74 



Prof. C. S. Sherrington. 



[July 30, 



in same way as in 2, continuous steady sensation from the conjugate 

 left retinal spot, 



And when the intensity of that continuous sensation from left 

 retina corresponds with an intensity of light stimulus more than half 

 that of each stimulus employed in repetition for the conjugate of the 

 right eye, 



Then the rate of intermission required for obtaining steady sensa- 

 tion from disc A is higher than that required for obtaining it from the 

 disc B. 



Of the two discs, seen under speeds sufficient to give stead) 7 sensation 

 from both, disc B appears the brighter. 



Experiment 4. — The disc A representing uniocular vision as before. 



When the disc B represents intermittent right retinal stimulation, 

 together with, in the same way as in 2 and 3, steady sensation from 

 the conjugate left retinal spot, 



And when the intensity of that steady sensation from left retina 

 corresponds with that due to a light stimulus of less than half the in- 

 tensity of each member of the series of repeated stimuli employed for 

 the conjugate spot of the right eye, 



Then the rate of intermission required for obtaining steady sensa- 

 tion from disc A is higher than that required for obtaining it from the 

 disc B. 



And of the two discs, both seen under speeds sufficient to yield 

 steady sensation, disc A appears the brighter, unless the field offered 

 to the left eye is given by closing that eye or otherwise screening with 

 a homogeneous darkness. 



Experiment 5. — -The disc A representing uniocular vision as before, 



And when the disc B represents intermittent right retinal stimula- 

 tion, the intervals of intermission exactly corresponding with periods of 

 illumination of the conjugate spot of the left retina, and the inter- 

 mittent stimuli being equal in intensity and duration for both right 

 and left conjugate spots ; 



Then the rate of intermission required for obtaining steady sensation 

 from disc A is higher than that required for obtaining it from 

 disc B. 



Of the two discs, both seen under speeds of intermission sufficient 

 to yield steady sensation, the disc B appears to be of a brightness not 

 obviously different from that of disc A. 



Experiment 6. — With disc A as before. 



When disc B represents intermittent right retinal stimulation, 

 similar in every way to that applied to the conjugate of the left 

 retina, except that its phases of light and shade precede or succeed 

 those applied to the other retina by an interval of half a phase 



length, 



Then the rate of intermission required for obtaining steady sensa- 



