Organic Ferments. 223 



lies, usually straight, either isolated or united in a chain of two to four 

 joints or more. Their diameter is generally ^^ of a mm. , and length 



from io to itSo of mm - 



They move by a sort of sliding motion, during which the body 



remains rigid or undulates slightly. They may spin round, balance 

 themselves on one end and vibrate their extremities, and they often 

 assume a bent position. They reproduce by fission. This organism lives 

 and produces butyric fermentation if placed in a solution of sugar con- 

 taining phosphates and ammoniacal salts. The result of its operations 

 is butyric acid C 4 H g 2 , which is the acid of rancid butter, and is also 

 formed in many other organic compounds. In solutions of sugar the 

 viscous, or mannitic ferment, is usually the first to appear, next the lactic, 

 and lastly the butyric. 



Putrefaction is another mode of fermentation, and, like the others, is 

 promoted by an active organism. Putrescible substances are albumi- 

 noids and their allies, the constituents of vital organisms, which in the 

 open air are usually unstable, because unless boiled they contain germs 

 or become inoculated after a time from the air. 



The active agent in putrefaction is the animal organism called vibrio. 

 This vibrio, according to Pasteur and others, is killed by contact with 

 free oxygen and can live only in a medium sheltered from air. In 

 general, therefore, a solution does not show any signs of vibrios until 

 the solution is covered with a film or pellicle formed by the action of 

 Bacteria and Monas crepusculum, which require free oxygen and cannot 

 live without it. Under this film the vibrios develop, and their growth 

 and reproduction effect a separation of the albuminoid matters into 

 more simple products, while the bacteria and mucors of the pellicle pro- 

 duce a still further splitting up of these products, reducing them to 

 water, ammonia and carbonic acid. 



Various opinions as to the intimate nature of fermentation have been 

 entertained. Leibig believed it to be a species of decomposition 

 which gradually spread by a sort of contagion from one particle to 

 another of the solution in consequence of the ferment; a mechanical 

 effect. 



Berzelius and Mitscherlich thought fermentation to be a chemical 

 action caused by the presence of the ferment as a mere catalytic agent. 

 This view is disproved by the fact that the ferment greatly increases in 

 quantity during the action, while in true catalysis the catalytic agent 

 undergoes no change in itself, simply inducing change in the other ele- 

 ments. 



Pasteur has expressed the opinion that fermentation goes along with 

 and depends upon a vital act the living and growing of the organism 

 called ferment, and that it begins and ends with that vital act. 



