MILK is the fluid secreted by the mammary glands of the division of vertebrate animals called Mammalia. These glands are in a rudimentary form in the Monotremes. In Omithorhynchus there is no nipple, but the mouth and tongue are closely applied over the area on which the ducts open, and the fluid is withdrawn by suction on the part of the young and compression of the gland by the mother. In Echidna the ducts of the gland open into a small pouch, foreshadowing the larger pouches of marsupials. In Marsupials the glands are more compact, and have a greater number of lobules. They are found behind the marsupial depressions or those of the pouch; they are not fewer than two on each side nor more than thirteen, six on each side and one midway. The ducts, long and slender during lacta-tion, open on a nipple which is covered by a reflexion of the skin at the back of the pouch, thus forming a kind of hood or sheath. The nipple is protruded beyond the hood during lactation, and is much elongated. The number of these nipples bears a relation to the number of young at a birth; thus the kangaroo, with one at a birth, has four nipples (two, generally the anterior pair, being in use), whilst the "Virginian opossum, which produces six or more at a birth, has thirteen nipples. Rodents show a corre-sponding provision for the nourishment of the young in the number of nipples. A seeming exception is the common guinea-pig, which frequently has eight, ten, or twelve young at intervals of two or three months, and yet the mother has only two teats to serve them, turn and turn about; the original stock of the domestic species breeds, however, only once annually, and has but one to two young, so the domestic variety is a curious anomaly due to the artificial circumstances of its life. In the porcupines there are two nipples, one midway between the fore and hind leg, and the other midway between this and the base of the fore leg. In the coypu, a creature often carrying its' young on its back whilst it swims across rivers, the teats project from the flanks near the shoulders, and are of considerable length, so that the young readily reach them. The Insectívora have, as a rule, more nipples than are found in any other order. Thus in the tenrec (Centetes) there are as many as twenty-two, and they are rarely fewer than fourteen, spread out in pairs from the pectoral to the inguinal regions. There are ten teats in the common hedgehog, six to eight in moles and shrews, two in sloths and armadillos. Ln Cetácea there are two long, narrow, flat glands lying between the dermal and abdominal muscles, with the sub-cutaneous blubber separating them from the skin. The peculiarity of the arrangement in these animals, where suckling is performed under water, is the large size of the central duct, which acts as a kind of reservoir, so that the young may obtain a considerable supply in a very short time. It would appear also that when suckling takes place the nose of the young is above the surface of the water. Among Ungulates, in the elephant the glands and teats are between the fore legs; in the rhinoceros they are inguinal; in the mare and ass the glands are two in number, and are found between the thighs, about 9 inches in front of the vulva; the tapir has two inguinal nipples, the peccary two ventral and two inguinal, the wild sow eight nipples, whilst in the domestic breeds there are at least ten, extend-ing from the pectoral to the inguinal regions. Ruminants have the glands aggregated into a round mass in the inguinal region, pendulous in full function, divisible into two glands, each of which has a large reservoir. When in use the teats, one pair or two pairs being the number, in connexion with the reservoirs become so large as to receive the special name of "udder." All the deer tribe, camels, the giraffe, and all kinds of cows have four teats; most antelopes and the gazelles have two teats, whilst a few antelopes have four. As to Carnívora, the felines have usually six nipples; the wolf, jackal, fox, dog have usually eight; the seals and the walrus have four, the otters two, the weasels six, the bears six; and in the kinkajou (Cercoleptes) the number is reduced to two. Amongst Quadrumana, the aye-aye (Chiromys) has only one pair of nipples, about an inch and a half in front of the vulva; many lemurs have in addition to those a pectoral pair; in all the platyrhine and catarhine Quadrumana there is only one pair of glands, restricted to the pectoral region. Here the teats are between the fore legs, and the young clings to the mother's breast in human fashion, but there is no protru-sion of the breast as in the human being. (For further details see Owen's Anatomy of Vertebrates, vol. iii. p. 769.)
