446 DISEASES OF THE HOESE'S FOOT 



D. DISLOCATIONS. 



The firm and rigid manner in which the bones of the 

 pedal articulation are held together renders dislocation of 

 this joint an exceedingly rare occurrence, and then it is 

 only liable to happen under the operation of great force. 

 In the literature to our hand we have only been successful 

 in discovering one reported instance, and, strange to say, 

 in this, a well -marked case, the cause was altogether 

 obscure. We quote the case at the end of this section. 



Fig. 165. — Diagram showing the Course taken by the Needle 



WHEN SbTONING THE FrOG. 



This is shown by the dotted curved line a, b. 



1, The navicular bone ; 2, the ^ilautar cushion ; 3, the os i)edis ; 4, the 

 perforans tendon. 



A partial dislocation of this articulation is the condition 

 met with in ' Buttress Foot.' In this case the fracture of 

 the pyramidal process, and the consequent lengthening of 

 the tendon of the extensor pedis, allows the os coron.Te to 

 occupy upon the articulatory surface of the os pedis a more 

 backward position than normally it should. 



It is quite probable, too, that slight lesions of the other 

 restraining ligaments and tendons of the articulation may 



