ILVCTEKiA 



■2-2^) 



through several inches (twelve or fifteen) of clean sand. Is 

 a sand filter effective? (0) Make cultures of milk. How 

 does fresh milk compare in the numl)er of its bacteria with 

 that which has stood for some time? (7) What is meant hy 

 Pasteurizino" milk? If possible, visit a milk station where 

 milk for babies is sold. What measures render it safe? 



Fig. 107. Inoculatinii- gelatin tubes with platinum loop 

 Note the way in wliich cnttoii phijjs are hehl between the fiugers 



Additional experiments. (1) Scrape the surface of a silvi'i 

 coin with a sterile knife and make a plate culture. Compare 

 with cultures made from cop[)er coins and paper momw. No 

 l)aper money is used in the Hawaiian Islands because ot the 

 danger of transmitting disease. (2) Make plate cultures from 

 the surface of a pencil that a child lias used for some time : 

 from the eds^e of a common drhdving cup, door handle, straps 



