184 
Vines . — The Proteases of Plants (///). 
The following experiment may be given in full. 50 cc. of neutral pitcher-liquid 
were made alkaline by the addition of Na 2 C 0 3 to 0-4 % : 1 grm. of Witte-peptone was 
added, and HCN to 0-2 %. iocc. of the liquid were boiled and put into a separate 
bottle as a control. After 96 hours’ digestion the boiled and the unboiled liquids 
were separately evaporated to half-bulk : the unboiled liquid then gave a marked 
tryptophane-reaction, the boiled liquid only a faint reaction. 
Conclusion : the pitcher-liquid peptonizes fibrin much more rapidly than it 
peptolyses Witte-peptone: fibrin-digestion inhibited by alkalinity, promoted by 
acidity ; the limit of acidity was not reached : peptolysis, slow in any case, much 
retarded by alkalinity, but not inhibited by small percentage of alkali that arrested 
fibrin-digestion. 
The fact that fibrin-digestion is so much more active than peptolysis, 
suggests at once the presence of two proteases ; for, were there a single 
‘ tryptic * protease, both digestive processes should be equally active : and 
further, that the ereptase is present in relatively small quantity. In its 
general proteolytic action, the liquid does not agree exactly with any of 
the other juices or extracts : in its reaction-range for fibrin-digestion it 
resembles the extracts of Yeast, Mushroom, and Malt, though with a 
higher HCl-limit : in its reaction-range for peptolysis it resembles papain, 
Pineapple juice, and extracts of Hyacinth-bulb. The subject requires 
further investigation : but for lack of a supply of pitcher-liquid I cannot 
pursue it at present, though I hope to do so later in the year. However, 
the results now given show a divergence in the reaction-ranges for fibrin- 
digestion and peptolysis sufficiently marked to suggest the presence of 
two proteases. 
Summary and Conclusion. 
The experiments detailed in the foregoing pages constitute a demon- 
stration of the differential effect of varied reaction upon the proteolytic 
activities of the juices and extracts of certain representative plants. In 
endeavouring to bring the facts together, it must be recognized that they 
are not capable of close comparison on account of the different chemical 
composition of the juices and extracts, and, more especially, of the 
difference of their initial reactions, two only being neutral (papain, 
Nepenthes- liquid), the rest more or less strongly acid. Nevertheless, it 
is possible to make a few general statements. Taking peptolysis first, it 
appears that it always took place within a range extending from distinct 
alkalinity to a degree of acidity beyond the natural : the difference between 
the individual cases is thus one of degree only. Fibrin-digestion, on the.other 
hand, was much less uniform, showing such wide and striking differences 
that it is possible to arrange the individual cases into two groups, thus : — 
( a ) those in which it was limited to acid reaction : Yeast, Mush- 
room, Malt, Nepenthes . 
