local disease, and having a strong
tendency, in severe cases, to destructive disorganization of the tissues
affected.

_Causes._--The causes of laminitis are as wide and variable as in any of
the local inflammations, and may be divided into two classes--the
predisposing and the exciting.

_Predisposing causes._--From personal observation I do not know that any
particular construction of foot or any special breed of horses is
predisposed to this disease, neither can I find anything to warrant the
assumption that it is in any way hereditary; so that while we may easily
cultivate a predisposition to the disease, it does not originate without
an exciting cause. Like most other tissues, a predisposition to
inflammation may be induced in the sensitive laminae by any cause which
lessens their power of withstanding the work imposed on them. It exists
to an extent in those animals unaccustomed to work, particularly if they
are plethoric, and in all that have been previous subjects of the
disease, for the same rule holds good here that we find in so many
diseases--i. e., that one attack impairs the functional activity of the
affected tissues and renders them more easy of a subsequent
inflammation. Unusual excitement by determining an excessive blood
supply, bad shoeing, careless paring of the feet by removing the sole
support, and high calkings without corresponding toe pieces must be
included under this head.

_Exciting causes._--The exciting causes of laminitis are many and
varied. The most common are concussion, overexertion, exhaustion, rapid
changes of temperature, ingestion of certain feeds, purgatives, and the
oft-mentioned metastasis.

(1) Concussion produces this disease by local overstimulation. The
excessive excitement is followed by an almost complete exhaustion of the
functional activity of the laminated tissues, the exhaustion by
congestion, and eventually by inflammation. But congestion here, as in
all other tissues, is not necessarily followed by inflammation; for,
although the principal symptoms belonging to true laminitis are present,
the congestion may be relieved before the processes of inflammation are
fully established. This is the condition in the many so-called cases of
laminitis which recover in from 24 to 48 hours. They should be called
congestion of the laminae.

Laminitis from concussion is common in trotting horses that are raced
when not in condition, especially if they carry the obnoxious toe