ANIMAL BIOLOGY. 



[Part I. 



The Cod. 1 To open up the body-cavity of the cod, the fish 

 should be laid on its side, a ventral incision made from the hip- 

 girdle (under the throat) to within half-an-inch of the anus, and 

 the side wall removed from the peritoneal cavity or ccelom thus 

 exposed. The cavity is lined with peritoneum, which is reflected 

 on to the viscera. It extends backwards, somewhat behind the 

 anus, and is bounded anteriorly by fas pericardio-peritoneal septum, 

 which separates it from the chamber which contains the heart. 

 Along the dorsal wall of the cavity runs the large air-bladder, 

 terminating anteriorly in a coiled caecum, and not communicating, 

 as in some fishes (e.g. trout, herring), with the gullet. 



FIG. 13. VISCERA OF COD-FISH. 



a. Anal aperture, c. &. d. Common bile duct. c. d. Cystic duct. g. Genital 

 aperture. G. B. Gall bladder. 7i. d. Hepatic ducts. H. K. Head kidney, ws. 

 (Esophagus. Py. Co.'. Pyloric cteca. lien. Kidney. 8m. Int. Small intestine. 

 St. Stomach. 11. Urinary aperture. U. Z>. Urinary bladder. Ur. Ureter. 



1. The Alimentary System. The gullet or oesophagus (us., 

 Fig. 13) is of about the same diameter as the stomach (St.], but 



1 Instead of the cod, tlie closely-allied haddock or whiting may be dissected. 

 Where this (or any other animal) is too large for dissection under water, it 

 should be pinned out with blanket-pins (or awls) on to a dissecting board of 

 convenient size. 



