September 1, 1916] 



SCIENCE 



319 



fast as it is decomposed and its concentration 

 remains constant. But under unfavorable con- 

 ditions the decomposition of "M. proceeds faster 

 than its formation; this results in injury and, 

 if carried far enough, in death. 



The processes which produce this result in 



such solutions as mixtures of NaCl and CaCl, 



are checked by a salt compound 4 of the type 



Na.XCaCl, formed by the reversible reaction 



2NaCl + X + CaCL ^± Na.XCaCl,, 



in which X is a constituent of the protoplasm. 

 The amount of this salt compound formed 

 in each mixture of N~aCl + CaCL, can be cal- 

 culated by the formula 

 Conc w 



A' = 



°Na»XCaCU 



( Conc NaCl) 2 ( ConC C a Cl 2 ) ( Conc x) 



In pure NaCl the amount of Na,XCaCl 4 will 

 be zero, but if increasing- amounts of CaCL, be 

 added the amount of Na..XCaCl 4 will increase 

 to a maximum and thenidecline until it again 

 reaches zero in pure CaCL. 



Let us assume that the maximum amount of 

 Na.,XCaCl 4 is found when the molecular pro- 

 portions 5 are 95.24 NaCl + 4.76 CaCL. It is 

 evident that we can get this same amount in 

 a different mixture (e. g., 50 NaCl -4- 50 CaCL) 

 by increasing the absolute concentrations of 

 NaCl or CaCL. "We should therefore get an 

 equally favorable result in both cases : but 

 this is contrary to the results of experiment. 

 If the phenomena of antagonism really in- 

 volve a salt compound like Na-XCaGL. it is 

 evident that some mechanism must exist 

 which insures that an increase in the total 

 concentration of salts will have little effect 

 as compared with that produced by a change 

 in their relative proportions. 



It is easy to see that such a mechanism must 

 exist if the formation of Na,XCaCl 4 takes 



■4 The actual proportion of Na and Ca in this 

 eomponnd may be supposed to differ according to 

 the proportion of these substances in the most 

 favorable mixture. In place of Na and Ca we 

 may have other antagonistic salts, and more than 

 two may enter into the compound. 



5 These are the proportions found in an in- 

 vestigation described in Proc. Am. Phil. Soc, 55, 

 1916. 



place at a surface. In a surface substances 

 usually exist in a different concentration from 

 that which they have elsewhere in the solu- 

 tion. If NaCl and CaCL, migrate into the 

 surface, so as to become more concentrated 

 there than in the rest of the solution, their 

 concentration in the surface must increase, as 

 their concentration in the solution increases, 

 up to the point where the surface is saturated. 

 Beyond this point an increase in their con- 

 centration in the solution produces no effect 

 on their concentration in the surface. When 

 this stage has been reached the formation of 

 lSra„XCaCl 4 , if it takes place in the surface, 

 will not be affected by an increase in the con- 

 centration of the salts in the solution. It will, 

 however, be affected by changes in the relative 

 proportions of the salts. The number of mol- 

 ecules in a unit of surface will remain nearly 

 constant, but if the proportion of NaCl in the 

 solution be increased some of the CaCL, in the 

 surface will be displaced by NaCl. 6 



Below the saturation point the relative pro- 

 portions of the salts will be of less importance 

 than their total concentration : this is the 

 case at low concentrations in the region of the 

 so-called " nutritive effects." 



It is evident that if we adopt this theory we 

 can see why the most favorable proportion 

 must remain approximately the same in spite 

 of variations in concentration. We thus ar- 

 rive at a satisfactory explanation of Weber's 

 law. 



It is evident that Weber's law will not apply 

 when the concentration is below the saturation 

 point. On the other hand at high concen- 

 trations effects of osmotic pressure, coagula- 

 tion, etc., may exert a disturbing influence. 



Thus far we have discussed effects in which 

 the criterion of antagonism is electrical re- 

 sistance or permeability. But it has been 

 shown by the writer that electrical resistance 

 and permeability are very accurate and sensi- 



e It may easily happen that NaCl and CaCL do 

 not migrate equally into the surface. If we as- 

 sume that 10 times as much CaCl, enters the sur- 

 face as NaCl we shall find the maximum amount 

 of NaXCaCL, in 95.24 NaCl 4- 4.76 CaCl». (Cf. 

 Proc. Am. Phil. Soc, 55, 1916.) 



