When general spasms set in it must be assumed that the poison has reached the nerve centres in toxic quantities, either through the circulation or as is alleged by Babes and others through the nerve trunks. When the poison is injected intravenously the general spasms are the first to appear. Again the section of the nerves of a limb before inoculation prevents spasms in its peripheral muscles when all the body beside has become tetanic (Tizzoni and Vaillard). The removal of the brain from a tetanized frog had no effect, while the removal of a portion of the spinal cord abolished the spasms in the muscles corresponding to that part. Moreover Gumbrecht cut the whole of the sensory nerves of a limb but the spasms occurred in its muscles notwithstanding. It must be admitted, therefore, that the general tetanic spasms are induced by disorder caused by the poison in the spinal nervous centres.
Gumprecht and Goldscheider claim that the poison reaches the spinal centres by way of the nerve trunks basing the conclusion on the observation that the spasms sometimes remain for a time more marked on that side of the body on which the wound or inoculation was made. Absorption through the circulation also is conceded.
Courmont and Doyon claim that the product of the bacillus tetani only operates as a ferment, which produces in the blood the real tetanizing agent, basing the conclusion on an apparent delay in its action, in man, as compared with strychnia, and on the prompt action of the injected blood of a tetanic animal in which this poison is presumably preformed. It should be noted, however, that the disease in man is only seen after accidental inoculation of the bacillus, and that time must be allowed for the increase of the microbe.
Vaillard and Vincent have shown that the promptitude and certainty of the result depend on the age of the culture employed. A culture of 5 days in bouillon at 20° to 22° C. will not harm a Guinea pig in a hypodermic dose of 0.25cc. to 0.5cc. A culture of 20 days old is deadly.
The action on the nerve cell of the spinal cord has been investigated by Goldscheider and Flatau, who found degeneration of the chromatin granules within a short time after inoculation. (Centr. für Allg. Path. Anat. 1897). W. K. Hunter found that the ganglion cell stained more diffusely than normal cells. There were also some capillary dilatation and punctiform hæmorrhages in certain cases (Brit. Med. Jour. 1897).
Péchoutre examined the lumbar enlargement of tetanic rabbits, by Nissl’s method and found the following lesions in the motor cells of the anterior horns: 1st. A partial or total disappearance of the distinct outer marginal line; enlargement of the cell and pericellular space; diffuse coloration of the achromatic substance; a disappearance of the regular concentric disposition of the granules of Nissl which were in part reduced to a fine powder; 2d. Encrease of nucleus and nucleolus.
Others have observed encrease of the cerebro-spinal fluid, thickening of the ependyma, nuclear proliferation in the neuroglia, and softening of the cord, but in many cases no appreciable lesions in the nerve centres have been found, and none can be affirmed as constant. Neuritis in the region of the wound is sometimes found especially if the lesion is a contused or painful one.
The muscles often show lesions the result of the violent contractions. There may be points of ecchymosis and partial rupture of individual fibres, they may be of a deep red, or again pale, soft and as if parboiled. There may be hyperæmia or œdema of the lungs, congestion of the larynx, ecchymosis on the pericardium and other serous and mucous membranes, and congestion of the liver, spleen and kidneys. Rigor mortis sets in rapidly and is usually very persistent. The muscles contain an excess of lactic acid.
Accessory Causes. Whatever contributes to traumas must be classed in this list. Solipeds, work oxen, and dogs are especially exposed in this sense. In all animals castration wounds; in horses and lambs amputation of the tail; in solipeds pricks, bruises and fistulæ of the feet; all kinds of surgical wounds; in females the parturient condition; and in the new born the umbilical sore form infection atria. The tendency to infection in wounds of the feet in animals, and of the hands and feet in man, is easily explained by contact with the virulent earth or dust. Children running barefoot, or injuring their bare knees and soldiers sleeping on the ground are similarly exposed. The contamination of the clothes is the main condition. It has been held that infection never takes place from the gastro-intestinal canal, but the facts that the bacillus is frequently present in the prima viæ and that the mucosa is often perforated by blood-sucking parasites, suggest that some cases (idiopathic) are probably due to intestinal infection. The gland ducts also and the follicles of Peyers’ patches and of the solitary glands offer available fields for the colonization of the bacillus and for infection atria.
General Symptoms in Animals. In experimental cases, in which there has been a large intravenous injection of the blood of a victim of tetanus the symptoms may set in speedily and violently. In casual cases, however, there is usually an incubation period varying on an average from three to fifteen days in the horse while it may be as short as two days in cow and sheep. Hoffmann quotes one incubation in the horse as but six hours after a wound in the neck, and another as twenty-five days, following a castration. The last is rather unreliable as infection may have taken place long after the operation. He quotes cases in the pig and goat, after castration as eight to fourteen days, and one in the dog almost immediately after a bite on the loins.