858 RESPIRATION AND OXIDATION. 



fluid, while, on the contrary, the total quantity of carbon dioxide, and 

 especially the quantity firmly combined, decreases with the quantity 

 of pus-corpuscles. 



II. THE EXCHANGE OF GAS BETWEEN THE BLOOD, ON THE ONE HAND, 

 AND PULMONARY AIR AND THE TISSUES, ON THE OTHER. 



In Chapter I (page 42) it was stated that we are to-day of the 

 opinion, derived especially from the researches of PFLUGER and his 

 pupils, that the oxidations of the animal body do not take place in the 

 fluids and juices, but are connected with the form-elements and tissues. 

 It is nevertheless true that oxidations take place in the blood itself, al- 

 though, only to a slight extent; but these oxidations depend, it seems, 

 upon the form-elements of the blood, hence it does not contradict the 

 above statement that the oxidations exclusively occur in the cells and 

 chiefly in the tissues. 



The gaseous exchange in the tissues, which has been designated 

 internal respiration, consists chiefly in that the oxygen passes from the 

 blood in the capillaries to the tissues, while the great bulk of the carbon 

 dioxide of the tissues originates therein and passes into the blood of the 

 capillaries. The exchange of gas in the lungs, which is called external 

 respiration, consists, as is seen by a comparison of the inspired and 

 expired air, in the blood taking oxygen from the air in the lungs and giving 

 off carbon dioxide. This does not exclude the fact that in the lungs, as in 

 every other tissue, an internal respiration takes place, namely, a com- 

 bustion with a consumption of oxygen and formation of carbon dioxide. 

 According to BOHR and HENRIQUES 1 the lungs take a variable but 

 sometimes a very important part in the total metabolism. This part, 

 which on an average is 33 per cent, but may even rise above 60 per 

 cent of the total ' metabolism, depends, these experimenters say, upon 

 the fact that the intermediary metabolic products formed in the tissues 

 are burnt in the lungs. It is also in part represented by the specific 

 work of the lungs. 



What kind of processes take part in this double exchange of gas? 

 Is the gaseous exchange simply the result of an unequal tension of the 

 blood on one side and the air in the lungs or tissues on the other? Do 

 the gases pass from a place of higher pressure to one of a lower, according 

 to the laws of diffusion, or are other forces and processes active? 



These questions are closely related to that of the tension of the 

 oxygen and carbon dioxide in the blood and in the air of the lungs and 

 tissues. 



1 Centralbl. f. Physiol., 6, and Maly's Jahresber., 27. 



