84 LEONELL C. STRONG 



3. Resvlts 



a. Difference between dBrA and dBrB. The first experiment 

 consisted in comparing the reactions of the two adenocarcino- 

 mas in the same medium. Over two hundred wild mice were 

 used for this purpose. If there is a variable factor present it 

 must be in the tumor cell itself. Not one mouse out of all 

 those inoculated ever grew the dBrB tumor progressively and 

 only one ever grew the dBrA (this will be discussed in experi- 

 ment 2) . We are therefore dealing with a race definitely proved 

 to be non-susceptible. There were, however, several positive 

 indications of the host-tumor reaction," as plotted in figure 2. 



The ordinates represent the percentage of positive apparent 

 reactions for any given observation period. The abscissae 

 represent the successive weekly periods of observation begin- 

 ning with the second week after the inoculation. It will be 

 noted that the dBrB tumor gave the greater percentage of 

 reaction indications throughout the experiment. Each tumor 

 produced a characteristic number of initial reactions (dBrB 

 14.79 per cent ± 1.69; dBrA 4..39 per cent ± 1.01). The 

 number of visible reactions decreased with every observation 

 until none (after ten observations in a few cases) remained. 



* In this paper the term 'reaction' is used to denote a palpable mass occurring 

 for a certain length of time at the site of the inoculation. It is, in all probability, 

 the implanted tissue surrounded by a reaction zone set up by the host. 'Indica- 

 tion' cannot be employed, since this implies a definite growth on the part of the 

 tumor cell. In a few cases we examined a small nodule microscopically, which 

 proved to be actual tumor tissue. All nodules could not be so examined, as this 

 procedure would interfere with the continuation of the experiment. We have 

 some indirect evidence to show that the palpable mass was (in most cases at 

 least), actual tumor tissue. When all normal individuals are lumped, we obtained 

 a percentage of visible masses of 5.97 ± 0.40%; for gonadectomized individuals, 

 3.75 ± 0.24%. The percentage for gonadectomized individuals is too low, due 

 to the depressing effect of the operation (as discussed later in this paper), so that 

 the two classes gave practically the same number of 'reactions.' Normal indi- 

 viduals were able to eliminate every reaction mass in a few weeks, whereas some 

 gonadectomized individuals that gave initial reactions continued to grow the 

 tumor mass progressively. This result tends to indicate that the reaction mas? 

 in normal individuals is due to an actual initial growth or indication on the part 

 of the tumor cell, which is then eliminated. 



