en harbour within
them the microbes of typhoid fever or of cholera (and probably other
diseases), without themselves suffering in health, and that
unsuspected they thus become distributing centres of these diseases.
The names "typhoid carrier" and "cholera carrier" have actually been
introduced to describe the condition of such persons. Then, again, by
his breath, and by coughing and spitting, a man acts as a carrier to
others of disease-microbes already lodged in him, as well as by actual
contact in the case of those infections which are called "contagious."
The numerous animals which surround and are associated with man act
very largely as casual carriers and distributors of disease microbes.
Thus dogs and even the cleanly cat are frequently carriers of disease.
But more especially those creatures which visit man's food stores and
food ready for consumption (such as bread, fruits, cold meat, etc.)
are active carriers. Rats and mice run over such stores and pollute
them. But the most widely active in this way is the common house-fly.

Whilst white men have developed an almost automatic resistance and
objection to the visits of flies to their lips, eyelids, and any wound
or scratch of the skin--a resistance which is not shown by many savage
races--they yet allow house-flies to swarm in their dwellings, to run
about and sample their food, with an indifference which is, when the
truth is known, truly horrible in its fatuity and foolhardiness. For
the fact is that the feet and proboscis of the common house-fly are
covered with microbes of all sorts, picked up by his explorations upon
every kind of filth. At every step which he takes he plants a few
dozen microbes, which include those of infantile diarrhoea, typhoid,
and other prevalent diseases. This is easily shown by allowing him to
walk over a smooth plate of sterilised nutritive gelatine and
preserving it afterwards free from the access of microbes from the
air. In twenty-four hours every footstep of the fly on the gelatine is
marked by an abundant and varied crop of microbes, which have
multiplied from the individuals let drop by the little pedestrian.
There is no doubt whatever that the house-fly is a main source of the
dissemination of the microbe of infantile diarrhoea, and the cause
annually of hundreds of thousands of deaths of children in the great
cities of Europe and America. Also in camps and infected districts he
is largely responsible for the introduction o