MIDBRAIN AND THALAMUS OF NECTURUS 291 



up in freely branched arborizations among the dendrites of 

 the neurons of the eminentia thalami (only one of which is 

 impregnated in this preparation; cf. fig. 48, em.th.). 



Slender axons are seen to pass between the stria medullaris 

 and the eminentia thalami; but the preparations do not show 

 whether these fibers arise from the stria and end in the eminence 

 or arise in the eminence and enter the stria. This connection 

 between the stria medullaris and the eminentia thalami is much 

 more clearly shown in our Golgi preparations of larval Amblys- 

 toma. There is also an obscure fibrous connection seen in some 

 preparations made by the method of vom Rath between the 

 eminentia thalami and the underlying preoptic nucleus, the 

 nature of which is not revealed. 



The axons of the neurons of the eminentia thalami seem to 

 be very short. In numerous Golgi preparations I have seen 

 them passing directly caudad to end apparently in the rostral 

 end of the pars ventralis thalami, though some of them may 

 continue still farther caudad in the tractus thalamo-peduncu- 

 laris ventralis. Some of these axons are shown in figure 48. 

 In some of our Golgi sections of larval Amblystoma taken in 

 the horizontal plane these fibers are well impregnated. Here 

 they are clearly seen to break up in an open neuropil within the 

 pars ventralis thalami a very short distance behind the emi- 

 nentia thalami. So short are these axons and so widely spread 

 are their terminal arborizations that these neurons might almost 

 be considered as belonging to Golgi's type II if it were not for 

 the fact that, in spite of their short course, their axons e\'idently 

 transmit nervous impulses from one functionally differentiated 

 region of the brain to another. 



The eminentia thalami is thus seen to receive nervous im- 

 pulses from the cerebral hemisphere by way of the fibers of 

 the commissura hippocampi (apparently as collaterals of these 

 fibers) and probably also in a similar way from the stria medul- 

 laris. It discharges nervous impulses into the adjacent pars 

 ventralis thalami, of which I consider it to be a specially dif- 

 ferentiated portion. 



