THE COD. 109 



colour, situated in the posterior part of the abdominal 

 cavity, above the termination of the intestine. 



no. The visceral layer of the peritoneum, a thin trans- 

 parent membrane, enveloping, somewhat loosely, the fore- 

 going viscera. 



in. The air-bladder or swim-bladder, covering the 

 whole of the dorsal wall of the abdomen, the peritoneal 

 lining of which is continued over its ventral surface : if in 

 the distended condition, its smooth median and sacculated 

 lateral regions render it readily distinguishable ; if collapsed, 

 it is less obvious. 



112. The ureter, a thin-walled tube, passing upwards 

 from the urinary aperture to the posterior end of the air- 

 bladder to join the kidney, which is at present concealed : 

 near its ventral end it gives off a bilobed diverticulum, the 

 urinary bladder. 



XIX. Continue forwards the median ventral incision 

 already made, by cutting through the hip-girdle 

 and between the right and left halves of the 

 shoulder-girdle : dissect away the left half of both 

 pectoral and pelvic girdles, working from below 

 upwards, and taking especial care not to cut too 

 deeply and so run the risk of injuring the hepatic 

 ( 125) and precaval ( 141) veins. Note 



113. The gullet (Fig. 31, tes\ a tube of about the same 

 diameter as the stomach, with which it is continuous 

 posteriorly, while in front it passes into the pharynx 

 ( XXX.)- 



114. The pericardial cavity; a small chamber con- 

 taining the heart ( 115) and separated by a strong fibrous 

 partition the pericardio-peritoneal septum from 

 the cavity of the abdomen : it is bounded above by the floor 

 of the mouth and bases of the gills, and below by the 



