l76 NATURAL HISTORY OF SELBORNE. 
excepted ; for it is so disposed as to carry " omnes quatuor digitos 
anticos'' all its four toes forward ; besides the least toe, which 
should be the back-toe, consists of one bone alone, and the other 
three only of two apiece. A construction most rare and pecu- 
liar, but nicely adapted to the purposes in which their feet are 
employed. This, and some peculiarities attending the nostrils 
and under mandible, have induced a discerning naturalist* to 
suppose that this species might constitute a genus per se.f 
In London a party of swifts frequents the Tower, playing and 
feeding over the river just below the bridge : others haunt some 
of the churches of the Borough next the fields ; but do not 
venture, like the house-martin, into the close crowded part of the 
town. 
The Swedes have besU 'red a very pertinent name on this 
swallow, calling it ring swala, from the perpetual rings or circles 
that it takes round the scene of its nidification. 
Swifts feed on coleoptera, or small beetles with hard cases over 
their wings, as well as on the softer insects; but it does not 
appear how they can procure gravel to grind their food, as swal- 
lows do, since they never settle on the ground. Young ones, 
over-run with hippoboscce^X are sometimes found, under their 
nests, fallen to the ground ; the number of vermin rendering their 
abode insupportable any longer. They frequent in this village 
several abject cottages : yet a succession still haunts the same 
unlikely roofs : a good proof this that the same birds return to 
the same spots. As they must stoop very low to get up under 
these humble eaves, cats lie in wait, and sometimes catch them 
on the wing. 
On the fifth of July, 1775, I again untiled part of a roof over 
• John Antony Scopoli, of Carniola, M.D. 
t The genus cypselus, or swift, is now universally accepted, though at the same time few natu- 
ralists seem to be aware of the extent to which it differs from hirundo' It is in the skeleton that 
this diversity is most apparent. The plumage is quite of a different character, and the amazingly 
thick skin of the swift affords another point of contrast. But it is in the structure and confor- 
mation of the sternum (that important bone to which the immense pectoral muscles are attached, 
and upon which, as birds of powerful flight, their whole frame may be said to be especially 
organized) that the distinctions between these genera are the most remarkable. The vast develop- 
ment of the sternal ridge in the swift has no counterpart in any of the swallows, which 
have the sternum much broader and more after the fashion of the dentirostral races; that of the 
swifts somewhat resembling those of the true falcons, wliile the moth-eater agani presents an 
approximation to the more powerfully winged owls. In each, however, the development being 
greatest in the fissirostral races. The skull is also very different in the swift and swallow genera, 
in the former being much wider in the gape, and approaching in form to the crania of the 
moth-eater genus. — Ed. 
t These insects, which so annoy all the swallow tribes, are now known as the craterina hinm- 
dinu of systematists. Hatched in the nest by the vital warmth of the birds, they live afterwards 
by sucking their blood. — Ed. 
