i8o 



Scientific Proceedings (108). 



elusion may therefore be drawn (at least in respect to uracil), 

 that, in the metabolism of yeast nucleic acid before the pyrimidine 

 is liberated and even before the nucleoside is formed, the pyrimidine 

 is altered in such a way that it may be further broken down and 

 its nitrogen converted into urea. 



96 (1556) 



The variable acidity of hemoglobin and the distribution of chlorides 



in the blood. 



* 



By Franklin C. McLean, H. A. Murray, Jr. 

 and L. J. Henderson. 



[From Boylston Chemical Laboratory, Harvard University.} 



We have undertaken an investigation of the shift of chlorides 

 between the serum and corpuscles of the blood described by 

 Koeppe and by Hamburger, and have studied this phenomenon 

 particularly in its relation to the heterogeneous acid-base equili- 

 brium between hemoglobin, oxygen, carbon dioxide, bicarbonate, 

 and the concentration of hydrogen ions. 



Such a shift in chlorides may be easily produced, in vitro, by 

 disturbing, in any way, the acid-base equilibrium, and is observed, 

 under physiological conditions, between arterial and venous 

 blood. 



For the purposes of the investigation we have used fresh 

 defibrinated ox blood, expelling the oxygen from combination with 

 hemoglobin by first passing through carbon dioxide at 38 0 and 

 then by boiling in vacuo at the same temperature. This can be 

 accomplished with only very slight hemolysis. The blood has 

 then been brought into equilibrium, at constant temperature 

 and at atmospheric pressure, with various tensions of carbon 

 dioxide, first in an atmosphere free from oxygen and then in an 

 atmosphere with oxygen present at the tension at which it is 

 present in atmospheric air. The whole blood has then been 

 analyzed for oxygen and carbon dioxide, free and combined, and 

 the serum, obtained by immediate centrifugalization under oil, 

 analyzed for carbon dioxide and chlorides. The atmosphere 



