THE DOG-FISH 213 



III. THE ABDOMINAL VISCEEA. 



Lay the dog-fish on its back on the dissecting -board, and 

 pin it down through the fins. Determine the positions of the 

 pectoral and pelvic girdles by feeling them through the skin, 

 the pectoral girdle being a little in front of the pectoral fins, 

 and the pelvic girdle a short way in front of the cloacal 

 aperture. 



Open the body -cavity by a median ventral incision, extend- 

 ing from the pelvic girdle behind to the pectoral girdle in front. 

 Cut through the body-wall transversely , just behind the pectoral 

 girdle, and pin the two flaps down to the dissecting -board. 

 Cut through the pelvic girdle in the median plane, and prolong 

 the cut backwards to the level of the cloacal aperture, but 

 keeping a little to its right side. Wash or sponge out the 

 body -cavity. 



Identify the positions and relations of the following organs 

 before proceeding further with the dissection. 



1. The liver is a very large solid organ of a brownish yellow 



colour, attached by a median suspensory ligament to 

 the anterior wall of the body-cavity. It consists or 

 two lobes of about equal size, which are united 

 together in front, and extend back along the sides of 

 the body-cavity for the greater part of its length. 



2. The stomach is a wide U-shaped tube lying between the 



lobes of the liver, and extending about two-thirds the 

 length of the body-cavity. 



3. The spleen is a large brownish red body attached to the 



loop of the stomach, and sending a long narrow lobe 

 along its distal .limb. 



4. The intestine is a wide and nearly straight tube, running 



along the right side of the body-cavity from the 

 stomach to the cloaca. 



5. In the female the ovary is single, and attached by a 



delicate fold of peritoneum to the mid-dorsal wall of 

 the body-cavity. The contained ova give its surface 

 a tuberculated appearance. 



