MECHANISM OF THE KNEE-JOINT. 241 



escaped notice, that a little behind the middle of the profile 

 curvatures of the femoral condyles, and more particularly on 

 the outer condyle, there is an angular break, in front of and 

 behind which the curvature is more rapid. Tracing the posterior 

 curvature backwards from the break at the outer edge of the 

 external condyle, where its position is indicated by a tubercle 

 about the middle of the popliteal notch, it passes backwards 

 along the condyloid margin, and also obliquely backwards and 

 inwards into the hitherto unnoticed prolonged superior pos- 

 terior internal angle of the condyle. The portion of the inner 

 edge of the outer condyle corresponding to the posterior part 

 of the curve now in question is concave inwards, and is the 

 margin of the space for the superior attachment of the 

 external crucial ligament, as the outer margin of Meyer's 

 curve limits the space for the attachment of the internal 

 crucial ligament. Within these limits the curve of the pos- 

 terior area of the condyle diminishes backwards, so as to 

 give it the appearance of a conchoidal surface. The posterior 

 area of the inner condyle and its curves are equally appreciable, 

 but flatter and less distinctly marked. 



The anterior area with its curve is most fully developed 

 on the inner condyle. The outer part of this area is the facet 

 previously mentioned in my reference to Meyer's oblique axis. 

 It limits the attachment of the posterior crucial ligament, and 

 its curvature diminishes from before backwards. The anterior 

 area on the external condyle, like the posterior on the internal, 

 is flatter, shorter, and less fully developed. 



The helicoid character of the curve of movement appeared 

 to me to indicate a screwed structure in the joint. The cha- 

 racters of the portions of the curve before and behind the 

 posterior break, and the corresponding and remarkable 

 peculiarity of the condyloid areas and their curves, taken along 

 with what I had already observed in the ankle, led me to 

 suspect that the movements of the knee-joint are combined 



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