a well known fluid, prepared by nature in the breasts of women, and the udders of other animals, for the nourishment of their young.—According to Dr Cullen*, milk is a connecting and intermediate substance between animals and vegetables. It seems Mat. Med., immediately to be secreted from the chyle, both being a white liquor of the same consistence: it is most copiously secreted after meals, and of an acetic nature. In most animals who live on vegetables, the milk is acetic; and it is uncertain, though at the same time no observation proves the contrary, whether it is not so likewise in carnivorous animals. But, whatever be in this, it is certain, that the milk of all animals who live on vegetables is acetic. Milk being derived from the chyle, we thence conclude its vegetable nature; for in those who live on both promiscuously, more milk is got, and more quickly, from the vegetable than the animal food. Milk, however, is not purely vegetable; though we have a vegetable liquor that resembles its taste, consistence, colour, aceticity, and the separability of the oily part, viz. an emulsion of the nucis oleifera and farinaceous substances. But these want the coagulable part of milk, which seems to be of animal nature, approaching to that of the coagulable lymph of the blood. Milk, then, seems to be of an intermediate nature, between chyle taken up from the intestines and the fully elaborated animal fluid.

Its contents are of three kinds: 1st, An oily part, which, whatever may be said concerning the origin of other oils in the body, is certainly immediately derived from the oil of the vegetables taken in; as with these it agrees very exactly in its nature, and would entirely, if we could separate it fully from the coagulable part. Another mark of their agreement is the separability, which proves that the mixture has been lately attempted, but not fully performed. 2dly, Besides this oily, there is a proper coagulable part; And, 3dly, Much water accompanies both, in which there is dissolved a saline saccharine substance. These three can be got separate in cheese, butter, and whey; but never perfectly so, a part of each being always blended with every other part.

Nothing is more common, from what has been said of its immediate nature, than to suppose that it requires no assimilation; and hence has been deduced the reason of its exhibition in the most weakly state of the human body. But wherever we can examine milk, we always find that it coagulates, suffers a decomposition, and becomes acetic. Again, Infants, who feed entirely on milk, are always troubled with eruptions, which every body observes are not of the same quality with the food taken; and therefore it appears, that, like all other food, milk turns naturally acetic in the stomach, and only enters the chyle and blood in consequence of a new recomposition. It approaches then to the nature of vegetable aliment, but is not capable of its noxious vinous fermentation, and therefore has an advantage over it; neither from this quality, like animal food, is it heating in the stomach, and productive of fever; though at the same time, from its quantity of coagulable matter, it is more nourishing than vegetables.

Milk is the food most universally suited to all ages and states of the body; but it seems chiefly designed by nature as the food of infants. When animals are in the fetus state, their solids are a perfect jelly, incapable of an assimilatory power. In such state nature has perfectly assimilated food, as the albumen ovi in the oviparous, and in the viviparous animals certainly somewhat of the same kind, as it was necessary the veffels should be filled with such a fluid as would make way for an after assimilation. When the infant has attained a considerable degree of firmness, as when it is separated from the mother, yet such a degree of weakness still remains as makes somewhat of the same indication necessary; it behoves the infant to have an alkalescent food ready prepared, and at the same time its noxious tendency to be avoided. Milk then is given, which is alkalescent, and, at the same time, has a sufficient quantity of acidity to correct that alkaliescence. As the body advances in growth, and the alkalescent tendency is greater, the animal, to obviate that tendency, is led to take vegetable food, as more suited to its strength of assimilation.

Dr Cullen observes, that milk is suited to almost all temperaments; and it is even so to stomachs disposed to aceticency, more than those substances which have undergone the vinous fermentation; nay, it even cures the heartburn, checks vinous fermentation; and precipitates the lees, when, by renewal of fermentation, the wine happens to be fouled. It therefore very properly accompanies a great deal of vegetable aliment; although sometimes its aceticency is troublesome, either from a large proportion taken in, or from the degree of it; for, according to certain unaccountable circumstances, different acids are formed in the stomach in different states of the body; in a healthy body, e.g., a mild one; in the hypochondriac disease sometimes, one of a very acid quality. When the acidity of milk is carried to a great degree, it may prove remarkably refrigerant, and occasion cold crudities, and the recurrence of intermittent fevers. To take the common notion of its passing unchanged into the blood, it can suffer no solution. But if we admit its coagulum in the stomach, then it may be reckoned among soluble or insoluble foods, according as that coagulum is more or less tenacious. Formerly rennet, which is employed to coagulate milk, was thought an acid; but, from late observations, it appears, that, if it be an acid, it is very different from other acids, and that its coagulum is stronger than that produced by acids. It has been imagined, that a rennet is to be found in the stomachs of all animals, which causes coagulation of milk; but according to Dr Cullen the coagulation of milk seems to be owing to a weak acid in the stomach, the relics of our vegetable food, inducing, in healthy persons, a weak and soluble coagulum; but in different stomachs this may be very different, in these becoming heavy and less soluble food, and sometimes even evacuated in a coagulated undissolved state both by stomach and stool.

