166 MEDICAL JURISPRUDENCE 4. Inhalation of Irrespirable Gases.—Inhalation of gases, such as carbon dioxide, carbon monoxide, hydrogen sulphide, or smoke from a burning house, will produce suffocation. Mode of Death.—Usually death is due to asphyxia, but it may be due to shock, when the heart stops by reflex action through the vagus nerves. Fatal Period.—Death occurs on an average from four to five minutes after complete withdrawal of air from the lungs, although cases have occur- red in which death was almost instantaneous when the windpipe was block- ed by a foreign body. Recovery may occur if treated within four minutes. Post-mortem Appearances.-—These appearances are external and internal. External Appearances.—These may be due to the cause producing suffo- cation, or to asphyxia. Appearances due to the cause producing Suffocation.—In homicidal smothering effected by the forcible application of the hand over the mouth and nostrils, bruises and abrasions are often found on the lips and angles of the mouth, and alongside the nostrils. The inner surface of the lips may be found lacerated from pressure on the teeth. The nose may be flattened, and its septum may be fractured from pressure of the hand, but these signs are, in my experience, very rare. There may be bruises and abrasions on the cheeks and malar regions, or on the lower jaw, if there has been a struggle. Rarely, fracture or dislocation of cervical vertebrae may occur, if the neck has been forcibly wrenched in an attempt at smothering with the hand. No local signs of violence will be found, if a soft cloth or pillow has been used to block the mouth and nostrils. In compression of the chest, external signs of injury may not be pre- sent, but the ribs are usually fractured on both sides. In homicidal com- pression of the chest brought about by the hands or knees of a murderer or by some other hard material, bruises and abrasions, symmetrical on both sides, are usually found on the skin together with extravasation of blood in the subcutaneous tissues. The ribs are also fractured symmetrically on both sides, and the sternum is fractured, though rarely. Appearances due to Asphyxia.—The face may be pale or suffused. The eyes are open, the eyeballs are prominent, and the conjunctivae are con- gested. The lips are livid, and the tongue is sometimes protruded. Bloody froth comes out of the mouth and nostrils. The skin shows punctiform ecchymoses with lividity of the limbs. Rupture of the tympanum may occur from a violent effort at respiration. Internal Appearances.—Mud or any other foreign matter may be found in the mouth, throat, larynx or trachea, when suffocation has been caused by the impaetion of a foreign substance in the air-passages. It may also be found in the pharynx or oesophagus. The mucous membrane of the trachea is usually bright red, covered with bloody froth and congested. The lungs are congested and emphysematous. They may be lacerated or contused even without anv fracture of the ribs, if death has been caused by pressure on the chest, Punctiform subpleural ecchymoses (Tardieu's spots) are usually present at the root, base, and lower margins of the lungs, and are characteristic of death by suffocation, though they may be present in asphyxial deaths from other causes. They are also found on the thymus, pericardium, and along the roots of the coronary vessels. The lungs may be found quite normal, if death has occurred rapidly. The right side of the heart is often full of dark fluid blood, and the left empty. The .blood does not readily coagulate; hence wounds caused after death may bleed. The brain is generally congested, and so are the abdominal organs, espe- cially the liver, spleen and Sidneys.