ZOOLOGY. 



INTRODUCTION. 



1. Definition of Biology and Zoology. 



All natural objects may be roughly divided into three groups con- 

 stituting the so-called Mineral, Animal, and Vegetable kingdoms. 

 The objects comprised in the mineral kingdom are all devoid of life, 

 and they exhibit the following characters : a. Their chemical com- 

 position is simple. They consist of either a single element, as is the 

 case, for instance, with native gold ; or, if combined, they almost 

 always occur in nature in the form of simple compounds, composed 

 of no more than two or three elements — as, for example, common 

 salt, limestone, plaster of Paris, and many others. 6. 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 crj'stals 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 chemical, 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 should be borne 

 in mind, however, that in the case of what are called " fossils " or 



