LESSONS 



ELEMENTARY PHYSIOLOGY 



LESSON I 



A GENERAL VIEW OF THE STRUCTURE AND 

 FUNCTIONS OF THE HUMAN BODY 



1. The Work of the Body as a whole.— The body of 

 a living man performs a great diversity of actions, some 

 of which are quite obvious ; others require more or less 

 careful observation ; and yet others can be detected only 

 by the employment of the most delicate appliances of 

 science. 



Thus, some part of the body of a living man is plainly 

 always in motion. Even in sleep, when the limbs, head, 

 and eyelids may be still, the incessant rise and fall of the 

 chest continue to renund us that we are viewing slumber 

 and not death. 



More careful observation, however, is needed to detect 

 the motion of the heart ; or the pulsation of the arteries ; 

 or the changes in the size of the pupil of the eye with 

 varying light ; or to ascertain that the air which is breathed 



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