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 wliich 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 obUquely 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 oyer 

 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 contmuous in 

 front with the presylvian fissure. 



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.^ 



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. 



Trniisvcrsc fissure 



Cerebellum 



Olj'nrliiry bulb 



Medulla oblongata Spinal cord 



Fig. 672. — Brain of Pig; Left View. 

 Fissures: ^, i', sulcus rhinalis (anterior et posterior) ; .2, lateral; S, suprasylvian; 4. ectomarginal ; 5, 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, 

 lips 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 usvially 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 

 olfactoritim. 



The cranial nerves present the following special features : 



The third, fotirth, sixth, and the ophthalmic and maxillary divisions of the 

 fifth nerve emerge together as in the ox. 



