86 Human Physiology. 



creatures; each shell composed of an immensity of molecules 

 of carbon, oxygen, and calcium. 



The microscope opens to us worlds on worlds of the infinitely 

 little, as the telescope displays to us new universes, vast and 

 sublime, in the filmy specks of the sky. What are we to think 

 of the dimensions of the atoms composing the perfect organi- 

 sation of each of the 17,000 eyes of the butterfly, or the 25,000 

 of the mordilla, each with its lens, pupil, retina, as perfect as 

 our own? What of those which form each of the elaborately 

 constructed 360,000 suckers on the head of one species of 

 Pteropoda the whole animal an inch long? 



A microscopic fungus is said to multiply into countless 

 millions in the body of a single fly; and a drop of water may 

 contain 500 millions of living animalcules, each an organised 

 being, feeding upon more minute organisations. One drop of 

 water may contain, and have ample space for, as many living 

 creatures as there are human beings on the earth an ocean in 

 which they move with great activity, eat with voracity, and. 

 multiply at such a rate that a philosopher has calculated that 

 they would in four days generate 170 billions. Such being the 

 case, what is the probable size of the compound molecules of 

 water, and what of the oxygen and hydrogen of which it is- 

 composed? Mr. Herbert Spencer says: 



" In the minutest visible fragment of matter there are millions- 

 of units severally oscillating with unimaginable speed; and 

 physicists show us that the amplitudes of their oscillations vary 

 from moment to moment, according as the temperatures of 

 surrounding objects vary. Nay, much more than this is now 

 inferable. Each unit is not simple, but compound not a 

 single thing, but a system of things. Spectrum-analysis has 

 made it manifest that every molecule of this so-called element- 

 ary substance is a cluster of minor molecules differing in their 

 weights and rhythms. Such being the complexity of matters 

 we lately thought simple, judge what is the complexity of 



