1906.] Experimental Analysis of the Growth of Cancer. 



207 



" descending side-branches " of the " rising main stem " depicted in the 

 earlier chart (fig. 3) is followed through four successive subinoculations till 

 each strain in turn presents a maximum followed by a fall. The same 

 phenomenon is repeated in the experiments recorded in the next chart 

 (fig. 5), where the further results of transplanting two strains derived from 

 48 E are represented. After giving a low percentage of success, both in turn 

 give a maximum. 



Fig. 5. — Graphic record to show how the further propagation of two tumours (49 C, 49 F) 

 obtained in an experiment with maximal percentage of success (84 per cent. 

 48 E) gives at first a diminished percentage of success, which, after a varying 

 number of transplantations (in one case six, in the other three), is succeeded by 

 a maximal success after the same interval of time after which the fall is 

 repeated. 



When the results of all our experiments are incorporated in one chart it 

 becomes very complex. The orderly sequence of increasing and diminishing 

 percentage of success in individual strains can be followed with difficulty. 

 The confusion, however, is only apparent and indicates how heterogeneous 

 the growth of the tumours viewed as a whole has become. The behaviour 

 of the component parts of this tumour when propagated in a large number 

 of animals represents what may be regarded as occurring simultaneously in 

 different parts of a single tumour, when allowed to grow for a long time 

 in one animal. During the whole course of propagation of Jensen's tumour, 

 after each successful transplantation, the differences in transplantability of 

 the daughter tumours indicate that heterogeneity of this kind develops. 

 Only when, after a number of passages, a tumour is obtained giving the 



