THE DIGESTIVE APPARATUS AND NUTRITION 243 



more food than one engaged in sedentary occupations. 

 Brain workers, however, need a varied and generous diet, 

 and along with it gre"at care should be taken to secure 

 sufficient outdoor exercise. More food is called for in 

 winter than in summer, and more of the carbohydrates to 

 supply the demand for additional heat. Those who work 

 vigorously in the open air, and especially in cold climates, 

 often consume prodigious quantities of fats without injury 

 to digestion. With the coming of old age the vital proc- 

 esses in general are carried on more slowly ; digestion and 

 especially the power of assimilation are enfeebled. Less 

 energy is called for as the activities are lessened, and less 

 food is then required, with longer intervals between 

 meals. Foods rich in proteids are less needful and should 

 be diminished in quantity, while those which yield a large 

 amount of heat should be substituted. 



355. What is Alcohol? All organic bodies are subject 

 to decay ; the complex compounds of which they are 

 composed are broken up into simpler ones, and that 

 which was living, organized matter becomes lifeless and 

 inorganic. This destruction of organic tissue is due 

 under ordinary circumstances to the process called fer- 

 mentation in some one or more forms. This is the growth 

 and rapid multiplication of minute organisms, of which 

 yeast is the most familiar example. When the decom- 

 position of organic matter takes place under certain con- 

 ditions and reaches a certain stage, it is called putrefaction. 

 This is always attended by the multiplication of the low 

 forms of life known as bacteria, and by the production of 

 poisonous and ill-smelling gases. Another form of fer- 

 mentation is that which occurs in the juices of fruits, 

 grains, and vegetables which contain sugar; and is called 

 vinous fermentation. In this form of decomposition the 



