572 



TEXT-BOOK OF PHYSIOLOGY 



but penetrated by white matter, which subdivides its contained gray cells 

 into four more or less distinct masses termed nuclei, viz.: an anterior, a 

 lateral, occupying the external part of the thalamus, a ventral, close to the 

 entire ventral surface, and a posterior, situated beneath the pulvinar. Be- 



Fio. 238. HORIZONTAL SECTION THROUGH THE CEREBRUM SHOWING THE NATURAL RELATIONS 



OF THE VARIOUS STRUCTURES. 



neath and somewhat internal to each optic thalamus there is a region, the 

 subthalamic, consisting of an intricate network of nerve-fibers and several 

 nuclei of gray matter, e.g., the red or tegmental nucleus, the subthalamic 

 nucleus, or Luys' body, and the substantia nigra. 



Though the thalamus has extensive connections with many portions of 



