844 THE NERVOUS SYSTEM OF THE PIG 
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 cruciate 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 medially over 
the frontal pole, continues backward near the dorso-medial border, and often ends by passing 
obliquely over the border to the medial surface of the hemisphere. It is usually continuous in 
front with the presylvian fissure. 
5. The presylvian fissure begins—apparently as a branch of the sulcus rhinalis anterior— 
about 2 em. in front of the lateral fissure, and curves over the lateral aspect of the frontal pole. 
6. The marginal fissure begins behind the cruciate fissure close to the dorso-medial 
border and extends in a gentle curve backward to the occipital pole. 
SA, 
~ Cerebellum 
1 
Hypo physis 
Olfactory bulb Pons 
Medulla oblengata Spinal cord 
Fic. 672.—Brain or Pic; Lerr View. 
Fissures: 1, 1’, sulcus rhinalis (anterior et posterior); 2, lateral; 3, suprasylvian; 4, ectomarginal; 6, coronal, Stumps 
of cranial nerves indicated by Roman numerals. 
7. The ectomarginal fissure lies above and nearly parallel to the posterior part of the 
suprasylvian fissure. 
8. The entomarginal fissure lies along the posterior part of the dorso-medial border. 
9. The calloso-marginal fissure consists of two separate parts. The more extensive pos- 
terior part is termed the splenial fissure. It extends from the tentorial aspect of the hemi- 
sphere in a direction parallel with the corpus callosum nearly to the middle of the medial 
surface; it is continued by the cruciate fissure and may be also connected with the coronal fissure 
by a branch which passes obliquely upward and forward. The anterior part, the genual fissure, 
lies about midway between the anterior part of the corpus callosum and the dorso-medial border. 
10. The cruciate fissure runs obliquely upward and forward from the anterior end of the 
splenial fissure on the inner surface of the hemisphere, cuts obliquely into the dorso-medial margin 
about its middle, and usually joins the dorsal branch of the suprasylvian fissure. 
11. The sulcus rhinalis extends in an undulating manner along the entire lower part 
of the lateral surface of the hemisphere and forms the upper limit of the rhinencephalon. 
The olfactory bulbs are very large and the tracts extremely broad and short. 
The trigonum olfactorium is so prominent as to suggest the designation tuberculum 
olfactorium. 
The cranial nerves present the following special features: 
The third, fourth, sixth, and the ophthalmic and maxillary divisions of the 
fifth nerve emerge together as in the ox. 
