FOOD 355 



alimentary canal. This lightness may be secured by the mere 

 expansion of steam in the dough, but it is usually caused by use of 

 yeast or baking powder, which produce carbon dioxide within the 

 batter. The gluten (proteid), always present in flour, is sticky 

 enough to retain the gas, which expands with the heat of cooking, 

 filling the loaf with countless bubbles and making it porous. Finally 

 the heat stiffens the gluten and starch and drives out much of the 

 enclosed gas and we have the " light," porous, and digestible bread 

 or pastry, instead .of an indigestible paste of uncooked flour and 

 water. 



" Special Foods." There are no foods for special organs. Fish 

 is not a " brain food," nor celery a " nerve food," nor meat a 

 " muscle food." The savage eats the heart of his fallen foe to ab- 

 sorb his courage, but we ought to be beyond that stage. If we use 

 a properly balanced diet our cells will select what they need in 

 proportion as we use them. The only way to increase the brain 

 power is to use the brain, not by eating foods rich in phosphorus 

 because the brain tissue contains this element. 



If eating strong muscle made us strong, we ought to have a diet 

 of the toughest meat possible. However the only way to persuade 

 nature to give us more strength, is by using what we have and 

 furnishing her a proper food supply to select from. 



To be sure, if phosphorous compounds are lacking, the nerves 

 will suffer; if proteid be absent, our muscle tissue might feel the 

 lack, but in a balanced diet this is never the case. An excess of any 

 element, above what is normally used in the body, does not develop 

 any special part, but is merely wasted. Extra proteid is not needed 

 for extra work; it is the fuel food that supplies the energy, the 

 proteid requirement being almost constant for all grown persons 

 and only slightly varying for younger people. 



Lipoid. A shortage of fat in the diet, not only reduces the energy 

 produced, but has long been associated with a lowering of nervous 

 activity. This is now explained by the discovery of a substance 

 called lipoid, in the cell walls of the body, especially in the outer 

 layer of the nerve fibers and brain cells. 



Lipoid resembles fat in many ways, but contains nitrogen and 



