(c) Gangrene of the Structures within the Hoof. - This complication is the one most to be dreaded. It occurs as a result of the great pressure exerted by an excessive exudation, and doubtless affects first the laminae and softer structures. Once commenced, however, it rapidly extends to death of the other structures (ligament, tendon, and even bone), and gives a fatal ending to the case.
That gangrene of the tissues ("mortification" as our older writers called it) has occurred is soon made evident to the veterinarian by the symptoms shown by the patient. The agonizingly acute pains suddenly subside, the feet are placed firmly and squarely to the ground, and the animal walks with ease. Perhaps but the night before the patient is seen racked with excruciating pain; the morning sees the astounding change of apparent absolute recovery. Too well, however, the eye of the experienced veterinary surgeon sees that such is not the case. Even before proceeding to take a record of the other symptoms, he knows that it is but the commencement of the end. Methodically, however, he notes the other conditions. The pulse he finds small and imperceptible, save at the radial. The thermometer registers a subnormal temperature, the extremities are cold, and cold sweats bedew the body. To the same experienced eye the countenance of the animal is almost suggestive of what has occurred. The drawn and haggard expression, to which we have previously referred, becomes more marked, and the angles of the lips are drawn back in what has been described by some writers as a 'sardonic' grin.
We can best express what the whole look of the animal's countenance indicates to us by saying that it gives us the impression that the animal himself knows that some serious change, and a change fatally inimical to his chances of life, has taken place in his feet.
It may be that in some odd cases, although it has not yet been our lot to meet with them, gangrene may terminate in the casting off of one or more hoofs. Needless to say, there can still be but one termination to the case.
(d) Periostitis and Ostitis. - This complication is referred to by other writers under the term of 'Peditis.' It signifies, of course, that the periosteum and the bone have become invaded by the inflammatory process. It is our opinion that these two conditions, even including an actual arthritis, always exist, even in an attack of laminitis that ends favourably. We do not claim, however, to be able to relate any means, save that of post-mortem examination, by which it may be singled out from the other changes occurring in the foot. The high fever and pain occasioned by the inroads of the inflammation into the other sensitive structures serves to effectually mask whatever evidence of it we might otherwise obtain. It may be sometimes only small in degree, but we feel confident that inflammation, at any rate of the outer layer of the periosteum, is in laminitis constant even, we repeat, in a mild case.
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 (Diseases Of The Bones. A. Periostitis And Ostitis).)
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.
The prognosis in laminitis should, in our opinion, always be guarded. No advice given in a work of this description can be of any real use, for every case must be judged entirely on its merits. The severity of the symptoms, the cause of the attack, the complications, and the idiosyncrasies of the patient, have all to be taken into account. These the veterinarian must be left to judge for himself.