48 Cheiroptbka. MAMMALIA. Cheiroptera. 
Order IIL— CHEIROPTERA. 
To tills small and well-marked class of mammals, it 
must be confessed, naturalists have not given that 
attention which the subject demands. Though for the 
most part composed of individuals of comparatively 
insignificant bulk, they have nevertheless important 
claims upon our consideration, both on account of the 
singular and characteristic modifications of organic 
structure they exhibit, and in respect of the part they 
play in the economy of creation. 
With regard to the habits of the bats and their man- 
ner of living, the first and most conspicuous peculiarity 
presented to ordinary observation has reference to their 
mode of flight, and the agency by which this function 
is performed. As the majority of our readers are 
aware, their titular name Cheiroptera, or Wing-handed 
family, points at once to the members of the body, 
primarily concerned in the office of flying ; but while 
the flight of birds is immediately brought about by a 
development of special integumentary appendages in 
the form of feathers, we have here the same purpose 
served by a membranous extension of the skin itself. 
The membrane is extremely delicate and elastic, 
extending in front from the neck and sides of the body 
to the extremity of the fingers of each upper limb, and 
behind to the tail and to the heels of the feet. It is 
thus that nature displays her indefinite resources, being 
in no way hindered by such arbitrary laws as operate 
in the fabrication of works of art. Look at the char- 
acter of a bat’s flight. Generally speaking its aerial 
progression is easy, regular, and sustained. It has a 
velocity sufficient to insure the overtaking and capture 
of its swiftest insect prey ; while its strength is such as 
to enable the maternal parent to carry one or two 
young ones on her back at the same time, during her 
passage through the air. Considering the solidity of 
their bony framework, and the absence of such air 
cavities as are found in birds, it would at first sight 
appear that bats have relatively a greater specific 
gravity than birds, and consequently a greater degree 
of aerial pressure to contend with. This apparent dis- 
advantage, however, is more than counterbalanced by 
a proportionably greater extent of surface presented by 
the wings as compared with the weight of the body, 
than obtains in the feathered tribe. We have here in 
short all the essential conditions for a rapid aerial pro- 
gression, namely, an appropriate form, a weak specific 
gravity, and a special modification of the anterior loco- 
motive organs, forming an elastic extensile membrane. 
These conditions enable the Cheiroptera to realize a 
capacity of flight second only in degree of perfection to 
that of birds. In no other family of the first great 
division of the animal kingdom is this physiological 
action witnessed, unless indeed we are to exalt the 
leaping powers of the Galeopithecus volans to a species 
of flight. This animal, more familiarly known as the 
flying cat, or flying lemur, is also provided with 
an elastic membrane of a more limited extent than 
that of bats, but covering and connecting together the 
anterior and posterior extremities ; this structure is not 
only incapable of raising the creature in the air, but 
performs rather the office of a parachute than that of 
an organ of flight. 
The remarkable adaptations thus rendered subser- 
vient to the purposes of flight, are further, and perhaps 
more cogently, illustrated by referring to the skeleton 
(Plate 34, fig. 110). Here we find the solid framework 
of the body more or less attenuated in all its elements, 
with the view of imparting lightness on the one hand, 
and of retaining strength on the other. Every bone 
indicates the care taken to provide against any unne- 
cessary weight. The skull is elongated from before 
backwards, and its constituent parts thinned out in a 
striking manner ; this elongation, however, is less con- 
spicuous in those bats which feed on insects, and there 
are several other cranial peculiarities indicating greater 
strength in the insectivorous than in the frugivorous 
species. Among these may be mentioned an increased 
breadth in the form of the jaws in the carnivorous kind, 
this group also having the cusps of the teeth sharp and 
pointed, while those of the fruit-eating section are 
broader, blunter, and deeply grooved longitudinally. 
All the bats display four canine teeth, but the number 
of incisors and molars or grinding teeth varies consider- 
ably. ■ Of the latter there are never less than three on 
either side of each jaw, while very frequently we find 
five in the upper and six in the lower, an arrangement 
which is occasionally reversed. With regard to the 
incisors, or cutting teeth, there are usually two or four 
in the upper jaw, and two, four, or sometimes six, in 
the inferior jaw. The backbone, or chain of bones, 
termed the vertebral column is chiefly remarkable for 
the large size of its spinal or neural canal, and the 
comparative breadth and strength of the bones of the 
neck. The vertebrae, to which the ribs are attached 
are eleven or twelve in number, according to circum- 
stances ; but those succeeding are more variable in this 
respect, from four to seven being assigned to this so 
called lumbar region. The bones of the tail, or coccy- 
geal vertebrae, exhibit a still more striking irregularity, 
and present, as it were, a gradual dwindling away 
towards the delicate filamentary extremity in those 
species of Vespertilio where they are most numerous. 
In the genus Pteropus, indeed, there is no tail what- 
ever, but in the species of Noctula we find six bones, 
while as many as twelve occur in the genus above 
mentioned. All the ribs, with the exception of the first 
pair, have an extraordinary length, relatively more, we 
may say, than occurs in any other mammalian family. 
The breastbone, or sternum, is also unusually long and 
broad, the anterior part, or manubrium, as it is called, 
having a surprising lateral expansion in certain of the 
genera, and most conspicuously so in the horse-shoe 
bats. In all the species this portion of the little flat 
chain of bones, collectively termed the sternum, is pro- 
vided with a more or less prominent central ridge on 
the under surface, evidently corresponding to the exag- 
gerated keel-like process developed in birds to give 
attachment to the strong pectoral muscles. We also 
