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Section IV. 

 RESPIRATORY SYSTEM. 



THE RESPIRATORY SYSTEM COMPRISES THE LARYNX, 

 THE TRACHEA, AND THE LUNGS. 



OF THE LARYNX. 



THE larynx is the organ producing the voice of the animal. 



Situation. — It is joined to the top of the trachea (or windpipe), 

 and is placed in the throat, between the posterior and broadest 

 parts of the branches of the lower jaw ; having the pharynx and 

 uppermost part of the esophagus situated above it; the superior 

 portions of the sterno-hyoidei and thyroidei below it ; the tongue 

 with its muscles, and theos hyoides, in front of it ; and the trachea 

 issuing from below and behind it. 



Attachment. — The larynx is retained in its place by its con- 

 nexion with the OS hyoides and pharynx ; by its muscles ; and by 

 its coalition with the trachea. 



Coiiformution. — The larynx has so complete a fleshy covering, 

 that it is not imtil it is divested of its muscles (which have been 

 heretofore described) that it is discovered to be composed of five 

 pieces of cartilage, so joined together as to be moveable on one an- 

 other, and open both superiorly and inferiorly to admit of the pas- 

 sage of air into and out of the trachea. These cartilages have 

 received the names of thyroid, cricoid (two) arytenoid, and epi- 

 glottis. 



THE THYROID or shield-like cartilage, by much the largest 

 of the five, forms the superior, anterior, and lateral parts of the 

 larynx. It consists of two broad lateral portions, continuous and 

 proniinent at the upper and anterior part of the neck, the promi- 

 nence corresponding to which in human anatomy has received the 

 name of pomuni Aclatni. Below this point of union the divisions 

 recede from each other, leaving a triangular space between them, 

 which is occupied by a ligament denominated the ligamentnnt 

 crico-thyroideiim. The four projecting corners from the posterior 

 parts of the thyroid cartilage are named lis cornua : the two supe- 

 rior are joined by capsular articulations to the body of the os hy- 

 oides ; the two inferior are connected by very short capsular liga- 

 ments to the cricoid cartilages ; the union of all which parts re- 

 ceives additional strength from expansions of membrane. At the 

 roots of the superior cornua arc two foramina that give )>assage 

 to nerves, of considerable importance, to the interior of the larynx. 



