THE GLOTTIS. 137 



head is raised, as in crawling up a wall or a tree, the glottis 

 may be said to be 'beneath' or 'under;' but the general 

 position of a snake being horizontal, the mouth then opened 

 would show you the opening of the tongue sheath nearest to 

 you and to the front ; and beyond that, behind, over, or upon 

 the tongue sheath, is another aperture, which is the glottis or 

 entrance to the larynx and trachea or windpipe. 



So there are in fact two sheaths or tubes lying one upon 

 the other, viz. the tongue sheath, and upon this and parallel 

 with it, the windpipe. 



After becoming better acquainted with the nature of that 

 tube which had impressed me so strangely, I lost no oppor- 

 tunity of making further observations, and on the following 

 feeding day at the Gardens I saw the air-tubes of several 

 snakes plainly. In September of that year, a new ' Horse- 

 shoe ' snake {Zanienis Jiippocrepis) arrived from Morocco. It 

 was a small and very pretty snake, and while enjoying the 

 privilege of a private inspection, the keeper got its mouth 

 open for me, enabling me to see the glottis, as well as to 

 both see and /^^/ the four upper rows of its beautiful little 

 teeth, closely placed, and as sharp as the finest pins. But 

 the action of the air-tube was very distinct. Probably little 

 Zanienis was breathrng harder and nervously under the 

 detention, but no word better describes the formation of the 

 aperture of the perfectly rounded tube, and the movement 

 of it, than iho. petite languette. 



Subsequently, there were opportunities of observing the 

 air-tube in two of the large African vipers, the ' River Jack ' 

 or ' Nose-horned ' vipers ( Vipera rJdnosceros) occupying the 

 same cage. Each struck a guinea-pig and held it. One of 



