PAR VAGUM. 
has published various experiments upon these 
nerves very similar to those which we had per- 
formed, and obtained nearly the same results. 
Longet states that the respirations become in- 
creased in frequency after dividing the recur- 
rents. Other experimenters have lately satisfied 
themselves of the accuracy of these experiments. 
Effects of the laryngeal nerves on phonation. 
—The effect of the lesion of the recurrent 
herves in enfeebling the voice was well known 
to Galen and the older physiologists.* We 
found in making this experiment that the voice, 
as Monro Secundus+ and others have stated, 
is not altogether lost, for in some cases, at 
_ Teast, the animal could still emit a faint howl. 
_ Longett has observed that the voice is com- 
pletely lost in old animals, while young animals 
are still able to produce acute sounds different 
from the natural voice if the crico-thyroid 
muscle moved through the external branch of 
__ the superior laryngeal be not paralysed, and he 
attributes this difference to the relative size of 
the larynx at these ages. We can have no 
_ doubts in attributing the effects of lesion of the 
inferior laryngeals upon the voice to the para- 
lysis of the muscles attached to the arytenoid 
cartilages. § 
Magendie mentions that an animal after 
section of the superior laryngeal nerves “ loses 
almost all its acute sounds it acquires, besides 
a constant gravity which it had not previously.”|| 
This he attributed to the arrestment of the 
movements of the arytenoid muscles, but we 
have shown that the section of these nerves has 
no such effect. Bischoff could perceive no 
change upon the voice after he had divided 
_ these nerves in two dogs. -Longet states that 
the division of those nerves above the origin of 
_ the erternal branch, or of the external branch 
__ alone, is followed by a disagreeable hoarseness 
of the voice.** If the variations in the length 
| of a tube alter the graveness and acuteness of 
_ the sounds which it emits, we would expect that 
the lesion of the superior laryngeals should, by 
arresting the movements of the crico-thyroid 
muscle, produce some change in this respect. 
Longet believes that the crico-thyroid muscles 
are, during their contraction, tensors of the 
' vocal chords, and that the changes upon the 
_ voice induced by dividing the superior laryn- 
| geals depend upon the effect which paralysis 
| of these muscles has upon the tension of the 
ts vocal chords.++ 
| Csophageal branches——Muscular contrac- 
| tions have been observed in the ceesophagus on 
_ * Vide Haller’s Elementa Physiologie, tom. iii. 
 p. 408, Lausan. 1766, 
_ + Observations on the Nervous System, p. 65. 
_ $ Opus supra cit., p. 14 and 15. 
__§ 1 have seen some cases of partial aphonia in 
the human species arising from the compression of 
one recurrent in the upper part of the chest by an 
-aneurism of the aorta. 
_ || Compendium of Physiology, p. 138, 1831. 
Opus cit. p. 27. 
_** Dupuytren had previously maintained that 
econ of the superior laryngeals was followed by a 
‘disagreeable hoarseness, Biblioth. Medic. tom. 
Xviii., 1807, as quoted by Longet. 
tt Opus cit, p. 8 and 37, 
895 
irritating the trank of the vagus, by Arnemann,* 
Cruikshank,+ Mayo,t{ and others. When the 
trunk of the vagus is irritated above the origin 
of the recurrent, the muscular fibres of the 
cesophagus along its whole length are thrown 
into active contraction. In experiments upon 
rabbits we found that the esophagus became 
impacted with food eaten after section of the 
vagi in the neck, when very little of it had 
reached the stomach and when no efforts at 
vomiting had occurred, while its muscular 
fibres could still readily be thrown into active 
contraction by direct excitation. From this we 
inferred that before the presence of the ingesta 
in this tube can excite its muscular fibres to 
contract and propel its contents onwards, the 
same conditions of the nervous system are ne- 
cessary as for the production of the excito- 
motory movements, and that certain of the fila- 
ments of the vagi act as incident and others as 
motor nerves. That the food also collects in 
the esophagus in the horse and sheep after 
division of the vagi may be inferred from the 
experiments of Dupuy § and others. In subse- 
quent experiments upon dogs we found that 
substances seem to pass pretty freely along the 
esophagus in that animal after section of the 
vagi. It would appear, however, that even 
in the dog the food is occasionally retained in 
the cesophagus after dividing the vagi.|| Arnold 
(opus eit. p. 144) observed in his experiments 
upon hens and pigeons that the cesophagus and 
crop were so relaxed after section of the vagi 
that when the animals shook their head and 
neck, or kept the head in a depending position, 
a quantity of chyme flowed from the bill. 
From a review of all these facts we are in- 
clined to agree in the opinion lately expressed 
by Dr. M. Hall, that in some animals the 
muscular contractions of the cesophagus are 
excito-motory, while in others they are called 
into action by direct excitation. We cannot 
at present determine whether the propulsion of 
the food along the csophagus in the human 
Species partakes more of the former or of the 
latter class of movements. Magendie has as- 
certained that various muscular movements go 
on in the lower 7 of the csophagus, more 
especially when the stomach is full, by which 
this tube is contracted during inspiration and 
relaxed during expiration, and that they are 
suspended by dividing the vagi. These we 
may class among the reflex muscular move- 
ments. The esophagus is endowed with little 
sensibility, and in the natural and healthy con- 
dition of the organ the ingesta are propelled 
along it to the stomach without exciting any 
sensation. From a consideration of all the 
* As quoted by Soemmering Corporis Hum. Fa- 
brica, tom. iv., p. 272, 1794. 
t+ Medical Facts and Observations, vol. vii., p. 
153, or Phil, Transact., 1795 
¢ Anatomical and Physiological Commentaries, 
No. ii., p. 15. 
§ Journal de Médecine, Chirurgie, &c. Dec. 
1846, tom. 37, p. 351. 
|| Baglivi Opera Omnia, p. 676, Anvers, 1715, et 
Valsalve Opera cum Epistolis Anatomicis, &c. 
ae Morgani Epist, Anatom. xiii. 37, Venei. 
