HUMAN PHYSIOLOGY 



A Text-Book for High Schools and Colleges 



BY 

 PERCY GOLDTHWAIT STILES 



ASSISTANT PROFESSOR OF PHYSIOLOGY IN HARVARD UNIVER- 

 SITY; INSTRUCTOR IN PHYSIOLOGY AND PERSONAL HYGIENE 

 IN THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY ; 

 FORMERLY ASSISTANT PROFESSOR OF PHYSIOLOGY IN 

 SIMMONS COLLEGE, BOSTON 



ILLUSTRATED 



PHILADELPHIA AND LONDON 



W. B. SAUNDERS COMPANY 

 1916 



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