PRODUCTS OF VITAL ACTIVITY. 



131 



This is introduced i-nto a flask with two necks, such as is shown 

 in Fig. 77. Having filled the flask with the culture liquid, the bent 

 neck is dipped into a porcelain dish containing the same. Heat is 

 then applied both to flask and dish, and the liquid in each is kept in 

 ebullition for half an hour. By this means the air is completely 

 driven out of the flask. This is now allowed to cool, while the fluid 

 in the shallow dish is kept hot, so that the liquid mounting from it 

 into the flask shall be free from air. When the flask is full it is 

 transferred to an incubating oven heated to 25 to 30 C., and the bent 

 tube is immersed in a dish containing mercury. The little funnel 

 attached to the upright tube is then filled with carbon dioxide and a 

 culture of the butyric-acid bacillus is introduced into the funnel. 

 By turning the stopcock in the upright tube a little of the culture is 



FIG. 77. 



admitted to the flask without admitting any air. Fermentation com- 

 mences very soon, as is seen by the bubbles of gas given off. The 

 liquid loses its transparency and the lactic acid is gradually con- 

 sumed, butyrate of lime taking the place of the lactate. 



Aerobic bacilli capable of producing butyric acid in culture solu- 

 tions containing grape sugar or milk sugar have also been described 

 by Liborius and by Hueppe. 



Fitz has shown that in culture solutions containing glycerin the 

 Bacillus pyocyanus produces butyric acid in addition to ethyl alco- 

 hol and succinic acid. Bacillus Fitzianus also produces some butyric 

 acid in solutions containing glycerin, although the principal product 

 of the fermentation caused by this microorganism is, according to 

 Fitz, ethyl alcohol, twenty-nine grammes of which may be obtained 

 from one hundred grammes of glycerin. 



