sions, the first consisting of men of the permanent army who serve in the militia as follows: Carabineers and non-commissioned officers of all other corps serve ten years, with unlimited leave; other corps, including cavalry, serving in the mobile militia three or four years, and in the territorial militia seven years. The levies of the second division serve three or four years (according to the branch of the service) in the mobile militia, and seven in the territorial. The levies of the third division serve nineteen years, with unlimited leave, in the territorial militia. The period of training for men of the second division is from two to six months, spread over a period of several years. The third division has thirty days' training. In time of war it does garrison duty, and constitutes the last reserve. The French territorial army, with its reserves, is organized similarly to the militia of England, on a purely local basis. After serving thirteen years in the active army and its reserve,

soldiers are assigned to twelve years' service in the territorial army and reserve. In Switzerland the entire army, comprising as it does every ablebodied citizen, is a militia, regarding which see Switzerland in the article ARMIES. See LANDSTURM; LANDWEHR; NATIONAL GUARD; VOLUNTEERS, MILITARY.

MILK (AS. meole, meoluc, Goth. miluks, OHG. miluk, Ger. Milch; connected with AS. melcan, OHG. melchan, Ger. melken, Lat. mulgere, Gk. duéλyev, amelgein, OChurch Slav. mlesti, Lith. milsti, to milk, Skt. marj, Av. maraz, to rub off). The liquid secreted by the mammary glands of all mammals, and used primarily to nourish their young. From the earliest time it has been esteemed an important and necessary article of food, and many hidden virtues were ascribed to it by the ancients. Its exact composition continued long unknown, and until the beginning of the

Aggregate

seventeenth century fat, casein, and whey were the only constituents recognized. In the early part of the eighteenth century Leeuwenhoeck discovered the microscopical characteristics of milk, and about the same time Boerhaave made a qualitative examination. The first quantitative analysis of milk recorded was made in 1737 by Geoffrey, who determined with considerable accuracy the casein, milk sugar, and mineral matter. Woman's milk contains 87.4 per cent. of water and 12.6 per cent. of solids, the latter including 3.8 per cent. of fat, 1.0 per cent. of casein, 1.3 per cent. of albumin, 6.2 per cent. of milk sugar, and 0.3 per cent. of ash (mineral matter left after burning). The milk from different animals varies considerably in composition, as shown in the following table:

KIND OF ANIMAL

minus the water are designated total solids. The proportion of total solids is a general indication of the richness of the milk. Among the solids the chief importance attaches to the fat. First, it is the measure of the value of milk for butter-making, and to a very great extent for cheese-making also; second, it is the constituent which more than any other gives milk its appearance of richness; third, it fluctuates more widely than any other constituent. Milk fat is a familiar substance in the form of butter, which contains about 85 per cent. of fat, some water, salt, and casein. The fat in milk is in the form of minute globules held in suspension, and on standing it rises to the surface as cream (q.v.), which contains some of the other constituents in smaller proportion. The globules may be readily seen by

In total solids Albumin

Cow....

Buffalo.

Goat.

Ewe...

Llama..

Mare...

Ass.

Camel.

Sow

Elephant..

Milk sugar

Ash

The above are general averages of a greater or less number of analyses, depending upon the kind of milk animal, each kind of which gives milk that varies more or less with the individual as well as with the species. There is, furthermore, some difficulty in arriving at a general average for any kind of mammal, since normal milk is obtained with difficulty from animals unaccustomed to being milked.

PROPERTIES OF Cows' MILK. Since, in general properties and composition, cows' milk is typical of all milks, is of chief commercial interest, and has been studied much more in detail, it will be the main subject of this article. The milk secreted immediately after parturition is termed colostrum (q.v.), or beastings, and differs considerably from normal milk in both physical and chemical characters. Milk from which the fat has been removed by skimming or by the separator is called skim milk (q.v.), and the residue left after churning cream is known as buttermilk (q.v.). Whey (q.v.) is the liquid remaining after the curd of the milk has been separated.

