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Show 482 DR. R. W. SHUFELDT ON [NOV. 16, through the annular ligament in the sole of the foot, it proceeds 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. The flexor perforatus medius secundus pedis (Plate XLIV. fig. 2, f.p2), 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 perforatus annularis primus pedis (Plate XLIV. fig. 2, f.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 lonyus 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 |
