1. Cerebral hæmorrhage or embolism.
  2. Mitral and tricuspid valvular lesions if the patient exerts himself.
  3. Rupture of a gastric or duodenal ulcer; rupture of liver, spleen, or extra-uterine gestation, or abdominal aneurism.
  4. Suffocation during an epileptic fit; vomited matter or other material drawn into the trachea or air-passages; croup.
  5. Arterio-sclerosis may lead to thrombosis, embolism, or aneurism.
  6. Poisoning, as by hydrocyanic acid, cyanide of potassium, inhalation of carbonic acid or coal gas, œdema of glottis following inhalation of ammonia.
  7. Rapid onset of some acute specific disease, such as pneumonia or diphtheria; collapse from cholera.
  8. Heat-stroke, lightning, shocks of electricity of high tension.
  9. Mental or physical shock.
  10. Exertion while the stomach is overloaded.
  11. Diabetic coma; uræmia.
  12. Status lymphaticus. This is a general hyperplastic condition of the lymphatic structures in the body, and is seen in enlargement of tonsils, thymus, spleen, as well as of Peyer's patches and mesenteric glands. It is a frequent cause of death during chloroform anæsthesia for slight operations in young people.

In addition, it may be as well to remember that death sometimes occurs suddenly in exophthalmic goitre, hypertrophy of the thymus, and in Addison's disease.

In some cases of sudden death nothing has been found post mortem, even when the autopsy has been made by skilled observers, and the brain and cord have been submitted to microscopical examination.

VI.—SIGNS OF DEATH

(1) Cadaveric appearance; ashy white colour. (2) Cessation of the circulation and respiration, no sound being heard by the stethoscope. Cessation of the circulation may be determined by (a) placing a ligature round the base of a finger (Magnus' test); (b) injecting a solution of fluorescin (Icard's test); (c) looking through the web of the fingers at a bright light (diaphanous test); (d) the dulling of a steel needle when thrust into the living body; (e) the clear outline of the dead heart when viewed in the fluorescent screen. (3) The state of the eye; the tension is at once lost; iris insensible to light, fundus yellow in colour; cornea dull and sunken. (4) The state of the skin; pale, livid, with loss of elasticity. (5) Extinction of muscular irritability. The above signs afford no means of determining how long life has been extinct. The following, however, do:

Cooling of the Body.—The average internal temperature of the body is from 98° to 100° F. The time taken in cooling is from fifteen to twenty hours, but it may be modified by the kind of death, the age of the person, the presence or absence of clothing on the body, the surrounding temperature, and the stillness or otherwise of the air about the body. Still, the body, other things being equal, may be said to be quite cold in about twelve hours.

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 hæmorrhage, 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 fœtus. 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.