250 DIGESTION. 



acids and glycerine, while Germans can scarcely perceive that the 

 two substances form even an emulsion. To speak candidly, we 

 are unable to find any motive for the action of the bile, or for its 

 effusion into the intestine, from the many conflicting opinions on 

 the subject, all of which, however, have been deduced from obser- 

 vations ; and do we even to this day know what actually becomes 

 of the resinous biliary acids in the intestine ? Who could have 

 anticipated from our previous knowledge, that an isolated loop of 

 intestine, with its slightly alkaline contents, would be able to digest 

 flesh ? and finally, what rich although as yet inexplicable results 

 may we not hope to obtain from Ludwig's continued experiments 

 regarding the influence of the nerves on the secretion of the diges- 

 tive juices ! In short, the intestinal canal always presents itself 

 to us as the scene of a number of highly mysterious processes, and 

 our ideas still range unsatisfied around the as yet unopened portals 

 of this almost impenetrable subject. Hence, if we see even the 

 most acute investigators rapidly passing from one view to another, 

 we must recollect that what we regard as true is in this case always 

 dependent on the stage of development which scientific inquiry has 

 attained at the time. 



In the digestive process, as in many other phenomena in the 

 living body, it might seem possible to anticipate the laws accord- 

 ing to which these processes, which are still obscure to us, run their 

 course ; but we are as little able to draw any conclusions regarding 

 the causal connexion of the phenomena as regarding the primary 

 object of each perceptible action. Hence we must rest satisfied, 

 according to the manner of our forefathers, with a mere representa- 

 tion, when we are unable to apprehend the internal connexion of 

 different phenomena. Thus we have such a representation when, 

 for instance, we compare the digestive canal with its minutest 

 absorbents to the roots of a plant, and then show that the animal 

 carries about and contains within itself the roots or radicles by 

 which it absorbs its proper nourishment, while the plant is firmly 

 rooted in the soil from which it draws its nutriment. The more 

 striking and apparently applicable such a picture may at first sight 

 appear, the more glaringly obvious become the differences on closer 

 investigation, and hence we may perhaps be permitted to devote a 

 few moments to the consideration of the above comparison. If, in 

 the first place, we take into consideration the radicles, which in 

 the higher animals pass into the internal surface of the intestine, 

 we come upon the capillaries, which envelope the whole canal with 

 the most delicate network, and then upon organs which in their 



