2 Mendel and Underhill — Papam-digestlon. 



earlier investigators were content to note that the extracts of various 

 parts of the plant, and preparations made from them, are able to dis- 

 solve proteids like fibrin in the presence of antiseptics, e. g. thymol 

 and hydrocyanic acid. It had long been known that parts of the 

 Carica papaya possess a vigorous action in softening meat and were 

 used by the natives of tropical countries, when Wurtz ' began his 

 more careful studies of the proteolytic enzyme present in the plant. 

 He gave to it the name papain, and ascertained that it dissolved 

 fibrin, raw meat, coagulated egg-white and gluten ; milk was clotted 

 by it and the precipitated casein subsequently dissolved. He further 

 found that a slightly purified enzyme mixture dissolved fibrin in 

 acid, neutral and alkaline media. Regarding the products formed, 

 Wurtz merely states in one case that 0.1 gram of his papain dissolved 

 one hundred grams of moist fibrin in a neutral medium in the pres- 

 ence of HCN in thirty-six hours ; from the products formed a small 

 quantity of a crystalline substance having the appearance of leucin 

 was isolated." No mention is made of tyrosin. Because of the 

 readiness with which it acts in neutral fluids, Wurtz concluded that 

 papain is closely related to trypsin. 



Somewhat later Martin' undertook a study of papain. He used a 

 commex'cial preparation in most of his experiments, while in a few 

 cases the dry juice of the unripe fruit was employed. The residts of 

 the digestive action of the commercial papain on fibrin and egg-albu- 

 min 'solution were reported. Prussic acid was used to prevent putre- 

 factive changes. A quantitative study of this enzyme j) reparation 

 indicated that it was active in the highest degree in neutral and 

 alkaline solutions (one-fourth per cent. Na„COg) ; in solutions of higher 

 alkalinity (one-half or one per cent. Na^CO,), the action, though well 

 marked, was not so great. Acid prevented the action of the papain 

 though in weakly acid solutions (0.05 per cent. HCl) some degree of 

 digestion may have taken place. Martin also investigated the pro- 

 ducts formed during the papain-digestion of fibrin in neutral and 

 alkaline media. He observed the early formation of a "globulin- 

 like" substance intermediate between the native proteid and the 

 derived alkali-proteid usually formed in proteolysis. We shall have 

 occasion to i-efer to this body later. It is not precipitated like alkali- 

 proteid when the digestive fluids are neutralized, but separates out 



' Wurtz and Bouchut : Comptes rendus de I'Academie des Sciences, 1879, 

 Ixxxix, p. 425. Wurtz : ibid., 1880, xc, p. 1379 ; 1880, xci, p. 787. 



'^ Wurtz : Comptes rendus de PAcademie des Sciences, 1880, xc, p. 1379. 

 3 Martin : Journal of Physiology, 1884, v, p. 213 ; 1885, vi, p. 336. 



