376 FUNCTIONS OF SPINAL CORD I REFLEX ACTION. 



excited 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 calied-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. Eut this in- 

 ference will not 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 by 

 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 cut 

 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. 



468. Now although the Frog cannot tell 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, 



