116 Proceedings of the Royal Society of Edinburgh. [Sess. 
The total result of the experiment may, for the sake of comparison, be 
expressed as follows : — 
Results of Peptolysis. 
Temperature. 
Pepton 
Witte. 
Pepton Roche. 
A. 
B. 
A. 
B. 
15° 
5*74 
3-0 
Negative. 
14 days. 
25° 
9*6 
9-4 
6 „ 
37° 
9*2 
95 
6 „ 
50° 
7T5 
6*45 
Negative. 
These results seem to indicate the presence in germinating barley of 
two different peptolytic enzymes, one of which can be readily extracted 
with water, while the other is apparently of the nature of an endo-enzyme 
and can only be obtained by destroying the cells of the seed tissues. The 
existence of these two enzymes is further indicated by the fact that their 
temperature curves differ materially. The optimum temperature for both 
seems to be between 25° and 37°. At 50°, however, while the hydrolysis of 
Pepton Witte proceeds vigorously, being considerably more marked than 
at 15°, the action on Pepton Roche seems to be inhibited, since no separation 
of tyrosin has ever been observed at this temperature. On the other hand, 
a slow but quite distinct action takes place at 15°. 
The inhibition of the Pepton Roche digestion at 50° was further 
accidentally demonstrated in this way. A number of digestions which had 
been incubated at 15° and 50° for six days, with a negative result, were 
put aside and overlooked for a couple of weeks. It was then found that 
those which had been at 15° for the whole period gave a distinct deposit of 
tyrosin, while those which had previously been exposed to a temperature 
of 50° showed no such deposit. Apparently the Pepton Roche digestion 
is not only prevented at 50° but the activity completely destroyed, while, 
as has been previously demonstrated, the hydrolysis of Pepton Witte pro- 
ceeds vigorously at this temperature. 
The digestions were all examined for the presence of moulds or bacteria, 
partly by microscopic examination and partly by adding a drop of the 
material to sterile meat-extract gelatine and incubating at 20°. This 
examination invariably showed the absence of any development of bacteria 
or fungi. In a few cases only, an isolated Penicillium spore seemed to 
have survived. 
For the sake of certainty on this point another experiment was devised. 
The barley was crushed, mixed with sand and kieselguhr, and ground in 
