854 



A MANUAL OF PHYSIOLOGY 



The corpuscles of Pacini, which exist in considerable numbers in 

 the neighbourhood of joints and ligaments, and in the periosteum of 



bones, would seem well fitted to play 

 the part of end-organs for the tactile 

 sensations caused by the movements of 

 flexion, extension, or rotation of one 

 bone on another, which form so large 

 a portion of all voluntary muscular 

 movements. And it has been stated 

 that paralysis of these bodies in the 

 limbs of a cat by section of the nerves 

 FIG. 328,-NERVE-ENDiNG IN g oin g to them causes a characteristic 

 TENDON NEAR THE INSER- uncertainty of movement which sug- 

 TION OF THE MUSCULAR gests that something necessary to nor- 

 FIBRES (GOLGI). ma l co-ordination has been taken away. 



Tendons also possess afferent nerve- 

 fibres, which terminate by breaking up into reticulated end-plates 

 (Fig. 328). We have already seen that the skeletal muscles possess 



n.'n.b. 



pr.c 



FIG. 329. MUSCLE SPINDLE (HALLIBURTON, AFTER RUFFINI). 



c, sheath of the spindle ; n.tr., trunk of nerve, which sends fibres through the sheath 

 into the spindle, where they form endings (pr.e., s.e., pl.e.) of various kinds; 

 m.n.d., bundle of motor fibres. 



numerous afferent fibres (p. 731). Some of these must be nerves 

 of ordinary sensation. For although, when a muscle is laid bare in 

 man and stimulated electrically, the sensation does not in general 

 amount to actual pain, it is capable, under the influence of strong 

 stimuli, of taking on a painful character. And nobody who has 

 felt the severe and sometimes almost intolerable pain of muscular 

 cramp would be likely to deny the existence of sensory muscular 

 nerves. But after deducting these, we must assume that a large 

 proportion of the afferent nerves of muscle have other functions, 

 and among them may be the conveyance of impulses connected 

 with the muscular sense. The muscle-spindles or neuro-muscular 

 spindles (Fig. 329), peculiar structures which occur in large num- 

 bers in most of the skeletal muscles, and have been carefully 

 studied by Huber, Sihler, Rufrmi, and other observers, are the 

 terminations of many of the sensory fibres. They are long narrow 

 bodies, with a thick sheath of connective tissue enclosing fine striped 

 muscular fibres. Medullated nerve-fibres enter the spindle, and 



