My attention was drawn to the subject when I was in charge of Government laboratories in the East some 15 years ago, and I carried out a series of analyses and experiments on behalf of the Government of India.

About the same period the Ministry of Health in England found that the manufacture of dried milk was assuming such extensive proportions that one of its medical officers undertook the preparation of a report on the product, and this document was published about five years ago.

The report was decidedly favorable to dried milk, and the development of this important modification of an all-important article of diet has been so remarkable that it seems desirable to bring it to the notice of this congress, with a view to a discussion on the subject. Dried milk is now chiefly used in Great Britain, the British colonies, and the Indian Empire, but curiously enough it was first suggested as a food for infants by the French in 1904, and in the same year a German observer published an account of the use of dried milk as a food for himself and his infant son. At the National Conference on Infant Mortality, held in London in 1906, two eminent medical men, Doctor Sommerville and Doctor Harper, strongly advocated the use of milk powder, and the present chief medical officer of the Ministry of Health, Sir George Newman, who was then medical officer of health of a London borough, commenced using it at

once.

In his annual report for 1907 he said: "Dried milk is an excellent substitute; not for breast milk and not for really good cow's milk, but for much of the milk on which infants are now fed." Since these earlier experiences dried milk has steadily increased in popularity as a food for infants and has won the warm approval of many eminent British and continental authorities.

The product has been employed on a large scale in Leicester, Sheffield, Birmingham, Manchester, Bradford, Liverpool, Birkenhead, Huddersfield, and several London boroughs and its introduction has led to the abandonment of infant milk depots and to the distribution of dried milk in lieu of Pasteurized or so-called humanized milk.

Parallel with the development of the employment of dried milk in infant feeding, there has been a remarkable decrease of the infantile mortality in Great Britain.

This was called attention to by medical speakers at the National Milk Conference which was held at the Guildhall of the city of London on October 16, 17, and 18, 1922-i. e., less than a year ago. Dr. Robert Hutchison, the eminent authority on food and dietetics, said: "I am of the opinion that no inconsiderable part of the decline in deaths from infantile diarrhea which has happily taken place in recent years is due to the ever-increasing use of dried milk for infant feeding, especially among the working classes." It has been estimated that since its introduction on a commercial scale some 15 years ago, the use of dried milk in welfare centers and in various institutions has increased more than 150 per cent, and during the same period the rate of infantile mortality for England and Wales has fallen 43 per cent; i. e., from 130 per 1,000 in 1908 to 77 per 1,000 in 1922 last year.

Of course, many other factors have been at work in reducing infant mortality but the association between the development in the use of dried milk and the marked saving of infant life has been striking.

This rapid increase in the use of waterless milk has been due to the great difficulties in the production and transport of a liquid milk supply suitable for infant feeding, and especially in insuring the use of such supply in the poorer districts of the great towns.

Prof. Leonard Hill has actually suggested that it may be cheaper to dry all milk and distribute it in powder than to attempt to continue our present methods of distribution. Such a suggestion may not be worthy of the consideration of this congress, but it is certain that of recent years there has been remarkable development in the manufacture of dried milk and that already no inconsiderable amount of milk is sold in the form of powder. As this congress is doubtless aware, some 10 processes for the manufacture of dried milk have been put forward from time to time; but so far as I can ascertain, all products at present on the market are prepared by one of two processes, viz., (a) the rapid drying of fresh milk on rollers heated by water or steam, and the subsequent powdering of the solids thus obtained with or without the admixture of lactose, or; (b) the projection of milk in the form of a fine spray into a chamber with a current of hot dry air, so that the milk solids fall on the floor in the form of fine powder.

The first of these methods claims most adherents, and it is fully realized by the modern manufacturer that no process will make dirty milk into a clean powder and, therefore, arrangements exist to collect milk in suitable churns under special precautions as to cleanliness. By all reputable manufacturers the milk is converted into powder within the shortest possible period after milking, whilst every part of an up-to-date dried milk factory is kept as clean as the proverbial new pin. By the roller process, if the milk is at all acid the cylinders "cry," as the manufacturers say, and the process is difficult so that, as pointed out by MM. Aviragnet and Dorlencourt, the two great French physicians, this is in itself a guaranty to the consumer of the freshness of the milk used in preparing milk powder by the roller process.

