FUNCTIONS OF SPINAL COBD I 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 taper, it is withdrawn ; and, if the experiment be made upon 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 impp.diTnp.Tit 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 

 Brain (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 Frog, 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 



