536 On Diptera as Spreaders of Disease. [September, 
or a man, and selecting — as it will do by preference, if such 
exist — a 'wound, or a place where the skin is broken, will 
convey the disease. 
Again, M. Pasteur has thoughtfully pointed out that if an 
animal has died of splenic fever, and has been carefully 
buried, the earth-worms may bring up portions of infectious 
matter to the surface, so that sheep grazing, or merely being 
folded over the spot in question, may take the plague and 
die. Hence he wisely counsels that the bodies of such ani- 
mals should be buried in sandy or calcareous soils where 
earth-worms are not numerous. But it is perfectly legitimate 
to go a step farther. If such worm-borings retain the 
slightest savour of animal matter, flies will settle upon them 
and will convey the infectious dust to the most unexpected 
places, giving wings to the plague. 
Now it is very true that no one has seen a fly feasting 
upon the blood of a heifer or sheep dying or just dead of 
splenic fever, has then watched it settle upon and bite some 
person, and has traced the following stages of the disease. 
But it is positively known that a person has been bitten by 
a fly, and has then exhibited all the symptoms of charbon, 
the place of the bite being the primary seat of the infection. 
We know also, beyond all doubt, the eagerness with which 
flies will suck up blood, and we likewise know the strange 
persistence of the disease “ germs.” 
Again, the avidity of flies for purulent matter is not a 
thing of mere possibility. In Egypt, where ophthalmia is 
common, and where the “ plague of flies ” seems never to 
have been removed, it is reported as almost impossible to 
keep these inseCts away from the eyes of the sufferers. The 
infection which they thus take up they convey to the eyes of 
persons still healthy, and thus the scourge is continually 
multiplied. 
A third case which seems established beyond question is 
the agency of mosquitoes in spreading elephantiasis. These 
so-called sanitary agents suck from the blood of one person 
the Filariae, the direCt cause of the disease, and transfer 
them to another. The manner in which this process is 
effected will appear simple enough if we reflect that the 
mosquito begins operations by injecting a few drops of fluid 
into its victim, so as to dilute the blood and make it easier 
to be sucked. 
So much being established it becomes in the highest degree 
probable that every infectious disease may be, and actually 
is, at times propagated by the agency of flies. Attention 
turned to this much negleCIed quarter will very probably go 
