74 



HUMAN BIOLOGY 



FIG. 68. OPEN MOUTH, showing palate and tonsils. 



two tubes open 

 from the phar- 

 ynx. One is the 

 trachea (tra'kea) 

 or windpipe, the 

 other is the esoph- 

 agus or gullet. 

 At the top of the 

 trachea is the 

 cartilaginous lar- 

 ynx, or voice box. 

 If the finger is 

 placed upon the 

 larynx or Adam's 

 apple, it is plainly 

 felt to move up 

 and down when 

 swallowing. The opening into the larynx is provided with 

 a lid of cartilage, the epiglottis. Inside the larynx, the 



vocal cords are stretched 

 from front to back. Just 

 below the larynx comes the 

 trachea proper, which is a 

 tube about three fourths of 

 an inch in diameter and 

 about four inches long (Fig. 

 69). It consists of hoops of 

 cartilage (Fig. 69) which are 

 not complete circles, but are 

 shaped somewhat like the 

 letter C, being completed at 

 the rear by involuntary mus- 

 cular tissue, whose function 



p. 



FIG. 69. LUNGS, P; with trachea, 

 TA ; thyroid gland, th ; larynx, L ; 

 and hyoid bone, //. 



