184 



INTRODUCTION TO NEUROLOGY 



the appropriate reaction to the movement which has excited the 

 particular semicircular canals involved. 



The fibers of the vestibular nerve enter the medulla oblongata 

 immediately behind the pons and terminate in a vestibular nu- 



Fig. 85. Diagram of the position of the semicircular canals in the head, 

 as seen from behind. On each side it will be seen that the three canals lie 

 in planes at right angles to one another. The external or horizontal canals 

 (E) of the two sides lie in the same plane. The anterior canal of one side 

 (A) lies in a plane parallel to that of the posterior canal (P) of the other 

 side. (After Ewald.) 



cleus which forms an eminence on the floor of the fourth ventricle 

 in this region (Figs. 71, 96). This nucleus has four subdivisions, 

 as follows: 



Nucleus nervi vestibuli medialis (of Schwalbe, also called nucleus dor- 



salis and principal nucleus). 

 Nucleus nervi vestibuli lateralis (of Deiters). 

 Nucleus nervi vestibuli superior (of Bechterew). 

 Nucleus nervi vestibuli spinalis. 



The arrangement of these nuclei and of some of their second- 

 ary connections is shown in Fig. 86. Some of these connections 

 are made with the motor nuclei and reticular formation of the 



