FUNCTIONS OF SPINAL CORD : REFLEX ACTION. 375 
the edge of the eyelid be touched with a straw, the lid imme¬ 
diately closes; if a candle be brought near the eye, the pupil 
contracts (§ 534); if liquid be poured into the mouth, it is 
swallowed; if the foot be pinched or be burnt with a lighted 
taper, it is withdrawn; and, if the experiment be made upon 
a Frog, the animal will leap away as if to escape from the 
source of irritation. The respiratory movements, too, are kept 
up with regularity; so that there is no impediment to the 
continuance of the circulation, and the organic life of the 
animal may thus endure for some time. In one of the experi¬ 
ments made with the view of ascertaining the degree in which 
the activity of the Cerebrum is essential to the maintenance 
of life, a pigeon was kept alive (if alive it could be called) for 
some months after the removal of its cerebrum,—running 
when it was pushed, flying when it was thrown into the air, 
drinking when its beak was plunged in water, swallowing 
food which was put in its mouth,—though at all other times, 
when left to itself, appearing like an animal in profound 
sleep. 
466. It is evident, therefore, that we are not to regard the 
Erain (according to the former opinion of Physiologists, and 
the belief which is still commonly entertained) as the only 
centre of nervous power, and as essential to the maintenance 
of the life of the body; and that we must attribute to the 
Spinal Cord no small amount of independent power. We 
might be disposed to infer, from the statements in the last 
paragraph, that an animal whose brain has been removed can 
still feel and judge and perform voluntary motions by means 
of the Spinal Cord; but this, again, would be putting a wrong 
interpretation upon the phenomena in question. It is ob¬ 
served that the motions performed by an animal in such 
circumstances are never spontaneous; they are always excited 
by a stimulus of some kind. Thus a decapitated Prog, after 
the first violent convulsive movements occasioned by the ope¬ 
ration have passed away, remains at rest until it is touched; 
and then its leg, or even its whole body, will be thrown into 
sudden action, which immediately subsides again. In the 
same manner, the action of swallowing is not performed, 
except when it is excited by the contact of food or liquid 
(§ 195); and even the respiratory movements, spontaneous as 
they seem to be, would not continue long, unless they were 
