

SYSTEMATIC SYNTHESIS OF ELEMENTS. 157 



phosphate of lime to give them hardness ; combined with 

 lime, potash, and soda, it exists in several of the fluids ; 

 it is a component of all the tissues ; it and Oxygen com- 

 bined are a gas, called carbonic acid gas, found in the 

 Blood and expired at every breath. 



45. HYDROGEN is a very light gas, not existing pure 

 in Nature, but very abundant as a component of water. 

 It is an element of all the Tissues and liquids in the 

 Body, and is obtained in both food and drink. 



46. OXYGEN is a gas, constituting nearly one fifth of 

 the Atmosphere, and eight ninths of the weight of water. 

 It also unites with Carbon, forming carbonic acid gas, 

 which in its turn unites with lime, potash, and soda. It 

 is also an element in each of the tissues and fluids. It 

 therefore constitutes a large part of the weight of the 

 Body, much more than any other element, or than all 

 of them. It is obtained in the air breathed, drank in 

 the form of water, and eaten in the food. 



47. THE THIRTEEN ELEMENTS MAY BE REVIEWED as 

 follows, under several heads : 



Oxygen, Nitrogen, Calcium, Potassium, 

 Hydrogen, Phosphorus, Magnesium, Sodium, Iron. 



Carbon, Sulphur, Silicon, Chlorine, 



48. THE FIRST GROUP OF THREE ELEMENTS are com- 

 ponents of all the tissues and liquids of the Body, in- 

 cluding the fat. This might at first view be thought to 

 argue their superior importance. 



49. THE SECOND GROUP OF THREE ELEMENTS are 

 components of all the tissues and liquids, except fat 

 and the sinewy tissue. They are very conspicuous in 

 the Brain, and are obtainable only from food, not from 

 air or water. They need the previous preparation that 

 food undergoes. Sinewy Tissue is comparatively inert ; 

 so is FAT : its valuable power consists in producing 

 heat. 



45. Describe . 46. Describe . 47. How ? 48. What said ? 49. What 

 said of ? 



