b CHEMISTRY INDISPENSABLE 



crumbles into smaller and smaller fragments, and at 

 length forms earth. A potato when planted in the 

 ground grows soft, loses its previous mealy taste, be- 

 comes sweet, then rotten, and at last entirely dis- 

 appears. Yet this apparent annihilation is but a 

 chemical metamorphosis ; from the offensive products 

 of putrescence the creative energy of nature pro- 

 duces a fresh plant, endowed with new life, and all 

 the diversified substances peculiar thereto, viz. su- 

 gar, starch, oil, etc. 



The tuber of the potato-plant forms one of our 

 most important articles of food. The starch con- 

 tained in it is insoluble in water, but when received 

 into the stomach rapidly undergoes a change, by 

 virtue of which it can be dissolved or digested, and 

 then introduced as a liquid into the blood. In the 

 lungs the blood comes into contact with the inhaled 

 atmospheric air, is thereby changed in color and 

 also in its constitution, whilst the heat developed 

 during this alteration is the source of that warmth 

 which we feel in our whole body. Hence it is evi- 

 dent that in our own organism, as in that of plants, 

 chemical action is perpetually going on ; the plant, 

 the animal, and in no less degree man himself, are 

 composed of material upon which chemical forces 

 are ever acting. And it is through chemical pro- 

 cesses, not only that their nourishment is prepared, 

 but aided in its digestion and conversion into ani- 

 mal or vegetable substance. Finally, when life has 

 ended, chemical processes again assert their mastery. 



