The peculiar stilty action which this disease induces brought into use the term “chest founder.” This term was meant to convey the idea of pain in the muscles of the chest, where the disease giving rise to it was supposed to exist, and it was not until Moorcroft and Turner traced the disease to the navicular bone that these meaningless terms ceased of employment, and the much more rational one, “navicularthritis,” came to be used in their stead. Whether this term is an appropriate one or not may be open to question, but it locates the disease, and in this respect it is distinctly useful.
Causes.—We cannot speak of the cause of navicular disease without referring to the influence of heredity. There can be no doubt that the property of transferring to the offspring the weakness inherited by the parent is just as marked in this as in any other affection, and the writer, in a long experience, has seen numerous instances of the disease handed down from the latter to the former. It must be understood that the transmission of hereditary taint or predisposition is what is understood here by hereditary disease. It is not that the disease in an active state is born with the animal, but that the parts are in that condition in which the disease may be easily excited in them by causes which would not affect an animal who was not the subject of hereditary weakness. It must not however, be stated that because a horse inherits a predisposition to navicular or any other disease that he should necessarily contract it. A good deal will depend upon the degree of intensity of the inheritance on the one hand, and the severity of the cause which acts upon it on the other. If it exists in such form as to be easily excited into action, it is not unlikely to appear, but where the hereditary predisposition is only possessed in a mild measure the animal may not meet with a cause sufficiently severe by which the predisposition can be made to assume an active state.
Exciting Causes.—They are numerous and varied. Conformation, action, shoeing, weight of body and general management, all play their respective parts in causing the disease.
Side View of Healthy Foot.
Side View of Diseased Foot.
Back View of Healthy Foot.