1912.] Certain Results of Drying Non-sporing Bacteria. 131 



In confirmation of this remarkable longevity in vacuo, in a second set of 

 observations, B. pyocyanms was found to have remained alive from May 26, 

 1911, to December 16, 1911 ; a period of exactly the same length as the above. 



One slip was tested on June 1, 1911, and was found alive. The growth 

 obtained from the slip on December 16 was in every way characteristic. 

 Within 48 hours, the litmus glucose broth was uniformly turbid, and was 

 decolorised except for a zone at the free surface, which retained a violet 

 tint ; the top of the fluid was covered with a thin, unwrinkled, faintly 

 greenish looking scum or zoogloea. Sub-cultures carried to peptone water on 

 December 18 showed within 24 hours general turbidity, and a delicate but 

 well marked green coloration ; a sub-culture from this carried to an agar 

 slant gave within 24 hours a full growth, which within 48 hours had 

 produced a typical green pigmentation of the medium in the neighbourhood 

 of the culture. 



The longevity of this bacillus in vacuo is the more remarkable since the 

 micro-organism somewhat rapidly dies in air-dried films. Under the latter 

 circumstances the date of death (as tested by daily transferring a slip to 

 a broth tube) varies within certain limits ; but we have never found the 

 microbe alive after the 9th day. 



Remarks. 



Taking the results obtained by complete drying in vacuo, two obvious 

 conclusions will appear. In the first place it is clear that the vulnerability 

 of different bacteria varies within wide limits. And in the second, as the 

 vitality of B. pyocyaneus in vacuo is notably prolonged beyond that of air- 

 dried slips, the prolongation can only be due to the absence of chemical 

 changes which obtain in the air, but are absent in the vacuum. 



In regard to the first of these two results we may provisionally hold that 

 it implies a difference in the composition, or the molecular construction of 

 the protoplasm. It has a parallel in the difference of resistance to heat. 

 The thermophilic bacteria thrive at a temperature of 70° C, whilst the 

 common death point of other (non-sporing) forms, when suspended in fluid, 

 ranges close about 60° C. 



The different resistance of different bacteria to drying in vacuo, and to 

 heat, indicates that the chemical constitution, or the molecular construction, 

 of the protoplasm varies ; that protoplasm is not a definite chemical 

 substance, but one of varying range. 



The selection of particular body-cells by particular poisons is one proof of 

 such a difference in the same organism. It is probably correct, indeed, 

 to hold that every functional difference amongst cells implies a protoplasmic 



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