1 860.] of the Vital to the Physical F&rces. 209 



the true view of the case, would appear from the circumstance that 

 recent experiments have shown that, to keep up a warm-blooded 

 animal to its full weight, a considerably larger amount of food is re- 

 quired than would suffice to supply the necessary waste of the body, as 

 determined by the loss of weight which it undergoes when food is 

 entirely withheld ; from which it seems quite clear that, in some mode 

 or other, the decomposition of a certain proportion of the food, i.e. 

 its descent from a higher to a lower form of chemical combination, is 

 necessary to the conversion of the rest into living organized tissue. 



The continual decay which is going on during the life of a Plant 

 (by the seasonal death of its leaves, as well as by the decomposition just 

 adverted to) restores to the inorganic world, in the form of carbonic 

 acid, water, and ammonia, a large part of the materials drawn from it 

 in the act of vegetation ; and, with the exception of those vegetable 

 products which are consumed as food by animals, or which are j)re- 

 served (like timber, flax, cotton, &c.) in a state of permanence, the 

 various forms of decomposition which take place after death complete 

 that restoration. But in returning, however slowly, to the condition of 

 water, carbonic acid, ammonia, &c., the constituents of plants give 

 forth an amount of heat equivalent to that which they would generate by 

 the process of ordinary combustion ; and thus they restore to the inor- 

 ganic world not only the materials but the forces, at the expense of 

 which the vegetable fabric was constructed. It is for the most part 

 only in the humblest plants, and in a particular phase of their lives, 

 that such a restoration takes place in the form of motion ; this motion 

 being, like growth and development, an expression of the vital activity 

 of the '' zoospores " of Algae, and being obviously intended for their 

 dispersion. 



Hence we seem justified in affirming that the correlation between 

 Heat and the Vital force of Plants is not less intimate than that which 

 exists between Heat and Motion. The special attribute of the vegeta- 

 ble germ is its power of effecting the metamorphosis, and of utilizing 

 the organizing force according to the plan of construction characteristic 

 of each species. 



It is a consideration of no little interest, that on this view the light, 

 heat, and mechanical power, which we now obtain from the combustion 

 of Coal, are really derived, through the vegetable life of the carboni- 

 ferous epoch, from the light and heat communicated to the Flora of 

 that epoch by the sun ; a fact which was discerned by the genius of 

 George Stephenson, before the general doctrine of the "correlation of 

 forces " had been given to the world by Mr. Grove. 



The results of the inquiry, therefore, so far as developed in this 

 discourse, (the forces specially concerned in producing the phenomena 

 of Animal life not having been included, for want of time) are in com- 

 plete harmony with the great doctrine of the conservation of force, 

 according to which it is no less true that nil Jit ad nihilumi than that 

 nil Jit ex nihilo. 



[W. B. C] 



