1881.] ' On Diptera as Spreaders of Disease . 535 
so long must any creature which is in the habit of flying 
about, and touching first one person and then another, be a 
possible medium of infection and death. 
Let us take the following case, by no means imaginary, 
but a generalisation from occurrences far too frequent : — A 
healthy man, sitting in his house or walking in the fields, 
especially in countries where the insectivorous birds have 
been shot down, suddenly feels a sharp prick on his neck or 
his cheek. Putting his hand to the place he perhaps 
crushes, perhaps merely brushes away, a fly which has bitten 
him so as to draw blood. The man thinks little of so trifling 
a hurt, but the next morning he finds the pundture exceed- 
ingly painful. An inflamed pimple forms, which quickly 
gets worse, whilst constitutional symptoms of a feverish kind 
come on. In alarm he seeks medical advice. The doCtor 
tells him that it is a malignant pustule, and takes at once 
the most adlive measures. In spite of all possible skill and 
care the patient too often succumbs to the bite of a mouche 
charbonneuse, or carbuncle-fly. But has any kind of fly the 
property of producing malignant pustule by some specific 
inherent power of its own ? Surely not. The antecedent 
circumstances are these : — A sheep or heifer is attacked with 
the disease known in France as charbon, in Germany as 
milz-brand, and in England as splenic fever. Its blood on 
examination would be found plentifully peopled with badteria. 
If a lancet were plunged into the body of the animal, and 
were then used to slightly scratch or cut the skin of a man, 
he would be inoculated with “ charbon.” The bite of the 
fly is precisely similar in its adtion. Its rostrum has been 
smeared with the poisoned blood, an infinitesimal particle 
of which is sufficient to enclose several of the disease- 
“ germs,” and these are then transferred to the blood of the 
next man or animal which the fly happens to bite. The 
disease is reproduced as simply and certainly as the spores 
of some species of fern give rise to their like if scattered 
upon soil suitable for their growth. But flies which do not 
bite may transfer infedtion. Everyone must know that if 
blood be spilt upon the ground a crowd of flies will settle 
upon and eagerly absorb it. Animals suffering from splenic 
fever in the later stages of the disease sometimes emit bloody 
urine. Often they are shot or slaughtered by way of stamping 
out the plague, and their carcases are buried deep in the 
ground. But some loss of blood is sure to happen, and this 
will mostly be left to soak into the ground. Here again the 
flies will come, and their feet and mouth will become charged 
with the contagion. Such a fly, settling upon another animal 
