542 FRANCIS W. PEABODY AND EDNA H. TOMPKINS 



more difficult to determine and can be approached only indirectly through 

 a study of the waste products of metabolism in the blood, urine and expired 

 air. Interference with the circulatory function of the removal of the 

 non-volatile products of metabolism can also be studied only indirectly, 

 as there is no method of investigating their accumulation in the tissues in 

 life. Some light on this subject may be gained by analyses of blood and 

 urine. With regard to disturbances in the circulatory function of trans- 

 porting metabolites from one organ to another within the body, there 

 is no evidence of importance to be obtained. 



In the diseases of the respiration and circulation, the pathological 

 effects on the metabolism are so largely due to insufficient supply of 

 oxygen that it may be well to review briefly the results to be expected 

 from oxygen-lack. Studies upon normal men, under conditions of low 

 oxygen pressure, will better represent what is to be expected in circulatory 

 and respiratory diseases, than will a consideration of any other patho- 

 logical condition in which the supply of oxygen to the body is abnormal. 



In the expedition to Pikes Peak, Douglas and his collaborators carried 

 out an investigation on the adaptability of the body to low oxygen tension. 

 The rapid pulse rate and increased blood pressure upon first entrance into 

 the low oxygen pressures seemed to be only emergency compensations. 

 They lasted only until those body changes occurred which were permanent 

 for the duration of the stay in the rarified atmosphere, and which might 

 correspondingly be expected in circulatory and respiratory disorders. 

 The percentage and total amount of hemoglobin, the erythrocyte count 

 and the percentage saturation of the arterial blood with oxygen gradually 

 increased. At the same time the total ventilation increased, and the 

 alveolar carbon dioxid tension dropped, thus causing a higher alveolar 

 oxygen tension than would otherwise have been possible. More recently, 

 work in the Air Medical Service, United States Army, has largely cor- 

 roborated these findings. If these compensatory factors fulfill their pur- 

 pose and provide sufficient oxygen to the tissues for all ordinary demands 

 of the body, there is only one change in the metabolism to be expected 

 an increase in the total heat production depending upon the excess energy 

 of the organs taking part in the compensation. The cardiac and respira- 

 tory muscles are the most important. Plesch(Z>) valued the heat produc- 

 tion of a heart with a rate of about 60 beats per minute as five per cent of 

 the total metabolism of the body, and showed that its caloric output varied 

 directly with its rate. He also estimated the heat production of the 

 respiratory muscles as one-fourth more than that of the heart. Evans 

 likewise showed, on isolated heart-lung preparations of dogs, that the 

 metabolism of the heart varies closely with the rate of contraction. There- 

 fore, the measure of increase in the metabolism is dependent upon the 

 grade of the compensations, and it may fall upon one or all of the three 



