The =spinal cord= weighs about 42 grams (Ellenberger-Baum). It is almost
circular in cross-section, except at the enlargements, where it is
somewhat flattened dorso-ventrally. The conus medullaris extends to the
anterior part of the third sacral segment. The epidural space is
occupied by a large quantity of fat.
The =brain= in adults of medium size weighs about 125 grams (ca. 4 to 4½
ounces). When viewed from above, it is seen to have an elongated oval
form. The occipital poles overlie the cerebellum to a small extent only;
the frontal poles are rounded and relatively large, but do not conceal
the ends of the olfactory bulbs. The =medulla= is relatively broad. The
cuneate tubercle is very large and is limited externally by a groove.
The corpus trapezoideum is very wide laterally. The =pons= is less
prominent than in the ox. The =cerebellum= is very wide and short. Its
anterior face is flattened and presents a depression for the corpora
quadrigemina. The vermis is large. The hemispheres consist of an inner
large and an outer small part. The =cerebral peduncles= are very short.
The posterior corpora quadrigemina are wide apart, rounded, and
relatively large. The internal geniculate body is prominent. The
=cerebral hemispheres= are somewhat bean-shaped in lateral profile, the
convex border being dorsal. The arrangement of the gyri and sulci is
simpler than in the horse or ox. The principal fissures are as follows:
1. The =lateral fissure= (of Sylvius) begins at the sulcus rhinalis and
runs upward and somewhat backward on the depressed part of the lateral
surface of the hemisphere; it appears unbranched on superficial
examination, but when the gyrus which almost completely conceals the
insula is raised, an anterior branch is exposed which forms the dorsal
boundary of the insula.
2. The =suprasylvian fissure= pursues a curved course approximately
parallel with the dorso-medial border of the hemisphere. Its posterior
end is separated by a short interval from the sulcus rhinalis posterior.
From its highest point a branch proceeds obliquely upward and forward,
crosses the dorso-medial border, and joins the splenial fissure.
3. The =diagonal fissure= crosses the anterior part of the lateral
surface. It is directed obliquely downward and backward.
4. The =coronal fissure= is constant and deep. It is directed upward and
inward over the frontal pole, continues backward near the dorso-medial
border, and usually ends by passing obliquely over the border to the
inner surface of the hemisphere.
5. The =presylvian fissure= begins—apparently as a branch of the sulcus
rhinalis anterior—about 2 cm. in front of the lateral fissure, and
curves over the lateral aspect of the frontal pole.
[Illustration: