272 DIGESTION. 



mineral acids ; but all experiments which have hitherto been made 

 to convert gum into sugar, or into any other substance, by means of 

 the digestive fluids, such as natural or artificial gastric juice, mixed 

 saliva, or pancreatic juice, have yielded thoroughly negative results. 

 Frerichs* found that gum remained entirely unchanged when 

 digested as long as 48 hours with saliva and gastric juice, nor was 

 it altered after having remained for 3 hours in the stomach of a 

 dog, both when it was introduced through a fistulous opening and 

 by the mouth. Blondlotf instituted a similar experiment. I 

 found! that the gum not only always remained unchanged during 

 lactic acid fermentation, and during the conversion of starch into 

 sugar by diastase, saliva, or pancreatic juice, but also convinced 

 myself, by parallel experiments, that the presence of this body 

 invariably retarded that process. I found, from quantitative deter- 

 minations, that after the gum had been digested for three or four 

 days in a fermenting or digesting mixture, nearly the original 

 quantity might be again recovered. These experiments, therefore, 

 render it very improbable that even a small portion of the gum is 

 converted into sugar during digestion. If, then, gum be actually 

 subservient to the purposes of animal life, it only remains to be 

 assumed that this body may be resorbed in an unchanged state 

 from the alimentary canal, either by the blood-vessels or the 

 lacteals. Tiedemann and Gmelin fed a goose exclusively on 

 gum for sixteen days, when it died; they found in the excrements 

 unchanged gum, which was also present in the acidly reacting 

 contents of the small and large intestines. Boussingault|| caused 

 a duck to swallow 50 grammes of gum-arabic, and in the course of 

 nine hours 46 grammes were recovered from the excrements. I daily 

 injected into the stomach of an old rabbit, which w r as otherwise 

 fed on cabbage-leaves, 10 grammes of gum-arabic dissolved in 90 

 parts of water; the excrements retained their ordinary form and 

 consistence, but gum was easily recognised in them. The daily 

 urine was collected, strongly concentrated, and treated with 

 absolute alcohol, and the undissolved residue was then extracted 

 with cold water. The aqueous solution, even in its most con- 

 centrated state, did not give any reaction corresponding to the 

 presence of gum, either when treated with silicate of potash, with 



* Handworterbuch der Physiologic. Bd. 3, Abth. 1, S. 806. 



f Trait^ de la digestion, p. 297. 



$ Simon's Arch. f. Chem. u. Mikrosk. Bd. 1, S. 76-82. 



Verdauung nach Versuchen. Bd. 2, S. 186. 



|| Ann. de Chim. et de Phys. 3 Ser. T. 18, p. 444. 



