112 PHARMACEUTICAL BACTERIOLOGY. 



A. Removing the Hair — Depilation. — This is done by means of chemicals, 

 as lime or sodium sulphite, or through the agency of rotting bacteria, as 

 Bacillus vulgaris {Proteus) and others. Just which of several species 

 of rotting bacteria is most active in this process has not been definitely 

 determined. 



B. Drenching or Bating. — ^After the hair has been removed, the hides 

 are macerated in an aqueous solution of the excrement or dung of pigeons, 

 hens and dogs. These substances set up a lactic acid fermentation due to 

 the microbes contained therein. The active organisms have not been iso- 

 lated as yet; Bacillus gasoformans and B. erodiens are perhaps active, but there 

 are also present many yeasts, moulds and other organisms which may have 

 their special effects. 



The first part of this process, known as "bating," is initiated by bird 

 dung; the second process, known as "puring," is due to the action of dog 

 dung. Attempts have been made to use pure cultures of the active microbes 

 to supplant these filth substances, but so far these efforts have not proven 

 whoUy successful. 



C. Tanning. — The bated hides are next treated in the tan pit (coarse 

 skins) or in bark liquor (soft thin skins) , where the souring process takes 

 place. This process is also due to bacterial activity. Our knowledge of 

 the action which takes place and of the bacteria involved is very incomplete. 



Bacteria are important factors in siloing; in curing tobacco, tea and 

 cacao. The flavor of different brands of tobacco is due to different bacteria, 

 and attempts have been made to isolate those producing desirable flavors 

 and to use them in pure culture. It is highly probable that the bouquet of 

 old wines is due to bacterial action. These are, however, matters which 

 require further study. Rotting bacteria are active in paper-making. In 

 the maceration process certain bacteria feed upon and decompose the less 

 resisting vegetable cell- walls, as those of the parenchymatous tissues, the 

 epidermal tissue, etc., leaving the more resisting fibrous lignified tissues' as 

 bast and wood fibers. The pulp is then poured on sieves and the rotted 

 or digested portions washed out. 



Bacteria are now practically employed in the purification of sewage. 

 This is done in what are known as "contact beds," in which the environ- 

 ment is made favorable to rapid development of those non-pathogenic rotting 

 bacteria which disintegrate the organic substances and at the same time 

 prevent the development of the pathogenic or otherwise objectionable mi- 

 crobes. It is highly probable that this method may be applied to the puri- 

 fication of streams and other large bodies of water. 



The possibilities in the practical utilization of bacteria in the arts and 

 industries are promising, and it may confidenfly be expected that wonderful 

 innovations along this line will be made in the very near future. 



