BACTERIA IN THE INDUSTRIES 719 



flavors can not be regulated by bacteriological methods alone, since it 

 has been shown by Loew l that an important factor in the tobacco fer- 

 mentation is contributed by the leaf-enzymes, which, of course, depend 

 intimately upon soil and climatic conditions. 



Opium Productions. In the preparation of opium for smoking pur- 

 poses, the raw product is subjected to a prolonged period of fermentation 

 by which the carbohydrates in the material are destroyed. According 

 to various observers, the process is carried out in most cases by a species 

 of aspergillus. 



Indigo Production. Indigo, which is obtained from the plants 

 "Isatis tinctoria" and "Indigofer tinctoria," is not present, as such, in 

 the plants. In some of these it is found in the form of indican, in others, 

 as indoxyl. It has been shown by Alvarez that the oxidation of indican 

 and indoxyl into indigo-blue is carried out largely by bacterial oxydases. 

 Sterilized indigo plants do not produce the blue color. Alvarez 2 has 

 isolated a bacillus closely related to the Bacillus mucosus capsulatus 

 group, to the action of which he attributes this oxidation. 



Bacteria in the Tanning of Hides. Raw animal hides are subject 

 to decomposition until treated by a process known as tanning. This 

 consists first in the depilation of the dried and salted skins, either by 

 partial putrefaction in an atmosphere saturated with water vapor or 

 by chemical treatment with solutions of milk of lime. After this, the 

 tanning proper consists in subjecting the skins to prolonged immersion 

 in solutions made up according to a, large variety of formulae the 

 principle of all of which, however, seems to be found in the mixing of 

 various organic ingredients, such as bran-mash, oak-bark, and often dried 

 animal excreta, in which fermentation and acid production occurs. Ac- 

 cording to Haenlein, 4 this acidification is the essential by which the 

 leather is sterilized and rendered soft. This author has described the 

 Bacillus corticalis, which he found in fir-tree bark and to which he 

 ascribes the acid fermentation of tanning liquors in which this ingredient 

 is employed. Wood, 4 who has worked extensively upon the subject, has 

 attempted to substitute pure cultures for the old uncertain chance mix- 

 tures employed. In spite of these investigations, however, while we 

 must acknowledge the probable importance of bacteria in the tanning 

 process, the subject is by no means on a scientific or exact basis. 



1 Loew, Rep. U. S. Dep. Agriculture, 59, 1899. 



2 Alvarez, Comptes rend, de 1'acad. des sci., vol. 105. 



3 Haenlein, Cent. f. Bakt., II, i, 1895. 



4 Wood, Jour. Soc. Chem. Industrv, 1895, 1899. 

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