MECHANISM OF PROCESS OF DEATH 73 



as equally toxic if we adopt death as the criterion, 

 but as unequally toxic if we take any other criterion. For 

 example at 90%, A appears to be seven times as toxic as B. 



It is clear that we cannot escape from this difficulty 

 by comparing the effects produced in equal times. 



In view of these facts it is obviously undesirable to 

 compare results obtained by the use of unlike criteria, 

 as is often done. 



Another method is to measure the degree of recovery 

 which is found where tissues are taken from toxic solu- 

 tions and replaced in sea water. This will be explained 

 more fully in Chapter III. It has many advantages which 

 entitle it to serious consideration. The writer has found 

 that death in many toxic substances, as measured by the 

 electrical method, follows approximately the course of a 

 monomolecular reaction. In such cases the constants 

 which express the reaction velocities of the two reactions 

 afford a measure of their relative toxicity. In cases 

 where such constants cannot be used, but where the com- 

 plete curve can be obtained, it would be possible to adopt, 

 as an arbitrary standard, the time necessary for the 

 reaction to proceed half way to the death point. But, 

 when the curves are related to each other as are A and B 

 in Fig. 31, it may be desirable to use some other criterion. 

 It is in any case desirable to give the whole curve, when- 

 ever possible, so that the reader may apply his own 

 criterion. The ease with which complete curves can be 

 obtained by determining electrical resistance may render 

 this method useful, especially since the writer has found 

 it possible to apply it to all sorts of plant tissues as well 

 as to some animal tissues. 



The electrical method is not restricted to solutions 

 of the same conductivity. For example, we find that 



