Medicine: One Millionth of an Inch

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In all the years that medical researchers have been studying and describing the virus of poliomyelitis, they had never seen the critter. Now, two teams of investigators working independently have isolated the virus, looked at it long and hard under the electron microscope, photographed it and measured it. It turns out to be a spherical particle almost exactly a millionth of an inch in diameter. Magnified tens of thousands of times against a plastic screen, the virus particles look like tennis balls on an asphalt court.

The reason for the long delay in completely isolating the virus was the difficulty of separating it from the substances in which it grows. Until recently, a relatively "pure" preparation was only 1% virus and 99% "gunk."

Two biochemists at the University of California, Drs. Howard L. Bachrach and Carleton E. Schwerdt, did it the hard way.'They grew polio virus of the Type II or Lansing strain in the nerve tissues of rats, and got the concentration up to about 10%. This preparation contained particles of two sizes, some a millionth of an inch in diameter, the others less than half as big. The researchers separated the two kinds in an ultracentrifuge. then they injected the materials into different groups of rats. Only the animals that received the millionth-of-an-inch particles caught polio. That, and similar tests, clinched the identification.

In the Detroit laboratories of Parke, Davis & Co., a research team headed by Virologist Alton R. Taylor started by growing polio virus of the Type I or Brunhilde strain in test tubes with tissues from animals. The company is not telling how the purification was achieved, and its photograph shows particles of different sizes.

The isolation of polio virus in apparently pure form will be of enormous help to researchers in their efforts to produce a safe and effective vaccine against the disease. Many of the hazards connected with the older and relatively impure virus preparations can be eliminated. Chemists can study the makeup of the particles as a first step to finding out why they behave as they do, and how to reduce their ravages.