306 



FIFTH PAIR OF NERVES. 



presented them to the animal, and it always 

 undid the paper and possessed itself of the 

 food ; but, he adds, " I do not regard this ex- 

 periment as satisfactory, because in other cir- 

 cumstances it appeared to me to want smell to 

 discover food which I put near him without 

 his knowledge" (a son insu). However, the 

 latter circumstance is overlooked by Magendie, 

 and his conclusion is, " une fois le nerf trifa- 

 cial coupe, toute trace de sensibilite disparait, 

 aucun corps odorant a distance ou en contact, 

 les corrosifs memes n'affectent plus en aucune 

 facon la pituitaire."* Doubtless this conclu- 

 sion is qualified by another immediately suc- 

 ceeding, " that does not prove that the seat of 

 smell is in the branches of the fifth pair ; but 

 it proves at least that the olfactory nerve has an 

 indispensable need of the branches of the fifth 

 pair to be able to enter into action ; that it is 

 devoid of general sensibility, and that it can 

 have only a special sensibility relative to 

 odorous bodies."f The latter must be ad- 

 mitted to come, if not quite, at least very near 

 to the general opinion, but it is altogether at 

 variance with the former, and one is rather at 

 fault for the author's precise meaning. Refe- 

 rence to later writings, however, leaves no 

 doubt upon that point. In the conjoint work 

 of Desmoulins and Magendie (1825) upon the 

 nervous system of the vertebrata, besides other 

 similar passages, will be found the following : 

 " La cinquieme paire, par ses branches nasales 

 dans les mammiferes, et par ses branches pro- 

 pres a la cavite pre-oculaire des trigonocephales 

 et des serpents a sonnettes, est done 1'organe 

 de Fodorat."J Notwithstanding the weight of 

 Magendie's authority, a careful review of the 

 matter will not permit us to assent to this con- 

 clusion, and compels us to avow not only that 

 it is not proved, but that the premises justify 

 a contrary one. [n the first place it is not war- 

 rantable to call the effluvia of ammonia or 

 acetic acid odours : they are no more odours 

 than the fumes of muriatic or nitric acid ; and, 

 though aware of the objection, he still calls 

 them odeurs fortes, and bases his inference 

 upon their operation. But he says the objec- 

 tion does not apply to oil of lavender or the 

 animal oil of Dippel : this, however, is but an 

 assumption at variance with fact; in the human 

 subject these agents may act feebly upon the 

 sensibility of the membrane of the nostrils, and 

 may not appear to possess irritating properties ; 

 but this will not prove that they act similarly 

 upon animals, whose organ of smell is more 

 sensitive than that of man, and accordingly 

 Dr. Eschricht, who combats the opinion of 

 Magendie, has found that, on application to 

 the nostrils of those animals upon which the 

 experiments of Magendie have been performed, 

 they produce all the same effects which am- 

 monia or nitric acid does. In the second place 

 his experiment of presenting food to a dog, 

 whose olfactories had been destroyed, enclosed 



* Journal de Physiologic, t. iv. p. 306. 



t Ibid. 



J T. ii. p. 712. 



$ Journal de Physiologic, t. vi. p. 350. 



in paper, and in which the animal undid the 

 paper, upon his own showing not only does 

 not justify his inference, but, so far as it 

 reaches, proves the contrary. To establish his 

 position the animal must have discovered the 

 food by smell, without knowing that it was in 

 the paper ; but it is manifest, from Magendie's 

 own relation, that when the animal undid the 

 paper, it knew, or was led by some circum- 

 stance to expect the food to be in it ; but that 

 when it was not already aware or in expecta- 

 tion that the food was near it, it did not dis- 

 cover it. To the writer it seems that the na- 

 tural inference from the experiment, as related, 

 is that the animal's proper sense of smell de- 

 pended upon the olfactory nerves, inasmuch as 

 it did not display fair evidence of its presence 

 after their destruction, and that the sensibility 

 displayed by the membrane of the nostrils after 

 the destruction of these nerves, and dependent 

 upon the fifth, has reference only to those im- 

 pressions which are objects of tactile or general 

 sensation, but not of the special sense. 



At the same time, however, that we express 

 our dissent from Magendie with regard to the 

 nervous connexion of the proper sense of smell, 

 it must be admitted that his researches posi- 

 tively indicate a distinction between the media 

 of perception in the case of different agents 

 operating on the olfactory organ, which it has 

 been too much the habit to regard as pro- 

 ducing their impressions all through the olfac- 

 tory nerves : they have gone a considerable way 

 in demonstrating the separation of those media; 

 a result which is made complete by the conti- 

 nuance of the simple sense after the loss of the 

 influence of the fifth nerve consequent upon 

 disease : further, they indicate that sensations 

 derived through the organ of smell are less 

 simple than they are usually accounted ; that 

 they may be, and probably are for the most 

 part, compound, resulting from the combina- 

 tion of impressions made upon the two senses 

 thus shewn to be enjoyed by the organ. 



Magendie's view has been adopted, and an 

 endeavour made to corroborate and establish it 

 by Desmoulins in * Reflexions' upon a case 

 communicated by Beclard, an<t published in 

 the fifth volume of the Journal of Physiology. 

 The case is that of a patient, in whom the 

 olfactory nerves and their bulbs were de- 

 stroyed by the growth of a tubercular disease 

 from the anterior lobes of the brain ; " yet he 

 took snuff with pleasure, appeared to distin- 

 guish its different qualities, and was affected 

 disagreeably by the smell of the suppuration of 

 an abscess with which one of his neighbours 

 was afflicted." From this case, from that of 

 Serres, related elsewhere, and the experiments 

 of Magendie viewed in connexion, Desmoulins 

 has adopted the opinion that " the nerves and 

 lobes called olfactory are alien to the sense of 

 smell, or at all events co-operate so little in it, 

 that the sense continues to be exerted without 

 them ; that, on the contrary, this sense resides 

 essentially in the branches of the fifth pair, 

 which are distributed to the nostrils." Serres' 

 case has been discussed elsewhere; that of 

 Beclard appears at first unanswerable; but 



