SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 263 



which is the part called the axis of the nerve. The two 

 latter substances are called nervine. 



598. THE NERVOUS FILAMENTS OR FIBRILL^ differ 

 in size in different cases, but each one is uniform in diam- 

 eter, and continuous from end to end. 



599. THE EXTREMITY OF A NERVE, CONNECTED WITH 

 ITS CENTRE or ganglia, is called its origin, inner, central, 

 or centripetal extremity, while THE OTHER extremity is 

 called its termination, outer, or centrifugal extremity, 

 though in case of sensation the influence acting through 

 the nerve begins at what is called the termination of the 

 nerve. 



600. IN THE COURSE OF THE NERVES numerous in- 

 stances occur of filaments or bundles of them passing 

 across from one nerve to another, particularly in the re- 

 gion of the neck. This constitutes what is called a plexus. 



FIG. 183. 



*^=- ^ 

 Fig. 183 represents a plex- 

 us, 7, formed by side nerves, 

 1 and 2, interchanging two 

 fibres; 3, a branch of three 

 fibres ; 4, another, of two ; 5 

 and 6, two branches of one 

 each. 



601. THE USE OF A PLEXUS is to allow nerves that 

 are extending from different centres to the same part to 

 be enclosed in a common sheath. 



602. There are THREE DIVISIONS WITH WHICH THE 

 NERVES CONNECT *. the Brain, the spinal cord, the Sym- 

 pathetic Ganglia; hence, 



603. THE NERVES ARE CALLED the Cranio-spinal 

 nerves, and the Sympathetic. 



604. THE SYMPATHETIC NERVES are of two kinds, a 

 white kind, finer than the Cranio-spinal, and a much 

 greater number of a reddish gray character. 



698. What said of ? 599. What said of -? 600. What occurs - ? Describe 

 Fig, 188. 601. What is ? 602. What ? 603. How ? 604. What said of ? 



