168 SENSE OF SMELL. 



fused. These experiments were repeated by Professor Chaussier, and 

 with like results. 1 They explain why we use effort to draw in air 

 loaded with an odour that is agreeable to us; and, on the contrary, 

 arrest the respiration, or make it pass entirely through the mouth 

 when odours are disagreeable. Still they are occasionally so diffusible 

 and expansible, that they reach, notwithstanding, the olfactory mem- 

 brane; and we are compelled to shut them off by calling in the aid of 

 the upper extremity. The air being the ordinary medium for the con- 

 veyance of odorous molecules, we can understand why the organ of 

 smell should form a part of the air passages. 



The use of the nose is to direct the air, charged with odours, to- 

 wards the upper part of the nasal fossae. Its situation is well adapted 

 for the reception of emanations from bodies beneath it, and its appro- 

 priate muscles allow the nostrils to be more or less expanded or con- 

 tracted. These uses assigned to the nose are demonstrated by the 

 fact, that they, whose noses are deformed especially the flat-nosed 

 or whose nostrils are directed forwards, instead of downwards, have 

 commonly the sense feebly developed. The loss of the nose, too, 

 either by accident or disease, has been found to destroy the sense com- 

 pletely; and by no means the least advantage of the rhinoplastic ope- 

 ration is the enjoyment afforded by the improvement of this sense. 

 M. Be'clard affirms, that an artificial nose, formed of paper or other 

 appropriate materials, is sufficient to restore it, so long as the substi- 

 tute is attached. 2 It is proper to remark, however, that in a case which 

 fell under the author's observation, although the nose had been lost by 

 syphilis, the smell persisted; and two cases of a similar kind occurred 

 to M. P. H. Berard. 3 



The mode in which olfaction is effected appears to be as follows: 

 The inspired air, loaded with odorous particles, traverses the nasal 

 fossae; and, in its passage, comes in contact with the pituitary mem- 

 brane, through the medium of the nasal mucus. The use of this mucus 

 seems to be, not only to keep the organ properly lubricated, but to 

 arrest the particles as they pass, not by any chemical attraction, but 

 in a mechanical manner. The olfactory nerves being distributed on 

 the membrane, receive the impression of the molecules, and, in this 

 manner, sensation is accomplished. 



The use of the different spongy or turbinated bones would seem to 

 be to enlarge the olfactory surface. According to some, however, they 

 form channels to direct the air towards the openings of the sinuses. 

 The sinuses, themselves, afford subjects for physiological discussion. 

 By many they are considered to add to the extent of olfactory surface: 

 by others, to furnish the nasal mucus. No hesitation would be felt in 

 pronouncing both the spongy bones and sinuses to be useful in olfaction, 

 were it not that the olfactory nerves or first pair have not been traced 

 on the pituitary membrane covering the middle and inferior spongy 

 bones, or on that lining the different sinuses ; that the sinuses are 



1 Adelon, op. cit., i. 335. 



2 Magendie, Precis Elementaire, 2de edit., i. 136, Paris, 1825. 



Art. Olfaction, Diet, de Medecine, 2de edit., xxii. 9, Paris, 1840. 



