ABSORPTION. 253 



run through the whole intestinal canal, almost from its beginning 

 to its termination. 



In the root-fibrils of the higher plants, whose leaves, twigs, 

 stems, and coarser roots are, as is well-known, invested by a 

 membrane that possesses only little permeability for liquids, we 

 find no canals or special organs corresponding to our ordinary ideas 

 of absorption, but rows of cells which from the delicacy of their 

 walls are specially adapted to endosmotic actions. It requires no 

 very profound knowledge of vegetable physiology to comprehend 

 that during the life of a plant, and even for some time after its 

 death, the cells of the root-fibrils continue to have the opportunity 

 of absorbing water and aqueous solutions from the moist soil sur- 

 rounding them, while they continue to be deprived of this fluid by 

 the cells lying immediately superior to them. If we only consider 

 the enormous evaporating surface which plants present in their 

 leaves and their stomata, and how these organs are exposed to 

 relatively higher degrees of temperature and a perpetually varying 

 atmosphere, we shall readily perceive how the juices occurring in 

 the leaves and in their vicinity gradually become concentrated, and 

 how the cells inclosing them must collapse if those in their imme- 

 diate vicinity do not transfer to them a portion of their water ; their 

 own fluid contents thus becoming more concentrated, and a neces- 

 sity for a continuous transmission of a similar kind downwards to 

 the cells of the root-fibrils being thus established. At certain 

 periods the formation of organic matter from the previously liquid 

 or gaseous nutrient matter of the plant may also, in no slight 

 degree, contribute to the increased concentration of the cell-juices, 

 and may thus react on the absorption through the roots. Finally, 

 if we bear in mind that the cells contain solutions of protein-sub- 

 stances, dextrin, sugar, &c., substances which possess far less 

 diffusibility than the salts which are contained in the moisture of 

 the soil, we are compelled to admit that plants present all the con- 

 ditions necessary for calling into play the most active endosmotic 

 currents, and that the terminations of the roots are excellently 

 adapted for the most abundant absorption. The admirable experi- 

 ments of Hales may serve to corroborate the correctness of the 

 view, that it is only mechanical laws which are here in force, 

 although some individual points still require elucidation in respect 

 to the process of absorption through the roots. 



We have already taken an opportunity of remarking that the 

 capillaries, which form a network around the intestinal canal, 

 constitute the medium through which a great part of the fluid 



