132 Drs. H. Chambers and S. Russ. Action of [May 1, 



A count of the two films which were prepared gave the following results : — 

 Film I gave 441 micro-organisms in 150 leucocytes. 

 Film II „ 541 „ 150 



It is clear that if the experimental plasma had contained substances 

 inhibitory to phagocytosis, their influence should still be manifest when 

 added to the control plasma. The difference between the counts of the two 

 films, amounting as it did to only 20 per cent., shows that the large reduction 

 previously observed with the radiated serum is mainly to be attributed to 

 a reduction in the opsonin normally present. 



The effective agent is here again the a-particle. By excluding this 

 type of radiation and exposing serum to the yS- and 7-rays, no appreciable 

 alteration in its opsonic content was obtained with quantities of the order 

 5 to 10 mgrm. EaBr 2 , and for exposures lasting about forty hours. 



A series of observations was made by taking a measured volume of serum 

 (12 - 5 cu. mm.) spread over an area of T5 sq. cm. on a thin mica sheet and 

 exposing it to the a-radiation from one of the capsules. A fresh sample of 

 serum was used for each exposure, as, owing to the very limited penetration 

 of the fluid by the a-rays, only just sufficient for an opsonic determination 

 was radiated. After the serum had been radiated for any selected interval, 

 its opsonic content was compared with that of the control. 



The results obtained are given in Table IV and shown graphically in 

 fig. 6 :— 



Table IV. 



Time of 



radiation. 



Percentage of opsonin in 

 radiated serum. 



Number of micro-organisms 

 in 100 leucocytes. 



Control. Experiment. 



h. 











2 



40 



82 



620 



506 



5 



15 



58 



620 



360 



10 



30 



59 





228 



14 







31 42 per cent.* 



430 



182 



18 



20 



35 47 „ * 



507 



244 



20 



15 



24 



210 



50 



36 



45 



14 



383 



53 



45 







9 



681 



64 



* A smaller quantity of Ea was used in these cases, the numbers on reduction give 31 and 

 35 per cent. 



The general character of the curve is of the simple exponential type, but 

 owing to the possibility that the method of estimating the amount of 



