CHAP. VIII.] THE SYMPATHETIC NERVES. 223 



cerebro-spinal nerves ; so that those fibres which at one part of the 

 nerve were superficial, would at another be deep-seated, and vice 

 versa. 



The mode of branching of these nerves is essentially the same 

 as that of the cerebro-spinal. But the frequent formation of ganglia 

 in the course of the trunks, and of their ramifications, constitutes 

 a remarkable feature. The branches attach themselves to the ex- 

 terior of arteries, forming very intricate plexuses, which entwine 

 around them, "hederse ad modum" (Scarpa). Along these vessels 

 the nerves are conveyed to the tissues ; but of the mode in which 

 their filaments connect themselves immediately with those textures 

 we are at present entirely ignorant. The ramifications of the sym- 

 pathetic seem to be limited to the trunk and head ; it has probably 

 no connexion, or at most a very limited one, with the extremities. 



The connexion of the sympathetic system with the brain and 

 spinal cord appears to take place through the cerebro-spinal nerves. 

 Certain filaments connect each spinal nerve to some portion of the 

 ganglionic chain which lies on each side of the spinal column. And 

 a similar connexion takes place between ganglia of the cephalic 

 portion of the sympathetic and the encephalic nerves, of which the 

 following may be cited as well-known instances : The third nerve is 

 connected with the ophthalmic ganglion ; the sixth with the superior 

 cervical ganglion the fifth nerve with the spheno-palatine and otic 

 ganglia. These connecting filaments have been called the roots of 

 the sympathetic ; and thus this nerve has been represented as taking 

 an extended origin from numerous points of the cerebro-spinal centre. 

 This is true : but, in dissecting the connexion between the sympa- 

 thetic and the spinal nerves, we find that, for the most part, two dis- 

 tinct fascicles connect them, one of which is white, being composed of 

 tubular fibres ; the other is gray, and consists of gelatinous fibres. 

 The former seem evidently cerebro- spinal fibres, which pass to or 

 from the periphery conjoined with the other elements of the sympa- 

 thetic : but, in the present state of our knowledge, it is difficult to 

 form a correct idea as to the precise object of the latter bundles, or 

 as to the central connexion which they form, whether with the gan- 

 glion on the posterior root of each spinal nerve, or with the spinal cord. 

 That the sympathetic has intimate and extensive connexions with 

 the brain and spinal cord, is abundantly proved, not only by the ana- 

 tomical statements above detailed, but by the circumstance of which 

 every one is conscious, that pain may be excited in parts supplied 

 from this system of nerves alone, as in the intestines ; as well as by 

 the fact that irritation of the spinal cord may produce contraction of 



