Abstract
Monkeys infected with the virus of poliomyelitis, develop after the height of paralysis, sub-normal temperature, difficulty in deglutition, inanition and bed sores and so it is extremely difficult to maintain them alive for long periods of time. However, by wrapping them in blankets, bottle feeding and other measures, it was possible to keep a small number alive for varying intervals after complete paralysis. The cord of these animals was tested for infectivity by titrating a 5% or 10% suspension made up of 6 to 8 segments. During the course of this work, the infectivity of cord removed at the height of paralysis varied between 0.000625 and 0.0025 cc. of a 5% suspension. The results are shown in Table I.
Further tests were made with 23-day-old cords, using the double inoculation technique. 1 One animal was inoculated intracerebrally with 1 cc. of a 20% suspension and 10 days later it again received 1 cc. intracerebrally and also 6 cc. intraperitoneally. This animal developed no symptoms of the disease. A second monkey was given 23-day cord which had been washed as free as possible of antibody. The animal from which it had been obtained was, after bleeding, infused with 2 liters of Ringer's solution. This, rather than isotonic gum acacia solution was used, for it was found that the latter sometimes reduced the infective power of spinal cord. One cc. intracerebrally and 6 cc. intraperitoneally of a 20% suspension and repeated in 11 days, gave no manifestations of poliomyelitis. It seems that the cord is no longer infective after 21 to 23 days.
The infectivity of the cord declines rapidly for the first few days after complete paralysis and then more gradually until the end of the third week, when it is no longer infective.
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