Cows' milk is an opaque, whitish liquid, sometimes faintly yellow or bluish, with a slight alkaline reaction and a sweetish taste when fresh. It is heavier than water, its specific gravity ranging usually from 1.029 to 1.035, the average for mixed milk being about 1.032. By removing the fat (skimming the cream) the specific gravity is raised, and by adding water it is lowered. This is the basis of a simple, but (when taken alone) unreliable, test of the quality of milk and of the practice of skimming. Chemically, milk consists of an aqueous solution of milk sugar, casein, albumin, and ash, with the fat in suspension, forming an emulsion. The water and the constituents dissolved in it constitute the milk serum, and the constituents (i.e. the dry matter)

means of a microscope. For a long time fat globules were believed to be surrounded by a membrane or proteid coating, which was destroyed by churning the cream, and thus allowed the fat to unite into a solid mass. This view is still held by some, but the prevailing belief at present is that the globules are free and Owe their spherical form to the surface tension. The globules vary greatly in size, being from 0 to of an inch in diameter. A pint of average milk has been estimated to contain not far from a million globules. The size of the globules varies with the period of lactation, diminishing toward the close, and to some extent with the breed and the individual. The globules in the Jersey and Guernsey milk are relatively large; in Holstein milk very small. The large globules rise more rapidly, and milk containing them creams more readily and completely.

Milk fat is a pale yellow substance consisting of a mixture of the glycerides of 8 or more fatty acids. Of these olein constitutes about 35 per cent., palmitin 25.7, myristin 20, laurin 7.5, butyrin 3.85, caprin 3.6 per cent., and the remainder is principally caprylin and stearin. By the action of caustic alkali these glycerides are broken up into their respective fatty acids and glycerin, and a certain relatively small proportion of these, including the butyric, caproic, and caprylic acids, are volatile. The characteristic flavor and aroma of milk and butter are due largely to butyrin, and this decomposes readily, forming butyric acid, which is evident in rancid or 'frowy' butter. The chief nitrogenous or albuminoid constituent of milk is casein, which is of prime importance in cheese-making. It is coagulated by rennet and by acids, and this is what gives sour milk its thick curdled appearThe acid developed in souring precipitates

ance.

the casein, which gradually separates from the soluble constituents, inclosing much of the fat. Casein is held in solution in milk by the presence of lime salts, and lime water causes it when curdled to separate in a much more finely divided condition. The albumin of milk is not curdled by acids or rennet, but is acted upon by heat. Fibrin, similar to that of blood, globulin, nuclein, and several other nitrogenous bodies, have been found in milk in small quantities, but are of little importance. The sugar in milk, chemically known as lactose, is not so sweet as cane sugar. It is in solution. The ash of milk consists of a mixture of a number of salts, but is composed principally of the phosphates of lime and potash, the chlorides of potash and soda, and small amounts of phosphate of iron and magnesia. Some of the phosphate of lime appears to be associated with the casein, which also contains some sulphur. Most of the salts are in solution. Besides the constituents named, milk contains normally a coloring matter, a trace of citric acid, urea, and several other bodies. The fat and the albumin of milk are the most variable constituents, the ash and the sugar the least so. The casein bears a quite constant ratio to the fat, rising and falling with it. VARIATIONS IN MILK. The richness of milk is to a certain extent an individual characteristic; i.e. some individuals normally give rich milk, while others, for no apparent reason, give milk containing several per cent. more water. The richness of milk has been increased by domestication, care, and breeding, and certain breeds of cows, sheep, goats, etc., have been produced which give a characteristically rich milk. The quality also varies with the stage of lactation. The milk given early in the lactation period is usually poorer than that secreted later, and grows richer toward the close of the period until the animal 'goes dry.' Young animals usually give poorer milk and less of it than after the third or fourth parturition, and the milk from the first part of any milking is poorer than the last part, or 'strippings.' The kind of food has little effect on the composition of milk, provided it is wholesome and the amount sufficient. Food influences the proportion of the different fatty acids composing the fat, and so has an effect on the hardness and other qualities of but

ter.

But the rather prevalent notion that the milk fat, for instance, can be permanently increased by feeding has been shown by much careful investigation to be a fallacy. Little is known of the physiological processes by which the constituents of the food are transformed into milk constituents. In some cases there appears to be a direct transmission of the constituents from the food to the milk, as is noticeable when cows eat garlic, onions, etc. The experiments of Jordan at the New York State Experiment Station have shown that milk fat is not derived solely from the fat of the food, for cows fed upon food from which the fats were practically completely extracted continued to secrete milk of normal composition for long periods, and, judging from the maintenance of their weight, did not draw upon their body fat to supply this ingredient. Under the conditions of the experiments, the carbohydrates seemed to be utilized to some extent in the elaboration of milk fat. The more the process of milk secretion is

understood the more apparent it becomes that richness and the volume of the yield are individual characters, and if cows have a tendency to give poor milk no amount of feeding will overcome it. The remedy lies in getting better COWS. For general statements regarding the composition of the milk of different breeds of cows, see CATTLE.

