The changes produced by the growth of bacteria in the molecular concentration and electrical conductivity of culture media / by G.N. Stewart.

  • Stewart, G. N. (George Neil), 1860-1930.
Date:
[1899?]
Catalogue details

Licence: Public Domain Mark

Credit: The changes produced by the growth of bacteria in the molecular concentration and electrical conductivity of culture media / by G.N. Stewart. Source: Wellcome Collection.

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    the decomposition products, as, for example, the red blood corpuscles are to urea, these products, although they would diminish the freez¬ ing point wTould not exert any osmotic pressure on the cell-wall. Experiments III and IV show the result of observations on the growth of B. subtilis, B. proteus Zenkeri, B. proteus vulgaris, B. Eriedlander, B. coli communis, Bacillus of hog-cholera, and B. lactis aerogenes. The cultures were all grown in a solution of Witte’s pep¬ tone. Plates VII and VIII represent in graphic form the results of Experiment III. As to the nature of the electrolytes produced by the bacteria, we knoAV already numerous bodies, especially among the decomposition products of putrefying proteids, which are capable of acting as ions, for example, such organic kations as the amines and ammonium, and such anions as the acids of the fatty series. I shall not further discuss these results at present. They are enough to sIloav that in such observations Ave have a practical method of measuring the amount of decomposition produced by, and therefore the rate of growth of, bacteria. It is possible that sufficiently great and constant differences might be observed between different kinds of bacteria when grown in the same or in different liquid media to enable us to use the method as a supplement to our present means of diagnosing betAveen nearly related forms. And for this purpose, since the curves of concentration and conductivity run practically parallel to each other, it may be that measurements of the electrical conduc¬ tivity alone might suffice. These would liaAre the great advantage over measurements of the freezing point that they could be carried out in tubes furnished with platinum electrodes fused through the glass, or perhaps passing through the plug, and the necessity of open¬ ing the tubes Avould thus be obviated. It is hoped that further observations, iioav in progress, may cast light upon this and some of the other interesting questions arising out of this research. Tabulated Results. The conductivity (Z) is given in reciprocal ohms X 10s and re¬ duced to 5° C. In the column headed A the lowering of the freez¬ ing point is given in degrees centigrade.