In the human race the glands are two in number, form-ing, along with the skin and fat, two rounded eminences, one on each side, on the front of the thorax. They extend from the third to the sixth or seventh rib, and from the side of the sternum to the axilla. In the centre projects a small conical body, the nipple. Around the nipple is a coloured circle, or areola, which is darker during pregnancy, and even in women who have borne children than in the virgin state. The surface of the nipple is wrinkled, and with a magnifying glass is seen to be covered with papillae. It is perforated by numerous openings, the mouths of the milk ducts. The tissue of the nipple contains numerous minute blood-vessels, and it has at the base muscular fibres arranged in concentric circles and in radiating bands. It has much of the character of erectile tissue, as in the corpora cavernosa of the penis, becoming turgid, firm, and prominent from excitement. The base of the gland lies on the pectoral muscle, a thin layer of fascia intervening. The surface is covered with fat, which gives it the smooth rounded outline. It is amply supplied with blood by the long thoracic artery, some other minute branches of the axillary artery, the internal intercostal artery, and the subjacent intercostals. The nerves come from the anterior and middle intercostal cutaneous branches, and the nipple is especially sensitive. The gland is composed of numerous lobes bound together by connective and adipose tissue, and each lobe is formed of smaller lobules. Each lobe has an excretory duct, and these ducts, from fifteen to twenty in number, converge towards the areola, beneath which they are dilated so as to form sinuses from -jt-th to |-th of an inch in calibre. From these sinuses arise the ducts which open on the surface of the nipple. The general structure will be understood by referring to the accompanying figures, along with the description.
== FIG. 1 ==
ous in full function, divisible into two glands, each of which has a large reservoir. When in use the teats, one pair or two pairs being the number, in connexion with the reservoirs become so large as to receive the special name of "udder." All the deer tribe, camels, the giraffe, and all kinds of cows have four teats; most antelopes and the gazelles have two teats, whilst a few antelopes have four. As to Carnívora, the felines have usually six nipples; the wolf, jackal, fox, dog have usually eight; the seals and the walrus have four, the otters two, the weasels six, the bears six; and in the kinkajou (Cercoleptes) the number is reduced to two. Amongst Quadrumana, the aye-aye (Chiromys) has only one pair of nipples, about an inch and a half in front of the vulva; many lemurs have in addition to those a pectoral pair; in all the platyrhine and catarhine Quadrumana there is only one pair of glands, restricted to the pectoral region. Here the teats are between the fore legs, and the young clings to the mother's breast in human fashion, but there is no protru-sion of the breast as in the human being. (For further details see Owen's Anatomy of Vertebrates, vol. iii. p. 769.)
In the human race the glands are two in number, form-ing, along with the skin and fat, two rounded eminences, one on each side, on the front of the thorax. They extend from the third to the sixth or seventh rib, and from the side of the sternum to the axilla. In the centre projects a small conical body, the nipple. Around the nipple is a coloured circle, or areola, which is darker during pregnancy, and even in women who have borne children than in the virgin state. The surface of the nipple is wrinkled, and with a magnifying glass is seen to be covered with papillae. It is perforated by numerous openings, the mouths of the milk ducts. The tissue of the nipple contains numerous minute blood-vessels, and it has at the base muscular fibres arranged in concentric circles and in radiating bands. It has much of the character of erectile tissue, as in the corpora cavernosa of the penis, becoming turgid, firm, and prominent from excitement. The base of the gland lies on the pectoral muscle, a thin layer of fascia intervening. The surface is covered with fat, which gives it the smooth rounded outline. It is amply supplied with blood by the long thoracic artery, some other minute branches of the axillary artery, the internal intercostal artery, and the subjacent intercostals. The nerves come from the anterior and middle intercostal cutaneous branches,
== FIG. 1 ==
FIG. 1.—Half-diagrammatic view of u section through a lobule of the mam-mary gland, after Klein (Atlas of Histology, plate xl. fig. 1), magnified 45 diameters, a, a duct dividing into two branches; &, &, 6, connective tissue surrounding and going between the ultimate pouches of the gland; c, c, c, the pouches or alveoli of the gland, the dots representing the cells lining them.
