120 MEDICAL JURISPRUDENCE by external compression on the chest and abdominal walls, e.g. from falls of earth; (d) by primary cessation of respiratory movements causing respi- ratory failure, e.g. narcotic poisoning and deaths^ from electrical injuries; (e) by breathing in vitiated atmospheres in which there is an excess of carbon dioxide or inert gases. II. Reduced oxygen-carrying capacity of the blood—ansemic anoxia occurring in acute poisoning by carbon monoxide, chlorates, nitrites, and ccal-tar derivatives. III. Depression of the oxidative processes in the tissues—histotoxic anoxia seen in acute cyanide poisoning. IV. Inefficient circulation of the blood through the tissues—stagnant anoxia occurring in deaths from traumatic shock, heat stroke, and acute irritant and corrosive poisoning. All these types of anoxia produce circulatory failure, which may lead to death. The post-mortem findings in all forms of death of medico-legal impor- tance should be divided into two groups, namely, the basic pathological changes of circulatory failure, such as visceral congestion and capillary haemorrhages, and the special pathological changes depending upon the particular type of death, e.g. local injuries to the neck in throttling, strangu- lation and hanging. Gordon is of opinion that tissue anoxia, however in- duced, leads to circulatory failure; hence the fundamental pathological changes are uniform in all forms of death, although they vary in degree. He adds that the relative absence of visceral congestion in deaths occurring" from sudden primary cardiac failure supports the view that the degree of visceral congestion is relatively less in rapid deaths as compared with deaths occurring slowly. He further remarks that asphyxia cannot be regarded as a distinct pathological entity which is recognizable on the basis of morbid anatomy. SUDDEN DEATH Sudden or unexpected death occurs from unnatural causes, such as vio- lence~~oT poison, as well as from natural causes. Unnatural deaths have always to be investigated by the police, but very often natural deaths form the basis of medico-legal investigations if they have occurred suddenly and under suspicious circumstances. In such cases a medical practitioner should not certify to the cause of death without holding a post-mortem examination even if there is strong evidence of disease. Causes.—The natural causes producing sudden death are— 1. Diseases of the heart, such as fatty degeneration of the heart, myo- cardial degeneration, angina pectoris, valvular diseases with compensatory failure, especially in aortic incompetence, spontaneous rupture of the heart or its valves, acute diseases of the endocardium and pericardium and con- genital abnormal conditions of the heart in infants and children. 2. XUgeases of the blood vessels especially occlusion of the lumen of the coronary artery from arteriosclerosis, thrombosis of the coronary artery, systemic embolism, pulmonary embolism, syphilitic aortitis, spontaneous rupture of the aorta in chronic arteriosclerosis and rupture of aneurysms or vericose veins. A case2 is recorded in which an enema caused fatal cardiac embolism. Two weeks after a suprapubic cystatomy was performed under laughing gas ansesthesia by Henry an orderly gave the patient, aged 72, a simple soap water enema. He suddenly gave a gasp and ceased to breathe. The autopsy showed that the pressure of the water dis- lodged some blood clots in the prostatic venous plexus, and that the patient died of an embolism in the right side of the heart. 2. C. P. Henry and Harisbury, Atlantic Med. Jour., Nov. 1927, p. 77.