ause the laminae can not relieve themselves of threatened congestion
by the general safety valve of perspiration. A cold wind or relatively
cold air allowed to play upon the body when heated and wet with sweat
has virtually the same result, for it arrests evaporation and rapidly
cools the external surface, thereby determining an excess of blood to
such organs and tissues as are protected from this outside influence. In
many instances this happens to be some of the internal organs, as the
lungs, if the previous work has been rapid and their functional activity
impaired; but in numerous other instances the determination is toward
the feet, and that it is so depends upon two very palpable facts: First,
that these tissues have been greatly excited and are already receiving
as much blood as they can accommodate consistently with health; second,
even though these tissues are classed with those of the surface, their
protection from atmospheric influences by means of the thick box of horn
incasing them renders them in this respect equivalent to internal
organs.

A more limited local action of cold may excite this disease, by driving
through water or washing the feet and legs while the animal is warm or
just in from work. Here a very marked reaction takes place in the
surface tissues of the limbs, and passive congestion of the foot results
from an interference with the return flow of blood which is being sent
to these organs in excess. These are more liable to be simple cases of
congestion, soon to recover, yet they may become true cases of
laminitis.

(5) Why it is that certain kinds of grain will cause laminitis does not
seem to be clearly understood. Certainly they possess no specific action
upon the laminae, for all animals are not alike affected; neither do they
always produce these results in the same animal. Some of these feeds
cause a strong tendency to indigestion, and the consequent irritation of
the alimentary canal may be so great as to warrant the belief that the
laminae are affected through sympathy. In other instances there is no
apparent interference with digestion nor evidence of any irritation of
the mucous membranes, yet the disease is in some manner dependent upon
the feed for its inception. Barley, wheat, and sometimes corn are the
grains most liable to cause this disease. With some horses there appears
to be a particular susceptibility to this influence of corn, and the use
of this grain is followed by inf