PAR VAGUM. 



893 



jectecl 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 oesophagus 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.f 



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 SPINAL ACCESSORY NEKVE. 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. 



f De Functionibus Nerv. Cerebralium, &c. p. 17, 

 1839. 



| 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-PHARYNGEAJ,, 

 we have stated, that, when this nerve is insula- 

 ted carefully from the neighbouring nerves, no 

 direct muscular movements follow its excitation. 

 Valentin (opuscit. p. 3b) and Longet (opus cit. 

 torn. ii. p. 223,) have trom these experiments ar- 

 rived at the same conclusions as we have on this 

 point. 



We may merely state in the mean time that 

 Longet (opuscit. torn. 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. 



|| Opuscit. torn. ii. p. 271. 



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 interior 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 tiie larynx, when violent 

 paroxysms of coughing and signs of great un- 

 easiness immediately follow. The division of 

 the inferior laryngeal nerves has no etiect 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 different 

 excitants to the superior laryngeal nerve before 

 it gave off its external brunch 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.f P'rom 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. Le9ons sur 

 les Phenomenes Physiques de la Vie, torn, ii, 

 p. 228, 1837. 



t Edin. Med. and Surg. Jour., pp. 138, 139, 1838. 



