2o6 BIOLOGY AND HUMAN LIFE 



which are swellings at the joints resulting from pressure. Per- 

 haps the most common and most serious foot troubles arise from 

 high heels (see Fig. 102) and fallen arches (see Fig. 103). 



Broken, or fallen, arches are due to a weakening of the 

 muscles of the foot, which may result from improper shoes or 

 from improper habits of walking. In most cases suitable exer- 

 cises will lead to a strengthening of the muscles and complete 

 correction of the defect. In other cases it is necessary to use 

 special arch supporters, but these should be obtained only with 

 the aid of competent physicians or foot specialists. 

 • In walking the swing of the leg should be in a plane running 

 directly front and back, and the line of support in the foot 

 should move in this plane also (see Fig. 104). 



THE SKIN AND THE APPENDAGES 



1. The structure of the skin 



The dermis 



The epidermis 



Outgrowths : hair and nails 



Living parts ; non-living parts ; manner of growth 

 Glands : sweat ; oil 

 Nerve endings 



2. The functions of the skin 



Protection ; excretion ; sensation ; temperature regulation 



3. Care of the skin etc. 



4. Hygiene of clothing 



Advantages and disadvantages of clothing 

 Advantages and disadvantages of particular materials 

 Tight garments, belts, garters, corsets 



5. Care of the hands 



6. Care of the feet 



Posture ; shoes ; heels ; corns 



