94 



ANATOMY OP THE CENTRAL NERVOUS STSTEil. 



significance of the lateral line and its associated structures as an organ of 

 equilibration is made probable through this anatomical relation. 



Wlien you are reminded (1) that in the acusticus region of the medulla 

 the long fibers of Manther arise, — fibers which end only in the posterior 

 region and with which, in the spinal cord, we became acquainted as the 

 Tr actus acustico-spinalis (Figs. 29 and 40); (2) that the great terminal cells 

 of these gigantic fibers ramify the acusticus region with their dendrites; 

 then it will be clear to you what an important center of association for the 

 most diverse regions lies in the middle of the medulla oblongata. The 

 physiological experiments and the considerations which are inyolved in these 

 anatomical relations lead to the conclusion that the part of the medulla just 



Fig. 50. — Section of the medulla of Alligator lucins at the level of the 

 motor nucleus of the Trigeminus. Simply the contour of the nerve is repre- 

 sented. Compare the thin Facialis in Fig. 49 with the large motor trunk of 

 the Trigeminus shown. 



described represents an important center for the maintenance of general 

 equilibrium. 



At the level of the acusticus nucleus the motor columns, which reach 

 toward the brain from the spinal cord, are not yet exhausted. They may be 

 best imagined as a thin plate which bends greatly toward the sagittal plane, 

 although somewhat removed from it, in the oblongata. From the dorsal 

 part of this plate near the spinal cord the Hypoglossus arose. In the acusti- 

 cus level there arises the Abducens: a part of the plate whose course may be 

 easily recognized on Fig. 49. The ventral portion does not send its fibers 

 out direct, biit collects them from some distance into little fasciculi, which 

 then all turn dorsally in order to bend laterally when they approach the gray 

 matter of the fioor. This curious knee-like course has already been met in 



