(413) 
digesting power. Whereas from the solution that was greatly 
contaminated by products of digestion, a precipitate fit for being 
filtered was only produced by complete saturation with ammonium 
sulfate, the pepsin will completely separate from solutions containing 
but few products of digestion, by half saturating the fluid with 
this salt. 
If the substance is slowly precipitated either by dialysis into water 
or under the influence of ammoniumsulfate, the precipitate is not 
amorph, but has the shape of small globules, resembling the globu- 
lites of albumen, which after HOFMeISTER’S method can be obtained 
from egg-albumen. The little globules of pepsin are however smaller, 
the largest have a diameter of about 15 & 20 w. 
When kept under ammoniumsulfate, pepsin can remain unaltered 
for a very long time. A preparation, entirely consisting of small 
globules, repeatedly washed out by decantation with half saturated 
ammoniumsulfate solution and finally kept in this fluid in an 
apartment, in which the temperature undergoes great variations, 
has already remained unaltered for four years. It shows not only 
no alteration when investigated with the microscope, but when freed 
from ammoniumsulfate and dissolved in hydrochloric acid, it also 
digests proteid matter very powerfully. 
Though I have treated some hundreds of mucous membranes of 
pigs’ stomachs I have not succeeded in preparing from them a pepsin 
of constant composition. By analysing some five preparations, purified 
as much as possible, the values found for the various elements varied 
between the following numbers: 
C Al N P 5 
maximum 50:77 7.27 15.06 0.75 1.6 
minimum 48.18 6.72 14.02 0.425 1.45 
I thus became convinced, that I could not hope for a better result 
if I continued the purification of the substance by dissolving it 
again and again in HCl 0.2°/) and then precipitating it by dialysis 
into water, on account of the great variability of the substance, the 
perseverance with which it retains contaminations and the great 
loss of substance, which is inevitable when purifying it and which 
would make the preparation of quantities such as are required for 
analysis, practically impossible. 
I therefore resolved to try whether the gastric juice of the dog, 
which now, owing to PawLow’s brilliant researches, can be obtained 
