608 THE NERVOUS SYSTEM 



tion with the cord. Short association fibers connect neighboring convolu- 

 tions within the centers, fibers which are chiefly the axones of the poly- 

 morphous cells of the fourth layer of the cortex. Long association fibers 

 run from one center to another, such as the cingulum, superior and inferior 

 longitudinal fasciculi, etc. The longer connectives run from association 

 to association centers, and from association to sensory and motor centers. 

 Flechsig believes that the sensory centers are not connected directly with 

 each other, but only indirectly through the association areas. 



Cases of injury and of disease of the human brain in the association areas 

 are not numerous, but such as there are tend to confirm Flechsig's hypothesis 

 that the function of these areas is that of the higher psychic activity. 



FIG. 407. The Association Fibers in the Centrum Ovale. A, Between adjacent con- 

 volutions; B, between frontal and occipital lobes; C, between frontal and temporal lobes, 

 the cingulum; D, between temporal and frontal lobes lesion of this tract causes paraphasia; 

 E, between occipital and temporal lobes lesion of this tract causes word-blindness; C.N, 

 caudate nucleus; O.T, optic thalamus. 



The Anterior or Frontal Association Center. The frontal area is 

 more closely connected with the motor areas and the centers for the somes- 

 thetic sense. With injury to this area the individual shows weakness in at- 

 tention, in reflection, and in control over the expressions of anger, self-appre- 

 ciation, and other activities that are expressive of personal volitions and 

 emotions. 



The American crowbar case is a classical instance of lesion of the frontal 

 lobe. A young man of twenty-five had an iron bar, an inch and a quarter 

 in diameter and over three feet long, driven through his skull and brain 

 by the premature explosion of a blast of powder. He not only recovered, 

 but lived for twelve years afterward. At the post-mortem examination the 

 puncture was found to be through the prefrontal lobe, anterior to the coro- 

 nal suture. 



This man was considered a most efficient workman and foreman before 

 the injury. After his recovery he was fitful, impatient of restraint, capri- 



