96 INTRODUCTION. 



pears to us they are subject: this law when it is general is call- 

 ed theory. Beyond this, we know nothing. But we admit 

 in general, that matter is inert, and every time we see it in 

 motion, we suppose a cause of motion that makes it act, and 

 which we call force. Thus, organic matter being in action 

 during the entire life of organic bodies, we say that life is 

 caused by a vital force.* 



This force has been considered as a different substance from 

 that of the organs, and of which these latter were the instru- 

 ments, at one time it has been considered rational, at another 

 the reverse. It has also been regarded as a faculty proper to 

 matter; either to organic solid matter, or to that which is fluid. 

 It has also been thought to be the result of organization, i. e. 

 of the assemblage of all the solid and liquid parts of an or- 

 ganized body, etc. 



It would, doubtless, have been better in a physical science, 

 like that of the organization of life, had we confined ourselves 

 to the observation of bodies and facts. 



100. The organic or vital phenomena, differing from each 

 other, the vital or organic forces that have been admitted, must 

 consequently be of several kinds. 



There are phenomena of organic formation, such as those of 

 nutrition, generation, the reparation of lesions, reproduction, 

 etc. A force or power of formation, has consequently been 

 admitted under the name of plastic force, formative force,t vi- 

 tal affinity, it is common to all organic bodies, and to all their 

 parts. 



101. The solids of organized bodies, and particularly of 

 animals, receive impressions from various agents, that are im- 

 mediately followed by movements more or less appreciable: 

 these are called movements of irritation, and the force or the 

 cause to which they are attributed, irritability.^ All animal 

 parts are more or less susceptible of it. We notice three prin- 

 cipal varieties of it. In the cellular tissue where it is weak, it 



* See Reil. Von der kbenskraft, in archiv- furv die physiologic. B. I. Halle, 

 1795. Chaussier. Table synoptique de la force vitale, etc. 



f See Blumenbach. Uber dm Bildnngstricb. Getting-. 



* See Gautier. de irritabilitatis notione, natura et morbis. Halx, 1793. 



