6o PROci:Ei>iXGS or the 



enzymes. Kesearch in this direction has, in the bands of Dr. 

 Vernon, already (1903) shown that what is generally known as 

 trypsin is a mixture of erepsin (panereato-erepsin) with what may 

 be termed trypsin proper. It is not inconceivable that analysis 

 may be carried still further, and that trypsin proper may itself be 

 found to be a mixture of a peptonising with a peptouising 

 enzyme. 



I now turn to proteid-digestiou in plants. The study of this 

 subject may be said to date from the publication, in 1875, of 

 DarvA'in's *■ Insectivorous Plants,' where an account is given of 

 digestion-experiments with Drosera, Dioncea, Nepenthes, etc. This 

 was accompanied, almost simultaneously, by the discovery (A^on 

 Gorup-Besanez, 7-1) of the presence of proteases in germinating 

 seeds ; and a number of similar discoveries gradually followed — 

 in Myxomycetes (Krukenberg, '79), the Papaw (Wurtz, '79), the 

 Pig (Bouchiit, 'SO), Moulds (Bourquelot, '93), Bacteria (Bitter, "87), 

 Pine-apple (Marcano, '91), Yeast (Salkowski, '89), Mushrooms, etc. 

 (Hjort, '97). My own contribution, made within the last three 

 years, consists of a number of observations on many different 

 plants or parts of plants, showing that a protease of some kind is 

 probably to be found in all parts of all plants at one stage or other 

 of their development. 



But now, as to the nature of the vegetable proteases. At first 

 it was thought that the protease was a pepsin, since it AAas active 

 in acid liquid ; but from the time of Wurtz's researches on papain, 

 when the investigation of the products of digestion became more 

 thorough, opinion gradually changed to the \\q\\ that the protease 

 was allied to trypsin. As a matter of fact, peptouisation has never 

 been found to take ]ilace under normal conditions without pepto- 

 lysis. Hence there is no evidence of the independent existence 

 in plants of a purely peptouising protease allied to pepsin ; if such 

 a protease exists at all, it exists in admixture with some pepto- 

 lysing enzyme. 



Some progress was made towards a comprehension of vegetable 

 proteolysis when I discovered — almost simultaneously with Cohn- 

 heim's discovery of it in the intestine of animals — that a protease 

 of the nature of erepsin is very generally present in plants. One 

 important point that I succeeded in establishing was this — that 

 many plant-juices or extracts can peptolyse, but cannot digest the 

 higher proteids, so that clearly erepsin occurs independently in 

 these cases. The present state of knowledge is then this — that 

 whilst all plants that have been investigated can effect peptolysis, 

 only a limited number have been found capable ol digesting 

 fibrin: the plants enumerated above all digest fibrin, and to that 

 list 1 may add the following: the fruit of the Kachri Grourd 

 (Cucuniis Melo var, utilissimus), discovered by Professor Green 

 ('92) ; also various other gourds discovered by me (Melon, 

 Cucumber, Vegetable Marrow) ; the etiolated shoots of Asparagus : 

 the. bulbs of the Hyacinth aud the Tulip ; and the leaves of 



