CHAPTER Mil 



RELATION OF THE INORGANIC SALTS OF THE 

 MEDIUM TO THE PHYSIOLOGIC.\L PROCESSES 

 IN PROTOPLASM 



The relation of the inorganic salts present in the 

 external medium to the properties and activities of 

 living cells has been the subject of much investigation 

 since Ringer's time, and the present brief account \vill 

 be confined to the more general and fundamental rela- 

 tions of this kind, especially those indicating that the 

 chief basis of the physiological action of the salts of 

 the medium is their action upon the protoplasmic surface 

 layers. Since much of the pioneer work in this field is 

 due to Overton, and since many of the results of his 

 studies are applicable to living protoplasm in general, 

 I shall first give a somewhat detailed summary- of his 

 earlier experiments on the action of salt solutions on 

 the muscle and nerve of frogs. ^ 



Overton first examined carefully the well-known 

 effect, reversible loss of irritability in isotonic solutions 

 of indifferent non-electrolytes such as sugar, using small 

 muscles; e.g., sartorius, cutaneus pectoris, and foot 

 muscles. He found that all indifferent non-electrolytes, 

 independently of their special composition (dextrose, 

 sucrose, lactose, erythrite, mannite, alanin, taurin, and 

 asparagin), produce this effect. The action is not 

 poisonous, since the addition of a small proportion of an 

 isotonic solution of sodium chloride to the non-electroKte 



» Overton, Arch. ges. Physiol., XCII (1902), 346; CV (1904), 176. 



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