220 FROM FISH TO PHILOSOPHER 



the relatively great increase in mass of these frontal lobes 

 that man s brain differs from the brain of the apes, and 

 it is the great development of the frontal lobes that 

 replaces the receding forehead of the ape by the pro- 

 truding forehead in man. 



Uniquely developed as they are in man, the frontal 

 lobes present a mystery. Not only are they inexcitable 

 electrically, but the nerve tracts leading to them can be 

 cut (leucotomy) with relatively slight effect on intelH- 

 gence. Leucotomy was first performed on man to give 

 rehef from intractable pain, and then it was discovered 

 that the operation could ameHorate certain forms of 

 mental illness, and for this latter purpose the operation 

 has now been performed on many thousands of patients. 

 In respect to intractable pain, the pain remains after the 

 operation, but it no longer causes any distress; it no 

 longer hurts, it is just there; the patient perceives his 

 pain with as much indifference as if he were perceiving 

 something outside his body. In respect to mental illness, 

 psychiatrists agree that agitation, depression and obses- 

 sion may sometimes be relieved, and by so much the 

 patient may be restored toward normal. But otherwise 

 the only notable effects are a reduction of restraint, judg- 

 ment, initiative, tact, and foresight; the patient tends to 

 become lazy, fat, carefree, a httle silly, and to lose his 

 inhibitions. Thus the frontal lobes appear, first, to im- 

 part a distressful quality to pain; and second, to project 

 a man beyond his immediate circumstances in space and 

 time, and to give him drive, and ethical and other types 

 of valuation. Perhaps these are the features that chiefly 

 distinguish human consciousness from that of the great 

 apes. 



The view presented here, that consciousness is a specific 

 concomitant of the evolution of motor activity, finds sup- 

 port in recent trends in neurology. The neurophysiolo- 

 gist, R. W. Sperry, in analyzing the neuroanatomic basis 

 of conscious experience, emphasizes that the actual neu- 



