154 
As indicated in the table, the presence of Na.CO, seems to aid in the 
enzymic action, as the liquefaction was greater in each case when this 
was present than in the tubes without any salt. The extract in all the 
tubes, with the exception of that containing Na,CO, gave a slightly acid 
reaction. The Na.CO, seemed to hinder the action somewhat, as that was 
so much lower than either of the others. | 
In the work of Hahn,® and of Hahn and Geret,” it would seem as if 
they draw conclusions in regard to the presence of proteolytic enzymes in 
pressed yeast from somewhat indefinite causes. In the one case Hahn 
used pressed yeast, mixing it with kieselguhr and squeezing from it a 
liquid in the same manner as Biichner extracted his zymase. This liquid 
was treated with chloroform, to which was added gelatine and a trace of 
phenol. The extract liquefied the gelatine. Then Hahn and Geret used 
extract obtained in the same way with chloroform alone, keeping the solu- 
tion at 37° C. for several weeks. The chloroform served to precipitate 
the proteids and keep the solution free from living organisms. A bulky 
precipitate was formed, which gradually disappeared. The liquid again 
became turbid, the second turbidity being due to the formation of amido 
compounds (tyrosin and leucin). From these experiments they conclude 
that they have extracted a proteolytic enzyme from the yeast. If the 
pressed yeast consisted of yeast only, there would be no question in regard 
to the results, but pressed yeast always contains a relatively large number 
of bacteria and a few moulds. Among the bacteria one is pretty sure to 
find some liquefiers. 
To test for the presence of liquefiers I made some gelatine plate cul- 
tures from pressed yeast; and a description of one which contained only 
one colony of a liquefying bacterium will serve to indicate the power of 
the enzyme which was excreted. When the liquefying colony was first 
noted it was 44 mm. in diameter but at the end of twelve hours it had 
liquefied a spot 19 mm. in diameter; in twenty-three hours the spot had 
increased to forty-seven. mm. in diameter and in forty-eight hours the 
gelatine of the entire plate was liquefied. Cultures were made into beef 
gelatine and the gelatine (6 cc.) was liquefied in forty-eight hours. The 
liquefied gelatine from a tube was filtered, and the filtrate used to deter- 
mine enzymic action of the bacteria as in the former experiments for the 
yeast. At the same time 60 grams of pressed yeast were mixed with 
*Hahn, M. Ber. d. deut. chem. Gesell., 1898, No. 2, pp. 200-201. 
1° Hahn, M., and Geret, L., 1.c., pp. 202-205. 
