ut. They were,
therefore, usually supposed to belong to the class of melanotic
formations, from presenting, as their distinguishing feature, a greater
or less degree of blackness. But, by recent investigations, it has been
proved, that the infiltrated carbon found in the bodies of coal miners
is not the result of any original disease, or change taking place within
the system,[4] but is carbon, which has been conveyed into the minute
pulmonary ramifications, in various forms, during respiration; and
which, while lodged in these tissues, produces irritation, terminating
in chronic ulcerative action of the parenchymatous substance. The very
minute bronchial ramifications first become impacted with carbon, and
consequently impervious to air; by gradual accumulation, this impacted
mass assumes a rather consistent form, mechanically compressing and
obliterating the air-cells, irritating the surrounding substance, and
promoting the progressive extension of the morbid action, till the whole
lobe is infiltrated with carbonaceous matter, which, sooner or later,
ends in ulceration and general disorganisation of the part. It is
evident, in tracing the disease through its various stages, up to that
of disorganisation, that wherever there is an impacted mass in any part
of the pulmonary structure, this is followed, sooner or later, by
softening, from its irritating effects upon the tissues by which it is
surrounded; and as this softening process advances, the innumerable sets
of vessels[5] composing the dense network of capillaries are broken
down, extending the cyst, so that, as the cysts enlarge, they gradually
approximate to each other, till all at last become merged in one great
cavity.

The majority of colliers, soon after they engage in their mining
operations, become afflicted with bronchial disease to a greater or less
extent.

Those who are hereditarily predisposed to pulmonary irritation, are, it
is my decided belief, more liable to "black phthisis" than others; but I
cannot suppose it possible, that any constitution, however robust and
sound, could resist the morbid effects resulting from carbon deposited
in the lungs. Tubercular phthisis is not at all prevalent in any collier
community with which I am acquainted, only occasional cases occurring,
and that amongst females. It is my impression, that a phthisical person,
engaged in the operations of a coal-pit, similar to those in
Haddingtonshire, would come under the influ