278 THE SPECIAL SENSES. 



tinguish a great many different kinds of odors, it has been found 

 difficult, indeed impossible, to classify them very satisfactorily 

 into groups. That is, it is not possible to pick out what might be 

 called the fundamental odor sensations. This sense was doubtless 

 used by primitive man chiefly in detecting and testing food, in protect- 

 ing himself from noxious surroundings, and perhaps also in controll- 

 ing his social relations. The olfactory sensations, in accordance with 

 this use made of them, give either pleasant or unpleasant sensa- 

 tions in a more marked and universal way than in the case of vision 

 or hearing, approaching, in this respect, rather the purely sensual 

 characteristics of the lower senses, the bodily appetites. Mankind 

 has been content to classify odors as agreeable and disagreeable, 

 and to designate the many different qualities of odors by the 

 names of the substances which in his individual experience 

 usually give rise to them. A number of observers have proposed 

 classifications more or less complete in character. One of the latest 

 and perhaps the best is that suggested by Zwaardemaker on the basis 

 of the nomenclatures introduced by previous observers. Adopting 

 first the general grouping into pure odors, odors mixed with sensa- 

 tions of common sensibility from the mucous membrane of the nose, 

 and odors mixed or confused with tastes, he separates the pure odors 

 or odors proper into nine classes, as follows: 



I. Odores setherei or ethereal odors, such as are given by the fruits, and 



depend upon the presence of ethereal substances or esters. 

 II. Odores aromatici or aromatic odors, which are typified by camphor 

 and citron, bitter almond and the resinous bodies. This class is 

 divided into five subgroups. 



III. Odores fragrantes, the fragrant or balsamic odors, comprising the vari- 



ous flower odors or perfumes. The class falls into three subgroups. 



IV. Odores ambrosiaci, the ambrosial odors, typified by amber and musk. 



This odor is present in the flesh, blood, or excrement of some ani- 

 mals, being referable in the last instance to the bile. 



V. Odores alliacei or garlic odors, such as are found in the onion, garlic, 

 sulphur, selenium and tellurium compounds. They fall into three 

 subgroups. 



VI. Odores empyreumatici or the burning odors, the odors given by roasted 

 coffee, baked bread, tobacco smoke, etc. The odors of benzol, phenol, 

 and the products of dry distillation of wood come into this class. 

 VII. Odores hircini or goat odors. The odor of this animal arises from the 

 caproic and caprylic acid contained in the sweat; cheese, sweat, 

 spermatic and vaginal secretions give odors of a similar quality. 

 VIII. Odores tetri or repulsive odors, such as are given by many of the nar- 

 cotic plants and acanthus. 



IX. Odores nauseosi or nauseating or fetid odors, such as are given by feces 

 and certain plants and the products of putrefaction. 



While the classification serves to emphasize a number of marked 

 resemblances or relations that exist among the odors, it does not 

 rest wholly upon a subjective kinship, that is, the different odors 

 brought together in one class do not in all cases arouse in us sensa- 



