218 METAMORPHOSIS OF TISSUE. 



in considerable quantity in the herbivora is so rapidly removed 

 from the blood either by respiration, or where this is inadequate for 

 the purpose, by the urine (see note to vol. i, p. 293, in the Appendix). 



We are still very imperfectly acquainted with those carbo- 

 hydrates and their metamorphic products which occur in the 

 animal juices ; but it is very probable that in addition to Scherer's 

 inosite, we may find other similar indifferent substances amongst 

 the extractive matters of the animal body. We are, however, 

 acquainted with many of the acids which are formed in the animal 

 body from the carbo-hydrates, as for instance, formic, acetic, and 

 butyric acids, which occur in large quantities in the sweat, and, in 

 addition to these, lactic acid, which is associated with them in 

 the muscular juice, in the parenchymatous juice of the smooth mus- 

 cles of the stomach, of the intestinal canal, and of the bladder, as 

 well as in the middle arterial coat. 



We have already seen that in the small intestine free acid is 

 commonly found as far as the middle of the ileum, notwithstanding 

 the access of pancreatic juice and bile ; here its use is assuredly 

 not merely to dissolve the nitrogenous substances which were 

 not digested in the stomach, but also essentially to promote the 

 resorption of the soluble constituents of the chyme. The admi- 

 rable experiments of Jolly* have shown us, that the endosmotic 

 equivalents of the acids are extremely small, as compared with 

 the equivalents of the alkalies, for he found the equivalent of 

 hydrated sulphuric acid = 0*350, but that of hydrated potash 

 = 215'725, and Grahamf found the diffusibility of the acids ex- 

 tremely great, and that of the alkalies very small; it, therefore, 

 stands in an inverse relation to the endosmotic equivalents. Graham 

 observed amongst other things that an acidified albuminous fluid 

 was much more diffusible than an alkaline solution of albumen. 

 Whenever, therefore, an alkaline and an acid fluid are separated 

 by a membrane, the main current of the interchanging fluids will 

 always be directed towards the alkaline side, and hence it is most 

 obvious that the acid of the small intestine must aid in essentially 

 promoting and facilitating the resorption of the contents. There 

 can therefore be no doubt that the carbo-hydrates, or rather their 

 acid products of metamorphosis, control some important function 

 in the intestinal canal which does not stand in any direct relation 

 to the process of respiration. We need hardly have recourse to 



* Zeitschr. f. rat. Med. Bd. 7, S. 83-147. 



t Ann. dc Chim. et de 1'hys. 3 Se'r. T. 29, p. 197-229 [or Phil. Trans, for 

 1850, p. l.J 



