SANITARY OFFICERS 247 



begins at once. In this connection it is worthy 

 of note that these flies have had all the details of 

 their life-history adapted to the necessities of the 

 case. A heap of stable manure is less inimical to 

 animal life than is decomposing flesh, and as in- 

 numerable beetles and flies help to clear it away, 

 the fecundity of the House Fly is not nearly so 

 high as that of the Blue-bottle and Flesh Fly, 

 whose work must be done much more expeditiously. 



We have mentioned that the House Fly lays 

 about 600 eggs ; the Blue-bottle lays from 500 to 

 1,000, but dissection has shown that the Flesh Fly is 

 able to deposit as many as 20,000 grubs. Of course, 

 these are not all deposited at once, or in the same 

 mass of corruption : they are laid in batches as 

 appears to be necessary. But it frequently happens 

 that a number of egg-laden Blue-bottles or Flesh 

 Flies will lay their eggs in the same mass of food, 

 which may not be sufficient to bring so vast an 

 army of maggots to their full size. In that case 

 some would feed on their weaker kindred, so that 

 some could come to maturity and continue the 

 race. The dead matter would become converted 

 rapidly into living matter, and so cease to pollute 

 the atmosphere ; but the futility of attempting to 

 get rid of the fly- nuisance by killing a few thousand 

 flies here and there is apparent. It is akin to 

 trying to empty the ocean with a tea-spoon. 



In addition to these sanitary officers whose com- 

 mission may be said to be rather general to clear 

 away nuisances of a certain kind wherever they 



