302 DIGESTION. 



specific permeability of the membranes does not, therefore, clear 

 up the obscurity regarding the absorption by the lacteals. 



We may not, perhaps, have sufficient grounds for the assump- 

 tion of an altogether special (or specific) permeability of the 

 different membranes ; we may well suppose that differences in 

 their thickness, tension, and other purely mechanical relations 

 render the membranes, which in a chemical point of view are 

 analogously constituted, more or less permeable for physically and 

 chemically differing substances, so that no individual membrane 

 could be characterised as absolutely impermeable. Independently 

 of the great similarity in the chemical constitution of these animal 

 membranes, those experiments on the resorbability of certain sub- 

 stances (poisons) through the blood-vessels or lymphatics, which 

 have given rise to so much literary discussion, are opposed to the 

 absolute impermeability of a membrane for the passage of certain 

 matters. Thus, for instance, it appears to us that, contrary to 

 Henle and Dusch's* view, it has been tolerably well proved by 

 the numerous experiments of Bischoff,f Ludwig,J and Stannius, 

 that the lymphatics can absorb strychnine, and convey it into the 

 blood, although far more slowly, and in smaller quantities, than 

 the capillaries. Hence we also believe that the caution which is 

 so necessary in this part of our inquiries demands that, instead of 

 assuming that a perfectly specific relation is shown by different 

 membranes towards different solutions, we should admit nothing 

 more than gradual differences in this respect. On this account we 

 have not ventured to maintain that albumen and fat, for instance, 

 are solely resorbed through the lymphatics, whilst salts and 

 alkaloids are alone resorbed through the blood-vessels. We must 

 not forget, in endeavouring to form some idea of absorption from 

 these experiments, that, on the one hand, we may probably still 

 be ignorant of the physical laws by which those molecular motions 

 are to be explained, and that, on the other hand, we may not be 

 sufficiently well acquainted with the course of those phenomena 

 which manifest themselves in the villi and in their elements during 

 absorption. The comprehension of these phenomena is so ex- 

 tremely difficult, that even the best observers are not agreed in 

 reference to many of them. It must be further borne in mind 

 that chemical as well as molecular movements are here brought 



* Zeitschr. f. rat. Mod. Bd. 4, S. 368-374. 



t Ibid. Vol. 5, p. 293. 



t Ibid. 



Arch. f. physiol. Heilk. Bd. 9, S. 23. 



