FERMENTATION OF TOBACCO. 167 



the contents, in consequence of which the activity of the microbe 

 is lessened. Closer studies both on the spontaneous heating of 

 hops, and especially into the transformation products of Bacillus 

 lupuliperda and their relation to the production of rancidity in 

 hops, constitute a productive field for future research. 



The above remarks on the spontaneous heating of stored vege- 

 table substances may now be supplemented by a few observations 

 concerning 



105. The Fermentation of Tobacco, 



which cannot well be included in subsequent chapters. The 

 tobacco leaves, when gathered, are allowed to become somewhat 

 withered, and are then arranged in moderate-sized heaps, where 

 they undergo a so-called "sweating." The rise of temperature 

 occurring during this process is, as determined by Muller-Thurgau, 

 a consequence of the activity of the leaf-cells, which transpire their 

 store of carbohydrates and convert their albuminoid matters into 

 amides, the heat thereby liberated effecting the gradual drying of 

 the leaves. The water vapour evolved condenses into the matting 

 employed to cover the heaps, which are then said to "sweat." The 

 alteration of the nitrogenous bodies in the leaves can also be 

 effected by "shed drying." On this point more will be said in a 

 later chapter dealing with Botrytis cinerea in the second volume. 



As soon as the tobacco leaves have finished sweating and 

 become "shed ripe," they are made to undergo fermentation, for 

 which purpose they are tied in bundles and arranged in great 

 heaps, containing as much as fifty tons of tobacco. Hereupon 

 active decomposition quickly ensues and the temperature rises. 

 NESSLER (I.) found this to be as much as 54 C. even on the second 

 day, but, as a rule, the heaps are not allowed to become warmer 

 than 50 C., further increase being prevented by turning the heap, 

 so that the outer layers of the first heap become the central por- 

 tion of the new one. This fermentation is due to the action of 

 bacteria, and was studied thoroughly by E. SUCHSLAND (I. and II.), 

 who, however, furnished but scanty reports thereon. A patent 

 was granted to him in connection with the use of pure cultures of 

 bacteria for the purpose of favourably influencing the fermentation 

 of tobacco. He prepared pure cultures of bacteria from fine West 

 Indian tobacco and transferred them to inferior German tobacco in 

 course of fermentation. By this means the flavour of the latter 

 was so greatly improved that it was no longer recognisable as such 

 even by connoisseurs and experienced smokers of native tobacco. 



The chemical changes hereby produced have been investigated 

 by J. BRHRENS (II.), according to whom the loss of matter amounts 

 to 4 to 5 per cent., and consists principally of soluble carbohy- 

 drates and fixed organic acids, the former disappearing almost 

 entirely. Carbonic acid is evolved as the result of these changes, 



