132 
and a small amount of thymol added to the extract to prevent any further 
development of the yeast. The liquefaction of the thymol gelatine did not 
run quite uniformly: In twenty-five days one tube had 8 cc. gelatine 
liquefied, another had 714 cc., while a third had 7144 cc. A second set hay- 
ing extract from cultures six weeks old, in ten days, one liquefied 2 cc. 
gelatine, a second one 2.2 cc., and a third one 2.5 ce. 
Wort in which yeast had been grown for ten days was filtered and 3 
ec. of the filtrate used in thymol gelatine tubes, but this was very weak in- 
enzyme. In ten days a cup-shaped depression was formed in the top of 
the gelatine, but no further action could be discerned. Both the wort 
gelatine and wort extracts were turbid when placed in the thymol gela- 
tine. It required eight days for the wort extract to become clear and ten 
days for the wort gelatine extract. 
As has been said already, the proteolytic enzymes are of two kinds, 
the peptie and the tryptic, the pepsin of the gastric juice and the trypsin 
of the pancreatic juice being taken as types. Besides differing in their 
decomposition products, they differ in other respects. Pepsin can act only 
in the presence of dilute acid and is injured by the presence of even a 
small quantity of the alkaline salt, Na.CO,, which is most favorable to the 
action of trypsin. Trypsin can also act in neutral or slightly acid solutions. 
A neutral salt in solution is deleterious to both enzymes, but especially 
so to pepsin, though according to Edkins*® trypsin is aided by the presence 
of from 1 to 2 per cent. NaCl, though greatly retarded by 8 per cent. The 
vegetable trypsins which have been investigated are most active in faintly 
acid solutions. 
In determining the kind of ferment, whether of a peptic or tryptic 
nature, the thymol gelatine was used for control, and the thymol gelatine 
with 1 per cent. NaCl, and 1 per cent. Na.CO, added. Tubes of egg albu- 
men were also used. 
The following table shows the result of the experiment: 
SGreen,J.R. Fermentation, 1899, p. 193. 
