138 INJUKY, RECOVERY, AND DEATH 



(H 2 0) 



D 



A 100 



o/ 

 /o 



B 



100-%' 



the solutions according to the scheme shown in Fig. 57. 

 In this figure the abscissae have the same significance as 

 in Fig. 56, while the ordinates represent various dilutions 

 of the mixtures. Thus all points on the line CD represent 

 distilled water, while a point such as E, halfway between 



A and C, represents a mixture 

 containing equal quantities of 

 distilled water and of A 0.1 M. 

 The points on the line EF, 

 therefore, represent the same 

 mixtures as the corresponding 

 points on the lowest line, ex- 

 cept that the concentrations 

 are in all cases just one-half 

 as great as those represented 

 on the base line. It is evident 

 that the growth in any concen- 

 tration may be expressed by 

 erecting at the proper point a 

 line perpendicular to the plane 

 of the paper. In this way, we 



may ^^ & ^^ m()del ^^ 



gives a complete description of the changes in growth 

 produced by diluting the various mixtures. Such a model 

 is shown in Fig. 58. 



In all of these cases the measurements are made after 

 growth has ceased and in consequence they represent a 

 final condition of development. If, however, we use 

 electrical conductivity as a criterion of antagonism, we 

 obtain curves which change constantly. (See Fig. 78). 

 In this case the best method of procedure is to construct 

 the time curves of the death process and to compare the 



FIG. 57. Diagram representing the 

 composition of solutions (this serves 

 as the base of the solid model shown in 

 Fig. 58): the lowest line represents 

 various mixtures of solutions of two 

 salts, A and B; the line EF represents 

 the same mixtures diluted with equal 

 volume of water; any line drawn 

 parallel to EF will express the same 

 mixtures diluted to a degree corres- 

 ponding to the position of the line, the 



represent distilled water. 



