THE LIVING MACHINE BUILDING FACTORS. 183 



whether it is necessary to assume that there are 

 forces needed to explain life which are different 

 from those found in other realms of nature, or 

 whether vital forces are all correlated with physi- 

 cal forces. It has been evident at a glance that 

 the living body is a machine. Like other ma- 

 chines it consists of parts adjusted to each other 

 for the accomplishment of definite ends, and its 

 action depends upon the adjustment of its parts. 

 Like other machines, it neither creates nor de- 

 stroys energy, but simply converts the potential 

 energy of its foods into some form of active 

 energy, and, like other machines, its power ceases 

 when the machine is broken. 



With this understanding the problem clearly 

 resolved itself into two separate ones. The first 

 was to determine to what extent known physical 

 and chemical laws and forces are adequate to an 

 explanation of the various phenomena of life 

 The second was to determine whether there are 

 any known forces which can furnish a natural 

 explanation of the origin of the living machine. 

 Manifestly, if the first of these problems is insolv- 

 able, the second is insolvable also. 



In the study of the first problem we have 

 reached the general conclusion that the secondary 

 phenomena of life are readily explained by the 

 application of physical and chemical forces act- 

 ing in the living machine. These secondary phe- 

 nomena include such processes as the digestion 

 and absorption of food, circulation, respiration, 

 excretion, bodily motion, etc. Nervous phenom- 

 ena also doubtless come under this head, at least 

 so far as concerns nervous force. We have been 

 obliged, however, to exclude from this correlation 

 the mental phenomena. Mental phenomena can 

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