White-fibered, or medullated, nerve tissue contains about 5 per cent of cholesterol. Gray-fibered tissue, which has an affinity for poliomyelitis virus,1 contains only 0.7 per cent. Could cholesterol act like a colloid and absorb or in some way inactivate the virus in vitro?
Ordinary commercial cholesterol crystals were obtained in the open market. A ball mill was set up in the icebox. One gram of cholesterol was added to 6 cc. of a 1 per cent suspension of potent purified virus, and the whole was ground for twelve hours. The material was then centrifugated. The white top layer of cholesterol excess was spooned off under sterile conditions. The remaining material was slightly opaque. One-tenth cubic centimeter of a 1 per cent solution of Flexner's M. V. strain of the virus produced quadriplegia in practically all the Macacus rhesus monkeys, which weighed about 5 pounds (2.3 Kg.). Because the cholesterol