Abstract
Chick interferon from allantoic fluids of eggs infected with influenza virus and from embryo fibroblast tissue culture was purified to a specific activity of 1.6 x 106 units per mg. protein; for allantoic fluid interferon this represented nearly 20,000-fold purification. Such material is thought to be still impure. Purified, but not crude, interferon was found to be strictly species specific.