22 THE LIVING WORLD. 



ical laboratory in any exact sense. vAll that our 

 chemists can succeed in showing is that organic 

 changes are governed by the same chemical laws as 

 those which regulate inorganic changes. And the 

 possibility of the manufacture by synthetical pro- 

 cesses of a number of the simpler organic compounds 

 gives us undeniable evidence that chemical laws are 

 the same in the body and in the laboratory. 



Properties of Life as Explained by Physical and 

 Chemical Laws. 



Recognizing, then, that all the energy of organ- 

 isms is derived from solar energy, and that the 

 chemical processes in the body are essentially sim- 

 ilar to those outside, the next question to be 

 answered is how far the vital manifestations of 

 organisms can be explained according to these laws ; 

 to see whether or not all of the activities of living 

 things can be explained by physical laws. And 

 here too when we reach the real opinion of various 

 thinkers, we find something like unanimity in many 

 points at least. Understanding the doctrine of the 

 conservation of energy, it is at once evident that all 

 of the energy displayed by organisms must be 

 transformed solar energy ; and hence all of the mani- 

 festations of the body which are measurable by 

 units used in measuring other physical forces must 

 come under this head. Here will of course be in- 

 cluded all the forms of motion, both molar and 

 ^molecular. The motions of the body, the heat of 

 the body, expansion and contraction of protoplasm, 

 all electrical phenomena, probably also nervous im- 



