Hart, Steenbock and Ellis (13) experimented with the milk of cows which had been confined for a year or more to rations consisting of air-dried grains and forage plants and which had never, during these months, been allowed to eat any fresh or green food. The object of these investigators was to determine whether such milk had less anti-scorbutic value than milk derived from cows provided with fresh foods of vegetable origin. Their results show clearly that the content 0} the anti-scorbutic substance in milk is dependent upon the diet. Summer pasture milk is much richer in this nutritive factor than milk from cows fed upon dried feeds. It is of special interest to mention that they found that even when cows were restricted to a diet, which, because of drying, had little anti-scorbutic value, the mammary gland tended to concentrate a relatively large amount of this factor in the milk. Thus the milk from dry-fed cows protected guinea pigs from scurvy only when 75 c.c. was given daily, whereas about 50 c.c. were required of milk from cows on pasture. Here we have further evidence of the role of the lactating mother in elaborating a food for her offspring, which is of better quality than her own supply.

Butcher and his coworkers (14) have conducted a considerable number of experiments with winter and with summer milks, which were secreted by cows kept on dry rations and on green food, respectively. Their data make it evident that 20 c.c. of summer milk were superior in anti-scorbutic potency to 60 c.c. of winter milk. Their results showed that when a cow passed from a green pasture ration to one of dry feed, her milk did not immediately undergo deterioration in respect to its anti-scorbutic value. Only after a period of five to eight weeks was there sufficient change in the quality of the milk to show its effects on guinea pigs. On ingesting fresh food, the milk immediately rose in anti-scorbutic value. Such experiments as the ones just described illustrate the great importance of the character of the diet of the lactating mother and the great importance of the method of feeding cows to be used for the production of milk destined for infant feeding.