REVIEW OF RESPONSE OF ISOTROPIC ORGANS 697 



ever, employing numerous specimens, that these mechanical 

 and electrical spasms take place, under normal conditions, 

 at the same point. In the case of phanerogamous plants, 

 this is found to be at or very near 60 C. (figs. 328, 329, 

 330). That these mechanical and electrical spasms, further, 

 constitute a true case of excitatory response, is proved 

 by the fact that induced physiological depression also 

 induces depression of the death-point. Fatigue may thus 

 lower the death-point by as much as 19 C. 



The response of contraction, initiated at the death-point, 

 is later converted into post-mortem relaxation, and galvano- 

 metiically the negativity initiated at the same moment 

 becomes subsequently a post-mortem positivity. 



With regard to the so-called Current of Injury it was 

 shown that this arises as the after-effect of strong stimulus. 

 It should be remembered that a cut, or the application of a 

 heated wire, constituting mechanical and thermal sections 

 respectively, will act as a strong stimulus, and, further, that 

 the after-effect of excitatory galvanometric negativity is 

 persistent when the stimulus is strong. The excitatory 

 effect, moreover, is transmitted from the point of application 

 to greater or less distances, according to the strength of 

 stimulus and the conductivity of the tissue. As this trans- 

 mitted effect undergoes diminution with distance, it is 

 obvious that the most intense negativity will be .induced at 

 the point of section, undergoing a gradual diminution as 

 we move further away from it. If, taking a given length of 

 isotropic tissue, we make two opposite terminal sections, we 

 shall clearly have a symmetrical, distribution of electrical 

 potential as regards the middle or equatorial zone, the two 

 ends being most negative, while the equator is relatively 

 most positive (fig. no). Two points symmetrically situated 

 as regards this equator would thus be equi-potential, while 

 a-symmetrical points would show appropriate differences of 

 potential, a zone near the equator being relatively positive 

 to one which is further away from it, or nearer to the 

 terminal section. These considerations, supported as they 



