88 LEONELL C. STRONG 



Was there a mistake made in the exceptional experiment N 

 by inoculating; the dBrB tumor into the right axilla and then 

 using these data as being derived from the dBrA tumor reac- 

 tion? We can check with the normal dBrB reaction (fig. 4, p. 85) . 



The exceptional dBrA reaction is even significantly greater 

 than the normal dBrB: 



1. Exceptional dBrA 55 negative : 23 reactions ±2.72 or 29.48% ± 3.49 



2. Normal dBrB 786 negative : 80 reactions ±5.74 or 9.23% ± 0.67 



Difference 20.25% ± 3.55 



The difference is thus 5.70 times its probable error 



We have not, therefore, made a mistake in tabulating the 

 data. Evidently the exceptional dBrA reaction was neither 

 produced by the normal dBrA tumor nor by the dBrB type. 

 The dBrA tumor must have undergone a significant change. 

 It is no longer the same as the normal dBrA tumor that has 

 retained a constant reaction potentiality during a year's ob- 

 servation. 



By microscopical examination the exceptional dBrA tumor 

 was found to be histologically identical with the original dBrA 

 (or even the dBrB for that matter) . What produced this signifi- 

 cant increase in the reaction capacity of the tumor cell? If 

 the same phenomenon of a sudden appearance of a change in 

 the somatic or physiological characteristic of a normal cell 

 was encountered by the geneticist, he would maintain that the 

 variation was produced by the process known as 'mutation.' 

 There seems to be no objection to using a similar mutational 

 process to explain the origin of the observed significant different 

 reaction capacity. 



The exceptional dBrA is not the original normal dBrA. We 

 have no right, therefore, to include it in the same category. 

 Comparing the corrected dBrA curve (after subtracting the 

 exceptional dBrA) with the dBrB curve, we obtain the curve 

 shown on page 89 (fig. 5). 



Every point of the dBrB curve is significantly greater than 

 the corresponding point of the NdBrA (normal dBrA) curve 

 with the exception of the last one. Since both curves are 

 approaching zero, there would naturally be convergence. For 