In the words of Hutchison, milk must be treated in the process of drying "as the surgeon treats a wound by aseptic methods, remembering that the source of danger is not so much the dropping of germs into the milk out of the air, as gross contamination by dirty hands, dirty vessels and utensils, and by gross purveyors of infection such as the house fly."

I think one of the qualities of dried milk which appeals most strongly to doctors and laymen is the constancy of its composition. Nothing is more notorious than the variation in the composition of the milk of one cow, but Dr. Charles Crowther has drawn attention to the remarkable variation in the milk of small herds as well. He points out that the variation of fat from day to day is not great in either morning or evening milk, when considered separately, but as between morning and evening milk the range of variation is relatively enormous.

He says: "The extremes in samples of undoubtedly genuine milk representing the mixed produce of not less than five Shorthorn or similar cows that have come under my notice are":

Fat (per cent).
Not fatty solids.

Morning Evening milk.

milk.

2.0-4.3
8.1

2.4-5.3 9.7

The upper limits would be raised still higher by the inclusion of Jersey or cows of similar type. Of course, the greater the herd the more constant would be the quality of either the morning or evening milk, but the disparity between the morning and evening milk would doubtless remain.

Crowther purposely drew his illustrations from the small herd "since it is the small herd which is the greatest difficulty in milk control work, and the interests of the small holder can not be ignored in the development of control measures."

Now dried milk of quite constant composition is on the market so that the physician can prescribe it with the same accuracy as a drug, whereas if he orders fresh milk, or indeed any modification of it, he is prescribing a "remedy" of more or less uncertain composition. I have elsewhere drawn attention to the gross impurity of some kinds of fresh milk and need only say here that in conjunction with my friend, Doctor Samut, the well-known Malta bacteriologist, I carried out some bacteriological examinations with regard to dried milk and found all samples free from not only pathogenic bacteria, but all organisms of the Coli group. The only organism we succeeded in isolating was the harmless Hay bacillus.

Now with regard to the adequacy of dried milk for the nourishment of the growing infant, there is emphatic evidence in its favor both in respect to vitamin value and digestibility.

There is no trustworthy evidence that artificial feeding at any period with fresh cow's milk is any better than feeding with heated cow's milk. On the contrary, reliable opinion on the whole favors heated milk against fresh, and the two French authorities I have quoted above point out that heated cow's milk is much less toxic than fresh. Professor Marfan, of Paris, savs "cow's milk is better raw than cooked for calves and better cooked than raw for infants."

Controversy with reference to heating has centered around the question of its effect on the remarkable substances known as " accessory food factors" and grouped together as "vitamins."

There has been some failure to realize that there are three varieties known as A, B, and C. A is present in milk fats and to a remarkable degree in cod-liver oil. Insufficiency or absence of A is one of the main causes of rickets. Curiously enough, its absence from a dietary can be compensated for by exposure to sunlight.

B vitamin is a substance found in fruits, vegetables, and milk. Its absence causes the disease known as beriberi.

C vitamin is present in fruits, tomatoes, and tubers and in milk. Its absence causes infantile scurvy.

Vitamin A is not destroyed by the heat, but is weakened by exposure to oxygen. B vitamin is not affected by heat. C vitamin is reduced in quantity by heat. It is destroyed altogether by double heating, reduced considerably by the longer periods of heating at lower temperature commonly practiced, but only slightly affected by rapid boiling or short heating at temperatures near the boiling point.

It may, therefore, be safely asserted that milk loses none of its vitamin content by the process of drying, whereas with commercial Pasteurization there is a tendency to reheat the milk in the home. and thus destroy all the vitamin C.

It is twice heated milk that produces infantile scurvy.

With regard to digestibility there can be no two opinions as to the virtues of dried milk in this direction. Goodhart and Hill say: "The chief value of dried milk lies in the firmness and softness of the curd formed by it, which is so much more digestible than that of fresh milk that some infants who can not digest fresh or even peptonized milk, will thrive on dried milk."

