Primary Cleavage Products. 405 
itated than usual by salt alone; and further, it is probable that 
on addition of acetic acid to the concentrated and salt-saturated 
fluid, a much larger proportion of deuterocaseose was precip- 
itated. In confirmation of this view it was noticed that the 
amount of deuterocaseose obtained by the later precipitation with 
ammonium sulphate was quite small; far smaller proportionally than 
obtained in D. That the body contained some protocaseose, was 
evident from its reaction with cupric sulphate and with acetic acid. 
Pure deuterocaseose evidently contains a smaller content of car- 
bon than protocaseose. It is equally evident that it is a body 
further removed from casein than protocaseose. Its general reac- 
tions show a closer relationship to peptone than to casein or the 
proto-body. Heterocaseose, on the other hand, judging from 
analysis of a single preparation, contains fully as much if not more 
carbon than casein itself. 
Nearly all of the caseoses show a somewhat higher percentage of 
sulphur than casein, but probably the increase (0:1 per cent.) is due 
mainly to a trace of sulphate in the ash, not accounted for. Owing 
to the large amount of phosphate in the ash of the different prepara- 
tions, phosphorus was sought for only twice. In both of these, how- 
ever (protocaseose D 1 and deuterocaseose D), the phosphorus in the 
ash was the exact equivalent of the total phosphorus found after 
fusion with potassium hydroxide and nitrate. This might indicate 
that in the cleavage of casein with pepsin-hydrochloric acid, the 
phosphorus of the casein is removed in the form of a phosphorized 
body, leaving the thus non-phosphorized matter to break down into 
the caseoses. With this thought in mind, we propose to study later 
the nature and composition of the insoluble, semi-gelatinous body 
separated in the first stage of digestion. We also hope to extend 
our work by a study of Weyl’s commercial ‘ casein-peptone,” pre- 
liminary examination of which -has shown us the presence in large 
quantities of caseoses. In this way and by a somewhat different 
method of isolating the individual caseoses, we hope to verify our 
present work and at the same time obtain products comparatively 
free from ash, with which to establish beyond question the composi- 
tion of the caseoses. We are also occupied in a study of pure casein- 
peptone, purified according to the method made use of by Kiihne 
and Chittenden in the study of fibrin-peptone. 