== FIG. 2 ==
Fro. 2.— A portion of the same gland, magnified about 400 diameters, showing one complete and two incomplete alveoli, a, a. a, short, columnar, epithelial cells lining the alveolus, each having an oval or rounded nucleus; b, 6, b, epithelium cells, containing, next the interior of the alveolus, a milk globule; c, c, c, c, milk globules wlueh have been set free from epithelial cells.
When a duct is traced into the gland, it is found to subdivide into smaller ducts, and these into still smaller, until the smallest ductlet is reached, round the end of which are clustered several alveoli or pouches. Each alveolus has a wall, lined with epithelium cells. In the wall of the alveolus there are capillary blood-vessels which bring the blood near the cells. By this blood the cells are nourished. There is a minute cavity in the centre of each alveolus into which cells or their products can accumulate. There can be no doubt that the formation of the milk globule takes place in these cells. Whilst milk is not being formed the cells have a granular appearance, and the lumen or central cavity of the alveolus is small; but during secretion the cavity is enlarged and shows a few milk globules, whilst one or more milk globules can be seen in the interior of the cell. If the milk globule in the cell be very large, the nucleus of the cell is pressed outwards and the protoplasm of the cell is reduced to a thin covering, over the globule, at this stage presenting a striking resemblance to a fat cell containing an oil globule. Thus each milk globule is formed in the protoplasm of the epithelium cell, and even at an early stage each milk globule consists of a minute drop of fat or oil surrounded by a thin albuminous envelope. It has not been clearly ascertained whether epithelial cells, after having secreted milk globules, degenerate and fall off, or whether they have the power of ejecting the milk globules. The fluid constituents of milk (water holding salts in solution) may be separated from the blood by a kind of filtration under blood pressure, as is the case in other secretory processes. The origin of the sugar of milk and of the casein is unknown. (For a description of the minute structure of the milk gland, see Klein's Atlas of Histology, p. 300, and references.) At the beginning of lactation the milk is rich in large irregularly-formed corpuscles (fig. 3, a, a, a) called colostrum corpuscles. These area contractile bodies, slow-ly changing their form and squeezing out the oily particles. At first FIG. 3.—A drop of milk magnified 300 diameters.
they are the only bodies co'ostrum present, but they are soon replaced by the ordinary milk globules. Such globules have bright refractive edges, the surface is smooth, they vary in size from -g-^o o-th to _g^-ijth of an inch in diameter, and each consists of a drop of fatty matter surrounded by a layer of albumen ("Ascherson's membrane").
A secretion of milk takes place in newly-born children, from the fourth to the eighth day, and also in rare cases in men (Hermann's Physiology, p. 158). During gestation in the human being the mammary glands increase in size; immediately after the birth of the child active secretion commences; and usually it is on the stoppage of the secretion, ten months afterwards, that the process of menstruation, which has been arrested by impregnation, again is re-established.
The secretion of milk is undoubtedly affected by the nervous system, as is shown by fear or mental distress arresting or injuring the quality of the secretion, and by the "rush" or feeling of fulness in the breast experienced by the mother when the child's mouth touches the nipple, or even when she sees her offspring. The nervous mechanism, however, is unknown, as it has been observed that secretion may continue even after section of all the nerves known to pass to the gland. The nature of the diet has a marked influence on the quality of the secretion. Thus the amount of casein and of fat is greater during an animal than during a vegetable diet. Fatty foods do not seem to increase the amount of fat or butter; an ample supply of carbo-hydrates (starches and sugars) increases the amount of sugar. These facts indicate that most if not all of the constituents of milk are formed from changes in the protoplasm of the epithelial cells. In some women the milk is deficient in fat and casein, and consequently is less nutritious. Prolonged lactation diminishes the amount of fat and sugar without materially affecting the amount of albuminous matter; but the milk is less nutritious and is unfit for the child. The occurrence of menstruation during lactation also deteriorates the milk. (j. a. M.)
