CLEANLINESS. 111 
which the dressing is said to be effected, they would 
have seen at once that the theory is untenable, as the 
quantity secreted inone day would scarcely suffice to 
anoint a single feather, much less the whole. We 
have just squeezed out all the oil contained in the 
double rump-gland of a common wren, and found it 
impossible to make it go over one of the tail feath- 
ers. ‘One fact,” says M. Le Vaillant, ‘is frequent- 
ly sufficient to demolisha theory ;” and the fact that 
the feathers of the rumpless fowls which have no 
gland are as smooth and proof against rain as those 
which possess the gland, furnishes a striking illus- 
tration of the remark. 
The fact, however, is unquestionable, that birds 
are sometimes seen pecking about the gland in ques- 
tion. But the observing of a bird thus engaged, so 
far from authorizing the received conclusion, might 
have shown that the point of the bill could never 
Squeeze out enough of fluid for the purpose alleged. 
The only legitimate inference would have been that 
some slight pain or irritation had caused the bird to 
peck the gland; and every schoolboy knows that 
the canal of this gland often becomes obstructed in 
his pet birds, and occasions a troublesome and some- 
times fatal engorgement. 
The remark of Blumenbach that the gland is lar- 
gest in aquatic birds, contains a generalization not 
‘warranted by facts; for grebes, divers, and such as 
want tails, have the gland much smaller, though their 
feathers are as smooth and as impenetrable by wa- 
ter as those of the terns and the gulls which have 
considerable tails. 
It is only requisite, indeed, for any one to watch a 
bird preening its feathers, to be convinced of the fal- 
lacy ofthe theory. Wehave attended for hours to va- 
rious species of birds when thus engaged ; and so far 
from constantly returning to the rump-gland, which 
by the hypothesis would be indispensable for dress- 
ing every successive feather it is rarely visited at 
