Chap, xil] OF DIGESTION. 185 



Dextrine, bread, the gelatine of bone, divers peptones, are 

 peptogens. 



Tbe nox-mal absorption of peptogenical substances into tbe small 

 intestine bas not apparently the result of charging with pepsine 

 the stomachal glands, and yet this effect seems to be obtain- 

 able by the injection of these substances into the serous vessels, 

 the subcutaneous cellular tissue, the stomacli, and the rectum. 



Pepsine is the special agent for the transformation of albu- 

 minoidal alimentary substances into peptones isomeric, but 

 soluble, assimilable, and no longer coagulating through heat. 



The two agents, acid and peptic, evaporate, moreover, in their 

 transformation, and are both necessary. Without the acid the 

 pepsine has no longer any action. Also when the alkaline 

 bile accidentally reflows into the stomach and neutralises ■ the 

 gastric juice, the work of digestion is suddenly arrested. The 

 acid disaggregates and softens the albuminoidal substances, and 

 by this preparatory modification renders the peptic action 

 possible. 



By observing the phases and phenonmena of digestion in the 

 stomach through the process of gastric fistulse, and, better still, 

 by recurring to artificial digestions, experimenters have succeeded 

 in determining with sufficient precision the action of pepsine on 

 the diverse categories of aliments. 



In efEect digestion is merely the result of simple, physical, and 

 chemical phenomena, which are accomplished very well apart 

 from the stomach. It is to Reaumur that the honour is due of 

 being the first to make trial of ax-tifioial digestions.^ But Spallan- 

 zani was the first who made successful trial thereof. Eberle 

 prepared artificial gastric juice by softening a stomachal mucous 

 membrane in water at 30° Reaumur, then in adding drop by drop 

 chlorohydric acid, or acetic acid. Miiller, Schwann, Tiedemann, 

 and Gmelin, Burkinje, Pappenheim, Lauret and Lassaigne, made 

 analogous experiments, which have since been often repeated. 



It is generiiUy of the caillette of a ruminant that we must 

 ^ Hintoire des I'Acadimie des Sciences, 1752. 



