FINAL EEVIEW. 403 



fibers for the cranial nerves, however, lie near the median line, ascend in the raphg 

 of the tegmentvim, and cross over In proximity to their respective nuclei. 



A disease- focus In the pons will affect, accordingly, in the majority of cases, 

 the opposite extremities, but the facial, abducens, or trigeminal of the same side as 

 itself. , 



Fig. 258 may show better than words this most Important symptom of many 

 lesions of the pons and medulla, viz.: crossed paralysis. It represents the motor 

 supply to the nerves of the face and extremities. It will be seen that a lesion at 

 A in the cerebrum, or In tlie right pes cerebri, would paralyze the left facial and the 

 left extremities; but that one at B, in the territory of the pons on the right side, 

 would paralyze the left extremities as before, but may affect the right facial; again, 

 that such a, lesion extending slightly over the middle line might render both facials 

 and the extremities of one side helpless. It will also be seen that a lesion in the 

 pons at C may affect the fibers going to the opposite side of the face as well as 

 those to the opposite extremities, not producing an alternating hemiplegia, but a 

 direct one, just as if situated higher in the cerebrum. Crossed hemiplegia can only 

 be produced, except when there are several lesions present, by affections of the 

 pons or by tumors, etc., located ventrally to the pons, destroying the cranial nerves 

 in their periphery and the pyramidal tracts. Since, besides the facial, the nuclei of 

 the sixth and fifth nerves lie in the pons, it follows that they also may partake in 

 the varied forms of paralysis induced by pontile lesions. The behavior of the acusticus 

 in this connection is not clearly understood. 



Through the pons also there pass fibers to the nuclei of the oblongata, which 

 preside over the muscles concerned in speech. In this way, with affections of the 

 pons and bulb, there arise at times disturbances of speech, while the power of speech 

 remains intact. This symptom is called, according to its severity, dysarthria, or 

 anarthria. 



Lesions in the tegmentum of the pons and the bulb may also lead to disturb- 

 ances of sensation. We have reason to believe that the central sensory paths lie in 

 the lemniscus, and that the median fillet especially contains those fibers which serve 

 the very important static sensation. Accordingly, after interruption of the inter- 

 olivary tract in the oblongata light disturbances of the muscular sense are observed. 

 But later clinical investigations make it appear probable that, at least in the bulb, the 

 . tracts for cutaneous tactile sensation do not lie in the median portion, but belong 

 to the long ti-acts, lying external to the interolivary tract. In the pons, also laterally 

 located lesions may produce crossed sensory disturbances. If the lesion be some- 

 where in the tegmentum of the bulb or pons, it affects not only those central tracts, 

 which pass to nuclei of the opposed side, but also the peripheral parts of many sen- 

 sory nerves. For instance, a lesion located laterally in the oblongata may encounter 

 on the right side the ascending trigeminal root, and the crossed sensory tracts, re- 

 sulting in right-sided facial and left-sided body anaesthesia. 



Generally a single focus does not destroy all the central and peripheral sensory 

 tracts; hence occasions no such complete hemianesthesia as occurs with disease of 

 the centrum ovale. One or another nerve remains usually free. This is especially 

 true of the taste-tracts and of the auditory tracts, in which complete intrapontile 

 interruption to the conducting paths has been seldom known. 



If a lesion, relatively large, is located anywhere near the median line, there 

 may result naturally double hemianesthesia: at all events, a rare occurrence. 



Difficulties of mastication and of deglutition are observed since the motor tri- 

 geminal, the glosso-pharyngeal, and hypoglossal nuclei are easily involved. 



