378 REFLEX ACTIONS OF THE SPINAL CORD. 
pneumogastric. If the trunk of the glosso-pharyngea'l nerve 
he pinched, an act of deglutition is made to take place; but 
if it be separated from the Medulla Oblongata, or the pneumo- 
gastric nerve be divided, or the Medulla Oblongata itself be 
destroyed, the movement can no longer be thus excited. 
Hence we see the necessity of the completeness of this 
nervous chain or circle—consisting of the nerve proceeding 
from the part stimulated to the ganglion, the ganglion itself, 
and the nerve proceeding from the ganglion to the muscles 
acted-on—in order that any such reflex movements may be 
produced. 
471. The functions of the Spinal Cord appear to be wholly 
restricted to the performance of movements of this character. 
The proportion they bear to the motions which are de¬ 
pendent upon sensation and will, varies greatly in different 
animals ; and it may be judged-of with tolerable accuracy, by 
comparing the relative sizes of the spinal cord and the brain. 
Thus in the lowest Fishes, the spinal cord seems the principal 
organ, and the brain an insignificant appendage to it. In 
Man, on the contrary, the spinal cord is so small in com¬ 
parison with the brain, as to have been regarded (though 
incorrectly, as we have seen) in the light of a mere bundle 
of nerves proceeding from it. In the former, the ordinary 
movements of the body seem principally to depend upon the 
spinal cord, being only controlled and directed by the brain; 
just as those of Articulated animals are chiefly dependent 
upon the ganglia of the trunk, being only guided by those of 
the head (§ 442). Eut in Man, those only are left to the 
spinal cord which are necessary for the maintenance of life; 
the ordinary motions of the body being for the most part 
voluntary. Still, as we have just now seen (§ 468), reflex 
movements may be excited through the spinal cord, even in 
Man, when the influence of the will is cut off; and it is 
curious to observe, that the stimulus is most powerful when 
it acts upon the soles of the feet, and that it ceases to produce 
the same effect, when, by the restoration of the functions of 
the injured part of the cord, the power of the will over the 
limbs, and also their sensibility, are regained. There is much 
reason to believe that, when we are walking steadily onwards, 
and the mind is intently occupied with some train of thought 
which engrosses its whole attention, the individual movements 
