ANGLE OF THE FETLOCK. 33 



I always endeavour to show how man's inven- 

 tions, especially in practical mechanics, have their 

 prototypes in nature. If the reader will compare the 

 accompanying illustration with the fetlock of the 

 horse on page 15, he will see that the angle of the 

 connecting piece (marked a'} is almost identical with 

 that of the fetlock. 



But something more than the mere arrangement 

 of the bones is required. The portion of the hoof 

 which comes first to the ground at each step must 

 be elastic, and this requirement brings us to one of 



SIDE BEARING OF RAILWAY CARRIAGE. 



the most important portions of the horse's hoof, it 

 being the chief source of elasticity. This is the FROG, 

 so called because when untouched by the knife it 

 really bears some resemblance to a crouching frog. 



It occupies the centre of the lower surface of the 

 hoof, and, as the reader may see from the accompany- 

 ing illustration, looks something like the letter Y. 

 The rounded portions at the ends of the bars are 

 called the ' glumes,' or heels of the frog. 



When the hoof is left in its natural form, the 

 frog fills up a considerable portion of the hoof. It 



D 



