210 THE BIOLOGY OF THE ANIMAL 



terior end attached ? Posterior end? Is it solid 

 or hollow ? Note the prominent ridge. On what 

 part of the urostyle is it found? What is its 

 shape? Near the anterior end and on each side 

 find a small hole or foramen, through which 

 nerves enter the urostyle. Draw the urostyle as 

 seen from the side. 



Examine the anterior portion of the vertebral 

 column. Of how many segments or vertebrae 

 does it consist ? Are the vertebrae quite alike in 

 general appearance ? Examine a single vertebra, 

 e.g., the third or fourth, and note that it is a 

 bony ring which bears several projections or proc- 

 esses. The ventral portion of the ring is the 

 centrum or body. What is its shape as seen 

 sidewise? What is the shape of its ends? Is it 

 composed of dense or of spongy bone? On the 

 dorsal side of the centrum is the neural arch. 

 How is it formed ? What is its shape as seen 

 from the end? On the dorsal side of the arch 

 find a single projection, the spinous process. 

 What is its shape ? Length ? In which direction 

 does it point ? On each side of the neural arch 

 find a transverse process. How do these 

 processes compare in shape, size, and structure 

 with the spinous process ? In which direction do 

 they extend ? Why called " transverse " ? Are 

 they attached to any other bones ? Find also a 

 pair of anterior articular and a pair of poste- 

 rior articular processes. What is the position 

 of each pair? Compare in all respects with the 

 transverse processes. Why are they called "ar- 

 ticular " processes ? Do you find any ribs ? Draw 

 the vertebra as seen from the end, from the side, 



