquiries, or as the rules of useful practice. The memoir under confideration is of this kind. The question itfelf is important, both to the husbandman, and to the medical practitioner; as it excites to inquiries which relate to an effential article, both of food and of regimen. It is, probably, for this laudable reason, that the refult of experiments made by thefe two ingenious gentlemen, is published at so early a period, and that it is not referved until the appearance of the memoirs of this learned fociety at large.

The memoir is pretty extenfive. The experiments, and the remarks on them, are too many to fuffer either an enumeration or an abridgement: we fhall therefore limit ourselves to fome few of the more leading facts; and to fuch obfervations as appear to us the most striking for their novelty and usefulness.

Omitting the introductory obfervations, which enumerate the general properties cominon to milk, known by every chemist, we shall immediately point out the peculiarities of each fpecies mentioned above.

Cow's milk. The animals, whofe milk was the fubject of examination, were of the fame age and ftrength, were fed in the fame ftable, and all other circumftances were as fimilar as it was poffible to make them, excepting their food. Some were fed, for the fpace of fifteen days, with the leaves of maïs, or Turkey wheat; others with cabbage; others with fmall potatoes; and others with common grafs. The milk of the former was very sweet; that of the fecond, was the leaft agreeable to the tafte; that of the third and fourth, was the moft ferous and infipid.

On diftilling 8 lbs. of each of thefe milks feparately, the authors found that each yielded about 8 ounces of a colourless

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fluid.

fluid. The odour of the milk taken from cows that were fed with cabbage, was by far the ftrongeft; the smell of that from the cows who had eaten grafs was moft aromatic; and this fluid was totally inodorous from the milk of those whofe food had been potatoes and Indian wheat. Leaving this diftilled aqueous fluid for the space of a month, it became, in each specimen, troubled, vifcid, and yielded a fetid fmell. It was, in general, observed, that the fluid from cabbage, degenerated first: but repeated experiments manifefted that this was not always the cafe. On expofing the fluids to a water bath of 25 degrees, (Reaumeur's thermometer,) a filament arofe, and they were clarified. The refiduum of the milk being expofed to an open fire, yielded firft a transparent fluid, yellow and fluid oil, an acid, volatile alkali, a thick black empyreumatic oil, and toward the clofe of the procefs, a quantity of inflammable gas. The remainder was a coal, containing a fixed alkali, with muriatic acid.

Thefe gentlemen obferve, that the more volatile fubftance which flies off and occafions the particular odour, is peculiar to animal bodies; and although, from its volatility, it eludes every inquiry into its fpecific nature, yet there is reafon to imagine that it is a conftituent part of the milk; and, confequently, not deftitute of utility. Hence they conclude, that it is not advisable to boil the milk employed either for common food, or for regimen. It was in the volatile part alone, that effects of the different kinds of food were perceptible. By the more fixed parts, no difcrimination could be made, whether the animal had fed on mild, aromatic, medicinal, or poisonous herbs.

The following remark furnishes an useful hint both to bufbandmen and nurses: By the fudden change of food, though it were from an inferior to a more nutritive kind, the quantity of milk has always fuffered a confiderable diminution, and feveral days were requifite to reftore the former abundance.

Cream. The differences arifing from the diverfity of food, did not manifeft themfelves either by letting the creams ftand until a green efflorefcence was formed of a cheefy nature, and which, with the addition of falt, could be eaten as cheese; nor by diftillation: but, by being agitated for the space of half an hour in oblong bottles, they formed a femi butter, with marked diftinctions. That from the cows fed with maïs, was infipid, very firm, and of a light colour:-from cows fed with potatoes, equally infipid, of fimilar colour, but fofter and more pinguidinous: cabbage gave a strong tafte: common pafturage yielded the greateft plenty of the moft delicate cream, both in flavour and colour,

Butter,

Butter. The authors inftituted feveral experiments to afcertain whether butter really exifts in the cream, and is merely feparated by agitation, or by the art of churning; or whether this process effectuates a chemical change. They are inclined to the latter opinion; because they found that the feparation of the particles of butter could not be produced in any other manner. Cream, left in the milk, yields fat cheese, but not butter. The oily parts do not rife into butter by exposure of cream to heat, nor by boiling it. The application of acids by feparating the cheefy matter blended with the cream, instead of facilitating, retards the fermentation of butter. Half an ounce of oil was mixed with four ounces of cream: this was gently agitated and expofed to moderate heat; part of the oil fwam on the furface, without uniting with the buttery particles in the cream; the other part rendered the formation of butter more difficult, and its confiftence fofter. Thus, whether folvents were applied to attach the buttery or cheefy particles of the cream, agitation was ftill neceffary, and the change into butter was rendered more difficult.

The colour of butter depends, in part, on the nature of the food employed, and partly on artifice; our authors enumerate the vegetable juices which are beft adapted to the purpose. The natural colour is according to the fucculent and aromatic nature of the pasture.

The rancidity of butter is found to proceed entirely from the coagulable, or cheefy matter which is mixed with it. The quantity of this mixture is increafed by the economical method of warming the milk in order to increase the quantity of cream, and by letting the cream remain for too long a time before it is churned. Thus the cream that rifes without the aid of warmth, and that is formed into butter while perfectly fresh, will yield the moft delicate kind, and may be preferved for the longeft time.

