446 IMPORTANCE OF THINGS MINUTE. 
When we descry an insect, smaller than a mite, 
moving with agility across the paper on which we 
write, we feel as incapable of forming any distinct 
conception of the minutiaB of the muscular fibres, 
which effect these movements, and of the still 
smaller vessels by which they are nourished, as 
we are of fully apprehending the magnitude of 
the universe. We are more perplexed in at- 
tempting to comprehend the organization of the 
minutest Infusoria, * than that of a whale ; and one 
* Ehrenberg has ascertained that the Infusoria, which have 
heretofore been considered as scarcely organized, have an internal 
structure resembhng that of the higher animals. He has disco- 
vered in them muscles, intestines, teeth, different kinds of glands, 
eyes, nerves, and male and female organs of reproduction. He 
finds that some are born alive, others produced by eggs, and 
some multiplied by spontaneous divisions of their bodies into two 
or more distinct animals. Their powers of reproduction are so 
great, that from one individual (Hydatina senta) a million were 
produced in ten days ; on the eleventh day four millions, and on 
the twelfth sixteen millions. The most astonishing result of his 
observations is, that the size of the smallest coloured spots on the 
body of Monas Termo, (the diameter of which is only -^^^^o^ of a line) 
is ^-g4g-^ of a line, and that the thickness of the skin of the sto- 
mach may be calculated at from ^f^-^ lca -o ^^ "sto^-jt^ ^^ ^ ^^"^• 
This skin must also have vessels of a still smaller size, the dimen- 
sions of which are too minute to be ascertained. Abhandlungen 
der Academie der Wissenschaften zu Berlin, 1831. 
Ehrenberg has described and figured more than 500 species of 
these Animalcules ; many of them are limited to a certain number 
of vegetable infusions ; a few are found in almost every infusion. 
Many vegetables produce several species, some of which are pro- 
pagated more readily than others in each particular infusion. 
The familiar case of the rapid appearance and propagation of 
animalcules in pepper water will suffice to illustrate the rest. 
