RESPIRATION 289 



bated by the body in other ways, one being the prompt stoppage 

 of ammonia formation and the excretion of alkaline urine, as 

 already explained ; and, whether in consequence of this or of other 

 causes, the so-called "alkaline reserve" of the blood decreases 

 greatly, as Henderson and Haggard showed (Chapter VIII). 

 Nevertheless the anoxaemia and alkalosis cannot be overcome. 

 The circulation rate steadily diminishes ; the heart, in consequence, 

 probably, of anoxaemia, begins to fail, apart altogether from its 

 inadequate supply of venous blood ; and finally there is complete 

 failure of the heart. If, however, the forced breathing is stopped 

 before cardiac failure has occurred, death may occur from pro- 

 longed apnoea and consequent acute asphyxia, as mentioned in 

 Chapter II. When the condition of shock has developed suffi- 

 ciently, the animal cannot be saved by adding CO2 to the air 

 breathed; but in the earlier stages this procedure is quite effective. 

 The hopeless condition to which the animal is reduced by the 

 forced artificial respiration is probably analogous to the condition 

 produced in various ways by prolonged anoxaemia, as in very 

 severe CO poisoning, or in a patient who has been allowed to 

 suffer for long from severe arterial anoxaemia. It is probably the 

 anoxaemia rather than the alkalosis that produces the serious 

 effect, since, as already mentioned, forced breathing of oxygen is 

 more easily tolerated than forced breathing of air. 



A condition of shock produced by forced artificial respiration 

 is, of course, not a natural occurrence; but Henderson showed 

 that excessive respiration can be produced by natural means in 

 two ways : firstly, by powerful afferent stimuli, as by electrical 

 stimulation of the sciatic nerve, even in the presence of anaesthesia 

 sufficient to abolish consciousness; and secondly, by the action of 

 ether in doses not sufficient to anaesthetize an animal completely. 

 The afferent stimuli, or the ether, increase the breathing to such 

 an extent as to diminish greatly the CO2 in the arterial blood, 

 thus producing great alkalosis or acapnia, with concomitant anox- 

 aemia. By these means, therefore, a condition of shock may easily 

 be produced in a patient; and it seems probable that in this way 

 the condition generally known as shock is frequently produced as 

 a matter of fact. 



Clinical evidence seems, nevertheless, to indicate that in many 

 ordinary cases of wound shock there has been no excessive 

 breathing. On the other hand there are many facts indicating 

 that the symptoms are due to absorption from injured tissues of 



