Huber-DeWitt, Nerve-Endings in Muscles. 201 



Our own observations pertain more particularly to the end- 

 ing of the spindle-nerves in the muscle-spindles. The method 

 used by us was selected with this end in view ; the method, 

 while showing the general structure of the muscle-spindles, was 

 not the method which would have been selected, had this been 

 the more particular aim of the research. Our observations on 

 the general structure of the muscle-spindle confirm, in the main, 

 observations previously made, and more particularly those made 

 by Sherrington and given in his account of these structures ; 

 this account will here be followed. 



Capsule of muscle-spindle. The capsule or perimysial 

 sheath of some writers, has essentially the same structure in all 

 vertebrates examined, although it varies much in thickness. It 

 may be said to be made up of concentrically arranged layers of 

 white fibrous tissue, the several layers being often in close ap- 

 position, or again more or less distinctly separated one from the 

 other, leaving larger or smaller clefts between them. The num- 

 ber of these concentric layers varies ; Sherrington places it at 

 six to eight, which number holds good for many of the muscle- 

 spindles seen by us, especially those found in mammalian mus- 

 cle. In amphibia, reptilia, and birds, the capsule of the spindle 

 may be said to be relatively thinner, consisting often of only two 

 to four concentric layers ; thicker capsules are, however, also 

 met. The fibrous tissue of the concentric lamellae is white 

 fibrous, practically devoid of yellow elastic tissue. This may 

 be seen in muscle-spindles overstained in methylene blue, our 

 experience having taught us that in tissues thus overstained, 

 the yellow elastic fibers are often clearly brought out ; it is also 

 seen in sections stained after Unna's method ; neither of these 

 methods shows any elastic fibers in the capsule of the muscle- 

 spindle. At the beginning of the muscle-spindle (proximal 

 end), the capsule becomes continuous with a somewhat thick- 

 ened perimysial sheath, which surrounds the muscle fibers 

 about to enter the muscle-spindle. The behavior of the cap- 

 sule at the distal end of the muscle-spindle depends somewhat 

 on its relative position in the muscle. The spindle may be em- 

 bedded in the muscle substance, in which case, as Sherrington 



