THE MUSCULAR SENSE. 591 



are tasted as well as usual; and most persons taste salines 

 better at the sides of the tongue than elsewhere ; so that the 

 salt and acid sensations seem to have a different apparatus, not 

 only from the sweet and bitter, but from one another, 



The Muscular Sense. The muscles are endowed with com- 

 mon sensibility, as proved by the pains of cramp and fatigue, 

 but in connection with them we have other sensations of great 

 importance, although they do not often Kecome so obtrusive 

 in consciousness as to arouse separate attention. Certain of 

 these feelings (muscle sensations proper] are due to the ex- 

 citation of sensory nerves ending within the muscles them- 

 selves : others (innervation sensations) have possibly a central 

 origin and accompany the starting of volitional impulses from 

 brain-cells; they are only felt in connection with the voluntary 

 skeletal muscles. 



We have at any moment a fairly accurate knowledge of the 

 position of various parts of our Bodies, even when we do not 

 see them ; and we can also judge fairly accurately the extent 

 of a movement made with the eyes shut. The afferent nerve 

 impulses concerned in the development of such judgments may 

 be various ; different parts of the skin are pressed or creased ; 

 different joints are subjected to pressure; different tendons 

 are put on the stretch and different muscles are in different 

 states of contraction, and it is by no means easy to determine 

 the part played in each case by the sensory nerves of the 

 different organs. Moreover, when we push against an object, 

 or lift it, we are able to form a judgment as to the amount of 

 effort exerted ; but here again pressure on skin and joints and 

 tension of tendons come in. Although under normal circum- 

 stances the skin sensations are undoubtedly of importance, they 

 are not necessary : persons with cutaneous paralysis can, apart 

 from sight, judge truly the position of a limb and the extent 

 of movement made by it ; and in many movements change in 

 joint pressure must be very little if any. We have then to 

 look to muscles and tendons themselves for an important 

 part of the sensations, and in both muscles and tendons there 

 are organs in connection with nerve-fibres which are certainly 

 sensory in nature : moreover, muscle sensory nerves, whether 

 through the organs of Golgi or some other end organ, appear 

 to be excited by mere passive change of form in the muscle : 

 with the eyes closed each of us can tell how much another 

 person has lifted one of our arms. 



