1920 in children in a population of less than 3,000,000, and in addition to these there were probably others.

The reason xerophthalmia was so widespread, despite the fact that Denmark did not take part in the war, is that this country is a dairy farming one which manufactures and exports butter. During the war butter, and consequently fresh milk, became so dear that the poor could scarcely procure any of it, and they were able to obtain only separated milk and buttermilk, which could always be had at a very low price. The number of cases of xerophthalmia increased, therefore, until 1918. In that year the disease was suddenly checked, as will be seen from the curve. (Fig. 7.)

The reasons were several, but the principal cause was undoubtedly that in 1918, on account of the German blockade, butter was rationed

FIG. 7.-Occurrence of xerophthalmia (keratomalacia) among Danish children, from 1909 to 1920, by years (434 cases). Reported by Dr. Olaf Blegvad.

in Denmark, so that every individual, including small children, was entitled to one-fourth kilogram of butter a week, and as there was practically no pork fat or margarin in the country everybody had to eat butter. Xerophthalmia ceased simultaneously. These facts show as clearly as an experiment that the absence of the fat-soluble A factor is the cause of xerophthalmia.

After the termination of the war the rationing of butter came to an end and xerophthalmia returned, but it was rare compared with its former incidence. It was particularly noticeable that the severe cases no longer occurred. The people and the Danish doctors had got to know the disease and had learned how to avoid and treat it.

The disease caused by lack of fat-soluble A factor is cured by supplying the latter to the afflicted organism, best in the form of fresh milk, cream, butter, or cod-liver oil. The xerophthalmia is the first to disappear, then the child begins to thrive and gradually throws

off the infections. The latter are therefore cured by the administration of the fat-soluble A factor. This is in harmony with the old clinical experience that chronic infectious diseases, particularly tuberculosis, are improved by a diet rich in fresh milk, butter, and codliver oil.

The fat-soluble A factor is thus particularly important not only for the eye lesion but also for establishing immunity, and it is clear that a great deal of it is used up in infectious diseases. Large quantities must also be consumed during growth. This is most clearly evident from McCollum's animal experiments, but the study of xerophthalmia points in the same direction, as it occurs practically only in children; that is to say, in growing individuals. Moreover, the disease appears especially in the spring months, at which season

Okt. Nov Dec. Jan. Febr. Marts Apr Maj. Juni. Jul. Qug. Sep

FIG. 8.-Distribution of 434 cases of xerophthalmia (keratomalacia) by mouths. ported by Dr. Olaf Blegvud.

Re

the most marked growth of the child takes place. The cases not occurring in this annual period of growth have always been complicated by serious infections or chronic diarrhea. This distribution of the cases is shown by the curve. (Fig. 8.)

It has been thought that the accumulation of cases in the spring was due to a different content of fat-soluble A factor in the winter milk (stall feeding) and the summer milk (grass feeding). It is possible that there is more fat-soluble A factor in the first grass milk, and that this has something to do with the disappearance of the disease in the summer, but a decreased fat-soluble A content in the milk can not be the cause of the many cases arising in the growth period of the spring, because precisely the same distribution is found of cases that have received no milk or milk products at all for a long while. It is also difficult to believe that milk from healthy cows could be deficient in the fat-soluble A factor. At any rate, it has not

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been proved, and the experience with xerophthalmia in Denmark is against the supposition.

What I have said here and proved to you testifies to the enormous importance of milk as a food for the child. No other article can replace milk. Absence of milk from the diet or the inclusion of unfavorably modified milk is the origin of most serious diseases.

By ordering milk, and especially cream and butter, this terrible eye disease is cured-which I believe will be discovered in every country when it is looked for—and these dairy products are of the greatest importance for growth and development and for the cure of our greatest infectious diseases.

Chairman CUMMINGS. Doctor Hamill has been good enough to consent to read a very short but excellent paper prepared by Doctor Blackham, who has had 28 years' experience in handling the milk problem in the Tropics.

(Doctor Hamill read Doctor Blackham's paper, "Milk in the Tropics.")

MILK IN THE TROPICS.

Col. ROBERT JAMES BLACKHAM, M. D., London; late honorary surgeon to the Viceroy of India.

In warm climates milk decomposes more rapidly than any other article of diet, and as every sample of it may become dangerous to health, its quality, supply, storage, and distribution are amongst the most important problems which face the statesman, the physician, the dairyman, the Government official, and the merchant whose lot may be cast for a longer or shorter period, either in one of our eastern dependencies or in the portion of this great country which borders on the tropical zone.

In some hot countries milk holds a high place in the dietary of the people, and in India, for example, it is ubiquitously used in some form or other by all classes of the community.

The word "milk" in Europe and America means cow's milk, but in the Tropics, or subtropical countries, it may mean cow's milk, buffalo's milk, goat's milk, or even sheep's milk.

The main source of supply in India is the buffalo, and in India and China practically all milk consists of a mixture of cow's and buffalo's milk.

