TUiMOR GROWTH AXD TISSUE GROWTH. 



By LEO LOEB. 



(Read January ly, igo8.) 



In the course of the last five years, partly through the aid of 

 their respective governments and partly through private initiative, 

 institutions have been founded in the majority of civilized countries 

 for the investigation of the causes and the conditions of growth of 

 malignant tumors ; or, as briefly named, for the investigation of 

 cancer. This fact proves more clearly than anything else could do 

 the widespread interest that has recently been aroused in this part 

 of pathological research. Pathological investigations share with 

 those of other sciences a double nature. On the one hand, their 

 problems are of a practical character. Pathology wants to find the 

 causes of diseases and the conditions that favor and inhibit their 

 progress, in order to lay a firm and scientific basis for their cure. 

 In this respect, patholog}- is an applied, a technical science. On the 

 other hand, pathology desires to analyze the conditions that ulti- 

 mately lead to death, in order to recognize some of the phenomena 

 of life. In that sense, patholog}^ is a pure science ; its aim is 

 philosophical. 



Tempting as it might be to relate something of the first attempts 

 of patholog}' to find the cause and the cure of cancer, I shall here, 

 rather, turn to the pureh- theoretical aspects of these investigations 

 and indicate some of the results of tumor investigations that have 

 some bearing upon one of the fundamental characteristics of living 

 matter — the ability to grow. Before entering, however, upon a nec- 

 essarily very limited discussion of some of the relations between 

 tissue and tumor-growth, it might be well to indicate what a tumor 

 is ; and, especially, what a cancer is. 



Perhaps I can best approach this delicate task by stating some 

 varieties of growth that are not included under the term tumors. 



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