264 FACULTIES OF BIRDS. 
indeed, from the observations of Sir Everard Home, 
that Montagu’s objections are valid, for in the adju- 
tant (Ciconia argala, Temminck), which has a bag 
precisely similar, he found that it cortained ‘ no- 
thing but air, which the bird has a power of expel- 
ling and filling the bag again at pleasure.” In the 
adjutant the bag communicates with the large air- 
cells on the back of the neck, and therefore we 
may fairly conclude it is intended to render the 
birds light and buoyant for running, since they are 
too heavy to fly without considerable difficulty. 
These birds are remarkable for the length of their 
legs, which must be very advantageous for swift- 
ness of running ; but it would be wrong to infer, as 
a general principle, that all birds with long legs are 
swiftfooted. On the contrary, the wading birds 
(Grallatores, Iuticer), which have proportionably 
much longer legs than the ostrich or the bustard, 
are not well adapted for walking-on land. Among 
these the flamingo (Phenicopterus rubur) is one of 
the longest-legged birds, yet it is in this respect 
far exceeded by the stilt (Himantopus melanopterus, 
Meyer), and the legs in the latter are, besides, slen- 
der and even, “‘so flexible,” as Wilson says of the 
American stilt, “that they may be bent considera- 
bly without danger of breaking.”* Aldrovand men- 
tions its pace as slow and laborious, and White of 
Selborne says, ‘‘ it must be matter of great curiosi- 
ty to see it move, to observe how it can wield such 
a length of lever with such feeble muscles as the 
thighs seem to be furnished with. At best one 
should expect it to be but a bad walker; but what 
adds to the wonder is, that it has no back toe. 
Now, without that steady prop to support its steps, 
it must be liable in speculation to perpetual vacil- 
lations, and seldom able to preserve the true centre 
of gravity.”t The truth is, that the legs are not 
formed for walking, but for wading; and we have 
* Amer. Ornith., vii., 55. + Letter 91. 
