122 



HUMAN ANATOMY. 



The fifth lumbar vertebra is much higher in front than behind. The trans- 

 verse process is broad at the base, springing in part from the body ; the spme is 

 relatively small. 



DIMENSIONS OF VERTEBR.^. 



(The measurements are given in centimetres.) 



GRADUAL CHANGES FROM ONE REGION TO ANOTHER. 



Bodies. — The height of the bodies increases as we descend the spine, very 

 gradually in each region but rather rapidly at the junction of two regions, as shown 

 in the table. The first two lumbars, like those above them, are rather deeper behind 

 than in front, but the reverse is true of the last two, and especially of the fifth, in 

 which the difference is considerable. The breadth of the bodies increases to the 

 first or second thoracic, then dwindles to the fourth or fifth, and then again increases 

 to the sacrum. The elevation at the sides of the upper surfaces of the bodies of the 

 cervical vertebrae diminishes in the lower part of that region ; in the seventh it is 

 limited to near the root of the pedicle. The same condition is found in the first 

 thoracic vertebra and to a slight extent in the next two. The downward prolonga- 

 tion of the front of the body of a cervical vertebra is slight in the lower part of the 

 neck. The first thoracic has an entire facet for the head of the first rib near the top 

 of the body and a part of one at the lower border for a portion of the head of the 

 second. As a rule, in the thoracic region the head of each rib rests in a facet on 

 two vertebrae and the intervening disk, the lower vertebra contributing more of the 

 joii|^ than the upper, and corresponding with the rib in name. Thus, the head 

 of the fourth rib hes between the third and fourth thoracic vertebrae, and its tubercle 

 rests on the transverse process of the fourth. Towards the lower part of the region 

 the heads have a tendency to take a lower relative position on the column coinci- 

 dently with the increase in size of the bodies. The head of the tenth rib usually 

 rests wholly on the body of the tenth vertebra or on it and the disk above, conse- 



^ Journal of Anatomy and Physiolog>\ vol. xvii., 1883. Anderson states that the vertical 

 diameters of the front and back of the cervical vertebrae are generally the same ; hence, prob- 

 ably, he thought it needless to give the posterior measurements. The close correspondence of 

 his anterior measurements with those of the author is very striking. 



