14 INTRODUCTION. 



genera of the same order nearer than those of the other orders, &c. 

 &c. This method is the ideal to which Natural History should tend; 

 for it is evident that if we can reach it, we shall have the exact and 

 complete expression of all nature. In fact, each being is determined 

 by its resemblance to others, and difference from them; and all these 

 relations would be fully given by the arrangement in question. In 

 a word, the natural method would be the whole science, and every 

 step towards it tends to advance the science to perfection. 



Life being the most important of all the properties^ 1 beings, and 

 the highest of all characters, it is not surprising that it has in all ages 

 been made the most general principle of distinction; and that natu- 

 ral beings have always been separated into two immense divisions, 

 the living and the inanimate. 



Of Living Beings, and Organization in general. 



If, in order to obtain a correct idea of the essence of life, we 

 consider it in those beings in which its effects are the most simple, 

 we quickly perceive that it consists in the faculty possessed by cer- 

 tain corporeal combinations, of continuing for a time and under a 

 determinate form, by constantly attracting into their composition a 

 part of surrounding substances, and rendering to the elements, por- 

 tions of their own. 



Life then is a vortex, more or less rapid, more or less complicated, 

 the direction of which is invariable, and which always carries along 

 molecules of similar kinds, but into which individual molecules are 

 continually entering, and from which they are continually departing; 

 so that the form of a living body is more essential to it than its 

 matter. 



As long as this motion subsists, the body in which it takes place is 

 living it lives. When it finally ceases, it dies. After death, the 

 elements which compose it, abandoned to the ordinary chemical 

 affinities, soon separate, from which, more or less quickly, results the 

 dissolution of the once living body. It was then by the vital motion 

 that its dissolution was arrested, and its elements were held in a tem- 

 porary union. 



All living bodies die after a certain period, whose extreme limit 

 is fixed for each species, and death appears to be a necessary conse- 

 quence of life, which, by its own action, insensibly alters the struc- 

 ture of the body, so as to render its continuance impossible. 



