THE FROG. 89 



each side and turn back the flaps so as to expose the 

 internal organs ; with forceps raise the hinder part of 

 the breastbone ; observe the heart lying next it, and a 

 thin membrane extending from it to the breastbone ; 

 with scissors cut this membrane close to the breast- 

 bone ; cut through the breastbone in the middle liue^ 

 and stretch its parts well out to the sides to dis< 

 close the heart and surrounding organs. Lay the 

 frog on its back; stretch the fore limbs out to their 

 fullest extent, and pin them down. 



'2. Insert the blowpipe into the mouth and inflate the 

 stomach. Study its shape. 



3. Trace the intestine from the stomach to the anus. 



4. An enlargement of the intestine near the anus is the 

 cloaca. 



.">. The thin membrane which attaches the intestine to 

 the back of the abdomen is the mesentery. In a 

 freshly killed specimen blood-vessels may be seen in 

 the mesentery. Trace these blood-vessels. 



6. The dark liver partly covers the stomach. 



7. Between the lobes of the liver is the greenish bile-sac. 



8. In the mesentery, near the stomach, is the pale pan- 

 creas. 



9. Further back in the mesentery is the small red spleen. 



10. If the previous inflation did not reveal the large 

 urinary bladder, insert the blowpipe into the anus, 

 and inflate the bladder through the cloaca. 



11. In the female, masses of dark, spherical eggs may be 

 seen. The eggs are in the ovary, which is very large 

 when full of eggs, and much folded and plaited. 



12. The egg-tube, or oviduct, is a long, coiled tube running 

 back to open into the cloaca. Cut a small hole in the 



