, WILLIAM R. AMBERSON 545 



and oxygen, the decay curve follows the monomolecular form, because, 

 under the conditions of the experiment, oxygen is always present in 

 excess. The oxygen tension required for a maximum brightness of 

 CypHdina luminescence is known to be quite small. Harvey ^ found 

 that the brightness of luminescence in this animal is not affected by 

 decreases in oxygen concentration until the tension has fallen below 

 the value of 53 mm. of mercury. Above this value the oxygen 

 may be considered to be in excess. It has not been possible in the 

 present work to boil out solutions to such a low value of oxygen 

 concentration, or to prevent its rediffusion during the pourings neces- 

 sary in their manipulation. 



I was interested to know, however, whether stirring would in 

 any way aff'ect the form of the decay curve. I found that stirring 

 has no affect, and that two simultaneous records with identical 

 solutions, one stirred, and the other not, follow each other side by 

 side down the curve of decay, within the limits of the photographic 

 error. The results of such an experiment are graphed in Fig. 3. 

 Complete mixing of enzyme and substrate is evidently produced by 

 the force vnih which the enzyme is added, and stirring does not add 

 to its completeness. 



4. The Influence of Enzyme Concentration. 



Actual concentrations of materials used are, of course, impossible 

 to ascertain. Accurate relative concentrations of luciferase may, 

 however, be obtained by dilution. Using this method I have studied 

 the effect upon reaction velocity when a certain concentration of 

 enzyme, which we will call C, is reduced by dilution to the values 



Cy C C 



— -> and -• Both enzyme solutions are added simultaneously to 



identical luciferin solutions at the same temperature. 



Typical records obtained in such a way are graphed in Fig. 4, in 



C 

 which the two enzyme concentration were C and — . The slope of 



the straight line plotting gives at once the values of the velocity 

 constants, as already shown in equation 2. The ratio of these slopes 



