George L. Streeter 311 
Lying lateral to the elevations formed by the nucleus funiculi teretis 
and the nucleus hypoglossi is the elongated wedge shaped elevation 
formed by the nucleus intercalatus (area plumiformis), which measures 
11 mm. long, and 2.2 mm. in greatest width. The frontal portion forms 
the body of the structure and is situated in the region of the striae. The 
tapering caudal extremity extends from this, between the eminentia 
hypoglossi and the vagus area, as far as the tip of the calamus scriptorius, 
overlapping a portion of the hypoglossal nucleus. The nucleus inter- 
calatus lies superficial in the floor throughout its entire extent, except 
in the frontal part, where it is more or less covered by the striae medul- 
Jares. This nucleus is probably not a part of the vestibular nucleus. 
In different parts of the floor of the ventricle can be seen a formation 
of fine ridges. They are particularly numerous in the region of the 
nucleus intercalatus, and from their regularity often present the ap- 
pearance of a “ bird feather.” They consist of small neuroglia elevations 
covered by a single layer of epithelium, and are devoid of nerve cells 
or fibres. They are present in fresh brains, but show more distinctly 
in hardened specimens. They radiate on the surface of the ventricular 
floor from regions where neuroglia processes (“ Kielsireifen ”) extend 
inward as partitions between the dorsal nuclei. It is possible that they 
serve as a support to these processes. 
Lateral to the nucleus intercalatus is the fovea vagi (ala cinerea), 
which represents the middle one-third of the vago-glossopharyngeal 
nucleus, and is the only part of this nucleus that lies superficial in the 
floor of the ventricle. The entire vago-glossopharyngeal nucleus is 13:9 
mm. long, and averages 2 mm. in width. Frontal to the fovea vagi, 
+he nucleus lies concealed beneath the vestibular nucleus. The distal 
one-third extends 2.5 mm. caudad to the tip of the calamus scriptorius, 
the extraventricular portion lying ventral to the nucleus gracilis, and 
dorsal to the hypoglossal area. The intraventricular portion of the 
caudal one-third of the nucleus is covered by a layer of loose vascular 
tissue. which is continuous with the obex, and which extends into the 
dorsal region of the central canal. This is the area postrema of Retzius. 
Separating it from the fovea vagi there is usually some thickening of the 
ependymal neuroglia forming a translucent cord-like elevation, the 
funiculus separans. The fasciculus solitarius lies lateral and ventral 
+o the vago-glossopharyngeal nucleus throughout its course. It no- 
where lies superficial, and bears no apparent relation to the funiculus 
separans. 
All that part of the floor of the ventricle that lies lateral to the 
anterior fovea (fovea trigemini) and the fovea vagi (ala cinerea) and the 
