CEREBRAL FUNCTION IN THE RAT 115 



de cerebrate animals will furnish significant evidence for this 

 problem. 



As yet we have not been able to effect a complete decerebra- 

 tion of the rat but by the destruction of large and varied areas 

 we have obtained evidence, perhaps not yet conclusive, that the 

 cerebral cortex is not functional in the formation of simple 

 habits. 



A number of animals were operated upon to destroy the cor- 

 tex over the dorsal, temporal, and frontal regions and such parts 

 of the orbital and occipital surfaces as could be reached from 

 above without lesion to the thalamus. Six of these survived 

 and all have been trained successfully in the formation of simple 

 habits. A record of the experiments is given below. 



In the diagrams of the brains of this series of animals (plate 

 II, figs 34 to 39) the solid black areas represent the parts from 

 which the cortex has been completely absorbed, the stippled 

 areas those in which there was degeneration or evident loss of 

 function through destruction of fibers. 



Experiment 34- A large opening was made in the calvarium 

 of a large adult male rat and a scalpel (curved on the flat) was 

 drawn around the frontal and temporal lobes on each side and 

 thrust backward to the tentorium. On the day following the 

 operation the animal began to walk about. He was very spastic, 

 with back arched constantly, and occasionally remained motion- 

 less for long periods in contorted positions. He would not eat, 

 but drank milk when it was placed in his mouth and when his 

 short vibrissae were touched with a pipette filled with milk he 

 grasped the end of it with his teeth. He would not do this in 

 response to a stick unless it were wet with milk. This reaction 

 suggests the retention of smell. He gave no detectable reactions 

 to light, to light contact, or to aromatic odors which are avoided 

 by normal rats. He reacted to loud sounds, to heavy contact 

 or diffuse pressure, and to, protopathic stimuli. 



On the second day he ate when his lips were pressed against 

 the food, but when. his movements carried him away from the 

 food he continued to gnaw at the edge of the food dish for some 

 time. During the ten days that he was kept alive he never 



