1. Three Shorthorn cows were grazed on the best available permanent pasture when the growth of grass was vigorous, and three other cows of similar lactational history continued to be stall-fed. At the time of the experiment they had been on winter rations for 6 months.

2. By suitable blending of morning and evening milkings the fat content of the milk from both groups of cows was adjusted daily to a common level. A part of each milk was then holder-pasteurized.

3. Four groups of specially prepared litter-mate male rats were fed ad lib., for a period of 8 weeks, on raw and pasteurized milks, both being supplemented with minerals. There were no differences in appetite or gain in weight.

4. In similar experiments sugar was added to the milks to double their caloric value. Again the growth and appetite of the animals were the same on the raw summer and “winter” milks. Pasteurization did not alter significantly the value of the milks, but the summer milk, whether raw or pasteurized, was superior to the pasteurized “winter” milk.

5. Guinea-pigs receiving the raw mineralized milks alone or with sugar died within a comparatively short time. There was no difference in growth performance or time of survival between the summer and “winter” milk groups.

6. These experiments give no indication of the presence of a specific new appetite or growth factor in pasture milk.