14 INTRODUCTION. 



different from each other, than an animal and a plant. 

 How different is the tree from the bird singing on its 

 branches, or the traveller resting beneath its shade. In 

 the one instance, the organism is immovably fixed to the 

 soil which gave it birth, and has neither the faculty of 

 moving itself, nor that of manifesting pleasure or pain. 

 The hatchet penetrates its tissues, and it falls without any 

 external signs of suffering. But in the other cases, the 

 organic beings are far more highly complicated. They are 

 endowed with the power of moving from place to place, have 

 a will and desires, senses to apprise them of the character 

 and qualities of external bodies, and introduce food into 

 their interior, where a special cavity is provided for its 

 elaboration before it is employed in the nutrition of their 

 organism. Plants have no such special receptacle in their 

 interior. They live, as it were, in the midst of their food. 

 It is furnished to them by nature in a condition fit for assi- 

 milation and circulation. They draw it at once from the 

 earth by their roots, and from the atmosphere by their 

 leaves. They therefore possess no special organs for its 

 preparation. It would seem impossible that there could 

 be anything in common between bodies so strikingly dis- 

 similar in their organization and habits. 



But if we consider the vital phenomena manifested by 

 animals and plants, we shall very soon see that there is 

 abundant reason for believing that the difference between 

 these organic productions of nature is not so great as we 

 at first thought. 



In the first place, both the animal and plant spring in- 

 variably from a being perfectly similar to themselves, to 

 which they adhere during a space of time more or less 

 long, and from which they are finally separated at a deter- 

 minate epoch, under the form of an egg or .a seed, which, 



