a

year of age, is the largest single factor determining infant mortality. Further investigation demonstrates the significant fact that 75 to 85 per cent of all infants who die of diarrhea are artificially fed. Thus Planchon, in investigating the relation feeding methods had to gastro-enteritis in Paris, shows that, while the diarrheal death rate in breast-fed infants varies from a minimum of 2 per thousand in winter to a maximum of but 20 per thousand during the hot months, the diarrheal deaths of the artificially fed fluctuate from a minimum of 12 per thousand in winter to a maximum of 158 per thousand in the

summer.

In Paris during the four summer months of 1897, 2,840 infants under 1 year died. Of these 1,470, or 51.7 per cent, died of diarrhea. Of these 1,470 who died of diarrhea, only 139 were breast fed, and 1,331, or over 90 per cent, were artificially fed.

The following table from Harrington (loc. cit.) illustrates admirably this point at Berlin. The figures given cover the quinquennium of 1900-1904 and relate to the incidence of deaths among the bottle fed and the breast fed when the method of feeding could be determined.

Again, Helle in analyzing the infantile death rate of the city of Graz shows that out of 170 deaths from intestinal disease in the fiscal year of 1903-4 but of these were breast fed, 48 were partly breast fed, 117 were bottle fed, and in one case the method of feeding was unknown.

Reference to Table 6 shows that the German city of Barmen, with an infant mortality rate of 132 (1906), enjoys the lowest rate of any city in Germany, and for a number of years has made a favorable showing in this respect. Kriege and Sentemann attribute this fortunate circumstance to the general prevalence of breast feeding in

a Planchon: Prevalence of Diarrhea in the Artificially Fed. Obstetrique, January, 1900.

that city, 63 per cent of all infants being nursed by their mothers, 15 per cent being partly breast fed, and only 22 per cent being bottle fed.

diseases of the digestive tube. Nothing, however, can more graphically illustrate this point than the accompanying chart from Budin which is here reproduced (p. 638).

PART II.-THE INFANT'S DIETARY.

In common with adults, the infant requires five elements of food for its sustenance, to wit: Proteid, carbohydrate, fat, mineral salts, and water. Owing, however, to the undeveloped state of its organs of assimilation it can not avail itself of any wide dietary range. By reason of its rapid growth and more active metabolism it requires food of special form and with the nutritive ingredients in special proportions to each other. Milks are the only class of food which fulfill these conditions, being, as they are, an animal product, designed by nature only to that end.

As this paper deals merely with the dietary of infants less than 1 year of age, woman's milk and its only feasible substitute, cow's milk, will alone be considered.

WOMAN'S MILK.

Woman's milk is the secretion of the human mammary gland. Under normal conditions of lactation it is in no sense a transudation from the blood and lymphatics, but is a true secretion elaborated by glandular tissue. True milk is not present in the mammary glands until two to four days after parturition, and occasionally not until the fifth day.

Colostrum. The secretion present in the mamma for the first few days after delivery differs materially from normal milk and is known as "colostrum." It is a fluid of a deep yellow tint, chiefly due to bodies it contains known as "colostrum corpuscles." It is not so sweet as milk, is strongly alkaline in reaction, of a specific gravity of 1,030 to 1,040, and is rich in salts and proteids. These proteids are of a nature similar to the proteids of the blood as they are coagulated by heat. Colostrum contains less sugar and fat than milk, and microscopically its fat globules vary in size and are interspersed with numerous bodies four or five times their size known as colostrum corpuscles." Composition of colostrum.-According to Pfeiffer's analysis, the composition of colostrum is as follows:

Proteid

Fat-

Per cent.

5.71

2.04

The colostrum corpuscles are very abundant during the first few days, but under normal conditions disappear after the tenth or twelfth day.

Function of colostrum.-The exact rôle of the colostrum is not as yet fully understood. We may infer from the nature of its composition and its proteids that it furnishes to the newborn child during its adjustment to its novel surroundings the full expansion of the lungs and the awakening of the digestive processes, nourishment of a character similar to that it received from the placenta as a fetus. That it serves a purpose is proven by its being the first secretion not only of the human breast but of that of all mammals.

Physical characteristics of woman's milk.-With the establishment of lactation the breast secretes a fluid of the following physical characteristics: It is of a bluish color and marked sweetish taste. Under normal conditions, with the exception of some skin cocci, it is practically sterile. These are most abundant in the "foremilk." Its specific gravity varies from 1.026 to 1.036 (average, 1.032 at 21° C.). Its reaction is either amphoteric or slightly alkaline when fresh. Dilute acetic acid merely produces a light flocculent precipitate, and its proteids are not appreciably coagulated by the action of rennet.

Composition. The exact average composition of breast milk is difficult to determine, as it is subject to rather wide variations between normal limits and at different stages during the act of being secreted. Thus the "foremilk " is relatively thin, the middle portion richer, and the "strippings" richest of all in fat content. Owing, moreover, to faulty methods, previous analyses of woman's milk have been erroneous. Even now its exact composition, beyond the relative proportions of its constituents, is imperfectly understood.

According to the most recent analyses of Pfeiffer, Koenig, Leeds, Harrington, Adriance, and others the average composition of human milk is as follows:

An average caloric value per kilogram, 710.5 calories; common normal variations of caloric value per kilogram, 550 calories to 844.25 calories.

Former analyses have for the most part assigned a higher amount of proteid and a lesser amount of sugar than this. The composition of milk is pretty nearly constant throughout lactation, except during the first month and toward the close. At the commencement of lactation the proteids and salts are high, and near its end the proteids have a tendency to diminish (Adriance).

Proteids. Our knowledge of the proteids of woman's milk is still incomplete. The most important proteid substances, however, are casein and lactalbumen. Some investigators mention a third, lactoglobulin. The casein is in chemical combination as calcium casein, and owing to its relative proportions to the other proteids is only slightly precipitated by dilute acids and not appreciably coagulated by rennet.

The lact albumen is believed to be similar to serumglobulin.

The proportions of lact albumen to casein have not been definitely agreed upon, but it exists in far greater proportions relative to the casein than in cow's milk. According to Koenig, the relative proportions are as 5 to 4. The total amount of proteids varies normally from 1 to 2 per cent and abnormally from 0.07 to 4.5 per cent. They are highest during the first few days of lactation; after the first few weeks they vary but little until toward its end, when they experience a decided decrease.

Fat.-Fat is present in woman's milk in the form of minute globules, and in perfect emulsion by virtue of the albuminous fluid in which they are suspended. It exists mainly in the form of the neutral fats, olein, palmitin, and stearin, and but small quantities of the fatty acids are present. Forty-three analyses by Leeds show variations in the fat content of woman's milk of between 2.11 and 6.89 per cent, with an average of 4 per cent. The percentage of fat present in woman's milk is but little affected by the period of lactation.

Sugar. Sugar is the most constant of the ingredients of human milk in its percentage. It is present as lactose in complete solution in the proportions of from 6 to 7 per cent. Its quantity is least in the first week. After the first month its variations are very slight.

Salts. Only one-fourth as much inorganic salts is present in woman's milk as in cow's milk, and, with the exception of the calcium in combination with the casein, are all in solution. They are present in the proportion of 20 per cent.

CLINICAL EXAMINATION OF WOMAN'S MILK.

It is often of importance to recognize the occurrence of quantitative and qualitative departures from the normal composition of woman's milk occurring during lactation, and their nature, as upon

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