THE CATFISH. 167 



spine, so that the fish may be placed on its back in the 

 water. With forceps pinch up a transverse fold of the 

 tough skin of the ventral surface opposite the anterior 

 dorsal fin, and cut through the fold with sharp scissors. 

 Continue the cut backward to the vent, and forward to 

 the bones of the pectoral arch, taking care not to injure 

 or displace any of the organs which lie directly beneath 

 the thin body wall. Turn back the flaps and expose 

 these organs. Observe a silvery membrane, the perito- 

 neum, lining the body cavity. 



Internal Features. The large red organ close up under 

 the pectoral arch is the liver. Two conic-pointed lobes 

 run from it forward and downward ; and two broad, flat 

 lobes extend backward. Turn these latter forward, and 

 observe under the one on the right side of the body a 

 capacious yellow gall bladder. 



Under the other, the left lobe, the esophagus extends 

 backward to the stomach, which lies entirely posterior to 

 the liver. Pass a probe into the stomach from the mouth. 

 The intestine arises from the left side of the stomach, and 

 curves forward and to the right side, and posteriorly around 

 the stomach, and makes a number of irregular turns in 

 passing through the posterior part of the body cavity. 



Behind the stomach it is partially concealed by the 

 reproductive organs, whitish organs in the male ; large, 

 yellowish organs in the female, varying much in size 

 with the age of the specimen and with the season. 



Observe that the intestine is looped up, and held in 

 place by a transparent membrane (the mesentery). Lift 

 this, and observe the blood vessels in it. Observe the 

 blood vessels and the nerve branches spread out over the 

 anterior end of the stomach. Turn the stomach over to 

 the right side, and observe an elongated, narrow, white 

 organ, the pancreas, lying along its dorsal side. 



