1 68a 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



excised lung following the injection of tracer materials 

 (323, 405), and 3) roentgenography, including 

 angiocardiography (202). These approaches are all 

 qualitative but have clearly established two features 

 of the pulmonary circulation : the distribution of the 

 pulmonary blood flow is ordinarily quite uniform 



but that it may be drastically modified by appro- 

 priate stimulation (fig. 13); structural abnormalities 

 are prepotent over physiological influences in deter- 

 mining the course taken by the blood (427). The 

 direct observations have also been used to account 

 for a variety of otherwise inexplicable clinical phe- 



• • 



♦ ♦ 



• • • .. m r i 



•• • ♦ 



•Supine 

 + Upright 



OXYGEN UPTAKE (cc/min) 



400 800 1200 1600 2000 



pig. 12. Relationship between oxygen uptake and cardiac output at rest (supine), during supine 

 exercise, and during upright exercise. The diagonal line (at the far left) is based on the method of 

 least squares and represents spontaneous variations in the cardiac output in 56 normal subjects at 

 rest. This line lies to the left of the exercise data and has a steeper slope. For any given oxygen uptake, 

 the cardiac output is lower during upright exercise than during supine exercise. [After Reeves el al. 

 (336)-] 



2400 



2800 



fig. 13. Variations in the distribution of the pulmonary blood flow. For each experiment, filtered 

 India ink was injected into a marginal ear vein of an unanesthetized rabbit loosely restrained in its 

 normal body position. .4.- uniform distribution of the India ink; B: "patchy' distribution following 

 introduction of a cardiac catheter into the right ventricle via the right external jugular vein (local 

 procaine anesthesia). [After Tuller el al. (405).] 



