152 



ANATOMY OF THE CENTEAL NEETOUS SYSTEM. 



The cortical center of the olfactory apparatus reaches in mammals its 

 highest development. Here there are developed numerous association- 

 bundles, and the surface is enormously enlarged, including whole lobes: 

 Lobus cornu Ammonis and Lotus pyriformis. 



These portions of the brain are to be looked upon as highly-organized 

 centers which receive their stimulation from the lower olfactory mechanism, 

 but which, through their structure, are made capable of extended inde- 

 pendent activity. 



Thus, in the vertebrate series there is added to the lower olfactory 

 mechanism a higher one, which gradually increases in extent. 



Having given a general view of the olfactory apparatus as at present 

 understood for the vertebrates, let us study in the accompanying figure (Fig. 



Fig. 100. — Schema of the olfactory apparatus of a lizard-brain. 



100) an ideal sagittal section through a lizard-brain, where the parts already 

 described may be again viewed, with their connections. The olfactory lobe 

 lies anteriorly, covered by the Formatio bulbaris, into which the Fila 

 olfactoria from the nasal mucous membrane pass. Posterior to the Lobus 

 olfactorius lies the Area olfactoria, and still farther back the Nuc. tsenise 

 (Tub. TJicBn.), above which are the epistriatum and striatum. Over 

 the whole is spread the mantle, which bears the cortex. Except for the 

 mantle connections, which appear first in the amphibia, the schema holds 

 for all vertebrates. That the cortical connections are not absolutely essential 

 to the sense of smell is demonstrated by the fact that fishes have a finely 

 developed olfactory apparatus, but possess no sort of a cortical connection. 



All portions of the brain which are in any way brought into relation 

 with the olfactory apparatus are connected with the corresponding portion 



