1886.] on the SympatJietic Nervous System. 533 



nerve, and upon tracing them outwards I find that they separate 

 entirely from the large fibres of the accessory which form its external 

 branch, to pass as the internal branch into the ganglion trunci vagi 

 (see Fig. 2, p. 536). Here, then, we see in the upper cervical region 

 that the internal branch of the spinal accessory nerve is formed on the 

 same plan as a white ramus communicans, the ganglion belonging to 

 which is the ganglion trunci vagi. 



Among the cranial nerves we find, especially in the vagus, glosso- 

 pharyngeal, and chorda tympani, groups of fine nerve-fibres belonging 

 to the same system. We can therefore say that the communication 

 between the so-called sympathetic and cerebro-spinal systems is not 

 symmetrical throughout, but consists of three distinct outflows of 

 characteristic visceral nerves, viz. : 1, cervico-cranial ; 2, thoracic ; 

 3, sacral, the break of continuity corresponding to the exit of the 

 nerve plexuses which supply the upj^er and lower extremities. 



These medullated visceral nerves then pass out from the central 

 nervous system into the various ganglia of the sympathetic, and it is 

 possible that these latter ganglia bear the same kind of relation to 

 them as the ganglia on the posterior roots bear to the sensory nerves. 

 Before, however, we can accept this view it is absolutely necessary to 

 account for the non-medullated nerves which arise from the sympa- 

 thetic ganglia. Now it is hopeless to follow, by anatomical means, 

 any special nerve-fibre through the confusion of a ganglion. What 

 we cannot effect by anatomical methods we can by physiological. If 

 we find two nerves, one of which enters a ganglion and the other 

 leaves it, and we find their function absolutely the same on both sides 

 of the ganglion, we have a perfect right to conclude that we are 

 dealing with the same nerve in different parts of its course. Thus, 

 in the case of the posterior root ganglion, the same sensory nerves 

 are found on each side of the ganglion, although they are in connec- 

 tion with nerve-cells of the ganglion itself. 



So also with the sympathetic ganglia ; we know, for instance, 

 that the nerves which increase the rate and strength of the heart's 

 beat, pass to the ganglion stellatum along the rami communicantes of 

 the second and following thoracic nerves, and we know also that the 

 same nerves pass to the heart from the ganglion stellatum, from the 

 annulus of Vieussens, and from the inferior cervical ganglion. Now 

 seeing that these nerves are known to pass out of the cord in anterior 

 roots, and from thence into the white rami communicantes of the 

 upper thoracic nerves it follows that they are medullated in this part 

 of their course, and are to be found among the bundles of very fine 

 medullated nerves which we have seen are characteristic of the 

 anterior roots of this region and of the white rami communicantes. 



We can then say with certainty that the accelerator nerves enter 

 the ganglia stellata as fine white medullated nerves. I am also able 

 to say with absolute certainty that the accelerator nerves in that 

 part of their course which lies between the chain of sympathetic 

 ganglia and the heart are entirely composed of non-medullated fibres. 



