1911.] Radium Radiations upon Normal Blood. 135 



were made in which the same volume of serum was radiated as in the 

 complement experiments. These three observations are indicated by the 

 thin line curve, fig. 8. The type of the curve is identical with that 



Fig. 8. — The crosses ( x ) on the complement curve indicate values obtained with the use 

 of sensitized sheep's corpuscles, the circles (o) those obtained with sensitized 

 human corpuscles. 



previously obtained, the only difference being a diminished rate of reduction 

 of opsonin, as was to be anticipated. 



Inspection of the complement curve shows that the reduction is slow at 

 first, the rate gradually increasing with time, as may be seen from the 

 convexity of the curve to the time axis. 



The experimental and control sera were, except for the radiation, kept 

 under identical conditions at room temperature. The spontaneous dis- 

 appearance of complement is therefore eliminated as a disturbing factor, by 

 a comparison between the two sera. It should be pointed out, however, that 

 fresh serum was used for every experiment, because it was found that the 

 complement in serum which has been kept for some days at 0° C. was more 

 affected by the radiation than fresh serum. 



The general character of the two curves (fig. 8) indicates the separate 

 identity of opsonin and complement. 



The complement curve suggests either that this substance becomes more 

 unstable under the action of the radiation, or that its amount is in some 

 way dependent upon some other substance present in serum. 



The small initial reduction in complement could, on the latter supposition, 

 be explained if this substance under the action of the radiation were 

 eventually reduced to complement; then, despite the simultaneous reduction 



20 



