454 THE AMERICAN NATURALIST [Vol. XLII 



femur almost touch, and the articular membrane is drawn 

 deep into the femoral cavity. The tendons find their 

 attachment to the outer and inner sides of the rim of the 

 tibia and, extending into the cavity of the femur, serve 

 for the attachment of a series of muscles, as shown in 

 Fig. 1, A and B. 



The flexor tendon in the earlier stages is only a 

 V-shaped thickening of the articular membrane, but later 

 the point of the V extends deeply as an internal pocket 

 for the attachment of muscles reaching nearly to the base 

 of the femur. There are two sets of muscles attached to 

 this tendon, extending obliquely to the right and .left 

 sides of the femur. The first of these, f\ in the figures 

 lying at about 45° to the long axis of the femur, and the 

 others marked / 2 , / 3 , etc., lying more nearly longitudinally. 



The extensor tendon attaches to the dorsal rim of the 

 tibia by a broad ribbon-like portion and soon expands into 

 a broad plate at right angles to this first portion and then 



narrows to a ribbon and extends deeply into the femur 

 even in the earliest stages. A short muscle, e, is attached 

 to the disk, followed by a series of others, somewhat as 

 the flexor muscles are arranged, only that there is but a 

 single series, finding their attachment to the middle 

 dorsal side of the femur. Tendons are first developed as 

 somewhat tubular processes, but always collapse after 



