butter. This substance, when obtained from woman's milk, is richer in oleine than that obtained from cow's milk. The butter made from cow's milk is composed, according to Robin and Verdeil, of these three substances : It is to the last of these ingredients, the butyrine, that the peculiar smell and taste of butter are due. The caseine, or cheesy matter, is the coagulable principle of milk, and also its nutritive element. It exists in that fluid in the proportion of from 2 to 4 per cent. It resembles albumen, but differs from it in holding in solution a larger percentage of phosphate of lime, and in being coagulable by all the acids and also by alcohol, but not by heat. The caseine of woman's milk is not so easily precipitated by acids as is the milk of the cow indeed it generally resists the action of the mineral acids, and even of the acetic; and it yields slowly even to the action of rennet. It is less abundant than in cow's milk, and its coagulum is less dense, and consequently more easily digested by the infant. The saccharine matter of milk may be obtained from whey by evaporation and crystallization. It is known as lactine, lactose, or sugar of milk; and it possesses the demulcent properties of the sugars in general. This ingredient is, in woman's milk, two per cent. more abundant than in cow's milk, and two per cent. less abundant than in mare's milk. It is nearly identical in composition with starch, and, like starch, is converted into true sugar by the action of sulphuric acid. The saline matter of milk is composed principally of chlorides of sodium and potassium, and phosphates of the alkalies, lime and magnesia. It is nearly identical with the saline matter of the blood, but has a larger proportion of the phosphates of lime and magnesia. The phosphate of lime is a very important ingredient, being that from which the earthy portion of the skeleton is built. It is held in solution chiefly by the cascine, and it has been suggested that "probably the reason of the introduction of caseine to the exclusion of other protein compounds, depends on the power it possesses of holding phosphate of lime in solution; not less than six per cent. of its weight of this earthy body being often obtained from it." The composition of milk varies with many circumstances. Thus, among cows, certain breeds yield a milk in which the fatty ingredient predominates; certain other breeds, a milk in which the cheesy ingredient predominates. And among women, it is found that the milk of a woman of twenty is richer in solids than that of a woman of thirty-five or forty; that the milk of the well-fed woman of whatever age, is always richer in solids than that of the ill-fed woman of the same age; and that the milk of the brunette is richer-in caseine, by 50 per cent., in sugar, by 15 per cent.-than the milk of the blonde. Food which is typically perfect must contain three classes of principles, viz.: the albuminous, oleaginous and the saccharine. Such food is the milk. It contains all these principles, and is the only secreted fluid in which they all exist in any considerable amount. It is therefore the food most perfectly adapted to the wants of the young animal. Whatever is required for the growth of the infant's body is found in its mother's milk: there is caseine for the muscular tissue, phosphate of lime for the osseous tissue, and sugar and fat for the adipose tissue. The experiments of Simon prove that the constitution of the milk varies from day to day, owing to temporary causes, and that it undergoes permanent modifications also, corresponding with the advancing age of the child. "The caseine and the sugar are reciprocally related to each other," the one increasing and the other decreasing from the time of parturition until a fixed proportion is attained. At the time of parturition the quantity of sugar is at its maximum, while the quantity of caseine is at its minimum. There is a gradual decrease of the former and increase of the latter during the first few months, when a nearly uniform standard is attained. Until about the end of a year after parturition, woman's milk becomes more and more nutritious in proportion to the increased size and strength of the child. Then it becomes suddenly deficient in caseine, and thus loses its nutritive element. The first milk is called the colostrum or protagala. It acts as a purgative upon the child, and clears its bowels of the meconium with which they are loaded at birth. This peculiar effect of the protogala is supposed to be due to the presence therein of the colostrum corpuscles. The colostral character of the milk usually ceases during the first week. Sometimes, however, it remains longer, and occasionally it returns at the expiration of twelve months, thus seeming to indicate that the lacteal flow should be no longer encouraged. Of the quantity of milk daily secreted by the human female it is difficult, if not impossible, to gain a definite idea. It has been estimated at from 32 to 64 ounces. This estimate is made by determining the weight of the child before and after nursing. About two ounces may be artificially withdrawn from either breast at any one time, but this, which must have been contained in the tubes and reservoirs, affords no data from which to estimate the quantity secreted at the time of the draught. By the draught is meant that sudden rush of blood into the gland, and of