THE ADRENAL SECRETION AND PULMONARY RESPIRATION. 123 



weakness of prevailing views as regards the intimate processes 

 of pulmonary respiration. Keichert, 93 referring to the inter- 

 change of and C0 2 between the alveoli and the blood, re- 

 marks, after reviewing the generally accepted doctrines: "It 

 is, however, impossible, under certain conditions, and possibly 

 under ordinary conditions, to account for the transmission of 

 all of either the or the C0 2 by the laws of diffusion. Bohr 94 

 found, in experiments upon dogs, that the tension of oxygen 

 in arterial blood is almost invariably higher than the partial 

 pressure of oxygen in the lungs, and in some instances consid- 

 erably higher. His records of C0 2 , while lacking uniformity, 

 are of like import, and indicate that the tension of C0 2 in the 

 blood is lower than the partial pressure of this gas in the 

 lungs. Although Bohr's results have met with much adverse 

 criticism, they have received substantial support in the recent 

 researches of Haldane and Smith 96 on mice, birds, dogs, and 

 other animals. They found that the normal oxygen-tension in 

 arterial blood is always higher than in alveolar air, and they 

 were consequently led to conclude that the transmission of 

 between the alveoli and the blood cannot be satisfactorily ex- 

 plained by mere diffusion. Moreover, about twice as much 

 argon exists in solution in the blood-plasma as can be accounted 

 for by physical laws. Facts of this kind are explicable on the 

 hypothesis that the living tissues are, as contended by Ludwig, 

 Bohr, and others, actively engaged in the process, but our 

 knowledge is as yet too incomplete and contradictory to justify 

 its acceptance." "In Bohr's experiments," says G. N. Stew- 

 art, 96 "in some of which the animals were made to breathe air 

 containing carbon dioxide in various proportions, the tension 

 of that gas in the air of the lungs varied from 5.8 to 34.6 

 millimeters of mercury, while in arterial blood, taken at the 

 same time, it usually ranged from 10 to 38 millimeters, and 

 was often less than in the alveolar air. If we accept these 

 results we seem shut up to the conclusion that carbon dioxide 

 does not pass through the walls of the alveoli by diffusion. 



98 Reichert: "American Text-book of Physiology," vol. i, 1900. 

 "Bohr: Skandinavisches Archiv fur Physiologic, Bd. ii, S. 236, 1891. 

 96 Haldane and Smith: Journal of Physiology, vol. xxii, p. 231, 1897. 

 96 G. N. Stewart: "Manual of Physiology," p. 242, fourth edition, 1900. 



