482 DR. R. W. SHUFELDT ON [NoV. 16, 



through the annular ligament in the sole of the foot, it proceeds to 

 the underside of the second toe, beneath the second phalanx of 

 which it expands to form a tubular sheath for the passage of the 

 deep flexor, while at the same time it becomes attached to the side 

 of this joint of the toe in question. 



The carneous portion of this muscle in the leg is to the outer side 

 of the loop for the biceps flexor cruris, and, owing to the fact that 

 it varies in form and size in different birds, it is as well to bear this 

 in mind. 



^he flexor per/or atus medius secundus pedis (Plate XLIV. fig. 2, 

 f.p^, as in all of the birds I have examined, is one of the best 

 developed perforated tendons at the back of the leg. Its fascia of 

 origin merges with the enveloping fascia about the knee-joint, while it 

 also arises by a strong tendon, common to it and the flexor perforatus 

 indicis secundus pedis, from the external aspect of the outer condyle 

 of the femur. 



Finally, it is attached more or less by carneous fibres down the 

 shafts of the leg-bones to a point below their middle, or rather the 

 middle of the leg. Below this the muscle terminates in a strong 

 tendon, which, taking an oblique course through the tibial cartilage, 

 passes as usual over the ankle-joint, through the hypotarsus, and 

 down the back of the tarso-metatarsus. 



In the foot it perforates the more superficial flexor of the basal 

 phalanx of the outermost of the two anterior toes, then the turn 

 bifurcates over the prebasal joint to allow the deep flexor to pass 

 through, these bifurcations becoming the insertions of this muscle, 

 and they are attached to the sides of the shaft of the second joint of 

 the toe alluded to, or the external one of the two in front. 



The flexor pe)-foratus annularis pritnus 2^edis (Plate XLIV. fig. 2, 

 /■p-a) in this bird seems to have acquired a more central position 

 on the back of the leg than in many others that I have dissected, 

 and, moreover, its tendon, as will be seen from the figure, is quite 

 superficial. 



It arises from between the condyles of the femur by a slight 

 semitendinous slip, and from the side of the flexor longus hallucis. 

 The muscle itself is somewhat of a fusiform outline and rather flat ; 

 it lies to the inner side of the loop for the biceps. About one third 

 the way down the back of the leg it terminates in a small though 

 very long tendon, which, passing quite superficially through the tibial 

 cartilage and over the ankle-joint and hypotarsus, runs in common with 

 the other flexors down the back of the tarso-metatarsus, turns to the 

 rear in the sole of the foot to become inserted on the underside of 

 the distal end of the basal phalanx of the reversed digit. In the 

 specimen before me this insertion is to the outer side of the deep 

 flexor, and the tendon is not slit for its passage. Nothing could be 

 more engaging than the examination of these reversed tendons in 

 the sole of the foot of this Ground-Cuckoo, for the greatest nicety 

 in accommodation has been accomplished as they have gradually 

 come to assume their present position. No doubt some of the 

 departures observed from the more common arrangement of them 

 are due to the reversion of the digit in question. 



Strong, fibrous bands are so disposed in this plantar region as to 



