GAS ANALYSIS AND OXYGEN 331 



7-8 cm. long, is graduated into thirty divisions, each 2 mm. long. 

 A detachable rubber cup of about 1 ml. capacity may be fitted over 

 the cylindrical glass cup. 



The sampling pipette consists of a piece of thin-walled glass tub- 

 ing having a 1-1.5 mm. bore, and it is drawn out to a tip which is 

 ground smooth in order to permit a snug fit into the bottom of the 

 glass cup. The mark on the pipette is placed so that the volume from 

 the mark to the tip is equal to 100 divisions on the capillary, i.e., 

 39.3 fA. The capillary and the pipette can be calibrated with a 

 microburette or by mercury weighing. (Interchangeable pipettes and 

 syringes are supplied by Mr. J. D. Graham, Department of Physi- 

 ology, University of Pennsylvania Medical School.) 



Collecting Blood Samples. Citrated blood samples may be 

 collected directly in the blood pipettes from finger pricks as de- 

 scribed by Scholander (1942c). A short tube, 15 mm. long, flanged 

 out at one end is held on the finger tip by a rubber band which 

 presses the flange against the skin. A few crystals of citrate are 

 placed in the tube; a tourniquet is wound around the finger toward 

 the tip. The finger is pricked through the tube using a spring blood 

 lance, and blood is quickly drawn into the pipette from the bottom 

 of the tube. 



The blood may be collected anaerobically in syringes and trans- 

 ferred to the pipettes. The transfer is made by setting the pipette on 

 a table with the tip protruding about 1 in. over the edge, pressing 

 the tip into the opening of the syringe nozzle while the syringe is 

 held horizontally, and then slowly filling the pipette by screwing 

 in the plunger (Roughton and Scholander, 1943). 



OXYGEN 



Roughton and Scholander (1943) described the oxygen method in 

 which an excess of carbon dioxide is used to extract the oxygen, the 

 carbon dioxide is then absorbed in alkali, and the volume of the 

 residual gas is measured in the capillary before and after the oxygen 

 is absorbed by alkaline pyrogallol. 



Roughton and Scholander Method for Oxygen 

 SPECIAL REAGENTS 



Caprylic Alcohol. 



Ferricyanide Solution. Dissolve 12.5 g. potassium ferricyanide, 3 g. 



