hy h. s. halcko wardlaw. 805 



Effect op Respiratory Movements. 



Hill and Flack considered, as was mentioned earlier, that the 

 smaller respiratory exchange during the holding of the breath 

 was due to hindrance of the circulation. They supposed that 

 the normal respiratory movements hastened the flow of blood. 

 Dogiel and Kowalewsky (1870) showed, however, that stoppage 

 of artificial respiration in curarised dogs for periods of less than 

 40 seconds exerted no hindering effect on the circulation. More 

 recently, Ebert (191 4) has shown that the state of distension 

 of the lungs has, of itself, no influence on the circulation through 

 them, and that the actual movements of inspiration and of expira- 

 tion respectively hasten and hinder the circulation to correspond- 

 ing extents. 



It is evident also in the present experiments, that the slower 

 respiratory exchange during the holding of the breath is not due 

 to a slowing of the circulation brought about by the absence of 

 the movements of bi-eathing. When the breath is held for 30 

 seconds, the four or five respirations, which would normally be 

 made in that time, do not occur to exert their effect on the circu- 

 lation. If circulatory disturbances due to the absence of respi- 

 ratory movements be the cause of the slower gaseous exchange 

 when the breath is held, then, as each succeeding respiration is 

 missed, the exchange will be retarded more and more. When 

 one respiratory movement is made during a period of 20 seconds, 

 instead of the normal four, then the respiratory exchange will 

 be increased, above that occurring when the breath is held, by 

 about one-fourth of the amount of increased respiratory exchange 

 occurring during normal respiration. The rate of the pulse of 

 this subject is the same, after holding the breath for 30 seconds, 

 as immediately before. 



The accompanying figures give the results of experiments in 

 which the effect of one respiratory movement in 20 seconds, and 

 of three respiratory movements, are compared Avith the effect on 

 the gaseous exchange of holding the breath for the same period. 

 The figures in column "a" represent the alveolar percentages of 

 carbon dioxide after holding the breath for 20 seconds. The 

 figures in columns "b" and "c" are the corresponding alveolar 



