NERVES OF THE DOGFISH 



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passing anteroventrally around the ventral border of the latter, 

 it turns abruptly anterodorsally across the orbital cavity and 

 soon reaches the dorsal oblique muscle which it innervates. 



The posterior rootlets of the abducens nerve appear emerging 

 from the ventral motor column of the medulla oblongata at the 

 transverse level of the anterior border of the internal opening of 

 the spiracle (fig. 20). There are about eight large rootlets that 



contribute to its formation, all arising in the ventral motor col- 

 umn. Peripherally, the nerve runs anteriorly intracranially, at 

 first at the ventrolateral border of the medulla; farther anteriorly 

 at the transverse level of the posterior border of the gasserian 

 ganglion, it enters a canal in the ventral floor of the cranium and 

 runs anterolateral^ toward the orbit. Emerging from the canal 

 mesial to the maxillary ramus of the trigeminal nerve, it passes 



