THE CELL. 23 



tion of pathologic variation in cell morphology. Thus parenchym- 

 atous cells, as hepatic and renal cells, frecjuently become com- 

 pressed by hyperplastic interstitial tissue sufficiently to change 

 their shape from polygonal or cuboidal to irregularly flattened or 

 fusiform. Columns of tumor cells may become pressed suffi- 

 ciently by the invaded tissue to produce scale like cells or the so- 

 called pearl cells. On the other hand, the same variety of tumor 

 cells developed in tissue in which mutual pressure is limited, 

 assume sphericity. 



Size. — Cells vary in size from the lymphoid cells that are 

 from 4 to 8 microns in diameter to the marrow cells that are 

 from 30 to 60 microns in diameter. The size of the cell is 

 characteristic of the tissue they compose. Equalization of the 

 surface and mass is a factor in the determination of the size of 

 cells. Function of cells als(.i has some l^earing upon their size; 

 thus, cells that have the power of independent motion and rap- 

 idly acting cells are usually small. Fpod is no doubt a deter- 

 mining factor in the size of cells. Ova are large because of the 

 storage of food. 



Pathologic variation in the size of cells is of common occur- 

 rence. Hypertrophy i? the abnormal enlargement of individual 

 cells. The size of red blood cells is variable in pernicious ane- 

 mia, (swamp fever), of the horse. Several cells may fuse. 

 forming a cell-complex, syncytium, or giant cell in and arouna 

 foreign bodies, and in tubercular and actinomycotic lesions. 



Growth.— Growth in cells is the exercise of that property or 

 function which results in their enlargement or it is the process 

 by which they are increased in size. That cells do grow is self- 

 evident and is common knowledge. A central, polymeric pro- 

 tein-molecule is supposed to be the essential structure of all 

 active cells. This central, p.ilymeric molecule is probably unsat- 

 urated and new simple molecules may be serially combined 

 with it and then the cell becomes larger and grows. This prop- 

 erty of cells is especially evident during the embryonic period 

 but gradually diminishes to the time of maturity, when it is 

 largely supplanted bv other functions. The growth of cells is 

 accompanied bv the" accummulation of energy. The larger a 

 cell, other things being equal, the greater the potential energy. 

 All 'functioning of cells, except growth, is accompanied by the 

 liberation of energy. Growth results in accummulation of poten- 

 tial energy and other functions convert potential into kinetic 

 energy though both types of energy may be produced simultane- 

 ously and may be interdependent ; thus the growth of muscle is 



