258 DIGESTION. 



Liebig, Jolly, Ludvvig, &c., we have no comprehensive theory of 

 endosmosis ; yet without such a theory we are as little able to 

 comprehend the causal connection of the complicated endosmotic 

 processes exhibited in the living body, as to deduce a priori the 

 result of certain endosmotic efYects depending upon definite 

 external circumstances. We cannot hope to establish a theory of 

 endosmosis before the laws of the diffusion of liquid fluids dis- 

 covered by Graham have been elucidated, and the influence of the 

 different nature of porous intermediate walls upon diffusive fluids, 

 that is to say, the relation between diffusion and endosmosis, 

 together with all the circumstances by which the latter is deter- 

 mined, has been adequately investigated. Not until then will it 

 be possible to prove or refute the co-operation of the vital 

 capacities of the organs during absorption. If, however, we still 

 continuously encounter a number of phenomena in the living body, 

 which seem to be at variance with the endosmotic laws \vith which 

 we are at present acquainted, and if many interesting experiments 

 (as, for instance, those of Bocker*) still appear to defy expla- 

 nation by simple molecular motion, this merely proves that we are 

 still deficient in the physical knowledge necessary for the com- 

 prehension, in a physical sense, of the causal connection of such 

 phenomena. We are further taught that, in order adequately to 

 comprehend the mechanism of absorption, our first task ought to 

 be that of accurately examining the physical conditions of endos- 

 motic actions, and comparing them with the relations which exist 

 in the living body. A great step forwards in science is, however, 

 always made, when we arrive at a clear conception of the problems 

 which we are especially called upon to solve. 



As we cannot discover the slightest logical justification in the 

 still imperfectly elucidated processes of absorption for the assump- 

 tion of vital forces having the power of directing one substance 

 hither and another thither, or of taking up what is useful and 

 rejecting what is noxious, we are thrown back upon the pro- 

 position from which we started, namely, that the capacity of a 

 substance for absorption stands in the same intimate relation to 

 its chemical quality as all its essential qualities do to one another 

 (compare vol. i, p. 404). If the capacity of a substance for 

 absorption be not a mere irrelevant property, those substances 

 which are exposed to similar relations of absorption must generally 

 present very definite analogies with one another ; the capacity for 

 absorption does and must always coincide with certain other 

 * Rhein. Monatsschrift. 1840, S. 754-759. 



