356 Analyses of a Series of Papers, by Mr. C. Bell, 



vated so as to be half covered by the upper eye-lid. This 

 condition of the eye during its insensible unexercised state, 

 we are required to explain. 



" It is a fact familiar to pathologists, that when debility 

 arises from affection of the brain, the influence is greatest on 

 those muscles which are, in their natural condition, most un- 

 der the command of the will. We may perceive this in the 

 progressive stages of debility in the drunkard, when succes- 

 sively the muscles of the tongue, the eyes, the face, the limbs, 

 become unmanageable; and, under the same circumstances, 

 the muscles which have a double office, as those of the chest, 

 lose their voluntary motions, and retain their involuntary mo- 

 tions, the force of the arms is gone long before the action of 

 breathing is affected. 



" If we transfer this principle, and apply it to the muscles of 

 the eye, we shall have an easy solution of the phenomena 

 above enumerated. The recti are voluntary muscles, and 

 they suffer debility before the oblique muscles are touched by 

 the same condition: and the oblique muscles prevailing, roll 

 the eye. 



" If it be further asked, why does the eye roll upwards and 

 inwards ? we have to recollect, that this is the natural condi- 

 tion of the eye, its position when the eye-lids are shut, and the 

 light excluded, and the recti at rest, and the obliqui balanced." 

 The circumstance of there being only nine nerves properly 

 enumerated as proceeding from the brain, and six of these dis- 

 tributing themselves to the eye; since the second, third, 

 fourth, fifth, sixth and seventh, go into the orbit, and, as the 

 author expresses it, may be said to be concentrated into a 

 space no larger than a nut-shell ; affords an opportunity of de- 

 monstrating the existence of a correspondence between the 

 compound functions of an organ, and the nerves transmitted 

 to it, according to what was stated hypothetically in the first 

 part of the paper. 



But it cannot be expected, in the investigation of a subject 

 rendered so difficult by reason of the number and complexity 

 of the nerves transmitted to a small organ like the eye, that it 

 is always possible to give demonstrative evidence, or to an- 

 swer opposition by means of experiments; and here the author 

 is obliged to trust more to reasoning, and to a minute atten- 

 tion to the anatomy, than to experiment. 



Of the Function of the Ophthalmic Branch of the fifth Nerve. 



We are, in the first place, to inquire by what nerve the com- 

 mon endowment of sensibility is bestowed upon the mem- 

 branes and surfaces of the eye. On recurring to this subject, 



we 



