230 DISEASES OF THE HORSE’S FOOT 
opposite foot, and may happen in a variety of ways. More 
often than nof it is met with in the feet of heavy draught 
animals, and is there caused by the calkin, either when 
being violently backed or suddenly turned round. It may 
also occur in horses with itchy legs, as a result of the 
animal rubbing the leg with the shoe of the opposite limb. 
The irritation in this case is nearly always due to parasitic 
infection (Symbiotes equi), and becomes sometimes so 
unbearable as to render the animal unmindful of the injury 
he may be inflicting so long as he experiences the relief 
obtained by the rubbing. 
Self-inflicted tread is also sometimes met with when 
horses are worked abreast at plough. The animal in the 
furrow, with one foot sometimes in and sometimes out of 
the hollow, is caused to make a false step, and so brings 
the injury about. 
Animals worked in pairs are further liable to receive a 
tread from the foot of their companion. This is commonly 
seen in heavy animals at agricultural labour in fields, 
where the walking is uneven, and abrupt turning constant. 
It is not uncommon either in animals at work in vans in 
town, and is occasionally met with in the feet of carriage- 
horses. 
‘Overreach ’ is the term used to indicate the injury in- 
flicted on the coronary portion of the heel of the fore-foot 
by the shoe of the hind. Ordinarily, overreach occurs 
when the animal is at a gallop, and is thus met with in its 
severest form in hunters and steeplechasers. It can only 
occur when the fore-foot is raised from the ground and the 
hind-foot of the same side reached right forward. When 
the feet separate the injury takes place. In its move- 
ment backwards the inner border of the shoe of the hind- 
foot catches the coronet of the fore, and tears it back- 
wards with it. Quite frequently a portion of the skin is 
removed entirely, but often it hangs as a triangular flap. 
The flap in such a case is always attached by its hindermost 
edge, and indicates plainly enough that the direction of the 
Llow that cut it must have been from before backwards. 
