CHAPTER 2 

 NATURAL HISTORY OF VERTEBRATE ANIMALS 



Everyone knows something concerning the human body and the 

 bodies of related animals. The more complete this knowledge, the 

 easier is the approach to many phases of zoological science. Because 

 the great majority of students thus possess some knowledge of 

 their own bodies, we shall examine first the structure and activities 

 of an animal that is like ourselves. The frog has the advantage of 

 being familiar in its natural surroundings, interesting in itself, 

 large enough to handle, and man-like to a degree that can be 

 appreciated only upon careful examination. It is sufficiently 

 complex to illustrate the most important features of higher animals, 

 and its structures and functions are relatively well known to science. 

 By studying the frog it is possible to review and extend one's 

 present knowledge and to discover certain biological principles 

 which will be elaborated in subsequent chapters. 



The term Natural History has no precise definition at the present 

 time. It was formerly used to designate the study of natural 

 objects, not only animals and plants but also non-U ving things 

 hke minerals. During the eighteenth and early nineteenth cen- 

 turies, many naturalists were primarily concerned with the col- 

 lection and classification of animals, although their studies afield 

 brought knowledge regarding habits and distribution. In recent 

 years the science of Ecology has taken over and refined some of the 

 diffuse subject matter of natural history; but the word Ecology, 

 which may be defined as the relation of organisms to their environ- 

 ment, conveys too restricted a meaning to serve as a title for 

 the present chapter, in which an attempt is made to review the 

 principal types of backboned animals, or Vertehrata, and to indi- 

 cate some of the more general features of their organization, behav- 

 ior, and general relationships. While this may seem an impos- 

 sible task within so brief a compass, we shall, nevertheless, be able 

 to consider certain facts of general biological interest by way of 



9 



