151 



them, by which they originally unite, to form the identical living 

 principle; this affinity afterwards preserves their union. In the 

 material which is subjected to the agency of life are the uncoin- 

 bined elements of life, otherwise said to be latent: there are also 

 the elements of heat which are latent. Now the affinity of life with 

 the materials is with its resemblance or its constituents ; heat is in- 

 cluded in this affinity, and is assimilated as a part of an identity, 

 the force of which is to produce itself, by an operation upon a 

 material which contains its elements. On this point I have scarcely 

 asserted more than the order of occurrence, which is almost sub- 

 jected to our observation. 



14. There is a close resemblance between the manner in which 

 life and the highest degrees of heat are maintained: in both the 

 process is one of assimilation, ind consists respectively in the union 

 of its elements. Ignition does not take place from the contact or 

 mutual exposure of that which contains the elements of fire. Thus, 

 wood or coals existing in oxygen would never inflame; but fire 

 assimilates itself from both, and, like life, is perpetuated by the 

 union of its elements, before separately existing, or otherwise 

 combined. 



15. Fire has another agreement with life, namely, that in each 

 the elements are combined from the two sources of earth and air. 



16. But with respect to the generation of animal heat there is 

 a difference between this process and the ordinary one of its ignition. 

 In general, the elements are assimilated only by that which is 

 actually ignited: a heated substance of 98 degrees is not capable of 

 assimilation. But this animal process can scarcely be expected to 

 be of the common kind, when it can take place only by so peculiar 

 an associate as that of a vital principle. 



17. That elements of this heat are contained in the blood can- 

 not be doubted, because we find that the blood is inflammable, and 

 also, that by the blood the animal heat is supported; not by blood 

 itself simply, nor by the other properties of life as related with 

 blood, nor by heat, as related either simply with blood, or the other 

 properties of life, but by a relation which involves them all. 



18. To say precisely the share which each of these has, or to 

 trace the mode which the relation observes, more minutely, would 

 be at least difficult, or perhaps, without a progressive refinement 

 upon these views, impossible. So much however has been said as 

 appears to be sanctioned by facts. 



19. As animal heat cannot be produced by the other spiritual 

 properties, heat being absent, so heat precedes and governs its own 

 production, and is not, as has been supposed by the chymists, a mere 

 effect of other agents, a product altogether independent of itself.* 



* Spontaneous ignition sometimes occurs: this is a point of analogy with 

 the origin of life by constitution; as the ordinary instances of ignition are 

 analogous with the perpetHation of life by derivation. In the animalization 

 of crnstaceous ova, the origin of life by constitution, or its creation, is partially 

 repeated. 



