MIGRATION. 265 



" well authenticated, that it falls into a lethargic state 

 during winter, and even that it passes that season at 

 the bottom of marshy waters *.'* It would have been 

 well if he had at least referred us to some of these 

 authenticated accounts ; for we have been unable to 

 trace any thing more satisfactory than what we have 

 already mentioned. 



We deem it unnecessary to enter at much length 

 upon a refutation of these opinions, as it must be 

 obvious that it is physiologically impossible for a 

 swallow or any other bird to live many minutes, much 

 less for months, under water. The frog and other 

 amphibious animals which do hybernate under water 

 have a peculiar formation of the heart which enables 

 them to do so, and which is not thus formed in swal- 

 lows. " Though entirely satisfied,'' says Pennant, " in 

 our own mind of the impossibility of these relations, 

 yet desirous of strengthening our opinion with some 

 better authority, we applied to that able anatomist, 

 Mr. John Hunter ; who was so obliging to inform 

 us that he had dissected many swallows, but found 

 nothing in them different from other birds as to the 

 organs of respiration. That all those animals which 

 he had dissected of the class that sleep during winter, 

 such as lizards, frogs, &c. had a very different con- 

 formation as to these organs. That all these animals, 

 he believes, do breathe in their torpid state ; and, as 

 far as his experience reaches, he knows they do ; and 

 that therefore he esteems it, a. very wild opinion that 

 terrestrial animals can remain any long time under 

 water without drowning t-" 



Independently of the established principles of phy- 

 siology, the matter has been experimentally tried, and 



* Griffith's Transl. vii, 61. " II parait constant qu'elle s'en- 

 gourdit pendant 1'hiver, et rneme qu'elle passe cetie saison au fond 

 de 1'eau des marais." Retjne Amm. i. 3 ( JG, edit. 1829. 



f Brit. Zool. ii, 253. 



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