PRINCIPLES OF ZOOLOGY: 



TOUCHING 



THE STRUCTURE, DEVELOPMENT, DISTRIBUTION, 

 AND NATURAL ARRANGEMENT 



OF THE 



RACES OF ANIMALS, LIVING AND EXTINCT 



WITH NUMEROUS ILLUSTRATIONS. 

 PART I. 



COMPARATIVE PHYSIOLOGY. 



FOR THE USE OF SCHOOLS AND COLLEGES. 



BY 



LOUIS AGASSIZ AND A. A. GOULD. 



REVISED EDITION. 



BOSTON: 

 GOULD AND LINCOLN, 



59 WASHINGTON STREET. 



1851. 



