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Show 344 MR. A. H. GARROD ON THE DEEP [Apr. 20, special tendon from the hallux-muscle to the second digit, there is a broad thin vinculum present, as in Gallus. In the Accipitres Diurnae the arrangement of the tendons therefore differs in different groups- in Baza their distribution being quite normal, that is as in the first-described manner; in Polyborus, Haliaetus, Tinnunculus, and Gera-no'clus this condition is combined with a special extra tendon to the second digit, which greatly increases its power of flexion. The arrangement observed in the Cathartidse is in no way allied to any of these, and adds another important point to the many now known to separate them off entirely from the Accipitres verse. The next arrangement to be described is a very different one. The two deep flexors descend beyond the ankle-joint independently, as usual; after passing which, generally about one third down the tarso-metatarse, they blend completely, before any slip has been given off. From the conjoined tendon thus formed the tendons of distribution spring, four in number, one to the hallux and others to each of the three anteriorly directed toes (fig. 4, p. 342), that to the former being generally separated off before any of the others. Among Homalogonatous birds the only group in which I have observed this condition is that of the Cathartidse-both Cathartes atratus and Sarcorhamphus gryphus possessing it, and so differing entirely from their supposed allies the diurnal Accipitres. Among Anomalogonatous birds the arrangement is very commonly found ; I have seen it in Coracias garrula, Podargus cuvieri, Buceros rhinoceros, Caprimulgus europaus, Steatornis caripensis, Cypselus alpinus. On looking at the plantar tendons thus arranged, without further dissection, the slip to the hallux from the conjoined deep flexor tendon seems to spring from its inner (that is, hallucial) side; whereas, from what has been said above, the long flexor of the hallux is situated external to the common flexor, at the ankle-joint. Further, in these birds, on straining upon the distal hallux slip with one hand, at the same time that the distal slips to the remaining toes are held in the other, the two elements of the conjoined tendons tend to divide up in the direction of the ultimate fibres ; and in doing so the line of rupture always develops in such a way that it leaves the thus further-separated hallux slip still on the inner side in connexion with the main flexor perforans tendon. A natural condition, like this thus artificially produced one, is found in some birds closely allied to those in which the last described arrangement obtains. It is found in Momotus lessoni, Dacelo gigantea, and Merops apiaster. In them the tendons of the flexor longus hallucis and of the flexor perforans digitorum pass down beyond the ankle-joint in the typical manner, the former external to the latter as usual. Opposite the upper end of the tarso-metatarse the flexor perforans digitorum gives off from its inner gide the flexor slip which supplies the hallux, the majority of the tendon descending as usual towards the foot. Opposite the middle |