Vertebral Column 



27 



Transverse processes strong, directed backwards and outwards, with somewhat 

 clubbed extremities carrying a costal facet, for the tubercle of the rib, on their front 

 aspects. 



Articular processes have joint surfaces in a nearly vertical plane, but looking very 

 slightly outwards as well as backwards in the upper pair, and in the opposite direction 

 in the lower pair. 



Spinous processes long and directed obliquely downwards, ending in a slightly 

 marked tubercle. 



Spinal foramen more or less circular and small, the canal being well covered behind 

 by the overlapping of the broad laminae and spines. 



At the ends of the series the vertebrae become modified, and the ribs, which 

 typically articulate by their heads with the bodies of two vertebras and the intervening 

 disc, show a tendency to confine their articulation to one vertebra. |These changes 

 enable certain of the segments to be recognised fairly easily and certainly. 



FIG. 23. First dorsal (right) contrasted with typical dorsal (left) to show their 

 characters, which have been somewhat exaggerated. 



The FIRST DORSAL VERTEBRA is like the last cervical in its general shape^but 

 possesses no foramen in its transverse process, and this, with the presence of the costal 

 facets, marks it at once as dorsal. The facets are in the form of one more or less 

 complete on the upper part of each side of the body, with a small part of a second facet 

 below, and one on the transverse process (Fig. 23). 



The upper surface of the body is concave from side to side like the cervical bodies. 



The upper intervertebral notches are deep, and the articular surfaces behind are 

 slightly more oblique than in the usual dorsal type and do not face at all outwards. 



The thick spine is longer than that of the last cervical, but otherwise rather like it, 

 and is directed almost horizontally. 



The spinal foramen is more of the cervical shape, and is somewhat larger than the 

 typical dorsal foramen, because it contains the terminal part of the cervical enlargement 

 of the cord. 



In the lower end of the series the modification of the costal articulations is marked, 

 in conjunction with other changes associated mostly with the decrease in the develop- 

 ment of the ribs carried by the vertebrae. 



