86 MAMMALIAN ANATOMY 



distinguished from the preceding and from all the others by its much 

 greater maximum cephalo-caudal length, Avhich exceeds by a fourth, 

 at least, its maximum dorso-ventral height. This increased length is 

 due partly to the increase in the length of the body, but mainly to 

 the greater cephalo-caudal length of the entire arch, and especially to 

 the prolongation toward the tail of the caudal articular processes 

 beyond the accessory processes. 



The processes arising from the neural arch are all stouter. The 

 spinous process is shorter, and has a greater inclination toward the 

 head. The caudal inter vertebral notch is larger. 



RECAPITULATION OF CHARACTERS OF THORACIC VERTEBRA. 



The vertebra with the greatest dorso-ventral height is the second, 

 from which the others decrease in the following order : the first ; then 

 from the third to the tenth, inclusive ; then the thirteenth, the twelfth, 

 and the eleventh. In transverse width they decrease from the first 

 toward the tail. The eighth has the greatest total cephalo-caudal 

 length and the first the least. 



The bodies do not vary much in size nor in shape, but the body 

 of the sixth is slightly smaller than that of any other. With this 

 exception, their cephalo-caudal diameters remain the same as far as 

 the ninth, from which point this diameter gradually, but slightly, 

 increases. 



The transverse diameters are scarcely greater in the vertebras 

 nearest the tail than in those nearest the head. The dorso-ventral 

 diameters in the first three or four vertebrae, however, are less than in 

 those which succeed them. The ventral surface of the first three and 

 the last two or three is less convex from side to side. The sides have 

 cephalic and caudal half-facets for the ribs in all except the eleventh, 

 twelfth, and thirteenth, which have single, complete cephalic facets. 

 The cephalic facet of the first vertebra is almost complete. 



The neural arches, and therefore the neural canals, are highest in 

 the first three vertebras. They are longest, in the cephalo-caudal line, 

 in the twelfth and thirteenth. They are widest in the first two 

 vertebrae and narrowest in the middle vertebras. The pedicles in- 

 crease in cephalo-caudal diameter from the first to the last, 



The transverse processes are present in the first ten. Their 

 origin on the arch gradually assumes a more dorsal position from the 



