36 GLANDS IN HEALTH AND DISEASE 



what we mean by the word "metabolism." Food 

 is taken into the system, and with the help of 

 enzymes or ferments and the oxygen of the air, 

 undergoes chemical changes in the body, yielding 

 carbon dioxide, moisture, and various nitrogenous 

 products that are eliminated principally through 

 the kidneys. The processes involved are digestion, 

 assimilation and excretion. Under the heading 

 of metabolism we may include all those changes 

 that occur in foodstuffs from the time they are 

 absorbed to the time they are excreted. Huxley 

 used the word "metabolism" to "denote the sum 

 total of those chemical changes which take place 

 in living matter, and in virtue of which we speak 

 of it as living" (metabolism comes from the Greek 

 meaning "change.") 



Lavoisier. Lavoisier, a Frenchman, more than 

 a hundred years ago showed that valuable infor- 

 mation as to the metabolic changes that go on in 

 the body can be obtained in one of three ways: 

 by estimating the amount of oxygen consumed, or 

 of carbon dioxide eliminated, or of heat evolved. 

 With regard to the heat evolved, it must be remem- 

 bered that the reactions of the body, like all chemi- 

 cal reactions, are accompanied by temperature 

 changes usually by an increase of temperature, 

 as in the case of the body. 



Since Lavoisier's time, chemists and physiologists 



