98 
Ebbesson 
Figure 6. Degeneration in medial corner of tectum and bordering nucleus opticus ventromedialis (VMO). 
from the dorsal column nuclei, described here 
for the first time, terminate profusely not 
only in the intercollicular nucleus, but a few 
axons, as in mammals, appear to reach the 
ventromedial corner of the central nucleus 
(Fig. 5). 
There is presently no electrophysiological 
data available that provide insights into the 
role of the intercollicular nucleus in reptiles. 
However, because of the known tectal pro- 
jection to it (Ebbesson, 1970&), multimodal 
integration appears likely. 
The Thalamus 
In lizards and other reptiles, direct spinal 
projections to the thalamus consist of two 
pathways (Ebbesson, 1966, 1967, 1969; 
Ebbesson and Goodman, 1975; Riss et al., 
1972). The dorsal pathway enters the dorsal 
thalamus via a course through the medial 
optic tectum and terminates in a poorly dif- 
ferentiated region (labeled nucleus inter- 
medius dorsalis thalami by Ebbesson, 1967) 
between the dorsal geniculate nucleus and 
the dorsolateral anterior nucleus. It has been 
suggested (Ebbesson, 1967 ; Ebbesson and 
Goodman, 1976), on the basis of its topo- 
graphic position and neurophysiological 
studies by Russian workers (see Ebbesson 
and Goodman, 1976), that this area is homol- 
ogous to the intralaminar nuclei of mammals 
which receive the so-called paleospinothala- 
mic pathway (Mehler, 1957). Riss et al. 
(1972) have recently also suggested that 
