Absorption and Excretion of Alimentary Nitrogen, i 3 
relative rapidity with which their proteins were digested, absorbed, 
and metabolized, as shown by the rate of nitrogen excretion during 
the height of digestion (figures in top row). From the nitrogen 
balance (figures in the bottom row) it is evident that the order 
would be practically reversed if the foods were ranked according to 
their ability to keep the body in nitrogenous equilibrium. It is ap- 
parent that rapid digestion does not necessarily further retention of 
protein. Presumably there is an optimum rate of digestion, which 
makes possible the fullest use of its products, and this rate may be 
exceeded. Rapid digestion can then cause imperfect retention. 
"Predigestion" has recently been shown by Voit and Zisterer to 
have this effect. 1 
9 (534) 
The cause of cardiac cohypertrophy. 
By HUGH A. STEWART. 
[From the Laboratory of the Department of Pathology, Columbia 
University.] 
In a series of twenty experiments in dogs in which cardiac 
hypertrophy was induced by the production of aortic insufficiency, 
it was found that all the chambers of the heart were heavier than 
normal. The largest increase was in the left ventricle, 48 per cent., 
but there was also found a very marked increase in the auricles 
which, relatively to their size, was almost as great as in the left 
ventricle. The cohypertrophy of the auricles has also been 
observed in man in cases of chronic interstitial nephritis and 
arteriosclerosis (Hirsch). 
It was found experimentally that the increased work of the 
left ventricle after the production of aortic insufficiency is not 
associated with a change in venous pressure such as has been as- 
sumed to be the direct cause of hypertrophy of the auricles. 
Tracings taken of the contractions of the right auricle along 
with a blood pressure tracing from the right carotid artery showed 
that the effect of the production of aortic insufficiency is to in- 
crease the force of auricular contraction. Similarly the increased 
work of the left ventricle produced by the compression of the 
thoracic aorta will also cause increased auricular contractions 
without any change in venous pressure. 
l Z. /. Biol., liii, 457- 
