THE SENSE OF TOUCH. 593 



spiral ribbon." The motor nerve also penetrates the capsule and 

 terminates in the polar extremities of the intra-fusal fiber. Sensor 

 end-organs supposed to be connected with the muscle sense are also 

 found in the tendons of muscles. 



Afferent Nerves. That muscles are abundantly supplied with 

 afferent nerves has been proved by different methods of investigation. 

 With histologic methods Sherrington has traced afferent fibers from 

 the muscle spindles directly into the spinal nerve ganglia. The con- 

 tractions of muscles from electric stimulation as well as the con- 

 tractions known as muscle cramp, due to unknown agents, give rise 

 to sensations of pain, a fact which indicates the presence in muscles 

 of afferent or sensor nerves. 



Cortical Area. Pathologic findings have shown that an im- 

 pairment or a loss of the muscle sense is associated with de- 

 structive lesions of perhaps the superior and inferior parietal 



FIG. 274. A NEURO-MUSCLE SPINDLE OF A CAT. (Ruffini.) c. Capsule, pr. e. 

 Primary ending. 5. e. Secondary ending, pi. e. Plate ending. (All these are 

 probably sensor in function.) (Starling's "Physiology.") 



convolutions (Fig. 226). In a case reported by Starr the removal 

 of a small tumor in the pia mater situated over the junction 

 of the superior and inferior parietal lobules was followed by a 

 loss of the muscle sense and marked ataxia in the right hand 

 for a period of six weeks, after which recovery took place. These 

 symptoms were attributed to injury of the cortex from unavoidable 

 surgical procedures. 



The muscle sensations, as stated in foregoing paragraphs, form 

 the basis of the perception not only of the direction and the duration 

 of a body movement and the resistance experienced, but also of the 

 position and the tension of the muscle groups. The latter fact 

 more especially makes it possible for the mind to direct the muscles 

 and to graduate the energy necessary to the accomplishment of a 

 definite purpose. 



Active Touch. Active touch or the application of the fingers 

 to the surfaces of external objects implies the cooperation of the 

 skin and the muscles. The sensations which are evoked are combina- 

 38 



