gE I eT Tr me 
TRANSACTIONS OF THE SECTIONS. 111 
of the glottis. It was also distinctly observed, that the only outward 
moyements of the arytenoid cartilages were merely produced by their 
return to their former position after they had been carried inwards. 
From these experiments it was concluded, that all the muscles which 
move the arytenoid cartilages receive their motor filaments from the 
inferior laryngeal or recurrent nerves; and as the force of the muscles 
which shut the glottis preponderates over that of those which dilate 
it, so the arytenoid cartilages are carried inwards when all the fila- 
ments of one or both of these nerves are irritated. 
These experiments also show us, that one only of the intrinsic mus- 
cles of the larynx receives its motor filaments from the superior laryn- 
geal, viz. the cricothyroid muscle, and that, consequently, the only 
change which the nerve can produce on the larynx as a motor nerve, 
is that of approximating the ericoid cartilage to the thyroid ; in other 
_ words, of shortening the larynx. We shall see how far this view is 
supported by the subsequent experiments upon the living animal. 
The superior laryngeal nerve was cut on both sides in two dogs and 
one rabbit, and these animals readily swallowed both solids and fluids, 
without exciting cough or the least difficulty of breathing. The lungs 
of these animals were carefully examined after death, and none of the 
- food taken could be detected in the air-tubes. In several animals the 
superior laryngeals were first cut, and the inferior laryngeals imme- 
diately afterwards ; and it was ascertained that the previous division 
of the superior laryngeal did not prevent the difficult breathing, and 
symptoms of suffocation, which not unfrequently follow the division of 
the inferior laryngeal nerves, especially in young animals. 
To procure still more positive assurance of the effect of section of 
the different laryngeal nerves upon the movements of the glottis, these 
four nerves were exposed in a full-grown cat, and the larynx was then 
dissected out, and brought forward, without disturbing the nerves. 
After watching for a little the vigorous movements of the muscles of 
_ the glottis, seen during the struggles, crying, and increased respiratory 
movements of the animal, the inferior laryngeals were then cut across, 
_ and instantly all the movements of the muscles of the glottis ceased, 
and the arytenoid cartilages assumed the position in which they are 
found after death. The superior laryngeals were then cut, without ef- 
_ fecting the slightest enlargement, or any other change, upon the glottis. 
As the arytenoid cartilages were now mechanically carried slightly in- 
1 wards during the rushing of the air through the diminished aperture of 
_ the glottis in inspiration, by which this aperture was still farther con- 
tracted, its edges were kept apart with the forceps until an opening 
_ was made into the trachea to prevent the immediate suffocation of the 
animal. 
The glottis was brought into view upon another cat, as in the pre- 
ceding experiment, and the motions of the muscles of the glottis were 
again watched for a short time. The superior laryngeals were then 
cut, without diminishing in the least any of the movements of the ary- 
tenoid cartilages. The sides of the glottis were approximated, as in 
erying, so as to form but a narrow fissure ; and in struggling the aper- 
