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These elements do not exist in the body in the free state, if we 

 except traces of uncombined Oxygen, Nitrogen and Hydrogen, but in 

 various combinations with one another forming exceedingly complex 

 compounds. These, for the sake of convenience, fall into two great 

 classes: — Organic and Inorganic, though the distinction is no longer 

 a strictly accurate one. The organic compounds may be considered 

 under the divisions, (a) Nitrogenous, {d) NoN-NrxROGENOus, accord- 

 ing as to whether Nitrogen enters into their composition or not. Many 

 of the elements above cited are common to both the Organic and 

 Inorganic compounds. 



The Nitrogenous compounds are the most numerous as to their 

 number as well as most complex as to their quantitative composition, 

 th(jugh they are made up of but four elements, Carbon, Hydrogen, 

 Nitrogen and Carbon, with occasionally small amounts of Phosphorus 

 and Sulphur. We can here only mention certain large groups ot 

 these compounds. 



Albuminoids or Proteids, a generic term including a number of 

 substances having the same percentage composition but different physical 

 properties. Sub-divisions coniprise. (i) Native Albumefis, of which the 

 white of. egg is an example; (2) Globulins, chief among which is 

 Myosin, the organic basis of muscle ; (3) Derived Albumens, the casein 

 or curd of milk and certain substances formed in the stomach during 

 digestion; and (4) Peptones or Soluble Albuminoids, formed by the action 

 of the digestive fluids on food, and which pass into the blood to nourish 

 the body. Besides these there are the Gelatins found in bones, etc., 

 and certain other waste products formed by the life functions ot the 

 various organs of the body. 



The NoN- nitrogenous organic compounds are made up entirely 

 of Carbon, Hydrogen and Oxygen. They consist of {a) Carbo-hydrates, 

 in which the Oxygen and Hydrogen are in proportion to form water ; 

 {b) Fats, richer in Carbon and Hydrogen than the Carbo-hydrates, {c) 

 Fatty acids and {d) Alcohols. 



Carbo-hydrates, Sugar, Starch, are represented in comparatively 

 small quantities in the body, though found in many of the fluids and 



