THE KINETICS OF INACTIVATION OF COMPLEMENT 



BY LIGHT. 



By S. C. brooks.* 

 {From the Harvard School of Tropical Medicine, Boston.) 



(Received for publication, August 29, 1920.) 



In order to determine the course of an ordinary chemical reaction 

 it is only necessary to mix the reagents and then to withdraw samples 

 for analysis at appropriate intervals. But in the study of light 

 reactions the case is far different, because the dimensions and trans- 

 parency of the radiated material exercise a preponderant influence 

 on the rate of reaction at any given intensity of illumination. 



Since a great part of the difficulty encountered in studying the 

 course of complement photoinactivation is due to the peculiar require- 

 ments imposed by these facts, which are often inadequately considered 

 in connection with physiological problems, we shall begin with a 

 discussion of these requirements, and of the means adopted to meet 

 them. 



I. 



In the first place, since the intensity of the light reaching each 

 part of the solution determines the rate of reaction at that point it 

 is essential that the average intensity of the light reaching each part 

 of the reaction mixture should remain constant during that part of 

 the course studied. This is a condition which can be met only by 

 special arrangements : either by having a cylindrical reaction chamber 

 parallel to a relatively long "line source" of light, and withdrawing 

 samples at intervals; or by exposing successive samples for a series 

 of different periods under otherwise identical conditions. The latter 

 alternative was adopted in these experiments. 



* The experiments upon which this paper is based were done by the writer 

 as Research Fellow in the Harvard School of Tropical Medicine. 



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