92 INTRODUCTION TO ZOOLOGY. 



7. If your specimen is a female, find the ovary 

 with its mucli contorted oviduct leading to the cloaca. 



8. In many specimens you will find slender masses 

 of fat. These are the fat bodies. 



9. Find the kidneys, which are elongated dark 

 bodies near the hind part of the backbone. From the. 

 kidneys, trace tubes, the ureters, backward to the 

 urinary bladder. 



10. Notice the lungs. Trace the trachea from the 

 larynx to the lungs, observing the bronchial tubes. 



11. Notice the great size of the lung cells, and the 

 small number of them which constitute a lung. 



12. Find the heart. Find where the aorta divides 

 into two branches, the right and the left aorta. Find 

 the three principal branches into which each aorta 

 divides : the carotid, leading to the head ; the pulmo- 

 cutaneous, leading one part to the lungs and the other 

 to the skin ; and the aorta proper, which leads to the 

 rest of the Isody generally. 



13. Trace the right and left aorta until they come 

 together, forming the dorsal aorta. Continue until 

 you find the iliac arteries, which lead to tlie hind legs. 



14. Find the veins which bring the blood back to 

 the heart. 



15. How many cavities are there in the heart? 



16. Make a diagram of the frog's circulation. 



The Nervous System. 



1. Find all the nerves you can that run from the 

 spinal cord to the body cavity. 



2. Notice the brachial plexus, sending nerves to 

 the fore legs. 



3 . Notice the plexus of nerves going to the hind legs. 

 Trace the principal nerve (sciatic) as far as you can. 



4. Cut away the top of the skull, exposing the 

 brain. Identify the following parts : optic lobes, 



