I 
2 96 Mr. Bell on the 
The course of inquiry leads us, in the next place, to ob- 
serve the vicinity of the root of this fourth nerve, to the 
origin of the respiratory of the face, and we find them arising 
from the same track of fibrous substance. The column of 
medullary matter which constitutes that part of the medulla 
oblongata from which the respiratory nerves arise, termi- 
nates upwards, or at its anterior extremity, just under the 
corpora quadrigemina, and there the fourth arises. Is it 
possible then, we say, that there can be any correspondence 
between the general act of respiration, and the rolling of the 
eye ? Led thus to make the experiment, I was gratified to 
find it so easy to give the proof. On stopping the nostrils 
with the handkerchief, every effort to blow the nose will be 
attended by a rapid rising of the cornea under the upper 
eyelid. And on every occasion when the eyelids suffer con- 
traction through the agency of the respiratory nerve of the 
face, as in sneezing, the eyeball is rolled upwards through 
the agency of the fourth nerve. 
I might, perhaps, be satisfied with having made the obser- 
vation of these two facts ; first, that there is such a combi- 
combine to one effort, but also that relation between the classes of muscles by which 
the one relaxes while the other contracts. I appended a weight to a tendon of an 
extensor muscle, which gently stretched it and drew out the muscle ; and I found 
that the contraction of the opponent flexor was attended with a descent of the 
weight, which indicated the relaxation of the extensor. To establish this connec- 
tion between two classes of muscles, whether they be grouped near together, as in 
the limbs, or scattered widely as the muscles of respiration, there must be particular 
and appropriate nerves to form this double bond, to cause them to conspire in 
relaxation as well as to combine in contraction. If such a relationship be es- 
tablished, through the distribution of nerves, between the muscles of the eyelids and 
the superior oblique muscle of the eyeball, the one will relax while the other 
contracts. 
