"S36 AIM AND PROGRESS OF PHYSICAL SCIENCE. 



organic matter which brought about decomposition. In short, 

 through all the different modes of expressing it, whether it was 

 termed the Arch'aus, the anima inscia, or the vital force and 

 the restorative power of nature, the faculty to build up the 

 body according to system, and to suitably accommodate it to 

 external circumstances, remained the most essential attribute 

 of this hypothetically controlling principle of the vitalistic 

 theory with which, therefore, by reason of its attributes, only 

 the name of soul fully harmonised. 



It is apparent, however, that this notion runs directly counter 

 to the law of the conservation of force. If vital force were 

 for a time to annul the gravity of a weight, it could be raised 

 without labour to any desired height, and subsequently, if the 

 action of gravity were again restored, could perform work of any 

 desired magnitude. And thus work could be obtained out of 

 nothing without expense. If vital force could for a time suspend 

 the chemical affinity of carbon for oxygen, carbonic acid could 

 be decomposed without work being employed for that purpose, 

 and the liberated carbon and oxygen could perform new 

 work. 



In reality, however, no trace of such an action is to be met 

 with as that of the living organism being able to generate an 

 amount of work without an equivalent expenditure. When we 

 consider the work done by animals, we find the operation com- 

 parable in every respect with that of the steam-engine. Animals, 

 like machines, can only move and accomplish work by being 

 continuously supplied with fuel (that is to say, food) and air 

 containing oxygen ; both give off again this material in a burnt 

 state, and at the same time produce heat and work. All investi- 

 gation, thus far, respecting the amount of heat which an animal 

 produces when at rest is in no way at variance with the assump- 

 tion that this heat exactly corresponds to the equivalent, ex- 

 pressed as work, of the forces of chemical affinity then in 

 action. 



As regards the work done by plants, a source of power, in 

 every way sufficient, exists in the solar rays which they require 

 for the increase of the organic matter of their structures. 



