This acute form often occurs, especially in acute sewer gas poisoning. Besides this, a sub-acute form of sewer gas poisoning is recognised which is attributable, in part at least, to the action of sulphuretted hydrogen, the prominent symptoms being irritation of the mucous membranes and of the intestinal canal. In other severe cases symptoms of the central nervous system preponderate (headache, giddiness, and delirium). These forms of poisoning can be caused not only by sulphuretted hydrogen, but also by other poisonous gases which are found in drains or sewers. As regards treatment, continued inhalation of oxygen, supported by artificial respiration, is often, in serious cases, effective. In severe poisonings also saline injections and bleeding may be advocated. Other symptoms (catarrh, &c.) must be treated symptomatically. CARBON BISULPHIDE Pure carbon bisulphide (CS₂) is a colourless, peculiar-smelling liquid which boils at 46° C. As Lehmann has shown, even 1·5 to 3·0 mg. CS₂ per litre of air produces distress—with acute symptoms of poisoning (congestion, giddiness, sickness, &c.). Industrial carbon bisulphide poisoning is, however, chronic in nature and induced by continuous inhalation of small quantities of the fumes. To understand the action of carbon bisulphide, its capacity for dissolving fats and fatty substances must be taken into account. Its injurious effect extends to the nerve tissues (central and peripheral nervous system) and the glandular tissues. Throughout chronic industrial carbon bisulphide poisoning, which has been described fully by Delpech, Laudenheimer, and others, nervous and psychical symptoms predominate, together with severe chronic digestive derangement. The patient after exposure for some time suffers from violent headache, giddiness, and sickness; he has sensations of cold, pains in the limbs, a feeling of ‘needles and pins,’ and itching in different parts of the body. Gradually a condition of general excitement develops. Sleeplessness, cramps, and palpitation set in. At the same time the nervous system becomes involved—hypersensitiveness, loss of sensation or complete numbness of some parts of the skin, diminution of muscular power, disturbances of movement, twitching, violent trembling, wasting of the muscles, and paralysis; the sight also is sometimes affected. The stage of excitement, in which the patient often becomes strikingly loquacious without cause, passes gradually, as the nervous symptoms develop, into the stage of depression; sometimes this takes weeks and months; excitement and gaiety give place to deep depression; other symptoms appear—weakness of memory, mental dulness, and difficulty in speaking. The powers of sensation become affected, paralysis increases, and digestive disturbances, anæmia, and general loss of strength are manifest. Occasionally definite mental disease (psychosis, mania, melancholia, dementia, &c.) develops.