318 NERVOUS SYSTEM. 



edly schematic, present a degree of ideality which inspires 

 some distrust with regard to the accuracy of the general 

 conclusions. 1 According to Luys, the fibres of the encepha- 

 lon have several directions, as follows : 



The gray matter of the cerebral hemispheres, as we shall 

 see farther on, is composed of a mass of nerve-cells, con- 

 nected together by their prolongations into a plexus, which, 

 in its turn, is connected with the fibres of the white sub- 

 stance. 



From this cortical cellular plexus, white fibres arise, 

 which may be divided, according to their direction and des- 

 tination, into two classes : The first class consists of curved 

 commissural fibres, which pass into the white substance to a 

 certain depth and return to the gray matter, connecting thus 

 the gray substance of adjacent convolutions. The existence 

 of these fibres and their direction are well established. The 

 second class consists of fibres which, arising from the gray 

 substance of the convolutions, connect these with the cor- 

 pora striata and the optic thalami. These may bo called the 

 converging fibres ; and their general direction, as far as it 

 has been ascertained, is as follows : 



Arising from the internal, concave surface of the corti- 

 cal substance of the cerebrum, the converging fibres, at first 

 running side by side with the curved commissural fibres, 

 separate from the latter as they curve backward to pass 

 again to the cortical substance, and are directed toward the 

 corpora striata and the optic thalami. The limits of the 

 irregular planes of separation of the commissural and the 

 converging fibres contribute to form the boundaries of the 

 ventricular cavities of the brain. If we study the course of 

 the converging fibres arising from all points in the concave 

 surface of the cerebral gray matter, we find that they take 

 various directions. The fibres from the anterior region of 

 the cerebrum pass backward, and form distinct fasciculi 



1 LUYS, Recherches sur le systeme ntrvrux cerebro-spinal, sa sti-ucfure, ses /one- 

 tions tt ses maladies, Paris, 1865. 



