GROWTH OF A TRANSPLANTABLE TUMOR IN MICE ols 
Figure 1 shows the percentage of observations showing growth 
for both races on successive observation weeks, all ages and both 
sexes combined. It will be noticed that the curves for the two 
races are very different in shape—that of the albino race (N)— 
(broken line) goes steadily down from these cond to the sixth weeks, 
and if the chart had been continued, the base line would have 
been approximated in a short time. On the other hand, the 
curve of the back-cross race (B.C.) (solid line) goes downward for 
the second and third weeks, but then strikes a level at close to 
13 per cent and remains there. This level represents roughly 
TABLE 2 
Back-cross stock (BC) 
2 WEEKS 3 WEEKS | 4 WEEKS | 5 WEEKS | 6 WEEKS TOTAL 
AGE = = % + 
SPs) ae Sea ON all i = 
20) 19 46] 19 44| 12 50} 11 50) 9 52) 70) 242 22.4 
18 2 a 8 9| O 9} O 9, 0 Dh a2 43 4.4 
16 4 5| 4 4; 4 5| 4 5) 3 6} 19 25 43.1 
12 3 11; 4 10; 1 P| 12) -A 12} 10 57 149 
10 6 30) 2 34] 2 So ae 30] 3 Oral USN Iey 8.5 
8 5 ZAQ| | 22 eel De 24; 2 PN eA ata 7/ 9.3 
6 4 Dee 6} 1 8} 2 Ol 2 Ala 33 26.6 
4 5 OW Sh We Ee 2 See 1S} 2 13) 14 61 18.6 
2 6 11) 4 ia il 14) 2 12} 3 11) 16 59 ZARS 
| 54 145} 41 154 24 | 169) 26 | 165] 25 | 166) 170) 799 17.54+0 83 
the proportion of mice which are going to show continued growth 
of the tumor. It indicates further that by the time that the 
race finds a more or less constant level at roughly 13 per cent, 
the genetic make-up of the individuals has become relatively 
fixed and the factors favoring tumor growth introduced by the 
Japanese waltzing race have exerted their influence. Table 3 
shows in tabular form the data upon which figure one is 
constructed. 
Table 4 includes the percentage of observations showing 
growth—divided according to the age of mice at inoculation, in 
four-day groupings. The common race (N) shows a slightly 
