782 



THE NERVOUS SYSTEM. 



fornix, with its corresponding anterior and posterior pillar and half of the septum 

 lucidum. 



The supracallosal gyrus, just mentioned, may be regarded as made up of the 

 peduncles of the corpus callosum, the longitudinal striae on the upper surface of the 

 same, and the fascia dentata with its upper part, the fasciola cinerea. These 

 structures are continuous with each other, as has already been mentioned in the 

 description of each. The name dentate gyrus is often used to designate the com- 

 bined fasciola cinerea and fascia dentata. 



The boundaries of the limbic lobe are the calloso-marginal fissure, the collateral 

 fissure, and the post-limbic fissure. 



FIG. 472. Top view of the brain of man, showing the localization of various functions. (After Ferrier.) 

 References the same as in the preceding figure. 



THE OLFACTORY LOBE (Fig. 473). This is situated on the orbital lobe (under 

 surface of frontal lobe). In general outline it is long and slender, widest behind. 

 It is divisible into two, anterior and posterior, olfactory lobules. The olfactory 

 lobe is developed as a hollow outgrowth from the ventral and lateral part of the 

 corresponding hemisphere vesicle, the cavity of which, in man and primates, is 

 eventually obliterated. In the adult condition the posterior lobule is found to have 

 remained on the hemisphere, and thus to form a part of it, while most of the ante- 

 rior lobule is attached only by a stalk to the posterior, it being freely separable in 

 the rest of its extent ; that is, after removal of the membranes. 



The anterior olfactory lobule is made up of (1) the olfactory bulb ; (2) the 

 olfactory tract ; (3) the trigonum olfactorium ; and (4) the area of Broca. 



The olfactory bulb is an oval mass of a grayish color, Avhich rests on the crib- 

 riform plate of the ethmoid bone, and forms the anterior expanded extremity of 

 the slender process of brain-substance, the olfactory tract (see page 792). From 

 the under part of this bulb are given off the olfactory nerves, which pass through 

 the cribriform foramina and are distributed to the mucous membrane of the nose. 



