RESPIRATORY CHANGES IN THE BLOOD 



303 



Petition 



For extracting the gases from the blood the older methods using the mercurial air 

 pumps of Ludwig, Geissler, or Sprengel have given place to much simpler and more 

 convenient microapparatus of Van Slyke, Fig. 237. The Van Slyke apparatus can be 

 used for the analysis of oxygen, or of carbon dioxide, and of the inert residue of nitrogen 

 by difference. 



The Van Slyke Blood Gas Apparatus. -The Van Slyke apparatus consists of a 50 cc. 

 pipette with three-way stop cocks, e and /, at the top and bottom. The top of the pip- 

 ette is graduated in i cc. and .02 cc. divisions. A . 

 reservoir of 80 cc. capacity is connected with the 

 bottom of the apparatus by a heavy black rubber 

 tubing of small bore and the whole apparatus filled 

 with mercury. The sample of blood to be analyzed 

 is introduced through the cup b into the pipette and 

 the gases evacuated and measured according to the 

 following technique. 



The solutions required are ammonia solution to 

 which is added the soluble saponine from 5 grams of 

 commercial soap bark and 4 cc. concentrated am- 

 monia per liter; redistilled caprillic alcohol to prevent & \mabort 

 foaming; and 10 per cent, potassium ferricyanide 



Volume of Gas Measured. 



Column of Water Solution 



Level of Mercury Surface 

 in Levelling Bulb. 

 vLevel of Mercury 

 Menijcuj m Pipette. 



FIG. 2370. 



FIG. 237. 



in normal potassium hydrate. A determination is made by the following steps. Intro- 

 duce 3 drops of caprillic alcohol and 6 cc. ammonia into the pipette, evacuate and wash 

 out the dissolved air, run 2 cc. of air-free ammonia back up in the cup as a seal. A 2 cc. 

 sample of fresh arterial blood drawn under oil is run from a 2 cc. graduated pipette into 

 the cup under the ammonia solution and drawn down into the pipette. Mix the solu- 

 tions until the blood is completely laked, which occurs in a few seconds. Next intro- 

 duce 0.4 cc. of 10 per cent, ferricyanide to set the oxygen free from the hemoglobin. 

 This dissociation is facilitated by lowering the mercury to about the 50 cc. mark on the 

 pipette thus producing a Toricellian vacuum in which the blood and reagent mixture is 



