( 421 ) 
The highly complicated proteid matter, which besides mucine, is 
the only albuminous element of the gastric juice of the dog, could 
only in so far be said to differ from the substance, prepared out 
of the mucous membrane of the pig’s stomach, by the fact that 
the latter was not sufficiently pure. As to the qualities and the 
decomposition-products, as far as the investigation of these was 
possible, they were exactly the same. As I mentioned before, such 
a substance may also be prepared out of the mucous membrane of 
the stomach of the dog and of the calf. 
This substance is, like other proteid substances, levogyr. I have 
not been able to detect any influence of the reaction of the solution 
upon the degree of rotation. 
When it is now taken into consideration that the substance obtained 
out of the gastric juice of the dog can ‚be made to acquire a degree 
of purity that is satisfactory for proteid matters, the hypothesis that 
this substance is the enzyme itself and does not own its activity to 
admixtures, does not appear to be a very bold one. 
The substance loses the action of pepsin by heating, at the exact 
temperature which decomposes it. 
When gastric juice, by half saturating it with ammoniumsulfate, 
is liberated from this substance, it loses its capacity to digest proteid. 
With respect to this it shonld be taken into consideration that the 
presence of ammoniumsulfate is highly detrimental to the action 
of pepsin. But I have repeatedly convinced myself, that the fluid, 
also when the salt was removed to a trace by dialysis, was quite 
unable to digest fibrin. If we now consider that !/,,0 mgr. of the 
substance prepared by me still shows a distinct though weak action 
on fibrin in 6 eem. HCl 0.2 °/o, then we may rightly conclude, 
that the filtrate freed from ammoniumsulfate by dialysis, does not 
contain any pepsin, all the enzyme thus being precipitated by the 
salt out of the gastric juice. And in this precipitate we find nothing 
but the proteid matter, which shows the action of the enzyme as 
strongly as possible. 
I find another argument for my view in the observation, that the 
digesting power of the gastric juice keeps pace with the quantity 
of the coagulation-product precipitated from it by heating. This 
is especially clear, when in the dog the secretion of gastric juice 
is increased by injection of diluted alcohol into the rectum during the 
pseudo-feeding. 
The gastric juice secreted under the influence of alcohol, is more 
considerable in quantity and surely as rich, but generally a little richer 
in acid than that secreted before; but poorer in pepsin. The coagulation- 
28 
Proceedings Royal Acad, Amsterdam, Vol, IV, 
