8 HUMAN PHYSIOLOGY. 



ANATOMY. An investigation of the living material and of the successive 

 changes it undergoes in the performance of its functions constitutes what has 

 been termed CHEMIC PHYSIOLOGY or PHYSIOLOGIC CHEMISTRY. 



By chemic analysis the animal body can be reduced to a number of liquid 

 and solid compounds which belong to both the inorganic and organic worlds. 

 These compounds, resulting from a proximate analysis, have been termed 

 proximate principles. That they may merit this term, however, they must 

 be obtained in the form under 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 elements 

 which are identical with elements found in many other organic as well as 

 inorganic compounds. The different chemic elements which are thus ob- 

 tained, 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; sulphur, 0.147; sodium, o.io; potassium, 

 0.026; chlorin, 0.085; fluorin, iron, silicon, magnesium, in small and vari- 

 able 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 hydro- 

 gen and oxygen are present in the majority of these compounds in the pro- 

 portion to form water, or as 2:1. The molecule of the carbohydrates just 

 mentioned consists 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 frequently termed monosaccharids; those 

 of the third group, disaccharids twice six; those of the first group, polysac- 

 charids multiples of six. 



Though but few of the members of the carbohydrate group are constituents 



