140 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



dialysis under pressure was suggested by Dr. Martin, the 

 director of the Lister Institute, and the filter is known generally 

 as a Martin filter. If, now, yeast juice is passed through such a 

 filter a residue is obtained soluble in water, and it is found that 

 neither this residue nor the liquid which passes through the 

 filter are either of them separately capable of causing alcoholic 

 fermentation. On the other hand, when brought together the 

 mixture produces fermentation almost equal to that in the 

 original juice. 



Fig. 22. — Appakatus tob Measuring Rate of 

 Evolution op COj. 



The proteolytic enzyme, as might be expected, remains 

 behind on the filter with the rest of the colloidal matter, and 

 on adding the residue to water, digestion of the albumin 

 rapidly proceeds. The addition of the filtered juice does not 

 increase this effect. So far, then, it is clear that the alcoholic 

 fermentation is due to at least two substances, one of a colloidal 

 and the other of a crystalloidal nature. 



It should be explained that in studying the amount and 

 rate of alcohoUc fermentation, the evolution of COg is taken as 

 a measure of this change. This rate of evolution is measured in 

 the special apparatus (Fig. 22). 



