' THE TRACHEA. 135 



It is probable that the inferior, constrictors of the pharynx, as 

 well as the stylo-pharyngeal muscles, assist in this use of the 

 Ihyreo-hyoidei. 



There is a well marked difference in the larynx of the tvo 

 sexes. In the female, it is generally smaller by one-third than 

 it is in the male; the thyroid cartilage is also less prominent, in 

 consequence of its two halves uniting at an angle more obtuse, 

 the pomum Adami is, therefore, seldom conspicuous. The rima 

 glottidis is also smaller in women. 



The nerves of the larynx come principally from the superior 

 and the inferior laryngeal branches of the par vagum. 



CHAPTER II. 



OF THE TRACHEA, AND THE GLANDS BORDERING UPON IT. 

 SECT. I. THE TRACHEA. 



THE Trachea, or Aspera Arteria,is a cylindrical canal of four 

 or five inches in length and about nine lines in diameter, com- 

 municating with the lungs for the transmission of air. It opens 

 into the larynx above, by being attached to the inferior mar- 

 gin of the cricoid cartilage, and terminates in the thorax oppo- 

 site the third dorsal vertebra, by two ramifications called Bron- 

 chia. In this course it is situated over the middle line of the 

 neck, beneath the sterno-thyroid muscles, and separated from 

 them by the deep-seated fascia of the neck and the adipose mat- 

 ter beneath it. It is placed in front of the oesophagus, between 

 the primitive carotid arteries and the internal jugular veins. 

 When it has got into the thorax, it inclines slightly to the right 

 side as it passes behind the curvature of the aorta. Of its two 

 branches, the right bronchus is larger than the other; it is also 

 less slanting, and an inch long before it divides; it sinks below 

 the right pulmonary artery, to penetrate the lung about the 

 fourth dorsal vertebra. The left bronchus being an inch longer 

 sinks into the lung of the left side, below the corresponding 



