THE CHEMICAL ELEMENTS 23 



27. Ash elements in animal. The proportions of the 

 ash elements are shown from analyses made of the fat 

 ox by Lawes and Gilbert. For comparison, the propor- 

 tions of ash elements in the human body are given: 



TABLE IV 



It appears that in the ash, other than oxygen, phos- 

 phorus and calcium take a leading place as to quantity, 

 although other elements, such as sulfur, potassium, and 

 sodium are essential to animal growth, even if present in 

 relatively small amounts. 



28. Classes of matter. A common and familiar 

 phenomenon is the destruction of vegetable or animal 

 matter by combustion, with the result that only a small 

 portion of the original material is left behind in visible 

 and solid forms. Fuel, such as wood or coal, is largely 

 consumed when ignited, and we have as a residue the 

 ash. If we incinerate hay, corn, or wheat we get a 

 similar result. The gradual decomposition of exposed 

 dead vegetable matter that occurs in warm weather is a 

 process essentially similar to the combustion of fuel, only 

 more prolonged. In view of these facts, it is customary 

 to classify all the tissues of plants and animals into the 

 combustible and incombustible portions, the former being 



