44 



strongly poisonous to marine animals in various stages of develop- 

 ment — i. e. , a fisli {Fundulus heteroclitus) , a jellyfish (Gonionemus sp. ), 

 and a sea urchin (Arbacia sp.). But the addition in small quantity 

 of a salt yielding another kind of cathion, such as magnesium, potas- 

 sium, and calcium, more or less neutralized this toxic effect, although 

 each of these salts was itself toxic in pure solution. As in the case of 

 plants, calcium was particularly effective. That it is the cathions 

 rather than the anions added to the solution which are chiefly effective 

 as counter agents is evident from the fact that of each base the chloride 

 only was used. Moreover, in only one mixture of three chlorides 

 could fertilized eggs of the sea urchin be brought to an advanced 

 stage of development, but sodium bromide could be successfully sub- 

 stituted for sodium chloride in the mixture.^ It is clear, therefore, 

 that the anions play a very subordinate part in the physiological 

 action of such mixtures. 



Loeb suggests that the physiological effect of a pure solution, 

 whether toxic or stimulating, is attributable to a reaction whereby 

 various cathions which are assumed to enter into combination with 

 the proteids of the organism are replaced by the cathion of the sur- 

 rounding solution, in accordance with the law of mass. Thus, in 

 case of an animal or organ immersed in a solution of sodium chloride, 

 ions of calcium and of potassium would be forced from their organic 

 compounds and sodium ions would be substituted for them. This 

 would cause a disturbance of equilibrium and finally a cessation of 

 irritability in the tissues. Such effect can be prevented, or, if it has 

 not proceeded to the point of disorganization, counteracted by the 

 addition to the solution of salts containing the corresponding cathions, 

 i. e., potassium and calcium. Hence the author derives his concep- 

 tion of a " physiologically balanced salt solution," examples of which 

 are sea water, the blood of animals, and a mixture of definite concen- 

 trations of the chlorides of potassium, sodium, and calcium. The 

 chief function of such a solution is regarded as the maintenance of 

 "a certain physical condition, a certain labile equilibrium, of the 

 protoplasm or the colloids. " ^ 



From considerations such as these, and from the discovery that a 

 close analog}^ as to absorption of water exists between the behavior of 

 a frog's gastrocnemius immersed in a solution of a potassium, sodium, 

 or calcium salt and that of potassium, sodium, and calcium soaps, ^ 

 the development of Loeb's theory of the existence and function of 

 "ion-proteid compounds" was logically inevitable. The hypothesis 

 is stated as follows: " Salts or electrolytes in general do not exist in 

 living tissues as such exclusively, but are partlj^ in combination with 



s 



' Amer. Journ. Physiology, 3, 442 (1900). 



2 Ibid., 3, 445 (1900). 



3 See Pfliiger's Archiv, 75, 803 (1899). 



