CHAPTER IX 



THE REGULATION OF THE SUPPLY OF OXYGEN 

 TO THE TISSUES 



FROM the consideration of the call of the tissues for oxygen, I pass 

 to the mechanism by which that call is met. The information about 

 the passage of oxygen from the blood to the organs may be considered 

 under two main headings: firstly the provision for bringing to the 

 organ the quantity of oxygen which is required, and secondly the 

 physical process by which the oxygen is transferred from the capillary 

 blood vessel to the cell. In the case of most organs of the body the 

 sole channel by which the organ receives its oxygen is its nutrient 

 artery. One organ, the liver, has two channels of supply; it is by 

 no means obvious whether the portal vein or the hepatic artery 

 provides the essential oxygen supply. I shall clear the ground by 

 first considering this question of the liver, then I shall pass to the 

 functional fluctuations in the oxygen supply of organs generally and 

 the mechanism by which these fluctuations are brought about. 



Concerning the liver, then, let me quote two text-books of physio- 

 logy currently read by students : (1) "The liver has a double blood 

 supply : the portal vein which supplies a rich capillary anastomosis 

 round every liver cell and carries venous blood from the alimentary 

 canal, and the hepatic artery, which carries oxygenated arterial blood 

 and supplies chiefly the connective tissue surrounding the bile ducts 

 and blood vessels in the division between the lobules, known as 

 Glisson's capsule." (2) "The hepatic artery, the chief function of 

 which is to distribute blood for the nutrition of Glisson's capsule, the 

 walls of the ducts and blood vessels, and other parts of the liver." 

 No one reading these statements would have been surprised had 

 a quantitative investigation of the oxygen supply of the liver shown 

 that the hepatic artery brought but a trifling quantity of blood to 

 the liver and found oxygen merely for the accessory structures. Yet 



