THE N. ACCESSORIUS. II7 



IX. — Ramus for M. Trapezius (Accessorius). 



A small motor twig (AV) which leaves the vagus com- 

 plex at the ventral edge of the jugular ganglion is worthy 

 of separate treatment. It passes caudad for a short dis- 

 tance in company with the r. cut. X, j and supplies the 

 m. trapezius. It is a very small nerve, containing only 

 from ten to twenty fibres, a much smaller number than 

 the cutaneous nerve which it accompanies. It is very 

 sharply separable from the latter by reason of the greater 

 size of its fibres. The sections are quite unambiguous 

 and leave no doubt that this nerve actually terminates in 

 the m. trapezius and does not merely pass through it. 

 The accompanying cutaneous fibres do not enter the 

 muscle, but pass to the skin mesally of it. The participa- 

 tion of spinal nerves in the innervation of this muscle has 

 been definitely excluded. There are no spinal nerves in 

 its vicinity and the entire course of the muscle has been 

 examired microscopically without revealing any spinal 

 fibres within or near it. As to the central relations of this 

 nerve, we can only say that its fibres arise from the com- 

 mon motor root of the vagus. 



The trapezius muscle arises from the ventral surface of 

 the parotic process of the skull (Parker's term) and ex- 

 tends back as a well defined round bundle at the lateral 

 edge of the dorso-lateral musculature to its insertion on 

 the dorsal part of the cleithrum. The dorso-lateral mus- 

 culature of the corresponding region arises from the dorsal 

 surface of the parotic process and from the skull dorsad 

 and cephalad of it. 



Vetter ('78, pp. 526 and 541) states that an independent 

 trapezius muscle from the cranium to any part of the 

 shoulder girdle is absent in the bony fishes and that the 



