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Mr. Bell on the 
the eyelids to counteract the force of the impulse, and to 
guard the delicate texture of the eye. If the eyelids be held 
open during the act of sneezing, no sensation of light will 
be experienced, because the contraction of the eyelids upon 
the eyeball is prevented. 
Can we believe this action of the muscle of the eyelids in 
combination with the action of the respiratory muscles, to be 
an accidental connection ? Is it not rather a provision to com- 
press and support the vascular system of the eye, and to 
guard it against the violent rush of blood which attends cer- 
tain acts of respiration ? If we open the eyelids of a child to 
examine the eye while it is crying, and struggling with pas- 
sion, by taking off the natural support from the eye, the 
blood at the same time being forced violently into the head 
by the act of respiration, we shall see the conjunctiva sud- 
denly fill with blood, and the eyelid everted. 
The respiratory nerve of the face performs two offices, 
one of which is voluntary, as in moving the cheeks and lips 
in speech ; and the other involuntary, as in moving the nos- 
trils in breathing during sleep or insensibility. In like manner 
that branch of the respiratory nerve which is prolonged to 
the eyelids performs a double office, contracting the eyelids 
by volition, and also producing those involuntary winking 
motions of the eyelids which disperse the tears, and preserve 
the lucid surface clear.* 
* Having distinguished the functions of the fifth and seventh nerves, a question 
still remains, whether the different operations performed by any one of them, de- 
pend on the exercise of distinct filaments ? I believe these filaments to be distinct 
nerves bound up together, and analogy would lead me to suppose them capable of 
distinct functions ; but I cannot demonstrate this unless in the spinal nerves, where 
the roots are separate. 
