RESPIRA TION 



255 



alkalies, for potassium has been demonstrated microchemically in 

 frog's erythrocytes (Macallum) (Frontispiece), and the titratable 

 alkalinity of ' laksd ' blood (pp. 24, 27) is greater than that of 

 unlaked blood, unless a long time is allowed in the case of the latter 

 for the alkalies of the corpuscles to reach the acid used in titration. 

 Some observers believe that a weak compound of carbon dioxide 

 can be formed with haemoglobin ; for a solution of haemoglobin 

 absorbs more of this gas than water, and the quantity absorbed is 

 not proportional to the pressure. The haemoglobin of the corpuscles 

 may therefore hold a portion of the carbon dioxide in combination. 



90 



80 



70 



1 



20C.C. 

 l8f.C. 

 16 C 

 T4C.C 

 I2CG 

 lOCjC. 



8CC. 



6C.C. 



4C.C. 



2C.C. 



03C.C. 



10 20 30 40 50 60 70 60 90 100 110 120 130 140 ISO 



FIG. 109. CURVES OF DISSOCIATION OF OXYGEN FOR HORSE'S BLOOD (B) AXD 



DOG ? S HEMOGLOBIN SOLUTION (H) AT 38 C. (BOHR). 



The figures along the base-line and the vertical axis at the left have the same 

 signification as in Fig. 108. The figures along the vertical at the right give the 

 actual number of c.c. of oxygen chemically combined by 100 c.c. of the blood 

 for each pressure of oxygen. Thus, with pressure 10 mm. 6 c.c. of oxygen were 

 taken up by the blood-pigment in 100 c.c. of blood. The interrupted line P 

 indicates the amount of oxygen dissolved in the plasma of the blood at each 

 partial pressure on the assumption that the plasma is two-thirds of the volume 

 of the blood. Thus, at 150 mm. oxygen pressure the plasma of 100 c.c. of blood 

 took up 0*3 c.c. oxygen. 



When blood is saturated with carbon dioxide and then separated 

 into serum and clot, the serum is found to yield more gas than the 

 clot ; but if the serum and clot are separately saturated, the latter 

 takes up more carbon dioxide than the former. From this it is 

 argued that a substance combined with carbon dioxide must in 

 blood saturated with the gas pass out of the corpuscles into the 

 serum. This cannot be haemoglobin, for it remains in the cor- 

 puscles, but it may very well be an alkali, combined with the carbon 

 dioxide and thus set free from its connection with the haemoglobin 

 And, as a matter of fact, under the circumstances described, it has 

 been found that alkalies do pass from the clot into the serum, and 

 chlorine from the serum into the corpuscles, which at the same 

 time gain water and become larger. The molecular concentration 

 (p. 398) of the serum of defibrinated blood, as measured by the 

 lowering of the freezing-point, increases when it is saturated with 

 carbon dioxide. On the other hand, when blood is saturated with 



