INTERNAL RESPIRATION. 867 



in WERIGO. Still ZUNTZ has presented weighty objections to WERIGO'S 

 experiments, and BOHR 1 has later also shown that we have no positive 

 basis for the above assumption. 



The conditions as to the elimination of carbon dioxide in the lungs 

 are not quite clear. On the one hand we have advocates of the view 

 that the gas exchange takes place simply according to physical laws 

 and is chiefly considered as a diffusion process. According to the former 

 views of BoHR, 2 which he has supported by recent experiments, a diffusion 

 does take place, but the lung is a gland which has the power of secreting 

 gases, and the gas exchange in the lungs is essentially a secretory proc- 

 ess. In his most recent work BOHR, S after a thorough criticism of the 

 methods used in the measurement of the lung diffusion and based upon a 

 new calculation of the extent of diffusion, has come to the conclusion 

 that the specific activity of the lungs consists in that a difference in 

 pressure necessary for the diffusion is brought about. 



That a true secretion of gases occurs in animals follows from the composition 

 and behavior of the gases in the swimming-bladder of fishes. These gases con- 

 sist of oxygen and nitrogen with only small quantities of carbon dioxide. In 

 fishes which do not live at any great depth the quantity of oxygen is ordinarily 

 as high as in the atmosphere, while fishes which live at great depths may, accord- 

 ing to BIOT and others, contain considerably more oxygen and even above 80 per 

 cent. MOREAU has also found that after emptying the swimming-bladder by 

 means of a trocar, new air collected after a time, and this air was richer in oxygen 

 than the atmospheric air, and contained even 85 per cent oxygen. BOHR, who 

 has proven and confirmed these statements, also found that this accumulation 

 is under the influence of the nervous system, because on the section of certain 

 branches of the pneumogastric nerve it is discontinued. It is beyond dispute that 

 there is here a secretion and not a diffusion of oxygen. Recently JAEGER 4 has 

 given a further explanation as to the secretory activity of the swimming-bladder. 



From what has been said above (page 858) in regard to the internal 

 respiration, one can conclude that it consists chiefly that in the capil- 

 laries the oxygen passes from the blood into the tissues, while the car- 

 bon dioxide passes from the tissues into the blood. 



The assertion of ESTOR and SAINT PIERRE that the quantity of oxygen 

 in the blood of the arteries decreases with the remoteness from the heart 

 has been shown to be incorrect by PFLUGER, S and the oxygen tension in 

 blood on entering the capillaries must be higher. The oxygen tension 



1 Holmgren, Wien. Sitzungsber., 48; Werigo, Pfliiger's Arch., 51 and 52; Zuntz, 

 ibid., 52; Bohr, see Nagel's Handbuch der Physiologic. 



2 Centralbl. f . Physiol., 21, 367. 



3 Ibid., 23, 374; Skand. Arch. f. Physiol., 22, 221 (1909). 



4 Biot, see Hermann's Handbuch d. Physiol., 4, Thl. 2, 151; Moreau, Compt. 

 Rend., 57; Bohr, Journ. of Physiol., 15. See also Hiifner, Arch. f. (Anat. u.) Physiol., 

 1892; Jaeger, Pfliiger's Arch., 94. 



5 Estor and Saint Pierre with Pfltiger in Pfliiger's Arch., 1. 



