The Influence of Environment 317 



express them in the form of the theory of physiologically 

 balanced salt solutions, by which we mean that in the ocean 

 {and in the blood or lymph) the salts exist in such ratio 

 that they mutually antagonize the injurious action which 

 one or several of them would have if they were alone in 

 solution.* This law of physiologically balanced solu- 

 tions seems to be the general expression of the effect 

 of changes in the constitution of the salt solutions for 

 marine or all aquatic organisms. 



This chapter would not be complete without an 

 intimation of the r61e of buffers in the sea water and 

 the blood, by which the reaction of these media is pre- 

 vented from changing in a way injurious to the organ- 

 ism. These buffers are the carbonates and phosphates. 

 Instead of saying that the organisms are adapted to 

 the medium, L. Henderson has pointed out the fitness 

 of the environment "for the development of organisms 

 and one of these elements of fitness are the buffers against 

 alterations of the hydrogen ion concentration. 2 The 

 ratio in which the salts of the different metals exist in 

 the sea water is another. It is obvious that the quan- 

 titative laws prevailing in the effect of environment 

 upon organisms leave no more room for the interfer- 

 ence of a "directing force" of the vitalist than do the 

 laws of the motion of the solar system. 



1 This theory was first expressed by the writer in Am. Jour. Physiol., 

 1900, iii., 434. 



* Henderson, L., The Fitness of the Environment. See also Michaelis, 

 L., Die Wasserstoffionenconzentration. Berlin, 1914. 



