MECHANISM OF GAS EXCHANGE 595 



proportion of the serum diminishes. Giirber attempts to 

 explain the process by supposing that hydrochloric acid is 

 separated from the sodium chloride by the mass action of 

 the carbonic acid (NaCl + H 2 C0 3 = HC1 + NaHC0 3 ), the 

 hydrochloric acid becoming fixed in the blood cells and the 

 carbonate remaining in the serum. Koppe in turn assumes 

 more complicated processes of wandering of the ions. Who- 

 ever is particularly interested in this question may find full 

 information in the excellent work of Hamburg ("Osmoti- 

 scher Druck und lonenlehre")- 37 "However we may the- 

 oretically regard them," say A. Lowy, "the processes of 

 interchange between the blood cells and the serum con- 

 stantly indicate the existence of some important means of 

 regulation with the purpose of maintaining the carbonic 

 acid tensions in the body at as low and unharmful a level 

 as possible. ' ' 



GAS EXCHANGE IN THE LUNG 



We may here turn to the much discussed question of the 

 kind of forces by which the gas exchange takes place in the 

 lungs. Bohr and his followers for a long time have main- 

 tained the view that the purely physical processes of dif- 

 fusion are not sufficient to explain the phenomena, and that 

 it is essential to ascribe to the endothelial cells of the alveoli 

 the ability to functionate as secretory elements. 



Mechanism of Gas Exchange. Any extensive historical 

 development of the general question, upon which a great 

 sum of most subtile physiological work has been expended, 

 may be the more appropriately dispensed with, as the 

 matter at issue seems at present to be finally settled. The 

 most recent studies upon this subject, those of Leon Fred- 

 ericq, Douglas and Haldane, 38 E. duBois-Beymond, 39 and 



87 Literature : Hamburger, Osmotischer Druck und lonenlehre, 1, 291 

 et seq., Wiesbaden, 1906; A. Lowy, Handb. d. Biochem., 4', 63-64, 1908. 



38 L. Fredericq, Arch, internat. de Physiol., 10, 391, 1911; J. S. Haldane 

 and C. G. Douglas (Oxford), VIII internat. Physiol. Kongr., Wien, Sept., 

 1910; Proc. Roy. Soc., 82B, 331, 1910; cited in Biochem. Centralbl., 10, No. 

 2633 ; Proc. Roy. Soc., 84B, 568. 



89 R. duBois-Reymond (Berlin), Arch. f. (Anat. u.) Physiol., 1910, 257; 

 Berliner, physiol. Ges., July 2, 1909; Centralbl. f. Physiol., 28, 953. 



