USCULAR FEELINGS. 565 



of cold as ft travels over some places. These "cold sensa- 

 tion''' spots are different from the "warm sensation" spots, 

 and from the "touch sensation" spots; and are constant in 

 the same individual. Excluding pain (" abnormal sensa- 

 tion"), there are in the skin three distinct sets of nerve- 

 fibres: One, when excited, arouses "touch" sensation; a 

 second, "warm" sensation; the third, "cold" sensation. 



The Muscular Sense. In connection with our muscles 

 we "have sensations of great importance, although they 

 do not often become so obtrusive in consciousness as to 

 arouse our attention. Certain of these feelings (muscle 

 sensations proper] are Hrm to f.hA PY^jj-.ftt.i^ nf ftp-nsjovy 

 nej-ves ending within the muscles themselves: the others 

 (innervation sensations) have probably a central origin 

 and accompany the starting of volitional impulses from 

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

 untary skeletal muscles. 



The proper muscle sensations only become marked on 

 powerful or long-continued muscular effort (cramp, fatigue), 

 but a lower grade of them, not distinctly perceived, proba- 

 bly accompanies all muscular activity. 



The innervation feelings are of far more consequence. 

 They accompany the slightest movement of a skeletal mus- 

 cle, and we derive from them means of determining with, 

 great accuracy the force and extent of the contraction 

 willed. The belief that their origin is central mainly rests 

 on the fact that we have sensations, not merely of executed 

 but of intended movements. The actual nature of the 

 movement performed is probably characterized by other 

 contemporary sensations, as from the muscle sense proper, 

 from pressure and folding of the skin, and so on. 



The innervation feelings thus stand apart and opposed 

 to all our others as primary factors in our mental life; they 

 represent the reactive work of the organism with respect 

 to its environment. Some distinguished physiologists, 

 however, deny their existence, ascribing them all to a 

 peripheral origin, either in sensory muscle-nerves, or in 

 skin-nerves affected when a part of the Body is moved. 



