Nos. 620-621] CANCER'S PLACE IN BIOLOGY 



pie, divides; the cellular divisions divide; these continue 

 to divide and form eventually, in a definite period, the 

 millions of cells which constitute the organism. This is 

 a simple statement of general facts, but coincidentally 

 with those facts there is an orderly sequence of cellular 

 changes which seems to he foreordained in the original 

 fertilized ovum; the cellular progeny does not retain, to 

 the same degree, all of the structural and functional char- 

 acteristics of the original cell (ovocyte). There is a 

 grouping of cells which is coincident with morphological 



and functional differences. Out of such differentiation 

 and specialization of cells, types of cells arise, groups of 

 which constitute what are called tissues (adenotex, chon- 

 drotex, endotheliotex, epitheliotex, erythrotex, fibrotex, 

 etc.) (Fig. 1). Two or more of the different tissues be- 

 come grouped to form organs (tongue, esophagus, stom- 

 ach, liver, kidneys, skin, etc.) which likewise are grouped 

 to build up structural and functional systems (respira- 

 tory, alimentary, nervous, osseous, etc.), the combined 

 qualities of which form the complete multicellular organ- 



