THE CEREBRO-SPINAL SYSTEM OF NERVES. 635 
follow are in themselves evidence of the strongest kind for the 
doctrine of a constant neuro-metabolic influence which we ad- 
vocate. It will not be forgotten that the depressor nerve, which 
exerts reflexly so important an influence over blood-pressure, 
is itself derived from the vagus. 
The Spinal Accessory or Eleventh Nerve.—This nerve arises 
from the medulla oblongata somewhat far back, and from the. 
spinal cord in the region of the fifth to the seventh vertebra. 
Leaving the lateral columns, its fibers run upward between the 
denticulate ligament and the posterior roots of the spinal nerve 
to enter the cranial cavity, which as they issue from the cra- 
nium subdivide into two bundles, one of which unites with the 
vagus, while the other pursues an independent course to reach 
the sterno-mastoid and trapezius muscles, to which they fur- 
nish the motor supply; so that it may be considered function- 
ally equivalent to the anterior root of a spinal nerve. The 
portion joining the vagus seems to supply a large part of the 
motor fibers of that nerve. 
Pathological.—Tonic contraction of the flexors of the head 
causes wry-neck, and when they are paralyzed the head is drawn 
to the sound side. 
The Hypoglossal or Twelfth Nerve.—It arises from the lowest 
part of the calamus scriptorius and perhaps from the olivary 
body. The manner of its emergence between the anterior 
pyramid and the olivary body, on a line with the anterior spi- 
nal roots, suggests that it corresponds to the latter ; the more so 
as it is motor in function, though also containing some vaso- 
motor fibers, in all probability destined for the tongue. Such 
sensory fibers as it may contain are derived from other sources 
(vagus, trigeminus). It supplies motor fibers to the tongue and 
the muscles, attached to the hyoid bone. 
Pathological.—Unilateral section of the nerve gives rise to 
a corresponding lingual paralysis, so that when the tongue 
is protruded it points to the injured side; when being drawn 
in, the reverse. Speech, singing, deglutition, and taste may 
also be abnormal, owing to the subject being unable to make 
the usual co-ordinated movements of the tongue essential for 
these acts, 
