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 15°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’. 
The vegetative forms of the Bacteria are able to bear the lowest temperatures 
to which they can well be exposed. Frisch? 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 —111°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. Nägeli says? 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 110°, 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 aerobiotie and 
anaerobiotic vegetation or forms *. 
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 Nägeli® 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. 
* Sitzgsber. d. Wiener Acad., Mai, 1877. 
5 Die niederen Pilze &c. (1877), p. 30, and see also p. 200. 
* See also on this point Nencki in Journ. f. pract. Chemie, neue Folge, XIX, XX; also Genning 
in the same publication. 
5 Bot. Ztg. 1882, 321. 
® Die niederen Pilze (1877), p. 28. 
