504 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



connected with it descend as far as to the region of the roots of 

 the vagus (fig. 257, viu). 



The numerous arcuate bands that belong to the central tract 

 of the auditory roots lie behind the transverse fasciculi of the 

 posterior division of the pons, which are connected with the 

 superior olivary body. 



The large scattered nerve-corpuscle formation of the posterior 

 division of the pons is continuous with the fibres just men- 

 tioned. If these, as Deiters holds, are to be regarded as scattered 

 masses belonging to the motor nuclei of the facial, hypoglossal, 

 vagus, and accessory nerves, their introduction into the audi- 

 tory tract may be regarded as indicating a central connection 

 of the sound-receiving and sound-producing organ (larynx) 

 within this sphere of reflex action in the posterior tract of the 

 cerebral peduncle. 



The relations of the similarly connected scattered masses with the 

 abducens are perhaps, physiologically speaking, not quite obscure, if 

 the reflex rolling outwards of the eyes, that occurs when sounds are 

 heard, is borne in mind. 



Transverse sections through the oblongata show in a natural 

 manner the type of a middle system which was only artificially 

 transferred by Deiters to the pons, and which is actually a 

 mioced system, composed of motor and sensory portions. To it 

 belong the ninth, tenth, and eleventh pairs ,of cerebral nerves, 

 whilst the twelfth pair occupy the position of an anterior 

 (internal) nerve-origin, and the ascending root of the fifth pair 

 that of & posterior origin (figs. 257, 258, x, xi, xn, S, G). 



The types of the last two origins are again found separated 

 in the anterior and posterior roots of the spinal cord ; the type 

 of the middle system, on the other hand, closes with the lowest 

 fasciculi of the root of the eleventh pair of cerebral nerves.* 

 The origins of the median or lateral mixed system of the 

 glossopharyngeal, vagi, and accessory nerves offer so many 

 points in common, that they may be considered together. 



The grey floor, in which the greater part of their nuclei of 

 origin are situated, exhibits an elevation below the striae, indi- 

 cating the position of the internal auditory nucleus, external to 

 which is the external auditory nucleus with the fasciculi of the 



