56 RESPIRATION 



During the war cases were very common of what, according as 

 one nervous symptom or another was most prominent, was desig- 

 nated as "chronic gas poisoning," "soldier's heart," "disordered 

 action of the heart," "neurasthenia," etc. In these cases "shortness 

 of breath" on exertion was a common and prominent symptom. 

 Their breathing was investigated by Meakins, Priestley, and my- 

 self 10 and we found a marked deviation from normality in its reg- 

 ulation. In many of these persons the frequency of the breathing 

 was very abnormally increased during rest, and in nearly all there 

 was on exertion a quite abnormal increase of frequency, with a 

 corresponding reduction of the normal increase of depth. The 

 symptoms were thus the same as those of fatigue of the respira- 

 tory center, and on extra exertion these patients were liable to 

 lose consciousness with asphyxial symptoms, just as in ordinary 

 overfatigue of the center. Another prominent symptom was that 

 the patients were unable to hold a deep breath for anything like 

 a normal period, even if they were given oxygen to help. Many of 

 them were also subject, particularly at night, to attacks of rapid 

 shallow breathing with a sense of impending suffocation. 



The condition of the breathing in these patients was evidently 

 such as would be produced by an abnormal increase in the readi- 

 ness with which the Hering-Breuer reflex is elicited, and we 

 therefore described the respiratory condition as one of "reflex re- 

 striction" in the depth of breathing. At the time we were not 

 aware of the symptoms of fatigue of the respiratory center. In the 

 condition of fatigue the shallow and rapid breathing is just what 

 would result from an increase in the strength of the Hering- 

 Breuer reflex, and a similar apparent exaggeration of this reflex 

 is present, as already seen in connection with the results of artificial 

 respiration, in the condition of apnoea. In view, therefore, of all 

 the facts relating to the respiratory movements in fatigue, apnoea, 

 and neurasthenia, it seems probable that the apparent increased 

 strength in the Hering-Breuer reflex is due to a diminution in 

 the persistency of the individual inspiratory and expiratory dis- 

 charges from the center, rather than to any real increase in the 

 inhibitory Hering-Breuer discharges up the vagus nerves. It is 

 thus only the weakness of the center that enables the Hering- 

 Breuer reflex to gain the upper hand. 



If we apply the same general conception to the other exag- 



10 Haldane, Meakins, and Priestley, Reports of the Chemical Warfare Meciical 

 Committee, No. 5, Reflex Restrictions of Breathing, 1918, and No. n, Chronic 

 Cases of Gas Poisoning, 1918; also Journ. of Physiol., LII, p. 433. 



