DETERMINATION OF THE RESPIRATORY EXCHANGE 321 



measuring the blood-flow through the organ in a given time. Such 

 experiments have been made upon the heart, muscles, kidneys, 

 salivary glands, and other tissues-. 



In the following table some of the results obtained are given. 

 The gaseous interchange may be expressed either in c.c. per minute 

 or in c.c. per gramme of tissue substance per minute. 



TABLE SHOWING EFFECT OF ACTIVITY UPON THE INTERNAL RESPIRATORY 



EXCHANGE. 



Resting. 



Active. 



Organ. 



Gas in c.c. per Min. 



0, 



CO, 



Gas in c.c. per Min. 

 2 C0 2 



The oxygen use of the heart is reduced during vagal stimulation 

 and increases after its cessation. The use of oxygen by the heart is 

 also greatly reduced by the injection of chloroform water into the blood. 



When the nerve of a muscle is divided, its metabolism is markedty 

 decreased; the respiratory quotient is practically unaltered by the 

 complete rest so induced. The oxygen use per minute per kilo- 

 gramme of substance has been estimated as follows: Muscle, 4 c.c.; 

 salivary gland, 25 c.c.; pancreas, 40 c.c.; intestine, 23 c.c.; kidney, 

 26 c.c. ; liver, 30 c.c. 



Energy displayed by a contracting muscle or a secreting gland is not 

 in itself a manifestation of oxidation in the sense that the work of an 

 internal combustion engine is a direct manifestation of the oxidative 

 explosion in the cylinder; they are more to be compared to the 

 running-down of an alarm clock. The closk is wound, and at a given 

 moment the potential energy of the spring is released. It must then 

 be rewound. It is during the period of " rewinding " that oxidation 

 is increased and an ample supply of blood is required. There is some 

 evidence that the pressure of oxygen in the tissue- juices of glands 

 approximates to that in the venous blood, while in muscle it is almost 

 nil. The latter, therefore, on any diminution of blood-flow suffers 

 from oxygen-want. 



The bloo 1 which leaves an organ is warmer, inore acid, and 

 altered in saline content. Each of these factors may aid the dis- 



21 



