( 422 ) 
product, which doubtless owes its origin to the substance which I 
consider to be the enzyme, is then always precipitated in a per- 
ceptibly smaller quantity. The determination of the relative quantity 
of pepsine in the gastric juice took place after the method of Merv, 
whereas the quantity of the coagulation-product was determined by 
boiling 50 cc. of the gastric juice over the flame and bringing the 
precipitate, after cooling, on a weighed filter, washing it out success- 
ively with water, alcohol and ether, drying it at 110° C. and 
weighing. 
That solutions of pepsine can be prepared, which act powerfully 
and yet show no proteid-reactions is, as I pointed out before and as 
has also been stated lately by Nenckr and SIEBER, no reason to 
deny to pepsin the nature of a proteid matter. 
By Briss and Novy an observation is mentioned, which might 
raise a doubt, as to whether pepsin can indeed be considered to be a 
proteid matter'). They found namely, that pepsin was not changed 
at all by formaldehyde, although this substance affects various 
proteid matters and makes them insoluble. I convinced myself of the 
justness of the observation. Solutions of pepsin in hydrochloric acid, 
to which formol is added to an amount of 2 to 3°/,, may be kept 
for days, without perceptibly losing any digesting power. Of course 
the amount of formaldehyde must be considerably decreased, either 
by diluting or by dialysis, before the solution is brought in contact 
with fibrin, because otherwise the fibrin itself would be affected by 
formol and made unsusceptible for digestion. 
It can not be maintained, however, that all proteidmatters _ 
are changed by formaldehyde. It is especially the proteidmatter 
here treated, which is not affected by this. I have dissolved 
the purified matter in 0.2 °/) HCl, while adding formol, and been 
able to precipitate it again from this solution, as well by dialysis, 
as by ammoniumsulfate, without it having lost any of the qualities 
of pepsin. 
The substance possesses not only the power of digesting albumen 
in an acid solution, but it also causes milk to coagulate, as I stated 
before. In accordance with NENCKI and SIEBER I also found that 
it forms “plastein” out of albumose. 
Nenckr and SieBER have argued, that there is no serious objection 
to the supposition, that one and the same molecule may have 
various enzym-actions. With that argument I quite agree. To stick 
1) Journal of exp. med. Vol. IV. p. 47. 
