Charles R. Essick 12 
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geal nerve emerging from the summit. This ridge can be traced an- 
teriorily as it passes between the facial and acoustic nerves and a very 
little part of the pontine portion may be seen just anterior to the seventh 
nerve as is indicated by vertically directed lines in contrast to the hori- 
zontally placed lines representing the direction of the pons fibers proper. 
Other figures, 9, 12, and 13, of the same plate, furnish good illustrations 
of this region. 
At the point where it emerges below the lateral recess, we see it turn- 
ing around the restiform body just caudal to the dorsal cochlear nucleus 
from which it is separated by a shallow sulcus. In some specimens it 
might easily be mistaken for the dorsal cochlear nucleus; but if one will 
carefully follow the cochlear nerve, the real dorsal cochlear nucleus can 
be made out in front of the attachment of the tela choroidea inferior, 
1. e., the dorsal cochlear nucleus lies in the lateral recess and is covered 
with ependymal cells; while the ponto-bulbar body, which often ap- 
proaches the dorsal cochlear nucleus in elevation and extent, is situated 
more caudal, and makes a curve of greater radius around the restiform 
body to gain the dorsal surface of the medulla. 
On the dorsal surface of the medulla, the ponto-bulbar body under- 
goes its greatest variation in different brains and, in fact, on the two 
sides of the same brain. Instead of the welt-like ridge which it presents 
in the more cephalic part of its course, it here spreads out into a flat- 
tened leaf-like structure overlapping the restiform body and the lateral 
part of the floor of the fourth ventricle. In its exact form it shows con- 
siderable variation. Of the fifty brains which were examined five of them 
presented the prominent mitten-like form 4.5—6.0 mm. wide with a 
free tip, projecting, as it were, out into the tela choroidea, as is seen in 
the Fig. 1. These would be called markedly well developed. On the 
other hand, in about 40% of the specimens this part of the ponto-bulbar 
body forms such a thin lamella that it is not noticeable macroscopically 
on at least one side of the brain. Between these two extremes there are 
all gradations. It may take the form of a single ridge usually 2 — 3 mm. 
in width; or may be divided into two finger-like ridges. In well devel- 
oped cases the caudal tip may help to form the roof of the fourth 
ventricle, forming a free end to the edge of which is attached the tela 
choroidea. In the specimen photographed, Fig. 1, there was a tip of 
this kind 1.5 mm. long. The fact that the tela choroidea is attached to 
it, makes it a thing easily damaged in removal of the pia. A drawing 
of an average human medulla is represented in Fig. 2 and this gives the 
usual position and size which the ponto-bulbar body presents in a dorsal 
