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Medical Research Laboratories use 60 to 65 monkeys in a single morning. Each is deeply anesthetized with ether. In a couple of minutes a skilled surgeon removes the kidneys. Then the monkey is killed with an overdose of ether. Patient technicians cut the kidneys into tiny pieces with nail scissors. The bits of tissue go into big glass bottles with a pink solution known by its formula designation: No. 199. Hundreds of bottles are rocked gently for six days in an incubator, and kidney cells grow in the fluid as though they were still in the living animal.
In a room with the safety rules and precautions of a radioisotope laboratory, 2 cc. of fluid containing live polio virus are added as a seed stock to each quart of tissue fluid. Back to the rocker go the bottles. The virus multiplies a thousandfold in the kidney cells, and after about four days the potentially deadly crop is ready for harvest. It is chilled in 2½gal. bottles for trucking from Toronto to Eli Lilly & Co. and to Parke, Davis.
Mixing the Vaccine. In a rambling pharmaceutical plant beside the Detroit River, the Parke. Davis technicians perform more alchemy. Using both Toronto-grown virus and their own crop, they filter the brew (to get rid of kidney cells, which might cause nephritis), make up 12½-gal. lots in steel tanks and add a dilute formaldehyde solution. When they are satisfied that the formaldehyde has killed every one of the billions of virus particles in the tank, they are ready to mix the vaccine.
So far, each step has been taken with only one type of polio virus present. But the hundreds of strains or varieties of polio virus are classified in three major types, any one of which can cause disease. So one strain of each of the three basic types must be in the vaccine. Dr. Salk's prescription calls for the Mahoney strain (Type I), MEF-I strain (Type II) and the Saukett strain* (Type III). Three tankfuls, each containing one type of virus in its inactivated state, are mixed. The formaldehyde is neutralized with sodium bisulfite.
Then begins a painstaking, month-long process of testing, with more tissue cultures and inoculations into live monkeys, rabbits, guinea pigs and mice to make sure that the vaccine is safe to inject into humans. These tests are made simultaneously on each batch of vaccine by the manufacturer, by Dr. Salk's laboratories and by the National Institutes of Health at Bethesda, Md.
Like Cherry Soda. Finally passed and put up in little glass bottles, the vaccine is a clear solution the color of cherry soda. But few children will have time to notice this resemblance. In a typical vaccination program at Colfax School in Pittsburgh, jabbering youngsters trooped by classes to the kindergarten room where Dr. Salk's assistants had set up desks and chairs beside tables loaded with labeled test tubes, vaccine bottles and stacks of hypodermic needles.