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.