290 C. JUDSON HERRICK 



from various somatic sensory centers (tectum, thalamus and 

 cerebral hemisphere) and their distribution by way of relatively 

 short axons into the cerebral peduncle. 



The eminentia thalami and tr actus cortico-thalamicus. Al- 

 though ha\dng no direct mesencephalic connections and, there- 

 fore, not properly falling within the scope of this paper, some 

 details of the structure of the eminentia thalami are incidentally 

 shown in the illustrations and these will be briefly referred to 

 here. 



This eminence, as has already been mentioned (p. 230), is 

 a strong projection of the ventricular surface immediatly be- 

 hind the interventricular foramen and above and behind the 

 hippocampal commissure, its caudal border being in imediate 

 contact with the pars ventralis thalami, from which it is separ- 

 ated by a vertical sulcus (figs. 41, 42, 43, 48, 63, 64, 68, em.th.). 

 Its relations are essentially as I have described them in Ambly- 

 stoma ('10, pp. 419, 426 and figs. 17, 18). I have provisionally 

 regarded it as a diencephalic structure, though further embryo- 

 logical research may show that it should be placed in the telen- 

 cephalon medium. It is in contact anteriorly with the fibers 

 of the commissura hippocampi, of the tractus cortico-habenularis 

 medialis and of the stria medullaris. From the first of these 

 tracts, and probably from the others also, collateral fibers are 

 freely discharged into the eminentia thalami. 



Golgi sections show that the neurons of this eminence are 

 very small and densely crowded. Their thick, contorted dend- 

 rites spread out in every direction (fig. 48). Some are directed 

 forward into the cerebral hemisphere among the fibers of the 

 commissura hippocampi and tractus cortico-habenularis medialis 

 (see Herrick, '10, p. 428) just as these fibers enter the com- 

 missure ridge. Others are directed lateralward and backward 

 among the fibers of the stria medullaris. Horizontal sections 

 by the Golgi method taken through the commissura hippocampi 

 just dorsally of its decussation show very delicate unmyelinated 

 fibers leaving this tract, which are probably collaterals of its 

 fibers. This tract is called the tractus cortico-thalamicus (fig. 

 43, tr.c.th.). Its fibers are very short and immediately break 



