CELLS AND CELL THEORY 21 



see Encyc. Brit. 3, pp. 36-49, (9th ed.) ; New Int. 

 Encyc. 13, pp. 683-685. 



Sec. 5. Cells and Cell Theory 



In Biology, the word "cell' denotes the funda- 

 mental form-element of every organized body. It 

 is a bioplastic mass of protoplasm, varying in size and 

 shape, generally of microscopic dimensions, capable, 

 under proper conditions, of performing the functions 

 of sensation, nutrition, reproduction and automatic or 

 spontaneous motion, and constituting in itself an en- 

 tire organism, or being capable of entering into the 

 structure of one. 



Such a cell, as a rule, has a nucleus and is usually 

 also provided with a wall or definite boundary; but 

 neither cell-nucleus nor cell-wall necessarily enters 

 into its structure. In ultimate morphological analysis, 

 all organized tissue is resolvable into cells or cell pro- 

 ducts. See " Protoplasm," and "Cell Theory," infra. 

 v Specifically, the word ' * cell ' ' denotes a nucleated 

 capsulated form-element of any structure or tissue 

 one of the independent protoplasmic bodies which 

 build up an animal fabric. A body consisting of cell 

 substances, cell-wall and cell-nucleus, as bone cells, 

 cartilage-cells, muscle-cells, nerve-cells, fat-cells, cells 

 of connective tissue, of mucous and serous membrane, 

 etc., of the blood, lymph, etc. This is the usual char- 

 acter of cells in animals, and is the ordinary techni- 

 cal anatomical sense of the word. 



