NERVE 81 



spheres reduces the animal to the condition of a somnolent 

 reflex machine. The bird sits on its perch, generally with, its 

 head turned back, as if sleeping. If a sudden noise is made, 

 if light is flashed in its eye, or if it is touched, it flies off its 

 perch and lights somewhere else. Clapping the hands and 

 letting peas fall on the floor both produce a start, but the 

 bird makes no endeavour to secure the peas, as it would do 

 in the normal state. 



In the dog, by a succession of operations, Goltz 

 removed the greater part of the cerebral cortex without 

 causing paralysis of the muscles. The animal became dull 

 and listless, and did not take food unless it was given to it. 

 It showed no sign of recognising persons or other dogs, and 

 did not respond in the usual way when petted or spoken to. 

 But it snapped when pinched, shut its eyes and turned its 

 head away from a bright light, and shook its ears at a loud 

 sound. It did not sit still, but walked constantly to and 

 fro when awake. It slept very heavily. In fact, all the 

 responses of the animal might be classed as reflex responses 

 to immediate excitation. 



In monkeys, removal of the cerebral cortex leads to 

 such loss of the so-called voluntary movements that all other 

 symptoms are masked. But recent experiments have shown 

 that, after removal of considerable parts of the cortex, 

 recovery of functions may occur. 



2. Cerebellar Arc. — If the part of brain behind the cerebrum, 

 including tlie cerebellum, be removed from the frog, all power 

 of balancing is lost and the animal lies on its back or belly as ic 

 may have been placed. But when the toes are pinched the legs 

 are drawn up into their characteristic attitude of flexion 

 alongside the body and are maintained there, while the 

 muscles feel firm. 



3. Spinal Arc — When the spinal cord is destroyed the 

 muscles are flaccid and soft, and the limbs remain in any 

 position they may be placed, and no response to pinching 

 occurs. 