Milk as Food.
The milk of various domesticated animals is more or less used by man for food. The milk of the cow, which may be taken as typical of all others, and is indeed by far the most important and valuable of all, is, when newly drawn, an opaque white fluid, with a yellowish tinge, soft, bland, and sweetish to the taste, and possessed of a faintly animal odour. This odour, according to Schreiner, is due to the presence of sulphuretted hydrogen, and disappears after a short exposure. The specific gravity of milk ordinarily ranges from P029 to T033, very seldom reaching P035 or falling so low as 1-027. In chemical constitution it consists of an emulsion of fatty globules (cream) in a watery alkaline solution of casein, and a variety of sugar, peculiar to milk, called lactose. The fat (which when separated we know as butter) and the lactose constitute the carbonaceous portion of the milk regarded as food. The casein, which forms the principal constituent of cheese, and a certain proportion of albumen which is present, form^the nitrogenous, while the complex saline substances and water are the mineral constituents. These various substances are present in the proportions which render milk a perfect and typical food suitable to the wants of the young of the various animals for whom it is provided by nature. The milk of all animals, so far as is known, contains them, although they are present in somewhat different propor-tions. It is probable that the milk of ruminants possesses certain physical and physiological distinctions from that of non-ruminant animals, which will account for the virtues attributed to the milk of the ass and mare. The following table exhibits the chemical constitution of the kinds of milk most frequently used by man:—
== TABLE ==
In addition to these constituents milk contains small pro-portions of the gases carbonic acid, sulphuretted hydrogen, nitrogen, and oxygen, and minute quantities of other prin-ciples, the constant presence and essential conditions of which have not been determined. These consist of galactin and lactochrome, substances peculiar to milk, discovered by Winter Blyth, with certain animal principles such as leucin, pepton, kreatin, tyrosin, &c. The salts in milk consist, according to the average of numerous analyses by Fleischmann, of the following constituents:—
Phosphoric acid ... 28'31
Chlorine 16-34
Lime 27-00
Soda 10-00
Milk thus is not to be regarded as a definite chemical compound nor even as a mixture of bodies in fixed and invariable proportions. Not only does the milk of different races and breeds of cows vary within comparatively wide limits ; the milk of the same animal is subject to extensive fluctuation. The principal causes of variation in the individual are age, period of lactation, nature and amount of food, state of health, and treatment, such as frequency of milking, &c. The following table indicates the range of normal variations:—
Water 90-00 to 83-65
Fat 2-80 ,, 4-50
Casein and albumin 3-30 ,, 5 '55
Sugar 3-00 „ 5-50
Ash 0-70 ,, 0-80
The average quantity of milk yielded by cows is also highly variable, both in individuals and breeds. As a rule the smaller breeds of cows yield a small amount of milk rich in cream (butter fat), while the yield of the larger breed is greater in quantity, but comparatively deficient in cream. A good milch cow should yield in a milk-giving period of from eight to nine months about 500 gallons of milk, from which nearly 500 H> of cheese or 200 lb of butter would be obtainable.
