1888.] and Distribution of the Cranial Nerves. 



383 



ganglia to supply the muscles of the vascular system, alimentary 

 canal, &c. 



The whole argument in that paper was based upon the structure 

 and distribution of the nerves of anterior roots, so that in speaking of 

 the sympathetic ganglia as ganglia of a splanchnic root, all the 

 evidence for vasomotor nerves, &c, went to show that these ganglia 

 might be considered as belonging to anterior (efferent) roots rather 

 than to posterior (afferent) roots. 



Again Onodi's observations that such ganglia are offshoots from 

 the spinal ganglia on the posterior root do not militate against the 

 motor character of these ganglia, since in the lower animals and in 

 the first two cervical nerves of the higher animals both anterior and 

 posterior roots pass into the spinal ganglion, so that there is no 

 difficulty in imagining that as the motor portion of the original 

 spinal ganglion travelled away from its parent ganglion mass, the 

 motor or efferent nerves would no longer pass into the spinal ganglion 

 but would pass free from it, being connected only with the separated 

 vagrant portions of the original ganglion, i.e., with the sympathetic 

 system. 



There is in fact no evidence to show that the anterior and posterior 

 roots are not truly efferent and afferent, and there is also no evidence 

 to show that the afferent ganglia have travelled away from their 

 original situation in the same way as the efferent ganglia. We may 

 therefore consider the ganglia of the afferent spinal nerves, both 

 somatic and splanchnic, as stationary in position, and as forming the 

 root ganglia of the various nerves, while the ganglia of the efferent 

 spinal nerves are vagrant, and form the so-called sympathetic 

 system. 



A complete segmental spinal nerve is then composed of (1) anterior 

 root with vagrant ganglion; (2) posterior root with stationary 

 ganglion. 



The anterior root again is divisible into two parts ; (1) a large- 

 fibred medullated, and (2) a small-fibred medullated part, of 

 which the latter only is in connexion with the ganglia of this root ; 

 the non-medullated fibres being these splanchnic ganglionated 

 fibres which have lost their medullary sheath in one or other of the 

 ganglia. 



If the cranial nerves are built up on the same type as the spinal 

 nerves, it follows that in them too we must have (1) an anterior root 

 and (2) a posterior root, with a root ganglion stationary in position 

 close to the exit of the nerves from the central nervous system into 

 which both anterior and posterior roots may or may not pass ; also 

 the anterior root must consist of a small-fibred ganglionated portion 

 and a large-fibred non-ganglionated portion, the ganglion on the 

 anterior root being in all probability vagrant and not stationary. 



