KNBB, FBTtOCK, ANKLK, ANB FOOT. 219 



vicular as the force of the contracting muscles lifts the tendon into place. 

 It is self-evident, then, that the more rapid the pace and the greater the 

 load, the greater must these contending forces be, and the greater the 

 liability to injury. For the same reason horses with excessive knee 

 action are more likely to suffer from this disease than others, concussion 

 of the foot and intense pressure on the tendon being common attendants 

 upon their usage. 



Besides these exciting causes must be considered those which predis- 

 pose to the disease. Most prominent among these is heredity. It may 

 be claimed, however, that an inherited predisposition to navicular disease 

 consists not so much in a special susceptibility of the tissues which are 

 involved in the process as in a vice of conformation which, as is well 

 known, is likely to be transmitted from parent to offspring. The faults 

 of conformation most likely to be followed by the development of navic- 

 ular disease are an insufficient plantar cushion, a small frog, high heels, 

 excessive knee action, and contracted heels. Finally, the environments 

 of domestication and use, such as dry stables, heavy pulling, bad shoe- 

 ing, punctured wounds, etc. , all have their influence in developing this 

 disease. 



Symptoms. In the early stages of navicular disease the symptoms 

 are generally very obscure. When the disease begins in inflammation 

 of the navicular bone the animal points the affected foot while at rest, 

 a time before any lameness is seen. While at work he apparently travels 

 as well as ever, but when placed in the stable one foot is set out in front 

 of the other, resting on the toe, with fetlock and knee fixed. After a 

 time, if the case is closely watched, the animal takes a few lam-e steps 

 while at work, but the lameness disappears as suddenly as it came and 

 the driver doubts if the animal was really lame at all. Later on the 

 patient has a lame spell which may last during a greater part of the 

 day, but the next morning it is gone; he leaves the stable all right, but 

 goes lame again during the day. In time he has a severe attack of 

 lameness, which may last for a week or more, when a remission takes 

 place and it may be weeks or months before another attack supervenes. 

 Finally, he becomes constantly lame, and the more he is used the greater 

 the lameness. 



In the lameness from navicular disease the affected leg always takes 

 a short step, and the toe of the foot first strikes the ground, so that the 

 shoe is most worn at this point. If the patient is made to move back- 

 wards the foot is set down with exceeding great care, and the weight 



