PROBLEMS OF MEASUREMENT OF MUTATION RATES 



29 



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 DAYS 



120 



160 



Figure 7. Proportion of Phaseolus-negative cells 

 in polycythemics treated with P^^ ^ q. jg ^j^g \^ 

 subject reported by Scheinberg and Reckel 

 {Science 131: 1887-1888, 1960); the first point is 

 seven days posttreatment with 2 mc. of P"^. G.P. 

 and A.R. are Ai, treated with 4 mc. of P^- on day 

 zero. An additional point was obtained for A.R. 

 424 days posttreatment: 1.5 X 10"*. 



were so very large. This is more than a twentyfold difference between 

 here and there. There must be something going on that is real 



Scheinberg, who worked with me on this at Oak Ridge, is working 

 with a pigeon system of blood groups that can be used for these ex- 

 periments. The positive pigeons have erythrocytes agglutinable by lima 



