(412) 
Physiology. — Prof. PrKELHARING makes a communication con- 
cerning ,pepsin’’. 
Some years ago I communicated to this meeting a new method 
for the preparation of pepsin. In artificial gastric juice, obtained by 
digesting the mucous membrane of the stomach with 0.5°/, H Cl 
for some days, I had found a substance, which is little soluble in 
water, containing about 0.02°/) HCl, but which becomes more easily 
soluble as well by a higher as by a lower amount of hydrochloric 
acid in the fluid. This substance appeared to be an extremely 
complicated proteid, which possessed to a very high degree the 
power of digesting proteid matter in acid solution. 1 supposed this 
substance might be the enzyme itself and not a proteid matter mixed 
with the enzyme and my grounds for this supposition were in the 
first place the extraordinary amount to which this substance was 
able to digest proteid matter and secondly the observation that the 
coagulation-temperature of this proteid matter, dissolved in hydrochloric 
acid, is just the same as the temperature, which makes the enzyme 
inactive. I had however to confine myself to a supposition, as my 
material was not of a sufficient degree of purity. I found that it 
always contained phosphorus, but the amount of phosphorus, though 
generally about 1°/,, was variable. 
On account of the great importance of the question concerning the 
nature of the enzymes, I have continued my efforts to obtain the 
substance in a purer state. At first I used for that purpose the 
mucous membrane of the stomach of the pig. The method of 
preparation was altered in some respects in order to improve the 
purifying of the substance and to increase the amount of pepsin. 
I can add to what was stated before, about the nature of the 
substance, that from its solutions it can also be precipitated by 
ammoniumsulfate. 
After treating the extract of the mucous membrane in the 
above mentioned way, with basic plumbic-acetate and ammonia and 
decomposing the precipitate with oxalic acid and dialysing and 
filtering the thus obtained concentrated solution, there could be 
obtained out of the filtrate, by saturating with ammonium sulfate, still 
a considerable quantity of pepsin, which when purified by dissolving 
in HCl 0.2°/, and dialysis, showed exactly the same qualities 
as the pepsin, prepared directly from the artificial gastric juice 
and from the lead-precipitate, it especially possessed as great a - 
1) Account of the Meeting on May 30, 1896. 