As milk is acetic, it may be rendered sometimes purgative by mixing with the bile; and some examples of this have been remarked. More commonly, however, it is reckoned among those foods which occasion coliciveness.

Hoffman, in his experiments on milk, found that all kinds of it contained much water; and when this was distilled, found the residuum very different in their solubility. But we must not thence conclude, that the same insolubility takes place in the stomach; for extracts made from vegetables with water are often very insoluble substances, and hardly diffusible through water itself: therefore, in Hoffman's extracts, if we may so call them, of milk, somewhat of the same kind might have appeared; and these substances, which in their natural state were not so, might appear very insoluble. However, we may allow that milk is always somehow insoluble in the intestines, as it is of a drying nature, and as cheese, &c. is very colitive. And this effect shows that milk is always coagulated in the stomach; for if it remained fluid, no faeces would be produced, whereas sometimes very hard ones are observed. In the blood veffels, from its animal nature, it may be considered as nutritious; but when we consider its vegetable contents, and aceticency in the prime vice, we find that, like animal food, it does not excite that degree of fever in the time of digestion, and that from its aceticency it will resist putrefaction. Hence its use in hectic fevers, which, whatever be their cause, appear only to be exacerbations of natural feverish pae- roxyfms, which occur twice every day, commonly af- ter meals, and at night. To obviate these, therefore, we give such an aliment as produces the least exacer- bation of these fevers; and of this nature is milk, on account of its acefcent vegetable nature.

There appears also somewhat peculiar to milk, which requires only a small exertion of the animal powers in order to its assimilation; and besides, in hectic com- plaints there is wanted an oily, bland food, approach- ing to the animal nature; so that on all these accounts milk is a diet peculiarly adapted to them, and, in gen- eral, to most convalescents, and to those of inflam- matory temperaments. So far of milk in general. We shall now speak of the particular kinds which are in common use.

The milks of women, mares, and asses, agree very much in their qualities, being very dilute, having little solid contents, and, when evaporated to dryness, having these very soluble, containing much saccharine matter, of a very ready acefcenty, and, when coagulated, their coagulum being tender and easily broke down. From this view they have less oil, and seem to have less coa- gulable matter than the rest.

The milks of cows, sheep, and goats, agree in op- posite qualities to the three just mentioned; but here there is somewhat more of gradation. Cows' milk comes nearest to the former milk; goats' milk is less fluid, less sweet, less glutinous, has the largest propor- tion of insoluble part after coagulation, and indeed the largest proportion of coagulable part; its oily and coa- gulable parts are not spontaneously separable, never throwing out a cream, or allowing butter to be read- ily extracted from it. Hence the virtues of these milks are obvious, being more nourishing, though at the same time less easily soluble in weak stomachs, than the three first, less acefcent than these, and to more rarely laxative, and peculiarly fitted for the diet of conva- lescents without fever. The three first again are less nourishing, more soluble, more laxative, as more acef- cent, and adapted to the convalescents with fever.

These qualities, in particular milks, are considerably diversified by different circumstances. First, Different animals, living on the same diet, give a considerable different milk; for there seems to be something in the constitution, abstracting from the aliment, which con- stitutes a considerable diversity of milk, not only in the same species of animals, but also in the same animal, at different ages, and at different distances after deli- very: this applies to the choice of nurses. Secondly, Milk follows the nature of the aliment more than any other juice in the human body, being more or less fluid and dilute, more or less solid and nourishing; in pro- portion as these qualities are more or less in the ali- ment. The nature of the aliment differs according to its time of growth, e.g., old grazes being always found more nourishing than young. Aliment, too, is always varied according to the season, as that is warm or dry, moist or cloudy.

The milk of each particular kind of animal is fitter for particular purposes, when fed on proper food.— Thus the cow delights in the succulent herbage of the vale: if the sheep be fed there he certainly rots, but on the higher and more dry side of the mountain he feeds pleasantly and healthy; while the goat never stops near the bottom, but ascends to the craggy sum- mit: and certainly the milks of these animals are al- ways best on their proper soil, and that of goats is best on a mountainous country. From a dissertation of Linnaeus, we have many observations concerning the diversity of plants on which each animal chooses to feed. All the Swedish plants which could be collect- ed together, were presented alternately to domestic animals, and then it appeared that the goat lived on the greatest variety, and even on many which were poi- sonous to the rest; that the cow chose the first succu- lent shoots of the plant, and neglected the fructification; which last was preferred by the goat. Hence may be deduced rules concerning the pasturage of dif- ferent animals; e.g., farmers find, that, in a pasture which was only fit to feed a certain number of sheep, an equal number of goats may be introduced, while the sheep are no less nourished than before.

