The fits may cease some time before death, or, on the other hand, death may occur during a paroxysm from fixation of the diaphragm and arrest of respiration.

Differential Diagnosis.—­There is little difficulty, as a rule, in diagnosing a case of fulminating tetanus, but there are several conditions with which it may occasionally be confused.  In strychnin poisoning, for example, the spasms come on immediately after the patient has taken a toxic dose of the drug; they are clonic in character, but 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.