244 



RESPIRATION 



exchange, on the part of the blood, of carbon dioxide for oxygen. The 

 living tissues are the seat of those combustion processes which consume 

 oxygen and produce carbon dioxide. These processes occur in all parts of 

 the body in the substance of the living active tissues, and are the true respira- 

 tory processes, sometimes called internal or tissue respiration. 



THE RESPIRATORY APPARATUS. 



The object of the respiratory movements being the interchange of gases 

 in the lungs, it is necessary that the atmospheric air shall pass into them 

 and that the changed air shall be expelled from them. The lungs are con- 

 tained in the chest or thorax, which is a closed cavity having no communica- 



FIG. 218. Outline Showing the General Form of the Larynx, Trachea, and Bronchi, as seen 

 from Before, h, The great cornu of the hyoid bone; e, epiglottis; t, superior, and *', inferior cornu 

 of the thyroid cartilage; c, middle of the cricoid cartilage; tr, the trachea, showing sixteen cartilag- 

 inous rings; b, the right, and b', the left bronchus. X . (Allen Thomson.) 



