Mortality. Friedberger and Fröhner sets the mortality in sheep and pigs at nearly 100 per cent.: in horses at 75 to 85 per cent.: and in cows at 70 to 80 per cent. In tetanus neonatorum in lambs, the deaths reach about 100 per cent. In this case the disease usually sets in within forty-eight hours after birth, and with a very high temperature difficult deglutition becomes a marked feature, so that if the patient is not speedily killed by dyspnœa, it soon perishes from starvation and exhaustion.
The cause of death is usually asphyxia, hyperpyrexia, or exhaustion.
Lesions. There are no constant or pathognomonic structural changes in tetanus. Those that are found are inconstant and as a rule secondary. A wound (entrance channel) can usually be made out, often in the region of the foot, or in connection with castration. In the new born there is the unhealed navel, and in parturient cows the catarrhal, septic or injured womb. In the seat of such wound may be found the foreign body (nail, splinter, etc.), and some pus or simple congestion or even necrosis. The nerve trunks leading from such infected wound may be hyperæmic. The presence of the bacillus in the wound may be determined by microscopic examination or inoculation on a small animal.
The changes in the nerve centres may be congestion of the horns of gray matter, and there may be slight hæmorrhage, exudation, especially shown in the encrease of the cerebro-spinal fluid, softening, cell proliferation, and granular invasion of the nervous tissue. In separate cases the myelon, the corpus striatum and the cerebellum have shown lesions. The meninges are occasionally hyperæmic. Spinal lesions have been noted especially in the bulbo-cervical and lumbar regions. Exceptionally in the horse there are blood extravasations from fractures or dislocations of the vertebræ.
In subjects dying of asphyxia the lungs and right heart are congested, and the blood may be black, only loosely coagulable and with free hæmoglobin. There is congestion of the intestinal as of the respiratory mucosa, and also of the liver, spleen and kidneys. The congested bladder usually contains urine contrary to what is the case in rabies.
Diagnosis. From strychnia poisoning tetanus is distinguished by the gradual and progressive approach of the spasms and by the absence of the intervals of complete relaxation which separate the rapidly recurring and violent spasms of strychnia. In tetanus the spasms may be modified but never completely intermitted, and more or less stiffness, trismus and protrusion of the haw constantly persist. In strychnia too, the paroxysm is far more intense than in the early stages of tetanus. The spasms of strychnia are general, while those of tetanus are often most intense in particular groups of muscles often at first in the vicinity of the inoculation wound.
From rabies, tetanus is easily distinguished by the absence of any history of a bite; by the persistence of the tonic spasms especially of the masseters and abdominal muscles during the intervals between the more violent paroxysms (in rabies there is temporary complete relaxation); by the absence of clonic spasms which alone occur in rabies; by the absence of the paralysis which characterizes advanced rabies; by the mental clearness and the absence of hallucinations or mischievous disposition which are marked features of rabies; by the absence of the depraved appetite of rabies; and by the fact that the brain does not contain the infecting germ as is the case in rabies.
From rheumatism of the neck (torticollis) tetanus is easily distinguished by the permanent trismus which is not shown in rheumatism, and by the fact that spasms are easily roused by any artificial excitement, indicating an extraordinary hyperæsthesia and excitability which are nearly absent in rheumatism. The steady unmistakable progress of tetanus is in itself diagnostic.
From meningitis tetanus is to be diagnosed by the presence of trismus without impairment of the mental faculties or fever. In meningitis the spasms are usually confined to particular groups of muscles and do not become generalized under active excitement as in tetanus. Even if the spasms of meningitis affect the jaws and pharynx they are rarely paroxysmal or roused by excitement as in tetanus. They may even be clonic.
Tetany is more commonly localized in particular groups of muscles, and shows longer and more irregular intervals between paroxysms than does tetanus. It is improved by thyroid extract, and may be roused at will to contraction by pressing on the nerve going to the affected muscles.