Definition. - The term 'laminitis' is used to indicate a spontaneous and diffuse inflammation of the whole of the sensitive structures of the foot, more particularly the sensitive laminae. Usually it occurs in the two front feet, often in all four, and occasionally in the hind alone.

Causes. - In dealing with the causes of laminitis, we will first dispose of those coming under the heading of traumatic. Correctly speaking, however, lesions of the laminae thus occurring do not present the same symptoms, nor run an identical course with the disease we now purpose describing, and for which we would prefer to entirely reserve the term 'laminitis.' The fact, however, that traumatic causes are detailed in other works on the same subject compels us to give them mention here.

Strictly traumatic causes giving rise to a limited inflammation of the sensitive laminae are violent blows upon the foot, either purely accidental, or self-inflicted by violent kicking.

A similar limited laminitis is to be found in the conditions we have described under 'Nail-bound and Punctured Foot.' It is met with also in the injuries resulting from tread and overreach, and in the tissue-changes accompanying corn.

The tenderness following upon excessive hammering in the forge, or of too long an application of the shoe in hot-fitting has also been described as laminitis.

With either of the conditions we have mentioned, it goes without saying that there is either a simple congestion or an actual inflammation, localized or general, of the laminae of the injured foot. In neither case, however, can the resulting mischief be closely compared with the lesions attending an attack of laminitis proper, a disease which appears to have an almost specific cause, and to run a course peculiarly its own.

The specific cause we have indicated as existing can, in the present state of our knowledge, be only vaguely described as a poisoned state of the blood-stream. This, as clinical evidence teaches us, may result from a variety of causes.

Among these, by far the most common is that state of the circulation induced by excessive feeding with too stimulating or too irritating a diet. In any case, where the use of old oats as a staple diet is departed from, and where the quantity and manner of using the substitute is left to the discretion of careless or unskilled attendants, trouble is likely to ensue. The food more prone, perhaps, than any other to bring about an attack is wheat improperly prepared - that is, uncooked or unground. So much so is this the case that one full meal of this provender to an animal unused to it is sufficient to lead to a train of symptoms often ending fatally.

Beans, peas, barley, rye, new maize, or even new oats, are all liable, if carelessly used, to have the same effect.

It is the laminitis following feeding on new oats that has caused us to apply to the food the adjective 'irritating.' Here, more often than not, the peristaltic action of the bowels is found to be abnormally in evidence, and the excessive use of the diet is always accompanied by a more or less fluid discharge of the intestinal contents.

In addition to the foods we have mentioned, many others might be enumerated, more especially the numerous 'made-up' feeding materials now on the market. Many are composed of substances that may be regarded as absolutely opposed to the correct feeding of a horse, and their use can only be followed by this and other evil results.

Another most fruitful cause of laminitis is a severe and continued inflammatory condition of the system elsewhere. It is the laminitis known to veterinary surgeons as 'metastatic,' and perhaps the two most notable examples of it are the laminitis following a prolonged attack of pneumonia, and the 'Parturient Laminitis' occurring as a concomitant of septic metritis.

Parturient laminitis it is that offers us the most striking illustration of the truth that a poisoned state of the blood-stream is a sure factor in the causation of an attack. From the direct evidence of our senses (namely, manual exploration of the infected womb, and the stench of the exuding discharge) we know that we have in the interior of the womb matter in a state of putrescence. From the experience of previous post-mortems we know, further, that the putrescent matter thus originating often gains the blood-stream, and forms foci of septic lesions elsewhere - liver or lung. When, therefore, during an attack of septic metritis a condition of laminitis supervenes, we are justified in attributing it to the escape of septic matter from the already infected uterus.

In the same category of laminitis from metastasis may also be placed the laminitis occurring as a result of an overdose of aloes. The enteritis thus set up is often followed by laminitis, and that of a serious type.

Prolonged and excessive work upon a hard road is also apt to induce an attack. When this occurs it in many cases resolves itself into a case of cruelty. (See reported case, No. 1, p. 279.)

Laminitis from this cause was frequent among coach and carriage horses in the pre-railroad period, and resulted from attempting to obtain from the animal a faster pace and a greater number of miles than he was physically capable of giving.

In our day, however, it is more often a result of gross feeding, combined with only that amount of work which the horse, if ordinarily fed, would be easily able to perform. An excellent example of this is the laminitis occurring in the Shire stallion when commencing his rounds of service in the spring and early summer. At this season these animals are constantly supplied with a more than sufficient supply of a highly stimulating and nutritious diet. In this case the blood is already in that state in which it is predisposed to the disease. Add to this the unwonted exercise - for during all the winter the animals are idle - and congestion of the venous apparatus of the extremities is not to be wondered at.