n6 ZOOTOMY. 



gives off an artery (y) which passes downwards alongside the ureter 

 ( 112) to supply the bladder, anterior anal fin and body muscles of that 

 region, and also anastomoses with the intestinal artery (/) by a small 

 branch. 



143. The kidneys, consisting of two irregular longi- 

 tudinal bands of soft reddish-brown tissue, lying one on each 

 side of the aorta ; to see them satisfactorily, the dorsal wall 

 of the air-bladder must be dissected away ; anteriorly they 

 pass each into the so-called head-kidney already seen ( 140) ; 

 posteriorly they unite and form a large median mass, lying 

 immediately behind the air-bladder and enclosed in the 

 haemal canal of the anterior caudal vertebras, which must 

 be cut away to display it ; it is from this hinder part of the 

 kidney that the unpaired ureter springs. 



144. The cardinal vein (Fig. 32, Led, r.cd\ a somewhat 

 irregular trunk, running through the substance of each 

 kidney. 



The middle part of the left cardinal is aborted for some distance, the 

 veins from the left kidney in this region passing into the right cardinal. 1 

 Posteriorly, the two become continuous with the caudal vein (c.v), 

 which passes through the haemal canal, ventral to the caudal artery. A 

 vein (y) bringing back the blood from the posterior part of the air 

 bladder, urinary bladder, anterior anal fin and body-wall, and anasto- 

 mosing with the portal, runs parallel to the corresponding artery ( 142), 

 and enters the caudal vein just as it emerges from the haemal canal. 



145. The sympathetic nerve is also imbedded in the kidney. 



XXVII. Dissect away the muscles, &c. lying in front 

 of the heart and at the bases of the gills, and bring 

 into view 



146. The ventral aorta (Fig. 32, v.ao), passing forwards 

 from the bulbus arteriosus and ending abruptly at about the 

 level of the ventral end of the first gill. 



1 Its anterior part is sometimes connected with the right cardinal by a 

 transverse anastomosis in this region. 



