THE ANIMAL KINGDOM. 17 



these animalcules to see us with the instruments which 

 we use to observe them, can we imagine what a terrific 

 impression we must make upon them, when they see 

 themselves in our hands ? 



Lastly, some of these animalcules have, in the interior 

 of the body, large cavities which incessantly empty and 

 fill themselves with coloured fluid. These cavities repre- 

 sent the heart of large animals, and their fluid the blood; 

 and this circulating system is relatively so large that it 

 may be stated, without any exaggeration, that some 

 microscopic beings have hearts fifty times as large and as 

 strong in proportion, as that of the horse or ox. 



If the wonderful organic perfection of those living cor- 

 puscles surpass all our preconceived ideas, their perpetual 

 activity afii'ords ground for no less astonishment. The life 

 of all animals is made up of alternate action and repose, of 

 movement which wastes the forces, and sleep which repairs 

 them; but the Infusoria are strangers to anything of the 

 kind; their life is an emblem of incessant agitation. 

 Ehrenberg, who observed them at all hours of the night, 

 always found them in movement, and accordingly con- 

 cluded that they had neither rest nor sleep! Even the 

 plant, exhausted by its life, mounting unseen through its 

 tissues, sleeps at the close of day; the animalcule, not- 

 withstanding its prodigious activity, does not. 



Struck with the fact, Owen thought that this extra- 

 ordinary activity might be due to the enormous develop- 

 ment of the digestive system in the Infusoria, seeing that 

 a man, a lion, or a tiger has only one stomach, an ox or a 

 camel four or five, whilst invisible Microzoa have some- 

 times a hundred! 



In proportion as science has been perfected the horizon 

 of life has been enlarged, and a microscopic world, full 