It is not easy to assign the difference between milk fresh drawn and that detained in the open air for some time: but certainly there is some material one, other- wise nature universally would not have directed infants to sucking; and indeed it seems, better than the other, fitted for digestion and nourishment. Physicians have supposed that this depended on the evaporation of some fat, rector: but our author cannot conceive any such, except common water here; and besides, these volatile parts can hardly be nutritious. A more plausible ac- count seems deducible from mixture: milk new drawn has been but lately mixed, and is exposed to sponta- neous separation, a circumstance hurtful to digestion; none of the parts being, by themselves, so easily affi- liated as when they are all taken together. Hence, then, milk new drawn is more intimately blended, and therefore then is most proper to the weakly and in- fants.

Another difference in the use of milk exposed for some time to the air, is taking it boiled or unboiled. Physicians have generally recommended the former; but the reason is not easily assigned. Perhaps it is this: Milk kept for some time exposed to the air has gone so far to a spontaneous separation; whereas the heat thoroughly blends the whole, and hence its refo- ration is not so easy in the stomach; and thus boiled milk is more cohesive than raw, and gives more feces. Again, When milk is boiled, a considerable quantity of air is detached, as appears from the froth on the sur- face; and air is the chief instrument of fermentation in bodies; so that after this process it is not liable to acefcenty: for these reasons it is proper for the robust and vigorous.

Another difference of milk is, according as it is fluid or coagulated. The coagulated is of two kinds, as induced by rennet, or the natural acefcenty of the milk. The former preparation makes the firmer and less easily soluble coagulum; though, when taken with the whey unseparated, it is less difficult of solution, though more so than any other coagulum in the same case. Many nations use the latter form, which is easier soluble, but very much acefcent, and therefore, in point of solution, should be confined to the vigorous, in point of acefcenty, to those who live on alkaline food; and in the last case, the Laplanders use it as their chief acefcent Milk.

acecent condiment. From the same considerations it is more cooling, and in its other effects like all other acecent vegetables.

Milk by evaporation yields a sweet saline matter, of which Dr Lewis gives the following proportion:

| Twelve ounces of | Left of dry matter | From which water extracted a sweet saline substance amounting to | |------------------|--------------------|---------------------------------------------------------------| | Cows milk | 13 drachms | 1\(\frac{1}{2}\) drachms. | | Goats milk | 12\(\frac{1}{2}\) | 1\(\frac{1}{2}\) | | Human milk | 8 | 6 | | Asses milk | 8 | 6 |

The saline substance extracted from asses milk was white, and sweet as sugar; those of the others brown or yellow, and considerably less sweet; that from cows milk had the least sweetness of any.

On distilling 12 quarts of milk in balneo mariae, at least nine quarts of pure phlegm were obtained; the liquor which afterwards arose was acidulous, and by degrees grew feebly more and more acid as the distillation was continued. After this came over a little spirit, and at last, an empyreumatic oil. The remaining solid matter adhered to the bottom of the retort, in the form of elegant shining black flowers, which being calcined and elixited yielded a portion of fixed alkaline salt.

Milk set in a warm place, throws up to the surface an unctuous cream, from which, by agitation, the butter is easily separated. The addition of alkaline salts prevents this separation, not (as some have supposed) by absorbing an acid from the milk, but by virtue of their property of intimately uniting oily bodies with watery liquors. Sugar, another grand intermediate between oils and water, has this effect in a greater degree, though that concrete is by no means alkaline, or an absorbent of acids.

The sweet saccharine part of the milk remains dissolved in the whey after the separation of the curd or cheesy matter, and may be collected from it in a white crystalline form, by boiling the whey till all remains of the curdled substance have fallen to the bottom; then filtering, evaporating it to a due consistence, setting it to float, and purifying the crystals by solution in water and a second crystallization. Much has been said of the medicinal virtues of this sugar of milk, but it does not seem to have any considerable ones: It is from cows milk that it has been generally prepared; and the crystals obtained from this kind of milk have but little sweetness.

