Milk powder prepared by spraying milk with heated air has been tested by Dutcher and Ackerson.42a Eight guinea pigs, used as controls, were fed a diet of oats ad libitum and 30 c.c. (daily) of fresh raw milk. Ten guinea pigs were fed oats and milk powder (prepared from the same herd milk). The milk powder was diluted bade to the same composition as the original raw milk and 30 c.c. were fed daily to each animal. The milk powder was prepared at intervals of 2 to 5 days by spraying milk into a blast of hot air in a cell four feet square. Each quart of milk came in contact with approximately 1,400 cubic feet of hot air. The air in the cell was kept at a temperature of 115° C. while the temperature at the spray nossle never exceeded 100° C. The milk powder was allowed to remain on the floor of the cell during the (hying process (2 to 3 hours). No attempt was made to approximate commercial conditions. The entire group of guinea pigs receiving the milk powder died with pronounced scurvy lesions in periods ranging from 16 days to 42 days.

At the end of 42 days all of the control animals, which had consumed their daily ration of raw milk, were living and in much better physical condition than the group receiving the dried milk.42b.

42a Dutcher and Ackerson, Science, 54, 442,1021.

42b Four series of experiments were carried out by Jephcott and Baxharach (Biochem. J. 15, 129, 1021) to determine the antisoorbutio potency of dried milk. In the first three, oompariaon was made of summer milk, winter milk and winter milk neutralised with sodium bicarbonate before drying. All three were dried by the roller process, in which the milk is in contact with the source of heat for not more than three seconds. The fourth variety was full-cream milk dried by the spray process; this variety of milk is subject to prolonged heating. The composition of the four varieties of milk powder varied but little; they each contained in the neighborhood of three-fourths per cent of moisture, 54 to 64 per oent of ash, 26 to 28 per oent of fat, 36 to 87 per cent of lactose, and 26 to 27 per cent of protein. Guinea pigs were fed with the usual scorbutic diet of oats and bran, and the milk was added in the form of a thin cream by mixing the powder with three times its weight of hot water. The results may be summarised as follows:

The question of how far the proportions of the relative constituents present in milk can be varied by alteration in the diet of the lactating animal has received much attention from investigators! especially in connection with the vitamin content.

It is the general experience of practical dairymen and of investigators in the field of animal nutrition that diminution in the amount of food below the physiological requirements of the animal results in decrease in the amount of milk secreted, and that increase in food causes increased production of milk, although the increase is not proportional to the amount of food given.43 The effect of underfeeding is less marked in the early stages of lactation than later. Eckles and Palmer report a case in which a constant flow of milk was maintained for 30 days by an animal receiving only sufficient food for body maintenance.44 When the lactating period has reached a certain stage, however, even moderate underfeeding reacts adversely upon the milk supply. Lane-Claypon 45 asserts that it is probable that many cases of failure of lactation in women have been caused by the absence of proper nourishment for the mother, and quotes the experience of institutions in which dinners are provided for nursing mothers. "It is the opinion of the officers who supervise the work at these centres that the provision of an adequate food supply for the mother almost invariably enables breast-feeding to be maintained, mothers who have previously been unable to feed their children being able to do so without difficulty when provided with sufficient food of a suitable nature.

Moreover, in many instances, where the milk supply was apparently becoming short, it has been completely regained and lactation continued up to the ninth month. No special foods or substances are either indicated or contra-indicated. The health of the mother must be maintained. Where this is effected owing to the idiosyncrasy of the individual for any particular foodstuff, that foodstuff should be avoided - that is all".

On the other hand, Ducaisnc 46 has called attention to the fact that during the siege of Paris healthy young women were able to produce enough milk for the maintenance, and in some cases for growth, of their infants while partially fasting themselves.

These results are not in accord with those obtained by several other investigators.

Stepp notes that accessory food substances are present in dried milk powders (Med. Klin. 17, 287, 1021).

43 See Lane-Claypon, Milk and its Hygienic Relations, London, 1016, p. 20; Eckles and Palmer, Mo. Agr. Exp. Sta. Res. Bulls. 24 and 25.

44 See also Hart, quoted by McCollum, Simmonds and Pits, J. Biol. Chem. 27, 33, 1016.

45 Lane-Claypon, 1. c, p. 157.

46 Ducaisnc, Gas. Med. Paris, 1871, 317.

While the character of the food of the animal doubtless influences the richness of the milk to some extent in the long run, it seems to affect the quality of the milk produced less than its quantity. According to Woll,47 although high feeding may produce an increase both in the amount of milk and in the butter-fat this rise is in no way proportional to the increased amount of food.

Ecklcs and Palmer 48 state that the effects of an induced subnormal plane of nutrition on the percentage of fat in the milk are variable, an increased fat percentage resulting in some cases, with no change in others, and in still others an actual decrease in the percentage of fat. The factors that appear to cause these variations are the state of flesh of the animal, the degree of underfeeding, and the season of the year in which the experiment is conducted.