EXPERIMENTS 209 



1) Examine skin of hand. Compare skin on back with that 

 of palm. Note character of surface and markings, especially 

 on balls of fingers. 



2) Make finger print by rolling ball of finger on a piece of 

 glass upon which a thin film of printers' ink has been spread by 

 roller or dabber. Apply finger to smooth white paper. 



a) Examine print with magnifying glass and note white dots 

 (mouths of sweat ducts) on ridges. 



b) Compare patterns of markings * of different fingers of 

 same individual and of different individuals. 



3) Moisten back of hand and repeatedly scrape surface with 

 edge of dull knife, as table knife. Collect detritus, place upon 

 glass slide with drop of water, and apply cover glass. Examine 

 under microscope and note flattened cells. 



4) With sharp knife or razor, slice off a thin slip of skin 

 over a callus on palm. Moisten and examine under microscope. 

 Note mouths of sweat ducts and horny character of skin. Dis- 

 tinguish separate cells after prolonged soaking. 



5, a) Make parings of nail, a narrow strip to show edge, 

 one broad to show surface. Examine under microscope dry 

 and after soaking in water. 



b) Compare shape and general structure with nails of 

 various animals, as dog, cat, cow, fowl, bird, horse, etc. 



6, a) Pull out hair and examine shaft and root in drop of 

 water under microscope. Note that root is incomplete. 



b) Compare with hair of dog and horse, with fur of cat and 

 rabbit, with feathers, with scales of fish, etc. 



7) Compare human skin with that of various animals, as to 

 general character, texture, thickness, etc. (Make use of suah 

 leather 2 as is obtainable, as cow, sheep, pig, horse, alligator, 

 snake, etc.) 



9) Dissolve in separate test tubes pieces of various samples 

 of soap, the size of a lima bean, by shaking gently in 2 tea- 

 spoonfuls of hot water. 



1 Finger prints are so characteristic and so constant as to 

 furnish one of the best means of identification. 



2 Leather is skin which has been tanned. The tanning process 

 consists in treating the leather with such chemicals as the tannin 

 of tan bark, which make insoluble the tissues "*f the skin. 



