GENERAL BIOLOGY 



skull, and bit by bit pick off the roof of the brain cavity with strong 

 forceps. Tag your specimen with your name and put it into a jar 

 of preserving fluid until the next exercise. 



3. DIGESTIVE SYSTEM. (Preserved Specimen.) 



Posterior to the heart note: (i) The liver with its larger left 

 lobe divded into two parts ; on raising the posterior border, the 

 gall bladder is seen as a greenish sac on the right side; also the 

 hepatic-portal vein, which enters the left lobe of the liver. The 

 stomach, an elongated white body on the left side under the pos- 

 terior edge of the liver. (3) A convoluted tube, the intestine pass- 

 ing from the stomach to the right and then posteriorly to finally 

 enter the pelvic cavity as an expanded rectum. It is slung by a 

 delicate membranous fold of peritoneum, the mesentery, which is 

 full of blood vessels. (4) The fat masses, long slender yellow 

 masses on each side in the dorsal part of the body cavity anterior 

 to the reproductive glands. 



Cut off all the dorsal part of the liver with strong scissors, cut 

 open the body wall in the pelvic region without injuring the rectum. 

 ( I ) the cloaca is now exposed ; a probe may be run through it into 

 the rectum. (2) Uncoil the intestine and fasten to one side to ex- 

 pose the spleen (a small red body near dorsal part of mesentery). 

 (3) The pancreas is also seen as a pale-colored compact mass in 

 the mesentery between the stomach, liver and small intestine. The 

 bile duct from the gall bladder passes through the pancreas to open 

 into the small intestine. (4) The oesophagus is a short straight 

 tube ; pass a probe from the mouth into the stomach. 



Make a drawing of your dissection to show all of these parts. 



4. URINO-GENITAL SYSTEM. (Preserved Specimen.) 



Remove the stomach, liver, mesentery and connected organs. 



(i) Posterior to the fat masses lie the reproductive glands, in 

 the male yellow oval testes; in the female, folded or lobed, yellow 

 ovaries (when the eggs are nearly ready for laying, each is 

 a large sphere, light on one side and dark on the other, and the 

 lobes of the ovary are so distended by great masses of ova as to 

 fill most of the body cavity). (2) Sexual ducts: in the male, each 

 testis sends numerous small thread-like ducts, vasa-efferentia, into 

 the kidney lying just posterior and dorsal to it. In the female the 

 oviduct is a long convoluted tube opening into the cloaca posteriorly 

 and passing forward on each side to open by a funnel into the body 



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