CHAPTER VI 



MATTER AND ENERGY IN THE LIVING 

 BODY 



30. Matter and chemical processes. As has 

 already been pointed out, the phenomena of 

 life depend on chemical changes occurring in 

 the body. These changes are largely oxida- 

 tions, that is the union of oxygen with cer- 

 tain constituents of the body, and decomposi- 

 tions, that is the splitting up of more complex 

 chemical substances into simpler ones. There 

 are also, to some extent, reductions, that is, 

 the taking of oxygen from chemical constitu- 

 ents ; and there are syntheses, the reverse of 

 decompositions, or the building up of com- 

 plex substances from simpler ones. 



81. We are still ignorant of the exact 

 nature of many of the chemical processes 

 occurring in living tissue, but they may be 

 shortly noticed. 



B 65 



