80 



rectus and superior oblique muscles ; the superior rectus 

 plays over its pulley, and the superior oblique passes beneath 

 the former to reach its insertion in the sclerotic coat. 



The presence of some such contrivance as is here ex- 

 hibited might have been inferred from its necessity, and yet 

 it has never been suspected to exist. The four recti muscles 

 running from the bottom or apex of the orbit, forward to grasp 

 the eye, must, without it, have had the power of retracting the 

 ball of the eye, and yet no such retraction has ever been ob- 

 served in the human eye. Retraction is certainly performed 

 in some of the lower classes of animals; but Mey are provided 

 with a strong retractor muscle, independent of the four recti 

 muscles. Again, the rotatory movements of the human eye, 

 which enlarge the sphere of vision, and contribute to ex- 

 pression, are not easily accounted for by the received ana- 

 tomy of the orbit, because the course of the muscles from 

 the bottom of the orbit forwards, manifestly gives them a 

 power of retracting rather than of rotating the eye upon its 

 centre. Thus, then, there appeared to be no pi'ovision for 



