LIMBS OF VERTEBRATES. 



375 



Fig. 372. Diagram of a Vertebra 

 with its Dody (5), rib (7), breast-bone 

 (6) ; 1, neural spine; 2, 3, fore and 

 hind oblique processes ; 4, transverse 

 processes. 



bodies of each vertebra of a lizard, bird or mammal being 



solid bone. Figs. 370 and 371 represent the relations of the 



notochord in an adult lamprey and a young fish. 

 The vertebra of a bony fish 



or higher vertebrate consists 



of a body, with a dorsal or 



neural spine ; a pair of oblique 



processes (zygapophyses) arching 



over and enclosing the spinal 



cord ; and transverse processes, 



bending downwards, to which 



the ribs are articulated ; certain 



of the thoracic ribs uniting 



with the sternum or breast-bone 



(Figs. 372 and 373). 



Vertebras like those of fishes, 



which are hollow or concave at 



each end, are said to be ampMccelous ; those hollow in front 



and convex behind procoelous, as in most toads and frogs 



and crocodiles, and most existing 

 lizards, and those convex in front 

 and concave behind opisthoccelous, 

 as in the garpike, some Amphib- 

 ians (the salamanders and cer- 

 tain toads, Pipa and Bombinator). 

 Vertebrates never have more 



Fig. 373. Thoracic vertebra of ,. 



buzzard (Buteo vulgaris). <; centrum than tWO pail'S OI limbs, ail ail- 

 or body ; g, superior spinous pro- . . , n . , . ,, 



cess ; tr, transverse process ; io, tenor and nmder pair ; the pecto- 



rib ; a, tuberculnm of the rib : /?. ca- . n /> i 



pituium of the rib.-After Gegen- 1 pair of fins of fishes represent 

 baur - the fore limbs of Amphibians and 



higher Vertebrates, and the arms of man ; the two ventral 

 fins represent the hind legs of higher Vertebrates, and the 

 legs of man. Each pair of limbs is connected by ligaments 

 and muscles to a girdle or set of bones, called respectively 

 the shoulder girdle and pelvic girdle, each girdle being con- 

 nected by muscles to the vertebral column. The shoulder 

 girdle consists of a clavicle (or collar-bone), scapula (or 

 shoulder-blade), and coracoid bone, usually a process of the 

 scapula. These bones differ greatly in the different classes, 



