Herrick. Morphology of Nervous System. 33 



tral band of the anterior commissure can here be traced 

 ventrad and cephalad. In longitudinal sections an olfac- 

 tory tract lying medianly from the ventricle can be followed 

 caudad and laterad to nearly the point at which the above- 

 mentioned portion of the anterior commissure disappears. 



In the black-snake, on the other hand, the anterior com- 

 missure is studied with great ease, and it exhibits greater 

 complication of structure than in other reptiles examined 

 (Plate X, Fig. 7). The commissure is readily separated into 

 three perfectly distinct portions or bundles. The most 

 ventral or ventro-cephalad bundle is the olfactory commis- 

 sure, which is composed of large and deeply-stained fibres 

 arching ventrad very soon after crossing to the opposite side 

 and continuing almost directly ventrad to near the surface. 

 They then turn cephalad and enter the medi-basal part of 

 the crus olfactorius. 



The second bundle (commissure of olfactory centres) lies 

 in contact with the olfactory commissure and follows its 

 course for some distance ventral, dividing into several dis- 

 tinct bundles of small size, which pass to the ventro-lateral 

 regions of the middle portion of the hemispheres. These 

 various bundles seem to enter cellular masses lying near 

 the ventral and ventro-lateral surfaces of the cerebrum, 

 and can be traced no further. A strong ecto-lateral tract 

 from the oltactory lies superficially to these niduli, which 

 are composed of small, dark, angular cells similar to those 

 which in other animals are associated with the olfactory 

 regions of the cortex. 



The relations so far described are in no way conjectural, 

 none of the fibres decussate, nor is there any connection 

 between the olfactory commissure and the commissure 

 of the olfactory centres. It might be supposed that the 

 ^wo tracts form a circuit broken by cellular matter in 

 the olfactory lobes and again by the cells of the olfactory 

 centres. - - ■• 



■•■•> The third' set of fibres- lies dorsad to those" just described, 



