With the cessation of life the body is subject to the unmodified action of its physical environment. There is no further production of heat and the body takes the temperature of the surroundings. The only exceptions are rare cases in which such active chemical changes take place in the dead body that heat is generated by chemical action. At a varying interval after death, usually within twelve hours, there is a general contraction and hardening of the muscles due to chemical changes, probably of the nature of coagulation, in them. This begins in the muscles of the head, extends to the extremities, and usually disappears in twenty-four hours. It is always most intense and most rapid in its onset when death is preceded by active muscular exertion. There have been cases of instantaneous death in battle where the body has remained in the position it held at the moment of death, this being due to the instantaneous onset of muscular rigidity. The blood remains fluid for a time after death and settles in the more dependent parts of the body, producing bluish red mottled discolorations. Later the blood coagulates in the vessels. The body loses moisture by evaporation. Drying of the surface takes place where the epidermis is thin, as over the transparent part of the eye and over areas deprived of epidermis. Decomposition and putrefaction of the body due to bacterial action takes place. The bacteria ever present in the alimentary canal make their way from this into the dead tissue. Certain of these bacteria produce gas which accumulates in the tissues and the body often swells enormously. A greenish discoloration appears, which is due to the union of the products of decomposition with the iron in the blood; this is more prominent over the abdomen and appears in lines along the course of the veins. The rapidity with which decomposition takes place varies, and is dependent upon many factors, such as the surrounding temperature, the nutrition of the body at the time of death, the cause of death. It is usually not difficult to recognize that a body is dead. In certain cases, however, the heart's action may be so feeble that no pulse is felt at the wrist, and the current of the expired air may not move a feather held to the nostril or cloud the surface of a mirror by the precipitation of moisture upon it. This condition, combined with unconsciousness and paralysis of all the voluntary muscles, may very closely simulate death. The only absolute evidence of death is given by such changes as loss of body heat, rigor mortis or stiffening of the muscles, coagulation of the blood and decomposition. CHAPTER III