Mendel and Underhill — Papa'ln-digestion. 3 



abundantly when these neutral fluids are heated. Its occurrence is too 

 characteristic and the quantities formed are too large to be ascribed 

 to traces of unprecipitated alkali-proteid. Peptones (in the older 

 sense) were obtained by concentrating the filtrates from the globulin- 

 like body and precipitating with a large excess of alcohol a substance 

 which gave the biuret reaction and was readily diffusible. From the 

 alcoholic solution, crystals of leucin were obtained. Martin experi- 

 enced more difficulty, however, in showing the presence of tyrosin. 

 No crystals could be obtained ; but when the alcoholic peptone- 

 filtrate was dried, an extract could be prepared from it with absolute 

 alcohol. This solution gave Millon's reaction and led Martin to con- 

 clude the presence of tyrosin. In his own words "we have, then, in 

 papain a proteolytic ferment acting almost exactly like trypsin : sim- 

 ilar in the proneness of decomposition in solution, in its erosion of 

 coagulated proteid: in the formation of an 'intermediate' body from 

 the proteid ; and the formation of a perfect peptone, and of leucin 

 and tyrosin." 1 Later Martin obtained impure crystals of tyrosin and 

 leucin from the dried papaw juice, and also apparently identified 

 them in small quantity among the products of the self -digestion of 

 this material. The crude way in which the material at his disposal 

 was prepared by no means excludes the possibility of previous decom- 

 position through the agency of bacteria and the formation of bac- 

 terial enz}^mes.' ! This might, at least, reasonably be assumed of a 

 "yellow brown powder of sickly smell" obtained by drying, chiefly 

 in the East Indies, the juice of the unripe fruit in the open air and 

 under glass. Furthermore the quantity of leucin and tyrosin — if 

 such they were — obtained in the digestions with large quantities of 

 proteid, was extremely small when compared with the typical results of 

 tryptic proteolysis ; and Martin himself has been far more cautious in 

 drawing any final conclusion than have those who have subsequently 

 quoted his investigations. For he says : " It is evident moreover 

 that too general a deduction cannot at present be drawn as to the 

 nature of the proteolytic change, as to whether the agent acts like 

 animal pepsin or like trypsin." 3 In studying the literature of papain- 

 proteolysis we have been surprised to find upon what scanty and 

 meagre data some of the current statements on the subject are based ; 

 and we have dwelt particularly upon these widely quoted observa- 

 tions of Martin to illustrate this point. 



1 Martin: loc. cit., 1884, v, p. 230. 



2 Some commercial preparations have been reported to contain spores and 

 dead forms of bacilli. (Dowdeswell : Practitioner, 1883, xxx, May.) 



3 Martin : Journal of Physiology, 1885, vi, p. 360. 



