54 



Fig. 19. There are two roots, forking and coming together again, as 

 shown in Pig. 20 B. These enter a small depression situated near 



the recessus prseopti- 

 cus, a little more caudad 

 than one -half the di- 

 stance from the front 

 margin of the prosen- 

 cephalon to the optic 

 chiasma. 



Penetrating the 

 brain substance , the 

 branches of the nerve 

 pass upward in the 

 median septum ; they 

 branch profusely and 

 are distributed to a 

 mesial eminence (emi- 

 nentia septalis ?), not 

 to the lateral portion 

 of the-brain-wall. This 

 is the same portion of 

 the brain substance in 

 which are found the 

 central terminations of 

 the nerve in Squalus. 

 The course of the 

 nerve on the surface 

 is as follows: starting 

 from its point of con- 

 nection, it passes for- 

 ward on a line nearly 

 parallel with the trac- 

 tus, but it does not 

 come to lie close to 

 that structure. It bears 

 a long ganglionic en- 

 largement lying against 

 the base of the brain. 

 In front of this proxi- 

 mal ganglion, it traverses the relatively short space between the 

 frontal margin of the prosencephalon and the bulbus and has another 



Fig. 19. Brain of adult Mustelus canis, from 

 above, and portion of the same from below, both nat. size. 



