A STUDY OF THE PROBLEM OF WATER ABSORPTION. 27 
obey certain laws. When the temperature is kept constant 
the osmotic pressure of a given solution depends only on the 
number of dissolved particles in that solution. The chemical 
nature of these particles has no effect on osmotic pressure; 
they may be the ions or the molecules of any chemical sub- 
stance; in other words, osmotic pressure obeys the gas laws. 
That this simple explanation of turgor and of its cause, the 
entrance into and retention of water by living cells, is in- 
adequate, becomes evident when one makes a study of the 
literature dealing with our problem. 
II. LITERATURE. 
It was long ago observed by Loeb (9) that the amount of 
water absorbed by muscle tissue when placed in equi- 
molecular solutions of various electrolytes depends on the 
nature of the dissolved substance. In a certain solution of 
potassium chloride, for example, the muscle tissue was found 
to gain from forty to fifty per cent of its original weight after 
eighteen hours, while in an equimolecular solution of sodium 
chloride it gained only seven per cent of its original weight. 
We see that the osmotic theory of the passage of water into 
cells is not in accord with these observations. 
In order to explain such facts and at the same time keep 
the osmotic theory of water absorption, it has been necessary 
to suppose that the permeability of the living membrane 
varies with external conditions. Fernbach (3) showed that 
dilute aleohol makes the plasma membrane of the yeast cell 
permeable to invertase. Harvey (6) found that neutral red 
and other basic dyes fail to enter cells in the presence of a 
very weak acid. He also found that weak alkalies enter cells, 
while strong alkalies do not, thus showing that permeability 
varies with alkalinity. Lavison (7) found that the proto- 
plasm of peas and lupines is permeable to the salts of heavy 
metals when they are offered in high concentrations, while 
these same salts do not enter the cells from solutions of low 
concentration. According to Paine (14) yeast cells take up 
sodium chloride, ammonium chloride, copper sulphate, and 
sodium phosphate from moderately concentrated solutions, 
