C 35 3 



has been maintained, that the frog cannot be 

 brought too much against the ground; and the 

 heels of the shoe have been accordingly thinned, 

 to allow of this taking place at every step. 



In practical matters which admit of much 

 theory, it is no unusual circumstance to find, 

 that a system, which for a time was considered 

 excellent, shall all at once lose its ground, and 

 be displaced by another, the very reverse, both as 

 to principle and effect. And on a mature con- 

 sideration of the subject, the best and simplest 

 practice has been found frequently to lie between 

 the two opposite systems. 



Now it must be remembered, that the frog has 

 several offices to perform ; among which, that of 

 breaking tlie force of the blow when the foot 

 strikes violently against the ground, is one of the 

 most important. And for the due performance 

 of this function, its flexibility and spongy nature 

 are most admirably calculated. But if, for want 

 of pressure and cleanliness, the frog becomes 

 very soft and ulcerated, it no longer is able to de- 

 fend the sensible parts immediately above it, from 

 being wounded and bruised . 



And as on the other hand, from being exposed 

 to too much pressure, it is found to acquire a de- 

 gree of hardness, nearly equal to that of anv other 



