404 



ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



ankle— in other words to the type of jointing actuall}^ characteristic of 

 the tetrapod hind-Hmb. We may take it that the hind-Hmb was the 

 more important in pushing the body forward and it is probably in 

 correlation with this that the fore-limb shows a simpler jointing— the 

 flexure in the wrist region being less marked than that in the ankle. 



The limb of the tetrapod is supported by a well-developed bony 

 skeleton which, while showing endless differences in detail, correlated 

 with variations in function, is arranged on a common general plan 



FORE-LIMB. 

 Scapula 



Pre-coracoid 

 Coracoid 



HIND-LIMB. 



Ulna 



\ ooo 



Metacarpals 



Fibula 



Tarsals 



Metatarsals 



Phalanges 

 Post-axial. 



Fig. 179. 

 Diagram of limb-skeleton of a Tetrapod. 



throughout the Tetrapoda. This common plan is shown diagrammatically 

 in Fig. 179. There is a general correspondence between the elements 

 that go to build up the skeleton of the pectoral and the pelvic limb 

 respectively although different sets of names have been allocated to 

 the individual elements as is indicated in Fig. 179. 



It should be mentioned that in describing the details of the tetrapod 

 limb it is customary to suppose the limb to be placed in a position 

 corresponding to that of the human arm when extended at right angles 

 to the long axis of the body, with the palm of the hand facing forwards. 

 The straight line passing outwards along the centre of the limb to the 