Dairy Treatment.—Cows are commonly milked by hand two or three times a day. A milking machine of American origin, which was introduced about the year 1862, has been entirely abandoned. The milk should be drawn from the animals in as clean a condition as possible, but notwithstanding every precaution some amount of hair and epithelial and other animal debris invariably enters the milk-pail. It has therefore to be immediately strained through a sieve with fine wire-cloth or hair strainer. As milk is peculiarly susceptible of taint, and absorbs odours of all kinds with great avidity, it is of the utmost con-sequence that all vessels in which it is placed or kept should be so made as to be easily purified and that they should be kept scrupulously clean. In Switzerland milk is strained with most beneficial effect through sprigs of washed fir tops, which inserted loosely and uprightly into the hole of a funnel arrest all hair, skin, clots, and slimy matter on the acicular leaves. The milk drains through in a clean condition with a fresh slightly aromatized flavour favourable to its keeping. A fresh sprig is used on each occasion of straining milk, so that there is freedom from the risk of taint which arises through the use of imperfectly cleaned wire gauze. The milk must be removed from the cow-house as quickly as possible; and, if intended for use as new milk and for sale in the neighbourhood of the dairy, it may at once be put up for delivery. But if it has to travel a distance, or if it is to be kept for creaming or cheese-making, it should be rapidly cooled down, and kept in a cool airy milk-room if prac-ticable, surrounded with fresh cold water.
The ordinary method of separating cream either for direct use or for butter making is by allowing it to form on the surface and skimming it off with a broad flat spoon; but ingenious adaptations of centrifugal machines—of which Laval's separator is one of the best known—have been introduced for the purpose of effecting the rapid and complete separation of the cream. The centrifugal force of such machines throws the denser portions of the fluid towards the sides of a rapidly revolving cylinder, collecting the cream on an inner layer, which is carried off by one channel while the impoverished milk escapes by another. The Laval separator gives very rich cream, as will be seen from the following analyses by Voelcker:—
== TABLE ==
After being kept some time, depending principally on the temperature at which it is maintained, milk begins to turn sour owing to the formation of lactic acid, by a process of fermentation, at the expense of the lactose or milk sugar. The acid so developed causes a coagulation of the casein, and the milk separates into a solid white curd, and a thin transparent yellow milk serum or whey. These changes can to a certain extent be artificially pro-duced, hindered, and controlled. The following are the results of analyses by Fleischmann:—
== TABLE ==
The simplest and most advantageous form in which milk can be disposed of as a commercial product is by its sale as sweet or new milk, and it is in this manner that the greater proportion of the milk produced within the reach of large centres of population is disposed of. New milk; cream, and skimmed milk are the only primary forms in which milk is sent into the market. CHEESE and BUTTER have been dealt with in separate articles (q.v.). Whey, the yellow liquid remaining after the separation of the curd in cheese making, is a source of milk sugar, employed to a limited extent in pharmacy; but it is prin-cipally used for feeding pigs. The buttermilk which re-mains after separating butter is a most wholesome and nutritious article of food.
Preservation of Milk.—The numerous methods which have been proposed for the preservation of milk in a condition fit for use over a lengthened period resolve themselves into (1) chemical treatment with alkaline salts and antiseptic bodies, (2) physical treatment, such as cooling or icing, boiling, and aeration, and (3) condensation with or without the addition of a preservative agent. All systems of preservation, however, are subject to serious disadvantages either from their serving their purpose for too limited a time, or their interfering with the natural constitution and properties of the milk. Of all preservatives cold is the most efficient and least objectionable. It has been shown by Soxhlet (Dingler's Polytech. Journal, ccxxiii. 329) that milk cooled by ice-water remains sweet and unaltered for fourteen days, but after that time acquires a rancid taste. After twenty-eight days it coagulates on boiling owing to the presence of acids resulting from the oxidation of the cream, and in thirty-four days it coagulates even in the ice-w-ater. It is also found that milk which has undergone aeration with atmospheric air has its keeping properties much improved. The aeration is effected by allowing the milk to fall from some height in a state of fine division by passing it through the meshes of a sieve. By another method air cooled by passing over ice is blown through the milk.
Milk keeps sweet for a longer time when boiled, but the smell, taste, and other properties are affected, partly owing to the escape of gases mixed with it when fresh. The unpleasant flavour com-municated by boiling can be avoided if the action takes place in a closed vessel and the milk is immediately cooled down in a refrigerator connected therewith. In the case of any suspicion of taint in milk either from disease in the cow, contamination from unhealthy persons, or the use of infected water in cleaning vessels, boiling is also strongly to be recommended, as it effectually destroys the germs of disease, in the carrying and spreading of which milk is a most active agent. It is with the utmost difficulty that boiled milk can be coagulated by means of rennet; but by treatment with acid it coagulates more rapidly and freely than if unboiled.
