The Microscope. 



115 



when the cell is unhampered by outside influences. This condition 

 of growth is practically impossible. The most potent modifier of 

 cell-form is pressure, and the result of pressure is that there are 

 nearly as many different cell-forms as there are cells. They may 

 appear as flat, thin scales (Fig. 2.), squamous cells; or long and 



thick, cylindrical or columnar cells (Fig. 4.), or short and thick, 

 columnar or cuboidal cells (Fig. 3.) They may be spindle-shaped, 

 stellate or star-shaped, or solid with many flattened sides — 

 polyhedral cells. The sizes vary quite as widely as the forms, 

 ranging between jo^^o^ to -^-^ of an inch in diameter. 



PR0T0PLA.SM. — The matter of which all cells are composed has 

 been variously named protoplasm, bioplasm, sarcode, etc. The first 

 of these terms is the one now generally employed. Protoplasm is a 

 nitrogenous, albuminous substance which is remarkable in that it 

 possesses the unique and wonderful quality called life. Wherever 

 life is found, either vegetable or animal, it is manifested through 

 protoplasm, and it has, for this reason, been called "the physical 

 basis of life." Attempts have been made to localize this matter in 

 the cell. It has been held that the nucleus is alone composed of it, 

 and again that it is the cell-body and not the nucleus. It seems 

 more reasonable to assume that the cell- contents are all protoplasmic, 

 though in a somewhat different state in the nucleus than in the cell- 

 body. 



Intercellular Substances. — Though all tissues originate from 

 cells it is seldom that a mature tissue will be formed entirely of 

 cells, but that the cellular elements will be separated by intercellular 

 substance. This substance may be structureless, fibrillated or 

 reticulated. As a structureless substance it is found widely dis- 

 tributed and serves as a cement joining the cells together. All of 

 the connective tissues have a fibrillated intercellular substance which 

 may sometimes be so abundant as to make up the larger portion of 

 a tissue. It must not be forgotten that this substance is derived 

 from cells and that it has no power of reproducing itself. Just 



