INTRODUCTION. xli 



principle, shewing itself by successive de- 

 velopements for a limited period, varying 

 according to the species, when it begins to 

 decline and finally is extinguished : that some- 

 times also, like heat, as in the seed of the 

 vegetable and egg of the animal, it is latent, 

 not manifesting itself by developement, till it 

 is submitted to the action of imponderable 

 fluids, conveyed by moisture or incubation. 



But to return to our author. " We have 

 seen," says he, " that the life which we remark 

 in certain bodies, in some sort resembled na- 

 ture, insomuch that it is not a being, but an 

 order of things animated by movements; which 

 has also its power, its faculties, and which 

 exercises them necessarily while it exists. 1 

 He also ascribes these vital movements to an 

 existing cause. Speaking of the imponder- 

 able incoercible fluids, and specifying heat, 

 electricity, the magnetic fluid, &c. to which 

 he is inclined to add light, he says, it is 

 certain that without them, or certain of them, 

 the phenomenon of life could not be produced 

 in any body. 2 Now, though heat, electricity, 

 &c. are necessary to put the principle of life 



1 Anim. sans Vertebr. i. 321. Ibid. i. 43. 



