13 
Vines . — The Proteases of Plants (VI). 
succeeded in demonstrating that a proteolytic enzyme is widely distributed 
in plants ; and it may be inferred that it is much more generally present 
than I have shown it to be. The next point to be considered is the probable 
nature of the enzyme. In the previously known cases, the evidence goes 
to prove that the enzymes are allied to the trypsin of animals, since they both 
peptonize and proteolyse actively. Amongst the plants that I have recently 
examined, there are only two, the Melon and the Mushroom, which approach 
those previously known in their power of peptonization and proteolysis. 
Whilst all the others readily proteolysed Witte-peptone, their action on the 
higher proteins, so far as it was tested, was relatively feeble, and in some 
cases altogether wanting. It may be that the precise conditions favourable 
for peptonization were not afforded in the experiments : that is a point for 
future investigation. But taking the facts as they stand, it is an inevitable 
conclusion that if in some cases, such as the Melon and the Mushroom, the 
enzyme may be regarded as a vegetable trypsin, this view cannot be 
extended to the others. It seemed to me, at first, that I had come upon 
an altogether new type of enzyme, an idea that occasioned a certain amount 
of temporary misgiving as to the accuracy of my observations. But it was 
pointed out to me by my colleague, Professor Gotch, that within the last 
year (1901-2), Cohnheim had described an enzyme, formed in the mucous 
membrane of the small intestine, which actively proteolyses peptone and 
casein, but does not act upon the higher proteins. It is to this enzyme, 
termed ‘ erepsin ’ by Cohnheim, that the apparently new proteolytic enzyme 
of plants would correspond. It would appear, therefore, that plants form 
two distinct kinds of proteases, the one a trypsin, the other an erepsin ; and 
so far as the facts go, they indicate that the former is generally associated 
with depositories of proteid nutriment, such as seeds, fruits, bulbs, latici- 
ferous tissue, the latter with ordinary foliage-leaves, stems, and roots 
The discovery of the ‘ erepsin ’ of plants, or ‘ereptase’, as I prefer to call 
it, and the wide and general distribution of this substance, necessarily 
involved a modification of the ‘ trypsin-theory ’ of the proteases of plants 
previously mentioned, and to this extent : those plants whose tissues or 
juices peptonized fibrin, were considered to contain ‘ trypsin ’, with possibly 
ereptase as well; those plants whose tissues or juices had no effect upon 
fibrin, but digested (peptolysed) Witte-peptone, as indicated by the trypto- 
phane-reaction, were considered to contain ereptase only. 
For some time (1903-4) I continued my researches from this point of 
view, adding to the number of plants that were found to have some kind of 
digestive activity, investigating also the conditions of the digestion- 
experiments with special reference to the effect of antiseptics upon the 
digestive processes, and giving the result of extracting the plant-material with 
NaCl-solution instead of distilled water. The experiments are described in 
two papers, published respectively in June 1903 ( 16 ), and in April 1904(17). 
