CHAP. 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 Dionaea 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. cle la Digestion,' 1867, torn. ii. pp. 188, 245. 



