INTERNAL ANATOMY. 



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passes outward and forward for about 7.0 mm. and bifurcates into an inner 

 and an outer ramus. The inner of these, c. 3, corresponding to the third cere- 

 bral nerve of the above table, passes at once through the overlying retractor 

 muscles of the head to its dorsal wall, courses forward between the eyes and 

 penetrates deeply into the integument, giving off a number of fine branches and 

 terminating in the gangUon of the rhinophore, at the base of the latter organ. 

 The outer ramus, c. 1, the first cerebral nerve, passes forward within the cone of 

 retractor muscles of the head. On the right side, just beyond its crossing above 

 the superior retractor muscle of the penis-sheath, it receives an anastomosing 

 branch from the third pedal nerve, which recurves posteriorly to it. A short 

 distance toward the cerebral gangUon from this union a branch is given off to 

 the above named muscle, seeming to be a direct continuation of the fibres from 

 the pedal nerve alone. Beyond this point the main trunk of the nerve curves 

 upward and is distributed to the dorsal wall of the head in front of the rhino- 

 phores. 



Outside of and behind the origin of the nerve-trunk A, just described above, 

 arises another nerve but sUghtly smaller in diameter, the second cerebral nerve. 

 At a short distance from its origin it bifurcates into nearly equal rami, which 

 pass downward and forward along the pharyngeal bulb. The upper of these 



