OUR BODIES AND HOW WE LIVE 



Cheap underclothes, as colored stockings, are often dyed 

 with preparations of lead. Such articles should be thor- 

 oughly washed before they are worn. Many hair dyes 

 contain lead, and may cause lead poisoning. 



256. Absorption of Infectious Matter by the Skin. The fact 

 that certain infectious matters are -easily and rapidly absorbed 

 by the skin has long been utilized by people who have learned 

 to safeguard themselves against the ravages of smallpox. A 

 bit of the outer skin is scraped away with a pocketknife or 

 some other convenient instrument. On the moist, denuded 

 skin is placed the vaccine matter from a quill, or even matter 

 obtained from a smallpox pustule. 



Many years ago, when smallpox was very common and 

 fatal in England, the attention of a young medical student, 

 named Jenner, was forcibly attracted to the nature of the dread 

 disease in the following manner. One day a young milkmaid 

 came to seek his advice. Speaking of smallpox, the girl said, 

 "I cannot take that disease, .for I have had cowpox." Jenner 

 began a long series of experiments and observations to explain 

 this remarkable fact. The actual discovery of vaccination was 

 delayed for many years (Fig. 117 and Sec. 427). 



257. Structure of the Hair. A hair is made up of horny 

 cells of the outer layer of the skin altered in shape and 

 structure. It grows from little sacs in the true skin called 

 hair follicles. 



Every hair has two parts, the root and the free end. 

 The root is somewhat pear-shaped and is sunk in its sac, 

 or follicle, like a post into the ground. In the bottom of 

 this sac is a little hair papilla, quite different from the papillae 

 of the skin. From this comes material for the growth of 

 the hair. As long as this papilla is not destroyed, the hair 

 will grow. If we pull out the hair from the roots, it will 



