102 DROSERA ROTUNDIFOLIA. [CHAE VI. 
(remembering what small quantities were given), that the ferment of 
Drosera does not act on or digest pepsin, but absorbs from it some 
albuminous impurity which induces inflection, and which in large 
quantity is highly injurious. Dr. Lauder Brunton at my request 
endeavoured to ascertain whether pepsin with hydrochloric acid would 
digest pepsin, and as far as he could judge, it had no such power. 
Gastric juice, therefore, apparently agrees in this respect with the 
secretion of Drosera. 
Urea.—It seemed to me an interesting inquiry whether this refuse 
of the living body, which contains much nitrogen, would, like so many 
other animal fiuids and substances, be absorbed by the glands of 
Drosera and cause mflection. Half-minim drops of a solution of one 
part to 437 of water were placed on the discs of four leaves, each drop 
containing the quantity usually employed by me, namely 53, ofa grain, 
or ‘0674 mg.; but the leaves were hardly at all affected. They were 
then tested with bits of meat, and soon became closely inflected. I 
repeated the same experiment on four leaves with some fresh urea 
prepared by Dr. Moore; after two days there was no inflection; 
I then gave them another dose, but still there was no inflection. 
These leaves were afterwards tested with similarly sized drops of an 
infusion of raw meat, and in 6 hrs. there was considerable inflection, 
which became excessive in 24 hrs. But the urea apparently was not 
quite pure, for when four leaves were immersed in 2 dr. (7°1 c.c.) 
of the sotution, so that all the glands, instead of merely those on the 
disc, were enabled to absorb any small amount of impurity in solution, 
there was considerable inflection after 24 hrs., certainly more than 
would have followed from a similar immersion in pure water. ‘lhat 
the urea, which was not perfectly white, should have contained a 
sufficient quantity of albuminous matter, or of some salt of ammonia, 
to have caused the above effect, is far from surprising, for, as we shall 
see in the next chapter, astonishingly small doses of ammonia are 
highly efficient. We may therefore conclude that the urea itself is 
not exciting or nutritious to Drosera; nor is it modified by the 
secretion, so as to be rendered nutritious, for, had this been the case, 
all the leaves with drops on their discs assuredly would have been 
well inflected. Dr. Lauder Brunton informs me that from experiments 
made at my request at St. Bartholomew’s Hospital it appears that urea 
is not acted on by artificial gastric juice, that is by pepsin with 
hydrochloric acid. 
Chitine.—The chitinous coats of insects naturally captured by the 
leaves do not appear in the least corroded. Small square pieces of the 
delicate wing and of the elytron of a Staphylinus were placed on some 
leaves, and after these had re-expanded, the pieces were carefully 
examined. ‘Their angles were as sharp as ever, and they did not differ 
in appearance from the other wing and elytron of the same insect 
which had been left in water. The elytron, however, had evidently 
yielded some nutritious matter, for the leaf remained clasped over it for 
four days; whereas the leaves with bits of the true wing re-expanded on 
SP ernie, 
ENN NCE eg nee 
lpi naa ENE PEPE OEA 