When milk is suffered to coagulate spontaneously, the whey proves acid, and on standing grows more and more so till the putrefactive state commences. Sour whey is used as an acid, preferably to the directly vegetable or the mineral acids, in some of the chemical arts; as for dissolving iron in order to the staining of linen and leather. This acid was commonly made use of in the bleaching of linen, for dissolving and extracting the earthy particles left in the cloth by the alkaline salts and lime employed for cleansing and whitening it. Butter milk is preferred to plain sour milk or sour whey: This last is supposed to give the cloth a yellow colour. Dr Home, in his ingenious treatise on this subject, recommends water acidulated with sulphuric acid (in the proportion of about half an ounce, or at most three quarters of an ounce, to a gallon), as preferable in many respects to the acid of milk, or of the more directly vegetable substances.

He observes, that the latter are often difficultly procurable, abound with oleaginous particles, and liable to corruption; whilst the vitriolic acid is cheap, and pure, and disposed to putrefy: That milk takes five days to perform its office, whilst the vitriolic acid does it in as many hours, perhaps in as many minutes: That this acid contributes also to whiten the cloth, and does not make it weaker though the cloth be kept in it for months. He finds, that acid, as well as alkalies, extract an oily matter from the cloth, and lose their acidity and alkalinity. Since this treatise appeared, the use of four milk is very generally superceded by oil of vitriol.

It is observable, that asses milk is greatly disposed, on standing for a little time, to become thick and ropy. In the Breslaw collection for the year 1720, there is a remarkable account of milk (which probably was that of the ass) grown so thick and tenacious as to be drawn out into long strings, which, when dried, were quite brittle.

New cows milk, suffered to stand for some days on the leaves of butterwort or sun-dew, becomes uniformly thick, slippery, and coherent, and of an agreeable sweet taste, without any separation of its parts. Fresh milk, added to this, is thickened in the same manner, and this successively. In some parts of Sweden, as we are informed in the Swedish Memoirs, milk is thus prepared for food.

New milk has a degree of glutinous quality, so as to be used for joining broken stone ware. There is a far greater tenacity in cheese properly prepared.

Milk, when examined by a microscope, appears composed of numerous globules swimming in a transparent fluid. It boils in nearly the same degree of heat with common water; some forts rather sooner, and some a little later: after boiling, it is less disposed to grow sour than in its natural state. It is coagulated by acids both mineral and vegetable, and by alkalies both fixed and volatile. The coagulum made by acids falls to the bottom of the serum; that made by alkalies swims on the surface, commonly forming (especially with volatile alkalies) a thick coriaceous skin. The serum, with alkalies, proves green or fainous; with acids, it differs little in appearance from the whey that separates spontaneously. The coagulum formed by acids is redissolved by alkalies, and that formed by alkalies is redissolved by acids; but the milk does not in either case resume its original properties. It is coagulated by most of the middle salts, whose basis is an earth or a metallic body; as solution of alum, fixed sal ammoniac, sugar of lead, green and blue vitriol; but not by the chalybeate or purging mineral waters, nor by the bitter salt extracted from the purging waters. Among the neutral salts that have been tried, there is not one that produces any coagulation. They all dilute the milk, and make it less disposed to coagulate with acids or alkalies: Nitre seems to have this effect in a greater degree than the other neutral salts. It is instantly coagulated by highly rectified MILK

refined spirit of wine, but scarcely by a phlegmatic spirit. It does not mingle with expressed oils. All the congloba are dissolved by gall.

It has generally been supposed by medical authors, that the milk of animals is of the same nature with chyle, and that the human milk always coagulates in the stomach of infants; but in a late dissertation upon the subject by Mr Clarke, member of the Royal Irish Academy, we find both these positions controverted. According to him, women's milk, in a healthy state, contains no coagulable, mucilaginous, or cheesy principle, in its composition; or it contains so little, that it cannot admit of any sensible proof. Dr Rutty states, that it does not afford even a fifth part of the curd which is yielded by cows' milk; and Dr Young denies that it is at all coagulable either by rennets or acids. This is confirmed by Dr Ferris, who in 1782 gained the Harveian prize medal at Edinburgh by a dissertation upon milk. Mr Clarke informs us, that he has made a vast number of experiments upon women's milk with a view to determine this point. He made use of ardent spirits, all the different acids, infusions of infants' stomachs, and procured the milk of a great many different women; but in no instance, excepting one or two, did he perceive any thing like curd. This took place in consequence of a spontaneous aceticity; and only a small quantity of soft flaky matter was formed, which floated in the serum. This he looked upon to be a morbid appearance.

