SEC. 9. ON THE DEVELOPMENT OF CUTANEOUS AND 

 SOME OTHER SENSATIONS. 



678. The sensations with which we have just dealt arise 

 through impulses passing along special nerves or parts of special 

 nerves, the optic nerve, the olfactory nerve &c. ; we have now to 

 deal with sensations arising through impulses along the nerves 

 of the body generally. These are of several kinds. In the first 

 place there are sensations which we may speak of as " cutaneous 

 sensations," the impulses giving rise to which are started in the 

 skin covering the body, or in the so-called mucous membrane 

 lining certain passages. These sensations, which as we shall see in 

 dealing with the senses are dependent on the existence of special 

 terminal organs in or near the skin, are sensations of " touch," 

 in the narrower meaning of that word, by which we appreciate 

 contact with and pressure on the skin, and the sensations of 

 " temperature," which again we may, as we shall see, divide into 

 sensations of " heat " and sensations of " cold." These sensations 

 may be excited in varying degree by impulses passing along any 

 nerve branches of which are supplied to the skin. Then there 

 are the sensations constituting the " muscular sense," to which 

 we have already referred, and these again may be excited in any 

 nerve having connections with the skeletal muscles. 



As we shall see in dealing with the senses, when a nerve is laid 

 bare and its fibres are stimulated directly either by pressure, 

 such as pinching, or by heat, or by cold, or in other ways, the 

 sensations which are caused do not enable us to appreciate 

 whether the stimulation is one of contact or pressure, or of 

 temperature, or of some other kind ; we only experience a 

 " feeling," which at all events when it reaches a certain intensity 

 we speak of as "pain." And we have reason to think that at 

 least from time to time impulses along various nerves give rise to 

 sensations which have been spoken of as those of "general 

 sensibility," by which in addition to other sensations, such as 

 those of touch and of the muscular sense, we become aware 'of 

 changes in the condition and circumstances of our body. When 

 the stimulation of the skin exceeds a certain limit of intensity, 

 the sense of touch or temperature is lost in, that is to say, is not 

 appreciated as separate from the sense of pain; and under 



