GENERAL PRINCIPLES OF ZOOLOGY. 



INTRODUCTION. 



Man's Relation to Other Animals. — The man who has learned 

 to observe nature in a disinterested manner sees himself in the 

 midst of a manifold variety of organisms, which in their structure, 

 and even more in their vital phenomena, disclose to him a simi- 

 larity to his own being. This similarity, with many of the 

 mammals, especially the anthropoid apes, has the sharpness of a 

 caricature. In the invertebrate animals it is softened; yet even 

 in the lowest organisms, for our knowledge of which we are 

 indebted to the microscope, it is still to be found : although here 

 the vital processes which have reached such an astonishing com- 

 plexity and perfection in ourselves can only be recognized in their 

 simplest outlines. Man is part of a great whole, the Animal 

 Kingdom, one form among the many thousand forms in which 

 animal organization has found expression. 



Purpose of Zoological Study. — If we would, therefore, fully 

 understand the structure of man, we mu.st, as it were, look at it 

 upon the background which is formed by the conditions of 

 organization of the other animals, and for this purpose we must 

 investigate these conditions. To such endeavors the scientific 

 knowledge of animal life, or Zoology, owes its origin and continued 

 advancement. But meanwhile the subject of zoology has widened ; 

 for, apart from its relations to man, zoology has to explain the 

 organization of animals and their relations to one another. This 

 is a rich field for scientific activity; its enormous range is a conse- 

 quence, on the one hand, of the well-nigh exhaustless variety of 

 animal organization, and, on the other hand, of the different 

 points of view from which the zoologist enters upon the solution 

 of his problem. 



