WONDERS OF THE MICROSCOPE. 
275 
cow, and forms a clot, these moulds are frequently found; 
they also find their way into the urinary bladder, the 
stomach, and lungs of man. Such anomalies may at first 
surprise us, but they may nevertheless admit of explanation, 
as the presence of the larvae of the tape-worm in deep-seated 
organs, and even in the brain, which was so long a stumbling 
block to science. 
• The plan of organization throughout the vegetable king¬ 
dom presents this remarkable feature of uniformity—that the 
fabric of the highest and most complicated plants consists of 
nothing else than an aggregation of the bodies termed cells— 
every one of which, among the lowest and simplest forms of 
vegetation may maintain an independent existence, and may 
multiply itself indefinitely, so as to form vast assemblages of 
similar bodies. Hence, as definitely stated by Schleiden, 
it is in the life history of the individual cell that we find the 
true basis of the study of vegetable life in general. 
In its most completely developed form, the vegetable cell 
may be considered as a closed membranous bag, or vesicle, 
containing fluid cell-sap : and thus we have to consider sepa¬ 
rately the cell-wall and the cell-contents. 
The cell wall is composed of two layers, of very different 
composition and properties. The inner of these, which has 
received the name of primordial utricle , is extremely thin and 
delicate. Its composition, by the effects of reagents, is found 
to be albuminous —that is, it agrees with the formative 
substance of the animal tissues in every particular. The 
external layer (cell-wall) is usually thick and strong in com¬ 
parison with the other, and may often be shown to consist 
of several layers; in composition it is nearly identical with 
starch. The typical form of the cell is either spherical or 
oval; but by pressure in growth cells assume almost every 
variety of shape. Cells are endowed with a peculiar vital 
force , by which they are capable of absorption and the 
elaboration of the absorbed matter, of growth, reproduction, 
and of secretion. One great fact which we would impress 
on the reader is, that each cell of a plant should be considered 
as having an independent or individual existence—that in 
one situation it may secrete colouring matter, in another 
starch, gum, sugar, oil, &c., and in another the material for 
the reproduction of its species. 
We now proceed to consider the elementary tissues of 
animals, and see how far they correspond with those of 
vegetables. As there are many among the lowest orders of 
plants and animals in which a single cell constitutes the 
entire individual—each living/br and by itself alone—so each 
