LECTURE VII. 



THE SUBTHALAMIC REGION, THE CORPORA QTJADRIGEMINA AND THE 



ORIGIN OF THE OPTIC NERVE. 



GENTLEMEN : In the last lecture we postponed tracing- the 

 fibres of the brain downward, in order to consider the structures 

 at the base of that organ. Let us again take up the thread of 

 our discourse. We had learned that, in the posterior thalamic 

 region, the bundles of the internal capsule (except so far as 

 they were distributed to the thalamus itself, or to the subjacent 

 ganglia) emerge free on the base of the brain and form the pes 

 pedunculi. Caudad and ventrad of the thalamus are located 

 the nucleus ruber and the corpus subthalamicum. From the 

 internal capsule a bundle of the tegmental radiation passes di- 

 rectly caudad to these structures, while another first passes 

 through the corpus striatum, and then enters into relation with 

 them, after passing through the internal capsule. 



Those bundles of tegmental fibres which passed through 

 the corpus striatum may be traced in part to the body of Luys 

 (corpus subthalamicum). Another portion of them, together 

 with the fibres originating in the putamen and the nucleus 

 caudatus, seem to pass into the stratum intermedium, which lies 

 dorsad of the substantia.nigra. 



The fibres of the regio subthalamica should be examined 

 anew, with the help of all available methods of investigation. 

 Hitherto they have been examined chiefly by means of sections 

 taken from the adult brain. (Meynert, Forel, Werriicke.) The 

 embryological researches of Flechsig and myself had already 

 enabled us to distinguish the tegmental fibres amidst the chaos 

 which prevails in that region. 



That bundle of tegmental fibres which passes external to 



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