COMMON SENSATION. 219 



without changing the position of the limb, and this rigidity 

 is accompanied with a peculiar sensation. Also, the sense of 

 muscular exhaustion or weariness is derived, in part at least, 

 from the muscles themselves; and the sense of resistance 

 consists partly in a feeling of the expenditure of a certain 

 amount of muscular exertion which meets with opposition. 

 That, however, is only one element in the sense of resistance, 

 and one which comes into play only when there is muscular 

 action; but suppose that the head is reclined, and that 

 something comes in contact with it, the force of the contact 

 and the hardness or softness of the object are both appre- 

 ciated, although no muscles are brought into play, and 

 although there are none in the part which has been touched. 

 Obviously, in such circumstances, what is appreciated is the 

 character and degree of the pressure exercised against the 

 skin. 



And now, if the student, having considered these different 

 varieties of feeling, will attempt to analyse what touch con- 

 sists in, he will find that it is not a different sense from 

 feeling, but only an application of it, accompanied with a 

 judgment of the mind. The hardness or softness, roughness 

 or smoothness, of the object touched, exercise different kinds 

 of pressure on the skin, and can be examined by means of 

 more or less muscular exertion; while the sense of the posi- 

 tion of the touching organ enables us to determine the form 

 and extent of the object. 



The sense of temperature has some claim to be considered 

 as distinct from all others; for rare instances are on record 

 of the loss of this sense in a limb, leading to the exposure 

 to severe injury from burning, while the other varieties of 

 common sensation remained. 



160. An important element in delicacy of touch consists in 

 the localization of the feeling excited by contact; and an at- 

 tempt has been made to measure the degree of sensitiveness of 

 different parts of the surface, by ascertaining how nearly two 

 points, say the points of a pair of compasses, may be approached 

 one to the other, and yet be distinguished as separate when 

 simultaneously laid against the skin. Judged in this way, 

 the tongue is more sensitive than the fingers, and the back 

 has very little sensation. But if the student try the experi- 



