PART I. 



GENERAL EXTERNAL MORPHOLOGY. 



CHAPTER I. 



INTRODUCTORY. 



I. The things met with every day can be separated into two dis- 

 tinct classes or groups, namely, those which are alive, such as 

 birds, insects, cattle, trees, flowers, and grasses, and those which 

 are never possessed of life, such as air, water, glass, and iron. 



Although it is impossible to give a complete and satisfactory 

 account of what life is, for all practical purposes the difference 

 between the two classes of objects is easily recognised, and a 

 more extended study of them leads to the conclusion that between 

 the living and the inanimate world there is a hard and fast line 

 of separation. 



The chief and most obvious peculiarity of living things is their 

 power of giving rise to new individuals — that is, their power of 

 reproduction. They are ordinarily separated into two classes, 

 namely animals and plants. The term Biology in its widest 

 sense is used to denote the study of all forms of living things, 

 that branch of it dealing with animals being known as Zoology, 

 while the science of Botany is concerned with the study of plants. 

 The most familiar animals have the power of moving about in 

 a way which is not possessed by plants. Moreover, the former 

 require as food, substances which have been derived from other 

 living things, such as flesh of all kinds, milk, bread, potatoes, 

 and similar materials ; while most common plants are capable of 

 utilising substances which belong entirely to the inanimate world, 



