116 The American Naturalist. (February, 
bodies there is to be seen a peculiar combination of carbon, 
nitrogen and hydrogen such as is not found in dead proteid 
matter. The structure of the molecule is different and is em- 
blematical of a still more complex molecule in which the 
atoms are similarly arranged. 
Thus, it is to be remembered that whenever an organ rich 
in cells is decomposed by dilute acid, adenin, guanin, xanthin 
and hypoxanthin are never obtained alone. They are not 
found as individuals, but in every tissue which has retained 
its original condition, the two special xanthin bases, for 
example, are found in combination with other groups of atoms, 
especially with phosphoric acid and albumin, as parts of a 
higher compound, the nuclein. From this higher compound, 
the individual components cannot be extracted by simple 
solvents or other like methods of isolation; a blow must be 
struck by which the complex molecule shall be shattered and 
the individual parts liberated, as by the action of a dilute 
mineral acid. In tissues very poor in nuclear elements, on the 
other hand, as in muscle tissue, we find only the decomposr 
tion products of nuclein; the chemical union between the 
individual fragments is broken, and the phosphoric acid, for 
example, no longer exists in organic combination, but as solu- 
ble alkali phosphates. In a similar manner, the xanthin and 
hypoxanthin, exist in a free condition capable of extraction 
by water alone. 
Further, in the transformation of adenin and guanin into 
hypoxanthin and xanthin respectively, with a splitting off of 
the NH group and the acquisition of oxygen we have a possi- 
ble illustration of the manner in which the migration of the 
amidogen group of albumin to urea takes place; a transforma- 
tion which no doubt goes on in the tissues and perhaps” 
every cell nucleus. 
Certainly then in the light of what has been said, the cell 
nucleus may be looked upon as in some manner standing 1? 
close relation to those processes which have to do with 
formation of organic substances. Whatever other functions 
it may possess, it evidently, through the inherent qualities 0 
the bodies entering into its composition, has a controlling 
