CLIMATE AND RACE — COON 289 



the mercury may fall to 71° F. at 6 a. m., reach the critical sweating 

 point of 93° F. at 10 : 15 a. m., hit a peak of 108° F. at 2 p. m., and fall to 

 93° F. again at 7 : 45 p. m. A hunter, who has nothing to work with but 

 his own body and a bow and arrows or a handful of spears, will be up 

 before daylight, and he will be on his way by the time the coolest point 

 of the dail}^ cycle will have been reached. He will be able to go out to 

 his hunting ground before the heat bothers him, and if he is lucky 

 he can make his kill early and take his time on the way home before 

 or during the heat of the day. If he is on a 2- or 3-day hunting trip, 

 he can nap under a bush in siesta time, and return on another morning. 

 An Arab who is herding camels or conducting a caravan will travel 

 by the light of the moon and stars and sleep under a lightproof black 

 tent in the middle of the afternoon. In Middle Eastern desert 

 countries even truck drivers prefer to work at night, to save their tires 

 as well as their own systems. If forced to do so, a desert-dwelling 

 human being can walk in the heat of the day, but if ho confines his 

 traveling to the nighttime he can go three times as far, without water, 

 before collapsing. 



Animals that live in the desert belong to two classes, those that 

 can do without water and those that use it to cool the body through 

 evaporation. The first category includes especially a number of 

 rodents, which derive water from desert vegetation and can even 

 extract it metabolically from dry seeds. Such animals have no 

 water to spare; they hide behind or under rocks or bushes during 

 the heat of the day, or burrow far underground, in some cases pulling 

 stoppers of earth in behind them. When the surface ground temper- 

 ature is 122° F. it may be only 83° at a depth of 1 foot 3 inches, while 

 at 6 feet it may fall as low as 68° F., with considerable humidity. 

 Animals that hide during the day to save water will die when forced 

 to spend a few hours in the bright sun in the heat of the day. 



The other class of animals is composed of larger forms, such as 

 the camel, oryx, and addax, which are able to hold up to a fifth of 

 their body bulk in stored water and to utilize it gradually. In this 

 sense they are no better off than a man weighing 120 pounds carrying 

 a 5-quart canteen. In cool spring weather they are at an advantage 

 over the man, however, for they can derive their moisture from herb- 

 age ; only in the hot and barren season do they depend on their speed 

 to carry them to water. In addition to their water-holding capacity, 

 these animals have something else in common. They all have long 

 legs and necks and are extremely gracile for their weight. Their 

 bones are long, fine, and hard; their musculature light. In treeless 

 country they can make high speeds. Even the cat family has its 

 desert representative, the long-legged cheetah, which is said to be 

 the fastest runner of all living things. 