In digestive troubles waterless milk is extensively prescribed by leading British physicians, and many French and Belgian doctor's regard it as un véritable aliment de choix for such conditions.

In the discussion which followed my paper on dried milk at the Birmingham Congress of the Royal Sanitary Institute, the value of the product in the dietary of typhoid fever and other specific fevers was emphasized; and after considerable experience of the employment of the products in various parts of the world, I have no hesitation in stating that it is much better than ordinary milk in this type of disease, and medical men who used it at my suggestion in Ireland, where typhoid is not uncommon, were eminently pleased with the results.

Indeed, so satisfactory have been these results of the use of dried milk in hospital practice that the replacement of the ordinary supply by reconstituted milk has been seriously contemplated.

There is another type of person with whom the use of dried milk is increasing, namely, nursing mothers.

Many products have been recommended as galactogogues (milk builders) but most medical practitioners are agreed that the best thing to make milk is milk itself. Of course, the important thing about milk used for this purpose is the solids it contains, and a common complaint with women is an inability-or, at least, a reluctance to take bulky liquids. By giving a reconstituted milk with double or even a larger proportion of the milk solids, one gets over this very serious difficulty to the family physician.

During the war, dried milk was extensively used among the British Expeditionary Forces. I have used it extensively for all purposes in the field both in the field ambulances for the wounded and sick and in "tea kitchens" for healthy men in the trenches and during active operations. My field ambulance commanders preferred it to condensed milk, and the workers in the "tea kitchens" found it admirably adapted for their purpose.

For military purposes, it will undoubtedly entirely displace condensed milk in future campaigns.

Prof. Georges Dreyer, of Oxford University, has said:

Dirty milk is an evil, but no milk is a worse one. Nevertheless, we have not to choose between these two evils for it is not necessary to put up with either. For myself, I feel sure that the drying of milk provides us, for the present, with a reasonable solution of our difficulties.

I see no serious obstacle to the efficient distribution to large industrial centers of a clean dried product which will provide a good substitute for fresh milk.

Such, gentlemen, are the main facts with reference to my subject; they offer you, at least, a wide field for discussion.

The eyes of both hemispheres are upon our deliberations, and there can be little doubt that what is said in this room must play a worldwide part with the shaping of public opinion on this big subject of the development of dried milk as a food.

Chairman ROSE. You have heard this brief on dried milk. Would you like to discuss it, even though the author is not present to answer questions? It would be obviously unfair to those absentees to read the paper of one and not the other, so I will ask the secretary to read the paper prepared by Dr. Cornelia Kennedy, assistant professor of agricultural chemistry, University of Minnesota.

(Secretary Hoover read Doctor Kennedy's paper on " Vitamins in preserved milks.")

VITAMINS IN PRESERVED MILKS.

CORNELIA KENNEDY, Ph. D., assistant professor agricultural biochemistry, University of Minnesota, University Farm, St. Paul, Minn.

For some years prior to the present decade, conflicting opinions were held in regard to the vitamin value of milk. This was an important question because milk forms the chief diet of all mammals for a more or less extended period during growth. About 1920 the various opinions which had been expressed on this subject became reconciled through the establishment of the fact that the vitamin content of milk depends primarily upon the food of the lactating animal (1). The origin of the vitamins in milk having thus been established, it seemed expedient also to determine if the vitamins once present in the milk would remain there during any process of treatment to which the milk might be subjected in its commercial usage. Here again much information of a contradictory nature. was put forth. However, the greater part of the work done in this connection was concerned with the stability of vitamin C in milk that had been either boiled, Pasteurized, or dried, because this vitamin is much more sensitive to external influences than either vitamins A or B. The chief interest in this work was centered in the study of the effects of temporary means of preservation such as the boiling and Pasteurization of milk, and much confusion arose because the investigators were not careful to define the conditions under which the experiments were carried out. It was only after it had been definitely shown (2) that temperature, time of heating, reaction of medium, and oxidation all play important rôles in the destruction of vitamin C that the presence of this vitamin in