Pref 



ace 



Both living and non-living things are composed of strikingly similar sub- 

 stances. The living ones are not only composed of like substances but all 

 living matter is put together in the same unique way. Kinships based on 

 these similarities form the central theme of this book. The author's experience 

 has indicated that the study of these relationships makes zoology more vital 

 and interesting to the student. 



The first chapter, "Relationships of the Living World," presents the gen- 

 eral plan of the text and is its introduction. Part I, "The Foundation," tells 

 of matter and energy as they occur in plants and animals, and familiar 

 natural processes. It includes a discussion of atoms and molecules and 

 references to the newer knowledge concerning them. This leads logically to 

 the cell, as a sample of the complete organization of living matter and the 

 focus of a great wave of contemporary investigation. 



Relationships are persistently evident in our world and universe. Many 

 of them are suggested in the Kinships of Animals and Man, and they are 

 emphasized in the special discussions of Part II, "Ecology." Among these 

 relationships are the competitions and unconscious cooperations of animals, 

 the associations of animals in communities, and photosynthesis, the most im- 

 portant food-making process in the world. 



Protoplasm must have water wherever it is. The inside of the animal body 

 is wet. Structures and functions of tissues and organs are affected by the 

 fact of their dependence upon fluid. In Part III, "The Internal Environment 

 of the Body," the main systems of the animal body, invertebrate and vertebrate 

 are studied with respect to their basic similarities. It is well known that modern 

 medicine is the internal ecology of the human body. 



Traces of history remain in animals and parts of animals showing the 

 broken story of their evolution. "The Evolution of Animals" is a series of 

 chapters which recount the great contribution of one or another group. Above 

 all, evolution appears as a story of the continuity of life. 