Of the various chemical compounds which have been suggested and more or less used for preserving milk, the most successful hitherto has been salicylic acid, which has the advantage of being j tasteless and inodorous. By briskly stirring in rather less than 2 grains to a pint of milk, it can be kept liquid and sweet in a tem-perature of from 65° to 68° Fahr. for twelve hours, and at 55° Fahr. for a whole day. If 4 grains be used to a pint, coagulation in the higher temperature is delayed from two or three days, and at the lower temperature the milk may be kept good from three to five days. Boracic acid and borax are also employed by dairymen, the former being known as glacialine salt. The presence of any chemical anti-septic in milk is, however, at best a matter of doubtful advantage.
Condensation. —Milk is now treated on a large scale by a process of concentration, the product of which comes into the market in two forms—as "plain condensed milk " and as " preserved milk." The credit of originating the industry is due to Mr Gail Borden of White Plains, New York, who began his experiments about 1849. In 1851 he introduced his plain condensed milk, which is simply milk from which between three-fourths and four-fifths of the water has been removed, and in 1861 he rendered important services to the army in the field by supplying preserved milk which was in effect milk similarly concentrated, with a proportion of sugar added, and hermetically sealed in tin cans. The manufacture was transplanted to Switzerland in 1865, after which condensing factories were established in England, Ireland, Denmark, Bavaria, Norway, and elsewhere. With the introduction of the condensing trade there has also been associated the factory system of dealing with dairy products, by which the milk of many dairies is carried to one centre and dealt with either for condensing or for cheese or butter making. The following epitome of the process of condens-ing milk is from a paper by Mr Willard of Cornell university, New York (Jour. Roy. Agric. Soc, 2d series, vol. viii., 1872). The milk when received at the factory is first passed, he says, " through a strainer to the receiving vat; from this it is conducted __', going through1 another strainer into the heating cans, each holding about 20 gallons ; these cans are set in hot water, and the milk is held in them till it reaches a ten^erature of 150° to 175° Eahr.; it then goes through another strainer into a large vat, at the bottom of which is a coil of copper pipe, through which steam is conducted, and here the milk is heated up to the boiling point. Then the best quality of white granulated sugar is added, in the proportion of \\ lb of sugar to the gallon of milk, when it is drawn into the vacuum-pan having a capacity of condensing 3000 quarts or more at a time. The milk remains in the vacuum-pan subjected to steam for about three hours, during which time about 75 per cent, of its bulk in water is removed, when it is drawn off into cans, holding 40 quarts each. The cans are only partially filled, and are i then set in a large vat containing cold water, the water being of a height equal to that of the milk in the cans. Here it is stirred until the temperature of the condensed fluid is reduced to a little below 70°; it is then turned into large drawing-cans with faucets, in order to facilitate the filling of the small cans, .... holding 1 lb each, which are immediately soldered to exclude the air."
In the case of plain condensed milk the concentration is usually carried farther than is practised in preparing the preserved milk, it being evaporated down to between one-fourth and one-fifth of the original bulk. It is not put up in sealed tins, being intended for immediate use, and keeps sweet only for a few days, varying with the state of the weather, whereas the sugared milk in sealed cans keeps for years. The large amount, however, of cane sugar added to preserved milk seriously disturbs its balance of proportion as a perfect food, and renders it unfit to be used alone in a dilute state as a substitute for mother's milk by infants, a purpose for which it is largely employed. It should also be observed that the relative proportion of fat is small, the milk being partially skimmed before it is operated on, so that the statement that preserved milk diluted with a small proportion of water is equal to cream is not to be relied on. Preserved milk, rich in cream, has always a more or less rancid oily taste, and cannot be obtained so sweet and even in flavour as that largely deprived of fat. According to a German patent of E. Klebs in Prague, plain condensed milk may be preserved by adding to every 100 litres of the original milk a solution of 50 grains of benzoate of magnesium in one litre of water.
