CHAPTER IV 



THE RESPIRATORY SYSTEM 



THE substances furnished to the circulation from the 

 alimentary canal are in a condition that, with reference to 



the atmosphere, will ad- 

 mit of free combination 

 with oxygen: this latter 

 agent is quite necessary 

 to prepare the tissues for 

 the functions of assimila- 

 tion and nutrition. Be- 

 sides this, the venous 

 blood is also charged with 

 carbonated products that, 

 when exposed to oxygen, 

 are eliminated and passed 

 off in the form of carbon 

 dioxid. To effect these 

 several purposes and thus 

 to maintain the motive 

 power of the system, 

 eliminating, at the same 

 time, deleterious sub- 

 stances, is the function of 

 the apparatus of respira- 



FlG. 69. Interior of the larynx : tion 

 i, Epiglottis ; 2, vocal cord ; 3, cavity 



of the trachea (after Testut). The repiratory organs 



consist of the larynx, 



trachea, and lungs. The larynx is composed of cartilages, 

 held together by ligaments, and contains the vocal cords. 

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