84 THE PHYSICAL KINSHIP 



elasticity in the presence of a varying environ- 

 ment. 



In the amphibians the characteristic five-toed or 

 five-fingered foot, which normally forms the ex- 

 tremities of the limbs of all vertebrates except 

 fishes, is first met with. It was this pentadactyl 

 peculiarity of the frog, inherited by men and women 

 through the reptiles and mammals, that gave rise 

 to the decimal system of numbers and other un- 

 handy facts in human life. The decimal system 

 arose out of the practice of early men performing 

 their calculations on their fingers. This method 

 of calculating is still used by primitive peoples all 

 over the world. The sum of the digits of the two 

 hands came, in the course of arithmetical evolu- 

 tion, to be used as a unit, and from this simple 

 beginning grew up the complicated system of tens 

 found among civilised peoples. It has all come 

 about as a result of amphibian initiative. Our 

 very arithmetics have been predetermined by the 

 anatomical peculiarities of the frog's foot. If these 

 unthinking foreordainers of human affairs had had 

 four or six toes on each foot instead of five, man 

 would no doubt have inherited them just as cheer- 

 fully as the number he did inherit, and the civilised 

 world would in this case be to-day using in all of 

 its mathematical activities a system of eights or 

 twelves instead of a system of tens. A system 

 of eights or twelves would be much superior in 

 flexibility to the existing system ; for eight is 

 a cube, and its half and double are squares; 

 and twelve can be divided by two, three, four, 



