On August 8, 1942, the veterinary ambulatory clinic of Iowa State College was called to treat a herd of 64 pigs for ascariasis. The caretaker reported that the pigs had been turned out on alfalfa pasture about two weeks before, and that the pigs were passing some round worms. The herd, except for a few poorly developed individuals, appeared to be a normal herd of 35 pound pigs.