THE COD. 119 



153. The thick muscular walls of the ventricle, raised 

 internally into a network of ridges, the columnae carnese. 



154. The aortic valves, consisting of two semilunar 

 flaps situated right and left, at the junction between the 

 ventricle and the bulbus arteriosus. 



155. The thick fibrous walls of the bulbus arteriosus. 



XXIX. Draw the gills of the left side downwards, so 

 as to feel the muscles (levatores arcuum branchi- 

 alium) connecting them with the skull on the 

 stretch : dissect away these muscles, as well as the 

 anterior part of the air-bladder, make out 



156. The branchial branches of the vagus, distributed to the bran- 

 chial arches in the same manner as in the Skate (p. 82, § 214). The origin 

 of the gastric, cardiac, and cutaneous branches of the vagus may le seen 

 at the same time, as well as its exit from tlie skull (see § 196). 



157. The glossopharyngeal, dividing, soon after its exit from the 

 skull, into two branches, a posterior going to the anterior face of the 

 first branchial arch, and an anterior passing at first forwards, and then 

 downwards, along the inner face of the hyomandibular to the pseudo- 

 branch (§ 196). 



158. The left epibranchial artery (Fig. 32, ep.br), 

 lying longitudinally along the dorsal ends of the gill arches, 

 and receiving the four efierent branchial arteries 

 {ef.br}, rf.br.^), one from each arch. After receiving the 

 last efferent artery the epibranchial trunk passes inwards 

 and backwards, and unites with its fellow of the opposite 

 side to form the dorsal aorta, but just before doing so, it 

 gives off a subclavian artery {s.d) on each side, which 

 suppHes the pectoral fin. The cceliac (cos) and mesen- 

 teric {m) arteries (§ 124) arise from the right epibranchial 

 just anterior to the subclavian. 



XXX. Cut through the lower jaw, the hyoid, and the 

 branchial arches, a little to the left of the middle 

 ventral line, so as to leave the tongue intact on 



