1252 THE SENSE OF SMELL. 



drugs are capable of inducing it. One of the most important of these 

 is strychnine, which may, in a diluted form and locally applied, be given 

 for the treatment of anosmia. Cocaine is said to produce hyperosmia 

 before it causes partial or complete loss of the sensation. 



Anosmia is not of infrequent occurrence. It may be complete and 

 congenital, as in cases where the olfactory nerves are absent ; and partial 

 anosmia may occur from a variety of causes, such as stenosis of the nasal 

 passages, catarrh and disease of the mucous membrane, and various 

 nervous affections. Habitual smoking produces partial anosmia, morphia 

 and cocaine locally applied rapidly induce it. It is questionable whether 

 the strongest odour, pure and simple, can produce complete anosmia. 

 When this is induced by the vapour of ammonia, we have to deal with 

 an odorous body which is at the same time a powerful irritant ; and the 

 complete anosmia which may result is, in all probability, due to 

 inflammation of the olfactory mucous membrane itself. 



There are some persons who, while acutely sensitive to most odours, 

 are incapable of recognising others. There are many individuals who 

 are unable to smell methyl-alcohol, hydrocyanic acid, and mignonette. 

 Cloquet x mentions the case of an individual who was unable to smell 

 vanilla, although sensitive to the perfume of flowers ; while Griinde, 

 quoted by Cloquet, mentions a man insensible to everything but 

 decaying and fffical matter. 



The classification of odours. — In judging of the acuteness of smell, we 

 have almost entirely confined our attention to our power of being stimulated 

 by different quantities of an odorous material. But almost no two odorous 

 bodies smell exactly alike, and we are able to experience throughout life an 

 almost infinite number of odours differing from each other in quality. Thus 

 we can distinguish the odour of almost every kind of flower, fruit, beast, etc. 

 Various attempts have been made to group these sensations together, but 

 without very satisfactory results. Albrecht v. Haller 2 divided odours into 

 (1) sweet smelling, (2) foul smelling, (3) neither the one nor the other. This, 

 which is a classification on purely physiological lines, gives us very little 

 information, and is rather a classification of the feelings that accompany sensa- 

 tion than of the sensations themselves. Fourcroy and Lorry have each classified 

 odours, but their basis is not physiological, it is purely chemical. Linne, whose 

 Avork is best known, classifies odours into the folloAving seven classes : — 



1. Aromatic odours, such as turpentine, peppermint, and lavender. 



2. Fragrant odours, such as those of the lily, jasmine, vanilla. 



3. Ambrosial odours, such as musk and ambergris. 



4. Alliaceous odours, such as chlorine, sulphuretted hydrogen, asafoetida. 



5. Goaty odours (Odores liircini), such as those of cheese, cat's urine, 

 rancid oil. 



6. Repulsive odours (Odores tebri), such as hyoscyamus, and many of the 

 family of the deadly nightshade. 



7. Nauseating odours, such as those of fseces, putrid flesh, etc. 



The above classification, which is drawn up upon partly a chemical and 

 partly a physiological basis, would hardly find general acceptance, and indicates 

 most forcibly the fact that any rigid classification is at present quite impossible. 

 In the case of the sense of taste, it is probable that there are only four sensa- 

 tions — those called sweet, sour, bitter, and salt ; and these four sensations are 

 universally recognised and have definite and well understood names. "Were it 



1 "Osphregiologie," Paris, 1821, p. 132. 



2 "Elemeuta Physiologic," 1763, p. 162. 



