THE FROG. 93 



which form the widest part of the brain ; cerebrum, 

 consisting of two elongated lobes in front of the optic 

 lobes ; olfactory lobes, very small, in front of the 

 cerebrum ; olfactory nerves, running under the ol- 

 factory lobes to the nostrils ; cerebellum, very small, 

 lying behind the optic lobes ; medulla oblongata, con- 

 tinuing into the spinal cord. 



5. Trace the optic nerves to the eyes. 



The Skeleton. 



1. Has the frog ribs? How many vertebrae has it? 



2. Notice the three long bones at the back of the 

 spinal column. The middle one is called the urostyle. 

 The bone on each side of it is called the ilium. What 

 makes the frog look humpbacked? 



3. Identify the bones of the fore leg and the 

 shoulder girdle. The bone in front, on the ventral 

 side, is the sternum. Of how many pieces is it 

 composed? 



4. The dorsal part of the girdle is composed of the 

 scapulae. The cartilaginous portion is called the 

 supra-scapula. Note the two coracoid bones, and 

 the two clavicles in front Of them, all extending from 

 the sternum to the scapula. 



5. The first bone in the arm is the humerus. The 

 next is the bone of the fore-arm, the radius. The bones 

 of the hand are the carpals, metacarpals, and phalanges. 



6. Study the bones of the hind leg. Identify the 

 femur, the tibia, the tarsal bones, the metatarsals, 

 and phalanges. 



7. Examine the skull. Is the lower jaw attached 

 directly to the skull? 



8. Observe the movement of the skull in nodding. 

 A rounded prominence on the skull, fitting into a con- 

 cavity of the first vertebra, is called a condyle. Do 

 you find one or two condyles ? 



