OF THE NERVOUS SYSTEM. 387 



to be seen in the accompanying figure. A portion of the anterior 

 fibres, we have already observed, pass upward and backward, with 

 the restiform bodies, to the cerebellum ; while the remainder run 

 forward through the tuber annulare and the corpus striatum, and 

 then radiate to the gray matter of the cerebrum. The posterior 

 fibres, constituting the restiform body, are distributed partly to the 

 cerebellum, and then pass forward, as previously described, under- 

 neath the tubercula quadrigemina to the optic thalmi, whence they 

 are also finally distributed to the gray matter of the cerebrum. 



The cerebrum and cerebellum, each of which is divided into two 

 lateral halves or " lobes," by the great longitudinal fissure, are both 

 provided with transverse commissures, by which a connection is 

 established between their right and left sides. The great trans- 

 verse commissure of the cerebrum is that layer of white substance 

 which is situated at the bottom of the longitudinal fissure, and 

 which is generally known by the name of the " corpus callosum." 

 It consists of nervous filaments, which originate from the gray 

 matter of one hemisphere, converge to the centre, where they be- 

 come parallel, cross the median line, and are finally distributed to 

 the corresponding parts of the hemisphere upon the opposite side. 

 The transverse commissure of the cerebellum is the pons Yarolii. 

 Its fibres converge from the gray matter of the cerebellum on one 

 side, and pass across to the opposite ; encircling the tuber annulare 

 with a band of parallel curved fibres, to which the name of " pons 

 Yarolii" has been given from their resemblance to an arched bridge. 



The cerebro-spinal system, therefore, consists of a series of gan- 

 glia situated in the cranio-spinal cavities, connected with each other 

 by transverse and longitudinal commissures, and sending out nerves 

 to the corresponding parts of the body. The spinal cord supplies 

 the integument and muscles of the neck, trunk, and extremities ; 

 while the ganglia of the brain, besides supplying the corresponding 

 parts of the head, preside also over the organs of special sense, and 

 perform various other functions of a purely nervous character. 



