CHAPTEE X. 



RESPIRATION. 



General considerations Physiological anatomy of the respiratory organs Respi- 

 ratory movements of the larynx Epiglottis Trachea and bronchial tubes 

 Parenchyma of the lungs Carbonaceous matter in the lungs Movements of 

 respiration Inspiration Muscles of inspiration Action of the diaphragm 

 Action of the scaleni Intercostal muscles Levatores costarurn Auxiliary 

 muscles of inspiration. 



THE characters of the blood are by no means identical in 

 the great divisions of the vascular system ; but thus far, phys- 

 iologists have been able to investigate only the differences 

 which exist between arterial and venous blood ; for the capil- 

 laries are so short, communicating directly with the arteries 

 on the one side and the veins on the other, that it has been 

 impossible to obtain - a specimen of blood which can be said 

 to belong to this system. In the capillaries, however, the 

 nutritive fluid, which is identical in all parts of the arterial 

 system, undergoes a remarkable change, rendering it unfit 

 for nutrition. It is then known as venous blood; and, 

 as we have seen, the only office of the veins is to carry it 

 back to the right side of the heart, to be sent to the lungs, 

 where it loses the vitiating materials it has collected in the 

 tissues, takes in a fresh supply of the vivifying oxygen, and 

 goes to the left or systemic heart, again prepared for nutri- 

 tion. As the processes of nutrition vary in different parts of 

 the organism, necessarily, there are corresponding variations 

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