RESPIRATION 125 



anoxaemia must now be described. A knowledge of them is of 

 great importance in practical medicine. If a pure anoxaemia is 

 produced very suddenly, as by breathing pure nitrogen, hydro- 

 gen, methane, or nitrous oxide, loss of consciousness occurs quite 

 suddenly and with no previous warning symptoms. Thus a miner 

 who puts his head into a cavity in the roof full of pure, or nearly 

 pure, methane drops suddenly as if he had been felled ; and when 

 he recovers after breathing pure air for a few seconds he some- 

 times even imagines that he has been knocked down by another 

 man, and acts accordingly. If the anoxaemia is produced with 

 only moderate rapidity the marked temporary disturbances, al- 

 ready referred to, in the breathing and circulation give, as a rule, 

 some warning of what is coming. But when the onset is gradual 

 there is little or no preliminary discomfort, and for this reason 

 the onset of pure anoxaemia is very insidious, and the condition 

 is, therefore, in practice a dangerous one, as is well seen in CO 

 poisoning, or in ascents to very high altitudes in balloons or aero- 

 planes, or in many clinical cases. Thus although CO is not very 

 poisonous as compared with other gaseous poisons, it is responsible 

 for a far larger number of deaths than any other gaseous poison 

 not used in warfare. 



As the slow onset of anoxaemia advances, the senses and intellect 

 become dulled without the person being aware of it; and if the 

 anoxaemia is suddenly relieved by means of oxygen or ordinary 

 air, the corresponding sudden increase in powers of vision, hear- 

 ing, etc., is an intense surprise. The power of memory is affected 

 early, and is finally almost annulled, so that persons who have ap- 

 parently never lost consciousness can nevertheless remember noth- 

 ing of what has occurred. Powers of sane judgment are much 

 impaired, and anoxaemic persons become subject more or less to 

 irrational fixed ideas, and to uncontrolled emotional outbursts. 

 Muscular coordination is also affected, so that a man cannot walk 

 straight or write steadily. With further increase in the anoxaemia, 

 power over the limbs is lost; the legs first being paralyzed, then 

 the arms, and finally the head. The senses are lost one by one, hear- 

 ing being apparently the last to go. The sense of painful impres- 

 sions on the skin seems to be lost early. Thus miners suffering from 

 CO poisoning, but not to the point of losing consciousness, are 

 often burnt by their lamps or candles without their being aware of 

 the burn at the time. 



In many respects the symptoms of anoxaemia resemble those 

 of drunkenness, and a man suffering from anoxaemia cannot be 



