90 PHYSIOLOGY FOR THE LABORATORY. 



c. The inner, true skin, or dermis. Has it blood-vessels 

 or nerves ? 



III. A BLISTER. 



When you have a water-blister, insert a needle under 

 the outer skin and find the liquid that collects between 

 the two layers of the skin. Whence does this liquid 

 come ? Why does it not exude through the pores of the 

 sweat glands ? 



IV. ATTACHMENT OF THE SKIN. 



Try to lift the skin up away from the underlying tis- 

 sues in the following places : back of the hand, cheek, 

 forehead, neck, palm of hand, and fingers. What differ- 

 ences in the mode of the attachment in the different 

 places ? Why should the skin be so firmly attached to 

 the palms and the fingers ? 



B. Finger-Prints. 

 Material. Printer's ink and paper. 



Spread a film of thin printer's ink on a piece of paper, 

 glass, or a stamping pad. Place the under surface of the 

 last joint of a finger on the ink and then on a piece of 

 clean paper. Study the print and find the arrangement of 

 the small ridges. 



a. Are they in an arch, a loop, or a whorl ? What is 

 their use ? 



5. Make a print of all your fingers and thumbs and 

 compare the results with those of others. 



