GENERAL CUTANEOUS SUBDIVISION. 119 



Here the fibers give collaterals inward and themselves turn inward 

 to come into relation directly or indirectly with the cells which 

 give origin to the motor nerves. A part of the tract, when it descends 

 over the lateral face of the mesencephalon, instead of going back- 

 ward along the same side of the brain crosses to the opposite side 

 through the ventral wall of the mesencephalon, helping to form 

 the large ventral commissure of this region of the brain. The 

 fibers then join the tract of the opposite side and continue with it 

 to similar endings. The tractus tecto-bulbaris et spinalis thus 

 consists of a crossed portion and of an uncrossed or direct portion. 

 Another tract from the tectum descends over the side of the mesen- 

 cephalon and bends forward to end in the inferior lobe, the tractus 

 tecto-lobaris. By means of tracts which run from the inferior 



orpus restiforme 

 Nuc. funic. dors. 



uniculus dors 



FIG. 60. A diagram representing the general cutaneous centers and fiber tracts 

 in the human brain. 



lobes to the forebrain and to the hindbrain and spinal cord, probably 

 wider connections are set up and more complex correlations 

 provided for. The several central tracts and nuclei belonging 

 to the cutaneous apparatus in fishes are shown in the accompany- 

 ing diagram (Fig. 59). The outline of a selachian brain is drawn 

 schematically and the various tracts are shown as seen from the 

 left side and as if projected upon the median plane. The cutaneous 

 components in the roots of the V, VII, IX, and X nerves are 

 shown, but the ganglia of those nerves are omitted. In Fig. 60, 

 the cutaneous fibers and the ascending lemniscus in man are shown. 



