Metazoa Rana. 



299 



The skeleton, looked at as a whole, consists of an axial 

 vertebral column terminated anteriorly by the skull, and 

 having attached to it two girdles, each bearing a pair of 

 appendages, which constitute the appendicular skeleton. It 

 will be advisable to compare the skeleton of the allied sala- 

 mander with that of the frog, since the skeleton of the latter 

 deviates considerably from the typical condition. 



FIG. ifo. TRANSVERSE SECTION OF TYPICAL LONG BONE (HUMERUS) (Quain.) 



The section shows three Haversian canals, with three concentric rings of 

 lacuna;, from each of which spring a number of canaliculi. 



The axial vertebral column is composed of a series of 

 vertebras articulated to each other, and all more or less re- 

 sembling each other. A typical vertebra, say from the 

 middle of the back, consists of a short cylindrical body 

 (centrum), from the dorsal side of which an arch arises, the 

 apex of the arch being prolonged upwards as a spinous 

 process. The arches of the successive vertebrae, when 

 placed together, thus form a canal in wfiich lies the spinal 



