AKIMALS AND THEIR PRODUCTS. Ill 



last three, the nitrogenous substances, furnish mate- 

 rial for muscles (lean meat), tendons (cords), and car- 

 tilage (gristle). Thus, these organic substances sup- 

 port respiration, and furnish material for all the soft 

 parts'of the body. The bones are formed from phos- 

 phate of lime, an inorganic substance contained in all 

 the nutritious grasses and in the grains. 



198. It has been stated that starch, gum, and sugar, 

 as parts of animal food, go to support respiration. 

 This requires to be explained. When wood is con- 

 sumed, the oxygen of- the air combines with the car- 

 bon of the wood, forming carbonic acid (CO'), and the 

 oxygen and hydrogen of the wood combine with each 

 other, forming water (HO), so that carbonic acid and 

 v^SiteTj vapor pass off, while the inorganic parts of the 

 wood fall to the hearth in the form of ash. If we 

 were to burn a handful of corn, the same would take 

 place. The organic part would pass off, as carbonic 

 acid and water ; and the inorganic part would fall 

 down, as ashes. But if, instead of being burnt, the 

 corn were to be eaten by an ox or other animal, let us 

 see what would become of it. It contains, among 

 other things, starch, gluten, oil, and phosphate of lime. 

 The digestible parts would be first converted into 

 chyle and then into blood. The blood would be im- 

 mediately forced through the lungs. In the lungs air 

 would come in contact with it. The oxygen of the 

 air combines with the carbon of the starch, and forms 

 carbonic acid ; while the other elements of the starch 

 combine with each other, forming water ; and the 

 animal exhales carbonic acid and watery vapor, the 



