GRAY MATTER OF THE PONS. 283 



(i) The recurrent part, the pars prima, runs dorso-medianward 

 to the colliculus facialis, passing lateral and then dorsal to the 

 lower end of the abducent nucleus; (2) it then ascends about one- 

 fifth of an inch (Cunningham) between the ventricular ependyma, 

 dorsally, and the abducent nucleus and medial longitudinal bundle, 

 ventrally, and this part is called the genu internum; and (3) 

 the pars secunda, bending sharply outward over the nucleus of the 

 sixth nerve, then plunges ventrally through the pons ; this emer- 

 gent part of the root runs between the nuclei of the facial and 

 trigeminal nerves. The root of the facial nerve is joined at the 

 genu internum by fibers from the medial longitudinal bundle 

 which rise in the oculumotor and hypoglossal nuclei and supply 

 the facial muscles above the orbit and the. orbicularis oris res- 

 pectively. 



Just dorsal to the facial nucleus is a small group of cell-bodies 

 which is said to constitute a salivary nucleus (Cunningham). 

 Its axones run to their destination through the nervus inter- 

 medius and its chorda tympani branch, and form the efferent 

 root of the nervus interdemedius. They are secretory and vaso- 

 dilator fibers to the submaxillary and sublingual glands. 



Vestibular Nucleus of the Auditory Nerve (N. Nervi Vestib- 

 ularis) (Fig. 88). This nucleus is made up of three parts: (i) 

 The chief nucleus (Schwalbe); (2) the nucleus of the descending 

 root, and (3) the nucleus of Deiters, which is lateral in position. 

 The superior parts of Schwalbe's and of Deiters's nuclei extend 

 into the pons just medial to the restiform body, and the nucleus 

 of Deiters is prolonged dorsally along that body toward the cere- 

 bellum. This dorsal extension of Deiters's nucleus is called 

 Flechsig's or Bechterew's nucleus. We shall recur to the vestib- 

 ular nucleus in the medulla where the greater part of it is located. 



Lesions in the pons are usually attended by crossed paralysis. 

 The paralysis and anaesthesia of parts supplied by spinal and 

 by bulbar cerebral nerves are on the opposite side, but the fifth, 

 sixth and seventh cerebral nerves of the same side as the lesion 

 are apt to be involved. If the spino-thalamic and anterior ascend- 

 ing cerebello-spinal tracts are involved and not the medial fillet, 

 the pain and temperature sense is lost, but there is no ataxia; if 



