THE FLYING-FOXES. 323 



c Rasselas,' we meet with a mechanician who, wishing to try a pair 

 of artificial wings which he had invented, fell headlong into a 

 lake a short distance from the tower whence he had first taken 

 his adventurous flight. Had this unfortunate man been able to 

 render his bones comparatively as light as those of the bat had 

 he been able to reduce the weight of his body to a tenth part, 

 and to render, at the same time, the muscles of his arm ten 

 times thicker and more powerful than they were, then, perhaps, 

 he might have been more successful : or, had he studied the 

 anatomy of the bat, he surely would have given up all idea of 

 ever rivalling a creature of a construction so different from 

 that of his own body ! 



All the European bats are insectivorous, but the large kalongs 

 or flying-foxes of India, the Eastern Archipelago, and the tropical 

 islands of the Pacific, chiefly live upon fruits. Certain modifica- 

 tions in the structure of the instruments of flight have been 

 made to harmonise with this difference of diet. Thus the 

 clavicle and the keel of the breastbone are more developed 

 in the insectivorous than in the herbivorous bats, for the very 

 obvious reason that the former are obliged to use greater exer- 

 tions in the pursuit of their swift and active prey, than the 

 latter in merely flying from place to place in search of their 

 stationary food. The existence of a tail, for the support and 

 extension of a broad membrane extending between the hind- 

 legs, compared with its absence or comparative inefficiency 

 in many of the frugivorous bats, also points out an interesting 

 relation to the different habits of the two groups the former 

 structure being calculated to afford a powerful and effective 

 rudder in guiding their rapid and varying evolutions in the pur- 

 suit of their insect food. 



Besides the bats, there are several other mammalia which, 

 although incapable of a prolonged flight, are assisted or sup- 

 ported in their movements by winglike expansions of the skin ; 

 and all these animals have a comparatively slender and light 

 body, for Providence would never have committed the mistake 

 of investing a huge bulky creature with so useless an ap- 

 pendage. 



Thus, by means of a parachute-like extension of its skin be- 

 tween the anterior and posterior limbs on each side, and between 



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