86 THE POPULAR SCIENCE MONTHLY. 



According to this view the odoriferous bodies, or their molecules, 

 have no more to do (in the sense of physical impact) in producing the 

 sensation of smell than a luminous body a candle or the sun has to 

 do (by impact) with the sensation of light. There is corporeal impact 

 or touch in neither case. Of course, with each molecule as a center of 

 activity, the effect will be more pronounced at the immediate surface 

 (as with all radiant energies) than at any distance. And, undoubted- 

 ly, particles of disintegrating, odorous matter are often brought in 

 contact with the Schneiderian membrane ; but the sensation of that 

 impact, if there be any, would be of touch, not of smell, as surely as 

 that, from that point of contact to the sensorium, the effect or influ- 

 ence is conveyed by a vibration a wave-motion in the " fluid " of the 

 nerve-duct as the undulations of the luminiferous ether are propa- 

 gated along the course of the optic nerve to the seat of sensation, 

 where they are translated into light and color. But, if, for any por- 

 tion of the distance between the internal sense and the fragrant body, 

 the odor, like light, is but a motion, it is safe to assume it for all. 

 The analogy of this mode of odors to that of light and sound is some- 

 thing in its favor. 







COLOK-BLINDNESS AND COLOK-PEKCEPTIOK* 



By SWAN M. BUENETT, M.D. 



TO physiologists that part of the function of vision which is con- 

 cerned in the perception of colors has always been one of great 

 interest, but it was not until the genius of Thomas Young offered 

 them his theory of vision that they had anything like a plausible 

 working hypothesis. This theory, as elaborated and promulgated by 

 Professor Helmholtz, has until very recently been the one most relied 

 upon in explanation of all the phenomena of colored vision. It is, 

 however, a pure hypothesis, since not one of its fundamental princi- 

 ples is a demonstrated or even a demonstrable fact. By a process of 

 deductive reasoning, and most probably with little, if any, experimen- 

 tation for it is said that Young prided himself on being independent 

 of the necessity of experiment the vivid imagination of this original 

 mind seized upon an hypothesis which seemed to satisfy the demands 

 of an acceptable theory, in so far as it accounted for all or nearly all 

 of the observed phenomena. At that time, however, and even when 

 Helmholtz resurrected and revivified the theory, the question of color- 

 blindness had not been investigated to the extent it has within the 

 past ten years, and most physiologists rested content with the belief 

 that at last the true theory of colors had been found, 



* A paper read before the Philosophical Society of Washington, December 18, 1880. 



