1911.] 



Radium Radiations upon Normal Blood. 



127 



5 ~fo IS 33 tS 



Fig. 2. 



An estimate of the number of a-particles required to heemolyse a red 

 corpuscle is possible owing to the precision with which the essential 

 quantities in the calculation are known, viz., the number of corpuscles per 

 cubic millimetre of blood, and the number of a-particles emitted per second 

 from a measured quantity of emanation.* 



From experiments in which the emanation was mixed with blood, a 

 calculation results in the number 2000 being required for the complete 

 haemolysis of a red corpuscle. From those in which the a-particles had to 

 penetrate two sheets of mica, a maximum estimate of the number in question 

 is 8000. In view of the different experimental conditions, the difference 

 between the two numbers is not significant. 



The Action of the a-Bat/s on Leucocytes. 



It has been found that the a-particles are capable of not only destroying 

 leucocytes, but also, by virtue of their action on the serum, rendering a 

 radiated region free of them. 



A simplification of Ponder'st method of obtaining leucocytes has been 

 used for these experiments. A drop of blood is put on a mica plate, 

 covered, but not touched, by a watch-glass to 1 prevent evaporation, and 

 incubated at 37° C. for about 20 minutes. On removal of the clot large 

 numbers of leucocytes are found on the surface of the mica, to which they 



* Rutherford and Geiger, ' Roy. Soc. Proc.,' A, 1908, vol. 81, p. 173. 

 t Ponder, 'Camb. Phil. Soc. Proc.,' 1909, vol. 15, Part I. 



