PROTOPLASM 417 



insolubility in oil, they would not be able to pass through an 

 oily continuous phase such as would be produced by an excess 

 of calcium ions. This theory gains support from the fact, 

 established by Osterhout,* that the permeability of Laminaria 

 is greatly increased by immersion in a solution of pure sodium 

 chloride, isotonic with sea-water, but containing no calcium 

 salts ; moreover the addition of calcium salts to the sodium 

 chloride restores the normal condition of the cell. 



Another example of the influence of electrolytes upon 

 protoplasm is provided by the use of the so-called Ringer 

 solution which is a physiologically balanced solution. Ringer 

 found that the isolated heart of the frog if perfused with pure 

 water soon stopped beating ; if a solution of sodium chloride, 

 isotonic with blood serum, was used in place of water, the 

 heart-beat continued rather longer. On comparing the effects 

 of calcium chloride with potassium chloride he found that 

 the former left the heart at rest in the contracted condition 

 while the latter left it completely relaxed ; there was thus an 

 antagonistic action between the two metals, and on making 

 a solution of the two salts in appropriate proportions he ob- 

 tained a liquid in which the heart-beat could be maintained 

 for several hours. The proportions of calcium to potassium in 

 such a solution are approximately those which obtain in sea 

 water. A point of some interest was elicited when attempts 

 were made to replace calcium or potassium by other divalent 

 or monovalent elements respectively ; thus it was found f 

 that the order of effectiveness in maintaining the movements 

 of the cilia of the epithelium of the frog's oesophagus was as 



follows : — 



K > Rb > Na > Cs > Li 



This sequence, it will be remembered, is the same as the pre- 

 cipitating power of these kations in the lyotrope series upon 

 colloids ; thus lithium, which is least effective in maintaining 

 the movements of the cilia, may be regarded as most toxic, 

 an effect which may be correlated with its precipitating effect 

 upon such a colloid as protoplasm. 



* Osterhout : " Science," 191 1, 34, 187 ; 1913, 38, 408. 

 ■f Overton : " Pfliiger's Archiv," 1904, 105, 176. 



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