BREATHING AND HISSING OF SNAKES. 147 



a certain portion of the respiratory tube, which is so con- 

 structed as to set the air in vibration. In reptiles and 

 mammals it is at the point where the windpipe opens into 

 the front of the pharynx, that this vibrating apparatus is 

 situated. Few of the animals of the former class, however, 

 can produce any other sound than a Jiiss, occasioned by the 

 passage of air through the narrow chink by which the 

 trachea communicates with the pharynx ; but this sound, 

 owing to the great capacity of their lungs, is often very 

 much prolonged' {Animal Physiology), — prolonged, but not 

 powerful, be it observed. 



Says Professor Owen: 'The true ^' cJiordce vocales'' are 

 absent in serpents, and the voice is reduced to a hissing 

 sound, produced by the action of the expired air upon 

 the margins of the glottis' {Anatomy of the Vertebrates). 



Speaking of the escape of air from the lungs, Dumeril 

 says : ' Lorsqu'il est passe plus vivement il laisse entendre 

 une sorte de vibration, qui le plus souvent, ne consiste que 

 dans le bruit d'un soufflement.' ^ 



Sometimes, according to the position of a snake, or when 

 the passage is well open and uninterrupted, the hiss par- 

 takes somewhat of a whistling sound, like the blowing 

 through a quill. I observed this particularly in a ' tree 

 boa ' {Epicratis cenchris), which hissed at me angrily one 

 day because I took the liberty of touching it when the 

 keeper opened its cage to arrange its blanket. The 'hiss,' 

 not loud, or by any means musical, differed from the 

 ordinary blowing only as a current of air passing through 

 a round tube would differ from the same current passing 



^ E7-petologie gaierale, tome i. p. I So. 