milk into the ducts, which takes place when the child is applied to the breast. No secretion is so readily affected by the general health and by the quality and character of the ingesta, as the milk. It may be vitiated in quality or increased or diminished in quality by sudden emotions. The taste and color and smell of cow's milk are readily affected by the food: and children have been salivated and purged and disordered in many ways through the mother's milk. The conditions most favorable. to the production of a copious supply of milk, are a good constitution, vigorous health, nutritious food and moderate exercise. When fresh milk is allowed tc. . nin at rest for twelve to twenty-four hours, the oil-globules rise to the surface, and form a rich yellowish-white layer, known as the cream. By agitation of the cream, as in churning, the globules of fatty matter unite, and form butter. The residue is buttermilk and consists of the caseine, sugar, serum or whey,and a very small quantity of butter. The milk that remains after the cream is removed contains the greatest part of the caseine and sugar, and is known as skimmed milk. If it is kept long enough, the sugar it contains is converted into lactic. acid, which coagulates the caseine and precipitates it in small flakes. The same thing may be accomplished by other acids, but most effectually by that which is contained in rennet. The active principle of this substance, which is simply an infusion of the dried abomasus, or fourth stomach of the calf, will coagulate about 30,000 times its weight of milk. If rennet be admixed with skimmed milk it immediately coagulates it, separating the caseine, or curd from the whey; and if, when the curd is removed, acetic acid be added, it will cause a still further coagulum, which is known as the ziega. The whey that is left, when the ziega and curd are removed, yields lactic acid, salts and some nitrogenous substances. Milk, although admirably adapted to promote the nutrition and rapid growth of the child, is lacking in some of the elements required for the proper support of the man. In adult life there is a ceaseless activity, and consequently a constant waste of cerebral and nervous tissue; and for the repair of these tissues certain phosphorized compounds, in which the milk is deficient, are absolutely necessary. Hence it is that milk is not suitable as the sole nourishment of the adult. Still, beyond question, it is the best form of aliment. out of the strict order of natural food, and may be used in moderation without injury or inconvenience. It is true that in certain abnormal states of the digestive organs, it cannot be taken with impunity; that "some invalids cannot enjoy and some dyspeptics cannot tolerate it; but these are exceptional cases, from morbid conditions, and ought not to form rules for persons in health." en a 30 East 19th St., New York. 35 PERISCOPE. Physiological History and Therapeutical Uses of Pepsine. AT a recent meeting of the New York Medical Journal Association, Dr. James S. Hawley presented a valuable and interesting paper under the above caption, from which we make the following extracts. After a few prefatory remarks concerning the object of the paper, the Doctor said that until a very recent date pepsine has been most laborionsly and carefully studied, chiefly from a physiological stand-point, and our knowledge in this direction is therefore most accurate and full. The fact that food taken into the stomach was reduced to a pultaceous condition by a solvent fluid poured out from the walls of the organ, was demonstrated in the latter part of the 18th century, by the experiments of of REAUMER and SPALANZANI. Previous to that time the contractile movements of the stomach were supposed to be the chief agents in the digestive function. This discovery gave a new direction to investigations, and soon after it was ascertained that the gastric fluid digested only a portion of the aliment taken in the stomach, viz., the albuminoids. The gastric fluid, therefore, although the principal, is not the only digestor. The composition of this solvent fluid remained for some time in doubt, but we now know that is a compound agent, the most important elements of which are a peculiar organic substance called pepsine and an acid secretion. The composition of the acid factor has long been a subject of dispute, but the most recent researches tend to confirm the idea of PROUT, who believed it to be hydrochloric acid; while others, perhaps the minority, still hold that lactic acid is the natural acid of the stomach. The organic body or ferment, is in itself destitute of digestive power, its activity being developed only by the addition of acid. Experiment has proved that any acid will render pepsine active, and we may therefore infer that the acid component is not necessarily the same under all circumstances in the living organism. The proportion of pepsine in the gastric juice is very small, as nearly as can be estimated not over 17 parts in 1000. A small amount of pepsine will therefore give digestive activity to a very large quantity of acidulated fluid. Pepsine is a protein body, and differs from other substances of the same class in containing a larger percentage of nitrogen. It differs from albumen in not being precipitated from its solutions by the same reagents. It is entirely soluble in cold water, from which it may be |