THE SUBTHALAMIC REGION, ETC. 117 



to this table, the nuclei of the individual muscles are arranged 

 in the order given below, from before backward, thus : 



Sphincter iridis. Musculus ciliaris. 



Levator palp. Rectus int. 



Rectus sup. Rectus inf. 

 Obliquus inf. 



The nerves to the internal muscles of the eye apparently 

 spring from the anterior nucleus. The crossed track and, per- 

 haps, also the median division of the posterior nucleus are 

 accredited to the rectus internus. Although clinical experience 

 teaches that there is both a direct and a crossed communication 

 between the oculo-motor nerve and the centres of the optic 

 nerve, yet the anatomical basis of this fact has not been dis- 

 covered. Net-works and bundles of fibres which might com- 

 plete the communication are to be found in this region. As yet, 

 however, no experimentum crucis has been performed, nor has 

 there been made any clinical observation supported by post- 

 mortem examination which would clear up this point. 



The nucleus of the oculo-motor lies ventrad of the aque- 

 duct of Sylvius ; that is to say, in its floor. Later on, as w r e 

 pass gradually backward in our study of the tegmentum, we 

 shall find the nuclei of most of the other cranial nerves in the 

 region of this floor. 



The cranial nerves all arise directly from their nuclei. To 

 each of these nuclei fibres pass from higher parts of the brain. 

 They come from the opposite side and decussate in the middle 

 line before entering the nucleus. Clinical experience goes to 

 show that the upper part of the cranial-nerve tracts that is, 

 above the nucleus extends to the cerebral cortex. 



The course of the fibres in the vicinity of the thalamus and in the regio 

 subthalamica is less certainly known than in most other parts of the brain. 

 Among the workers in this difficult field, Meynert, Forel, Gudclen, Flechsig, 

 Wernicke, and the author are to be mentioned. 



The origin of the optic nerve has been principally worked out by Meynert, 

 J. Stilling, Tartuferi.Gudden, Bellonci, and Monakow. 



You will, gentlemen, have a better comprehension of many 

 pathological nervous phenomena if you will, for the time, adopt 



