INTRODUCTION. XXvii 







cation with the brain be not interrupted. The sense 

 most extended is that of the touch, which is enjoyed 

 by all parts of the surface of the body ; the others are 

 thought, by very respectable physiologists, to be only 

 more exalted modifications of it, and are susceptible of 

 more delicate impressions. It is scarcely necessary to 

 mention that the other sensations are executed by the 

 eye, the ear, the tongue, and the nose. 



The Sense of Touch is the most important of all, and 

 the least liable to error in its reports. To exercise it, 

 it is necessary for the body, under examination, to come 

 into contact with ours: hence, its operations are so me- 

 chanical, that but little is left to the imagination, and 

 they, therefore, serve to verify and to correct the im- 

 pressions on the other senses, more particularly those 

 on the eye. It is the sense of touch by which we learn 

 accurately the dimensions of bodies, and the figures of 

 such as are hard. The hand, or any other part, by be- 

 ing applied to them in various directions, informs us 

 whether they are flat, round or angular. A greater or 

 less degree of pressure informs us whether they are 

 soft or hard, and by rubbing, we ascertain whether 

 they are rough or polished. The resistance they make 

 to motion, teaches us whether they can or cannot be 

 moved, and their being impelled against us shows the 

 momentum with which they act, as well as its direc- 

 tion. Our ideas of heat and of cold are also derived 

 from this source. It is not asserted that all parts of 

 the surface of the body enjoy equally the sense of touch ; 

 on the contrary, this sensibility is more or less active, 

 according to the organization of the part, and as its 

 nerves are more or less numerous and exposed ; hence 

 we find it most exquisite and perfect in the ends of 

 the fingers. This, therefore, being the most import- 

 ant of the senses, the magnitude of its influence on 



