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COMPARATIVE ANATOMY AND PATHOLOGY. 
Schneiderian membrane is dry, the faculty of smelling is lost, or 
very imperfect. It is also necessary that the odorous particles pass 
in a current over the membrane; hence, by stopping or diminishing 
the breathing, or by giving force to the inspiration, we at our plea- 
sure increase or diminish the perception of odours. Whoever has 
observed the manner in which the hound sometimes labours to 
catch the scent, will perfectly understand this process. 
Protected by this mucous coat, the olfactory nerve here termi- 
nates in countless minute ramifications, and it is the impression 
made on these ramifications by certain effluvia, of inconceivable 
minuteness, and that impression conveyed to the brain, which we 
designate the sense of smell. 
The supposed Influence of the fifth Nerve . — The discoveries of 
modern times, with regard to the function of this nerve, constitute 
a new era in physiology. It has not only been demonstratively 
proved that all the anterior and lateral parts of the head, and the 
mucous membranes oi the conjunctiva, the nose, and the mouth, 
owe their sensibility to it, and all the muscles of mastication, with 
their associate organs are indebted to it for their motor power, but 
it is intimately connected with the sympathetic nerve, as that still 
continues to be erroneously -called, and also with various parts 
of the ganglionic system. This being now universally acknow- 
ledged, several physiologists, and of no mean repute, have consi- 
dered it as discharging all the functions which used to be attri- 
buted to the nerves of peculiar sensation. At the head of this new 
school stands one who has distinguished himself by many valuable 
physiological discoveries, with which, however, have been mingled 
a more than equal number of hasty and erroneous guesses, and 
the whole combined with a system of reckless cruelty, which has 
scarcely a parallel in the records of science. 
Among other opinions which Dr. Magendie has broached is this, 
that the olfactory nerve is not the nerve of smell, but that this pro- 
perty belongs to the nasal branch of the fifth pair. No modern 
anatomist has doubted that the fifth pair is the nerve of common 
sensation, as it regards the nose, the eye, and the ear : the question 
is, as to the peculiar sensations of smelling, seeing, and hearing. 
These things are essentially different, and it is the duty of the 
physiologist not to confound them. Magendie destroys the olfac- 
tory nerve, and then he applies to the nostril ammonia, oil of 
lavender, and other substances, from which proceed a strong and 
acrid gas. The animal is conscious of their influence, and rubs 
his nostrils and sneezes; and “therefore,” says he, “ although the 
olfactory nerve is destroyed, the sense of smell remains.” It was 
forgotten that all the substances with which he experimented were 
excitants of the common sensibility of the nostrils; and he only 
