CHAPTER XXV. 

 TUMORS. 



IT will promote clearness of conception if the term tumor is 

 restricted to abnormal masses of tissue produced without obvious 

 reason and performing no function of use to the organism. 



In the introductory chapter an attempt was made to show that 

 under normal conditions the parts of the body develop in an orderly 

 manner, which fits them for the performance of work useful to the 

 whole organism, as well as for maintaining their own nutrition and 

 structure. It was also pointed out that parts of the body, when 

 occasion arises, frequently fulfil what appear to be their duties to 

 the whole body, even if their own nutrition or structure suffers 

 in consequence. From these observations we must conclude that 

 throughout the life of the individual each part is controlled in its 

 activities by influences having direct reference to the well-being of 

 the whole body. Those influences control not only the functional 

 activities of the tissues after the body has reached the adult state, 

 but also control or guide the activities of the cells elaborating the 

 body during development. The nature of those influences and 

 the mechanism of their control are unknown to us. We are ignorant 

 of any reason why the tissues of the body should develop to a cer- 

 tain point and then have their nutritive and formative activities 

 restricted to a maintenance of the structures then existent. We 

 attribute these phenomena to the force of heredity, but the expla- 

 nation is incomplete, for that term merely expresses the fact that 

 the offspring of an individual develops into a likeness to its parent. 



In the development of tumors these guiding or controlling influ- 

 ences are in abeyance, sometimes in greater, sometimes in less de- 

 gree. The tissues do not grow to meet a functional demand imposed 

 upon them by the needs of the body, as appears to be invariably the 

 case in the increase of tissue during the development of the indi- 

 vidual. Instances of growth bringing about such adaptation to 

 altered demands occur after the body has attained full development, 



341 



