330 Journal of Comparative Neurology. 



muscle fibers are not merely the ends of larger ones which have 

 become attenuated near their insertion, but they run for nearly 

 the whole length of the muscle, maintaining the same diameter 

 and the same relation to the larger ones. They do not appear 

 to differ from the ordinary fibers except in size, in their con- 

 stant relation to the finer nerve fibers and particularly in the 

 fact that they are in places more closely enveloped by a dense 

 and very rich plexus of these finer nerve fibers and by a nucle- 

 ated connective tissue interstitial substance." 



The point in this description to which I here direct atten- 

 tion is the fact that the large and small nerve fibers leave the 

 brain together and are apparently approximately equal in 

 length. In fact, the smaller fibers in general may be a trifle 

 longer, for they usually end farther out on the muscle towards 

 its insertion than do the larger ones. The size of the nerve 

 fibers is evidently correlated with the size of the muscle fibers 

 to be innervated. I have verified this observation on several 

 other bony fishes; viz., the cod, the gold fish and the cat fish, 

 whose eye-muscles show the same peculiarity of innervation. 



In Section 5 of the same memoir is described a similar 

 condition in connection with certain muscles (presumably all of 

 the visceral type) about the beginning of the oesophagus of 

 Menidia. On page 264 the description of the innervation of 

 the m. pharyngeus transversus is as follows: "This is a large 

 stout muscle extending between the two inferior pharyngeal 

 bones. It is incompletely divided into two parts, a large ven- 

 tral part which is supplied by a small number of very coarse 

 and heavily myelinated fibers, like those for the other branchial 

 muscles which can be traced back into the common motor com- 

 ponent [of the vagus nerve], and a smaller dorsal part which is 

 dorsally confluent with the general constrictor muscles of the 

 oesophagus and like them is supplied by many very fine fibers 

 whose origin could not be traced. The muscular fibers of the 

 ventral part are very large and thick, those of the dorsal part 

 smaller, but not so small as those of the proper constrictor of 

 the oesophagus." Here again we have a case where nerve 

 fibers of the same length and type (both viscero-motor) differ 



