270 NERVOUS SYSTEM OF VERTEBRATES. 



between this area and the thalamus have not been clearly appre- 

 ciated. Thus, the nucleus of origin of the fasciculus longitudinalis 

 medialis has been spoken of as lying in the hypothalamus (Edinger). 

 If a section through the inferior lobes of the sturgeon brain be 

 compared with one through the III nerve (Figs. 133, 116) it will 

 be seen that the tectum mesencephali and lateral walls are the 

 same in both, and also that the fasciculus longitudinalis medialis 



Radix mesenc.Y 



Tr. tecto- bul- 



\ .^Hl 



Tr. tecto-cerebel. 



Tr. lobo-bulbaris V |W N Tr . bulbo-tectal 



Tr. haben.-pedunc. 

 Tr. lobo-bulbaris 



Tr, sacco-thal. 



Tr. thal.-saccus . 



Saccus 

 Fig. 133. Transverse section through the corpora mammillaria of the sturgeon. 



and the fundamental bundles of the lateral tracts extend forward 

 into the thalamus. In front of the nucleus of the fasciculus longi- 

 tudinalis medialis the nucleus of the tractus strio-thalamicus and 

 the tract itself continue forward at about the same level. These 

 several structures represent the brain base or stem. The greatly 

 expanded inferior lobes ventral to them are anomalous structures. 

 The characteristic structure of the inferior lobes extends up to 



