588 SIGHT. 



folded during the attempt to close them farther. In fact, if my 

 cornea is felt at this moment, it is found just where it was 

 before ; and the circumstance of light being seen, although the 

 eyes were shut at first, disproves Sir C. Bell's statement, that, 

 " at the instant in which the eyelids are closed, the eye-ball 

 makes a movement which raises the cornea under the upper 

 lid." He also says that, if the eyelid is prevented from closing 

 by palsy or adhesion, the sudden approach of any thing to the 

 eye causes the cornea to ascend. I have no doubt that it will 

 ascend or descend, in order to get out of danger from the ap- 

 proaching body. 



But the crowning wonder of the whole is that one of the ob- 

 liques is not supplied by a nerve of the respiratory set. The 

 superior oblique is supplied by the fourth the pathetic or in- 

 ternal motor a pair evidently of voluntary motion, but which 

 is called by Sir C. Bell respiratory. Neither this, however, 

 nor any other respiratory nerve goes to the inferior oblique, 

 which is most unluckily supplied by the third only.? Further, the 

 oblique muscle, which is not supplied by the fourth or any 

 other respiratory (I 'am really ashamed of thus repeating the 

 word in so absurd a sense) nerve, but by a nerve of volun- 

 tary motion, is the more important muscle of the two in turn- 

 ing the eye upwards and inwards. For, not only does he con- 

 tend that this is its proper action (p. 312.), but that, when the 

 superior oblique is divided and it and its nerve rendered useless, 



g Sir C. Bell does not allude to this difficulty ; but quietly advances an opinion 

 which he may at any time adduce as his means of getting over it, should others 

 discover it. He fancies that nerves relax as well as contract muscles ; and 

 " that the influence of the fourth nerve is, on certain occasions, to cause a re- 

 laxation of the muscle to which it goes," in which case the eye-ball must be 

 rolled upwards. Thus the inferior oblique muscle acts because the fourth pair 

 lias relaxed the superior. The plain answer to this is, first, that the inferior 

 oblique muscle acts not only when it is unopposed, but when the superior oblique 

 is in action. Sir C. Bell speaks of their combined action, and it must move in 

 this by the positive stimulus of some nerve. Secondly, it of course is furnished 

 with a nerve, and this is a branch of the third not a respiratory pair, but a 

 pair of voluntary motion that supplies the straight muscles of the eye. In 

 fact, to suppose a muscle, not belonging to a cavity or canal, to move without 

 an exciting nerve, would be impossible ; and, were such a muscle to have no 

 nerve, its ^muscular structure would be useless a merely elastic substance 

 would have answered the purpose of lengthening under opposition and short- 

 ening when no longer stretched. 



