FERMENTATION. 1 39 



on which to act. If, however, the supply of either oxygen 

 or alcohol be cut off, the ordinary mode of life of the 

 mycoderma is at once interfered with. It uses up part of 

 its own protoplasm by internal metabolism, continues to act 

 on the acetic acid, and converts it into simple substances, 

 water and carbon dioxide, at the same time retaining 

 molecules of carbon, hydrogen, and oxygen for its own use. 

 The mycoderma is, then, no longer so much an enzyme-former 

 or an organism with a thick celled wall, that acts principally 

 on the suitable nutrient medium by means of its chemical 

 products, and gives rise to a definite chemical process ; but 

 is now rather a mass of protoplasm endowed only with 

 its primary digestive powers, by means of which it can 

 convert organic matter into its very simplest forms or ele- 

 ments. There is very complete oxidation, and instead of 

 alcohol and acetic acid being formed as intermediate products 

 that can be easily separated, the substances are at once 

 converted into water and carbon dioxide, the ultimate 

 products of perfect oxidation. 



It is sometimes said that the mycoderma in the true 

 vinegar fermentation is in a weakly condition ; it is cer- 

 tainly not in its most active condition, but the state appears 

 to be one rather of quiescence or advanced development, in 

 which the formation of a thick membrane and the produc- 

 tion of a separable enzyme are characteristic features, rather 

 than one that can be spoken of as a condition " of incomplete 

 or tardy development." 



To show that the process was not merely a physical one, 

 as was suggested even by Pasteur, Mayer showed that by 

 simply heating the acidifying fluid to a temperature at 

 which the mycoderma is killed all oxidation is arrested, and 

 he also showed that the temperature at which oxidation of 

 concentrated alcohol goes on in spongy platinum is at a 

 temperature above 35° C, at which point it is completely 

 stopped in the presence of the mycoderma aceti, in addition 

 to which " physiological acidification " can only take place 

 in a weak solution of alcohol. 



Pasteur's observations and results led to the adoption 

 of what is known as the Orleans process of making vine- 

 gar, which, as given by Schiitzenberger, is as follows : — 

 " The mycoderma aceti is made up of small, slightly 

 elongated cells, with a transverse diameter of from 1.5 



