downing] A SCHOOL OUTLINE 233 



uses as he chisels away the shell of a nut with the sharp front 

 teeth. Think of the lower jaw as a lever, the fulcrum at the point 

 where it hinges. The weight is the resistance to be overcome by 

 the teeth in biting into an object. The power is applied by these 

 jaw muscles we have felt. Have pupils draw a diagram of the 

 long jaw of a hound and the short jaw of a squirrel, marking on 

 each fulcrum, weight and power. Take a stick, like a ruler ; 

 fasten one end by a single screw to the wall or table and attach 

 a weight at the other end. Tie a string near the middle of the 

 ruler ; run this up over a pulley made by putting a small spool 

 or a nail in the wall ; attach weights to the free end of the string 

 to balance the weight at the outer end of the ruler, thus holding 

 the latter horizontal. The apparatus will roughly represent the 

 arrangements of mechanical elements in the squirrel's jaw. Notice 

 how much power is required to balance the weight attached at 

 the end of the ruler. Now use a longer stick ; have the weight at 

 its end and the distance from the fulcrum to the point of attach- 

 ment of the string about the same as before. Do you need more 

 or less weight on the string to hold the stick horizontal? Would 

 it then be best for an animal that needed to bite hard like a 

 squirrel on a nut, to have a short jaw or a long jaw? What sort 

 of a dog can bite hardest? Has he a long or short jaw? Why 

 does a hound have a long head ? Compare a cat's teeth with those 

 of a dog. Are they alike? Are they like your own? Are they 

 like those of a horse or cow or sheep? How are the sharp, cut- 

 ting teeth of the dog or cat well adapted to its method of eating? 

 What do you feed a horse or cow? Why do they have flat- 

 crowned teeth? State the relation of kind of teeth to the habits 

 of the animal. 



Note the position of the organs of special sense — eyes, ears, 

 nose, tongue. Why are these sense organs on the head end? 

 What is the use of a cat's whiskers? 



Lesson XVIII. Wild Relations. — Observations in the lower 

 grades (or with the lower grade outlines) have established some 

 things from which we may draw extensive inferences We have 

 seen that the cat is a warmth-loving creature. She loves to lie 

 stretched before the fire and curls up to sleep in the warmest cor- 

 ners. She goes out regretfully in winter and then gingerly treads 

 the snowy paths. From these observed perculiarities what would 

 you infer regarding the probable habitat of the great cats — her 

 wild relations? 



Have the children endeavor to form clear mental pictures of 

 the following wild relations : fox, wolf, coyote, jackal, otocyon. bay 



