Dr. Latham'j Efay on the Trachea' or Windpipes of Birds, 9^ 



tending to the above circumftances, be mofr. times got at the know- 

 ledge of; but we cannot thereby discriminate thcfpecies. And it is alfo 

 more disappointing, that, at fome feafons of the year, in particular 

 Subjects, thefe internal marks are fo nearly obliterated as to deceive 

 a very good comparative anatomift, and much lefs likely to be afcer- 

 tained by any one who may be but flighrly verled in fuch matters. 

 But the particular circumirance of the trachea, as will hereafter be 

 pointed out, never alters; except in being more or lefs complete in 

 its period of oflincation during the life of the bird. I ought not 

 however to omit, that in a very careful comparifon many traits of 

 difference between one fpecies and another may be detected by the 

 fkilful anatomift (although fuch may not have either labyrinth, or 

 any enlargement of the trachea to diftinguiih them by), arifing 

 from the Structure of the rings themfelves, aided by the mufcles ap- 

 propriated to their motion ; and it may be with confidence aflerted, 

 that one mean at lead, if not the principal, of producing a loud 

 noife, and on the contrary, may arife from the peculiar construction 

 of thefe tracheal rings, which in many birds are found to be more or 

 lefs complete in themfelves ; fome of them wanting even a large 

 portion of the circle, whilft others are not only perfect, but of a 

 flrono-and elaflic ligamentous nature, and fome few fo greatly indu- 

 rated as to approach almoft to the texture of bone*. — Added to which 

 is the great difference of mufcular appendages; for, in the birds which 

 have a weak voice, the mufcles are fo likewife : on the contrary, very 

 flrong mufcles are obfervable in thofe whofe cry is loud, by which 

 ftructure-the rings, the Strength of which is ever proportional, are 

 put into violent action, and the bird thereby enabled to throw out 

 the air. with great force f. It is certain, alfo, that, in birds which 



* As in the Peacock, Goofanders, Smew, and fome others. 



-j- See a curious and elaborate diflertation on this fubjeft in Magazln Enc^ciepedique, 

 torn. ii. p. 334 et feq. 



i Fing, 



