THE BRAIN Ii\ THE EDENTATA. 



287 



margin of the olfactory tract as a narrow band of grey substance with an irregular 

 tuberculated margin. The pyriforni lobe, the anterior part of which is formed by this 

 tuberculated worm-like process, will be found to expand posteriorly and form a large 

 rounded prominence, which is often known as the natiform eminence. This expanded 

 portion of the pyriform. lobe we may distinguish as the lobus injriformis posticus, to 

 distinguish it from the lohus pt/riformls aniiciis, which is merely the tapering cephalic 

 extremity of the same histological formation. These two parts of tlie pyriform lobe are 

 separated the one from the other by a depression, the vallecula S/jlvii, which extends 

 obliquely in a mesial direction toward the perforated space. 



Fig. 1. 



bulb, olfact. 



lob. pyriform. ant 



loc. perforat 



lob. pyriform. 

 post. 



nerv. III. . 



pons Varol.. 



pyramid. - 



ped. olfact. 



■ tubercul. olfact. 

 • tract, olfact. 



vail. Syl. 

 tract, opt. 



crus cerebri 

 Corp. geaiculat. po6t^ 



■gangl. interped. 



nerv. V. 



•fiss. flocculi 

 ■paraflocc. dors, 

 parafioco. veatr. 



trapezium 



medulla oblong. 



Ventral surface of brain of Ofijcicropus. Xat. size. 



The terms " lohus pynformis " and " tractm olfactorius " have been applied in a 

 sense slightly different from that which the majority of writers attach to them. This 

 attempt at a greater precision in description needs some sliglit explanation. It is 

 customary to restrict the term " lohus pijriformis" to that expanded posterior area of the 

 lobe (as we understand it) which is situated behind the vallecula S//lcii, and for which 

 the terms " natiform eminence," " hippocampal lobule," and many other variants of 

 these terms are regarded as alternative names. 



The anterior tapering part of the same histological formation, which we haA^e already 



40* 



