.

Whether the cause of the fever has been an injury to the tissues, such
as a severe bruise, a broken bone, an inflamed lung, or excessive work,
which has surcharged the blood with the waste products of the combustion
of the tissues, which were destroyed to produce force, or the toxins of
influenza in the blood, or the presence of irritating material, either
in the form of living organisms or of their products, as in glanders or
tuberculosis--the general train of symptoms are much the same, varying
as the amount of the irritant differs in quantity, or when some special
quality in them has a specific action on one or another tissue.

There is in fever at first a relaxation of the small blood vessels,
which may have been preceded by a contraction of the same if there was a
chill, and as a consequence there is an acceleration of the current of
the blood. There is, then, an elevation of the peripheral temperature,
followed by a lowering of tension in the arteries and an acceleration in
the movement of the heart. These conditions may be produced by a primary
irritation of the nerve centers of the brain from the effects of heat,
as is seen in thermic fever, or sunstroke, or by the entrance into the
blood stream of disease-producing organisms or their chemical products,
as in anthrax, rinderpest, influenza, etc.

There are times when it is difficult to distinguish between the
existence of fever as a disease and a temporary feverish condition which
is the result of excessive work. Like the condition of congestion of the
lungs, which is normal up to a certain degree in the lungs of a race
horse after a severe race, and morbid when it produces more than
temporary phenomena or when it causes distinct lesions, the temperature
may rise from physiological causes as much as four degrees, so fever,
or, as it is better termed, a feverish condition, may follow any work or
other employment of energy in which excessive tissue change has taken
place; but if the consequences are ephemeral, and no recognizable lesion
is apparent, it is not considered morbid. This condition, however, may
predispose to severe organic disturbance and local inflammations which
will cause disease, as an animal in this condition is liable to take
cold and develop lung fever or a severe enteritis, if chilled or
otherwise exposed.

Fever in all animals is characterized by the same general phenomena, but
we find the intensity of the symptoms modified by the specie