2 35 
Hind . — St tidies in Permeability . ///, 
N 
added to 100 c.c. of acid. There was immediately produced a marked 
lOOO x 
decrease in the hydrogen-ion concentration of the acid, very similar to that 
produced by i c.c. of potato extract. 
To obtain further proof that in the case of the liquid obtained from 
the potato it is the protein that affects the acid, the proteins of the potato 
were extracted. These were found to act in the same way, in regard to 
the acid, as did the peptone solution and also the liquid expressed from 
potatoes. 
It has been thought by some investigators that lipoid substances play 
an important part in the absorption of substances by the cell, and lecithin 
has been suggested as particularly active in this regard. A colloidal 
solution of commercial lecithin in water was prepared, and i c.c. of this was 
added to ioo c.c. of 
N 
acid ; measurements before and after the addition 
IOOO 
