SENSES OF SMELL, TASTE, HUNGER AND THIRST 747 



which must be infinitely small. In animals of this kind, the sense of 

 smell must, of course, become prepotent in determining their behavior, 

 both volitionally and reflexly. 



Qualitative Differences in the Olfactory Sensations. The modali- 

 ties of smell are very numerous and their number is increased still 

 further by newly acquired sensations. Thus, a chemist is generally 

 trained to recognize a much larger number of substances than the 

 layman, but even that person whose olfactory impressions have been 

 most minutely associated, is quite unable to classify them in accordance 

 with their qualities. In most cases, one must be content with charac- 

 terizing them as agreeable or disagreeable. A. von Haller, however, 

 has divided them into odores suaveolentes, odores intermedia and 

 odores factores. In this regard the sense of smell differs very greatly 

 from the others, because it does not permit of at least a general arrange- 

 ment of these sensations into a fundamental and a complex group. 

 The following classification of Zwaardemaker which is based upon the 

 observations of Linne, tends to overcome this defect in a slight degree 

 by recognizing at least certain vague similarities between them: 



1. Ethereal odors, depend upon the presence of such substances as the esters. 

 They are emitted by different fruits. 



2. Aromatic odors are given off by such substances as camphor, resinous oils 

 and citron. 



3. Fragrant odors, comprise the various odors of flowers and perfumes. 



4. Ambrosial odors, are typified by amber and musk. 



5. Garlic odors, are emitted by the onion, garlic, sulphur, and the compounds 

 of selenium and tellurium. 



6. Burning odors, are given off by benzol, phenol, tobacco smoke and similar 

 substances. 



7. Caproic odors, find their origin in the caproic and caprillic acids of sweat, 

 cheese, and the spermatic and vaginal secretions. 



8. Repulsive odors, are yielded by many plants, such as acanthus. 



9. Nauseating or fetid odors, are given off by putrefying substances of animal 

 origin. 



A conflict between these sensations arises whenever two odors 

 are permitted to act at the same time. While the result then ob- 

 tained, ' is largely dependent upon the odors selected, the strongest 

 most generally predominates in consciousness. At other times, they 

 may alternate with one another without, however, being fused into an 

 intermediate compound sensation. An actual fusion does not result, 

 as a rule, unless they belong to one and the same group of odors. 

 A mixture of two or more odors which presents a modality quite 

 different from those of the fundamental odors, may be effected by 

 such substances as vanillin and bromin, turpentine and xylol, and 

 others. 1 Certain odoriferous substances may also be mixed in certain 

 proportions to annul their individual effects. A neutralization of 

 this kind is obtained by mixing 4 grains of iodoform with 200 grains 

 of balsam Peru. 



1 Nagel, Zeitschr. fur Psych, und Physiol. der Sinnesorgane, xv. 



