VERTEBRATE CEPHALOGENESIS. IV 341 



uli belong more to the subconscious domain of reaction to the 

 environment than is the case with either the eye or ear. Even 

 when conscious attention is directed to the reactions of the nasal 

 organs, they can only partly be brought into the realm of defi- 

 niteness. This is proved by the fact that from the days of Aris- 

 totle down to the discovery of the terminal nerve there was never 

 a hint of anything more than an olfactive function. Even in 

 man to-day the olfactive function is a vague and uncertain sense 

 in itself and needs, in order to make certain the interpretation 

 of the stimulus, the assistance of other sense organs, e.g., the 

 eye or the ear. To illustrate, most persons are sure they can 

 recognize the odor of the rose, specifically, a given variety of 

 rose, with whose characteristics they are familiar, but blind- 

 folded and lacking tactile stimuli they cannot identify with cer- 

 tainty the source of the odor, often indeed it may call up the 

 memory of violet odor or some other odor. It is different with 

 the eye. By sight alone and within a considerable range of 

 distances we can recognize any object of definite form which we 

 have seen before. The ear stands between the nose and eye 

 with regard to definiteness and certainty of the results of the 

 stimuli. While we can 'smell' an odor and not be able to iden- 

 tify it, and can hear a tone and not be able to place it in the 

 scale, we can always recognize objects by sight, by either their 

 form, color, size, motion, or all combined. All three senses are 

 quite equally and similarly limited by the upper and lower 

 limits of intensity of stimuli. Although the nasal senses lack 

 conscious definiteness, when compared with the eye or ear, 

 they are not on that account less determinative of physiological 

 (and psychological) reactions. They are primitive and funda- 

 mental senses. When stimulated, the nerve reactions, even 

 though subconscious, may be propagated far and wide through- 

 out the nervous apparatus, much like 'sympathetic' reactions. 

 Rarely is there an instantaneous response such as so frequently 

 results from stimuli of the auditory nerve. The cranial nerves 

 of the nasal chamber have not the intimate associations with 

 the 'voluntary' muscular apparatus that the auditory apparatus 

 has. Our knowledge of both the peripheral and central rela- 



