( 419 ) 
From the cleavage-products, into which the substance is split by 
heating, I have up till now only studied the coagulation-product more 
accurately, which is precipitated when the heating is done rapidly. 
Formerly I already stated that by boiling with mineral acids, purine- 
bases can be obtained out of this. To this I can only add that I 
have been able to prepare out of the pepsin of the pig a basis which 
was found to be xanthine. At first I found no reducing substance 
after boiling the coagulation-product with mineral acid. Further 
investigation however taught me, as is already stated by FRIEDEN- 
THAL ') and also by NENcKI and Sieper, that when so treated a 
reducing substance is indeed liberated, which shows the qualities 
of a pentose. Nevertheless, although this proteid matter contains 
purinebases and a carbohydrate group, it will not do to continue to 
group it any longer among the nucleo-proteids, as it contains no 
phosphorus. That no phosphorus was found in it, when it was 
prepared out of the pure pepsin of the dog, is a matter of course. 
But also when it was precipitated from the fresh gastric juice by 
boiling and then carefully washed, successively with water, alcohol 
and ether, I could not find a trace of phosphorus in it. When inves- 
tigating the coagulation-product out of the pepsin of the mucous 
membrane of the pig I had already been doubtful, whether this 
substance might indeed be considered to be a nucleo-proteid, on 
account of the failing of all my efforts, to prepare a nucleic acid 
out of it. 
It did produce an acid, when treated with alkali, but this acid 
was a proteid matter, which proved to be little soluble in water, 
insoluble in diluted acid and easily soluble in warm alcohol. 
This acid is best prepared in the following way: 
The coagulation product is dissolved in 1°/) hydrate of potassium 
and is boiled with this in the water-bath for five minutes. The 
fluid which was first entirely colourless, then acquires a light yellow 
tint. It is now made acid with hydrochloric acid. Hereby a consider- 
able precipitate is formed under development of sulfureted hydrogen, 
which, when cooled, is filtered off. It is of a pure white colour. 
The filtrate is also colourless, but this becomes yellow again with 
alcalic reaction. The filtrate gives biuret reaction and produces, 
after boiling with hydrochloric acid, pentose. 
The precipitate is washed out with 0.5°/, HCI, dissolved in 
boiling aleohol of 85°/) and filtered, when hot. On cooling it, the 
1) HNGELMANN’s Archiv. f. Physiol. 1900, S. 189. 
