Proceedings of the Linnean Society of London - University Library

2 4
PROCEEDINGS OF THE
this—that theii' protease should be poiu'ed out at the surface
so as to digest proteids supplied from without by the captured
insects : Avhereas in ordiuary plants the protease is retained
within the tissues to digest, and so to render mobile, the proteids
that are formed and stored there.
Another consideration of general interest is the relation
between the proteases of plants and the digestive processes of the
animals that consume the plants. In our own case, the matter
may not be of much importance, since most of our vegetable food .
has been cooked before we eat it, and consequently the proteases
have been destroyed. But in the herbivorous animals, more
particularly the Ruminants, the case is altogether different. Here
the vegetable food that has been eaten is placed under conditions
that are altogether favorable to the action of the proteases which
it contains, so that there is reason to believe that digestion in
these animals is, in no small degree, a process of autolysis, the
food providing at once the nutriment and the means of
digesting it.
To pass now to another part of the subject. Quite recently a
very remarkable discovery has been made by Pawlow concerning
the origin of one of the animal proteases, namely trypsin. It "s^as
known that perfectly fresh and pure pancreatic juice had little or
no digestive power, but the cause of this had not been traced.
Pawlou 's experiments brought to light the fact that the addition
of a small quantity of the intestinal secretion (snccus tntericus)
to inert pancreatic juice immediately renders it active. The
explanation of these facts is that in the pure pancreatic secretion,
free trypsin is not present, but its mother-substance, trypsinogen,
from which it has to be liberated. On the addition of intestinal
juice, this liberation is effected by means of a substance which it
contains, which Pawlow has termed Kinase^ and has aptly de-
scribed it as a " ferment of ferments.''
Curiously enough, my thoughts had been turned in the same
direction in the course of ray work on the proteases of plants.
It had been known since the time of Schtinbein that the juices and
tissues of various plants possess the property of causing tincture
of guaiacum to turn blite either with or without the addition of
peroxide of hydrogen. The reaction is one of oxidation ; and
it has been ascertained of late years by Bertrand and others,
that it is effected by certain definite substances termed oxidases
and peroxidases. Various opinions have been hazarded as to
the probable significance of these substances in the economy
of the plant, but no coherent theory on the subject has yet been
established. Incidentally I observed that whenever a juice or
a tissue gave a good guaiacura-reaction, it also proved itself to
be proteolytic. This observation was not altogether new : indeed
at one time it had been thought that all enzymes reacted with
gxiaiacum, whicli is not the case. But it led me to inquire into
the meaning of this association of oxidase and enzyme in the
plant. Is it a coincidence or a correlation ?—this is the problem