Chronic encephalitis or meningitis may succeed the acute stage, or may
be due to stable miasma, blood poison, narcotism, lead poisoning, etc.
This form may not be characterized in its initial stages by
excitability, quick and hard pulse, and high fever. The animal usually
appears at first stupid; eats slowly; the pupil of the eye does not
respond to light quickly; the animal often throws his head up or shakes
it as if suffering sudden twinges of pain. He is slow and sluggish in
his movements, or there may be partial paralysis of one limb, one side
of the face, neck, or body. These symptoms, with some variations, may be
present for several days and then subside, or the disease may pass into
the acute stage and terminate fatally. Chronic encephalitis may effect
an animal for ten days or two weeks without much variation in the
symptoms before the crisis is reached. If improvement commences, the
symptoms usually disappear in the reverse order to that in which they
developed, with the exception of the paralytic effects, which remain
intractable or permanent. Paralysis of certain sets of muscles is a very
common result of chronic, subacute, and acute encephalitis, and is due
to softening of the brain or to exudation into the cavities of the brain
or arachnoid space.

Softening and abscess of the brain are terminations of cerebritis. It
may also be due to an insufficient supply of blood as a result of
diseased cerebral arteries and of apoplexy. The symptoms are drowsiness,
vertigo, or attacks of giddiness, increased timidity, or fear of
familiar objects, paralysis of one limb, hemiplegia, imperfect control
of the limbs, and usually a weak, intermittent pulse. In some cases the
symptoms are analogous to those of apoplexy. The character of the
symptoms depends upon the seat of the softening or abscess within the
brain.

Cerebral sclerosis sometimes follows inflammation in the structure of
the brain affecting the connective tissues, which eventually become
hypertrophied and press upon nerve cells and fibers, causing their
ultimate disappearance, leaving the parts hard and indurated. This
condition gives rise to a progressive paralysis and may extend along a
certain bundle of fibers into the spinal cord. Complete paralysis almost
invariably supervenes and causes death.

_Lesions._--On making post-mortem examinations of horses which have died
in the first stages of either of these diseases we find an excessive
engorgement of t