DISEASES. 645 



faces assume a perpendicular direction ; its structure is modified ; 

 its substance becomes more compact, and the small vascular open- 

 ings are obliterated, while the largest are increased in size. The 

 work of obliteration is specially observable at the patilobe emi- 

 nences, which appear to be crushed. The lateral cartilages are 

 also much compressed, condensed and modified in their struc- 

 ture. 



The navicular bone is also compressed, the sheath and its sup- 

 port not allowing the easy play of the tendons, and it is in this 

 way that navicular disease may follow hoof-bound. But there 

 is a specially noticeable modification in the keratogenous appara- 

 tus, which, as a consequence of the arterial obliterations, fails to 

 receive freely and actively the necessary amount of blood. The 

 horny secretion proper to the podophyllous tissue, the white or 

 soft horn, is reduced; the podophyllous tissue itself is atro- 

 phied ; its lamellae are less prominent and their separations are 

 diminished in dej^th ; the adherence of the podophyllous or kera- 

 phyllous tissues still exists where the circulation of the blood is 

 not interrupted, but beyond, they are easily separated and often 

 present deep excavations toward the sole. 



If hoof-bound advances slowly, the same atrophy of the sub- 

 horny tissues takes place. Then, however, it proceeds by degrees, 

 the tissues accommodating themselves in size to the gradually 

 diminishing dimensions of the cavity where they are contained, 

 and there is an equal proportion between the size of the hoof and 

 the volume of the tissues enclosed in it. These being less com- 

 pressed, there is less pain. In this manner an excessive contrac- 

 tion of the heels may sometim.es exist without marked lameness. 



IV. Prognosis. — This is the more serious as the disease is 

 more developed. Total hoof-bound if excessively tenacious, and 

 resists the best curative measures, though if there is only a slight 

 contraction at the heels, it is generally amenable to judicious 

 treatment. The duration of the disease is an important factor in 

 the question of the success of the treatment, as the condition of 

 the OS coronae, os pedis, navicular bone, sesamoid sheath, plantar 

 cushion and the atrophy of the keratogenous membranes have all 

 to be taken into consideration. 



The age of the diseased animal and any existing complications 

 are, of course, circumstances which influence the prognosis in an 

 important degree. 



