ZOOLOGY. 



INTRODUCTION. 

 1. DEFINITION OF BIOLOGY AND ZOOLOGY. 



ALL natural objects may be roughly divided into three 

 groups constituting the so-called Mineral, Animal, and Vegeta- 

 ble kingdoms. The objects comprised in the mineral kingdom 

 are all devoid of life, and they exhibit the following characters : 

 a. Their chemical composition is simple. They consist of 

 either a single element, as is the case, for instance, with native 

 gold ; or, if combined, they are almost always in nature in the 

 form of simple compounds, composed of no more than two or 

 three elements as, for example, common salt, limestone, plas- 

 ter of Paris, and many others, b. Mineral bodies are, when 

 unmixed, composed of similar particles, which have no definite 

 relations to one another, or, in other words, they are homo- 

 geneous, c. The form of mineral bodies is either altogether 

 indefinite, when they are said to be " amorphous ; " or, if they 

 have a definite shape, they are crystalline, in which case they 

 are usually bounded by plane surfaces and straight lines, d. 

 When mineral bodies increase in size, as crystals may do, the 

 increase is produced simply by the addition of particles from 

 the outside (technically called '" accretion "). e. Mineral bodies 

 exhibit no phenomena which are not purely physical and chem- 

 ical, and they show no tendency to periodic changes of any 

 kind. 



All the bodies which exhibit these characteristics properly 

 belong to the mineral kingdom, and fall to be treated of by the 

 sciences of Geology, Mineralogy, Chemistry, and Physics. It 



