66 Insect Life : Its Why and Wherefore 
truth is that the whole life history of the 
flea is mixed up with the presence of dirt. 
The cleaner the person, the cleaner the 
bedclothes, the cleaner the house, the more 
scarce will the “ pulex irritans ” be. Has 
the flea really a use ? Yes. Although I 
cannot claim that my illustration is original, 
it has a very distinct work to do. We 
should all be acquainted with the fact that 
our body is covered with a fine and wonder- 
fully constructed cover which we call 
skin. This is connected closely with the 
nerve centres and blood-vessels of the body. 
In its turn again this finer skin is covered 
by an outer skin called the epidermis, 
which, Nature has ordered, shall for obvious 
reasons be kept clean by the use of some- 
thing that shall remove all the dirt, dust 
and other deposits which accumulate upon 
its surface, and thus block and choke up 
the minute pores, or little orifices, by 
which the air should circulate. Little 
flakes of dead skin, even the dried up 
moisture which exudes from our bodies in 
the form of sweat, may serve to effectually 
bar the passage of sweet air through these 
channels. Water (in these days with the 
