ON THE NERVES. 
579 
moment at an end. It contains likewise(and we here first of all 
meet with it) the mingled substance, and probably the mingled 
influence, of the cerebrum and the cerebellum ; and we shall pre¬ 
sently see that it first brings to view the origin and source of 
a new' description of nervous influence—the organic. There are 
few parts of the brain in which there is apparently so essential a 
difference between the biped and the quadruped as the medulla 
oblongata. The small, yet prominent bold surface of the first, 
forms an evident contrast with the wider, flatter, tamer appear¬ 
ance of the latter. We observe in both the medium line or fis¬ 
sure prolonged from the spinal chord, and continued over the 
pons varolii. It contains the basilar artery. 
The Corpora Pyramidalia, —On each side there are two longi¬ 
tudinal eminences— corpora pyramidalia, bold and protuberant 
in the human being, and also in carnivorous animals, as you will 
observe in this brain of the dog—broader and flatter in the rumi- 
nantia and the solipeda. These tw'O eminences are the continu¬ 
ation of the medullary longitudinal bands or tracks of which I 
have spoken,’and the commencement of the central columns of 
the inferior surface of the chord. The fissure between them is 
deep; in fact, it penetrates through the me<iulla: it divides it 
into two parts, which are held together more by exceedingly fine 
cellular, than by medullary substance. 
The Nerves proceeding jrom the Pyramidalia. — Running 
transversely across the medulla oblongata, and close to the pos¬ 
terior edge of the pons, and between it and a transverse medul¬ 
lary ridge, that has not yet been noticed by our anatomists, al¬ 
though sufficiently evident, is another sulcus of little depth. The 
medullary ridge running parallel with the pons, is one of the 
origins of the portio dura of the seventh pair of nerves, and 
which springing from the motor column of the spinal chord as 
well as the lateral column, is, as we shall presently see, a nerve 
of common motion, as well as an organic one. Springing from 
this sulcus we also find the sixth pair of nerves, or the abductor; 
and more posteriorly, and apparently from the sulcus between 
the central and lateral columns, but actually from the central 
column, arise the linguales. 
The Corpora OUvaria in the Human Being, —These eminences 
are very distinct in the human brain. They are found in the sul¬ 
cus between the corpora pyramidalia and the lateral column. 
They are rounded and prominent anteriorly, and gradually sink 
to the level of the medulla oblongata posteriorly. It is difficult 
to reconcile the accounts w'hich anatomists give of their structure. 
Some say that they derive their name from a mixture of yellow 
cineritious matter which they contain. Others describe an oval 
