weights, and in green horses put to work on city pavements to which they
are unaccustomed. Concussion from long drives on dirt roads is at times
productive of the same results, notably when the weather is extremely
warm, or at least when the relative change of temperature is great. But
the exhaustion of these circumstances must prove an exciting cause as
well as the long-continued concussion. This combination of causes must
also determine the disease at times in hunters, for the weight of the
rider increases the demands made upon the function of these tissues, and
their powers are the sooner exhausted.

(2) Overexertion, as heavy pulling or rapid work, even when there is no
immoderate concussion, occasionally results in this disease. Here also
exhaustion is a conjunctive cause, for overexertion can not be long
continued without exhaustion.

(3) Exhaustion is nearly as prolific a source of laminitis as is
concussion, for when the physical strength is impaired, even though
temporarily, some part of the economy is rendered more vulnerable to
disease than others. To this cause we must ascribe those cases which
follow a hard day's work, in which at no time has there been
overexertion or immoderate concussion.

The tendency to laminitis in horses on sea voyages results from the
continual constrained position the animal maintains on account of the
rocking motion of the vessel.

If one foot has been blistered, or if one limb is incapacitated from any
cause, the opposite member, doing double duty, soon becomes exhausted,
and congestion, followed by inflammation, results. When one foot only
becomes laminitic, it is customary to find the corresponding member
participating at a later date; not always because of sympathy, but
because one foot had to do the work of two.

(4) Rapid changes of temperature act as an exciting cause of laminitis
by impairing the normal blood supply.

This change of temperature may be induced by drinking large quantities
of cold water while in an overheated condition. Here the internal heat
is rapidly reduced, the neighboring tissues and blood vessels
constrained, and the blood supply to these organs greatly diminished,
while the quantity sent to the surface is correspondingly increased.
True, in many cases there has not been sufficient labor performed to
impair the powers of the laminae, and laminitis is more readily induced
than congestion or inflammation of the skin or other surface organs,
bec