IOWA ACADEMY OF SCIENCES. 
45 
In the metabolism of matter, the proteids assuredly have 
the pivotal place. The assimilation of proteid involves 
the reconstruction of the molecule, — “aggregate” — upon 
an altogether different plan, whereby a state of the great- 
est instability is given. The condition for this instability 
is the intramolecular introduction of oxygen. 
The members of the nuclein series begin with nucleic 
acid, a compound of phosphoric acid and the nuclein bases 
adenin, hypoxanthin, guanin, and xanthin. Of these bases, 
adenin is fundamental, because its molecule contains no 
oxygen, and the other bases are derivable from it. Adenin 
may be looked upon as of the utmost importance in syn- 
thetic processes, since under conditions of reduction the 
oxygen-free adenin may be transformed into a new body 
with avidity for oxygen; and this, in turn, may be again 
transformed by the addition of new “aggregates.” Hence 
adenin may be the starting-point in the synthesis of 
nucleins of successive grades, — the nuclein of chromatin r 
that of the nucleolus, and the nucleo-proteids of the cyto- 
plasm. That nucleins do arise from the synthesis of sim- 
ple proteids and phosphates has been shown by Miescher 
in the salmon, where the muscles are converted into the 
material of the ova during the ascent of the fish to the 
breeding-grounds. 
The study of the nuclein series points to the nucleus as 
the center for the initial syntheses. The many instances 
of the reciprocal relations between nucleus and cytoplasm 
here receive almost startling explanation. The work of 
Mathews on the pancreas-cell demonstrated the origin 
from the chromatin of fibrils of nucleo-proteid which are 
spun out into the cytoplasm. We appear to have here, be- 
fore our very eyes, the basis of the “intracellular pan- 
genesis” of de Yries. Place beside this result the work of 
Loeb on the seat of oxidation in the cell, and it is clear 
that the nucleus holds a controlling place in cell-life 
because synthetic steps are initiated there. We are thus 
enabled to appreciate the significance of the position 
assumed by the nucleus in the growing cell; the changes 
in the microscopical appearance of the nucleus during 
