CHAPTEE XVII. 



Metathalamus and Hypothalamus. 



the eegio subthalamica and the steuctuees at the base of 



the brain. 



At the end of the last chapter we had approached a region of the brain 

 which, extraordinarily complicated in struetnre, hitherto belonged to the 

 parts of the brain that were least understood and explained. I now purpose 

 to bring before you the most important structures of this regio subfhalamica. 



If you examine Fig. 173 or Fig. 174 it is apparent that the thalamus 



Corpus call 05 



Fornix 



PsalteriuD 



Tsenia 



Nucl. roed. thil 



Nucl. post. long, bdl 



Tegmental nucleus 



Subst. nigia 



Pes peduncuh 



Nuol. caud- 



N. lat thai. 



Cupsuia Int. 



Insula 



N. vent. thai. 



Lam. med. ext. 



''^T%s-y- Region of thalamic fillet 



Corp. subthal. 



Inf. thalamic pedicle. 



Opticus 



Comm. ant. 



Nucl. caud. 



- Cornu Ammon. 



- Lob. temp. 



Fig. 176. — Section through the regio subthalamica 



lies upon the internal capsule. Farther posteriorly this relation ceases. 

 Several small, gray ganglionic masses shift between it and the internal cap- 

 sule, into which masses converge numerous fiber-tracts from the nucleus 

 lentiformis, from the capsula interna, and from the thalamus itself. The 

 posterior, basal region of the interbrain where this occurs has received the 

 name of regio subfhalamica. The metathalamus has become more thoroughly 

 understood only through the investigations of Luys^ Forel, Flechsig, Wer- 

 nicke, Monalcow, and Kblliher, Yet we are still far distant from an under- 

 standing of the complicated relations which are presented in this small 

 region, a region where fibers of very different origin meet with one another, 



(271) 



