130 GREAT NORTHERN RORQUAL. 



prey. One of his plates, his eighth, is supplied for 

 the express purpose of illustrating its appearance 

 and size. This account seems generally to have 

 been received, and is propagated in our latest English 

 and foreign treatises ; and yet we are persuaded 

 that it is wholly erroneous. No description has 

 been given of the canal which conveys the air into 

 the sack ; anatomical observation contradicts the 

 assertion, and the bladder exhibited in the plates 

 appears to be nothing more than gas generated by 

 decomposition, and collected in the loose cellular 

 membrane of the lower jaw, as it rapidly does in 

 other parts of the body. We may add, that the pro- 

 cess of its formation has been actually witnessed by 

 Messrs. Quoy and Gaimard. A whale of this species 

 was killed by the crew of the vessel in which they 

 sailed. "When alive, and during the next day, the 

 mouth was shut. The day after, this reputed swim- 

 ming bladder began to appear, and speedily it pre- 

 sented an insuperable obstacle to the shutting of the 

 jaws (Voyage, p. 83). The simplest seems the most 

 plausible, as it is probably the correct account of the 

 matter. The Rorqual has not, in the upper jaw, 

 that large segment of a circle in which the Mysti- 

 cetus collects its food ; but to compensate for this, 

 has it in the lower : when it opens its prodigious 

 mouth, the water, rushing in, opens these folds, and 

 so forms, as it were, a great well in which its prey 

 is collected ; on shutting its mouth and contracting 

 the folds, it expels the water, whilst the strainer 

 formed by the baleen retains the fish, &c. which 



