Tetanus (LOCK-JAW). a disease in which painful involuntary tonic contractions of the muscles of the body occur. Tetanus is generally traceable to injury with breach of surface of the skin, it is an occasional result of compound fracture, and in rare instances originates from a comparatively simple lesion (traumatic tetanus). In some cases no history of a scratch or bruise can be traced (idiopathic tetanus). Of late years it has been shown that the cause of the malady is the introduction or growth within the nervous structures of the body of a micro-organism, the bacillus tetani. The first symptoms in the case of traumatic tetanus usually occur after the lapse of 5 or 6 days from the time of injury; they may, however, appear much earlier, and in some instances are delayed till the end of three or four weeks. At the outset the muscles of the jaws or neck are commonly involved, stiff neck or difficulty in masticating or in swallowing being complained of. As time goes on the spasm becomes more pronounced, and extends to other voluntary muscles, and often to the diaphragm, producing difficulty in breathing. Sometimes the spasm is almost confined to the muscles of the jaw, whence the term lock-jaw; usually, however, the spasm is widely distributed. The body may be arched backwards by spasm of the muscles of the back, producing what is called opisthotonos; and in other cases the body is bent forwards or to one or other side (emprosthotonos or pleurosthotonos). The spasm is aggravated, or attacks of spasm may be brought on, by noises, slight muscular efforts, and other trivial disturbances. Tongue-biting is a common symptom; and the contraction, when it involves the muscles of the face, gives the patient a remarkable appearance, to which the term risus sardonicus has been applied. The pulse is rapid, sweats are common, the temperature is usually raised, and attains in some instances before death a high degree of elevation. The treatment of tetanus consists in maintaining absolute quiet in a darkened room, and administering chloroform or opium. In some instances division of a nerve above the seat of injury (if such exists) has been resorted to; quite recently a substance has been obtained from the blood of animals affected with tetanus which has been employed as an antidote to the disease in man; there appears some reason for hoping that this may prove efficacious in curing what has hitherto been regarded as an almost necessarily fatal disease.