186 PHYSICAL CHEMISTRY 



are added to each liter of sea water, but some algae are not bene- 

 fitted by it. This high concentration of nitrates is not maintained 

 very long owing to the presence of denitrifying bacteria, which 

 are especially active and abundant in tropical seas. 



The constituents of sea water are either nutritive or protective, 

 or both. The H 2 0, S0 4 and C0 2 are used by green plants in 

 the manufacture of protoplasm, and they require also P0 4 and 

 either NH 3 , N0 3 or N0 2 , which exist in traces in natural sea 

 water. Traces of I, Ca, Mg, Fe, Cu, Mn, Si, etc., may serve 

 a nutritive function to some organisms. The chief constituents 

 of the sea water may, however, be considered protective in that 

 they are not used up. Their presence in definite proportions is 

 necessary in order to preserve life. 



The work of Ringer, O. Loew, Loeb and others suggests that 

 these constituents have antagonistic actions, so that a balance 

 is necessary. Osterhout maintains that they either increase or 

 decrease the permeability of cells. These antagonisms of the 

 ions of sea water were demonstrated by the perfused heart of 

 the conch (Strombus) at Tortugas, Fla. The sea water freezes 

 at — 2.03 and isotonic solutions were made as follows: 0.59 

 rn NaCl, 0.6 m EC1, 0.36 m CaCl 2 , and 0.38 m MgCl 2 . Na, K 

 and OH ions increase the rate of the heart beat and stop it in 

 systole whereas Mg, H and Ca ions decrease the rate and stop 

 it in diastole. These antagonisms are not perfect, however, 

 although they are slightly more perfect in the action of these 

 ions on the pulsations of the medusa, Cassiopea. The reason 

 for the failure of complete antagonism is probably found in the 

 fact that the organism is made of a number of structures, each 

 pair of antagonistic ions having a certain antagonistic ratio for 

 each structure, and this ratio being different for each structure. 

 In order to obtain the same antagonistic ratio for all structures, 

 a combination of the antagonistic pairs must be made, and the 

 result is sea water. To use Osterhout's hypothesis, Na, K and 

 OH ions increase the permeability and Mg, Ca and H ions de- 

 crease the permeability, but it is necessary to have all present 

 in a certain proportion in order that the permeability of all the 

 structures in the organism be normal. It is not sufficient to have 

 a definite ratio between H and OH, Na and Ca, K and Mg, Na 

 and Mg, or K and Ca. 



