Marvels of the Universe 



245 



THE INTERMEDIATE STAGE, MAGNIFIED. 



When the grub is full grown its skin hardens into a brown 

 oval case in which the grub changes to the chrysalis. A few 

 thrown off and the complete Fly emerges. 



the glass, although quite dead, 



lat 



er one e 



nd 



down. Each pad is like a cushion, and from 

 it project numerous small cone-like-looking 

 objects, each of which ends in what at first 

 sight appears to be a minute hair, in some 

 instances surmounted by a little pad. 



In times gone by it was thought the Fly 

 exuded from its pad an adliesi\-e fluid, which 

 glued it on the ceiling or pane of glass ; but 

 this is believed now not to be quite correct. 

 Since more perfect microscopes have been 

 available, it has been found that each hair 

 is really a tube ; and hence each may be 

 considered as a perfect suctorial arrangement, 

 complete in itself. Experiments, however, 

 of somewhat recent date most certainly 

 show that it is highly probable flies can 

 at will pour out some sort of adherent 

 material — ven.^ possibly from the tubes them- 

 selves : for the}^ have been, and indeed 

 frequently are, found with their feet only firmly adherent to 

 when all suctorial powers must necessarily ha\'e ceased to exist. 



The foot, however, has unfortunately one more very special interest — a painful one to the 

 human subject ; for it is b\' this means that it certainly can carry germs of infection. The bacteria 

 of disease are known to be 

 exceedingly small, so small, 

 indeed, that many thou- 

 sands can be comfortably 

 located on the point of a 

 needle. Hence, if the Fly 

 alights on any poisonous 

 matter, it is quite conceiv- 

 able how bacteria can be 

 lodged either upon the hair- 

 like suckers themselves or 

 between them. A photograph 

 has been devised to show 

 this, which depicts part of a 

 pad magnified at five hundred 

 fhameters, upon which a 

 photograph of the bacilli of 

 consumption (for convenience 

 of representation magnified 

 twice as much) has been 

 cast. The number of germs 

 that could be carried even 

 by a single pad of one foot of a House Fly is therefore painfully evident. It shows, indeed, that 

 the House Fly is a living terror to mankind, and it cannot be wondered at that the Medical 

 Officers of Health in all districts are now making such a stir for the extermination of one of the 

 most dangerous pests that can occupy our houses. 





'.-• • > 





—'•"<■ 







T^ 



The pale 



PORTION OF 



threads and dark 

 attaclfs Flies in 



FLY'S WING. HIGHLY MAGNIFIED. 



patches in this photo show the minute fung 

 the autumn and kills off thousands of them. 



V h i c h 



