192 ANDREW JACKSON HOWE. 



loses its function. This looks as if vital activities 

 were intelligent enough to be compensating in the dis- 

 play of economics. All birds that are excellent swim- 

 mers make a wretched appearance while walking on 

 land. The bat which flies quite easily can scarcely 

 crawl when upon its fettered feet. The transforming 

 processes that give a horse length of limb, and raise 

 the creature upon the end of a single digit for each foot, 

 have not given the animal perfect legs, but have al- 

 lowed splint bones to remain alongside the shank or 

 cannon bone. This defect in fashioning the mechan- 

 ism of the horse's fore-leg often proves serious. The 

 rudimentary metacarpal bone, called by farriers a 

 " splint," is so nearly independent that it sometimes 

 becomes detached or loosened, and then the animal 

 gets lame, the creature has a splint in the leg! All 

 horses have splints or splint-bones in the fore-legs, but 

 only occasionally does lameness spring from a loosen- 

 ing of the undeveloped metacarpal. Cows and camels 

 have the merest signs of splint-bones, and are, there- 

 fore, exempt from the splint lameness peculiar to the 

 horse. 



The Italian mole, which rarely if ever comes to 

 the light of day, has an eye-mark in the skin, but no 

 eye that can see. A retrograde action, caused by the 

 withdrawal of light, at length made the animal blind. 

 The creature has a rudimentary optic apparatus which 

 indicates that its progenitors were not eyeless, and 

 perhaps not blind. A similar remark may be made in 

 regard to cave fishes which are blind. Living in the 

 dark, generation after generation, allowed the eye de- 

 veloping part of the creature to retrograde. To com- 

 pensate for this loss of sight the cave dweller had the 

 rays of its fins lengthened and ivudeivd more scnsi- 



