REFLEX ACTION WITHOUT SENSATION. 377 
but loss of sensation also. Further, in several cases of this 
kind, in which the injury was confined to a small portion of 
the cord, and the part below was not seriously disturbed, it 
has been noticed that motions may be excited in the limbs by 
stimuli applied directly to them,—as, for instance, by tickling 
the sole of the foot, pinching the skin, or applying a hot plate 
to its surface; and this without the least sensation, on the 
part of the patient, either of the cause of the movement, or 
of the movement itself; the nervous communication, which 
would otherwise have conveyed the impression to the brain 
and there given rise to sensation, being interrupted in the 
spinal cord. 
469. By such cases, then, it appears to be clearly proved, 
that the actions performed by the Spinal Cord, when the 
Brain has been removed, or its power destroyed, or its com¬ 
munication with the part cut-off, do not depend upon Sensa¬ 
tion ; but upon a property peculiar to the Spinal Cord, by 
which impressions, made upon certain parts, necessarily excite 
motions of an automatic character. By other experiments it 
has been shown to be necessary for the exercise of this Reflex 
function (as it has been termed), that an impression should be 
conveyed by one set of nervous fibres, from the point where 
the stimulus is applied, to the Spinal Cord; and that a motor 
impulse, conveyed by another set of filaments, should issue 
from the Cord to the muscles. The excitor and motor fila¬ 
ments distributed to any part are commonly bound up in 
the same trunk, and are connected with the same part of the 
Spinal Cord; so that, if this portion or segment be com¬ 
pletely separated from the rest, it may still execute the reflex 
movements of the parts to which its nerves are distributed; 
—just as a single segment of a Centipede will continue to 
move its legs, provided its own ganglion be entire (§ 443). 
470. But in other instances it happens that we can more 
clearly distinguish between the excitor and the motor nerves, 
from their being distributed separately, and being connected 
with distinct portions of the spinal cord. Thus in the act of 
deglutition (§ 195), the chief excitor nerve is the glosso-pha - 
ryngeal (§ 459); this conveys the impression made by the 
contact of food with the pharynx, to the Medulla Oblongata; 
but it does not convey the motor influence to the muscles, 
this being accomplished by branches of another nerve, the 