As an illustration of the variation of the milk of ordinary cows of mixed breeding, the data obtained by Van Slyke in New York from the analysis of the mixed milk of 15,000 cows each month from May to October may be cited. The total solids ranged from 11.17 to 13.91 and averaged 12.67 per cent., and the fat from 3.04 to 4.06 and averaged 3.75 per cent. The content of total solids and of fat was lowest during the summer months and increased in the fall. In the analysis of over three thousand samples of milk at the Massachusetts Experiment Station, the total solids varied from 10.02 to 19.55 and averaged 13.57 per cent., and the fat from 1.5 to 10.70 and averaged 4.32 per cent. The analysis of eight hundred samples made at the experiment stations in different parts of the country varied in total solids from 9.3 to 19.7 per cent., averaging 12.8 per cent., and in fat from 1.7 to 6.5, averaging 3.7 per cent.

MILK FERMENTATIONS. Milk is subject to a great variety of fermentations, for it is a favorable medium for the growth of many kinds of bacteria, yeasts, and other fungi which cause numerous changes in its constituents. Thus, while one class of organisms curdles milk by the production of lactic acid, another class gives it an alkaline reaction, at the same time curdling it; others impart to it a deep blue, violet, yellow, green, or red color, by the production of pigments in the milk; others give it a bitter or other unpleasant taste; another class produces alcohol from the milk sugar, and is taken advantage of in the preparation of such beverages as koumiss and kephir (qq.v.), and still others cause putrefaction. The most common and familiar change is the souring of milk, due usually to the action of lactic-acid bacteria. Under ordinary conditions normal milk nearly always undergoes some sort of lactic fermentation on standing. The production of lactic acid soon curdles the milk and obscures all other forms of fermentation, and the acid stops the growth of other bacteria so that no subsequent effects are usually seen. The popular belief that the electricity in the air during thunderstorms sours milk appears to be unfounded, but its rapid souring at such times is due to the climatic condiThe same difficulty in keeping milk is experienced tions prevailing, which hasten bacterial growth. during very hot weather. Curdling is not always due to the formation of acid; milk apparently 'sour' may have no acid taste. In such cases the cause is due to alkaline fermentation, induced by another class of organisms. The milk becomes coagulated into a soft slimy mass, which is usually bitter and has an alkaline or neutral reaction. Ordinarily this form of fermentation is not very apparent, as the organisms causing it grow slowly and the lactic-acid organisms get the start of them. The organisms which produce butyric acid in milk attack and decompose the fats, giving a rancid odor. In the ordinary handling of milk the latter are of little importance, but it is supposed that they have an important

effect upon the keeping properties of butter. Several organisms have been described which impart a bitter taste to milk, due, in some cases at least, to the production of a bitter principle. Milk which has been boiled is likely to develop a bitter taste, for the reason that the heating kills the lactic-acid germs, while the bacteria causing the bitter taste usually possess endospores which are not destroyed by heat, and so have a clear field for action. A slimy fermentation of milk is a somewhat common occurrence, and occasionally produces great trouble in dairies, since it destroys the milk for all ordinary uses. Such milk becomes thick and ropy, will not cream, cannot be churned, and is unfit for drinking. It may be caused by a variety of organisms. There are several forms of the trouble. One known as the 'lange wei' (long or stringy whey) is made use of in the manufacture of Edam cheese in Holland, to control the gassy fermentation of the curd.

In addition to the fermentations and other changes in milk due to micro-organisms, rennet, an unorganized ferment obtained from the stomach of the calf and from some plants, ferments milk, causing it to curdle. This ferment is employed in cheese-making to produce the curd. Babcock and Russell have discovered an unorganized ferment termed galactase in milk, which they believe to be a normal and inherent constituent, and which is active in the ripening of cheese, causing the characteristic changes in the green cheese which make it suitable for eating.

The chief sources of bacteria in milk are the cow herself, the milker, the dust of the stable, and the dairy utensils. It has long been believed that pure milk drawn from a healthy cow contains no bacteria, and that all bacterial contamination of the milk comes from external sources. However, the large calibre of the milk duct makes it possible for bacteria to enter it and grow to a considerable extent, so that it becomes a matter of extreme difficulty to obtain milk from the cow, even with the greatest precautions, which shall not be contaminated. The hairs of the cow are always covered with dirt and dust, and the air of the stable is charged with dust from the fodder and bedding material, so that it is impossible to prevent some of this dirt falling into the milk pail. Thus large numbers of bacteria, especially in poorly ventilated stables, reach the milk. Any dirt upon the hands or clothing of the milker will have abundant chance to get into the milk pails and cans. The milk vessels themselves are an important source of contamination, the corners and creases retaining bacteria which have not been removed or killed by the washing. The warm milk furnishes favorable conditions for the growth of these micro-organisms which have gained access, and which for a time multiply rapidly.

