Burrows: iStidv of Body Cells. 601 



effecting the ivurganization lu'cessary tor true cancer to develop. 

 Long use of coal tar leads to tiie de\'el()pment of cancer.^'^ 



What I have hoped to present in this paper is not only the general 

 picture of the cell the tissue culture has so far revealed, but methods 

 by which the further details of these general problems may be at- 

 tacked. From the above observations it is evident that the problems 

 relative to life are not to be solved by chemical and morphological 

 methods, but by the application of mechanism. Heredity, as we 

 have seen, is dependent wholly on the chemistry of the system, but 

 the importance of these chemical substances will not be understood 

 until the mechanisms peculiar for the various manifestations of life 

 have been isolated, their parts and the energy relation between these 

 parts have been fully determined. Upon this latter knowledge rests 

 also the ultimate control of cancer. Cancer, as it has been seen, does 

 not arise from embryonal cells. It is not the mere displacement of 

 cell (Ribbert) , but a specific reorganization of parts. Such a re- 

 organization means a breaking down of the normal relation of cells 

 in the adult. The normal heterogenicity is maintained through the 

 fact that each kind of cell moves through the liberation of the same 

 surface-tension-lowering substance. Each tissue repels its neighbor 

 like each cell repels each other cell of the same or of another kind. 

 It is a breaking down of this barrier through the synthesis of a new 

 substance which conditions new surface relations. It is an invasion 

 of connective tissue by the epithelium (Thiersch and Remak) . This 

 synthesis becomes possible through the specific rearrangement of 

 cells. Such rearrangements may result from developmental defects 

 or through the action of stimulating substances. In the body not 

 only quality but quantit}^ is an absolute factor. Systemic life and 

 elemental life are not comparable. The cells do not age. Differen- 

 tiation is not an age phenomenon. The law of the conservation of 

 energy holds for the body like it holds for all natural phenomena. 

 Advancement in biology is to be made through the development of 

 methods for the study of the mechanics of these systems. Mor- 

 phology and chemistry must be supplemented by these methods. All 

 parts of these machines are not visible. Rhythmical heart-muscle 

 contraction is not a specific chemical reaction. It is peculiar to a 

 large number of animals. These animals differ chemically from 

 each other. A watch is a watch whether it is made of gold or silver. 



The heart contracts as the result of a special arrangement of its 

 parts and the specific dynamic properties of these parts, and not 

 through the specific chemical constitution of the particular protein 

 which compose its parts. 



