THE FROG. 37 



lobe? Behind the optic nerves is a small projection, the 

 pituitary body. How many nerves can you find arising 

 from the side of the medulla? 



With a sharp scalpel split the brain horizontally and 

 examine the cavities found. Are they all connected? 

 The larger cavities are called ventricles. Those in the 

 hemispheres are the first and second, that in the 'twixt- 

 brain the third, and that in the medulla the fourth. Are 

 there ventricles in the optic lobes? Draw the brain, show- 

 ing all cavities and connections found. 



In the prepared skeleton how many elements (vertebra?) 

 do you find in the back-bone? Can you find neural and 

 haemal arches (p. 27)? On either side of each vertebra 

 find a transverse process. How do these compare with 

 the ribs of a fish (p. 28)? Are they the same? Give the 

 reasons for your conclusion. Notice the long bone (uro- 

 style *) terminating the vertebral column. Connecting 

 the hind limbs with the back-bone is the pelvic arch. Is 

 it a true girdle? With what part of the vertebral column 

 does it join? Connected with the fore limbs is the shoulder- 

 girdle. Does it join the vertebral column? 



Extending along the median line below, in connection 

 with the shoulder-girdle is the breast-bone, or sternum. 

 How many parts in it? Are all equally hard? The part 

 extending in front of the girdle is the omosternum, the 

 xiphisternum projects behind. Connecting the breast-bone 

 with the shoulder are two bones on either side; the ante- 

 rior is the clavicle, the posterior the coracoid. Extending 

 dorsally from the shoulder-joint is the shoulder-blade 

 (scapula), and above it the supra-scapula (partly cartilage). 

 At the junction of coracoid and scapula is the glenoid 



* This is composed of the coalesced caudal vertebrae of the tad- 

 pole. 



