22 PROCEEDINGS OF THE 



I now returned to the consideration of the cases in which I had 

 failed to observe the digestion of fibrin ; and on applying to tliem 

 the tryptophane-test, 1 was somewhat surprised to find that it 

 frequently gave a distinct and even strong reaction, especially 

 when the material used consisted of pieces of the root, leaf, bulb, 

 etc. under examination. It was clear that a protease was present 

 which, though it did not act upou fibrin, digested the proteids 

 contained in the juice or tissue of the plant itself. Seeing that 

 these proteases, though possessing but slight peptonising power, 

 were strongly proteolytic, 1 varied the mode of experiment by 

 submitting to their action such simple proteids as albumoses and 

 peptones, with most satisfactory results. 



I thus reached the further conclusion that whilst in certain 

 plants (e. g. Pineapple, Papaw, Nepenthes, Teast, etc.) there are 

 proteases which closely resemble trypsin in their mode of action, 

 in the majority of cases there are proteases which differ from 

 trypsin in that they cannot peptonise fibrin though they resemble 

 trypsin in proteolysing albumoses and peptones. These pro- 

 teases seemed to belong to an altogether new type of enzyme ; 

 a consideration that led me to feel some misgiving as to my 

 observations. Fortunately I happened, at this junctui'e, to hear of 

 Cohnheim's recent discovery in the intestine of animals, of an 

 enzyme possessing somewhat similar properties. This enzyme, to 

 which he has given the name Erepsin, proteolyses albumoses and 

 peptones, but cannot peptonise a more complex proteid than 

 casein. I thus obtained confirmation of the surmise that the 

 proteases which I had discovered were not tryptic, although they 

 were proteolytic. 



I must not overburden with detail this slight sketch of the 

 growth of knowledge with regard to the distribution and nature 

 of proteases in both plants and animals. I will, however, venture 

 upon a few remarks of a general nature. With regard to the 

 distribution of the proteases in the body, they have been found, 

 as I have said, in all parts of the plant — leaves, stems, roots, bulbs, 

 tubers, fruits, seeds ; and the inference might be drawn that 

 herein the plant differs from the animal organism, in which these 

 enzymes are confined to the digestive tract. But this inference 

 would be only partially true even of the higher animals. No 

 doubt the enzymes are especially secreted by the digestive organs ; 

 but recent researches, more especially those of Hedin, have shown 

 that they are widely distributed throughout the tissues of the 

 animal body. 



Then as to the I'elation to each other of the three known types 

 of proteases — the peptic, the tryptic, the ereptic. The relation 

 between trypsni and erepsin has already been sufficiently indicated. 

 "With regard to pepsi«, it has long been generally held, though 

 with some dissentients, that pepsin is an enzyme which can only 

 peptonise but cannot further decompose proteids. But of late 

 years there has been an accumulation of evidence tending to 

 show that this view is too arbitrary : to show that pepsin can, as a 



