CHAPTER IX 

 ENERGY TRANSFORMATIONS IN LIVING MATTER 



REGARDED from the physical standpoint, all the acts which con- 

 stitute our existence are due to transformations of energy in the 

 world outside us and in our own bodies. It is by the medium of 

 such energy transformations occurring in our sense organs that 

 we are made aware of the existence of the external world, and 

 kept informed of the changes going on in it, and it is by such 

 transformations going on in the various living cells which consti- 

 tute our bodies that energy is obtained for all those operations by 

 which the body is nourished and enabled to adapt itself to the rest 

 of the world around it. 



The same statement is true of all organised and living matter, 

 however high or low its degree of organisation may be. Whether 

 the living matter belong to the vegetable or animal division, to 

 micro-organism or man, it is alike a field for the display and recep- 

 tion of energy transformations, and its life manifests itself by the 

 taking in of energy in one or more forms and the giving of it up in 

 others. 



In dealing with the physical aspect of the phenomena of living 

 organisms, it may be well to discuss in some detail how closely such 

 phenomena are associated with those observable in the inorganic 

 world. 



In the first place, the bodies of living organisms are built up 

 from the same chemical elements as are found in inorganic struc- 

 tures. In the process of organisation the chemical constitution 

 becomes so complex, and the physical organisation of the complex 

 chemical molecules, whereby living matter is eventually formed, 

 so intricate, that the organic chemist and physical chemist have 

 hitherto not been able to follow the process, and hence we know 

 but little regarding the constitution and structure of living matter. 



Although the intermediate stages in the process cannot be 

 followed by any means at present known to us, we can learn some- 

 thing by watching the ends of the process, by noting the ingesta 



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