mi: \/:/, 701 



(I \\OLIONIO NERVES. These nerves, collectively representing the great 

 ni/nijxtthf ti<- Ki/sti'ni. form below and on the sides of the spine, two long cords, 

 rendered moniliform by the presence of ganglionic enlargements, and in 

 tlu- constitution of which nearly all the cerebro-spinal nerves concur; their 

 nullifications, frequently ganglionic also, arc destined to the viscera of tho 

 iurk. the thorax, and the abdomen. 



In these nerves of organic life are found tho two kinds of nerve-tubes, or 

 til ires of centripetal and centrifugal conductibility. 



But these tubes appear to have only very indirect relations with the 

 brain, for the will has no influence over the organs which receive their 

 nervous fibres from tho great sympathetic ; and, besides this, in health, the 

 excitations developed in these organs are all reflected by the spinal cord, 

 and do not provoke in any way the special activity of the encephalon they 

 are not felt. 



As the nerves of tho great sympathetic system are principally formed of 

 fine tubes, we ought perhaps to seek in this anatomical condition the cause 

 of the special properties of these nerves ; what tends to make this appear 

 likely is the fact, that the cerebro-spinal nerves contain some of these 

 tubes in their elements, and that they share, with the ganglionic ramuscules, 

 the faculty of bringing into play the reflex power of the spinal cord. But 

 this is only a probability, and is unsupported by any direct proof. 



However this may be, it must be remarked that the special anatomical 

 and physiological characteristics of the sympathetic nerves should not cause 

 them to be considered as a system independent of tho first, or cerebro-spinal 

 nerves. The fibres composing both have, in fact, a common origin in the 

 medullary axis, or rather those of the ganglionic nerves emanate from the 

 nerves of animal life. In the considerations which follow, we will therefore 

 omit this distinction of the nerves into two groups. 



ORIGIN OF THE NERVES. We ought to distinguish in these cords their 

 real or deep origin, and their superficial or apparent origin. The latter is 

 represented by the point of emergence of the roots of the nerves, which are 

 ordinarily spread in a fan shape, then united, generally after a very brief 

 course, into a single trunk, which offers at its commencement a ganglionic 

 enlargement, if fibres of general sensibility enter into its constitution. 

 Their real origin is the point of departure of these roots in tho depth of 

 the cerebro- spinal axis. This is not well known, perhaps, of any nerve, even 

 of those whoso radicles are easily followed into the substance of the nervous 

 res. 



DISTRIBUTION OF NERVES. Tho nervous trunks, formed by tho radicles 

 of which we: have just spoken, issue in pairs from the foramina at the base 

 of the cranium or in the walls of the spine, to be distributed to all parts of 

 tip Ixxly by dividing into successively decreasing branches. Those among 

 branches which ramify in the organs of animal life, generally follow 

 the track of tho deep vessels or tho subcutaneous veins, and are always 

 found most superficial. Their ramescence is effected in a very simple 

 manner, by the successive emission of tho fasciculi composing the principal 

 trunks, until they are completely expended. These branches pursue their 

 course nearly always in a direct line ; only some, as tho ramifications of tho 

 two principal nerves of tho tongue, describe very marked flexuosities, with 

 tin- s:i!in- protective intention as the arteries of that organ. j\na*tomoge 

 s.niit tinu s join these branches to one another; and anastomoses, often 

 enough complicated, unite many nerves together, and form what are called 

 l-l<'.m*<*. JJut in tin se anastomoses, no matter how complicated they may 



