Abstract
The electrical conductance of bacteria (B. coli and B. butyricus) unicellular algæ (Chlorella sp.) yeasts (Saccharomyces sp.) and mammalian red-blood cells has been studied by a method which yields figures for the gross conductance dependable within 1/10 per cent. Polarization capacity was compensated for by variable condensers in parallel with the variable resistance. While most of the studies here reported were made on the alga, Chlorella, there is apparently no fundamental difference between this and the other organisms.
The difference between the conductance of the suspending fluid and that of the suspension of cells is expressed in per cent. of the former and called the net conductance. This will always be negative in sign, because living cells are poor conductors of electricity. Rather large variations in the net conductance are produced by factors, such as irregular distribution of cells in the suspension, which it is impracticable to eliminate and which may affect the net conductance of any one sample by several per cent. For this reason enough samples were used in each experiment to make the error of the mean less than three per cent.
It is possible to calculate the limits between which the observed net conductance should fall, the relative conductance of the cells themselves and their volume concentration being known.
If r is the resistance of the suspending fluid and kr that of the cells and n the concentration of the cells in volume per cent., then the total resistance should lie between
These formulas give curves convex to the axis of concentrations when they are plotted against resistances as ordinates. But when the cells form less than about 65 per cent. of the total volume the observed curves are nearly linear, possibly because of variations in the relative extent to which the current lines are able to evade the more highly resistant cell material.
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