It has been known for many years by veterinarians and cattle raisers that cattle fairly frequently and for no apparent reason bleed considerably and perhaps fatally. Studies of this condition were made originally and independently in 1921 by Schofield1in Canada and by Roderick2in this country. They determined that this hemorrhagic disease arises from eating improperly cured hay or silage made from the common sweet clovers. It was recognized early that if the hemorrhagic manifestations had not proceeded too far the hemorrhage could be controlled by withdrawal of the spoiled hay from the diet or by the injection of freshly drawn blood serum of healthy animals.3At first it was thought that the liver was damaged by the ingested spoiled hay, but this could not be confirmed by Roderick. However, he noted that the delayed coagulability of the blood involved a reduction in the prothrombin content