-_— - 
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Det ee § 
PAR VAGUM. | 
jected to considerable suffering before the nerve 
can be exposed, this result cannot be taken as 
a conclusive test that it contains no fila- 
ments of common sensation. We also found 
that division of this branch on both sides ren- 
dered the second stage of deglutition difficult, 
by paralysing the muscles of the pharynx. The 
morsels of food were forced through the now 
passive bag of the pharynx to the commence- 
ment of the wsophagus by the repeated efforts 
of the muscles of the tongue and those attached 
to the larynx and hyoid bone. From these 
facts, we concluded that the pharyngeal branches 
of the vagus are chiefly, perhaps entirely, com- 
posed of motiferous filaments, and- that they 
convey outwards the motive influence by which 
the muscles of the pharynx and soft palate are 
excited to contraction in the reflex muscular 
movements of deglutition.* It is possible that 
they may also contain a few sensiferous and 
incident filaments. Valentin, on irritating these 
branches in different animals immediately after 
death, saw the pharynx contract in a marked 
manner through its whole length.+ 
Volkmann states, as we have already had 
occasion to mention, that various muscles of 
the soft palate and pharynx were thrown into 
contraction on excitation of the vagus within 
the cranium.{ He further observes, that he 
could not perceive any movements in the mus- 
cles of the pharynx or soft palate on irritating 
the spinal accessory within the cranium. This 
last result is certainly one which we would not 
expect, but the remarks we have to make upon 
it will be more appropriately introduced in the 
article Sprnat Accessory Nerve.§ Longet 
observed very marked contractions in the pha- 
rynx on galvanizing the pharyngeal branch of 
the vagus in the horse and the dog.|| Though 
the experiments we have referred to, in illus- 
tration of the functions of the pharyngeal 
branches of the vagus, differ in some respects, 
they all agree in this, that extensive and active 
muscular movements of the pharynx may be 
produced by their excitation, and that they 
therefore contain many motor filaments. We 
have adduced some facts which would seem to 
shew that they contain few, if any, motor fila- 
ments. 
Laryngeal branches—When the superior 
* Edin. Med. and Surg. Jour. 1838. 
+ De Functionibus Nerv. Cerebralium, &c, p. 17, 
¢ Volkmann concludes, as we have already men- 
tioned, from his experiments that the stylo-pharyn- 
geus and middle constrictor muscle of the pharynx 
do noi derive their motor filaments from the pha- 
ryngeal branch of the vagus, but from the glosso- 
pharyngeal. In the article GLosso-PHARYNGEAL, 
_ we have stated, that, when this nerve is insula- 
ted carefully from the neighbouring nerves, no 
direct muscular movements follow its excitation. 
Valentin (opus cit. p. 38) and Longet (opus cit. 
_ tom. ii. p.223) have from these experiments ar- 
rived at the same conclusions as we have on this 
point. 
§ We may merely state in the mean time that 
_ Longet (opus cit. tom, ii. p.27) has drawn from 
_ his experiments the conclusion that the spinal ac- 
cessory furnishes all the motor filaments of the 
muscles of the larynx. 
|| Opus cit. tom. ii. p. 271. 
893 
laryngeal nerve is laid bare in a living animal 
and pinched with-the forceps, the animal gives 
indications of severe suffering, while on re- 
peating the same experiment on the inferior la- 
ryngeal the animal seldom gives any indication 
of suffering pain. When an opening is made 
into the trachea, and a probe introduced through 
it into the interior of that tube and passed up- 
wards, it excites little or no uneasiness until it 
reaches the interior of the larynx, when violent 
paroxysms of coughing and signs of great un- 
easiness immediately tollow. The division of 
the inferior laryngeal nerves has no eflect in 
diminishing the severity of these paroxysms of 
coughing or in quieting the struggles of the 
animal, while they instantly cease on cutting 
across the internal branch of the superior la- 
ryngeal nerves. Before Magendie published 
his observations upon the functions of these 
nerves it appears to have been generally be- 
lieved that the different intrinsic muscles of the 
larynx received motor filaments both from the 
superior and inferior laryngeal nerves. Magen- 
die has, on the other hand, maintained that the 
superior laryngeal moves those muscles which 
shut the superior aperture of the larynx, and 
the inferior laryngeal those which open it, and 
he supposed that this view sufficiently ex- 
plained the closure of the superior aperture of 
the larynx on the division of both inferior la- 
ryngeal.* We found that on applying ditlerent 
excitants to the superior laryngeal nerve before 
it gave off its external branch in several animals 
immediately after death, that the crico-thyroid 
muscle was thrown into powerful contraction 
and the cricoid approximated to the thyroid 
cartilage, while all the muscles attached to the 
arytenoid cartilages remained quiescent. On 
irritating the inferior laryngeals all the muscles 
attached to the arytenoid cartilages were thrown 
into contraction, and as the force of those mus- 
cles which close the superior aperture of the 
larynx preponderates over that of those which 
open it, the arytenoid cartilages were drawn 
forwards and inwards, and the superior aperture 
of the larynx was closed. By applying the ex- 
citation to the nerves for a short time and in 
rapid succession,, the superior aperture of the 
larynx could be made to close and open alter- 
nately,—to close during the period of excitation 
and to open during the intervals,—and it was 
also remarked that the outward movement, or 
that of opening, was dependent upon the elas- 
ticity of the parts. The inferences from these 
results were strengthened by an examination of 
the anatomical distribution of the laryngeal 
nerves, and confirmed by experiments upon 
living animals.t From these and other facts 
related in the paper referred to, we arrived at 
the following conclusions. The superior la- 
ryngeal furnishes one only of the intrinsic 
muscles (the crico-thyroid) of the larynx with 
motor filaments, while it supplies nearly all the 
sensiferous and incident filaments of the larynx, 
* Compendium of Physiology, pp. 132 and 399. 
Milligan’s Translation, 4th ed. 1831. Legons sur 
les Phénomenes Physiques de la Vie, tom, ii, 
p- 228, 1837. 
+ Edin. Med. and Surg, Jour., pp. 138, 139, 1838. 
