34: SPECIAL SENSES. 



erties which greatly overshadow their odorous qualities ; and 

 it was the neglect of this distinction that led to the errors 

 of interpretation in the observations of Magendie. It is un- 

 necessary, in this connection, to discuss the different varieties 

 of odors recognized by some of the earlier writers, as the 

 fragrant, aromatic, fetid, nauseous, etc., distinctions suffi- 

 ciently evident from their mere enumeration ; and it is plain 

 enough that there are emanations, like those from delicately- 

 scented flowers, which are easily recognizable by the sense of 

 smell, while they make no impression upon the ordinary sen- 

 sory nerves. The very marked individual differences in the 

 delicacy of the olfactory organs in the human subject and in 

 different animals is an evidence of this fact. Hunting-dogs 

 recognize odors to which we are absolutely insensible ; and 

 certain races of men are said to possess a wonderful delicacy 

 of the sense of smell. Like all of the other special senses, 

 olf action may be cultivated by attention and practice ; as is 

 exemplified in the delicate discrimination of wines, qualities 

 of drugs, etc., by experts. 



After what we have said concerning the situation of the 

 true olfactory membrane in the upper part of the nasal fossae 

 and the necessity of particles impinging upon this membrane 

 in order that their odorous properties may be appreciated, it 

 is almost unnecessary to state that the passage of odorous 

 emanations to this membrane by inspiring through the nos- 

 trils is essential to olf action, so that animals or men, after di- 

 vision of the trachea, being unable to pass the air through 

 the nostrils, are deprived of the sense of smell. The act of 

 inhalation through the nose, when we wish to appreciate a 

 particular odor, is an illustration of the mechanism by which 

 the odorous particles may be brought at will in contact with 

 the olfactory membrane. A very curious and interesting case 

 illustrating the necessity of the free passage of air through 

 the nostrils is detailed by Dr. Ogle. In this patient, there 

 was adhesion of the posterior pillars of the fauces to the back 

 of the pharynx, so that no air could pass through the nasal 



