NERVOUS SYSTEM. 331 



expended*. The nerves are very unequally distributed to different 

 parts : the organs of sense, the skin, muscles, and mucous mem- 

 branes are plentifully supplied with them : the serous, fibrous, 

 and medullary membranes receive but few ; and none have yet 

 been detected in either cartilage or tendonf. 



Ganglion. — A ganglion is a little knot or swelling upon a nerve, 

 perfectly natural to it. We find them in various parts of the 

 body ; more especially about the neck, chest, and abdomen. 

 They will be pointed out in tracing the distribution of those nerves 

 to which they appertain. Bichat discovered that neither the 

 sympathetic nerve nor the ganglia it forms, possess sensibility. 



Origin and Distribution of the Nerves. 



It has been observed, that the ten pairs of nerves connected with 

 the brain are denominated cerebral; while the thirty-six pairs 

 connected with the spinal marrow, are contra-distinguished as 

 the spinal. All the nerves being symmetrical in number and dis- 

 tribution, on either side of the body, take their origins by pairs, 

 and these pairs are numbered, and so distinguished from one 

 another, according to the order in which they arise — proceeding 

 from below upward within the head, from before backward within 

 the spine. In addition to this distinction of ordinal number, how- 

 ever, every pair of cerebral nerves has obtained a particular epithet 

 significant of the specific purpose they serve, the part they supply, 

 or else some peculiarity in their division or distribution. 



* Wherever we trace nerves of motion, we find that before entering- the 

 muscles, they interchange branches, and form an intricate mass of nerves, 

 or what is termed a plexus. The filaments of nerves which go to the skin 

 regularly diverge to their destination. — Nervous System. By C. Bell, F.R.S. 



t And yet the granulations of these parts possess sensibility, of which 

 I have had very marked evidence, in the case of broken-knee. The horse 

 has never failed to snatch up the leg, every time the granulating edges of 

 the extensor tendon were touched with the probe. 



