MALIGNANCY 29 



it is certain that too strong a revulsion against theory 

 tends to atrophy the imagination, which is the most powerful 

 weapon of analysis. If our hypotheses and experiments 

 are always closely related to the particular matter in hand, 

 we learn to distrust unduly the tentative inductions we owe 

 to those who do not fear to put forward provisional results 

 which seem to have no immediate bearing on investigation. 

 Thus we do not commonly speak of an organism as a 

 republic of cells, or a federation of organs, and though this 

 seems unprofitable to many, we do so with advantage, since 

 it helps to clarify our ideas on general metabolism. The 

 conception is even more useful when it tends to show that 

 symbiosis is not only found in groups or societies, but in 

 those close cell-systems to which we commonly restrict the 

 term " individual." The more such ideas are studied the 

 more fruitful they become, though progress has not so far 

 advanced but that it is commonly taken for granted that the 

 essence of symbiotic life is mutual or inter-organic help. 

 We ignore the fact that when two individuals, and definite 

 cell-colonies may with advantage be called such, preserve 

 individuality, there is in their relations a certain real, if 

 subdued, hostility. Mutual help, even if indirect, un- 

 doubtedly exists, but how easily their relationship may 

 become one of parasite and host all zoologists are aware. 

 There is often a great reluctance to admit that what is true 

 of an organism as commonly conceived, is also true of 

 loosely knit human societies, and that the converse is not 

 mere fancy. But when we observe that this fundamental 

 reserve hostility is in fact self-protection in those political 

 federations which help each member even while they 

 provide against encroachment on the part of others, or of 

 the federal authorities, and then compare such observations 

 with organic life, it may not, to those with scientific imagina- 



