544 MECHANISM OF SECRETION OF GASTRIC JUICE, 



described till some years later. Langley l showed that the method of 

 separating pepsin from pepsinogen was applicable also to the remiin, 

 since rennet-ferment was destroyed by sodium carbonate, whilst rennet- 

 zyinogen is affected much less powerfully. Hammarsten has also shown 

 that the amount of rennet-ferment that can be extracted from the 

 cardiac end of the stomach is proportionally much greater than that 

 obtainable from the pyloric mucous membrane. Griitzner 2 has shown 

 that in the gastric glands of the dog, the rennet-ferment diminishes in 

 amount during digestion, and that the amount of diminution runs 

 parallel to that of pepsin. It seems that where pepsin is greatest in 

 quantity, there also is rennet-ferment most abundant, and it seems 

 probable that the granules of the chief cells contain the zymogens both 

 of rennet-ferment and pepsin. We cannot say whether the granules are of 

 one kind or whether there are separate forms of granules for the separate 

 ferments. But though in general the zymogen of the rennet-ferment, 

 and not the actual ferment, is existent in the gastric cells, yet in 

 some cases, e.g. the calf and sheep, the zymogen is presumably in a 



2 4 



8 10 12 14 16 18 20 22 24 26 28 30 32 



34 



FIG. 44. The figures at the abscissa on the base line refer to the 

 number of hours elapsed since the last meal. The length of the 

 ordinates indicates the amount of pepsin yielded at any time. F is 

 the record of variation in the fundus mucous membrane, P of 

 variation in the pyloric mucous membrane. After Griitzner. 



much less stable condition, for a watery extract of the stomach of 

 these animals yields rennet-ferment in large quantities. As regards 

 the differentiation of the rennet-ferment from the proteolytic, they can 

 be separated from one another by chemical means, although we have 

 no morphological signs of their distinction. Hammarsten's method of 

 separating the two ferments chemically depends upon the fact that 

 the gradual addition of lead acetate precipitates the pepsin sooner than 

 the remiin. 3 



The variations in the amount and composition of gastric juice 

 during the course of digestion. The amount of pepsin that can be 

 extracted from the mucous membrane has been estimated by Griitzner. 4 

 He compared concurrently that obtained from the fundus with that 

 yielded by the pyloric region. In the above chart (Fig. 44), which shows 

 the chief variation during the lapse of some hours after a meal, the most 



1 "On the Destruction of the Ferments of the Alimentary Canal," Journ. PhysioL, 

 Cambridge and London, 1882, vol. iii. 



2 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xvi. 



3 The conditions of formation of the hydrochloric acid of the gastric juice are treated 

 of in a preceding article (see pp. 351 et seq.). 



4 Arch.f. d. ges. PhysioL, Bonn, 1879, Bd. xx. 



