15 



smoke and flame, to which we are accustomed in our stoves; but it is 

 similar in character, though very different in degree. The heat of the body 

 in health rarely exceeds 99 Fahr., whereas that usual in a stove is many 

 times as much; even in an oven attached to a stove the temperature may 

 register 400 Fahr. or more. 



Are we not all familiar with the fact that 



ONE RESULT OF ACTIVE EXERCISE IS TO QUICKEN THIS PROCESS 



of combustion in the body? In cold weather we instinctively run, dance, or 

 otherwise take active exercise to " get warm " ; while in hot weather we 

 move about slowly and as little as we can in order " to keep cool." If the 

 body becomes disordered by disease, then combustion may increase too 

 rapidly; the patient "burns" with fever; and if the temperature rise and 

 remain too high he " burns out " that is, he dies. In an invalid, weakened 

 by long illness, the process of combustion proceeds too slowly; the tem- 

 perature is " below the normal," blankets and hot-water bottles are needed 

 to keep the body warm enough to live. 



SOMETIMES THE FURNACE IS CHOKED WITH IMPERFECTLY 

 CONSUMED FUEL.' 



The amount of fuel-food eaten has been in excess of the body's needs 

 or unsuited to its capacity for digestion. Measures are resorted to to clear 

 out the accumulation, by means of purgatives or otherwise, while food is 

 temporarily withheld. 



Evidently, then, there are many points of general resemblance between 

 the combustion with which we are familiar in engine or kitchen-stove and 

 that proceeding so marvellously within our bodies. 



The results of Lavoisier's observations led his followers to make many 

 further discoveries bearing on food as a source of energy to the body. The 

 fact was discovered that 



IF A PORTION OF DRY FOOD IS BURNED, IT WILL GIVE OUT A 

 DEFINITE, MEASURABLE AMOUNT OF HEAT. 



An ounce of lean meat, for instance, yields just so much heat, an ounce 

 of butter yields so much, an ounce of sugar so much ; consequently, their 

 relative worth as sources of heat to the body can be accurately measured ; 

 though that is not exactly the point I now want to make, which is this: 

 After a large number of experiments had been made and many years of 

 devoted labour had been expended, the further fact was proved that, when 

 digested, these foods supplied an amount of energy equal to the amount of 

 heat they produced when burned outside the body. The result of all 'this 

 scientific work is that the energy-\ r alue of anything we eat can now be as 

 accurately measured as the weight of flour, sugar, and raisins are measured 

 for a cake or pudding. It is true that 



THE HOUSEWIFE USES OUNCES AND POUNDS 



as her scale of measurement, whereas the student of food-values uses what 

 he calls "calories" ("calor" is the Latin word for heat) when he estimates 

 how much heat or its equivalent, energy is given up to the body by the 

 portion of meat, bread, jam, or fruit consumed at a meal. 



