Subsequent to being obliged to stand in mud and other damp or wet media, exposure to desiccating influences such as stabling upon dry floors, or at service on hot and dry road surfaces causes the insensitive parts of the feet to become dry, hard and brittle. This favors "checking" of the protecting structures and it frequently results in the formation of large fissures which expose the underlying sensitive parts of the feet and lameness is the inevitable outcome. The function of the feet--bearing the weight of the animal at all times when the subject is not recumbent, and in addition to this, the increased strain put upon them at heavy draft work, together with the concussion and buffeting occasioned by locomotion, make the feet susceptible to frequent affections of various kinds. Being almost completely encased by a somewhat inexpansible and insensitive wall and sole, renders the foot subject to pathologic changes peculiar to itself. The very nature of the structure of the foot together with the function of the sensitive lamina is sufficient cause for an affection unlike that seen involving other tissues--laminitis. An exhaustive consideration of foot affections is a study in itself and one that comes within the realm of pathologic shoeing; nevertheless, a practical knowledge of diseases of the foot is indispensable in the diagnosis of lameness wherein the foot may be at fault. The peculiar nature of foot affections renders them difficult of classification on any sort of basis that is helpful in the consideration of this subject. Injuries are the most constant cause of foot lameness, yet one must admit that there results complications because of infection in most instances; and that in some cases the injury is slight--just enough to permit the introduction of vulnerant organisms into the tissues. Therefore, one might well classify affections of the feet as infectious and non-infectious. There can be grouped in the class of infectious affections such conditions as nail pricks, calk wounds and canker. In the class of non-infectious affections one may consider conditions such as laminitis, strain and fractures. FOOTNOTES: [Footnote 1: A System of Veterinary Medicine by E. Wallis Hoare, F.R.C.V.S., Vol. I, page 519.] [Footnote 2: Ibid, page 807.] [Footnote 3: Vol. I, page 534, Veterinary Medicine, by James Law, F.R.C.V.S.] SECTION II. DIAGNOSTIC PRINCIPLES. _To observe attentively is to remember distinctly._--_Poe_. Before treatment is administered in constitutional disturbances resulting in disease, _cause_ is logically sought; so, in order to handle effectively any case of lameness, it is necessary first to discover the source of the trouble and contributing conditions affecting the structures. Hence, diagnostic ability is the prime requisite; and a thorough knowledge of pathologic anatomy or of surgical technic is of little value if this knowledge is not applied with the insight of the trained diagnostician.