14 HUMAN PHYSIOLOGY 



13. Iodine is found in thyroiodine, a substance present in the 

 thyroid gland of adult man. 



14. Fluorine, united with calcium, is present in the enamel of 

 the teeth. 



15. Silicon is found in the hair; in which form it is present is 

 not known. 



The chemical compounds found in the body may, from a 

 physiological standpoint, be divided into the following 

 groups : 



1. Inorganic compounds (water and salts), i.e. saturated 

 compounds which cannot be transformed into more saturated 

 compounds by chemical processes in the body and, hence, 

 cannot furnish the body with energy for its functions. Their 

 importance for life is due to their physical properties ; they 

 also take part in chemical actions, but no utilizablc energy is 

 thereby gained. 



2. Organic compounds which serve as sources of energy 

 for the organism (proteids, fats, carbohydrates) ; the stored -up 

 chemical energy is set free by their physiological combus- 

 tion. 



3. Organic compounds which, as end-products of meta- 

 bolism, are formed by the physiological combustion (nitrog- 

 enous end-products of metabolism, such as urea and others) 

 and are destined to be excreted from the body. 



1. THE INORGANIC COMPOUNDS OF THK BODY 



I. Water is the most abundant constituent of our body, 

 amounting to about 65$ of the body weight of the adult. 

 In new-born children the proportion of water is above 70^. 

 The following table indicates the amount of water in the 

 different tissues and organs : 



Adipose tissue 15$ Pancreas 78^ 



Bones 50$ Blood 79^ 



Liver 70$ Lungs 79^ 



Skin 70$ Heart 



Spleen 77$ Kidneys 



Muscles 77$ Vitreous humor 



Brain and spinal cord. 78$ Cerebro-spinal fluid.. . 



Intestine 78$ 



