Abstract
All existing evidence seems to indicate that the active agent responsible for transmissible lysis of bacteria is distributed in the medium as if it were particulate. 1 Several authors are inclined to consider these particles as autonomous units of an organized protoplasm.
In this connection it is of interest to measure and in other ways to identify these particles as such. Several attempts have been made to measure them. In most instances, these particles were 2 , 3 , 4 , 5 forced through membranes of presumably known porosity. Because of the limited value of this method, von Angerer 6 tried to arrive at more reliable figures by the nephelometric method, and Bechold 7 used an ingenious gold cast method. While the figures obtained by these various procedures are not identical, they are sufficiently close to indicate, at least, that in all cases authors were dealing with particles of approximately the same order of magnitude.
A recent paper of Northrop and Anson 8 offers means to inquire into this question by the use of a different technique. By a suitable modification of the classical procedure for establishing diffusion rates, 9 they have proposed a comparatively simple method for obtaining the diffusion constants of complex biological substances. The size of the particles in solution can be calculated from these diffusion constants by the use of Einstein's equation. 10
Following the procedure as used by them∗ for carbon monoxide hemoglobin, we have obtained the following results for B. coli bacteriophage:
Using this average value of D = (.0188) in the Einstein equation, 10 the radius of an average size particle of phage is calculated as having approximately the value of 6.1 × 10-7 cm. (or 6 μμ). Of course, one has still to determine whether such particles represent the units of bacteriophage or serve merely as carriers for a more highly dispersed agent. 11
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