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TEXTBOOK OF ZOOLOGY 



certain muscles are specialized for feeding and others to assist in 

 respiration. The segmental myotomes divided dorsally and ven- 

 trally by the lateral line are the chief muscles of locomotion, since 

 most of the power is delivered by lateral strokes of the tail against 

 the water. The myotomes are modified in the regions of the paired 

 fins to supply certain muscles to them. The action of the fins serves 



OUFACTORY BULB 

 OI_FACTORY TRACT 



OPTIC N. 



TROCHLEAR M. 

 OCULOMOTOR N. 



TRIGEMIMUS N. 

 PACIAL- fsl. 

 CEREBRUM 

 PINEAU BODY 

 OPTIC LOBE 

 CEREBELLUM 



AUDITORY N. 

 POSTERIOR LOBES 



MEDULLA OBLONGATA 



VAGUS IM. 

 GLOSSOPHARYNGEAL N. 



Fig. 256. — Dorsal view of brain and cranial nerves of Ameiurus natalis Le Sueur. 

 (Drawn by Titus Evans from dissections by Rose Newman.) 



to help in equilibration and in guiding the body as it is forced 

 through the water. The fins act somewhat as a combination keel 

 and rudder. "Without them the fish is unable to hold its upright 

 position and guide itself through the water. 



In connection with the mouth and feeding process there are sev- 

 eral distinct muscles. The adductor mandihularis elevates the lower 

 jaw while the geniohyoid ancf mylohyoid raise the floor of the mouth 

 and tongue. There are eight different sets of muscles connected with 

 the respiratory movements of the opereula and gills. 



