NATURE OF LIFE AND LIVING MATERIAL 3 



relation to plant life. Many of the facts are not a part of public 

 information; hence a special terminology and vocabulary are neces- 

 sary and unavoidable. In the study of Biology one encounters con- 

 cepts that are among the most profound and abstruse which the 

 human mind attempts; consequently, the study challenges the best 

 effort of which the individual is capable. 



We generally recognize that the human body has many char- 

 acteristics that are common to all living things. To an inquiring 

 mind this raises the question of the extent of Man's relationship to 

 other animals and as to the nature of the phenomena which con- 

 stitute living. Since Man is only one of a wide variety of objects 

 that are alive, an understanding of the broad principles of life 

 processes wherever they may occur is necessary to a comprehension 

 of Man as a living being and of his position in relation to the world 

 about him. Human biology is therefore only one aspect of Animal 

 Biology. The task we have set for ourselves here is an examination 

 of the principles of vital phenomena in general and of the manner 

 in which these operate in the animal body, including the human 

 body. 



Life. Before proceeding farther, we must establish and agree on 

 a meaning of the term life. The word has been devised by Man 

 to distinguish the peculiarities of a particular sort of object in the 

 world about him. The word Life calls to mind certain attributes 

 of a class of bodies in the same fashion that the word Rock brings 

 to mind the characters that are common to a class of materials 

 with which we are all familiar. In order for an object to be recog- 

 nized as living it must possess in greater or less degree five features, 

 none of which is solely a property of living bodies. 



Irritability: We recognize this character as a part of our own 

 lives because of the five senses that make us aware of our sur- 

 roundings, smell, taste, touch, sight, and hearing. In other forms 

 of life we may recognize the same general property although they 

 may not be equipped with special sense organs. All living objects 



