i88 



OUR BODIES AND HOW WE LIVE 



the tips of the fingers. They are arranged in rows, like 

 hills of corn, and sometimes in whorl-like patterns, which 

 are plainly seen with a magnifying glass on the palms of 

 the hands or the balls of the fingers. 



Experiment 60. Dip the end of a wooden toothpick into some 

 thick ink and spread it very thin over the end of the forefinger, or 

 press the end of the finger on a color pad. Now press the finger tip on 



a piece of heavy, uncoated paper. 

 Study the impression made by 

 the ridges on the finger. 



Experiment 61. The living skin 

 can be examined only in a gen- 

 eral way. Stretch and pull it, and 

 notice that it is elastic. Examine 

 the outer skin carefully with a 

 strong magnifying glass. Study 

 the papillae on the palms. Scrape 

 off with a blunt knife a few bits of 

 the scarfskin, and examine them 

 with a magnifying glass. 



FIG. 116. Papillae of the Skin in 

 the Palm of the Hand. 



In each papilla are seen vascular loops 

 (dark lines) running up from the vas- 

 cular network below; the tactile cor- 

 puscles (white lines) which supply the 

 papillae are also shown. 



255. How the Skin may 

 absorb Poison. The outer 

 skin helps to protect the true 

 skin from poisons. Lead, mercury, and other injurious 

 substances will not enter the blood and affect the health, 

 unless they are actually rubbed through the dermis ; but if 

 there is a scratch or sore, so that the true skin is exposed, 

 the poisons may be absorbed into the blood with great 

 rapidity. 



Workers in lead, looking-glass silverers, and phosphorus 

 match makers ought, therefore, to take great care to cover 

 the smallest scratches on their hands. " Lead colic " and 

 "wrist drop" are familiar instances of lead poisoning. 



