98 MAMMALIAN ANATOMY 



The neural canal increases very slightly in width and height from 

 the first to the last. 



The transverse processes are very short and straight in the first ; 

 then they increase in length and curvature. In the first three or 

 four vertebra? the end is cut off squarely ; in the rest it is narrowed to 

 a point. In the vertebra? near the tail, usually beginning with the 

 fifth, the caudal edge of the transverse process may present a decided 

 angle, and its dorsal surface may be more strongly marked by ridges 

 for muscular attachment. 



The accessory processes are probably the most trustworthy of all 

 the distinguishing characters. They are longest and strongest in the 

 first, and then regularly diminish, until they become rudimentary on 

 the sixth and disappear on the seventh. Sometimes they are rudi- 

 mentary on the fifth and wanting on the sixth. 



The mammillary processes likewise decrease in size in the same 

 order, but, as they are less prominent, the character is hardly as trust- 

 worthy. 



The spinous processes increase in length from the first to the last, 

 and increase in cephalo-caudal diameter to the fourth ; beyond this 

 they become more pointed. 



The articular processes present no important changes in form, but 

 the caudal articular processes of the seventh lumbar are so large and 

 so widely separated that they form a constant character for the recog- 

 nition of that vertebra. 



THE SACRAL VERTEBRA. 



The three vertebra? which follow the seventh lumbar (Fig. 70) are 

 known as the false vertebrae ; they have lost their individuality by 

 coalescence. The single bone thus formed, called the Sacrum, is joined 

 at parts of its lateral surfaces to the hip-bones, completing the pelvic 

 girdle, and forming part of the dorsal bony wall of the pelvis. 



That the sacrum is composed of three vertebra? is always apparent. 

 In young specimens they may be readily broken apart at the places 

 of coalescence, which even in old specimens are plainly visible. The 

 union of the vertebra? takes place at four points, and involves four 

 parts of the contiguous vertebra? : 



(1) The ends of the bodies are joined together by the ossification 

 of the intervertebral cartilages ; of course, by the union of the caudal 



