158 OF FOOD, AND THE DIGESTIVE PROCESS. 



heat, contained from 18.5 to 24.7 grains of this acid in the litre. When 

 fibrin or other albuminous compound is acted on by artificial gastric juice, it 

 swells up, and according to Briicke, 1 becomes converted into a substance 

 identical with syntonin, which is gradually changed into peptone, and subse- 

 quently undergoes solution. . The conversion of albumen into peptone, 

 Briicke regards as complete, when it is no longer capable of being precipi- 

 tated by potassium ferrocyanide. Meissner's description of the process is 

 more complicated. He considers the first product of the artificial digestion 

 of fibrin to be a substance insoluble in water, which soon splits up into para- 

 peptone (= syutouin) and into peptone (of which last he recognizes three 

 modifications, termed respectively, a, b, and c peptone) ; small quantities 

 of dyspeptoue, and of metapeptone, are also occasionally found. All 

 these substances are distinguished from one another by their relative solu- 

 bility in acids or in neutral solutions, and their precipitability by nitric acid 

 and potassium ferrocyauide. Gelatin and gelatin-yielding tissues, as con- 

 nective tissue, tendons, ligaments, etc., are only slowly acted on by the gastric 

 juice, the fluid resulting from their solution retaining for some time its power 

 of solidifying; ultimately, however, they are reduced to a syrupy fluid, the 

 osmotic powers of which are somewhat increased. 2 From the experiments 

 of Dr. Smith on Alexis St. Martin, it appears probable that the conversion 

 of starch or dextrin into glycose may be effected in the stomach to some 

 extent, since evidence of the presence of grape-sugar was found an hour and 

 a half after bread and water had been introduced through the fistulous ori- 

 fice, the man carefully avoiding to swallow his saliva during that period. 

 There seems also to be good evidence that cane-sugar may be converted 

 into grape-sugar. In both instances the active agent is probably the mucus 

 of the stomach. It has been noticed by Hoppe-Seyler, that when large quan- 

 tities of cane-sugar are taken, a condition of gastric catarrh, attended with 

 the secretion of much mucus, is induced, and that the cane-sugar then un- 

 dergoes, probably in consequence of its rapid transformation into grape- 

 sugar, speedy absorption. Oleaginous substances appear to be merely 

 liquefied and finely divided, in which state they are diffused through the 

 pulpy chyme. 



110. It is only when either alimentary or some other substances capable 

 of exciting irritation are present in the stomach, that the gastric juice is 

 poured forth. So long as it is empty, the secretion which moistens its walls 

 is neutral or even alkaline ; but as soon as food is taken, acid is poured forth, 

 and this in increasing quantities, until a certain time after the commence- 

 ment of the digestive process, when the acidity of the stomach is at its maxi- 

 mum. In proportion as the alimentary matter is dissolved, however, and is 

 either at once absorbed, or escapes through the pyloric orifice, the acidity of 

 the stomach diminishes; and as soon as its cavity is emptied, the secretion 

 of its walls is neutral again. 3 The circumstance that the stomach does not 

 itself undergo digestion, even when that process is being actively performed 

 on its contents, is of considerable interest, and must be attributed to the 

 saturation of the whole mucous membrane with blood containing a large 

 proportion of alkaline salts, for it has been shown by Dr. Pavy, that if one 

 or two vessels of the stomach be tied, the parts thus deprived of the circu- 

 lation of the blood rapidly undergo digestion, and perforating ulcers occur, 



1 Vorlesungen liber Physiologic, 1874, p. 301. 



z See Henle and Meissrier, Bericht, 1800, p. 209; nnd Hcnle and Pfeufter's Zeit- 

 pchrift, Bd. xiv, 1862, p. 303; Mohlenfeld, Pilugcr's Arcliiv, 1872, Bd. v, p. 381 ; v. 

 "Wittich, idem, p. 435. 



3 Sec Dr. Bence Jones, in the Medical Time?, June 14th, 1852; and Dr. Marcet, 

 Journal of the Chemical Soc., 1802. 



