Recent experiments at the Maine Agricultural Experiment Station, conducted under the direction of Dr. John W. Gowen, have led to the important discovery that milk from cows that have been treated with ultra-violet light, from mercury-vapor quartz lamps, contains a much larger amount of the substance—presumably a vitamine, or vitamines—that prevents rickets in children and young animals. At any rate, it was found that the milk from cows deprived of sunlight and ultra-violet light was quite deficient in the anti-rachitic factor. Animals and birds fed on the sunless milk uniformly developed rickets. The Holstein-Friesian cows used in the experiments were of nearly the same age and calving date and all received like treatment as to feed, temperature, etc., and stood side by side in the same barn. “Throughout the treatment,” says Dr. Gowen, “these cows did not leave the barn. For one month none of the cows received ultra-violet light. For the second month two cows received ultra-violet light 15 minutes a day, generated from a Cooper-Hewitt alternating current light at three feet above their backs. For the third month these cows received ultra-violet light for 30 minutes a day under the same conditions. In the meantime Rhode Island Red chickens were allowed to develop rickets, shown both clinically and by X-ray photographs. They were divided into two lots, one lot of these chickens receiving milk from the ultra-violet cows, the other of two lots of chickens, milk from the control cows. Both lots received all the milk they wished. The chickens have now been under treatment 50 days. The lot receiving milk from cows exposed to ultra-violet light are in good condition with no appearance of rickets in X-ray plates. The lot receiving normal milk has moved progressively toward more extreme clinical and X-ray rickets. The experiment was repeated, using the milk from these same cows on White Leghorn chickens showing clinical and X-ray rickets. Five chickens were in each lot. After 38 days’ treatment four of the lot receiving milk from the ultra-violet cows are almost cured of rickets, showing only a very slight stiffness. The fifth chicken shows some stiffness. Four of the lot receiving the normal milk show constantly increasing symptoms of the more advanced stages of clinical rickets.