GLOSSO-PHARYNGEAL NERVE. 



499 



many different dogs. Seventeen of these were 

 upon the living animal, with the view of as- 

 certaining if this nerve were to be considered 

 both a nerve of sensation and motion, and what 

 are the effects of its section upon the associated 

 movements of deglutition, and on the sense of 

 taste. The other ten were performed on ani- 

 mals immediately after they had been deprived 

 of sensation, for the purpose of satisfying my- 

 self to what extent it was to be considered a 

 motor nerve. The most remarkable effect wit- 

 nessed in these experiments was an extensive 

 convulsive movement of the muscles of the 

 throat and lower part of the face on irritating 

 this nerve in the living animal, provided the 

 irritation was applied to the trunk of the nerve 

 before it had given off its pharyngeal branches, 

 or to one of these pharyngeal branches sepa- 

 rately. These movements were equally well 

 marked upon pinching the cranial end of the 

 cut nerve after it had been divided at its exit 

 from the foramen lacerum, as when the trunk 

 of the nerve and all its branches were entire. 

 In some of these experiments we observed a 

 remarkable difference between the effects of irri- 

 tating this nerve before and after it had given off 

 its pharyneeal branches, which is valuable on 

 this account, that it may explain the discrepan- 

 cies between the results obtained by Panizza, 

 Dr. M. Hall, and the late Mr. Broughton on 

 the one hand, and Dr. Alcock on the other. 

 For though I do not mean to affirm that pinch- 

 ing the lingual portion of the nerve is never 

 followed by indications of suffering, (for from 

 the irregularity in the origin of the pharyngeal 

 twigs, and the difficulty of judging at the 

 bottom of a deep wound in the living animal 

 at what particular part these are all given off, it 

 is generally impossible to decide where the 

 lingual portion may be said to begin,) yet I 

 have no hesitation in saying that if in several 

 of these experiments we had operated only on 

 that portion of the nerve which first presented 

 itself, and not proceeded to dissect it back- 

 wards towards its place of exit from the cra- 

 nium, we should have gone away with the 

 impression that the irritation of this nerve was 

 followed by no convulsive movements, and 

 little if any indications of suffering. 



From a review of all the experiments which 

 I have performed upon the glosso-pharyngeal 

 nerves, I am inclined to draw the following 

 conclusions : 



1. That this is a nerve of common sensation, 

 as indicated by the unequivocal expression of 

 pain by the animal, when the nerve is pricked, 

 pinched, or cut. 



2. That mechanical or chemical irritation 

 of this nerve before it has given off its pha- 

 ryngeal branches, or of any of these branches 

 individually, is followed by extensive muscular 

 movements of the throat and lower part of the 

 face. 



3. That the muscular movements thus ex- 

 cited depend, not upon any influence extending 

 downwards along the branches of the nerve to 

 the muscles moved, but upon a reflex action 

 transmitted through the central organs of the 

 nervous system. 



4. That these pharyngeal branches of live 

 glosso-pharyngeal nerve possess endowments 

 connected with the peculiar sensations of the 

 mucous membrane upon which they are distri- 

 buted, though we cannot pretend to say posi- 

 tively in what these consist. 



5. That this cannot be the sole nerve upon 

 which all these sensations depend, since the 

 perfect division of the trunk of the nerve on 

 both sides does not interfere with the perfect 

 performance of the function of deglutition. 



6. That mechanical or chemical irritation 

 of the nerve, immediately after the animal has 

 been killed, is not followed by any muscular 

 movements when sufficient care is taken to in- 

 sulate it from the pharyngeal branch of the par 

 vagum. And we here observe an important 

 difference between the movements excited by 

 irritation of the glosso-pharyngeal and those of 

 a motor nerve, for while the movements pro- 

 duced by the irritation of the glosso-pharyngeal 

 are arrested as soon as the functions of the 

 central organs of the nervous system have 

 ceased, those from irritation of a motor nerve 

 such as the pharyngeal branch of the par 

 vagum, continue for some time after this, and 

 when all connexion between it and the medulla 

 oblongata has been cut off by the section of 

 the nerve. 



7. That the sense of taste is sufficiently 

 acute, after perfect section of the nerve on both 

 sides, to enable the animal readily to recog- 

 nize bitter substances. 



8. That it probably may participate with 

 other nerves in the performance of the function 

 of taste, but it certainly is not the special nerve 

 of that sense. 



The sense of thirst which is referred to the 

 fauces and pharynx does not appear to de- 

 pend entirely upon the presence of this nerve. 

 The animals in which it was divided lapped 

 water of their own accord. I observed one of 

 those in which the nerves were found satisfac- 

 torily divided, rise, though feeble, walk up to 

 a dish containing water, lap some of it, and 

 return again to the straw upon which he was 

 previously lying. 



In all experiments upon the glosso-pharyn- 

 geal nerve in the dog, too great care cannot be 

 taken to avoid the pharyngeal branch of the 

 par vagum, which is sometimes situated in im- 

 mediate contact with it, at other times one or 

 two lines below it, and is frequently united to 

 it by a considerable communicating branch, so 

 that it may readily be mistaken for a large pha- 

 ryngeal branch of the glosso-pharyngeal. This 

 precaution is the more necessary, as I am con- 

 fident that these two nerves differ from each 

 other in function, and this must consequently 

 seriously affect the results. I attribute the dif- 

 ficulty of deglutition after section of this nerve 

 in the living animal, and the muscular move- 

 ments on irritating it in the animal recently 

 killed, observed by two of the preceding ex- 

 perimenters, to a want of sufficient precaution in 

 separating these nerves from each other. These 

 results were only observed by me when the 

 pharyngeal branch of the par vagum was im- 

 plicated in the experiment. 



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