XX11 INTRODUCTION. 



fitting influence of heat and moisture that it may become a 

 living plant similar to the parent. But seeds which had been 

 buried deep in the earth for a period beyond computation, 

 have been found to vegetate and grow when exposed again 

 to the influence of air, heat, and moisture. Earth turned up 

 from the bottom of wells and mines, has been found to give 

 birth to plants whose seeds had been mixed with it, and 

 which may have remained for many thousand ages beneath 

 the surface of the ground. 



Death, as well as life, is a law of Nature, and life with all 

 its powers is but the gift of a season. The organised fabric, 

 so marvellously formed, contains within itself the germs of 

 decay. The circulating fluids become more thick, the textures 

 more rigid, and the vital organs less fitted to perform their 

 functions. The balance is lost between the waste of the 

 system and the means of supplying its parts with nutriment ; 

 and thus, independently of all external injury, the time ar- 

 rives when the mechanism of the body can no longer work 

 with the vigour required to maintain the animal functions. 



And when life at length ceases to animate the organised 

 fabric, the change that ensues in the body marks the cessa- 

 tion of all those powers which had enabled it to resist the 

 chemical effects of the agents with which it had been sur- 

 rounded from the period of its existence. Some of its parts 

 are exceedingly hard and durable, as the bones ; but they 

 are no otherwise distinguished, in their subjection to che- 

 mical agencies, from the flesh and softer parts which are 

 subject to so rapid a change. The heat which pervaded the 

 animal frame, and which may be believed to have arisen from 

 within by the exercise of the vital actions, is gone, the muscles 

 have lost their power, and all the gifts of thought and con- 

 sciousness have been seemingly taken away. 



The living kingdom, we see, comprehends two great divi- 

 sions, the vegetable and the animal ; and each of these king- 

 doms is divided into innumerable species and tribes of crea- 

 tures, distinguished by their form, powers, functions, and 



