356 CHEMISTR 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 l 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 no 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 marked oft 1 , but merge into one another. 
(1) No proteolysis, acid reaction due to lactic acid. (2) Proteolysis 
and amylolvsis proceed together, both lactic and hydrochloric acids 
present. (3) Stoppage of amylolvsis 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. Akad. d. Wissmsch., Wien, 1872, Bd. lxv. Abth. 3, S. 126 ; 
" Vorlesungen," Wien, 1885, Aufl. 4, Bd. i. S. 321. See also W. de Bary, Arch. f. eager. 
Path. u. Pharmakol., Leipzig, 1886, Bd. xx. S. 243. 
2 Ztschr. f. physiol. Cheni., Strassbvtrg, 1886, Bd. x. S. 361. See also Ellenberger and 
Hofmeister, Jahresb. it. d. Fortschr. <!. Thier-Chem., Wiesbaden, 18S5. 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, " Klinik 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. 
