the muscles are relaxed between the fits. If the dose is
not lethal, the spasms soon cease. In _hydrophobia_ a history of having
been bitten by a rabid animal is usually forthcoming; the spasms, which
are clonic in character, affect chiefly the muscles of respiration and
deglutition, and pass off entirely in the intervals between attacks.
Certain cases of _haemorrhage into the lateral ventricles_ of the brain
also simulate tetanus, but an analysis of the symptoms will prevent
errors in diagnosis. _Cerebro-spinal meningitis_ and _basal meningitis_
present certain superficial resemblances to tetanus, but there is no
trismus, and the spasms chiefly affect the muscles of the neck and
back. _Hysteria and catalepsy_ may assume characters resembling those
of tetanus, but there is little difficulty in distinguishing between
these diseases. Lastly, in the _tetany_ of children, or that following
operations on the thyreoid gland, the spasms are of a jerking character,
affect chiefly the hands and fingers, and yield to medicinal treatment.

#Chronic Tetanus.#--The difference between this and acute tetanus is
mainly one of degree. Its incubation period is longer, it is more slow
and insidious in its progress, and it never reaches the same degree of
severity. Trismus is the most marked and constant form of spasm; and
while the trunk muscles may be involved, those of respiration as a rule
escape. Every additional day the patient lives adds to the probability
of his ultimate recovery. When the disease does prove fatal, it is from
exhaustion, and not from respiratory or cardiac spasm. The usual
duration is from six to ten weeks.

#Delayed Tetanus.#--During the European War acute tetanus occasionally
developed many weeks or even months after a patient had been injured,
and when the original wound had completely healed. It usually followed
some secondary operation, _e.g._, for the removal of a foreign body, or
the breaking down of adhesions, which aroused latent organisms.

#Local Tetanus.#--This term is applied to a form of the disease in which
the hypertonus and spasms are localised to the muscles in the vicinity
of the wound. It usually occurs in patients who have had prophylactic
injections of anti-tetanic serum, the toxins entering the blood being
probably neutralised by the antibodies in circulation, while those
passing along the motor nerves are unaffected.

When it occurs in the _limbs_, attention is usually directed to the fac