528 THE POPULAR SCIENCE MONTHLY. 



The membrane of the bat's wing is a structure of extreme and 

 peculiar delicacy as regards the sense of touch, and the perfection of 

 this sense is doubtless contributed to by a special condition of its 

 blood-vessels. Although the sense of touch depends, of course, di- 

 rectly on the nerves, the functional activity of the nerves depends 

 upon the quantity and the sufficiently rapid renewal of the blood sent 

 to them. This is shown by the familiar examples of numbness brought 

 about by checking the supply of blood to any part with a ligature, as 

 also by the increased sensibility occasioned by inflammation ; that is, 

 through a more copious supply of blood. Now, in most animals, as 

 in ourselves, the heart pulsates w T ith rhythmical contractility ; but 

 the blood-vessels which distribute the blood over the body are not 

 themselves contractile, however highly elastic they may be. In the 

 bat's wing, however, the vessels which convey blood toward the heart 

 (i. e., the veins) have been found by Dr. Wharton Jones to be them- 

 selves positively contractile, and so fitted in a most exceptional man- 

 ner to help on the blood-supply, thus indirectly augmenting the power 

 of touch. 



This exceptional condition of the vascular system may, then, have 

 something to do with that exceptional perfection of the power of sen- 

 sation before referred to, and which was experimentally demonstrated 

 by Spallanzani. He found, not having the fear of anti-vivisectionists 

 before his eyes, that bats deprived of sight, and as far as possible also 

 of smell and hearing, were still able not only to avoid ordinary obsta- 

 cles to their flight in strange localities, but even to pass between threads 

 purposely extended in vai - ious directions across the room in which 

 the experiments were made. This skill it is believed is due to an exces- 

 sively delicate power of sensation possessed by the flying membrane 

 a power enabling the creatures by atmospheric pressure and vibration 

 to feel, before contact, the nearness of adjacent objects. Dr. Dobson, 

 who has paid more attention to bats, perhaps, than any other living 

 naturalist, is disposed to think, and very reasonably so, that tactile 

 power may be thus greatly increased by such increase of the surface 

 on which tactile sensations may be received as is found in the bat's 

 wing, and that this is the explanation of the mysterious power re- 

 vealed to us by Spallanzani. 



The flight of the bat compared with that of most birds is exces- 

 sively fluttering ; but it is a true and perfect flight, and therefore 

 very different from the analogous action of other beasts called " fly- 

 ing," such as the flying-squirrels, the flying-opossums, and the flying- 

 lemur. In these animals the skin of the flanks can indeed be extended 

 outward to the arm and the leg, and when so stretched (as when these 

 animals take long jumps) seems as a sort of parachute to sustain them 

 somewhat in the air, and so far break their fall as to enable them to 

 flit from one bough to another; but they cannot truly fly. The flying- 

 lemur is the best furnished in this respect, as it has not only a very 



