76 DROSERA ROTUNDIPOLIA. [Chap. VL 



" fl. A third experiment of the same kind gave: 

 " Quantity of librin digested in four hours by 10 cub. cent, of 

 the liquid: 



"Hydrochloric acid .. .. 0.2915 



Propionic acid .. .. .. 0.1490 



Butyric acid 0.1044 



Valerianic acid 0.0520 



" Comparing, as before, the three last numbers with the first 

 taken as 100, the digestive power of propionic acid is represented by 

 16.8; that of butyric acid by 35.8; and that of valerianic by 17.8. 



" The mean of these three sets of observations (hydrochloric 

 acid being taken as 100) gives for 



" Propionic acid . . . . . . 15.8 



Butyric acid 32.0 



Valerianic acid . . . . . . 21.4 



" 7. A further experiment was made to ascertain whether the 

 digestive activity of butyric acid (which was selected as being 

 apparently the most eflicacious) was relatively greater at ordinary 

 temperatures than at the temperature of the body. It was found 

 that whereas 10 cub. cent, of a liquid containing the ordinary pro- 

 portion of hydrochloric acid digested 0.1311 gramme, a similar 

 liquid prepared with butyric acid digested 0.0455 gramme of fibrin. 



" Hence, taking the quantities digested with hydrochloric acid 

 at the temperature of the body as 100, we have the digestive power 

 of hydrochloric acid at the temperature of 16" to 18 Cent, repre- 

 sented by 44.9; that of butyric acid at the same temperature 

 being 15.6." 



We here see that at the lower of these two temperatures, hydro- 

 chloric acid with pepsin digests, within the same time, rather less 

 than half the quantity of fibrin compared with what it digests at 

 the higher temperature; and the power of butyric acid is reduced 

 in the same proportion under similar conditions and temperatures. 

 We have also seen that butyric acid, which is mtich more effica- 

 cious than propionic or valerianic acids, digests with pepsin at the 

 higher temperature less than a third of the fibrin which is digested 

 at the same temperature by hydrochloric acid. 



I will now give in detail my experiments on the digestive 

 power of the secretion of Drosera, dividing the substances 

 tried into two series; namely, those which are digested more 

 or less completely, and those which are not digested. We 

 shall presently see that all these substances are acted on by 

 the gastric juice of the higher animals in the same manner. 

 I b% leave to call attention to the experiments under the 



