USES OF THE FROG. 67 



In the first place it is soft and yielding, so as to 

 take off the jar which would ensue if the horse trod 

 first upon the wall. 



In the next place, it communicates the pressure 

 through the sole to the walls, so as to enable the 

 hoof to expand and contract laterally. 



Lieutenant Douglas, in his valuable work on 

 horseshoeing, is very emphatic on this point : — 



' A little reflection on this important subject will 

 show how very important frog-pressure is, as, even 

 when the horse is resting as he stands in the stall, 

 some portion of his weight must fall from the lower 

 pastern bone upon the navicular bone, which rests 

 upon the back sinew, which in its turn should receive 

 support from the sensitive and insensitive parts of 

 the frog underneath it. 



* How much more then must this necessary sup- 

 port be needed when the animal is in motion, espe- 

 cially if at a fast gallop, or landing on hard ground 

 after being leaped over a hedge. If the frog is there 

 to receive the shock, the horse lands on his feet with 

 all the ease and comfort that a cat does upon hers 

 after a jump ; but when the frog has been cut away 

 there is nothing to break the fall, and, as is often 

 the case, the animal is ruined by the jar having 

 brought on irritation of the sheath which covers the 

 back sinew, and inflammation sets in. 



v 2 