Adulteration.—Practically the invariable mode of sophisticating milk for sale consists in the addition of water and in the subtrac-tion of cream,—in other words, passing off skimmed or partly skimmed as new milk. Now and again there are found certain little refinements on these simple frauds, such as adding a quantity of sugar to correct the specific gravity, flour or starch to increase opacity, and a touch of colouring matter to cover the bluish tinge which would betray skimmed milk. In the United Kingdom no official standard of what constitutes pure milk has been promul-gated, but the so-called Somerset House standard has been generally recognized in law courts. According to this, new milk should contain as a minimum of solids not fat 8'6 per cent, and of fat 2'5 per cent., and of water a maximum of 88'9 per cunt. The most satisfactory manner of discovering the probable genuineness of a sample of milk is by chemical analysis carried sufficiently far to determine the amount of fat and of other solids present. Numerous attempts have been made to place in the hands of dairy-men, dealers, and consumers of milk a trustworthy method of estimating the condition and value of the article by simple quantitive tests for cream or fat—at once the most valuable con-stituent and one the presence of which in average proportion is indicative of the quality of the whole. The simplest but at the same time the least trustworthy and efficient method is by means of the so-called " creamometer," which consists merely of a graduated glass tube in which a measured amount of milk is placed and the amount of cream it throws up is read off by means of the scale. Specific gravity determinations have by themselves no significance, seeing milk deprived of its cream can by dilution with water be brought to correspond exactly with the original milk. But by a combination of two methods,—first taking the specific gravity, next observing the yield of cream by the " creamometer," and finally taking the specific gravity of the milk deprived of cream, regard being had to the temperature of the milk in these observations, an approximately accurate idea of the value of a sample may be obtained. Among so-called " lactoscopes," the operations of which are based on the fact that milk rich in cream is a much more opaque fluid than that from which cream has been taken or to which water is added, that invented by Professor Feser of Munich is one of the simplest and most useful. It con-sists of a glass tube open at the upper end and attenuated at its lower extremity. Into this narrower portion is fused a small cylindrical rod of opaque milk glass on which black lines are marked. These lines are invisible when the lower portion of the tube is filled with a measured quantity of milk, but on addition cl water they become visible. When the black lines become by the gradual admixture of water perfectly distinct, the richness of the milk in cream globules is indicated by the height to which the mixture of milk and water has risen in the wide portion of the tube, which has engraved on it a scale showing on one side the amount of water added and on the other the proportion of cream equivalent to the transparency resulting from such addition.
Statistics.—In the year 1878 it was calculated by Mr J. C. Morton that the total yield of milk from the 2,250,000 cows and heifers in milk or in calf in England and Scotland amounted to about 1,000,000,000 gallons yearly. He assumed that about one-sixth of that quantity (167,000,000 gallons) went to feed calves, and that the daily consumption of the population was 1,000,000 gallons, being rather more than a quarter of a pint per head, which accounts for 365,000,000, still leaving 468,000,000 gallons to be used for butter and cheese making. Two-thirds of this quantity, or 312,000,000 gallons, Mr Morton assumes was used for cheese-making, yielding 2,800,000 cwts. of cheese (rather less than 1 lb per gallon of milk), and the remainder, 156,000,000 gallons, of milk devoted to butter-making would yield 530,000 lb of butter, or 1 lb of butter for every 21 pints of milk. In these figures no account is taken of Ireland,.whence at that period there were sent to England alone yearly 3,500,000 tt> of salted butter. In June 1882 the number of cows and heifers in milk and in calf in Great Britain did not vary greatly from the number on which Mr Morton's estimate for 1878 was based, being 2,267,175, whilst in Ireland the number was 1,398,905, making the total for