98 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



The use of tonometers is described by D. B. Dill in the Appendix of 

 L. J. Henderson's book "Blood," 1928. 



Tonometers in which the beef blood is to be equilibrated to CO2 at 

 partial pressures of 20, 40, and 100 mm. Hg are ordinarily prepared a day in 

 advance. These tonometers are of the Barcroft type of 250 and 350 cc. 

 and have the exact capacity etched on each one. The dry tubes are fitted 

 with rubber stoppers. The stopcocks, which are well lubricated, are 

 held in place by rubber bands. The procedure consists in removing a 

 fraction of the air in the tonometer and replacing it with CO2. If the 

 capacities in cc. of the three tubes used are designated a, b, and c, then 

 the volumes to be replaced with CO2 are respectively 20a/B, 40b/B, and 

 lOOc/B where the numbers represent the partial pressures required, and B 

 the barometric pressure in mm. Hg. The tonometer of volume a, for 

 example, is connected to the gas pipette and the Hg lowered for the cal- 

 culated volume, 20a/B. This air is expelled through the side arm of 

 the pipette. The tonometer is disconnected and a bladder of CO2 is 

 attached to the side arm, and the apparatus flushed with CO2. The 

 proper amount of CO2 is then drawn into the pipette, the tonometer con- 

 nected and the gas run into it. 



By means of a 10 cc. syringe 6 cc. of the beef blood is introduced into 

 the tonometer through its stopcock. With another syringe mercury is 

 forced through the stopcock until the capillary pores are filled. 



The tonometer is held upright between the hands and gently agitated 

 for 10 minutes. The stopcock is turned to the side arm, and the tonometer 

 connected by a short tube to the outflow tube of a clean Van Slyke appa- 

 ratus, the stopcock of which is turned to the outflow tube. The leveling 

 bulb is raised until the mercury appears in the side arm of the tonometer. 

 The stopcock of the latter is turned to connect with the chamber and 1.5 cc. 

 of blood is drawn into the Van Slyke. The stopcocks are closed and the 

 tonometer disconnected. Then the blood except exactly 1 cc. is expelled 

 through the outlet tube. 



1. Place 3 cc. of water in the cup. Insert a drop pipette to the bottom 

 of the cup and, while 1 cc. of the water is allowed to flow into the burette, 

 inject from the pipette about 4 drops of caprylic alcohol. The alcohol, 

 thus washed into the burette, will prevent foaming. 



2. By means of a drop pipette remove the excess water from the 

 cup. 



3. Run into the burette 0.5 cc. of 10 per cent lactic acid and close the 

 cock. 



4. Evacuate the bulb by lowering the mercury nearly to the lower 

 cock. Turn the cock. Shake the remnant of mercury with the blood for 

 3 minutes. Immediately read the volume of the gas in the manner 

 demonstrated. (The lower cock is opened, the mercury in the leveling 



