Bakewell, — Is Life a Distinct Force ? 415 



see. The process by winch a seed becomes a tree, producing other seeds 

 like that from which it sprang, is clearly not the result of any one single 

 force, unless we assume that that force was created and designed ad hoc ; 

 neither heat, nor motion, nor light, nor electricity, nor chemical affinity, 

 could alone cause the growth of a tree from a seed. Expose a seed to an 

 amount of heat which will kill it without changing its chemical composition, 

 and all the forces of nature will not enable that seed to germinate. What 

 then do we kill ? Even suppose that a living seed, exposed to the influence 

 of heat and moisture, will swell by the mechanical process of endosmosis, 

 suppose even we allow that the ovule will germinate, what possible com- 

 bination of these or any other forces could make the radicle invariably push 

 its way downwards into the soil, and the plumule as invariably thrust itself 

 upwards towards the light ? "What combination of forces acting mechanic- 

 ally and without intelligence could enable the cells of the young part to 

 differentiate themselves and form the various tissues of which the plant is 

 composed. Forces such as light and heat must always act under similar 

 circumstances in the same way, unless guided and directed by a Supreme 

 Intelligence. We are therefore driven, as it seems to me, to the conclusion 

 that the force or energy which produces the phenomena that we collectively 

 designate life, must be a force or energy of a special kind, created, if I may 

 be allowed such an old-fashioned expression, ad hoc. In other words, that 

 there is a vital force, which, acting on protoplasm, enables it to move to 

 nourish itself, and to reproduce its like. 



I need say nothing about the other two qualities which enter into the 

 definition of living matter — self- nutrition and reproduction — as it is nowhere 

 disputed that these powers belong exclusively to living matter. 



Though, as I think, I have proved the vital force is a distinct and 

 special force, it has so much relation to the other forces of nature as to be 

 convertible into them. Thus in warm-blooded animals it is convertible into 

 heat. That their animal heat is not the mere product of the chemical 

 actions going on in their bodies is proved by the fact that precisely the same 

 actions are going on in cold-blooded animals which do not maintain them- 

 selves at a heat above that of the surrounding media. The muscular move- 

 ments of a lizard, for instance, in the tropics are extremely active, far more 

 so than those of most of the warm-blooded vertebrates — yet the lizard is 

 much cooler than the surrounding atmosphere. We see another proof that 

 the vital force of warm-blooded vertebrates is converted into heat, in the 

 extreme difficulty of maintaining the animal heat of those who are weakly. 

 Among human beings we who are practical physicians have constantly to 

 recognize this fact. The same external temperature which is pleasant and 

 even inspiriting to persons in vigorous health is depressing and injurious, 

 and indeed often fatal, to those who are weak, 



