CLEANLINESS. 7 



boy knows that the canal of this gland often be- 

 comes obstructed in his pet birds, and occasions a 

 troublesome and sometimes fatal engorgement *. 



The remark of Blumenbach t that the gland is 

 largest in aquatic birds, contains a generalization 

 not warranted by facts ; for grebes, divers, and such 

 as want tails, have the gland much smaller J, though 

 their feathers are as smooth and as impenetrable by 

 water 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 of the theory. We have attended for hours to 

 various species of birds when thus engaged ; and so 

 far from constantly returning to the rump-gland, 

 which by the hypothesis would be indispensable for 

 dressing every successive feather, it is rarely visited 

 at all during the operation, and when it is, the sole 

 object 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 question at rest. 

 Independently 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 impos- 

 sible 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 



* Raumur, Oiseaux Domestiques, ii. 332. 

 t See p, 4. $ Ray's Willughby, p. 3. J.R- 



