io2 PHYSICAL CHEMISTRY 



Clendon, 1912 d). The mineral acids penetrate, but the fatty 

 acids more quickly. It is probable that both of these acids in- 

 crease the permeability. 



The same caution should be observed in considering the 

 permeability of cells to bases. E. N. Harvey (1911) stained 

 Elodea leaves with the indicator, neutral red, and studied the 

 * penetration of bases. Ammonia and the amines penetrated more 

 quickly than the alkalis. All of these bases probably increased 

 the permeability. 



In the experiments of Czapek (1910) the cells were evidently 

 killed and the permeability irreversibly increased. Czapek de- 

 termined the exit of tannin from Echeveria leaves by the failure 

 of alkaloids to cause a precipitate within the cells. Monovalent 

 alcohols and ketones, ether, urethane, di and tri acetin, sodium 

 oleate, oleic acid, lecithin and cholesterin increased the perme- 

 ability of the cells to tannin, when the surface, tension of their 

 solutions in water sank to about 0.68. Mineral acids increased 

 the permeability when the concentration just exceeded 1/6400 

 normal, the same concentration at which Kahlenberg and True 

 (1896) had found the growth of Lupinus to be stopped. Their 

 action is evidently due to the H ions. 



The experiments of Osterhout (1911) are especially valuable 

 because he was careful that the cells were not killed. He found 

 that the permeability of Spirogyra is increased by pure solutions 

 of NaCl and that this action is inhibited by the addition of 

 OaCl 2 . A solution of NaCl may be hypertonic and yet fail to 

 plasmolyze the cells because it penetrates, but if a little CaCl 2 

 solution be added, plasmolysis occurs even though the osmotic 

 pressure of the salt solution is slightly reduced. 



The electric conductivity method was used to determine perme- 

 ability of animal cells by several investigators (G. N. Stewart, 

 1897, McClendon, 1910 c). Osterhout (1912 a) extended this 

 method to seaweed, finding that the conductivity of leaves of 

 Laminaria (kelp) is increased by immersing them in NaCl, and 

 decreased by immersing them in CaCl 2 solutions in a reversible 

 manner. He claims that the size of the cells was not changed 

 by the solutions and since the conductivity of the solutions was 

 the same as that of sea water, the result is not due to a change 

 ■in the conduction in the intercellular substance. He concludes, 



