44 THE INTERNAL 



The human eye, unassisted, can see nothing of all these 

 mysteries, and therefore it must be observed, that none of 

 the following facts can be brought to light without the 

 aid of the microscope. To meet the temporary require- 

 ments of my readers, I have given pictures of the most 

 important objects, obtained by means of a good microscope. 

 If we remove the outer, compact membrane of the 

 snow-berry ( Symphoricarpos racemosaj a plant common 

 enough in our gardens, we come to a mass of substance 

 composed of small, slippery, shining white granules. Each 

 of these is a separate perfect cell. (PL I, Fig. 1.) If we 

 strip off the outer membrane of the leaf of the common 

 pink, we find a velvety, green tissue, a portion of which 

 may easily be scraped off. In water, this separates into 

 little green points ; these, too, are perfect cells which only 

 differ from the foregoing in containing a quantity of 

 green granules in addition to the viscid yellowish substance 

 and transparent fluid sap (PL I, Fig. 2.) These two 

 kinds of cells, and in like manner all living, vegetating 

 cells, have this in common : their wall consists of a double 

 layer, a firm colourless one, the proper cell-membrane and 

 a semi-fluid, viscid and rather yellowish substance, which 

 invests the whole internal surface of the cell-membrane, 

 and thus constitutes one of the coats of the cell. The 

 latter layer is connected most closely with the life of the 

 cell. Not unfrequently, and then not necessarily separated 

 from the cell-membrane, the yellowish, viscid substance is 

 found wholly or in particular, denser, streak-like portions, 

 in continuous flowing movement, which is called the 

 circulation of the cell-sap. The proper cell-wall is composed 

 of cellulose, a substance formed of carbon, hydrogen and 

 oxygen ; the semi-fluid investment, on the other hand, 

 called by Hugo von Mohl the primordial utricle, contains 