The general opinion that women's milk is coagulable has arisen from a single circumstance, viz. that infants frequently vomit the milk they suck in a state of apparent coagulation. This greatly perplexed Dr Young; who, after having tried in vain to coagulate human milk artificially, concluded, that the process took place spontaneously in the stomach; and that it would always do so if the milk were allowed to remain in a degree of heat equal to about 96 degrees of Fahrenheit. Mr Clarke took equal quantities of three different kinds of milk, and put them into bottles slightly corked, and these bottles into water, the temperature of which was kept up by a spirit of wine lamp as near as possible to 96° of Fahrenheit: but after frequently examining each bottle during the course of the experiment, at the expiration of several hours there was not the smallest tendency towards coagulation to be perceived in any of them; the cream was only thrown to the surface in a thick and adhesive form, and entirely separated from the fluid below, which had something of a gray and wheyish appearance. As the matter vomited by infants is sometimes more adhesive than we can suppose cream to be, Mr Clarke supposed that the curd might be so entangled with the cream, as to be with difficulty separated from it; but having collected a quantity of rich cream from the milk of different women, he repeated the experiment with precisely the same event, not being able in any one instance to produce the smallest quantity of curd. To determine, however, what effects might be produced upon milk by the stomach of an infant, Mr Clarke made the following experiment: Having taken out the stomach of a fetus which had been deprived of life by the use of instruments, he infused it in a small quantity of hot water, so as to make a strong infusion. He added a tea-spoonful of this infusion to equal quantities of cows and human milk; the consequence of which was, that the cow's milk was firmly coagulated in a short time, but the human milk was not altered in the least; neither was the least coagulation produced by adding a second and third spoonful to the human milk. "Upon the whole, then, (says Mr Clarke), I am persuaded it will be found, that human milk, in a healthy state, contains little or no curd, and that the general opinion of its nature and properties is founded upon fallacious analogy and superficial observations made on the matter vomited by infants. We may presume, that the cream of women's milk, by its inferior specific gravity, will swim on the surface of the contents of the stomach; and being of an oily nature, that it will be of more difficult digestion than any other constituent part of milk. When an infant then sucks very plentifully, so as to over-distend the stomach, or labours under any weaknesses in the powers of digestion, it cannot appear unreasonable to suppose, that the cream shall be first rejected by vomiting. Analogous to this, we know that adults affected with dyspepsia often bring up greasy fluids from the stomach by eructation, and this especially after eating fat meat. We have, in some instances, known this to blaze when thrown into the fire like spirit of wine or oil." Our author derives a confirmation of his opinion from the following observation, viz. that curds vomited by infants of a few days old are yellow, while they become white in a fortnight or three weeks. This he accounts for from the yellow colour of the cream thrown up by the milk of women during the first four or five days after delivery.

Mr Clarke likewise controverts that common opinion of the human milk being so prone to acidity, that a great number of the distempers of children are to be accounted for from that principle. "Whoever (says he) takes the trouble of attentively comparing human milk with that of ruminant animals, will soon find it to be much less prone to run into the acetic or acid process. I have very often exposed equal quantities of human and cows' milk in degrees of temperature, varying from the common summer heat, or 65°, to 100°; and I have constantly found that cows' milk acquires a greater degree of acidity in 36 hours than the human did in many days: cows' milk becomes offensive putrid in four or five days; a change which healthy human milk, exposed in the same manner, will not undergo in many weeks, nay, sometimes in many months. I once kept a few ounces of a nurse's milk, delivered about six or seven days, for more than two years in a bottle moderately corked. It stood on the chimney-piece, and was frequently opened to be examined. At the end of this period it showed evident marks of moderate acidity, whether examined by the taste, smell, or paper stained with vegetable blues or purples; the latter it changed to a florid red colour, whereas cows' milk kept a few days changed the colour of the same paper to a green, thereby clearly showing its putrefactive tendency."

Our author next goes on to consider of the probability there is of milk becoming so frequently and strongly acid as to occasion most of the distempers of infants. He begins with an attempt to show that the phenomena commonly looked upon to be indications of acrimony are by no means certain. Curdled milk... has already been shown to be no sign of acidity; and the other appearance, which has commonly been thought to be so certain, viz. green faeces, is, in the opinion of Mr Clarke, equally fallacious. In support of this he quotes a letter from Dr Sydenham to Dr Cole; in which he says, that the green matter vomited by hysterical women is not any proof of acrid humours being the cause of that disease, for sick people do the same. The opinion of green faeces being an effect of acidity, proceeds upon the supposition that a mixture of bile with an acid produces a green colour: but it is found, that the vegetable acid, which only can exist in the human body, is unable to produce this change of colour, though it can be effected by the strong mineral acids. As nothing equivalent to any of these acids can be supposed to exist in the bowels of infants, we must therefore take some other method of accounting for the green faeces frequently evacuated by them. "Why should sour milk, granting its existence, give rise to them in infants and not in adults? Have butter milk, summer fruits of the most acidulent kind, lemon or orange juice, always this effect in adults by their admixture with bile? This is a question which, I believe, cannot be answered in the affirmative."

