1188 



PHYSIOLOGY 



some constituent common to both plasma and corpuscles, and it is 

 natural to think first of the alkalies of the blood. When blood-plasma 

 is calcined, the ash is found to be distinctly alkaline and to contain an 

 amount of sodium greater than is necessary to combine with the other 

 acid radicals, e.g. Cl, S0 4 , and P0 4 , and this excess becomes greater if 

 we consider that a great part of the P0 4 and S0 4 is derived from the 

 oxidation of the sulphur and phosphorus present in organic combina- 

 tion in the plasma. We may therefore conclude that a considerable 

 part at any rate of the carbon dioxide exists in the plasma as sodium 

 carbonate or sodium bicarbonate. In the same way a certain pro- 



40 



10 20 30 40 50 60 70 80 90 100 110 120 130 



FIG. 498. Curve of CO. 2 tension in blood. 



Ordinates = c.c. C0. 2 in 100 c.c. blood ; abscissas = tension of CO., in mm. Hg. ; 

 o as determined by Jaquet ; x as determined by Bohr. 



portion of the carbon dioxide which is held by the corpuscles is probably 

 in combination with sodium. Haemoglobin also has the power of 

 combining with carbon dioxide, and unstable compounds may be formed 

 between carbon dioxide and the proteins of the plasma itself. Accord- 

 ing to Loewy one hundred cubic centimetres of arterial blood from the 

 dog would yield normally about 40 c.c. of carbon dioxide. These 40 c.c. 

 would be divided as follows : 



In simple solution in the plasma and corpuscles . . 



, . , ((a) in corpuscles 6-81 

 As sodium bicarbonate ;, ( . . r 



\ (o) m plasma .... 12-0 / 



In organic combination with haemoglobin in corpuscles . 7-5 ) 



In organic combination with proteins of the plasma . 11-8 / 



1-9 c.c. 

 18-8 c.c. 



= 19-3 c.c. 



It will be noted that although we are dealing here with arterial 

 blood, in which the tension of carbon dioxide is comparatively low, 



