124 DROSERA ROTUNDIFOLIA. Cuap. VI 
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 fluids and substances, be 
absorbed by the glands of Drosera and cause inflection. Half- 
minim drops of a solution of one part to 487 of water were 
placed on the discs of four leaves, each drop containing the 
quantity usually employed by me, namely 535 of a 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 ml.) of 
the solution, 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 im- 
mersion in pure water. That the urea, which was not per- 
‘fectly 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 urea itself 
is not exciting or nutritious to Droscra; 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. Bartho- 
lomew’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 