On the whole, Dr Clarke considers the disease of acidity in the bowels, though so frequently mentioned, to be by no means common. He owns indeed, that it may sometimes occur in infancy as well as in adults, from weakness of the stomach, colic, or improper food; and an indubitable evidence is afforded by faeces which stain the blue or purple colour of vegetables to a red, though nothing can be inferred with certainty from the colour or smell.

The doctor next proceeds to state several reasons for his opinion, that the greater number of infantile diseases are not owing to acidity; 1. Women's milk in a healthy state contains little or no coagulable matter or curd. 2. It shows less tendency out of the body to become acidulent than many other kinds of milk. 3. The appearances which have been generally supposed to characterize its acidity do not afford satisfactory evidence of such a morbid cause. 4. Granting this to be the case, we have plenty of mild absorbents, capable of destroying all the acid which can be supposed to be generated in the bowels of an infant; yet many children are observed to die in consequence of these diseases supposed to arise from acidity. 5. Though the milk of all ruminant animals is of a much more acidulent nature than that of the human species, yet the young of these animals never suffer anything like the diseases attributed to acidity in infants. 6. History informs us that whole nations use sour curdled milk as a considerable part of their food, without feeling any inconvenience; which, however, must have been the case, if acidity in the stomach were productive of such deleterious effect as has been supposed.

The reasoning of Dr Clarke seems here to be very plausible, and nothing has as yet been offered to contradict it. The reviewers in taking notice of the treatise only observe, that the doctor's positions are supported by great probability; yet "they have seen them, or think they have seen them, contradicted by the appearance of diseases and the effects of medicines;" so that they must leave the subject to farther examination.

In a memoir by Messrs Parmentier and Deyoux, members of the royal college of pharmacy, &c., in Paris, we have a great number of experiments on the milk of asses, cows, goats, sheep, and mares, as well as women. The experiments on cows' milk, were made with a view to determine whether any change was made in the milk by the different kinds of food eaten by the animal. For this purpose some were fed with the leaves of maize or Turkey wheat; some with cabbage; others with small potatoes; and others with common grass. The milk of those fed with the maize or Turkey wheat was extremely sweet; that from the potatoes and common grass much more furred and infipid; and that from the cabbages the most disagreeable of all. By distillation only eight ounces of a colourless fluid were obtained from as many pounds of each of these milks; which from those who fed upon grass had an aromatic flavour; a disagreeable one from cabbage; and none at all from the potatoes and Turkey wheat. This liquid became fetid in the space of a month, whatever substance the animal had been fed with, acquiring at the same time a viscidity and becoming turbid; that from cabbage generally, but not always, becoming first putrid. All of them separated a filamentous matter, and became clear on being exposed to the heat of 25° of Reaumur's thermometer. In the residuums of the distillation no difference whatever could be perceived. As the only difference therefore existing in cows' milk lies in the volatile part, our authors conclude, that it is improper to boil milk either for common or medicinal purposes. They observed also that any sudden change of food, even from a worse to a better kind was attended by a very remarkable diminution in the quantity of milk. All the residuums of the distillations yielded, in a strong fire, a yellow oil and acid, a thick and black empyreumatic oil, a volatile alkali, and towards the end a quantity of inflammable air, and at last a coal remained containing some fixed alkali with muriatic acid.

On agitating in long bottles the creams from the milk of cows fed with different substances, all of them were formed into a kind of half-made butter; of which that formed from the milk from maize was white, firm, and infipid; that from potatoes was softer and more pinguedinous; but that from common grass was the best of all. Cabbage, as in other cases, gave a strong taste.

In the course of their experiments, it was endeavoured to determine whether butter is actually contained in the cream, or whether it be a chemical production of the operation of churning. They could not find any reason absolutely satisfactory on either side, but incline to the latter opinion; because when cream is allowed to remain among the milk, and the whole curdled promiscuously, only fat cheese, without any butter, is produced. The oily parts cannot be separated into butter either by acids or any other means than churning; even the artificial mixture of oil with the cream is insufficient for the purpose.

The serum of milk was reduced by filtration to a clear and pellucid liquor; and, by mixture with fixed alkali, deposited a portion of cheesy matter which had been been dissolved in the whey. The sugar of milk was also found in this liquor.

