CELL MASSES IN THE FOREBRAIN 401 
consists of fibers which connect the olfactory centers with the 
hypothalamus and lower motor correlation centers. From this 
bundle fibers rise radially into the dense cell mass formirig the 
floor of the ventricle (figs. 21 to 24, 34). 
The whole mass in the latero-basal wall is the corpus striatum. 
It consists of two portions, a lateral much larger part containing 
large cells and a medial smaller part containing small cells (figs. 
21, 22). The coarser fascicles of the crus rise in a curve through 
the lateral part into the dorsal ventricular ridge and the general 
pallium (figs. 32, 33). The finer fascicles of the medial bundle 
rise in almost straight lines radially in the rostral end of the 
medial part (fig. 34). In man the condensation of the pallial 
portion of the crus fibers into a plate-like internal capsule has 
taken place within a lateral large-celled area, the greater part of 
which is situated external to the capsule and is known as the 
lentiform nucleus. The remainder of the large cells together 
with a dense small celled area next the ventricle constitute the 
caudate nucleus. é 
- In the turtle the large-celled and small-celled areas are clearly 
distinct from one another. The small-celled area will be called 
the caudate nucleus, the large-celled area the lentiform nucleus. 
The caudate nucleus presents well marked head and _ tail 
portions. Far rostrad (fig. 26) this nucleus forms the floor of 
the ventricle between the ventral and middle ventricular grooves 
and occupies almost the entire thickness of the latero-basal 
wall. At its medial border it is continuous with the lateral 
parolfactory nucleus. This relation has been described for both 
reptiles and mammals in a previous paper (’13b, p. 389). Its 
basal surface is largely covered by the medial forebrain bundle 
from which fascicles enter the caudate. Followed rostrad in 
transverse sections the caudate is seen to be covered in by the 
layers of the olfactory tubercle which are continuous with the 
parolfactory area medially and the pyriform lobe laterally 
(fig. 27). In these layers are imbedded the olfactory tract 
fibers as elsewhere described. Continuing forward, the tuber- 
culum and olfactory nuclei increase in thickness and the caudate 
grows smaller (fig. 28) until just behind the peduncle the caudate 
