_Symptoms._--Headache and giddiness, foaming at mouth, vomiting, convulsions, tetanic spasms, stertorous breathing, dilated pupil. The breath smells of gas; there is profound stupor; the patient, if alive, exhales gas from the lungs when removed into a fresh room or into the air. Smell of gas in the room and in patient's breath. _Post-Mortem Appearances._--Pallor of skin and internal tissues; florid colour of neck, back, and muscles, if much CO present in the coal gas; fluid florid blood; infiltration of lungs. _Treatment._--Fresh air, artificial respiration, cold affusion, diffusible stimulants; inhalation of oxygen freely. =Sulphuretted Hydrogen= is characterized by its odour, like that of rotten eggs. It is extremely poisonous. _Symptoms._--Giddiness, pain and oppression in stomach, nausea, loss of power; delirium, tetanus, and convulsions. _Post-Mortem Appearances._--Fluid and black blood (sulph-haemoglobin), smell of H_{2}S on opening the body; loss of contractility of muscles, rapid putrefaction. _Treatment._--Fresh air, stimulants, inhalation of chlorine. _Tests._--Acetate of lead throws down a brown or black precipitate according to the quantity of the gas. =Sewer Gas.=--Cesspool emanations usually consist of a mixture of sulphuretted hydrogen, sulphide of ammonium, and nitrogen; but sometimes it is only deoxidized air with an excess of carbonic acid gas. _Symptoms._--If poison concentrated, death may ensue at once; if gas diluted, or exposure only short, insensibility, lividity, hurried respiration, weak pulse, dilated pupils, elevation of temperature to 104 deg., tonic convulsions not unlike those of tetanus. _Treatment._--Fresh air, oxygen, with artificial respiration. Stimulants, hypodermic of strychnine, and alternate hot and cold douche. =Irritant Gases= are--(1) Nitrous acid gas; (2) sulphurous acid gas; (3) hydrochloric acid gas; (4) chlorine; (5) bromine; (6) ammonia. They have the common property of causing irritation and inflammation of the eyes, throat, and air-passages, and may cause spasm of the glottis, bronchitis, and pneumonia. =Sulphurous Acid Gas.=--One of the products of combustion of common coal. =Hydrochloric Acid Gas.=--Irrespirable when concentrated, and very irritating when diluted. Very destructive to vegetable life. =Chlorine.=--Used in bleaching, and as a disinfectant. Greenish-yellow colour, suffocating odour. In poisoning, inhalation of sulphuretted hydrogen gives relief. XXVIII.--VEGETABLE IRRITANTS The chief vegetable purgatives are aloes, colocynth, gamboge, jalap, scammony, seeds of castor-oil plant, croton-oil, elaterium, the hellebores, and colchicum. All these have, either alone or combined, proved fatal. The active principle in aloes is aloin; of jalap, jalapin; of white hellebore, veratria; and of colchicum, colchicin. Morrison's pills contain aloes and colocynth; aloes is also the chief ingredient in Holloway's pills.