for the requisite supply of vitamins may mean the ingestion of large quantities. Man's requirements are far from being established on a quantitative basis to-day. In so far as current experi mental evidence goes, it gives no warrant for the assumption of magical vitamin potencies in a spoonful or two of milk. Furthermore, inasmuch as the vitamins are apparently not manufactured anew in the organism but are derived by animals from their feed, it is easily understood why there may be differences between summer and winter milk in some sections. Failure to recognize this doubtless accounts for some of the contradictory reports, particularly with regard to vitamins A and C. The problems of dairy feeding thus have come to have a direct relation to the nutritive quality of milk with respect to its vitamins.

The current enthusiasm for the vitamin hypothesis, and the demonstrations that have supported it, have perhaps been allowed to overshadow a feature of the composition of milk that deserves to be more widely heralded, namely, the inorganic elements therein. Milk remains to-day as the most available source of calcium, an element present to the extent of several pounds in the adult human body. The typical American dietary with a large abundance of cereal grains of various sorts, of meats and potatoes, of sugar and fats, with a sparse inclusion of green vegetables and fruits, deals with products for the most part notably poor in calcium. In harmony with what one might thus expect, Professor Sherman's fundamental studies indicate that a deficit in calcium is perhaps the most probable immediate error in the eating habits of the present day. From this standpoint alone the more liberal use of milk in one form or another must make an appeal to those interested in the promotion of national health. The bodily store of calcium is large and is drawn upon with apparent physiological ease; but this should not lead us to overlook or underestimate the fact that a prolonged negative balance may mean real harm for the organism.

Milk is not a cure-all. There are a few persons who have an undeniable idiosyncrasy, usually some anaphylactic manifestation, which may preclude the use of this food in their diet; other persons have a fancied dietary grievance against milk. They are not the mass of our population. Nevertheless, these are days of extreme propaganda with the admonition to eat more of this or that. Milk doubtless is vital to national health, but the wholesale advice to 66 drink more milk" meets with real or fancied limitations in some It is, however, often agreeable or advantageous to increase the intake of certain ingredients of milk by the use of products other than fluid milk. Herein lies the pressing opportunity for the intelligent introduction of some of the increasing varieties of milk-made foods.

Chairman CUMMING. Doctor Blackham, who was to have presented We will, therefore. a paper, "Milk in the Tropics," is not here. proceed with the paper following, which is to be presented by Dr. H. C. Sherman, professor of food chemistry, Columbia University. [Applause.]

THE OPTIMUM AMOUNT OF MILK FOR CHILDREN.

HENRY CLAPP SHERMAN, Ph. D., professor of food chemistry, Columbia University, New York City.

In view of the fact that most physicians and dietitians advocate a quart of milk per day for every child, while some believe that a smaller amount may do as well, the New York Association for Improving the Condition of the Poor, with the cooperation of the department of chemistry of Columbia University, undertook a somewhat extended series of experiments upon children from 3 years to over 13 years of age, to determine what quantity of milk per day, taken as part of a normal diet, would induce the best storage of calcium and phosphorus in the body of the growing child and hence, presumably, the best development of bones and teeth.

The investigation was made possible by a grant from the research fund established by Mrs. Elizabeth Milbank Anderson.

Groups of average children who had volunteered for the experiment were taken as visitors to the suburban house maintained by the association, where they lived normally for periods of from 10 to 50 days under the constant personal observation of my colleague in the research, Miss Edith Hawley. The research worker maintained constant supervision and control of the children, sleeping in the same room with them, preparing and serving their food, eating with them, and recording and analyzing the complete food intake and excretory output of each child separately throughout the entire time that each was under investigation. In this way the balance of intake and output was determined with the highest possible accuracy while at the same time all the children led perfectly normal lives."

