536 MECHANISM OF SECRETION OF GASTRIC JUICE. 



it may be regarded as established that the pyloric glands do secrete 

 pepsin. 



The results of experiments that have been made to ascertain 

 whether pepsin or pepsinogen is contained in saline extracts of the 

 pyloric mucous membrane, lead to the conclusion that pepsinogen 

 may be present. The fact that the amount of pepsin obtainable from 

 the pyloric mucous membrane is increased rather than diminished l as 

 digestion advances is susceptible of one of two explanations. It may 

 be that during digestion the intracellular formation is more rapid than 

 the secretion, and thus an absolute increase in the pepsin contents of 

 the cells occurs. Or it may be that in course of absorption of certain 

 products of digestion by the pyloric mucous membrane, a certain 

 amount of pepsin becomes " infiltratec? " in the membrane. At any 

 rate, there is something fundamentally different in this respect between 

 the secretion of pepsin at the pyloric end of the stomach and in 

 the fundus glands, for in the latter the amount of pepsin decreases 

 as digestion advances, whilst in the former there is an increase. Nor 

 is there any evident change in the histological appearance of the pyloric 

 cells corresponding to a secretory process. It is probable, as Langley 

 has suggested, that the precursor of pepsin (" mesostate," as it may con- 

 veniently be called) is not so highly specialised as in the fundus glands ; 

 or there may be a series of mesostates, the more highly developed 

 splitting off the enzyme earlier than the more lowly. The observations 

 of King, which are confirmatory of the much older observations of 

 Briicke, that a series of hydrochloric acid extracts will continue to show 

 proteolytic powers, suggests that there are several mesostates of 

 different grades coexistent in the cell. It is, moreover, possible that 

 only in the most highly specialised mesostates does the condition of 

 secretory granules obtain. From all this it appears probable that the 

 formation of pepsin is a subsidiary function of the pyloric mucous 

 membrane, and that it yet remains to be discovered whether the cells 

 of the pyloric glands possess other more important functions. 



The methods of obtaining gastric juice. The older observers 

 obtained samples of gastric juice by causing animals to swallow hollow 

 perforated balls, containing pieces of sponge. In this way Keaumur, 2 

 Stevens, 3 and Spallanzani 4 obtained a fluid which caused meat to 

 become digested, and which was marked by antiseptic properties. 

 Tiedemann and Gmelin 5 made fasting animals swallow pebbles, which, 

 acting as mechanical irritants, permitted a certain quantity of gastric 

 juice to be secreted, and this was obtained by killing the animals shortly 

 afterwards. 



Beaumont had under observation in 1822 a man who had a gun-shot 

 wound in the left side. There resulted from this a permanent fistula 

 into the stomach. A valve, formed of the mucous membrane, became 

 established over the opening, and on depressing this, introducing a 

 tube, and turning the man on his left side, a flow of gastric juice was 

 obtained. 



1 See Griitzner's chart (Fig. 44), in the section on the variations in composition of gastric 

 juice during digestion. 



2 " Sur la digestion/' Hist. Acad. roy. d. sc. de (Paris], 1752. 



3 "De alimentorum concoctione," Ed'in., 1877. 



4 "Experiences sur la digestion de I'homme et de diffe'rentes especes d'aniraaux," 

 Geneve, 1783. 



5 "Die Verdauung nach Versuchen," 1826. 



