=Hypostasis= or =post-mortem staining= is due to the settling down of the blood in the most dependent parts of the body while the body is cooling. It is a sure sign of death, and occurs in all forms of death, even in that due to haemorrhage, although not so marked in degree. Post-mortem staining (_cadaveric lividity_) begins to appear in from eight to twelve hours after death, and its position on the body will help to determine the length of time the body has lain in the position in which it was found. The staining is of a dull red or slaty blue colour. It must be distinguished from ecchymosis the result of a bruise, by making an incision into the part; in the case of hypostasis a few small bloody points of divided arteries will be seen, in the case of ecchymosis the subcutaneous tissues are infiltrated with blood-clot. Internally, hypostasis must not be mistaken for congestion of the brain or lungs, or the results of inflammation of the intestines. If the intestine is pulled straight, inflammatory redness is continuous, hypostasis is disconnected. About the neck hypostasis must not be mistaken for the mark of a cord or other ligature. When the blood is of a bright red colour after death (as happens in poisoning by CO or HCN, or in death from cold), the hypostasis is bright red also. =Cadaveric Rigidity--Rigor Mortis.=--For some time after death the muscles continue to contract under stimuli. When this irritability ceases--and it seldom exceeds two hours--rigidity and hardening sets in, and in _all_ cases precedes putrefaction. It is caused by the coagulation of the muscle plasma. It commences in the muscles of the back of the neck and lower jaw, and then passes into the muscles of the face, front of the neck, chest, upper extremities, and lastly to the lower extremities. It has been noticed in the new-born infant, as well as in the foetus. It lasts from sixteen to twenty hours or more. In lingering diseases, after violent exertion, and in warm climates, it sets in quickly, and disappears in two or three hours; in those who are in perfect health and die from accident or asphyxia, it may not come on until from ten to twenty-four hours, and may last three or four days. After death from convulsions or strychnine-poisoning, the body may pass at once into rigor mortis. Rigor mortis must be distinguished from _cadaveric spasm_ or the _death clutch_; in the former, articles in the hands are readily removable, in the latter this is not the case. In tetanic spasm the limbs when bent return to their former position; not so in rigor mortis.