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" On careful examination we find that not every kind of 

 nuisance finds, in the economy of Nature, some animal 

 adapted for it perfect removal. Thus there is no generally 

 diffused insect which buries human excretions, certainly not 

 if in quantity. The dissolved pollutions in the waters are not 

 duly met, and the tiny, solid impurities floating in the air 

 seem also to be overlooked. Further, we find one and the 

 same nuisance simultaneously attacked by burying-beetles, 

 by Silphae, and by blow-flies. Or animal droppings may be 

 at once visited by GeotriipidcB, by Brachelytra and dung-flies. 

 Now, what should we think of an army where part of the 

 soldiers were equipped with the repeating breech-loaders, part 

 with muzzle-loaders, and part with matchlocks ? What would 

 be our thoughts if we found the commanders anxious to keep 

 up the number of the matchlock men, whilst allowing the 

 regiments armed with breech-loaders to decrease ? Or what 

 should we think of a carrier who employed between the same 

 two places, and for the same classes of goods, barges, stage- 

 waggons, and pack-horses, giving continually a larger propor- 

 tion of the traffic to the last .'' Yet these two imaginary cases 

 are exactly parallel to what we actually observe in Nature's 

 arrangements for the disposal of offal. 



" Further, let us suppose a city where the scavengers, night 

 men, and knackers, after being engaged in their ordinary 

 duties were allowed, without any previous cleansing and 

 disinfection to act as surgeons, sick nurses, provision dealers, 

 bakers, or cooks ? Yet this is precisely what we observe in 

 the animal world. The Diptera (two-winged flies) one 

 moment plunging themselves into matters loathsome and 

 infectious are in the next in close contact with our food and 

 our persons. Thus we see that ' Nature's sanitary service ' 

 does not form a well-organised system in which provision is 

 made for every kind of nuisance, and where every task is 

 committed only to that creature which is capable of executing 

 it in the most perfect manner. On the very contrary, we find 

 important matters overlooked, comparative trifles meeting 

 with abundant attention. We see the true sanitary agents 

 elbowed out of the field by imperfect rivals, who, like quacks, 

 prosper in virtue of their own shortcomings. This state of 

 thino-s agrees ill with the old theory that the animal forms of 



