=LOCKJAW.=--This disease, very frequently called tetanus, is an infectious disease in which the body muscles are spasmodically contracted or stiffened. The muscles that move the jaw are frequently affected and the animal is unable to open the mouth. Because of this condition the disease is commonly known as lockjaw. The spread of the disease does not occur through healthy animals coming in contact with animals having tetanus, but by inoculation. The germ of tetanus is present in the soil, manure and dust. It enters the body by way of wounds, especially punctured and bruised wounds. The injury may result from stepping on a nail, and the germs are planted in the deeper structures of the foot. Such a wound usually has poor drainage, the horn of the hoof closing the mouth or opening. Here the germs grow and produce a poisonous toxin that is said to be the most powerful produced by any bacteria. This toxin acts on the nerve centers of the brain and spinal cord, causing extensive spasmodic contraction of the body muscles. Tetanus sometimes occurs in the absence of any noticeable wound. It may be in such cases that the seat of the infection is a slight abrasion of the skin, or the lining membranes of the respiratory and digestive tracts. The tetanus bacillus is a slender, spore-producing bacterium. The spore is located at one end of the rod in the form of a round head, that gives the organism a pin shape, hence the name of pin bacillus. It is very resistant to outside conditions and the action of the chemical disinfectants. It is because of its ability to resist the action of disinfectants and the fact that it develops best when protected or covered by the tissues and wound secretions, that this disease so often follows ordinary wound treatment. [Illustration: LOCKJAW Note the rigid, tense position of the muscles.] From a few days to several weeks may lapse from the time of infection with the germs until the development of the stiffness and spasms. Sometimes the wound by which the organism has entered the tissues has healed before the symptoms of tetanus are manifested. In case the symptoms develop a few days after the inoculation the disease is severe or acute in form, and less violent or subacute if the symptoms are manifested after the second week. The above statement does not hold true in all cases, but it may be considered true in a general way. Of the domestic animals the horse is the most commonly affected. The symptoms shown by this animal are very characteristic. Any person that has had the opportunity to see and examine a horse suffering from tetanus should have no trouble in recognizing the disease in other animals.