Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/314/
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” (à son insu). However, the 
latter circumstance is overlooked by Magendie, 
and his conclusion is, “ une fois le nerf trifa¬ 
cial coupé, toute trace de sensibilité disparait, 
aucun corps odorant à distance ou en contact, 
les corrosifs mêmes n’affectent plus en aucune 
façon 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 cinquième paire, par ses branches nasales 
dans les mammifères, et par ses branches pro¬ 
pres à la cavité pre-oculaire des trigonocéphales 
et des serpents a sonnettes, est donc l’organe 
de l’odorat.”I 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. In 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 feet; 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 Physiologie, t. iv. p. 306. 
t Ibid. 
I T. ii. p. 712. 
§ Journal de Physiologie, 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 M.agendie’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, and published in 
the fifth volume of the Journal of Physiology. 
The case is that of a patient, in whom thé 
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 u 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 tfie 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
        

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