APPENDIX II. 



ON THE SOURCE OF MUSCULAR POWER. 

 A LECTUKE GIVEN AT THE EOYAL INSTITUTION, 



BY EDWARD FRANKLAND, Ph.D., F.R.S. 



Professor of Chemistry, R.I. 



Introduction. What is the source of muscular power ? 

 Twenty years ago, if this question had been asked, 

 there were but few philosophers who would have hesi- 

 tated to reply, " The source of muscular power is that 

 peculiar force which is developed by living animals, 

 and which we term the vital force /" But the progress 

 of scientific discovery has rendered the view implied 

 in such an answer so utterly untenable that, at the 

 present moment, no one possessing any knowledge 

 of physical science would venture to return such a 

 reply. We now know that an animal, however high 

 its organization may be, can no more generate an 

 amount of force capable of moving a grain of sand, 

 than a stone can fall upwards or a locomotive drive 

 a train without fuel. All that such an animal can 

 do is to liberate that store of force, or potential 

 energy, which is locked up in its food. It is the 



