Injuries by electrical currents of high pressure are not uncommon; speaking generally, 1,000 to 2,000 volts will kill. In America, where electricity is adopted as the official means of destroying criminals, 1,500 volts is regarded as the lethal dose, but there are many instances of persons having been exposed to higher voltages without bad effects. The alternating current is supposed to be more fatal than the continuous. Much depends on whether the contact is good (perspiring hands or damp clothes). Death has been attributed in these cases to respiratory arrest or sudden cessation of the heart's action. The best treatment is artificial respiration, but the inhalation of nitrite of amyl may prove useful. Rescuers must be careful that they, also, do not receive a shock. The patient should be handled with india-rubber gloves or through a blanket thrown over him. XXII.--DEATH FROM COLD OR HEAT =Cold.=--The weak, aged, or infants, readily succumb to low temperatures. The symptoms are increasing lassitude, drowsiness, coma, with sometimes illusions of sight. Post mortem, bright red patches are found on the skin surface, and the blood remains fluid for long. =Heat.=--Death may result from syncope, the result of exposure to great heat. =Sunstroke.=--The person loses consciousness and falls down insensible; the body temperature may be 112 deg. F., the pulse is full, and a peculiar pungent odour is given off from the skin. Coma, convulsions with (rarely) delirium, may precede death. _Treatment_ consists in lowering the body temperature by application of cold cloths, stimulants, strychnine or digitalin hypodermically. XXIII.--PREGNANCY The signs of the existence of pregnancy are of two kinds, uncertain and certain, or maternal and foetal. Amongst the former class are included--Cessation of menstruation (which may occur without pregnancy); morning vomiting; salivation; enlargement of the breasts and of the abdomen; quickening. It must be borne in mind that every woman with a big abdomen is not necessarily pregnant. The tests which afford conclusive evidence of the existence of a foetus in the uterus are--Ballottement, the uterine souffle, intermittent uterine contractions, foetal movements, and, above all, the pulsation of the foetal heart. The uterine souffle is synchronous with the maternal pulse; the foetal heart is not, being about 120 beats per minute.