Cheiropteka.- 



-MA5DIALIA.- 



-ClIEIKOrTERA. 



49 



discover an increase of development of the other bones 

 which enter into the constitution of the shoulder. The 

 clavicles are elongated and much arched superiorly, the 

 bladebone or scapula being likewise very surprisingly 

 developed, more especially in the insect-devouring 

 species. All these arrangements beaiitifiilly illustrate 

 the adaptability of this mechanism to the peculiar habits 

 of the Cheiroptera, while they at the same time aSbrd 

 to the unprejudiced truth-seeker the most satisfactory 

 evidences of creative design. The teleological argu- 

 ment, indeed, may be still more vigorously enforced by 

 a consideration of the osseous elements which enter 

 into the formation of the arm, forearm, and hand. To 

 a certain extent we have already touched upon this 

 mechanism, when speaking of the characteristic function 

 of flight. It is here, therefore, only necessary further 

 to observe, that the upper extremity of the humerus or 

 first bone of the arm is large and rounded, while the 

 remainder is cj'lindrical and slender throughout. The 

 two bones of the forearm, namely the radius and ulna, 

 are curiously modified; the former being extremely 

 long, and the latter only faintly represented by a 

 slender styliform process, or in some cases by a mere 

 rudimentary flat bony nodule. By this significant 

 disposition of parts all rotatory motion is efl'ectuallj' 

 prevented, and those movements of pronation and 

 supination, so essential to the welfare of the human 

 and quadrumanous species, are entirely dispensed 

 with. Had not these changes of structure been intro- 

 duced, the comfort, nay the very existence of these 

 creatures, would have been jeopardized. Such is the 

 foresight of the Divine Architect! And before con- 

 cluding this part of the subject, we have further to 

 observe that six small bones enter into the framewoi'k 

 of the wrist, two behind, and four in front ; one of the 

 former row being singularly bulky, probably because 

 two other carpal bones, usually assumed to be absent, 

 do in reality enter into its constitution. Succeeding 

 these are the immensely elongated metacarpals and 

 wire-like fingers, the phalanges of which diverge from 

 one another in the expanded condition of the wing, and 

 spread out to reach the lower margin of the elastic skin 

 membrane formerly described. The second digit is 

 the shortest, and the third the longest, while the thumb 

 is comparatively insignificant, and terminated by a 

 hooked phalanx. Finallj', the bones of the pelvis, and 

 those of the lower limb, although they share in the 

 general diminution of the osseous fobric quantitively, 

 do not in other respects relatively exhibit those devia- 

 tions from the normal type of skeletal structure which 

 obtain in the shoulder and superior extremities. 



Before proceeding to consider the habits of Cheir- 

 optera, there are several other interesting peculiarities 

 of organization which cannot pass unnoticed. One of 

 the most important of these is the great development 

 of the ears among those bats living upon insects. In 

 some species the external auricles attain a prodigious 

 size (fig. 10), being frequently as large as the head, and 

 occasionally nearly as long as the entire body; and 

 this curious feature is, moreover, combined with an 

 increased development of the internal acoustic appar- 

 atus, and a special enlargement of that part of the 

 auditory organ termed the cochlea. The eyes of bats are 

 Vol. I. 



small, and in those kinds which have large ears they 

 arc almost concmiled from view. The skin, generally, is 



Fig. 10. 



Ikad of the I.ou^ 



_.. i^^,,i ^I'lucutiis ;iiiritiis). 



clothed with a soft downy hair, except on the winged 

 and interfemoral expansions. The sense of smell is 

 remarkably acute, more particularly in the insect- 

 hunting group. Here again we find an increased 

 development of the external organ, precisely analogous 

 to the external ear. Certain individuals are provided 

 with leaf-like appendages attaclied to the nostrils, and 

 consequently we are fairly entitled to presume that, 

 as in the case of hearing, the auricles are created with 

 the obvious intention of catching sonorous vibrations, 

 so also are the nasal leaflets designed to collect the 

 odorous particles emitted from the bodies of the insects 

 on which these animals prey (fig. 11). The sense of 

 touch is likewise exceedingly sharp. For a long time 



Fig. 11 



Head of tlie Greater Ilorse-shoe Bat (Efiinoloiihua feiTum-equinum). 



it was a question with naturalists how the Cheiroptera 

 regulated their flight in caves and recesses of almost 

 absolute darkness, there being no doubt as to the well 

 ascertained fact that their movements, under these 

 circumstances, were conducted with the same skill, 

 ease, and rapidity as in twilight. To solve this problem 

 the eminent physiologist, Spallanzani, instituted a series 

 of cruel experiments. He actually deprived a number 

 of bats of their sight by extracting the eyes, and filling 

 the sockets with pieces of leather. They were then 



G 



