796 



THE NATURE BOOK 



upper arm bone {humerus) of a Bat is 

 abnormal, tlie chief fore-arm bone (radius) 

 more abnormal, antl the finger bones 

 most abnormal of all. The peculiarities 

 of these bones may perhajis be best 

 realised by comparing their pro]:)ortions 

 with the proportions of the corresponding 

 bones in ourselves. Though the latter 

 may exhibit considerable variation in 

 different individuals, it may be said that 

 in the average human male the distances 

 between the breast-bone and the shoulder- 

 joint, the shoulder-joint and the elbow, 

 the elbow and the wrist, and the wrist 

 and the middle finger-tip, are roughly 

 in the proportion 3:6:5:3. In the 

 Long-Eared Bat the corresponding pro- 

 portions may be taken as 1.4 : 3 : 5 : 8. 

 If we were in imagination to set our- 

 selves the task of converting a human 

 fore-limb (seven inches, say, from breast- 

 bone to shoulder, fourteen from shoulder 

 to elbow, ele\-en from elbow to wrist, 

 and seven from wrist to middle finger-tip) 

 into a fore-limb of similar proportions 

 and structure to that of a Long-Eared 

 Bat : if, that is, we were to endeavour 

 so to modify a human skeleton that its 

 owner might have reasonable prospects 

 of being able to fly, we should find that, 

 to begin with, the following extensions 

 would be necessary. Leaving the collar- 

 bone at seven inches, the u]:)per arm bone 

 would have to be lengthened to fifteen 

 inches, the fore-arm to twenty-five inches, 

 and the middle finger-bones to forty 

 inches. The limb, that is, outside the 

 trunk, would have to be extended to 

 two and a half times its previous length. 

 The thumb might be left at seven inches 

 in length, starting from the wrist, but would 

 ha\-e to be armed with a prodigious claw. 

 The fingers, varying from twenty inches 

 to forty inches in length, would have to be 

 connected with each other, with the 

 inner surface of the arm bones, with 

 the side of the body, and with the outer 

 surface of the leg bones (as far down as 

 the ankle), bj'an elastic folding membrane 

 richly supplied with nerves, muscles, 

 and blood-vessels. When the arm was 

 extended outwards and the fingers opened 

 fan-wise this membrane would cover an 

 area (^f about thirty square feet, and an 

 additional spread of sail would be secured 

 by a triangular membrane whose apex 



was at the elbow-joint and base a lin.e 

 connecting wrist and shoulder, and also 

 by a membrane connecting the inner 

 surface of the leg bones as far as the ankle 

 with a prolongation of the vertebrae 

 in the form of a tail. The total wing 

 area on both sides of the body might be 

 as much as eighty square feet, but even 

 this would hardly support more than a 

 tenth of the original weight. The latter 

 would have to be enormously lessened, by 

 a re-arrangement and lightening of bone 

 and muscle, before our human Bat could 

 fly. He would have to develop a hump- 

 back and a pigeon-chest. His neck ver- 

 tebrae would have to describe a S-shaped 

 curve so that the back of his head 

 might nestle between his shoulder-blades. 

 Several of his skull bones would have to 

 be reduced to cartilage. His breast-bone 

 and ribs would have to coalesce for the 

 support of his psctoral muscles. His 

 peh^is and lower limbs would have to be 

 greatly reduced, and his thigh-bones would 

 have to be rotated at the hip-joints in 

 such fashion that his knees were directed 

 backward — a position, it may be noted, 

 which is aspired to by those who would 

 skate the " spread-eagle." Finally, the 

 folds of his ear would have to be ironed 

 out and pulled upwards so as to form 

 a conch nearly a yard in height, and his 

 tragus (the small projecting lobe which 

 is directed from front to back across 

 the ear-opening) would have to be 

 lengthened in the same direction for 

 about a foot. 



The necessities of an aerial existence 

 of which the wakeful portion (often limited 

 to an hour or so per diem during favour- 

 able conditions of weather) is spent in 

 the incessant pursuit of fl^'ing insects 

 have naturally influenced the domestic 

 economy of Bats. They pair normally in 

 late summer or autumn. Shortly alter 

 this hibernation may ensue, and the young 

 may not be born until May or June of the 

 year following. Hibernation naturally 

 o\'ertakes their growth, and they are not 

 mature for a twelvemonth. It is rare for 

 more than a single infant to be produced 

 at a birth, for the excellent reason thac 

 tlie mother carries her infant about with 

 her m flight, and tends it unceasingly 

 until, when ])erhaps a month old. it is fit 

 to catch flics for itself. It chngs to her 



