106 
DROSERA ROTUNDIFOLIA. [Cuap. VI. 
Summary and Concluding Remarks on the Digestive Power of 
Drosera. 
When the glands on the disc are excited either by the 
absorption of nitrogenous matter or by mechanical irritation, 
their secretion increases in quantity and becomes acid. 
They likewise transmit some influence to the glands of the 
exterior tentacles, causing them to secrete more copiously ; 
and their secretion likewise becomes acid. With animals, 
according to Schiff,* mechanical irritation excites the glands 
of the stomach to secrete an acid, but not pepsin. Now, I 
have every reason to believe (though the fact is not fully 
established), that although the glands of Drosera are con- 
tinually secreting viscid fluid to replace that lost by 
evaporation, yet they do not secrete the ferment proper for 
digestion when mechanically irritated, but only after ab- 
sorbing 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 absorbed 
certain soluble substances, which he designates 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.t 
* ¢Phys. de la Digestion,’ 1867, 
tom. ii. pp. 188, 245. 
+ [it will be seen from the facts 
given in a footnote at p. 81, that 
even if we accept Schifi’s peptogen 
theory, the evidence on the bo- 
tanical side is against the existence 
of the above suggested parallelism. 
Moreover, Schiff's peptogen theory 
is not generally accepted by physio- 
logists. Professor Sanderson has 
called my attention to Ewald’s views 
on this question as given in his 
* Klinik der Verdauungs krankheiten, 
(i) Die Lehre von der Verdauung,’ 
1886, p. 91. Ewald does not believe 
in any special action of the so-called 
peptogens. He writes, “I find that 
acid and pepsin make their appearance 
almost immediately after the intro- 
duction of a starch solution into the 
stomach. The same thing naturally 
follows on the introduction of Schiff’s 
peptogens, so that no inconsiderable 
quantity of acid and pepsin is in 
readiness for a subsequent act of 
digestion, which is, in consequence, 
rendered far more energetic.” 
Haidenhain, in Hermann’s ‘ Hand- 
buch der Physiologie,’ vol. v. part i. 
p- 158, also criticises Schiff’s theory, 
and shows that the observations on 
which this theory is founded are to 
some extent untrustworthy, owing to 
a fault inthe method employed—F. D.] 
