become
active, and abnormal deposits of bone are the result.

_(b) Suppurative Periostitis_.--This condition simply indicates that
the inflammation is complicated by the presence of pus organisms. It is,
therefore, a common termination of the simple acute form attending the
infliction of a wound. The wound becomes contaminated, and the case of
simple periostitis is soon changed into the suppurative form. Once having
gained entrance to the wound, the pus increases in quantity, and slowly
runs between the membrane and the bone. This, however, it does not do to
any large extent, showing rather a tendency to penetrate the outer fibrous
layer and gain the outside of the membrane.

Suppurative periostitis is met with in foot cases, commonly in connection
with punctured foot. It occurs, too, as a complication in suppurating corn,
in severe tread, in complicated sand-crack, as a result of the spread of
suppurative matter in acute coronitis, and in sub-horny quittor.

In ordinary cases of suppurative periostitis the pus formed is yellow
in colour, creamy thick, and free from pronounced odour--the so-called
'laudable' pus of the older writers. It so happens in many cases of foot
trouble, however, that putrefactive organisms gain entrance side by side
with those of pus. In this case the characters of the discharge are
very different. It is distinctly more fluid, is of a pink or even light
chocolate colour, and extremely offensive. In these instances the pus
shows a marked tendency to spread, strips the periosteum from the bone,
perforates the outer layer of the membrane, and finally infiltrates the
surrounding tissues.

This forms a near approach to what is known in human surgery as an
_infective_ periostitis, and in our subjects is nearly always met with in
cases of severe prick. Its rapidly spreading character makes it always
a dangerous condition, and a punctured foot exuding a discharge of this
nature should always be regarded as serious. The close contiguity of
the joint (it can never be _far_ distant in foot cases), the spreading
character of the disease, and the rapidity with which the horse succumbs to
arthritis, are all factors to be taken into consideration, and to lead to a
warning-note being struck when attending a case of such kind.

A further instance of infective periostitis is that met with in acute
laminitis. The discharge obtained from the sole in these cases very often
bears the character we have just descri