214 Journal of Comparative Neurology. 



They are within the connective tissue sheath surrounding each 

 intrafusal fiber. 



Maimnalia. In mammaha we have stained the nerves go- 

 ing to muscle-spindles in the dog, cat, rabbit, Guinea pig, and 

 rat, and lately we have confined our attention to the spindles 

 found in the intrinsic plantar muscles, where, as Sherrington 

 has stated, they are very plentiful. The spindle-nerves were 

 stained by injecting a i % solution of methylene blue in normal 

 salt into the abdominal aorta, after bleeding the animal. The 

 intrinsic plantar muscles were exposed about one hour after the 

 injection, removed to a slide and observed until the nerve end- 

 ings seemed stained ; the tissues were fixed in ammonium 

 molybdate and sectioned in paraffin, the sections being further 

 stained in alum carmine or alum cochineal; other muscles were 

 fixed in ammonium picrate, teased, cleared, and mounted in 

 glycerine-picrate. The former method brings out very clearly 

 the relation of the ultimate ending of the spindle-nerve to the 

 intrafusal fibers ; the latter, the course and the structure of the 

 spindle-nerves as they approach the spindle, as also their gen- 

 eral distribution in the spindle. 



In all mammalia examined by us, muscles with only one 

 area of nerve distribution and those with several areas in which 

 spindle-nerves terminated — compound spindles — were found. 

 The latter were more numerous in the dog, cat and rabbit than 

 in the smaller mammals — Guinea pig and rat — examined by us. 

 In the dog, several very large muscle-spindles were found, hav- 

 ing as many as four areas of nerve distribution. 



The general structure of the muscle-spindles of mammalia, 

 as also the distribution and structure of the spindle-nerves, has 

 been discussed in the preceding pages. We may here, how- 

 ever, reiterate the following points regarding the spindle- 

 nerves : 



From one to four large medullated nerves end in the smaller 

 spindles and from five to eight in the larger, compound spindles. 



Single spindle-nerves are surrounded by a thick^sheath of 

 Henle ; small bundles of spindle-nerves, by,a connective tissue 

 sheath, which becomes in part continuous with the capsule, in 



