I STUDIES ON RESPIRATION. VII 



plished by introducing the reagent into the apparatus^ in a separate 

 tube, having an outlet which is flush with the inside of the stopper. 

 When the time comes to bring the reagent into contact with the 

 organism the tube is inverted and the current of air carries the re- 

 agent over into the tube containing the organism. In order that 

 the height of the Hquid in the latter tube may not be unduly raised 

 it may be provided at the bottom with rubber tubing, into which, 

 after thorough mixing, some of the liquid may be received and clamped 

 off. 



If the reagent is volatile it is necessary to substitute for it (during 

 the measurement of normal respiration) a non-volatile liquid having 

 the same buffer action.^ The volatile reagent may be placed in the 

 rubber tubing, attached to the tube containing the organisms, and 

 clamped off until the time comes to bring it into contact with the 

 organisms. The clamp is then opened and, after thorough mixing, 

 the height of the liquid is adjusted as described above. 



Since respiration is affected by acidity and alkalinity it is desirable 

 to add an indicator to the liquid containing the organisms in order 

 to follow its reaction. The color of this indicator may be affected 

 by the color of the organism or by that of the medium, but in most 

 cases it affords useful information regarding changes in the reaction 

 of the liquid. 



There have been few previous investigations on this subject. War- 

 burg* found that the consumption of oxygen by fertilized eggs of the 

 sea urchin {Strongylocentrotiis) fell off when the eggs were transferred 

 from sea water to a solution of NaCl (isotonic with sea water) . This 

 is explained by the fact, previously discovered by Loeb,^ that NaCl 

 causes cytolysis of the eggs. Loeb had found that this injury could 

 be prevented by the addition of a trace of NaCN. Warburg ac- 

 cordingly added NaCN to the solution of NaCl and found that the 

 amount of oxygen consumed was five times- the normal. Addition 

 of CaCl2 brought it back to the normal amount. 



2 For a description of this see Osterhout, W. J. V., J. Gen. Physiol, 1918-19, i, 17. 

 ' See Osterhout, W. J. V., /. Biol. Chem., 1918, xxxv, 237. 

 * Warburg, O., Z. physiol. Chem., 1910, Ixvi, 305; Biochem. Z., 1910, xxix, 414. 

 ^ Loeb, J., Die chemische Entwicklungserregung des tierischen Eies, Berlin, 

 1909. 



