70 Anatomical Evidence 



fore-limb of a lizard, and yet we find that the bones, 

 muscles, nerves, and blood-vessels are fundamentally 

 the same. Similar material is, as it were, built into 

 different styles in different types. Experts on muscu- 

 lature tell us that in fishes, where the fore-limbs are 

 usually balancing fins, there are the fundamental 

 blocks of muscle that are found specialized in con- 

 nection with the fore-limbs of reptiles and higher 

 Vertebrates. The bird has a quite unique ankle-joint, 

 for after embryonic development the two rows of 

 ankle-bones (tarsal elements) are quite unrecogniz- 

 able. It is as different as possible from the ankle-joint 

 of, let us say, a crocodile, where there are as usual 

 two rows of ankle-bones. But when we work into the 

 development of the bird's ankle we find that it began 

 like a reptile's, and that it remains in spite of appear- 

 ances curiously like a reptile's, for it is an inter-tarsal 

 ankle-joint. The plane of movement is between the 

 proximal and the distal row of ankle-bones, though 

 no separate bones are left. This may seem a pedanti- 

 cally trivial matter, but it is a straw which shows very 

 clearly how the evolutionary wind has blown. The 

 mammal's ankle-joint has diverged on a line of its 

 own ; it is cruro-tarsal, not inter-tarsal. 



The anatomist also discloses one of Nature's ways, 

 so to speak, of making apparently novel things out of 

 what is very old. The beautiful three-linked chain of 

 little bones or ossicles by which the vibrations of the 

 drum are conveyed to the inner ear — why, it was once 

 part of the commonplace framework of the jaws. The 

 elephant's trunk is a long nose and a pulled-out por- 



