<prompt> Persistent contracted stage is seen in?Rigor mortisAlgor mortisHeat stiffeningCold stiffening  <response>: Ans. is c i.e., Heat stiffeningoRigor mortis in tropical countries e.g. India, it begins 1-2 hours after death, takes further 2 hours to develop and lasts for 18-36 hours in summer and 24-48 hours in winter.oAlgor mortis is cooling of the body after death. After death, dead body behaves like an inert substance and therefore, if atmospheric temperature is low, body loses its heat by conduction, convection, radiation and evaporation, so as to attain the atmospheric temperature, i.e. the body cools. No cooling of dead body occurs if atmospheric temperature is higher than that of body. Cooling of body starts 12 to 1 hour after death.oHeat stiffening is permanent.oOn warming the part of body, cold stiffening disappears.oGas putrefactive rigidity disappears on incision due to release of gases.Differential diagnosis of post mortem stiffening1. Rigor mortisIt is defined as contraction, stiffening, shortening and opacity of muscles after death. It is preceded by a period of relaxation. It occurs after molecular cellular death. In tropical countries e.g. India, it begins 1-2 hours after death, takes further 2 hours to develop and lasts for 18-36 hours in summer and 24-48 hours in winter. In temperate countries, it begins in 3-6 hours, takes further 2-3 hours to develop and lasts for 2-3 days.2. Heat stiffeningIn body exposed to extensive heat 65degC there results stiffening and flexion of all joints, known as Pugilistic or boxers or defence posture, due to denaturation and coagulation of proteins. However, heat stiffening is permanent unlike rigor mortis which passes off after few hours.3. Cold stiffeningDue to exposure to freezing temperature, body becomes stiff due to freezing solidification of fats and body fluids. On warming the part of body, cold stiffening disappears, differentiating it from rigor mortis.4. Putrefactive gas stiffeningDuring decomposition, body part becomes rigid because of collection of gases in subcutaneous tissues and the pressure exerted by these gases. It can be differentiated from rigor mortis as other signs of putrefaction are present and putrefactive rigidity disappears on incision due to release of gases.5. Cadaveric spasm instantaneous rigor or cataleptic rigidityThe muscles, which were in contraction or spasm at the time of death, continue to be in spasm even after death, without the stage of primary relaxation. 