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 

Before 1 After sefore an After 3efore 4 After 
Fic. 117.—ABouiTIon oF Response IN NervE, Puant, anp Mera 
BY THE ACTION OF THE SAME ‘ Porson’ 
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 
