74 NERVE COMPONENTS OF BONY FISHES. 



Fig 7, which is drawn from the same specimen plotted on 

 Fig. 3, but to a larger scale. In this figure the sensory 

 fibres are indicated in yellow, the ganglion being a lighter 

 shade of the same; the motor fibres of b are drawn in 

 light blue, the motor fibres of c in a. darker blue. 



Now taking up the rami arising from this complex in 

 order, we have first a ramus coiniminicans arising from 

 the cephalic tip of the ganglion b (r. com. b.) consisting 

 wholly of sensory fibres, and pursuing a typical course 

 cephalad and dorsad over the upper surface of the supra- 

 occipital bone. Leaving this bone, it then runs up in the 

 intermuscular septum laterally of the interspinous muscles 

 to join the r. lateralis accessorius in two strands (Fig. 3), 

 the latter nerve having at this level turned mesally from its 

 former lateral position. to run in the same intermuscular 

 septum, which position it maintains from this point caudad. 



Close behind the last there arises a minute motor twig 

 {is. m. b.), which pursues a course similar to that of a r. 

 spinosus, though the true r. spicosus of this segment lies 

 a little farther caudad. It supplies the interspinal muscles 

 and does not join the r. lateralis accessorius, though it 

 distributes near the latter nerve. The true r. spinosus of 

 b {r. sp. b.), as it runs back over the supra-occipital bone 

 sends a few fibres into the dorsal musculature and then 

 joins the r. lateralis accessorius in the intermuscular 

 septum in the typical manner, save that it does not anasto- 

 mose with the r. communicans of the next following 

 segment. It is exclusively motor. 



The r. medius b (r. ;;/. b.) arises between the two 

 nerves last mentioned and contains motor fibres and a 

 smaller number of sensory. Its stem at once divides into 

 two branches, each of which takes some of both motor and 

 sensory fibres and penetrates the dorsal musculature. 



