IMMEDIATE FUNCTION OF SMELL. 171 



sensibility or feeling ; and that some of them are unquestionably sup- 

 plied with nerves of special sensibility; the eye with the optic; and 

 the ear with the auditory; but that neither the one nor the other can 

 exert its special function, without the integrity of the fifth. The olfac- 

 tory nerve is probably in this category, is the nerve of special sensi- 

 bility. It is true, that in the experiments of M. Magendie the animal 

 appeared to be affected by odorous substances, after the division of the 

 first pair; but a source of fallacy existed here, in discriminating accu- 

 rately between the general and special sensibility. Some of the sub- 

 stances employed were better adapted for eliciting the former than the 

 latter ; ammonia and acetic acid, for example. 



The immediate function of the sense of smell is to appreciate odours. 

 In this it cannot be supplied by any other sense. The function is in- 

 stinctive; requires no education; and is exerted as soon as the parts 

 have attained the necessary degree of development. In many respects 

 the sense is intimately connected with that of taste; and the impres- 

 sions made upon each are frequently confounded. In the nutritive 

 function, the smell serves as a kind of advanced guard or sentinel to 

 the taste ; and warns us of the disagreeable or agreeable nature of the 

 aliment; but if a substance repugnant to the smell be agreeable to the 

 taste, the smell soon loses its aversion, or at least becomes less disa- 

 greeably impressed. The smell is not, however, in man so useful as a 

 sentinel to the taste, as it is to animals: there are many bodies, those 

 containing prussic acid for example, which are extremely pleasing by 

 the odours they exhale, and yet are noxious to man. In the animal 

 kingdom, this sense is greatly depended upon, and is rarely a fallacious 

 guide. It enables animals to make the proper selection of the noxious 

 from the innocent; the alimentary from that which is devoid of nutri- 

 ment ; the agreeable from the disagreeable ; and the power appears to 

 be instinctive or dependent upon inappreciable varieties of structure in 

 the organs concerned in olfaction. 



As an intellectual sense, smell is not entitled to a higher rank than 

 taste. Its mediate functions are very limited. It enables the chemist, 

 mineralogist, and perfumer, to discriminate bodies from each other. 

 We can, likewise, by it form a slight but only a slight idea regard- 

 ing the distance and direction of bodies, owing to the greater intensity 

 of odours near an odorous body, than at a distance from it. Under 

 ordinary circumstances, the information of this kind derived by olfac- 

 tion is inconsiderable; but in the blind; and in the savage, who is 

 accustomed to exercise all his external senses more than the civilized, 

 its sphere of utility and accuracy is largely augmented. Of this we 

 shall have to speak presently. We find it, too, surprisingly developed 

 in certain animals; in which it is considered, by the eloquent Buffon, as 

 an eye that sees objects not only where they are, but where they have 

 been, as an organ of gustation, by which the animal tastes not only 

 what it can touch and seize, but even what is remote, and cannot be 

 attained; and he esteems it a universal organ of sensation, by which 

 animals are most readily and most frequently impressed ; by which they 

 act and determine, and recognise whatever is in accordance with, or in 



