612 



THE SENSES 



The Stimulation of the Olfactory Membrane. The extent of the 

 nasal mucous surfaces, and of the frontal and antral sinuses connected with 

 them, might suggest that the sensory olfactory surface is widely distributed, 

 but such is not the case. Air impregnated with vapor of camphor has been 

 injected into the frontal sinus through a fistulous opening, and odorous sub- 

 stances have been injected into the antrum of Highmore; but in neither case 

 was any odor perceived by the patient. All parts of the nasal cavities are 

 endowed with cutaneous sensibility by the nasal branches of the first and 



FIG. 429- Principal Constituent Elements of the Olfactory Bulb of a Mammal. (Van Gehuch- 



ten.) 



second divisions of the fifth nerve, hence the sensations of cold, heat, itching, 

 tickling, and pain, and the sensation of tension or pressure in the nostrils. 

 That these nerves cannot perform the functions of the olfactory nerves is 

 proved by cases in which the sense of smell is lost, while the mucous mem- 

 brane of the nose remains susceptible to the various modifications of the 

 sense of touch. But it is often difficult to distinguish the sensation of smell 

 from that of mere feeling, and to ascertain what belongs to each separately. 

 This is true particularly of the sensations excited by acrid vapors in the nose, 

 as of ammonia, horse-radish, mustard, etc., and the difficulty is the greater 

 when it is remembered that these acrid vapors have nearly the same action 

 upon the mucous membrane of the eyelids. 



