974 THE CENTRAL NERVOUS SYSTEM 



we have little real knowledge to guide us to a decision. Extensive 

 destruction and loss of substance of the prefrontal region may 

 sometimes occur without any marked symptoms. But usually 

 there is restriction of mental power, or it may be loss of moral 

 restraint. Thus in the famous ' American crowbar case,' an iron 

 bar completely transfixed the left frontal lobe of a man engaged 

 in blasting. Although stunned for the moment, he was able in 

 an hour to climb a long flight of stairs, and to answer the inquiries 

 of the surgeon. Finally, he recovered, and lived for nearly thirteen 

 years without either sensory or motor deficiency, except that he 

 suffered occasionally from epileptic convulsions. But his intellect 

 was impaired; he became fitful and vacillating, profane in his 

 language and inefficient in his work, although previously decent in 

 conversation and a diligent and capable workman. 



Flechsig supposes that his great anterior association centre in the 

 frontal lobe is concerned in the retention of the memory of all conscious 

 bodily experiences, especially those connected with voluntary acts. 

 The great posterior association centre he imagines to be engaged in the 

 formation and collection of ideas of external objects and of the ' word 

 pictures ' which represent them, and with the preparation of speech in 

 respect of the thoughts to be expressed and the form of expression, the 

 office of the Broca's area (but see p. 971) being to execute the mechanical 

 part of the process by transforming these thoughts into actual spoken 

 words. This posterior association centre may be looked upon as the 

 seat of intellect in the narrower sense, as the anterior is of will and feeling. 



The experiments of Franz on the relation of the cerebral association 

 areas, and especially the frontal area, to certain acquired habits are of 

 interest. Cats were allowed to acquire certain habits involving simple 

 mental processes, and then it was seen how these were affected by 

 cortical lesions. After bilateral extirpation of the frontal lobes (the 

 area anterior to the crucial sulcus) newly-formed, but not long-standing, 

 habits are lost. This cannot be due to shock, since other brain lesions 

 are not followed by loss of the habits. Extirpation of one frontal area 

 usually causes a partial loss of newly-acquired habits, or, rather, a slow- 

 ing of the association process leading to unusual delay in the execution 

 of the movements connected with the habit. Habits once lost after 

 removal of the frontal lobes may be relearned. 



The influence of psychical events upon bodily functions is well known, 

 and has been more than once illustrated in preceding pages. The con- 

 verse question of the influence of bodily states upon psychical events 

 has also been raised, especially in connection with the genesis of emotion . 

 Some psychologists assume that the bodily changes associated with such 

 emotions as grief, fear, rage, or love, are not evoked as a consequence of 

 the emotions, but that the bodily changes follow directly the perception 

 of the exciting fact e.g., a spectacle which causes fear or rage, ' and 

 that our feeling of the same changes as they occur is the emotion ' 

 (James). Sherrington, however, has shown that in dogs in which, by 

 transection of the vagi and the spinal cord, all sensation of viscera, skin, 

 and muscles behind the level of the shoulder was eliminated, no obvious 

 emotional defect was caused. Notwithstanding the immense abridg- 

 ment of the field of sensation, anger, joy, fear, disgust (as on being 

 offered dog's flesh, which most dogs refuse to eat), were as marked as 

 ever, and were evoked by the same objects as before the operation. 



