294 ON THE DEEP PLANTAR TENDONS IN BIRDS. 
in Baza their distribution being quite normal, that is as in the first- 
described manner ; in Polyborus, Haliaétus, Tinnunculus, and Geranoétus 
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 Cathartide 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 vere. 
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. 292), 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 Cathartide—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 cuviert, 
Buceros rhinoceros, Caprimulqus europeus, 
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 fleeor 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 digi- 
