gangrene, but the local results of bacterial action and the
constitutional disturbance associated with toxin absorption are present
in all; the prognosis therefore is grave in the extreme.

From what has been said, it will be gathered that in dry gangrene there
is no urgent call for operation to save the patient's life, the primary
indication being to prevent the access of bacteria to the dead part, and
especially to the surface exposed at the line of demarcation. In moist
gangrene, on the contrary, organisms having already obtained a footing,
immediate removal of the dead and dying tissues, as a rule, offers the
only hope of saving life.

VARIETIES OF GANGRENE

#Varieties of Gangrene essentially due to Interference with the
Circulation#

While the varieties of gangrene included in this group depend primarily
on interference with the circulation, it is to be borne in mind that the
clinical course of the affection may be profoundly influenced by
superadded infection with micro-organisms. Although the bacteria do not
play the most important part in producing tissue necrosis, their
subsequent introduction is an accident of such importance that it may
change the whole aspect of affairs and convert a dry form of gangrene
into one of the moist type. Moreover, the low state of vitality of the
tissues, and the extreme difficulty of securing and maintaining asepsis,
make it a sequel of great frequency.

#Senile Gangrene.#--Senile gangrene is the commonest example of local
death produced by a _gradual_ diminution in the quantity of blood
passing through the parts, as a result of arterio-sclerosis or other
chronic disease of the arteries leading to diminution of their calibre.
It is the most characteristic example of the dry type of gangrene. As
the term indicates, it occurs in old persons, but the patient's age is
to be reckoned by the condition of his arteries rather than by the
number of his years. Thus the vessels of a comparatively young man who
has suffered from syphilis and been addicted to alcohol are more liable
to atheromatous degeneration leading to this form of gangrene than are
those of a much older man who has lived a regular and abstemious life.
This form of gangrene is much more common in men than in women. While it
usually attacks only one foot, it is not uncommon for the other foot to
be affected after an interval, and in some cases it is bilateral from
the outset. It must clearly be understood that any