the United Kingdom 3,682,317. If we take approximately Mr Morton's data as the basis of calcu-lation, the 3,682,317 milk cows and heifers in the United King-dom would yield, at 440 gallons per head, 1,620,219,480 gallons of milk. Further, assuming that one-sixth of this is consumed by calves, one-third consumed by population, one-third used for cheese-making, and one-sixth used for butter-making, we have as the yield of cheese 4,846,000 cwts. and as the yield of butter 920,000 cwts. As Ireland is much more a butter-producing than a cheese-yielding country, the quantity of cheese made is probably overestimated in these figures, and the amount of butter made is correspondingly understated. To bring out the consumption of dairy products for the year the following imports must be added:—
== TABLE ==
Thus we find the total supply of cheese to the United Kingdom in 1882 was 6,538,495 cwts., and of butter the supply was 3,087,42S cwts. Estimating the home produce of both articles at the same value as the imports, the cheese supply cost £18,320,000, and the butter £16,150,000. Adding to these the probable cost of the milk consumed as such (say 550,000,000 gallons at Is. per gallon = £27,500,000), we have for the year 1882 in round numbers £62,000,000 expended on dairy produce within the United Kingdom.
The total number of milch cows at present (1883) in the United States is stated at 15,000,000, which, taking the 440 gallons basis, yield annually 6,600,000,000 gallons, or nearly 30,000,000 tons of milk. In America the factory system of treating milk has attained much greater dimensions than in Europe, and that perfection of treatment, combined with the cheapness of raising and feeding stock, enables the American companies to enter the European markets with large quantities of cheese and other dairy products of uniformly good quality which find a ready and remtfnerative sale.
Koumiss.—Under this name is properly understood a fermented drink prepared from mare's milk by the Tartar tribes of the Russian empire and by all the nomad races of the northern parts of Asia. It is made by diluting mare's milk with about one-sixth part of its quantity of water, and adding as a ferment about one-eighth part of very sour milk or of old koumiss. This mixture is placed in a wooden vessel which is covered over with a thick cloth, and so left for about twenty-four hours in a moderately warm situation. During that time a thick coagulum rises to the surface, which is thoroughly reincorporated by churning. After standing for another day, the whole mass is again thoroughly churned and mixed up, and in this state it forms new koumiss, having an agreeable subacid taste. The liquor is mostly stored and preserved by the Tartars in skin bottles, in which the fermentation continues developing its alcoholic qualities, and mellowing and improving its taste. Genuine Tartar koumiss has the following composition :—alcohol 3'21, lactic acid 019, sugar 2-10, albuminoids 1-86, fat 178; salts 0-509, carbonic acid 0T77, and water 93'46. A distilled spirit is prepared from koumiss, which is drunk among the Tartars under the name of araca or arsa. Koumiss has of late years come into prominent notice as a remedial agent in cases of pulmonary consumption, and generally as a nutritious form of food easily assimilated by delicate stomachs. It is probable that all its virtues reside in the original milk from which it is prepared, in which case the koumiss can only be regarded as valuable in so far that it is a convenient form under which the essential properties of the milk can be preserved for use. Under the name of koumiss a preparation of cow's milk is now very generally sold. It is made by adding to each quart of new milk about a tablespoonful of common sugar and brewer's yeast, allowing the fermentation to proceed a sufficient length, then bottling and corking as in the case of aerated waters. Such a preparation contains about the same proportion of alcohol as genuine koumiss, but a non-alcoholic variety can also be obtained, made by a process of natural fermentation, which continuing after bottling develops a large amount of carbonic acid and renders the liquor highly effervescent. (J. PA.)
Footnote
Ewe's milk is exceedingly variable, especially in its percentage of fat. The above analysis is one of nine by Dr Voelcker, in which the fat was found to range from about 2 to 12| per cent.
The above article was written by two authors:
-- Pt 1: James A. Manson...
-- Pt 2: James Paton...