2& 



GASES IN THE STOMACH. 



fistula into the stomach of a dog. Pavy did the same with the ear of a rabbit, and in both the 

 objects introduced were digested. [Frenzel has modified this experiment, and shown that the 

 legs of a living frog are digested by artificial gastric juice, the tissues being first killed and then 

 digested. His experiments go to show that the alkalinity of the blood is not the protective 

 medium. ] The margins of a gastric ulcer and of gastric fistulse in man are attacked by the 

 gastric juice. John Hunter (1772) discussed the question why the stomach does not digest 

 itself. Not unfrequently after death the posterior wall of the stomach is found digested, [more 

 especially if the person die after a full meal and the body be kept in a warm place, whereby the 

 contents of the stomach may escape into the peritoneum. CI. Bernard showed, that if a rabbit 

 be killed and placed in an oven at the temperature of the body, the walls of the stomach are 

 attacked by its own gastric juice. Pishes also are frequently found with their stomach par- 

 tially digested after death]. It would seem, therefore, that, so long as the circulation continues,* 

 the tissues are protected from the action of the acid by the alkaline blood ; this action cannot 

 take place if the reaction be alkaline {Pavy). [This, however, does not explain why the pan- 

 creatic juice does not digest the pancreas.] Ligature of the arteries of the stomach, causes 

 digestive softening of the gastric mucous membrane. The thick layer of mucus may also aid in 

 protecting the stomach from the action of its own gastric juice {CI. Bernard). 



167. GASES IN THE STOMACH. The stomach always contains a certain 

 quantity of gas, derived partly from the gases swallowed with the saliva, partly from 

 gases which pass backwards from the duodenum. 



The air in the stomach is constantly undergoing changes, whereby its O is 

 absorbed by the blood, and for 1 vol. of O absorbed 2 vols, of C0 2 are returned to 

 the stomach from the blood. Hence, the amount of O in the stomach is very 

 small, the C0 2 very considerable (Planer). 



Gases in the Stomach. Vol. per cent. {Planer). 



By the acid of the stomach a part of the C0 2 is set free from the saliva, which 

 contains much C0 2 .( 146). The N acts as an indifferent substance. 



Abnormal development of gases in persons suffering from gastric catarrh, occurs when the 

 gastric contents are neutral in reaction ; during the butyric acid fermentation H and C0 2 are 

 formed ; the acetic acid and lactic acid fermentations do not cause the 

 formation of gases. Marsh-gas (CH 4 ) has been found, but it comes from 

 the intestine, as it can only be formed when no O is present ( 184). 



168- STRUCTURE OF THE PANCREAS. The pancreas is a com- 

 pound tubular gland, and in its general arrangement into lobes, lobules, 

 and system of ducts and acini, it corresponds exactly to the true 

 salivary glands. The epithelium lining the ducts is not at all, or only 

 faintly, striated. The acini are tubular or flasked-shaped, and often 

 convoluted. They consist of a membrana propria, resembling that of 

 the salivary glands, lined by a single layer of somewhat cylindrical 

 cells, with a more or less conical apex, directed towards the very narrow 

 lumen of the acini. [As in the salivary glands, there is a narrow 

 intermediary part of the ducts opening into the acini, and lined by 

 flattened epithelium.] The cells lining the acini consist of two zones 

 (fig. 186) : 



(1) The smaller outer or parietal layer is transparent, homogeneous, 

 sometimes faintly striated, and readily stained with carmine and log- 

 wood ; and (2) the inner layer (Bernard's granular layer) is granular, and stains but slightly 

 with carmine (fig. 186). It undoubtedly contributes to the secretion by giving off material, 

 the granules being dissolved, while the zone itself becomes smaller. The spherical nucleus lies 

 between the two zones. [The lumen of the acini is very small, and spindle-shaped or branched 

 cells (centro-acinar cells) lie in it, and send their processes between the secretory cells, thus 

 acting as supporting cells for the elements of the wall of the acini. During secretion, there is a 



Fig. 186. 



Section of the fresh 



pancreas. 



