THE ENGLISH SPARROW. 231 



sternum. Study a typical vertebra from near the middle 

 of the cervical region. Note : 



1. Its relatively light centrum. 



2. Its wide, neural arch, notched before and behind, 

 with the neural spine small or absent. 



3. Its articular processes (zygapophyses). How do 

 these meet in adjacent vertebrae? 



4. The saddle-shaped, articular faces of the centrum. 



5. The wide, transverse processes at the sides of the 

 anterior end, each perforated at its base by a wide fora- 

 men, and produced posteriorly into a long, slender point. 

 This process is homologous with the ribs which arise in 

 the same position on the vertebrae farther back. 



The thoracic vertebrce are those which bear ribs articu- 

 lating with the sternum. Note the Y-shaped processes 

 uniting the tops of the neural spines of these vertebrae. 

 Observe on all the vertebrae the lateral notches opposite 

 the neural canal, for the exit of the spinal nerves. 



These thoracic ribs consist of two portions : 



1. A vertebral portion, flattened and curved, having two 

 articulating surfaces at its proximal end, a head which 

 articulates with the centrum of the vertebra, and a tuber- 

 cle which articulates with the transverse process, and 

 having a flattened uncinate process which projects back- 

 ward, overlapping the next succeeding rib. 



2. A sternal portion, slender and nearly straight, ex- 

 tending obliquely forward to articulate with the sternum. 



Of what advantage is the joint in the middle of the 

 rib ? The series of overlapping uncinate processes ? 



The sacral vertebrce succeed the thoracic, and are solidly 

 anchylosed, and support the bones of the pelvis. Observe 

 that the first three and the last four of these have their 

 lateral processes directed laterally, but in the intervening 

 three or four these processes are directed dorsally. 



The caudal vertebrce are the remaining free ones, with 



