MEASUREMENTS 31 



Because we have become accustomed to certain standards, others 

 sound strange to us. We can read that GoHath stood 6 cubits and a span 

 and carried a spear weighing 600 shekels of iron. Was this GoHath one 

 to inspire awe? Should his spear be feared? Not unless we have an evalu- 

 ation of these standards. It turns out that Goliath was about 9 feet tall 

 and had a 25- or 30-pound spear. Cubits and shekels could be as useful 

 to an ancient population as our units are to us. Would the average Ameri- 

 can know any more about Goliath if he were described as about 270 cm 

 tall? 



It would be entirely possible for any laboratory to devise its own set 

 of standards. As long as these standards were used consistently the 

 laboratory could continue to function as an independent unit. There 

 obviously could be very little communication between laboratories, how- 

 ever, and science could not have made the advances that it has. It is only 

 because of the universal agreement upon one set of standards that a 

 measurement made in western United States will be the same as a com- 

 parable measurement made in western Germany. 



The metric system is in almost universal use in science, even though 

 English-speaking countries continue to use another system in their com- 

 merce. Three quantities, length, mass, and time, were selected as a set 

 of basic standards, and most other quantities are derived from these. For 

 example, volume is length cubed, and velocity is length divided by time. 

 Probably some other set of basic standards could be devised, but these 

 three have worked well and have become so ingrained in our thinking 

 that it is difficult to imagine another system. 



The principal advantage of the metric system is the ease of computa- 

 tion. Multiplying or dividing by ten is much easier than working with 

 a system in which a pound contains 16 oz and a typical small length 

 is ys2 in. The system of pounds and yards was based originally on some 

 arbitrary standards. The metric system was intended to represent cer- 

 tain natural features, just as the meter was a fraction of the earth's 

 circumference and weight units were based upon a volume of water. 

 After the metric standards were established, methods of measurement 

 improved, and it was necessary to admit that a meter was not precisely 

 the value it was supposed to be. But the "standard meter," a unit accepted 

 by international agi^eement, could still be used. Nearly all figures used 

 in this book are expressed in metric units. 



Most of the measurements in biology are essentially the same as those 

 used in the physical sciences. Occasionally, however, biological phe- 

 nomena do not lend themselves to this simple, direct expression, and it is 