No systematic breeding of cattle by the private owner exists, but notwithstanding a considerable number of pure breeds of cattle are found in the East. This is a somewhat surprising fact, and, further, it is not generally realized that India has several fine varieties, and exports milk cattle to all parts of the tropical and subtropical world, and that this export trade is a severe drain on her own national milk supply.

The "dairy" in a typical tropical town such as Bombay or Calcutta is often not a dairy at all in the western sense of the word. The dairymen are merely importers of milk, most of which comes in from the suburbs in open vessels, carried underneath the seats of ordinary third-class carriages, as there are neither milk cans nor milk trains.

The filthy condition of these third-class carriages in the Tropics, the clouds of dust flying directly into the open vessels, and the disgusting habits of the passengers beggar description. The milk has already been drawn under most primitive conditions, and after a slow journey of three or four hours at a temperature in the neighborhood of 90° F., often much more, very seldom less, its bacterial content when it reaches the consumer more than rivals that of ordinary sewage. The position of the milk problem in India is succinctly stated in the following resolution of the Government which declares that

The adulteration of milk is almost universal in Indian bazaars, and a large amount of the milk consumed is contaminated. In most cities the milk supply is in the hands of men ignorant of the elements of sanitation and addicted to uncleanly practices. Moreover, the milk when stored and in transit to market is liable to contamination in several ways. On the other hand, the price of milk is already high, and the problem of improving the purity of the supply without increasing the price to such an extent as to cause hardships to the poorer classes is a difficult one.

The last paragraph of this Government resolution is an important one, as it is not generally realized either in Europe or America that milk is not only dear but very scarce in many parts of the Tropics.

During my residence in India I had charge of Government laboratories and was struck by the fact that the sanitarian and analyst practicing in the Tropics are confronted with difficulties unknown to their colleagues in temperate climates, not the least of these being the absence of reliable milk standards with which to compare their results.

I have found that the chemical composition of cow's milk in the Tropics may be summarized as follows:

It will be seen that both cow's milk and buffalo's milk are extremely variable products in the Tropics, and that the results, generally speaking, with regard to cow's milk do not compare favorably with European analyses. The butterfat, especially in buffalo's milk, was found to be most in warm, moist climates such as Bengal, and least in comparatively cool and dry climates such as the Punjab.

Chemical analyses of milk are useful as they enable us to say if a sample of milk is genuine or otherwise, but they do not reveal anything as to its contamination with dirt or microbes. A milk may pass all chemical tests and still be not only dirty but actually infected with pathogenic organisms.

I have endeavored to establish bacteriological standards for milk in the Tropics, but do not propose to occupy your time with this very important aspect of milk examination. I would here emphasize the fact that no examination of milk can be regarded as complete unless its bacterial content is examined, as might be expected from what I have said above regarding the way in which many samples reach a typical India town. My experience is that much tropical milk is richer in intestinal bacteria than ordinary sewage.

The measures necessary to reform the milk supply in the Tropics fall naturally under four headings: Educational, sanitary, economic, and legislative, but a large book might be written on this aspect of the question alone, and I shall only refer briefly to the first two headings.

As Rosenau says "education is one of the chief spokes in the milk wagon." Now, the essential difference between breeding of cattle in the Tropics and temperate climates is that whereas cattle are bred for food in Europe and America, meat is little used by the natives of hot countries and, therefore, the aim of the breeder is to produce stock, of which the cows will be good milkers and the bulls efficient draft animals. In India both sexes are sacred animals, the bull, bullock, and cow are hung round with ornaments and usually well fed, according to native ideas and ideals, but the tropical peasant is ignorant of the most elementary notions of hygiene as applied to cattle breeding. He is himself as poor as a sparrow, and his home lacks the comfort and security of the sparrow's nest. It is little wonder that he houses even sacred animals under conditions which offend every sanitary principle, and his ideas of feeding and tending would horrify the western dairyman. Calves are allowed to die through sheer neglect, although the slaughtering of one of these animals for food might be quite sufficient to raise a religious riot.

The governments of tropical dependencies have started government dairies, but these are run for the benefit of troops and officials, and mighty little has been done to encourage scientific breeding, so that there is still vast scope for educational propaganda on the subject. The great difficulty in the way is the poverty to which I have referred; it is far more important than prejudice, which can be readily overcome, as the oriental is a very intelligent man and takes most kindly and promptly to all modern advantages of transport and communication, while he is fully alive to the value of education and a great respecter of learning. We sometimes forget that most orientals are descendants of a civilization much older than our own.

Space will only permit me to refer very sketchily to the feeding of tropical cattle and to emphasize the point so well known to all who have studied the subject that the quality of a milk must depend on the food supplied to the animal which produces it.

The native buffalo or cow is turned out to find its living on burnt and bare patches, while even cows from Europe quickly deteriorate under a diet consisting of straw and hay rapidly ripened in tropical warmth and burnt to a cinder by a tropical sun. Such "green" food lacks the sappiness so essential to milk cattle, and it is obvious that under such conditions their milk must be an entirely different product to that produced from animals fed on the luscious pasturage of Europe, some parts of America, and some of the British colonies.