Aids to Microscopic Inquiry. 163 



AIDS TO MICKOSCOPIC INQUIRY. 

 III. — Heat and Organization. 



Life, as we know it in connection with organization, wonld 

 be quite impossible without heat. If we start with the sim- 

 plest form of plant or animal, we find that its life consists in 

 an assemblage of actions, no one of which can be distinguished 

 from the effects of physical force. As we ascend in the scale 

 of being, the phenomena of sensation, consciousness, intelli- 

 gence, and volition come gradually into view. We do not see 

 them manifested, except in connection with organization, and 

 we can prove that physical changes take place whenever a 

 living creature experiences or performs a mental process of any 

 kind. How, and why, mental phenomena are associated with 

 the motions of physical particles we are profoundly ignorant, 

 and our minds are so constituted that we cannot possibly regard 

 any change in the position or arrangement of atoms or mole- 

 cules as resembling in kind the changes which take place in 

 our mental condition when sensations are felt, ideas are formed, 

 or desires evoked. But however distinct mental operations 

 may be from the physical movements of living beings, the 

 latter must be regarded from a strictly physical point of view. 

 If, for example, no man can think without a certain portion of 

 brain substance passing into anew state, we must look to phy- 

 sics and chemistry to elucidate the transition, and if we cannot 

 explain it by the laws pertaining to these sciences, we had bet- 

 ter honestly and frankly confess our ignorance rather than 

 try to mask it under such a term as vital force — a phrase by 

 which no precise meaning is conveyed. 



Now, if we separate from manifestations of life all those 

 phenomena which belong to metaphysics, the mass that re- 

 main may be regarded as under the special dominion of heat. 

 We do not say that they are only divers manifestations of heat, 

 for this would be obviously incorrect. All forces may prove to 

 be ultimately resolvable into one force ; but if science ever 

 reaches this point of development, it will still be convenient to 

 give separate names to the distinct manifestations in which the 

 ultimate force may be displayed. 



Heat may be best considered, with Tyndall, as " a mode of 

 motion," and temperature will be found to be an essential and 

 dominant condition of living organisms, determining what other 

 motions can take place. If we heat a bar of iron, we expand 

 it, and at the same time augment its affinity for oxygen, so that 

 if that gas be present, combination must ensue. When we 

 come to considerations specially drawn from chemistry, we 



VOL. VI. — NO. III. M 



