THE SENSE OF SMELL, 609 



other more vivid, though no general principles governing this relation have 

 been discovered in the case of tastes. In the art of cooking, however, atten- 

 tion has at all times been paid to the consonance or harmony of flavors in 

 their combination or order of succession, just as in painting and music the 

 fundamental principles of harmony have been employed empirically while 

 the theoretical laws were unknown. 



Frequent and continued repetitions of the same taste render the perception 

 of it less and less distinct, in the same way that a color becomes more and 

 more dull and indistinct the longer the eye is fixed upon it. There is fatigue 

 of the taste organ at some point. 



THE SENSE OF SMELL. 



The sensation of smell is produced by the action of odorous particles on a 

 special end-apparatus, which in turn causes nerve impulses that arouse changes 

 in a special area in the sensorium. The stimulating cause is the direct action 

 of chemical substances as in the sense of taste. In this case, however, the 

 substances must reach the sensory membrane in a gaseous state, or in ex- 



FIG. 426. Nerves of the Septum Nasi, Seen from the Right Side. Xf . /, The olfactory bulb; 

 i, the olfactory nerves passing through the foramina of the cribriform plate, and descending to 

 be distributed on the septum; 2, the internal or septal twig of the nasal branch ot the opntnai- 

 mic nerve; 3, naso-palatine nerves. (From Sappey, after Hirschfeld and Leveille.) 



tremely fine division so that it can quickly enter into solution in the moisture 

 on the sensitive mucous surface. The odorous particles are carried to the 

 membrane by inspiratory currents of air. 



The Olfactory Apparatus. The essential parts of the olfactory ap- 

 paratus are the nasal sensory or olfactory membrane to receive the special 

 stimuli, and the nervous apparatus to conduct the olfactory nerve-impulse to 

 the sensory area in the cortex cerebri for its perception. 



The nose is not entirely an organ for the seat of smell. In fact the nasal 

 39 



