ON THE DEEP PLANTAR “TENDONS IN BIRDS. 291 
the outer side of the tendon of the flexor perforans digitorum, crosses it 
Fig. 1. 
Gallus bankiva. 
superficially in its downward and inward course to the lower surface 
of the base of the hallux, whence it traverses the flexor surface 
of that digit to the base of the ungual phalanx at which spot it 
is inserted. The flexor perforans digitorum continues down to the 
sole of the foot as a single tendon, where it immediately splits into 
three parts, one to the ungual phalanx of each of the three anteriorly 
directed digits. Opposite the lower part of the tarso-metatarse the Page 342. 
flexor longus hallucis sends downwards a fibrous vinculum (V) which 
joins the flexor perforans digitorum tendon just before it commences to 
trifurcate. In all cases this vinculum is always directed downwards 
from the hallux-muscle to the digits-muscle, so that, when the tendon 
of the flexor perforans digitorum alone is pulled upon, the three anterior 
digits alone are flexed; but when the flexor longus hallucis is put in 
action, the digits as well as the hallux are simultaneously flexed. 
The proportion borne by this vinculum to the main tendon of the 
- flexor longus hallucis varies considerably. In some birds it is com- 
paratively feeble and insignificant ; whilst in others, with but a small 
hallux, it is much larger than the hallucial moiety, and seems to be 
u 2 
