SENSE OF TASTE. 535 



' It is important to distinguish between the sense of smell and 

 general sensibility. The mucous membrane of the nose has, in 

 common with other mucous membranes and the skin, th$ power 

 to recognize such physical properties in objects as consistency, 

 temperature, etc. Thus if a sharp instrument was to be brought 

 in contact with this membrane, it would be recognized as sharp, 

 but this recognition is not due to the excitation of the olfactory 

 nerves, but to the fibers of the trigeminus. The mucous mem- 

 brane is therefore supplied by two nerves, the olfactory and the 

 fifth. One is not liable to confound sharpness with odor, but the 

 irritating effects of certain substances are often confounded with 

 the sense of smell, when, as a matter of fact, it is not the olfactory, 

 but the fifth pair, which is excited. Thus if acetic acid is brought 

 in contact with the mucous membrane of the nose, it will excite 

 the fibers of the fifth pair and will produce an irritating effect, 

 but it would be incorrect to say that we smelled it. If, however, 

 vinegar was substituted for the acetic acid, we should have the 

 irritating effect of the acetic acid it contains, and in addition the 

 olfactory nerves would be excited by the aromatic ingredients 

 which, with the acid, form vinegar ; and it would therefore be cor- 

 rect to say that we smelled the vinegar. 



The acuteness of the sense of smell differs in different indi- 

 viduals, but in most it is well marked. It has been estimated that 

 -g-Q of a milligram of musk may be detected by this sense, 

 le emanations from objects which excite the sense of smell pro- 

 duce this effect by stimulating the olfactory cells, and the impulses 

 are carried by the olfactory nerves to the brain. 



Case of Julia Brace. A remarkable instance of the acuteness 

 of the sense of smell is that of Julia Brace, an inmate of the 

 Hartford Asylum, who became entirely deaf and blind at the 

 age of four years and five months. The history of this case is 

 given in the Life and Education of Laura D. Bridgman, by 

 M. S. Lamson. This girl could select by the sense of smell her 

 own clothes from a mass of dresses belonging to a hundred and 

 thirty or forty persons. "She could discriminate, merely by 

 smelling them, the recently washed stockings of the boys at the 

 asylum from those of the girls. Among a hundred and twenty or 

 thirty teaspoons used at the asylum she could distinguish those 

 of the steward from those of the pupils." Her sense of touch was 

 also acute. " By putting the eye of a cambric needle upon the tip 

 of her tongue, she could feel the thread as it entered the eye and 

 pressed upon her tongue, and she would thus thread the needle." 



Sense of Taste. The sense of taste exists to a slight degree 

 in the middle of the dorsum of the tongue,, but is especially de- 

 veloped in the posterior third of the dorsum. It is also present 

 in its tip and edges and in the soft palate, but the exact area in 

 which it resides has never been determined. 



