20 PROCEEDINGS OF THE 



digesting enzyme or ferment, in the various parts of the plant- 

 body is the rule rather than the exception. 



I must not omit to mention that my results had been — 

 although quite unknown to nie — somewhat anticipated by the 

 researches of Buscalioni and Fermi which were published in 1898. 

 The method adopted by these authors for detecting digestive 

 power consisted in observing whether or not the juices of various 

 plants, or portions of their tissue, did or did not effect the lique- 

 faction of gelatine, of course under strictly antiseptic conditions. 

 Whilst their results and mine differ in many points of detail, 

 they are entirely concordant as regards the main conclusion, the 

 wide distribution of proteases in plants. 



The method employed by me was altogether different from 

 that of Buscalioni and Fermi, and was devised in connection with 

 the attempt to determine the nature and mode of action of the 

 proteases of plants. At the time Avhen investigation in this 

 direction first began, our knowledge of proteid-digestion in 

 animals amounted roughly to this, that there were two enzymes 

 concerned in the process — the pepsin of the stomach, the trypsin 

 of the pancreas : that the former acted only in an acid medium, 

 the latter most actively in an alkaline medium ; that the former 

 merely converted the more complex proteids into simpler sub- 

 stances of the same group, that is eflfected peptouisation ; whilst 

 the latter not only peptonised but also decomposed the simpler 

 proteids into non-proteid substances, that is effected proteolysis. 



It was from this point of view that Darwin and other observers 

 of his time interpreted their discoveries as to the digestion of 

 proteids by insectivorous plants. Inasmuch as the liquids of 

 insectivorous plants were found to be active only when acid, it 

 was naturally assumed that the enzyme which they contain must 

 be closely allied to the pepsin of animals ; an assumption that was 

 also made by von Gorup-Besanez with regard to the enzyme 

 which he extracted from germinating seeds. The first divergent 

 opinion was expressed by Wurtz, who found that the substance 

 which he extracted from the Pap:iw, and called papain, was 

 active not only in acid but also in neutral and alkaline media ; 

 and he consequently suggested that it was allied rather with 

 trypsin than with pepsin. This opinion was not conclusive, 

 because Wurtz had not sufiiciently examined the products of 

 papain-digestion. The missing evidence was supplied by the 

 researches of Martin, who found leucin and tyrosiu among the 

 products of digestion, substances which are characteristic of 

 digestion by trypsin. Within a few years Prof. Eeynolds Green 

 observed in the Lupin and the Castor-oil plant, that the protease 

 of seeds is proteolytic like trypsin ; and he followed up this 

 discovery by ascertaining that this is true also of the protease 

 of the Kachri Gourd. In the meantime. Prof. Chittenden had 

 demonstrated that the protease of the Pineapple possesses similar 

 properties. Since then I have found, in Nepenthes, Yeast, the 

 Mushroom, in fact in every one without exception, of the very 



