252 



Food and its Digestion. 



of a long tramp, he must have something which would 

 "last him longer" than the meat of the deer, which Dr. 

 Beaumont found was digested in an hour and a half, 

 and surely no ocular demonstration is necessary to prove 

 to one who makes the essay, that pork and boiled cabbage 

 require a longer time and greater effort of digestion than 

 roast beef and potatoes — the experience of the sensations 

 is sufficient. 



Digestion is that process by which the food is reduced 

 to a form in which it can be absorbed from the intestinal 

 canal, absorbed by means of the lacteals and bloodvessels. 

 (The word comes from the Latin Digero gessi, gestum, to 

 force apart, separate). This is a process peculiar to the 

 animal kingdom — it does not occur in the vegetable king- 

 dom — vegetables being dependent for their nutrition upon 

 a supply of inorganic substances, such as water, saline 

 matters, carbonic acid, and ammonia. These materials 

 constitute the food on which plants subsist, being con- 

 verted in their interior into other substances by the nu- 

 tritive process. These materials are being continually 

 supplied to vegetables under such a form as can be readily 

 absorbed. 



Carbonic acid and ammonia exist in the atmosphere 

 under a gaseous form, and they are also found in solution 

 along with the requisite saline matters in the water with 

 which the soil is penetrated. All these substances are 

 therefore at once ready for absorption by the vegetable. 



of this vegetable, will range himself with the political economist in his 

 determined opposition to the use of it by any population as their principal 

 article of food, because he knows that the potato is wanting in some of the 

 most important saline constituents of the body, the phosphates, sulphates 

 and chlorides — e. g. a given weight of potatoes contains scarcely ^ of the 

 phosphate of magnesia present in the same quantity of wheat, and we may 

 calculate about 13 pounds of potatoes as the quantity which a man ought 

 daily to consume, in order to replace the waste of the body by a sufficient 

 supply of histogenetic constituents in his food. But the mixture of the 

 potato with other alimentary substances, especially with meat or milk, will 

 remove all these objections, and restore it to its proper rank in the scale 

 of diet. 



