ALKALI RESERVE 



129 



cury is thus regained if many analyses are run. It requires 

 only straining through cloth or 

 chamois skin to prepare it for 

 use again.) 



Procedure. Drawing the 

 Blood. (For at least an hour 

 before the blood is drawn the 

 subject should avoid vigorous 

 muscular exertion as this, pre- 

 sumably because of the lactic 

 acid formed, lowers the bi- 

 carbonate of the blood.) About 

 6 or 7 c.c. of venous blood are 

 aspirated into a centrifuge tube 

 (see Fig. 10) which contains a 

 little powdered potassium oxa- 

 late and some paraffin oil. The 

 tube is subjected to a minimum 

 of agitation after the blood is in 

 it. The slight amount of agita- 

 tion necessary to assure mixture 

 with the oxalate is accomplished 

 by stirring with the inlet tube, 

 rather than by inverting or 

 shaking. The tube and contents are then centrifuged. 



Saturation of Plasma with Carbon Dioxide. After centrifuga- 

 tion about 3 c.c. of the plasma (if it is desired to keep the plasma 



ParafTin OH- 

 Polo.sslaa> Oxal&le*&' 



FIG. 10. Tube Used in Collecting 

 Blood. (Jour. Biol. Chem., 1917, 

 30, 289.) (Hawk.) 



FIG. 11. Separatory Funnel Used in Saturating Blood Plasma with 

 Carbon Dioxide. (Jour. Biol. Chem., 1917, 30, 289.) (Hawk.) 



for the estimation of carbon dioxide at a later time it should be 

 transferred to a paraffined tube, covered with a layer of paraffin 

 oil, stoppered and kept cold; under which conditions it is claimed 



