Unity and Interdependence in. Living World 647 



Such a construction might well be called cell polarity. One of these 

 so-called poles has a higher rate of metabolic activity than the remain- 

 der of the protoplasm and consequently assumes the necessary and 

 desirable control of the cell as a whole. 



2. Unity Between the Various Cells of Each Tissue. — We have sug- 

 gested how unity and correlation might occur within an individual cell. 

 This would be worth very little in a complex, multicellular organism 

 if each cell did as it pleased. There must be unity and cooperation 

 between the various cells of each tissue of a living organism if life proc- 

 esses are to be accomplished efficiently. The explanation suggested for 

 the unity within a single cell might be extended and elaborated so that 

 cooperation between various cells might be accomplished. Electrical 

 phenomena, chemicals, and impulses of the nervous system probably 

 integrate to a great extent the various cells of a tissue so that real har- 

 mony and cooperation exist. Electricity within cells and the electrical 

 phenomena associated with nerve impulses suggest probable causes of 

 integration. Various chemicals pass more or less freely from one cell 

 to another, hence playing an important role in unity between cells. The 

 chemical secretions in the ductless (endocrine) glands of higher animals 

 will illustrate this process of coordination. (See discussion of ductless 

 glands.) It has been demonstrated in certain cells that there are minute 

 strands which extend from one cell to another, .and evidently through 

 such structures coordination might also be secured. All that has been 

 said up to this point has dealt with the proper coordination of cells. 

 There are times when certain cells, or certain parts of cells, must be 

 subordinated, because all units cannot have the same degree of activity. 

 This subordination of certain parts is just as important as the coordina- 

 tion process and is probably accomplished in much the same way. 



3. Unity Between the Various Tissues of Each Organ. — An organ is 

 an assemblage of different tissues, all of which work for a common pur- 

 pose (perform a common function). Even though the various tissues 

 of a certain organ are closely associated in the construction of that 

 organ, there must be a specific integrating influence or force in order 

 to make these various tissues function together as a unit. This is ac- 

 complished in much the same way as in individual cells and tissues, 

 except on a larger scale. 



4. Unity Between the Various Organs of Each System. — If each sys- 

 tem of a living organism is to function normally and efficiently, there 

 must be unity between the various organs which compose that particu- 

 lar system. The higher types of organisms with their greater numbers 



