584 PHYSIOLOGY 



on both sides of the stimulated spot we should have a phenomenon exactly 

 analogous to the process of simultaneous contrast. In the same way the 

 increased briskness of the antagonistic reflex which follows the temporary 

 inhibition accompanying the primary reflex can be compared to the negative 

 after-image resulting on prolonged stimulation of any point in the retina, 

 while alternating after-images, positive and negative, which may succeed a 

 single positive stimulation, have their analogue in the alternating rhythmic 

 movements of flexion and extension of the two legs which may follow single 

 stimulation of one of them. The phenomena of binocular contrast show 

 that the retinae are not alone concerned in the production of these pheno- 

 mena, but that we are dealing also with the central connections of the optic 

 nerves, the activities of which must be regulated by the same laws as those 

 determined from our study of the more lowly activities of the spinal cord. 



