430 ON THE DIGBSTITE TEBMENT OF NEPENTHES. 



of the pitchers, I was struck with the much greater rapidity with 

 which digestion took place in the former case ; and I inferred 

 that the secretion contained a larger quantity of free ferment than 

 the extract. From this I was led to make some experiments as 

 to the origin of the ferment in the gland-cells, with the view, if 

 possible, of placing our knowledge of the origin of the digestive 

 ferment in plants upon a level with that which we possess of the 

 origin of ferments in animals. Ebstein and Griitzner*, in their 

 researches upon digestion, found that a glycerin extract of much 



greater digestive power could be obtained from a gastric mucous 

 membrane which had been previously treated with dilute hydro- 

 chloric acid than from a perfectly fresh one ; but of this fact 

 they volunteered no explanation. Heidenbaint, in his re- 

 searches on the digestive ferment of the pancreas, found that 

 from this organ also a more active glycerin extract could be ob- 

 tained when it had been previously treated with dilute acid. 

 On the evidence of his own experiments, and on that furnished by 

 those of Ebstein and Griitzner, he has arrived at the following 

 conclusions. He believes that the gland-cells do not directly 

 secrete the digestive ferment, but that they give rise to a neu- 

 tral substance, which he terms Zymogen, consisting of a com- 

 bination of the ferment with (probably) an albuminoid. It is 

 only when this zymogen is decomposed by the action of various 

 agents (dilute acids, moisture, warmth, &c.) that the ferment is 

 set free in the active state, in the gastric juice as pepsin, in the 

 pancreatic secretion as pancreatin. 



From a consideration of these views, I inferred that the great 

 difference in rapidity of action existing between the process of 

 digestion when the secretion itself was used, and that when 

 the glycerin extract was used, might be due to the fact that m 

 the former case the ferment was present in its free state, whereas 

 in the latter much of it might still be in the form of zymogen. A 

 therefore endeavoured to discover if by any means I could ob- 

 tain a more active glycerin extract. I treated some pitchers 01 

 Nepenthes (hybrida and gracilis} with dilute acetic acid (1 p er 

 cent.) for twenty-four hours previously to the preparation of the 

 glycerin extract ; and I instituted comparative experiments be- • 

 tween the glycerin extract so obtained and the glycerin extract 



* Pfliiger's Arch, fur die ges. Phys. 1873, Bd. viii. pp. 122-151. 

 f Ibid. 1875, Bd. x. p. 581. 



