COMPOSITION OF GASTRIC JUICE. 157 



different ages, since M. Wasmann has remarked that the pepsin of the 

 stomach of the pig is entirely destitute of the power to coagulate milk, 

 although the pepsin of the stomach of the calf possesses it in a very high de- 

 gree; from which he is led to suppose that the power of the latter depends 

 upon a particular modification of pepsin, or perhaps upon another substance 

 accompanying it, which ceases to be formed when the young animal is no 

 longer nourished by the milk of its mother. 1 



109. The peculiar organic constituent of the Gastric juice, to which the 

 name of Pepsin ( 54) has been given, and which, according to Briicke, 2 is 

 neither an albuminous substance nor a ferment, appears to be secreted and 

 stored up in the cells of the stomach in a neutral state during the intervals 

 of digestion, and to be only mingled with the acid at the moment of dis- 

 charge. 3 Bru'cke noticed, that if the stomach of an animal were thoroughly 

 washed with water till all trace of acidity was removed, a fresh portion of 

 pepsin, possessing a perfectly neutral reaction, could be obtained on further 

 maceration ; and Bernard found that on injecting successively lactate of iron 

 and ferrocyanide of potassium into the jugular vein of a rabbit, no blue dis- 

 coloration of the blood, secretions, or tissues generally was observable on ac- 

 count of their alkaline reaction, though this could be immediately produced 

 by the addition of sulphuric or other acid. On examining the stomach, 

 however, he found that whilst the gastric follicles were free from color, the 

 surface of the mucous membrane was uniformly tinted. From these experi- 

 ments, the inference may be fairly drawn that the pepsin of the gastric 

 juice is secreted by the cells lining the gastric follicles, whilst the acid is 

 formed, or at least excreted, by the most superficial cellular layers of the mu- 

 cous membrane. 1 It must not be supposed that the whole of the albuminous 

 compounds introduced into the stomach under ordinary circumstances are 

 converted into peptone. Some forms of albumen, as white of egg, undergo, 

 in part, direct absorption, whilst a part is absorbed as soon as it is converted 

 into syntonin (Bru'cke). The solvent power of the gastric juice in the living 

 body is difficult to determine, since it differs with the animal and with the 

 nature of the food. The gastric juice of Carnivora is the most active, then 

 that of Herbivora, whilst that of man appears to be comparatively feeble; 

 and in this point, therefore, he appears to be most closely allied to the Her- 

 bivora. Lehmauu and Corvisart estimated that on the average 20 oz. 

 of the gastric juice of the dog were required to dissolve 1 oz. of coagulated 

 albumen ; but M. Koopmaus showed that whilst the strongly acid gastric 

 juice of the Caruivora was best adapted for the solution of animal albumen, 

 the weakly acid gastric juice of the Herbivora was far more efficacious in 

 dissolving vegetable albumen or gluten. In Brucke's experiment with arti- 

 ficial gastric juice, 6 it was found that at a temperature of 65 F., the most 

 active fluid for raw fibrin contained 12^ to 15 grains of muriatic acid in one 

 litre (1.76 pints), whilst the most active fluid for albumen, coagulated by 



1 See Prof. Graham's Elements of Chemistry, pp. 1031-1033. 



2 Vorlesungen iiber Physiologie, 1874, p. 295. 



3 See Bernard, Le9ons, "1859, p, 376 ; and Schitf, Physiologie de la Digestion, 18G8, 

 e9<>ns 21-24. 



4 Schiff considers that, as in the case of the Pancreas, a kind of " charging " of the 

 glandular follicles occurs during the intervals of digestion, the pepsin being derived 

 from certain peptogenic materials in the blood supplied by the previous digestion of 

 albuminous compounds, or of dextrin. This view is strongly opposed by Fick (Ver- 

 hand. d. Phys. Med. Gesells , N. F., B. ii, 53), who found that the stomach of a dog 

 secreted active gastric juice fifteen hours after the last full meal, and that in rabbits, 

 fasting did not diminish the digestive activity of the stomach, whilst the ingestion 

 of dextrin did not augment it. 



6 Nederland. Lancet, t. v, 1856. Op. cit., p. 300. 



