350 ELIZABETH CAROLINE CROSBY 
just discussed, i.e., the nucleus of the lateral olfactory tract, the 
ventro-medial nucleus, and the more lateral part of the dorso- 
lateral area, make up such an amygdaloid complex. 
The second type of impulse which enters the lateral wall of 
the hemisphere is somatic, being transmitted by the somatic 
sensory radiations from the lateral and medial nuclei of the thala- 
mus to the ventro-lateral areas (caudate and lentiform nuclei). 
These areas, then, are centers for the correlation of somatic 
sensory impulses in the hemisphere and are, therefore, the fore- 
runners of the mammalian corpus striatum. They discharge 
into the lower brain centers through the lateral forebrain bundle. 
A part of the somatic sensory fibers pass beyond the ventro- 
lateral large celled area (Johnston’s nucleus lentiformis) into the 
dorsal area, so that at the level of the primordial general cortex 
(figs. 5, 6, 15), this dorsal area is entered almost exclusively by 
the somatic correlation fibers and hence is a somatic correlation 
center of striatal type. This area at its anterior end probably 
exhibits the highest type of somatic correlation tissue found in 
the brain of the alligator, and the entrance of association fibers 
from the adjacent cortical centers into its dorsal part has given 
the conditions favorable for the differentiation of primordial 
general cortex (i.e., cortex approaching the neopallial in type). 
It will be remembered that behind the level of this thicken- 
ing representing primordial or transitional general cortex the 
lateral part of the dorso-lateral area receives olfactory fibers and 
probably some somatic fibers, and belongs to the amygdaloid 
complex. Whether this portion becomes a somatic part of the 
amygdaloid complex of higher forms, as Johnston (715) believes 
is the case with the dorsal ventricular ridge in turtles, or whether 
it is a step toward the enormous striatum complex found in birds, 
cannot be decided without a much greater knowledge of other 
vertebrate forms than the writer possesses. In any case, it is 
very evident that the dorso-lateral area must be regarded as a 
structure of intermediate or transitional type, containing pri- 
mordia related to three diverse structures in the mammalian 
brain, viz., corpus striatum, amygdaloid complex, and . the 
general cortex. 
