Cuap. VI.J DIGESTION. 97 
inevitably caught by the viscid secretion surrounding the 
many glands. 
Gluten.—This substance is composed of two albuminoids, 
one soluble, the other insoluble in alcohol.* Some was 
prepared by merely washing wheaten flour in water. A 
provisional trial was made with rather large pieces placed on 
two leaves; these, after 21 hrs., were closely inflected, and 
remained so for four days,when one was killed and the 
other had its glands extremely blackened, but was not 
afterwards cbserved. Smaller bits were placed on two 
leaves ; these were only slightly inflected in two days, but 
afterwards became much more so. Their secretion was not 
so strongly acid as that of leaves excited by casein. The bits 
of gluten, after lying for three days on the leaves, were more 
transparent than other bits left for the same time in water. 
After seven days both leaves re-expanded, but the gluten 
seemed hardly at all reduced in bulk. The glands which 
had been in contact with it were extremely black. Still 
smaller bits of half putrid gluten were now tried on two 
leaves ; these were well inflected in 24 hrs., and thoroughly 
in four days, the glands in contact being much blackened. 
After five days one leaf began to re-expand, and after eight 
days both were fully re-expanded, some gluten being still left 
on their;discs. Four little chips of dried gluten, just dipped 
in water, were next tried, and these acted rather differently 
from fresh gluten. One leaf was almost fully re-expanded in 
three days, and the other three leaves in four days. The 
chips were greatly softened, almost liquefied, but not nearly 
all dissolved. The glands which had been in contact with 
them, instead of being much blackened, were of avery pale 
colour, and many of them were evidently killed. 
In not one of these ten cases was the whole of the gluten 
dissolved, even when very small bits were given. I there- 
fore asked Dr. Burdon Sanderson to_try gluten in artificial 
digestive fluid of pepsin with hydrochloric acid; and_ this 
dissolved the whole. The gluten, however, was acted on 
much more slowly than fibrin; the proportion dissolved 
within four hours being as 40°8 of gluten to 100 of fibrin. 
‘Gluten was also tried in two other digestive fluids, in which 
hydrochloric acid was replaced by propionic and butyric 
acids, and it was completely dissolved by these fluids at the 
* Watts’ ‘Dict. of Chemistry,’ vol. ii. 1872, p. 873. 
H 
