OBSERVATIONS OK VISION. 



529 



luminous lines, branched, and somewhat 

 connected with each other, darting from 

 every part of the field of view, towards a cen- 

 tre a little exterior and superior to the axis of 

 the eye. This centre corresponds to the in- 

 sertion of the optic nerve, and the appear- 

 ance of lines is probably occasioned by that 

 motion of the retina which is produced by 

 the sudden return of the circulating fluid, into 



the veins accompanying the ramifications of 

 the arteria centralis, after having been de- 

 tained by the pressure which is now inter- 

 mitted. As such an obstruction and such a 

 readmission must require particular circum- 

 stances, in order to be effected in a sensible 

 degree, it may naturally be supposed that 

 this experiment will not always easily suc- 

 ceed. 



VOL. 11. 



S T 