In their experiments upon the milk of various animals, it was found that the milk of asses yielded by distillation an insipid liquor, and deposited a liquor similar to the lymph of cows' milk. It is coagulated by all the acids, but not into an uniform mass; exhibiting only the appearance of distinct flocculi. It affords but little cream, which is converted with difficulty into a soft butter that soon becomes rancid. It has but a small quantity of saccharine particles, and these are often mixed with muriatic felspar and common salt. Goats' milk has a thick cream, and agreeable to the taste; and the milk itself may be preserved longer in a sound state than any other species, the scum on its surface being naturally convertible into palatable cheese. It is easily made into firm butter, which does not soon become rancid, and has a good flavour. The butter milk contains a large quantity of cheesy matter, which readily coagulates; but has still less saccharine matter than that of asses. Sheep's milk can scarcely be distinguished from that of a cow, and easily parts with its cream by standing. It is of a yellow colour, an agreeable flavour, and yields a great proportion of butter; but this is not solid, and soon becomes rancid. Mares' milk is the most insipid and least nutritious of any; notwithstanding which it has been much recommended for weak and consumptive patients: in which cases it is probable that it proves efficacious by being more consonant than any other to the debilitated powers of digestion. It boils with a smaller fire than any other kind of milk, is easily coagulated, and the distilled water does not soon change its nature. It has but a small quantity of cheesy matter, and very few oily particles: the cream cannot be made into butter; and the whey contains about as much sugar as cows or goats' milk.

In this memoir our authors remark, that in order to augment the quantity, as well as to improve the quality, of the milk of animals, they should be well fed, their stalls kept clean, and their litter frequently renewed: they should be milked at stated hours, but not drained; great attention should also be paid to the breed; because inferior cattle are maintained at as great expense as the most valuable kinds. No change ought to be made in the food; though if the milk be employed for medicinal purposes, it may be improved by a proper mixture of herbs, &c.

In their experiments on women's milk, Messrs Parmentier and Deyeux differ somewhat from Dr Clarke. They first tried the milk of a woman who had been delivered four months; and observed, that after the cream had been separated the other part appeared of a more perfect white, and that it could not be coagulated either by vinegar or mineral acids; which they attributed to a superabundance of serum. But they found that in proportion to the age of the milk it was found to be more easily coagulable; and this was confirmed by experiments made upon the milk of 20 nurses. Its coagulability was not increased by heat. The cream, by agitation, formed a viscid unctuous matter, but could not be changed into perfect butter; but they found that it was extremely difficult to determine the proportions of the various component parts in human milk, as it differs remarkably, not only in different subjects, but in the same subject at different times. In a nurse aged about 32 years, who was extremely subject to nervous affections, the milk was one day found almost quite colourless and transparent. In two hours after, a second quantity drawn from the breast was viscid like the white of an egg. It became whiter in a short time, but did not recover its natural colour before the evening. It was afterwards found that these changes were occasioned by her having some violent hysterical fits in the meantime.

Sugar of Milk. Different methods have been proposed for obtaining the sugar of milk. The following is an account of a method used by some of the Tartar nations of preserving their milk by means of frost: in which operation great quantities of the sugar of milk are accidentally formed. The account was given by Mr Fabrig of Peterburgh, who undertook a journey, by order of the academy of Peterburgh, among the Mogul tribes who inhabit the country beyond the lake Baikal, on the banks of the river Salenga. These people allow their milk to freeze in large quantity in iron kettles; and, when it is perfectly congealed, they place them over a gentle fire to soften the edges of the cake, after which it may be taken out with a wooden spatula. They commence these operations at the beginning of the cold, when they have milk in the greatest abundance; after which it may be preserved with great ease throughout the whole winter. Mr Fabrig having frequent opportunities of seeing these cakes, soon observed, that the surface of them was covered to a considerable depth with a farinaceous powder; and having established a dairy upon the same plan with those of the Moguls, he found the same thing take place with himself. This powder was extremely sweet, and he received platefuls of it from the natives, who used it in their food, and sweetened their other viands with it. Having caused a number of cakes of frozen milk to be conveyed to the top of his house, where they were directly exposed to the violent cold, he found that the separation of the saccharine powder was greatly promoted by this means. He scraped the cakes every week to the depth of two inches, and afterwards spread out the powder upon an earthen plate in order to destroy the remains of moisture which might have prevented it from keeping for any length of time. When exposed in this manner it had a very agreeable and strong saccharine taste; dissolved in warm water; and when strongly stirred by means of a chocolate stick, would at all times produce an excellent and well tasted milk. Raw milk affords a much larger quantity of this saccharine matter than such as has been boiled, or which has had the cream taken off it. Neither must the milk be suddenly exposed to the cold before it has lost its natural heat; for the sudden contact of the cold drives all the cheesy and fat part towards the middle, while the external parts consist of little else than water. In order to allow the parts of the milk to be all properly mixed together, Mr Fabrig allowed the milk when newly taken from the cows to cool, and then poured it out into shallow kettles.

