102 MARION HINES 
Taking for its anterior limit that part of the midline where the 
two lateral choroid plexuses are continuous over the telencephalic 
roof and the velum transversum as its posterior boundary, its 
length is approximately that of the 39.1 mm. However, it was 
impossible to identify a dorsal outpouching in the region of the 
paraphyseal arch. This may be due in part to the fact that the 
embryo was sectioned at 100y, coronal to the cerebral hemisphere. 
_A thinner section in the transverse plane is more advantageous 
for the study of this region. In the 39.1-mm. this structure was 
present for about 175y. : 
The septum continues its growth into the venimiclel The 
area of the septum ependymale measures approximately the same 
and cannot be distinguished morphologically from the area in- — 
tercalata. The extent of the lamina epithelialis resembles that 
of the 39.1-mm. embryo. 
Within the telencephalon the ventricular ridges have the 
same relationship to each other as that described for the 39.1-mm. 
embryo, H 1638. The lateral limb of the caudate nucleus is large | 
and ends in the ventromedial horn of the lateral ventricle. The 
medial limb of the same complex terminates at the base of the 
olfactory bulb. The angulus ventralis separates this medial 
limb from the septal region. The hippocampus forms a rounded 
hillock upon the medial wall which tends to flatten out anterior 
to the angulus terminalis. The sulcus limitans hippocampi lies 
beneath it, extending from the tip of the temporal pole to a 
region slightly anterior to the rostral limit of the fascia dentata. 
The fissure of the choroid plexus is completely closed. The vault 
of the hemisphere is higher in the region of the paraphysis than 
in the 39.1-mm. The anterior and ventro-posterior extension 
is not greater than that of the last brain described. 
The outer contour is not materially changed. The island of 
Reil is visible on the lateral surface, so that the hemisphere may 
be divided into various regions indicative of its future lobulation. 
The olfactory bulb is large and its cavity opens into the ventricle. 
Along its medial boundary of constriction, extending dorsally 
anterior to the lamina terminalis lies the fissura prima of His. 
Posterior to the terminal plate, the fissura hippocampi can be 
