Cuap. VI. DIGESTION. 129 
some influence to the glands of the exterior ten- 
tacles, causing them to secrete more copiously; and 
their secretion likewise becomes acid. With ani- 
mals, according to Schiff,* mechanical irritation ex- 
cites the glands of the stomach to secrete an acid, 
but not pepsin. Now, I have every reason to be- 
lieve (though the fact is not fully established), that 
although the glands of Drosera are continually secret- 
ing viscid fluid to replace that lost by evaporation, 
yet they do not secrete the ferment proper for di- 
gestion when mechanically irritated, but only after 
absorbing certain matter, probably of a nitrogenous 
nature. I infer that this is the case, as the secretion 
from a large number of leaves which had been 
irritated by particles of glass placed on their discs 
did not digest albumen; and more especially from 
the analogy of Dionza and Nepenthes. In like 
manner, the glands of the stomach of animals secrete 
pepsin, as Schiff asserts, only after they have ab- 
sorbed certain soluble substances, which he desig- 
nates as peptogenes. There is, therefore, a remarkable 
parallelism between the glands of Drosera and those 
of the stomach in the secretion of their proper acid 
and ferment. 
The secretion, as we have seen, completely dissolves 
albumen, muscle, fibrin, areolar tissue, cartilage, the 
fibrous basis of bone, gelatin, chondrin, casein in the 
state in which it exists in milk, and gluten which has 
been subjected to weak hydrochloric acid. Syntonin 
and legumin excite the leaves so powerfully and 
quickly that there can hardly be a doubt that both 
would be dissolved by the secretion. The secretion 
* (Phys. de la Digestion,’ 1867, tom. ii. pp. 188, 245. 
