_Definition_.--Chronic inflammatory changes occurring in connection with the navicular bursa, affecting variously the bursa itself, the perforans tendon, or the navicular bone, and characterized by changes in the form of the hoof and persisting lameness. The disease is commonly noticed in thoroughbreds or in horses of the lighter breeds, and is but seldom observed in heavy cart animals. Usually it is met with in one or both fore-feet. Although of extremely rare occurrence, it has been noticed in the hind. _History_.--To English veterinarians appears to belong the credit of discovering navicular disease. As early as 1752 we find one, Jeremiah Bridges, in 'No Foot, No Horse,' drawing attention to 'coffin-joint lameness,' and advocating for its treatment setoning of the frog. It appears, too, that Moorcroft, prior to his departure for India in 1808, was acquainted with what was then known as coffin-joint[A] lameness, having drawn attention to it in 1804 in a letter to Sir Edward Codrington.[B] In 1819 Moorcroft made it even plainer still that he was fully acquainted with what we now know as navicular disease. This we learn from a letter written by him to Sewell, in which he laid claim to being the originator of neurectomy. In this letter he says: [Footnote A: The coffin-joint at this time included the navicular bursa.] [Footnote B: Percival's 'Hippopathology,' vol. iv., p. 132.] 'On dissecting feet affected with these lamenesses, the flexor tendon was now and then observed to have been broken, partially or entirely, but more commonly to have been bruised and inflamed in its course under the navicular or shuttle bone, or at its insertion into the bone of the foot. Sometimes, although seldom, the navicular bone itself has been found to have been fractured; at others its surface has been deprived of its usual coating, and studded with projecting points or ridges of new growth, or exhibiting superficial excavations more or less extensive.'[A] [Footnote A: _Ibid_.]