3 5 8 CHE MIS TR V OF THE DIGEST! I E PR CESSES. 
place in solution. He dissolved sodium chloride and lactic acid together 
in water, placed the solution in the bottom of a cylindrical vessel, and 
then carefully poured a layer of distilled water on the top. After some 
days, part of the upper layer was removed and analysed : it was found to 
contain more than sufficient chlorine to balance all the sodium present : 
that is to say, it contained free hydrochloric acid. Similar results were 
obtained with a mixture of monosodium phosphate, and other acid salts, 
in common solution with sodium chloride. 
These results of Thomsen and Maly will lie again referred to in 
discussing the mode of origin of hydrochloric acid. They are introduced 
here to show that any weaker acids in gastric juice along with the 
hydrochloric acid must in part be uncombined. Any organic acids 
present during digestion will also be in part free and in part combined, 
and as these have very small avidities compared with hydrochloric acid, 
they will be almost completely free. This has a bearing of some import- 
ance. Any organic acids formed in the stomach by bacterial action on 
carbohydrates will be found as free acids, and will not reduce the amount 
of free hydrochloric acid, 1 but salts of organic acids entering the stomach 
with the' food will reduce the amount of acidity due to free hydrochloric, 
because, from the organic salts, free acids will be formed, by hydrochloric 
acid combining with their bases. 
Source of the hydrochloric acid. — The only possible source of chlorine 
lies in the chlorides of the food, and from this either directly, or indirect ly 
through the blood, the hydrochloric acid must necessarily have its origin. 
That the chlorides present in the 1)1 1 plasma are the source of the acid, 
has been experimentally proved by Voit 2 and Calm. 3 
Following a method first used by Voit, Calm fed dogs exclusively 
on meat which had previously had all its salts extracted by boiling it 
repeatedly with distilled water. An animal fed in this manner continues 
to excrete a dimini shing quantity of chlorides in the urine for a period 
varying from two to five days. After this only traces of chlorides are 
found in the urine, but the tissues and blood still cling on to their 
necessary minimum quantity of chlorides, digestion goes on, and the 
animal lives. At this period, if the contents of the stomach are washed 
out with distilled water, the secretion is found to contain free acid and 
to possess digestive power. If now the animal's reserve stock of chlorine 
be still further reduced by administering diuretics, such as potassium 
nitrate, which cause some additional chlorides to be excreted: or if free 
hydrochloric acid be repeatedly removed by pumping out the contents of 
the stomach with the aid of distilled water, a condition is finally reached 
in which the stomach secretes a completely neutral fluid, which is 
altogether inactive so long as it is neutral, but quickly digests fibrin if 
1 part per 1000 of hydrochloric acid be added to it. When this 
stage is reached the animal rapidly fails : but if a small quantity of 
sodium chloride be now given to it.it rapidly recovers, and soon becomes 
in every respect normal. 
This experiment also shows that the secretion of pepsin is independ- 
ent of that of acid, and that in the absence of hydrochloric acid no 
1 In fact will slightly increase it by combining to a certain extent with the bases of the 
chlorides. 
- Sitzungsb. d. h.-bayer. ATcad. d. Wissensch. vu Miinchen, 1S69, Bel. ii. S. 483. See 
also M. Gruber, Beitr. ~. Physiol. C. Ludwig :. s. Geburtst., Leipzig, 1887. 
3 Ztschr. f. physiol. Chcni, Strassburg, 1886, Bd. x. S. 522. 
