.) 
| Baly, vol. i. p. 263, 2nd edit. 
PAR VAGUM. 
mucous secretions were not poured out from the 
mucous surface of the stomach and intestines, 
though it presented the inflammation usual in 
such cases.* We have carefully repeated these 
experiments, and obtained different results. The 
quantity of watery and mucous secretions was 
nearly the same inanimals after the vagi had been 
divided, as in animals upon which this operation 
had not been performed.t These experiments 
upon the effects of lesion of the vagi upon the dif- 
ferent secretions poured out from the inner sur- 
face of the digestive canal, though they do not 
prove that the function of secretion is indepen- 
dent of the nervous system, seeing that nume- 
rous filaments of the sympathetic uerve are also 
distributed there, are yet sufficient to neutralize 
the evidence drawn from the effects of lesion of 
the vagi upon these secretions adduced by 
those who maintain that secretion is dependent 
upon the nervous system. 
Effects of lesion of the vagi upon the 
rapidity of absorption from the inner surface of 
the stomach.—lIt has been stated by Dupuyt 
and Brachet, that the most active poisons in- 
troduced into the stomach after division of the 
vagi in much larger quantities than usual, pro- 
duce their effects much more slowly. On the 
other hand Miiller mentions that in thirty ex- 
periments on Mammalia performed under his 
direction by M. Wernscheidt, “ not the least 
difference could be perceived in the action of 
narcotic poisons introduced into the stomach, 
whether the nervus vagus had been divided on 
both sides or not, provided the animals were of 
the same species and size.”§ We have made 
several comparative experiments on this point,|| 
and obtained results which agreed nearly with 
those mentioned by Miiller. 
The following short summary contains the 
principal conclusions founded upon the facts 
and observations above detailed, at which we 
have arrived regarding the functions of the 
nervus vagus. 
1. Though the trunk of the nervus vagus at 
its attachment to the encephalon principally 
consists of sensiferous and incident filaments, 
it yet contains a few motor filaments. The 
motor filaments contained in some of the 
branches of the vagus chiefly come from the 
spinal accessory. 
2. The filaments of the auricular branch of 
the vagus are sensiferous and incident. 
2. The pharyngeal branches of the vagus are 
principally if not entirely motor, and move the 
muscles of the pharynx and soft palate in 
obedience to certain impressions made upon 
the incident filaments of the glosso-pharyngeal 
and fifth pair of nerves distributed upon the 
mucous surface of these organs. 
4. The superior laryngeal branch is chiefly 
composed of sensiferous and incident filaments 
which are abundantly distributed upon the 
* Philos. Trans., 1812, p- 102. 
+ Opus cit. for 1839, vol. li. 
t Opus cit. p. 366. » 
| Opus cit. p. 186. 
Muller’s Elements of Physiology, translated by 
§ Opus cit. vol. li. 
901 
mucops surface of the larynx, and much more 
sparingly upon the inner surface of the lower 
part of the pharynx. The few motor filaments 
contained in the superior laryngeal are dis- 
tributed in, and move the crico-thyroid muscle. 
When the superior laryngeal branches are 
divided or tied, every excitation of the inner 
surface of the larynx fails to excite sensation, 
or any reflex and muscular movement, and the 
two crico-thyroid muscles are paralysed. 
5. The inferior laryngeal or recurrent 
branch is ramified in, and regulates the move- 
ments of all the muscles attached to the aryte- 
noid cartilages, viz. the crico-arytenvideus pos- 
ticus and lateralis, the thyro-arytenoideus, and 
the arytenoidei. The inferior laryngeal also 
furnish the sensiferous filaments to the upper~ 
part of the trachea, a few to the mucous surface 
of the larynx, and still fewer to the pharynx. 
The sensiferous filaments of the inferior laryn- 
geal are, however, few in number and do not 
impart much sensibility to the parts in which 
they are distributed, presenting a striking con- 
trast in this respect to the superior laryngeal. 
When the inferior laryngeal is cut or tied, the 
muscles attached to the arytenoid cartilages are 
no longer moved voluntarily as in speech, or 
involuntarily as in the muscular movements of 
respiration ; and the arytenoid cartilages may 
be mechanically carried inwards by the cur- 
rents of air rushing into the lungs, so as to shut 
up the superior aperture of the larynx and pro- 
duce suffocation. When any excitation is 
applied to the inner surface of the tarynx in the 
healthy state, this does not produce the con- 
traction of the muscles which approximate the 
arytenoid cartilages by acting directly upon 
them through the mucous membrane; but this 
muscular contraction is effected indirectly and 
by a reflex action, in the performance of which 
the superior laryngeal acts as the incident or 
afferent nerve, and the inferior laryngeal as the 
motor or efferent nerve. It is also probable 
that these filaments of the inferior laryngeal 
distributed in the muscular fibres of the trachea 
are motor. The inferior laryngeal branch is the 
principal nerve of phonation, and when para- 
lysed the voice becomes very faint. The 
effects of the paralysis of the superior laryngeal 
upon the voice are much less marked and are 
much more doubtful. 
5. The esophageal branches of the vagus are 
partly afferent and partly efferent nerves. In 
some animals, as in the rabbit, the section of 
the vagi in the neck is followed by the sus- 
pension of the movements of the esophagus 
during deglutition, and the food is no longer 
conveyed along it in the usual manner. This 
lesion of the vagi does not produce these effects 
by destroying the contractility of the muscular 
fibres of the cesophagus, but by breaking the 
continuity of the nervous circle necessary for 
the accomplishment of all reflex movements. 
In some other animals, as in the dog, the food 
is still propelled along the esophagus after 
section of the vagi, so that it is probable that in 
these animals the muscular fibres of the ceso- 
phagus are also called into contraction by direct 
excitation. 
