Proceedings of the Linnean Society of London - University Library

LIXNEAX SOCIETY (tl' LOXDOX. 59
ABSTEACT8.
Abstract of Prof. Yines's discourse on Proteid Digestion in
Animals and Plants ;
read 1st December, 1904.
Tin: foundation of our knowledge of gastric digestion in animals
was laid by Aan llelmont as long ago as early in the ITtli century
(Oi-tas Medkhw, 1648), who held that it was effected by an "acid
ferment." But in spite of continued research by Reaumur,
Stevens, Spallanzani, and others, it was not until two hundred
years later that the ferment was actually detected. This important
discovery wa-^ made in 1S3G by the celebrated Sclnvann, who gave
to the ferment the name " pepsin."
In the course of subseqiient investigation, it came to be recognised
that the digestion of the food is not by any means completed in the
stomach, but that the greater part of the digestive process is carried
on in the small intestine {duodenum) by the pancreatic secretion.
Claude Bernard ascertained in 1850 that the pancreatic juice contains
a ferment that digests proteids ; to this ferment the name
" trypsin " was given by Iviihne in 1876.
These two proteid-enzymes, or proteases, pepsin and trypsin,
were found to differ as well in the conditions of their activity as
in the products. Pepsin acts only in an acid liquid, whereas
ti-ypsin is most active in an alkaline liquid. Both proteases
decompose, by hydrolysis, the higher proteids, such as albumin and
fibrin, into others of simpler constitution v.hich Lehmann (1850)
termed '• peptones " ; but it has since been shown that under this
term were included two classes of substances known as " albumoses "
aud peptones proper. Although there has been a good deal of
discussion on the point, it may be regarded as established that the
action of pepsin goes no further than this : that it is, in fact, a
merely ]ieptonisiug protease. It is, however, well-known that the
action of trypsin is more far-reaching, going on to the decomposition
of a portion, at least, of the peptone into non-proteid,
erystallisable, nitrogenous bodies belonging to what ai'e now known
as the groups of amido-acids (c. f)., leucin, tyrosin, tryptophane,
etc.) and hexon-bases (c. (j. arginin, lysin, and histidin). Trypsin
not only peptonises the higher proteids, but also decomposes, or
peptolyses, albumoses and peptones.
These two were the only proteases known until quite recently
(1901)a new protease, termed "erejisin'" by Cohuheim its discoverer,
was added to the list. Like trypsin, this protease peptolyses
peptones, and is active in alkaline liquids ; but its peptonising
power is much less marked, as it is without action on albumin and
fibrin, though it can peptonise casein.
The discovery of erepsin suggested tlie possibility that trypsin
might be, not a single enzyme, as had hitherto been thought, but
a mixture of enzymes ; possibly of peptonising with peptolysiug