236 HABITS OP BIRDS. 



chest. All these organs being 1 put in play by the air 

 in the lungs, they jerk and vibrate more rapidly 

 according to the rapidity with which the air passes*. 



At the request of Mr. Pennant, the celebrated John 

 Hunter examined the vocal organs of many singing- 

 birds, and found that the loudest songsters have the 

 strongest muscles in those parts. The sky-lark, whose 

 clear and vigorous note is often heard when he call 

 no longer be followed in his ascent by the most pene- 

 trating eye, had the muscles here stronger than any 

 other bird that was examined. Mr. Hunter also 

 observed that, among singing-birds, the muscles of 

 the male, following the same rule, are stronger than 

 those of the female, whose voice is always less power- 

 ful ; and it is worthy of remark that he could discover 

 no difference in the vocal organs of the male and 

 female in birds which do not sing. 



Baron Cuvier again found in all singing-birds five 

 pairs of constrictor muscles, namely, two pairs before, 

 two behind, two small, two oblique, and two trans- 

 verse, while in most birds which do not sing there is 

 in general only one pairf- The most minute account 

 of the action of these muscles has been given by M. 

 Meckel in his work on comparative anatomy, and by 

 Dr. BennatiJ; but it would be difficult to present 

 any intelligible statement of their details in an 

 abridged form. 



All these observations, however, are by no means 

 new, for the famous Jesuit, Athariasius Kircher, gives 

 the following minute and surprisingly accurate account 

 of the vocal organs of the nightingale. " In the first 

 place," says he, " we find its tongue very short, but the 

 other vocal organs (larynx) fibrous and muscular in 

 an astonishing manner, though in other respects it 



* Mem. Acad. des Sciences, pour 1753, p. 229. 



f Lecons d'Anat. Compares. 

 I Annales des Sciences Naturelles, xxiii. 32, &c. 



