

SENSE OF TOUCH. 121 



which they are capable of acquiring by attention, the impressions must 

 not be too constantly or too strongly made. The occasional use of the 

 sense 'of smell, under the guidance of volition, may be the test on which 

 the chemist, perfumer, or wine-merchant, may rely in the discrimi- 

 nation of the numerous odorous characteristics of bodies ; but, if the 

 olfactory nerves be constantly, or too frequently, stimulated by excit- 

 ants, of this or any other kind, dependence can no longer be placed 

 upon them as a means of discrimination. The maxim that " habit 

 blunts feeling," is true only in such cases as the last. Education can. 

 indeed, render it extremely acute/ Volition, on the other hand, en- 

 ables us to deaden the force of sensations. By corrugating the eye- 

 brows and approximating the eyelids, we can diminish the quantity of 

 light when it is too powerful. We can breathe through the mouth, 

 when a disagreeable odour is exhaled around us; or can completely shut 

 off its passage by the nostrils, with the aid of the upper extremity. 

 Over the hearing we have less command as regards its individual ac- 

 tion : the upper extremity is here always called into service, when we 

 desire to dimmish the intensity of any sonorous impression. 



Lastly. It is a common observation, that the loss of one sense occa- 

 sions greater vividness in others. This is only true as regards the senses 

 that administer chiefly to the intellect, those of touch, audition, and 

 vision, for example. Those of smell and taste may be destroyed ; and 

 yet the more intellectual senses may be uninfluenced. In the singular 

 condition of artificial somnambulism or hypnotism, the author has seen 

 the various senses rendered astonishingly acute. 



The cause of the superiority of the remaining intellectual senses, 

 when one has been lost, is not owing to any superior organization in 

 those senses ; but is another example of the influence of education. 

 The remaining senses are exerted attentively to compensate for thfc 

 privation ; and they become surprisingly delicate. 



"We proceed to the consideration of the separate senses, beginning 

 with that of tact or touch, because it is most generally distributed, and 

 may be regarded as that from which the others are derived. They are 

 all, indeed, modifications of the sense of touch. In the taste, the sapid 

 body; in the smell, the odorous particle; in the hearing, the sonorous 

 vibration ; and in the sight, the particle of light, must impinge upon 

 or touch the nervous part of the organ, before sensation can, in any of 

 the cases, be effected. 



SENSE OF TACT OR TOUCH PALPATION. 



The sense of tact or touch is the general feeling or sensibility, pos- 

 sessed by the skin especially, which instructs us regarding the tempe- 

 rature and general qualities of bodies. By some, touch is restricted 

 to the sense of resistance alone ; and hence they have conceived it 

 necessary to raise into a distinct sense one of the attributes of tact or 

 touch. The sense of heat, for example, has been separated from tact ; 

 but although the appreciation of external bodies by tact or touch differs 



1 Berard, Rapport du Physique et du Moral, p. 245; Paris, 1823. 



