these vagrant ganglia being the ganglia of the sympathetic 
the relation be- 
tween the spinal and cranial nerves. In order to make a com- 
parison between these two, it is necessary to have a clear idea 
of a complete spinal nerve. According to Gaskell such a nerve 
consists of — I. A posterior root composed of afferent fibres,, 
both somatic and splanchnic, the ganglion of which root is' 
stationary in position, and is always situated near the entrance 
of the fibres into the central nervous system. 2. An anterior 
root composed of (i) efferent, non-ganghonated, splanchnic 
and somatic fibres, and (2) efferent, ganglionated, splanchnic 
fibres, characterized by the fineness of their calibre, the gang- 
lion of which is vagrant and has traveled to a variable distance 
from the central nervous system. The cranial nerves are then 
considered seriatim. 
The optic and olfactory nerves do not conform to the type 
of a segmental nerve and are not discussed. 
The Illd nerve is efferent in function. It consists of large 
and small fibres ; as it approaches the oculomotor ganglion the 
large fibres pass off to supply the eye muscles and the small 
fibres form a separate group and pass into this ganglion, which 
is therefore considered a typical motor ganglion. The IVth 
nerve is also efferent in function, and consists of a large fibred 
and a small fibred portion, but no ganglion cells have been 
found along its course. As to the afferent fibres of these 
nerves— both the Hid and IVth possess within themselves de- 
generated structures which appear to Gaskell to have been 
originally the nerve cells and nerve fibres corresponding to 
the cells and fibres of the stationary ganglion on the posterior 
root of a spinal nerve. These two nerves, then, form the 
primary segmental nerves of the first and second segments, 
the function of the degenerated sensory elements being per- 
formed by the ramus ophthalmicus profundtis of the Vth. 
The Vlth is purely motor; it contains somatic fibres, 
while the so-called motor part of the Vth contains splanchnic 
efferent fibres, but no somatic ones ; therefore, taking these two 
nerves together, we have a complete segmental nerve, as far as 
efferent fibres are concerned. Here, again, we find that the 
roots of the motor part of the Vth contain within themselves 
the remains of nerve fibres and ganglia which would corres- 
pond to the afferent fibres and posterior ganglion. The ratmis 
^axillaris superior of the Vth, which with the ramus ophthal- 
