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 1 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 " infiltrated " 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 Klug, 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 Eeaumur, 2 
Stevens, 3 and Spallanzani i 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," Edin., 1877. 
4 " Experiences sur la digestion de l'homme et de differentes especes d'animaux," 
Geneve, 1783. 
5 "Die Verdaimng nach Versuchen," 1826. 
