426 



tissues more or less exposed. It is not confined to being a complica- 

 tion of laminitis, but may be seen whenever the necessary conditions 

 for inducing it are present. Williams has described the horn 3' tissue 

 under these circumstances as being "weak, cheesy, or sijongy, like 

 macerated horn, or even grumous," and this certainly conveys a good 

 idea of its appearance and general characteristics. This crumbling- 

 horn when critically examined shows almost an entii-e absence of the 

 cohesive matter which unites the healthy fibers, Avhile the fibers 

 themselves are irregular and granular in appearance. Pumiced sole 

 depends upon an impairment of the horn-secreting i)OAvers of the sen- 

 sitive sole, or upon a separation occurring between the horu}'^ and soft 

 tissues which maintain its vitality. The normal sole phj'siologically 

 maintains a proper thinness by crumbling off in scales as it passes 

 be\-ond the life-maintaining influence of the producing tissues, and 

 anj'thing which i)revents, suspends, or destroys this influence causes 

 the crumbling process to become excessive. 



Punctured wounds of the feet, where accomi^anied b}" any consider- 

 able destruction of the soft or horn-secreting tissues, present the same 

 peculiarities in this respect in the immediate neighborhood of the 

 injury. Bruises of the sole are occasionally followed by this change 

 in the horn where the exudation has been excessive and has separated 

 it from the living tissues. True, in these cases we rarely see the soft 

 tissues laid bare, for the reason that new horn is constantly secreted 

 and replaces that undergoing the process of disintegration. 



Laminitis presents three diiferent conditions under which pumiced 

 sole may appear : First, where free exudation separates the horn from 

 the other tissues, or where the process of inflammation arrests the pro- 

 duction of horn bj' impairing or desti'oying the horn-secreting mem- 

 brane; secondly, where depression of the coffin bone causes pressure 

 upon and arrests the formation of horn ; and, thirdly, where the eleva- 

 tion of the sole compresses the soft tissues against the pedal bone and 

 induces the same condition. Pumiced sole, as it results from simple 

 exudation and separation of tissues, is of no imi)ortance, for the reason 

 given above in connection Avith bruises; but where suppuration occurs 

 in restricted portions of the foot in conjunction with laminitis it always 

 lays bare the tissues beneath and impairs the animaVs value tempora- 

 rily. In these cases recovery takes iilace after a few weeks' time by 

 the tissues horning over, as in injuries which have been attended with 

 the same process. Depression of the coffin bone is not a sufficient 

 cause within itself to cause pumiced sole, for if the relative change in 

 the bone takes place slowly, or if the horn is thin, the sole becomes 

 convex from the gradual pressure and the soft tissues adapt them- 

 selves to the change vrithout having their function materially impaired. 

 But when the dro])ping is sudden and the soft tissues entirely 

 destroyed, the horn rapidly crumbles away and the toe of the bone 

 comes through. In many of these cases the soft tissues remain uncov- 

 ered for months, and when they eventually become covered it is with 



