120 BACTERIOLOGY. 



which are made within, but eliminated from the cell. The 

 fact that filtered cultures of phosphorescing- bacteria fail 

 to give off light does not disprove this view. The phos- 

 phorescing substance, like most of the bacterial pigments, 

 may be insoluble in water. It undoubtedly is very unstable 

 since any chemical treatment yields inert products. Vari 

 ous aldehyde derivatives are known to phosphoresce in 

 alkaline solutions, and it is possible that similar products 

 are elaborated by certain bacteria. 



Heat Production. 



The heat of the animal body is ascribed to the oxida- 

 tion or combustion of the assimilated food. In the cleav- 

 age of complex bodies heat is almost invariably generated. 

 Inasmuch as in the various fermentations, the process is es- 

 sentially one of cleavage, it follows that an evolution of 

 heat must be expected. It matters little, whether the fer- 

 mentative change is induced by bacteria, yeasts, or by 

 moulds, in either case heat will be produced. Several in- 

 stances may be mentioned to show to what extent thermo- 

 genic bacteria may raise the temperature of the medium in 

 which they grow. 



In ordinary alcoholic fermentation, due to the yeast- 

 plant, the temperature of the liquid may rise to an appre- 

 ciable extent. It is well known that turnips, potatoes, etc. , 

 especially if moist, when placed in large heaps in a closed 

 room will warm up to 50 or 60°, as a result of. fermentation. 

 A strong odor of tri-methylamin will be recognized and 

 many of the tubers will show an evolution of gaseous pro- 

 ducts. Similar spontaneous heating is observed at times 

 in masses of hops and the same fish-odor is present. 



Another interesting case is met with in the curingf of 

 tobacco. After a preliminary drying the leaves are packed 

 in large masses and subjected to a fermentation. The tem- 



