Natural History 467 



Gazelle, is the "spareness" of build; the limbs are "all muscle "- 

 "muscle as hard as steel." There is, however, great elasticity 

 in the skeleton of the fore-limbs and in the connection of the 

 shoulder-blade to the backbone. It is easy to interpret the re- 

 duction in the number of digits as a lessening of friction, and the 

 same might be said in regard to the transformation of claws into 

 hoofs, but some of the peculiarities of desert animals are not so 

 easily explained. Are the markedly swollen nostrils of gazelles 

 and their relatives adapted to facilitate respiration in their racing, 

 or have they to do with filtering the air from the driven sand? 

 Opinions seem to be very discrepant in regard to the protective 

 value of the coloration of desert animals. A sandy-brown shade 

 is certainly very common, and apparent exceptions, such as 

 zebras, may admit of ready explanation. In the open the zebra 

 can look after itself and show quick heels ; in the oasis it may be 

 that the striping is very inconspicuous. It is said that the huge 

 giraffes are very inconspicuous in a grove of acacia-trees. 



The two-humped Bactrian Camel and the one-humped 

 Arabian Dromedary show various fitnesses for sandy deserts. 

 Thus the two toes have short nails instead of hoofs, and are 

 almost embedded in a strongly developed expansible sole-pad 

 with an elastic cushion between it and the bones. The result is 

 a surface which expands under pressure, and is well suited for 

 moving over the loose sand. In the closely related Llamas from 

 the Andes each toe has its own sole-pad, which is adapted for the 

 mountain paths. Many desert animals can go for a long time 

 without food or drink, and this is especially true of dromedaries. 

 In the paunch of these animals, and in camels, there are numerous 

 side-pockets with narrow openings which can be closed by circular 

 muscles, and these become filled with fluid. But we must not 

 make too much of this, for the water-pockets are also seen in the 

 Llama. Indeed, there are traces of them in the American 

 Peccary, which is related to the family of pigs. What has hap- 

 pened in the case of the Camel and Dromedary is probably that 



