324 PROPERTIES OF THE COLLOIDAL CONSTITUENTS 



remains stationary at this level for some hours, and then slowly sinks 

 until it finally reaches the level of 320 ohms, which represents zero 

 resistance on the part of the surfaces within the tissue. The permea- 

 bility of the cell-surfaces in calcium chloride solutions, therefore, at 

 first decreases and later increases. 



A mixture of 1000 c.c. of molecular sodium chloride + 15 c.c. of 

 molecular calcium chloride was then diluted until it had the same 

 conductivity as sea-water. A similar column of Laminaria tissue, when 

 placed in this mixture, neither gained nor lost resistance, and had the 

 same conductivity after twenty-four hours as it normally has in sea- 

 water. The antagonistic action of calcium chloride upon the toxicity 

 of sodium chloride is therefore seen to depend upon the maintenance 

 of the normal permeability of the cells. 



In general it was found that while the salts of monovalent cations 

 such as sodium, potassium, csesium, rubidium, lithium and ammo- 

 nium increase the permeability of the tissue from the beginning, the 

 salts of divalent cations, such as magnesium, calcium, barium, stron- 

 tium, manganese, cobalt, iron, nickel, zinc, cadmium and tin agree 

 in bringing about an initial decrease of conductivity followed by a 

 relatively gradual increase. The initial decrease is, however, very 

 slight in the case of magnesium. Acids resemble the divalent cations 

 in causing an initial decrease followed by an increase of permeability, 

 but both the increase and the decrease are much more rapid than 

 they are in solutions of neutral salts of divalent cations. Alkalies 

 resemble the salts of the monovalent cations in causing an increase of 

 permeability from the first. 



If the increase in permeability does not exceed a certain limit, the 

 return of the tissue to normal sea-water results in the restoration of 

 normal permeability and the tissue is not permanently injured. If, 

 however, the increase of permeability exceeds this limit then the 

 normal permeability is not recoverable and the attainment of absolute 

 permeability, i. e., zero resistance of the surfaces of the cells to the 

 passage of electrolytes across them, indicates death of the tissue. The 

 toxic action of pure salts is therefore seen to originate in the irreparable 

 impairment of the normal resistance which the surface of the cell 

 opposes to the penetration or exit of water and inorganic salts. 



Having regard to the fact that the Proteins of the cell are the only 

 abundant constituents which are capable of entering into combination 

 with all of these diverse substances we may assume that the alterations 

 of Permeability which attend immersion of living tissue in abnormal 

 inorganic environments are due to alterations in the physical consist- 

 ency of the interstitial protein solution or jelly which holds the lipoidal 

 elements in suspension. Alterations in the consistency of the Inter- 

 stitial Protein Medium, and especially alteration of the texture of the 

 spongework of which it is composed, must necessarily modify the 

 spacing of the superficial lipoidal elements, and by widening or narrow- 

 ing the interstitial pores, increase or decrease the permeability of the 



