CHEMIC COMPOSITION OF THE HUMAN BODY. 9 



which they exist in the living condition. The organic compounds 

 consist of representatives of the carbohydrate, fatty, and proteid 

 groups of organic bodies ; the inorganic compounds consist of water, 

 various acids, and inorganic salts. 



The compounds or proximate principles thus obtained can be further 

 resolved by an ultimate analysis into a small number of chemic ele- 

 ments which are identical with elements found in many other organic 

 as well as inorganic compounds. The different chemic elements 

 which are thus obtained, and the percentage in which they exist in 

 the body, are as follows viz., oxygen, 72 per cent.; hydrogen, 9.10; 

 nitrogen, 2.5; carbon, 13.50; phosphorus, 1.15; calcium, 1.30; sul- 

 phur, 0.147; sodium, o.io; potassium, 0.026; chlorin, 0.085; fluorin, 

 iron silicon, magnesium, in small and variable amounts. 



THE CARBOHYDRATES. 



The carbohydrates constitute a group of organic bodies, consisting 

 mainly of starches and sugars, having their origin for the most part 

 in the vegetable world. In many respects they are closely related, 

 and by appropriate means are readily converted into one another. 

 In composition they consist of the elements carbon, hydrogen, and 

 oxygen. As their name implies, the hydrogen and oxygen are present 

 in the majority of these compounds in the proportion to form water, 

 or as 2:1. The molecule of the carbohydrates just mentioned con- 

 sists of either six atoms of carbon or a multiple of six ; in the latter 

 case the quantity of hydrogen and oxygen taken up by the carbon 

 is increased, though the ratio remains unchanged. 



The carbohydrates may be divided into three groups viz.: (i) 

 Amyloses, including starch, dextrin, glycogen, and cellulose; (2) 

 dextroses, including dextrose, levulose, galactose ; (3) saccharoses, 

 including saccharose, lactose, and maltose. According to the number 

 of carbon atoms entering into the second group (six), they are fre- 

 quently termed monosaccharids ; those of the third group, disaccha- 

 rids twice six ; those of the first group, polysaccharids multiples 

 of six. 



Though but few of the members of the carbohydrate group are 

 constituents of the human body, yet on account of their importance 

 as foods, and their relation to one another, a few of their chemic 

 features will be stated in this connection. 



