ELEMENTARY ANATOMY. 



[LESS. 



notochord, as in some Elasmobranchs, or to mere cartila- 

 ginous rudiments in its sheath. 



Sometimes (as in the first coccygeal vertebra of the croco- 

 dile) a vertebra may be bi-convex, or have a ball at each end ; 

 and very rarely two prominences or two hollows may exist 

 side by side on one surface of a centrum, as in some cervical 

 vertebras of Chelonians. 



The articulating processes (zygapophyses) are very con- 

 stant structures, and are substantially as in man, except that 



FIG. 49. LATERAL VIEW OF FOUR TRUNK-VERTEBRAE OF SIREN. 

 c, capitular process ; t, tubercular process ; i, interzygapophysial ridge. 



in fishes they cannot be said to articulate truly. A strong 

 interzygapophysial ridge may connect together the pre- and 



post-zygapophyses of each 

 side of a vertebra, as in 

 Siren. 



The transverse processes 

 are structures too complex 

 to be more than referred to 

 under this general heading. 

 The conditions exhibited by 

 them in man are such as 

 obtain generally, but by no 

 means universally, in Verte- 

 brates above fishes. Two 

 transverse processes may be 

 developed from each side of 

 the same vertebra and in 

 the same plane. This may 

 be seen in the posterior coc- 

 cygeal vertebras of Apes and 

 other Mammals, and at least 

 occasionally in some verte- 

 bras of Polypterus. 

 The spinous processes of man are less developed than in the 

 Vertebrata generally. They are, however, considerably more so 



FIG. 50. UPPER SURFACE OF TWELFTH 

 CAUDAL VERTEBRA OF LEOPARD, . 



in, metapophyses ; p, processes serially 

 continuous with those which support 

 the posterior zygapophyses in the an- 

 terior vertebra ; t, transverse processes ; 

 t', anterior transverse process. 

 (From Prof. Flower's '''Osteology.") 



