200 THE POPULAR SCIENCE MONTHLY. 



large animal can be properly adapted for Saharan conditions (lia- 

 bility to attack from lions and other great beasts of prey included), 

 unless it combines these three attributes of a soft tread, a swift, 

 swinging gait, and a long neck, enabling it to reach its food above 

 or below, as necessitated by the height of its legs and body. Os- 

 triches, giraffes, and camels alike, all feed to a considerable extent 

 indeed on foliage of trees. 



Of all these animals, however, the most purely desert-haunting 

 is the camel itself, and it exhibits, therefore, a few special pecul- 

 iarities not equally well developed in any other creature. In the 

 first place, desert journeys imply continued privation, or even at 

 times complete absence of food. Now, whenever in the animal 

 kingdom such a necessity frequently arises in the ordinary life- 

 history of a species, natural selection has provided against it by 

 favoring the survival of those individuals which can lay up spare 

 material against the period of famine in their own tissues. A 

 starving sheep. Prof. Huxley well remarks, is as much a carnivore 

 as the lion that would devour it ; it subsists strictly upon its own 

 fat and its own muscle, which it slowly unbuilds to use up in the 

 needful action of its heart, its lungs, its limbs, and its internal 

 organs generally. Hence, in hard times, those animals which 

 have the largest reserve-fund of fat at their disposal will survive 

 longest, and species which often encounter hard times learn or- 

 ganically by hereditary experience to supply such a reserve-fund 

 against possible contingencies. Thus the bear and the dormouse 

 go to sleep sleek and plump for the annual hibernation, and wake 

 up mere loose and baggy masses of skin and bone. The zebu 

 and other troj)ical oxen gather a huge hump of fat between the 

 shoulders in the wet months while grass is plentiful, to serve them 

 as a store of food during the dry season. But in the camel and 

 dromedary this special provision against famine reaches the high- 

 est point, and produces the hump or humps on the back — one in 

 the Arabian or African, two in the Bactrian or Indian variety. 



Structurally, of course, the humps are nothing — mere lumps of 

 fat, collected under a convenient fold of the skin, and utterly un- 

 provided for in the framework of the skeleton. When the animal 

 is at its best and well fed, they are full and plump, standing up 

 on his back firm and upright ; but on a long journey they are 

 gradually absorbed to keep up the fires that work the heart and 

 legs, and in the caravan camels which arrive at the coast, the skin 

 hangs over, an empty bag, upon the creature's flanks, bearing wit- 

 ness to the scarcity of external food during the course of his long, 

 forced march from the interior. A starved small camel in this 

 state of health far more closely resembles a Peruvian llama than 

 any one who has only seen the fine, well-kept beasts in European 

 menageries or zoological gardens could readily imagine. 



