HEMOCONCENTRA TION 



417 



approximates the response of the normal leukocytes of the mouse, guinea 

 pig, and rabbit. The reduction of white count in polycythemia is also 

 close to a value of 0.3-0.6 per cent change per roentgen. Some of the 



100 



50 



Accumulated dose, r 

 100 150 200 



250 



300 



(a) White-cell count, x-ray exposure 



100 

 40 



10 

 100 



40 



10 



(b) Lymphocyte count, x-ray exposure 



(c) White-cell count, P"*^ exposure 



Fig. 2a, h. The depression of leukocyte formation by x-irradiation, calculated from 

 Jacobson and Marks (8). These values are averaged for leukocyte count and ac- 

 cumulated dosage for chronic exposures for the interval 20-40 days. Part c is the 

 relative response of leukemia and polycythemia leukocyte count to radiation therapy 

 with radioactive phosphate. Half the leukemias and the polycythemias approach 

 the average sensitivity curve of the normal leukocytes as measured in the small 



animals. 



leukemias seem to be as responsive to irradiation as a 2.5 per cent change 

 per accumulated roentgen equivalent physical (rep). 



Recently it has been possible to measure the rate of formation of red 

 blood cells from the quantitative disappearance of labeled iron from the 

 plasma. This method has been used to determine the relative rates of 



