GENERAL SURVEY AND CONCLUSION 189 



same drug, administered in large or small doses, might 

 have opposite effects, and in preceding chapters we 

 have seen that the same statement holds good of plants 

 and metals also. 



Stimulus of light. Even the responses of such a 

 highly specialised organ as the retina are strictly 

 paralleled by inorganic responses. We have seen how 

 the stimulus of light evokes in the artificial retina 

 responses which coincide in all their detail with those 

 produced in the real retina. This was seen in ineffective 



nmww flWl^. 



Before f After Before f After Before * After 



FIG. 117. ABOLITION OF EESPONSE IN NEKVE, PLANT, AND METAL 



BY THE ACTION OF THE SAME POISON ' 



The first half in each set shows the normal response, the second half the abolition 

 of response after the application of the reagent. 



stimuli becoming effective after repetition, in the relation 

 between stimulus and response, and in the effects pro- 

 duced by temperature ; also in the phenomenon of after- 

 oscillation. These similarities went even further, the 

 very abnormalities of retinal response finding their 

 reflection in the inorganic. 



Thus living response in all its diverse manifestations 

 is found to be only a repetition of responses seen in the 

 inorganic. There is in it no element of mystery or 

 caprice, such as we must admit to be applied in the 



