[Illustration: FIG. 118.--SHOWING CHANGES IN THE OS PEDIS WITH LAMINITIS OF LONG STANDING, (_a_, Viewed from the front; _b_, viewed from the side.) The porous condition of the bone, which is here shown, is a result of a rarefying or rarefactive ostitis. This specimen also illustrated (what the photograph cannot show) an accompanying condition of condensation of bone, or osteoplastic ostitis. (For a fuller description of the changes occurring in these forms of ostitis, see Chapter XI.)] When the case is a serious one we have ample evidence to show that ostitis exists, and exists in a severe form. The bones become vastly altered in shape, a process of absorption leads to the formation of large, irregular cavities within their substance, and what of the bone is left is rendered hard and ivory-like (condensed) near what was the original centre, while the edges and other portions show often a tendency to become brittle and porous. Fig. 118 illustrates the effects of a severe ostitis in pedal bones removed from hoofs with laminitis of several weeks' standing. _(e) Chronic Laminitis_.--The most common complication--or, perhaps, rather we should term it 'sequel'--to acute laminitis is the chronic form of the disease. For this condition we have reserved a separate section of our work. It will be found described in Section B 1 of this chapter. _Diagnosis and Prognosis_.--One is almost tempted to state that the diagnosis of laminitis offers no difficulty. In the very early stages, however, it may, as we have already indicated, be mistaken for the oncoming of Enteritis, Lymphangitis, or even Pneumonia. The paddling of the feet may help us. If this is absent, however, nothing but a most careful examination, or, if necessary, the withholding of our opinion until the following visit will prevent a blunder being made. Even when well established, laminitis has been mistaken for paralysis, for tetanus, for rheumatic affections of the loins, or even for some undiscovered affection of the muscles of the arms and chest. This latter is no doubt suggested to the uninitiated by the reluctance the animal shows to move the muscles _apparently_ of that region, and led the older writers to give to the disease its name of 'Chest-founder.' It is only fair to add, however, that these blunders in diagnosis are nearly always committed by persons without a veterinary training. Thus warned, the veterinary surgeon of average ability should have no difficulty in establishing a distinction between the diseases we have enumerated as likely to be confounded with it, and the one this chapter is describing.