662 THE MICROSCOPE. 



it ; thus in the columnar epithelial cells covering the villi 

 of the intestines, in which the pabulum flows from the 

 free surface towards the attached extremity, the germinal 

 mass is found near the centre or near the free edge of the 

 cells ; but in the mucus-forming cells from the mouth and 

 fauces, in which the pabulum flows in the opposite direc- 

 tion, the germinal mass is found to be placed quite at the 

 attached end of the cells, where it has consequently easier 

 access to the pabulum, upon which its growth and secretive 

 power depends. 



Cell-wall and Cell-contents. — In the mucus cells above 

 mentioned, and in many other cells, two kinds of formed 

 material are produced from the original germinal matter ; 

 these are spoken of as the cell-wall, and the peculiar 

 matter found inclosed in it, the cell-contents. For instance, 

 in the starch-containing cell of the potato, the cell-wall is 

 formed around and invests the germinal matter, while the 

 starch is deposited as small insoluble particles in the very 

 substance of the germinal matter. So that by the death 

 of particles on the surface of the cell-wall the cellulose 

 cell-wall is produced, while by the death of some of the 

 particles further inwards, and therefore under different 

 conditions, starch is formed. This outer part of the ger- 

 minal matter, which eventually lies between the starch 

 grains on the inside and the cell wall on the outside, is 

 known as the " primordial utricle " of the vegetable cell. 

 Fat-cells or adipose vesicles are formed in precisely the 

 same way ; fat may, moreover, be deposited amongst the 

 germinal matter of other cells, such as the cartilage or 

 nerve cell. 



Of the so-called Intercellular Substance. — In cartilage, 

 tendon, and some other tissues there is no line of sepa- 

 ration between the portions of formed material which 

 belong to each respective mass of germinal matter ; and 

 hence it has been supposed that these tissues were deve- 

 loped in a different way to the epithelial structures. A 

 "cell," or elementary part of adult cartilage or tendon, 

 merely differs from the epithelial cells, spoken of above, 

 in not having a distinct margin around its own particular 

 formed material, and if a line were drawn midway between 

 the various germinal masses, it would roughly mark out 



