166 Popular Science Monthly 



Wliy Monkeys Use Their Fists Explosives Are Simpler in Com- 



Instead of Their Hands 



WHEN next you go to the zoo, watch 

 the monkeys use their hands. 

 Notice how they seize things with their 

 fists. They do not use their finger-ends 

 as we do. While the higher monkeys, 

 such as gorillas and chimpanzees may be 

 taught to use their 

 fingers, they never 

 learn to use them as 

 easily as do human 

 beings. 



The monkey is 

 primarily a tree- 

 dweller. It lives in 

 forests and swings 

 from tree to tree, 

 using its hands as 

 hooks with which it 

 grasps the branches. 

 The thumb is not 

 brought into play. 

 Some South Amer- 

 ican monkeys have 

 lost the thumb 

 through disuse; all 

 that is left of it is 

 indicated by a little 

 lump under the skin. 



In the higher monkeys the wrist is 

 built like yours. It has the same number 

 of bones. But the monkey has never 

 used his wrist, and so it has lost the 

 flexibility. The monkey can use its feet 

 to better advantage than its hands. 



Man, on the other hand, has used his 

 feet so long simply for the purpose of 

 walking, that he would experi- 

 ence considerable difficulty in 

 using them as he uses his hands. 

 Yet, it is amazing how quickly 

 a man can learn to use his toes 

 as he does his fingers. If you 

 don't believe this, just try to 

 write with your toes. At first 

 the letters will be very large and 

 awkward. But with a little 

 practice you will find that- you 

 can write with your foot more 

 easily than with your left hand, 

 if you are naturally right- 

 handed. It is an attractive 

 exercise with which to wliile 

 away an hour. We know you 

 will try the experiment. 



An educated chimpanzee threading a 

 needle. His thumb is not well developed 



position than They Seem 



HERE, gentlest of readers, we have 

 an object lesson in explosives. The 

 inventor of a particularly new and violent 

 kind is throwing it against a tree in 

 demonstration of the fact that it will not 

 "go off" in the absence of the proper 

 kind of primer. It 

 even may be lighted 

 with a match, and it 

 will burn like a pitch 

 torch — but no ex- 

 plosion. But should 

 you attempt to set 

 it off with a certain 

 primer, you will ar- 

 rive elsewhere v/ith 

 promptness and ex- 

 ceeding dispatch. 



Most smokeless 

 powders will admit 

 of similar treatment. 

 These features about 

 explosives seem most 

 unusual, until one 

 looks into the physi- 

 cal principles back 

 of their action. Ex- 

 plosion is simply a 

 burning. The quicker the burning the 

 higher the "high" explosive. If an ob- 

 ject burns; i. e., is converted into gas 

 quickly, the expansion resulting is capable 

 of exerting tremendous force on whatever 

 happens to contain the object. Here is 

 the force that drives projecciles such 

 tremendous distances. 



Throwin^i this explosive against a tree will 

 not detonate it; a special primer is necessary 



