112 HABITS OF BIRDS. 
all during the operation ; and when it is, the sole ob- 
ject seems to be to trim the pencil of feathers which 
surrounds the gland. Had we any doubts upon the 
subject, the simple experiment of covering the gland 
in one hen or duck so as to prevent the bird having 
access to it, and leaving it uncovered in another, for 
a few days or weeks, would, by the state of the 
feathers in each, set the questionat rest. Independ- 
ently of such an experiment, common to all birds, 
the circumstance of the feathers on the head being 
equally trim, smooth, and glossy with those on the 
body, though they cannot be oiled, as it is impossi- 
ble to reach the head with the bill—the only instru- 
ment by which the oil could be applied—is of itself 
fatal to the theory. 
Should we be asked what we consider to be the 
use of the gland, we must at once say that we do 
not know; but our ignorance of its real use furnish- 
es no support to the conjectural theory which the 
preceding facts prove to be erroneous, no less than 
some others connected with cleanliness which we 
shall now mention. 
The Mohammedan Arabs of the desert, when they 
cannot procure water to perform the stated ablutions 
enjoined by the Koran, have recourse to dry sand, 
with which they rub their bodies as a substitute; 
and it is no doubt as a substitute for washing that 
some birds, thence called pulverizers (Pulvinatores), 
are fond of squatting in dust and hustling it into their 
feathers. A familiar instance of pulverizing may be 
observed in the barndoor fowl, even the unfledged 
chickens of which we have observed muddling in the 
dust by instinct, it should seem, as they were too 
young to have learned the practice from experience 
or by imitation. Now, had the feathers of these 
pulverizers been previously smeared with any unc- 
tuous matter, such as that in the rump-gland, the 
dust would have adhered, and thus tended to soil 
rather than to cleanse them. 
