The poison of Expired Air. It is well known that air once breathed is unfit for further respiration, and this change is due to the carbonic oxid it contains and to a peculiar poison caused by tissue waste and called by some "crowd poison." Without participating in the controversy regarding the importance of carbonic oxid as a toxic factor it may be stated that it is the most reliable index of air contamination and that Mosso found it occasioned unconsciousness and suspension of respiration if in excess of the proportion of 21 to 233. Angus Smith has shown that if the normal proportion of carbonic oxid in the air were increased to 0.1 per cent, that systemic disturbances with increased respiration and decreased pulse rate were produced. But that this is not the chief poisonous agent in expired air has been shown by the researches of Brown-Sequard, d'Arsonval and Wurtz who experimented with the condensed vapors exhaled by dogs and man. These when injected into animals produced choleraic diarrhea, dilitation of the pupil, rapid lowering of the temperature, even as much as 5°, increase of the heart-beat to 240 or 280 and death from cardiac syncope. It has not yet been proven that carbon monoxide or nitrous acid exist in expired air in sufficient quantities to produce poisoning if inhaled.

That poisonous materials are expelled from the body in the perspiration is proved by the experiments of Arloing (12) who found that the sweat of a man who had been dancing, when injected into dogs caused drowsiness and violent diarrhea. That from the lower limbs injected into rabbits caused great nervous excitability, clonic spasms followed by paralysis and death. In the former case post mortem examination showed congestion of the entire alimentary canal, yellow patches on the liver surface and white clots in the heart cavities.

It was thought at one time that ochlosis or sweat poisoning was the cause of the serious and fatal symptoms which result from the varnishing of the body or from large burns. It is now believed that they are due to increased radiation of body heat and the formation of a body resembling peptotoxin.