Chronic Ostitis of the Os Pedis in Laminitis.

The contraction in this case interferes with the downward movements of the os pedis during progression, while in a state of rest there is a more or less constant pressure upon the sensitive structures, due to the correct downward displacement of the pedal-bone being opposed by the amount of contraction present.

You will note the ossification of the flexor pedis at its attachment to the pedal bone.

The alterations to be met with are best observed by taking a foot so diseased and making of it two sectionsone longitudinal, from before backwards; the other horizontal, and in such a position as to cut the os pedis through at its centre.

It is this change, together with the appearance of the rings, that indicates the loosening of the attachment of the os pedis to the wall, and its afterwards backward and downward direction (see Fig. 124).

118.SHOWING CHANGES IN THE OS PEDIS WITH LAMINITIS OF LONG STANDING, (a, Viewed from the front; b, viewed from the side.)

From the position on the os pedis of the indentation made in it by the keraphyllocele (see Fig. 133) it has been argued that pressure of the toe-clip is a cause of the new growth.