Several species of bacteria classed as pathogenic organisms are capable of living or even in creasing in milk, but since they do not ferment the milk or alter its appearance sufficiently to be detected by a physical examination, their presence is not readily determined. Except in very rare instances the milk becomes contaminated after it has been drawn and in practically all these cases the cause of contamination is some form of uncleanliness, either of the stables, the water, the utensils, or the attendants. It is gratifying to

know, however, that through the efforts of the United States Department of Agriculture, the agricultural experiment stations, and the dairymen themselves, the sanitary management of dairies is being constantly improved, and through the vigilance of State appointed dairy inspectors unsanitary conditions are destroyed as soon as discovered.

MILK ADULTERATION AND CONTROL. The milk supply of towns and cities has for many years been regulated by laws and ordinances, and subjected to inspection. The object of this was formerly to prevent adulteration, but of recent years the inspection has often extended to the herds and stables and all that relates to the milk trade. It has come to be realized that such factors as the health of the cows, hygienic condition of the stables, and cleanliness in the handling of the milk are quite as essential to pure wholesome milk as freedom from adulteration. Hence the veterinary inspection, which has been introduced in some cities, should be extended. Milk is most often tampered with by removing a part of the cream, or by diluting it with water or skim milk. Coloring matter is sometimes added to make it appear richer, but the addition of chalk, burnt sugar, or similar substances is now rare. Preservatives, such as formaldehyde, borax, and salicylic acid, are sometimes added to prevent milk souring. Opinions differ as to the injuriousness of these preservatives, but their use is generally condemned on the ground that they are unnecessary in pure milk, and that they are a cloak for unsanitary practices in the dairy. The standards for milk adopted by different States vary from 11.5 to 13 per cent. for total solids and from 2.5 to 3.5 per cent. for fat. Milk found below these standards is held to be adulterated. A standard of 12.5 per cent. of total solids and at least 3 per cent. of fat seems fair.

Various means of testing milk as to its quality have been suggested from time to time. Of these the lactometer is the simplest, and has been extensively used by milk inspectors who have a large number of samples to examine daily, to detect watering or skimming. It is a form of hydrometer, which shows the specific gravity of milk upon a graduated scale. But there are so many factors that affect the specific gravity, and this may vary so much in pure milk, that the lactometer reading is only an indication and cannot be relied upon as final. The most reliable and satisfactory of the simple milk tests is the Babcock test, which has come into very widespread use in the milk inspection of towns and cities, and in determining the fat content of milk as a basis for paying for the product at creameries. (See CREAMERY; BUTTERMAKING.) This test is made in a special bottle having a narrow graduated neck. A definite quantity of milk is treated in the bottle with sulphuric acid to dissolve the curd and set the fat free. The bottle is then whirled rapidly in a centrifugal apparatus for a few minutes, to aid in separating the fat; hot water is added to bring the fat up into the neck, after which the bottle is whirled a second time and the column of fat read off on the graduated scale. The reading gives the percentage of fat without calculation. A large number of samples may be tested simultaneously, and the method has been shown to be very accurate after a little practice. It shows only the fat content, which is the com

mon measure of richness; but from it and the lactometer reading the total solids and other constituents can be calculated. A bacteriological examination is rarely made in connection with the ordinary milk inspection.

In

MILK AS FOOD. Milk is peculiarly adapted to be a food for man principally because it contains the four classes of nutrients-protein, fat, carbohydrates, and mineral matter-in more nearly the proper proportions to serve as a complete food than perhaps any other single food material. (See FOOD.) A quart of milk contains about four ounces of nutritive material, or about the same as three-quarters of a pound of beef or six ounces of bread. Although these quantities of milk, beef, and bread supply like amounts of total nutrients, their nutritive values are not the same. other words, they would not be equally useful as food, owing to the relative proportion in which the nutrients are present. Protein, fat, and carbohydrates occur in milk in about equal proportions. The chief nutrients in bread are carbohydrates and protein, and in meat protein and fat. Either milk or bread eaten alone would make a better balanced food for man than meat. In general, milk and cream together furnish to the diet of average American families about 20 per cent. of the total food, 11 per cent. of the total protein, and also of the total fat, and about 5 per cent. of the total carbohydrates. Dairy products (milk, cheese, butter, and cream) furnish over 22 per cent. of the total food, 12 per cent. of the protein, 32 per cent. of the fat, and 5 per cent. of the carbohydrates.

