MECHANISM OF THE KNEE-JOINT. 235 



condyles corresponding to, and rolling upon, the semilunar 

 fibro-cartilages ; and distinct from their remaining or central 

 portions, which are in contact with and roll upon the central 

 cartilaginous facets of the tibial condyles. The oblique curved 

 surface at the fore part of the inner condyle is a distinct facet, 

 which at the close of extension and at the commencement of 

 flexion moves upon and is in contact with the internal anterior 

 cartilaginous surface of the intercondyloid spine of the tibia ; 

 and with the tibial attachment of the anterior crucial liga- 

 ment ; and in extreme flexion is then, and then only, in contact 

 with one of the seven facets of the patella, which patellar facet, 

 in no other position of the joint, touches any other cartilagi- 

 nous surface, but is provisionally sheathed with a synovial 

 fold. 



The two tibial condyloid articular surfaces also present 

 distinct semilunar facets, and central facets for the central 

 facets of the femoral articular surfaces. 



In consequence of this facetted configuration, and the 

 peculiar curvatures of the opposite cartilaginous surfaces, the 

 latter are in no position of the joint coincident throughout ; 

 but gape more or less in different parts of their extent. 



In addition to the previously-recognised function of the 

 semilunar fibro-cartilages as tough elastic structures for adapt- 

 ing the opposite femoral and tibial surfaces to one another, 

 the so-called Haversian glands, in addition to their lubricating 

 function, are arranged for a similar purpose. Every space or 

 gap between the opposite surfaces of the patella, femur, and 

 tibia, not provided for by the semilunar fibro-cartilages, is sup- 

 plied, when it appears, with an invariable, vascular, fatty 

 synovial pad, which is forced into the chink or pulled out 

 again by special arrangements ; and thus, not only do these 

 pads support, and render steady, the movements of the joints, 

 but lubricate the moving surfaces during action. 



Since the publication of these results, I have annually 



