RESPIRATION 



69 



sure is reduced to 2.6 mm.-^* This curve was totally at variance 

 with Paul Bert's results, and made it very difficult to understand 

 the effects on animals breathing air with a low oxygen pressure. 

 In 1904 Loewy and Zuntz^^ published further experiments with 

 defibrinated blood giving results much nearer to those of Paul 

 Bert. Meanwhile the subject was taken up by Bohr/^ who not only 

 confirmed Paul Bert in the main, but for the first time showed that 

 the dissociation curve for blood or haemoglobin solutions has a 

 very peculiar shape, with a double bend (Figure 19), and that the 



100 



20 30 40 50 60 70 80 90 100 HO 120 130 \A0 150 

 Figure 19. 

 Curves representing the percentage saturation of haemoglobin 

 with oxygen at different partial pressures of oxygen and CO2. 

 Dog's blood at 38°C. Ordinates ^ percentage saturation with 

 oxygen ; abscissae = partial pressures of oxygen in millimeters 

 of mercury. (Bohr, Hasselbalch, and Krogh.) 



curve for a haemoglobin solution differs considerably from that 

 for blood. For this reason he inferred that the haemoglobin in 

 blood C'haemochrome") differs chemically from crystallized 

 haemoglobin. Bohr, Hasselbalch and Krogh^''' then made the 

 important discovery that the dissociation curve of haemoglobin or 

 "haemochrome" is greatly influenced by the partial pressure of 

 the CO2 present (Figure 19), the CO2 helping to expel oxygen 

 from its combination, so that, as the blood takes up CO2 in its 

 passage through the capillaries, oxygen is liberated from the oxy- 

 haemoglobin more readily than would otherwise be the case. 



"Hiifner, ArcA. f. (Anat. u.) Physiol., p. i, 1890. 



"Loewy and Zuntz, Arch. f. (Anat. u.) Physiol., p. 166, 1904. 



"Bohr, Centralbl. f. Physiol., 17, p. 688, 1904. 



^^ Skand. Arch. f. Physiol., 16, p. 602, 1904. 



