220 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



72, 73, 96, 97, 98, 99, 100, 102, 103, 104, 108, 113, 114, 115, 

 120, 125, and 127.) 



2. The central tract of the motor cranial nerves is only 

 accurately known in the case of the facial and hypoglossal. 

 The facial tract arises in the vicinity of the lower third of the 

 central convolutions. Apparently this supplies the lower branches 

 only ; the cortical centre of the frontal branches is not known 

 (gyms augularis 1 ?). It then passes inward across the lenticular 

 nucleus, and is finally found in the internal capsule, very close 

 to the pyramidal tract. It cannot be (clinically) distinguished 

 from the latter. Its fibres then abandon the general motor in- 

 nervation tract apparently in company with the " bundle from 

 the pes to the tegmentum," which has been frequently men- 

 tioned. They certainly are separated in the pons (see diagram, 

 Fig. 68). It is not known how it reaches the nucleus. At all 

 events it reaches the opposite facial nucleus, which lies in the 

 caudal part of the pons. From this the nerve is given off. (See 

 Figs. 47, 121, 122, 124, 125, 126, and 132.) 



In the most ventral portion of the anterior central convolu- 

 tion is apparently situated the cortical centre of the hypoglossal 

 nerve. At all events bundles pass from this region, ventrad of 

 those going to the facial, whose destruction is followed by 

 bilateral disturbances of the hypoglossal. On its way from the 

 cortex to the internal capsule it passes over the upper edge of 

 the lenticular nucleus, and must lie very near the speech-tract, 

 just outside the commencement of the tail of the nucleus 

 caudatus. In one case, which came under my observation, a 

 diseased spot not larger than a 5-cent piece broke down both 

 tracts at this point. In the internal capsule the hypoglossal 

 tract probably lies between that of the facial and that of the 

 extremities. Inside the pons its fibres must become separated 

 from the pyramids. They apparently withdraw from the latter 

 on the median side of the fillet, and pass upward and backward 

 in the raphe. It is only on reaching the oblongata that they 

 pass to the nucleus of the opposite (and the one on thv- same]) 



