THE BONES OF THE TRUNK 



27 



foramina which correspond with the costo- transverse foramen in 

 cervical vertebrae. 



The lumbar transverse processes (costal elements) of man are serially- 

 homologous with the ribs, and also, in the case of the lower thoracic vertebrae, 

 with the external tubercles of the transverse processes. In the lumbar region 

 each transverse process (costal element) has fused with the accessory process 

 (true transverse process), and so the costo- transverse foramen in the transverse 

 process of a cervical vertebra is represented only by a few nutrient foramina. 



The neural foramen is larger than in the thoracic vertebrae, but 

 not so large as in the cervical, its shape being triangular with 

 rounded angles. 



The Fifth Lumbar Vertebra. — ^The distinctive characters of this 



Fig. 17. — The Fifth Lumbar Vertebra (Superior View), 



vertebra are as follows : (i) it is the most massive of all the lumbar . 

 vertebrae ; (2) the greater d^pth of the body in front is more con- 

 spicuous than in the others ; (3) the transverse processes are thick 

 and conical ; and (4) the inferior articular processes are wide 

 apart. 



The lumbar vertebrae receive their blood-supply from the lumbar 

 arteries. 



Ossification of the True Vertebrae. 



Each true vertebra ossifies in cartilage from three primary, and five secondary, 

 centres. One primary centre is for the principal part of the body, and two are 

 for the neural arch and its processes, including also a small portion of the body 

 at either side adjacent to the pedicle. The centres for the neural arch appear 