The investigation as a whole consisted of four progressive series of experiments, including in all 21 children ranging in age from about 3 to about 14 years, and covering a total of 417 experimental days. In the first series of experiments the children received ordinary mixed diet, including 750 grams (about three-fourths of a quart) of milk for each child daily, this being the approximate amount to which they were supposed to be accustomed in their home dietaries. This diet resulted in their storing calcium in quantities approximately proportional to their body weights. In the second series, when the amount of milk was increased to 1,000 grams (1 quart) per child per day, the rate at which the children stored calcium was materially improved. Very careful studies with systematic increases and decreases in the daily allowance of milk led to the conclusion that, whether at 3 or at 13 years of age, the child must be fed a quart of milk per day to insure the optimum storage of calcium and phosphorus and the best development of bones and teeth.

The third and fourth series of experiments were planned to ascertain whether children utilize the calcium of vegetables as well as that of milk, and whether, with a larger use of vegetables, the consumption of milk could be reduced without detriment. This was found not to be the case. While liberal use of vegetables in the dietaries of children is doubtless good dietetics, the vegetables should be used along with the full allowance of a quart of milk per day.

All of our many experiments in which about one-half of the milk of the diet was replaced by vegetables of equal calcium content showed plainly the superiority of the milk over the vegetables as a source of calcium for growing children, and that even when vegetables are freely used the child should still have the full quart of milk per day if optimum results are to be insured.

The full scientific account of the experiments has been published in the Journal of Biological Chemistry for August, 1922, and a shorter and less technical account has been given in the Journal of Home Economics for September, 1922. The results as a whole emphasize strongly and in most convincing fashion the importance of the quantity of milk consumed. In view of these results and of our present knowledge of the practical equivalence of raw, Pasteurized, condensed, and dried milks from the nutritional standpoint, it would appear that the form in which milk is used may be largely left to the choice of the consumer and the nature of the available supply, and that we may well devote ourselves more especially to the effort of insuring the consumption by every growing child of the equivalent in some form of a quart of whole milk per day. It should also be emphasized that these experiments show the importance of continuing the consumption of a quart of milk per day up to at least the age of 13 to 14 years.

As pointed out editorially in the Journal of the American Medical Association in the discussion of the experiments above described: "The dietary rule of a quart of milk each day for every child is much more than a precept based on individual opinions or drawn by analogy from the results of feeding experiments with lower animals; it now rests on scientific evidence obtained by extensive and intensive experiments directly upon the children themselves."

The method of investigation used in the experiments above described, depending as it does upon the measurement of the storage of calcium and phosphorus in the growing body, is applicable only to children of ages at which active growth is to be expected. To study the effect of different levels of milk consumption upon the later development and health of human beings would involve so many and such long experiments as to be quite impracticable. It is, however, possible to determine by means of studies with laboratory animals of rapid development, like the rat, the effect of different levels of milk consumption when all other conditions of life are maintained strictly uniform. This has been studied in the writer's laboratory through several generations of experimental animals, with results which show plainly that the more liberal allowance of milk, corresponding approximately to 1 quart of milk per day in the human dietary, greatly increases the vigor of the young adult, and confers improved health and vigor and much better success in the bearing and rearing of young throughout middle life. the same change in dietary (namely, an increased proportion of milk in a food supply already adequate according to current standards) actually postponing old age in the same individuals in which it has induced earlier maturity.

In view of such evidence it seems a mistake to limit the recommendation of a quart of milk per day to the ages from infancy to puberty. Undoubtedly it would better be extended, probably to all

ages. Certainly it seems to me the boy should have his quart of milk per day until he is a man full grown, and the girl should continue to take her quart of milk per day until as a woman she has weaned her last child.

Chairman CUMMING. Professor Bloch will now address us on "Blindness and other diseases in children arising in consequence of deficient nutrition." Professor Bloch, of Denmark, years ago discovered an eye disease which occurred in children and which later was recognized by Doctor Mendel as being due to a deficiency in vitamins. [Applause.]

BLINDNESS AND OTHER DISEASES IN CHILDREN ARISING IN CONSEQUENCE OF DEFICIENT NUTRITION (LACK OF FAT-SOLUBLE A FACTOR).

