CHAPTER XI. — MODE OF LIFE OF THE BACTERIA. 479 



spore-formation becomes constantly more sparing. Growth and formation of spores 

 cease below a temperature of i5°C. Fitz by comparing the forms in a mixture 

 which had completed its fermentation in the same time at different temperatures 

 found that the optimum of his Bacillus butylicus in solution of glycerine was 40 C, 

 that of another species unnamed and grown by itself 37°-40°C. The maximum in 

 both species was 45°-45-5°C. 



The upper limit of temperature at which vegetating Bacteria can continue 

 to exist appears to be little higher than that observed in the case of most other 

 plants. Cohn found that it approached near to the maximum of vegetation in 

 Bacillus subtilis, being 50-55 C. Fitz found it in the second of his two species just 

 mentioned at about 56 C. According to Eidam, ' Bacterium Termo ' was killed when 

 the liquid in which it was vegetating was heated during 14 hours up to 45 , and 

 during 3 hours to 50 . From Buchner's experiments mentioned above with the 

 Bacillus of anthrax it appears that the dried rods are killed at the same degree 

 of temperature as the spores. Further details will be found in special works on 

 the Bacteria 1 . 



The vegetative forms of the Bacteria are able to bear the lowest temperatures 

 to which they can well be exposed. Frisch 2 found putrefactive Bacteria and 

 species of Bacillus, among them B. Anthracis, still retaining the power of develop- 

 ment after being frozen in liquid at a temperature of — 1 1 1 ° C. 



It is in accordance with the analogy of other organisms that the temperatures at 

 which Bacteria vegetate and lose their vitality should vary with the character of the 

 substratum. Nageli says s that by making changes in the nutrient solution the death 

 of the Fission-fungi may be ensured within a certain time at any temperature between 

 30° and no , but he does not distinguish here between germination of spores and 

 vegetative states. 



The Bacteria differ much from one another in respect of the necessity for a 

 supply of oxygen. At one end of the series the vegetation is promoted in the 

 highest degree, other conditions being the same, by the largest possible supply of 

 atmospheric air containing free oxygen ; this is the case with Bacillus subtilis, and 

 Arthrobacterium aceti ; at the opposite end, as in B. butyricus, it is promoted by the 

 exclusion of free oxygen. Accordingly Pasteur distinguishes between aerobiotic and 

 anaerobiotie vegetation or forms 4 . 



Cases have been observed by Engelmann ° lying between these two extremes, in 

 which a less pressure of oxygen is required than that which is afforded by the com- 

 position of the atmosphere. According to Nageli c the aerobiotic forms will also 

 vegetate when deprived of a supply of free oxygen. 



As regards the proper nutriment of Bacteria it is to be presumed that those 

 which have the green colour of chlorophyll, if they really contain chlorophyll 



1 See also Pfeffer, Physiol. II. 



2 Sitzgsber. d. Wiener Acad., Mai, 1877. 



3 Die niederen Pilze &c. (1877), P- 3°> an & see also p. 200. 



4 See also on this point Ncncki in Jouin. f. pract. Chemie, neuc Folge, XIX, XX ; also Genning 

 in the same publication. 



5 Bot. Ztg. 1882, 321. 



6 Die niederen Pilze (1877), P- 2 8- 



