Proceedings of the Linnean Society of London - University Library

6o PROci:Ei>iXGS or the
enzymes. Kesearch in this direction has, in the bands of Dr.
Vernon, already (1903) shown that what is generally known as
trypsin is a mixture of erepsin (panereato-erepsin) with what may
be termed trypsin proper. It is not inconceivable that analysis
may be carried still further, and that trypsin proper may itself be
found to be a mixture of a peptonising with a peptouising
enzyme.
I now turn to proteid-digestiou in plants. The study of this
subject may be said to date from the publication, in 1875, of
DarvA'in's * Insectivorous Plants,' where an account is given of
digestion-experiments with Drosera, Dioncea, Nepenthes, etc. This
was accompanied, almost simultaneously, by the discovery (A^on
Gorup-Besanez, 7-1) of the presence of proteases in germinating
seeds ; and a number of similar discoveries gradually followed
in Myxomycetes (Krukenberg, '79), the Papaw (Wurtz, '79), the
Pig (Bouchiit, 'SO), Moulds (Bourquelot, '93), Bacteria (Bitter, "87),
Pine-apple (Marcano, '91), Yeast (Salkowski, '89), Mushrooms, etc.
(Hjort, '97). My own contribution, made within the last three
years, consists of a number of observations on many different
plants or parts of plants, showing that a protease of some kind is
probably to be found in all parts of all plants at one stage or other
of their development.
But now, as to the nature of the vegetable proteases. At first
it was thought that the protease was a pepsin, since it AAas active
in acid liquid ; but from the time of Wurtz's researches on papain,
when the investigation of the products of digestion became more
thorough, opinion gradually changed to the \\q\\ that the protease
was allied to trypsin. As a matter of fact, peptouisation has never
been found to take ]ilace under normal conditions without peptolysis.
Hence there is no evidence of the independent existence
in plants of a purely peptouising protease allied to pepsin ;
a protease exists at all, it exists in admixture with some peptolysing
enzyme.
Some progress was made towards a comprehension of vegetable
proteolysis when I discovered— almost simultaneously with Cohnheim's
discovery of it in the intestine of animals—that a protease
of the nature of erepsin is very generally present in plants. One
important point that I succeeded in establishing was this—that
many plant-juices or extracts can peptolyse, but cannot digest the
higher proteids, so that clearly erepsin occurs independently in
these cases. The present state of knowledge is then this—that
whilst all plants that have been investigated can effect peptolysis,
only a limited number have been found capable ol digesting
—
if such
fibrin: the plants enumerated above all digest fibrin, and to that
list 1 may add the following: the fruit of the Kachri Grourd
(Cucuniis Melo var, utilissimus), discovered by Professor Green
('92) ; also various other gourds discovered by me (Melon,
Cucumber, Vegetable Marrow) ; the etiolated shoots of Asparagus :
the. bulbs of the Hyacinth aud the Tulip ; and the leaves of