356 CHEM1STR Y OF THE DIGESTIVE PROCESSES. 



It was long believed that this action was due to the growth of the 

 Bacillus acidi lactici on sugar only, either that of the food or that produced 

 by the action of ptyalin on the starch of the food. Briicke * has shown, 

 however, that starch can be also changed into lactic acid without con- 

 version by ptyalin, by demonstrating that soluble starch, erythrodextrin 

 and lactic acid, are found in the stomach of the dog after a meal contain- 

 ing boiled starch. Now the saliva of the dog contains 110 ptyalin, so that 

 these products must be formed directly from starch. Traces of sugar 

 are also found, and Briicke supposes that sugar is first formed by the 

 action of the bacterium but immediately becomes converted into lactic acid 

 by its further action. A similar change in starch paste takes place on 

 standing in the air. 



Goldschmidt 2 divides gastric digestion in the horse into four stages, 

 which are, however, not sharply markea off, but merge into one another. 

 (1) No proteolysis, acid reaction due to lactic acid. (2) Proteolysis 

 and amylolysis proceed together, both lactic and hydrochloric acids 

 present. (3) Stoppage of amylolysis in the middle part of the stomach, 

 in this portion only hydrochloric acid, elsewhere lactic acid. (4) Stop- 

 page of amylolysis everywhere ; hydrochloric acid only present in all 

 parts of the stomach. Ewald and Boas 3 describe a similar state of 

 affairs in the healthy human stomach under normal conditions after 

 a carbohydrate meal. In the first stage (from ten to thirty minutes after 

 the meal) lactic acid alone is present ; in the second, lactic and hydro- 

 chloric acids are present together, but the former rapidly disappears so 

 soon as any free hydrochloric acid is present ; and in the third stage, 

 hydrochloric acid alone is present. This disappearance of the lactic acid 

 is very interesting, as showing that it is rapidly absorbed in the 

 stomach. 



Other inorganic acids free in pure gastric juice besides hydrochloric 

 acid. It must not be assumed, from the usual mode of stating the 

 results of quantitative analysis of gastric juice, 4 that hydrochloric acid is 

 the only inorganic acid present in the gastric juice. All the phosphoric 

 acid is not united, in the gastric juice, to calcium, magnesium, and iron 

 to complete saturation, as usually set forth in such analytical results ; 

 nor are all the bases saturated by the hydrochloric acid, and only that 

 amount of hydrochloric acid free, which is left over after so saturating 

 them. 5 Suppose a solution in water of neutral chlorides is taken, say 

 such a solution as the gastric juice would be, minus its free hydrochloric 

 acid and its phosphates, and to this phosphoric acid is added. As soon 



1 Briicke, Sitzungsb. d. k. AJcad. d. Wissensch. , Wien, 1872, Bd. Ixv. Abth. 3, S. 126 ; 

 " Vorlesungen," Wien, 1885, Aufl. 4, Bd. i. S. 321. See also W. de Bary, Arch. f. exper. 

 Path. u. PharmakoL, Leipzig, 1886, Bd. xx. S. 243. 



2 Ztschr. f. physioL Chem., Strassburg, 1886, Bd. x. S. 361. See also Ellenberger and 

 Hofmeister, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1885, Bd. xv. S. 284, 301 ; 

 1886, Bd. xvi. S. 260, 261. 



3 Virchow's Archiv, 1885, Bd. ci. S. 325 ; 1886, Bd. civ. S. 271 ; Ewald, " Kliiiik der 

 Verdauungskrankheiten," 1890, Bd. i. S. 83. 



4 See p. 350. 



5 This was merely an assumption made by Schmidt, in order to conclusively show that 

 gastric juice contained an excess of hydrochloric acid above even this quantity. Fortunately, 

 the excess of hydrochloric acid was sufficient to allow Schmidt to give this form of proof ; 

 but if the quantity of phosphates had been greater, or the excess of hydrochloric acid less, 

 Schmidt's process might easily have yielded a negative result, and yet the gastric juice 

 have contained free hydrochloric acid ; indeed, the massed equivalent in chlorine of the total 

 bases might have been greater than the total quantity of chlorine present, and still there 

 might have been free hydrochloric acid present. 



