554 THE SENSE OF TOUCH. 



the taste of cheese improves it. There appears, therefore, to 

 exist the same relation between tastes as between colors, of 

 which those that are opposed or complementary render each 

 other more vivid, though no general principles governing this 

 relation have been discovered in the case of tastes. In the art 

 of cooking, however, attention 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. Thus, after frequently tasting first 

 one and then the other of two kinds of wine, it becomes im- 

 possible to discriminate between them. 



The simple contact of a sapid substance with the surface of 

 the gustatory organ seldom gives rise to a distinct sensation of 

 taste ; it needs to be diffused over the surface, and brought into 

 intimate contact with the sensitive parts by compression, fric- 

 tion, and motion between the tongue and palate. 



The sense of taste seems capable of being excited also by in- 

 ternal causes, such as changes in the conditions of the nerves 

 or nerve-centres, produced by congestion or other causes, which 

 excite subjective sensations in the other organs of sense. But 

 little is known of the subjective sensations of taste ; for it is 

 difficult to distinguish the phenomena from the effects of ex- 

 ternal causes, such as changes in the nature of the secretions 

 of the mouth. 



SENSE OF TOUCH. 



The sense of touch is not confined to particular parts of the 

 body of small extent, like the other senses ; on the contrary, 

 all parts capable of perceiving the presence of a stimulus by 

 ordinary sensation are, in certain degrees, the seat of this sense ; 

 for touch is simply a modification or exaltation of common 

 sensation or sensibility. The nerves on which the sense of 

 touch depends are, therefore, the same as those which confer 

 ordinary sensation on the different parts of the body, viz., those 

 derived from the posterior roots of the nerves of the spinal 

 cord, and the sensitive cerebral nerves. 



But, although all parts of the body supplied with sensitive 

 nerves are thus, in some degree, organs of touch, yet the sense 

 is exercised in perfection only in those parts the sensibility of 

 which is extremely delicate, e.g., the skin, the tongue, and the 