Our author is of opinion that this method of making milk would be of great service to navigators to supply themselves with milk during long sea voyages: and he he affirms us, from his own experience, that it will always succeed, if proper attention be paid to it. He is of opinion, however, that all countries are not equally proper for the preparation of this faecararine matter; and indeed this seems very evidently to be the case, as the process appears to be a crystallization of the faecararine parts of the milk, and a separation of them from the aqueous ones by means of extreme cold. The country in which he made the experiments is one of the most elevated in all Asia; and so cold, that, though it lies only in the 60th degree of north latitude, its rivers are frozen up for six months of the year. A very dry cold wind also prevails throughout almost the whole year; and the dry winds generally come from the north, being almost always preceded by a warm wind from the south, which blows for some time. The dry rarefied air increases the evaporation from the ice cakes, and leaves nothing but the faecararine or pure constituent parts of the milk, which with the addition of water can always recompone the fluid.

the wine trade. The coopers know very well the use of skimmed milk, which makes an innocent and efficacious forcing for the fining down of all white wines, arracks, and small spirits; but it is by no means to be used for red wines, because it discharges their colour. Thus, if a few quarts of well skimmed milk be put into a hogshead of red wine, it will soon precipitate the greater part of the colour, and leave the whole nearly white: and this is of known use in the turning of red wines, when pricked, into white; in which a small degree of acidity is not so much perceived.

Milk is, from this quality of discharging colour from wines, of use also to the wine coopers, for the whitening of wines that have acquired a brown colour from the cask, or from having been hastily boiled before fermenting; for the addition of a little skimmed milk, in these cases, precipitates the brown colour, and leaves the wines almost limpid, or of what they call a water whiteness, which is much coveted abroad in wines as well as in brandies.

Milk of Lime; Milk of Sulphur. The name of milk is given to substances very different from milk properly so called, and which resemble milk only in colour. Such is water in which quicklime has been flasked, which acquires a whiteness from the small particles of the lime being suspended in it, and has hence been called the milk of lime. Such also is the solution of liver of sulphur, when an acid is mixed with it, by which white particles of sulphur are made to float in the liquor.

Milk of Vegetables. For the same reason that milk of animals may be considered as a true animal emulsion, the emulsive liquors of vegetables may be called vegetable milks. Accordingly emulsions made with almonds are commonly called milk of almonds. But besides this vegetable milk, which is in some measure artificial, many plants and trees contain naturally a large quantity of emulsive or milky juices. Such are lettuce, spurge, fig tree, and the tree which furnishes the elastic American resin. The milky juices obtained from all these vegetables derive their whiteness from an oily matter, mixed and undissolved in a watery or mucilaginous liquor. Most resinous gums were originally such milky juices, which afterwards become solid by the evaporation of their more fluid and volatile parts.

Milk-Poison. See Medicine Index.

Milk-Hedge, the English name of a shrub growing on the coast of Coromandel, where it is used for hedging. The whole shrub grows very bushy, with numerous erect branches, which are composed of cylindrical joints as thick as a tobacco pipe, of a green colour, and from three to five inches long: the joints are thicker than the other parts, but always give way first on any accidental violence offered to the plant. When broken it yields a milk of an excessively caustic quality, which blisters any part of the skin it touches. When the joints are broken off at each end, the tube then contains very little milk. In this state Mr Ives ventured to touch it with his tongue, and found it a little sweet. In the hedges it is seldom very woody; but when it is, the wood is very solid, and the bark gray and cracked. This plant, he informs us, has acquired great reputation in curing the venereal disease, on the following account: A poor Portuguese woman, the eldest female of her family, had wrought surprising cures in the most inveterate venereal disorders, even such as the European physicians had pronounced incurable. These facts became so notorious, that the servants of the Company, and especially their surgeons, were induced to offer her a very considerable premium for a discovery of the medicine; but she always refused to comply, giving for a reason, that while it remained a secret, it was a certain provision for the maintenance of the family in the present as well as in future generations. On account of this denial the English surgeons were sometimes at the pains to have her motions without doors carefully watched; and as they were not able to discover that she ever gathered of any other plant or tree but this, they conjectured that the milk of this tree was the specific employed. Mr Ives inquired at the black doctors concerning the virtues of this plant; who all agreed, that it will cure the lues venera, but differed as to the manner of administering it; some saying that a joint of it should be eaten every morning; others that the milk only should be dropped upon sugar; and then put into milk, oil, &c. and given daily to the patient.

Milk-Whit. See Astronomy Index.