Huber-DeWitt, Nerve- Endings in Muscles. 205 



nuclei, the nuclei being found in an axial core, not striated and 

 probably sarcoplastic in nature. The capsule of these simpler 

 spindles consists of two to three concentrically arranged mem- 

 branous lamellae of fibrous tissue, between which clefts or 

 spaces may now and then be made out. These lamellae are 

 not, we believe, elastic in nature (" mehrere Lagen elasticher 

 Membranen "), as Sihler has stated. 



We may finally refer to the fact that the muscle-spindles 

 have, according to Cattaneo, a distinct blood supply. One or 

 two relatively large vessels go to each spindle. The vessels 

 pass along the border of the spindle either on or in the capsule 

 and give off branches which have a spiral or wavy cours e. Our 

 own observations on this point are confined to the muscle-spin- 

 dles found in the rabbit. In relatively thick sections of one of 

 the intrinsic plantar muscles previously injected with gelatine 

 blue, these spindle-vessels may readily be seen. From the 

 larger branches found in the capsule of the spindle, secondary 

 branches are given off, which have a spiral or wavy course and 

 anastomose to form an open network surrounding the spindle ; 

 from this, relatively long, straight branches may be traced be- 

 tween the intrafusal fibers of the spindle. 



Spindle-nerves. Nearly all writers who have given obser- 

 vations on muscle-spindles, have recognized large medullated 

 nerve fibers going to these organs, and have described a branch- 

 ing of these nerve fibers, either before entering the spindle, or 

 after their entrance. Sherrington, as previously stated, was the 

 first to show conclusively that such fibers are spinal ganglion — 

 sensory — fibers, which do not degenerate when all the motor 

 nerve fibers going to the muscle have been removed. We find 

 his account of the general distribution of the spindle-nerves 

 very accurate and applying not only to the mammalia studied 

 by him — cat and monkey — but also, with very little modifica- 

 tion to other vertebrates possessing muscle-spindles containing 

 more than one intrafusal fiber. As he has stated, usually more 

 than one large medullated fiber, "7 ^i — 18 ji " (or even longer) 

 in diameter, is distributed to one spindle ; two to four may be 

 given as the number for the smaller spindles and five to eight 



