138 PRODUCTS OF VITAL ACTIVITY. 
formed by oxidation of the alcohol, producing from it carbon diox- 
ide and water. 
The formation of acetic acid from alcohol is shown by the follow- 
ing formula : Ethyl alcohol CH,.CH,.0OH+ 0, = CH,.COOH+H,0. 
Butyric acid is produced by a considerable number of bacteria, 
one of which, named Bacillus butyricus, has received the special at- 
tention of Prazmowski. This is strictly anaérobic. In solutions of 
starch, dextrin, sugar, or salts of lactic acid, when oxygen is ex- 
cluded it produces butyric acid in considerable quantity, and at the 
same time carbon dioxide and hydrogen gas are set free. Duclaux 
gives the following formula of a solution containing lactate of lime 
in which the action of the butyric-acid ferment may be well studied : 
‘Water, . : ; 8 to 10 litres. 
Lactate of lime (pure), : . ; : 225 grammes. 
Phosphate of ammonia, : . 5 : 0.75 
Phosphate of potash,. : - ; 0.4 i 
Sulphate of magnesa, : 5 ‘ ‘ 0.4 ne 
Sulphate of ammonia, r : : 0.2 “ 
gaia 
: 
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ry 
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a 
This is introduced into 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 
