CHEIROPTERA. 



599 



in most species it is more or less lanceolate in 

 its form; in Vespertdio spasma it is forked, 

 and in the great Bat of Britain, Vespertilio 

 noctula, it is short, blunted, with a rounded 

 head, thickish, and I have observed it beset 

 with numerous minute glands, which do not 

 occur in those species having the thin lan- 

 ceolate form of this part. Its use is probably 

 to prevent the rush of air into the open ear 

 during flight; and where it does not exist, 

 as in the Horse-shoe Bats ( Rhinolophus}, its 

 place is supplied by a large rounded lobe which 

 is capable of still more effectually closing the 

 external meatus. 



In the internal ear there is an equal diver- 

 sity of structure in the two groups in question. 

 The cochlea is particularly developed in the 

 insectivorous group; being much larger than 

 the semicircular canals; the circumference of 

 that of Rhinolophus is no less than four times 

 the circumference of the canals, and its cavity 

 exhibits ten times the diameter of one of them. 

 In Pteropns this disproportion is very much 

 less. The meatus is short and, as well as the 

 tympanic cavity, extremely large and open. 



But it is in the sense of touch probably that 

 the most extraordinary and interesting pecu- 

 liarities are to be observed. Spallanzani hav- 

 ing observed the power which these animals 

 possess of flying with perfect accuracy in the 

 dark, and of avoiding every obstacle that pre- 

 sents itself with the same unerring certainty as 

 in the light, instituted a series of experiments, 

 the results of which proved that bats when 

 deprived of sight by the extirpation of the 

 eyes, and, as far as possible, of hearing and 

 smell by the obliteration of the external pas- 

 sages of those senses, were still capable of 

 directing their flight with the same security 

 and accuracy as before, directing their course 

 through passages only just large enough to 

 admit them without coming into contact with 

 the sides, and even avoiding numerous small 

 threads which were stretched across the room 

 in various directions, the wings never, even 

 by accident, touching any of them. These 

 marvellous results led him to believe that these 

 animals are endowed with a sixth sense, the 

 immediate operation as well as the locality of 

 which is, of course, unknown to and unap- 

 preciable by us : but the sagacity of Cuvier* 

 removed the mystery without weakening the 

 interest of these curious facts, by referring to 

 the flying membrane as the seat of this extra- 

 ordinary faculty. According to this view of 

 the subject, the whole surface of the wings on 

 both sides may be considered as an enor- 

 mously expanded organ of touch, of the most 

 exquisite sensibility to the peculiar sensation 

 for which it is intended ; and it is, therefore, 

 by the varied modification of the impulsion of 

 the atmosphere upon this surface, that the 

 knowledge of the propinquity of foreign bodies 

 is communicated. This membrane is every 

 where furnished with oblique or transverse 

 bands, consisting of lines of minute dots re- 



d'Anatomie Comparee, t. ii. p 582. 



sembling in some measure strings of very small 

 glands or cutaneous follicles. May there not 

 be some connexion between these peculiar 

 little bodies and the extraordinary function just 

 described ? 



The tendency to an extraordinary develop- 

 ment of the dermal system is not confined to 

 the organs now mentioned, of the senses of 

 touch and of hearing. The organ of smell is 

 in many insectivorous Bats, as in the whole 

 family Rhinolophidtf, furnished with foli- 

 aceous appendages, formed of the integument 

 doubled, folded, and cut into the most curious 

 and grotesque forms. These nasal leaflets are 

 found principally or exclusively to belong to 

 a group, the habits of which are more com- 

 pletely lucifugous and retired than any others ; 

 they are found in the darkest penetralia of 

 caverns, and other places where there is not 

 even the imperfect light which the other genera 

 of Bats enjoy. It is probable that this deve- 

 lopment of skin around the nose is intended 

 to give increased power and delicacy to the 

 organ of smell, as well as to regulate the access 

 of the odoriferous particles, and thus to super- 

 sede the sense of vision, in situations where the 

 latter would be unavailable. 



In the genus Nycteris a curious faculty is 

 observed, namely, the power of inflating the sub- 

 cutaneous tissue with air. The skin adheres 

 to the body only at certain points, where it is 

 connected by means of a loose cellular mem- 

 brane ; it is therefore susceptible of being raised 

 from the surface, on the back as well as on the 

 under parts. These large spaces are filled with 

 air at the will of the animal, by means of large 

 cheek pouches, which are pierced at the bottom, 

 and thus communicate with the subcutaneous 

 spaces just mentioned. When the animal 

 therefore wishes to inflate its skin, it inspires, 

 closes the nostrils, and then contracting the 

 cavity of the chest, the air is forced through 

 the openings in the cheek pouches under the 

 skin, from whence it is prevented from returning 

 by means of a true sphincter, with which those 

 openings are furnished, and by large valves on 

 the neck and back. By this curious me- 

 chanism the bat has the power of so com- 

 pletely blowing up the spaces under the skin, 

 as to give the idea, as Geoffrey observes, " of a 

 little balloon furnished with wings, a head, and 

 feet." 



The digestive organs of the Cheiroptera ex- 

 hibit as distinct a division into the two prin- 

 cipal groups before-mentioned, as any other 

 part of their anatomy. The teeth have been 

 already alluded to, and the characters of these 

 important organs, important as indicating, in 

 the most unerring manner, the nature of the 

 food, are well-marked in the two groups. The 

 flattened crowns of the molares, so similar to 

 those of the Quadrumana which are found to 

 belong to the frugivorous Bats, are strikingly 

 contrasted with the many-pointed tuberculous 

 teeth of the insect-feeders, and exhibit an in- 

 teresting affinity to the two important orders of 

 animals to which the Cheiroptera may be con- 

 sidered intermediate; the former division re- 



