376 FUNCTIONS OF SPINAL CORD :—REFLEX ACTION. 
- exeited by the presence of venous blood in the vessels—espe- 
cially in those of the lungs. These movements are all necessarily 
linked with the stimulus that excites them ;—that is, the | 
same stimulus will always produce the same movement, when 
the condition of the body is the same. Hence it is evident 
that the judgment and will are not concerned in producing © 
them ; but that they may be rather compared to the move- 
ments of an automaton, which are called-forth by touching 
certain springs. 
467. The next question is, whether these movements can 
be performed without any feeling or sensation, on the part of © 
the animal, of the cause that produces them. It is difficult — 
to imagine that an animal, executing such regular and 
various actions, which so strongly resemble those it would. 
execute in its complete state, and which are so perfectly © 
adapted to their obvious purposes, can do so without con- 
sciousness ; and accordingly some Physiologists have regarded 
them as furnishing proof that the Spinal Cord possesses the 
property of sensibility, or, in other words, that an animal 
whose Brain has been removed can still feel. But this in- 
ference will fot bear a close examination. Such movements 
take place, not only when the Brain has been removed and 
the Spinal Cord remains entire, but even when the Spinal” 
Cord has been itself cut across into two or more portions ~ 
Thus if the head of a Frog be cut off, and its Spinal Cord be 
divided in the middle of the back, so that its fore-legs remain 
connected with the upper part, and the hind-legs with the 
lower, each pair of members may be excited to movement 
a stimulus applied to itself; but the two pairs will not” 
execute any consentaneous motions, as they will do when the — 
Spinal Cord is undivided. Or, when the Spinal Cord is eut_ 
across without removal of the Brain, the lower limbs may be 
excited to movement, though completely paralysed to the will; 
whilst the upper remain under the control of the animal’s 
sensation and conscious power.. y 
468, Now although the Frog cannot tel us that it has no 
sensation in its lower limbs, we have very strong evidence to 
that effect; for cases are ‘of no infrequent occurrence in. 
Man, in which, the Spinal Cord having been injured in 
the middle of the back by disease or accident, there is not 
only loss of voluntary control over the motions of the legs, | 