As regards the digestibility of all its ingredients, milk is one of the most digestible of animal foods. It has been found that on an average an adult digests about 97 per cent. of the protein, 95 per cent. of the fat, and 98 per cent. of the carbohydrates of milk. According to American experiments, a child one year old eating milk digests on an average only about 90 per cent. of the protein, 96 per cent. of the fat, and 86 per cent. of the carbohydrates of cows' milk. When milk is taken into the stomach it is speedily curdled by the action of the pepsin and acid of the gastric juice. When eaten alone or in large quantities, the casein gathers in large lumps, which in some persons may be difficult to digest. This is particularly the case with infants and with adults whose digestion is weak. The casein of human milk is precipitated in more flocculent form than that of cows' milk, and is thus more easily digested and does not cause irritation. Lime, which tends to prevent the curdling of the casein of cows' milk in lumps, is frequently added as lime water to milk that is to be fed to infants or to adults of delicate digestion. The results of experiments upon the effect of cooking milk are conflicting. The more common experience seems to indicate that cooking or heating the milk renders it more difficult to digest. Some persons, however, cannot take fresh milk with comfort, but can digest boiled

milk.

Milk is often said to be a 'perfect food.' It is so for the young of the species of animal producing it, but there are three reasons why it cannot be considered a perfect food for adults. (1) The proportion of water is so large that great quantities (from 4 to 5 quarts) would have to be consumed each day in order to obtain the necessary nutrients. (2) The protein is present

in rather large quantities as compared with the fats and carbohydrates. Thus the milk necessary to furnish the 0.28 pound of protein per day, estimated to be required by a man at moderately active work, would yield only 2700 calories of energy, while milk in sufficient quantity to furnish the 3400 calories estimated as necessary would yield 0.34 pound of protein. (3) It is a well recognized fact that the digestive functions require that food itself, besides the water taken with it, shall have a certain bulk. Cattle cannot generally be maintained in health upon a condensed ration such as grain; they seem to require a certain distention of the stomach, such as is brought about by the fibre (cellulose or woody matter) of grass or hay. In like manner it seems desirable that man should have a certain amount of bulky material to produce distention or to promote peristaltic action of the intestines, or for other purposes not well understood. Of course, the nutritive constituents of milk, considered separately, are highly concentrated foods. While, therefore, milk alone cannot be considered as a perfect diet for adults, it is of special value as a food for invalids, because it is, as a rule, easily taken, easily digested, and does not generally irritate the alimentary canal. Furthermore, a milk diet is more readily under the control of the physician both as regards quantity and quality than a mixed diet is. If for any reason a child cannot be nourished on mother's milk, the most useful substitute is modified cows' milk. Various infant foods and milk substitutes have been proposed and are sold under divers trade names.

At

As a food for adults cows' milk is unusually well adapted for use in connection with other foods, either in its uncooked form in tea and coffee, as a beverage, as bread and milk, etc., or incorporated and cooked with other materials. In many culinary products it can be used instead of water. Analysis of bread, rolls, etc., made with milk would show about one-tenth more protein and one-twentieth more fuel value than bread made with water. Milk is very generally used in many kinds of cake and pastry and in custards. Where desirable from economical reasons, or as a means of increasing the proportional amount of protein in a diet, skim milk can be advantageously substituted for whole milk. the price ordinarily paid in our large cities milk is a food of reasonable cheapness, and at the prices prevailing in small cities and country towns it is an economical food. Condensed milk is a more nutritious food, pound for pound, than fresh milk, since it has been concentrated by evaporation. It is, however, usually diluted before it is used, and then approximates fresh milk more or less closely in composition and food value. If the condensed milk contains added sugar its carbohydrate content is, of course, higher than that of unsweetened condensed milk, and when diluted, proportionally higher than that of fresh milk. Cream, which contains the greater part of the fat of the milk, as well as some protein and carbohydrates, is chiefly valuable in the diet as a source of energy. Curds obtained in the manufacture of cheese are eaten to a limited extent. They consist quite largely of the casein of milk, and hence supply the body with building material as well as energy. Butter and cheese (qq.v.), the principal milk products used as food, are of great importance as articles of diet.