24 



H. MAISIN 



and slightly increased from the 42nd day to the 98th day. After 0-1 r, the 

 reticulocytes are also significantly increased by the 14th and the 28th day. 

 The increase is slightly significant on the 42nd day and present, but not 

 significant on the 56th day. 



Table VII. Differential cell count in peripheral blood 



Time after 



irradiation 



(days) 



Red cells per mm^ blood 



Ir 



Controls 



White cells per mm^ 

 blood 

 1 r Controls 



Reticulocytes per 1000 red 



cells 



1 r Controls t-test 



Time after 



irradiation 



(days) 



Table VIII. Differential cell count in peripheral blood 



Red cells per mm^ blood 



0-1 r 



Controls 



White cells per mm^ 

 blood 

 0-1 r Controls 



Reticulocytes per 1000 red 



cells 

 0-1 r Controls t-test 



Finally the results of the red and white cell counts per mm^ in the 

 peripheral blood are also recorded in Tables VII and VIII. The results for 

 pre-irradiated rats are not very different to those for the controls, whatever 

 the X-ray dose. 



What kmd of explanation can be found for these last experimental results? 

 First of aU, these low doses of X-rays activate the marrow for a certain time, 

 1 r more than 0-1 r, but even so low a dose administered for so short a time as 

 1"9 has an influence on the marrow activity. The erythropoietic activity (as 

 measured by ^^Fe incorporation) shows more precise enhancement than the 

 number of cells of the marrow, much more after 1 r, less so after 0-1 r. It is 

 thus possible that, when the differential count of the white and red pre- 

 cursors was made, the difference in the number of marrow cells was essentially 

 due to the red-cell precursors. After 0-1 r, when the ^^Fe incorporation showed 

 less increase, the total number of marrow cells was only slightly enhanced. It 



