Symptoms.--Exposure to severe cold produces loss of energy, lethargy, followed by drowsiness, with an intense desire to sleep, which, if gratified, passes on to stupor and coma. There may be delusions before the coma. The primary cause of death is attributed to the lessened dissociation of oxygen from the hæmoglobin to the tissues, and a lessened power of the latter to utilise it. =Diagnosis.=--The general appearance of the deceased, and the absence of any other cause of death, together with the appearances just mentioned, will assist in forming an opinion on this difficult subject. The body lies as if in a deep and calm, sleep, without any external appearance to guide us as to the cause of death, except perhaps a swelling of the extremities, which has come on prior to death. If a body be found buried in snow, and putrefaction present, death did not in all probability take place from cold, provided that the cold has been severe and continuous. Death from cold is generally accidental, except in newly-born children, when it may be either accidental or homicidal, according to circumstances. When freezing of the body has taken place prior to the onset of _rigor mortis_, the latter comes on after the body thaws. This, combined with the other _post-mortem_ signs given above, affords evidence of the strong probability that death had resulted from exposure to cold. In view of the red colour of the skin being similar to that caused by poisoning with CO, a spectroscopic examination of the blood should be made. DEATH FROM EXPOSURE TO HEAT The results from exposure to excessive heat manifest themselves in various ways. Any condition which may lessen the resistance of the body to external heat predisposes to heat-stroke; such as privation, fatigue, mental emotions, alcohol, over-eating, and especially previous attacks of the disease. =Sunstroke= occurs in those who work under the direct rays of the sun, when the air is hot, still, and humid. =Heat-stroke= or thermic fever affects those working in places which are excessively hot and confined, as in glass-works, foundries, stoke-holds, boiler-houses, sugar-refineries, paper-mills, &c. =Heat exhaustion= and prostration are brought about in a similar manner, but the effects are not the same, and usually transient and less severe. Sunstroke or heat-stroke may occur in two forms, the _asphyxial_ or _apoplectic_, and the _hyperpyrexial_; it is also classified as sthenic or asphyxial, and asthenic or syncopal. _Asphyxial_ sunstroke or _heat apoplexy_ is probably the least frequent; prodromal symptoms are headache, vertigo, disturbances of vision, dyspnœa, and dry skin. In some cases sudden unconsciousness, with or without convulsions, may occur, and death rapidly follows.