RESPIRATION IN THE MAMMALIA. 153 



The Birds rank above all the animal creation in vital 

 energy, as well as in muscular action. This appears to 

 be in consequence of the double effects of the respiration 

 on the circulating fluid, as it passes through the lungs. 



RESPIRATION IN THE MAMMALIA. 



But notwithstanding, we see in the birds, a wonder- 

 ful adaptation of the respiratory apparatus to the wants 

 and conveniences of that order, still we shall find, that 

 the construction of the pulmonary system of Man and 

 the other Mammalia, involve physiological advantages 

 not to be found in any other class of animals. 



The points in which this superiority exists will be 

 noticed in the progress of the description of the organs 

 of respiration in Man, to which we now proceed, and 

 which may be considered as the type of the same parts 

 in all the other Mammalia. 



Respiration in Man. In our own species, the thorax 

 or chest which contains the respiratory organs, as well 

 as all the other vital parts, is entirely surrounded by a 

 frame work of bone, so that these parts are defended 

 with great care from external injury. These bones 

 consist of the spine, the ribs, and the sternum, or breast 

 bone. 



Trunk of the Human Skeleton. ^The trunk of the 

 Human Skeleton is represented by Fig. 95, of which , 

 is the sternum, b b, the spine, and cccc, the ribs. These 

 bones, it is well known, are connected together in the 

 living system, by muscles and ligaments, and by which 

 they are moved in a slight degree in the act of respira- 

 tion. 



In what respect do the birds rank above all other animals 1- What is 

 said of the perfection of the pnlmonary system in man 1 What are the 

 parts of the human skeleton which enclose the organs of respiration ? 



