The Killing Action and Rate of Production of Single Particles of Paramecin 51

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Abstract
In Paramecium aurelia, when a variable number of killers of stock 51 of variety 4 are introduced into fluid with a constant number of animals of 3 sensitive stocks (29, 32 and 31), there is an approx. doubling of the number of sensitives killed as the number of killers is doubled in all 3 stocks. But for any "dosage" of paramecin, the ratio of numbers killed in these 3 stocks during a 24-hr. period is approx. 1:1.5:2. In studies on stock 31 alone, the following facts have been found. (1) When the number of killers in a volume of fluid for a unit time-period is doubled, the number of sensitives killed by the fluid after the removal of the killers is also doubled. (2) One killer produces in 5 hrs. enough paramecin to kill on the avg, one sensitive animal. (3) If one killer is kept in different samples of fluid in successive fractions of the 5-hr. interval, a sensitive is generally killed in one and one only of these samples. The fact that any one sample either has the full amt. of paramecin or none at all is evidence that paramecin is produced in single units. (4) When paramecin-fluid was removed with as little disturb- ance as possible, 50% of the total number of sensitives killed were killed in the original dish from which 80% of the fluid had been removed, and 70% in the original dish from which half had been removed. It is evident from this that paramecin tends to collect on the bottom of the dish. (5) When the number of sensitive animals is varied at each constant level of paramecin, a fairly constant number of sensitives, that closely approximates the number of killers, is killed at each level of paramecin cone. regardless of the cone. of sensitives (between 120 and 2400 per 0.2 ml.) These results lead to the following 3 main conclusions, the first and last of which have also been reached on the basis of different types of expts. by Sonneborn, Dippell and Jacobson (1947)[long dash](1) Paramecin occurs in the form of unit-particles. (2) Under the conditions of these expts., killers are on the avg. responsible for the production in the culture medium of one unit-particle of paramecin per killer animal per 5 hrs. (3) A sensitive para-mecium can be killed by a single unit-particle of paramecin.
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