The pellicules that rife on the furface of skimmed milk, on exposure to the open air, manifefted themselves to be a portion. of the coagulable or cheefy fubftance. When this was totally feparated, the fluid remaining, was whey, incapable of coagu lation, &c,

By boiling this cheefy fubftance, which was feparated by means of acids, together with fixed fofile alkali, a volatile alkali was difengaged. Mefl. P. and D. think that this is generated by the process; and they imagine, according to the theory of Lavoisier, that the fixed alkali, acting on the coal and oil contained in this cheefy fubftance, difengages the mephitic and inflammable air, the combination of which is fuppofed to form the volatile alkali,

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The

The ferum. This, by filtration, became perfectly limpid. The application of fome fixed alkali, or aerial volatile alkali, depofited a fediment, which was a portion of the cheesy subftance diffolved in diluted acid of the whey. The falt, found in the ferum, was the fugar of milk, and the acid termed by Scheele the fachlactique. Contrary to their expectations from the report of other chemifts, they did not find any fixed alkali in the ferum. Their obfervations induce them to conclude, that the conftituent parts of the whey are the faccharine particles, and a fmall portion of the cheefy fubftance. Other falts are merely accidental.

Having thus, by a variety of experiments, invefligated the nature of milk in general, and the peculiarities of its conftituent principles from their experiments on cow's milk, these affiduous inquirers proceed to analyfe various other fpecies, and to investigate the specific differences which are apparent in that of other females. Omitting every detail, and paffing over every procefs in filence, we fhall confine ourselves to the report made by Mefi. P. and D. in confequence of their experi

ments.

Woman's milk. Their first experiments were made on that taken from a woman four months after her delivery. They ob/erved that, after the cream had rifen, the other part appeared of a more perfect white; and that neither vinegar, nor diluted mineral acids, were able to coagulate it, which is attributed to a fuperabundance of ferum. From fubfequent experiments, made on milks taken from twenty nurfes at different periods, they confirmed the remarks of other chemifts, that the quantity of cheefy fubftance increases according to the age of the milk, and that it becomes more eafily coagulable by acids, Exposure to heat does not increase its coagulability. The cream could not be changed into perfect butter: but it formed a vifcid uncuous fubftance. The fweetness of this milk to the taste, is rather to be attributed to the developement of the faccharine particles, than to their fuperior quantity. It is extremely difficult to afcertain the relative proportions of the different parts of milk in the human fpecies, as they not only vary in different fubjects, but in the fame fubject at different times. Mefl. P. and D. remark, that thefe changes are frequently obvious to the fight.-The following narrative is worthy of the notice of every physiologist:

A nurfe, aged about thirty-two years, who was fubject to nervous affections, frequently furnished milk for examination. We were one day furprized that the milk, which we had procured in the morning, was colourlefs, and almoft tranfparent. In two hours, à fecond quantity was vifcid as the white of an egg; foon after, it

became

became whiter, but it was not before the evening that it had acquired its natural itate. We examined the milk of this woman four days fucceffively, without obferving any remarkable change: but on the fifth day, the milk was as at the preceding period; and we learned that fhe had been attacked, in the night, with hysteric fits. During two months, fimilar appearances and variations took place, which always correfponded with the ftate of her health.'

These gentlemen fuggeft the hint, that a due attention to fuch changes, might, in fome cafes, furnish a diagnostic to the practitioner, in conjunction with the other fecretions.

Affes milk,-in colour, tafte, and confiftence, resembles woman's milk: but a chemical analyfis manifefts the following peculiarities. The odour of the diftilled vapour is fcarcely perceptible; and though it does not appear to contain any thing in folution, yet it depofits a fediment fimilar to the lymph of cow's milk. All the acids coagulate this milk, but in a fingular manner. The coagulum does not exhibit one uniform mafs, but diftinct floculi. The cream is not abundant, and is changed, with difficulty, into a foft butter, which foon becomes rancid. The faccharine particles are in fmall quantities, and are very frequently mixed with muriatic felenites, and common falt...

'Goat's milk. The cream is thick and agreeable to the tafte. The milk may be preferved longer than any other species, when exposed to the atmosphere; and the fkim on its furface will, of itself, be changed, by time, into palatable cheese. The butter is firm, eafily formed, does not readily become rancid, and is of a good flavour. The butter-milk contains a large portion of cheesy fubftance, which readily coagulates. The fugar is not in fo large a proportion as in the two preceding.

Sheep's milk. It is difficult to diftinguish this milk from that of a cow. Its cream eafily feparates by ftanding. It is yellow, of an agreeable flavour, and affords much butter: but it is not folid, and foon becomes rancid, till the acids, &c. coagulate it. From the characteristic properties of the two kinds of milk, it is not difficult to perceive wherefore a due mixture of goats' and fheeps' milk, is supposed to make the beft kind of cheese.

Mare's milk. This is lefs fluid than that of women, or of affes, but more infipid. It requires a smaller degree of heat than any other, to excite ebullition; it is not difficult to coagulate-the diftilled water does not eafily degenerate-the oily particles are fmaller in quantity than in any of the preceding; the cheesy matter is also but in small proportions, and yet difficult to feparate. Its cream cannot be worked into butter-the whey contains about the fame proportion of fugar with the whey of cows' and goats' milk.

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