692 
PHYSIOLOGY: MENDEL AND JUDSON 
of gelatine plates and Mg and Ca salts, at least under certain condi- 
tions, retard the swelling and may even cause shrinkage. OH' increases 
swelling and H- decreases swelling if the reaction of the medium is on 
the alkaline side of the isoelectric point for the colloid, which seems to 
be the case in regard to blood and animal proteins within the body or 
in sea water. 
We may therefore conclude that OH', Na", and K' increase the per- 
meability of the plasma membrane by causing it to swell and that Ca' *, 
Mg' ', and H' (at least on the alkahne side of the isoelectric point) in- 
hibit increase in permeability by inhibiting swelling. 
1 /. Biol. Chem., 25, 669 (1916). 
* These vials were obtained from Hynson, Westcott and Company, Baltimore, Maryland. 
' There is reason to support the view that the cell surface is composed of emulsoids rather 
than suspensoids. 
SOME INTERRELATIONS BETWEEN DIET, GROWTH, AND 
THE CHEMICAL COMPOSITION OF THE BODY 
By Lafayette B. Mendel and Sarah E. Judson 
SHEFFIELD LABORATORY OF PHYSIOLOGICAL CHEMISTRY. YALE UNIVERSITY 
Read before the Academy, November 13, 1916. Received, November 14, 1916 
Changes which normally occur in the water, ether extract, and ash 
content of the body during its most active growth have been determined 
for the white mouse. Based on eighty-eight analyses of the entire body 
at different stages of growth, the following results were obtained: (a) 
increase in solids from 16% at birth to a maximum of 35% at fifty 
days with a subsequent decrease to 33%; (b) decrease in the propor- 
tion of water in the fat-free substance from 85.5% at birth to 73% in 
the adult mouse; (c) rapid increase in fat during the first twelve days 
from L85% to about 10%, followed by a slow increase to about 12%; 
(d) absolute and relative increase in ash content from 25 mg., 1.86%, 
in a mouse weighing one and a half grams at birth, to 950 mg., 3%, of 
ash in the adult mouse. 
The ash content of mice growing normally on an artificial food mix- 
ture of milk powder, casein, starch, salts, and butter fat, (protein 30%, 
fat 32%, and ash 5.5%), is uniformly higher at corresponding stages 
of growth than the ash content of mice fed on a ration of mixed grain, 
dog bread, and small amounts of milk. It is not known to what this 
difference is due, but it is not related to differences in the amount of 
protein or salts in the food. Since the ash content of normal animals 
may be thus increased by differences in diet alone, it would seem that 
