222 



INNEKVATION. 



CHAP. VIII.] 



Fig. 61. 



regards the auditory nerve, there are also some grounds for the 

 statement that the vesicles of gray matter are deposited at its peri- 

 pheral expansion in the internal ear."* 



Of the Ganglionic or Sympathetic Nerves. The composition of 

 these nerves is essentially similar to that of the cerebro-spinal 

 nerves. They consist of a series of nerve-fibres bound together by 

 areolar tissue which forms their neurilemma. This sheath is, how- 

 ever, denser than in the cerebro-spinal nerves, so that the nerve- 

 fibres are more difficult of separation, and the fasciculated character 

 is not so obvious. It consists almost entirely of white fibrous tissue 

 longitudinally disposed, which are crossed by some fine circular 

 fibres of yellow tissue, surrounding the nerves at various distances 

 from each other. When a nerve is torn up by needles, and treated 

 by acetic acid, numerous small oval cell-nuclei are seen lying in and 

 among the fibres, with their long axes parallel to the latter. 



The sympathetic nerves 

 contain the fibres of both 

 kinds, the tubular and the 

 gelatinous, in very variable 

 quantity in different nerves. 

 Thus, the former are nume- 

 rous in the ramifications of 

 the solar plexus and in the 

 cardiac nerves ; and the lat- 

 ter almost exclusively com- 

 pose one of the fascicles by 

 which the sympathetic com- 

 municates with the spinal 

 nerves (fig. 61, e) : they are 

 also numerous, while the tu- 

 bular fibres are few, in the 

 sympathetic cordinthe neck. 

 In some nerves, the tubular 

 fibres are quite on the sur- 

 face ; and in others, they are 

 enclosed in the axis of the 

 nervous trunk. It is pro- 

 bable that the same change 



Roots of a dorsal spinal nerve, and its union with /. _i ono l^+ w n ffop fihrPS 



sympathetic : c, c. Anterior fissure of the spinal cord. 01 piaCC DetWCt 



a. Anterior root. p. Posterior root, with its ganglion. _,__ 4-"U oco -ncvr>v> n<a flint 



a'. Anterior branch, p'. Posterior branch, s. Sympathetic. OCCUTS HI these nerVCS as 



e. Its double junction with the anterior branch of the .-.-U'^-u wp ho V p nntippH 111 the 



spinal nerve by a white and a gray filament. WHICH WC naVC 



* See further on these points the chapters on Smell, Vision, and Hearing. 



