384 DISEASES OF THE HORSE’S FOOT 
in connection with punctured foot. It occurs, too, as a com- 
plication 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 sur- 
rounding 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 
described, and when one considers the thinness of the 
keratogenous membrane, one is bound to admit that changes 
so grave occurring in it cannot fail to spread and infect the 
periosteum. 
(c) Osteoplastic Periostitis—This is more particularly a 
chronic process, and is, as the suffix ‘plastic’ indicates, 
associated with bone-forming changes in the membrane. 
It may occur as a consequence of slight but continued 
