SECTION X 



THE EESPIPvATORY SYSTEM 



Revised for the Fifth Edition 

 By R. J. TERRY, A.B., M.D., 



PROFESSOR OF ANATOMY IN WASHINGTON UNIVERSITT 



R 



ESPIRATION consists in the absorption by the organism of oxygen and 

 the discharge of a waste-product, carbon dioxide. 



Among unicellular animals the oxygen is taken up directly from the medium — water or air — 

 in which they hve, and the carbon dioxide given off into it. With the cells which make up the 

 body of higher animals the principle is the same, but the interchange of gases is indirect. The 

 blood stands as an intermediate element between the cells of the body and the medium inhabited 



Fig. 960. — Dissection of a Male Negro, Age 43 Years, to Show the Organs of Res- 

 piration IN Situ. 



Frontal sinus 

 Nasal cavityi 



{ 



— Thyreoid gland 



Vagus nerve 



Mediastinal. 



pleura 



by the animals, and serves as a carrier of the gases between them. Moreover, special organs 

 are provided for the rapid interchange between air and blood, which constitute the so-called 

 respiratory system. 



The respiratory system of air-breathing vertebrates consists of tubular and 

 cavernous organs constructed so as to permit of the atmospheric air reaching the 



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