C. E. BLOCH, M. D., professor of medicine, University of Copenhagen, Denmark. While blindness in children has been on the decrease in the greater part of the civilized world, the opposite has taken place in Denmark. Blindness in children has increased not only absolutely, but also relatively to the population. Many causes have contributed to the diminution of blindness in other countries, but the chief one undoubtedly is that gonorrheal ophthalmo-blennorrhea in the newborn has become a rare disease as a result of the special measures which have been adopted against it everywhere. That gonorrheal ophthalmia has become a rarity also applies to Denmark, but in spite of this the percentage of blindness in children is increasing.

There is, however, another disease of the eye peculiar to childhood which leads to blindness. This is xerophthalmia. It was first described in the middle of the last century by German ophthalmologists. According to all previous reports xerophthalmia had a very serious prognosis, as it occurred particularly in the final stage of a cachectic condition due to a protracted wasting disease, such as tuberculosis, syphilis, typhoid fever, acute or chronic digestive diseases, etc., and especially in badly nourished and debilitated children. In the middle and close of the last century and in the beginning of this, "epidemics" of an eye disease were described which were undoubtedly identical with xerophthalmia. These epidemics occurred among negro children in Brazil, during periods of fasting in Russia, when famine and summer diarrhea accompanied one another in Japan, and it was always the badly nourished and diseased children of the poorer classes who were attacked. The majority of the authors who have described these epidemics, therefore, associate xerophthalmia in children with a bad and deficient diet. Primitive medicine in Japan, Russia, and other countries has from ancient times treated this eye disease with fat substances, especially codliver oil and liver, and Mori has declared that the disease is due to lack of fat in the diet.

In Europe xerophthalmia is considered to be extremely rare. few cases have previously been recorded in badly nourished children in England and Denmark, while in Germany Czerny and Keller and, according to them, several others have now and again observed

xerophthalmia in the final stage of the nutritional disease they call "Mehlnährschaden."

The children's department of the Danish State Hospital was opened in 1911. Even by the next spring a number of children. were admitted with a curious eye disease which proved to be xerophthalmia, and in the following year the number increased to an alarming extent. I thus had the opportunity of studying this disease in its different forms and stages, about which I published communications, some long and others short, in 1914, 1916, 1917, 1918, and 1922. My investigations indicated that the disease was due to a lack of a particular substance. This substance was present in fresh milk, but not in separated milk or buttermilk. It was therefore united with the butterfat, and it was also found in abundant quantities in codliver oil. My investigations further showed that the disease could not be attributed to the absence of fat as such, because even though the children had received margarin or pork fat, they could easily get xerophthalmia.

In England and the United States a large number of experimental investigations into nutrition were carried out partly before and partly at the same time as my work. From these inquiries we became further acquainted with the cause of xerophthalmia and the disease associated with it. It was from the animal experiments of Osborne and Mendel, and especially of McCollum and his collaborators, that we now know that the cause of xerophthalmia is the lack of the fatsoluble A factor. This body, which is united with certain fat substances and is notably found in large quantities in butter and codliver oil, must be constantly supplied to the organism, particularly the growing organism, in order that growth shall take place; deprivation for a long period leads to xerophthalmia and death.

When a child, particularly one in the first few years of life, is deprived of its mother's milk or fresh milk, as well as cream and butter, and is kept for a long time on a diet consisting of puddings made with separated milk or buttermilk, bread and other farinaceous foods, potato mash, a little pork and other meat, margarin and pork fat, it will become ill as a result of the absence of the fat-soluble A factor. Even if the child eats a little vegetable, fruit, and green stuff now and again it will not help much, for a small child can digest only trifling amounts of green stuff.

A deficiency of the fat-soluble A factor may also occur in children who have received a quantity of pure milk, but in such cases the milk must have been stale and modified adversely, the fat-soluble A factor being destroyed by oxidation and repeated heating.

The disease is ushered in by the child's ceasing to gain weight. Later on there is a loss of weight and the child remains motionless and apathetic. In other words, there is inhibition of growth and depressed psychic and bodily vitality. These children are liable to be attacked by some infectious disease which usually takes the form of a simple catarrhal infection of the mucous membranes, particularly of the respiratory organs and middle ear. B. coli infections of the urinary tract and infectious dermatitis are also frequently observed. These infections are extraordinarily persistent and often have a fatal