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Show 484 DR. R. W. SHUFELDT ON [Nov. 16, It will at once be seen that Geococcyx ^rn\anUS ({ZtllTZ with the vast majority of birds, has no ^c}±tef°nJZf(h^e he flexing of the second or prebasal phalanx of ^/tartf toe C J ^ e reversed one). Provision is made for this in various ways n different birds. Here, in the subject before us, a special slip « ^ °» for attachment from the deep flexor tendon as it passes ™ *e prebasal joint in question, which slip virtually fulfils the function of a flexor perforatus annularis secundus pedis, did such a muscle with an independent tendon exist. fi The /too/- perforans diyitorum profundus (Plate ALv. ug. g /.».»). This muscle is deep to all the flexors, and is situated directly on the posterior aspect of the tibia and fibula. It arises by two heads, one from the upper part of the tibia immediately below the overhanging rim of its summit, and the other, smaller, from the back of the hiad of the fibula. In the Corvidae there is a well-developed third head, which comes off from above the fibular notch of the outer condyle of the femur, and in these birds, too, there is no fibular head to this muscle, but two tibial ones instead. Geococcyx agrees however, with most birds in having this muscle attached nearly the whole length of the posterior aspect of the shaft of the tibia by lightly attached carneous fibres. . About a centimetre about the tibial cartilage it terminates n a strong subcompressed tendon, which, passing beneath the cartilage referred to, crosses the ankle-joint in front of all the other flexor tendons, and then passes through the inner of the two longitudinal perforations of the hypotarsal apophysis of the tarso-metatarsus Down the posterior aspect of the shaft of this bone the tendon still maintains its anterior position and exhibits a predisposition to ossify. But this does not actually take place in the specimen before me. Above the distal trochlea^ it makes the fibrous connection with the tendon of the flexor longus hallucis already described. This band is shown in the figure. Once within the limits of the post-trochlear space, the tendon of this muscle behaves in a manner common to most birds-that is, it quadrifurcates, and each branch takes a course close up to the joints on their plantar aspects, and running through the slits in the perforated tendons pass in each case to the ends of the toes, where they become attached or inserted upon the iufero-proximal tubercles of the unequal phalanges. The one passing along under the fourth digit sends up a slip which is attached to the underside of the shaft of the prebasal joint, thus making good the deficiency here of what is represented in the other toes by an independent tendon. The tibial head of this muscle at its origin is directly covered by the soleus, while in the aperture existing between the two heads we can discern the popliteus. These flexor muscles, and others on both the front and rear ot this limb, are moulded upon each other in a manner that can only be justly appreciated by a personal examination. In some the connections are quite feeble, the intervening tissue being easily separable, while in others the intimacy is very close, and great care is |
