254 PHYSIOLOGY CHAP. 



blooded or of warm-blooded animals from the solvent power of the 

 gastric juice. Pavy's experiments were immediately confirmed by 

 Bernard, and in 1862 by Inzani and Lussana also. 



Pavy explained the resistance of the living stomach to the 

 action of the gastric juice as follows. Since this' organ is highly 

 vascular, the alkalinity of the blood and lymph neutralises the 

 acidity of the gastric juice in proportion as the mucous membrane 

 is impregnated, and throws the pepsin out of court. The rabbit's 

 ear and the frog's leg, being poor in vessels, are incapable of 

 neutralising the juice, and become digested. In support of his 

 argument, Pavy succeeded in obtaining auto-digestion of certain 

 zones of the dog's stomach, in which he had interrupted the 

 circulation, a fact subsequently confirmed by Virchow, Panum, 

 and Cohnheim. We shall presently see the weak points of this 

 theory. 



Bernard explained the phenomenon on the assumption that 

 the gastric mucosa is protected during life by its epithelium, " qui 

 se detruit et se renouvelle avec une grande facilite ; de la, quand 

 la vie cesse, sa rapide alterabilite." Next to the epithelium he 

 attached great importance to the layer of mucus that varnishes the 

 stomach walls, so that " le sue gastrique se trouve comme dans une 

 vase de porcelaine." This same view was also adopted by Inzani 

 and Lussana, although, with the object of confirming it, they 

 destroyed or modified the protective epithelium of living animals 

 by various means, without observing any subsequent digestion of 

 the gastric walls. 



SchifFs experiments (1868) plainly showed that the epithelium 

 is not indispensable to the integrity of the gastric mucosa. He 

 was unable to produce lesions of the mucous membrane in fistula- 

 dogs, after scratching off the epithelium of the stomach in places 

 with his nail. He kept a dog, in which he had produced an open 

 sore in the mucous membrane, alive for more than six weeks 

 without inducing auto-digestion of the stomach walls. He found, 

 indeed, that dead epithelium is also highly resistant to digestion, 

 for when he repeated Spallanzani's experiment of introducing 

 pieces of ox-stomach into the stomach of a dog, he found that the 

 muscular coat became soft and was partially digested, while the 

 epithelium, under the microscope, remained wholly intact. 



Gaglio (1884) took up this interesting question in our 

 laboratory, starting from an acute criticism of Pavy. If living 

 tissues are digested by the gastric juice, on what does the special 

 immunity of the stomach depend ? Is it really a universal fact 

 that all living tissues save the stomach are attacked and digested 

 by the gastric juice ? Seeing that the pancreas secretes a juice 

 that has a peculiarly solvent action on proteins, which are 

 digested along the entire tract of the small intestine, why did 

 Pavy not ask himself why the pancreas and intestine also escaped 



