60 A SHORT HISTORY OF SCIENCE 



the heart of modern chemistry." The facts seem rather to be 

 that Empedocles put together and hospitably accepted and 

 clarified the theories of his various predecessors. He is the 

 first sanitarian of whom we have any record, for Empedocles 

 is credited with having cut down a hill of his native city and 

 thus cured a plague by letting in the north wind, and to have 

 done a similar service to the neighboring "parsley" city of Selinus 

 (Selinunte) by simply draining a local marsh. 

 The following is a fragment from the writings of Empedocles : 



So all beings breathe in and out; all have bloodless tubes of 

 flesh spread over the outside of the body, and at the openings of these 

 the outer layers of skin are pierced all over with close-set ducts, so 

 that the blood remains within, while a facile opening is cut for the air 

 to pass through. Then whenever the soft blood speeds away from 

 these, the air speeds bubbling in with impetuous wave, and when- 

 ever the blood leaps back the air is breathed out; as when a girl, 

 playing with a clepsydra of shining brass, takes in her fair hand the 

 narrow opening of the tube and dips it in the soft mass of silvery 

 water, the water does not at once flow into the vessel, but the body of 

 air within pressing on the close-set holes checks it till she uncovers 

 the compressed stream; but then when the air gives way the de- 

 termined amount of water enters. And so in the same way when the 

 water occupies the depths of the bronze vessel, as long as the narrow 

 opening and passage is blocked up by human flesh, the air outside, 

 striving eagerly to enter,*holds back the water inside behind the gates 

 of the resounding tube, keeping control of its end, until she lets go 

 with her hand. Then, on the other hand, the very opposite takes 

 place to what happened before; the determined amount of water 

 runs off as the air enters. Thus in the same way when the soft blood, 

 surging violently through the members, rushes back into the interior, 

 a swift stream of air comes in with hurrying wave, and whenever it 

 [the blood] leaps back, the air is breathed out again in equal quantity. 



Fairbanks. 



ANAXAGORAS. (500-428 B.C.) For the student of science 

 Anaxagoras, a native of Clazomene in Asia Minor, is more im- 

 portant than Empedocles. Turning aside from wealth and civic 

 distinction in his enthusiasm for science, he seems to have occupied 



