206 A TEXTBOOK OF PHYSIOLOGY 



fined places where there is fuel burning with deficient oxygen-supply. 

 To relieve CO poisoning, oxygen should be administered, and artificial 

 respiration performed. 



The whole of the body is very susceptible to a deficiency of oxygen ; 

 it leads to acid formation and lessened alkalinity of the tissues. 

 (Edema, cloudy swelling, and fatty degeneration, according to recent 

 research, are associated with such diminished alkalinity. Lack of 

 oxygen great!} 7 affects the working capacity of the muscles, especially 

 of the heart -muscle. Irritant gas poisons, by producing oedema of the 

 lungs, cause oxygen-want. Recovery is very slow or may not occur after 

 prolonged oxygen-w^ant. Symptoms of oxygen-want may also be 

 induced by poisons which form methsemoglobin. Such poisons are the 

 chlorates of sodium and potassium, nitrites, and dinitrobenzene. 



T, Tracing of the ratio movements; A, tracing of abdominal movements. In top 

 tracing is shown the respiratory movements and time (o w) during which 

 breath coiild be held in Turin. In lower tracing the same at Monte Rosa 

 (1500J feet above sea-level). The increased depth of respiration and inability 

 to hold the breath long is well seen. (Mosso.) 



Asphyxia is caused by interference with the ventilation of the lungs. 

 It may be produced by breathing an irrespirable gas, as already 

 described, but it may also be produced by such means as occlusion of 

 the trachea or opening the chest cavity. When studied experiment- 

 ally as, for example, by clamping the trachea asphyxia is divided 

 into three stages (Fig. 171): 



1. The stage of increasing dyspnoea. 



2. The convulsive stage. 



3. The stage of exhaustion. 



When the trachea is clamped, the first stage lasts about a minute. 

 The breathing is markedly increased in depth, expiration being pro- 



