OXYGEN-BINDING CAPACITY OF BLOOD 125 



and run under the ammonia in the cup of the apparatus. All but 

 a few drops of the liquid in the cup is now run into the 50 c.c. 

 chamber, the ammonia following the blood and washing it in. 

 A few additional drops of the ammonia may be added from a 

 dropper to make the washing complete. 



The blood and ammonia in the apparatus are mixed and 

 allowed to stand until the blood is completely laked. This requires 

 about thirty seconds when saponin is present and five minutes 

 when it is not. After laking is complete 0.4 c.c. of a saturated 

 (40 gms. to 100 c.c. of water) potassium ferricyanide solution is 

 introduced to set free the oxygen combined with the hemoglobin. 

 (The cyanide solution is made air-free by boiling or by shaking 

 in an evacuated flask and is kept in a burette under a layer of 

 paraffin oil 2 or 3 cm. thick to exclude air.) The apparatus is now 

 evacuated until only a few drops of mercury remain above the 

 lower stop-cock, and is shaken, preferably with a rotary motion, 

 to whirl the blood in a thin layer about the wall of the chamber. 

 If the blood was completely laked before the cyanide was added, 

 extraction of the oxygen is completed in half a minute. The water 

 solution is now drawn down into the bulb of the apparatus below 

 the lower cock, and the extracted gases measured as in the deter- 

 mination of carbon dioxide. After the gas volume has been read 

 the chamber is evacuated, and the blood readmitted and shaken 

 again for thirty seconds in the vacuum. The reading is then 

 repeated. If it shows an increase a third extraction should be 

 performed. 



In order to determine the oxygen bound by the hemoglobin 

 it is necessary to subtract from the gas measured the volume of 

 air physically dissolved by 2 c.c. of blood at atmospheric pressure 

 and the prevailing room temperature. The volume of gas thus 

 corrected may be reduced to standard conditions, 0, 760 mm., 



by multiplying by (0.999. - 0.00460 X bar i"f ter , * being the 



7bO 



temperature in degrees Centigrade. If this result is multiplied 

 by 50 it gives the cubic centimeters of oxygen bound by the 

 hemoglobin in 100 c.c. of blood. The amounts of air dissolved are 

 given in the table on page 126, which also gives the factors by which 

 one may directly transpose the readings into terms of percentage 

 of normal hemoglobin on the basis of Haldane's average, viz., 18.5 

 per cent oxygen = 100 per cent hemoglobin. 



