156 life's beginning on the earth 



realized. What information can we possibly hope to ob- 

 tain from a determination of the energy output of the 

 muscle — or of any machine? Suppose we determine with 

 the utmost accuracy the mileage per gallon for a motor car: 

 could we ever hope to learn the mode of functioning of the 

 motor in this way? Obviously not. There is as little 

 hope of knowing the functioning of a muscle by determining- 

 its energy output. 



But even the examination of the motor will not enable 

 anybody to understand how it works. We know of course 

 that the successive explosions of the gasoline vapors furnish 

 the driving force. Suppose, however, that an automobile 

 motor fell into the hands of a savage who does not know 

 that gasoline is needed to run the motor, and who is igno- 

 rant of the importance of explosions of gasoline vapors. 

 What could such a savage learn about the working of the 

 motor, by taking it apart, by noting all of its parts and their 

 mutual relation? Even if he did this with considerable 

 skill, it would not enable him to grasp its purpose and 

 working. 



The fact is that we are just as ignorant of a muscle as 

 that savage is of the automobile motor. We can take a 

 muscle apart and observe all the structures of which it is 

 composed, as numerous scientists have done with the utmost 

 care for more than a century. With the greatest ingenuity 

 they have worked out methods to render visible all details 

 of a muscle under the microscope. But all the knowledge 

 thus accumulated does not furnish us with any clue as to 

 the working mechanism of the muscle-machine. We shall 

 never arrive at a profound knowledge 1 of a machine if we 

 limit our studies to a description of the component parts. 

 We must be able to make that machine with our hands. In 

 addition we should make a variety both of simple and of 

 complex machines of the type in question. In the case of 

 the gasoline motor, the simplest type would be ;i plain box 



