136 NATURE STUDY REVIEW [9 :5— May, 1913 



Are anv insects found around this plant other than the green- 

 house white fly? 

 2. A study of commercial tobacco. 



( a ) A bit of pkig tobacco as big as half a pea, in an inch of 

 water in a test tube or other glass vessel, will soon give the 

 water a dark brown color, showing that tobacco contains sub- 

 stances that are highly soluble in water. The most important 

 of these substances is, of course, nicotine. 



(b) Try a similar amount of tobacco in about a half -inch 

 of saliva collected in a test tube, and note that saliva also dissolves 

 the substances in the tobacco. 



(c) Take a bit of the raw white of egg and on it place a 

 drop or two of the liquid from (a). Xote that the wdiite of egg 

 takes this into itself. Point out that this white of egg is not un- 

 like the living matter that makes up the cells of which our bodies 

 are made up. 



(d) Tut a drop of the solution from (a) on a fly or other 

 insect and note the result. If you think it not unwise, take a 

 medicine dropper and inject some of the solution in the mouth of 

 a mouse. Keep the animal out of sight of course, till "all is 

 over" and then present the final result for examination. 



(e) Have a little girl with a particularly white and clean 

 little finger, immerse it in some of the tobacco solution for a few 

 minutes, and note the discoloration. 



(f) Now take a bit of tobacco no larger than a pea and 

 place it on a thin metal plate supported over an alcohol or other 

 flame. Place flies or other insects caged in wire screening, over 

 the fumes, and note results. The odors that come from the 

 heated tobacco disclose the volatile character of nicotine. 



(g) A bit of tobacco may now be held by pliers and burned 

 in the alcohol flame, the odors again being noted and any other 

 facts considered that the teacher deems it wise .to present, such 

 as the efifect of this burning on the nicotine itself. 



P). IlV(;ii:XIC CONSIDKRATTOXS AX[) CONCLUSIONS. 



W'hv do housewives sometimes take a solution of tobacco 

 and s])rinkle it on houseplants? Why are pieces of tobacco some- 

 times i)lace<l among articles of clothing that have been laid away 

 for the summer or winter? \Miy do entomologists (bug-men) 

 find empty cigar boxes especially good for keeping their pre- 

 served specimens in? Do you know of any other good uses to 

 which to put tobacco ? 



Would you think tobacco a good thing to feed to your pet 

 animals, especially young ones? Why do not foot-ball trainers 



