698 OPERATIONS ON THE FOOT. 



synovia, and' a darker hue in the coloration of the trochlear carti- 

 lage with the corresponding face of the tendon, the synovia be- 

 coming reddish and thick, the surrounding cellular tissue becom- 

 ing, also, inflamed and infiltrated. At a later period, when the 

 disease has somewhat progressed, there is a thickening of the 

 walls of the capsule, which is then filled with a clear citrine ser- 

 osity. There is then, a kind of hygroma, a chronic dropsical con- 

 dition of the sheath. In the interior of this are also to be found 

 fibrous bands, running from the tendon to the bone. If the dis- 

 ease is older, erosions are found upon the diarthrodial surface 

 of the navicular varying in number and in size, and the tendon 

 is roughened on its anterior face with longitudinal fissures. At 

 times, it becomes atrophied and thin, dry and brittle; and has 

 been found, it is said, ruptured transversely. In many cases, the 

 cartilage covering the bone has disappeared and the bone is ex- 

 posed, hollowed and affected with osteoporosis. The union of the 

 bone with the tendon has also been found among the varieties of 

 determination. 



IV. Diagnosis. — This disease is at first easily mistaken for 

 some form of rheumatic affection. "Where pain is the main symp- 

 tom it is easily detected, but where there are no other signs of in- 

 flammation, it is just the lack of proportion between the intensity 

 of the lameness and the serious symptoms, such as the absence 

 of heat ; of special sensibility ; of pulsations in the digits, which 

 distiaguishes navicular disease from other affections of the feet. 

 The error with contracted heels is easier, as here the change of 

 form of the foot being primitive, at once attracts the attention of 

 the practitioner ; while this alteration in the foot is absent in 

 navicularthritiB at the outset of the disease. 



V. Prognosis. — Generally, it is unfavorable, as most com- 

 monly the veterinarian is called only when the disease has already 

 made serious progress and passed into the chronic stage ; and 

 again, because of the difficulty of reaching the disease by reason 

 of its peculiar location. 



VI. Etiology. — To properly understand the etiology of this 

 disease, one must bear in mind the part played by the anterior 

 legs in the action of locomotion. Columns of support more than 

 of impulsion, it is their office to sustain the weight of the body 

 when it is thrown forward by the extension of the hind legs. The 

 reaction of the ground is first felt at the shoulders, through the 



