220 D. DAVIDSON BLACK 



tion between the midbrain and diencephalon. The corpora habe- 

 nulae are not well developed, but on each side their site is marked 

 by the beginning of the fasciculus retroflexus. The bundle 

 passes down and comes into relation with the dorso-mesial sur- 

 face of the red nucleus. From this point onwards it is applied 

 to the mesial surface of this nucleus in its course to the ganglion 

 intgrpedunculare. At no point does the fasciculus pierce the 

 red nucleus. Throughout the major part of its course this bun- 

 dle is accompanied by a small collection of gray matter, as is • 

 usually the case, normally. The ganglion interpedunculare con- 

 sists of a somewhat diffuse collection of cells between and ven- 

 tral to the red nuclei toward their caudal ends. 



Thalamic mass 



Cephalad to the red nucleus there is found a large irregularly 

 arranged nuclear mass, in the lateral portions of which the lem- 

 niscus medialis becomes lost. This area may be roughly divided 

 into a dorsal cellular portion and a ventral fibrillar area. 



The dorsal cellular area. Posteriorly, the habenular bodies 

 (NuM., figs. 44 to 46) may be distinguished, together with the 

 fibers of the fasciculus retroflexus of Meynert which arise in 

 these nuclei. 



The cells making up the thalamic nuclei are of two varieties : 



a. Both large and medium sized, well developed multipolar 

 cells whose cytoplasm takes the carmine stain deeply and which 

 do not differ in any marked degree from those found in the pul- 

 yinar of the normal thalamus. 



b. Scattered between these large cells are numerous small em- 

 bryonic or neuroglial elements, having a small amount of cyto- 

 plasm which does not take the carmine stain deeply. These 

 cells are far more numerous than the large multipolar variety, 

 and are found both in the dorsal nuclear portion of the thalamus 

 and in the ventral field, though far more abundant in the former 

 area. The large cells, on the contrary, are almost entirely con- 

 fined to the dorsal nuclear area. 



These cellular elements are arranged in irregular groups so that 

 it is possible to distinguish certain irregularly arranged nuclei in 

 the dorsal area. 



