126 THE UNIVERSE 



terior of this lengthened heart larger valvules, to the 

 number of six or eight, are folded back against the wall 

 to let the blood pass forward, and re-open directly after- 

 wards, during each contraction, in order to prevent its 

 flowing backwards. Vessels arranged in loops are distri- 

 buted to all the members- 



The course of the blood in the colossal insect seen upon 

 the screen resembles so many little streams bearing 

 globules more or less heaped up; this is proved by the 

 strictest evidence, and yet who would believe that Cuvier 

 and his school would never credit this phenomenon'? In- 

 stead of looking, which was so easy, they preferred to 



72. CVimmon Ephemera — E. communis. 



deny the circulation in the insect, and to regard its won- 

 derful heart as a simple secreting vessel shaken by con- 

 tractile shocks. It is thus that physiological science ad- 

 vances; a hundred battles are requisite to make men 

 admit the most easily verified truth. 



With us, as Avitli all the large animals, the air rushes 

 into the respiratory apparatus, Avithout the least check, 

 by a simple and most ample opening; all the impurities in 

 the air may be swallowed, to the defilement of our lungs. 



Insects, on the contrary, inspire the atmospheric air 

 through several orifices, and this is well purified before 

 it is introduced into the organism. For this puriDOse all 



