Etiology and Classification.—­As it is with some other diseases, one may unprofitably theorize on cause and readily enumerate many conditions which are apparently contributory toward producing the affection.  Causes may well be grouped, however, and a more definite understanding of laminitis is possible as a result.  Such collocation would include conditions which directly or indirectly affect the digestion, such as puerperal laminitis, drinking of large quantities of cold water and exposure to cold and rain when the body is warm.  All of these various conditions might be said to affect the vaso-constrictor nerves in such manner that the natural tendency (because of the peculiar structure of the sensitive laminae and their mode of attachment to the non-sensitive wall) which solipeds have for this affection is indirectly due to this one cause—­vaso-constriction.  According to Dr. D.M.  Campbell, the effect of toxic materials, which may be absorbed from the digestive tract or the uterus in parturient females, upon the vaso-constrictor nerves, is such that a passive congestion of the sensitive laminae occurs and laminitis is the result.  He believes that even the chilling of the surface of the body when very warm, by a cold rain, constitutes a condition wherein the effect upon the vaso-constrictors is the same.

This grouping does not include the effect of direct injuries of any and all kinds to which the feet are subjected such as:  Concussion in fast road work, injuries occasioned by tight or ill fitting shoes, contusions of any kind resulting in non-infectious inflammation of the sensitive laminae, as well as the causes which produce laminitis where weight is borne by one foot when its fellow is out of function.

A classification which is practical is that of acute and chronic laminitis.  To the practicing veterinarian it is this manner of consideration that is essential in the handling of these cases.

Symptomatology.—­In the acute attack the condition is so well described by Dr. R.C.  Moore[30] that we quote him in part as follows: 

The acute form is generally ushered in very suddenly.  Often a horse that is perfectly free from symptoms of the disease is found a few hours later so stiff and sore that he will scarcely move.  They stand like they were riveted to the ground.  If forced to move the evidence of pain subsides to some extent after they have gone a short distance, to return more severe than ever after they have been allowed to stand for a short time.  If the disease is confined to the two front feet, the hind feet are placed well under the center of the body to support the weight and the front ones are advanced in front of a perpendicular line so as to lessen the weight they must bear.  If they are made to move, the same position of the feet is maintained.  If made to turn in a small circle, they do so by using the hind feet as a pivot, bringing the front parts around by placing as little weight on them as possible.

     Placing the hind feet so far under the body, arches the back and
     often leads to errors in diagnosis, the condition sometimes being
     taken for diseases of the loins or kidneys.