80 ACTIVITIES OF BACTERIA. 



Wochenschr. , 1890, No. 51, 1186). The following are pro- 

 ducers of indol : The colon group as a whole, glanders, 

 diphtheria, proteus, and most vibriones. With the excep- 

 tion of the vibriones, according to Levandowsky, those 

 mentioned as producers of indol also produce phenol. 

 We have demonstrated phenol production only in Bacte- 

 rium coli and vulgare, and have found only traces of 

 phenol in five-days' -old cultures. 



8. Decomposition of Fats. 



Pure melted butter is no nutrient medium for bacteria. 

 Rancid changes in butter depend upon (1) a pure chem- 

 ical decomposition of butter througli the action of oxygen 

 under the influence of sunlight (Duclaux, Ritsert); (2) a 

 lactic or butyric acid fermentation of the mills- sugar pres- 

 ent in the butter. Compare v. Klecki (C. B. xv, 354). 

 Finally, fat is also appropriated by bacteria with produc- 

 tion of acids if it is mixed with gelatin as a nutrient me- 

 dium. V. Sommaruga (Z. H. xviii, 441). 



9. Putrefaction. (Supplement to 1 to 7.) 



By putrefaction the laity understand every decomposi- 

 tion brought about by bacteria, accompanied by the 

 formation of fouI=smelling substances. 



The scientific view is, that the albuminous bodies and 

 their relatives (glue, albuminoid substances) are the sub- 

 stratum for putrefaction, being often first peptonized and 

 then further broken up. 



Typical putrefaction occurs only with a deficient or lim- 

 ited supply of oxygen. Active passage of air through a 

 putrefying culture of bacteria — an occurrence which never 

 takes place in natural putrefaction — modifies the putrefac- 

 tive powers most actively. This is accomplished (1) bio- 

 logically, by killing or checking the growth of the anaerobic 

 putrefactive bacteria, and (2) by the influence of oxygen 

 upon the products or intermediate products of the aerobic 

 and facultative anaerobic bacteria. Finally, it is probable 

 that the same bacteria from the very start produce differ- 

 ent putrefactive products when grown anaerobically from 

 those produced under aerobic conditions. 



