124 



HUMAN ANATOMY. 



as well as from the pedicle. The homologies of the costal elements are shown in 

 Fig. 158. 



The Spinous Processes. — These are short and bifid in the third, fourth, and 

 fifth cervical vertebrae ; longer and usually not forked in the sixth ; and longer, larger, 

 and knobbed in the seventh. The type is that of the last mentioned in the upper 

 thoracic, only the spine is a little longer, stronger, and more slanting. At about the 

 fourth a sudden change occurs : the process becomes longer, sharper, and more 

 descending. At about the tenth it shortens again, points more backward, and 

 approaches the lumbar type, which is generally reached in the last thoracic. The 

 spine of the last lumbar is usually much smaller than those above it. 



The Articular Processes. — The change from the cervical type to the thoracic 

 is gradual, but that from the thoracic to the lumbar occurs suddenly at the junction 

 of those regions. The inferior processes of the last thoracic face outward. Not infre- 

 quently the change occurs a space higher, but rarely one lower. Occasionally the 

 facets between the regions face in an intermediate direction. Sometimes the change 

 is normal on one side and not on the other. 



Superior articular process 



Fig. 152. 



Promontorv 



Transverse process 



Lines of union 

 between fused 

 sacral vertebrae 



Iliacus 



Anterior sacral 

 foramina 



Pyri/ormis 



Coccygeus 



Notch for fifth sacral nerve Apex 



The sacrum, anterior surface. 



THE SACRUM. 



• 



This bone ' is composed of five fused and modified vertebrae, of which the three 

 upper support the pelvis laterally. The vertebra; decrease very much in size from 

 above downward, the lower being bent strongly forward. The first vertebra is com- 

 paratively but little changed ; the last consists of little more than the body. The 



' Os sacrum. 



