Abstract
Crude beef-blood fibrin as the only source of protein in a synthetic diet supports growth at a level comparable to that of casein. Fibrin can be extracted with organic solvents as readily as casein. With water it swells more than casein. It can be easily dried, ground and incorporated into synthetic diets. Before purification beef-fibrin contains liberal quantities of vitamins A and D which can be removed by extraction with alcohol. Alcohol-extracted fibrin is practically free of vitamin B1. Fibrin is low in phosphorus and consequently can be used in rachitogenic diets. As fibrin is available at a price approximately the same as casein it may be used in synthetic diets when casein is not suitable.