616 MUSCULAR SYSTEM 
tarse. Tendon A goes to ii. iii, and iv. Tendon P toi. and by 
vinculum to ii. also, consequently, owing to the vinculum’s distal 
position, its action is confined to two toes. This type, to a certain 
extent intermediate between I. and II., is characteristic of Acci- 
pitres, except Cathartide (see V.), and Pandion, in which last, 
but tendon P splits into 4, sending a slip to each toe directly, 
and in this case is therefore a complete fleaor communis. 
IV. The prevalent type where the hallux is absent or very 
small. Both muscles are strong and almost equally developed, 
their tendons inite about the middle of the metatarse, the joint 
tendon A+P going to the front toes, the hallux receiving no 
tendon, and consequently there is no crossing. This type, genetically 
connected with II., occurs in Casuarius, Dromxus, Rhea, Struthio, 
Turniz, Pterocles and Phenicopterus, Palamedea, Dicholophus, Tubin- 
ares, Colymlr. 
VY. Tendons A and P unite at a variable distance below the 
ankle joint, passing it in the ordinary way, and there is no crossing 
behind the metatarse, tendon P running directly into A from its 
fibular side. Muscle A generally much stronger than muscle P. 
In the simplest case (V,a) the united tendons A+P split into 4 
equally strong tendons, either just above the base of the toes, or 
successively first to the hallux and lastly to iv.imas in Buceros, 
Cypselus and Colius. Secondly an exaggerated condition of this 
(V,a) prevails (as V,b) in Momotidx, Todidx, Meropide and in some 
Alcedinide, where the tendon of the hallux is split off directly 
from the tibial and ventral side of A above its fusion with P. 
Thirdly there is a condition (V,c), hitherto known in the Trochilidx 
only, where A and P are completely divided from each other into 
a deep mass (A) which goes to i. and iii., and into a plantar mass 
supplying i. and iv. Careful and, from their small size, difficult 
preparations of this have been made by Prof. Stewart and Mr. 
Bourne for the Museum of the College of Surgeons in London, and 
any other description and figures of these Trochiline tendons are 
either incorrect or misleading. Lastly comes the modification found 
in the Cathartidx, where the fusion of the two principal tendons (as 
in V,a and V,b) is followed by a splitting into a ventral mass (P) to 
li. iii, and iv., and into a deep mass (A) to i. ii. and iii. This 
arrangement can be easily derived from type V,a, but almost 
equally well from the variable type III., as indicated by Pandion 
(fig. XI.) In the latter case the Cathartide would appear as a 
peculiar departure from primitive Accipitrine conditions, 
VI. Vinculum present, going from P to A. Tendon A single, 
going only to iii. Tendon P going to i. ii. and iv., and by the 
vinculum to iii. also, 2.2. to all the toes. This most peculiar type 
prevails in all the anomalogonatous zygodactyl Birds, Picidx, Rham- 
