176 DISEASES OF THE FEET. 



being consequently set up in the secreting membrane from undue 

 concussion. A " seated shoe " is a shoe which affords pressure only 

 to the wall of the hoof, and is made concave on its upper surface, 

 so as to take all pressure off the sole. The effects of fast work 

 on hard ground will aid in inducing the process of perverted 

 secretion. If these influences be kept up for some time, that por- 

 tion of the hoof, namely, the upper part, which has been secreted 

 under them, will be liable to split, and consequently to form a sand- 

 crack at any moment, which it will naturally do at the point which 

 receives the greatest amount of strain; that being, usually, the 

 inner quarter of the fore, and the toe of the hind foot. It some- 

 times occurs at the toe of the fore foot, when the hoof is very flat. 

 I have met with cases of sandcrack which were brought on by 

 indigestion, on account of the secreting membrane of the hoof par- 

 ticipating in the general derangement set up in the digestive 

 organs. Although the fissure occurs in a moment, the process 

 which induces the weak condition of horn is necessarily a slow one. 

 As far as I can judge, the horses most liable to sandcrack are cart 

 and cab horses which are worked on hard ground. It appears to 

 me that sandcrack as a rule occurs in two ways : (1) by concussion, 

 which is specially productive of sandcrack in the fore feet ; and (2) 

 by undue strain, as in the hind feet of cart horses which have to 

 drag heavy loads, especially when they are shod behind with toe- 

 pieces. 



SYMPTOMS. — The injury first begins by a small fissure close 

 to the coronet, and extends upwards, downwards, and inwards, as 

 the mischief is aggravated by concussion, or by strain. At first 

 the crack may be so short and narrow as to escape notice unless 

 closely examined. As long as it is confined to the exterior portion 

 of the wall, there will be no lameness ; but if it implicates the entire 

 thickness of the wall, the sensitive, underlying tissues will protrude 

 through the crack, and will get pinched and wounded as it opens 

 and shuts during movement, with the unavoidable result, when 

 work is prolonged, of making the animal lame, especially if the toe 

 of the hind foot is tJie seat of the injury. A rest may cause the 

 disappearance of the lameness, which will certainly return on the 

 resumption of work under previous conditions. In time, the fissure 

 may extend from the coronet to the ground, and may gape con- 

 siderably. The exposed sensitive tissues, owing to irritation and 

 putrefactive contamination, may discharge pus, which may or may 

 not be mixed with blood. This discharge may be more or less 

 frothy from the fact of the air which enters the crack, becoming 

 churned up with the discharge as the fissure opens and shuts at 

 each step. 



