FIFTH PAIR OF NERVES. 



299 



states " that several very delicate filaments go 

 from the carotid plexus to the semilunar gan- 

 glion, particularly to the first and third branches 

 of the nerve, and upon those points the gan- 

 glionic matter is accumulated in greater abun- 

 dance."* Besides this connection between the 

 sympathetic and the ganglion, others exist 

 between it and the branches of the ganglion. 



The ganglion appears to constitute an essen- 

 tial part of the fifth nerve throughout verte- 

 brate animals, and to be uniformly present. 

 It also presents in all the common character 

 of being composed both of white and cineri- 

 tious matter, though the comparative amount 

 of the two constituents varies according to 

 the class, the order, or even the individual. 

 The presence of the two structures the author 

 would regard as essential to the constitution 

 of cerebro-spinal ganglia, and he would ex- 

 clude from such those enlargements presented 

 by nerves in certain situations, but from which 

 cmeritious matter appears to be absent. In 

 Mammalia, Birds, and Reptiles, the fifth nerve 

 is provided with a single ganglion, but in Fish 

 and in both orders of that class it possesses 

 for the most part two ganglia and two gan- 

 glionic fasciculi; this however is not uniformly 

 so, for in some, e. g. the lophius piscatorius, 

 the ganglion is single. 



VITAL PROPERTIES OF THE FIFTH PAIR 

 OF NERVES. The discussion of the vital 

 properties of the fifth nerve the writer pro- 

 poses may be fitly arranged under the following 

 heads: 1. its sensibility; 2. its influence upon 

 the faculties of sensation and volition, as also 

 upon the ordinary sensibility of the parts to 

 which it is distributed; 3. its relation to the 

 special senses and connection with the function 

 of nutrition. 



1. Sensibility. Numerous experiments per- 

 formed and repeated by different physiologists 

 have established the fact, that the fifth nerve 

 enjoys exquisite sensibility. Bell appears to 

 have been the first who directed attention 

 particularly to this point : in his paper, pub- 

 lished in the Philosophical Transactions for the 

 year 1821, it is stated that, touching the su- 

 perior maxillary branch of the fifth nerve, 

 when exposed in an ass, " gave acute pain." 

 In the first of Mayo's experiments upon the 

 fifth nerve, published in his Commentaries 

 in 1822, it was also found that " on pinching 

 the opposite extremities" (those connected with 

 the brain) " of the infraorbital and inferior 

 maxillary nerves in an ass, the animal struggled 

 violently as^ at the moment of dividing the 

 nerves: these latter results uniformly attend 

 the division of the nerves above-mentioned, and 

 of that branch of the fifth which joins the 

 portio dura."f Similar results were obtained 

 by the writer last quoted from experiments 

 of the same description upon the dog and the 

 rabbit, and upon the pigeon, in regard to the 

 first division of the fifth. He also found 

 " that on pinching the gustatory nerves in 

 living rabbits pain was evinced." Magendie 



* Journ. Compl. torn. xxiv. 



t Commentaries, No. 1, p. 110. 



carried the inquiry farther, and in the fourth 

 volume* of the Journal of Physiology, has 

 related an experiment in which he exposed 

 the fifth nerve within the cranium in the rabbit 

 and dog, and found that the slightest touch 

 produced signs of acute sensibility. From 

 the preceding facts we infer that the ganglionic 

 portion of the nerve at least is exquisitely 

 sensitive, and that it is endowed with sen- 

 sibility through its entire extent: further, the 

 experiment of Magendie indicates that the sen- 

 sibility of the nerve is proper and independent 

 of the influence of other nerves, he having ex- 

 perimented upon it at a point prior to its 

 junction with any other. 



With regard to the non-ganglionic portion 

 of the nerve, our data are at present altogether 

 analogical: it is so situated that satisfactory 

 experiments upon it separately are hardly to 

 be accomplished, so that we are left to infer 

 of it as probable what has been ascertained 

 of other non-ganglionic nervous cords, yiz. the 

 anterior roots of the spinal nerves. The 

 question in regard to the functions of the 

 different portions of the spinal nerves has been 

 inquired into by Magendie, by whom the 

 endowments of both sets of roots have been 

 tested in various modes, and who has inferred 

 that the anterior roots are not devoid of sen- 

 sibility, and if they be sensitive it is probable 

 that the lesser packet of the fifth is sensitive 

 also.t 



2. Influence of the fifth nerve upon sensation 

 and volition. It is hardly necessary to remark 

 that this point has been the subject of much 

 dispute, as well with regard to the fact itself 

 as to the relative claims of the several inquirers 

 to whom we are indebted for the investigation 

 of the matter: however, physiologists now 

 seem to be generally agreed that the nerve 

 is one of compound function, being subservient 

 to both the faculties of sensation and volition, 

 and that the faculty of sensation is dependent 

 upon its ganglionic, that of voluntary motion 

 upon its non-ganglionic portion, and that it 

 thus resembles the spinal nerves. That the 

 nerve is one of compound function, and sub- 

 servient to the two faculties, was announced 

 by Bell in the paper already alluded to. He 

 there distinguishes the nerves into two classes ; 

 one original and symmetrical, the other super- 

 added and irregular. To the former class he 

 refers the spinal nerves, the suboccipital, and 

 the fifth nerve, and assigns to them the fol- 

 lowing characters, namely, they have all double 

 origins; they have all ganglia on one of their 

 roots ; they go out laterally to certain divisions 

 of the body ; they do not interfere to unite 

 the divisions of the frame ; they are all mus- 

 cular nerves, ordering the voluntary motions 

 of the frame ; they are all exquisitely sensible, 

 and the source of the common sensibility of 

 the surfaces of the body : to it he refers the 

 nerves of the spine, the suboccipital, and the 

 Jiflhnerve.l It has been already stated that 



* P. 314. 



t Journal de Physiologie, t. ii. p. 368. 



$ Philosophical Transactions, 1821, p. 404. 



