SUSCEPTIBILITY TO TRANSPLANTABLE TUMORS 77 



2) black (non-agouti) and, 3) cinnamon (brown agouti). The 

 inbreeding was started by Doctor Little while at the Bussey 

 Institution (1909) and is still being continued at the Carnegie 

 Institution Station, Cold Spring Harbor. This is the parent 

 strain of mice, in that it gave rise to the two adenocarcinomata 

 employed in this investigation. We will refer to this strain as 

 the susceptible race. By a susceptible race we mean one in 

 which there is 100 per cent indications of progressive tumor 

 'takes' upon inoculation with a bit of the transplantable tissue. 



The albino stocJx, This is one of the non-susceptible races 

 employed. By a non-susceptible race we mean one in which 

 every mouse inoculated with the tissue fails to grow the trans- 

 planted tissue to an appreciable size. This stock has been used 

 as a control on the experiments with the wild mice. The albino 

 strain was obtained from Dr. H. J. Bagg, of Memorial Hospital. 

 He has inbred this strain, brother-to-sister matings, since 1912. 

 Mice of this strain were given serial numbers preceded by the 

 capital letter A. 



b. The tumors employed. We have used two adenocarcinomata 

 of the mammary gland that arose spontaneously and independ- 

 ently of each other in the pure dilute brown strain. The first 

 arose some three weeks before the other. The first was desig- 

 nated as dBrA; the second, dBrB. Microscopically, the two 

 tumors are indistinguishable, as shown by the accompanying 

 microphotograph (fig. 1, p. 78). The shght difference is not real 

 as might be supposed, but due to a slight defect in the staining 

 of the dBrB tumor We are in agreement, then, with the con- 

 clusion of Dr. James Ewing that these two tumors are histo- 

 logically identical. 



The preliminary experiments dealing with the inoculation of 

 these two tissues into the pure dilute brown stock were performed 

 by Doctor Little during the spring of 1920. He determined 

 that either tissue grows progressively in 100 per cent of the mice 

 inoculated, regardless of whether the tissue is placed in separate 

 individuals or on opposite sides of the same mouse. There is 

 no appreciable difference in the tumors (rate of growth, etc.). 

 Within limits, there is apparently no effect of one tumor upon 



