6 INTRODUCTION. 



been made the most general principle of distinction ; and that natural 

 beings have always been separated into two immense divisions, the 

 living and the inanimate. 



Of LIVING BEINGS, AND ORGANISATION 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 certain 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 portions 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 

 with it molecules of similar kinds, into which individual particles 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 is, is living it 

 lives. When it finally ceases, the body dies. After death, the elements 

 which compose it, the body being 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 consequence 

 of life, which, by its own action, insensibly alters the structure of the 

 body, so as to render its continuance impossible. 



In fact, the living body undergoes gradual, but continual changes, 

 during the whole term of its existence. At first, it increases in dimen- 

 sions, according to certain proportions, and within limits, fixed for each 

 species, and for each one of its parts ; it then augments in density in 

 the most of its parts: it is this second kind of change that appears 

 to be the cause of natural death. 



If we examine the various living bodies more closely, AVC find they 

 possess a common structure, which a little reflection soon convinces us 

 is essentially necessary to a vortex such as the vital motion. It 

 appears that solids are necessary to these bodies for the maintenance 

 of their forms ; and fluids for the preservation of motion in them. 

 Their tissue, accordingly, is composed of network and plates, or of 



