406 ON SENSATION, AND THE ORGANS OF THE SENSES. 



considerable control over the secretions, will greatly diminish the acuteness of 

 the smell ; and it will have the further effect of preventing the reception of 

 any impressions of irritation from acrid vapours, which are entirely different 

 in their character from true odorous impressions, and which are not trans- 

 mitted through the Olfactory nerve ( 441). The nasal passages may indeed 

 be considered as having, in the air-breathing Vertebrata, two distinct offices ; 

 they constitute the organ of smell, through the distribution of the olfactory 

 nerve upon a part of their surface; but they also constitute the portals of the 

 respiratory organs, having for their office to take cognizance of the aeriform 

 matter which enters them, and to give warning of that which would be inju- 

 rious ; this latter function is performed by the Fifth pair, as by the Par Vagum 

 in the glottis. It is through this nerve, that the act of sneezing is excitable : 

 the evident purpose of which, is the ejection of a strong blast of air through 

 the nasal passages, in such a manner as to drive out any offending matter 

 they may contain. 



532. The importance of the sense of Smell among many of the lower 

 Animals, in guiding them to their food, or in giving them warning of danger 

 and also in exciting the sexual feelings, is well known. To Man its utility 

 is very subordinate under ordinary circumstances ; but it may be greatly in- 

 creased when other senses are deficient. Thus, in the well-known case of 

 James Mitchell, who was deaf, blind and dumb, from his birth, it was the 

 principal means of distinguishing persons, and enabled him at once to per- 

 ceive the entrance of a stranger. It is recorded that a blind gentleman, who 

 had an antipathy to cats, was possessed of a sensibility so acute in this re- 

 spect, that he perceived the proximity of one that had been accidentally shut 

 up in a closet adjoining his room. Among Savage tribes, whose senses are 

 more cultivated than those of civilized nations, more direct use being made of 

 the powers of observation, the scent is almost as acute as in the lower Mam- 

 malia; it is asserted by Humboldt, that the Peruvian Indians in the middle of 

 the night can thus distinguish the different races, whether European, Ameri- 

 can-Indian, or Negro.* The agreeable or disagreeable character assigned to 

 particular odours, is by no means constant amongst different individuals. 

 Many of the lower Animals pass their whole lives in the midst of odours, 

 which are to Man (in his civilized condition at least) in the highest degree 

 revolting ; and will even refuse to touch food, until it is far advanced in pu- 

 tridity. It more frequently happens in regard to odours and savours, than 

 with respect to other sensory impressions, that habit makes that agreeable, 

 and even strongly relished, which was at first avoided; the taste of the epi- 

 cure for game that has acquired ihefumet, for olives, for assafoetida, &c., 

 are instances of this. As to the length of time, during which impressions 

 made upon the organ of smell remain upon it, no certain knowledge can be 

 obtained. It is difficult to say that the effluvia have been completely removed 

 from the nasal passages ; since it is not improbable that the odorous particles 

 (supposing such to exist) are absorbed or dissolved by the mucous secretion ; 

 it is probably in this manner that we may account for the fact, well known to 

 every medical man, that the cadaverous odour is frequently experienced for 

 days after a post-mortem examination.t 



The author has been assured by a competent witness, that a lad in the state of Som- 

 nambulism, had his sense of smell so remarkably heightened, as to be able to assign (with- 

 out the least hesitation) a glove placed in his hand, to its right owner, in the midst of 

 about thirty persons, the boy himself being blindfolded. 



f This may partly be attributed also to the effluvia adhering to the dress. It has been 

 remarked that dark cloths retain these more strongly than light. 



