382 NOVUM ORGANUM. 



tion, take place solely in animate bodies ; inanimate bodies also share 

 in it, as has been said of flame and air. Moreover the dead spirit, 

 which is contained in every tangible animate substance, is perpetually 

 at work digesting the coarser parts, and changing them into spirit, to 

 be afterwards expelled ; whence arises the diminution of weight, and 

 the dessication, which we have mentioned elsewhere. Nor, in cov\- 

 sldering Assimilation, must we reject that accretion which is commonly 

 distinguished from alimentation, as when clay between stones hardens, 

 and is converted into stony matter ; when the scaly substance on the 

 teeth turns into a substance no less hard than are the teeth them 

 selves, &c. For we are of opinion that there exists in all bodies a 

 desire for Assimilation^ as well as for combining with homogeneous 

 substances ; but this virtue is restrained, as is the former, though not 

 by the same means. But these means, as well as the method of 

 escape from them, should be investigated with all diligence, because 

 they bear upon the rekindling of old age. Lastly, it seems worthy 

 of note, that, in the nine motions already spoken of, bodies seem 

 only to desire the preservation of their own Nature ; but in this tenth 

 the propagation of it. 



12. Let the twelfth Motion be that of Excitation; a motion which 

 seems to belong to the same genus as that of Assimilation, and which 

 we sometimes call indiscriminately by that name. For it is a motion 

 diffusive, communicative, transitive, and multiplicative, as is the other; 

 and agreeing with it, for the most part, in effect, but differing in the 

 mode of effect, and the subject-matter. The Motion of Assimilation 

 proceeds, as it were, with authority and power, for it commands and 

 compels the assimilated body to be turned into the assimilating. But 

 the Motion of Excitation proceeds, as it were, with art, by insinua 

 tion, and stealthily, and only invites and disposes the excited body 

 towards the Nature of the exciting. Moreover, the Motion of Assimi 

 lation multiplies and transforms bodies and substances ; thus more 

 flame is produced, more air, more spirit, more flesh. But in the 

 Motion of Excitation virtues only are multiplied and transferred ; 

 more heat being engendered, more magnetic action, more putrefac 

 tion. This motion is especially conspicuous in heat and cold. For 

 heat does not diffuse itself in heating a body by communication of 

 heat in the first instance, but only by exciting the parts of the body to 

 that motion which is the Form of Heat, about which we have spoken 

 in the First Vintage concerning the Nature of Heat. Therefore heat 

 is excited far more slowly, and with far greater difficulty, in stone or 

 metal, than in air, on account of the tinfitness and unreadiness of 

 those bodies for that motion ; so that it is probable that in the interior 

 of the earth there may exist materials which altogether reject heat, 

 because, through their greater condensation, they are destitute of that 

 spirit with which the Motion of Excitation generally begins. In like 

 manner the magnet endues iron with a new disposition of parts, and 

 a conformable motion, and loses nothing of its own virtue. In like 

 manner leaven, yeast, curd, and some poisons, excite and invite a 

 successive and continual motion in dough, beer, cheese, or the human 



