324 NATURAL THEOLOGY. 



muscles of the eye — itself introductory to obser- 

 vations on the nerves of the orbit. The discussion 

 relating to these is too strictly and minutely ana- 

 tomical for our present purpose. It will be suffi- 

 cient if I state the deduction, — that by the eight 

 muscles around the eye, and the six nerves, whose 

 extremities reach them, two sets of motions are 

 provided ; the first for the voluntary direction of 

 the eyeball in strict sympathy with vision ; the 

 other in connexion with the mechanical and hy- 

 draulic apparatus for the protection of the organ. 

 When we enjoy the sense of vision, the voluntary 

 muscles are excited ; but, in sleep, another class 

 preponderates, over which we have no voluntary 

 power ; and this is the condition of rest as well as 

 of safety to the organ. 



