122 DISEASES OF THE HORSE'S FOOT 



It is worthy of mention, however, that loss of the frog's 

 function does not operate to nearly so serious an extent in 

 horses with high, upright heels as in those with the heels 

 low and excessively sloping. 



In illustrating this, Mr. Dollar, in his work on shoeing, 

 mentions the case of a pair of trotting horses of similar 

 age, size, and weight, each having weak fore-heels. In 

 one case the hoofs were flat, in the other upright. The 

 horse with the flat hoofs suffered from contraction, while 

 the other did not. 



The reason appears to be that in the animal with upright 

 hoofs the proportion of body-weight borne by the heels is 

 considerably less than in those with the hoofs flat and 

 sloping. 



Certain conditions of the horn-producing membranes also 

 predispose to contraction. For example, in horses reared 

 on marshy soils, and afterwards transferred to standing in 

 town stables, we find that a dry and brittle condition of the 

 horn supervenes. This we may regard as a low form of 

 laminitis, brought about by the heat of the material upon 

 which the animal is standing, and the congestion of the 

 feet engendered by his enforced standing for long periods 

 in one position, as opposed to the more or less continuous 

 exercise when at pasture. With the hoof in this condition 

 it loses by evaporation the moisture that normally it 

 should contain, and, as we might expect, a certain degree 

 of contraction of its structure is the inevitable result. 



We thus see that contraction brought about in this way 

 is not so much caused by the heat of the stable, as it 

 is by the decreased ability of the horn to retain its own 

 moisture. 



On the other hand, it cannot be denied that excessive 

 warmth and dryness combined tend also to an undue 

 abstraction of moisture, even from the horn of the healthy 

 foot ; and this explains in great measure how it is that 

 lameness, as a rule, and especially that proceeding from 

 contracted heels, is far more frequent and of greater in- 

 tensity in the hot, dry months of summer, than in the 



