2 4 PROCEEDINGS OF THE 



this — that theii' protease should be poiu'ed out at the surface 

 so as to digest proteids supplied from without by the captured 

 insects : Avhereas in ordiuary plants the protease is retained 

 within the tissues to digest, and so to render mobile, the proteids 

 that are formed and stored there. 



Another consideration of general interest is the relation 

 between the proteases of plants and the digestive processes of the 

 animals that consume the plants. In our own case, the matter 

 may not be of much importance, since most of our vegetable food . 

 has been cooked before we eat it, and consequently the proteases 

 have been destroyed. But in the herbivorous animals, more 

 particularly the Ruminants, the case is altogether different. Here 

 the vegetable food that has been eaten is placed under conditions 

 that are altogether favorable to the action of the proteases which 

 it contains, so that there is reason to believe that digestion in 

 these animals is, in no small degree, a process of autolysis, the 

 food providing at once the nutriment and the means of 

 digesting it. 



To pass now to another part of the subject. Quite recently a 

 very remarkable discovery has been made by Pawlow concerning 

 the origin of one of the animal proteases, namely trypsin. It "s^as 

 known that perfectly fresh and pure pancreatic juice had little or 

 no digestive power, but the cause of this had not been traced. 

 Pawlou 's experiments brought to light the fact that the addition 

 of a small quantity of the intestinal secretion (snccus tntericus) 

 to inert pancreatic juice immediately renders it active. The 

 explanation of these facts is that in the pure pancreatic secretion, 

 free trypsin is not present, but its mother-substance, trypsinogen, 

 from which it has to be liberated. On the addition of intestinal 

 juice, this liberation is effected by means of a substance which it 

 contains, which Pawlow has termed Kinase^ and has aptly de- 

 scribed it as a " ferment of ferments.'' 



Curiously enough, my thoughts had been turned in the same 

 direction in the course of ray work on the proteases of plants. 

 It had been known since the time of Schtinbein that the juices and 

 tissues of various plants possess the property of causing tincture 

 of guaiacum to turn blite either with or without the addition of 

 peroxide of hydrogen. The reaction is one of oxidation ; and 

 it has been ascertained of late years by Bertrand and others, 

 that it is effected by certain definite substances termed oxidases 

 and peroxidases. Various opinions have been hazarded as to 

 the probable significance of these substances in the economy 

 of the plant, but no coherent theory on the subject has yet been 

 established. Incidentally I observed that whenever a juice or 

 a tissue gave a good guaiacura-reaction, it also proved itself to 

 be proteolytic. This observation was not altogether new : indeed 

 at one time it had been thought that all enzymes reacted with 

 gxiaiacum, whicli is not the case. But it led me to inquire into 

 the meaning of this association of oxidase and enzyme in the 

 plant. Is it a coincidence or a correlation ? — this is the problem 



