342 DISEASES OF THE FEET. 



avoids elevating it to any extent, from an instinctive know- 

 ledge that the concussive shock would be materially increased 

 when (after such elevation) it is again brought to the ground. 

 In addition to shortness of step and rigidity of movement, the 

 wear of the shoes is characteristic. They are worn at the toes ; 

 the patient avoids bringing his heels down, and he digs his toes 

 into the ground. Wlien the animal is lame in one foot only, this 

 peculiar appearance of the shoe is of great assistance to correct 

 diagnosis. 



Professor Dick says that "the S5rrnptoms of the early, and, 

 in a practical point of view, the most important stage of the 

 disease, are a peculiar shifting of the feet, and a shortness of 

 the step ; while a degree of heat is found in the foot, more 

 especially about the heel and coronet. There is a continual 

 pointing or holding of the foot in a relaxed position, dryness 

 of the hoof, throbbing of the plantar arteries (?) and pain on 

 pressure in the hollow of the pastern. The other parts of the 

 limbs are clean and fine ; there is general tenderness of the foot 

 on pressure, with tripping and stumbling ; and finally, the foot is 

 contracted." 



Contraction of the foot always succeeds navicular disease, and 

 in some instances the atrophy is not confined to the foot, but 

 extends to the muscles of the shoulders and fore arm. Tliis 

 wasting has, however, no further connection with the disease 

 than that it results from diminished function, due to limited 

 action, as already explained. 



Pathology. — The parts involved are the navicular bone, the 

 articular cartilage, the synovial membrane of the bursa, and 

 the tendon of the flexor pedis perforans. The inflammation 

 is first limited to the cancelli of the bone, or the cartilage, as 

 illustrated by the following plates. 



The tendon passes under the bone, as a rope under a pulley, 

 their surfaces being in a more complete co-adaptation from the 

 circumstance of the bone having a process or eminence across 

 its middle, to which the tendon is fitted by a corresponding 

 hollow in its substance. As a rule, it is the crest of the 

 bone that shows the earliest signs of caries ; whilst calcifica- 

 tion of the cartilage is usually seen upon either side. Inflam- 

 mation having been set up in the vascular cancellated structure 

 of the bone, the progress of that inflammation may lead to a 



