Abstract
Summary
1. Effects of incubation time and temperature, age of embryo and route of inoculation on multiplication of a Type 2 chick-embryo propagated poliomyelitis virus were studied. The distribution of the virus in chick embryo tissues and fluids, and its action on the hatchability of infected embryos, were investigated. 2. Optimal conditions for multiplication of the virus were inoculating 6- to 9-day-old embryos via either the allantoic cavity or the yolk sac, and incubating for 4 to 6 days at 35°-37°C. 3. The best source of the virus was the embryo proper. No greater concentration of virus was found in the head than in the body. 4. Although the embryos seemed to overcome the infection by the 12 th or 13 th day, relatively few hatched out. The majority died between the 22nd and 27th day of total incubation. 5. The mouse LD50 titers of the chick-embryo-adapted virus were essentially unaffected by 9 consecutive freezings and thawings of the same virus preparation.
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