238 ANATOJIT OF THE CENTEAL XEETOUS SYSTEJI. 



these fibers are developed as distinct meduUated tracts from the indifEerent 

 mass of nerye-fibers wheneyer they are brought into use more frequently 

 than other tracts. These association-fibers lie for the great part close be- 

 neath the cortex, another part in the medullary layer of the hemispheres. 

 Such a system is, as you see, thoroughly adapted to bringing all parts of the 

 brain in communication with one another. The manifold processes of asso- 

 ciation in thought, in motion, and in sensation, for which the brain serves, 

 may possibly find their anatomical basis in the fibers. 



It is not improbable that these fibers play an important rOle in the spreading of 

 the epileptic seizures. It is possible, in animals, to call forth, first, contractions in 

 the muscles by irritating the region of the cortex with which they are respectively 

 connected, and, second, convulsions of the entire affected side by increasing the irri- 

 tation. The sequence of these convulsions corresponds to the arrangement of the 

 affected centers in the cerebral cortex. As this impulse spreads a neighboring motor 



Fig. 155. — Schema of the fibrse propria of the cortex. 



center is never skipped over. The convulsions, when they have completely spread 

 over one-half of the body, involve the other half under certain conditions (intensity 

 of the irritation, disposition of the animal experimented on). Extirpation of the 

 single motor centers occasions an omission of the groups of muscles involved from 

 the general convulsive seizure. 



It is not necessary that the cortical point from which such a convulsive seizure 

 starts belong directly to the motor region. The convulsions thus produced have the 

 greatest similarity to the symptoms of partial or general epilepsy in man. Since 

 the Avritings of HitgUUngs Jackson, especially, forms of epilepsy have been recog- 

 nized that begin with contractions or convulsions in one limb and at times spread 

 over the other limbs or the entire body. In the latter ease they present a typical 

 picture of an epileptic seizure, Consciousness almost never disappears entirely so 

 long as the attack remains partial. After the attack paralyses sometimes remain, 

 which are mostly localized in the parts first attacked. This partial, or cortical, 

 epilepsy is not to be separated from the classical epilepsy. The latter probably rep- 

 resents a form in which the initial symptoms follow one another in more rapid suc- 

 cession. 



It is not necessary, however, that the spreading of an impulse from one point 



