546 FRANCIS W. PEABODY 'AND EDNA H. TOMPKINS 



that it is due to acidosis. One factor may be the extra work of the re- 

 spiratory muscles. Reach and Roder found that an increase in the 

 minute-volume of air breathed is accompanied by an increase in metab- 

 olism, and also that an increase in the depth of breathing causes a rise in 

 metabolism, even if the minute-volume remains constant. According to 

 them an increase of minute-volume is brought about with less energy if 

 the rate of breathing is increased than if the depth is increased. This 

 observation has some bearing on the diseases of the respiration and cir- 

 culation, for the dyspnea produced in these conditions is associated with a 

 rise in the minute-volume of air breathed, and this rise is frequently de- 

 pendent more on an increase of the rate than of the depth. Minkowski 

 summarized his review on the metabolism in circulatory and respiratory 

 diseases by the statement that most observations show either normal or 

 slightly elevated metabolism, and he attributed the latter to muscular com- 

 pensations. Reinhardt found increased carbon dioxid output in em- 

 physema, and also explained it on the basis of the increased muscular 

 effort of respiration. Hellin, working on rabbits with extirpation of one 

 lung, ^Carpenter and Benedict (a) on a man with obliteration of the left 

 lung, Voit on a man with the use of but one lung due to pleural exudate, all 

 found no abnormality in the metabolism. Lundsgaard(&) (c) (d) states 

 that the degree of unsaturation of the venous blood agrees with that of the 

 oxygen absorption in compensated and uncompensated circulatory diseases. 

 It is normal in the former and increased in the latter. Harrop(c) also 

 found no abnormalities in the venous and arterial oxygen in cardiac cases 

 without arhythmia, compensated and at rest, and remarked that the oxygen 

 consumption was increased in decompensated cases and normal in com- 

 pensated. Aub and Stern reported a case of heart block under thyroid 

 therapy. Unfortunately no metabolism observation could be obtained be- 

 fore the institution of the therapy, but seventy days after its cessation the 

 metabolism was normal. 



While the gaseous exchange can only be determined in patients who 

 are in moderately good clinical condition, investigations on the chemical 

 changes in the body produced by diseases of the circulation and respiration 

 can be carried out by other methods which throw direct or indirect light on 

 the metabolism. As suggested above, the effect of disease on the external 

 or pulmonary respiration, a function which is interfered with in both 

 circulatory and respiratory disease, may be approached from the stand- 

 point of the blood gases with a view to determine whether there is dis- 

 turbance of oxygen absorption or carbon dioxid excretion. In this con- 

 nection it is, of course, the arterial blood, in comparison with the venous, 

 which is of particular interest, and only comparatively recently has a 

 method been developed by which arterial blood can be safely and easily 

 obtained in man. In 1912 Hiirter published a considerable series of 

 observations on the arterial blood gases. In compensated heart disease 



