CAPILLARY RESPIROMETRV 321 



Double Dewar flasks are used to maintain constant temperature 

 for the period of measurement (1-2 hr.l. The outer flask is sur- 

 rounded by a 1 in. layer of cotton packing; it has all. capacity 

 and is used three fourths filled with water. The inner flask has a 4 

 oz. capacity and is two thirds filled with water. 



The respirometer tube is cleaned by filling it with cleaning solu- 

 tion and after 30 min. it is rinsed with distilled water, followed by 

 0.01 M sodium bicarbonate, and finally distilled water again. It is 

 then dried by drawing filtered air through it, and is allowed to stand 

 overnight to eliminate any temperature differences within the glass. 



A respiration experiment on a Paramecium is carried out as fol- 

 lows: 



1. Fill the tube to within 4 mm. of the chamber end with 0.5 N 

 sodium hydroxide by filling the cup at the top of the tube with al- 

 kali and allowing the tube to fill by gravity. When the solution 

 reaches the proper position pour out that remaining in the cup. 



2. Place a droplet of tap water containing the organism over 

 the end of the respirometer chamber and force about 2 mm. of this 

 tap water into the 0.56 mm. capillary by inserting a needle through 

 the drop into the capillary and then withdrawing it, 



3. Observe the end of the tube until the Paramecium enters it 

 and then quickly wipe off the surface tap water and seal the end of 

 the capillary with a piece of vaselined cover slip. 



4. Fill the cup around the upper part of the tube with the sodium 

 hydroxide soln. and place the respirometer in the Dewar flasks. 



5. After 1 hr. remove the alkali from the cup with a fine pipette 

 and plug the top of the cup with cotton. 



6. After 1 hr. more focus the microscope (magnification lOOX) 

 on the meniscus of the liquid in the capillary and record the rate of 

 fall of the meniscus. During these measurements, note the temper- 

 ature and barometric pressure. If these vary sufficiently to result in 

 significant errors, discard the experiment. 



The errors introduced by changes in (1) temperature, {£} baro- 

 metric pressure, (3) height of the liquid in the tube, (4) volume on 

 dilution of the alkali soln., (5) volume of the dissolved gas phase with 

 change in partial pressure, (6) bore of the capillary, and (7) surface 

 tension of the liquid in the capillary, have been discussed by Cun- 

 ningham and Kirk (1942) . The original paper of these authors should 



