20 Vines . — Tryptophane in Proteolysis . 
object being to ascertain whether they were ‘ tryptic ’ or ‘ pep- 
tic.’ But, as I have already pointed out, there is a consider- 
able body of accun^ulated facts tending to show that pepsin 
itself is capable of effecting ‘tryptic’ proteolysis. Hence the 
question now is whether or not such a thing as a { peptic 5 
enzyme exists at all ; an enzyme, that is, which only hydro- 
lyses the higher proteids to peptones, and does not decom- 
pose the proteid molecule. The ascertained facts seem to 
answer this question in the negative : but in view of Glaess- 
ner’s (22) contention that the apparently ‘ tryptic ’ action of 
pepsin is due, not to pepsin itself, but to another enzyme, his 
‘ pseudo-pepsin,’ this answer cannot at present be definitively 
accepted. The onus probandi remains, however, with those 
who accept Glaessner’s interpretation of the facts, and assume 
the secretion by the stomach of an enzyme which combines in so 
singular a manner the properties of pepsin with those of trypsin. 
In the mean time, the terms ‘ peptic ’ and ‘ tryptic ’ must be used 
with the reservation that they may refer, not, as hitherto, to 
what seemed to be fundamentally different processes of diges- 
tion, but to different modes of one and the same process. If it 
should turn out that they are inapplicable in their old sense, 
they may still be used to indicate the marked differences 
which exist between pepsin-digestion and trypsin-digestion. 
Even if pepsin be finally proved to be ‘tryptic’ in action, it 
will still be necessary to employ some terms to express the 
fact that it acts much more slowly than does trypsin, and, 
as far as it is possible to institute a quantitative estimate, that 
it produces tryptophane and other ultimate products in rela- 
tively much smaller quantity. Moreover the two enzymes 
differ materially as to the medium in which they respectively 
act : the one acts, whilst the other does not, in a H Cl solution ; 
and conversely, the one acts in an alkaline liquid whilst the 
other does not. 
In respect of the reaction of the medium, the vegetable 
enzymes may be taken to show affinity with pepsin on the 
one hand and trypsin on the other. The results described in 
the foregoing pages may be conveniently summarized in the 
