EXTKRNAL ANATOMY. TARSUS. 113 
thus become the most important parts of the leg, and we 
shall now proceed to the details of each. 
(10.5.) The Tarsus, by which name we shall always 
designate the shank, is either feathered, as in many of the 
rapacious genera, or naked, as "in the generality of birds. 
The first of these different structures is most prevalent 
in the owl family, where the whole of the legs, from the 
thigh down to the claws, are generally covered with soft 
feathers, those upon the tarsus and toes being short and 
and compact. Several of the falcon family equally pos- 
sess this structure ; hut in these the toes are always 
naked, as in the Buteo lagapus, or rough-legged buzzard 
of Britain. The only instances of feathered tarsi which 
occur out of the circle of theiJopforc,t,are found among the 
Tetraonid^e, or grouse, where the feet and toes (Jig.5i)-(i) 
are generally as thickly clothed as any among the owls. 
It has been thought that this additional clothing has 
been given to 
the grouse, the 
greatest number 
of which live in 
the coldest re- 
gions, as a pro- 
tection to the 
rigours of win- 
ter, and we can have no doubt of the feet being 
preserved much warmer by such a comfortable cover- 
ing ; yet this reason totally fails in the case of the 
owls, for these are spread over all latitudes, and many of 
those from India have feathered tarsi, although the toes 
are usually bare. The sand-grouse again, of the genus 
Bterocles, which seem to delight in basking on the hot 
sands of the African deserts, have their tarsi (ft) covered 
with feathers, not so thick, indeed, as the ptarmigans, yet 
stiU sufficient to serve as an additional covering. It is dif- 
ficult, therefore, to arrive at any just conclusion regarding 
the use of feathers upon the tarsi, because we cannot re- 
duce the above facts to one common principle. 
(106). A naked tarsus is protected by SCALES. Next 
1 
