GENERAL ANATOMY. 



facial; 2d, the others, adhering to the external membrane of 

 the artery, penetrate with it into organs which are soft and 

 pulpy: after becoming much ramified they disappear, and 

 seem to dissolve in the external membrane; 3d, finally, not- 

 withstanding the denial of Behrends, nervous ramifications 

 are seen traversing the external membrane of the arteries, and 

 terminate in the middle membrane. The nerves of the arte- 

 ries belong either to the sympathetic nerves, or to the spinal 

 and trigemini. 



779. The structure of the nerves has been examined by 

 different anatomists. Delia Torre found there fibres and the 

 globules common to all the nervous system; Prochaska and 

 Reil have made better known their interior disposition. Ac- 

 cording to their researches, the nerves are composed of cords, 

 and these of very fine filaments, whose tenuity is equal to 

 the filaments of silk, and which, in the optic nerve alone are 

 equal in size to a large hair. These filaments, which are of 

 the same nature as the medullary fibres or filaments of the 

 brain and spinal marrow, differ only in being more distinct, 

 more clearly separated from each other; and in being sur- 

 rounded by an envelope or proper membrane: this envelope 

 is called neurilema, neurhymen, which signifies membrane of 

 the nerves; Galen made use of this expression, of which Reil 

 first made a precise application. The neurilema forms a ge- 

 neral envelope to the nerves, and furnishes partial envelopes 

 to the nervous cords, as well as to the component filaments: 

 it resists strongly. When it is empty, it represents an assem- 

 blage of little canals. These canals uniting together, open, 

 into each other at different distances. It is not then correct 

 to say that the nerves are composed of filaments separate 

 throughout their whole length; the communications of these 

 filaments with each other make them no longer the same: 

 examined on the superior and inferior part of the nerve, the 

 nervous cords are not simply adherent, but they send to each 

 other reciprocal filaments. The same disposition exists in 

 the plexuses, where there is an intimate communication be- 

 tween all the nerves, by means of the cords and filaments 

 they send to each other. What the plexuses present on a 



