CEACKED HEELS. 155 



diminishes its strength by separating the layers which compose it, one from 

 another, and deprives it of the oil which renders it soft and pliable. When 

 the epithelium dries after having been thus treated, it is liable to crack, and 

 thus to expose the true skin to irritation from dirt and grit, and from im- 

 purities contained in the surrounding air or in the water which may gain access 

 to the part. The action of Avater in weakening the protective influence of the 

 epidermis by dissolving out the oil previously contained in it, is well shown by 

 the fact that washing a horse's feet with warm water is much more liable to 

 give cracked heels than washing them with cold water ; the former being the 

 better means of the two for removing the oil, and for softening the epithelium. 

 Besides, if the water of a country contains much mineral matter (such as salts 

 of lime) which has a tendency to increase the power water possesses to remove 

 oil from the skin, we shall find that horses in such a district are peculiarly 

 liable to cracked heels. Water containing such mineral matter would, with 

 a weakened epidermis, probably have a directly irritating effect on the true 

 skin. The foregoing remarks have been made with special reference to cracked 

 heels. The role of infection in the production of grease is, as I have already 

 indicated, an open question. 



The moisture and accumulated filth, as well as the ammonia to 

 be found in unsanitary stables, play a large part in the production 

 of cracked heels and grease. Dew taken up by the feet from the 

 ground over which animals travel, and sweat running down and 

 drying on the pasterns, especially if there be a cold wind blowing 

 at the time, often cause cracked heels in horses which are subject 

 to these influences, as w^e may see in the cases of race horses that 

 are worked in the early mornings. Other things being equal, 

 horses which do their work at fast paces, are more likely to get 

 their heels chapped, than are those whose work is slow ; for the 

 skin that covers their pasterns is subject to more violent and rapid 

 flexion and extension than that of slow going animals, and will 

 proportionately suffer from any derangement of the lubricating 

 apparatus, which, here, is the oil glands of the skin. The feeding 

 of horses on unwholesome oats appears to have a predisposing 

 influence in the production of cracked heels. 



As a rule, white pasterns are more liable to suffer from cracked 

 heels, especially among " pleasure horses," than dark-coloured ones ; 

 because dirt and stains show more prominently on them, and con- 

 sequently they get oftener washed, and have soajD and other alkaline 

 preparations more frequently applied to them, Grease is much 

 more common among Shires, than among light horses. Experience 

 tells us that cold has a well-marked effect in producing this disease. 

 We knew from experiment that if blood, after having been expelled 

 from the blood-vessels and kept out of them for some time, be 

 allowed to return to the vessels, it will act as an irritant to their 

 walls, and will set up inflammation. This appears to be the mode 

 in which cold produces inflammation of the skin of the pastern ; 

 for it renders the part bloodless for the time being. 



Want of exercise, no doubt, has a strong predisposing influence 



