Chap. VL] 



DIGESTION. 



81 



glands are excited by the absorption of a minute quantity 

 of already soluble animal matter, a conclusion which is sup- 

 ported by what we shall hereafter see with respect to Dionsea. 

 Dr. Hooker likewise found that, although the fluid within the 

 pitchers of Nepenthes possesses extraordinary power of di- 

 gestion, yet when removed from the pitchers before they have 

 been excited and placed in a vessel, it has no such power, al- 

 though it is already acid; and we can account for this 

 fact only on the supposition that the proper ferment is not 

 secreted until some exciting matter is absorbed.* 



On three other occasions eight leaves were strongly ex- 

 cited with albumen moistened with saliva; they were then 

 cut off, and allowed to soak for several hours or for a whole 



[With regard to Drosera 

 Messrs. Rees and Will C Bot. 

 Zeitung,* 1875, p. 715) state that 

 a glycerine extract of Drosera 

 leaves In a state of unexcited 

 secretion, and fairly free from 

 Insects, had no digestive action. 

 But that the same extract, arti- 

 ficially acidulated, digested fibrin 

 thoroughly well. 



The authors believe that the 

 natural acid of the glands was 

 possibly destroyed in the process 

 of preparing the extract. No 

 conclusion can therefore be 

 drawn from their results as to 

 the acidity of unexcited leaves. 

 It is probable, however, Judging 

 from Von Gorup's work on Ne- 

 penthes, that Drosera does not 

 secrete the requisite amount of 

 acid until it has been stimulated 

 by the capture of Insects. Rees 

 and Will's experiments are not 

 quite conclusive on this point, 

 but they tend to show that what 

 Is wanting In the secretion of 

 unexcited leaves is the acid, not 

 the ferment. The experiments 

 of Von Gorup and Will on Ne- 

 penthes, as given In the ' Bot. 

 Zeltung,' 1876, p. 473, do not con- 

 firm Hooker's results on Nepen- 

 thes. The authors state that the 

 secretion collected from pitchers 

 which are free from Insects is 

 neutral, while the fluid of pitch- 

 ers which contain the remains 

 of insects is distinctly acid. The 

 neutral secretion of the unex- 

 cited pitchers has no digestive 

 power until It Is acidulated, 

 when It rapldiv dissolves fibrin. 



It seems, therefore, that the 

 analogr with animal digestion 

 polnteo out at p. 106 does not 



altogether hold good. For Schlff 

 states that in the gastric juice 

 produced by mechanical irrita- 

 tion, the element absent is the 

 ferment, not the acid. 



On the other hand an Inter- 

 esting point of resemblance of a 

 dififerent kind has been made out 

 by Vines in his paper on the di- 



festlve ferment of Nepenthes 

 Journal of the Linn. Soc' vol. 

 XV. p. 427; also, ' Journal of 

 Anatomy and Physiology,' series 

 II. vol. xl. p. 124). 



The work was undertaken In- 

 dependently of Von Gorup and 

 carried out by a different meth- 

 od, namely, the preparation of a 

 glycerine extract. Vines having 

 found that the extract was far 

 less active than the natural se- 

 cretion used by Von Gorup, was 

 led to an Interesting explanation 

 of this fact by Ebsteln and Grtttz- 

 ner's work on animal digestion. 

 These writers show that the 

 glycerine extract gains in diges- 

 tive activity If It is prepared 

 from mucous membrane previ- 

 ously treated with acid. Vines 

 accordingly treated Nepenthes 

 with one per cent, acetic add 

 for 24 hrs. previously to the 

 preparation of the extract, and 

 thus obtained glycerine of much 

 greater peptic activity. This 

 fact would lead us to believe 

 that the act of secretion In Ne- 

 penthes Is preceded by the pro- 

 duction of a mother substance, 

 or pepsinogen, from which the 

 peptic ferment Is formed by ac- 

 tion of add Just as the pancre- 

 atic ferment may, according to 

 Heldenhaln, be produce<l by the 

 action of addon zymogen. F. D.] 



