302 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, and with the fact, revealed by comparative anatomy, 

 that this sense is the oldest phylogenetically, give either pleasant 

 or unpleasant sensations 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 agree- 

 able and disagreeable, and to designate the many different quali- 

 ties 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 Zwaarde- 

 maker on the basis of the nomenclatures introduced by previous 

 observers. Adopting first the general grouping into pure odors, 

 odors mixed with sensations 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, which 



depend upon the presence of ethereal substances or esters. 

 II. Odores aromatic! 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- 



