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This impurity was apparently quite removed together with the preci- 
pitate, which was formed when dialysing. For when afterwards the 
pepsin which was still in solution, was precipitated by half satura- 
ting with ammoniumsulfate and purified by dissolving it in hydro- 
chloric acid and dialysis, there was not found in it the slightest 
trace of phosphorus. Nevertheless this pepsin was equally able to 
digest proteid matter as was that which was separated directly by 
dialysis out of the gastric juice. 
NENCKr and Sreser did find phosphorus in the pepsin, prepared 
by them out of the gastric juice of the dog, even when the pepsin 
was washed out with alcohol and had thus been altered. However they 
found the amount of P not only small, but also in various prepa- 
rations very different. In the pepsin, precipitated by dialysis and not 
washed out, it varied between 0.073°/, and 0.148°/,, in the prepara- 
tions washed out with alcohol between 0.045°/, and 0.091°/). 
They take for granted that pepsin contains lecithine; partly at 
Jeast, not as an impurity, but in a combination to be compared 
with the compounds of Jecithine with glycose, morphin, etc., espe- 
cially studied by Brna. 
I am not prepared to deny the possibility of the presence of a 
compound of pepsin with lecithine in the gastric juice, nevertheless I 
wish to lay stress on this : that the existence of the enzyme should not be 
considered as being connected with the presence of lecithine or any other 
P-containing group in the molecule of the pepsin, now that I have 
succeeded in preparing very powerful pepsin, in which either no 
phosphorus at all, or only a very insignificant trace of it could 
be shown. 
Contamination of the pepsin with phosphorus can, besides by leci- 
thine, also be caused by other substances. In the gastric juice, obtai- 
ned by pseudo-feeding, there always occurs, at least in the dog used 
by me, some mucus, which can easily be removed by filtration. This 
consists of a P-containing proteid matter. When taken from the filter 
and washed out with water and alcohol, it scarcely dissolves at 
all in diluted hydrochloric acid, but by digesting with pepsin and 
hydrochloric acid, it gradually loses the gelatinous character and 
dissolves for the greater part, while a sediment, easily soluble in 
alkali, is formed. 
This mucine is probably a nueleo-proteid and it is certainly 
possible, that when kept in contact with the gastric juice for some 
time and partly digested, it may yield P-containing decomposition- 
products to the solution. I have therefore immediately filtered the 
gastric juice, obtained in each quarter of an hour, 
