THe CHEMISTRY OF THRE “PROTEINS 105 
not complete. Even on prolonged action, when the biuret re- 
action is absent or only very faint, a complex product together 
with amino acids results. This complex polypeptide, as it is 
termed, contains the whole of the proline and phenylalanine 
contained in the protein, together with other amino acids. 
It is apparently not identical with Kiihne’s antipeptone which 
gave the biuret reaction. On complete hydrolysis by acid, it 
yielded the same quantity of proline and phenylalanine as would 
result from the protein by acid hydrolysis. 
In the animal body the action of trypsin is preceded by that 
of pepsin. If a protein be first digested by pepsin and then by 
trypsin, the same complex polypeptide might be expected to 
result, but this was not the case. It was less in amount, and 
did not contain the whole amount of the proline and phenylala- 
nine of the protein, a certain portion of these being found with 
the other amino acids, which had been split off. It would thus 
appear as if the protein molecule contained a special nucleus, 
as suggested by Kossel, who believes that it consists mainly of 
the diamino acids; these make up go per cent. of the pro- 
tamine molecule, the protein molecule containing less of this 
nucleus and more monoamino acids than the protamine. 
Histones are a transition product between the protein and 
protamine. Unfortunately, by the method adopted by Fischer, 
a nucleus consisting mainly of diamino acids could not be 
definitely determined, since the phosphotungstic acid used not 
only precipitated the complex polypeptide, but also the diamino 
acids, so that it was impossible to tell whether they were free 
or combined together in this polypeptide. Subsequent work, 
if attended with such far-reaching results, will certainly decide 
this question, especially as less complex combinations of amino 
acids have already been isolated from proteins. New amino 
acids and oxyamino acids may still be discovered ; Skraup’s 
results point to the existence of two more diamino acids and 
other oxy-amino acids; their exact constitution is still very 
uncertain. His work cannot be further mentioned here. 
The hydrolysis of various proteins has been carried out by 
Abderhalden and several co-workers in the hope of being able 
to obtain closer relationships between the members of the 
various classes of proteins, and more distinctions between the 
classes. Abderhalden’s book on physiological chemistry brings 
out these points as well as many others of great interest. 
