bergson's philosophy op the organism. 15 



animal is less economical than that of an organism need 

 be, for it has to adapt itself to varying physical con- 

 ditions and has, as far as possible, to maintain an 

 uniform type of metabolism. But even so it is more 

 economical than a heat-engine, and there can be no doubt 

 that the cold-blooded animal is still more economical. 

 The tendency in the organism is therefore for energy 

 transformations to take place without degradation. 



But in the green plant we see a process which seems 

 to be essentially different from that of the animal. In 

 this case the source of energy is solar radiation, and 

 substances of low chemical potential — water, carbon 

 dioxide and simple nitrogen compounds, such as nitrate 

 — are transformed into substances of high chemical 

 potential — carbohydrates, oils and proteids. This 

 process is difficult to compare with that of the animal. 

 It presents a likeness to a reversed Carnot cycle in that 

 energy passes from a state of low to one of high potential. 

 There is no transformation of chemical potential energy 

 into mechanical energy; or at least this is minimal, 

 being represented only by such movements in the plant 

 as the ascent of the sap in trees against gravity; the 

 movements of tendrils, etc., and the internal circulation 

 of protoplasm in the cells. There is little heat 

 production, except perhaps in a brief phase of the process 

 of germination of the seed — at any rate this loss of energy 

 is minimal. On the other hand, there is a continual 

 accumulation of energy in the form of the substance of 

 the plant. Now just how this transformation of carbon 

 dioxide and water into carbohydrate occurs, seems still to 

 elude the plant physiologist. We usually say that the 

 energy necessary is absorbed from the ether, that the 

 plant is in fact an ether-engine, a conclusion which ought 

 to lead on to the thermodynamical investigation of the 



