CHAPTER XVI. 



THERMOGENIC BACTERIA. 



103. Spontaneous Combustion. 



THE state of our knowledge on the thermic side of the process 

 of fermentation does not extend beyond a few crude, isolated 

 determinations, so that nearly everything in this department has 

 still to be accomplished; even the primary question whether 

 there exist fermentative organisms with purely exothermic and 

 others with purely endothermic cell-activity being as yet unsolved. 

 One thing only has been established for certain, viz., that many 

 microbes under certain conditions generate heat and give it off to 

 the environment. Hence the chemical changes then occurring are 

 exothermic processes. 



An example of this is afforded by the organisms effecting the 

 so-called spontaneous heating of hay and cotton. For sundry 

 researches hereon we are indebted to F. CORN (VIII.), from which 

 it appears that fission fungi, allied to the hay bacillus already 

 several times referred to, are here concerned. That the heating 

 is actually the result of microbial activity was proved by Haepke, 

 who ascertained that sterilised cotton - waste, under otherwise 

 identical conditions, only became heated when moistened with 

 washing-water from fresh unsterilised waste. The heating only 

 occurs in presence of oxygen, and comes to a standstill when this 

 substance is lacking, the action being the result of brisk oxidising 

 activity (respiration) on the part of the bacteria in question. The 

 fluffy greasy waste material formed during the cleaning and spin- 

 ning of raw cotton, consisting of cotton fibres, seed capsules, &c., 

 spontaneously rises in temperature up to 67 C., according to the 

 observations of Haepke, and becomes gradually converted into 

 a humous mass with evolution of the vapours of trimethylamine. 

 This observer attributes the fermentation occurring in this case to 

 various species of micrococcus. 



The heating of vegetable matter to high temperatures should 

 not, however, always be ascribed to the action of fission fungi. 

 For example, the temperature in badly managed heaps of germinat- 

 ing (malting) barley may rise to 60 C. and over, the cause of 

 which, according to the researches of COHN (IX. and X.), is a 

 mould, viz., the Aspergillus fumigatus nearly allied to the common 

 mould fungus. That the diastase in the germinating barley is 

 thereby greatly injured is certain. 



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